Bug Summary

File:lib/Analysis/ScalarEvolution.cpp
Warning:line 8907, column 15
Value stored to 'MaxBECount' during its initialization is never read

Annotated Source Code

1//===- ScalarEvolution.cpp - Scalar Evolution Analysis --------------------===//
2//
3// The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file contains the implementation of the scalar evolution analysis
11// engine, which is used primarily to analyze expressions involving induction
12// variables in loops.
13//
14// There are several aspects to this library. First is the representation of
15// scalar expressions, which are represented as subclasses of the SCEV class.
16// These classes are used to represent certain types of subexpressions that we
17// can handle. We only create one SCEV of a particular shape, so
18// pointer-comparisons for equality are legal.
19//
20// One important aspect of the SCEV objects is that they are never cyclic, even
21// if there is a cycle in the dataflow for an expression (ie, a PHI node). If
22// the PHI node is one of the idioms that we can represent (e.g., a polynomial
23// recurrence) then we represent it directly as a recurrence node, otherwise we
24// represent it as a SCEVUnknown node.
25//
26// In addition to being able to represent expressions of various types, we also
27// have folders that are used to build the *canonical* representation for a
28// particular expression. These folders are capable of using a variety of
29// rewrite rules to simplify the expressions.
30//
31// Once the folders are defined, we can implement the more interesting
32// higher-level code, such as the code that recognizes PHI nodes of various
33// types, computes the execution count of a loop, etc.
34//
35// TODO: We should use these routines and value representations to implement
36// dependence analysis!
37//
38//===----------------------------------------------------------------------===//
39//
40// There are several good references for the techniques used in this analysis.
41//
42// Chains of recurrences -- a method to expedite the evaluation
43// of closed-form functions
44// Olaf Bachmann, Paul S. Wang, Eugene V. Zima
45//
46// On computational properties of chains of recurrences
47// Eugene V. Zima
48//
49// Symbolic Evaluation of Chains of Recurrences for Loop Optimization
50// Robert A. van Engelen
51//
52// Efficient Symbolic Analysis for Optimizing Compilers
53// Robert A. van Engelen
54//
55// Using the chains of recurrences algebra for data dependence testing and
56// induction variable substitution
57// MS Thesis, Johnie Birch
58//
59//===----------------------------------------------------------------------===//
60
61#include "llvm/Analysis/ScalarEvolution.h"
62#include "llvm/ADT/Optional.h"
63#include "llvm/ADT/STLExtras.h"
64#include "llvm/ADT/ScopeExit.h"
65#include "llvm/ADT/Sequence.h"
66#include "llvm/ADT/SmallPtrSet.h"
67#include "llvm/ADT/Statistic.h"
68#include "llvm/Analysis/AssumptionCache.h"
69#include "llvm/Analysis/ConstantFolding.h"
70#include "llvm/Analysis/InstructionSimplify.h"
71#include "llvm/Analysis/LoopInfo.h"
72#include "llvm/Analysis/ScalarEvolutionExpressions.h"
73#include "llvm/Analysis/TargetLibraryInfo.h"
74#include "llvm/Analysis/ValueTracking.h"
75#include "llvm/IR/ConstantRange.h"
76#include "llvm/IR/Constants.h"
77#include "llvm/IR/DataLayout.h"
78#include "llvm/IR/DerivedTypes.h"
79#include "llvm/IR/Dominators.h"
80#include "llvm/IR/GetElementPtrTypeIterator.h"
81#include "llvm/IR/GlobalAlias.h"
82#include "llvm/IR/GlobalVariable.h"
83#include "llvm/IR/InstIterator.h"
84#include "llvm/IR/Instructions.h"
85#include "llvm/IR/LLVMContext.h"
86#include "llvm/IR/Metadata.h"
87#include "llvm/IR/Operator.h"
88#include "llvm/IR/PatternMatch.h"
89#include "llvm/Support/CommandLine.h"
90#include "llvm/Support/Debug.h"
91#include "llvm/Support/ErrorHandling.h"
92#include "llvm/Support/MathExtras.h"
93#include "llvm/Support/raw_ostream.h"
94#include "llvm/Support/SaveAndRestore.h"
95#include <algorithm>
96using namespace llvm;
97
98#define DEBUG_TYPE"scalar-evolution" "scalar-evolution"
99
100STATISTIC(NumArrayLenItCounts,static llvm::Statistic NumArrayLenItCounts = {"scalar-evolution"
, "NumArrayLenItCounts", "Number of trip counts computed with array length"
, {0}, false}
101 "Number of trip counts computed with array length")static llvm::Statistic NumArrayLenItCounts = {"scalar-evolution"
, "NumArrayLenItCounts", "Number of trip counts computed with array length"
, {0}, false}
;
102STATISTIC(NumTripCountsComputed,static llvm::Statistic NumTripCountsComputed = {"scalar-evolution"
, "NumTripCountsComputed", "Number of loops with predictable loop counts"
, {0}, false}
103 "Number of loops with predictable loop counts")static llvm::Statistic NumTripCountsComputed = {"scalar-evolution"
, "NumTripCountsComputed", "Number of loops with predictable loop counts"
, {0}, false}
;
104STATISTIC(NumTripCountsNotComputed,static llvm::Statistic NumTripCountsNotComputed = {"scalar-evolution"
, "NumTripCountsNotComputed", "Number of loops without predictable loop counts"
, {0}, false}
105 "Number of loops without predictable loop counts")static llvm::Statistic NumTripCountsNotComputed = {"scalar-evolution"
, "NumTripCountsNotComputed", "Number of loops without predictable loop counts"
, {0}, false}
;
106STATISTIC(NumBruteForceTripCountsComputed,static llvm::Statistic NumBruteForceTripCountsComputed = {"scalar-evolution"
, "NumBruteForceTripCountsComputed", "Number of loops with trip counts computed by force"
, {0}, false}
107 "Number of loops with trip counts computed by force")static llvm::Statistic NumBruteForceTripCountsComputed = {"scalar-evolution"
, "NumBruteForceTripCountsComputed", "Number of loops with trip counts computed by force"
, {0}, false}
;
108
109static cl::opt<unsigned>
110MaxBruteForceIterations("scalar-evolution-max-iterations", cl::ReallyHidden,
111 cl::desc("Maximum number of iterations SCEV will "
112 "symbolically execute a constant "
113 "derived loop"),
114 cl::init(100));
115
116// FIXME: Enable this with EXPENSIVE_CHECKS when the test suite is clean.
117static cl::opt<bool>
118VerifySCEV("verify-scev",
119 cl::desc("Verify ScalarEvolution's backedge taken counts (slow)"));
120static cl::opt<bool>
121 VerifySCEVMap("verify-scev-maps",
122 cl::desc("Verify no dangling value in ScalarEvolution's "
123 "ExprValueMap (slow)"));
124
125static cl::opt<unsigned> MulOpsInlineThreshold(
126 "scev-mulops-inline-threshold", cl::Hidden,
127 cl::desc("Threshold for inlining multiplication operands into a SCEV"),
128 cl::init(1000));
129
130static cl::opt<unsigned> AddOpsInlineThreshold(
131 "scev-addops-inline-threshold", cl::Hidden,
132 cl::desc("Threshold for inlining multiplication operands into a SCEV"),
133 cl::init(500));
134
135static cl::opt<unsigned> MaxSCEVCompareDepth(
136 "scalar-evolution-max-scev-compare-depth", cl::Hidden,
137 cl::desc("Maximum depth of recursive SCEV complexity comparisons"),
138 cl::init(32));
139
140static cl::opt<unsigned> MaxValueCompareDepth(
141 "scalar-evolution-max-value-compare-depth", cl::Hidden,
142 cl::desc("Maximum depth of recursive value complexity comparisons"),
143 cl::init(2));
144
145static cl::opt<unsigned>
146 MaxAddExprDepth("scalar-evolution-max-addexpr-depth", cl::Hidden,
147 cl::desc("Maximum depth of recursive AddExpr"),
148 cl::init(32));
149
150static cl::opt<unsigned> MaxConstantEvolvingDepth(
151 "scalar-evolution-max-constant-evolving-depth", cl::Hidden,
152 cl::desc("Maximum depth of recursive constant evolving"), cl::init(32));
153
154//===----------------------------------------------------------------------===//
155// SCEV class definitions
156//===----------------------------------------------------------------------===//
157
158//===----------------------------------------------------------------------===//
159// Implementation of the SCEV class.
160//
161
162#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
163LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void SCEV::dump() const {
164 print(dbgs());
165 dbgs() << '\n';
166}
167#endif
168
169void SCEV::print(raw_ostream &OS) const {
170 switch (static_cast<SCEVTypes>(getSCEVType())) {
171 case scConstant:
172 cast<SCEVConstant>(this)->getValue()->printAsOperand(OS, false);
173 return;
174 case scTruncate: {
175 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(this);
176 const SCEV *Op = Trunc->getOperand();
177 OS << "(trunc " << *Op->getType() << " " << *Op << " to "
178 << *Trunc->getType() << ")";
179 return;
180 }
181 case scZeroExtend: {
182 const SCEVZeroExtendExpr *ZExt = cast<SCEVZeroExtendExpr>(this);
183 const SCEV *Op = ZExt->getOperand();
184 OS << "(zext " << *Op->getType() << " " << *Op << " to "
185 << *ZExt->getType() << ")";
186 return;
187 }
188 case scSignExtend: {
189 const SCEVSignExtendExpr *SExt = cast<SCEVSignExtendExpr>(this);
190 const SCEV *Op = SExt->getOperand();
191 OS << "(sext " << *Op->getType() << " " << *Op << " to "
192 << *SExt->getType() << ")";
193 return;
194 }
195 case scAddRecExpr: {
196 const SCEVAddRecExpr *AR = cast<SCEVAddRecExpr>(this);
197 OS << "{" << *AR->getOperand(0);
198 for (unsigned i = 1, e = AR->getNumOperands(); i != e; ++i)
199 OS << ",+," << *AR->getOperand(i);
200 OS << "}<";
201 if (AR->hasNoUnsignedWrap())
202 OS << "nuw><";
203 if (AR->hasNoSignedWrap())
204 OS << "nsw><";
205 if (AR->hasNoSelfWrap() &&
206 !AR->getNoWrapFlags((NoWrapFlags)(FlagNUW | FlagNSW)))
207 OS << "nw><";
208 AR->getLoop()->getHeader()->printAsOperand(OS, /*PrintType=*/false);
209 OS << ">";
210 return;
211 }
212 case scAddExpr:
213 case scMulExpr:
214 case scUMaxExpr:
215 case scSMaxExpr: {
216 const SCEVNAryExpr *NAry = cast<SCEVNAryExpr>(this);
217 const char *OpStr = nullptr;
218 switch (NAry->getSCEVType()) {
219 case scAddExpr: OpStr = " + "; break;
220 case scMulExpr: OpStr = " * "; break;
221 case scUMaxExpr: OpStr = " umax "; break;
222 case scSMaxExpr: OpStr = " smax "; break;
223 }
224 OS << "(";
225 for (SCEVNAryExpr::op_iterator I = NAry->op_begin(), E = NAry->op_end();
226 I != E; ++I) {
227 OS << **I;
228 if (std::next(I) != E)
229 OS << OpStr;
230 }
231 OS << ")";
232 switch (NAry->getSCEVType()) {
233 case scAddExpr:
234 case scMulExpr:
235 if (NAry->hasNoUnsignedWrap())
236 OS << "<nuw>";
237 if (NAry->hasNoSignedWrap())
238 OS << "<nsw>";
239 }
240 return;
241 }
242 case scUDivExpr: {
243 const SCEVUDivExpr *UDiv = cast<SCEVUDivExpr>(this);
244 OS << "(" << *UDiv->getLHS() << " /u " << *UDiv->getRHS() << ")";
245 return;
246 }
247 case scUnknown: {
248 const SCEVUnknown *U = cast<SCEVUnknown>(this);
249 Type *AllocTy;
250 if (U->isSizeOf(AllocTy)) {
251 OS << "sizeof(" << *AllocTy << ")";
252 return;
253 }
254 if (U->isAlignOf(AllocTy)) {
255 OS << "alignof(" << *AllocTy << ")";
256 return;
257 }
258
259 Type *CTy;
260 Constant *FieldNo;
261 if (U->isOffsetOf(CTy, FieldNo)) {
262 OS << "offsetof(" << *CTy << ", ";
263 FieldNo->printAsOperand(OS, false);
264 OS << ")";
265 return;
266 }
267
268 // Otherwise just print it normally.
269 U->getValue()->printAsOperand(OS, false);
270 return;
271 }
272 case scCouldNotCompute:
273 OS << "***COULDNOTCOMPUTE***";
274 return;
275 }
276 llvm_unreachable("Unknown SCEV kind!")::llvm::llvm_unreachable_internal("Unknown SCEV kind!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 276)
;
277}
278
279Type *SCEV::getType() const {
280 switch (static_cast<SCEVTypes>(getSCEVType())) {
281 case scConstant:
282 return cast<SCEVConstant>(this)->getType();
283 case scTruncate:
284 case scZeroExtend:
285 case scSignExtend:
286 return cast<SCEVCastExpr>(this)->getType();
287 case scAddRecExpr:
288 case scMulExpr:
289 case scUMaxExpr:
290 case scSMaxExpr:
291 return cast<SCEVNAryExpr>(this)->getType();
292 case scAddExpr:
293 return cast<SCEVAddExpr>(this)->getType();
294 case scUDivExpr:
295 return cast<SCEVUDivExpr>(this)->getType();
296 case scUnknown:
297 return cast<SCEVUnknown>(this)->getType();
298 case scCouldNotCompute:
299 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!")::llvm::llvm_unreachable_internal("Attempt to use a SCEVCouldNotCompute object!"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 299)
;
300 }
301 llvm_unreachable("Unknown SCEV kind!")::llvm::llvm_unreachable_internal("Unknown SCEV kind!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 301)
;
302}
303
304bool SCEV::isZero() const {
305 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
306 return SC->getValue()->isZero();
307 return false;
308}
309
310bool SCEV::isOne() const {
311 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
312 return SC->getValue()->isOne();
313 return false;
314}
315
316bool SCEV::isAllOnesValue() const {
317 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(this))
318 return SC->getValue()->isAllOnesValue();
319 return false;
320}
321
322bool SCEV::isNonConstantNegative() const {
323 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(this);
324 if (!Mul) return false;
325
326 // If there is a constant factor, it will be first.
327 const SCEVConstant *SC = dyn_cast<SCEVConstant>(Mul->getOperand(0));
328 if (!SC) return false;
329
330 // Return true if the value is negative, this matches things like (-42 * V).
331 return SC->getAPInt().isNegative();
332}
333
334SCEVCouldNotCompute::SCEVCouldNotCompute() :
335 SCEV(FoldingSetNodeIDRef(), scCouldNotCompute) {}
336
337bool SCEVCouldNotCompute::classof(const SCEV *S) {
338 return S->getSCEVType() == scCouldNotCompute;
339}
340
341const SCEV *ScalarEvolution::getConstant(ConstantInt *V) {
342 FoldingSetNodeID ID;
343 ID.AddInteger(scConstant);
344 ID.AddPointer(V);
345 void *IP = nullptr;
346 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
347 SCEV *S = new (SCEVAllocator) SCEVConstant(ID.Intern(SCEVAllocator), V);
348 UniqueSCEVs.InsertNode(S, IP);
349 return S;
350}
351
352const SCEV *ScalarEvolution::getConstant(const APInt &Val) {
353 return getConstant(ConstantInt::get(getContext(), Val));
354}
355
356const SCEV *
357ScalarEvolution::getConstant(Type *Ty, uint64_t V, bool isSigned) {
358 IntegerType *ITy = cast<IntegerType>(getEffectiveSCEVType(Ty));
359 return getConstant(ConstantInt::get(ITy, V, isSigned));
360}
361
362SCEVCastExpr::SCEVCastExpr(const FoldingSetNodeIDRef ID,
363 unsigned SCEVTy, const SCEV *op, Type *ty)
364 : SCEV(ID, SCEVTy), Op(op), Ty(ty) {}
365
366SCEVTruncateExpr::SCEVTruncateExpr(const FoldingSetNodeIDRef ID,
367 const SCEV *op, Type *ty)
368 : SCEVCastExpr(ID, scTruncate, op, ty) {
369 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&(((Op->getType()->isIntegerTy() || Op->getType()->
isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy
()) && "Cannot truncate non-integer value!") ? static_cast
<void> (0) : __assert_fail ("(Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate non-integer value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 371, __PRETTY_FUNCTION__))
370 (Ty->isIntegerTy() || Ty->isPointerTy()) &&(((Op->getType()->isIntegerTy() || Op->getType()->
isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy
()) && "Cannot truncate non-integer value!") ? static_cast
<void> (0) : __assert_fail ("(Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate non-integer value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 371, __PRETTY_FUNCTION__))
371 "Cannot truncate non-integer value!")(((Op->getType()->isIntegerTy() || Op->getType()->
isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy
()) && "Cannot truncate non-integer value!") ? static_cast
<void> (0) : __assert_fail ("(Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate non-integer value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 371, __PRETTY_FUNCTION__))
;
372}
373
374SCEVZeroExtendExpr::SCEVZeroExtendExpr(const FoldingSetNodeIDRef ID,
375 const SCEV *op, Type *ty)
376 : SCEVCastExpr(ID, scZeroExtend, op, ty) {
377 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&(((Op->getType()->isIntegerTy() || Op->getType()->
isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy
()) && "Cannot zero extend non-integer value!") ? static_cast
<void> (0) : __assert_fail ("(Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot zero extend non-integer value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 379, __PRETTY_FUNCTION__))
378 (Ty->isIntegerTy() || Ty->isPointerTy()) &&(((Op->getType()->isIntegerTy() || Op->getType()->
isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy
()) && "Cannot zero extend non-integer value!") ? static_cast
<void> (0) : __assert_fail ("(Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot zero extend non-integer value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 379, __PRETTY_FUNCTION__))
379 "Cannot zero extend non-integer value!")(((Op->getType()->isIntegerTy() || Op->getType()->
isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy
()) && "Cannot zero extend non-integer value!") ? static_cast
<void> (0) : __assert_fail ("(Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot zero extend non-integer value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 379, __PRETTY_FUNCTION__))
;
380}
381
382SCEVSignExtendExpr::SCEVSignExtendExpr(const FoldingSetNodeIDRef ID,
383 const SCEV *op, Type *ty)
384 : SCEVCastExpr(ID, scSignExtend, op, ty) {
385 assert((Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) &&(((Op->getType()->isIntegerTy() || Op->getType()->
isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy
()) && "Cannot sign extend non-integer value!") ? static_cast
<void> (0) : __assert_fail ("(Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot sign extend non-integer value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 387, __PRETTY_FUNCTION__))
386 (Ty->isIntegerTy() || Ty->isPointerTy()) &&(((Op->getType()->isIntegerTy() || Op->getType()->
isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy
()) && "Cannot sign extend non-integer value!") ? static_cast
<void> (0) : __assert_fail ("(Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot sign extend non-integer value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 387, __PRETTY_FUNCTION__))
387 "Cannot sign extend non-integer value!")(((Op->getType()->isIntegerTy() || Op->getType()->
isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy
()) && "Cannot sign extend non-integer value!") ? static_cast
<void> (0) : __assert_fail ("(Op->getType()->isIntegerTy() || Op->getType()->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot sign extend non-integer value!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 387, __PRETTY_FUNCTION__))
;
388}
389
390void SCEVUnknown::deleted() {
391 // Clear this SCEVUnknown from various maps.
392 SE->forgetMemoizedResults(this);
393
394 // Remove this SCEVUnknown from the uniquing map.
395 SE->UniqueSCEVs.RemoveNode(this);
396
397 // Release the value.
398 setValPtr(nullptr);
399}
400
401void SCEVUnknown::allUsesReplacedWith(Value *New) {
402 // Clear this SCEVUnknown from various maps.
403 SE->forgetMemoizedResults(this);
404
405 // Remove this SCEVUnknown from the uniquing map.
406 SE->UniqueSCEVs.RemoveNode(this);
407
408 // Update this SCEVUnknown to point to the new value. This is needed
409 // because there may still be outstanding SCEVs which still point to
410 // this SCEVUnknown.
411 setValPtr(New);
412}
413
414bool SCEVUnknown::isSizeOf(Type *&AllocTy) const {
415 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
416 if (VCE->getOpcode() == Instruction::PtrToInt)
417 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
418 if (CE->getOpcode() == Instruction::GetElementPtr &&
419 CE->getOperand(0)->isNullValue() &&
420 CE->getNumOperands() == 2)
421 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(1)))
422 if (CI->isOne()) {
423 AllocTy = cast<PointerType>(CE->getOperand(0)->getType())
424 ->getElementType();
425 return true;
426 }
427
428 return false;
429}
430
431bool SCEVUnknown::isAlignOf(Type *&AllocTy) const {
432 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
433 if (VCE->getOpcode() == Instruction::PtrToInt)
434 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
435 if (CE->getOpcode() == Instruction::GetElementPtr &&
436 CE->getOperand(0)->isNullValue()) {
437 Type *Ty =
438 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
439 if (StructType *STy = dyn_cast<StructType>(Ty))
440 if (!STy->isPacked() &&
441 CE->getNumOperands() == 3 &&
442 CE->getOperand(1)->isNullValue()) {
443 if (ConstantInt *CI = dyn_cast<ConstantInt>(CE->getOperand(2)))
444 if (CI->isOne() &&
445 STy->getNumElements() == 2 &&
446 STy->getElementType(0)->isIntegerTy(1)) {
447 AllocTy = STy->getElementType(1);
448 return true;
449 }
450 }
451 }
452
453 return false;
454}
455
456bool SCEVUnknown::isOffsetOf(Type *&CTy, Constant *&FieldNo) const {
457 if (ConstantExpr *VCE = dyn_cast<ConstantExpr>(getValue()))
458 if (VCE->getOpcode() == Instruction::PtrToInt)
459 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(VCE->getOperand(0)))
460 if (CE->getOpcode() == Instruction::GetElementPtr &&
461 CE->getNumOperands() == 3 &&
462 CE->getOperand(0)->isNullValue() &&
463 CE->getOperand(1)->isNullValue()) {
464 Type *Ty =
465 cast<PointerType>(CE->getOperand(0)->getType())->getElementType();
466 // Ignore vector types here so that ScalarEvolutionExpander doesn't
467 // emit getelementptrs that index into vectors.
468 if (Ty->isStructTy() || Ty->isArrayTy()) {
469 CTy = Ty;
470 FieldNo = CE->getOperand(2);
471 return true;
472 }
473 }
474
475 return false;
476}
477
478//===----------------------------------------------------------------------===//
479// SCEV Utilities
480//===----------------------------------------------------------------------===//
481
482/// Compare the two values \p LV and \p RV in terms of their "complexity" where
483/// "complexity" is a partial (and somewhat ad-hoc) relation used to order
484/// operands in SCEV expressions. \p EqCache is a set of pairs of values that
485/// have been previously deemed to be "equally complex" by this routine. It is
486/// intended to avoid exponential time complexity in cases like:
487///
488/// %a = f(%x, %y)
489/// %b = f(%a, %a)
490/// %c = f(%b, %b)
491///
492/// %d = f(%x, %y)
493/// %e = f(%d, %d)
494/// %f = f(%e, %e)
495///
496/// CompareValueComplexity(%f, %c)
497///
498/// Since we do not continue running this routine on expression trees once we
499/// have seen unequal values, there is no need to track them in the cache.
500static int
501CompareValueComplexity(SmallSet<std::pair<Value *, Value *>, 8> &EqCache,
502 const LoopInfo *const LI, Value *LV, Value *RV,
503 unsigned Depth) {
504 if (Depth > MaxValueCompareDepth || EqCache.count({LV, RV}))
505 return 0;
506
507 // Order pointer values after integer values. This helps SCEVExpander form
508 // GEPs.
509 bool LIsPointer = LV->getType()->isPointerTy(),
510 RIsPointer = RV->getType()->isPointerTy();
511 if (LIsPointer != RIsPointer)
512 return (int)LIsPointer - (int)RIsPointer;
513
514 // Compare getValueID values.
515 unsigned LID = LV->getValueID(), RID = RV->getValueID();
516 if (LID != RID)
517 return (int)LID - (int)RID;
518
519 // Sort arguments by their position.
520 if (const auto *LA = dyn_cast<Argument>(LV)) {
521 const auto *RA = cast<Argument>(RV);
522 unsigned LArgNo = LA->getArgNo(), RArgNo = RA->getArgNo();
523 return (int)LArgNo - (int)RArgNo;
524 }
525
526 if (const auto *LGV = dyn_cast<GlobalValue>(LV)) {
527 const auto *RGV = cast<GlobalValue>(RV);
528
529 const auto IsGVNameSemantic = [&](const GlobalValue *GV) {
530 auto LT = GV->getLinkage();
531 return !(GlobalValue::isPrivateLinkage(LT) ||
532 GlobalValue::isInternalLinkage(LT));
533 };
534
535 // Use the names to distinguish the two values, but only if the
536 // names are semantically important.
537 if (IsGVNameSemantic(LGV) && IsGVNameSemantic(RGV))
538 return LGV->getName().compare(RGV->getName());
539 }
540
541 // For instructions, compare their loop depth, and their operand count. This
542 // is pretty loose.
543 if (const auto *LInst = dyn_cast<Instruction>(LV)) {
544 const auto *RInst = cast<Instruction>(RV);
545
546 // Compare loop depths.
547 const BasicBlock *LParent = LInst->getParent(),
548 *RParent = RInst->getParent();
549 if (LParent != RParent) {
550 unsigned LDepth = LI->getLoopDepth(LParent),
551 RDepth = LI->getLoopDepth(RParent);
552 if (LDepth != RDepth)
553 return (int)LDepth - (int)RDepth;
554 }
555
556 // Compare the number of operands.
557 unsigned LNumOps = LInst->getNumOperands(),
558 RNumOps = RInst->getNumOperands();
559 if (LNumOps != RNumOps)
560 return (int)LNumOps - (int)RNumOps;
561
562 for (unsigned Idx : seq(0u, LNumOps)) {
563 int Result =
564 CompareValueComplexity(EqCache, LI, LInst->getOperand(Idx),
565 RInst->getOperand(Idx), Depth + 1);
566 if (Result != 0)
567 return Result;
568 }
569 }
570
571 EqCache.insert({LV, RV});
572 return 0;
573}
574
575// Return negative, zero, or positive, if LHS is less than, equal to, or greater
576// than RHS, respectively. A three-way result allows recursive comparisons to be
577// more efficient.
578static int CompareSCEVComplexity(
579 SmallSet<std::pair<const SCEV *, const SCEV *>, 8> &EqCacheSCEV,
580 const LoopInfo *const LI, const SCEV *LHS, const SCEV *RHS,
581 unsigned Depth = 0) {
582 // Fast-path: SCEVs are uniqued so we can do a quick equality check.
583 if (LHS == RHS)
584 return 0;
585
586 // Primarily, sort the SCEVs by their getSCEVType().
587 unsigned LType = LHS->getSCEVType(), RType = RHS->getSCEVType();
588 if (LType != RType)
589 return (int)LType - (int)RType;
590
591 if (Depth > MaxSCEVCompareDepth || EqCacheSCEV.count({LHS, RHS}))
592 return 0;
593 // Aside from the getSCEVType() ordering, the particular ordering
594 // isn't very important except that it's beneficial to be consistent,
595 // so that (a + b) and (b + a) don't end up as different expressions.
596 switch (static_cast<SCEVTypes>(LType)) {
597 case scUnknown: {
598 const SCEVUnknown *LU = cast<SCEVUnknown>(LHS);
599 const SCEVUnknown *RU = cast<SCEVUnknown>(RHS);
600
601 SmallSet<std::pair<Value *, Value *>, 8> EqCache;
602 int X = CompareValueComplexity(EqCache, LI, LU->getValue(), RU->getValue(),
603 Depth + 1);
604 if (X == 0)
605 EqCacheSCEV.insert({LHS, RHS});
606 return X;
607 }
608
609 case scConstant: {
610 const SCEVConstant *LC = cast<SCEVConstant>(LHS);
611 const SCEVConstant *RC = cast<SCEVConstant>(RHS);
612
613 // Compare constant values.
614 const APInt &LA = LC->getAPInt();
615 const APInt &RA = RC->getAPInt();
616 unsigned LBitWidth = LA.getBitWidth(), RBitWidth = RA.getBitWidth();
617 if (LBitWidth != RBitWidth)
618 return (int)LBitWidth - (int)RBitWidth;
619 return LA.ult(RA) ? -1 : 1;
620 }
621
622 case scAddRecExpr: {
623 const SCEVAddRecExpr *LA = cast<SCEVAddRecExpr>(LHS);
624 const SCEVAddRecExpr *RA = cast<SCEVAddRecExpr>(RHS);
625
626 // Compare addrec loop depths.
627 const Loop *LLoop = LA->getLoop(), *RLoop = RA->getLoop();
628 if (LLoop != RLoop) {
629 unsigned LDepth = LLoop->getLoopDepth(), RDepth = RLoop->getLoopDepth();
630 if (LDepth != RDepth)
631 return (int)LDepth - (int)RDepth;
632 }
633
634 // Addrec complexity grows with operand count.
635 unsigned LNumOps = LA->getNumOperands(), RNumOps = RA->getNumOperands();
636 if (LNumOps != RNumOps)
637 return (int)LNumOps - (int)RNumOps;
638
639 // Lexicographically compare.
640 for (unsigned i = 0; i != LNumOps; ++i) {
641 int X = CompareSCEVComplexity(EqCacheSCEV, LI, LA->getOperand(i),
642 RA->getOperand(i), Depth + 1);
643 if (X != 0)
644 return X;
645 }
646 EqCacheSCEV.insert({LHS, RHS});
647 return 0;
648 }
649
650 case scAddExpr:
651 case scMulExpr:
652 case scSMaxExpr:
653 case scUMaxExpr: {
654 const SCEVNAryExpr *LC = cast<SCEVNAryExpr>(LHS);
655 const SCEVNAryExpr *RC = cast<SCEVNAryExpr>(RHS);
656
657 // Lexicographically compare n-ary expressions.
658 unsigned LNumOps = LC->getNumOperands(), RNumOps = RC->getNumOperands();
659 if (LNumOps != RNumOps)
660 return (int)LNumOps - (int)RNumOps;
661
662 for (unsigned i = 0; i != LNumOps; ++i) {
663 if (i >= RNumOps)
664 return 1;
665 int X = CompareSCEVComplexity(EqCacheSCEV, LI, LC->getOperand(i),
666 RC->getOperand(i), Depth + 1);
667 if (X != 0)
668 return X;
669 }
670 EqCacheSCEV.insert({LHS, RHS});
671 return 0;
672 }
673
674 case scUDivExpr: {
675 const SCEVUDivExpr *LC = cast<SCEVUDivExpr>(LHS);
676 const SCEVUDivExpr *RC = cast<SCEVUDivExpr>(RHS);
677
678 // Lexicographically compare udiv expressions.
679 int X = CompareSCEVComplexity(EqCacheSCEV, LI, LC->getLHS(), RC->getLHS(),
680 Depth + 1);
681 if (X != 0)
682 return X;
683 X = CompareSCEVComplexity(EqCacheSCEV, LI, LC->getRHS(), RC->getRHS(),
684 Depth + 1);
685 if (X == 0)
686 EqCacheSCEV.insert({LHS, RHS});
687 return X;
688 }
689
690 case scTruncate:
691 case scZeroExtend:
692 case scSignExtend: {
693 const SCEVCastExpr *LC = cast<SCEVCastExpr>(LHS);
694 const SCEVCastExpr *RC = cast<SCEVCastExpr>(RHS);
695
696 // Compare cast expressions by operand.
697 int X = CompareSCEVComplexity(EqCacheSCEV, LI, LC->getOperand(),
698 RC->getOperand(), Depth + 1);
699 if (X == 0)
700 EqCacheSCEV.insert({LHS, RHS});
701 return X;
702 }
703
704 case scCouldNotCompute:
705 llvm_unreachable("Attempt to use a SCEVCouldNotCompute object!")::llvm::llvm_unreachable_internal("Attempt to use a SCEVCouldNotCompute object!"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 705)
;
706 }
707 llvm_unreachable("Unknown SCEV kind!")::llvm::llvm_unreachable_internal("Unknown SCEV kind!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 707)
;
708}
709
710/// Given a list of SCEV objects, order them by their complexity, and group
711/// objects of the same complexity together by value. When this routine is
712/// finished, we know that any duplicates in the vector are consecutive and that
713/// complexity is monotonically increasing.
714///
715/// Note that we go take special precautions to ensure that we get deterministic
716/// results from this routine. In other words, we don't want the results of
717/// this to depend on where the addresses of various SCEV objects happened to
718/// land in memory.
719///
720static void GroupByComplexity(SmallVectorImpl<const SCEV *> &Ops,
721 LoopInfo *LI) {
722 if (Ops.size() < 2) return; // Noop
723
724 SmallSet<std::pair<const SCEV *, const SCEV *>, 8> EqCache;
725 if (Ops.size() == 2) {
726 // This is the common case, which also happens to be trivially simple.
727 // Special case it.
728 const SCEV *&LHS = Ops[0], *&RHS = Ops[1];
729 if (CompareSCEVComplexity(EqCache, LI, RHS, LHS) < 0)
730 std::swap(LHS, RHS);
731 return;
732 }
733
734 // Do the rough sort by complexity.
735 std::stable_sort(Ops.begin(), Ops.end(),
736 [&EqCache, LI](const SCEV *LHS, const SCEV *RHS) {
737 return CompareSCEVComplexity(EqCache, LI, LHS, RHS) < 0;
738 });
739
740 // Now that we are sorted by complexity, group elements of the same
741 // complexity. Note that this is, at worst, N^2, but the vector is likely to
742 // be extremely short in practice. Note that we take this approach because we
743 // do not want to depend on the addresses of the objects we are grouping.
744 for (unsigned i = 0, e = Ops.size(); i != e-2; ++i) {
745 const SCEV *S = Ops[i];
746 unsigned Complexity = S->getSCEVType();
747
748 // If there are any objects of the same complexity and same value as this
749 // one, group them.
750 for (unsigned j = i+1; j != e && Ops[j]->getSCEVType() == Complexity; ++j) {
751 if (Ops[j] == S) { // Found a duplicate.
752 // Move it to immediately after i'th element.
753 std::swap(Ops[i+1], Ops[j]);
754 ++i; // no need to rescan it.
755 if (i == e-2) return; // Done!
756 }
757 }
758 }
759}
760
761// Returns the size of the SCEV S.
762static inline int sizeOfSCEV(const SCEV *S) {
763 struct FindSCEVSize {
764 int Size;
765 FindSCEVSize() : Size(0) {}
766
767 bool follow(const SCEV *S) {
768 ++Size;
769 // Keep looking at all operands of S.
770 return true;
771 }
772 bool isDone() const {
773 return false;
774 }
775 };
776
777 FindSCEVSize F;
778 SCEVTraversal<FindSCEVSize> ST(F);
779 ST.visitAll(S);
780 return F.Size;
781}
782
783namespace {
784
785struct SCEVDivision : public SCEVVisitor<SCEVDivision, void> {
786public:
787 // Computes the Quotient and Remainder of the division of Numerator by
788 // Denominator.
789 static void divide(ScalarEvolution &SE, const SCEV *Numerator,
790 const SCEV *Denominator, const SCEV **Quotient,
791 const SCEV **Remainder) {
792 assert(Numerator && Denominator && "Uninitialized SCEV")((Numerator && Denominator && "Uninitialized SCEV"
) ? static_cast<void> (0) : __assert_fail ("Numerator && Denominator && \"Uninitialized SCEV\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 792, __PRETTY_FUNCTION__))
;
793
794 SCEVDivision D(SE, Numerator, Denominator);
795
796 // Check for the trivial case here to avoid having to check for it in the
797 // rest of the code.
798 if (Numerator == Denominator) {
799 *Quotient = D.One;
800 *Remainder = D.Zero;
801 return;
802 }
803
804 if (Numerator->isZero()) {
805 *Quotient = D.Zero;
806 *Remainder = D.Zero;
807 return;
808 }
809
810 // A simple case when N/1. The quotient is N.
811 if (Denominator->isOne()) {
812 *Quotient = Numerator;
813 *Remainder = D.Zero;
814 return;
815 }
816
817 // Split the Denominator when it is a product.
818 if (const SCEVMulExpr *T = dyn_cast<SCEVMulExpr>(Denominator)) {
819 const SCEV *Q, *R;
820 *Quotient = Numerator;
821 for (const SCEV *Op : T->operands()) {
822 divide(SE, *Quotient, Op, &Q, &R);
823 *Quotient = Q;
824
825 // Bail out when the Numerator is not divisible by one of the terms of
826 // the Denominator.
827 if (!R->isZero()) {
828 *Quotient = D.Zero;
829 *Remainder = Numerator;
830 return;
831 }
832 }
833 *Remainder = D.Zero;
834 return;
835 }
836
837 D.visit(Numerator);
838 *Quotient = D.Quotient;
839 *Remainder = D.Remainder;
840 }
841
842 // Except in the trivial case described above, we do not know how to divide
843 // Expr by Denominator for the following functions with empty implementation.
844 void visitTruncateExpr(const SCEVTruncateExpr *Numerator) {}
845 void visitZeroExtendExpr(const SCEVZeroExtendExpr *Numerator) {}
846 void visitSignExtendExpr(const SCEVSignExtendExpr *Numerator) {}
847 void visitUDivExpr(const SCEVUDivExpr *Numerator) {}
848 void visitSMaxExpr(const SCEVSMaxExpr *Numerator) {}
849 void visitUMaxExpr(const SCEVUMaxExpr *Numerator) {}
850 void visitUnknown(const SCEVUnknown *Numerator) {}
851 void visitCouldNotCompute(const SCEVCouldNotCompute *Numerator) {}
852
853 void visitConstant(const SCEVConstant *Numerator) {
854 if (const SCEVConstant *D = dyn_cast<SCEVConstant>(Denominator)) {
855 APInt NumeratorVal = Numerator->getAPInt();
856 APInt DenominatorVal = D->getAPInt();
857 uint32_t NumeratorBW = NumeratorVal.getBitWidth();
858 uint32_t DenominatorBW = DenominatorVal.getBitWidth();
859
860 if (NumeratorBW > DenominatorBW)
861 DenominatorVal = DenominatorVal.sext(NumeratorBW);
862 else if (NumeratorBW < DenominatorBW)
863 NumeratorVal = NumeratorVal.sext(DenominatorBW);
864
865 APInt QuotientVal(NumeratorVal.getBitWidth(), 0);
866 APInt RemainderVal(NumeratorVal.getBitWidth(), 0);
867 APInt::sdivrem(NumeratorVal, DenominatorVal, QuotientVal, RemainderVal);
868 Quotient = SE.getConstant(QuotientVal);
869 Remainder = SE.getConstant(RemainderVal);
870 return;
871 }
872 }
873
874 void visitAddRecExpr(const SCEVAddRecExpr *Numerator) {
875 const SCEV *StartQ, *StartR, *StepQ, *StepR;
876 if (!Numerator->isAffine())
877 return cannotDivide(Numerator);
878 divide(SE, Numerator->getStart(), Denominator, &StartQ, &StartR);
879 divide(SE, Numerator->getStepRecurrence(SE), Denominator, &StepQ, &StepR);
880 // Bail out if the types do not match.
881 Type *Ty = Denominator->getType();
882 if (Ty != StartQ->getType() || Ty != StartR->getType() ||
883 Ty != StepQ->getType() || Ty != StepR->getType())
884 return cannotDivide(Numerator);
885 Quotient = SE.getAddRecExpr(StartQ, StepQ, Numerator->getLoop(),
886 Numerator->getNoWrapFlags());
887 Remainder = SE.getAddRecExpr(StartR, StepR, Numerator->getLoop(),
888 Numerator->getNoWrapFlags());
889 }
890
891 void visitAddExpr(const SCEVAddExpr *Numerator) {
892 SmallVector<const SCEV *, 2> Qs, Rs;
893 Type *Ty = Denominator->getType();
894
895 for (const SCEV *Op : Numerator->operands()) {
896 const SCEV *Q, *R;
897 divide(SE, Op, Denominator, &Q, &R);
898
899 // Bail out if types do not match.
900 if (Ty != Q->getType() || Ty != R->getType())
901 return cannotDivide(Numerator);
902
903 Qs.push_back(Q);
904 Rs.push_back(R);
905 }
906
907 if (Qs.size() == 1) {
908 Quotient = Qs[0];
909 Remainder = Rs[0];
910 return;
911 }
912
913 Quotient = SE.getAddExpr(Qs);
914 Remainder = SE.getAddExpr(Rs);
915 }
916
917 void visitMulExpr(const SCEVMulExpr *Numerator) {
918 SmallVector<const SCEV *, 2> Qs;
919 Type *Ty = Denominator->getType();
920
921 bool FoundDenominatorTerm = false;
922 for (const SCEV *Op : Numerator->operands()) {
923 // Bail out if types do not match.
924 if (Ty != Op->getType())
925 return cannotDivide(Numerator);
926
927 if (FoundDenominatorTerm) {
928 Qs.push_back(Op);
929 continue;
930 }
931
932 // Check whether Denominator divides one of the product operands.
933 const SCEV *Q, *R;
934 divide(SE, Op, Denominator, &Q, &R);
935 if (!R->isZero()) {
936 Qs.push_back(Op);
937 continue;
938 }
939
940 // Bail out if types do not match.
941 if (Ty != Q->getType())
942 return cannotDivide(Numerator);
943
944 FoundDenominatorTerm = true;
945 Qs.push_back(Q);
946 }
947
948 if (FoundDenominatorTerm) {
949 Remainder = Zero;
950 if (Qs.size() == 1)
951 Quotient = Qs[0];
952 else
953 Quotient = SE.getMulExpr(Qs);
954 return;
955 }
956
957 if (!isa<SCEVUnknown>(Denominator))
958 return cannotDivide(Numerator);
959
960 // The Remainder is obtained by replacing Denominator by 0 in Numerator.
961 ValueToValueMap RewriteMap;
962 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
963 cast<SCEVConstant>(Zero)->getValue();
964 Remainder = SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
965
966 if (Remainder->isZero()) {
967 // The Quotient is obtained by replacing Denominator by 1 in Numerator.
968 RewriteMap[cast<SCEVUnknown>(Denominator)->getValue()] =
969 cast<SCEVConstant>(One)->getValue();
970 Quotient =
971 SCEVParameterRewriter::rewrite(Numerator, SE, RewriteMap, true);
972 return;
973 }
974
975 // Quotient is (Numerator - Remainder) divided by Denominator.
976 const SCEV *Q, *R;
977 const SCEV *Diff = SE.getMinusSCEV(Numerator, Remainder);
978 // This SCEV does not seem to simplify: fail the division here.
979 if (sizeOfSCEV(Diff) > sizeOfSCEV(Numerator))
980 return cannotDivide(Numerator);
981 divide(SE, Diff, Denominator, &Q, &R);
982 if (R != Zero)
983 return cannotDivide(Numerator);
984 Quotient = Q;
985 }
986
987private:
988 SCEVDivision(ScalarEvolution &S, const SCEV *Numerator,
989 const SCEV *Denominator)
990 : SE(S), Denominator(Denominator) {
991 Zero = SE.getZero(Denominator->getType());
992 One = SE.getOne(Denominator->getType());
993
994 // We generally do not know how to divide Expr by Denominator. We
995 // initialize the division to a "cannot divide" state to simplify the rest
996 // of the code.
997 cannotDivide(Numerator);
998 }
999
1000 // Convenience function for giving up on the division. We set the quotient to
1001 // be equal to zero and the remainder to be equal to the numerator.
1002 void cannotDivide(const SCEV *Numerator) {
1003 Quotient = Zero;
1004 Remainder = Numerator;
1005 }
1006
1007 ScalarEvolution &SE;
1008 const SCEV *Denominator, *Quotient, *Remainder, *Zero, *One;
1009};
1010
1011}
1012
1013//===----------------------------------------------------------------------===//
1014// Simple SCEV method implementations
1015//===----------------------------------------------------------------------===//
1016
1017/// Compute BC(It, K). The result has width W. Assume, K > 0.
1018static const SCEV *BinomialCoefficient(const SCEV *It, unsigned K,
1019 ScalarEvolution &SE,
1020 Type *ResultTy) {
1021 // Handle the simplest case efficiently.
1022 if (K == 1)
1023 return SE.getTruncateOrZeroExtend(It, ResultTy);
1024
1025 // We are using the following formula for BC(It, K):
1026 //
1027 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / K!
1028 //
1029 // Suppose, W is the bitwidth of the return value. We must be prepared for
1030 // overflow. Hence, we must assure that the result of our computation is
1031 // equal to the accurate one modulo 2^W. Unfortunately, division isn't
1032 // safe in modular arithmetic.
1033 //
1034 // However, this code doesn't use exactly that formula; the formula it uses
1035 // is something like the following, where T is the number of factors of 2 in
1036 // K! (i.e. trailing zeros in the binary representation of K!), and ^ is
1037 // exponentiation:
1038 //
1039 // BC(It, K) = (It * (It - 1) * ... * (It - K + 1)) / 2^T / (K! / 2^T)
1040 //
1041 // This formula is trivially equivalent to the previous formula. However,
1042 // this formula can be implemented much more efficiently. The trick is that
1043 // K! / 2^T is odd, and exact division by an odd number *is* safe in modular
1044 // arithmetic. To do exact division in modular arithmetic, all we have
1045 // to do is multiply by the inverse. Therefore, this step can be done at
1046 // width W.
1047 //
1048 // The next issue is how to safely do the division by 2^T. The way this
1049 // is done is by doing the multiplication step at a width of at least W + T
1050 // bits. This way, the bottom W+T bits of the product are accurate. Then,
1051 // when we perform the division by 2^T (which is equivalent to a right shift
1052 // by T), the bottom W bits are accurate. Extra bits are okay; they'll get
1053 // truncated out after the division by 2^T.
1054 //
1055 // In comparison to just directly using the first formula, this technique
1056 // is much more efficient; using the first formula requires W * K bits,
1057 // but this formula less than W + K bits. Also, the first formula requires
1058 // a division step, whereas this formula only requires multiplies and shifts.
