Bug Summary

File:lib/Transforms/Scalar/LoopStrengthReduce.cpp
Warning:line 4718, column 5
Forming reference to null pointer

Annotated Source Code

Press '?' to see keyboard shortcuts

clang -cc1 -triple x86_64-pc-linux-gnu -analyze -disable-free -disable-llvm-verifier -discard-value-names -main-file-name LoopStrengthReduce.cpp -analyzer-store=region -analyzer-opt-analyze-nested-blocks -analyzer-checker=core -analyzer-checker=apiModeling -analyzer-checker=unix -analyzer-checker=deadcode -analyzer-checker=cplusplus -analyzer-checker=security.insecureAPI.UncheckedReturn -analyzer-checker=security.insecureAPI.getpw -analyzer-checker=security.insecureAPI.gets -analyzer-checker=security.insecureAPI.mktemp -analyzer-checker=security.insecureAPI.mkstemp -analyzer-checker=security.insecureAPI.vfork -analyzer-checker=nullability.NullPassedToNonnull -analyzer-checker=nullability.NullReturnedFromNonnull -analyzer-output plist -w -mrelocation-model pic -pic-level 2 -mthread-model posix -fmath-errno -masm-verbose -mconstructor-aliases -munwind-tables -fuse-init-array -target-cpu x86-64 -dwarf-column-info -debugger-tuning=gdb -momit-leaf-frame-pointer -ffunction-sections -fdata-sections -resource-dir /usr/lib/llvm-8/lib/clang/8.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-8~svn345461/build-llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-8~svn345461/build-llvm/include -I /build/llvm-toolchain-snapshot-8~svn345461/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/x86_64-linux-gnu/c++/6.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/6.3.0/../../../../include/c++/6.3.0/backward -internal-isystem /usr/include/clang/8.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-8/lib/clang/8.0.0/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -O2 -Wno-unused-parameter -Wwrite-strings -Wno-missing-field-initializers -Wno-long-long -Wno-maybe-uninitialized -Wno-comment -std=c++11 -fdeprecated-macro -fdebug-compilation-dir /build/llvm-toolchain-snapshot-8~svn345461/build-llvm/lib/Transforms/Scalar -ferror-limit 19 -fmessage-length 0 -fvisibility-inlines-hidden -fobjc-runtime=gcc -fdiagnostics-show-option -vectorize-loops -vectorize-slp -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2018-10-27-211344-32123-1 -x c++ /build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp -faddrsig
1//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
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 transformation analyzes and transforms the induction variables (and
11// computations derived from them) into forms suitable for efficient execution
12// on the target.
13//
14// This pass performs a strength reduction on array references inside loops that
15// have as one or more of their components the loop induction variable, it
16// rewrites expressions to take advantage of scaled-index addressing modes
17// available on the target, and it performs a variety of other optimizations
18// related to loop induction variables.
19//
20// Terminology note: this code has a lot of handling for "post-increment" or
21// "post-inc" users. This is not talking about post-increment addressing modes;
22// it is instead talking about code like this:
23//
24// %i = phi [ 0, %entry ], [ %i.next, %latch ]
25// ...
26// %i.next = add %i, 1
27// %c = icmp eq %i.next, %n
28//
29// The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
30// it's useful to think about these as the same register, with some uses using
31// the value of the register before the add and some using it after. In this
32// example, the icmp is a post-increment user, since it uses %i.next, which is
33// the value of the induction variable after the increment. The other common
34// case of post-increment users is users outside the loop.
35//
36// TODO: More sophistication in the way Formulae are generated and filtered.
37//
38// TODO: Handle multiple loops at a time.
39//
40// TODO: Should the addressing mode BaseGV be changed to a ConstantExpr instead
41// of a GlobalValue?
42//
43// TODO: When truncation is free, truncate ICmp users' operands to make it a
44// smaller encoding (on x86 at least).
45//
46// TODO: When a negated register is used by an add (such as in a list of
47// multiple base registers, or as the increment expression in an addrec),
48// we may not actually need both reg and (-1 * reg) in registers; the
49// negation can be implemented by using a sub instead of an add. The
50// lack of support for taking this into consideration when making
51// register pressure decisions is partly worked around by the "Special"
52// use kind.
53//
54//===----------------------------------------------------------------------===//
55
56#include "llvm/Transforms/Scalar/LoopStrengthReduce.h"
57#include "llvm/ADT/APInt.h"
58#include "llvm/ADT/DenseMap.h"
59#include "llvm/ADT/DenseSet.h"
60#include "llvm/ADT/Hashing.h"
61#include "llvm/ADT/PointerIntPair.h"
62#include "llvm/ADT/STLExtras.h"
63#include "llvm/ADT/SetVector.h"
64#include "llvm/ADT/SmallBitVector.h"
65#include "llvm/ADT/SmallPtrSet.h"
66#include "llvm/ADT/SmallSet.h"
67#include "llvm/ADT/SmallVector.h"
68#include "llvm/ADT/iterator_range.h"
69#include "llvm/Analysis/IVUsers.h"
70#include "llvm/Analysis/LoopAnalysisManager.h"
71#include "llvm/Analysis/LoopInfo.h"
72#include "llvm/Analysis/LoopPass.h"
73#include "llvm/Analysis/ScalarEvolution.h"
74#include "llvm/Analysis/ScalarEvolutionExpander.h"
75#include "llvm/Analysis/ScalarEvolutionExpressions.h"
76#include "llvm/Analysis/ScalarEvolutionNormalization.h"
77#include "llvm/Analysis/TargetTransformInfo.h"
78#include "llvm/Transforms/Utils/Local.h"
79#include "llvm/Config/llvm-config.h"
80#include "llvm/IR/BasicBlock.h"
81#include "llvm/IR/Constant.h"
82#include "llvm/IR/Constants.h"
83#include "llvm/IR/DerivedTypes.h"
84#include "llvm/IR/Dominators.h"
85#include "llvm/IR/GlobalValue.h"
86#include "llvm/IR/IRBuilder.h"
87#include "llvm/IR/InstrTypes.h"
88#include "llvm/IR/Instruction.h"
89#include "llvm/IR/Instructions.h"
90#include "llvm/IR/IntrinsicInst.h"
91#include "llvm/IR/Intrinsics.h"
92#include "llvm/IR/Module.h"
93#include "llvm/IR/OperandTraits.h"
94#include "llvm/IR/Operator.h"
95#include "llvm/IR/PassManager.h"
96#include "llvm/IR/Type.h"
97#include "llvm/IR/Use.h"
98#include "llvm/IR/User.h"
99#include "llvm/IR/Value.h"
100#include "llvm/IR/ValueHandle.h"
101#include "llvm/Pass.h"
102#include "llvm/Support/Casting.h"
103#include "llvm/Support/CommandLine.h"
104#include "llvm/Support/Compiler.h"
105#include "llvm/Support/Debug.h"
106#include "llvm/Support/ErrorHandling.h"
107#include "llvm/Support/MathExtras.h"
108#include "llvm/Support/raw_ostream.h"
109#include "llvm/Transforms/Scalar.h"
110#include "llvm/Transforms/Utils.h"
111#include "llvm/Transforms/Utils/BasicBlockUtils.h"
112#include <algorithm>
113#include <cassert>
114#include <cstddef>
115#include <cstdint>
116#include <cstdlib>
117#include <iterator>
118#include <limits>
119#include <map>
120#include <utility>
121
122using namespace llvm;
123
124#define DEBUG_TYPE"loop-reduce" "loop-reduce"
125
126/// MaxIVUsers is an arbitrary threshold that provides an early opportunity for
127/// bail out. This threshold is far beyond the number of users that LSR can
128/// conceivably solve, so it should not affect generated code, but catches the
129/// worst cases before LSR burns too much compile time and stack space.
130static const unsigned MaxIVUsers = 200;
131
132// Temporary flag to cleanup congruent phis after LSR phi expansion.
133// It's currently disabled until we can determine whether it's truly useful or
134// not. The flag should be removed after the v3.0 release.
135// This is now needed for ivchains.
136static cl::opt<bool> EnablePhiElim(
137 "enable-lsr-phielim", cl::Hidden, cl::init(true),
138 cl::desc("Enable LSR phi elimination"));
139
140// The flag adds instruction count to solutions cost comparision.
141static cl::opt<bool> InsnsCost(
142 "lsr-insns-cost", cl::Hidden, cl::init(true),
143 cl::desc("Add instruction count to a LSR cost model"));
144
145// Flag to choose how to narrow complex lsr solution
146static cl::opt<bool> LSRExpNarrow(
147 "lsr-exp-narrow", cl::Hidden, cl::init(false),
148 cl::desc("Narrow LSR complex solution using"
149 " expectation of registers number"));
150
151// Flag to narrow search space by filtering non-optimal formulae with
152// the same ScaledReg and Scale.
153static cl::opt<bool> FilterSameScaledReg(
154 "lsr-filter-same-scaled-reg", cl::Hidden, cl::init(true),
155 cl::desc("Narrow LSR search space by filtering non-optimal formulae"
156 " with the same ScaledReg and Scale"));
157
158#ifndef NDEBUG
159// Stress test IV chain generation.
160static cl::opt<bool> StressIVChain(
161 "stress-ivchain", cl::Hidden, cl::init(false),
162 cl::desc("Stress test LSR IV chains"));
163#else
164static bool StressIVChain = false;
165#endif
166
167namespace {
168
169struct MemAccessTy {
170 /// Used in situations where the accessed memory type is unknown.
171 static const unsigned UnknownAddressSpace =
172 std::numeric_limits<unsigned>::max();
173
174 Type *MemTy = nullptr;
175 unsigned AddrSpace = UnknownAddressSpace;
176
177 MemAccessTy() = default;
178 MemAccessTy(Type *Ty, unsigned AS) : MemTy(Ty), AddrSpace(AS) {}
179
180 bool operator==(MemAccessTy Other) const {
181 return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace;
182 }
183
184 bool operator!=(MemAccessTy Other) const { return !(*this == Other); }
185
186 static MemAccessTy getUnknown(LLVMContext &Ctx,
187 unsigned AS = UnknownAddressSpace) {
188 return MemAccessTy(Type::getVoidTy(Ctx), AS);
189 }
190
191 Type *getType() { return MemTy; }
192};
193
194/// This class holds data which is used to order reuse candidates.
195class RegSortData {
196public:
197 /// This represents the set of LSRUse indices which reference
198 /// a particular register.
199 SmallBitVector UsedByIndices;
200
201 void print(raw_ostream &OS) const;
202 void dump() const;
203};
204
205} // end anonymous namespace
206
207#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
208void RegSortData::print(raw_ostream &OS) const {
209 OS << "[NumUses=" << UsedByIndices.count() << ']';
210}
211
212LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void RegSortData::dump() const {
213 print(errs()); errs() << '\n';
214}
215#endif
216
217namespace {
218
219/// Map register candidates to information about how they are used.
220class RegUseTracker {
221 using RegUsesTy = DenseMap<const SCEV *, RegSortData>;
222
223 RegUsesTy RegUsesMap;
224 SmallVector<const SCEV *, 16> RegSequence;
225
226public:
227 void countRegister(const SCEV *Reg, size_t LUIdx);
228 void dropRegister(const SCEV *Reg, size_t LUIdx);
229 void swapAndDropUse(size_t LUIdx, size_t LastLUIdx);
230
231 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
232
233 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
234
235 void clear();
236
237 using iterator = SmallVectorImpl<const SCEV *>::iterator;
238 using const_iterator = SmallVectorImpl<const SCEV *>::const_iterator;
239
240 iterator begin() { return RegSequence.begin(); }
241 iterator end() { return RegSequence.end(); }
242 const_iterator begin() const { return RegSequence.begin(); }
243 const_iterator end() const { return RegSequence.end(); }
244};
245
246} // end anonymous namespace
247
248void
249RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) {
250 std::pair<RegUsesTy::iterator, bool> Pair =
251 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
252 RegSortData &RSD = Pair.first->second;
253 if (Pair.second)
254 RegSequence.push_back(Reg);
255 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
256 RSD.UsedByIndices.set(LUIdx);
257}
258
259void
260RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) {
261 RegUsesTy::iterator It = RegUsesMap.find(Reg);
262 assert(It != RegUsesMap.end())((It != RegUsesMap.end()) ? static_cast<void> (0) : __assert_fail
("It != RegUsesMap.end()", "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 262, __PRETTY_FUNCTION__))
;
263 RegSortData &RSD = It->second;
264 assert(RSD.UsedByIndices.size() > LUIdx)((RSD.UsedByIndices.size() > LUIdx) ? static_cast<void>
(0) : __assert_fail ("RSD.UsedByIndices.size() > LUIdx", "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 264, __PRETTY_FUNCTION__))
;
265 RSD.UsedByIndices.reset(LUIdx);
266}
267
268void
269RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
270 assert(LUIdx <= LastLUIdx)((LUIdx <= LastLUIdx) ? static_cast<void> (0) : __assert_fail
("LUIdx <= LastLUIdx", "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 270, __PRETTY_FUNCTION__))
;
271
272 // Update RegUses. The data structure is not optimized for this purpose;
273 // we must iterate through it and update each of the bit vectors.
274 for (auto &Pair : RegUsesMap) {
275 SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
276 if (LUIdx < UsedByIndices.size())
277 UsedByIndices[LUIdx] =
278 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false;
279 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
280 }
281}
282
283bool
284RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
285 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
286 if (I == RegUsesMap.end())
287 return false;
288 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
289 int i = UsedByIndices.find_first();
290 if (i == -1) return false;
291 if ((size_t)i != LUIdx) return true;
292 return UsedByIndices.find_next(i) != -1;
293}
294
295const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
296 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
297 assert(I != RegUsesMap.end() && "Unknown register!")((I != RegUsesMap.end() && "Unknown register!") ? static_cast
<void> (0) : __assert_fail ("I != RegUsesMap.end() && \"Unknown register!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 297, __PRETTY_FUNCTION__))
;
298 return I->second.UsedByIndices;
299}
300
301void RegUseTracker::clear() {
302 RegUsesMap.clear();
303 RegSequence.clear();
304}
305
306namespace {
307
308/// This class holds information that describes a formula for computing
309/// satisfying a use. It may include broken-out immediates and scaled registers.
310struct Formula {
311 /// Global base address used for complex addressing.
312 GlobalValue *BaseGV = nullptr;
313
314 /// Base offset for complex addressing.
315 int64_t BaseOffset = 0;
316
317 /// Whether any complex addressing has a base register.
318 bool HasBaseReg = false;
319
320 /// The scale of any complex addressing.
321 int64_t Scale = 0;
322
323 /// The list of "base" registers for this use. When this is non-empty. The
324 /// canonical representation of a formula is
325 /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
326 /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
327 /// 3. The reg containing recurrent expr related with currect loop in the
328 /// formula should be put in the ScaledReg.
329 /// #1 enforces that the scaled register is always used when at least two
330 /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
331 /// #2 enforces that 1 * reg is reg.
332 /// #3 ensures invariant regs with respect to current loop can be combined
333 /// together in LSR codegen.
334 /// This invariant can be temporarily broken while building a formula.
335 /// However, every formula inserted into the LSRInstance must be in canonical
336 /// form.
337 SmallVector<const SCEV *, 4> BaseRegs;
338
339 /// The 'scaled' register for this use. This should be non-null when Scale is
340 /// not zero.
341 const SCEV *ScaledReg = nullptr;
342
343 /// An additional constant offset which added near the use. This requires a
344 /// temporary register, but the offset itself can live in an add immediate
345 /// field rather than a register.
346 int64_t UnfoldedOffset = 0;
347
348 Formula() = default;
349
350 void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
351
352 bool isCanonical(const Loop &L) const;
353
354 void canonicalize(const Loop &L);
355
356 bool unscale();
357
358 bool hasZeroEnd() const;
359
360 size_t getNumRegs() const;
361 Type *getType() const;
362
363 void deleteBaseReg(const SCEV *&S);
364
365 bool referencesReg(const SCEV *S) const;
366 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
367 const RegUseTracker &RegUses) const;
368
369 void print(raw_ostream &OS) const;
370 void dump() const;
371};
372
373} // end anonymous namespace
374
375/// Recursion helper for initialMatch.
376static void DoInitialMatch(const SCEV *S, Loop *L,
377 SmallVectorImpl<const SCEV *> &Good,
378 SmallVectorImpl<const SCEV *> &Bad,
379 ScalarEvolution &SE) {
380 // Collect expressions which properly dominate the loop header.
381 if (SE.properlyDominates(S, L->getHeader())) {
382 Good.push_back(S);
383 return;
384 }
385
386 // Look at add operands.
387 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
388 for (const SCEV *S : Add->operands())
389 DoInitialMatch(S, L, Good, Bad, SE);
390 return;
391 }
392
393 // Look at addrec operands.
394 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
395 if (!AR->getStart()->isZero() && AR->isAffine()) {
396 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
397 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
398 AR->getStepRecurrence(SE),
399 // FIXME: AR->getNoWrapFlags()
400 AR->getLoop(), SCEV::FlagAnyWrap),
401 L, Good, Bad, SE);
402 return;
403 }
404
405 // Handle a multiplication by -1 (negation) if it didn't fold.
406 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
407 if (Mul->getOperand(0)->isAllOnesValue()) {
408 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
409 const SCEV *NewMul = SE.getMulExpr(Ops);
410
411 SmallVector<const SCEV *, 4> MyGood;
412 SmallVector<const SCEV *, 4> MyBad;
413 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
414 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
415 SE.getEffectiveSCEVType(NewMul->getType())));
416 for (const SCEV *S : MyGood)
417 Good.push_back(SE.getMulExpr(NegOne, S));
418 for (const SCEV *S : MyBad)
419 Bad.push_back(SE.getMulExpr(NegOne, S));
420 return;
421 }
422
423 // Ok, we can't do anything interesting. Just stuff the whole thing into a
424 // register and hope for the best.
425 Bad.push_back(S);
426}
427
428/// Incorporate loop-variant parts of S into this Formula, attempting to keep
429/// all loop-invariant and loop-computable values in a single base register.
430void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
431 SmallVector<const SCEV *, 4> Good;
432 SmallVector<const SCEV *, 4> Bad;
433 DoInitialMatch(S, L, Good, Bad, SE);
434 if (!Good.empty()) {
435 const SCEV *Sum = SE.getAddExpr(Good);
436 if (!Sum->isZero())
437 BaseRegs.push_back(Sum);
438 HasBaseReg = true;
439 }
440 if (!Bad.empty()) {
441 const SCEV *Sum = SE.getAddExpr(Bad);
442 if (!Sum->isZero())
443 BaseRegs.push_back(Sum);
444 HasBaseReg = true;
445 }
446 canonicalize(*L);
447}
448
449/// Check whether or not this formula satisfies the canonical
450/// representation.
451/// \see Formula::BaseRegs.
452bool Formula::isCanonical(const Loop &L) const {
453 if (!ScaledReg)
454 return BaseRegs.size() <= 1;
455
456 if (Scale != 1)
457 return true;
458
459 if (Scale == 1 && BaseRegs.empty())
460 return false;
461
462 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
463 if (SAR && SAR->getLoop() == &L)
464 return true;
465
466 // If ScaledReg is not a recurrent expr, or it is but its loop is not current
467 // loop, meanwhile BaseRegs contains a recurrent expr reg related with current
468 // loop, we want to swap the reg in BaseRegs with ScaledReg.