1059 //
1060 // It doesn't matter whether the subtraction step is done in the calculation
1061 // width or the input iteration count's width; if the subtraction overflows,
1062 // the result must be zero anyway. We prefer here to do it in the width of
1063 // the induction variable because it helps a lot for certain cases; CodeGen
1064 // isn't smart enough to ignore the overflow, which leads to much less
1065 // efficient code if the width of the subtraction is wider than the native
1066 // register width.
1067 //
1068 // (It's possible to not widen at all by pulling out factors of 2 before
1069 // the multiplication; for example, K=2 can be calculated as
1070 // It/2*(It+(It*INT_MIN/INT_MIN)+-1). However, it requires
1071 // extra arithmetic, so it's not an obvious win, and it gets
1072 // much more complicated for K > 3.)
1073
1074 // Protection from insane SCEVs; this bound is conservative,
1075 // but it probably doesn't matter.
1076 if (K > 1000)
1077 return SE.getCouldNotCompute();
1078
1079 unsigned W = SE.getTypeSizeInBits(ResultTy);
1080
1081 // Calculate K! / 2^T and T; we divide out the factors of two before
1082 // multiplying for calculating K! / 2^T to avoid overflow.
1083 // Other overflow doesn't matter because we only care about the bottom
1084 // W bits of the result.
1085 APInt OddFactorial(W, 1);
1086 unsigned T = 1;
1087 for (unsigned i = 3; i <= K; ++i) {
1088 APInt Mult(W, i);
1089 unsigned TwoFactors = Mult.countTrailingZeros();
1090 T += TwoFactors;
1091 Mult = Mult.lshr(TwoFactors);
1092 OddFactorial *= Mult;
1093 }
1094
1095 // We need at least W + T bits for the multiplication step
1096 unsigned CalculationBits = W + T;
1097
1098 // Calculate 2^T, at width T+W.
1099 APInt DivFactor = APInt::getOneBitSet(CalculationBits, T);
1100
1101 // Calculate the multiplicative inverse of K! / 2^T;
1102 // this multiplication factor will perform the exact division by
1103 // K! / 2^T.
1104 APInt Mod = APInt::getSignedMinValue(W+1);
1105 APInt MultiplyFactor = OddFactorial.zext(W+1);
1106 MultiplyFactor = MultiplyFactor.multiplicativeInverse(Mod);
1107 MultiplyFactor = MultiplyFactor.trunc(W);
1108
1109 // Calculate the product, at width T+W
1110 IntegerType *CalculationTy = IntegerType::get(SE.getContext(),
1111 CalculationBits);
1112 const SCEV *Dividend = SE.getTruncateOrZeroExtend(It, CalculationTy);
1113 for (unsigned i = 1; i != K; ++i) {
1114 const SCEV *S = SE.getMinusSCEV(It, SE.getConstant(It->getType(), i));
1115 Dividend = SE.getMulExpr(Dividend,
1116 SE.getTruncateOrZeroExtend(S, CalculationTy));
1117 }
1118
1119 // Divide by 2^T
1120 const SCEV *DivResult = SE.getUDivExpr(Dividend, SE.getConstant(DivFactor));
1121
1122 // Truncate the result, and divide by K! / 2^T.
1123
1124 return SE.getMulExpr(SE.getConstant(MultiplyFactor),
1125 SE.getTruncateOrZeroExtend(DivResult, ResultTy));
1126}
1127
1128/// Return the value of this chain of recurrences at the specified iteration
1129/// number. We can evaluate this recurrence by multiplying each element in the
1130/// chain by the binomial coefficient corresponding to it. In other words, we
1131/// can evaluate {A,+,B,+,C,+,D} as:
1132///
1133/// A*BC(It, 0) + B*BC(It, 1) + C*BC(It, 2) + D*BC(It, 3)
1134///
1135/// where BC(It, k) stands for binomial coefficient.
1136///
1137const SCEV *SCEVAddRecExpr::evaluateAtIteration(const SCEV *It,
1138 ScalarEvolution &SE) const {
1139 const SCEV *Result = getStart();
1140 for (unsigned i = 1, e = getNumOperands(); i != e; ++i) {
1141 // The computation is correct in the face of overflow provided that the
1142 // multiplication is performed _after_ the evaluation of the binomial
1143 // coefficient.
1144 const SCEV *Coeff = BinomialCoefficient(It, i, SE, getType());
1145 if (isa<SCEVCouldNotCompute>(Coeff))
1146 return Coeff;
1147
1148 Result = SE.getAddExpr(Result, SE.getMulExpr(getOperand(i), Coeff));
1149 }
1150 return Result;
1151}
1152
1153//===----------------------------------------------------------------------===//
1154// SCEV Expression folder implementations
1155//===----------------------------------------------------------------------===//
1156
1157const SCEV *ScalarEvolution::getTruncateExpr(const SCEV *Op,
1158 Type *Ty) {
1159 assert(getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) &&((getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(
Ty) && "This is not a truncating conversion!") ? static_cast
<void> (0) : __assert_fail ("getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) && \"This is not a truncating conversion!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1160, __PRETTY_FUNCTION__))
1160 "This is not a truncating conversion!")((getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(
Ty) && "This is not a truncating conversion!") ? static_cast
<void> (0) : __assert_fail ("getTypeSizeInBits(Op->getType()) > getTypeSizeInBits(Ty) && \"This is not a truncating conversion!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1160, __PRETTY_FUNCTION__))
;
1161 assert(isSCEVable(Ty) &&((isSCEVable(Ty) && "This is not a conversion to a SCEVable type!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(Ty) && \"This is not a conversion to a SCEVable type!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1162, __PRETTY_FUNCTION__))
1162 "This is not a conversion to a SCEVable type!")((isSCEVable(Ty) && "This is not a conversion to a SCEVable type!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(Ty) && \"This is not a conversion to a SCEVable type!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1162, __PRETTY_FUNCTION__))
;
1163 Ty = getEffectiveSCEVType(Ty);
1164
1165 FoldingSetNodeID ID;
1166 ID.AddInteger(scTruncate);
1167 ID.AddPointer(Op);
1168 ID.AddPointer(Ty);
1169 void *IP = nullptr;
1170 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1171
1172 // Fold if the operand is constant.
1173 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1174 return getConstant(
1175 cast<ConstantInt>(ConstantExpr::getTrunc(SC->getValue(), Ty)));
1176
1177 // trunc(trunc(x)) --> trunc(x)
1178 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op))
1179 return getTruncateExpr(ST->getOperand(), Ty);
1180
1181 // trunc(sext(x)) --> sext(x) if widening or trunc(x) if narrowing
1182 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1183 return getTruncateOrSignExtend(SS->getOperand(), Ty);
1184
1185 // trunc(zext(x)) --> zext(x) if widening or trunc(x) if narrowing
1186 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1187 return getTruncateOrZeroExtend(SZ->getOperand(), Ty);
1188
1189 // trunc(x1+x2+...+xN) --> trunc(x1)+trunc(x2)+...+trunc(xN) if we can
1190 // eliminate all the truncates, or we replace other casts with truncates.
1191 if (const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Op)) {
1192 SmallVector<const SCEV *, 4> Operands;
1193 bool hasTrunc = false;
1194 for (unsigned i = 0, e = SA->getNumOperands(); i != e && !hasTrunc; ++i) {
1195 const SCEV *S = getTruncateExpr(SA->getOperand(i), Ty);
1196 if (!isa<SCEVCastExpr>(SA->getOperand(i)))
1197 hasTrunc = isa<SCEVTruncateExpr>(S);
1198 Operands.push_back(S);
1199 }
1200 if (!hasTrunc)
1201 return getAddExpr(Operands);
1202 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1203 }
1204
1205 // trunc(x1*x2*...*xN) --> trunc(x1)*trunc(x2)*...*trunc(xN) if we can
1206 // eliminate all the truncates, or we replace other casts with truncates.
1207 if (const SCEVMulExpr *SM = dyn_cast<SCEVMulExpr>(Op)) {
1208 SmallVector<const SCEV *, 4> Operands;
1209 bool hasTrunc = false;
1210 for (unsigned i = 0, e = SM->getNumOperands(); i != e && !hasTrunc; ++i) {
1211 const SCEV *S = getTruncateExpr(SM->getOperand(i), Ty);
1212 if (!isa<SCEVCastExpr>(SM->getOperand(i)))
1213 hasTrunc = isa<SCEVTruncateExpr>(S);
1214 Operands.push_back(S);
1215 }
1216 if (!hasTrunc)
1217 return getMulExpr(Operands);
1218 UniqueSCEVs.FindNodeOrInsertPos(ID, IP); // Mutates IP, returns NULL.
1219 }
1220
1221 // If the input value is a chrec scev, truncate the chrec's operands.
1222 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
1223 SmallVector<const SCEV *, 4> Operands;
1224 for (const SCEV *Op : AddRec->operands())
1225 Operands.push_back(getTruncateExpr(Op, Ty));
1226 return getAddRecExpr(Operands, AddRec->getLoop(), SCEV::FlagAnyWrap);
1227 }
1228
1229 // The cast wasn't folded; create an explicit cast node. We can reuse
1230 // the existing insert position since if we get here, we won't have
1231 // made any changes which would invalidate it.
1232 SCEV *S = new (SCEVAllocator) SCEVTruncateExpr(ID.Intern(SCEVAllocator),
1233 Op, Ty);
1234 UniqueSCEVs.InsertNode(S, IP);
1235 return S;
1236}
1237
1238// Get the limit of a recurrence such that incrementing by Step cannot cause
1239// signed overflow as long as the value of the recurrence within the
1240// loop does not exceed this limit before incrementing.
1241static const SCEV *getSignedOverflowLimitForStep(const SCEV *Step,
1242 ICmpInst::Predicate *Pred,
1243 ScalarEvolution *SE) {
1244 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1245 if (SE->isKnownPositive(Step)) {
1246 *Pred = ICmpInst::ICMP_SLT;
1247 return SE->getConstant(APInt::getSignedMinValue(BitWidth) -
1248 SE->getSignedRange(Step).getSignedMax());
1249 }
1250 if (SE->isKnownNegative(Step)) {
1251 *Pred = ICmpInst::ICMP_SGT;
1252 return SE->getConstant(APInt::getSignedMaxValue(BitWidth) -
1253 SE->getSignedRange(Step).getSignedMin());
1254 }
1255 return nullptr;
1256}
1257
1258// Get the limit of a recurrence such that incrementing by Step cannot cause
1259// unsigned overflow as long as the value of the recurrence within the loop does
1260// not exceed this limit before incrementing.
1261static const SCEV *getUnsignedOverflowLimitForStep(const SCEV *Step,
1262 ICmpInst::Predicate *Pred,
1263 ScalarEvolution *SE) {
1264 unsigned BitWidth = SE->getTypeSizeInBits(Step->getType());
1265 *Pred = ICmpInst::ICMP_ULT;
1266
1267 return SE->getConstant(APInt::getMinValue(BitWidth) -
1268 SE->getUnsignedRange(Step).getUnsignedMax());
1269}
1270
1271namespace {
1272
1273struct ExtendOpTraitsBase {
1274 typedef const SCEV *(ScalarEvolution::*GetExtendExprTy)(const SCEV *, Type *);
1275};
1276
1277// Used to make code generic over signed and unsigned overflow.
1278template <typename ExtendOp> struct ExtendOpTraits {
1279 // Members present:
1280 //
1281 // static const SCEV::NoWrapFlags WrapType;
1282 //
1283 // static const ExtendOpTraitsBase::GetExtendExprTy GetExtendExpr;
1284 //
1285 // static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1286 // ICmpInst::Predicate *Pred,
1287 // ScalarEvolution *SE);
1288};
1289
1290template <>
1291struct ExtendOpTraits<SCEVSignExtendExpr> : public ExtendOpTraitsBase {
1292 static const SCEV::NoWrapFlags WrapType = SCEV::FlagNSW;
1293
1294 static const GetExtendExprTy GetExtendExpr;
1295
1296 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1297 ICmpInst::Predicate *Pred,
1298 ScalarEvolution *SE) {
1299 return getSignedOverflowLimitForStep(Step, Pred, SE);
1300 }
1301};
1302
1303const ExtendOpTraitsBase::GetExtendExprTy ExtendOpTraits<
1304 SCEVSignExtendExpr>::GetExtendExpr = &ScalarEvolution::getSignExtendExpr;
1305
1306template <>
1307struct ExtendOpTraits<SCEVZeroExtendExpr> : public ExtendOpTraitsBase {
1308 static const SCEV::NoWrapFlags WrapType = SCEV::FlagNUW;
1309
1310 static const GetExtendExprTy GetExtendExpr;
1311
1312 static const SCEV *getOverflowLimitForStep(const SCEV *Step,
1313 ICmpInst::Predicate *Pred,
1314 ScalarEvolution *SE) {
1315 return getUnsignedOverflowLimitForStep(Step, Pred, SE);
1316 }
1317};
1318
1319const ExtendOpTraitsBase::GetExtendExprTy ExtendOpTraits<
1320 SCEVZeroExtendExpr>::GetExtendExpr = &ScalarEvolution::getZeroExtendExpr;
1321}
1322
1323// The recurrence AR has been shown to have no signed/unsigned wrap or something
1324// close to it. Typically, if we can prove NSW/NUW for AR, then we can just as
1325// easily prove NSW/NUW for its preincrement or postincrement sibling. This
1326// allows normalizing a sign/zero extended AddRec as such: {sext/zext(Step +
1327// Start),+,Step} => {(Step + sext/zext(Start),+,Step} As a result, the
1328// expression "Step + sext/zext(PreIncAR)" is congruent with
1329// "sext/zext(PostIncAR)"
1330template <typename ExtendOpTy>
1331static const SCEV *getPreStartForExtend(const SCEVAddRecExpr *AR, Type *Ty,
1332 ScalarEvolution *SE) {
1333 auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType;
1334 auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr;
1335
1336 const Loop *L = AR->getLoop();
1337 const SCEV *Start = AR->getStart();
1338 const SCEV *Step = AR->getStepRecurrence(*SE);
1339
1340 // Check for a simple looking step prior to loop entry.
1341 const SCEVAddExpr *SA = dyn_cast<SCEVAddExpr>(Start);
1342 if (!SA)
1343 return nullptr;
1344
1345 // Create an AddExpr for "PreStart" after subtracting Step. Full SCEV
1346 // subtraction is expensive. For this purpose, perform a quick and dirty
1347 // difference, by checking for Step in the operand list.
1348 SmallVector<const SCEV *, 4> DiffOps;
1349 for (const SCEV *Op : SA->operands())
1350 if (Op != Step)
1351 DiffOps.push_back(Op);
1352
1353 if (DiffOps.size() == SA->getNumOperands())
1354 return nullptr;
1355
1356 // Try to prove `WrapType` (SCEV::FlagNSW or SCEV::FlagNUW) on `PreStart` +
1357 // `Step`:
1358
1359 // 1. NSW/NUW flags on the step increment.
1360 auto PreStartFlags =
1361 ScalarEvolution::maskFlags(SA->getNoWrapFlags(), SCEV::FlagNUW);
1362 const SCEV *PreStart = SE->getAddExpr(DiffOps, PreStartFlags);
1363 const SCEVAddRecExpr *PreAR = dyn_cast<SCEVAddRecExpr>(
1364 SE->getAddRecExpr(PreStart, Step, L, SCEV::FlagAnyWrap));
1365
1366 // "{S,+,X} is <nsw>/<nuw>" and "the backedge is taken at least once" implies
1367 // "S+X does not sign/unsign-overflow".
1368 //
1369
1370 const SCEV *BECount = SE->getBackedgeTakenCount(L);
1371 if (PreAR && PreAR->getNoWrapFlags(WrapType) &&
1372 !isa<SCEVCouldNotCompute>(BECount) && SE->isKnownPositive(BECount))
1373 return PreStart;
1374
1375 // 2. Direct overflow check on the step operation's expression.
1376 unsigned BitWidth = SE->getTypeSizeInBits(AR->getType());
1377 Type *WideTy = IntegerType::get(SE->getContext(), BitWidth * 2);
1378 const SCEV *OperandExtendedStart =
1379 SE->getAddExpr((SE->*GetExtendExpr)(PreStart, WideTy),
1380 (SE->*GetExtendExpr)(Step, WideTy));
1381 if ((SE->*GetExtendExpr)(Start, WideTy) == OperandExtendedStart) {
1382 if (PreAR && AR->getNoWrapFlags(WrapType)) {
1383 // If we know `AR` == {`PreStart`+`Step`,+,`Step`} is `WrapType` (FlagNSW
1384 // or FlagNUW) and that `PreStart` + `Step` is `WrapType` too, then
1385 // `PreAR` == {`PreStart`,+,`Step`} is also `WrapType`. Cache this fact.
1386 const_cast<SCEVAddRecExpr *>(PreAR)->setNoWrapFlags(WrapType);
1387 }
1388 return PreStart;
1389 }
1390
1391 // 3. Loop precondition.
1392 ICmpInst::Predicate Pred;
1393 const SCEV *OverflowLimit =
1394 ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep(Step, &Pred, SE);
1395
1396 if (OverflowLimit &&
1397 SE->isLoopEntryGuardedByCond(L, Pred, PreStart, OverflowLimit))
1398 return PreStart;
1399
1400 return nullptr;
1401}
1402
1403// Get the normalized zero or sign extended expression for this AddRec's Start.
1404template <typename ExtendOpTy>
1405static const SCEV *getExtendAddRecStart(const SCEVAddRecExpr *AR, Type *Ty,
1406 ScalarEvolution *SE) {
1407 auto GetExtendExpr = ExtendOpTraits<ExtendOpTy>::GetExtendExpr;
1408
1409 const SCEV *PreStart = getPreStartForExtend<ExtendOpTy>(AR, Ty, SE);
1410 if (!PreStart)
1411 return (SE->*GetExtendExpr)(AR->getStart(), Ty);
1412
1413 return SE->getAddExpr((SE->*GetExtendExpr)(AR->getStepRecurrence(*SE), Ty),
1414 (SE->*GetExtendExpr)(PreStart, Ty));
1415}
1416
1417// Try to prove away overflow by looking at "nearby" add recurrences. A
1418// motivating example for this rule: if we know `{0,+,4}` is `ult` `-1` and it
1419// does not itself wrap then we can conclude that `{1,+,4}` is `nuw`.
1420//
1421// Formally:
1422//
1423// {S,+,X} == {S-T,+,X} + T
1424// => Ext({S,+,X}) == Ext({S-T,+,X} + T)
1425//
1426// If ({S-T,+,X} + T) does not overflow ... (1)
1427//
1428// RHS == Ext({S-T,+,X} + T) == Ext({S-T,+,X}) + Ext(T)
1429//
1430// If {S-T,+,X} does not overflow ... (2)
1431//
1432// RHS == Ext({S-T,+,X}) + Ext(T) == {Ext(S-T),+,Ext(X)} + Ext(T)
1433// == {Ext(S-T)+Ext(T),+,Ext(X)}
1434//
1435// If (S-T)+T does not overflow ... (3)
1436//
1437// RHS == {Ext(S-T)+Ext(T),+,Ext(X)} == {Ext(S-T+T),+,Ext(X)}
1438// == {Ext(S),+,Ext(X)} == LHS
1439//
1440// Thus, if (1), (2) and (3) are true for some T, then
1441// Ext({S,+,X}) == {Ext(S),+,Ext(X)}
1442//
1443// (3) is implied by (1) -- "(S-T)+T does not overflow" is simply "({S-T,+,X}+T)
1444// does not overflow" restricted to the 0th iteration. Therefore we only need
1445// to check for (1) and (2).
1446//
1447// In the current context, S is `Start`, X is `Step`, Ext is `ExtendOpTy` and T
1448// is `Delta` (defined below).
1449//
1450template <typename ExtendOpTy>
1451bool ScalarEvolution::proveNoWrapByVaryingStart(const SCEV *Start,
1452 const SCEV *Step,
1453 const Loop *L) {
1454 auto WrapType = ExtendOpTraits<ExtendOpTy>::WrapType;
1455
1456 // We restrict `Start` to a constant to prevent SCEV from spending too much
1457 // time here. It is correct (but more expensive) to continue with a
1458 // non-constant `Start` and do a general SCEV subtraction to compute
1459 // `PreStart` below.
1460 //
1461 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(Start);
1462 if (!StartC)
1463 return false;
1464
1465 APInt StartAI = StartC->getAPInt();
1466
1467 for (unsigned Delta : {-2, -1, 1, 2}) {
1468 const SCEV *PreStart = getConstant(StartAI - Delta);
1469
1470 FoldingSetNodeID ID;
1471 ID.AddInteger(scAddRecExpr);
1472 ID.AddPointer(PreStart);
1473 ID.AddPointer(Step);
1474 ID.AddPointer(L);
1475 void *IP = nullptr;
1476 const auto *PreAR =
1477 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
1478
1479 // Give up if we don't already have the add recurrence we need because
1480 // actually constructing an add recurrence is relatively expensive.
1481 if (PreAR && PreAR->getNoWrapFlags(WrapType)) { // proves (2)
1482 const SCEV *DeltaS = getConstant(StartC->getType(), Delta);
1483 ICmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
1484 const SCEV *Limit = ExtendOpTraits<ExtendOpTy>::getOverflowLimitForStep(
1485 DeltaS, &Pred, this);
1486 if (Limit && isKnownPredicate(Pred, PreAR, Limit)) // proves (1)
1487 return true;
1488 }
1489 }
1490
1491 return false;
1492}
1493
1494const SCEV *ScalarEvolution::getZeroExtendExpr(const SCEV *Op,
1495 Type *Ty) {
1496 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&((getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(
Ty) && "This is not an extending conversion!") ? static_cast
<void> (0) : __assert_fail ("getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) && \"This is not an extending conversion!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1497, __PRETTY_FUNCTION__))
1497 "This is not an extending conversion!")((getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(
Ty) && "This is not an extending conversion!") ? static_cast
<void> (0) : __assert_fail ("getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) && \"This is not an extending conversion!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1497, __PRETTY_FUNCTION__))
;
1498 assert(isSCEVable(Ty) &&((isSCEVable(Ty) && "This is not a conversion to a SCEVable type!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(Ty) && \"This is not a conversion to a SCEVable type!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1499, __PRETTY_FUNCTION__))
1499 "This is not a conversion to a SCEVable type!")((isSCEVable(Ty) && "This is not a conversion to a SCEVable type!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(Ty) && \"This is not a conversion to a SCEVable type!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1499, __PRETTY_FUNCTION__))
;
1500 Ty = getEffectiveSCEVType(Ty);
1501
1502 // Fold if the operand is constant.
1503 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1504 return getConstant(
1505 cast<ConstantInt>(ConstantExpr::getZExt(SC->getValue(), Ty)));
1506
1507 // zext(zext(x)) --> zext(x)
1508 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1509 return getZeroExtendExpr(SZ->getOperand(), Ty);
1510
1511 // Before doing any expensive analysis, check to see if we've already
1512 // computed a SCEV for this Op and Ty.
1513 FoldingSetNodeID ID;
1514 ID.AddInteger(scZeroExtend);
1515 ID.AddPointer(Op);
1516 ID.AddPointer(Ty);
1517 void *IP = nullptr;
1518 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1519
1520 // zext(trunc(x)) --> zext(x) or x or trunc(x)
1521 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1522 // It's possible the bits taken off by the truncate were all zero bits. If
1523 // so, we should be able to simplify this further.
1524 const SCEV *X = ST->getOperand();
1525 ConstantRange CR = getUnsignedRange(X);
1526 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1527 unsigned NewBits = getTypeSizeInBits(Ty);
1528 if (CR.truncate(TruncBits).zeroExtend(NewBits).contains(
1529 CR.zextOrTrunc(NewBits)))
1530 return getTruncateOrZeroExtend(X, Ty);
1531 }
1532
1533 // If the input value is a chrec scev, and we can prove that the value
1534 // did not overflow the old, smaller, value, we can zero extend all of the
1535 // operands (often constants). This allows analysis of something like
1536 // this: for (unsigned char X = 0; X < 100; ++X) { int Y = X; }
1537 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1538 if (AR->isAffine()) {
1539 const SCEV *Start = AR->getStart();
1540 const SCEV *Step = AR->getStepRecurrence(*this);
1541 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1542 const Loop *L = AR->getLoop();
1543
1544 if (!AR->hasNoUnsignedWrap()) {
1545 auto NewFlags = proveNoWrapViaConstantRanges(AR);
1546 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(NewFlags);
1547 }
1548
1549 // If we have special knowledge that this addrec won't overflow,
1550 // we don't need to do any further analysis.
1551 if (AR->hasNoUnsignedWrap())
1552 return getAddRecExpr(
1553 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1554 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1555
1556 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1557 // Note that this serves two purposes: It filters out loops that are
1558 // simply not analyzable, and it covers the case where this code is
1559 // being called from within backedge-taken count analysis, such that
1560 // attempting to ask for the backedge-taken count would likely result
1561 // in infinite recursion. In the later case, the analysis code will
1562 // cope with a conservative value, and it will take care to purge
1563 // that value once it has finished.
1564 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1565 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1566 // Manually compute the final value for AR, checking for
1567 // overflow.
1568
1569 // Check whether the backedge-taken count can be losslessly casted to
1570 // the addrec's type. The count is always unsigned.
1571 const SCEV *CastedMaxBECount =
1572 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1573 const SCEV *RecastedMaxBECount =
1574 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1575 if (MaxBECount == RecastedMaxBECount) {
1576 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1577 // Check whether Start+Step*MaxBECount has no unsigned overflow.
1578 const SCEV *ZMul = getMulExpr(CastedMaxBECount, Step);
1579 const SCEV *ZAdd = getZeroExtendExpr(getAddExpr(Start, ZMul), WideTy);
1580 const SCEV *WideStart = getZeroExtendExpr(Start, WideTy);
1581 const SCEV *WideMaxBECount =
1582 getZeroExtendExpr(CastedMaxBECount, WideTy);
1583 const SCEV *OperandExtendedAdd =
1584 getAddExpr(WideStart,
1585 getMulExpr(WideMaxBECount,
1586 getZeroExtendExpr(Step, WideTy)));
1587 if (ZAdd == OperandExtendedAdd) {
1588 // Cache knowledge of AR NUW, which is propagated to this AddRec.
1589 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1590 // Return the expression with the addrec on the outside.
1591 return getAddRecExpr(
1592 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1593 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1594 }
1595 // Similar to above, only this time treat the step value as signed.
1596 // This covers loops that count down.
1597 OperandExtendedAdd =
1598 getAddExpr(WideStart,
1599 getMulExpr(WideMaxBECount,
1600 getSignExtendExpr(Step, WideTy)));
1601 if (ZAdd == OperandExtendedAdd) {
1602 // Cache knowledge of AR NW, which is propagated to this AddRec.
1603 // Negative step causes unsigned wrap, but it still can't self-wrap.
1604 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1605 // Return the expression with the addrec on the outside.
1606 return getAddRecExpr(
1607 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1608 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1609 }
1610 }
1611 }
1612
1613 // Normally, in the cases we can prove no-overflow via a
1614 // backedge guarding condition, we can also compute a backedge
1615 // taken count for the loop. The exceptions are assumptions and
1616 // guards present in the loop -- SCEV is not great at exploiting
1617 // these to compute max backedge taken counts, but can still use
1618 // these to prove lack of overflow. Use this fact to avoid
1619 // doing extra work that may not pay off.
1620 if (!isa<SCEVCouldNotCompute>(MaxBECount) || HasGuards ||
1621 !AC.assumptions().empty()) {
1622 // If the backedge is guarded by a comparison with the pre-inc
1623 // value the addrec is safe. Also, if the entry is guarded by
1624 // a comparison with the start value and the backedge is
1625 // guarded by a comparison with the post-inc value, the addrec
1626 // is safe.
1627 if (isKnownPositive(Step)) {
1628 const SCEV *N = getConstant(APInt::getMinValue(BitWidth) -
1629 getUnsignedRange(Step).getUnsignedMax());
1630 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT, AR, N) ||
1631 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_ULT, Start, N) &&
1632 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_ULT,
1633 AR->getPostIncExpr(*this), N))) {
1634 // Cache knowledge of AR NUW, which is propagated to this
1635 // AddRec.
1636 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1637 // Return the expression with the addrec on the outside.
1638 return getAddRecExpr(
1639 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1640 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1641 }
1642 } else if (isKnownNegative(Step)) {
1643 const SCEV *N = getConstant(APInt::getMaxValue(BitWidth) -
1644 getSignedRange(Step).getSignedMin());
1645 if (isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT, AR, N) ||
1646 (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_UGT, Start, N) &&
1647 isLoopBackedgeGuardedByCond(L, ICmpInst::ICMP_UGT,
1648 AR->getPostIncExpr(*this), N))) {
1649 // Cache knowledge of AR NW, which is propagated to this
1650 // AddRec. Negative step causes unsigned wrap, but it
1651 // still can't self-wrap.
1652 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1653 // Return the expression with the addrec on the outside.
1654 return getAddRecExpr(
1655 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1656 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1657 }
1658 }
1659 }
1660
1661 if (proveNoWrapByVaryingStart<SCEVZeroExtendExpr>(Start, Step, L)) {
1662 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNUW);
1663 return getAddRecExpr(
1664 getExtendAddRecStart<SCEVZeroExtendExpr>(AR, Ty, this),
1665 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1666 }
1667 }
1668
1669 if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
1670 // zext((A + B + ...)<nuw>) --> (zext(A) + zext(B) + ...)<nuw>
1671 if (SA->hasNoUnsignedWrap()) {
1672 // If the addition does not unsign overflow then we can, by definition,
1673 // commute the zero extension with the addition operation.
1674 SmallVector<const SCEV *, 4> Ops;
1675 for (const auto *Op : SA->operands())
1676 Ops.push_back(getZeroExtendExpr(Op, Ty));
1677 return getAddExpr(Ops, SCEV::FlagNUW);
1678 }
1679 }
1680
1681 // The cast wasn't folded; create an explicit cast node.
1682 // Recompute the insert position, as it may have been invalidated.
1683 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1684 SCEV *S = new (SCEVAllocator) SCEVZeroExtendExpr(ID.Intern(SCEVAllocator),
1685 Op, Ty);
1686 UniqueSCEVs.InsertNode(S, IP);
1687 return S;
1688}
1689
1690const SCEV *ScalarEvolution::getSignExtendExpr(const SCEV *Op,
1691 Type *Ty) {
1692 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&((getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(
Ty) && "This is not an extending conversion!") ? static_cast
<void> (0) : __assert_fail ("getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) && \"This is not an extending conversion!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1693, __PRETTY_FUNCTION__))
1693 "This is not an extending conversion!")((getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(
Ty) && "This is not an extending conversion!") ? static_cast
<void> (0) : __assert_fail ("getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) && \"This is not an extending conversion!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1693, __PRETTY_FUNCTION__))
;
1694 assert(isSCEVable(Ty) &&((isSCEVable(Ty) && "This is not a conversion to a SCEVable type!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(Ty) && \"This is not a conversion to a SCEVable type!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1695, __PRETTY_FUNCTION__))
1695 "This is not a conversion to a SCEVable type!")((isSCEVable(Ty) && "This is not a conversion to a SCEVable type!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(Ty) && \"This is not a conversion to a SCEVable type!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1695, __PRETTY_FUNCTION__))
;
1696 Ty = getEffectiveSCEVType(Ty);
1697
1698 // Fold if the operand is constant.
1699 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1700 return getConstant(
1701 cast<ConstantInt>(ConstantExpr::getSExt(SC->getValue(), Ty)));
1702
1703 // sext(sext(x)) --> sext(x)
1704 if (const SCEVSignExtendExpr *SS = dyn_cast<SCEVSignExtendExpr>(Op))
1705 return getSignExtendExpr(SS->getOperand(), Ty);
1706
1707 // sext(zext(x)) --> zext(x)
1708 if (const SCEVZeroExtendExpr *SZ = dyn_cast<SCEVZeroExtendExpr>(Op))
1709 return getZeroExtendExpr(SZ->getOperand(), Ty);
1710
1711 // Before doing any expensive analysis, check to see if we've already
1712 // computed a SCEV for this Op and Ty.
1713 FoldingSetNodeID ID;
1714 ID.AddInteger(scSignExtend);
1715 ID.AddPointer(Op);
1716 ID.AddPointer(Ty);
1717 void *IP = nullptr;
1718 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1719
1720 // sext(trunc(x)) --> sext(x) or x or trunc(x)
1721 if (const SCEVTruncateExpr *ST = dyn_cast<SCEVTruncateExpr>(Op)) {
1722 // It's possible the bits taken off by the truncate were all sign bits. If
1723 // so, we should be able to simplify this further.
1724 const SCEV *X = ST->getOperand();
1725 ConstantRange CR = getSignedRange(X);
1726 unsigned TruncBits = getTypeSizeInBits(ST->getType());
1727 unsigned NewBits = getTypeSizeInBits(Ty);
1728 if (CR.truncate(TruncBits).signExtend(NewBits).contains(
1729 CR.sextOrTrunc(NewBits)))
1730 return getTruncateOrSignExtend(X, Ty);
1731 }
1732
1733 // sext(C1 + (C2 * x)) --> C1 + sext(C2 * x) if C1 < C2
1734 if (auto *SA = dyn_cast<SCEVAddExpr>(Op)) {
1735 if (SA->getNumOperands() == 2) {
1736 auto *SC1 = dyn_cast<SCEVConstant>(SA->getOperand(0));
1737 auto *SMul = dyn_cast<SCEVMulExpr>(SA->getOperand(1));
1738 if (SMul && SC1) {
1739 if (auto *SC2 = dyn_cast<SCEVConstant>(SMul->getOperand(0))) {
1740 const APInt &C1 = SC1->getAPInt();
1741 const APInt &C2 = SC2->getAPInt();
1742 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() &&
1743 C2.ugt(C1) && C2.isPowerOf2())
1744 return getAddExpr(getSignExtendExpr(SC1, Ty),
1745 getSignExtendExpr(SMul, Ty));
1746 }
1747 }
1748 }
1749
1750 // sext((A + B + ...)<nsw>) --> (sext(A) + sext(B) + ...)<nsw>
1751 if (SA->hasNoSignedWrap()) {
1752 // If the addition does not sign overflow then we can, by definition,
1753 // commute the sign extension with the addition operation.
1754 SmallVector<const SCEV *, 4> Ops;
1755 for (const auto *Op : SA->operands())
1756 Ops.push_back(getSignExtendExpr(Op, Ty));
1757 return getAddExpr(Ops, SCEV::FlagNSW);
1758 }
1759 }
1760 // If the input value is a chrec scev, and we can prove that the value
1761 // did not overflow the old, smaller, value, we can sign extend all of the
1762 // operands (often constants). This allows analysis of something like
1763 // this: for (signed char X = 0; X < 100; ++X) { int Y = X; }
1764 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op))
1765 if (AR->isAffine()) {
1766 const SCEV *Start = AR->getStart();
1767 const SCEV *Step = AR->getStepRecurrence(*this);
1768 unsigned BitWidth = getTypeSizeInBits(AR->getType());
1769 const Loop *L = AR->getLoop();
1770
1771 if (!AR->hasNoSignedWrap()) {
1772 auto NewFlags = proveNoWrapViaConstantRanges(AR);
1773 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(NewFlags);
1774 }
1775
1776 // If we have special knowledge that this addrec won't overflow,
1777 // we don't need to do any further analysis.
1778 if (AR->hasNoSignedWrap())
1779 return getAddRecExpr(
1780 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1781 getSignExtendExpr(Step, Ty), L, SCEV::FlagNSW);
1782
1783 // Check whether the backedge-taken count is SCEVCouldNotCompute.
1784 // Note that this serves two purposes: It filters out loops that are
1785 // simply not analyzable, and it covers the case where this code is
1786 // being called from within backedge-taken count analysis, such that
1787 // attempting to ask for the backedge-taken count would likely result
1788 // in infinite recursion. In the later case, the analysis code will
1789 // cope with a conservative value, and it will take care to purge
1790 // that value once it has finished.
1791 const SCEV *MaxBECount = getMaxBackedgeTakenCount(L);
1792 if (!isa<SCEVCouldNotCompute>(MaxBECount)) {
1793 // Manually compute the final value for AR, checking for
1794 // overflow.
1795
1796 // Check whether the backedge-taken count can be losslessly casted to
1797 // the addrec's type. The count is always unsigned.
1798 const SCEV *CastedMaxBECount =
1799 getTruncateOrZeroExtend(MaxBECount, Start->getType());
1800 const SCEV *RecastedMaxBECount =
1801 getTruncateOrZeroExtend(CastedMaxBECount, MaxBECount->getType());
1802 if (MaxBECount == RecastedMaxBECount) {
1803 Type *WideTy = IntegerType::get(getContext(), BitWidth * 2);
1804 // Check whether Start+Step*MaxBECount has no signed overflow.
1805 const SCEV *SMul = getMulExpr(CastedMaxBECount, Step);
1806 const SCEV *SAdd = getSignExtendExpr(getAddExpr(Start, SMul), WideTy);
1807 const SCEV *WideStart = getSignExtendExpr(Start, WideTy);
1808 const SCEV *WideMaxBECount =
1809 getZeroExtendExpr(CastedMaxBECount, WideTy);
1810 const SCEV *OperandExtendedAdd =
1811 getAddExpr(WideStart,
1812 getMulExpr(WideMaxBECount,
1813 getSignExtendExpr(Step, WideTy)));
1814 if (SAdd == OperandExtendedAdd) {
1815 // Cache knowledge of AR NSW, which is propagated to this AddRec.
1816 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1817 // Return the expression with the addrec on the outside.
1818 return getAddRecExpr(
1819 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1820 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1821 }
1822 // Similar to above, only this time treat the step value as unsigned.
1823 // This covers loops that count up with an unsigned step.
1824 OperandExtendedAdd =
1825 getAddExpr(WideStart,
1826 getMulExpr(WideMaxBECount,
1827 getZeroExtendExpr(Step, WideTy)));
1828 if (SAdd == OperandExtendedAdd) {
1829 // If AR wraps around then
1830 //
1831 // abs(Step) * MaxBECount > unsigned-max(AR->getType())
1832 // => SAdd != OperandExtendedAdd
1833 //
1834 // Thus (AR is not NW => SAdd != OperandExtendedAdd) <=>
1835 // (SAdd == OperandExtendedAdd => AR is NW)
1836
1837 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNW);
1838
1839 // Return the expression with the addrec on the outside.
1840 return getAddRecExpr(
1841 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1842 getZeroExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1843 }
1844 }
1845 }
1846
1847 // Normally, in the cases we can prove no-overflow via a
1848 // backedge guarding condition, we can also compute a backedge
1849 // taken count for the loop. The exceptions are assumptions and
1850 // guards present in the loop -- SCEV is not great at exploiting
1851 // these to compute max backedge taken counts, but can still use
1852 // these to prove lack of overflow. Use this fact to avoid
1853 // doing extra work that may not pay off.
1854
1855 if (!isa<SCEVCouldNotCompute>(MaxBECount) || HasGuards ||
1856 !AC.assumptions().empty()) {
1857 // If the backedge is guarded by a comparison with the pre-inc
1858 // value the addrec is safe. Also, if the entry is guarded by
1859 // a comparison with the start value and the backedge is
1860 // guarded by a comparison with the post-inc value, the addrec
1861 // is safe.
1862 ICmpInst::Predicate Pred;
1863 const SCEV *OverflowLimit =
1864 getSignedOverflowLimitForStep(Step, &Pred, this);
1865 if (OverflowLimit &&
1866 (isLoopBackedgeGuardedByCond(L, Pred, AR, OverflowLimit) ||
1867 (isLoopEntryGuardedByCond(L, Pred, Start, OverflowLimit) &&
1868 isLoopBackedgeGuardedByCond(L, Pred, AR->getPostIncExpr(*this),
1869 OverflowLimit)))) {
1870 // Cache knowledge of AR NSW, then propagate NSW to the wide AddRec.
1871 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1872 return getAddRecExpr(
1873 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1874 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1875 }
1876 }
1877
1878 // If Start and Step are constants, check if we can apply this
1879 // transformation:
1880 // sext{C1,+,C2} --> C1 + sext{0,+,C2} if C1 < C2
1881 auto *SC1 = dyn_cast<SCEVConstant>(Start);
1882 auto *SC2 = dyn_cast<SCEVConstant>(Step);
1883 if (SC1 && SC2) {
1884 const APInt &C1 = SC1->getAPInt();
1885 const APInt &C2 = SC2->getAPInt();
1886 if (C1.isStrictlyPositive() && C2.isStrictlyPositive() && C2.ugt(C1) &&
1887 C2.isPowerOf2()) {
1888 Start = getSignExtendExpr(Start, Ty);
1889 const SCEV *NewAR = getAddRecExpr(getZero(AR->getType()), Step, L,
1890 AR->getNoWrapFlags());
1891 return getAddExpr(Start, getSignExtendExpr(NewAR, Ty));
1892 }
1893 }
1894
1895 if (proveNoWrapByVaryingStart<SCEVSignExtendExpr>(Start, Step, L)) {
1896 const_cast<SCEVAddRecExpr *>(AR)->setNoWrapFlags(SCEV::FlagNSW);
1897 return getAddRecExpr(
1898 getExtendAddRecStart<SCEVSignExtendExpr>(AR, Ty, this),
1899 getSignExtendExpr(Step, Ty), L, AR->getNoWrapFlags());
1900 }
1901 }
1902
1903 // If the input value is provably positive and we could not simplify
1904 // away the sext build a zext instead.
1905 if (isKnownNonNegative(Op))
1906 return getZeroExtendExpr(Op, Ty);
1907
1908 // The cast wasn't folded; create an explicit cast node.
1909 // Recompute the insert position, as it may have been invalidated.
1910 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
1911 SCEV *S = new (SCEVAllocator) SCEVSignExtendExpr(ID.Intern(SCEVAllocator),
1912 Op, Ty);
1913 UniqueSCEVs.InsertNode(S, IP);
1914 return S;
1915}
1916
1917/// getAnyExtendExpr - Return a SCEV for the given operand extended with
1918/// unspecified bits out to the given type.
1919///
1920const SCEV *ScalarEvolution::getAnyExtendExpr(const SCEV *Op,
1921 Type *Ty) {
1922 assert(getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) &&((getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(
Ty) && "This is not an extending conversion!") ? static_cast
<void> (0) : __assert_fail ("getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) && \"This is not an extending conversion!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1923, __PRETTY_FUNCTION__))
1923 "This is not an extending conversion!")((getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(
Ty) && "This is not an extending conversion!") ? static_cast
<void> (0) : __assert_fail ("getTypeSizeInBits(Op->getType()) < getTypeSizeInBits(Ty) && \"This is not an extending conversion!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1923, __PRETTY_FUNCTION__))
;
1924 assert(isSCEVable(Ty) &&((isSCEVable(Ty) && "This is not a conversion to a SCEVable type!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(Ty) && \"This is not a conversion to a SCEVable type!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1925, __PRETTY_FUNCTION__))
1925 "This is not a conversion to a SCEVable type!")((isSCEVable(Ty) && "This is not a conversion to a SCEVable type!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(Ty) && \"This is not a conversion to a SCEVable type!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 1925, __PRETTY_FUNCTION__))
;
1926 Ty = getEffectiveSCEVType(Ty);
1927
1928 // Sign-extend negative constants.
1929 if (const SCEVConstant *SC = dyn_cast<SCEVConstant>(Op))
1930 if (SC->getAPInt().isNegative())
1931 return getSignExtendExpr(Op, Ty);
1932
1933 // Peel off a truncate cast.
1934 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Op)) {
1935 const SCEV *NewOp = T->getOperand();
1936 if (getTypeSizeInBits(NewOp->getType()) < getTypeSizeInBits(Ty))
1937 return getAnyExtendExpr(NewOp, Ty);
1938 return getTruncateOrNoop(NewOp, Ty);
1939 }
1940
1941 // Next try a zext cast. If the cast is folded, use it.
1942 const SCEV *ZExt = getZeroExtendExpr(Op, Ty);
1943 if (!isa<SCEVZeroExtendExpr>(ZExt))
1944 return ZExt;
1945
1946 // Next try a sext cast. If the cast is folded, use it.
1947 const SCEV *SExt = getSignExtendExpr(Op, Ty);
1948 if (!isa<SCEVSignExtendExpr>(SExt))
1949 return SExt;
1950
1951 // Force the cast to be folded into the operands of an addrec.
1952 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Op)) {
1953 SmallVector<const SCEV *, 4> Ops;
1954 for (const SCEV *Op : AR->operands())
1955 Ops.push_back(getAnyExtendExpr(Op, Ty));
1956 return getAddRecExpr(Ops, AR->getLoop(), SCEV::FlagNW);
1957 }
1958
1959 // If the expression is obviously signed, use the sext cast value.
1960 if (isa<SCEVSMaxExpr>(Op))
1961 return SExt;
1962
1963 // Absent any other information, use the zext cast value.
1964 return ZExt;
1965}
1966
1967/// Process the given Ops list, which is a list of operands to be added under
1968/// the given scale, update the given map. This is a helper function for
1969/// getAddRecExpr. As an example of what it does, given a sequence of operands
1970/// that would form an add expression like this:
1971///
1972/// m + n + 13 + (A * (o + p + (B * (q + m + 29)))) + r + (-1 * r)
1973///
1974/// where A and B are constants, update the map with these values:
1975///
1976/// (m, 1+A*B), (n, 1), (o, A), (p, A), (q, A*B), (r, 0)
1977///
1978/// and add 13 + A*B*29 to AccumulatedConstant.
1979/// This will allow getAddRecExpr to produce this:
1980///
1981/// 13+A*B*29 + n + (m * (1+A*B)) + ((o + p) * A) + (q * A*B)
1982///
1983/// This form often exposes folding opportunities that are hidden in
1984/// the original operand list.
1985///
1986/// Return true iff it appears that any interesting folding opportunities
1987/// may be exposed. This helps getAddRecExpr short-circuit extra work in
1988/// the common case where no interesting opportunities are present, and
1989/// is also used as a check to avoid infinite recursion.
1990///
1991static bool
1992CollectAddOperandsWithScales(DenseMap<const SCEV *, APInt> &M,
1993 SmallVectorImpl<const SCEV *> &NewOps,
1994 APInt &AccumulatedConstant,
1995 const SCEV *const *Ops, size_t NumOperands,
1996 const APInt &Scale,
1997 ScalarEvolution &SE) {
1998 bool Interesting = false;
1999
2000 // Iterate over the add operands. They are sorted, with constants first.