469 auto I =
470 find_if(make_range(BaseRegs.begin(), BaseRegs.end()), [&](const SCEV *S) {
471 return isa<const SCEVAddRecExpr>(S) &&
472 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
473 });
474 return I == BaseRegs.end();
475}
476
477/// Helper method to morph a formula into its canonical representation.
478/// \see Formula::BaseRegs.
479/// Every formula having more than one base register, must use the ScaledReg
480/// field. Otherwise, we would have to do special cases everywhere in LSR
481/// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
482/// On the other hand, 1*reg should be canonicalized into reg.
483void Formula::canonicalize(const Loop &L) {
484 if (isCanonical(L))
485 return;
486 // So far we did not need this case. This is easy to implement but it is
487 // useless to maintain dead code. Beside it could hurt compile time.
488 assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.")((!BaseRegs.empty() && "1*reg => reg, should not be needed."
) ? static_cast<void> (0) : __assert_fail ("!BaseRegs.empty() && \"1*reg => reg, should not be needed.\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 488, __PRETTY_FUNCTION__))
;
489
490 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
491 if (!ScaledReg) {
492 ScaledReg = BaseRegs.back();
493 BaseRegs.pop_back();
494 Scale = 1;
495 }
496
497 // If ScaledReg is an invariant with respect to L, find the reg from
498 // BaseRegs containing the recurrent expr related with Loop L. Swap the
499 // reg with ScaledReg.
500 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
501 if (!SAR || SAR->getLoop() != &L) {
502 auto I = find_if(make_range(BaseRegs.begin(), BaseRegs.end()),
503 [&](const SCEV *S) {
504 return isa<const SCEVAddRecExpr>(S) &&
505 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
506 });
507 if (I != BaseRegs.end())
508 std::swap(ScaledReg, *I);
509 }
510}
511
512/// Get rid of the scale in the formula.
513/// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
514/// \return true if it was possible to get rid of the scale, false otherwise.
515/// \note After this operation the formula may not be in the canonical form.
516bool Formula::unscale() {
517 if (Scale != 1)
518 return false;
519 Scale = 0;
520 BaseRegs.push_back(ScaledReg);
521 ScaledReg = nullptr;
522 return true;
523}
524
525bool Formula::hasZeroEnd() const {
526 if (UnfoldedOffset || BaseOffset)
527 return false;
528 if (BaseRegs.size() != 1 || ScaledReg)
529 return false;
530 return true;
531}
532
533/// Return the total number of register operands used by this formula. This does
534/// not include register uses implied by non-constant addrec strides.
535size_t Formula::getNumRegs() const {
536 return !!ScaledReg + BaseRegs.size();
537}
538
539/// Return the type of this formula, if it has one, or null otherwise. This type
540/// is meaningless except for the bit size.
541Type *Formula::getType() const {
542 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
543 ScaledReg ? ScaledReg->getType() :
544 BaseGV ? BaseGV->getType() :
545 nullptr;
546}
547
548/// Delete the given base reg from the BaseRegs list.
549void Formula::deleteBaseReg(const SCEV *&S) {
550 if (&S != &BaseRegs.back())
551 std::swap(S, BaseRegs.back());
552 BaseRegs.pop_back();
553}
554
555/// Test if this formula references the given register.
556bool Formula::referencesReg(const SCEV *S) const {
557 return S == ScaledReg || is_contained(BaseRegs, S);
558}
559
560/// Test whether this formula uses registers which are used by uses other than
561/// the use with the given index.
562bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
563 const RegUseTracker &RegUses) const {
564 if (ScaledReg)
565 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
566 return true;
567 for (const SCEV *BaseReg : BaseRegs)
568 if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
569 return true;
570 return false;
571}
572
573#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
574void Formula::print(raw_ostream &OS) const {
575 bool First = true;
576 if (BaseGV) {
577 if (!First) OS << " + "; else First = false;
578 BaseGV->printAsOperand(OS, /*PrintType=*/false);
579 }
580 if (BaseOffset != 0) {
581 if (!First) OS << " + "; else First = false;
582 OS << BaseOffset;
583 }
584 for (const SCEV *BaseReg : BaseRegs) {
585 if (!First) OS << " + "; else First = false;
586 OS << "reg(" << *BaseReg << ')';
587 }
588 if (HasBaseReg && BaseRegs.empty()) {
589 if (!First) OS << " + "; else First = false;
590 OS << "**error: HasBaseReg**";
591 } else if (!HasBaseReg && !BaseRegs.empty()) {
592 if (!First) OS << " + "; else First = false;
593 OS << "**error: !HasBaseReg**";
594 }
595 if (Scale != 0) {
596 if (!First) OS << " + "; else First = false;
597 OS << Scale << "*reg(";
598 if (ScaledReg)
599 OS << *ScaledReg;
600 else
601 OS << "<unknown>";
602 OS << ')';
603 }
604 if (UnfoldedOffset != 0) {
605 if (!First) OS << " + ";
606 OS << "imm(" << UnfoldedOffset << ')';
607 }
608}
609
610LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Formula::dump() const {
611 print(errs()); errs() << '\n';
612}
613#endif
614
615/// Return true if the given addrec can be sign-extended without changing its
616/// value.
617static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
618 Type *WideTy =
619 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
620 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
621}
622
623/// Return true if the given add can be sign-extended without changing its
624/// value.
625static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
626 Type *WideTy =
627 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
628 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
629}
630
631/// Return true if the given mul can be sign-extended without changing its
632/// value.
633static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
634 Type *WideTy =
635 IntegerType::get(SE.getContext(),
636 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
637 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
638}
639
640/// Return an expression for LHS /s RHS, if it can be determined and if the
641/// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
642/// is true, expressions like (X * Y) /s Y are simplified to Y, ignoring that
643/// the multiplication may overflow, which is useful when the result will be
644/// used in a context where the most significant bits are ignored.
645static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
646 ScalarEvolution &SE,
647 bool IgnoreSignificantBits = false) {
648 // Handle the trivial case, which works for any SCEV type.
649 if (LHS == RHS)
650 return SE.getConstant(LHS->getType(), 1);
651
652 // Handle a few RHS special cases.
653 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
654 if (RC) {
655 const APInt &RA = RC->getAPInt();
656 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
657 // some folding.
658 if (RA.isAllOnesValue())
659 return SE.getMulExpr(LHS, RC);
660 // Handle x /s 1 as x.
661 if (RA == 1)
662 return LHS;
663 }
664
665 // Check for a division of a constant by a constant.
666 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
667 if (!RC)
668 return nullptr;
669 const APInt &LA = C->getAPInt();
670 const APInt &RA = RC->getAPInt();
671 if (LA.srem(RA) != 0)
672 return nullptr;
673 return SE.getConstant(LA.sdiv(RA));
674 }
675
676 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
677 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
678 if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
679 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
680 IgnoreSignificantBits);
681 if (!Step) return nullptr;
682 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
683 IgnoreSignificantBits);
684 if (!Start) return nullptr;
685 // FlagNW is independent of the start value, step direction, and is
686 // preserved with smaller magnitude steps.
687 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
688 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
689 }
690 return nullptr;
691 }
692
693 // Distribute the sdiv over add operands, if the add doesn't overflow.
694 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
695 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
696 SmallVector<const SCEV *, 8> Ops;
697 for (const SCEV *S : Add->operands()) {
698 const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
699 if (!Op) return nullptr;
700 Ops.push_back(Op);
701 }
702 return SE.getAddExpr(Ops);
703 }
704 return nullptr;
705 }
706
707 // Check for a multiply operand that we can pull RHS out of.
708 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
709 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
710 SmallVector<const SCEV *, 4> Ops;
711 bool Found = false;
712 for (const SCEV *S : Mul->operands()) {
713 if (!Found)
714 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
715 IgnoreSignificantBits)) {
716 S = Q;
717 Found = true;
718 }
719 Ops.push_back(S);
720 }
721 return Found ? SE.getMulExpr(Ops) : nullptr;
722 }
723 return nullptr;
724 }
725
726 // Otherwise we don't know.
727 return nullptr;
728}
729
730/// If S involves the addition of a constant integer value, return that integer
731/// value, and mutate S to point to a new SCEV with that value excluded.
732static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
733 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
734 if (C->getAPInt().getMinSignedBits() <= 64) {
735 S = SE.getConstant(C->getType(), 0);
736 return C->getValue()->getSExtValue();
737 }
738 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
739 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
740 int64_t Result = ExtractImmediate(NewOps.front(), SE);
741 if (Result != 0)
742 S = SE.getAddExpr(NewOps);
743 return Result;
744 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
745 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
746 int64_t Result = ExtractImmediate(NewOps.front(), SE);
747 if (Result != 0)
748 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
749 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
750 SCEV::FlagAnyWrap);
751 return Result;
752 }
753 return 0;
754}
755
756/// If S involves the addition of a GlobalValue address, return that symbol, and
757/// mutate S to point to a new SCEV with that value excluded.
758static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
759 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
760 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
761 S = SE.getConstant(GV->getType(), 0);
762 return GV;
763 }
764 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
765 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
766 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
767 if (Result)
768 S = SE.getAddExpr(NewOps);
769 return Result;
770 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
771 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
772 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
773 if (Result)
774 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
775 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
776 SCEV::FlagAnyWrap);
777 return Result;
778 }
779 return nullptr;
780}
781
782/// Returns true if the specified instruction is using the specified value as an
783/// address.
784static bool isAddressUse(const TargetTransformInfo &TTI,
785 Instruction *Inst, Value *OperandVal) {
786 bool isAddress = isa<LoadInst>(Inst);
787 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
788 if (SI->getPointerOperand() == OperandVal)
789 isAddress = true;
790 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
791 // Addressing modes can also be folded into prefetches and a variety
792 // of intrinsics.
793 switch (II->getIntrinsicID()) {
794 case Intrinsic::memset:
795 case Intrinsic::prefetch:
796 if (II->getArgOperand(0) == OperandVal)
797 isAddress = true;
798 break;
799 case Intrinsic::memmove:
800 case Intrinsic::memcpy:
801 if (II->getArgOperand(0) == OperandVal ||
802 II->getArgOperand(1) == OperandVal)
803 isAddress = true;
804 break;
805 default: {
806 MemIntrinsicInfo IntrInfo;
807 if (TTI.getTgtMemIntrinsic(II, IntrInfo)) {
808 if (IntrInfo.PtrVal == OperandVal)
809 isAddress = true;
810 }
811 }
812 }
813 } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
814 if (RMW->getPointerOperand() == OperandVal)
815 isAddress = true;
816 } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
817 if (CmpX->getPointerOperand() == OperandVal)
818 isAddress = true;
819 }
820 return isAddress;
821}
822
823/// Return the type of the memory being accessed.
824static MemAccessTy getAccessType(const TargetTransformInfo &TTI,
825 Instruction *Inst, Value *OperandVal) {
826 MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
827 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
828 AccessTy.MemTy = SI->getOperand(0)->getType();
829 AccessTy.AddrSpace = SI->getPointerAddressSpace();
830 } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
831 AccessTy.AddrSpace = LI->getPointerAddressSpace();
832 } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
833 AccessTy.AddrSpace = RMW->getPointerAddressSpace();
834 } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
835 AccessTy.AddrSpace = CmpX->getPointerAddressSpace();
836 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
837 switch (II->getIntrinsicID()) {
838 case Intrinsic::prefetch:
839 case Intrinsic::memset:
840 AccessTy.AddrSpace = II->getArgOperand(0)->getType()->getPointerAddressSpace();
841 AccessTy.MemTy = OperandVal->getType();
842 break;
843 case Intrinsic::memmove:
844 case Intrinsic::memcpy:
845 AccessTy.AddrSpace = OperandVal->getType()->getPointerAddressSpace();
846 AccessTy.MemTy = OperandVal->getType();
847 break;
848 default: {
849 MemIntrinsicInfo IntrInfo;
850 if (TTI.getTgtMemIntrinsic(II, IntrInfo) && IntrInfo.PtrVal) {
851 AccessTy.AddrSpace
852 = IntrInfo.PtrVal->getType()->getPointerAddressSpace();
853 }
854
855 break;
856 }
857 }
858 }
859
860 // All pointers have the same requirements, so canonicalize them to an
861 // arbitrary pointer type to minimize variation.
862 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
863 AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
864 PTy->getAddressSpace());
865
866 return AccessTy;
867}
868
869/// Return true if this AddRec is already a phi in its loop.
870static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
871 for (PHINode &PN : AR->getLoop()->getHeader()->phis()) {
872 if (SE.isSCEVable(PN.getType()) &&
873 (SE.getEffectiveSCEVType(PN.getType()) ==
874 SE.getEffectiveSCEVType(AR->getType())) &&
875 SE.getSCEV(&PN) == AR)
876 return true;
877 }
878 return false;
879}
880
881/// Check if expanding this expression is likely to incur significant cost. This
882/// is tricky because SCEV doesn't track which expressions are actually computed
883/// by the current IR.
884///
885/// We currently allow expansion of IV increments that involve adds,
886/// multiplication by constants, and AddRecs from existing phis.
887///
888/// TODO: Allow UDivExpr if we can find an existing IV increment that is an
889/// obvious multiple of the UDivExpr.
890static bool isHighCostExpansion(const SCEV *S,
891 SmallPtrSetImpl<const SCEV*> &Processed,
892 ScalarEvolution &SE) {
893 // Zero/One operand expressions
894 switch (S->getSCEVType()) {
895 case scUnknown:
896 case scConstant:
897 return false;
898 case scTruncate:
899 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
900 Processed, SE);
901 case scZeroExtend:
902 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
903 Processed, SE);
904 case scSignExtend:
905 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
906 Processed, SE);
907 }
908
909 if (!Processed.insert(S).second)
910 return false;
911
912 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
913 for (const SCEV *S : Add->operands()) {
914 if (isHighCostExpansion(S, Processed, SE))
915 return true;
916 }
917 return false;
918 }
919
920 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
921 if (Mul->getNumOperands() == 2) {
922 // Multiplication by a constant is ok
923 if (isa<SCEVConstant>(Mul->getOperand(0)))
924 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
925
926 // If we have the value of one operand, check if an existing
927 // multiplication already generates this expression.
928 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
929 Value *UVal = U->getValue();
930 for (User *UR : UVal->users()) {
931 // If U is a constant, it may be used by a ConstantExpr.
932 Instruction *UI = dyn_cast<Instruction>(UR);
933 if (UI && UI->getOpcode() == Instruction::Mul &&
934 SE.isSCEVable(UI->getType())) {
935 return SE.getSCEV(UI) == Mul;
936 }
937 }
938 }
939 }
940 }
941
942 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
943 if (isExistingPhi(AR, SE))
944 return false;
945 }
946
947 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
948 return true;
949}
950
951/// If any of the instructions in the specified set are trivially dead, delete
952/// them and see if this makes any of their operands subsequently dead.
953static bool
954DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
955 bool Changed = false;
956
957 while (!DeadInsts.empty()) {
958 Value *V = DeadInsts.pop_back_val();
959 Instruction *I = dyn_cast_or_null<Instruction>(V);
960
961 if (!I || !isInstructionTriviallyDead(I))
962 continue;
963
964 for (Use &O : I->operands())
965 if (Instruction *U = dyn_cast<Instruction>(O)) {
966 O = nullptr;
967 if (U->use_empty())
968 DeadInsts.emplace_back(U);
969 }
970
971 I->eraseFromParent();
972 Changed = true;
973 }
974
975 return Changed;
976}
977
978namespace {
979
980class LSRUse;
981
982} // end anonymous namespace
983
984/// Check if the addressing mode defined by \p F is completely
985/// folded in \p LU at isel time.
986/// This includes address-mode folding and special icmp tricks.
987/// This function returns true if \p LU can accommodate what \p F
988/// defines and up to 1 base + 1 scaled + offset.
989/// In other words, if \p F has several base registers, this function may
990/// still return true. Therefore, users still need to account for
991/// additional base registers and/or unfolded offsets to derive an
992/// accurate cost model.
993static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
994 const LSRUse &LU, const Formula &F);
995
996// Get the cost of the scaling factor used in F for LU.
997static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
998 const LSRUse &LU, const Formula &F,
999 const Loop &L);
1000
1001namespace {
1002
1003/// This class is used to measure and compare candidate formulae.
1004class Cost {
1005 TargetTransformInfo::LSRCost C;
1006
1007public:
1008 Cost() {
1009 C.Insns = 0;
1010 C.NumRegs = 0;
1011 C.AddRecCost = 0;
1012 C.NumIVMuls = 0;
1013 C.NumBaseAdds = 0;
1014 C.ImmCost = 0;
1015 C.SetupCost = 0;
1016 C.ScaleCost = 0;
1017 }
1018
1019 bool isLess(Cost &Other, const TargetTransformInfo &TTI);
1020
1021 void Lose();
1022
1023#ifndef NDEBUG
1024 // Once any of the metrics loses, they must all remain losers.
1025 bool isValid() {
1026 return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds
1027 | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u)
1028 || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds
1029 & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u);
1030 }
1031#endif
1032
1033 bool isLoser() {
1034 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1034, __PRETTY_FUNCTION__))
;
1035 return C.NumRegs == ~0u;
1036 }
1037
1038 void RateFormula(const TargetTransformInfo &TTI,
1039 const Formula &F,
1040 SmallPtrSetImpl<const SCEV *> &Regs,
1041 const DenseSet<const SCEV *> &VisitedRegs,
1042 const Loop *L,
1043 ScalarEvolution &SE, DominatorTree &DT,
1044 const LSRUse &LU,
1045 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
1046
1047 void print(raw_ostream &OS) const;
1048 void dump() const;
1049
1050private:
1051 void RateRegister(const SCEV *Reg,
1052 SmallPtrSetImpl<const SCEV *> &Regs,
1053 const Loop *L,
1054 ScalarEvolution &SE, DominatorTree &DT,
1055 const TargetTransformInfo &TTI);
1056 void RatePrimaryRegister(const SCEV *Reg,
1057 SmallPtrSetImpl<const SCEV *> &Regs,
1058 const Loop *L,
1059 ScalarEvolution &SE, DominatorTree &DT,
1060 SmallPtrSetImpl<const SCEV *> *LoserRegs,
1061 const TargetTransformInfo &TTI);
1062};
1063
1064/// An operand value in an instruction which is to be replaced with some
1065/// equivalent, possibly strength-reduced, replacement.
1066struct LSRFixup {
1067 /// The instruction which will be updated.
1068 Instruction *UserInst = nullptr;
1069
1070 /// The operand of the instruction which will be replaced. The operand may be
1071 /// used more than once; every instance will be replaced.
1072 Value *OperandValToReplace = nullptr;
1073
1074 /// If this user is to use the post-incremented value of an induction
1075 /// variable, this set is non-empty and holds the loops associated with the
1076 /// induction variable.
1077 PostIncLoopSet PostIncLoops;
1078
1079 /// A constant offset to be added to the LSRUse expression. This allows
1080 /// multiple fixups to share the same LSRUse with different offsets, for
1081 /// example in an unrolled loop.