2001 unsigned i = 0;
2002 while (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
2003 ++i;
2004 // Pull a buried constant out to the outside.
2005 if (Scale != 1 || AccumulatedConstant != 0 || C->getValue()->isZero())
2006 Interesting = true;
2007 AccumulatedConstant += Scale * C->getAPInt();
2008 }
2009
2010 // Next comes everything else. We're especially interested in multiplies
2011 // here, but they're in the middle, so just visit the rest with one loop.
2012 for (; i != NumOperands; ++i) {
2013 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[i]);
2014 if (Mul && isa<SCEVConstant>(Mul->getOperand(0))) {
2015 APInt NewScale =
2016 Scale * cast<SCEVConstant>(Mul->getOperand(0))->getAPInt();
2017 if (Mul->getNumOperands() == 2 && isa<SCEVAddExpr>(Mul->getOperand(1))) {
2018 // A multiplication of a constant with another add; recurse.
2019 const SCEVAddExpr *Add = cast<SCEVAddExpr>(Mul->getOperand(1));
2020 Interesting |=
2021 CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
2022 Add->op_begin(), Add->getNumOperands(),
2023 NewScale, SE);
2024 } else {
2025 // A multiplication of a constant with some other value. Update
2026 // the map.
2027 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin()+1, Mul->op_end());
2028 const SCEV *Key = SE.getMulExpr(MulOps);
2029 auto Pair = M.insert({Key, NewScale});
2030 if (Pair.second) {
2031 NewOps.push_back(Pair.first->first);
2032 } else {
2033 Pair.first->second += NewScale;
2034 // The map already had an entry for this value, which may indicate
2035 // a folding opportunity.
2036 Interesting = true;
2037 }
2038 }
2039 } else {
2040 // An ordinary operand. Update the map.
2041 std::pair<DenseMap<const SCEV *, APInt>::iterator, bool> Pair =
2042 M.insert({Ops[i], Scale});
2043 if (Pair.second) {
2044 NewOps.push_back(Pair.first->first);
2045 } else {
2046 Pair.first->second += Scale;
2047 // The map already had an entry for this value, which may indicate
2048 // a folding opportunity.
2049 Interesting = true;
2050 }
2051 }
2052 }
2053
2054 return Interesting;
2055}
2056
2057// We're trying to construct a SCEV of type `Type' with `Ops' as operands and
2058// `OldFlags' as can't-wrap behavior. Infer a more aggressive set of
2059// can't-overflow flags for the operation if possible.
2060static SCEV::NoWrapFlags
2061StrengthenNoWrapFlags(ScalarEvolution *SE, SCEVTypes Type,
2062 const SmallVectorImpl<const SCEV *> &Ops,
2063 SCEV::NoWrapFlags Flags) {
2064 using namespace std::placeholders;
2065 typedef OverflowingBinaryOperator OBO;
2066
2067 bool CanAnalyze =
2068 Type == scAddExpr || Type == scAddRecExpr || Type == scMulExpr;
2069 (void)CanAnalyze;
2070 assert(CanAnalyze && "don't call from other places!")((CanAnalyze && "don't call from other places!") ? static_cast
<void> (0) : __assert_fail ("CanAnalyze && \"don't call from other places!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2070, __PRETTY_FUNCTION__))
;
2071
2072 int SignOrUnsignMask = SCEV::FlagNUW | SCEV::FlagNSW;
2073 SCEV::NoWrapFlags SignOrUnsignWrap =
2074 ScalarEvolution::maskFlags(Flags, SignOrUnsignMask);
2075
2076 // If FlagNSW is true and all the operands are non-negative, infer FlagNUW.
2077 auto IsKnownNonNegative = [&](const SCEV *S) {
2078 return SE->isKnownNonNegative(S);
2079 };
2080
2081 if (SignOrUnsignWrap == SCEV::FlagNSW && all_of(Ops, IsKnownNonNegative))
2082 Flags =
2083 ScalarEvolution::setFlags(Flags, (SCEV::NoWrapFlags)SignOrUnsignMask);
2084
2085 SignOrUnsignWrap = ScalarEvolution::maskFlags(Flags, SignOrUnsignMask);
2086
2087 if (SignOrUnsignWrap != SignOrUnsignMask && Type == scAddExpr &&
2088 Ops.size() == 2 && isa<SCEVConstant>(Ops[0])) {
2089
2090 // (A + C) --> (A + C)<nsw> if the addition does not sign overflow
2091 // (A + C) --> (A + C)<nuw> if the addition does not unsign overflow
2092
2093 const APInt &C = cast<SCEVConstant>(Ops[0])->getAPInt();
2094 if (!(SignOrUnsignWrap & SCEV::FlagNSW)) {
2095 auto NSWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
2096 Instruction::Add, C, OBO::NoSignedWrap);
2097 if (NSWRegion.contains(SE->getSignedRange(Ops[1])))
2098 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW);
2099 }
2100 if (!(SignOrUnsignWrap & SCEV::FlagNUW)) {
2101 auto NUWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
2102 Instruction::Add, C, OBO::NoUnsignedWrap);
2103 if (NUWRegion.contains(SE->getUnsignedRange(Ops[1])))
2104 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
2105 }
2106 }
2107
2108 return Flags;
2109}
2110
2111/// Get a canonical add expression, or something simpler if possible.
2112const SCEV *ScalarEvolution::getAddExpr(SmallVectorImpl<const SCEV *> &Ops,
2113 SCEV::NoWrapFlags Flags,
2114 unsigned Depth) {
2115 assert(!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) &&((!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) && "only nuw or nsw allowed"
) ? static_cast<void> (0) : __assert_fail ("!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) && \"only nuw or nsw allowed\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2116, __PRETTY_FUNCTION__))
2116 "only nuw or nsw allowed")((!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) && "only nuw or nsw allowed"
) ? static_cast<void> (0) : __assert_fail ("!(Flags & ~(SCEV::FlagNUW | SCEV::FlagNSW)) && \"only nuw or nsw allowed\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2116, __PRETTY_FUNCTION__))
;
2117 assert(!Ops.empty() && "Cannot get empty add!")((!Ops.empty() && "Cannot get empty add!") ? static_cast
<void> (0) : __assert_fail ("!Ops.empty() && \"Cannot get empty add!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2117, __PRETTY_FUNCTION__))
;
2118 if (Ops.size() == 1) return Ops[0];
2119#ifndef NDEBUG
2120 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2121 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2122 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&((getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
"SCEVAddExpr operand types don't match!") ? static_cast<void
> (0) : __assert_fail ("getEffectiveSCEVType(Ops[i]->getType()) == ETy && \"SCEVAddExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2123, __PRETTY_FUNCTION__))
2123 "SCEVAddExpr operand types don't match!")((getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
"SCEVAddExpr operand types don't match!") ? static_cast<void
> (0) : __assert_fail ("getEffectiveSCEVType(Ops[i]->getType()) == ETy && \"SCEVAddExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2123, __PRETTY_FUNCTION__))
;
2124#endif
2125
2126 // Sort by complexity, this groups all similar expression types together.
2127 GroupByComplexity(Ops, &LI);
2128
2129 Flags = StrengthenNoWrapFlags(this, scAddExpr, Ops, Flags);
2130
2131 // If there are any constants, fold them together.
2132 unsigned Idx = 0;
2133 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2134 ++Idx;
2135 assert(Idx < Ops.size())((Idx < Ops.size()) ? static_cast<void> (0) : __assert_fail
("Idx < Ops.size()", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2135, __PRETTY_FUNCTION__))
;
2136 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2137 // We found two constants, fold them together!
2138 Ops[0] = getConstant(LHSC->getAPInt() + RHSC->getAPInt());
2139 if (Ops.size() == 2) return Ops[0];
2140 Ops.erase(Ops.begin()+1); // Erase the folded element
2141 LHSC = cast<SCEVConstant>(Ops[0]);
2142 }
2143
2144 // If we are left with a constant zero being added, strip it off.
2145 if (LHSC->getValue()->isZero()) {
2146 Ops.erase(Ops.begin());
2147 --Idx;
2148 }
2149
2150 if (Ops.size() == 1) return Ops[0];
2151 }
2152
2153 // Limit recursion calls depth
2154 if (Depth > MaxAddExprDepth)
2155 return getOrCreateAddExpr(Ops, Flags);
2156
2157 // Okay, check to see if the same value occurs in the operand list more than
2158 // once. If so, merge them together into an multiply expression. Since we
2159 // sorted the list, these values are required to be adjacent.
2160 Type *Ty = Ops[0]->getType();
2161 bool FoundMatch = false;
2162 for (unsigned i = 0, e = Ops.size(); i != e-1; ++i)
2163 if (Ops[i] == Ops[i+1]) { // X + Y + Y --> X + Y*2
2164 // Scan ahead to count how many equal operands there are.
2165 unsigned Count = 2;
2166 while (i+Count != e && Ops[i+Count] == Ops[i])
2167 ++Count;
2168 // Merge the values into a multiply.
2169 const SCEV *Scale = getConstant(Ty, Count);
2170 const SCEV *Mul = getMulExpr(Scale, Ops[i]);
2171 if (Ops.size() == Count)
2172 return Mul;
2173 Ops[i] = Mul;
2174 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+Count);
2175 --i; e -= Count - 1;
2176 FoundMatch = true;
2177 }
2178 if (FoundMatch)
2179 return getAddExpr(Ops, Flags);
2180
2181 // Check for truncates. If all the operands are truncated from the same
2182 // type, see if factoring out the truncate would permit the result to be
2183 // folded. eg., trunc(x) + m*trunc(n) --> trunc(x + trunc(m)*n)
2184 // if the contents of the resulting outer trunc fold to something simple.
2185 for (; Idx < Ops.size() && isa<SCEVTruncateExpr>(Ops[Idx]); ++Idx) {
2186 const SCEVTruncateExpr *Trunc = cast<SCEVTruncateExpr>(Ops[Idx]);
2187 Type *DstType = Trunc->getType();
2188 Type *SrcType = Trunc->getOperand()->getType();
2189 SmallVector<const SCEV *, 8> LargeOps;
2190 bool Ok = true;
2191 // Check all the operands to see if they can be represented in the
2192 // source type of the truncate.
2193 for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
2194 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(Ops[i])) {
2195 if (T->getOperand()->getType() != SrcType) {
2196 Ok = false;
2197 break;
2198 }
2199 LargeOps.push_back(T->getOperand());
2200 } else if (const SCEVConstant *C = dyn_cast<SCEVConstant>(Ops[i])) {
2201 LargeOps.push_back(getAnyExtendExpr(C, SrcType));
2202 } else if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(Ops[i])) {
2203 SmallVector<const SCEV *, 8> LargeMulOps;
2204 for (unsigned j = 0, f = M->getNumOperands(); j != f && Ok; ++j) {
2205 if (const SCEVTruncateExpr *T =
2206 dyn_cast<SCEVTruncateExpr>(M->getOperand(j))) {
2207 if (T->getOperand()->getType() != SrcType) {
2208 Ok = false;
2209 break;
2210 }
2211 LargeMulOps.push_back(T->getOperand());
2212 } else if (const auto *C = dyn_cast<SCEVConstant>(M->getOperand(j))) {
2213 LargeMulOps.push_back(getAnyExtendExpr(C, SrcType));
2214 } else {
2215 Ok = false;
2216 break;
2217 }
2218 }
2219 if (Ok)
2220 LargeOps.push_back(getMulExpr(LargeMulOps));
2221 } else {
2222 Ok = false;
2223 break;
2224 }
2225 }
2226 if (Ok) {
2227 // Evaluate the expression in the larger type.
2228 const SCEV *Fold = getAddExpr(LargeOps, Flags, Depth + 1);
2229 // If it folds to something simple, use it. Otherwise, don't.
2230 if (isa<SCEVConstant>(Fold) || isa<SCEVUnknown>(Fold))
2231 return getTruncateExpr(Fold, DstType);
2232 }
2233 }
2234
2235 // Skip past any other cast SCEVs.
2236 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddExpr)
2237 ++Idx;
2238
2239 // If there are add operands they would be next.
2240 if (Idx < Ops.size()) {
2241 bool DeletedAdd = false;
2242 while (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[Idx])) {
2243 if (Ops.size() > AddOpsInlineThreshold ||
2244 Add->getNumOperands() > AddOpsInlineThreshold)
2245 break;
2246 // If we have an add, expand the add operands onto the end of the operands
2247 // list.
2248 Ops.erase(Ops.begin()+Idx);
2249 Ops.append(Add->op_begin(), Add->op_end());
2250 DeletedAdd = true;
2251 }
2252
2253 // If we deleted at least one add, we added operands to the end of the list,
2254 // and they are not necessarily sorted. Recurse to resort and resimplify
2255 // any operands we just acquired.
2256 if (DeletedAdd)
2257 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2258 }
2259
2260 // Skip over the add expression until we get to a multiply.
2261 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2262 ++Idx;
2263
2264 // Check to see if there are any folding opportunities present with
2265 // operands multiplied by constant values.
2266 if (Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx])) {
2267 uint64_t BitWidth = getTypeSizeInBits(Ty);
2268 DenseMap<const SCEV *, APInt> M;
2269 SmallVector<const SCEV *, 8> NewOps;
2270 APInt AccumulatedConstant(BitWidth, 0);
2271 if (CollectAddOperandsWithScales(M, NewOps, AccumulatedConstant,
2272 Ops.data(), Ops.size(),
2273 APInt(BitWidth, 1), *this)) {
2274 struct APIntCompare {
2275 bool operator()(const APInt &LHS, const APInt &RHS) const {
2276 return LHS.ult(RHS);
2277 }
2278 };
2279
2280 // Some interesting folding opportunity is present, so its worthwhile to
2281 // re-generate the operands list. Group the operands by constant scale,
2282 // to avoid multiplying by the same constant scale multiple times.
2283 std::map<APInt, SmallVector<const SCEV *, 4>, APIntCompare> MulOpLists;
2284 for (const SCEV *NewOp : NewOps)
2285 MulOpLists[M.find(NewOp)->second].push_back(NewOp);
2286 // Re-generate the operands list.
2287 Ops.clear();
2288 if (AccumulatedConstant != 0)
2289 Ops.push_back(getConstant(AccumulatedConstant));
2290 for (auto &MulOp : MulOpLists)
2291 if (MulOp.first != 0)
2292 Ops.push_back(getMulExpr(
2293 getConstant(MulOp.first),
2294 getAddExpr(MulOp.second, SCEV::FlagAnyWrap, Depth + 1)));
2295 if (Ops.empty())
2296 return getZero(Ty);
2297 if (Ops.size() == 1)
2298 return Ops[0];
2299 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2300 }
2301 }
2302
2303 // If we are adding something to a multiply expression, make sure the
2304 // something is not already an operand of the multiply. If so, merge it into
2305 // the multiply.
2306 for (; Idx < Ops.size() && isa<SCEVMulExpr>(Ops[Idx]); ++Idx) {
2307 const SCEVMulExpr *Mul = cast<SCEVMulExpr>(Ops[Idx]);
2308 for (unsigned MulOp = 0, e = Mul->getNumOperands(); MulOp != e; ++MulOp) {
2309 const SCEV *MulOpSCEV = Mul->getOperand(MulOp);
2310 if (isa<SCEVConstant>(MulOpSCEV))
2311 continue;
2312 for (unsigned AddOp = 0, e = Ops.size(); AddOp != e; ++AddOp)
2313 if (MulOpSCEV == Ops[AddOp]) {
2314 // Fold W + X + (X * Y * Z) --> W + (X * ((Y*Z)+1))
2315 const SCEV *InnerMul = Mul->getOperand(MulOp == 0);
2316 if (Mul->getNumOperands() != 2) {
2317 // If the multiply has more than two operands, we must get the
2318 // Y*Z term.
2319 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2320 Mul->op_begin()+MulOp);
2321 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2322 InnerMul = getMulExpr(MulOps);
2323 }
2324 SmallVector<const SCEV *, 2> TwoOps = {getOne(Ty), InnerMul};
2325 const SCEV *AddOne = getAddExpr(TwoOps, SCEV::FlagAnyWrap, Depth + 1);
2326 const SCEV *OuterMul = getMulExpr(AddOne, MulOpSCEV);
2327 if (Ops.size() == 2) return OuterMul;
2328 if (AddOp < Idx) {
2329 Ops.erase(Ops.begin()+AddOp);
2330 Ops.erase(Ops.begin()+Idx-1);
2331 } else {
2332 Ops.erase(Ops.begin()+Idx);
2333 Ops.erase(Ops.begin()+AddOp-1);
2334 }
2335 Ops.push_back(OuterMul);
2336 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2337 }
2338
2339 // Check this multiply against other multiplies being added together.
2340 for (unsigned OtherMulIdx = Idx+1;
2341 OtherMulIdx < Ops.size() && isa<SCEVMulExpr>(Ops[OtherMulIdx]);
2342 ++OtherMulIdx) {
2343 const SCEVMulExpr *OtherMul = cast<SCEVMulExpr>(Ops[OtherMulIdx]);
2344 // If MulOp occurs in OtherMul, we can fold the two multiplies
2345 // together.
2346 for (unsigned OMulOp = 0, e = OtherMul->getNumOperands();
2347 OMulOp != e; ++OMulOp)
2348 if (OtherMul->getOperand(OMulOp) == MulOpSCEV) {
2349 // Fold X + (A*B*C) + (A*D*E) --> X + (A*(B*C+D*E))
2350 const SCEV *InnerMul1 = Mul->getOperand(MulOp == 0);
2351 if (Mul->getNumOperands() != 2) {
2352 SmallVector<const SCEV *, 4> MulOps(Mul->op_begin(),
2353 Mul->op_begin()+MulOp);
2354 MulOps.append(Mul->op_begin()+MulOp+1, Mul->op_end());
2355 InnerMul1 = getMulExpr(MulOps);
2356 }
2357 const SCEV *InnerMul2 = OtherMul->getOperand(OMulOp == 0);
2358 if (OtherMul->getNumOperands() != 2) {
2359 SmallVector<const SCEV *, 4> MulOps(OtherMul->op_begin(),
2360 OtherMul->op_begin()+OMulOp);
2361 MulOps.append(OtherMul->op_begin()+OMulOp+1, OtherMul->op_end());
2362 InnerMul2 = getMulExpr(MulOps);
2363 }
2364 SmallVector<const SCEV *, 2> TwoOps = {InnerMul1, InnerMul2};
2365 const SCEV *InnerMulSum =
2366 getAddExpr(TwoOps, SCEV::FlagAnyWrap, Depth + 1);
2367 const SCEV *OuterMul = getMulExpr(MulOpSCEV, InnerMulSum);
2368 if (Ops.size() == 2) return OuterMul;
2369 Ops.erase(Ops.begin()+Idx);
2370 Ops.erase(Ops.begin()+OtherMulIdx-1);
2371 Ops.push_back(OuterMul);
2372 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2373 }
2374 }
2375 }
2376 }
2377
2378 // If there are any add recurrences in the operands list, see if any other
2379 // added values are loop invariant. If so, we can fold them into the
2380 // recurrence.
2381 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2382 ++Idx;
2383
2384 // Scan over all recurrences, trying to fold loop invariants into them.
2385 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2386 // Scan all of the other operands to this add and add them to the vector if
2387 // they are loop invariant w.r.t. the recurrence.
2388 SmallVector<const SCEV *, 8> LIOps;
2389 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2390 const Loop *AddRecLoop = AddRec->getLoop();
2391 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2392 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2393 LIOps.push_back(Ops[i]);
2394 Ops.erase(Ops.begin()+i);
2395 --i; --e;
2396 }
2397
2398 // If we found some loop invariants, fold them into the recurrence.
2399 if (!LIOps.empty()) {
2400 // NLI + LI + {Start,+,Step} --> NLI + {LI+Start,+,Step}
2401 LIOps.push_back(AddRec->getStart());
2402
2403 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2404 AddRec->op_end());
2405 // This follows from the fact that the no-wrap flags on the outer add
2406 // expression are applicable on the 0th iteration, when the add recurrence
2407 // will be equal to its start value.
2408 AddRecOps[0] = getAddExpr(LIOps, Flags, Depth + 1);
2409
2410 // Build the new addrec. Propagate the NUW and NSW flags if both the
2411 // outer add and the inner addrec are guaranteed to have no overflow.
2412 // Always propagate NW.
2413 Flags = AddRec->getNoWrapFlags(setFlags(Flags, SCEV::FlagNW));
2414 const SCEV *NewRec = getAddRecExpr(AddRecOps, AddRecLoop, Flags);
2415
2416 // If all of the other operands were loop invariant, we are done.
2417 if (Ops.size() == 1) return NewRec;
2418
2419 // Otherwise, add the folded AddRec by the non-invariant parts.
2420 for (unsigned i = 0;; ++i)
2421 if (Ops[i] == AddRec) {
2422 Ops[i] = NewRec;
2423 break;
2424 }
2425 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2426 }
2427
2428 // Okay, if there weren't any loop invariants to be folded, check to see if
2429 // there are multiple AddRec's with the same loop induction variable being
2430 // added together. If so, we can fold them.
2431 for (unsigned OtherIdx = Idx+1;
2432 OtherIdx < Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2433 ++OtherIdx)
2434 if (AddRecLoop == cast<SCEVAddRecExpr>(Ops[OtherIdx])->getLoop()) {
2435 // Other + {A,+,B}<L> + {C,+,D}<L> --> Other + {A+C,+,B+D}<L>
2436 SmallVector<const SCEV *, 4> AddRecOps(AddRec->op_begin(),
2437 AddRec->op_end());
2438 for (; OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2439 ++OtherIdx)
2440 if (const auto *OtherAddRec = dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]))
2441 if (OtherAddRec->getLoop() == AddRecLoop) {
2442 for (unsigned i = 0, e = OtherAddRec->getNumOperands();
2443 i != e; ++i) {
2444 if (i >= AddRecOps.size()) {
2445 AddRecOps.append(OtherAddRec->op_begin()+i,
2446 OtherAddRec->op_end());
2447 break;
2448 }
2449 SmallVector<const SCEV *, 2> TwoOps = {
2450 AddRecOps[i], OtherAddRec->getOperand(i)};
2451 AddRecOps[i] = getAddExpr(TwoOps, SCEV::FlagAnyWrap, Depth + 1);
2452 }
2453 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2454 }
2455 // Step size has changed, so we cannot guarantee no self-wraparound.
2456 Ops[Idx] = getAddRecExpr(AddRecOps, AddRecLoop, SCEV::FlagAnyWrap);
2457 return getAddExpr(Ops, SCEV::FlagAnyWrap, Depth + 1);
2458 }
2459
2460 // Otherwise couldn't fold anything into this recurrence. Move onto the
2461 // next one.
2462 }
2463
2464 // Okay, it looks like we really DO need an add expr. Check to see if we
2465 // already have one, otherwise create a new one.
2466 return getOrCreateAddExpr(Ops, Flags);
2467}
2468
2469const SCEV *
2470ScalarEvolution::getOrCreateAddExpr(SmallVectorImpl<const SCEV *> &Ops,
2471 SCEV::NoWrapFlags Flags) {
2472 FoldingSetNodeID ID;
2473 ID.AddInteger(scAddExpr);
2474 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2475 ID.AddPointer(Ops[i]);
2476 void *IP = nullptr;
2477 SCEVAddExpr *S =
2478 static_cast<SCEVAddExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2479 if (!S) {
2480 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2481 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2482 S = new (SCEVAllocator)
2483 SCEVAddExpr(ID.Intern(SCEVAllocator), O, Ops.size());
2484 UniqueSCEVs.InsertNode(S, IP);
2485 }
2486 S->setNoWrapFlags(Flags);
2487 return S;
2488}
2489
2490static uint64_t umul_ov(uint64_t i, uint64_t j, bool &Overflow) {
2491 uint64_t k = i*j;
2492 if (j > 1 && k / j != i) Overflow = true;
2493 return k;
2494}
2495
2496/// Compute the result of "n choose k", the binomial coefficient. If an
2497/// intermediate computation overflows, Overflow will be set and the return will
2498/// be garbage. Overflow is not cleared on absence of overflow.
2499static uint64_t Choose(uint64_t n, uint64_t k, bool &Overflow) {
2500 // We use the multiplicative formula:
2501 // n(n-1)(n-2)...(n-(k-1)) / k(k-1)(k-2)...1 .
2502 // At each iteration, we take the n-th term of the numeral and divide by the
2503 // (k-n)th term of the denominator. This division will always produce an
2504 // integral result, and helps reduce the chance of overflow in the
2505 // intermediate computations. However, we can still overflow even when the
2506 // final result would fit.
2507
2508 if (n == 0 || n == k) return 1;
2509 if (k > n) return 0;
2510
2511 if (k > n/2)
2512 k = n-k;
2513
2514 uint64_t r = 1;
2515 for (uint64_t i = 1; i <= k; ++i) {
2516 r = umul_ov(r, n-(i-1), Overflow);
2517 r /= i;
2518 }
2519 return r;
2520}
2521
2522/// Determine if any of the operands in this SCEV are a constant or if
2523/// any of the add or multiply expressions in this SCEV contain a constant.
2524static bool containsConstantSomewhere(const SCEV *StartExpr) {
2525 SmallVector<const SCEV *, 4> Ops;
2526 Ops.push_back(StartExpr);
2527 while (!Ops.empty()) {
2528 const SCEV *CurrentExpr = Ops.pop_back_val();
2529 if (isa<SCEVConstant>(*CurrentExpr))
2530 return true;
2531
2532 if (isa<SCEVAddExpr>(*CurrentExpr) || isa<SCEVMulExpr>(*CurrentExpr)) {
2533 const auto *CurrentNAry = cast<SCEVNAryExpr>(CurrentExpr);
2534 Ops.append(CurrentNAry->op_begin(), CurrentNAry->op_end());
2535 }
2536 }
2537 return false;
2538}
2539
2540/// Get a canonical multiply expression, or something simpler if possible.
2541const SCEV *ScalarEvolution::getMulExpr(SmallVectorImpl<const SCEV *> &Ops,
2542 SCEV::NoWrapFlags Flags) {
2543 assert(Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&((Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
"only nuw or nsw allowed") ? static_cast<void> (0) : __assert_fail
("Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) && \"only nuw or nsw allowed\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2544, __PRETTY_FUNCTION__))
2544 "only nuw or nsw allowed")((Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) &&
"only nuw or nsw allowed") ? static_cast<void> (0) : __assert_fail
("Flags == maskFlags(Flags, SCEV::FlagNUW | SCEV::FlagNSW) && \"only nuw or nsw allowed\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2544, __PRETTY_FUNCTION__))
;
2545 assert(!Ops.empty() && "Cannot get empty mul!")((!Ops.empty() && "Cannot get empty mul!") ? static_cast
<void> (0) : __assert_fail ("!Ops.empty() && \"Cannot get empty mul!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2545, __PRETTY_FUNCTION__))
;
2546 if (Ops.size() == 1) return Ops[0];
2547#ifndef NDEBUG
2548 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
2549 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
2550 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&((getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
"SCEVMulExpr operand types don't match!") ? static_cast<void
> (0) : __assert_fail ("getEffectiveSCEVType(Ops[i]->getType()) == ETy && \"SCEVMulExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2551, __PRETTY_FUNCTION__))
2551 "SCEVMulExpr operand types don't match!")((getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
"SCEVMulExpr operand types don't match!") ? static_cast<void
> (0) : __assert_fail ("getEffectiveSCEVType(Ops[i]->getType()) == ETy && \"SCEVMulExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2551, __PRETTY_FUNCTION__))
;
2552#endif
2553
2554 // Sort by complexity, this groups all similar expression types together.
2555 GroupByComplexity(Ops, &LI);
2556
2557 Flags = StrengthenNoWrapFlags(this, scMulExpr, Ops, Flags);
2558
2559 // If there are any constants, fold them together.
2560 unsigned Idx = 0;
2561 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
2562
2563 // C1*(C2+V) -> C1*C2 + C1*V
2564 if (Ops.size() == 2)
2565 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1]))
2566 // If any of Add's ops are Adds or Muls with a constant,
2567 // apply this transformation as well.
2568 if (Add->getNumOperands() == 2)
2569 if (containsConstantSomewhere(Add))
2570 return getAddExpr(getMulExpr(LHSC, Add->getOperand(0)),
2571 getMulExpr(LHSC, Add->getOperand(1)));
2572
2573 ++Idx;
2574 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
2575 // We found two constants, fold them together!
2576 ConstantInt *Fold =
2577 ConstantInt::get(getContext(), LHSC->getAPInt() * RHSC->getAPInt());
2578 Ops[0] = getConstant(Fold);
2579 Ops.erase(Ops.begin()+1); // Erase the folded element
2580 if (Ops.size() == 1) return Ops[0];
2581 LHSC = cast<SCEVConstant>(Ops[0]);
2582 }
2583
2584 // If we are left with a constant one being multiplied, strip it off.
2585 if (cast<SCEVConstant>(Ops[0])->getValue()->equalsInt(1)) {
2586 Ops.erase(Ops.begin());
2587 --Idx;
2588 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isZero()) {
2589 // If we have a multiply of zero, it will always be zero.
2590 return Ops[0];
2591 } else if (Ops[0]->isAllOnesValue()) {
2592 // If we have a mul by -1 of an add, try distributing the -1 among the
2593 // add operands.
2594 if (Ops.size() == 2) {
2595 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(Ops[1])) {
2596 SmallVector<const SCEV *, 4> NewOps;
2597 bool AnyFolded = false;
2598 for (const SCEV *AddOp : Add->operands()) {
2599 const SCEV *Mul = getMulExpr(Ops[0], AddOp);
2600 if (!isa<SCEVMulExpr>(Mul)) AnyFolded = true;
2601 NewOps.push_back(Mul);
2602 }
2603 if (AnyFolded)
2604 return getAddExpr(NewOps);
2605 } else if (const auto *AddRec = dyn_cast<SCEVAddRecExpr>(Ops[1])) {
2606 // Negation preserves a recurrence's no self-wrap property.
2607 SmallVector<const SCEV *, 4> Operands;
2608 for (const SCEV *AddRecOp : AddRec->operands())
2609 Operands.push_back(getMulExpr(Ops[0], AddRecOp));
2610
2611 return getAddRecExpr(Operands, AddRec->getLoop(),
2612 AddRec->getNoWrapFlags(SCEV::FlagNW));
2613 }
2614 }
2615 }
2616
2617 if (Ops.size() == 1)
2618 return Ops[0];
2619 }
2620
2621 // Skip over the add expression until we get to a multiply.
2622 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scMulExpr)
2623 ++Idx;
2624
2625 // If there are mul operands inline them all into this expression.
2626 if (Idx < Ops.size()) {
2627 bool DeletedMul = false;
2628 while (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(Ops[Idx])) {
2629 if (Ops.size() > MulOpsInlineThreshold)
2630 break;
2631 // If we have an mul, expand the mul operands onto the end of the operands
2632 // list.
2633 Ops.erase(Ops.begin()+Idx);
2634 Ops.append(Mul->op_begin(), Mul->op_end());
2635 DeletedMul = true;
2636 }
2637
2638 // If we deleted at least one mul, we added operands to the end of the list,
2639 // and they are not necessarily sorted. Recurse to resort and resimplify
2640 // any operands we just acquired.
2641 if (DeletedMul)
2642 return getMulExpr(Ops);
2643 }
2644
2645 // If there are any add recurrences in the operands list, see if any other
2646 // added values are loop invariant. If so, we can fold them into the
2647 // recurrence.
2648 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scAddRecExpr)
2649 ++Idx;
2650
2651 // Scan over all recurrences, trying to fold loop invariants into them.
2652 for (; Idx < Ops.size() && isa<SCEVAddRecExpr>(Ops[Idx]); ++Idx) {
2653 // Scan all of the other operands to this mul and add them to the vector if
2654 // they are loop invariant w.r.t. the recurrence.
2655 SmallVector<const SCEV *, 8> LIOps;
2656 const SCEVAddRecExpr *AddRec = cast<SCEVAddRecExpr>(Ops[Idx]);
2657 const Loop *AddRecLoop = AddRec->getLoop();
2658 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2659 if (isLoopInvariant(Ops[i], AddRecLoop)) {
2660 LIOps.push_back(Ops[i]);
2661 Ops.erase(Ops.begin()+i);
2662 --i; --e;
2663 }
2664
2665 // If we found some loop invariants, fold them into the recurrence.
2666 if (!LIOps.empty()) {
2667 // NLI * LI * {Start,+,Step} --> NLI * {LI*Start,+,LI*Step}
2668 SmallVector<const SCEV *, 4> NewOps;
2669 NewOps.reserve(AddRec->getNumOperands());
2670 const SCEV *Scale = getMulExpr(LIOps);
2671 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i)
2672 NewOps.push_back(getMulExpr(Scale, AddRec->getOperand(i)));
2673
2674 // Build the new addrec. Propagate the NUW and NSW flags if both the
2675 // outer mul and the inner addrec are guaranteed to have no overflow.
2676 //
2677 // No self-wrap cannot be guaranteed after changing the step size, but
2678 // will be inferred if either NUW or NSW is true.
2679 Flags = AddRec->getNoWrapFlags(clearFlags(Flags, SCEV::FlagNW));
2680 const SCEV *NewRec = getAddRecExpr(NewOps, AddRecLoop, Flags);
2681
2682 // If all of the other operands were loop invariant, we are done.
2683 if (Ops.size() == 1) return NewRec;
2684
2685 // Otherwise, multiply the folded AddRec by the non-invariant parts.
2686 for (unsigned i = 0;; ++i)
2687 if (Ops[i] == AddRec) {
2688 Ops[i] = NewRec;
2689 break;
2690 }
2691 return getMulExpr(Ops);
2692 }
2693
2694 // Okay, if there weren't any loop invariants to be folded, check to see if
2695 // there are multiple AddRec's with the same loop induction variable being
2696 // multiplied together. If so, we can fold them.
2697
2698 // {A1,+,A2,+,...,+,An}<L> * {B1,+,B2,+,...,+,Bn}<L>
2699 // = {x=1 in [ sum y=x..2x [ sum z=max(y-x, y-n)..min(x,n) [
2700 // choose(x, 2x)*choose(2x-y, x-z)*A_{y-z}*B_z
2701 // ]]],+,...up to x=2n}.
2702 // Note that the arguments to choose() are always integers with values
2703 // known at compile time, never SCEV objects.
2704 //
2705 // The implementation avoids pointless extra computations when the two
2706 // addrec's are of different length (mathematically, it's equivalent to
2707 // an infinite stream of zeros on the right).
2708 bool OpsModified = false;
2709 for (unsigned OtherIdx = Idx+1;
2710 OtherIdx != Ops.size() && isa<SCEVAddRecExpr>(Ops[OtherIdx]);
2711 ++OtherIdx) {
2712 const SCEVAddRecExpr *OtherAddRec =
2713 dyn_cast<SCEVAddRecExpr>(Ops[OtherIdx]);
2714 if (!OtherAddRec || OtherAddRec->getLoop() != AddRecLoop)
2715 continue;
2716
2717 bool Overflow = false;
2718 Type *Ty = AddRec->getType();
2719 bool LargerThan64Bits = getTypeSizeInBits(Ty) > 64;
2720 SmallVector<const SCEV*, 7> AddRecOps;
2721 for (int x = 0, xe = AddRec->getNumOperands() +
2722 OtherAddRec->getNumOperands() - 1; x != xe && !Overflow; ++x) {
2723 const SCEV *Term = getZero(Ty);
2724 for (int y = x, ye = 2*x+1; y != ye && !Overflow; ++y) {
2725 uint64_t Coeff1 = Choose(x, 2*x - y, Overflow);
2726 for (int z = std::max(y-x, y-(int)AddRec->getNumOperands()+1),
2727 ze = std::min(x+1, (int)OtherAddRec->getNumOperands());
2728 z < ze && !Overflow; ++z) {
2729 uint64_t Coeff2 = Choose(2*x - y, x-z, Overflow);
2730 uint64_t Coeff;
2731 if (LargerThan64Bits)
2732 Coeff = umul_ov(Coeff1, Coeff2, Overflow);
2733 else
2734 Coeff = Coeff1*Coeff2;
2735 const SCEV *CoeffTerm = getConstant(Ty, Coeff);
2736 const SCEV *Term1 = AddRec->getOperand(y-z);
2737 const SCEV *Term2 = OtherAddRec->getOperand(z);
2738 Term = getAddExpr(Term, getMulExpr(CoeffTerm, Term1,Term2));
2739 }
2740 }
2741 AddRecOps.push_back(Term);
2742 }
2743 if (!Overflow) {
2744 const SCEV *NewAddRec = getAddRecExpr(AddRecOps, AddRec->getLoop(),
2745 SCEV::FlagAnyWrap);
2746 if (Ops.size() == 2) return NewAddRec;
2747 Ops[Idx] = NewAddRec;
2748 Ops.erase(Ops.begin() + OtherIdx); --OtherIdx;
2749 OpsModified = true;
2750 AddRec = dyn_cast<SCEVAddRecExpr>(NewAddRec);
2751 if (!AddRec)
2752 break;
2753 }
2754 }
2755 if (OpsModified)
2756 return getMulExpr(Ops);
2757
2758 // Otherwise couldn't fold anything into this recurrence. Move onto the
2759 // next one.
2760 }
2761
2762 // Okay, it looks like we really DO need an mul expr. Check to see if we
2763 // already have one, otherwise create a new one.
2764 FoldingSetNodeID ID;
2765 ID.AddInteger(scMulExpr);
2766 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
2767 ID.AddPointer(Ops[i]);
2768 void *IP = nullptr;
2769 SCEVMulExpr *S =
2770 static_cast<SCEVMulExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
2771 if (!S) {
2772 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
2773 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
2774 S = new (SCEVAllocator) SCEVMulExpr(ID.Intern(SCEVAllocator),
2775 O, Ops.size());
2776 UniqueSCEVs.InsertNode(S, IP);
2777 }
2778 S->setNoWrapFlags(Flags);
2779 return S;
2780}
2781
2782/// Get a canonical unsigned division expression, or something simpler if
2783/// possible.
2784const SCEV *ScalarEvolution::getUDivExpr(const SCEV *LHS,
2785 const SCEV *RHS) {
2786 assert(getEffectiveSCEVType(LHS->getType()) ==((getEffectiveSCEVType(LHS->getType()) == getEffectiveSCEVType
(RHS->getType()) && "SCEVUDivExpr operand types don't match!"
) ? static_cast<void> (0) : __assert_fail ("getEffectiveSCEVType(LHS->getType()) == getEffectiveSCEVType(RHS->getType()) && \"SCEVUDivExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2788, __PRETTY_FUNCTION__))
2787 getEffectiveSCEVType(RHS->getType()) &&((getEffectiveSCEVType(LHS->getType()) == getEffectiveSCEVType
(RHS->getType()) && "SCEVUDivExpr operand types don't match!"
) ? static_cast<void> (0) : __assert_fail ("getEffectiveSCEVType(LHS->getType()) == getEffectiveSCEVType(RHS->getType()) && \"SCEVUDivExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2788, __PRETTY_FUNCTION__))
2788 "SCEVUDivExpr operand types don't match!")((getEffectiveSCEVType(LHS->getType()) == getEffectiveSCEVType
(RHS->getType()) && "SCEVUDivExpr operand types don't match!"
) ? static_cast<void> (0) : __assert_fail ("getEffectiveSCEVType(LHS->getType()) == getEffectiveSCEVType(RHS->getType()) && \"SCEVUDivExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2788, __PRETTY_FUNCTION__))
;
2789
2790 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
2791 if (RHSC->getValue()->equalsInt(1))
2792 return LHS; // X udiv 1 --> x
2793 // If the denominator is zero, the result of the udiv is undefined. Don't
2794 // try to analyze it, because the resolution chosen here may differ from
2795 // the resolution chosen in other parts of the compiler.
2796 if (!RHSC->getValue()->isZero()) {
2797 // Determine if the division can be folded into the operands of
2798 // its operands.
2799 // TODO: Generalize this to non-constants by using known-bits information.
2800 Type *Ty = LHS->getType();
2801 unsigned LZ = RHSC->getAPInt().countLeadingZeros();
2802 unsigned MaxShiftAmt = getTypeSizeInBits(Ty) - LZ - 1;
2803 // For non-power-of-two values, effectively round the value up to the
2804 // nearest power of two.
2805 if (!RHSC->getAPInt().isPowerOf2())
2806 ++MaxShiftAmt;
2807 IntegerType *ExtTy =
2808 IntegerType::get(getContext(), getTypeSizeInBits(Ty) + MaxShiftAmt);
2809 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS))
2810 if (const SCEVConstant *Step =
2811 dyn_cast<SCEVConstant>(AR->getStepRecurrence(*this))) {
2812 // {X,+,N}/C --> {X/C,+,N/C} if safe and N/C can be folded.
2813 const APInt &StepInt = Step->getAPInt();
2814 const APInt &DivInt = RHSC->getAPInt();
2815 if (!StepInt.urem(DivInt) &&
2816 getZeroExtendExpr(AR, ExtTy) ==
2817 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2818 getZeroExtendExpr(Step, ExtTy),
2819 AR->getLoop(), SCEV::FlagAnyWrap)) {
2820 SmallVector<const SCEV *, 4> Operands;
2821 for (const SCEV *Op : AR->operands())
2822 Operands.push_back(getUDivExpr(Op, RHS));
2823 return getAddRecExpr(Operands, AR->getLoop(), SCEV::FlagNW);
2824 }
2825 /// Get a canonical UDivExpr for a recurrence.
2826 /// {X,+,N}/C => {Y,+,N}/C where Y=X-(X%N). Safe when C%N=0.
2827 // We can currently only fold X%N if X is constant.
2828 const SCEVConstant *StartC = dyn_cast<SCEVConstant>(AR->getStart());
2829 if (StartC && !DivInt.urem(StepInt) &&
2830 getZeroExtendExpr(AR, ExtTy) ==
2831 getAddRecExpr(getZeroExtendExpr(AR->getStart(), ExtTy),
2832 getZeroExtendExpr(Step, ExtTy),
2833 AR->getLoop(), SCEV::FlagAnyWrap)) {
2834 const APInt &StartInt = StartC->getAPInt();
2835 const APInt &StartRem = StartInt.urem(StepInt);
2836 if (StartRem != 0)
2837 LHS = getAddRecExpr(getConstant(StartInt - StartRem), Step,
2838 AR->getLoop(), SCEV::FlagNW);
2839 }
2840 }
2841 // (A*B)/C --> A*(B/C) if safe and B/C can be folded.
2842 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(LHS)) {
2843 SmallVector<const SCEV *, 4> Operands;
2844 for (const SCEV *Op : M->operands())
2845 Operands.push_back(getZeroExtendExpr(Op, ExtTy));
2846 if (getZeroExtendExpr(M, ExtTy) == getMulExpr(Operands))
2847 // Find an operand that's safely divisible.
2848 for (unsigned i = 0, e = M->getNumOperands(); i != e; ++i) {
2849 const SCEV *Op = M->getOperand(i);
2850 const SCEV *Div = getUDivExpr(Op, RHSC);
2851 if (!isa<SCEVUDivExpr>(Div) && getMulExpr(Div, RHSC) == Op) {
2852 Operands = SmallVector<const SCEV *, 4>(M->op_begin(),
2853 M->op_end());
2854 Operands[i] = Div;
2855 return getMulExpr(Operands);
2856 }
2857 }
2858 }
2859 // (A+B)/C --> (A/C + B/C) if safe and A/C and B/C can be folded.
2860 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(LHS)) {
2861 SmallVector<const SCEV *, 4> Operands;
2862 for (const SCEV *Op : A->operands())
2863 Operands.push_back(getZeroExtendExpr(Op, ExtTy));
2864 if (getZeroExtendExpr(A, ExtTy) == getAddExpr(Operands)) {
2865 Operands.clear();
2866 for (unsigned i = 0, e = A->getNumOperands(); i != e; ++i) {
2867 const SCEV *Op = getUDivExpr(A->getOperand(i), RHS);
2868 if (isa<SCEVUDivExpr>(Op) ||
2869 getMulExpr(Op, RHS) != A->getOperand(i))
2870 break;
2871 Operands.push_back(Op);
2872 }
2873 if (Operands.size() == A->getNumOperands())
2874 return getAddExpr(Operands);
2875 }
2876 }
2877
2878 // Fold if both operands are constant.
2879 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
2880 Constant *LHSCV = LHSC->getValue();
2881 Constant *RHSCV = RHSC->getValue();
2882 return getConstant(cast<ConstantInt>(ConstantExpr::getUDiv(LHSCV,
2883 RHSCV)));
2884 }
2885 }
2886 }
2887
2888 FoldingSetNodeID ID;
2889 ID.AddInteger(scUDivExpr);
2890 ID.AddPointer(LHS);
2891 ID.AddPointer(RHS);
2892 void *IP = nullptr;
2893 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
2894 SCEV *S = new (SCEVAllocator) SCEVUDivExpr(ID.Intern(SCEVAllocator),
2895 LHS, RHS);
2896 UniqueSCEVs.InsertNode(S, IP);
2897 return S;
2898}
2899
2900static const APInt gcd(const SCEVConstant *C1, const SCEVConstant *C2) {
2901 APInt A = C1->getAPInt().abs();
2902 APInt B = C2->getAPInt().abs();
2903 uint32_t ABW = A.getBitWidth();
2904 uint32_t BBW = B.getBitWidth();
2905
2906 if (ABW > BBW)
2907 B = B.zext(ABW);
2908 else if (ABW < BBW)
2909 A = A.zext(BBW);
2910
2911 return APIntOps::GreatestCommonDivisor(A, B);
2912}
2913
2914/// Get a canonical unsigned division expression, or something simpler if
2915/// possible. There is no representation for an exact udiv in SCEV IR, but we
2916/// can attempt to remove factors from the LHS and RHS. We can't do this when
2917/// it's not exact because the udiv may be clearing bits.
2918const SCEV *ScalarEvolution::getUDivExactExpr(const SCEV *LHS,
2919 const SCEV *RHS) {
2920 // TODO: we could try to find factors in all sorts of things, but for now we
2921 // just deal with u/exact (multiply, constant). See SCEVDivision towards the
2922 // end of this file for inspiration.