1082 int64_t Offset = 0;
1083
1084 LSRFixup() = default;
1085
1086 bool isUseFullyOutsideLoop(const Loop *L) const;
1087
1088 void print(raw_ostream &OS) const;
1089 void dump() const;
1090};
1091
1092/// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
1093/// SmallVectors of const SCEV*.
1094struct UniquifierDenseMapInfo {
1095 static SmallVector<const SCEV *, 4> getEmptyKey() {
1096 SmallVector<const SCEV *, 4> V;
1097 V.push_back(reinterpret_cast<const SCEV *>(-1));
1098 return V;
1099 }
1100
1101 static SmallVector<const SCEV *, 4> getTombstoneKey() {
1102 SmallVector<const SCEV *, 4> V;
1103 V.push_back(reinterpret_cast<const SCEV *>(-2));
1104 return V;
1105 }
1106
1107 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1108 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1109 }
1110
1111 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1112 const SmallVector<const SCEV *, 4> &RHS) {
1113 return LHS == RHS;
1114 }
1115};
1116
1117/// This class holds the state that LSR keeps for each use in IVUsers, as well
1118/// as uses invented by LSR itself. It includes information about what kinds of
1119/// things can be folded into the user, information about the user itself, and
1120/// information about how the use may be satisfied. TODO: Represent multiple
1121/// users of the same expression in common?
1122class LSRUse {
1123 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1124
1125public:
1126 /// An enum for a kind of use, indicating what types of scaled and immediate
1127 /// operands it might support.
1128 enum KindType {
1129 Basic, ///< A normal use, with no folding.
1130 Special, ///< A special case of basic, allowing -1 scales.
1131 Address, ///< An address use; folding according to TargetLowering
1132 ICmpZero ///< An equality icmp with both operands folded into one.
1133 // TODO: Add a generic icmp too?
1134 };
1135
1136 using SCEVUseKindPair = PointerIntPair<const SCEV *, 2, KindType>;
1137
1138 KindType Kind;
1139 MemAccessTy AccessTy;
1140
1141 /// The list of operands which are to be replaced.
1142 SmallVector<LSRFixup, 8> Fixups;
1143
1144 /// Keep track of the min and max offsets of the fixups.
1145 int64_t MinOffset = std::numeric_limits<int64_t>::max();
1146 int64_t MaxOffset = std::numeric_limits<int64_t>::min();
1147
1148 /// This records whether all of the fixups using this LSRUse are outside of
1149 /// the loop, in which case some special-case heuristics may be used.
1150 bool AllFixupsOutsideLoop = true;
1151
1152 /// RigidFormula is set to true to guarantee that this use will be associated
1153 /// with a single formula--the one that initially matched. Some SCEV
1154 /// expressions cannot be expanded. This allows LSR to consider the registers
1155 /// used by those expressions without the need to expand them later after
1156 /// changing the formula.
1157 bool RigidFormula = false;
1158
1159 /// This records the widest use type for any fixup using this
1160 /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1161 /// fixup widths to be equivalent, because the narrower one may be relying on
1162 /// the implicit truncation to truncate away bogus bits.
1163 Type *WidestFixupType = nullptr;
1164
1165 /// A list of ways to build a value that can satisfy this user. After the
1166 /// list is populated, one of these is selected heuristically and used to
1167 /// formulate a replacement for OperandValToReplace in UserInst.
1168 SmallVector<Formula, 12> Formulae;
1169
1170 /// The set of register candidates used by all formulae in this LSRUse.
1171 SmallPtrSet<const SCEV *, 4> Regs;
1172
1173 LSRUse(KindType K, MemAccessTy AT) : Kind(K), AccessTy(AT) {}
1174
1175 LSRFixup &getNewFixup() {
1176 Fixups.push_back(LSRFixup());
1177 return Fixups.back();
1178 }
1179
1180 void pushFixup(LSRFixup &f) {
1181 Fixups.push_back(f);
1182 if (f.Offset > MaxOffset)
1183 MaxOffset = f.Offset;
1184 if (f.Offset < MinOffset)
1185 MinOffset = f.Offset;
1186 }
1187
1188 bool HasFormulaWithSameRegs(const Formula &F) const;
1189 float getNotSelectedProbability(const SCEV *Reg) const;
1190 bool InsertFormula(const Formula &F, const Loop &L);
1191 void DeleteFormula(Formula &F);
1192 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1193
1194 void print(raw_ostream &OS) const;
1195 void dump() const;
1196};
1197
1198} // end anonymous namespace
1199
1200static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1201 LSRUse::KindType Kind, MemAccessTy AccessTy,
1202 GlobalValue *BaseGV, int64_t BaseOffset,
1203 bool HasBaseReg, int64_t Scale,
1204 Instruction *Fixup = nullptr);
1205
1206/// Tally up interesting quantities from the given register.
1207void Cost::RateRegister(const SCEV *Reg,
1208 SmallPtrSetImpl<const SCEV *> &Regs,
1209 const Loop *L,
1210 ScalarEvolution &SE, DominatorTree &DT,
1211 const TargetTransformInfo &TTI) {
1212 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1213 // If this is an addrec for another loop, it should be an invariant
1214 // with respect to L since L is the innermost loop (at least
1215 // for now LSR only handles innermost loops).
1216 if (AR->getLoop() != L) {
1217 // If the AddRec exists, consider it's register free and leave it alone.
1218 if (isExistingPhi(AR, SE))
1219 return;
1220
1221 // It is bad to allow LSR for current loop to add induction variables
1222 // for its sibling loops.
1223 if (!AR->getLoop()->contains(L)) {
1224 Lose();
1225 return;
1226 }
1227
1228 // Otherwise, it will be an invariant with respect to Loop L.
1229 ++C.NumRegs;
1230 return;
1231 }
1232
1233 unsigned LoopCost = 1;
1234 if (TTI.shouldFavorPostInc()) {
1235 const SCEV *LoopStep = AR->getStepRecurrence(SE);
1236 if (isa<SCEVConstant>(LoopStep)) {
1237 // Check if a post-indexed load/store can be used.
1238 if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) ||
1239 TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) {
1240 const SCEV *LoopStart = AR->getStart();
1241 if (!isa<SCEVConstant>(LoopStart) &&
1242 SE.isLoopInvariant(LoopStart, L))
1243 LoopCost = 0;
1244 }
1245 }
1246 }
1247 C.AddRecCost += LoopCost;
1248
1249 // Add the step value register, if it needs one.
1250 // TODO: The non-affine case isn't precisely modeled here.
1251 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1252 if (!Regs.count(AR->getOperand(1))) {
1253 RateRegister(AR->getOperand(1), Regs, L, SE, DT, TTI);
1254 if (isLoser())
1255 return;
1256 }
1257 }
1258 }
1259 ++C.NumRegs;
1260
1261 // Rough heuristic; favor registers which don't require extra setup
1262 // instructions in the preheader.
1263 if (!isa<SCEVUnknown>(Reg) &&
1264 !isa<SCEVConstant>(Reg) &&
1265 !(isa<SCEVAddRecExpr>(Reg) &&
1266 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
1267 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
1268 ++C.SetupCost;
1269
1270 C.NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1271 SE.hasComputableLoopEvolution(Reg, L);
1272}
1273
1274/// Record this register in the set. If we haven't seen it before, rate
1275/// it. Optional LoserRegs provides a way to declare any formula that refers to
1276/// one of those regs an instant loser.
1277void Cost::RatePrimaryRegister(const SCEV *Reg,
1278 SmallPtrSetImpl<const SCEV *> &Regs,
1279 const Loop *L,
1280 ScalarEvolution &SE, DominatorTree &DT,
1281 SmallPtrSetImpl<const SCEV *> *LoserRegs,
1282 const TargetTransformInfo &TTI) {
1283 if (LoserRegs && LoserRegs->count(Reg)) {
1284 Lose();
1285 return;
1286 }
1287 if (Regs.insert(Reg).second) {
1288 RateRegister(Reg, Regs, L, SE, DT, TTI);
1289 if (LoserRegs && isLoser())
1290 LoserRegs->insert(Reg);
1291 }
1292}
1293
1294void Cost::RateFormula(const TargetTransformInfo &TTI,
1295 const Formula &F,
1296 SmallPtrSetImpl<const SCEV *> &Regs,
1297 const DenseSet<const SCEV *> &VisitedRegs,
1298 const Loop *L,
1299 ScalarEvolution &SE, DominatorTree &DT,
1300 const LSRUse &LU,
1301 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1302 assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula")((F.isCanonical(*L) && "Cost is accurate only for canonical formula"
) ? static_cast<void> (0) : __assert_fail ("F.isCanonical(*L) && \"Cost is accurate only for canonical formula\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1302, __PRETTY_FUNCTION__))
;
1303 // Tally up the registers.
1304 unsigned PrevAddRecCost = C.AddRecCost;
1305 unsigned PrevNumRegs = C.NumRegs;
1306 unsigned PrevNumBaseAdds = C.NumBaseAdds;
1307 if (const SCEV *ScaledReg = F.ScaledReg) {
1308 if (VisitedRegs.count(ScaledReg)) {
1309 Lose();
1310 return;
1311 }
1312 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs, TTI);
1313 if (isLoser())
1314 return;
1315 }
1316 for (const SCEV *BaseReg : F.BaseRegs) {
1317 if (VisitedRegs.count(BaseReg)) {
1318 Lose();
1319 return;
1320 }
1321 RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs, TTI);
1322 if (isLoser())
1323 return;
1324 }
1325
1326 // Determine how many (unfolded) adds we'll need inside the loop.
1327 size_t NumBaseParts = F.getNumRegs();
1328 if (NumBaseParts > 1)
1329 // Do not count the base and a possible second register if the target
1330 // allows to fold 2 registers.
1331 C.NumBaseAdds +=
1332 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(TTI, LU, F)));
1333 C.NumBaseAdds += (F.UnfoldedOffset != 0);
1334
1335 // Accumulate non-free scaling amounts.
1336 C.ScaleCost += getScalingFactorCost(TTI, LU, F, *L);
1337
1338 // Tally up the non-zero immediates.
1339 for (const LSRFixup &Fixup : LU.Fixups) {
1340 int64_t O = Fixup.Offset;
1341 int64_t Offset = (uint64_t)O + F.BaseOffset;
1342 if (F.BaseGV)
1343 C.ImmCost += 64; // Handle symbolic values conservatively.
1344 // TODO: This should probably be the pointer size.
1345 else if (Offset != 0)
1346 C.ImmCost += APInt(64, Offset, true).getMinSignedBits();
1347
1348 // Check with target if this offset with this instruction is
1349 // specifically not supported.
1350 if (LU.Kind == LSRUse::Address && Offset != 0 &&
1351 !isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1352 Offset, F.HasBaseReg, F.Scale, Fixup.UserInst))
1353 C.NumBaseAdds++;
1354 }
1355
1356 // If we don't count instruction cost exit here.
1357 if (!InsnsCost) {
1358 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1358, __PRETTY_FUNCTION__))
;
1359 return;
1360 }
1361
1362 // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as
1363 // additional instruction (at least fill).
1364 unsigned TTIRegNum = TTI.getNumberOfRegisters(false) - 1;
1365 if (C.NumRegs > TTIRegNum) {
1366 // Cost already exceeded TTIRegNum, then only newly added register can add
1367 // new instructions.
1368 if (PrevNumRegs > TTIRegNum)
1369 C.Insns += (C.NumRegs - PrevNumRegs);
1370 else
1371 C.Insns += (C.NumRegs - TTIRegNum);
1372 }
1373
1374 // If ICmpZero formula ends with not 0, it could not be replaced by
1375 // just add or sub. We'll need to compare final result of AddRec.
1376 // That means we'll need an additional instruction. But if the target can
1377 // macro-fuse a compare with a branch, don't count this extra instruction.
1378 // For -10 + {0, +, 1}:
1379 // i = i + 1;
1380 // cmp i, 10
1381 //
1382 // For {-10, +, 1}:
1383 // i = i + 1;
1384 if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd() && !TTI.canMacroFuseCmp())
1385 C.Insns++;
1386 // Each new AddRec adds 1 instruction to calculation.
1387 C.Insns += (C.AddRecCost - PrevAddRecCost);
1388
1389 // BaseAdds adds instructions for unfolded registers.
1390 if (LU.Kind != LSRUse::ICmpZero)
1391 C.Insns += C.NumBaseAdds - PrevNumBaseAdds;
1392 assert(isValid() && "invalid cost")((isValid() && "invalid cost") ? static_cast<void>
(0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1392, __PRETTY_FUNCTION__))
;
1393}
1394
1395/// Set this cost to a losing value.
1396void Cost::Lose() {
1397 C.Insns = std::numeric_limits<unsigned>::max();
1398 C.NumRegs = std::numeric_limits<unsigned>::max();
1399 C.AddRecCost = std::numeric_limits<unsigned>::max();
1400 C.NumIVMuls = std::numeric_limits<unsigned>::max();
1401 C.NumBaseAdds = std::numeric_limits<unsigned>::max();
1402 C.ImmCost = std::numeric_limits<unsigned>::max();
1403 C.SetupCost = std::numeric_limits<unsigned>::max();
1404 C.ScaleCost = std::numeric_limits<unsigned>::max();
1405}
1406
1407/// Choose the lower cost.
1408bool Cost::isLess(Cost &Other, const TargetTransformInfo &TTI) {
1409 if (InsnsCost.getNumOccurrences() > 0 && InsnsCost &&
1410 C.Insns != Other.C.Insns)
1411 return C.Insns < Other.C.Insns;
1412 return TTI.isLSRCostLess(C, Other.C);
1413}
1414
1415#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1416void Cost::print(raw_ostream &OS) const {
1417 if (InsnsCost)
1418 OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s ");
1419 OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s");
1420 if (C.AddRecCost != 0)
1421 OS << ", with addrec cost " << C.AddRecCost;
1422 if (C.NumIVMuls != 0)
1423 OS << ", plus " << C.NumIVMuls << " IV mul"
1424 << (C.NumIVMuls == 1 ? "" : "s");
1425 if (C.NumBaseAdds != 0)
1426 OS << ", plus " << C.NumBaseAdds << " base add"
1427 << (C.NumBaseAdds == 1 ? "" : "s");
1428 if (C.ScaleCost != 0)
1429 OS << ", plus " << C.ScaleCost << " scale cost";
1430 if (C.ImmCost != 0)
1431 OS << ", plus " << C.ImmCost << " imm cost";
1432 if (C.SetupCost != 0)
1433 OS << ", plus " << C.SetupCost << " setup cost";
1434}
1435
1436LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Cost::dump() const {
1437 print(errs()); errs() << '\n';
1438}
1439#endif
1440
1441/// Test whether this fixup always uses its value outside of the given loop.
1442bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1443 // PHI nodes use their value in their incoming blocks.
1444 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1445 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1446 if (PN->getIncomingValue(i) == OperandValToReplace &&
1447 L->contains(PN->getIncomingBlock(i)))
1448 return false;
1449 return true;
1450 }
1451
1452 return !L->contains(UserInst);
1453}
1454
1455#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1456void LSRFixup::print(raw_ostream &OS) const {
1457 OS << "UserInst=";
1458 // Store is common and interesting enough to be worth special-casing.
1459 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1460 OS << "store ";
1461 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1462 } else if (UserInst->getType()->isVoidTy())
1463 OS << UserInst->getOpcodeName();
1464 else
1465 UserInst->printAsOperand(OS, /*PrintType=*/false);
1466
1467 OS << ", OperandValToReplace=";
1468 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1469
1470 for (const Loop *PIL : PostIncLoops) {
1471 OS << ", PostIncLoop=";
1472 PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1473 }
1474
1475 if (Offset != 0)
1476 OS << ", Offset=" << Offset;
1477}
1478
1479LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRFixup::dump() const {
1480 print(errs()); errs() << '\n';
1481}
1482#endif
1483
1484/// Test whether this use as a formula which has the same registers as the given
1485/// formula.
1486bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1487 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1488 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1489 // Unstable sort by host order ok, because this is only used for uniquifying.
1490 llvm::sort(Key);
1491 return Uniquifier.count(Key);
1492}
1493
1494/// The function returns a probability of selecting formula without Reg.
1495float LSRUse::getNotSelectedProbability(const SCEV *Reg) const {
1496 unsigned FNum = 0;
1497 for (const Formula &F : Formulae)
1498 if (F.referencesReg(Reg))
1499 FNum++;
1500 return ((float)(Formulae.size() - FNum)) / Formulae.size();
1501}
1502
1503/// If the given formula has not yet been inserted, add it to the list, and
1504/// return true. Return false otherwise. The formula must be in canonical form.
1505bool LSRUse::InsertFormula(const Formula &F, const Loop &L) {
1506 assert(F.isCanonical(L) && "Invalid canonical representation")((F.isCanonical(L) && "Invalid canonical representation"
) ? static_cast<void> (0) : __assert_fail ("F.isCanonical(L) && \"Invalid canonical representation\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1506, __PRETTY_FUNCTION__))
;
1507
1508 if (!Formulae.empty() && RigidFormula)
1509 return false;
1510
1511 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1512 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1513 // Unstable sort by host order ok, because this is only used for uniquifying.
1514 llvm::sort(Key);
1515
1516 if (!Uniquifier.insert(Key).second)
1517 return false;
1518
1519 // Using a register to hold the value of 0 is not profitable.
1520 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&(((!F.ScaledReg || !F.ScaledReg->isZero()) && "Zero allocated in a scaled register!"
) ? static_cast<void> (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1521, __PRETTY_FUNCTION__))
1521 "Zero allocated in a scaled register!")(((!F.ScaledReg || !F.ScaledReg->isZero()) && "Zero allocated in a scaled register!"
) ? static_cast<void> (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1521, __PRETTY_FUNCTION__))
;
1522#ifndef NDEBUG
1523 for (const SCEV *BaseReg : F.BaseRegs)
1524 assert(!BaseReg->isZero() && "Zero allocated in a base register!")((!BaseReg->isZero() && "Zero allocated in a base register!"
) ? static_cast<void> (0) : __assert_fail ("!BaseReg->isZero() && \"Zero allocated in a base register!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1524, __PRETTY_FUNCTION__))
;
1525#endif
1526
1527 // Add the formula to the list.
1528 Formulae.push_back(F);
1529
1530 // Record registers now being used by this use.
1531 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1532 if (F.ScaledReg)
1533 Regs.insert(F.ScaledReg);
1534
1535 return true;
1536}
1537
1538/// Remove the given formula from this use's list.
1539void LSRUse::DeleteFormula(Formula &F) {
1540 if (&F != &Formulae.back())
1541 std::swap(F, Formulae.back());
1542 Formulae.pop_back();
1543}
1544
1545/// Recompute the Regs field, and update RegUses.
1546void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1547 // Now that we've filtered out some formulae, recompute the Regs set.
1548 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1549 Regs.clear();
1550 for (const Formula &F : Formulae) {
1551 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1552 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1553 }
1554
1555 // Update the RegTracker.
1556 for (const SCEV *S : OldRegs)
1557 if (!Regs.count(S))
1558 RegUses.dropRegister(S, LUIdx);
1559}
1560
1561#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1562void LSRUse::print(raw_ostream &OS) const {
1563 OS << "LSR Use: Kind=";
1564 switch (Kind) {
1565 case Basic: OS << "Basic"; break;
1566 case Special: OS << "Special"; break;
1567 case ICmpZero: OS << "ICmpZero"; break;
1568 case Address:
1569 OS << "Address of ";
1570 if (AccessTy.MemTy->isPointerTy())
1571 OS << "pointer"; // the full pointer type could be really verbose
1572 else {
1573 OS << *AccessTy.MemTy;
1574 }
1575
1576 OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1577 }
1578
1579 OS << ", Offsets={";
1580 bool NeedComma = false;
1581 for (const LSRFixup &Fixup : Fixups) {
1582 if (NeedComma) OS << ',';
1583 OS << Fixup.Offset;
1584 NeedComma = true;
1585 }
1586 OS << '}';
1587
1588 if (AllFixupsOutsideLoop)
1589 OS << ", all-fixups-outside-loop";
1590
1591 if (WidestFixupType)
1592 OS << ", widest fixup type: " << *WidestFixupType;
1593}
1594
1595LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRUse::dump() const {
1596 print(errs()); errs() << '\n';
1597}
1598#endif
1599
1600static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1601 LSRUse::KindType Kind, MemAccessTy AccessTy,
1602 GlobalValue *BaseGV, int64_t BaseOffset,
1603 bool HasBaseReg, int64_t Scale,
1604 Instruction *Fixup/*= nullptr*/) {
1605 switch (Kind) {
1606 case LSRUse::Address:
1607 return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1608 HasBaseReg, Scale, AccessTy.AddrSpace, Fixup);
1609
1610 case LSRUse::ICmpZero:
1611 // There's not even a target hook for querying whether it would be legal to
1612 // fold a GV into an ICmp.
1613 if (BaseGV)
1614 return false;
1615
1616 // ICmp only has two operands; don't allow more than two non-trivial parts.
1617 if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1618 return false;
1619
1620 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1621 // putting the scaled register in the other operand of the icmp.
1622 if (Scale != 0 && Scale != -1)
1623 return false;
1624
1625 // If we have low-level target information, ask the target if it can fold an
1626 // integer immediate on an icmp.
1627 if (BaseOffset != 0) {
1628 // We have one of:
1629 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1630 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1631 // Offs is the ICmp immediate.
1632 if (Scale == 0)
1633 // The cast does the right thing with
1634 // std::numeric_limits<int64_t>::min().
1635 BaseOffset = -(uint64_t)BaseOffset;
1636 return TTI.isLegalICmpImmediate(BaseOffset);
1637 }
1638
1639 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1640 return true;
1641
1642 case LSRUse::Basic:
1643 // Only handle single-register values.
1644 return !BaseGV && Scale == 0 && BaseOffset == 0;
1645
1646 case LSRUse::Special:
1647 // Special case Basic to handle -1 scales.
1648 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1649 }
1650
1651 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1651)
;
1652}
1653
1654static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1655 int64_t MinOffset, int64_t MaxOffset,
1656 LSRUse::KindType Kind, MemAccessTy AccessTy,
1657 GlobalValue *BaseGV, int64_t BaseOffset,
1658 bool HasBaseReg, int64_t Scale) {
1659 // Check for overflow.
1660 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1661 (MinOffset > 0))
1662 return false;
1663 MinOffset = (uint64_t)BaseOffset + MinOffset;
1664 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1665 (MaxOffset > 0))
1666 return false;
1667 MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1668
1669 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1670 HasBaseReg, Scale) &&
1671 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1672 HasBaseReg, Scale);
1673}
1674
1675static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1676 int64_t MinOffset, int64_t MaxOffset,
1677 LSRUse::KindType Kind, MemAccessTy AccessTy,
1678 const Formula &F, const Loop &L) {
1679 // For the purpose of isAMCompletelyFolded either having a canonical formula
1680 // or a scale not equal to zero is correct.
1681 // Problems may arise from non canonical formulae having a scale == 0.
1682 // Strictly speaking it would best to just rely on canonical formulae.
1683 // However, when we generate the scaled formulae, we first check that the
1684 // scaling factor is profitable before computing the actual ScaledReg for
1685 // compile time sake.
1686 assert((F.isCanonical(L) || F.Scale != 0))(((F.isCanonical(L) || F.Scale != 0)) ? static_cast<void>
(0) : __assert_fail ("(F.isCanonical(L) || F.Scale != 0)", "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1686, __PRETTY_FUNCTION__))
;
1687 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1688 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1689}
1690
1691/// Test whether we know how to expand the current formula.
1692static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1693 int64_t MaxOffset, LSRUse::KindType Kind,
1694 MemAccessTy AccessTy, GlobalValue *BaseGV,
1695 int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1696 // We know how to expand completely foldable formulae.
1697 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1698 BaseOffset, HasBaseReg, Scale) ||
1699 // Or formulae that use a base register produced by a sum of base
1700 // registers.
1701 (Scale == 1 &&
1702 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1703 BaseGV, BaseOffset, true, 0));
1704}
1705
1706static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1707 int64_t MaxOffset, LSRUse::KindType Kind,
1708 MemAccessTy AccessTy, const Formula &F) {
1709 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1710 F.BaseOffset, F.HasBaseReg, F.Scale);
1711}
1712
1713static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1714 const LSRUse &LU, const Formula &F) {
1715 // Target may want to look at the user instructions.
1716 if (LU.Kind == LSRUse::Address && TTI.LSRWithInstrQueries()) {
1717 for (const LSRFixup &Fixup : LU.Fixups)
1718 if (!isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1719 (F.BaseOffset + Fixup.Offset), F.HasBaseReg,
1720 F.Scale, Fixup.UserInst))
1721 return false;
1722 return true;
1723 }
1724
1725 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1726 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1727 F.Scale);
1728}
1729
1730static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1731 const LSRUse &LU, const Formula &F,
1732 const Loop &L) {
1733 if (!F.Scale)
1734 return 0;
1735
1736 // If the use is not completely folded in that instruction, we will have to
1737 // pay an extra cost only for scale != 1.
1738 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1739 LU.AccessTy, F, L))
1740 return F.Scale != 1;
1741
1742 switch (LU.Kind) {
1743 case LSRUse::Address: {
1744 // Check the scaling factor cost with both the min and max offsets.
1745 int ScaleCostMinOffset = TTI.getScalingFactorCost(
1746 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1747 F.Scale, LU.AccessTy.AddrSpace);
1748 int ScaleCostMaxOffset = TTI.getScalingFactorCost(
1749 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1750 F.Scale, LU.AccessTy.AddrSpace);
1751
1752 assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&((ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >=
0 && "Legal addressing mode has an illegal cost!") ?
static_cast<void> (0) : __assert_fail ("ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && \"Legal addressing mode has an illegal cost!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1753, __PRETTY_FUNCTION__))
1753 "Legal addressing mode has an illegal cost!")((ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >=
0 && "Legal addressing mode has an illegal cost!") ?
static_cast<void> (0) : __assert_fail ("ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && \"Legal addressing mode has an illegal cost!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1753, __PRETTY_FUNCTION__))
;
1754 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1755 }
1756 case LSRUse::ICmpZero:
1757 case LSRUse::Basic:
1758 case LSRUse::Special:
1759 // The use is completely folded, i.e., everything is folded into the
1760 // instruction.
1761 return 0;
1762 }
1763
1764 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1764)
;
1765}
1766
1767static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1768 LSRUse::KindType Kind, MemAccessTy AccessTy,
1769 GlobalValue *BaseGV, int64_t BaseOffset,
1770 bool HasBaseReg) {
1771 // Fast-path: zero is always foldable.
1772 if (BaseOffset == 0 && !BaseGV) return true;
1773
1774 // Conservatively, create an address with an immediate and a
1775 // base and a scale.
1776 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1777
1778 // Canonicalize a scale of 1 to a base register if the formula doesn't
1779 // already have a base register.
1780 if (!HasBaseReg && Scale == 1) {
1781 Scale = 0;
1782 HasBaseReg = true;
1783 }
1784
1785 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1786 HasBaseReg, Scale);
1787}
1788
1789static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1790 ScalarEvolution &SE, int64_t MinOffset,
1791 int64_t MaxOffset, LSRUse::KindType Kind,
1792 MemAccessTy AccessTy, const SCEV *S,
1793 bool HasBaseReg) {
1794 // Fast-path: zero is always foldable.
1795 if (S->isZero()) return true;
1796
1797 // Conservatively, create an address with an immediate and a
1798 // base and a scale.
1799 int64_t BaseOffset = ExtractImmediate(S, SE);
1800 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1801
1802 // If there's anything else involved, it's not foldable.
1803 if (!S->isZero()) return false;
1804
1805 // Fast-path: zero is always foldable.
1806 if (BaseOffset == 0 && !BaseGV) return true;
1807
1808 // Conservatively, create an address with an immediate and a
1809 // base and a scale.
1810 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1811
1812 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1813 BaseOffset, HasBaseReg, Scale);
1814}
1815
1816namespace {
1817
1818/// An individual increment in a Chain of IV increments. Relate an IV user to
1819/// an expression that computes the IV it uses from the IV used by the previous
1820/// link in the Chain.
1821///
1822/// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1823/// original IVOperand. The head of the chain's IVOperand is only valid during
1824/// chain collection, before LSR replaces IV users. During chain generation,
1825/// IncExpr can be used to find the new IVOperand that computes the same
1826/// expression.
1827struct IVInc {
1828 Instruction *UserInst;
1829 Value* IVOperand;
1830 const SCEV *IncExpr;
1831
1832 IVInc(Instruction *U, Value *O, const SCEV *E)
1833 : UserInst(U), IVOperand(O), IncExpr(E) {}
1834};
1835
1836// The list of IV increments in program order. We typically add the head of a
1837// chain without finding subsequent links.
1838struct IVChain {
1839 SmallVector<IVInc, 1> Incs;
1840 const SCEV *ExprBase = nullptr;
1841
1842 IVChain() = default;
1843 IVChain(const IVInc &Head, const SCEV *Base)
1844 : Incs(1, Head), ExprBase(Base) {}
1845
1846 using const_iterator = SmallVectorImpl<IVInc>::const_iterator;
1847
1848 // Return the first increment in the chain.
1849 const_iterator begin() const {
1850 assert(!Incs.empty())((!Incs.empty()) ? static_cast<void> (0) : __assert_fail
("!Incs.empty()", "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1850, __PRETTY_FUNCTION__))
;
1851 return std::next(Incs.begin());
1852 }
1853 const_iterator end() const {
1854 return Incs.end();
1855 }
1856
1857 // Returns true if this chain contains any increments.
1858 bool hasIncs() const { return Incs.size() >= 2; }
1859
1860 // Add an IVInc to the end of this chain.
1861 void add(const IVInc &X) { Incs.push_back(X); }
1862
1863 // Returns the last UserInst in the chain.
1864 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1865
1866 // Returns true if IncExpr can be profitably added to this chain.
1867 bool isProfitableIncrement(const SCEV *OperExpr,
1868 const SCEV *IncExpr,
1869 ScalarEvolution&);
1870};
1871
1872/// Helper for CollectChains to track multiple IV increment uses. Distinguish
1873/// between FarUsers that definitely cross IV increments and NearUsers that may
1874/// be used between IV increments.
1875struct ChainUsers {
1876 SmallPtrSet<Instruction*, 4> FarUsers;
1877 SmallPtrSet<Instruction*, 4> NearUsers;
1878};
1879
1880/// This class holds state for the main loop strength reduction logic.
1881class LSRInstance {
1882 IVUsers &IU;
1883 ScalarEvolution &SE;
1884 DominatorTree &DT;
1885 LoopInfo &LI;
1886 const TargetTransformInfo &TTI;
1887 Loop *const L;
1888 bool Changed = false;
1889
1890 /// This is the insert position that the current loop's induction variable
1891 /// increment should be placed. In simple loops, this is the latch block's
1892 /// terminator. But in more complicated cases, this is a position which will
1893 /// dominate all the in-loop post-increment users.
1894 Instruction *IVIncInsertPos = nullptr;
1895
1896 /// Interesting factors between use strides.
1897 ///
1898 /// We explicitly use a SetVector which contains a SmallSet, instead of the
1899 /// default, a SmallDenseSet, because we need to use the full range of
1900 /// int64_ts, and there's currently no good way of doing that with
1901 /// SmallDenseSet.
1902 SetVector<int64_t, SmallVector<int64_t, 8>, SmallSet<int64_t, 8>> Factors;
1903
1904 /// Interesting use types, to facilitate truncation reuse.
1905 SmallSetVector<Type *, 4> Types;
1906
1907 /// The list of interesting uses.
1908 SmallVector<LSRUse, 16> Uses;
1909
1910 /// Track which uses use which register candidates.
1911 RegUseTracker RegUses;
1912
1913 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1914 // have more than a few IV increment chains in a loop. Missing a Chain falls
1915 // back to normal LSR behavior for those uses.
1916 static const unsigned MaxChains = 8;
1917
1918 /// IV users can form a chain of IV increments.
1919 SmallVector<IVChain, MaxChains> IVChainVec;
1920
1921 /// IV users that belong to profitable IVChains.
1922 SmallPtrSet<Use*, MaxChains> IVIncSet;
1923
1924 void OptimizeShadowIV();
1925 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1926 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1927 void OptimizeLoopTermCond();
1928
1929 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1930 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1931 void FinalizeChain(IVChain &Chain);
1932 void CollectChains();
1933 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1934 SmallVectorImpl<WeakTrackingVH> &DeadInsts);
1935
1936 void CollectInterestingTypesAndFactors();
1937 void CollectFixupsAndInitialFormulae();
1938
1939 // Support for sharing of LSRUses between LSRFixups.
1940 using UseMapTy = DenseMap<LSRUse::SCEVUseKindPair, size_t>;
1941 UseMapTy UseMap;
1942
1943 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1944 LSRUse::KindType Kind, MemAccessTy AccessTy);
1945
1946 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
1947 MemAccessTy AccessTy);
1948
1949 void DeleteUse(LSRUse &LU, size_t LUIdx);
1950
1951 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1952
1953 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1954 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1955 void CountRegisters(const Formula &F, size_t LUIdx);
1956 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1957
1958 void CollectLoopInvariantFixupsAndFormulae();
1959
1960 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1961 unsigned Depth = 0);
1962
1963 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1964 const Formula &Base, unsigned Depth,
1965 size_t Idx, bool IsScaledReg = false);
1966 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1967 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1968 const Formula &Base, size_t Idx,
1969 bool IsScaledReg = false);
1970 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1971 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1972 const Formula &Base,
1973 const SmallVectorImpl<int64_t> &Worklist,
1974 size_t Idx, bool IsScaledReg = false);
1975 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1976 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1977 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1978 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1979 void GenerateCrossUseConstantOffsets();
1980 void GenerateAllReuseFormulae();
1981
1982 void FilterOutUndesirableDedicatedRegisters();
1983
1984 size_t EstimateSearchSpaceComplexity() const;
1985 void NarrowSearchSpaceByDetectingSupersets();
1986 void NarrowSearchSpaceByCollapsingUnrolledCode();
1987 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1988 void NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
1989 void NarrowSearchSpaceByDeletingCostlyFormulas();
1990 void NarrowSearchSpaceByPickingWinnerRegs();
1991 void NarrowSearchSpaceUsingHeuristics();
1992
1993 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1994 Cost &SolutionCost,
1995 SmallVectorImpl<const Formula *> &Workspace,
1996 const Cost &CurCost,
1997 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1998 DenseSet<const SCEV *> &VisitedRegs) const;
1999 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
2000
2001 BasicBlock::iterator
2002 HoistInsertPosition(BasicBlock::iterator IP,
2003 const SmallVectorImpl<Instruction *> &Inputs) const;
2004 BasicBlock::iterator
2005 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
2006 const LSRFixup &LF,
2007 const LSRUse &LU,
2008 SCEVExpander &Rewriter) const;
2009
2010 Value *Expand(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2011 BasicBlock::iterator IP, SCEVExpander &Rewriter,
2012 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2013 void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
2014 const Formula &F, SCEVExpander &Rewriter,
2015 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2016 void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2017 SCEVExpander &Rewriter,
2018 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2019 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
2020
2021public:
2022 LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
2023 LoopInfo &LI, const TargetTransformInfo &TTI);
2024
2025 bool getChanged() const { return Changed; }
2026
2027 void print_factors_and_types(raw_ostream &OS) const;
2028 void print_fixups(raw_ostream &OS) const;
2029 void print_uses(raw_ostream &OS) const;
2030 void print(raw_ostream &OS) const;
2031 void dump() const;
2032};
2033
2034} // end anonymous namespace
2035
2036/// If IV is used in a int-to-float cast inside the loop then try to eliminate
2037/// the cast operation.
2038void LSRInstance::OptimizeShadowIV() {
2039 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2040 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2041 return;
2042
2043 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
2044 UI != E; /* empty */) {
2045 IVUsers::const_iterator CandidateUI = UI;
2046 ++UI;
2047 Instruction *ShadowUse = CandidateUI->getUser();
2048 Type *DestTy = nullptr;
2049 bool IsSigned = false;
2050
2051 /* If shadow use is a int->float cast then insert a second IV
2052 to eliminate this cast.
2053
2054 for (unsigned i = 0; i < n; ++i)
2055 foo((double)i);
2056
2057 is transformed into
2058
2059 double d = 0.0;
2060 for (unsigned i = 0; i < n; ++i, ++d)
2061 foo(d);
2062 */
2063 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
2064 IsSigned = false;
2065 DestTy = UCast->getDestTy();
2066 }
2067 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
2068 IsSigned = true;
2069 DestTy = SCast->getDestTy();
2070 }
2071 if (!DestTy) continue;
2072
2073 // If target does not support DestTy natively then do not apply
2074 // this transformation.
2075 if (!TTI.isTypeLegal(DestTy)) continue;
2076
2077 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2078 if (!PH) continue;
2079 if (PH->getNumIncomingValues() != 2) continue;
2080
2081 // If the calculation in integers overflows, the result in FP type will
2082 // differ. So we only can do this transformation if we are guaranteed to not
2083 // deal with overflowing values
2084 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PH));
2085 if (!AR) continue;
2086 if (IsSigned && !AR->hasNoSignedWrap()) continue;
2087 if (!IsSigned && !AR->hasNoUnsignedWrap()) continue;
2088
2089 Type *SrcTy = PH->getType();
2090 int Mantissa = DestTy->getFPMantissaWidth();
2091 if (Mantissa == -1) continue;
2092 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
2093 continue;
2094
2095 unsigned Entry, Latch;
2096 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2097 Entry = 0;
2098 Latch = 1;
2099 } else {
2100 Entry = 1;
2101 Latch = 0;
2102 }
2103
2104 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
2105 if (!Init) continue;
2106 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
2107 (double)Init->getSExtValue() :
2108 (double)Init->getZExtValue());
2109
2110 BinaryOperator *Incr =
2111 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
2112 if (!Incr) continue;
2113 if (Incr->getOpcode() != Instruction::Add
2114 && Incr->getOpcode() != Instruction::Sub)
2115 continue;
2116
2117 /* Initialize new IV, double d = 0.0 in above example. */
2118 ConstantInt *C = nullptr;
2119 if (Incr->getOperand(0) == PH)
2120 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2121 else if (Incr->getOperand(1) == PH)
2122 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2123 else
2124 continue;
2125
2126 if (!C) continue;
2127
2128 // Ignore negative constants, as the code below doesn't handle them
2129 // correctly. TODO: Remove this restriction.