2923
2924 const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS);
2925 if (!Mul || !Mul->hasNoUnsignedWrap())
2926 return getUDivExpr(LHS, RHS);
2927
2928 if (const SCEVConstant *RHSCst = dyn_cast<SCEVConstant>(RHS)) {
2929 // If the mulexpr multiplies by a constant, then that constant must be the
2930 // first element of the mulexpr.
2931 if (const auto *LHSCst = dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2932 if (LHSCst == RHSCst) {
2933 SmallVector<const SCEV *, 2> Operands;
2934 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2935 return getMulExpr(Operands);
2936 }
2937
2938 // We can't just assume that LHSCst divides RHSCst cleanly, it could be
2939 // that there's a factor provided by one of the other terms. We need to
2940 // check.
2941 APInt Factor = gcd(LHSCst, RHSCst);
2942 if (!Factor.isIntN(1)) {
2943 LHSCst =
2944 cast<SCEVConstant>(getConstant(LHSCst->getAPInt().udiv(Factor)));
2945 RHSCst =
2946 cast<SCEVConstant>(getConstant(RHSCst->getAPInt().udiv(Factor)));
2947 SmallVector<const SCEV *, 2> Operands;
2948 Operands.push_back(LHSCst);
2949 Operands.append(Mul->op_begin() + 1, Mul->op_end());
2950 LHS = getMulExpr(Operands);
2951 RHS = RHSCst;
2952 Mul = dyn_cast<SCEVMulExpr>(LHS);
2953 if (!Mul)
2954 return getUDivExactExpr(LHS, RHS);
2955 }
2956 }
2957 }
2958
2959 for (int i = 0, e = Mul->getNumOperands(); i != e; ++i) {
2960 if (Mul->getOperand(i) == RHS) {
2961 SmallVector<const SCEV *, 2> Operands;
2962 Operands.append(Mul->op_begin(), Mul->op_begin() + i);
2963 Operands.append(Mul->op_begin() + i + 1, Mul->op_end());
2964 return getMulExpr(Operands);
2965 }
2966 }
2967
2968 return getUDivExpr(LHS, RHS);
2969}
2970
2971/// Get an add recurrence expression for the specified loop. Simplify the
2972/// expression as much as possible.
2973const SCEV *ScalarEvolution::getAddRecExpr(const SCEV *Start, const SCEV *Step,
2974 const Loop *L,
2975 SCEV::NoWrapFlags Flags) {
2976 SmallVector<const SCEV *, 4> Operands;
2977 Operands.push_back(Start);
2978 if (const SCEVAddRecExpr *StepChrec = dyn_cast<SCEVAddRecExpr>(Step))
2979 if (StepChrec->getLoop() == L) {
2980 Operands.append(StepChrec->op_begin(), StepChrec->op_end());
2981 return getAddRecExpr(Operands, L, maskFlags(Flags, SCEV::FlagNW));
2982 }
2983
2984 Operands.push_back(Step);
2985 return getAddRecExpr(Operands, L, Flags);
2986}
2987
2988/// Get an add recurrence expression for the specified loop. Simplify the
2989/// expression as much as possible.
2990const SCEV *
2991ScalarEvolution::getAddRecExpr(SmallVectorImpl<const SCEV *> &Operands,
2992 const Loop *L, SCEV::NoWrapFlags Flags) {
2993 if (Operands.size() == 1) return Operands[0];
2994#ifndef NDEBUG
2995 Type *ETy = getEffectiveSCEVType(Operands[0]->getType());
2996 for (unsigned i = 1, e = Operands.size(); i != e; ++i)
2997 assert(getEffectiveSCEVType(Operands[i]->getType()) == ETy &&((getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
"SCEVAddRecExpr operand types don't match!") ? static_cast<
void> (0) : __assert_fail ("getEffectiveSCEVType(Operands[i]->getType()) == ETy && \"SCEVAddRecExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2998, __PRETTY_FUNCTION__))
2998 "SCEVAddRecExpr operand types don't match!")((getEffectiveSCEVType(Operands[i]->getType()) == ETy &&
"SCEVAddRecExpr operand types don't match!") ? static_cast<
void> (0) : __assert_fail ("getEffectiveSCEVType(Operands[i]->getType()) == ETy && \"SCEVAddRecExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 2998, __PRETTY_FUNCTION__))
;
2999 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
3000 assert(isLoopInvariant(Operands[i], L) &&((isLoopInvariant(Operands[i], L) && "SCEVAddRecExpr operand is not loop-invariant!"
) ? static_cast<void> (0) : __assert_fail ("isLoopInvariant(Operands[i], L) && \"SCEVAddRecExpr operand is not loop-invariant!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3001, __PRETTY_FUNCTION__))
3001 "SCEVAddRecExpr operand is not loop-invariant!")((isLoopInvariant(Operands[i], L) && "SCEVAddRecExpr operand is not loop-invariant!"
) ? static_cast<void> (0) : __assert_fail ("isLoopInvariant(Operands[i], L) && \"SCEVAddRecExpr operand is not loop-invariant!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3001, __PRETTY_FUNCTION__))
;
3002#endif
3003
3004 if (Operands.back()->isZero()) {
3005 Operands.pop_back();
3006 return getAddRecExpr(Operands, L, SCEV::FlagAnyWrap); // {X,+,0} --> X
3007 }
3008
3009 // It's tempting to want to call getMaxBackedgeTakenCount count here and
3010 // use that information to infer NUW and NSW flags. However, computing a
3011 // BE count requires calling getAddRecExpr, so we may not yet have a
3012 // meaningful BE count at this point (and if we don't, we'd be stuck
3013 // with a SCEVCouldNotCompute as the cached BE count).
3014
3015 Flags = StrengthenNoWrapFlags(this, scAddRecExpr, Operands, Flags);
3016
3017 // Canonicalize nested AddRecs in by nesting them in order of loop depth.
3018 if (const SCEVAddRecExpr *NestedAR = dyn_cast<SCEVAddRecExpr>(Operands[0])) {
3019 const Loop *NestedLoop = NestedAR->getLoop();
3020 if (L->contains(NestedLoop)
3021 ? (L->getLoopDepth() < NestedLoop->getLoopDepth())
3022 : (!NestedLoop->contains(L) &&
3023 DT.dominates(L->getHeader(), NestedLoop->getHeader()))) {
3024 SmallVector<const SCEV *, 4> NestedOperands(NestedAR->op_begin(),
3025 NestedAR->op_end());
3026 Operands[0] = NestedAR->getStart();
3027 // AddRecs require their operands be loop-invariant with respect to their
3028 // loops. Don't perform this transformation if it would break this
3029 // requirement.
3030 bool AllInvariant = all_of(
3031 Operands, [&](const SCEV *Op) { return isLoopInvariant(Op, L); });
3032
3033 if (AllInvariant) {
3034 // Create a recurrence for the outer loop with the same step size.
3035 //
3036 // The outer recurrence keeps its NW flag but only keeps NUW/NSW if the
3037 // inner recurrence has the same property.
3038 SCEV::NoWrapFlags OuterFlags =
3039 maskFlags(Flags, SCEV::FlagNW | NestedAR->getNoWrapFlags());
3040
3041 NestedOperands[0] = getAddRecExpr(Operands, L, OuterFlags);
3042 AllInvariant = all_of(NestedOperands, [&](const SCEV *Op) {
3043 return isLoopInvariant(Op, NestedLoop);
3044 });
3045
3046 if (AllInvariant) {
3047 // Ok, both add recurrences are valid after the transformation.
3048 //
3049 // The inner recurrence keeps its NW flag but only keeps NUW/NSW if
3050 // the outer recurrence has the same property.
3051 SCEV::NoWrapFlags InnerFlags =
3052 maskFlags(NestedAR->getNoWrapFlags(), SCEV::FlagNW | Flags);
3053 return getAddRecExpr(NestedOperands, NestedLoop, InnerFlags);
3054 }
3055 }
3056 // Reset Operands to its original state.
3057 Operands[0] = NestedAR;
3058 }
3059 }
3060
3061 // Okay, it looks like we really DO need an addrec expr. Check to see if we
3062 // already have one, otherwise create a new one.
3063 FoldingSetNodeID ID;
3064 ID.AddInteger(scAddRecExpr);
3065 for (unsigned i = 0, e = Operands.size(); i != e; ++i)
3066 ID.AddPointer(Operands[i]);
3067 ID.AddPointer(L);
3068 void *IP = nullptr;
3069 SCEVAddRecExpr *S =
3070 static_cast<SCEVAddRecExpr *>(UniqueSCEVs.FindNodeOrInsertPos(ID, IP));
3071 if (!S) {
3072 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Operands.size());
3073 std::uninitialized_copy(Operands.begin(), Operands.end(), O);
3074 S = new (SCEVAllocator) SCEVAddRecExpr(ID.Intern(SCEVAllocator),
3075 O, Operands.size(), L);
3076 UniqueSCEVs.InsertNode(S, IP);
3077 }
3078 S->setNoWrapFlags(Flags);
3079 return S;
3080}
3081
3082const SCEV *
3083ScalarEvolution::getGEPExpr(GEPOperator *GEP,
3084 const SmallVectorImpl<const SCEV *> &IndexExprs) {
3085 const SCEV *BaseExpr = getSCEV(GEP->getPointerOperand());
3086 // getSCEV(Base)->getType() has the same address space as Base->getType()
3087 // because SCEV::getType() preserves the address space.
3088 Type *IntPtrTy = getEffectiveSCEVType(BaseExpr->getType());
3089 // FIXME(PR23527): Don't blindly transfer the inbounds flag from the GEP
3090 // instruction to its SCEV, because the Instruction may be guarded by control
3091 // flow and the no-overflow bits may not be valid for the expression in any
3092 // context. This can be fixed similarly to how these flags are handled for
3093 // adds.
3094 SCEV::NoWrapFlags Wrap = GEP->isInBounds() ? SCEV::FlagNSW
3095 : SCEV::FlagAnyWrap;
3096
3097 const SCEV *TotalOffset = getZero(IntPtrTy);
3098 // The array size is unimportant. The first thing we do on CurTy is getting
3099 // its element type.
3100 Type *CurTy = ArrayType::get(GEP->getSourceElementType(), 0);
3101 for (const SCEV *IndexExpr : IndexExprs) {
3102 // Compute the (potentially symbolic) offset in bytes for this index.
3103 if (StructType *STy = dyn_cast<StructType>(CurTy)) {
3104 // For a struct, add the member offset.
3105 ConstantInt *Index = cast<SCEVConstant>(IndexExpr)->getValue();
3106 unsigned FieldNo = Index->getZExtValue();
3107 const SCEV *FieldOffset = getOffsetOfExpr(IntPtrTy, STy, FieldNo);
3108
3109 // Add the field offset to the running total offset.
3110 TotalOffset = getAddExpr(TotalOffset, FieldOffset);
3111
3112 // Update CurTy to the type of the field at Index.
3113 CurTy = STy->getTypeAtIndex(Index);
3114 } else {
3115 // Update CurTy to its element type.
3116 CurTy = cast<SequentialType>(CurTy)->getElementType();
3117 // For an array, add the element offset, explicitly scaled.
3118 const SCEV *ElementSize = getSizeOfExpr(IntPtrTy, CurTy);
3119 // Getelementptr indices are signed.
3120 IndexExpr = getTruncateOrSignExtend(IndexExpr, IntPtrTy);
3121
3122 // Multiply the index by the element size to compute the element offset.
3123 const SCEV *LocalOffset = getMulExpr(IndexExpr, ElementSize, Wrap);
3124
3125 // Add the element offset to the running total offset.
3126 TotalOffset = getAddExpr(TotalOffset, LocalOffset);
3127 }
3128 }
3129
3130 // Add the total offset from all the GEP indices to the base.
3131 return getAddExpr(BaseExpr, TotalOffset, Wrap);
3132}
3133
3134const SCEV *ScalarEvolution::getSMaxExpr(const SCEV *LHS,
3135 const SCEV *RHS) {
3136 SmallVector<const SCEV *, 2> Ops = {LHS, RHS};
3137 return getSMaxExpr(Ops);
3138}
3139
3140const SCEV *
3141ScalarEvolution::getSMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
3142 assert(!Ops.empty() && "Cannot get empty smax!")((!Ops.empty() && "Cannot get empty smax!") ? static_cast
<void> (0) : __assert_fail ("!Ops.empty() && \"Cannot get empty smax!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3142, __PRETTY_FUNCTION__))
;
3143 if (Ops.size() == 1) return Ops[0];
3144#ifndef NDEBUG
3145 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
3146 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
3147 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&((getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
"SCEVSMaxExpr operand types don't match!") ? static_cast<
void> (0) : __assert_fail ("getEffectiveSCEVType(Ops[i]->getType()) == ETy && \"SCEVSMaxExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3148, __PRETTY_FUNCTION__))
3148 "SCEVSMaxExpr operand types don't match!")((getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
"SCEVSMaxExpr operand types don't match!") ? static_cast<
void> (0) : __assert_fail ("getEffectiveSCEVType(Ops[i]->getType()) == ETy && \"SCEVSMaxExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3148, __PRETTY_FUNCTION__))
;
3149#endif
3150
3151 // Sort by complexity, this groups all similar expression types together.
3152 GroupByComplexity(Ops, &LI);
3153
3154 // If there are any constants, fold them together.
3155 unsigned Idx = 0;
3156 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
3157 ++Idx;
3158 assert(Idx < Ops.size())((Idx < Ops.size()) ? static_cast<void> (0) : __assert_fail
("Idx < Ops.size()", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3158, __PRETTY_FUNCTION__))
;
3159 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
3160 // We found two constants, fold them together!
3161 ConstantInt *Fold = ConstantInt::get(
3162 getContext(), APIntOps::smax(LHSC->getAPInt(), RHSC->getAPInt()));
3163 Ops[0] = getConstant(Fold);
3164 Ops.erase(Ops.begin()+1); // Erase the folded element
3165 if (Ops.size() == 1) return Ops[0];
3166 LHSC = cast<SCEVConstant>(Ops[0]);
3167 }
3168
3169 // If we are left with a constant minimum-int, strip it off.
3170 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(true)) {
3171 Ops.erase(Ops.begin());
3172 --Idx;
3173 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(true)) {
3174 // If we have an smax with a constant maximum-int, it will always be
3175 // maximum-int.
3176 return Ops[0];
3177 }
3178
3179 if (Ops.size() == 1) return Ops[0];
3180 }
3181
3182 // Find the first SMax
3183 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scSMaxExpr)
3184 ++Idx;
3185
3186 // Check to see if one of the operands is an SMax. If so, expand its operands
3187 // onto our operand list, and recurse to simplify.
3188 if (Idx < Ops.size()) {
3189 bool DeletedSMax = false;
3190 while (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(Ops[Idx])) {
3191 Ops.erase(Ops.begin()+Idx);
3192 Ops.append(SMax->op_begin(), SMax->op_end());
3193 DeletedSMax = true;
3194 }
3195
3196 if (DeletedSMax)
3197 return getSMaxExpr(Ops);
3198 }
3199
3200 // Okay, check to see if the same value occurs in the operand list twice. If
3201 // so, delete one. Since we sorted the list, these values are required to
3202 // be adjacent.
3203 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
3204 // X smax Y smax Y --> X smax Y
3205 // X smax Y --> X, if X is always greater than Y
3206 if (Ops[i] == Ops[i+1] ||
3207 isKnownPredicate(ICmpInst::ICMP_SGE, Ops[i], Ops[i+1])) {
3208 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
3209 --i; --e;
3210 } else if (isKnownPredicate(ICmpInst::ICMP_SLE, Ops[i], Ops[i+1])) {
3211 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
3212 --i; --e;
3213 }
3214
3215 if (Ops.size() == 1) return Ops[0];
3216
3217 assert(!Ops.empty() && "Reduced smax down to nothing!")((!Ops.empty() && "Reduced smax down to nothing!") ? static_cast
<void> (0) : __assert_fail ("!Ops.empty() && \"Reduced smax down to nothing!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3217, __PRETTY_FUNCTION__))
;
3218
3219 // Okay, it looks like we really DO need an smax expr. Check to see if we
3220 // already have one, otherwise create a new one.
3221 FoldingSetNodeID ID;
3222 ID.AddInteger(scSMaxExpr);
3223 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
3224 ID.AddPointer(Ops[i]);
3225 void *IP = nullptr;
3226 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
3227 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
3228 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
3229 SCEV *S = new (SCEVAllocator) SCEVSMaxExpr(ID.Intern(SCEVAllocator),
3230 O, Ops.size());
3231 UniqueSCEVs.InsertNode(S, IP);
3232 return S;
3233}
3234
3235const SCEV *ScalarEvolution::getUMaxExpr(const SCEV *LHS,
3236 const SCEV *RHS) {
3237 SmallVector<const SCEV *, 2> Ops = {LHS, RHS};
3238 return getUMaxExpr(Ops);
3239}
3240
3241const SCEV *
3242ScalarEvolution::getUMaxExpr(SmallVectorImpl<const SCEV *> &Ops) {
3243 assert(!Ops.empty() && "Cannot get empty umax!")((!Ops.empty() && "Cannot get empty umax!") ? static_cast
<void> (0) : __assert_fail ("!Ops.empty() && \"Cannot get empty umax!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3243, __PRETTY_FUNCTION__))
;
3244 if (Ops.size() == 1) return Ops[0];
3245#ifndef NDEBUG
3246 Type *ETy = getEffectiveSCEVType(Ops[0]->getType());
3247 for (unsigned i = 1, e = Ops.size(); i != e; ++i)
3248 assert(getEffectiveSCEVType(Ops[i]->getType()) == ETy &&((getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
"SCEVUMaxExpr operand types don't match!") ? static_cast<
void> (0) : __assert_fail ("getEffectiveSCEVType(Ops[i]->getType()) == ETy && \"SCEVUMaxExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3249, __PRETTY_FUNCTION__))
3249 "SCEVUMaxExpr operand types don't match!")((getEffectiveSCEVType(Ops[i]->getType()) == ETy &&
"SCEVUMaxExpr operand types don't match!") ? static_cast<
void> (0) : __assert_fail ("getEffectiveSCEVType(Ops[i]->getType()) == ETy && \"SCEVUMaxExpr operand types don't match!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3249, __PRETTY_FUNCTION__))
;
3250#endif
3251
3252 // Sort by complexity, this groups all similar expression types together.
3253 GroupByComplexity(Ops, &LI);
3254
3255 // If there are any constants, fold them together.
3256 unsigned Idx = 0;
3257 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(Ops[0])) {
3258 ++Idx;
3259 assert(Idx < Ops.size())((Idx < Ops.size()) ? static_cast<void> (0) : __assert_fail
("Idx < Ops.size()", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3259, __PRETTY_FUNCTION__))
;
3260 while (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(Ops[Idx])) {
3261 // We found two constants, fold them together!
3262 ConstantInt *Fold = ConstantInt::get(
3263 getContext(), APIntOps::umax(LHSC->getAPInt(), RHSC->getAPInt()));
3264 Ops[0] = getConstant(Fold);
3265 Ops.erase(Ops.begin()+1); // Erase the folded element
3266 if (Ops.size() == 1) return Ops[0];
3267 LHSC = cast<SCEVConstant>(Ops[0]);
3268 }
3269
3270 // If we are left with a constant minimum-int, strip it off.
3271 if (cast<SCEVConstant>(Ops[0])->getValue()->isMinValue(false)) {
3272 Ops.erase(Ops.begin());
3273 --Idx;
3274 } else if (cast<SCEVConstant>(Ops[0])->getValue()->isMaxValue(false)) {
3275 // If we have an umax with a constant maximum-int, it will always be
3276 // maximum-int.
3277 return Ops[0];
3278 }
3279
3280 if (Ops.size() == 1) return Ops[0];
3281 }
3282
3283 // Find the first UMax
3284 while (Idx < Ops.size() && Ops[Idx]->getSCEVType() < scUMaxExpr)
3285 ++Idx;
3286
3287 // Check to see if one of the operands is a UMax. If so, expand its operands
3288 // onto our operand list, and recurse to simplify.
3289 if (Idx < Ops.size()) {
3290 bool DeletedUMax = false;
3291 while (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(Ops[Idx])) {
3292 Ops.erase(Ops.begin()+Idx);
3293 Ops.append(UMax->op_begin(), UMax->op_end());
3294 DeletedUMax = true;
3295 }
3296
3297 if (DeletedUMax)
3298 return getUMaxExpr(Ops);
3299 }
3300
3301 // Okay, check to see if the same value occurs in the operand list twice. If
3302 // so, delete one. Since we sorted the list, these values are required to
3303 // be adjacent.
3304 for (unsigned i = 0, e = Ops.size()-1; i != e; ++i)
3305 // X umax Y umax Y --> X umax Y
3306 // X umax Y --> X, if X is always greater than Y
3307 if (Ops[i] == Ops[i+1] ||
3308 isKnownPredicate(ICmpInst::ICMP_UGE, Ops[i], Ops[i+1])) {
3309 Ops.erase(Ops.begin()+i+1, Ops.begin()+i+2);
3310 --i; --e;
3311 } else if (isKnownPredicate(ICmpInst::ICMP_ULE, Ops[i], Ops[i+1])) {
3312 Ops.erase(Ops.begin()+i, Ops.begin()+i+1);
3313 --i; --e;
3314 }
3315
3316 if (Ops.size() == 1) return Ops[0];
3317
3318 assert(!Ops.empty() && "Reduced umax down to nothing!")((!Ops.empty() && "Reduced umax down to nothing!") ? static_cast
<void> (0) : __assert_fail ("!Ops.empty() && \"Reduced umax down to nothing!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3318, __PRETTY_FUNCTION__))
;
3319
3320 // Okay, it looks like we really DO need a umax expr. Check to see if we
3321 // already have one, otherwise create a new one.
3322 FoldingSetNodeID ID;
3323 ID.AddInteger(scUMaxExpr);
3324 for (unsigned i = 0, e = Ops.size(); i != e; ++i)
3325 ID.AddPointer(Ops[i]);
3326 void *IP = nullptr;
3327 if (const SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) return S;
3328 const SCEV **O = SCEVAllocator.Allocate<const SCEV *>(Ops.size());
3329 std::uninitialized_copy(Ops.begin(), Ops.end(), O);
3330 SCEV *S = new (SCEVAllocator) SCEVUMaxExpr(ID.Intern(SCEVAllocator),
3331 O, Ops.size());
3332 UniqueSCEVs.InsertNode(S, IP);
3333 return S;
3334}
3335
3336const SCEV *ScalarEvolution::getSMinExpr(const SCEV *LHS,
3337 const SCEV *RHS) {
3338 // ~smax(~x, ~y) == smin(x, y).
3339 return getNotSCEV(getSMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
3340}
3341
3342const SCEV *ScalarEvolution::getUMinExpr(const SCEV *LHS,
3343 const SCEV *RHS) {
3344 // ~umax(~x, ~y) == umin(x, y)
3345 return getNotSCEV(getUMaxExpr(getNotSCEV(LHS), getNotSCEV(RHS)));
3346}
3347
3348const SCEV *ScalarEvolution::getSizeOfExpr(Type *IntTy, Type *AllocTy) {
3349 // We can bypass creating a target-independent
3350 // constant expression and then folding it back into a ConstantInt.
3351 // This is just a compile-time optimization.
3352 return getConstant(IntTy, getDataLayout().getTypeAllocSize(AllocTy));
3353}
3354
3355const SCEV *ScalarEvolution::getOffsetOfExpr(Type *IntTy,
3356 StructType *STy,
3357 unsigned FieldNo) {
3358 // We can bypass creating a target-independent
3359 // constant expression and then folding it back into a ConstantInt.
3360 // This is just a compile-time optimization.
3361 return getConstant(
3362 IntTy, getDataLayout().getStructLayout(STy)->getElementOffset(FieldNo));
3363}
3364
3365const SCEV *ScalarEvolution::getUnknown(Value *V) {
3366 // Don't attempt to do anything other than create a SCEVUnknown object
3367 // here. createSCEV only calls getUnknown after checking for all other
3368 // interesting possibilities, and any other code that calls getUnknown
3369 // is doing so in order to hide a value from SCEV canonicalization.
3370
3371 FoldingSetNodeID ID;
3372 ID.AddInteger(scUnknown);
3373 ID.AddPointer(V);
3374 void *IP = nullptr;
3375 if (SCEV *S = UniqueSCEVs.FindNodeOrInsertPos(ID, IP)) {
3376 assert(cast<SCEVUnknown>(S)->getValue() == V &&((cast<SCEVUnknown>(S)->getValue() == V && "Stale SCEVUnknown in uniquing map!"
) ? static_cast<void> (0) : __assert_fail ("cast<SCEVUnknown>(S)->getValue() == V && \"Stale SCEVUnknown in uniquing map!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3377, __PRETTY_FUNCTION__))
3377 "Stale SCEVUnknown in uniquing map!")((cast<SCEVUnknown>(S)->getValue() == V && "Stale SCEVUnknown in uniquing map!"
) ? static_cast<void> (0) : __assert_fail ("cast<SCEVUnknown>(S)->getValue() == V && \"Stale SCEVUnknown in uniquing map!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3377, __PRETTY_FUNCTION__))
;
3378 return S;
3379 }
3380 SCEV *S = new (SCEVAllocator) SCEVUnknown(ID.Intern(SCEVAllocator), V, this,
3381 FirstUnknown);
3382 FirstUnknown = cast<SCEVUnknown>(S);
3383 UniqueSCEVs.InsertNode(S, IP);
3384 return S;
3385}
3386
3387//===----------------------------------------------------------------------===//
3388// Basic SCEV Analysis and PHI Idiom Recognition Code
3389//
3390
3391/// Test if values of the given type are analyzable within the SCEV
3392/// framework. This primarily includes integer types, and it can optionally
3393/// include pointer types if the ScalarEvolution class has access to
3394/// target-specific information.
3395bool ScalarEvolution::isSCEVable(Type *Ty) const {
3396 // Integers and pointers are always SCEVable.
3397 return Ty->isIntegerTy() || Ty->isPointerTy();
3398}
3399
3400/// Return the size in bits of the specified type, for which isSCEVable must
3401/// return true.
3402uint64_t ScalarEvolution::getTypeSizeInBits(Type *Ty) const {
3403 assert(isSCEVable(Ty) && "Type is not SCEVable!")((isSCEVable(Ty) && "Type is not SCEVable!") ? static_cast
<void> (0) : __assert_fail ("isSCEVable(Ty) && \"Type is not SCEVable!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3403, __PRETTY_FUNCTION__))
;
3404 return getDataLayout().getTypeSizeInBits(Ty);
3405}
3406
3407/// Return a type with the same bitwidth as the given type and which represents
3408/// how SCEV will treat the given type, for which isSCEVable must return
3409/// true. For pointer types, this is the pointer-sized integer type.
3410Type *ScalarEvolution::getEffectiveSCEVType(Type *Ty) const {
3411 assert(isSCEVable(Ty) && "Type is not SCEVable!")((isSCEVable(Ty) && "Type is not SCEVable!") ? static_cast
<void> (0) : __assert_fail ("isSCEVable(Ty) && \"Type is not SCEVable!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3411, __PRETTY_FUNCTION__))
;
3412
3413 if (Ty->isIntegerTy())
3414 return Ty;
3415
3416 // The only other support type is pointer.
3417 assert(Ty->isPointerTy() && "Unexpected non-pointer non-integer type!")((Ty->isPointerTy() && "Unexpected non-pointer non-integer type!"
) ? static_cast<void> (0) : __assert_fail ("Ty->isPointerTy() && \"Unexpected non-pointer non-integer type!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3417, __PRETTY_FUNCTION__))
;
3418 return getDataLayout().getIntPtrType(Ty);
3419}
3420
3421const SCEV *ScalarEvolution::getCouldNotCompute() {
3422 return CouldNotCompute.get();
3423}
3424
3425bool ScalarEvolution::checkValidity(const SCEV *S) const {
3426 bool ContainsNulls = SCEVExprContains(S, [](const SCEV *S) {
3427 auto *SU = dyn_cast<SCEVUnknown>(S);
3428 return SU && SU->getValue() == nullptr;
3429 });
3430
3431 return !ContainsNulls;
3432}
3433
3434bool ScalarEvolution::containsAddRecurrence(const SCEV *S) {
3435 HasRecMapType::iterator I = HasRecMap.find(S);
3436 if (I != HasRecMap.end())
3437 return I->second;
3438
3439 bool FoundAddRec = SCEVExprContains(S, isa<SCEVAddRecExpr, const SCEV *>);
3440 HasRecMap.insert({S, FoundAddRec});
3441 return FoundAddRec;
3442}
3443
3444/// Try to split a SCEVAddExpr into a pair of {SCEV, ConstantInt}.
3445/// If \p S is a SCEVAddExpr and is composed of a sub SCEV S' and an
3446/// offset I, then return {S', I}, else return {\p S, nullptr}.
3447static std::pair<const SCEV *, ConstantInt *> splitAddExpr(const SCEV *S) {
3448 const auto *Add = dyn_cast<SCEVAddExpr>(S);
3449 if (!Add)
3450 return {S, nullptr};
3451
3452 if (Add->getNumOperands() != 2)
3453 return {S, nullptr};
3454
3455 auto *ConstOp = dyn_cast<SCEVConstant>(Add->getOperand(0));
3456 if (!ConstOp)
3457 return {S, nullptr};
3458
3459 return {Add->getOperand(1), ConstOp->getValue()};
3460}
3461
3462/// Return the ValueOffsetPair set for \p S. \p S can be represented
3463/// by the value and offset from any ValueOffsetPair in the set.
3464SetVector<ScalarEvolution::ValueOffsetPair> *
3465ScalarEvolution::getSCEVValues(const SCEV *S) {
3466 ExprValueMapType::iterator SI = ExprValueMap.find_as(S);
3467 if (SI == ExprValueMap.end())
3468 return nullptr;
3469#ifndef NDEBUG
3470 if (VerifySCEVMap) {
3471 // Check there is no dangling Value in the set returned.
3472 for (const auto &VE : SI->second)
3473 assert(ValueExprMap.count(VE.first))((ValueExprMap.count(VE.first)) ? static_cast<void> (0)
: __assert_fail ("ValueExprMap.count(VE.first)", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3473, __PRETTY_FUNCTION__))
;
3474 }
3475#endif
3476 return &SI->second;
3477}
3478
3479/// Erase Value from ValueExprMap and ExprValueMap. ValueExprMap.erase(V)
3480/// cannot be used separately. eraseValueFromMap should be used to remove
3481/// V from ValueExprMap and ExprValueMap at the same time.
3482void ScalarEvolution::eraseValueFromMap(Value *V) {
3483 ValueExprMapType::iterator I = ValueExprMap.find_as(V);
3484 if (I != ValueExprMap.end()) {
3485 const SCEV *S = I->second;
3486 // Remove {V, 0} from the set of ExprValueMap[S]
3487 if (SetVector<ValueOffsetPair> *SV = getSCEVValues(S))
3488 SV->remove({V, nullptr});
3489
3490 // Remove {V, Offset} from the set of ExprValueMap[Stripped]
3491 const SCEV *Stripped;
3492 ConstantInt *Offset;
3493 std::tie(Stripped, Offset) = splitAddExpr(S);
3494 if (Offset != nullptr) {
3495 if (SetVector<ValueOffsetPair> *SV = getSCEVValues(Stripped))
3496 SV->remove({V, Offset});
3497 }
3498 ValueExprMap.erase(V);
3499 }
3500}
3501
3502/// Return an existing SCEV if it exists, otherwise analyze the expression and
3503/// create a new one.
3504const SCEV *ScalarEvolution::getSCEV(Value *V) {
3505 assert(isSCEVable(V->getType()) && "Value is not SCEVable!")((isSCEVable(V->getType()) && "Value is not SCEVable!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(V->getType()) && \"Value is not SCEVable!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3505, __PRETTY_FUNCTION__))
;
3506
3507 const SCEV *S = getExistingSCEV(V);
3508 if (S == nullptr) {
3509 S = createSCEV(V);
3510 // During PHI resolution, it is possible to create two SCEVs for the same
3511 // V, so it is needed to double check whether V->S is inserted into
3512 // ValueExprMap before insert S->{V, 0} into ExprValueMap.
3513 std::pair<ValueExprMapType::iterator, bool> Pair =
3514 ValueExprMap.insert({SCEVCallbackVH(V, this), S});
3515 if (Pair.second) {
3516 ExprValueMap[S].insert({V, nullptr});
3517
3518 // If S == Stripped + Offset, add Stripped -> {V, Offset} into
3519 // ExprValueMap.
3520 const SCEV *Stripped = S;
3521 ConstantInt *Offset = nullptr;
3522 std::tie(Stripped, Offset) = splitAddExpr(S);
3523 // If stripped is SCEVUnknown, don't bother to save
3524 // Stripped -> {V, offset}. It doesn't simplify and sometimes even
3525 // increase the complexity of the expansion code.
3526 // If V is GetElementPtrInst, don't save Stripped -> {V, offset}
3527 // because it may generate add/sub instead of GEP in SCEV expansion.
3528 if (Offset != nullptr && !isa<SCEVUnknown>(Stripped) &&
3529 !isa<GetElementPtrInst>(V))
3530 ExprValueMap[Stripped].insert({V, Offset});
3531 }
3532 }
3533 return S;
3534}
3535
3536const SCEV *ScalarEvolution::getExistingSCEV(Value *V) {
3537 assert(isSCEVable(V->getType()) && "Value is not SCEVable!")((isSCEVable(V->getType()) && "Value is not SCEVable!"
) ? static_cast<void> (0) : __assert_fail ("isSCEVable(V->getType()) && \"Value is not SCEVable!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3537, __PRETTY_FUNCTION__))
;
3538
3539 ValueExprMapType::iterator I = ValueExprMap.find_as(V);
3540 if (I != ValueExprMap.end()) {
3541 const SCEV *S = I->second;
3542 if (checkValidity(S))
3543 return S;
3544 eraseValueFromMap(V);
3545 forgetMemoizedResults(S);
3546 }
3547 return nullptr;
3548}
3549
3550/// Return a SCEV corresponding to -V = -1*V
3551///
3552const SCEV *ScalarEvolution::getNegativeSCEV(const SCEV *V,
3553 SCEV::NoWrapFlags Flags) {
3554 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3555 return getConstant(
3556 cast<ConstantInt>(ConstantExpr::getNeg(VC->getValue())));
3557
3558 Type *Ty = V->getType();
3559 Ty = getEffectiveSCEVType(Ty);
3560 return getMulExpr(
3561 V, getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty))), Flags);
3562}
3563
3564/// Return a SCEV corresponding to ~V = -1-V
3565const SCEV *ScalarEvolution::getNotSCEV(const SCEV *V) {
3566 if (const SCEVConstant *VC = dyn_cast<SCEVConstant>(V))
3567 return getConstant(
3568 cast<ConstantInt>(ConstantExpr::getNot(VC->getValue())));
3569
3570 Type *Ty = V->getType();
3571 Ty = getEffectiveSCEVType(Ty);
3572 const SCEV *AllOnes =
3573 getConstant(cast<ConstantInt>(Constant::getAllOnesValue(Ty)));
3574 return getMinusSCEV(AllOnes, V);
3575}
3576
3577const SCEV *ScalarEvolution::getMinusSCEV(const SCEV *LHS, const SCEV *RHS,
3578 SCEV::NoWrapFlags Flags) {
3579 // Fast path: X - X --> 0.
3580 if (LHS == RHS)
3581 return getZero(LHS->getType());
3582
3583 // We represent LHS - RHS as LHS + (-1)*RHS. This transformation
3584 // makes it so that we cannot make much use of NUW.
3585 auto AddFlags = SCEV::FlagAnyWrap;
3586 const bool RHSIsNotMinSigned =
3587 !getSignedRange(RHS).getSignedMin().isMinSignedValue();
3588 if (maskFlags(Flags, SCEV::FlagNSW) == SCEV::FlagNSW) {
3589 // Let M be the minimum representable signed value. Then (-1)*RHS
3590 // signed-wraps if and only if RHS is M. That can happen even for
3591 // a NSW subtraction because e.g. (-1)*M signed-wraps even though
3592 // -1 - M does not. So to transfer NSW from LHS - RHS to LHS +
3593 // (-1)*RHS, we need to prove that RHS != M.
3594 //
3595 // If LHS is non-negative and we know that LHS - RHS does not
3596 // signed-wrap, then RHS cannot be M. So we can rule out signed-wrap
3597 // either by proving that RHS > M or that LHS >= 0.
3598 if (RHSIsNotMinSigned || isKnownNonNegative(LHS)) {
3599 AddFlags = SCEV::FlagNSW;
3600 }
3601 }
3602
3603 // FIXME: Find a correct way to transfer NSW to (-1)*M when LHS -
3604 // RHS is NSW and LHS >= 0.
3605 //
3606 // The difficulty here is that the NSW flag may have been proven
3607 // relative to a loop that is to be found in a recurrence in LHS and
3608 // not in RHS. Applying NSW to (-1)*M may then let the NSW have a
3609 // larger scope than intended.
3610 auto NegFlags = RHSIsNotMinSigned ? SCEV::FlagNSW : SCEV::FlagAnyWrap;
3611
3612 return getAddExpr(LHS, getNegativeSCEV(RHS, NegFlags), AddFlags);
3613}
3614
3615const SCEV *
3616ScalarEvolution::getTruncateOrZeroExtend(const SCEV *V, Type *Ty) {
3617 Type *SrcTy = V->getType();
3618 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot truncate or zero extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate or zero extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3620, __PRETTY_FUNCTION__))
3619 (Ty->isIntegerTy() || Ty->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot truncate or zero extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate or zero extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3620, __PRETTY_FUNCTION__))
3620 "Cannot truncate or zero extend with non-integer arguments!")(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot truncate or zero extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate or zero extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3620, __PRETTY_FUNCTION__))
;
3621 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3622 return V; // No conversion
3623 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3624 return getTruncateExpr(V, Ty);
3625 return getZeroExtendExpr(V, Ty);
3626}
3627
3628const SCEV *
3629ScalarEvolution::getTruncateOrSignExtend(const SCEV *V,
3630 Type *Ty) {
3631 Type *SrcTy = V->getType();
3632 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot truncate or zero extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate or zero extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3634, __PRETTY_FUNCTION__))
3633 (Ty->isIntegerTy() || Ty->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot truncate or zero extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate or zero extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3634, __PRETTY_FUNCTION__))
3634 "Cannot truncate or zero extend with non-integer arguments!")(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot truncate or zero extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate or zero extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3634, __PRETTY_FUNCTION__))
;
3635 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3636 return V; // No conversion
3637 if (getTypeSizeInBits(SrcTy) > getTypeSizeInBits(Ty))
3638 return getTruncateExpr(V, Ty);
3639 return getSignExtendExpr(V, Ty);
3640}
3641
3642const SCEV *
3643ScalarEvolution::getNoopOrZeroExtend(const SCEV *V, Type *Ty) {
3644 Type *SrcTy = V->getType();
3645 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot noop or zero extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot noop or zero extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3647, __PRETTY_FUNCTION__))
3646 (Ty->isIntegerTy() || Ty->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot noop or zero extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot noop or zero extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3647, __PRETTY_FUNCTION__))
3647 "Cannot noop or zero extend with non-integer arguments!")(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot noop or zero extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot noop or zero extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3647, __PRETTY_FUNCTION__))
;
3648 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&((getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
"getNoopOrZeroExtend cannot truncate!") ? static_cast<void
> (0) : __assert_fail ("getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) && \"getNoopOrZeroExtend cannot truncate!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3649, __PRETTY_FUNCTION__))
3649 "getNoopOrZeroExtend cannot truncate!")((getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
"getNoopOrZeroExtend cannot truncate!") ? static_cast<void
> (0) : __assert_fail ("getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) && \"getNoopOrZeroExtend cannot truncate!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3649, __PRETTY_FUNCTION__))
;
3650 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3651 return V; // No conversion
3652 return getZeroExtendExpr(V, Ty);
3653}
3654
3655const SCEV *
3656ScalarEvolution::getNoopOrSignExtend(const SCEV *V, Type *Ty) {
3657 Type *SrcTy = V->getType();
3658 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot noop or sign extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot noop or sign extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3660, __PRETTY_FUNCTION__))
3659 (Ty->isIntegerTy() || Ty->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot noop or sign extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot noop or sign extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3660, __PRETTY_FUNCTION__))
3660 "Cannot noop or sign extend with non-integer arguments!")(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot noop or sign extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot noop or sign extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3660, __PRETTY_FUNCTION__))
;
3661 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&((getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
"getNoopOrSignExtend cannot truncate!") ? static_cast<void
> (0) : __assert_fail ("getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) && \"getNoopOrSignExtend cannot truncate!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3662, __PRETTY_FUNCTION__))
3662 "getNoopOrSignExtend cannot truncate!")((getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
"getNoopOrSignExtend cannot truncate!") ? static_cast<void
> (0) : __assert_fail ("getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) && \"getNoopOrSignExtend cannot truncate!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3662, __PRETTY_FUNCTION__))
;
3663 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3664 return V; // No conversion
3665 return getSignExtendExpr(V, Ty);
3666}
3667
3668const SCEV *
3669ScalarEvolution::getNoopOrAnyExtend(const SCEV *V, Type *Ty) {
3670 Type *SrcTy = V->getType();
3671 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot noop or any extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot noop or any extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3673, __PRETTY_FUNCTION__))
3672 (Ty->isIntegerTy() || Ty->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot noop or any extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot noop or any extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3673, __PRETTY_FUNCTION__))
3673 "Cannot noop or any extend with non-integer arguments!")(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot noop or any extend with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot noop or any extend with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3673, __PRETTY_FUNCTION__))
;
3674 assert(getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&((getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
"getNoopOrAnyExtend cannot truncate!") ? static_cast<void
> (0) : __assert_fail ("getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) && \"getNoopOrAnyExtend cannot truncate!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3675, __PRETTY_FUNCTION__))
3675 "getNoopOrAnyExtend cannot truncate!")((getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) &&
"getNoopOrAnyExtend cannot truncate!") ? static_cast<void
> (0) : __assert_fail ("getTypeSizeInBits(SrcTy) <= getTypeSizeInBits(Ty) && \"getNoopOrAnyExtend cannot truncate!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3675, __PRETTY_FUNCTION__))
;
3676 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3677 return V; // No conversion
3678 return getAnyExtendExpr(V, Ty);
3679}
3680
3681const SCEV *
3682ScalarEvolution::getTruncateOrNoop(const SCEV *V, Type *Ty) {
3683 Type *SrcTy = V->getType();
3684 assert((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot truncate or noop with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate or noop with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3686, __PRETTY_FUNCTION__))
3685 (Ty->isIntegerTy() || Ty->isPointerTy()) &&(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot truncate or noop with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate or noop with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3686, __PRETTY_FUNCTION__))
3686 "Cannot truncate or noop with non-integer arguments!")(((SrcTy->isIntegerTy() || SrcTy->isPointerTy()) &&
(Ty->isIntegerTy() || Ty->isPointerTy()) && "Cannot truncate or noop with non-integer arguments!"
) ? static_cast<void> (0) : __assert_fail ("(SrcTy->isIntegerTy() || SrcTy->isPointerTy()) && (Ty->isIntegerTy() || Ty->isPointerTy()) && \"Cannot truncate or noop with non-integer arguments!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3686, __PRETTY_FUNCTION__))
;
3687 assert(getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&((getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
"getTruncateOrNoop cannot extend!") ? static_cast<void>
(0) : __assert_fail ("getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) && \"getTruncateOrNoop cannot extend!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3688, __PRETTY_FUNCTION__))
3688 "getTruncateOrNoop cannot extend!")((getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) &&
"getTruncateOrNoop cannot extend!") ? static_cast<void>
(0) : __assert_fail ("getTypeSizeInBits(SrcTy) >= getTypeSizeInBits(Ty) && \"getTruncateOrNoop cannot extend!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 3688, __PRETTY_FUNCTION__))
;
3689 if (getTypeSizeInBits(SrcTy) == getTypeSizeInBits(Ty))
3690 return V; // No conversion
3691 return getTruncateExpr(V, Ty);
3692}
3693
3694const SCEV *ScalarEvolution::getUMaxFromMismatchedTypes(const SCEV *LHS,
3695 const SCEV *RHS) {
3696 const SCEV *PromotedLHS = LHS;
3697 const SCEV *PromotedRHS = RHS;
3698
3699 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3700 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3701 else
3702 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3703
3704 return getUMaxExpr(PromotedLHS, PromotedRHS);
3705}
3706
3707const SCEV *ScalarEvolution::getUMinFromMismatchedTypes(const SCEV *LHS,
3708 const SCEV *RHS) {
3709 const SCEV *PromotedLHS = LHS;
3710 const SCEV *PromotedRHS = RHS;
3711
3712 if (getTypeSizeInBits(LHS->getType()) > getTypeSizeInBits(RHS->getType()))
3713 PromotedRHS = getZeroExtendExpr(RHS, LHS->getType());
3714 else
3715 PromotedLHS = getNoopOrZeroExtend(LHS, RHS->getType());
3716
3717 return getUMinExpr(PromotedLHS, PromotedRHS);
3718}
3719
3720const SCEV *ScalarEvolution::getPointerBase(const SCEV *V) {
3721 // A pointer operand may evaluate to a nonpointer expression, such as null.
3722 if (!V->getType()->isPointerTy())
3723 return V;
3724
3725 if (const SCEVCastExpr *Cast = dyn_cast<SCEVCastExpr>(V)) {
3726 return getPointerBase(Cast->getOperand());
3727 } else if (const SCEVNAryExpr *NAry = dyn_cast<SCEVNAryExpr>(V)) {
3728 const SCEV *PtrOp = nullptr;
3729 for (const SCEV *NAryOp : NAry->operands()) {
3730 if (NAryOp->getType()->isPointerTy()) {
3731 // Cannot find the base of an expression with multiple pointer operands.
3732 if (PtrOp)
3733 return V;
3734 PtrOp = NAryOp;
3735 }
3736 }
3737 if (!PtrOp)
3738 return V;
3739 return getPointerBase(PtrOp);
3740 }
3741 return V;
3742}
3743
3744/// Push users of the given Instruction onto the given Worklist.
3745static void
3746PushDefUseChildren(Instruction *I,
3747 SmallVectorImpl<Instruction *> &Worklist) {
3748 // Push the def-use children onto the Worklist stack.