2130 if (!C->getValue().isStrictlyPositive()) continue;
2131
2132 /* Add new PHINode. */
2133 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
2134
2135 /* create new increment. '++d' in above example. */
2136 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2137 BinaryOperator *NewIncr =
2138 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
2139 Instruction::FAdd : Instruction::FSub,
2140 NewPH, CFP, "IV.S.next.", Incr);
2141
2142 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2143 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2144
2145 /* Remove cast operation */
2146 ShadowUse->replaceAllUsesWith(NewPH);
2147 ShadowUse->eraseFromParent();
2148 Changed = true;
2149 break;
2150 }
2151}
2152
2153/// If Cond has an operand that is an expression of an IV, set the IV user and
2154/// stride information and return true, otherwise return false.
2155bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
2156 for (IVStrideUse &U : IU)
2157 if (U.getUser() == Cond) {
2158 // NOTE: we could handle setcc instructions with multiple uses here, but
2159 // InstCombine does it as well for simple uses, it's not clear that it
2160 // occurs enough in real life to handle.
2161 CondUse = &U;
2162 return true;
2163 }
2164 return false;
2165}
2166
2167/// Rewrite the loop's terminating condition if it uses a max computation.
2168///
2169/// This is a narrow solution to a specific, but acute, problem. For loops
2170/// like this:
2171///
2172/// i = 0;
2173/// do {
2174/// p[i] = 0.0;
2175/// } while (++i < n);
2176///
2177/// the trip count isn't just 'n', because 'n' might not be positive. And
2178/// unfortunately this can come up even for loops where the user didn't use
2179/// a C do-while loop. For example, seemingly well-behaved top-test loops
2180/// will commonly be lowered like this:
2181///
2182/// if (n > 0) {
2183/// i = 0;
2184/// do {
2185/// p[i] = 0.0;
2186/// } while (++i < n);
2187/// }
2188///
2189/// and then it's possible for subsequent optimization to obscure the if
2190/// test in such a way that indvars can't find it.
2191///
2192/// When indvars can't find the if test in loops like this, it creates a
2193/// max expression, which allows it to give the loop a canonical
2194/// induction variable:
2195///
2196/// i = 0;
2197/// max = n < 1 ? 1 : n;
2198/// do {
2199/// p[i] = 0.0;
2200/// } while (++i != max);
2201///
2202/// Canonical induction variables are necessary because the loop passes
2203/// are designed around them. The most obvious example of this is the
2204/// LoopInfo analysis, which doesn't remember trip count values. It
2205/// expects to be able to rediscover the trip count each time it is
2206/// needed, and it does this using a simple analysis that only succeeds if
2207/// the loop has a canonical induction variable.
2208///
2209/// However, when it comes time to generate code, the maximum operation
2210/// can be quite costly, especially if it's inside of an outer loop.
2211///
2212/// This function solves this problem by detecting this type of loop and
2213/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2214/// the instructions for the maximum computation.
2215ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
2216 // Check that the loop matches the pattern we're looking for.
2217 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2218 Cond->getPredicate() != CmpInst::ICMP_NE)
2219 return Cond;
2220
2221 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2222 if (!Sel || !Sel->hasOneUse()) return Cond;
2223
2224 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2225 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2226 return Cond;
2227 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2228
2229 // Add one to the backedge-taken count to get the trip count.
2230 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2231 if (IterationCount != SE.getSCEV(Sel)) return Cond;
2232
2233 // Check for a max calculation that matches the pattern. There's no check
2234 // for ICMP_ULE here because the comparison would be with zero, which
2235 // isn't interesting.
2236 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2237 const SCEVNAryExpr *Max = nullptr;
2238 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2239 Pred = ICmpInst::ICMP_SLE;
2240 Max = S;
2241 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2242 Pred = ICmpInst::ICMP_SLT;
2243 Max = S;
2244 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2245 Pred = ICmpInst::ICMP_ULT;
2246 Max = U;
2247 } else {
2248 // No match; bail.
2249 return Cond;
2250 }
2251
2252 // To handle a max with more than two operands, this optimization would
2253 // require additional checking and setup.
2254 if (Max->getNumOperands() != 2)
2255 return Cond;
2256
2257 const SCEV *MaxLHS = Max->getOperand(0);
2258 const SCEV *MaxRHS = Max->getOperand(1);
2259
2260 // ScalarEvolution canonicalizes constants to the left. For < and >, look
2261 // for a comparison with 1. For <= and >=, a comparison with zero.
2262 if (!MaxLHS ||
2263 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2264 return Cond;
2265
2266 // Check the relevant induction variable for conformance to
2267 // the pattern.
2268 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2269 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2270 if (!AR || !AR->isAffine() ||
2271 AR->getStart() != One ||
2272 AR->getStepRecurrence(SE) != One)
2273 return Cond;
2274
2275 assert(AR->getLoop() == L &&((AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? static_cast<void> (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2276, __PRETTY_FUNCTION__))
2276 "Loop condition operand is an addrec in a different loop!")((AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? static_cast<void> (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2276, __PRETTY_FUNCTION__))
;
2277
2278 // Check the right operand of the select, and remember it, as it will
2279 // be used in the new comparison instruction.
2280 Value *NewRHS = nullptr;
2281 if (ICmpInst::isTrueWhenEqual(Pred)) {
2282 // Look for n+1, and grab n.
2283 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2284 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2285 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2286 NewRHS = BO->getOperand(0);
2287 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2288 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2289 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2290 NewRHS = BO->getOperand(0);
2291 if (!NewRHS)
2292 return Cond;
2293 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2294 NewRHS = Sel->getOperand(1);
2295 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2296 NewRHS = Sel->getOperand(2);
2297 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2298 NewRHS = SU->getValue();
2299 else
2300 // Max doesn't match expected pattern.
2301 return Cond;
2302
2303 // Determine the new comparison opcode. It may be signed or unsigned,
2304 // and the original comparison may be either equality or inequality.
2305 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2306 Pred = CmpInst::getInversePredicate(Pred);
2307
2308 // Ok, everything looks ok to change the condition into an SLT or SGE and
2309 // delete the max calculation.
2310 ICmpInst *NewCond =
2311 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2312
2313 // Delete the max calculation instructions.
2314 Cond->replaceAllUsesWith(NewCond);
2315 CondUse->setUser(NewCond);
2316 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2317 Cond->eraseFromParent();
2318 Sel->eraseFromParent();
2319 if (Cmp->use_empty())
2320 Cmp->eraseFromParent();
2321 return NewCond;
2322}
2323
2324/// Change loop terminating condition to use the postinc iv when possible.
2325void
2326LSRInstance::OptimizeLoopTermCond() {
2327 SmallPtrSet<Instruction *, 4> PostIncs;
2328
2329 // We need a different set of heuristics for rotated and non-rotated loops.
2330 // If a loop is rotated then the latch is also the backedge, so inserting
2331 // post-inc expressions just before the latch is ideal. To reduce live ranges
2332 // it also makes sense to rewrite terminating conditions to use post-inc
2333 // expressions.
2334 //
2335 // If the loop is not rotated then the latch is not a backedge; the latch
2336 // check is done in the loop head. Adding post-inc expressions before the
2337 // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2338 // in the loop body. In this case we do *not* want to use post-inc expressions
2339 // in the latch check, and we want to insert post-inc expressions before
2340 // the backedge.
2341 BasicBlock *LatchBlock = L->getLoopLatch();
2342 SmallVector<BasicBlock*, 8> ExitingBlocks;
2343 L->getExitingBlocks(ExitingBlocks);
2344 if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2345 return LatchBlock != BB;
2346 })) {
2347 // The backedge doesn't exit the loop; treat this as a head-tested loop.
2348 IVIncInsertPos = LatchBlock->getTerminator();
2349 return;
2350 }
2351
2352 // Otherwise treat this as a rotated loop.
2353 for (BasicBlock *ExitingBlock : ExitingBlocks) {
2354 // Get the terminating condition for the loop if possible. If we
2355 // can, we want to change it to use a post-incremented version of its
2356 // induction variable, to allow coalescing the live ranges for the IV into
2357 // one register value.
2358
2359 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2360 if (!TermBr)
2361 continue;
2362 // FIXME: Overly conservative, termination condition could be an 'or' etc..
2363 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2364 continue;
2365
2366 // Search IVUsesByStride to find Cond's IVUse if there is one.
2367 IVStrideUse *CondUse = nullptr;
2368 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2369 if (!FindIVUserForCond(Cond, CondUse))
2370 continue;
2371
2372 // If the trip count is computed in terms of a max (due to ScalarEvolution
2373 // being unable to find a sufficient guard, for example), change the loop
2374 // comparison to use SLT or ULT instead of NE.
2375 // One consequence of doing this now is that it disrupts the count-down
2376 // optimization. That's not always a bad thing though, because in such
2377 // cases it may still be worthwhile to avoid a max.
2378 Cond = OptimizeMax(Cond, CondUse);
2379
2380 // If this exiting block dominates the latch block, it may also use
2381 // the post-inc value if it won't be shared with other uses.
2382 // Check for dominance.
2383 if (!DT.dominates(ExitingBlock, LatchBlock))
2384 continue;
2385
2386 // Conservatively avoid trying to use the post-inc value in non-latch
2387 // exits if there may be pre-inc users in intervening blocks.
2388 if (LatchBlock != ExitingBlock)
2389 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2390 // Test if the use is reachable from the exiting block. This dominator
2391 // query is a conservative approximation of reachability.
2392 if (&*UI != CondUse &&
2393 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2394 // Conservatively assume there may be reuse if the quotient of their
2395 // strides could be a legal scale.
2396 const SCEV *A = IU.getStride(*CondUse, L);
2397 const SCEV *B = IU.getStride(*UI, L);
2398 if (!A || !B) continue;
2399 if (SE.getTypeSizeInBits(A->getType()) !=
2400 SE.getTypeSizeInBits(B->getType())) {
2401 if (SE.getTypeSizeInBits(A->getType()) >
2402 SE.getTypeSizeInBits(B->getType()))
2403 B = SE.getSignExtendExpr(B, A->getType());
2404 else
2405 A = SE.getSignExtendExpr(A, B->getType());
2406 }
2407 if (const SCEVConstant *D =
2408 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2409 const ConstantInt *C = D->getValue();
2410 // Stride of one or negative one can have reuse with non-addresses.
2411 if (C->isOne() || C->isMinusOne())
2412 goto decline_post_inc;
2413 // Avoid weird situations.
2414 if (C->getValue().getMinSignedBits() >= 64 ||
2415 C->getValue().isMinSignedValue())
2416 goto decline_post_inc;
2417 // Check for possible scaled-address reuse.
2418 if (isAddressUse(TTI, UI->getUser(), UI->getOperandValToReplace())) {
2419 MemAccessTy AccessTy = getAccessType(
2420 TTI, UI->getUser(), UI->getOperandValToReplace());
2421 int64_t Scale = C->getSExtValue();
2422 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2423 /*BaseOffset=*/0,
2424 /*HasBaseReg=*/false, Scale,
2425 AccessTy.AddrSpace))
2426 goto decline_post_inc;
2427 Scale = -Scale;
2428 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2429 /*BaseOffset=*/0,
2430 /*HasBaseReg=*/false, Scale,
2431 AccessTy.AddrSpace))
2432 goto decline_post_inc;
2433 }
2434 }
2435 }
2436
2437 LLVM_DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Change loop exiting icmp to use postinc iv: "
<< *Cond << '\n'; } } while (false)
2438 << *Cond << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Change loop exiting icmp to use postinc iv: "
<< *Cond << '\n'; } } while (false)
;
2439
2440 // It's possible for the setcc instruction to be anywhere in the loop, and
2441 // possible for it to have multiple users. If it is not immediately before
2442 // the exiting block branch, move it.
2443 if (&*++BasicBlock::iterator(Cond) != TermBr) {
2444 if (Cond->hasOneUse()) {
2445 Cond->moveBefore(TermBr);
2446 } else {
2447 // Clone the terminating condition and insert into the loopend.
2448 ICmpInst *OldCond = Cond;
2449 Cond = cast<ICmpInst>(Cond->clone());
2450 Cond->setName(L->getHeader()->getName() + ".termcond");
2451 ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2452
2453 // Clone the IVUse, as the old use still exists!
2454 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2455 TermBr->replaceUsesOfWith(OldCond, Cond);
2456 }
2457 }
2458
2459 // If we get to here, we know that we can transform the setcc instruction to
2460 // use the post-incremented version of the IV, allowing us to coalesce the
2461 // live ranges for the IV correctly.
2462 CondUse->transformToPostInc(L);
2463 Changed = true;
2464
2465 PostIncs.insert(Cond);
2466 decline_post_inc:;
2467 }
2468
2469 // Determine an insertion point for the loop induction variable increment. It
2470 // must dominate all the post-inc comparisons we just set up, and it must
2471 // dominate the loop latch edge.
2472 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2473 for (Instruction *Inst : PostIncs) {
2474 BasicBlock *BB =
2475 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2476 Inst->getParent());
2477 if (BB == Inst->getParent())
2478 IVIncInsertPos = Inst;
2479 else if (BB != IVIncInsertPos->getParent())
2480 IVIncInsertPos = BB->getTerminator();
2481 }
2482}
2483
2484/// Determine if the given use can accommodate a fixup at the given offset and
2485/// other details. If so, update the use and return true.
2486bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2487 bool HasBaseReg, LSRUse::KindType Kind,
2488 MemAccessTy AccessTy) {
2489 int64_t NewMinOffset = LU.MinOffset;
2490 int64_t NewMaxOffset = LU.MaxOffset;
2491 MemAccessTy NewAccessTy = AccessTy;
2492
2493 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2494 // something conservative, however this can pessimize in the case that one of
2495 // the uses will have all its uses outside the loop, for example.
2496 if (LU.Kind != Kind)
2497 return false;
2498
2499 // Check for a mismatched access type, and fall back conservatively as needed.
2500 // TODO: Be less conservative when the type is similar and can use the same
2501 // addressing modes.
2502 if (Kind == LSRUse::Address) {
2503 if (AccessTy.MemTy != LU.AccessTy.MemTy) {
2504 NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(),
2505 AccessTy.AddrSpace);
2506 }
2507 }
2508
2509 // Conservatively assume HasBaseReg is true for now.
2510 if (NewOffset < LU.MinOffset) {
2511 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2512 LU.MaxOffset - NewOffset, HasBaseReg))
2513 return false;
2514 NewMinOffset = NewOffset;
2515 } else if (NewOffset > LU.MaxOffset) {
2516 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2517 NewOffset - LU.MinOffset, HasBaseReg))
2518 return false;
2519 NewMaxOffset = NewOffset;
2520 }
2521
2522 // Update the use.
2523 LU.MinOffset = NewMinOffset;
2524 LU.MaxOffset = NewMaxOffset;
2525 LU.AccessTy = NewAccessTy;
2526 return true;
2527}
2528
2529/// Return an LSRUse index and an offset value for a fixup which needs the given
2530/// expression, with the given kind and optional access type. Either reuse an
2531/// existing use or create a new one, as needed.
2532std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2533 LSRUse::KindType Kind,
2534 MemAccessTy AccessTy) {
2535 const SCEV *Copy = Expr;
2536 int64_t Offset = ExtractImmediate(Expr, SE);
2537
2538 // Basic uses can't accept any offset, for example.
2539 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2540 Offset, /*HasBaseReg=*/ true)) {
2541 Expr = Copy;
2542 Offset = 0;
2543 }
2544
2545 std::pair<UseMapTy::iterator, bool> P =
2546 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2547 if (!P.second) {
2548 // A use already existed with this base.
2549 size_t LUIdx = P.first->second;
2550 LSRUse &LU = Uses[LUIdx];
2551 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2552 // Reuse this use.
2553 return std::make_pair(LUIdx, Offset);
2554 }
2555
2556 // Create a new use.
2557 size_t LUIdx = Uses.size();
2558 P.first->second = LUIdx;
2559 Uses.push_back(LSRUse(Kind, AccessTy));
2560 LSRUse &LU = Uses[LUIdx];
2561
2562 LU.MinOffset = Offset;
2563 LU.MaxOffset = Offset;
2564 return std::make_pair(LUIdx, Offset);
2565}
2566
2567/// Delete the given use from the Uses list.
2568void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2569 if (&LU != &Uses.back())
2570 std::swap(LU, Uses.back());
2571 Uses.pop_back();
2572
2573 // Update RegUses.
2574 RegUses.swapAndDropUse(LUIdx, Uses.size());
2575}
2576
2577/// Look for a use distinct from OrigLU which is has a formula that has the same
2578/// registers as the given formula.
2579LSRUse *
2580LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2581 const LSRUse &OrigLU) {
2582 // Search all uses for the formula. This could be more clever.
2583 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2584 LSRUse &LU = Uses[LUIdx];
2585 // Check whether this use is close enough to OrigLU, to see whether it's
2586 // worthwhile looking through its formulae.
2587 // Ignore ICmpZero uses because they may contain formulae generated by
2588 // GenerateICmpZeroScales, in which case adding fixup offsets may
2589 // be invalid.
2590 if (&LU != &OrigLU &&
2591 LU.Kind != LSRUse::ICmpZero &&
2592 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2593 LU.WidestFixupType == OrigLU.WidestFixupType &&
2594 LU.HasFormulaWithSameRegs(OrigF)) {
2595 // Scan through this use's formulae.
2596 for (const Formula &F : LU.Formulae) {
2597 // Check to see if this formula has the same registers and symbols
2598 // as OrigF.
2599 if (F.BaseRegs == OrigF.BaseRegs &&
2600 F.ScaledReg == OrigF.ScaledReg &&
2601 F.BaseGV == OrigF.BaseGV &&
2602 F.Scale == OrigF.Scale &&
2603 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2604 if (F.BaseOffset == 0)
2605 return &LU;
2606 // This is the formula where all the registers and symbols matched;
2607 // there aren't going to be any others. Since we declined it, we
2608 // can skip the rest of the formulae and proceed to the next LSRUse.
2609 break;
2610 }
2611 }
2612 }
2613 }
2614
2615 // Nothing looked good.
2616 return nullptr;
2617}
2618
2619void LSRInstance::CollectInterestingTypesAndFactors() {
2620 SmallSetVector<const SCEV *, 4> Strides;
2621
2622 // Collect interesting types and strides.
2623 SmallVector<const SCEV *, 4> Worklist;
2624 for (const IVStrideUse &U : IU) {
2625 const SCEV *Expr = IU.getExpr(U);
2626
2627 // Collect interesting types.
2628 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2629
2630 // Add strides for mentioned loops.
2631 Worklist.push_back(Expr);
2632 do {
2633 const SCEV *S = Worklist.pop_back_val();
2634 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2635 if (AR->getLoop() == L)
2636 Strides.insert(AR->getStepRecurrence(SE));
2637 Worklist.push_back(AR->getStart());
2638 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2639 Worklist.append(Add->op_begin(), Add->op_end());
2640 }
2641 } while (!Worklist.empty());
2642 }
2643
2644 // Compute interesting factors from the set of interesting strides.