3749 for (User *U : I->users())
3750 Worklist.push_back(cast<Instruction>(U));
3751}
3752
3753void ScalarEvolution::forgetSymbolicName(Instruction *PN, const SCEV *SymName) {
3754 SmallVector<Instruction *, 16> Worklist;
3755 PushDefUseChildren(PN, Worklist);
3756
3757 SmallPtrSet<Instruction *, 8> Visited;
3758 Visited.insert(PN);
3759 while (!Worklist.empty()) {
3760 Instruction *I = Worklist.pop_back_val();
3761 if (!Visited.insert(I).second)
3762 continue;
3763
3764 auto It = ValueExprMap.find_as(static_cast<Value *>(I));
3765 if (It != ValueExprMap.end()) {
3766 const SCEV *Old = It->second;
3767
3768 // Short-circuit the def-use traversal if the symbolic name
3769 // ceases to appear in expressions.
3770 if (Old != SymName && !hasOperand(Old, SymName))
3771 continue;
3772
3773 // SCEVUnknown for a PHI either means that it has an unrecognized
3774 // structure, it's a PHI that's in the progress of being computed
3775 // by createNodeForPHI, or it's a single-value PHI. In the first case,
3776 // additional loop trip count information isn't going to change anything.
3777 // In the second case, createNodeForPHI will perform the necessary
3778 // updates on its own when it gets to that point. In the third, we do
3779 // want to forget the SCEVUnknown.
3780 if (!isa<PHINode>(I) ||
3781 !isa<SCEVUnknown>(Old) ||
3782 (I != PN && Old == SymName)) {
3783 eraseValueFromMap(It->first);
3784 forgetMemoizedResults(Old);
3785 }
3786 }
3787
3788 PushDefUseChildren(I, Worklist);
3789 }
3790}
3791
3792namespace {
3793class SCEVInitRewriter : public SCEVRewriteVisitor<SCEVInitRewriter> {
3794public:
3795 static const SCEV *rewrite(const SCEV *S, const Loop *L,
3796 ScalarEvolution &SE) {
3797 SCEVInitRewriter Rewriter(L, SE);
3798 const SCEV *Result = Rewriter.visit(S);
3799 return Rewriter.isValid() ? Result : SE.getCouldNotCompute();
3800 }
3801
3802 SCEVInitRewriter(const Loop *L, ScalarEvolution &SE)
3803 : SCEVRewriteVisitor(SE), L(L), Valid(true) {}
3804
3805 const SCEV *visitUnknown(const SCEVUnknown *Expr) {
3806 if (!(SE.getLoopDisposition(Expr, L) == ScalarEvolution::LoopInvariant))
3807 Valid = false;
3808 return Expr;
3809 }
3810
3811 const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) {
3812 // Only allow AddRecExprs for this loop.
3813 if (Expr->getLoop() == L)
3814 return Expr->getStart();
3815 Valid = false;
3816 return Expr;
3817 }
3818
3819 bool isValid() { return Valid; }
3820
3821private:
3822 const Loop *L;
3823 bool Valid;
3824};
3825
3826class SCEVShiftRewriter : public SCEVRewriteVisitor<SCEVShiftRewriter> {
3827public:
3828 static const SCEV *rewrite(const SCEV *S, const Loop *L,
3829 ScalarEvolution &SE) {
3830 SCEVShiftRewriter Rewriter(L, SE);
3831 const SCEV *Result = Rewriter.visit(S);
3832 return Rewriter.isValid() ? Result : SE.getCouldNotCompute();
3833 }
3834
3835 SCEVShiftRewriter(const Loop *L, ScalarEvolution &SE)
3836 : SCEVRewriteVisitor(SE), L(L), Valid(true) {}
3837
3838 const SCEV *visitUnknown(const SCEVUnknown *Expr) {
3839 // Only allow AddRecExprs for this loop.
3840 if (!(SE.getLoopDisposition(Expr, L) == ScalarEvolution::LoopInvariant))
3841 Valid = false;
3842 return Expr;
3843 }
3844
3845 const SCEV *visitAddRecExpr(const SCEVAddRecExpr *Expr) {
3846 if (Expr->getLoop() == L && Expr->isAffine())
3847 return SE.getMinusSCEV(Expr, Expr->getStepRecurrence(SE));
3848 Valid = false;
3849 return Expr;
3850 }
3851 bool isValid() { return Valid; }
3852
3853private:
3854 const Loop *L;
3855 bool Valid;
3856};
3857} // end anonymous namespace
3858
3859SCEV::NoWrapFlags
3860ScalarEvolution::proveNoWrapViaConstantRanges(const SCEVAddRecExpr *AR) {
3861 if (!AR->isAffine())
3862 return SCEV::FlagAnyWrap;
3863
3864 typedef OverflowingBinaryOperator OBO;
3865 SCEV::NoWrapFlags Result = SCEV::FlagAnyWrap;
3866
3867 if (!AR->hasNoSignedWrap()) {
3868 ConstantRange AddRecRange = getSignedRange(AR);
3869 ConstantRange IncRange = getSignedRange(AR->getStepRecurrence(*this));
3870
3871 auto NSWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
3872 Instruction::Add, IncRange, OBO::NoSignedWrap);
3873 if (NSWRegion.contains(AddRecRange))
3874 Result = ScalarEvolution::setFlags(Result, SCEV::FlagNSW);
3875 }
3876
3877 if (!AR->hasNoUnsignedWrap()) {
3878 ConstantRange AddRecRange = getUnsignedRange(AR);
3879 ConstantRange IncRange = getUnsignedRange(AR->getStepRecurrence(*this));
3880
3881 auto NUWRegion = ConstantRange::makeGuaranteedNoWrapRegion(
3882 Instruction::Add, IncRange, OBO::NoUnsignedWrap);
3883 if (NUWRegion.contains(AddRecRange))
3884 Result = ScalarEvolution::setFlags(Result, SCEV::FlagNUW);
3885 }
3886
3887 return Result;
3888}
3889
3890namespace {
3891/// Represents an abstract binary operation. This may exist as a
3892/// normal instruction or constant expression, or may have been
3893/// derived from an expression tree.
3894struct BinaryOp {
3895 unsigned Opcode;
3896 Value *LHS;
3897 Value *RHS;
3898 bool IsNSW;
3899 bool IsNUW;
3900
3901 /// Op is set if this BinaryOp corresponds to a concrete LLVM instruction or
3902 /// constant expression.
3903 Operator *Op;
3904
3905 explicit BinaryOp(Operator *Op)
3906 : Opcode(Op->getOpcode()), LHS(Op->getOperand(0)), RHS(Op->getOperand(1)),
3907 IsNSW(false), IsNUW(false), Op(Op) {
3908 if (auto *OBO = dyn_cast<OverflowingBinaryOperator>(Op)) {
3909 IsNSW = OBO->hasNoSignedWrap();
3910 IsNUW = OBO->hasNoUnsignedWrap();
3911 }
3912 }
3913
3914 explicit BinaryOp(unsigned Opcode, Value *LHS, Value *RHS, bool IsNSW = false,
3915 bool IsNUW = false)
3916 : Opcode(Opcode), LHS(LHS), RHS(RHS), IsNSW(IsNSW), IsNUW(IsNUW),
3917 Op(nullptr) {}
3918};
3919}
3920
3921
3922/// Try to map \p V into a BinaryOp, and return \c None on failure.
3923static Optional<BinaryOp> MatchBinaryOp(Value *V, DominatorTree &DT) {
3924 auto *Op = dyn_cast<Operator>(V);
3925 if (!Op)
3926 return None;
3927
3928 // Implementation detail: all the cleverness here should happen without
3929 // creating new SCEV expressions -- our caller knowns tricks to avoid creating
3930 // SCEV expressions when possible, and we should not break that.
3931
3932 switch (Op->getOpcode()) {
3933 case Instruction::Add:
3934 case Instruction::Sub:
3935 case Instruction::Mul:
3936 case Instruction::UDiv:
3937 case Instruction::And:
3938 case Instruction::Or:
3939 case Instruction::AShr:
3940 case Instruction::Shl:
3941 return BinaryOp(Op);
3942
3943 case Instruction::Xor:
3944 if (auto *RHSC = dyn_cast<ConstantInt>(Op->getOperand(1)))
3945 // If the RHS of the xor is a signbit, then this is just an add.
3946 // Instcombine turns add of signbit into xor as a strength reduction step.
3947 if (RHSC->getValue().isSignBit())
3948 return BinaryOp(Instruction::Add, Op->getOperand(0), Op->getOperand(1));
3949 return BinaryOp(Op);
3950
3951 case Instruction::LShr:
3952 // Turn logical shift right of a constant into a unsigned divide.
3953 if (ConstantInt *SA = dyn_cast<ConstantInt>(Op->getOperand(1))) {
3954 uint32_t BitWidth = cast<IntegerType>(Op->getType())->getBitWidth();
3955
3956 // If the shift count is not less than the bitwidth, the result of
3957 // the shift is undefined. Don't try to analyze it, because the
3958 // resolution chosen here may differ from the resolution chosen in
3959 // other parts of the compiler.
3960 if (SA->getValue().ult(BitWidth)) {
3961 Constant *X =
3962 ConstantInt::get(SA->getContext(),
3963 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
3964 return BinaryOp(Instruction::UDiv, Op->getOperand(0), X);
3965 }
3966 }
3967 return BinaryOp(Op);
3968
3969 case Instruction::ExtractValue: {
3970 auto *EVI = cast<ExtractValueInst>(Op);
3971 if (EVI->getNumIndices() != 1 || EVI->getIndices()[0] != 0)
3972 break;
3973
3974 auto *CI = dyn_cast<CallInst>(EVI->getAggregateOperand());
3975 if (!CI)
3976 break;
3977
3978 if (auto *F = CI->getCalledFunction())
3979 switch (F->getIntrinsicID()) {
3980 case Intrinsic::sadd_with_overflow:
3981 case Intrinsic::uadd_with_overflow: {
3982 if (!isOverflowIntrinsicNoWrap(cast<IntrinsicInst>(CI), DT))
3983 return BinaryOp(Instruction::Add, CI->getArgOperand(0),
3984 CI->getArgOperand(1));
3985
3986 // Now that we know that all uses of the arithmetic-result component of
3987 // CI are guarded by the overflow check, we can go ahead and pretend
3988 // that the arithmetic is non-overflowing.
3989 if (F->getIntrinsicID() == Intrinsic::sadd_with_overflow)
3990 return BinaryOp(Instruction::Add, CI->getArgOperand(0),
3991 CI->getArgOperand(1), /* IsNSW = */ true,
3992 /* IsNUW = */ false);
3993 else
3994 return BinaryOp(Instruction::Add, CI->getArgOperand(0),
3995 CI->getArgOperand(1), /* IsNSW = */ false,
3996 /* IsNUW*/ true);
3997 }
3998
3999 case Intrinsic::ssub_with_overflow:
4000 case Intrinsic::usub_with_overflow:
4001 return BinaryOp(Instruction::Sub, CI->getArgOperand(0),
4002 CI->getArgOperand(1));
4003
4004 case Intrinsic::smul_with_overflow:
4005 case Intrinsic::umul_with_overflow:
4006 return BinaryOp(Instruction::Mul, CI->getArgOperand(0),
4007 CI->getArgOperand(1));
4008 default:
4009 break;
4010 }
4011 }
4012
4013 default:
4014 break;
4015 }
4016
4017 return None;
4018}
4019
4020const SCEV *ScalarEvolution::createAddRecFromPHI(PHINode *PN) {
4021 const Loop *L = LI.getLoopFor(PN->getParent());
4022 if (!L || L->getHeader() != PN->getParent())
4023 return nullptr;
4024
4025 // The loop may have multiple entrances or multiple exits; we can analyze
4026 // this phi as an addrec if it has a unique entry value and a unique
4027 // backedge value.
4028 Value *BEValueV = nullptr, *StartValueV = nullptr;
4029 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
4030 Value *V = PN->getIncomingValue(i);
4031 if (L->contains(PN->getIncomingBlock(i))) {
4032 if (!BEValueV) {
4033 BEValueV = V;
4034 } else if (BEValueV != V) {
4035 BEValueV = nullptr;
4036 break;
4037 }
4038 } else if (!StartValueV) {
4039 StartValueV = V;
4040 } else if (StartValueV != V) {
4041 StartValueV = nullptr;
4042 break;
4043 }
4044 }
4045 if (BEValueV && StartValueV) {
4046 // While we are analyzing this PHI node, handle its value symbolically.
4047 const SCEV *SymbolicName = getUnknown(PN);
4048 assert(ValueExprMap.find_as(PN) == ValueExprMap.end() &&((ValueExprMap.find_as(PN) == ValueExprMap.end() && "PHI node already processed?"
) ? static_cast<void> (0) : __assert_fail ("ValueExprMap.find_as(PN) == ValueExprMap.end() && \"PHI node already processed?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4049, __PRETTY_FUNCTION__))
4049 "PHI node already processed?")((ValueExprMap.find_as(PN) == ValueExprMap.end() && "PHI node already processed?"
) ? static_cast<void> (0) : __assert_fail ("ValueExprMap.find_as(PN) == ValueExprMap.end() && \"PHI node already processed?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4049, __PRETTY_FUNCTION__))
;
4050 ValueExprMap.insert({SCEVCallbackVH(PN, this), SymbolicName});
4051
4052 // Using this symbolic name for the PHI, analyze the value coming around
4053 // the back-edge.
4054 const SCEV *BEValue = getSCEV(BEValueV);
4055
4056 // NOTE: If BEValue is loop invariant, we know that the PHI node just
4057 // has a special value for the first iteration of the loop.
4058
4059 // If the value coming around the backedge is an add with the symbolic
4060 // value we just inserted, then we found a simple induction variable!
4061 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(BEValue)) {
4062 // If there is a single occurrence of the symbolic value, replace it
4063 // with a recurrence.
4064 unsigned FoundIndex = Add->getNumOperands();
4065 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
4066 if (Add->getOperand(i) == SymbolicName)
4067 if (FoundIndex == e) {
4068 FoundIndex = i;
4069 break;
4070 }
4071
4072 if (FoundIndex != Add->getNumOperands()) {
4073 // Create an add with everything but the specified operand.
4074 SmallVector<const SCEV *, 8> Ops;
4075 for (unsigned i = 0, e = Add->getNumOperands(); i != e; ++i)
4076 if (i != FoundIndex)
4077 Ops.push_back(Add->getOperand(i));
4078 const SCEV *Accum = getAddExpr(Ops);
4079
4080 // This is not a valid addrec if the step amount is varying each
4081 // loop iteration, but is not itself an addrec in this loop.
4082 if (isLoopInvariant(Accum, L) ||
4083 (isa<SCEVAddRecExpr>(Accum) &&
4084 cast<SCEVAddRecExpr>(Accum)->getLoop() == L)) {
4085 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
4086
4087 if (auto BO = MatchBinaryOp(BEValueV, DT)) {
4088 if (BO->Opcode == Instruction::Add && BO->LHS == PN) {
4089 if (BO->IsNUW)
4090 Flags = setFlags(Flags, SCEV::FlagNUW);
4091 if (BO->IsNSW)
4092 Flags = setFlags(Flags, SCEV::FlagNSW);
4093 }
4094 } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(BEValueV)) {
4095 // If the increment is an inbounds GEP, then we know the address
4096 // space cannot be wrapped around. We cannot make any guarantee
4097 // about signed or unsigned overflow because pointers are
4098 // unsigned but we may have a negative index from the base
4099 // pointer. We can guarantee that no unsigned wrap occurs if the
4100 // indices form a positive value.
4101 if (GEP->isInBounds() && GEP->getOperand(0) == PN) {
4102 Flags = setFlags(Flags, SCEV::FlagNW);
4103
4104 const SCEV *Ptr = getSCEV(GEP->getPointerOperand());
4105 if (isKnownPositive(getMinusSCEV(getSCEV(GEP), Ptr)))
4106 Flags = setFlags(Flags, SCEV::FlagNUW);
4107 }
4108
4109 // We cannot transfer nuw and nsw flags from subtraction
4110 // operations -- sub nuw X, Y is not the same as add nuw X, -Y
4111 // for instance.
4112 }
4113
4114 const SCEV *StartVal = getSCEV(StartValueV);
4115 const SCEV *PHISCEV = getAddRecExpr(StartVal, Accum, L, Flags);
4116
4117 // Okay, for the entire analysis of this edge we assumed the PHI
4118 // to be symbolic. We now need to go back and purge all of the
4119 // entries for the scalars that use the symbolic expression.
4120 forgetSymbolicName(PN, SymbolicName);
4121 ValueExprMap[SCEVCallbackVH(PN, this)] = PHISCEV;
4122
4123 // We can add Flags to the post-inc expression only if we
4124 // know that it us *undefined behavior* for BEValueV to
4125 // overflow.
4126 if (auto *BEInst = dyn_cast<Instruction>(BEValueV))
4127 if (isLoopInvariant(Accum, L) && isAddRecNeverPoison(BEInst, L))
4128 (void)getAddRecExpr(getAddExpr(StartVal, Accum), Accum, L, Flags);
4129
4130 return PHISCEV;
4131 }
4132 }
4133 } else {
4134 // Otherwise, this could be a loop like this:
4135 // i = 0; for (j = 1; ..; ++j) { .... i = j; }
4136 // In this case, j = {1,+,1} and BEValue is j.
4137 // Because the other in-value of i (0) fits the evolution of BEValue
4138 // i really is an addrec evolution.
4139 //
4140 // We can generalize this saying that i is the shifted value of BEValue
4141 // by one iteration:
4142 // PHI(f(0), f({1,+,1})) --> f({0,+,1})
4143 const SCEV *Shifted = SCEVShiftRewriter::rewrite(BEValue, L, *this);
4144 const SCEV *Start = SCEVInitRewriter::rewrite(Shifted, L, *this);
4145 if (Shifted != getCouldNotCompute() &&
4146 Start != getCouldNotCompute()) {
4147 const SCEV *StartVal = getSCEV(StartValueV);
4148 if (Start == StartVal) {
4149 // Okay, for the entire analysis of this edge we assumed the PHI
4150 // to be symbolic. We now need to go back and purge all of the
4151 // entries for the scalars that use the symbolic expression.
4152 forgetSymbolicName(PN, SymbolicName);
4153 ValueExprMap[SCEVCallbackVH(PN, this)] = Shifted;
4154 return Shifted;
4155 }
4156 }
4157 }
4158
4159 // Remove the temporary PHI node SCEV that has been inserted while intending
4160 // to create an AddRecExpr for this PHI node. We can not keep this temporary
4161 // as it will prevent later (possibly simpler) SCEV expressions to be added
4162 // to the ValueExprMap.
4163 eraseValueFromMap(PN);
4164 }
4165
4166 return nullptr;
4167}
4168
4169// Checks if the SCEV S is available at BB. S is considered available at BB
4170// if S can be materialized at BB without introducing a fault.
4171static bool IsAvailableOnEntry(const Loop *L, DominatorTree &DT, const SCEV *S,
4172 BasicBlock *BB) {
4173 struct CheckAvailable {
4174 bool TraversalDone = false;
4175 bool Available = true;
4176
4177 const Loop *L = nullptr; // The loop BB is in (can be nullptr)
4178 BasicBlock *BB = nullptr;
4179 DominatorTree &DT;
4180
4181 CheckAvailable(const Loop *L, BasicBlock *BB, DominatorTree &DT)
4182 : L(L), BB(BB), DT(DT) {}
4183
4184 bool setUnavailable() {
4185 TraversalDone = true;
4186 Available = false;
4187 return false;
4188 }
4189
4190 bool follow(const SCEV *S) {
4191 switch (S->getSCEVType()) {
4192 case scConstant: case scTruncate: case scZeroExtend: case scSignExtend:
4193 case scAddExpr: case scMulExpr: case scUMaxExpr: case scSMaxExpr:
4194 // These expressions are available if their operand(s) is/are.
4195 return true;
4196
4197 case scAddRecExpr: {
4198 // We allow add recurrences that are on the loop BB is in, or some
4199 // outer loop. This guarantees availability because the value of the
4200 // add recurrence at BB is simply the "current" value of the induction
4201 // variable. We can relax this in the future; for instance an add
4202 // recurrence on a sibling dominating loop is also available at BB.
4203 const auto *ARLoop = cast<SCEVAddRecExpr>(S)->getLoop();
4204 if (L && (ARLoop == L || ARLoop->contains(L)))
4205 return true;
4206
4207 return setUnavailable();
4208 }
4209
4210 case scUnknown: {
4211 // For SCEVUnknown, we check for simple dominance.
4212 const auto *SU = cast<SCEVUnknown>(S);
4213 Value *V = SU->getValue();
4214
4215 if (isa<Argument>(V))
4216 return false;
4217
4218 if (isa<Instruction>(V) && DT.dominates(cast<Instruction>(V), BB))
4219 return false;
4220
4221 return setUnavailable();
4222 }
4223
4224 case scUDivExpr:
4225 case scCouldNotCompute:
4226 // We do not try to smart about these at all.
4227 return setUnavailable();
4228 }
4229 llvm_unreachable("switch should be fully covered!")::llvm::llvm_unreachable_internal("switch should be fully covered!"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4229)
;
4230 }
4231
4232 bool isDone() { return TraversalDone; }
4233 };
4234
4235 CheckAvailable CA(L, BB, DT);
4236 SCEVTraversal<CheckAvailable> ST(CA);
4237
4238 ST.visitAll(S);
4239 return CA.Available;
4240}
4241
4242// Try to match a control flow sequence that branches out at BI and merges back
4243// at Merge into a "C ? LHS : RHS" select pattern. Return true on a successful
4244// match.
4245static bool BrPHIToSelect(DominatorTree &DT, BranchInst *BI, PHINode *Merge,
4246 Value *&C, Value *&LHS, Value *&RHS) {
4247 C = BI->getCondition();
4248
4249 BasicBlockEdge LeftEdge(BI->getParent(), BI->getSuccessor(0));
4250 BasicBlockEdge RightEdge(BI->getParent(), BI->getSuccessor(1));
4251
4252 if (!LeftEdge.isSingleEdge())
4253 return false;
4254
4255 assert(RightEdge.isSingleEdge() && "Follows from LeftEdge.isSingleEdge()")((RightEdge.isSingleEdge() && "Follows from LeftEdge.isSingleEdge()"
) ? static_cast<void> (0) : __assert_fail ("RightEdge.isSingleEdge() && \"Follows from LeftEdge.isSingleEdge()\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4255, __PRETTY_FUNCTION__))
;
4256
4257 Use &LeftUse = Merge->getOperandUse(0);
4258 Use &RightUse = Merge->getOperandUse(1);
4259
4260 if (DT.dominates(LeftEdge, LeftUse) && DT.dominates(RightEdge, RightUse)) {
4261 LHS = LeftUse;
4262 RHS = RightUse;
4263 return true;
4264 }
4265
4266 if (DT.dominates(LeftEdge, RightUse) && DT.dominates(RightEdge, LeftUse)) {
4267 LHS = RightUse;
4268 RHS = LeftUse;
4269 return true;
4270 }
4271
4272 return false;
4273}
4274
4275const SCEV *ScalarEvolution::createNodeFromSelectLikePHI(PHINode *PN) {
4276 auto IsReachable =
4277 [&](BasicBlock *BB) { return DT.isReachableFromEntry(BB); };
4278 if (PN->getNumIncomingValues() == 2 && all_of(PN->blocks(), IsReachable)) {
4279 const Loop *L = LI.getLoopFor(PN->getParent());
4280
4281 // We don't want to break LCSSA, even in a SCEV expression tree.
4282 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
4283 if (LI.getLoopFor(PN->getIncomingBlock(i)) != L)
4284 return nullptr;
4285
4286 // Try to match
4287 //
4288 // br %cond, label %left, label %right
4289 // left:
4290 // br label %merge
4291 // right:
4292 // br label %merge
4293 // merge:
4294 // V = phi [ %x, %left ], [ %y, %right ]
4295 //
4296 // as "select %cond, %x, %y"
4297
4298 BasicBlock *IDom = DT[PN->getParent()]->getIDom()->getBlock();
4299 assert(IDom && "At least the entry block should dominate PN")((IDom && "At least the entry block should dominate PN"
) ? static_cast<void> (0) : __assert_fail ("IDom && \"At least the entry block should dominate PN\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4299, __PRETTY_FUNCTION__))
;
4300
4301 auto *BI = dyn_cast<BranchInst>(IDom->getTerminator());
4302 Value *Cond = nullptr, *LHS = nullptr, *RHS = nullptr;
4303
4304 if (BI && BI->isConditional() &&
4305 BrPHIToSelect(DT, BI, PN, Cond, LHS, RHS) &&
4306 IsAvailableOnEntry(L, DT, getSCEV(LHS), PN->getParent()) &&
4307 IsAvailableOnEntry(L, DT, getSCEV(RHS), PN->getParent()))
4308 return createNodeForSelectOrPHI(PN, Cond, LHS, RHS);
4309 }
4310
4311 return nullptr;
4312}
4313
4314const SCEV *ScalarEvolution::createNodeForPHI(PHINode *PN) {
4315 if (const SCEV *S = createAddRecFromPHI(PN))
4316 return S;
4317
4318 if (const SCEV *S = createNodeFromSelectLikePHI(PN))
4319 return S;
4320
4321 // If the PHI has a single incoming value, follow that value, unless the
4322 // PHI's incoming blocks are in a different loop, in which case doing so
4323 // risks breaking LCSSA form. Instcombine would normally zap these, but
4324 // it doesn't have DominatorTree information, so it may miss cases.
4325 if (Value *V = SimplifyInstruction(PN, getDataLayout(), &TLI, &DT, &AC))
4326 if (LI.replacementPreservesLCSSAForm(PN, V))
4327 return getSCEV(V);
4328
4329 // If it's not a loop phi, we can't handle it yet.
4330 return getUnknown(PN);
4331}
4332
4333const SCEV *ScalarEvolution::createNodeForSelectOrPHI(Instruction *I,
4334 Value *Cond,
4335 Value *TrueVal,
4336 Value *FalseVal) {
4337 // Handle "constant" branch or select. This can occur for instance when a
4338 // loop pass transforms an inner loop and moves on to process the outer loop.
4339 if (auto *CI = dyn_cast<ConstantInt>(Cond))
4340 return getSCEV(CI->isOne() ? TrueVal : FalseVal);
4341
4342 // Try to match some simple smax or umax patterns.
4343 auto *ICI = dyn_cast<ICmpInst>(Cond);
4344 if (!ICI)
4345 return getUnknown(I);
4346
4347 Value *LHS = ICI->getOperand(0);
4348 Value *RHS = ICI->getOperand(1);
4349
4350 switch (ICI->getPredicate()) {
4351 case ICmpInst::ICMP_SLT:
4352 case ICmpInst::ICMP_SLE:
4353 std::swap(LHS, RHS);
4354 LLVM_FALLTHROUGH[[clang::fallthrough]];
4355 case ICmpInst::ICMP_SGT:
4356 case ICmpInst::ICMP_SGE:
4357 // a >s b ? a+x : b+x -> smax(a, b)+x
4358 // a >s b ? b+x : a+x -> smin(a, b)+x
4359 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
4360 const SCEV *LS = getNoopOrSignExtend(getSCEV(LHS), I->getType());
4361 const SCEV *RS = getNoopOrSignExtend(getSCEV(RHS), I->getType());
4362 const SCEV *LA = getSCEV(TrueVal);
4363 const SCEV *RA = getSCEV(FalseVal);
4364 const SCEV *LDiff = getMinusSCEV(LA, LS);
4365 const SCEV *RDiff = getMinusSCEV(RA, RS);
4366 if (LDiff == RDiff)
4367 return getAddExpr(getSMaxExpr(LS, RS), LDiff);
4368 LDiff = getMinusSCEV(LA, RS);
4369 RDiff = getMinusSCEV(RA, LS);
4370 if (LDiff == RDiff)
4371 return getAddExpr(getSMinExpr(LS, RS), LDiff);
4372 }
4373 break;
4374 case ICmpInst::ICMP_ULT:
4375 case ICmpInst::ICMP_ULE:
4376 std::swap(LHS, RHS);
4377 LLVM_FALLTHROUGH[[clang::fallthrough]];
4378 case ICmpInst::ICMP_UGT:
4379 case ICmpInst::ICMP_UGE:
4380 // a >u b ? a+x : b+x -> umax(a, b)+x
4381 // a >u b ? b+x : a+x -> umin(a, b)+x
4382 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType())) {
4383 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4384 const SCEV *RS = getNoopOrZeroExtend(getSCEV(RHS), I->getType());
4385 const SCEV *LA = getSCEV(TrueVal);
4386 const SCEV *RA = getSCEV(FalseVal);
4387 const SCEV *LDiff = getMinusSCEV(LA, LS);
4388 const SCEV *RDiff = getMinusSCEV(RA, RS);
4389 if (LDiff == RDiff)
4390 return getAddExpr(getUMaxExpr(LS, RS), LDiff);
4391 LDiff = getMinusSCEV(LA, RS);
4392 RDiff = getMinusSCEV(RA, LS);
4393 if (LDiff == RDiff)
4394 return getAddExpr(getUMinExpr(LS, RS), LDiff);
4395 }
4396 break;
4397 case ICmpInst::ICMP_NE:
4398 // n != 0 ? n+x : 1+x -> umax(n, 1)+x
4399 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
4400 isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
4401 const SCEV *One = getOne(I->getType());
4402 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4403 const SCEV *LA = getSCEV(TrueVal);
4404 const SCEV *RA = getSCEV(FalseVal);
4405 const SCEV *LDiff = getMinusSCEV(LA, LS);
4406 const SCEV *RDiff = getMinusSCEV(RA, One);
4407 if (LDiff == RDiff)
4408 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4409 }
4410 break;
4411 case ICmpInst::ICMP_EQ:
4412 // n == 0 ? 1+x : n+x -> umax(n, 1)+x
4413 if (getTypeSizeInBits(LHS->getType()) <= getTypeSizeInBits(I->getType()) &&
4414 isa<ConstantInt>(RHS) && cast<ConstantInt>(RHS)->isZero()) {
4415 const SCEV *One = getOne(I->getType());
4416 const SCEV *LS = getNoopOrZeroExtend(getSCEV(LHS), I->getType());
4417 const SCEV *LA = getSCEV(TrueVal);
4418 const SCEV *RA = getSCEV(FalseVal);
4419 const SCEV *LDiff = getMinusSCEV(LA, One);
4420 const SCEV *RDiff = getMinusSCEV(RA, LS);
4421 if (LDiff == RDiff)
4422 return getAddExpr(getUMaxExpr(One, LS), LDiff);
4423 }
4424 break;
4425 default:
4426 break;
4427 }
4428
4429 return getUnknown(I);
4430}
4431
4432/// Expand GEP instructions into add and multiply operations. This allows them
4433/// to be analyzed by regular SCEV code.
4434const SCEV *ScalarEvolution::createNodeForGEP(GEPOperator *GEP) {
4435 // Don't attempt to analyze GEPs over unsized objects.
4436 if (!GEP->getSourceElementType()->isSized())
4437 return getUnknown(GEP);
4438
4439 SmallVector<const SCEV *, 4> IndexExprs;
4440 for (auto Index = GEP->idx_begin(); Index != GEP->idx_end(); ++Index)
4441 IndexExprs.push_back(getSCEV(*Index));
4442 return getGEPExpr(GEP, IndexExprs);
4443}
4444
4445uint32_t ScalarEvolution::GetMinTrailingZerosImpl(const SCEV *S) {
4446 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
4447 return C->getAPInt().countTrailingZeros();
4448
4449 if (const SCEVTruncateExpr *T = dyn_cast<SCEVTruncateExpr>(S))
4450 return std::min(GetMinTrailingZeros(T->getOperand()),
4451 (uint32_t)getTypeSizeInBits(T->getType()));
4452
4453 if (const SCEVZeroExtendExpr *E = dyn_cast<SCEVZeroExtendExpr>(S)) {
4454 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
4455 return OpRes == getTypeSizeInBits(E->getOperand()->getType())
4456 ? getTypeSizeInBits(E->getType())
4457 : OpRes;
4458 }
4459
4460 if (const SCEVSignExtendExpr *E = dyn_cast<SCEVSignExtendExpr>(S)) {
4461 uint32_t OpRes = GetMinTrailingZeros(E->getOperand());
4462 return OpRes == getTypeSizeInBits(E->getOperand()->getType())
4463 ? getTypeSizeInBits(E->getType())
4464 : OpRes;
4465 }
4466
4467 if (const SCEVAddExpr *A = dyn_cast<SCEVAddExpr>(S)) {
4468 // The result is the min of all operands results.
4469 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
4470 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
4471 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
4472 return MinOpRes;
4473 }
4474
4475 if (const SCEVMulExpr *M = dyn_cast<SCEVMulExpr>(S)) {
4476 // The result is the sum of all operands results.
4477 uint32_t SumOpRes = GetMinTrailingZeros(M->getOperand(0));
4478 uint32_t BitWidth = getTypeSizeInBits(M->getType());
4479 for (unsigned i = 1, e = M->getNumOperands();
4480 SumOpRes != BitWidth && i != e; ++i)
4481 SumOpRes =
4482 std::min(SumOpRes + GetMinTrailingZeros(M->getOperand(i)), BitWidth);
4483 return SumOpRes;
4484 }
4485
4486 if (const SCEVAddRecExpr *A = dyn_cast<SCEVAddRecExpr>(S)) {
4487 // The result is the min of all operands results.
4488 uint32_t MinOpRes = GetMinTrailingZeros(A->getOperand(0));
4489 for (unsigned i = 1, e = A->getNumOperands(); MinOpRes && i != e; ++i)
4490 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(A->getOperand(i)));
4491 return MinOpRes;
4492 }
4493
4494 if (const SCEVSMaxExpr *M = dyn_cast<SCEVSMaxExpr>(S)) {
4495 // The result is the min of all operands results.
4496 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
4497 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
4498 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
4499 return MinOpRes;
4500 }
4501
4502 if (const SCEVUMaxExpr *M = dyn_cast<SCEVUMaxExpr>(S)) {
4503 // The result is the min of all operands results.
4504 uint32_t MinOpRes = GetMinTrailingZeros(M->getOperand(0));
4505 for (unsigned i = 1, e = M->getNumOperands(); MinOpRes && i != e; ++i)
4506 MinOpRes = std::min(MinOpRes, GetMinTrailingZeros(M->getOperand(i)));
4507 return MinOpRes;
4508 }
4509
4510 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
4511 // For a SCEVUnknown, ask ValueTracking.
4512 unsigned BitWidth = getTypeSizeInBits(U->getType());
4513 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
4514 computeKnownBits(U->getValue(), Zeros, Ones, getDataLayout(), 0, &AC,
4515 nullptr, &DT);
4516 return Zeros.countTrailingOnes();
4517 }
4518
4519 // SCEVUDivExpr
4520 return 0;
4521}
4522
4523uint32_t ScalarEvolution::GetMinTrailingZeros(const SCEV *S) {
4524 auto I = MinTrailingZerosCache.find(S);
4525 if (I != MinTrailingZerosCache.end())
4526 return I->second;
4527
4528 uint32_t Result = GetMinTrailingZerosImpl(S);
4529 auto InsertPair = MinTrailingZerosCache.insert({S, Result});
4530 assert(InsertPair.second && "Should insert a new key")((InsertPair.second && "Should insert a new key") ? static_cast
<void> (0) : __assert_fail ("InsertPair.second && \"Should insert a new key\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4530, __PRETTY_FUNCTION__))
;
4531 return InsertPair.first->second;
4532}
4533
4534/// Helper method to assign a range to V from metadata present in the IR.
4535static Optional<ConstantRange> GetRangeFromMetadata(Value *V) {
4536 if (Instruction *I = dyn_cast<Instruction>(V))
4537 if (MDNode *MD = I->getMetadata(LLVMContext::MD_range))
4538 return getConstantRangeFromMetadata(*MD);
4539
4540 return None;
4541}
4542
4543/// Determine the range for a particular SCEV. If SignHint is
4544/// HINT_RANGE_UNSIGNED (resp. HINT_RANGE_SIGNED) then getRange prefers ranges
4545/// with a "cleaner" unsigned (resp. signed) representation.
4546ConstantRange
4547ScalarEvolution::getRange(const SCEV *S,
4548 ScalarEvolution::RangeSignHint SignHint) {
4549 DenseMap<const SCEV *, ConstantRange> &Cache =
4550 SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED ? UnsignedRanges
4551 : SignedRanges;
4552
4553 // See if we've computed this range already.
4554 DenseMap<const SCEV *, ConstantRange>::iterator I = Cache.find(S);
4555 if (I != Cache.end())
4556 return I->second;
4557
4558 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S))
4559 return setRange(C, SignHint, ConstantRange(C->getAPInt()));
4560
4561 unsigned BitWidth = getTypeSizeInBits(S->getType());
4562 ConstantRange ConservativeResult(BitWidth, /*isFullSet=*/true);
4563
4564 // If the value has known zeros, the maximum value will have those known zeros
4565 // as well.
4566 uint32_t TZ = GetMinTrailingZeros(S);
4567 if (TZ != 0) {
4568 if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED)
4569 ConservativeResult =
4570 ConstantRange(APInt::getMinValue(BitWidth),
4571 APInt::getMaxValue(BitWidth).lshr(TZ).shl(TZ) + 1);
4572 else
4573 ConservativeResult = ConstantRange(
4574 APInt::getSignedMinValue(BitWidth),
4575 APInt::getSignedMaxValue(BitWidth).ashr(TZ).shl(TZ) + 1);
4576 }
4577
4578 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
4579 ConstantRange X = getRange(Add->getOperand(0), SignHint);
4580 for (unsigned i = 1, e = Add->getNumOperands(); i != e; ++i)
4581 X = X.add(getRange(Add->getOperand(i), SignHint));
4582 return setRange(Add, SignHint, ConservativeResult.intersectWith(X));
4583 }
4584
4585 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
4586 ConstantRange X = getRange(Mul->getOperand(0), SignHint);
4587 for (unsigned i = 1, e = Mul->getNumOperands(); i != e; ++i)
4588 X = X.multiply(getRange(Mul->getOperand(i), SignHint));
4589 return setRange(Mul, SignHint, ConservativeResult.intersectWith(X));
4590 }
4591
4592 if (const SCEVSMaxExpr *SMax = dyn_cast<SCEVSMaxExpr>(S)) {
4593 ConstantRange X = getRange(SMax->getOperand(0), SignHint);
4594 for (unsigned i = 1, e = SMax->getNumOperands(); i != e; ++i)
4595 X = X.smax(getRange(SMax->getOperand(i), SignHint));
4596 return setRange(SMax, SignHint, ConservativeResult.intersectWith(X));
4597 }
4598
4599 if (const SCEVUMaxExpr *UMax = dyn_cast<SCEVUMaxExpr>(S)) {
4600 ConstantRange X = getRange(UMax->getOperand(0), SignHint);
4601 for (unsigned i = 1, e = UMax->getNumOperands(); i != e; ++i)
4602 X = X.umax(getRange(UMax->getOperand(i), SignHint));
4603 return setRange(UMax, SignHint, ConservativeResult.intersectWith(X));
4604 }
4605
4606 if (const SCEVUDivExpr *UDiv = dyn_cast<SCEVUDivExpr>(S)) {
4607 ConstantRange X = getRange(UDiv->getLHS(), SignHint);
4608 ConstantRange Y = getRange(UDiv->getRHS(), SignHint);
4609 return setRange(UDiv, SignHint,
4610 ConservativeResult.intersectWith(X.udiv(Y)));
4611 }
4612
4613 if (const SCEVZeroExtendExpr *ZExt = dyn_cast<SCEVZeroExtendExpr>(S)) {
4614 ConstantRange X = getRange(ZExt->getOperand(), SignHint);
4615 return setRange(ZExt, SignHint,
4616 ConservativeResult.intersectWith(X.zeroExtend(BitWidth)));
4617 }
4618
4619 if (const SCEVSignExtendExpr *SExt = dyn_cast<SCEVSignExtendExpr>(S)) {
4620 ConstantRange X = getRange(SExt->getOperand(), SignHint);
4621 return setRange(SExt, SignHint,
4622 ConservativeResult.intersectWith(X.signExtend(BitWidth)));
4623 }
4624
4625 if (const SCEVTruncateExpr *Trunc = dyn_cast<SCEVTruncateExpr>(S)) {
4626 ConstantRange X = getRange(Trunc->getOperand(), SignHint);
4627 return setRange(Trunc, SignHint,
4628 ConservativeResult.intersectWith(X.truncate(BitWidth)));
4629 }
4630
4631 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(S)) {
4632 // If there's no unsigned wrap, the value will never be less than its
4633 // initial value.
4634 if (AddRec->hasNoUnsignedWrap())
4635 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(AddRec->getStart()))
4636 if (!C->getValue()->isZero())
4637 ConservativeResult = ConservativeResult.intersectWith(
4638 ConstantRange(C->getAPInt(), APInt(BitWidth, 0)));
4639
4640 // If there's no signed wrap, and all the operands have the same sign or
4641 // zero, the value won't ever change sign.
4642 if (AddRec->hasNoSignedWrap()) {
4643 bool AllNonNeg = true;
4644 bool AllNonPos = true;
4645 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
4646 if (!isKnownNonNegative(AddRec->getOperand(i))) AllNonNeg = false;
4647 if (!isKnownNonPositive(AddRec->getOperand(i))) AllNonPos = false;
4648 }
4649 if (AllNonNeg)
4650 ConservativeResult = ConservativeResult.intersectWith(
4651 ConstantRange(APInt(BitWidth, 0),
4652 APInt::getSignedMinValue(BitWidth)));
4653 else if (AllNonPos)
4654 ConservativeResult = ConservativeResult.intersectWith(
4655 ConstantRange(APInt::getSignedMinValue(BitWidth),
4656 APInt(BitWidth, 1)));
4657 }
4658
4659 // TODO: non-affine addrec
4660 if (AddRec->isAffine()) {
4661 const SCEV *MaxBECount = getMaxBackedgeTakenCount(AddRec->getLoop());
4662 if (!isa<SCEVCouldNotCompute>(MaxBECount) &&
4663 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth) {
4664 auto RangeFromAffine = getRangeForAffineAR(
4665 AddRec->getStart(), AddRec->getStepRecurrence(*this), MaxBECount,
4666 BitWidth);
4667 if (!RangeFromAffine.isFullSet())
4668 ConservativeResult =
4669 ConservativeResult.intersectWith(RangeFromAffine);
4670
4671 auto RangeFromFactoring = getRangeViaFactoring(
4672 AddRec->getStart(), AddRec->getStepRecurrence(*this), MaxBECount,
4673 BitWidth);
4674 if (!RangeFromFactoring.isFullSet())
4675 ConservativeResult =
4676 ConservativeResult.intersectWith(RangeFromFactoring);
4677 }
4678 }
4679
4680 return setRange(AddRec, SignHint, ConservativeResult);
4681 }
4682
4683 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
4684 // Check if the IR explicitly contains !range metadata.
4685 Optional<ConstantRange> MDRange = GetRangeFromMetadata(U->getValue());
4686 if (MDRange.hasValue())
4687 ConservativeResult = ConservativeResult.intersectWith(MDRange.getValue());
4688
4689 // Split here to avoid paying the compile-time cost of calling both
4690 // computeKnownBits and ComputeNumSignBits. This restriction can be lifted
4691 // if needed.
4692 const DataLayout &DL = getDataLayout();
4693 if (SignHint == ScalarEvolution::HINT_RANGE_UNSIGNED) {
4694 // For a SCEVUnknown, ask ValueTracking.
4695 APInt Zeros(BitWidth, 0), Ones(BitWidth, 0);
4696 computeKnownBits(U->getValue(), Zeros, Ones, DL, 0, &AC, nullptr, &DT);
4697 if (Ones != ~Zeros + 1)
4698 ConservativeResult =
4699 ConservativeResult.intersectWith(ConstantRange(Ones, ~Zeros + 1));
4700 } else {
4701 assert(SignHint == ScalarEvolution::HINT_RANGE_SIGNED &&((SignHint == ScalarEvolution::HINT_RANGE_SIGNED && "generalize as needed!"
) ? static_cast<void> (0) : __assert_fail ("SignHint == ScalarEvolution::HINT_RANGE_SIGNED && \"generalize as needed!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4702, __PRETTY_FUNCTION__))
4702 "generalize as needed!")((SignHint == ScalarEvolution::HINT_RANGE_SIGNED && "generalize as needed!"
) ? static_cast<void> (0) : __assert_fail ("SignHint == ScalarEvolution::HINT_RANGE_SIGNED && \"generalize as needed!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4702, __PRETTY_FUNCTION__))
;
4703 unsigned NS = ComputeNumSignBits(U->getValue(), DL, 0, &AC, nullptr, &DT);
4704 if (NS > 1)
4705 ConservativeResult = ConservativeResult.intersectWith(
4706 ConstantRange(APInt::getSignedMinValue(BitWidth).ashr(NS - 1),
4707 APInt::getSignedMaxValue(BitWidth).ashr(NS - 1) + 1));
4708 }
4709
4710 return setRange(U, SignHint, ConservativeResult);
4711 }
4712
4713 return setRange(S, SignHint, ConservativeResult);
4714}
4715
4716// Given a StartRange, Step and MaxBECount for an expression compute a range of
4717// values that the expression can take. Initially, the expression has a value
4718// from StartRange and then is changed by Step up to MaxBECount times. Signed
4719// argument defines if we treat Step as signed or unsigned.
4720static ConstantRange getRangeForAffineARHelper(APInt Step,
4721 ConstantRange StartRange,
4722 APInt MaxBECount,
4723 unsigned BitWidth, bool Signed) {
4724 // If either Step or MaxBECount is 0, then the expression won't change, and we
4725 // just need to return the initial range.
4726 if (Step == 0 || MaxBECount == 0)
4727 return StartRange;
4728
4729 // If we don't know anything about the inital value (i.e. StartRange is
4730 // FullRange), then we don't know anything about the final range either.
4731 // Return FullRange.
4732 if (StartRange.isFullSet())
4733 return ConstantRange(BitWidth, /* isFullSet = */ true);
4734
4735 // If Step is signed and negative, then we use its absolute value, but we also
4736 // note that we're moving in the opposite direction.