2645 for (SmallSetVector<const SCEV *, 4>::const_iterator
2646 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2647 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2648 std::next(I); NewStrideIter != E; ++NewStrideIter) {
2649 const SCEV *OldStride = *I;
2650 const SCEV *NewStride = *NewStrideIter;
2651
2652 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2653 SE.getTypeSizeInBits(NewStride->getType())) {
2654 if (SE.getTypeSizeInBits(OldStride->getType()) >
2655 SE.getTypeSizeInBits(NewStride->getType()))
2656 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2657 else
2658 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2659 }
2660 if (const SCEVConstant *Factor =
2661 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2662 SE, true))) {
2663 if (Factor->getAPInt().getMinSignedBits() <= 64)
2664 Factors.insert(Factor->getAPInt().getSExtValue());
2665 } else if (const SCEVConstant *Factor =
2666 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2667 NewStride,
2668 SE, true))) {
2669 if (Factor->getAPInt().getMinSignedBits() <= 64)
2670 Factors.insert(Factor->getAPInt().getSExtValue());
2671 }
2672 }
2673
2674 // If all uses use the same type, don't bother looking for truncation-based
2675 // reuse.
2676 if (Types.size() == 1)
2677 Types.clear();
2678
2679 LLVM_DEBUG(print_factors_and_types(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_factors_and_types(dbgs()); } } while
(false)
;
2680}
2681
2682/// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2683/// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2684/// IVStrideUses, we could partially skip this.
2685static User::op_iterator
2686findIVOperand(User::op_iterator OI, User::op_iterator OE,
2687 Loop *L, ScalarEvolution &SE) {
2688 for(; OI != OE; ++OI) {
2689 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2690 if (!SE.isSCEVable(Oper->getType()))
2691 continue;
2692
2693 if (const SCEVAddRecExpr *AR =
2694 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2695 if (AR->getLoop() == L)
2696 break;
2697 }
2698 }
2699 }
2700 return OI;
2701}
2702
2703/// IVChain logic must consistently peek base TruncInst operands, so wrap it in
2704/// a convenient helper.
2705static Value *getWideOperand(Value *Oper) {
2706 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2707 return Trunc->getOperand(0);
2708 return Oper;
2709}
2710
2711/// Return true if we allow an IV chain to include both types.
2712static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2713 Type *LType = LVal->getType();
2714 Type *RType = RVal->getType();
2715 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy() &&
2716 // Different address spaces means (possibly)
2717 // different types of the pointer implementation,
2718 // e.g. i16 vs i32 so disallow that.
2719 (LType->getPointerAddressSpace() ==
2720 RType->getPointerAddressSpace()));
2721}
2722
2723/// Return an approximation of this SCEV expression's "base", or NULL for any
2724/// constant. Returning the expression itself is conservative. Returning a
2725/// deeper subexpression is more precise and valid as long as it isn't less
2726/// complex than another subexpression. For expressions involving multiple
2727/// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2728/// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2729/// IVInc==b-a.
2730///
2731/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2732/// SCEVUnknown, we simply return the rightmost SCEV operand.
2733static const SCEV *getExprBase(const SCEV *S) {
2734 switch (S->getSCEVType()) {
2735 default: // uncluding scUnknown.
2736 return S;
2737 case scConstant:
2738 return nullptr;
2739 case scTruncate:
2740 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2741 case scZeroExtend:
2742 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2743 case scSignExtend:
2744 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2745 case scAddExpr: {
2746 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2747 // there's nothing more complex.
2748 // FIXME: not sure if we want to recognize negation.
2749 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2750 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2751 E(Add->op_begin()); I != E; ++I) {
2752 const SCEV *SubExpr = *I;
2753 if (SubExpr->getSCEVType() == scAddExpr)
2754 return getExprBase(SubExpr);
2755
2756 if (SubExpr->getSCEVType() != scMulExpr)
2757 return SubExpr;
2758 }
2759 return S; // all operands are scaled, be conservative.
2760 }
2761 case scAddRecExpr:
2762 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2763 }
2764}
2765
2766/// Return true if the chain increment is profitable to expand into a loop
2767/// invariant value, which may require its own register. A profitable chain
2768/// increment will be an offset relative to the same base. We allow such offsets
2769/// to potentially be used as chain increment as long as it's not obviously
2770/// expensive to expand using real instructions.
2771bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2772 const SCEV *IncExpr,
2773 ScalarEvolution &SE) {
2774 // Aggressively form chains when -stress-ivchain.
2775 if (StressIVChain)
2776 return true;
2777
2778 // Do not replace a constant offset from IV head with a nonconstant IV
2779 // increment.
2780 if (!isa<SCEVConstant>(IncExpr)) {
2781 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2782 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2783 return false;
2784 }
2785
2786 SmallPtrSet<const SCEV*, 8> Processed;
2787 return !isHighCostExpansion(IncExpr, Processed, SE);
2788}
2789
2790/// Return true if the number of registers needed for the chain is estimated to
2791/// be less than the number required for the individual IV users. First prohibit
2792/// any IV users that keep the IV live across increments (the Users set should
2793/// be empty). Next count the number and type of increments in the chain.
2794///
2795/// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2796/// effectively use postinc addressing modes. Only consider it profitable it the
2797/// increments can be computed in fewer registers when chained.
2798///
2799/// TODO: Consider IVInc free if it's already used in another chains.
2800static bool
2801isProfitableChain(IVChain &Chain, SmallPtrSetImpl<Instruction*> &Users,
2802 ScalarEvolution &SE, const TargetTransformInfo &TTI) {
2803 if (StressIVChain)
2804 return true;
2805
2806 if (!Chain.hasIncs())
2807 return false;
2808
2809 if (!Users.empty()) {
2810 LLVM_DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " users:\n"; for (Instruction *Inst
: Users) { dbgs() << " " << *Inst << "\n"
; }; } } while (false)
2811 for (Instruction *Instdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " users:\n"; for (Instruction *Inst
: Users) { dbgs() << " " << *Inst << "\n"
; }; } } while (false)
2812 : Users) { dbgs() << " " << *Inst << "\n"; })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " users:\n"; for (Instruction *Inst
: Users) { dbgs() << " " << *Inst << "\n"
; }; } } while (false)
;
2813 return false;
2814 }
2815 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")((!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? static_cast<void> (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2815, __PRETTY_FUNCTION__))
;
2816
2817 // The chain itself may require a register, so intialize cost to 1.
2818 int cost = 1;
2819
2820 // A complete chain likely eliminates the need for keeping the original IV in
2821 // a register. LSR does not currently know how to form a complete chain unless
2822 // the header phi already exists.
2823 if (isa<PHINode>(Chain.tailUserInst())
2824 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2825 --cost;
2826 }
2827 const SCEV *LastIncExpr = nullptr;
2828 unsigned NumConstIncrements = 0;
2829 unsigned NumVarIncrements = 0;
2830 unsigned NumReusedIncrements = 0;
2831 for (const IVInc &Inc : Chain) {
2832 if (Inc.IncExpr->isZero())
2833 continue;
2834
2835 // Incrementing by zero or some constant is neutral. We assume constants can
2836 // be folded into an addressing mode or an add's immediate operand.
2837 if (isa<SCEVConstant>(Inc.IncExpr)) {
2838 ++NumConstIncrements;
2839 continue;
2840 }
2841
2842 if (Inc.IncExpr == LastIncExpr)
2843 ++NumReusedIncrements;
2844 else
2845 ++NumVarIncrements;
2846
2847 LastIncExpr = Inc.IncExpr;
2848 }
2849 // An IV chain with a single increment is handled by LSR's postinc
2850 // uses. However, a chain with multiple increments requires keeping the IV's
2851 // value live longer than it needs to be if chained.
2852 if (NumConstIncrements > 1)
2853 --cost;
2854
2855 // Materializing increment expressions in the preheader that didn't exist in
2856 // the original code may cost a register. For example, sign-extended array
2857 // indices can produce ridiculous increments like this:
2858 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2859 cost += NumVarIncrements;
2860
2861 // Reusing variable increments likely saves a register to hold the multiple of
2862 // the stride.
2863 cost -= NumReusedIncrements;
2864
2865 LLVM_DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << costdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " Cost: " << cost << "\n"
; } } while (false)
2866 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " Cost: " << cost << "\n"
; } } while (false)
;
2867
2868 return cost < 0;
2869}
2870
2871/// Add this IV user to an existing chain or make it the head of a new chain.
2872void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2873 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2874 // When IVs are used as types of varying widths, they are generally converted
2875 // to a wider type with some uses remaining narrow under a (free) trunc.
2876 Value *const NextIV = getWideOperand(IVOper);
2877 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2878 const SCEV *const OperExprBase = getExprBase(OperExpr);
2879
2880 // Visit all existing chains. Check if its IVOper can be computed as a
2881 // profitable loop invariant increment from the last link in the Chain.
2882 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2883 const SCEV *LastIncExpr = nullptr;
2884 for (; ChainIdx < NChains; ++ChainIdx) {
2885 IVChain &Chain = IVChainVec[ChainIdx];
2886
2887 // Prune the solution space aggressively by checking that both IV operands
2888 // are expressions that operate on the same unscaled SCEVUnknown. This
2889 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2890 // first avoids creating extra SCEV expressions.
2891 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2892 continue;
2893
2894 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2895 if (!isCompatibleIVType(PrevIV, NextIV))
2896 continue;
2897
2898 // A phi node terminates a chain.
2899 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2900 continue;
2901
2902 // The increment must be loop-invariant so it can be kept in a register.
2903 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2904 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2905 if (!SE.isLoopInvariant(IncExpr, L))
2906 continue;
2907
2908 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2909 LastIncExpr = IncExpr;
2910 break;
2911 }
2912 }
2913 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2914 // bother for phi nodes, because they must be last in the chain.
2915 if (ChainIdx == NChains) {
2916 if (isa<PHINode>(UserInst))
2917 return;
2918 if (NChains >= MaxChains && !StressIVChain) {
2919 LLVM_DEBUG(dbgs() << "IV Chain Limit\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain Limit\n"; } } while
(false)
;
2920 return;
2921 }
2922 LastIncExpr = OperExpr;
2923 // IVUsers may have skipped over sign/zero extensions. We don't currently
2924 // attempt to form chains involving extensions unless they can be hoisted
2925 // into this loop's AddRec.
2926 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2927 return;
2928 ++NChains;
2929 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2930 OperExprBase));
2931 ChainUsersVec.resize(NChains);
2932 LLVM_DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInstdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Head: (" << *UserInst << ") IV=" <<
*LastIncExpr << "\n"; } } while (false)
2933 << ") IV=" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Head: (" << *UserInst << ") IV=" <<
*LastIncExpr << "\n"; } } while (false)
;
2934 } else {
2935 LLVM_DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInstdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Inc: (" << *UserInst << ") IV+" <<
*LastIncExpr << "\n"; } } while (false)
2936 << ") IV+" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Inc: (" << *UserInst << ") IV+" <<
*LastIncExpr << "\n"; } } while (false)
;
2937 // Add this IV user to the end of the chain.
2938 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2939 }
2940 IVChain &Chain = IVChainVec[ChainIdx];
2941
2942 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2943 // This chain's NearUsers become FarUsers.
2944 if (!LastIncExpr->isZero()) {
2945 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2946 NearUsers.end());
2947 NearUsers.clear();
2948 }
2949
2950 // All other uses of IVOperand become near uses of the chain.
2951 // We currently ignore intermediate values within SCEV expressions, assuming
2952 // they will eventually be used be the current chain, or can be computed
2953 // from one of the chain increments. To be more precise we could
2954 // transitively follow its user and only add leaf IV users to the set.
2955 for (User *U : IVOper->users()) {
2956 Instruction *OtherUse = dyn_cast<Instruction>(U);
2957 if (!OtherUse)
2958 continue;
2959 // Uses in the chain will no longer be uses if the chain is formed.
2960 // Include the head of the chain in this iteration (not Chain.begin()).
2961 IVChain::const_iterator IncIter = Chain.Incs.begin();
2962 IVChain::const_iterator IncEnd = Chain.Incs.end();
2963 for( ; IncIter != IncEnd; ++IncIter) {
2964 if (IncIter->UserInst == OtherUse)
2965 break;
2966 }
2967 if (IncIter != IncEnd)
2968 continue;
2969
2970 if (SE.isSCEVable(OtherUse->getType())
2971 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2972 && IU.isIVUserOrOperand(OtherUse)) {
2973 continue;
2974 }
2975 NearUsers.insert(OtherUse);
2976 }
2977
2978 // Since this user is part of the chain, it's no longer considered a use
2979 // of the chain.
2980 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2981}
2982
2983/// Populate the vector of Chains.
2984///
2985/// This decreases ILP at the architecture level. Targets with ample registers,
2986/// multiple memory ports, and no register renaming probably don't want
2987/// this. However, such targets should probably disable LSR altogether.
2988///
2989/// The job of LSR is to make a reasonable choice of induction variables across
2990/// the loop. Subsequent passes can easily "unchain" computation exposing more
2991/// ILP *within the loop* if the target wants it.
2992///
2993/// Finding the best IV chain is potentially a scheduling problem. Since LSR
2994/// will not reorder memory operations, it will recognize this as a chain, but
2995/// will generate redundant IV increments. Ideally this would be corrected later
2996/// by a smart scheduler:
2997/// = A[i]
2998/// = A[i+x]
2999/// A[i] =
3000/// A[i+x] =
3001///
3002/// TODO: Walk the entire domtree within this loop, not just the path to the
3003/// loop latch. This will discover chains on side paths, but requires
3004/// maintaining multiple copies of the Chains state.
3005void LSRInstance::CollectChains() {
3006 LLVM_DEBUG(dbgs() << "Collecting IV Chains.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Collecting IV Chains.\n";
} } while (false)
;
3007 SmallVector<ChainUsers, 8> ChainUsersVec;
3008
3009 SmallVector<BasicBlock *,8> LatchPath;
3010 BasicBlock *LoopHeader = L->getHeader();
3011 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
3012 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
3013 LatchPath.push_back(Rung->getBlock());
3014 }
3015 LatchPath.push_back(LoopHeader);
3016
3017 // Walk the instruction stream from the loop header to the loop latch.
3018 for (BasicBlock *BB : reverse(LatchPath)) {
3019 for (Instruction &I : *BB) {
3020 // Skip instructions that weren't seen by IVUsers analysis.
3021 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
3022 continue;
3023
3024 // Ignore users that are part of a SCEV expression. This way we only
3025 // consider leaf IV Users. This effectively rediscovers a portion of
3026 // IVUsers analysis but in program order this time.
3027 if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
3028 continue;
3029
3030 // Remove this instruction from any NearUsers set it may be in.
3031 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
3032 ChainIdx < NChains; ++ChainIdx) {
3033 ChainUsersVec[ChainIdx].NearUsers.erase(&I);
3034 }
3035 // Search for operands that can be chained.
3036 SmallPtrSet<Instruction*, 4> UniqueOperands;
3037 User::op_iterator IVOpEnd = I.op_end();
3038 User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
3039 while (IVOpIter != IVOpEnd) {
3040 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
3041 if (UniqueOperands.insert(IVOpInst).second)
3042 ChainInstruction(&I, IVOpInst, ChainUsersVec);
3043 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3044 }
3045 } // Continue walking down the instructions.
3046 } // Continue walking down the domtree.
3047 // Visit phi backedges to determine if the chain can generate the IV postinc.
3048 for (PHINode &PN : L->getHeader()->phis()) {
3049 if (!SE.isSCEVable(PN.getType()))
3050 continue;
3051
3052 Instruction *IncV =
3053 dyn_cast<Instruction>(PN.getIncomingValueForBlock(L->getLoopLatch()));
3054 if (IncV)
3055 ChainInstruction(&PN, IncV, ChainUsersVec);
3056 }
3057 // Remove any unprofitable chains.
3058 unsigned ChainIdx = 0;
3059 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
3060 UsersIdx < NChains; ++UsersIdx) {
3061 if (!isProfitableChain(IVChainVec[UsersIdx],
3062 ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
3063 continue;
3064 // Preserve the chain at UsesIdx.
3065 if (ChainIdx != UsersIdx)
3066 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
3067 FinalizeChain(IVChainVec[ChainIdx]);
3068 ++ChainIdx;
3069 }
3070 IVChainVec.resize(ChainIdx);
3071}
3072
3073void LSRInstance::FinalizeChain(IVChain &Chain) {
3074 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")((!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? static_cast<void> (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3074, __PRETTY_FUNCTION__))
;
3075 LLVM_DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Final Chain: " << *
Chain.Incs[0].UserInst << "\n"; } } while (false)
;
3076
3077 for (const IVInc &Inc : Chain) {
3078 LLVM_DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Inc: " << *
Inc.UserInst << "\n"; } } while (false)
;
3079 auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
3080 assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand")((UseI != Inc.UserInst->op_end() && "cannot find IV operand"
) ? static_cast<void> (0) : __assert_fail ("UseI != Inc.UserInst->op_end() && \"cannot find IV operand\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3080, __PRETTY_FUNCTION__))
;
3081 IVIncSet.insert(UseI);
3082 }
3083}
3084
3085/// Return true if the IVInc can be folded into an addressing mode.
3086static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
3087 Value *Operand, const TargetTransformInfo &TTI) {
3088 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
3089 if (!IncConst || !isAddressUse(TTI, UserInst, Operand))
3090 return false;
3091
3092 if (IncConst->getAPInt().getMinSignedBits() > 64)
3093 return false;
3094
3095 MemAccessTy AccessTy = getAccessType(TTI, UserInst, Operand);
3096 int64_t IncOffset = IncConst->getValue()->getSExtValue();
3097 if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
3098 IncOffset, /*HaseBaseReg=*/false))
3099 return false;
3100
3101 return true;
3102}
3103
3104/// Generate an add or subtract for each IVInc in a chain to materialize the IV
3105/// user's operand from the previous IV user's operand.
3106void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
3107 SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
3108 // Find the new IVOperand for the head of the chain. It may have been replaced
3109 // by LSR.
3110 const IVInc &Head = Chain.Incs[0];
3111 User::op_iterator IVOpEnd = Head.UserInst->op_end();
3112 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
3113 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
3114 IVOpEnd, L, SE);
3115 Value *IVSrc = nullptr;
3116 while (IVOpIter != IVOpEnd) {
3117 IVSrc = getWideOperand(*IVOpIter);
3118
3119 // If this operand computes the expression that the chain needs, we may use
3120 // it. (Check this after setting IVSrc which is used below.)
3121 //
3122 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
3123 // narrow for the chain, so we can no longer use it. We do allow using a
3124 // wider phi, assuming the LSR checked for free truncation. In that case we
3125 // should already have a truncate on this operand such that
3126 // getSCEV(IVSrc) == IncExpr.
3127 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
3128 || SE.getSCEV(IVSrc) == Head.IncExpr) {
3129 break;
3130 }
3131 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3132 }
3133 if (IVOpIter == IVOpEnd) {
3134 // Gracefully give up on this chain.
3135 LLVM_DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Concealed chain head: " <<
*Head.UserInst << "\n"; } } while (false)
;
3136 return;
3137 }
3138
3139 LLVM_DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generate chain at: " <<
*IVSrc << "\n"; } } while (false)
;
3140 Type *IVTy = IVSrc->getType();
3141 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
3142 const SCEV *LeftOverExpr = nullptr;
3143 for (const IVInc &Inc : Chain) {
3144 Instruction *InsertPt = Inc.UserInst;
3145 if (isa<PHINode>(InsertPt))
3146 InsertPt = L->getLoopLatch()->getTerminator();
3147
3148 // IVOper will replace the current IV User's operand. IVSrc is the IV
3149 // value currently held in a register.