4737 bool Descending = Signed && Step.isNegative();
4738
4739 if (Signed)
4740 // This is correct even for INT_SMIN. Let's look at i8 to illustrate this:
4741 // abs(INT_SMIN) = abs(-128) = abs(0x80) = -0x80 = 0x80 = 128.
4742 // This equations hold true due to the well-defined wrap-around behavior of
4743 // APInt.
4744 Step = Step.abs();
4745
4746 // Check if Offset is more than full span of BitWidth. If it is, the
4747 // expression is guaranteed to overflow.
4748 if (APInt::getMaxValue(StartRange.getBitWidth()).udiv(Step).ult(MaxBECount))
4749 return ConstantRange(BitWidth, /* isFullSet = */ true);
4750
4751 // Offset is by how much the expression can change. Checks above guarantee no
4752 // overflow here.
4753 APInt Offset = Step * MaxBECount;
4754
4755 // Minimum value of the final range will match the minimal value of StartRange
4756 // if the expression is increasing and will be decreased by Offset otherwise.
4757 // Maximum value of the final range will match the maximal value of StartRange
4758 // if the expression is decreasing and will be increased by Offset otherwise.
4759 APInt StartLower = StartRange.getLower();
4760 APInt StartUpper = StartRange.getUpper() - 1;
4761 APInt MovedBoundary =
4762 Descending ? (StartLower - Offset) : (StartUpper + Offset);
4763
4764 // It's possible that the new minimum/maximum value will fall into the initial
4765 // range (due to wrap around). This means that the expression can take any
4766 // value in this bitwidth, and we have to return full range.
4767 if (StartRange.contains(MovedBoundary))
4768 return ConstantRange(BitWidth, /* isFullSet = */ true);
4769
4770 APInt NewLower, NewUpper;
4771 if (Descending) {
4772 NewLower = MovedBoundary;
4773 NewUpper = StartUpper;
4774 } else {
4775 NewLower = StartLower;
4776 NewUpper = MovedBoundary;
4777 }
4778
4779 // If we end up with full range, return a proper full range.
4780 if (NewLower == NewUpper + 1)
4781 return ConstantRange(BitWidth, /* isFullSet = */ true);
4782
4783 // No overflow detected, return [StartLower, StartUpper + Offset + 1) range.
4784 return ConstantRange(NewLower, NewUpper + 1);
4785}
4786
4787ConstantRange ScalarEvolution::getRangeForAffineAR(const SCEV *Start,
4788 const SCEV *Step,
4789 const SCEV *MaxBECount,
4790 unsigned BitWidth) {
4791 assert(!isa<SCEVCouldNotCompute>(MaxBECount) &&((!isa<SCEVCouldNotCompute>(MaxBECount) && getTypeSizeInBits
(MaxBECount->getType()) <= BitWidth && "Precondition!"
) ? static_cast<void> (0) : __assert_fail ("!isa<SCEVCouldNotCompute>(MaxBECount) && getTypeSizeInBits(MaxBECount->getType()) <= BitWidth && \"Precondition!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4793, __PRETTY_FUNCTION__))
4792 getTypeSizeInBits(MaxBECount->getType()) <= BitWidth &&((!isa<SCEVCouldNotCompute>(MaxBECount) && getTypeSizeInBits
(MaxBECount->getType()) <= BitWidth && "Precondition!"
) ? static_cast<void> (0) : __assert_fail ("!isa<SCEVCouldNotCompute>(MaxBECount) && getTypeSizeInBits(MaxBECount->getType()) <= BitWidth && \"Precondition!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4793, __PRETTY_FUNCTION__))
4793 "Precondition!")((!isa<SCEVCouldNotCompute>(MaxBECount) && getTypeSizeInBits
(MaxBECount->getType()) <= BitWidth && "Precondition!"
) ? static_cast<void> (0) : __assert_fail ("!isa<SCEVCouldNotCompute>(MaxBECount) && getTypeSizeInBits(MaxBECount->getType()) <= BitWidth && \"Precondition!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4793, __PRETTY_FUNCTION__))
;
4794
4795 MaxBECount = getNoopOrZeroExtend(MaxBECount, Start->getType());
4796 ConstantRange MaxBECountRange = getUnsignedRange(MaxBECount);
4797 APInt MaxBECountValue = MaxBECountRange.getUnsignedMax();
4798
4799 // First, consider step signed.
4800 ConstantRange StartSRange = getSignedRange(Start);
4801 ConstantRange StepSRange = getSignedRange(Step);
4802
4803 // If Step can be both positive and negative, we need to find ranges for the
4804 // maximum absolute step values in both directions and union them.
4805 ConstantRange SR =
4806 getRangeForAffineARHelper(StepSRange.getSignedMin(), StartSRange,
4807 MaxBECountValue, BitWidth, /* Signed = */ true);
4808 SR = SR.unionWith(getRangeForAffineARHelper(StepSRange.getSignedMax(),
4809 StartSRange, MaxBECountValue,
4810 BitWidth, /* Signed = */ true));
4811
4812 // Next, consider step unsigned.
4813 ConstantRange UR = getRangeForAffineARHelper(
4814 getUnsignedRange(Step).getUnsignedMax(), getUnsignedRange(Start),
4815 MaxBECountValue, BitWidth, /* Signed = */ false);
4816
4817 // Finally, intersect signed and unsigned ranges.
4818 return SR.intersectWith(UR);
4819}
4820
4821ConstantRange ScalarEvolution::getRangeViaFactoring(const SCEV *Start,
4822 const SCEV *Step,
4823 const SCEV *MaxBECount,
4824 unsigned BitWidth) {
4825 // RangeOf({C?A:B,+,C?P:Q}) == RangeOf(C?{A,+,P}:{B,+,Q})
4826 // == RangeOf({A,+,P}) union RangeOf({B,+,Q})
4827
4828 struct SelectPattern {
4829 Value *Condition = nullptr;
4830 APInt TrueValue;
4831 APInt FalseValue;
4832
4833 explicit SelectPattern(ScalarEvolution &SE, unsigned BitWidth,
4834 const SCEV *S) {
4835 Optional<unsigned> CastOp;
4836 APInt Offset(BitWidth, 0);
4837
4838 assert(SE.getTypeSizeInBits(S->getType()) == BitWidth &&((SE.getTypeSizeInBits(S->getType()) == BitWidth &&
"Should be!") ? static_cast<void> (0) : __assert_fail (
"SE.getTypeSizeInBits(S->getType()) == BitWidth && \"Should be!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4839, __PRETTY_FUNCTION__))
4839 "Should be!")((SE.getTypeSizeInBits(S->getType()) == BitWidth &&
"Should be!") ? static_cast<void> (0) : __assert_fail (
"SE.getTypeSizeInBits(S->getType()) == BitWidth && \"Should be!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4839, __PRETTY_FUNCTION__))
;
4840
4841 // Peel off a constant offset:
4842 if (auto *SA = dyn_cast<SCEVAddExpr>(S)) {
4843 // In the future we could consider being smarter here and handle
4844 // {Start+Step,+,Step} too.
4845 if (SA->getNumOperands() != 2 || !isa<SCEVConstant>(SA->getOperand(0)))
4846 return;
4847
4848 Offset = cast<SCEVConstant>(SA->getOperand(0))->getAPInt();
4849 S = SA->getOperand(1);
4850 }
4851
4852 // Peel off a cast operation
4853 if (auto *SCast = dyn_cast<SCEVCastExpr>(S)) {
4854 CastOp = SCast->getSCEVType();
4855 S = SCast->getOperand();
4856 }
4857
4858 using namespace llvm::PatternMatch;
4859
4860 auto *SU = dyn_cast<SCEVUnknown>(S);
4861 const APInt *TrueVal, *FalseVal;
4862 if (!SU ||
4863 !match(SU->getValue(), m_Select(m_Value(Condition), m_APInt(TrueVal),
4864 m_APInt(FalseVal)))) {
4865 Condition = nullptr;
4866 return;
4867 }
4868
4869 TrueValue = *TrueVal;
4870 FalseValue = *FalseVal;
4871
4872 // Re-apply the cast we peeled off earlier
4873 if (CastOp.hasValue())
4874 switch (*CastOp) {
4875 default:
4876 llvm_unreachable("Unknown SCEV cast type!")::llvm::llvm_unreachable_internal("Unknown SCEV cast type!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 4876)
;
4877
4878 case scTruncate:
4879 TrueValue = TrueValue.trunc(BitWidth);
4880 FalseValue = FalseValue.trunc(BitWidth);
4881 break;
4882 case scZeroExtend:
4883 TrueValue = TrueValue.zext(BitWidth);
4884 FalseValue = FalseValue.zext(BitWidth);
4885 break;
4886 case scSignExtend:
4887 TrueValue = TrueValue.sext(BitWidth);
4888 FalseValue = FalseValue.sext(BitWidth);
4889 break;
4890 }
4891
4892 // Re-apply the constant offset we peeled off earlier
4893 TrueValue += Offset;
4894 FalseValue += Offset;
4895 }
4896
4897 bool isRecognized() { return Condition != nullptr; }
4898 };
4899
4900 SelectPattern StartPattern(*this, BitWidth, Start);
4901 if (!StartPattern.isRecognized())
4902 return ConstantRange(BitWidth, /* isFullSet = */ true);
4903
4904 SelectPattern StepPattern(*this, BitWidth, Step);
4905 if (!StepPattern.isRecognized())
4906 return ConstantRange(BitWidth, /* isFullSet = */ true);
4907
4908 if (StartPattern.Condition != StepPattern.Condition) {
4909 // We don't handle this case today; but we could, by considering four
4910 // possibilities below instead of two. I'm not sure if there are cases where
4911 // that will help over what getRange already does, though.
4912 return ConstantRange(BitWidth, /* isFullSet = */ true);
4913 }
4914
4915 // NB! Calling ScalarEvolution::getConstant is fine, but we should not try to
4916 // construct arbitrary general SCEV expressions here. This function is called
4917 // from deep in the call stack, and calling getSCEV (on a sext instruction,
4918 // say) can end up caching a suboptimal value.
4919
4920 // FIXME: without the explicit `this` receiver below, MSVC errors out with
4921 // C2352 and C2512 (otherwise it isn't needed).
4922
4923 const SCEV *TrueStart = this->getConstant(StartPattern.TrueValue);
4924 const SCEV *TrueStep = this->getConstant(StepPattern.TrueValue);
4925 const SCEV *FalseStart = this->getConstant(StartPattern.FalseValue);
4926 const SCEV *FalseStep = this->getConstant(StepPattern.FalseValue);
4927
4928 ConstantRange TrueRange =
4929 this->getRangeForAffineAR(TrueStart, TrueStep, MaxBECount, BitWidth);
4930 ConstantRange FalseRange =
4931 this->getRangeForAffineAR(FalseStart, FalseStep, MaxBECount, BitWidth);
4932
4933 return TrueRange.unionWith(FalseRange);
4934}
4935
4936SCEV::NoWrapFlags ScalarEvolution::getNoWrapFlagsFromUB(const Value *V) {
4937 if (isa<ConstantExpr>(V)) return SCEV::FlagAnyWrap;
4938 const BinaryOperator *BinOp = cast<BinaryOperator>(V);
4939
4940 // Return early if there are no flags to propagate to the SCEV.
4941 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
4942 if (BinOp->hasNoUnsignedWrap())
4943 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNUW);
4944 if (BinOp->hasNoSignedWrap())
4945 Flags = ScalarEvolution::setFlags(Flags, SCEV::FlagNSW);
4946 if (Flags == SCEV::FlagAnyWrap)
4947 return SCEV::FlagAnyWrap;
4948
4949 return isSCEVExprNeverPoison(BinOp) ? Flags : SCEV::FlagAnyWrap;
4950}
4951
4952bool ScalarEvolution::isSCEVExprNeverPoison(const Instruction *I) {
4953 // Here we check that I is in the header of the innermost loop containing I,
4954 // since we only deal with instructions in the loop header. The actual loop we
4955 // need to check later will come from an add recurrence, but getting that
4956 // requires computing the SCEV of the operands, which can be expensive. This
4957 // check we can do cheaply to rule out some cases early.
4958 Loop *InnermostContainingLoop = LI.getLoopFor(I->getParent());
4959 if (InnermostContainingLoop == nullptr ||
4960 InnermostContainingLoop->getHeader() != I->getParent())
4961 return false;
4962
4963 // Only proceed if we can prove that I does not yield poison.
4964 if (!isKnownNotFullPoison(I)) return false;
4965
4966 // At this point we know that if I is executed, then it does not wrap
4967 // according to at least one of NSW or NUW. If I is not executed, then we do
4968 // not know if the calculation that I represents would wrap. Multiple
4969 // instructions can map to the same SCEV. If we apply NSW or NUW from I to
4970 // the SCEV, we must guarantee no wrapping for that SCEV also when it is
4971 // derived from other instructions that map to the same SCEV. We cannot make
4972 // that guarantee for cases where I is not executed. So we need to find the
4973 // loop that I is considered in relation to and prove that I is executed for
4974 // every iteration of that loop. That implies that the value that I
4975 // calculates does not wrap anywhere in the loop, so then we can apply the
4976 // flags to the SCEV.
4977 //
4978 // We check isLoopInvariant to disambiguate in case we are adding recurrences
4979 // from different loops, so that we know which loop to prove that I is
4980 // executed in.
4981 for (unsigned OpIndex = 0; OpIndex < I->getNumOperands(); ++OpIndex) {
4982 // I could be an extractvalue from a call to an overflow intrinsic.
4983 // TODO: We can do better here in some cases.
4984 if (!isSCEVable(I->getOperand(OpIndex)->getType()))
4985 return false;
4986 const SCEV *Op = getSCEV(I->getOperand(OpIndex));
4987 if (auto *AddRec = dyn_cast<SCEVAddRecExpr>(Op)) {
4988 bool AllOtherOpsLoopInvariant = true;
4989 for (unsigned OtherOpIndex = 0; OtherOpIndex < I->getNumOperands();
4990 ++OtherOpIndex) {
4991 if (OtherOpIndex != OpIndex) {
4992 const SCEV *OtherOp = getSCEV(I->getOperand(OtherOpIndex));
4993 if (!isLoopInvariant(OtherOp, AddRec->getLoop())) {
4994 AllOtherOpsLoopInvariant = false;
4995 break;
4996 }
4997 }
4998 }
4999 if (AllOtherOpsLoopInvariant &&
5000 isGuaranteedToExecuteForEveryIteration(I, AddRec->getLoop()))
5001 return true;
5002 }
5003 }
5004 return false;
5005}
5006
5007bool ScalarEvolution::isAddRecNeverPoison(const Instruction *I, const Loop *L) {
5008 // If we know that \c I can never be poison period, then that's enough.
5009 if (isSCEVExprNeverPoison(I))
5010 return true;
5011
5012 // For an add recurrence specifically, we assume that infinite loops without
5013 // side effects are undefined behavior, and then reason as follows:
5014 //
5015 // If the add recurrence is poison in any iteration, it is poison on all
5016 // future iterations (since incrementing poison yields poison). If the result
5017 // of the add recurrence is fed into the loop latch condition and the loop
5018 // does not contain any throws or exiting blocks other than the latch, we now
5019 // have the ability to "choose" whether the backedge is taken or not (by
5020 // choosing a sufficiently evil value for the poison feeding into the branch)
5021 // for every iteration including and after the one in which \p I first became
5022 // poison. There are two possibilities (let's call the iteration in which \p
5023 // I first became poison as K):
5024 //
5025 // 1. In the set of iterations including and after K, the loop body executes
5026 // no side effects. In this case executing the backege an infinte number
5027 // of times will yield undefined behavior.
5028 //
5029 // 2. In the set of iterations including and after K, the loop body executes
5030 // at least one side effect. In this case, that specific instance of side
5031 // effect is control dependent on poison, which also yields undefined
5032 // behavior.
5033
5034 auto *ExitingBB = L->getExitingBlock();
5035 auto *LatchBB = L->getLoopLatch();
5036 if (!ExitingBB || !LatchBB || ExitingBB != LatchBB)
5037 return false;
5038
5039 SmallPtrSet<const Instruction *, 16> Pushed;
5040 SmallVector<const Instruction *, 8> PoisonStack;
5041
5042 // We start by assuming \c I, the post-inc add recurrence, is poison. Only
5043 // things that are known to be fully poison under that assumption go on the
5044 // PoisonStack.
5045 Pushed.insert(I);
5046 PoisonStack.push_back(I);
5047
5048 bool LatchControlDependentOnPoison = false;
5049 while (!PoisonStack.empty() && !LatchControlDependentOnPoison) {
5050 const Instruction *Poison = PoisonStack.pop_back_val();
5051
5052 for (auto *PoisonUser : Poison->users()) {
5053 if (propagatesFullPoison(cast<Instruction>(PoisonUser))) {
5054 if (Pushed.insert(cast<Instruction>(PoisonUser)).second)
5055 PoisonStack.push_back(cast<Instruction>(PoisonUser));
5056 } else if (auto *BI = dyn_cast<BranchInst>(PoisonUser)) {
5057 assert(BI->isConditional() && "Only possibility!")((BI->isConditional() && "Only possibility!") ? static_cast
<void> (0) : __assert_fail ("BI->isConditional() && \"Only possibility!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5057, __PRETTY_FUNCTION__))
;
5058 if (BI->getParent() == LatchBB) {
5059 LatchControlDependentOnPoison = true;
5060 break;
5061 }
5062 }
5063 }
5064 }
5065
5066 return LatchControlDependentOnPoison && loopHasNoAbnormalExits(L);
5067}
5068
5069ScalarEvolution::LoopProperties
5070ScalarEvolution::getLoopProperties(const Loop *L) {
5071 typedef ScalarEvolution::LoopProperties LoopProperties;
5072
5073 auto Itr = LoopPropertiesCache.find(L);
5074 if (Itr == LoopPropertiesCache.end()) {
5075 auto HasSideEffects = [](Instruction *I) {
5076 if (auto *SI = dyn_cast<StoreInst>(I))
5077 return !SI->isSimple();
5078
5079 return I->mayHaveSideEffects();
5080 };
5081
5082 LoopProperties LP = {/* HasNoAbnormalExits */ true,
5083 /*HasNoSideEffects*/ true};
5084
5085 for (auto *BB : L->getBlocks())
5086 for (auto &I : *BB) {
5087 if (!isGuaranteedToTransferExecutionToSuccessor(&I))
5088 LP.HasNoAbnormalExits = false;
5089 if (HasSideEffects(&I))
5090 LP.HasNoSideEffects = false;
5091 if (!LP.HasNoAbnormalExits && !LP.HasNoSideEffects)
5092 break; // We're already as pessimistic as we can get.
5093 }
5094
5095 auto InsertPair = LoopPropertiesCache.insert({L, LP});
5096 assert(InsertPair.second && "We just checked!")((InsertPair.second && "We just checked!") ? static_cast
<void> (0) : __assert_fail ("InsertPair.second && \"We just checked!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5096, __PRETTY_FUNCTION__))
;
5097 Itr = InsertPair.first;
5098 }
5099
5100 return Itr->second;
5101}
5102
5103const SCEV *ScalarEvolution::createSCEV(Value *V) {
5104 if (!isSCEVable(V->getType()))
5105 return getUnknown(V);
5106
5107 if (Instruction *I = dyn_cast<Instruction>(V)) {
5108 // Don't attempt to analyze instructions in blocks that aren't
5109 // reachable. Such instructions don't matter, and they aren't required
5110 // to obey basic rules for definitions dominating uses which this
5111 // analysis depends on.
5112 if (!DT.isReachableFromEntry(I->getParent()))
5113 return getUnknown(V);
5114 } else if (ConstantInt *CI = dyn_cast<ConstantInt>(V))
5115 return getConstant(CI);
5116 else if (isa<ConstantPointerNull>(V))
5117 return getZero(V->getType());
5118 else if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
5119 return GA->isInterposable() ? getUnknown(V) : getSCEV(GA->getAliasee());
5120 else if (!isa<ConstantExpr>(V))
5121 return getUnknown(V);
5122
5123 Operator *U = cast<Operator>(V);
5124 if (auto BO = MatchBinaryOp(U, DT)) {
5125 switch (BO->Opcode) {
5126 case Instruction::Add: {
5127 // The simple thing to do would be to just call getSCEV on both operands
5128 // and call getAddExpr with the result. However if we're looking at a
5129 // bunch of things all added together, this can be quite inefficient,
5130 // because it leads to N-1 getAddExpr calls for N ultimate operands.
5131 // Instead, gather up all the operands and make a single getAddExpr call.
5132 // LLVM IR canonical form means we need only traverse the left operands.
5133 SmallVector<const SCEV *, 4> AddOps;
5134 do {
5135 if (BO->Op) {
5136 if (auto *OpSCEV = getExistingSCEV(BO->Op)) {
5137 AddOps.push_back(OpSCEV);
5138 break;
5139 }
5140
5141 // If a NUW or NSW flag can be applied to the SCEV for this
5142 // addition, then compute the SCEV for this addition by itself
5143 // with a separate call to getAddExpr. We need to do that
5144 // instead of pushing the operands of the addition onto AddOps,
5145 // since the flags are only known to apply to this particular
5146 // addition - they may not apply to other additions that can be
5147 // formed with operands from AddOps.
5148 const SCEV *RHS = getSCEV(BO->RHS);
5149 SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(BO->Op);
5150 if (Flags != SCEV::FlagAnyWrap) {
5151 const SCEV *LHS = getSCEV(BO->LHS);
5152 if (BO->Opcode == Instruction::Sub)
5153 AddOps.push_back(getMinusSCEV(LHS, RHS, Flags));
5154 else
5155 AddOps.push_back(getAddExpr(LHS, RHS, Flags));
5156 break;
5157 }
5158 }
5159
5160 if (BO->Opcode == Instruction::Sub)
5161 AddOps.push_back(getNegativeSCEV(getSCEV(BO->RHS)));
5162 else
5163 AddOps.push_back(getSCEV(BO->RHS));
5164
5165 auto NewBO = MatchBinaryOp(BO->LHS, DT);
5166 if (!NewBO || (NewBO->Opcode != Instruction::Add &&
5167 NewBO->Opcode != Instruction::Sub)) {
5168 AddOps.push_back(getSCEV(BO->LHS));
5169 break;
5170 }
5171 BO = NewBO;
5172 } while (true);
5173
5174 return getAddExpr(AddOps);
5175 }
5176
5177 case Instruction::Mul: {
5178 SmallVector<const SCEV *, 4> MulOps;
5179 do {
5180 if (BO->Op) {
5181 if (auto *OpSCEV = getExistingSCEV(BO->Op)) {
5182 MulOps.push_back(OpSCEV);
5183 break;
5184 }
5185
5186 SCEV::NoWrapFlags Flags = getNoWrapFlagsFromUB(BO->Op);
5187 if (Flags != SCEV::FlagAnyWrap) {
5188 MulOps.push_back(
5189 getMulExpr(getSCEV(BO->LHS), getSCEV(BO->RHS), Flags));
5190 break;
5191 }
5192 }
5193
5194 MulOps.push_back(getSCEV(BO->RHS));
5195 auto NewBO = MatchBinaryOp(BO->LHS, DT);
5196 if (!NewBO || NewBO->Opcode != Instruction::Mul) {
5197 MulOps.push_back(getSCEV(BO->LHS));
5198 break;
5199 }
5200 BO = NewBO;
5201 } while (true);
5202
5203 return getMulExpr(MulOps);
5204 }
5205 case Instruction::UDiv:
5206 return getUDivExpr(getSCEV(BO->LHS), getSCEV(BO->RHS));
5207 case Instruction::Sub: {
5208 SCEV::NoWrapFlags Flags = SCEV::FlagAnyWrap;
5209 if (BO->Op)
5210 Flags = getNoWrapFlagsFromUB(BO->Op);
5211 return getMinusSCEV(getSCEV(BO->LHS), getSCEV(BO->RHS), Flags);
5212 }
5213 case Instruction::And:
5214 // For an expression like x&255 that merely masks off the high bits,
5215 // use zext(trunc(x)) as the SCEV expression.
5216 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS)) {
5217 if (CI->isNullValue())
5218 return getSCEV(BO->RHS);
5219 if (CI->isAllOnesValue())
5220 return getSCEV(BO->LHS);
5221 const APInt &A = CI->getValue();
5222
5223 // Instcombine's ShrinkDemandedConstant may strip bits out of
5224 // constants, obscuring what would otherwise be a low-bits mask.
5225 // Use computeKnownBits to compute what ShrinkDemandedConstant
5226 // knew about to reconstruct a low-bits mask value.
5227 unsigned LZ = A.countLeadingZeros();
5228 unsigned TZ = A.countTrailingZeros();
5229 unsigned BitWidth = A.getBitWidth();
5230 APInt KnownZero(BitWidth, 0), KnownOne(BitWidth, 0);
5231 computeKnownBits(BO->LHS, KnownZero, KnownOne, getDataLayout(),
5232 0, &AC, nullptr, &DT);
5233
5234 APInt EffectiveMask =
5235 APInt::getLowBitsSet(BitWidth, BitWidth - LZ - TZ).shl(TZ);
5236 if ((LZ != 0 || TZ != 0) && !((~A & ~KnownZero) & EffectiveMask)) {
5237 const SCEV *MulCount = getConstant(APInt::getOneBitSet(BitWidth, TZ));
5238 const SCEV *LHS = getSCEV(BO->LHS);
5239 const SCEV *ShiftedLHS = nullptr;
5240 if (auto *LHSMul = dyn_cast<SCEVMulExpr>(LHS)) {
5241 if (auto *OpC = dyn_cast<SCEVConstant>(LHSMul->getOperand(0))) {
5242 // For an expression like (x * 8) & 8, simplify the multiply.
5243 unsigned MulZeros = OpC->getAPInt().countTrailingZeros();
5244 unsigned GCD = std::min(MulZeros, TZ);
5245 APInt DivAmt = APInt::getOneBitSet(BitWidth, TZ - GCD);
5246 SmallVector<const SCEV*, 4> MulOps;
5247 MulOps.push_back(getConstant(OpC->getAPInt().lshr(GCD)));
5248 MulOps.append(LHSMul->op_begin() + 1, LHSMul->op_end());
5249 auto *NewMul = getMulExpr(MulOps, LHSMul->getNoWrapFlags());
5250 ShiftedLHS = getUDivExpr(NewMul, getConstant(DivAmt));
5251 }
5252 }
5253 if (!ShiftedLHS)
5254 ShiftedLHS = getUDivExpr(LHS, MulCount);
5255 return getMulExpr(
5256 getZeroExtendExpr(
5257 getTruncateExpr(ShiftedLHS,
5258 IntegerType::get(getContext(), BitWidth - LZ - TZ)),
5259 BO->LHS->getType()),
5260 MulCount);
5261 }
5262 }
5263 break;
5264
5265 case Instruction::Or:
5266 // If the RHS of the Or is a constant, we may have something like:
5267 // X*4+1 which got turned into X*4|1. Handle this as an Add so loop
5268 // optimizations will transparently handle this case.
5269 //
5270 // In order for this transformation to be safe, the LHS must be of the
5271 // form X*(2^n) and the Or constant must be less than 2^n.
5272 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS)) {
5273 const SCEV *LHS = getSCEV(BO->LHS);
5274 const APInt &CIVal = CI->getValue();
5275 if (GetMinTrailingZeros(LHS) >=
5276 (CIVal.getBitWidth() - CIVal.countLeadingZeros())) {
5277 // Build a plain add SCEV.
5278 const SCEV *S = getAddExpr(LHS, getSCEV(CI));
5279 // If the LHS of the add was an addrec and it has no-wrap flags,
5280 // transfer the no-wrap flags, since an or won't introduce a wrap.
5281 if (const SCEVAddRecExpr *NewAR = dyn_cast<SCEVAddRecExpr>(S)) {
5282 const SCEVAddRecExpr *OldAR = cast<SCEVAddRecExpr>(LHS);
5283 const_cast<SCEVAddRecExpr *>(NewAR)->setNoWrapFlags(
5284 OldAR->getNoWrapFlags());
5285 }
5286 return S;
5287 }
5288 }
5289 break;
5290
5291 case Instruction::Xor:
5292 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS)) {
5293 // If the RHS of xor is -1, then this is a not operation.
5294 if (CI->isAllOnesValue())
5295 return getNotSCEV(getSCEV(BO->LHS));
5296
5297 // Model xor(and(x, C), C) as and(~x, C), if C is a low-bits mask.
5298 // This is a variant of the check for xor with -1, and it handles
5299 // the case where instcombine has trimmed non-demanded bits out
5300 // of an xor with -1.
5301 if (auto *LBO = dyn_cast<BinaryOperator>(BO->LHS))
5302 if (ConstantInt *LCI = dyn_cast<ConstantInt>(LBO->getOperand(1)))
5303 if (LBO->getOpcode() == Instruction::And &&
5304 LCI->getValue() == CI->getValue())
5305 if (const SCEVZeroExtendExpr *Z =
5306 dyn_cast<SCEVZeroExtendExpr>(getSCEV(BO->LHS))) {
5307 Type *UTy = BO->LHS->getType();
5308 const SCEV *Z0 = Z->getOperand();
5309 Type *Z0Ty = Z0->getType();
5310 unsigned Z0TySize = getTypeSizeInBits(Z0Ty);
5311
5312 // If C is a low-bits mask, the zero extend is serving to
5313 // mask off the high bits. Complement the operand and
5314 // re-apply the zext.
5315 if (APIntOps::isMask(Z0TySize, CI->getValue()))
5316 return getZeroExtendExpr(getNotSCEV(Z0), UTy);
5317
5318 // If C is a single bit, it may be in the sign-bit position
5319 // before the zero-extend. In this case, represent the xor
5320 // using an add, which is equivalent, and re-apply the zext.
5321 APInt Trunc = CI->getValue().trunc(Z0TySize);
5322 if (Trunc.zext(getTypeSizeInBits(UTy)) == CI->getValue() &&
5323 Trunc.isSignBit())
5324 return getZeroExtendExpr(getAddExpr(Z0, getConstant(Trunc)),
5325 UTy);
5326 }
5327 }
5328 break;
5329
5330 case Instruction::Shl:
5331 // Turn shift left of a constant amount into a multiply.
5332 if (ConstantInt *SA = dyn_cast<ConstantInt>(BO->RHS)) {
5333 uint32_t BitWidth = cast<IntegerType>(SA->getType())->getBitWidth();
5334
5335 // If the shift count is not less than the bitwidth, the result of
5336 // the shift is undefined. Don't try to analyze it, because the
5337 // resolution chosen here may differ from the resolution chosen in
5338 // other parts of the compiler.
5339 if (SA->getValue().uge(BitWidth))
5340 break;
5341
5342 // It is currently not resolved how to interpret NSW for left
5343 // shift by BitWidth - 1, so we avoid applying flags in that
5344 // case. Remove this check (or this comment) once the situation
5345 // is resolved. See
5346 // http://lists.llvm.org/pipermail/llvm-dev/2015-April/084195.html
5347 // and http://reviews.llvm.org/D8890 .
5348 auto Flags = SCEV::FlagAnyWrap;
5349 if (BO->Op && SA->getValue().ult(BitWidth - 1))
5350 Flags = getNoWrapFlagsFromUB(BO->Op);
5351
5352 Constant *X = ConstantInt::get(getContext(),
5353 APInt::getOneBitSet(BitWidth, SA->getZExtValue()));
5354 return getMulExpr(getSCEV(BO->LHS), getSCEV(X), Flags);
5355 }
5356 break;
5357
5358 case Instruction::AShr:
5359 // For a two-shift sext-inreg, use sext(trunc(x)) as the SCEV expression.
5360 if (ConstantInt *CI = dyn_cast<ConstantInt>(BO->RHS))
5361 if (Operator *L = dyn_cast<Operator>(BO->LHS))
5362 if (L->getOpcode() == Instruction::Shl &&
5363 L->getOperand(1) == BO->RHS) {
5364 uint64_t BitWidth = getTypeSizeInBits(BO->LHS->getType());
5365
5366 // If the shift count is not less than the bitwidth, the result of
5367 // the shift is undefined. Don't try to analyze it, because the
5368 // resolution chosen here may differ from the resolution chosen in
5369 // other parts of the compiler.
5370 if (CI->getValue().uge(BitWidth))
5371 break;
5372
5373 uint64_t Amt = BitWidth - CI->getZExtValue();
5374 if (Amt == BitWidth)
5375 return getSCEV(L->getOperand(0)); // shift by zero --> noop
5376 return getSignExtendExpr(
5377 getTruncateExpr(getSCEV(L->getOperand(0)),
5378 IntegerType::get(getContext(), Amt)),
5379 BO->LHS->getType());
5380 }
5381 break;
5382 }
5383 }
5384
5385 switch (U->getOpcode()) {
5386 case Instruction::Trunc:
5387 return getTruncateExpr(getSCEV(U->getOperand(0)), U->getType());
5388
5389 case Instruction::ZExt:
5390 return getZeroExtendExpr(getSCEV(U->getOperand(0)), U->getType());
5391
5392 case Instruction::SExt:
5393 return getSignExtendExpr(getSCEV(U->getOperand(0)), U->getType());
5394
5395 case Instruction::BitCast:
5396 // BitCasts are no-op casts so we just eliminate the cast.
5397 if (isSCEVable(U->getType()) && isSCEVable(U->getOperand(0)->getType()))
5398 return getSCEV(U->getOperand(0));
5399 break;
5400
5401 // It's tempting to handle inttoptr and ptrtoint as no-ops, however this can
5402 // lead to pointer expressions which cannot safely be expanded to GEPs,
5403 // because ScalarEvolution doesn't respect the GEP aliasing rules when
5404 // simplifying integer expressions.
5405
5406 case Instruction::GetElementPtr:
5407 return createNodeForGEP(cast<GEPOperator>(U));
5408
5409 case Instruction::PHI:
5410 return createNodeForPHI(cast<PHINode>(U));
5411
5412 case Instruction::Select:
5413 // U can also be a select constant expr, which let fall through. Since
5414 // createNodeForSelect only works for a condition that is an `ICmpInst`, and
5415 // constant expressions cannot have instructions as operands, we'd have
5416 // returned getUnknown for a select constant expressions anyway.
5417 if (isa<Instruction>(U))
5418 return createNodeForSelectOrPHI(cast<Instruction>(U), U->getOperand(0),
5419 U->getOperand(1), U->getOperand(2));
5420 break;
5421
5422 case Instruction::Call:
5423 case Instruction::Invoke:
5424 if (Value *RV = CallSite(U).getReturnedArgOperand())
5425 return getSCEV(RV);
5426 break;
5427 }
5428
5429 return getUnknown(V);
5430}
5431
5432
5433
5434//===----------------------------------------------------------------------===//
5435// Iteration Count Computation Code
5436//
5437
5438static unsigned getConstantTripCount(const SCEVConstant *ExitCount) {
5439 if (!ExitCount)
5440 return 0;
5441
5442 ConstantInt *ExitConst = ExitCount->getValue();
5443
5444 // Guard against huge trip counts.
5445 if (ExitConst->getValue().getActiveBits() > 32)
5446 return 0;
5447
5448 // In case of integer overflow, this returns 0, which is correct.
5449 return ((unsigned)ExitConst->getZExtValue()) + 1;
5450}
5451
5452unsigned ScalarEvolution::getSmallConstantTripCount(const Loop *L) {
5453 if (BasicBlock *ExitingBB = L->getExitingBlock())
5454 return getSmallConstantTripCount(L, ExitingBB);
5455
5456 // No trip count information for multiple exits.
5457 return 0;
5458}
5459
5460unsigned ScalarEvolution::getSmallConstantTripCount(const Loop *L,
5461 BasicBlock *ExitingBlock) {
5462 assert(ExitingBlock && "Must pass a non-null exiting block!")((ExitingBlock && "Must pass a non-null exiting block!"
) ? static_cast<void> (0) : __assert_fail ("ExitingBlock && \"Must pass a non-null exiting block!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5462, __PRETTY_FUNCTION__))
;
5463 assert(L->isLoopExiting(ExitingBlock) &&((L->isLoopExiting(ExitingBlock) && "Exiting block must actually branch out of the loop!"
) ? static_cast<void> (0) : __assert_fail ("L->isLoopExiting(ExitingBlock) && \"Exiting block must actually branch out of the loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5464, __PRETTY_FUNCTION__))
5464 "Exiting block must actually branch out of the loop!")((L->isLoopExiting(ExitingBlock) && "Exiting block must actually branch out of the loop!"
) ? static_cast<void> (0) : __assert_fail ("L->isLoopExiting(ExitingBlock) && \"Exiting block must actually branch out of the loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5464, __PRETTY_FUNCTION__))
;
5465 const SCEVConstant *ExitCount =
5466 dyn_cast<SCEVConstant>(getExitCount(L, ExitingBlock));
5467 return getConstantTripCount(ExitCount);
5468}
5469
5470unsigned ScalarEvolution::getSmallConstantMaxTripCount(const Loop *L) {
5471 const auto *MaxExitCount =
5472 dyn_cast<SCEVConstant>(getMaxBackedgeTakenCount(L));
5473 return getConstantTripCount(MaxExitCount);
5474}
5475
5476unsigned ScalarEvolution::getSmallConstantTripMultiple(const Loop *L) {
5477 if (BasicBlock *ExitingBB = L->getExitingBlock())
5478 return getSmallConstantTripMultiple(L, ExitingBB);
5479
5480 // No trip multiple information for multiple exits.
5481 return 0;
5482}
5483
5484/// Returns the largest constant divisor of the trip count of this loop as a
5485/// normal unsigned value, if possible. This means that the actual trip count is
5486/// always a multiple of the returned value (don't forget the trip count could
5487/// very well be zero as well!).
5488///
5489/// Returns 1 if the trip count is unknown or not guaranteed to be the
5490/// multiple of a constant (which is also the case if the trip count is simply
5491/// constant, use getSmallConstantTripCount for that case), Will also return 1
5492/// if the trip count is very large (>= 2^32).
5493///
5494/// As explained in the comments for getSmallConstantTripCount, this assumes
5495/// that control exits the loop via ExitingBlock.
5496unsigned
5497ScalarEvolution::getSmallConstantTripMultiple(const Loop *L,
5498 BasicBlock *ExitingBlock) {
5499 assert(ExitingBlock && "Must pass a non-null exiting block!")((ExitingBlock && "Must pass a non-null exiting block!"
) ? static_cast<void> (0) : __assert_fail ("ExitingBlock && \"Must pass a non-null exiting block!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5499, __PRETTY_FUNCTION__))
;
5500 assert(L->isLoopExiting(ExitingBlock) &&((L->isLoopExiting(ExitingBlock) && "Exiting block must actually branch out of the loop!"
) ? static_cast<void> (0) : __assert_fail ("L->isLoopExiting(ExitingBlock) && \"Exiting block must actually branch out of the loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5501, __PRETTY_FUNCTION__))
5501 "Exiting block must actually branch out of the loop!")((L->isLoopExiting(ExitingBlock) && "Exiting block must actually branch out of the loop!"
) ? static_cast<void> (0) : __assert_fail ("L->isLoopExiting(ExitingBlock) && \"Exiting block must actually branch out of the loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5501, __PRETTY_FUNCTION__))
;
5502 const SCEV *ExitCount = getExitCount(L, ExitingBlock);
5503 if (ExitCount == getCouldNotCompute())
5504 return 1;
5505
5506 // Get the trip count from the BE count by adding 1.
5507 const SCEV *TCExpr = getAddExpr(ExitCount, getOne(ExitCount->getType()));
5508
5509 const SCEVConstant *TC = dyn_cast<SCEVConstant>(TCExpr);
5510 if (!TC)
5511 // Attempt to factor more general cases. Returns the greatest power of
5512 // two divisor. If overflow happens, the trip count expression is still
5513 // divisible by the greatest power of 2 divisor returned.
5514 return 1U << std::min((uint32_t)31, GetMinTrailingZeros(TCExpr));
5515
5516 ConstantInt *Result = TC->getValue();
5517
5518 // Guard against huge trip counts (this requires checking
5519 // for zero to handle the case where the trip count == -1 and the
5520 // addition wraps).
5521 if (!Result || Result->getValue().getActiveBits() > 32 ||
5522 Result->getValue().getActiveBits() == 0)
5523 return 1;
5524
5525 return (unsigned)Result->getZExtValue();
5526}
5527
5528/// Get the expression for the number of loop iterations for which this loop is
5529/// guaranteed not to exit via ExitingBlock. Otherwise return
5530/// SCEVCouldNotCompute.
5531const SCEV *ScalarEvolution::getExitCount(const Loop *L,
5532 BasicBlock *ExitingBlock) {
5533 return getBackedgeTakenInfo(L).getExact(ExitingBlock, this);
5534}
5535
5536const SCEV *
5537ScalarEvolution::getPredicatedBackedgeTakenCount(const Loop *L,
5538 SCEVUnionPredicate &Preds) {
5539 return getPredicatedBackedgeTakenInfo(L).getExact(this, &Preds);
5540}
5541
5542const SCEV *ScalarEvolution::getBackedgeTakenCount(const Loop *L) {
5543 return getBackedgeTakenInfo(L).getExact(this);
5544}
5545
5546/// Similar to getBackedgeTakenCount, except return the least SCEV value that is
5547/// known never to be less than the actual backedge taken count.
5548const SCEV *ScalarEvolution::getMaxBackedgeTakenCount(const Loop *L) {
5549 return getBackedgeTakenInfo(L).getMax(this);
5550}
5551
5552bool ScalarEvolution::isBackedgeTakenCountMaxOrZero(const Loop *L) {
5553 return getBackedgeTakenInfo(L).isMaxOrZero(this);
5554}
5555
5556/// Push PHI nodes in the header of the given loop onto the given Worklist.
5557static void
5558PushLoopPHIs(const Loop *L, SmallVectorImpl<Instruction *> &Worklist) {
5559 BasicBlock *Header = L->getHeader();
5560
5561 // Push all Loop-header PHIs onto the Worklist stack.
5562 for (BasicBlock::iterator I = Header->begin();
5563 PHINode *PN = dyn_cast<PHINode>(I); ++I)
5564 Worklist.push_back(PN);
5565}
5566
5567const ScalarEvolution::BackedgeTakenInfo &
5568ScalarEvolution::getPredicatedBackedgeTakenInfo(const Loop *L) {
5569 auto &BTI = getBackedgeTakenInfo(L);
5570 if (BTI.hasFullInfo())
5571 return BTI;
5572
5573 auto Pair = PredicatedBackedgeTakenCounts.insert({L, BackedgeTakenInfo()});
5574
5575 if (!Pair.second)
5576 return Pair.first->second;
5577
5578 BackedgeTakenInfo Result =
5579 computeBackedgeTakenCount(L, /*AllowPredicates=*/true);
5580
5581 return PredicatedBackedgeTakenCounts.find(L)->second = std::move(Result);
5582}
5583
5584const ScalarEvolution::BackedgeTakenInfo &
5585ScalarEvolution::getBackedgeTakenInfo(const Loop *L) {
5586 // Initially insert an invalid entry for this loop. If the insertion
5587 // succeeds, proceed to actually compute a backedge-taken count and
5588 // update the value. The temporary CouldNotCompute value tells SCEV
5589 // code elsewhere that it shouldn't attempt to request a new
5590 // backedge-taken count, which could result in infinite recursion.
5591 std::pair<DenseMap<const Loop *, BackedgeTakenInfo>::iterator, bool> Pair =
5592 BackedgeTakenCounts.insert({L, BackedgeTakenInfo()});
5593 if (!Pair.second)
5594 return Pair.first->second;
5595
5596 // computeBackedgeTakenCount may allocate memory for its result. Inserting it
5597 // into the BackedgeTakenCounts map transfers ownership. Otherwise, the result
5598 // must be cleared in this scope.
5599 BackedgeTakenInfo Result = computeBackedgeTakenCount(L);
5600
5601 if (Result.getExact(this) != getCouldNotCompute()) {
5602 assert(isLoopInvariant(Result.getExact(this), L) &&((isLoopInvariant(Result.getExact(this), L) && isLoopInvariant
(Result.getMax(this), L) && "Computed backedge-taken count isn't loop invariant for loop!"
) ? static_cast<void> (0) : __assert_fail ("isLoopInvariant(Result.getExact(this), L) && isLoopInvariant(Result.getMax(this), L) && \"Computed backedge-taken count isn't loop invariant for loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5604, __PRETTY_FUNCTION__))
5603 isLoopInvariant(Result.getMax(this), L) &&((isLoopInvariant(Result.getExact(this), L) && isLoopInvariant
(Result.getMax(this), L) && "Computed backedge-taken count isn't loop invariant for loop!"
) ? static_cast<void> (0) : __assert_fail ("isLoopInvariant(Result.getExact(this), L) && isLoopInvariant(Result.getMax(this), L) && \"Computed backedge-taken count isn't loop invariant for loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5604, __PRETTY_FUNCTION__))
5604 "Computed backedge-taken count isn't loop invariant for loop!")((isLoopInvariant(Result.getExact(this), L) && isLoopInvariant
(Result.getMax(this), L) && "Computed backedge-taken count isn't loop invariant for loop!"
) ? static_cast<void> (0) : __assert_fail ("isLoopInvariant(Result.getExact(this), L) && isLoopInvariant(Result.getMax(this), L) && \"Computed backedge-taken count isn't loop invariant for loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5604, __PRETTY_FUNCTION__))
;
5605 ++NumTripCountsComputed;
5606 }
5607 else if (Result.getMax(this) == getCouldNotCompute() &&
5608 isa<PHINode>(L->getHeader()->begin())) {
5609 // Only count loops that have phi nodes as not being computable.
5610 ++NumTripCountsNotComputed;
5611 }
5612
5613 // Now that we know more about the trip count for this loop, forget any
5614 // existing SCEV values for PHI nodes in this loop since they are only
5615 // conservative estimates made without the benefit of trip count
5616 // information. This is similar to the code in forgetLoop, except that
5617 // it handles SCEVUnknown PHI nodes specially.
5618 if (Result.hasAnyInfo()) {
5619 SmallVector<Instruction *, 16> Worklist;
5620 PushLoopPHIs(L, Worklist);
5621
5622 SmallPtrSet<Instruction *, 8> Visited;
5623 while (!Worklist.empty()) {
5624 Instruction *I = Worklist.pop_back_val();
5625 if (!Visited.insert(I).second)
5626 continue;
5627
5628 ValueExprMapType::iterator It =
5629 ValueExprMap.find_as(static_cast<Value *>(I));
5630 if (It != ValueExprMap.end()) {
5631 const SCEV *Old = It->second;
5632
5633 // SCEVUnknown for a PHI either means that it has an unrecognized
5634 // structure, or it's a PHI that's in the progress of being computed
5635 // by createNodeForPHI. In the former case, additional loop trip
5636 // count information isn't going to change anything. In the later
5637 // case, createNodeForPHI will perform the necessary updates on its
5638 // own when it gets to that point.