3150 Value *IVOper = IVSrc;
3151 if (!Inc.IncExpr->isZero()) {
3152 // IncExpr was the result of subtraction of two narrow values, so must
3153 // be signed.
3154 const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
3155 LeftOverExpr = LeftOverExpr ?
3156 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
3157 }
3158 if (LeftOverExpr && !LeftOverExpr->isZero()) {
3159 // Expand the IV increment.
3160 Rewriter.clearPostInc();
3161 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
3162 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
3163 SE.getUnknown(IncV));
3164 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
3165
3166 // If an IV increment can't be folded, use it as the next IV value.
3167 if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
3168 assert(IVTy == IVOper->getType() && "inconsistent IV increment type")((IVTy == IVOper->getType() && "inconsistent IV increment type"
) ? static_cast<void> (0) : __assert_fail ("IVTy == IVOper->getType() && \"inconsistent IV increment type\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3168, __PRETTY_FUNCTION__))
;
3169 IVSrc = IVOper;
3170 LeftOverExpr = nullptr;
3171 }
3172 }
3173 Type *OperTy = Inc.IVOperand->getType();
3174 if (IVTy != OperTy) {
3175 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&((SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy
) && "cannot extend a chained IV") ? static_cast<void
> (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3176, __PRETTY_FUNCTION__))
3176 "cannot extend a chained IV")((SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy
) && "cannot extend a chained IV") ? static_cast<void
> (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3176, __PRETTY_FUNCTION__))
;
3177 IRBuilder<> Builder(InsertPt);
3178 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
3179 }
3180 Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
3181 DeadInsts.emplace_back(Inc.IVOperand);
3182 }
3183 // If LSR created a new, wider phi, we may also replace its postinc. We only
3184 // do this if we also found a wide value for the head of the chain.
3185 if (isa<PHINode>(Chain.tailUserInst())) {
3186 for (PHINode &Phi : L->getHeader()->phis()) {
3187 if (!isCompatibleIVType(&Phi, IVSrc))
3188 continue;
3189 Instruction *PostIncV = dyn_cast<Instruction>(
3190 Phi.getIncomingValueForBlock(L->getLoopLatch()));
3191 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
3192 continue;
3193 Value *IVOper = IVSrc;
3194 Type *PostIncTy = PostIncV->getType();
3195 if (IVTy != PostIncTy) {
3196 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types")((PostIncTy->isPointerTy() && "mixing int/ptr IV types"
) ? static_cast<void> (0) : __assert_fail ("PostIncTy->isPointerTy() && \"mixing int/ptr IV types\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3196, __PRETTY_FUNCTION__))
;
3197 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
3198 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
3199 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
3200 }
3201 Phi.replaceUsesOfWith(PostIncV, IVOper);
3202 DeadInsts.emplace_back(PostIncV);
3203 }
3204 }
3205}
3206
3207void LSRInstance::CollectFixupsAndInitialFormulae() {
3208 for (const IVStrideUse &U : IU) {
3209 Instruction *UserInst = U.getUser();
3210 // Skip IV users that are part of profitable IV Chains.
3211 User::op_iterator UseI =
3212 find(UserInst->operands(), U.getOperandValToReplace());
3213 assert(UseI != UserInst->op_end() && "cannot find IV operand")((UseI != UserInst->op_end() && "cannot find IV operand"
) ? static_cast<void> (0) : __assert_fail ("UseI != UserInst->op_end() && \"cannot find IV operand\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3213, __PRETTY_FUNCTION__))
;
3214 if (IVIncSet.count(UseI)) {
3215 LLVM_DEBUG(dbgs() << "Use is in profitable chain: " << **UseI << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Use is in profitable chain: "
<< **UseI << '\n'; } } while (false)
;
3216 continue;
3217 }
3218
3219 LSRUse::KindType Kind = LSRUse::Basic;
3220 MemAccessTy AccessTy;
3221 if (isAddressUse(TTI, UserInst, U.getOperandValToReplace())) {
3222 Kind = LSRUse::Address;
3223 AccessTy = getAccessType(TTI, UserInst, U.getOperandValToReplace());
3224 }
3225
3226 const SCEV *S = IU.getExpr(U);
3227 PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3228
3229 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3230 // (N - i == 0), and this allows (N - i) to be the expression that we work
3231 // with rather than just N or i, so we can consider the register
3232 // requirements for both N and i at the same time. Limiting this code to
3233 // equality icmps is not a problem because all interesting loops use
3234 // equality icmps, thanks to IndVarSimplify.
3235 if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst))
3236 if (CI->isEquality()) {
3237 // Swap the operands if needed to put the OperandValToReplace on the
3238 // left, for consistency.
3239 Value *NV = CI->getOperand(1);
3240 if (NV == U.getOperandValToReplace()) {
3241 CI->setOperand(1, CI->getOperand(0));
3242 CI->setOperand(0, NV);
3243 NV = CI->getOperand(1);
3244 Changed = true;
3245 }
3246
3247 // x == y --> x - y == 0
3248 const SCEV *N = SE.getSCEV(NV);
3249 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3250 // S is normalized, so normalize N before folding it into S
3251 // to keep the result normalized.
3252 N = normalizeForPostIncUse(N, TmpPostIncLoops, SE);
3253 Kind = LSRUse::ICmpZero;
3254 S = SE.getMinusSCEV(N, S);
3255 }
3256
3257 // -1 and the negations of all interesting strides (except the negation
3258 // of -1) are now also interesting.
3259 for (size_t i = 0, e = Factors.size(); i != e; ++i)
3260 if (Factors[i] != -1)
3261 Factors.insert(-(uint64_t)Factors[i]);
3262 Factors.insert(-1);
3263 }
3264
3265 // Get or create an LSRUse.
3266 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3267 size_t LUIdx = P.first;
3268 int64_t Offset = P.second;
3269 LSRUse &LU = Uses[LUIdx];
3270
3271 // Record the fixup.
3272 LSRFixup &LF = LU.getNewFixup();
3273 LF.UserInst = UserInst;
3274 LF.OperandValToReplace = U.getOperandValToReplace();
3275 LF.PostIncLoops = TmpPostIncLoops;
3276 LF.Offset = Offset;
3277 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3278
3279 if (!LU.WidestFixupType ||
3280 SE.getTypeSizeInBits(LU.WidestFixupType) <
3281 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3282 LU.WidestFixupType = LF.OperandValToReplace->getType();
3283
3284 // If this is the first use of this LSRUse, give it a formula.
3285 if (LU.Formulae.empty()) {
3286 InsertInitialFormula(S, LU, LUIdx);
3287 CountRegisters(LU.Formulae.back(), LUIdx);
3288 }
3289 }
3290
3291 LLVM_DEBUG(print_fixups(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_fixups(dbgs()); } } while (false)
;
3292}
3293
3294/// Insert a formula for the given expression into the given use, separating out
3295/// loop-variant portions from loop-invariant and loop-computable portions.
3296void
3297LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3298 // Mark uses whose expressions cannot be expanded.
3299 if (!isSafeToExpand(S, SE))
3300 LU.RigidFormula = true;
3301
3302 Formula F;
3303 F.initialMatch(S, L, SE);
3304 bool Inserted = InsertFormula(LU, LUIdx, F);
3305 assert(Inserted && "Initial formula already exists!")((Inserted && "Initial formula already exists!") ? static_cast
<void> (0) : __assert_fail ("Inserted && \"Initial formula already exists!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3305, __PRETTY_FUNCTION__))
; (void)Inserted;
3306}
3307
3308/// Insert a simple single-register formula for the given expression into the
3309/// given use.
3310void
3311LSRInstance::InsertSupplementalFormula(const SCEV *S,
3312 LSRUse &LU, size_t LUIdx) {
3313 Formula F;
3314 F.BaseRegs.push_back(S);
3315 F.HasBaseReg = true;
3316 bool Inserted = InsertFormula(LU, LUIdx, F);
3317 assert(Inserted && "Supplemental formula already exists!")((Inserted && "Supplemental formula already exists!")
? static_cast<void> (0) : __assert_fail ("Inserted && \"Supplemental formula already exists!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3317, __PRETTY_FUNCTION__))
; (void)Inserted;
3318}
3319
3320/// Note which registers are used by the given formula, updating RegUses.
3321void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3322 if (F.ScaledReg)
3323 RegUses.countRegister(F.ScaledReg, LUIdx);
3324 for (const SCEV *BaseReg : F.BaseRegs)
3325 RegUses.countRegister(BaseReg, LUIdx);
3326}
3327
3328/// If the given formula has not yet been inserted, add it to the list, and
3329/// return true. Return false otherwise.
3330bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3331 // Do not insert formula that we will not be able to expand.
3332 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Formula is illegal") ? static_cast<void>
(0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3333, __PRETTY_FUNCTION__))
3333 "Formula is illegal")((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Formula is illegal") ? static_cast<void>
(0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3333, __PRETTY_FUNCTION__))
;
3334
3335 if (!LU.InsertFormula(F, *L))
3336 return false;
3337
3338 CountRegisters(F, LUIdx);
3339 return true;
3340}
3341
3342/// Check for other uses of loop-invariant values which we're tracking. These
3343/// other uses will pin these values in registers, making them less profitable
3344/// for elimination.
3345/// TODO: This currently misses non-constant addrec step registers.
3346/// TODO: Should this give more weight to users inside the loop?
3347void
3348LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3349 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3350 SmallPtrSet<const SCEV *, 32> Visited;
3351
3352 while (!Worklist.empty()) {
3353 const SCEV *S = Worklist.pop_back_val();
3354
3355 // Don't process the same SCEV twice
3356 if (!Visited.insert(S).second)
3357 continue;
3358
3359 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3360 Worklist.append(N->op_begin(), N->op_end());
3361 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3362 Worklist.push_back(C->getOperand());
3363 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3364 Worklist.push_back(D->getLHS());
3365 Worklist.push_back(D->getRHS());
3366 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3367 const Value *V = US->getValue();
3368 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3369 // Look for instructions defined outside the loop.
3370 if (L->contains(Inst)) continue;
3371 } else if (isa<UndefValue>(V))
3372 // Undef doesn't have a live range, so it doesn't matter.
3373 continue;
3374 for (const Use &U : V->uses()) {
3375 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3376 // Ignore non-instructions.
3377 if (!UserInst)
3378 continue;
3379 // Ignore instructions in other functions (as can happen with
3380 // Constants).
3381 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3382 continue;
3383 // Ignore instructions not dominated by the loop.
3384 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3385 UserInst->getParent() :
3386 cast<PHINode>(UserInst)->getIncomingBlock(
3387 PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3388 if (!DT.dominates(L->getHeader(), UseBB))
3389 continue;
3390 // Don't bother if the instruction is in a BB which ends in an EHPad.
3391 if (UseBB->getTerminator()->isEHPad())
3392 continue;
3393 // Don't bother rewriting PHIs in catchswitch blocks.
3394 if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator()))
3395 continue;
3396 // Ignore uses which are part of other SCEV expressions, to avoid
3397 // analyzing them multiple times.
3398 if (SE.isSCEVable(UserInst->getType())) {
3399 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3400 // If the user is a no-op, look through to its uses.
3401 if (!isa<SCEVUnknown>(UserS))
3402 continue;
3403 if (UserS == US) {
3404 Worklist.push_back(
3405 SE.getUnknown(const_cast<Instruction *>(UserInst)));
3406 continue;
3407 }
3408 }
3409 // Ignore icmp instructions which are already being analyzed.
3410 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3411 unsigned OtherIdx = !U.getOperandNo();
3412 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3413 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3414 continue;
3415 }
3416
3417 std::pair<size_t, int64_t> P = getUse(
3418 S, LSRUse::Basic, MemAccessTy());
3419 size_t LUIdx = P.first;
3420 int64_t Offset = P.second;
3421 LSRUse &LU = Uses[LUIdx];
3422 LSRFixup &LF = LU.getNewFixup();
3423 LF.UserInst = const_cast<Instruction *>(UserInst);
3424 LF.OperandValToReplace = U;
3425 LF.Offset = Offset;
3426 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3427 if (!LU.WidestFixupType ||
3428 SE.getTypeSizeInBits(LU.WidestFixupType) <
3429 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3430 LU.WidestFixupType = LF.OperandValToReplace->getType();
3431 InsertSupplementalFormula(US, LU, LUIdx);
3432 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3433 break;
3434 }
3435 }
3436 }
3437}
3438
3439/// Split S into subexpressions which can be pulled out into separate
3440/// registers. If C is non-null, multiply each subexpression by C.
3441///
3442/// Return remainder expression after factoring the subexpressions captured by
3443/// Ops. If Ops is complete, return NULL.
3444static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3445 SmallVectorImpl<const SCEV *> &Ops,
3446 const Loop *L,
3447 ScalarEvolution &SE,
3448 unsigned Depth = 0) {
3449 // Arbitrarily cap recursion to protect compile time.
3450 if (Depth >= 3)
3451 return S;
3452
3453 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3454 // Break out add operands.
3455 for (const SCEV *S : Add->operands()) {
3456 const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3457 if (Remainder)
3458 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3459 }
3460 return nullptr;
3461 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3462 // Split a non-zero base out of an addrec.
3463 if (AR->getStart()->isZero() || !AR->isAffine())
3464 return S;
3465
3466 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3467 C, Ops, L, SE, Depth+1);
3468 // Split the non-zero AddRec unless it is part of a nested recurrence that
3469 // does not pertain to this loop.
3470 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3471 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3472 Remainder = nullptr;
3473 }
3474 if (Remainder != AR->getStart()) {
3475 if (!Remainder)
3476 Remainder = SE.getConstant(AR->getType(), 0);
3477 return SE.getAddRecExpr(Remainder,
3478 AR->getStepRecurrence(SE),
3479 AR->getLoop(),
3480 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3481 SCEV::FlagAnyWrap);
3482 }
3483 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3484 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3485 if (Mul->getNumOperands() != 2)
3486 return S;
3487 if (const SCEVConstant *Op0 =
3488 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3489 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3490 const SCEV *Remainder =
3491 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3492 if (Remainder)
3493 Ops.push_back(SE.getMulExpr(C, Remainder));
3494 return nullptr;
3495 }
3496 }
3497 return S;
3498}
3499
3500/// Return true if the SCEV represents a value that may end up as a
3501/// post-increment operation.
3502static bool mayUsePostIncMode(const TargetTransformInfo &TTI,
3503 LSRUse &LU, const SCEV *S, const Loop *L,
3504 ScalarEvolution &SE) {
3505 if (LU.Kind != LSRUse::Address ||
3506 !LU.AccessTy.getType()->isIntOrIntVectorTy())
3507 return false;
3508 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S);
3509 if (!AR)
3510 return false;
3511 const SCEV *LoopStep = AR->getStepRecurrence(SE);
3512 if (!isa<SCEVConstant>(LoopStep))
3513 return false;
3514 if (LU.AccessTy.getType()->getScalarSizeInBits() !=
3515 LoopStep->getType()->getScalarSizeInBits())
3516 return false;
3517 // Check if a post-indexed load/store can be used.
3518 if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) ||
3519 TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) {
3520 const SCEV *LoopStart = AR->getStart();
3521 if (!isa<SCEVConstant>(LoopStart) && SE.isLoopInvariant(LoopStart, L))
3522 return true;
3523 }
3524 return false;
3525}
3526
3527/// Helper function for LSRInstance::GenerateReassociations.
3528void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3529 const Formula &Base,
3530 unsigned Depth, size_t Idx,
3531 bool IsScaledReg) {
3532 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3533 // Don't generate reassociations for the base register of a value that
3534 // may generate a post-increment operator. The reason is that the
3535 // reassociations cause extra base+register formula to be created,
3536 // and possibly chosen, but the post-increment is more efficient.
3537 if (TTI.shouldFavorPostInc() && mayUsePostIncMode(TTI, LU, BaseReg, L, SE))
3538 return;
3539 SmallVector<const SCEV *, 8> AddOps;
3540 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3541 if (Remainder)
3542 AddOps.push_back(Remainder);
3543
3544 if (AddOps.size() == 1)
3545 return;
3546
3547 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3548 JE = AddOps.end();
3549 J != JE; ++J) {
3550 // Loop-variant "unknown" values are uninteresting; we won't be able to
3551 // do anything meaningful with them.
3552 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3553 continue;
3554
3555 // Don't pull a constant into a register if the constant could be folded
3556 // into an immediate field.
3557 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3558 LU.AccessTy, *J, Base.getNumRegs() > 1))
3559 continue;
3560
3561 // Collect all operands except *J.
3562 SmallVector<const SCEV *, 8> InnerAddOps(
3563 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3564 InnerAddOps.append(std::next(J),
3565 ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3566
3567 // Don't leave just a constant behind in a register if the constant could
3568 // be folded into an immediate field.
3569 if (InnerAddOps.size() == 1 &&
3570 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3571 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3572 continue;
3573
3574 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3575 if (InnerSum->isZero())
3576 continue;
3577 Formula F = Base;
3578
3579 // Add the remaining pieces of the add back into the new formula.
3580 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3581 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3582 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3583 InnerSumSC->getValue()->getZExtValue())) {
3584 F.UnfoldedOffset =
3585 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3586 if (IsScaledReg)
3587 F.ScaledReg = nullptr;
3588 else
3589 F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3590 } else if (IsScaledReg)
3591 F.ScaledReg = InnerSum;
3592 else
3593 F.BaseRegs[Idx] = InnerSum;
3594
3595 // Add J as its own register, or an unfolded immediate.
3596 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3597 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3598 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3599 SC->getValue()->getZExtValue()))
3600 F.UnfoldedOffset =
3601 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3602 else
3603 F.BaseRegs.push_back(*J);
3604 // We may have changed the number of register in base regs, adjust the
3605 // formula accordingly.
3606 F.canonicalize(*L);
3607
3608 if (InsertFormula(LU, LUIdx, F))
3609 // If that formula hadn't been seen before, recurse to find more like
3610 // it.
3611 // Add check on Log16(AddOps.size()) - same as Log2_32(AddOps.size()) >> 2)
3612 // Because just Depth is not enough to bound compile time.
3613 // This means that every time AddOps.size() is greater 16^x we will add
3614 // x to Depth.
3615 GenerateReassociations(LU, LUIdx, LU.Formulae.back(),
3616 Depth + 1 + (Log2_32(AddOps.size()) >> 2));
3617 }
3618}
3619
3620/// Split out subexpressions from adds and the bases of addrecs.
3621void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3622 Formula Base, unsigned Depth) {
3623 assert(Base.isCanonical(*L) && "Input must be in the canonical form")((Base.isCanonical(*L) && "Input must be in the canonical form"
) ? static_cast<void> (0) : __assert_fail ("Base.isCanonical(*L) && \"Input must be in the canonical form\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3623, __PRETTY_FUNCTION__))
;
3624 // Arbitrarily cap recursion to protect compile time.