5639 if (!isa<PHINode>(I) || !isa<SCEVUnknown>(Old)) {
5640 eraseValueFromMap(It->first);
5641 forgetMemoizedResults(Old);
5642 }
5643 if (PHINode *PN = dyn_cast<PHINode>(I))
5644 ConstantEvolutionLoopExitValue.erase(PN);
5645 }
5646
5647 PushDefUseChildren(I, Worklist);
5648 }
5649 }
5650
5651 // Re-lookup the insert position, since the call to
5652 // computeBackedgeTakenCount above could result in a
5653 // recusive call to getBackedgeTakenInfo (on a different
5654 // loop), which would invalidate the iterator computed
5655 // earlier.
5656 return BackedgeTakenCounts.find(L)->second = std::move(Result);
5657}
5658
5659void ScalarEvolution::forgetLoop(const Loop *L) {
5660 // Drop any stored trip count value.
5661 auto RemoveLoopFromBackedgeMap =
5662 [L](DenseMap<const Loop *, BackedgeTakenInfo> &Map) {
5663 auto BTCPos = Map.find(L);
5664 if (BTCPos != Map.end()) {
5665 BTCPos->second.clear();
5666 Map.erase(BTCPos);
5667 }
5668 };
5669
5670 RemoveLoopFromBackedgeMap(BackedgeTakenCounts);
5671 RemoveLoopFromBackedgeMap(PredicatedBackedgeTakenCounts);
5672
5673 // Drop information about expressions based on loop-header PHIs.
5674 SmallVector<Instruction *, 16> Worklist;
5675 PushLoopPHIs(L, Worklist);
5676
5677 SmallPtrSet<Instruction *, 8> Visited;
5678 while (!Worklist.empty()) {
5679 Instruction *I = Worklist.pop_back_val();
5680 if (!Visited.insert(I).second)
5681 continue;
5682
5683 ValueExprMapType::iterator It =
5684 ValueExprMap.find_as(static_cast<Value *>(I));
5685 if (It != ValueExprMap.end()) {
5686 eraseValueFromMap(It->first);
5687 forgetMemoizedResults(It->second);
5688 if (PHINode *PN = dyn_cast<PHINode>(I))
5689 ConstantEvolutionLoopExitValue.erase(PN);
5690 }
5691
5692 PushDefUseChildren(I, Worklist);
5693 }
5694
5695 // Forget all contained loops too, to avoid dangling entries in the
5696 // ValuesAtScopes map.
5697 for (Loop *I : *L)
5698 forgetLoop(I);
5699
5700 LoopPropertiesCache.erase(L);
5701}
5702
5703void ScalarEvolution::forgetValue(Value *V) {
5704 Instruction *I = dyn_cast<Instruction>(V);
5705 if (!I) return;
5706
5707 // Drop information about expressions based on loop-header PHIs.
5708 SmallVector<Instruction *, 16> Worklist;
5709 Worklist.push_back(I);
5710
5711 SmallPtrSet<Instruction *, 8> Visited;
5712 while (!Worklist.empty()) {
5713 I = Worklist.pop_back_val();
5714 if (!Visited.insert(I).second)
5715 continue;
5716
5717 ValueExprMapType::iterator It =
5718 ValueExprMap.find_as(static_cast<Value *>(I));
5719 if (It != ValueExprMap.end()) {
5720 eraseValueFromMap(It->first);
5721 forgetMemoizedResults(It->second);
5722 if (PHINode *PN = dyn_cast<PHINode>(I))
5723 ConstantEvolutionLoopExitValue.erase(PN);
5724 }
5725
5726 PushDefUseChildren(I, Worklist);
5727 }
5728}
5729
5730/// Get the exact loop backedge taken count considering all loop exits. A
5731/// computable result can only be returned for loops with a single exit.
5732/// Returning the minimum taken count among all exits is incorrect because one
5733/// of the loop's exit limit's may have been skipped. howFarToZero assumes that
5734/// the limit of each loop test is never skipped. This is a valid assumption as
5735/// long as the loop exits via that test. For precise results, it is the
5736/// caller's responsibility to specify the relevant loop exit using
5737/// getExact(ExitingBlock, SE).
5738const SCEV *
5739ScalarEvolution::BackedgeTakenInfo::getExact(ScalarEvolution *SE,
5740 SCEVUnionPredicate *Preds) const {
5741 // If any exits were not computable, the loop is not computable.
5742 if (!isComplete() || ExitNotTaken.empty())
5743 return SE->getCouldNotCompute();
5744
5745 const SCEV *BECount = nullptr;
5746 for (auto &ENT : ExitNotTaken) {
5747 assert(ENT.ExactNotTaken != SE->getCouldNotCompute() && "bad exit SCEV")((ENT.ExactNotTaken != SE->getCouldNotCompute() &&
"bad exit SCEV") ? static_cast<void> (0) : __assert_fail
("ENT.ExactNotTaken != SE->getCouldNotCompute() && \"bad exit SCEV\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5747, __PRETTY_FUNCTION__))
;
5748
5749 if (!BECount)
5750 BECount = ENT.ExactNotTaken;
5751 else if (BECount != ENT.ExactNotTaken)
5752 return SE->getCouldNotCompute();
5753 if (Preds && !ENT.hasAlwaysTruePredicate())
5754 Preds->add(ENT.Predicate.get());
5755
5756 assert((Preds || ENT.hasAlwaysTruePredicate()) &&(((Preds || ENT.hasAlwaysTruePredicate()) && "Predicate should be always true!"
) ? static_cast<void> (0) : __assert_fail ("(Preds || ENT.hasAlwaysTruePredicate()) && \"Predicate should be always true!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5757, __PRETTY_FUNCTION__))
5757 "Predicate should be always true!")(((Preds || ENT.hasAlwaysTruePredicate()) && "Predicate should be always true!"
) ? static_cast<void> (0) : __assert_fail ("(Preds || ENT.hasAlwaysTruePredicate()) && \"Predicate should be always true!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5757, __PRETTY_FUNCTION__))
;
5758 }
5759
5760 assert(BECount && "Invalid not taken count for loop exit")((BECount && "Invalid not taken count for loop exit")
? static_cast<void> (0) : __assert_fail ("BECount && \"Invalid not taken count for loop exit\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5760, __PRETTY_FUNCTION__))
;
5761 return BECount;
5762}
5763
5764/// Get the exact not taken count for this loop exit.
5765const SCEV *
5766ScalarEvolution::BackedgeTakenInfo::getExact(BasicBlock *ExitingBlock,
5767 ScalarEvolution *SE) const {
5768 for (auto &ENT : ExitNotTaken)
5769 if (ENT.ExitingBlock == ExitingBlock && ENT.hasAlwaysTruePredicate())
5770 return ENT.ExactNotTaken;
5771
5772 return SE->getCouldNotCompute();
5773}
5774
5775/// getMax - Get the max backedge taken count for the loop.
5776const SCEV *
5777ScalarEvolution::BackedgeTakenInfo::getMax(ScalarEvolution *SE) const {
5778 auto PredicateNotAlwaysTrue = [](const ExitNotTakenInfo &ENT) {
5779 return !ENT.hasAlwaysTruePredicate();
5780 };
5781
5782 if (any_of(ExitNotTaken, PredicateNotAlwaysTrue) || !getMax())
5783 return SE->getCouldNotCompute();
5784
5785 return getMax();
5786}
5787
5788bool ScalarEvolution::BackedgeTakenInfo::isMaxOrZero(ScalarEvolution *SE) const {
5789 auto PredicateNotAlwaysTrue = [](const ExitNotTakenInfo &ENT) {
5790 return !ENT.hasAlwaysTruePredicate();
5791 };
5792 return MaxOrZero && !any_of(ExitNotTaken, PredicateNotAlwaysTrue);
5793}
5794
5795bool ScalarEvolution::BackedgeTakenInfo::hasOperand(const SCEV *S,
5796 ScalarEvolution *SE) const {
5797 if (getMax() && getMax() != SE->getCouldNotCompute() &&
5798 SE->hasOperand(getMax(), S))
5799 return true;
5800
5801 for (auto &ENT : ExitNotTaken)
5802 if (ENT.ExactNotTaken != SE->getCouldNotCompute() &&
5803 SE->hasOperand(ENT.ExactNotTaken, S))
5804 return true;
5805
5806 return false;
5807}
5808
5809/// Allocate memory for BackedgeTakenInfo and copy the not-taken count of each
5810/// computable exit into a persistent ExitNotTakenInfo array.
5811ScalarEvolution::BackedgeTakenInfo::BackedgeTakenInfo(
5812 SmallVectorImpl<ScalarEvolution::BackedgeTakenInfo::EdgeExitInfo>
5813 &&ExitCounts,
5814 bool Complete, const SCEV *MaxCount, bool MaxOrZero)
5815 : MaxAndComplete(MaxCount, Complete), MaxOrZero(MaxOrZero) {
5816 typedef ScalarEvolution::BackedgeTakenInfo::EdgeExitInfo EdgeExitInfo;
5817 ExitNotTaken.reserve(ExitCounts.size());
5818 std::transform(
5819 ExitCounts.begin(), ExitCounts.end(), std::back_inserter(ExitNotTaken),
5820 [&](const EdgeExitInfo &EEI) {
5821 BasicBlock *ExitBB = EEI.first;
5822 const ExitLimit &EL = EEI.second;
5823 if (EL.Predicates.empty())
5824 return ExitNotTakenInfo(ExitBB, EL.ExactNotTaken, nullptr);
5825
5826 std::unique_ptr<SCEVUnionPredicate> Predicate(new SCEVUnionPredicate);
5827 for (auto *Pred : EL.Predicates)
5828 Predicate->add(Pred);
5829
5830 return ExitNotTakenInfo(ExitBB, EL.ExactNotTaken, std::move(Predicate));
5831 });
5832}
5833
5834/// Invalidate this result and free the ExitNotTakenInfo array.
5835void ScalarEvolution::BackedgeTakenInfo::clear() {
5836 ExitNotTaken.clear();
5837}
5838
5839/// Compute the number of times the backedge of the specified loop will execute.
5840ScalarEvolution::BackedgeTakenInfo
5841ScalarEvolution::computeBackedgeTakenCount(const Loop *L,
5842 bool AllowPredicates) {
5843 SmallVector<BasicBlock *, 8> ExitingBlocks;
5844 L->getExitingBlocks(ExitingBlocks);
5845
5846 typedef ScalarEvolution::BackedgeTakenInfo::EdgeExitInfo EdgeExitInfo;
5847
5848 SmallVector<EdgeExitInfo, 4> ExitCounts;
5849 bool CouldComputeBECount = true;
5850 BasicBlock *Latch = L->getLoopLatch(); // may be NULL.
5851 const SCEV *MustExitMaxBECount = nullptr;
5852 const SCEV *MayExitMaxBECount = nullptr;
5853 bool MustExitMaxOrZero = false;
5854
5855 // Compute the ExitLimit for each loop exit. Use this to populate ExitCounts
5856 // and compute maxBECount.
5857 // Do a union of all the predicates here.
5858 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
5859 BasicBlock *ExitBB = ExitingBlocks[i];
5860 ExitLimit EL = computeExitLimit(L, ExitBB, AllowPredicates);
5861
5862 assert((AllowPredicates || EL.Predicates.empty()) &&(((AllowPredicates || EL.Predicates.empty()) && "Predicated exit limit when predicates are not allowed!"
) ? static_cast<void> (0) : __assert_fail ("(AllowPredicates || EL.Predicates.empty()) && \"Predicated exit limit when predicates are not allowed!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5863, __PRETTY_FUNCTION__))
5863 "Predicated exit limit when predicates are not allowed!")(((AllowPredicates || EL.Predicates.empty()) && "Predicated exit limit when predicates are not allowed!"
) ? static_cast<void> (0) : __assert_fail ("(AllowPredicates || EL.Predicates.empty()) && \"Predicated exit limit when predicates are not allowed!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5863, __PRETTY_FUNCTION__))
;
5864
5865 // 1. For each exit that can be computed, add an entry to ExitCounts.
5866 // CouldComputeBECount is true only if all exits can be computed.
5867 if (EL.ExactNotTaken == getCouldNotCompute())
5868 // We couldn't compute an exact value for this exit, so
5869 // we won't be able to compute an exact value for the loop.
5870 CouldComputeBECount = false;
5871 else
5872 ExitCounts.emplace_back(ExitBB, EL);
5873
5874 // 2. Derive the loop's MaxBECount from each exit's max number of
5875 // non-exiting iterations. Partition the loop exits into two kinds:
5876 // LoopMustExits and LoopMayExits.
5877 //
5878 // If the exit dominates the loop latch, it is a LoopMustExit otherwise it
5879 // is a LoopMayExit. If any computable LoopMustExit is found, then
5880 // MaxBECount is the minimum EL.MaxNotTaken of computable
5881 // LoopMustExits. Otherwise, MaxBECount is conservatively the maximum
5882 // EL.MaxNotTaken, where CouldNotCompute is considered greater than any
5883 // computable EL.MaxNotTaken.
5884 if (EL.MaxNotTaken != getCouldNotCompute() && Latch &&
5885 DT.dominates(ExitBB, Latch)) {
5886 if (!MustExitMaxBECount) {
5887 MustExitMaxBECount = EL.MaxNotTaken;
5888 MustExitMaxOrZero = EL.MaxOrZero;
5889 } else {
5890 MustExitMaxBECount =
5891 getUMinFromMismatchedTypes(MustExitMaxBECount, EL.MaxNotTaken);
5892 }
5893 } else if (MayExitMaxBECount != getCouldNotCompute()) {
5894 if (!MayExitMaxBECount || EL.MaxNotTaken == getCouldNotCompute())
5895 MayExitMaxBECount = EL.MaxNotTaken;
5896 else {
5897 MayExitMaxBECount =
5898 getUMaxFromMismatchedTypes(MayExitMaxBECount, EL.MaxNotTaken);
5899 }
5900 }
5901 }
5902 const SCEV *MaxBECount = MustExitMaxBECount ? MustExitMaxBECount :
5903 (MayExitMaxBECount ? MayExitMaxBECount : getCouldNotCompute());
5904 // The loop backedge will be taken the maximum or zero times if there's
5905 // a single exit that must be taken the maximum or zero times.
5906 bool MaxOrZero = (MustExitMaxOrZero && ExitingBlocks.size() == 1);
5907 return BackedgeTakenInfo(std::move(ExitCounts), CouldComputeBECount,
5908 MaxBECount, MaxOrZero);
5909}
5910
5911ScalarEvolution::ExitLimit
5912ScalarEvolution::computeExitLimit(const Loop *L, BasicBlock *ExitingBlock,
5913 bool AllowPredicates) {
5914
5915 // Okay, we've chosen an exiting block. See what condition causes us to exit
5916 // at this block and remember the exit block and whether all other targets
5917 // lead to the loop header.
5918 bool MustExecuteLoopHeader = true;
5919 BasicBlock *Exit = nullptr;
5920 for (auto *SBB : successors(ExitingBlock))
5921 if (!L->contains(SBB)) {
5922 if (Exit) // Multiple exit successors.
5923 return getCouldNotCompute();
5924 Exit = SBB;
5925 } else if (SBB != L->getHeader()) {
5926 MustExecuteLoopHeader = false;
5927 }
5928
5929 // At this point, we know we have a conditional branch that determines whether
5930 // the loop is exited. However, we don't know if the branch is executed each
5931 // time through the loop. If not, then the execution count of the branch will
5932 // not be equal to the trip count of the loop.
5933 //
5934 // Currently we check for this by checking to see if the Exit branch goes to
5935 // the loop header. If so, we know it will always execute the same number of
5936 // times as the loop. We also handle the case where the exit block *is* the
5937 // loop header. This is common for un-rotated loops.
5938 //
5939 // If both of those tests fail, walk up the unique predecessor chain to the
5940 // header, stopping if there is an edge that doesn't exit the loop. If the
5941 // header is reached, the execution count of the branch will be equal to the
5942 // trip count of the loop.
5943 //
5944 // More extensive analysis could be done to handle more cases here.
5945 //
5946 if (!MustExecuteLoopHeader && ExitingBlock != L->getHeader()) {
5947 // The simple checks failed, try climbing the unique predecessor chain
5948 // up to the header.
5949 bool Ok = false;
5950 for (BasicBlock *BB = ExitingBlock; BB; ) {
5951 BasicBlock *Pred = BB->getUniquePredecessor();
5952 if (!Pred)
5953 return getCouldNotCompute();
5954 TerminatorInst *PredTerm = Pred->getTerminator();
5955 for (const BasicBlock *PredSucc : PredTerm->successors()) {
5956 if (PredSucc == BB)
5957 continue;
5958 // If the predecessor has a successor that isn't BB and isn't
5959 // outside the loop, assume the worst.
5960 if (L->contains(PredSucc))
5961 return getCouldNotCompute();
5962 }
5963 if (Pred == L->getHeader()) {
5964 Ok = true;
5965 break;
5966 }
5967 BB = Pred;
5968 }
5969 if (!Ok)
5970 return getCouldNotCompute();
5971 }
5972
5973 bool IsOnlyExit = (L->getExitingBlock() != nullptr);
5974 TerminatorInst *Term = ExitingBlock->getTerminator();
5975 if (BranchInst *BI = dyn_cast<BranchInst>(Term)) {
5976 assert(BI->isConditional() && "If unconditional, it can't be in loop!")((BI->isConditional() && "If unconditional, it can't be in loop!"
) ? static_cast<void> (0) : __assert_fail ("BI->isConditional() && \"If unconditional, it can't be in loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 5976, __PRETTY_FUNCTION__))
;
5977 // Proceed to the next level to examine the exit condition expression.
5978 return computeExitLimitFromCond(
5979 L, BI->getCondition(), BI->getSuccessor(0), BI->getSuccessor(1),
5980 /*ControlsExit=*/IsOnlyExit, AllowPredicates);
5981 }
5982
5983 if (SwitchInst *SI = dyn_cast<SwitchInst>(Term))
5984 return computeExitLimitFromSingleExitSwitch(L, SI, Exit,
5985 /*ControlsExit=*/IsOnlyExit);
5986
5987 return getCouldNotCompute();
5988}
5989
5990ScalarEvolution::ExitLimit
5991ScalarEvolution::computeExitLimitFromCond(const Loop *L,
5992 Value *ExitCond,
5993 BasicBlock *TBB,
5994 BasicBlock *FBB,
5995 bool ControlsExit,
5996 bool AllowPredicates) {
5997 // Check if the controlling expression for this loop is an And or Or.
5998 if (BinaryOperator *BO = dyn_cast<BinaryOperator>(ExitCond)) {
5999 if (BO->getOpcode() == Instruction::And) {
6000 // Recurse on the operands of the and.
6001 bool EitherMayExit = L->contains(TBB);
6002 ExitLimit EL0 = computeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
6003 ControlsExit && !EitherMayExit,
6004 AllowPredicates);
6005 ExitLimit EL1 = computeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
6006 ControlsExit && !EitherMayExit,
6007 AllowPredicates);
6008 const SCEV *BECount = getCouldNotCompute();
6009 const SCEV *MaxBECount = getCouldNotCompute();
6010 if (EitherMayExit) {
6011 // Both conditions must be true for the loop to continue executing.
6012 // Choose the less conservative count.
6013 if (EL0.ExactNotTaken == getCouldNotCompute() ||
6014 EL1.ExactNotTaken == getCouldNotCompute())
6015 BECount = getCouldNotCompute();
6016 else
6017 BECount =
6018 getUMinFromMismatchedTypes(EL0.ExactNotTaken, EL1.ExactNotTaken);
6019 if (EL0.MaxNotTaken == getCouldNotCompute())
6020 MaxBECount = EL1.MaxNotTaken;
6021 else if (EL1.MaxNotTaken == getCouldNotCompute())
6022 MaxBECount = EL0.MaxNotTaken;
6023 else
6024 MaxBECount =
6025 getUMinFromMismatchedTypes(EL0.MaxNotTaken, EL1.MaxNotTaken);
6026 } else {
6027 // Both conditions must be true at the same time for the loop to exit.
6028 // For now, be conservative.
6029 assert(L->contains(FBB) && "Loop block has no successor in loop!")((L->contains(FBB) && "Loop block has no successor in loop!"
) ? static_cast<void> (0) : __assert_fail ("L->contains(FBB) && \"Loop block has no successor in loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6029, __PRETTY_FUNCTION__))
;
6030 if (EL0.MaxNotTaken == EL1.MaxNotTaken)
6031 MaxBECount = EL0.MaxNotTaken;
6032 if (EL0.ExactNotTaken == EL1.ExactNotTaken)
6033 BECount = EL0.ExactNotTaken;
6034 }
6035
6036 // There are cases (e.g. PR26207) where computeExitLimitFromCond is able
6037 // to be more aggressive when computing BECount than when computing
6038 // MaxBECount. In these cases it is possible for EL0.ExactNotTaken and
6039 // EL1.ExactNotTaken to match, but for EL0.MaxNotTaken and EL1.MaxNotTaken
6040 // to not.
6041 if (isa<SCEVCouldNotCompute>(MaxBECount) &&
6042 !isa<SCEVCouldNotCompute>(BECount))
6043 MaxBECount = BECount;
6044
6045 return ExitLimit(BECount, MaxBECount, false,
6046 {&EL0.Predicates, &EL1.Predicates});
6047 }
6048 if (BO->getOpcode() == Instruction::Or) {
6049 // Recurse on the operands of the or.
6050 bool EitherMayExit = L->contains(FBB);
6051 ExitLimit EL0 = computeExitLimitFromCond(L, BO->getOperand(0), TBB, FBB,
6052 ControlsExit && !EitherMayExit,
6053 AllowPredicates);
6054 ExitLimit EL1 = computeExitLimitFromCond(L, BO->getOperand(1), TBB, FBB,
6055 ControlsExit && !EitherMayExit,
6056 AllowPredicates);
6057 const SCEV *BECount = getCouldNotCompute();
6058 const SCEV *MaxBECount = getCouldNotCompute();
6059 if (EitherMayExit) {
6060 // Both conditions must be false for the loop to continue executing.
6061 // Choose the less conservative count.
6062 if (EL0.ExactNotTaken == getCouldNotCompute() ||
6063 EL1.ExactNotTaken == getCouldNotCompute())
6064 BECount = getCouldNotCompute();
6065 else
6066 BECount =
6067 getUMinFromMismatchedTypes(EL0.ExactNotTaken, EL1.ExactNotTaken);
6068 if (EL0.MaxNotTaken == getCouldNotCompute())
6069 MaxBECount = EL1.MaxNotTaken;
6070 else if (EL1.MaxNotTaken == getCouldNotCompute())
6071 MaxBECount = EL0.MaxNotTaken;
6072 else
6073 MaxBECount =
6074 getUMinFromMismatchedTypes(EL0.MaxNotTaken, EL1.MaxNotTaken);
6075 } else {
6076 // Both conditions must be false at the same time for the loop to exit.
6077 // For now, be conservative.
6078 assert(L->contains(TBB) && "Loop block has no successor in loop!")((L->contains(TBB) && "Loop block has no successor in loop!"
) ? static_cast<void> (0) : __assert_fail ("L->contains(TBB) && \"Loop block has no successor in loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6078, __PRETTY_FUNCTION__))
;
6079 if (EL0.MaxNotTaken == EL1.MaxNotTaken)
6080 MaxBECount = EL0.MaxNotTaken;
6081 if (EL0.ExactNotTaken == EL1.ExactNotTaken)
6082 BECount = EL0.ExactNotTaken;
6083 }
6084
6085 return ExitLimit(BECount, MaxBECount, false,
6086 {&EL0.Predicates, &EL1.Predicates});
6087 }
6088 }
6089
6090 // With an icmp, it may be feasible to compute an exact backedge-taken count.
6091 // Proceed to the next level to examine the icmp.
6092 if (ICmpInst *ExitCondICmp = dyn_cast<ICmpInst>(ExitCond)) {
6093 ExitLimit EL =
6094 computeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, ControlsExit);
6095 if (EL.hasFullInfo() || !AllowPredicates)
6096 return EL;
6097
6098 // Try again, but use SCEV predicates this time.
6099 return computeExitLimitFromICmp(L, ExitCondICmp, TBB, FBB, ControlsExit,
6100 /*AllowPredicates=*/true);
6101 }
6102
6103 // Check for a constant condition. These are normally stripped out by
6104 // SimplifyCFG, but ScalarEvolution may be used by a pass which wishes to
6105 // preserve the CFG and is temporarily leaving constant conditions
6106 // in place.
6107 if (ConstantInt *CI = dyn_cast<ConstantInt>(ExitCond)) {
6108 if (L->contains(FBB) == !CI->getZExtValue())
6109 // The backedge is always taken.
6110 return getCouldNotCompute();
6111 else
6112 // The backedge is never taken.
6113 return getZero(CI->getType());
6114 }
6115
6116 // If it's not an integer or pointer comparison then compute it the hard way.
6117 return computeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
6118}
6119
6120ScalarEvolution::ExitLimit
6121ScalarEvolution::computeExitLimitFromICmp(const Loop *L,
6122 ICmpInst *ExitCond,
6123 BasicBlock *TBB,
6124 BasicBlock *FBB,
6125 bool ControlsExit,
6126 bool AllowPredicates) {
6127
6128 // If the condition was exit on true, convert the condition to exit on false
6129 ICmpInst::Predicate Cond;
6130 if (!L->contains(FBB))
6131 Cond = ExitCond->getPredicate();
6132 else
6133 Cond = ExitCond->getInversePredicate();
6134
6135 // Handle common loops like: for (X = "string"; *X; ++X)
6136 if (LoadInst *LI = dyn_cast<LoadInst>(ExitCond->getOperand(0)))
6137 if (Constant *RHS = dyn_cast<Constant>(ExitCond->getOperand(1))) {
6138 ExitLimit ItCnt =
6139 computeLoadConstantCompareExitLimit(LI, RHS, L, Cond);
6140 if (ItCnt.hasAnyInfo())
6141 return ItCnt;
6142 }
6143
6144 const SCEV *LHS = getSCEV(ExitCond->getOperand(0));
6145 const SCEV *RHS = getSCEV(ExitCond->getOperand(1));
6146
6147 // Try to evaluate any dependencies out of the loop.
6148 LHS = getSCEVAtScope(LHS, L);
6149 RHS = getSCEVAtScope(RHS, L);
6150
6151 // At this point, we would like to compute how many iterations of the
6152 // loop the predicate will return true for these inputs.
6153 if (isLoopInvariant(LHS, L) && !isLoopInvariant(RHS, L)) {
6154 // If there is a loop-invariant, force it into the RHS.
6155 std::swap(LHS, RHS);
6156 Cond = ICmpInst::getSwappedPredicate(Cond);
6157 }
6158
6159 // Simplify the operands before analyzing them.
6160 (void)SimplifyICmpOperands(Cond, LHS, RHS);
6161
6162 // If we have a comparison of a chrec against a constant, try to use value
6163 // ranges to answer this query.
6164 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS))
6165 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(LHS))
6166 if (AddRec->getLoop() == L) {
6167 // Form the constant range.
6168 ConstantRange CompRange =
6169 ConstantRange::makeExactICmpRegion(Cond, RHSC->getAPInt());
6170
6171 const SCEV *Ret = AddRec->getNumIterationsInRange(CompRange, *this);
6172 if (!isa<SCEVCouldNotCompute>(Ret)) return Ret;
6173 }
6174
6175 switch (Cond) {
6176 case ICmpInst::ICMP_NE: { // while (X != Y)
6177 // Convert to: while (X-Y != 0)
6178 ExitLimit EL = howFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit,
6179 AllowPredicates);
6180 if (EL.hasAnyInfo()) return EL;
6181 break;
6182 }
6183 case ICmpInst::ICMP_EQ: { // while (X == Y)
6184 // Convert to: while (X-Y == 0)
6185 ExitLimit EL = howFarToNonZero(getMinusSCEV(LHS, RHS), L);
6186 if (EL.hasAnyInfo()) return EL;
6187 break;
6188 }
6189 case ICmpInst::ICMP_SLT:
6190 case ICmpInst::ICMP_ULT: { // while (X < Y)
6191 bool IsSigned = Cond == ICmpInst::ICMP_SLT;
6192 ExitLimit EL = howManyLessThans(LHS, RHS, L, IsSigned, ControlsExit,
6193 AllowPredicates);
6194 if (EL.hasAnyInfo()) return EL;
6195 break;
6196 }
6197 case ICmpInst::ICMP_SGT:
6198 case ICmpInst::ICMP_UGT: { // while (X > Y)
6199 bool IsSigned = Cond == ICmpInst::ICMP_SGT;
6200 ExitLimit EL =
6201 howManyGreaterThans(LHS, RHS, L, IsSigned, ControlsExit,
6202 AllowPredicates);
6203 if (EL.hasAnyInfo()) return EL;
6204 break;
6205 }
6206 default:
6207 break;
6208 }
6209
6210 auto *ExhaustiveCount =
6211 computeExitCountExhaustively(L, ExitCond, !L->contains(TBB));
6212
6213 if (!isa<SCEVCouldNotCompute>(ExhaustiveCount))
6214 return ExhaustiveCount;
6215
6216 return computeShiftCompareExitLimit(ExitCond->getOperand(0),
6217 ExitCond->getOperand(1), L, Cond);
6218}
6219
6220ScalarEvolution::ExitLimit
6221ScalarEvolution::computeExitLimitFromSingleExitSwitch(const Loop *L,
6222 SwitchInst *Switch,
6223 BasicBlock *ExitingBlock,
6224 bool ControlsExit) {
6225 assert(!L->contains(ExitingBlock) && "Not an exiting block!")((!L->contains(ExitingBlock) && "Not an exiting block!"
) ? static_cast<void> (0) : __assert_fail ("!L->contains(ExitingBlock) && \"Not an exiting block!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6225, __PRETTY_FUNCTION__))
;
6226
6227 // Give up if the exit is the default dest of a switch.
6228 if (Switch->getDefaultDest() == ExitingBlock)
6229 return getCouldNotCompute();
6230
6231 assert(L->contains(Switch->getDefaultDest()) &&((L->contains(Switch->getDefaultDest()) && "Default case must not exit the loop!"
) ? static_cast<void> (0) : __assert_fail ("L->contains(Switch->getDefaultDest()) && \"Default case must not exit the loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6232, __PRETTY_FUNCTION__))
6232 "Default case must not exit the loop!")((L->contains(Switch->getDefaultDest()) && "Default case must not exit the loop!"
) ? static_cast<void> (0) : __assert_fail ("L->contains(Switch->getDefaultDest()) && \"Default case must not exit the loop!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6232, __PRETTY_FUNCTION__))
;
6233 const SCEV *LHS = getSCEVAtScope(Switch->getCondition(), L);
6234 const SCEV *RHS = getConstant(Switch->findCaseDest(ExitingBlock));
6235
6236 // while (X != Y) --> while (X-Y != 0)
6237 ExitLimit EL = howFarToZero(getMinusSCEV(LHS, RHS), L, ControlsExit);
6238 if (EL.hasAnyInfo())
6239 return EL;
6240
6241 return getCouldNotCompute();
6242}
6243
6244static ConstantInt *
6245EvaluateConstantChrecAtConstant(const SCEVAddRecExpr *AddRec, ConstantInt *C,
6246 ScalarEvolution &SE) {
6247 const SCEV *InVal = SE.getConstant(C);
6248 const SCEV *Val = AddRec->evaluateAtIteration(InVal, SE);
6249 assert(isa<SCEVConstant>(Val) &&((isa<SCEVConstant>(Val) && "Evaluation of SCEV at constant didn't fold correctly?"
) ? static_cast<void> (0) : __assert_fail ("isa<SCEVConstant>(Val) && \"Evaluation of SCEV at constant didn't fold correctly?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6250, __PRETTY_FUNCTION__))
6250 "Evaluation of SCEV at constant didn't fold correctly?")((isa<SCEVConstant>(Val) && "Evaluation of SCEV at constant didn't fold correctly?"
) ? static_cast<void> (0) : __assert_fail ("isa<SCEVConstant>(Val) && \"Evaluation of SCEV at constant didn't fold correctly?\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6250, __PRETTY_FUNCTION__))
;
6251 return cast<SCEVConstant>(Val)->getValue();
6252}
6253
6254/// Given an exit condition of 'icmp op load X, cst', try to see if we can
6255/// compute the backedge execution count.
6256ScalarEvolution::ExitLimit
6257ScalarEvolution::computeLoadConstantCompareExitLimit(
6258 LoadInst *LI,
6259 Constant *RHS,
6260 const Loop *L,
6261 ICmpInst::Predicate predicate) {
6262
6263 if (LI->isVolatile()) return getCouldNotCompute();
6264
6265 // Check to see if the loaded pointer is a getelementptr of a global.
6266 // TODO: Use SCEV instead of manually grubbing with GEPs.
6267 GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(LI->getOperand(0));
6268 if (!GEP) return getCouldNotCompute();
6269
6270 // Make sure that it is really a constant global we are gepping, with an
6271 // initializer, and make sure the first IDX is really 0.
6272 GlobalVariable *GV = dyn_cast<GlobalVariable>(GEP->getOperand(0));
6273 if (!GV || !GV->isConstant() || !GV->hasDefinitiveInitializer() ||
6274 GEP->getNumOperands() < 3 || !isa<Constant>(GEP->getOperand(1)) ||
6275 !cast<Constant>(GEP->getOperand(1))->isNullValue())
6276 return getCouldNotCompute();
6277
6278 // Okay, we allow one non-constant index into the GEP instruction.
6279 Value *VarIdx = nullptr;
6280 std::vector<Constant*> Indexes;
6281 unsigned VarIdxNum = 0;
6282 for (unsigned i = 2, e = GEP->getNumOperands(); i != e; ++i)
6283 if (ConstantInt *CI = dyn_cast<ConstantInt>(GEP->getOperand(i))) {
6284 Indexes.push_back(CI);
6285 } else if (!isa<ConstantInt>(GEP->getOperand(i))) {
6286 if (VarIdx) return getCouldNotCompute(); // Multiple non-constant idx's.
6287 VarIdx = GEP->getOperand(i);
6288 VarIdxNum = i-2;
6289 Indexes.push_back(nullptr);
6290 }
6291
6292 // Loop-invariant loads may be a byproduct of loop optimization. Skip them.
6293 if (!VarIdx)
6294 return getCouldNotCompute();
6295
6296 // Okay, we know we have a (load (gep GV, 0, X)) comparison with a constant.
6297 // Check to see if X is a loop variant variable value now.
6298 const SCEV *Idx = getSCEV(VarIdx);
6299 Idx = getSCEVAtScope(Idx, L);
6300
6301 // We can only recognize very limited forms of loop index expressions, in
6302 // particular, only affine AddRec's like {C1,+,C2}.
6303 const SCEVAddRecExpr *IdxExpr = dyn_cast<SCEVAddRecExpr>(Idx);
6304 if (!IdxExpr || !IdxExpr->isAffine() || isLoopInvariant(IdxExpr, L) ||
6305 !isa<SCEVConstant>(IdxExpr->getOperand(0)) ||
6306 !isa<SCEVConstant>(IdxExpr->getOperand(1)))
6307 return getCouldNotCompute();
6308
6309 unsigned MaxSteps = MaxBruteForceIterations;
6310 for (unsigned IterationNum = 0; IterationNum != MaxSteps; ++IterationNum) {
6311 ConstantInt *ItCst = ConstantInt::get(
6312 cast<IntegerType>(IdxExpr->getType()), IterationNum);
6313 ConstantInt *Val = EvaluateConstantChrecAtConstant(IdxExpr, ItCst, *this);
6314
6315 // Form the GEP offset.
6316 Indexes[VarIdxNum] = Val;
6317
6318 Constant *Result = ConstantFoldLoadThroughGEPIndices(GV->getInitializer(),
6319 Indexes);
6320 if (!Result) break; // Cannot compute!
6321
6322 // Evaluate the condition for this iteration.
6323 Result = ConstantExpr::getICmp(predicate, Result, RHS);
6324 if (!isa<ConstantInt>(Result)) break; // Couldn't decide for sure
6325 if (cast<ConstantInt>(Result)->getValue().isMinValue()) {
6326 ++NumArrayLenItCounts;
6327 return getConstant(ItCst); // Found terminating iteration!
6328 }
6329 }
6330 return getCouldNotCompute();
6331}
6332
6333ScalarEvolution::ExitLimit ScalarEvolution::computeShiftCompareExitLimit(
6334 Value *LHS, Value *RHSV, const Loop *L, ICmpInst::Predicate Pred) {
6335 ConstantInt *RHS = dyn_cast<ConstantInt>(RHSV);
6336 if (!RHS)
6337 return getCouldNotCompute();
6338
6339 const BasicBlock *Latch = L->getLoopLatch();
6340 if (!Latch)
6341 return getCouldNotCompute();
6342
6343 const BasicBlock *Predecessor = L->getLoopPredecessor();
6344 if (!Predecessor)
6345 return getCouldNotCompute();
6346
6347 // Return true if V is of the form "LHS `shift_op` <positive constant>".
6348 // Return LHS in OutLHS and shift_opt in OutOpCode.
6349 auto MatchPositiveShift =
6350 [](Value *V, Value *&OutLHS, Instruction::BinaryOps &OutOpCode) {
6351
6352 using namespace PatternMatch;
6353
6354 ConstantInt *ShiftAmt;
6355 if (match(V, m_LShr(m_Value(OutLHS), m_ConstantInt(ShiftAmt))))
6356 OutOpCode = Instruction::LShr;
6357 else if (match(V, m_AShr(m_Value(OutLHS), m_ConstantInt(ShiftAmt))))
6358 OutOpCode = Instruction::AShr;
6359 else if (match(V, m_Shl(m_Value(OutLHS), m_ConstantInt(ShiftAmt))))
6360 OutOpCode = Instruction::Shl;
6361 else
6362 return false;
6363
6364 return ShiftAmt->getValue().isStrictlyPositive();
6365 };
6366
6367 // Recognize a "shift recurrence" either of the form %iv or of %iv.shifted in
6368 //
6369 // loop:
6370 // %iv = phi i32 [ %iv.shifted, %loop ], [ %val, %preheader ]
6371 // %iv.shifted = lshr i32 %iv, <positive constant>
6372 //
6373 // Return true on a successful match. Return the corresponding PHI node (%iv
6374 // above) in PNOut and the opcode of the shift operation in OpCodeOut.
6375 auto MatchShiftRecurrence =
6376 [&](Value *V, PHINode *&PNOut, Instruction::BinaryOps &OpCodeOut) {
6377 Optional<Instruction::BinaryOps> PostShiftOpCode;
6378
6379 {
6380 Instruction::BinaryOps OpC;
6381 Value *V;
6382
6383 // If we encounter a shift instruction, "peel off" the shift operation,
6384 // and remember that we did so. Later when we inspect %iv's backedge
6385 // value, we will make sure that the backedge value uses the same
6386 // operation.
6387 //
6388 // Note: the peeled shift operation does not have to be the same
6389 // instruction as the one feeding into the PHI's backedge value. We only
6390 // really care about it being the same *kind* of shift instruction --
6391 // that's all that is required for our later inferences to hold.
6392 if (MatchPositiveShift(LHS, V, OpC)) {
6393 PostShiftOpCode = OpC;
6394 LHS = V;
6395 }
6396 }
6397
6398 PNOut = dyn_cast<PHINode>(LHS);
6399 if (!PNOut || PNOut->getParent() != L->getHeader())
6400 return false;
6401
6402 Value *BEValue = PNOut->getIncomingValueForBlock(Latch);
6403 Value *OpLHS;
6404
6405 return
6406 // The backedge value for the PHI node must be a shift by a positive
6407 // amount
6408 MatchPositiveShift(BEValue, OpLHS, OpCodeOut) &&
6409
6410 // of the PHI node itself
6411 OpLHS == PNOut &&
6412
6413 // and the kind of shift should be match the kind of shift we peeled
6414 // off, if any.
6415 (!PostShiftOpCode.hasValue() || *PostShiftOpCode == OpCodeOut);
6416 };
6417
6418 PHINode *PN;
6419 Instruction::BinaryOps OpCode;
6420 if (!MatchShiftRecurrence(LHS, PN, OpCode))
6421 return getCouldNotCompute();
6422
6423 const DataLayout &DL = getDataLayout();
6424
6425 // The key rationale for this optimization is that for some kinds of shift
6426 // recurrences, the value of the recurrence "stabilizes" to either 0 or -1
6427 // within a finite number of iterations. If the condition guarding the
6428 // backedge (in the sense that the backedge is taken if the condition is true)
6429 // is false for the value the shift recurrence stabilizes to, then we know
6430 // that the backedge is taken only a finite number of times.
6431
6432 ConstantInt *StableValue = nullptr;
6433 switch (OpCode) {
6434 default:
6435 llvm_unreachable("Impossible case!")::llvm::llvm_unreachable_internal("Impossible case!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6435)
;
6436
6437 case Instruction::AShr: {
6438 // {K,ashr,<positive-constant>} stabilizes to signum(K) in at most
6439 // bitwidth(K) iterations.
6440 Value *FirstValue = PN->getIncomingValueForBlock(Predecessor);
6441 bool KnownZero, KnownOne;
6442 ComputeSignBit(FirstValue, KnownZero, KnownOne, DL, 0, nullptr,
6443 Predecessor->getTerminator(), &DT);
6444 auto *Ty = cast<IntegerType>(RHS->getType());
6445 if (KnownZero)
6446 StableValue = ConstantInt::get(Ty, 0);
6447 else if (KnownOne)
6448 StableValue = ConstantInt::get(Ty, -1, true);
6449 else
6450 return getCouldNotCompute();
6451
6452 break;
6453 }
6454 case Instruction::LShr:
6455 case Instruction::Shl:
6456 // Both {K,lshr,<positive-constant>} and {K,shl,<positive-constant>}
6457 // stabilize to 0 in at most bitwidth(K) iterations.
6458 StableValue = ConstantInt::get(cast<IntegerType>(RHS->getType()), 0);
6459 break;
6460 }
6461
6462 auto *Result =
6463 ConstantFoldCompareInstOperands(Pred, StableValue, RHS, DL, &TLI);
6464 assert(Result->getType()->isIntegerTy(1) &&((Result->getType()->isIntegerTy(1) && "Otherwise cannot be an operand to a branch instruction"
) ? static_cast<void> (0) : __assert_fail ("Result->getType()->isIntegerTy(1) && \"Otherwise cannot be an operand to a branch instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6465, __PRETTY_FUNCTION__))
6465 "Otherwise cannot be an operand to a branch instruction")((Result->getType()->isIntegerTy(1) && "Otherwise cannot be an operand to a branch instruction"
) ? static_cast<void> (0) : __assert_fail ("Result->getType()->isIntegerTy(1) && \"Otherwise cannot be an operand to a branch instruction\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6465, __PRETTY_FUNCTION__))
;
6466
6467 if (Result->isZeroValue()) {
6468 unsigned BitWidth = getTypeSizeInBits(RHS->getType());
6469 const SCEV *UpperBound =
6470 getConstant(getEffectiveSCEVType(RHS->getType()), BitWidth);
6471 return ExitLimit(getCouldNotCompute(), UpperBound, false);
6472 }
6473
6474 return getCouldNotCompute();
6475}
6476
6477/// Return true if we can constant fold an instruction of the specified type,
6478/// assuming that all operands were constants.
6479static bool CanConstantFold(const Instruction *I) {
6480 if (isa<BinaryOperator>(I) || isa<CmpInst>(I) ||
6481 isa<SelectInst>(I) || isa<CastInst>(I) || isa<GetElementPtrInst>(I) ||
6482 isa<LoadInst>(I))
6483 return true;
6484
6485 if (const CallInst *CI = dyn_cast<CallInst>(I))
6486 if (const Function *F = CI->getCalledFunction())
6487 return canConstantFoldCallTo(F);
6488 return false;
6489}
6490
6491/// Determine whether this instruction can constant evolve within this loop
6492/// assuming its operands can all constant evolve.
6493static bool canConstantEvolve(Instruction *I, const Loop *L) {
6494 // An instruction outside of the loop can't be derived from a loop PHI.
6495 if (!L->contains(I)) return false;
6496
6497 if (isa<PHINode>(I)) {
6498 // We don't currently keep track of the control flow needed to evaluate
6499 // PHIs, so we cannot handle PHIs inside of loops.
6500 return L->getHeader() == I->getParent();
6501 }
6502
6503 // If we won't be able to constant fold this expression even if the operands
6504 // are constants, bail early.
6505 return CanConstantFold(I);
6506}
6507
6508/// getConstantEvolvingPHIOperands - Implement getConstantEvolvingPHI by
6509/// recursing through each instruction operand until reaching a loop header phi.
6510static PHINode *
6511getConstantEvolvingPHIOperands(Instruction *UseInst, const Loop *L,
6512 DenseMap<Instruction *, PHINode *> &PHIMap,
6513 unsigned Depth) {
6514 if (Depth > MaxConstantEvolvingDepth)
6515 return nullptr;
6516
6517 // Otherwise, we can evaluate this instruction if all of its operands are
6518 // constant or derived from a PHI node themselves.
6519 PHINode *PHI = nullptr;
6520 for (Value *Op : UseInst->operands()) {
6521 if (isa<Constant>(Op)) continue;
6522
6523 Instruction *OpInst = dyn_cast<Instruction>(Op);
6524 if (!OpInst || !canConstantEvolve(OpInst, L)) return nullptr;
6525
6526 PHINode *P = dyn_cast<PHINode>(OpInst);
6527 if (!P)
6528 // If this operand is already visited, reuse the prior result.
6529 // We may have P != PHI if this is the deepest point at which the
6530 // inconsistent paths meet.
6531 P = PHIMap.lookup(OpInst);
6532 if (!P) {
6533 // Recurse and memoize the results, whether a phi is found or not.
6534 // This recursive call invalidates pointers into PHIMap.
6535 P = getConstantEvolvingPHIOperands(OpInst, L, PHIMap, Depth + 1);
6536 PHIMap[OpInst] = P;
6537 }
6538 if (!P)
6539 return nullptr; // Not evolving from PHI
6540 if (PHI && PHI != P)
6541 return nullptr; // Evolving from multiple different PHIs.
6542 PHI = P;
6543 }
6544 // This is a expression evolving from a constant PHI!
6545 return PHI;
6546}
6547
6548/// getConstantEvolvingPHI - Given an LLVM value and a loop, return a PHI node
6549/// in the loop that V is derived from. We allow arbitrary operations along the
6550/// way, but the operands of an operation must either be constants or a value
6551/// derived from a constant PHI. If this expression does not fit with these
6552/// constraints, return null.
6553static PHINode *getConstantEvolvingPHI(Value *V, const Loop *L) {
6554 Instruction *I = dyn_cast<Instruction>(V);
6555 if (!I || !canConstantEvolve(I, L)) return nullptr;
6556
6557 if (PHINode *PN = dyn_cast<PHINode>(I))
6558 return PN;
6559
6560 // Record non-constant instructions contained by the loop.
6561 DenseMap<Instruction *, PHINode *> PHIMap;
6562 return getConstantEvolvingPHIOperands(I, L, PHIMap, 0);
6563}
6564
6565/// EvaluateExpression - Given an expression that passes the
6566/// getConstantEvolvingPHI predicate, evaluate its value assuming the PHI node
6567/// in the loop has the value PHIVal. If we can't fold this expression for some
6568/// reason, return null.
6569static Constant *EvaluateExpression(Value *V, const Loop *L,
6570 DenseMap<Instruction *, Constant *> &Vals,
6571 const DataLayout &DL,
6572 const TargetLibraryInfo *TLI) {
6573 // Convenient constant check, but redundant for recursive calls.
6574 if (Constant *C = dyn_cast<Constant>(V)) return C;
6575 Instruction *I = dyn_cast<Instruction>(V);
6576 if (!I) return nullptr;
6577
6578 if (Constant *C = Vals.lookup(I)) return C;
6579
6580 // An instruction inside the loop depends on a value outside the loop that we
6581 // weren't given a mapping for, or a value such as a call inside the loop.
6582 if (!canConstantEvolve(I, L)) return nullptr;
6583
6584 // An unmapped PHI can be due to a branch or another loop inside this loop,
6585 // or due to this not being the initial iteration through a loop where we
6586 // couldn't compute the evolution of this particular PHI last time.
6587 if (isa<PHINode>(I)) return nullptr;
6588
6589 std::vector<Constant*> Operands(I->getNumOperands());
6590
6591 for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
6592 Instruction *Operand = dyn_cast<Instruction>(I->getOperand(i));
6593 if (!Operand) {
6594 Operands[i] = dyn_cast<Constant>(I->getOperand(i));
6595 if (!Operands[i]) return nullptr;
6596 continue;
6597 }
6598 Constant *C = EvaluateExpression(Operand, L, Vals, DL, TLI);
6599 Vals[Operand] = C;
6600 if (!C) return nullptr;
6601 Operands[i] = C;
6602 }
6603
6604 if (CmpInst *CI = dyn_cast<CmpInst>(I))
6605 return ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
6606 Operands[1], DL, TLI);
6607 if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
6608 if (!LI->isVolatile())
6609 return ConstantFoldLoadFromConstPtr(Operands[0], LI->getType(), DL);
6610 }
6611 return ConstantFoldInstOperands(I, Operands, DL, TLI);
6612}
6613
6614
6615// If every incoming value to PN except the one for BB is a specific Constant,
6616// return that, else return nullptr.
6617static Constant *getOtherIncomingValue(PHINode *PN, BasicBlock *BB) {
6618 Constant *IncomingVal = nullptr;
6619
6620 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
6621 if (PN->getIncomingBlock(i) == BB)
6622 continue;
6623
6624 auto *CurrentVal = dyn_cast<Constant>(PN->getIncomingValue(i));
6625 if (!CurrentVal)
6626 return nullptr;
6627
6628 if (IncomingVal != CurrentVal) {
6629 if (IncomingVal)
6630 return nullptr;
6631 IncomingVal = CurrentVal;
6632 }
6633 }
6634
6635 return IncomingVal;
6636}
6637
6638/// getConstantEvolutionLoopExitValue - If we know that the specified Phi is
6639/// in the header of its containing loop, we know the loop executes a
6640/// constant number of times, and the PHI node is just a recurrence
6641/// involving constants, fold it.
6642Constant *
6643ScalarEvolution::getConstantEvolutionLoopExitValue(PHINode *PN,
6644 const APInt &BEs,
6645 const Loop *L) {
6646 auto I = ConstantEvolutionLoopExitValue.find(PN);
6647 if (I != ConstantEvolutionLoopExitValue.end())
6648 return I->second;
6649
6650 if (BEs.ugt(MaxBruteForceIterations))
6651 return ConstantEvolutionLoopExitValue[PN] = nullptr; // Not going to evaluate it.
6652
6653 Constant *&RetVal = ConstantEvolutionLoopExitValue[PN];
6654
6655 DenseMap<Instruction *, Constant *> CurrentIterVals;
6656 BasicBlock *Header = L->getHeader();
6657 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!")((PN->getParent() == Header && "Can't evaluate PHI not in loop header!"
) ? static_cast<void> (0) : __assert_fail ("PN->getParent() == Header && \"Can't evaluate PHI not in loop header!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6657, __PRETTY_FUNCTION__))
;
6658
6659 BasicBlock *Latch = L->getLoopLatch();
6660 if (!Latch)
6661 return nullptr;
6662
6663 for (auto &I : *Header) {
6664 PHINode *PHI = dyn_cast<PHINode>(&I);
6665 if (!PHI) break;
6666 auto *StartCST = getOtherIncomingValue(PHI, Latch);
6667 if (!StartCST) continue;
6668 CurrentIterVals[PHI] = StartCST;
6669 }
6670 if (!CurrentIterVals.count(PN))
6671 return RetVal = nullptr;
6672
6673 Value *BEValue = PN->getIncomingValueForBlock(Latch);
6674
6675 // Execute the loop symbolically to determine the exit value.
6676 if (BEs.getActiveBits() >= 32)
6677 return RetVal = nullptr; // More than 2^32-1 iterations?? Not doing it!
6678
6679 unsigned NumIterations = BEs.getZExtValue(); // must be in range
6680 unsigned IterationNum = 0;
6681 const DataLayout &DL = getDataLayout();
6682 for (; ; ++IterationNum) {
6683 if (IterationNum == NumIterations)
6684 return RetVal = CurrentIterVals[PN]; // Got exit value!
6685
6686 // Compute the value of the PHIs for the next iteration.
6687 // EvaluateExpression adds non-phi values to the CurrentIterVals map.
6688 DenseMap<Instruction *, Constant *> NextIterVals;
6689 Constant *NextPHI =
6690 EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
6691 if (!NextPHI)
6692 return nullptr; // Couldn't evaluate!
6693 NextIterVals[PN] = NextPHI;
6694
6695 bool StoppedEvolving = NextPHI == CurrentIterVals[PN];
6696
6697 // Also evaluate the other PHI nodes. However, we don't get to stop if we
6698 // cease to be able to evaluate one of them or if they stop evolving,
6699 // because that doesn't necessarily prevent us from computing PN.
6700 SmallVector<std::pair<PHINode *, Constant *>, 8> PHIsToCompute;
6701 for (const auto &I : CurrentIterVals) {
6702 PHINode *PHI = dyn_cast<PHINode>(I.first);
6703 if (!PHI || PHI == PN || PHI->getParent() != Header) continue;
6704 PHIsToCompute.emplace_back(PHI, I.second);
6705 }
6706 // We use two distinct loops because EvaluateExpression may invalidate any
6707 // iterators into CurrentIterVals.
6708 for (const auto &I : PHIsToCompute) {
6709 PHINode *PHI = I.first;
6710 Constant *&NextPHI = NextIterVals[PHI];
6711 if (!NextPHI) { // Not already computed.
6712 Value *BEValue = PHI->getIncomingValueForBlock(Latch);
6713 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
6714 }
6715 if (NextPHI != I.second)
6716 StoppedEvolving = false;
6717 }
6718
6719 // If all entries in CurrentIterVals == NextIterVals then we can stop
6720 // iterating, the loop can't continue to change.
6721 if (StoppedEvolving)
6722 return RetVal = CurrentIterVals[PN];
6723
6724 CurrentIterVals.swap(NextIterVals);
6725 }
6726}
6727
6728const SCEV *ScalarEvolution::computeExitCountExhaustively(const Loop *L,
6729 Value *Cond,
6730 bool ExitWhen) {
6731 PHINode *PN = getConstantEvolvingPHI(Cond, L);
6732 if (!PN) return getCouldNotCompute();
6733
6734 // If the loop is canonicalized, the PHI will have exactly two entries.
6735 // That's the only form we support here.
6736 if (PN->getNumIncomingValues() != 2) return getCouldNotCompute();
6737
6738 DenseMap<Instruction *, Constant *> CurrentIterVals;
6739 BasicBlock *Header = L->getHeader();
6740 assert(PN->getParent() == Header && "Can't evaluate PHI not in loop header!")((PN->getParent() == Header && "Can't evaluate PHI not in loop header!"
) ? static_cast<void> (0) : __assert_fail ("PN->getParent() == Header && \"Can't evaluate PHI not in loop header!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6740, __PRETTY_FUNCTION__))
;
6741
6742 BasicBlock *Latch = L->getLoopLatch();
6743 assert(Latch && "Should follow from NumIncomingValues == 2!")((Latch && "Should follow from NumIncomingValues == 2!"
) ? static_cast<void> (0) : __assert_fail ("Latch && \"Should follow from NumIncomingValues == 2!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 6743, __PRETTY_FUNCTION__))
;
6744
6745 for (auto &I : *Header) {
6746 PHINode *PHI = dyn_cast<PHINode>(&I);
6747 if (!PHI)
6748 break;
6749 auto *StartCST = getOtherIncomingValue(PHI, Latch);
6750 if (!StartCST) continue;
6751 CurrentIterVals[PHI] = StartCST;
6752 }
6753 if (!CurrentIterVals.count(PN))
6754 return getCouldNotCompute();
6755
6756 // Okay, we find a PHI node that defines the trip count of this loop. Execute
6757 // the loop symbolically to determine when the condition gets a value of
6758 // "ExitWhen".
6759 unsigned MaxIterations = MaxBruteForceIterations; // Limit analysis.
6760 const DataLayout &DL = getDataLayout();
6761 for (unsigned IterationNum = 0; IterationNum != MaxIterations;++IterationNum){
6762 auto *CondVal = dyn_cast_or_null<ConstantInt>(
6763 EvaluateExpression(Cond, L, CurrentIterVals, DL, &TLI));
6764
6765 // Couldn't symbolically evaluate.
6766 if (!CondVal) return getCouldNotCompute();
6767
6768 if (CondVal->getValue() == uint64_t(ExitWhen)) {
6769 ++NumBruteForceTripCountsComputed;
6770 return getConstant(Type::getInt32Ty(getContext()), IterationNum);
6771 }
6772
6773 // Update all the PHI nodes for the next iteration.
6774 DenseMap<Instruction *, Constant *> NextIterVals;
6775
6776 // Create a list of which PHIs we need to compute. We want to do this before
6777 // calling EvaluateExpression on them because that may invalidate iterators
6778 // into CurrentIterVals.
6779 SmallVector<PHINode *, 8> PHIsToCompute;
6780 for (const auto &I : CurrentIterVals) {
6781 PHINode *PHI = dyn_cast<PHINode>(I.first);
6782 if (!PHI || PHI->getParent() != Header) continue;
6783 PHIsToCompute.push_back(PHI);
6784 }
6785 for (PHINode *PHI : PHIsToCompute) {
6786 Constant *&NextPHI = NextIterVals[PHI];
6787 if (NextPHI) continue; // Already computed!
6788
6789 Value *BEValue = PHI->getIncomingValueForBlock(Latch);
6790 NextPHI = EvaluateExpression(BEValue, L, CurrentIterVals, DL, &TLI);
6791 }
6792 CurrentIterVals.swap(NextIterVals);
6793 }
6794
6795 // Too many iterations were needed to evaluate.
6796 return getCouldNotCompute();
6797}
6798
6799const SCEV *ScalarEvolution::getSCEVAtScope(const SCEV *V, const Loop *L) {
6800 SmallVector<std::pair<const Loop *, const SCEV *>, 2> &Values =
6801 ValuesAtScopes[V];
6802 // Check to see if we've folded this expression at this loop before.
6803 for (auto &LS : Values)
6804 if (LS.first == L)
6805 return LS.second ? LS.second : V;
6806
6807 Values.emplace_back(L, nullptr);
6808
6809 // Otherwise compute it.
6810 const SCEV *C = computeSCEVAtScope(V, L);
6811 for (auto &LS : reverse(ValuesAtScopes[V]))
6812 if (LS.first == L) {
6813 LS.second = C;
6814 break;
6815 }
6816 return C;
6817}
6818
6819/// This builds up a Constant using the ConstantExpr interface. That way, we
6820/// will return Constants for objects which aren't represented by a
6821/// SCEVConstant, because SCEVConstant is restricted to ConstantInt.
6822/// Returns NULL if the SCEV isn't representable as a Constant.
6823static Constant *BuildConstantFromSCEV(const SCEV *V) {
6824 switch (static_cast<SCEVTypes>(V->getSCEVType())) {
6825 case scCouldNotCompute:
6826 case scAddRecExpr:
6827 break;
6828 case scConstant:
6829 return cast<SCEVConstant>(V)->getValue();
6830 case scUnknown:
6831 return dyn_cast<Constant>(cast<SCEVUnknown>(V)->getValue());
6832 case scSignExtend: {
6833 const SCEVSignExtendExpr *SS = cast<SCEVSignExtendExpr>(V);
6834 if (Constant *CastOp = BuildConstantFromSCEV(SS->getOperand()))
6835 return ConstantExpr::getSExt(CastOp, SS->getType());
6836 break;
6837 }
6838 case scZeroExtend: {
6839 const SCEVZeroExtendExpr *SZ = cast<SCEVZeroExtendExpr>(V);
6840 if (Constant *CastOp = BuildConstantFromSCEV(SZ->getOperand()))
6841 return ConstantExpr::getZExt(CastOp, SZ->getType());
6842 break;
6843 }
6844 case scTruncate: {
6845 const SCEVTruncateExpr *ST = cast<SCEVTruncateExpr>(V);
6846 if (Constant *CastOp = BuildConstantFromSCEV(ST->getOperand()))
6847 return ConstantExpr::getTrunc(CastOp, ST->getType());
6848 break;
6849 }
6850 case scAddExpr: {
6851 const SCEVAddExpr *SA = cast<SCEVAddExpr>(V);
6852 if (Constant *C = BuildConstantFromSCEV(SA->getOperand(0))) {
6853 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
6854 unsigned AS = PTy->getAddressSpace();
6855 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
6856 C = ConstantExpr::getBitCast(C, DestPtrTy);
6857 }
6858 for (unsigned i = 1, e = SA->getNumOperands(); i != e; ++i) {
6859 Constant *C2 = BuildConstantFromSCEV(SA->getOperand(i));
6860 if (!C2) return nullptr;
6861
6862 // First pointer!
6863 if (!C->getType()->isPointerTy() && C2->getType()->isPointerTy()) {
6864 unsigned AS = C2->getType()->getPointerAddressSpace();
6865 std::swap(C, C2);
6866 Type *DestPtrTy = Type::getInt8PtrTy(C->getContext(), AS);
6867 // The offsets have been converted to bytes. We can add bytes to an
6868 // i8* by GEP with the byte count in the first index.
6869 C = ConstantExpr::getBitCast(C, DestPtrTy);
6870 }
6871
6872 // Don't bother trying to sum two pointers. We probably can't
6873 // statically compute a load that results from it anyway.
6874 if (C2->getType()->isPointerTy())
6875 return nullptr;
6876
6877 if (PointerType *PTy = dyn_cast<PointerType>(C->getType())) {
6878 if (PTy->getElementType()->isStructTy())
6879 C2 = ConstantExpr::getIntegerCast(
6880 C2, Type::getInt32Ty(C->getContext()), true);
6881 C = ConstantExpr::getGetElementPtr(PTy->getElementType(), C, C2);
6882 } else
6883 C = ConstantExpr::getAdd(C, C2);
6884 }
6885 return C;
6886 }
6887 break;
6888 }
6889 case scMulExpr: {
6890 const SCEVMulExpr *SM = cast<SCEVMulExpr>(V);
6891 if (Constant *C = BuildConstantFromSCEV(SM->getOperand(0))) {
6892 // Don't bother with pointers at all.
6893 if (C->getType()->isPointerTy()) return nullptr;
6894 for (unsigned i = 1, e = SM->getNumOperands(); i != e; ++i) {
6895 Constant *C2 = BuildConstantFromSCEV(SM->getOperand(i));
6896 if (!C2 || C2->getType()->isPointerTy()) return nullptr;
6897 C = ConstantExpr::getMul(C, C2);
6898 }
6899 return C;
6900 }
6901 break;
6902 }
6903 case scUDivExpr: {
6904 const SCEVUDivExpr *SU = cast<SCEVUDivExpr>(V);
6905 if (Constant *LHS = BuildConstantFromSCEV(SU->getLHS()))
6906 if (Constant *RHS = BuildConstantFromSCEV(SU->getRHS()))
6907 if (LHS->getType() == RHS->getType())
6908 return ConstantExpr::getUDiv(LHS, RHS);
6909 break;
6910 }
6911 case scSMaxExpr:
6912 case scUMaxExpr:
6913 break; // TODO: smax, umax.
6914 }
6915 return nullptr;
6916}
6917
6918const SCEV *ScalarEvolution::computeSCEVAtScope(const SCEV *V, const Loop *L) {
6919 if (isa<SCEVConstant>(V)) return V;
6920
6921 // If this instruction is evolved from a constant-evolving PHI, compute the
6922 // exit value from the loop without using SCEVs.
6923 if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(V)) {
6924 if (Instruction *I = dyn_cast<Instruction>(SU->getValue())) {
6925 const Loop *LI = this->LI[I->getParent()];
6926 if (LI && LI->getParentLoop() == L) // Looking for loop exit value.
6927 if (PHINode *PN = dyn_cast<PHINode>(I))
6928 if (PN->getParent() == LI->getHeader()) {
6929 // Okay, there is no closed form solution for the PHI node. Check
6930 // to see if the loop that contains it has a known backedge-taken
6931 // count. If so, we may be able to force computation of the exit
6932 // value.
6933 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(LI);
6934 if (const SCEVConstant *BTCC =
6935 dyn_cast<SCEVConstant>(BackedgeTakenCount)) {
6936 // Okay, we know how many times the containing loop executes. If
6937 // this is a constant evolving PHI node, get the final value at
6938 // the specified iteration number.
6939 Constant *RV =
6940 getConstantEvolutionLoopExitValue(PN, BTCC->getAPInt(), LI);
6941 if (RV) return getSCEV(RV);
6942 }
6943 }
6944
6945 // Okay, this is an expression that we cannot symbolically evaluate
6946 // into a SCEV. Check to see if it's possible to symbolically evaluate
6947 // the arguments into constants, and if so, try to constant propagate the
6948 // result. This is particularly useful for computing loop exit values.
6949 if (CanConstantFold(I)) {
6950 SmallVector<Constant *, 4> Operands;
6951 bool MadeImprovement = false;
6952 for (Value *Op : I->operands()) {
6953 if (Constant *C = dyn_cast<Constant>(Op)) {
6954 Operands.push_back(C);
6955 continue;
6956 }
6957
6958 // If any of the operands is non-constant and if they are
6959 // non-integer and non-pointer, don't even try to analyze them
6960 // with scev techniques.
6961 if (!isSCEVable(Op->getType()))
6962 return V;
6963
6964 const SCEV *OrigV = getSCEV(Op);
6965 const SCEV *OpV = getSCEVAtScope(OrigV, L);
6966 MadeImprovement |= OrigV != OpV;
6967
6968 Constant *C = BuildConstantFromSCEV(OpV);
6969 if (!C) return V;
6970 if (C->getType() != Op->getType())
6971 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
6972 Op->getType(),
6973 false),
6974 C, Op->getType());
6975 Operands.push_back(C);
6976 }
6977
6978 // Check to see if getSCEVAtScope actually made an improvement.
6979 if (MadeImprovement) {
6980 Constant *C = nullptr;
6981 const DataLayout &DL = getDataLayout();
6982 if (const CmpInst *CI = dyn_cast<CmpInst>(I))
6983 C = ConstantFoldCompareInstOperands(CI->getPredicate(), Operands[0],
6984 Operands[1], DL, &TLI);
6985 else if (const LoadInst *LI = dyn_cast<LoadInst>(I)) {
6986 if (!LI->isVolatile())
6987 C = ConstantFoldLoadFromConstPtr(Operands[0], LI->getType(), DL);
6988 } else
6989 C = ConstantFoldInstOperands(I, Operands, DL, &TLI);
6990 if (!C) return V;
6991 return getSCEV(C);
6992 }
6993 }
6994 }
6995
6996 // This is some other type of SCEVUnknown, just return it.
6997 return V;
6998 }
6999
7000 if (const SCEVCommutativeExpr *Comm = dyn_cast<SCEVCommutativeExpr>(V)) {
7001 // Avoid performing the look-up in the common case where the specified
7002 // expression has no loop-variant portions.
7003 for (unsigned i = 0, e = Comm->getNumOperands(); i != e; ++i) {
7004 const SCEV *OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
7005 if (OpAtScope != Comm->getOperand(i)) {
7006 // Okay, at least one of these operands is loop variant but might be
7007 // foldable. Build a new instance of the folded commutative expression.
7008 SmallVector<const SCEV *, 8> NewOps(Comm->op_begin(),
7009 Comm->op_begin()+i);
7010 NewOps.push_back(OpAtScope);
7011
7012 for (++i; i != e; ++i) {
7013 OpAtScope = getSCEVAtScope(Comm->getOperand(i), L);
7014 NewOps.push_back(OpAtScope);
7015 }
7016 if (isa<SCEVAddExpr>(Comm))
7017 return getAddExpr(NewOps);
7018 if (isa<SCEVMulExpr>(Comm))
7019 return getMulExpr(NewOps);
7020 if (isa<SCEVSMaxExpr>(Comm))
7021 return getSMaxExpr(NewOps);
7022 if (isa<SCEVUMaxExpr>(Comm))
7023 return getUMaxExpr(NewOps);
7024 llvm_unreachable("Unknown commutative SCEV type!")::llvm::llvm_unreachable_internal("Unknown commutative SCEV type!"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 7024)
;
7025 }
7026 }
7027 // If we got here, all operands are loop invariant.
7028 return Comm;
7029 }
7030
7031 if (const SCEVUDivExpr *Div = dyn_cast<SCEVUDivExpr>(V)) {
7032 const SCEV *LHS = getSCEVAtScope(Div->getLHS(), L);
7033 const SCEV *RHS = getSCEVAtScope(Div->getRHS(), L);
7034 if (LHS == Div->getLHS() && RHS == Div->getRHS())
7035 return Div; // must be loop invariant
7036 return getUDivExpr(LHS, RHS);
7037 }
7038
7039 // If this is a loop recurrence for a loop that does not contain L, then we
7040 // are dealing with the final value computed by the loop.
7041 if (const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V)) {
7042 // First, attempt to evaluate each operand.
7043 // Avoid performing the look-up in the common case where the specified
7044 // expression has no loop-variant portions.
7045 for (unsigned i = 0, e = AddRec->getNumOperands(); i != e; ++i) {
7046 const SCEV *OpAtScope = getSCEVAtScope(AddRec->getOperand(i), L);
7047 if (OpAtScope == AddRec->getOperand(i))
7048 continue;
7049
7050 // Okay, at least one of these operands is loop variant but might be
7051 // foldable. Build a new instance of the folded commutative expression.
7052 SmallVector<const SCEV *, 8> NewOps(AddRec->op_begin(),
7053 AddRec->op_begin()+i);
7054 NewOps.push_back(OpAtScope);
7055 for (++i; i != e; ++i)
7056 NewOps.push_back(getSCEVAtScope(AddRec->getOperand(i), L));
7057
7058 const SCEV *FoldedRec =
7059 getAddRecExpr(NewOps, AddRec->getLoop(),
7060 AddRec->getNoWrapFlags(SCEV::FlagNW));
7061 AddRec = dyn_cast<SCEVAddRecExpr>(FoldedRec);
7062 // The addrec may be folded to a nonrecurrence, for example, if the
7063 // induction variable is multiplied by zero after constant folding. Go
7064 // ahead and return the folded value.
7065 if (!AddRec)
7066 return FoldedRec;
7067 break;
7068 }
7069
7070 // If the scope is outside the addrec's loop, evaluate it by using the
7071 // loop exit value of the addrec.
7072 if (!AddRec->getLoop()->contains(L)) {
7073 // To evaluate this recurrence, we need to know how many times the AddRec
7074 // loop iterates. Compute this now.
7075 const SCEV *BackedgeTakenCount = getBackedgeTakenCount(AddRec->getLoop());
7076 if (BackedgeTakenCount == getCouldNotCompute()) return AddRec;
7077
7078 // Then, evaluate the AddRec.
7079 return AddRec->evaluateAtIteration(BackedgeTakenCount, *this);
7080 }
7081
7082 return AddRec;
7083 }
7084
7085 if (const SCEVZeroExtendExpr *Cast = dyn_cast<SCEVZeroExtendExpr>(V)) {
7086 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
7087 if (Op == Cast->getOperand())
7088 return Cast; // must be loop invariant
7089 return getZeroExtendExpr(Op, Cast->getType());
7090 }
7091
7092 if (const SCEVSignExtendExpr *Cast = dyn_cast<SCEVSignExtendExpr>(V)) {
7093 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
7094 if (Op == Cast->getOperand())
7095 return Cast; // must be loop invariant
7096 return getSignExtendExpr(Op, Cast->getType());
7097 }
7098
7099 if (const SCEVTruncateExpr *Cast = dyn_cast<SCEVTruncateExpr>(V)) {
7100 const SCEV *Op = getSCEVAtScope(Cast->getOperand(), L);
7101 if (Op == Cast->getOperand())
7102 return Cast; // must be loop invariant
7103 return getTruncateExpr(Op, Cast->getType());
7104 }
7105
7106 llvm_unreachable("Unknown SCEV type!")::llvm::llvm_unreachable_internal("Unknown SCEV type!", "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 7106)
;
7107}
7108
7109const SCEV *ScalarEvolution::getSCEVAtScope(Value *V, const Loop *L) {
7110 return getSCEVAtScope(getSCEV(V), L);
7111}
7112
7113/// Finds the minimum unsigned root of the following equation:
7114///
7115/// A * X = B (mod N)
7116///
7117/// where N = 2^BW and BW is the common bit width of A and B. The signedness of
7118/// A and B isn't important.
7119///
7120/// If the equation does not have a solution, SCEVCouldNotCompute is returned.
7121static const SCEV *SolveLinEquationWithOverflow(const APInt &A, const SCEV *B,
7122 ScalarEvolution &SE) {
7123 uint32_t BW = A.getBitWidth();
7124 assert(BW == SE.getTypeSizeInBits(B->getType()))((BW == SE.getTypeSizeInBits(B->getType())) ? static_cast<
void> (0) : __assert_fail ("BW == SE.getTypeSizeInBits(B->getType())"
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 7124, __PRETTY_FUNCTION__))
;
7125 assert(A != 0 && "A must be non-zero.")((A != 0 && "A must be non-zero.") ? static_cast<void
> (0) : __assert_fail ("A != 0 && \"A must be non-zero.\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 7125, __PRETTY_FUNCTION__))
;
7126
7127 // 1. D = gcd(A, N)
7128 //
7129 // The gcd of A and N may have only one prime factor: 2. The number of
7130 // trailing zeros in A is its multiplicity
7131 uint32_t Mult2 = A.countTrailingZeros();
7132 // D = 2^Mult2
7133
7134 // 2. Check if B is divisible by D.
7135 //
7136 // B is divisible by D if and only if the multiplicity of prime factor 2 for B
7137 // is not less than multiplicity of this prime factor for D.
7138 if (SE.GetMinTrailingZeros(B) < Mult2)
7139 return SE.getCouldNotCompute();
7140
7141 // 3. Compute I: the multiplicative inverse of (A / D) in arithmetic
7142 // modulo (N / D).
7143 //
7144 // If D == 1, (N / D) == N == 2^BW, so we need one extra bit to represent
7145 // (N / D) in general. The inverse itself always fits into BW bits, though,
7146 // so we immediately truncate it.
7147 APInt AD = A.lshr(Mult2).zext(BW + 1); // AD = A / D
7148 APInt Mod(BW + 1, 0);
7149 Mod.setBit(BW - Mult2); // Mod = N / D
7150 APInt I = AD.multiplicativeInverse(Mod).trunc(BW);
7151
7152 // 4. Compute the minimum unsigned root of the equation:
7153 // I * (B / D) mod (N / D)
7154 // To simplify the computation, we factor out the divide by D:
7155 // (I * B mod N) / D
7156 const SCEV *D = SE.getConstant(APInt::getOneBitSet(BW, Mult2));
7157 return SE.getUDivExactExpr(SE.getMulExpr(B, SE.getConstant(I)), D);
7158}
7159
7160/// Find the roots of the quadratic equation for the given quadratic chrec
7161/// {L,+,M,+,N}. This returns either the two roots (which might be the same) or
7162/// two SCEVCouldNotCompute objects.
7163///
7164static Optional<std::pair<const SCEVConstant *,const SCEVConstant *>>
7165SolveQuadraticEquation(const SCEVAddRecExpr *AddRec, ScalarEvolution &SE) {
7166 assert(AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!")((AddRec->getNumOperands() == 3 && "This is not a quadratic chrec!"
) ? static_cast<void> (0) : __assert_fail ("AddRec->getNumOperands() == 3 && \"This is not a quadratic chrec!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 7166, __PRETTY_FUNCTION__))
;
7167 const SCEVConstant *LC = dyn_cast<SCEVConstant>(AddRec->getOperand(0));
7168 const SCEVConstant *MC = dyn_cast<SCEVConstant>(AddRec->getOperand(1));
7169 const SCEVConstant *NC = dyn_cast<SCEVConstant>(AddRec->getOperand(2));
7170
7171 // We currently can only solve this if the coefficients are constants.
7172 if (!LC || !MC || !NC)
7173 return None;
7174
7175 uint32_t BitWidth = LC->getAPInt().getBitWidth();
7176 const APInt &L = LC->getAPInt();
7177 const APInt &M = MC->getAPInt();
7178 const APInt &N = NC->getAPInt();
7179 APInt Two(BitWidth, 2);
7180 APInt Four(BitWidth, 4);
7181
7182 {
7183 using namespace APIntOps;
7184 const APInt& C = L;
7185 // Convert from chrec coefficients to polynomial coefficients AX^2+BX+C
7186 // The B coefficient is M-N/2
7187 APInt B(M);
7188 B -= sdiv(N,Two);
7189
7190 // The A coefficient is N/2
7191 APInt A(N.sdiv(Two));
7192
7193 // Compute the B^2-4ac term.
7194 APInt SqrtTerm(B);
7195 SqrtTerm *= B;
7196 SqrtTerm -= Four * (A * C);
7197
7198 if (SqrtTerm.isNegative()) {
7199 // The loop is provably infinite.
7200 return None;
7201 }
7202
7203 // Compute sqrt(B^2-4ac). This is guaranteed to be the nearest
7204 // integer value or else APInt::sqrt() will assert.
7205 APInt SqrtVal(SqrtTerm.sqrt());
7206
7207 // Compute the two solutions for the quadratic formula.
7208 // The divisions must be performed as signed divisions.
7209 APInt NegB(-B);
7210 APInt TwoA(A << 1);
7211 if (TwoA.isMinValue())
7212 return None;
7213
7214 LLVMContext &Context = SE.getContext();
7215
7216 ConstantInt *Solution1 =
7217 ConstantInt::get(Context, (NegB + SqrtVal).sdiv(TwoA));
7218 ConstantInt *Solution2 =
7219 ConstantInt::get(Context, (NegB - SqrtVal).sdiv(TwoA));
7220
7221 return std::make_pair(cast<SCEVConstant>(SE.getConstant(Solution1)),
7222 cast<SCEVConstant>(SE.getConstant(Solution2)));
7223 } // end APIntOps namespace
7224}
7225
7226ScalarEvolution::ExitLimit
7227ScalarEvolution::howFarToZero(const SCEV *V, const Loop *L, bool ControlsExit,
7228 bool AllowPredicates) {
7229
7230 // This is only used for loops with a "x != y" exit test. The exit condition
7231 // is now expressed as a single expression, V = x-y. So the exit test is
7232 // effectively V != 0. We know and take advantage of the fact that this
7233 // expression only being used in a comparison by zero context.
7234
7235 SmallPtrSet<const SCEVPredicate *, 4> Predicates;
7236 // If the value is a constant
7237 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
7238 // If the value is already zero, the branch will execute zero times.
7239 if (C->getValue()->isZero()) return C;
7240 return getCouldNotCompute(); // Otherwise it will loop infinitely.
7241 }
7242
7243 const SCEVAddRecExpr *AddRec = dyn_cast<SCEVAddRecExpr>(V);
7244 if (!AddRec && AllowPredicates)
7245 // Try to make this an AddRec using runtime tests, in the first X
7246 // iterations of this loop, where X is the SCEV expression found by the
7247 // algorithm below.
7248 AddRec = convertSCEVToAddRecWithPredicates(V, L, Predicates);
7249
7250 if (!AddRec || AddRec->getLoop() != L)
7251 return getCouldNotCompute();
7252
7253 // If this is a quadratic (3-term) AddRec {L,+,M,+,N}, find the roots of
7254 // the quadratic equation to solve it.
7255 if (AddRec->isQuadratic() && AddRec->getType()->isIntegerTy()) {
7256 if (auto Roots = SolveQuadraticEquation(AddRec, *this)) {
7257 const SCEVConstant *R1 = Roots->first;
7258 const SCEVConstant *R2 = Roots->second;
7259 // Pick the smallest positive root value.
7260 if (ConstantInt *CB = dyn_cast<ConstantInt>(ConstantExpr::getICmp(
7261 CmpInst::ICMP_ULT, R1->getValue(), R2->getValue()))) {
7262 if (!CB->getZExtValue())
7263 std::swap(R1, R2); // R1 is the minimum root now.
7264
7265 // We can only use this value if the chrec ends up with an exact zero
7266 // value at this index. When solving for "X*X != 5", for example, we
7267 // should not accept a root of 2.
7268 const SCEV *Val = AddRec->evaluateAtIteration(R1, *this);
7269 if (Val->isZero())
7270 // We found a quadratic root!
7271 return ExitLimit(R1, R1, false, Predicates);
7272 }
7273 }
7274 return getCouldNotCompute();
7275 }
7276
7277 // Otherwise we can only handle this if it is affine.
7278 if (!AddRec->isAffine())
7279 return getCouldNotCompute();
7280
7281 // If this is an affine expression, the execution count of this branch is
7282 // the minimum unsigned root of the following equation:
7283 //
7284 // Start + Step*N = 0 (mod 2^BW)
7285 //
7286 // equivalent to:
7287 //
7288 // Step*N = -Start (mod 2^BW)
7289 //
7290 // where BW is the common bit width of Start and Step.
7291
7292 // Get the initial value for the loop.
7293 const SCEV *Start = getSCEVAtScope(AddRec->getStart(), L->getParentLoop());
7294 const SCEV *Step = getSCEVAtScope(AddRec->getOperand(1), L->getParentLoop());
7295
7296 // For now we handle only constant steps.
7297 //
7298 // TODO: Handle a nonconstant Step given AddRec<NUW>. If the
7299 // AddRec is NUW, then (in an unsigned sense) it cannot be counting up to wrap
7300 // to 0, it must be counting down to equal 0. Consequently, N = Start / -Step.
7301 // We have not yet seen any such cases.
7302 const SCEVConstant *StepC = dyn_cast<SCEVConstant>(Step);
7303 if (!StepC || StepC->getValue()->equalsInt(0))
7304 return getCouldNotCompute();
7305
7306 // For positive steps (counting up until unsigned overflow):
7307 // N = -Start/Step (as unsigned)
7308 // For negative steps (counting down to zero):
7309 // N = Start/-Step
7310 // First compute the unsigned distance from zero in the direction of Step.
7311 bool CountDown = StepC->getAPInt().isNegative();
7312 const SCEV *Distance = CountDown ? Start : getNegativeSCEV(Start);
7313
7314 // Handle unitary steps, which cannot wraparound.
7315 // 1*N = -Start; -1*N = Start (mod 2^BW), so:
7316 // N = Distance (as unsigned)
7317 if (StepC->getValue()->equalsInt(1) || StepC->getValue()->isAllOnesValue()) {
7318 APInt MaxBECount = getUnsignedRange(Distance).getUnsignedMax();
7319
7320 // When a loop like "for (int i = 0; i != n; ++i) { /* body */ }" is rotated,
7321 // we end up with a loop whose backedge-taken count is n - 1. Detect this
7322 // case, and see if we can improve the bound.
7323 //
7324 // Explicitly handling this here is necessary because getUnsignedRange
7325 // isn't context-sensitive; it doesn't know that we only care about the
7326 // range inside the loop.
7327 const SCEV *Zero = getZero(Distance->getType());
7328 const SCEV *One = getOne(Distance->getType());
7329 const SCEV *DistancePlusOne = getAddExpr(Distance, One);
7330 if (isLoopEntryGuardedByCond(L, ICmpInst::ICMP_NE, DistancePlusOne, Zero)) {
7331 // If Distance + 1 doesn't overflow, we can compute the maximum distance
7332 // as "unsigned_max(Distance + 1) - 1".
7333 ConstantRange CR = getUnsignedRange(DistancePlusOne);
7334 MaxBECount = APIntOps::umin(MaxBECount, CR.getUnsignedMax() - 1);
7335 }
7336 return ExitLimit(Distance, getConstant(MaxBECount), false, Predicates);
7337 }
7338
7339 // If the condition controls loop exit (the loop exits only if the expression
7340 // is true) and the addition is no-wrap we can use unsigned divide to
7341 // compute the backedge count. In this case, the step may not divide the
7342 // distance, but we don't care because if the condition is "missed" the loop
7343 // will have undefined behavior due to wrapping.
7344 if (ControlsExit && AddRec->hasNoSelfWrap() &&
7345 loopHasNoAbnormalExits(AddRec->getLoop())) {
7346 const SCEV *Exact =
7347 getUDivExpr(Distance, CountDown ? getNegativeSCEV(Step) : Step);
7348 return ExitLimit(Exact, Exact, false, Predicates);
7349 }
7350
7351 // Solve the general equation.
7352 const SCEV *E = SolveLinEquationWithOverflow(
7353 StepC->getAPInt(), getNegativeSCEV(Start), *this);
7354 return ExitLimit(E, E, false, Predicates);
7355}
7356
7357ScalarEvolution::ExitLimit
7358ScalarEvolution::howFarToNonZero(const SCEV *V, const Loop *L) {
7359 // Loops that look like: while (X == 0) are very strange indeed. We don't
7360 // handle them yet except for the trivial case. This could be expanded in the
7361 // future as needed.
7362
7363 // If the value is a constant, check to see if it is known to be non-zero
7364 // already. If so, the backedge will execute zero times.
7365 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(V)) {
7366 if (!C->getValue()->isNullValue())
7367 return getZero(C->getType());
7368 return getCouldNotCompute(); // Otherwise it will loop infinitely.
7369 }
7370
7371 // We could implement others, but I really doubt anyone writes loops like
7372 // this, and if they did, they would already be constant folded.
7373 return getCouldNotCompute();
7374}
7375
7376std::pair<BasicBlock *, BasicBlock *>
7377ScalarEvolution::getPredecessorWithUniqueSuccessorForBB(BasicBlock *BB) {
7378 // If the block has a unique predecessor, then there is no path from the
7379 // predecessor to the block that does not go through the direct edge
7380 // from the predecessor to the block.
7381 if (BasicBlock *Pred = BB->getSinglePredecessor())
7382 return {Pred, BB};
7383
7384 // A loop's header is defined to be a block that dominates the loop.
7385 // If the header has a unique predecessor outside the loop, it must be
7386 // a block that has exactly one successor that can reach the loop.
7387 if (Loop *L = LI.getLoopFor(BB))
7388 return {L->getLoopPredecessor(), L->getHeader()};
7389
7390 return {nullptr, nullptr};
7391}
7392
7393/// SCEV structural equivalence is usually sufficient for testing whether two
7394/// expressions are equal, however for the purposes of looking for a condition
7395/// guarding a loop, it can be useful to be a little more general, since a
7396/// front-end may have replicated the controlling expression.
7397///
7398static bool HasSameValue(const SCEV *A, const SCEV *B) {
7399 // Quick check to see if they are the same SCEV.
7400 if (A == B) return true;
7401
7402 auto ComputesEqualValues = [](const Instruction *A, const Instruction *B) {
7403 // Not all instructions that are "identical" compute the same value. For
7404 // instance, two distinct alloca instructions allocating the same type are
7405 // identical and do not read memory; but compute distinct values.
7406 return A->isIdenticalTo(B) && (isa<BinaryOperator>(A) || isa<GetElementPtrInst>(A));
7407 };
7408
7409 // Otherwise, if they're both SCEVUnknown, it's possible that they hold
7410 // two different instructions with the same value. Check for this case.
7411 if (const SCEVUnknown *AU = dyn_cast<SCEVUnknown>(A))
7412 if (const SCEVUnknown *BU = dyn_cast<SCEVUnknown>(B))
7413 if (const Instruction *AI = dyn_cast<Instruction>(AU->getValue()))
7414 if (const Instruction *BI = dyn_cast<Instruction>(BU->getValue()))
7415 if (ComputesEqualValues(AI, BI))
7416 return true;
7417
7418 // Otherwise assume they may have a different value.
7419 return false;
7420}
7421
7422bool ScalarEvolution::SimplifyICmpOperands(ICmpInst::Predicate &Pred,
7423 const SCEV *&LHS, const SCEV *&RHS,
7424 unsigned Depth) {
7425 bool Changed = false;
7426
7427 // If we hit the max recursion limit bail out.
7428 if (Depth >= 3)
7429 return false;
7430
7431 // Canonicalize a constant to the right side.
7432 if (const SCEVConstant *LHSC = dyn_cast<SCEVConstant>(LHS)) {
7433 // Check for both operands constant.
7434 if (const SCEVConstant *RHSC = dyn_cast<SCEVConstant>(RHS)) {
7435 if (ConstantExpr::getICmp(Pred,
7436 LHSC->getValue(),
7437 RHSC->getValue())->isNullValue())
7438 goto trivially_false;
7439 else
7440 goto trivially_true;
7441 }
7442 // Otherwise swap the operands to put the constant on the right.
7443 std::swap(LHS, RHS);
7444 Pred = ICmpInst::getSwappedPredicate(Pred);
7445 Changed = true;
7446 }
7447
7448 // If we're comparing an addrec with a value which is loop-invariant in the
7449 // addrec's loop, put the addrec on the left. Also make a dominance check,
7450 // as both operands could be addrecs loop-invariant in each other's loop.
7451 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(RHS)) {
7452 const Loop *L = AR->getLoop();
7453 if (isLoopInvariant(LHS, L) && properlyDominates(LHS, L->getHeader())) {
7454 std::swap(LHS, RHS);
7455 Pred = ICmpInst::getSwappedPredicate(Pred);
7456 Changed = true;
7457 }
7458 }
7459
7460 // If there's a constant operand, canonicalize comparisons with boundary
7461 // cases, and canonicalize *-or-equal comparisons to regular comparisons.
7462 if (const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS)) {
7463 const APInt &RA = RC->getAPInt();
7464
7465 bool SimplifiedByConstantRange = false;
7466
7467 if (!ICmpInst::isEquality(Pred)) {
7468 ConstantRange ExactCR = ConstantRange::makeExactICmpRegion(Pred, RA);
7469 if (ExactCR.isFullSet())
7470 goto trivially_true;
7471 else if (ExactCR.isEmptySet())
7472 goto trivially_false;
7473
7474 APInt NewRHS;
7475 CmpInst::Predicate NewPred;
7476 if (ExactCR.getEquivalentICmp(NewPred, NewRHS) &&
7477 ICmpInst::isEquality(NewPred)) {
7478 // We were able to convert an inequality to an equality.
7479 Pred = NewPred;
7480 RHS = getConstant(NewRHS);
7481 Changed = SimplifiedByConstantRange = true;
7482 }
7483 }
7484
7485 if (!SimplifiedByConstantRange) {
7486 switch (Pred) {
7487 default:
7488 break;
7489 case ICmpInst::ICMP_EQ:
7490 case ICmpInst::ICMP_NE:
7491 // Fold ((-1) * %a) + %b == 0 (equivalent to %b-%a == 0) into %a == %b.
7492 if (!RA)
7493 if (const SCEVAddExpr *AE = dyn_cast<SCEVAddExpr>(LHS))
7494 if (const SCEVMulExpr *ME =
7495 dyn_cast<SCEVMulExpr>(AE->getOperand(0)))
7496 if (AE->getNumOperands() == 2 && ME->getNumOperands() == 2 &&
7497 ME->getOperand(0)->isAllOnesValue()) {
7498 RHS = AE->getOperand(1);
7499 LHS = ME->getOperand(1);
7500 Changed = true;
7501 }
7502 break;
7503
7504
7505 // The "Should have been caught earlier!" messages refer to the fact
7506 // that the ExactCR.isFullSet() or ExactCR.isEmptySet() check above
7507 // should have fired on the corresponding cases, and canonicalized the
7508 // check to trivially_true or trivially_false.
7509
7510 case ICmpInst::ICMP_UGE:
7511 assert(!RA.isMinValue() && "Should have been caught earlier!")((!RA.isMinValue() && "Should have been caught earlier!"
) ? static_cast<void> (0) : __assert_fail ("!RA.isMinValue() && \"Should have been caught earlier!\""
, "/tmp/buildd/llvm-toolchain-snapshot-5.0~svn298304/lib/Analysis/ScalarEvolution.cpp"
, 7511, __PRETTY_FUNCTION__))
;
7512 Pred = ICmpInst::ICMP_UGT;
7513 RHS = getConstant(RA - 1);
7514 Changed = true;