3625 if (Depth >= 3)
3626 return;
3627
3628 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3629 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3630
3631 if (Base.Scale == 1)
3632 GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3633 /* Idx */ -1, /* IsScaledReg */ true);
3634}
3635
3636/// Generate a formula consisting of all of the loop-dominating registers added
3637/// into a single register.
3638void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3639 Formula Base) {
3640 // This method is only interesting on a plurality of registers.
3641 if (Base.BaseRegs.size() + (Base.Scale == 1) <= 1)
3642 return;
3643
3644 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3645 // processing the formula.
3646 Base.unscale();
3647 Formula F = Base;
3648 F.BaseRegs.clear();
3649 SmallVector<const SCEV *, 4> Ops;
3650 for (const SCEV *BaseReg : Base.BaseRegs) {
3651 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3652 !SE.hasComputableLoopEvolution(BaseReg, L))
3653 Ops.push_back(BaseReg);
3654 else
3655 F.BaseRegs.push_back(BaseReg);
3656 }
3657 if (Ops.size() > 1) {
3658 const SCEV *Sum = SE.getAddExpr(Ops);
3659 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3660 // opportunity to fold something. For now, just ignore such cases
3661 // rather than proceed with zero in a register.
3662 if (!Sum->isZero()) {
3663 F.BaseRegs.push_back(Sum);
3664 F.canonicalize(*L);
3665 (void)InsertFormula(LU, LUIdx, F);
3666 }
3667 }
3668}
3669
3670/// Helper function for LSRInstance::GenerateSymbolicOffsets.
3671void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3672 const Formula &Base, size_t Idx,
3673 bool IsScaledReg) {
3674 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3675 GlobalValue *GV = ExtractSymbol(G, SE);
3676 if (G->isZero() || !GV)
3677 return;
3678 Formula F = Base;
3679 F.BaseGV = GV;
3680 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3681 return;
3682 if (IsScaledReg)
3683 F.ScaledReg = G;
3684 else
3685 F.BaseRegs[Idx] = G;
3686 (void)InsertFormula(LU, LUIdx, F);
3687}
3688
3689/// Generate reuse formulae using symbolic offsets.
3690void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3691 Formula Base) {
3692 // We can't add a symbolic offset if the address already contains one.
3693 if (Base.BaseGV) return;
3694
3695 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3696 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3697 if (Base.Scale == 1)
3698 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3699 /* IsScaledReg */ true);
3700}
3701
3702/// Helper function for LSRInstance::GenerateConstantOffsets.
3703void LSRInstance::GenerateConstantOffsetsImpl(
3704 LSRUse &LU, unsigned LUIdx, const Formula &Base,
3705 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3706 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3707 for (int64_t Offset : Worklist) {
3708 Formula F = Base;
3709 F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3710 if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind,
3711 LU.AccessTy, F)) {
3712 // Add the offset to the base register.
3713 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3714 // If it cancelled out, drop the base register, otherwise update it.
3715 if (NewG->isZero()) {
3716 if (IsScaledReg) {
3717 F.Scale = 0;
3718 F.ScaledReg = nullptr;
3719 } else
3720 F.deleteBaseReg(F.BaseRegs[Idx]);
3721 F.canonicalize(*L);
3722 } else if (IsScaledReg)
3723 F.ScaledReg = NewG;
3724 else
3725 F.BaseRegs[Idx] = NewG;
3726
3727 (void)InsertFormula(LU, LUIdx, F);
3728 }
3729 }
3730
3731 int64_t Imm = ExtractImmediate(G, SE);
3732 if (G->isZero() || Imm == 0)
3733 return;
3734 Formula F = Base;
3735 F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3736 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3737 return;
3738 if (IsScaledReg)
3739 F.ScaledReg = G;
3740 else
3741 F.BaseRegs[Idx] = G;
3742 (void)InsertFormula(LU, LUIdx, F);
3743}
3744
3745/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3746void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3747 Formula Base) {
3748 // TODO: For now, just add the min and max offset, because it usually isn't
3749 // worthwhile looking at everything inbetween.
3750 SmallVector<int64_t, 2> Worklist;
3751 Worklist.push_back(LU.MinOffset);
3752 if (LU.MaxOffset != LU.MinOffset)
3753 Worklist.push_back(LU.MaxOffset);
3754
3755 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3756 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3757 if (Base.Scale == 1)
3758 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3759 /* IsScaledReg */ true);
3760}
3761
3762/// For ICmpZero, check to see if we can scale up the comparison. For example, x
3763/// == y -> x*c == y*c.
3764void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3765 Formula Base) {
3766 if (LU.Kind != LSRUse::ICmpZero) return;
3767
3768 // Determine the integer type for the base formula.
3769 Type *IntTy = Base.getType();
3770 if (!IntTy) return;
3771 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3772
3773 // Don't do this if there is more than one offset.
3774 if (LU.MinOffset != LU.MaxOffset) return;
3775
3776 // Check if transformation is valid. It is illegal to multiply pointer.
3777 if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
3778 return;
3779 for (const SCEV *BaseReg : Base.BaseRegs)
3780 if (BaseReg->getType()->isPointerTy())
3781 return;
3782 assert(!Base.BaseGV && "ICmpZero use is not legal!")((!Base.BaseGV && "ICmpZero use is not legal!") ? static_cast
<void> (0) : __assert_fail ("!Base.BaseGV && \"ICmpZero use is not legal!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3782, __PRETTY_FUNCTION__))
;
3783
3784 // Check each interesting stride.
3785 for (int64_t Factor : Factors) {
3786 // Check that the multiplication doesn't overflow.
3787 if (Base.BaseOffset == std::numeric_limits<int64_t>::min() && Factor == -1)
3788 continue;
3789 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3790 if (NewBaseOffset / Factor != Base.BaseOffset)
3791 continue;
3792 // If the offset will be truncated at this use, check that it is in bounds.
3793 if (!IntTy->isPointerTy() &&
3794 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3795 continue;
3796
3797 // Check that multiplying with the use offset doesn't overflow.
3798 int64_t Offset = LU.MinOffset;
3799 if (Offset == std::numeric_limits<int64_t>::min() && Factor == -1)
3800 continue;
3801 Offset = (uint64_t)Offset * Factor;
3802 if (Offset / Factor != LU.MinOffset)
3803 continue;
3804 // If the offset will be truncated at this use, check that it is in bounds.
3805 if (!IntTy->isPointerTy() &&
3806 !ConstantInt::isValueValidForType(IntTy, Offset))
3807 continue;
3808
3809 Formula F = Base;
3810 F.BaseOffset = NewBaseOffset;
3811
3812 // Check that this scale is legal.
3813 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3814 continue;
3815
3816 // Compensate for the use having MinOffset built into it.
3817 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3818
3819 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3820
3821 // Check that multiplying with each base register doesn't overflow.
3822 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3823 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3824 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3825 goto next;
3826 }
3827
3828 // Check that multiplying with the scaled register doesn't overflow.
3829 if (F.ScaledReg) {
3830 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3831 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3832 continue;
3833 }
3834
3835 // Check that multiplying with the unfolded offset doesn't overflow.
3836 if (F.UnfoldedOffset != 0) {
3837 if (F.UnfoldedOffset == std::numeric_limits<int64_t>::min() &&
3838 Factor == -1)
3839 continue;
3840 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3841 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3842 continue;
3843 // If the offset will be truncated, check that it is in bounds.
3844 if (!IntTy->isPointerTy() &&
3845 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3846 continue;
3847 }
3848
3849 // If we make it here and it's legal, add it.
3850 (void)InsertFormula(LU, LUIdx, F);
3851 next:;
3852 }
3853}
3854
3855/// Generate stride factor reuse formulae by making use of scaled-offset address
3856/// modes, for example.
3857void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3858 // Determine the integer type for the base formula.
3859 Type *IntTy = Base.getType();
3860 if (!IntTy) return;
3861
3862 // If this Formula already has a scaled register, we can't add another one.
3863 // Try to unscale the formula to generate a better scale.
3864 if (Base.Scale != 0 && !Base.unscale())
3865 return;
3866
3867 assert(Base.Scale == 0 && "unscale did not did its job!")((Base.Scale == 0 && "unscale did not did its job!") ?
static_cast<void> (0) : __assert_fail ("Base.Scale == 0 && \"unscale did not did its job!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3867, __PRETTY_FUNCTION__))
;
3868
3869 // Check each interesting stride.
3870 for (int64_t Factor : Factors) {
3871 Base.Scale = Factor;
3872 Base.HasBaseReg = Base.BaseRegs.size() > 1;
3873 // Check whether this scale is going to be legal.
3874 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3875 Base)) {
3876 // As a special-case, handle special out-of-loop Basic users specially.
3877 // TODO: Reconsider this special case.
3878 if (LU.Kind == LSRUse::Basic &&
3879 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3880 LU.AccessTy, Base) &&
3881 LU.AllFixupsOutsideLoop)
3882 LU.Kind = LSRUse::Special;
3883 else
3884 continue;
3885 }
3886 // For an ICmpZero, negating a solitary base register won't lead to
3887 // new solutions.
3888 if (LU.Kind == LSRUse::ICmpZero &&
3889 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3890 continue;
3891 // For each addrec base reg, if its loop is current loop, apply the scale.
3892 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3893 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]);
3894 if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) {
3895 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3896 if (FactorS->isZero())
3897 continue;
3898 // Divide out the factor, ignoring high bits, since we'll be
3899 // scaling the value back up in the end.
3900 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3901 // TODO: This could be optimized to avoid all the copying.
3902 Formula F = Base;
3903 F.ScaledReg = Quotient;
3904 F.deleteBaseReg(F.BaseRegs[i]);
3905 // The canonical representation of 1*reg is reg, which is already in
3906 // Base. In that case, do not try to insert the formula, it will be
3907 // rejected anyway.
3908 if (F.Scale == 1 && (F.BaseRegs.empty() ||
3909 (AR->getLoop() != L && LU.AllFixupsOutsideLoop)))
3910 continue;
3911 // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate
3912 // non canonical Formula with ScaledReg's loop not being L.
3913 if (F.Scale == 1 && LU.AllFixupsOutsideLoop)
3914 F.canonicalize(*L);
3915 (void)InsertFormula(LU, LUIdx, F);
3916 }
3917 }
3918 }
3919 }
3920}
3921
3922/// Generate reuse formulae from different IV types.
3923void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3924 // Don't bother truncating symbolic values.
3925 if (Base.BaseGV) return;
3926
3927 // Determine the integer type for the base formula.
3928 Type *DstTy = Base.getType();
3929 if (!DstTy) return;
3930 DstTy = SE.getEffectiveSCEVType(DstTy);
3931
3932 for (Type *SrcTy : Types) {
3933 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
3934 Formula F = Base;
3935
3936 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
3937 for (const SCEV *&BaseReg : F.BaseRegs)
3938 BaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
3939
3940 // TODO: This assumes we've done basic processing on all uses and
3941 // have an idea what the register usage is.
3942 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3943 continue;
3944
3945 F.canonicalize(*L);
3946 (void)InsertFormula(LU, LUIdx, F);
3947 }
3948 }
3949}
3950
3951namespace {
3952
3953/// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
3954/// modifications so that the search phase doesn't have to worry about the data
3955/// structures moving underneath it.
3956struct WorkItem {
3957 size_t LUIdx;
3958 int64_t Imm;
3959 const SCEV *OrigReg;
3960
3961 WorkItem(size_t LI, int64_t I, const SCEV *R)
3962 : LUIdx(LI), Imm(I), OrigReg(R) {}
3963
3964 void print(raw_ostream &OS) const;
3965 void dump() const;
3966};
3967
3968} // end anonymous namespace
3969
3970#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
3971void WorkItem::print(raw_ostream &OS) const {
3972 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3973 << " , add offset " << Imm;
3974}
3975
3976LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void WorkItem::dump() const {
3977 print(errs()); errs() << '\n';
3978}
3979#endif
3980
3981/// Look for registers which are a constant distance apart and try to form reuse
3982/// opportunities between them.
3983void LSRInstance::GenerateCrossUseConstantOffsets() {
3984 // Group the registers by their value without any added constant offset.
3985 using ImmMapTy = std::map<int64_t, const SCEV *>;
3986
3987 DenseMap<const SCEV *, ImmMapTy> Map;
3988 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3989 SmallVector<const SCEV *, 8> Sequence;
3990 for (const SCEV *Use : RegUses) {
3991 const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
3992 int64_t Imm = ExtractImmediate(Reg, SE);
3993 auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
3994 if (Pair.second)
3995 Sequence.push_back(Reg);
3996 Pair.first->second.insert(std::make_pair(Imm, Use));
3997 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
3998 }
3999
4000 // Now examine each set of registers with the same base value. Build up
4001 // a list of work to do and do the work in a separate step so that we're
4002 // not adding formulae and register counts while we're searching.
4003 SmallVector<WorkItem, 32> WorkItems;
4004 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
4005 for (const SCEV *Reg : Sequence) {
4006 const ImmMapTy &Imms = Map.find(Reg)->second;
4007
4008 // It's not worthwhile looking for reuse if there's only one offset.
4009 if (Imms.size() == 1)
4010 continue;
4011
4012 LLVM_DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generating cross-use offsets for "
<< *Reg << ':'; for (const auto &Entry : Imms
) dbgs() << ' ' << Entry.first; dbgs() << '\n'
; } } while (false)
4013 for (const auto &Entrydo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generating cross-use offsets for "
<< *Reg << ':'; for (const auto &Entry : Imms
) dbgs() << ' ' << Entry.first; dbgs() << '\n'
; } } while (false)
4014 : Imms) dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generating cross-use offsets for "
<< *Reg << ':'; for (const auto &Entry : Imms
) dbgs() << ' ' << Entry.first; dbgs() << '\n'
; } } while (false)
4015 << ' ' << Entry.first;do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generating cross-use offsets for "
<< *Reg << ':'; for (const auto &Entry : Imms
) dbgs() << ' ' << Entry.first; dbgs() << '\n'
; } } while (false)
4016 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generating cross-use offsets for "
<< *Reg << ':'; for (const auto &Entry : Imms
) dbgs() << ' ' << Entry.first; dbgs() << '\n'
; } } while (false)
;
4017
4018 // Examine each offset.
4019 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
4020 J != JE; ++J) {
4021 const SCEV *OrigReg = J->second;
4022
4023 int64_t JImm = J->first;
4024 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
4025
4026 if (!isa<SCEVConstant>(OrigReg) &&
4027 UsedByIndicesMap[Reg].count() == 1) {
4028 LLVM_DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigRegdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Skipping cross-use reuse for "
<< *OrigReg << '\n'; } } while (false)
4029 << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Skipping cross-use reuse for "
<< *OrigReg << '\n'; } } while (false)
;
4030 continue;
4031 }
4032
4033 // Conservatively examine offsets between this orig reg a few selected
4034 // other orig regs.
4035 ImmMapTy::const_iterator OtherImms[] = {
4036 Imms.begin(), std::prev(Imms.end()),
4037 Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) /
4038 2)
4039 };
4040 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
4041 ImmMapTy::const_iterator M = OtherImms[i];
4042 if (M == J || M == JE) continue;
4043
4044 // Compute the difference between the two.
4045 int64_t Imm = (uint64_t)JImm - M->first;
4046 for (unsigned LUIdx : UsedByIndices.set_bits())
4047 // Make a memo of this use, offset, and register tuple.
4048 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
4049 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
4050 }
4051 }
4052 }
4053
4054 Map.clear();
4055 Sequence.clear();
4056 UsedByIndicesMap.clear();
4057 UniqueItems.clear();
4058
4059 // Now iterate through the worklist and add new formulae.
4060 for (const WorkItem &WI : WorkItems) {
4061 size_t LUIdx = WI.LUIdx;
4062 LSRUse &LU = Uses[LUIdx];
4063 int64_t Imm = WI.Imm;
4064 const SCEV *OrigReg = WI.OrigReg;
4065
4066 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
4067 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
4068 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
4069
4070 // TODO: Use a more targeted data structure.
4071 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
4072 Formula F = LU.Formulae[L];
4073 // FIXME: The code for the scaled and unscaled registers looks
4074 // very similar but slightly different. Investigate if they
4075 // could be merged. That way, we would not have to unscale the
4076 // Formula.
4077 F.unscale();
4078 // Use the immediate in the scaled register.
4079 if (F.ScaledReg == OrigReg) {
4080 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
4081 // Don't create 50 + reg(-50).
4082 if (F.referencesReg(SE.getSCEV(
4083 ConstantInt::get(IntTy, -(uint64_t)Offset))))
4084 continue;
4085 Formula NewF = F;
4086 NewF.BaseOffset = Offset;
4087 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4088 NewF))
4089 continue;
4090 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
4091
4092 // If the new scale is a constant in a register, and adding the constant
4093 // value to the immediate would produce a value closer to zero than the
4094 // immediate itself, then the formula isn't worthwhile.
4095 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
4096 if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
4097 (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
4098 .ule(std::abs(NewF.BaseOffset)))
4099 continue;
4100
4101 // OK, looks good.
4102 NewF.canonicalize(*this->L);
4103 (void)InsertFormula(LU, LUIdx, NewF);
4104 } else {
4105 // Use the immediate in a base register.
4106 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
4107 const SCEV *BaseReg = F.BaseRegs[N];
4108 if (BaseReg != OrigReg)
4109 continue;
4110 Formula NewF = F;
4111 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
4112 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
4113 LU.Kind, LU.AccessTy, NewF)) {
4114 if (TTI.shouldFavorPostInc() &&
4115 mayUsePostIncMode(TTI, LU, OrigReg, this->L, SE))
4116 continue;
4117 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
4118 continue;
4119 NewF = F;
4120 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
4121 }
4122 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
4123
4124 // If the new formula has a constant in a register, and adding the
4125 // constant value to the immediate would produce a value closer to
4126 // zero than the immediate itself, then the formula isn't worthwhile.
4127 for (const SCEV *NewReg : NewF.BaseRegs)
4128 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
4129 if ((C->getAPInt() + NewF.BaseOffset)
4130 .abs()
4131 .slt(std::abs(NewF.BaseOffset)) &&
4132 (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
4133 countTrailingZeros<uint64_t>(NewF.BaseOffset))
4134 goto skip_formula;
4135
4136 // Ok, looks good.
4137 NewF.canonicalize(*this->L);
4138 (void)InsertFormula(LU, LUIdx, NewF);
4139 break;
4140 skip_formula:;
4141 }
4142 }
4143 }
4144 }
4145}
4146
4147/// Generate formulae for each use.
4148void
4149LSRInstance::GenerateAllReuseFormulae() {
4150 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
4151 // queries are more precise.
4152 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4153 LSRUse &LU = Uses[LUIdx];
4154 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4155 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
4156 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4157 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
4158 }
4159 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4160 LSRUse &LU = Uses[LUIdx];
4161 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4162 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
4163 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4164 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
4165 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4166 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
4167 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4168 GenerateScales(LU, LUIdx, LU.Formulae[i]);
4169 }
4170 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4171 LSRUse &LU = Uses[LUIdx];
4172 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4173 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
4174 }
4175
4176 GenerateCrossUseConstantOffsets();
4177
4178 LLVM_DEBUG(dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
4179 "After generating reuse formulae:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
4180 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
;
4181}
4182
4183/// If there are multiple formulae with the same set of registers used
4184/// by other uses, pick the best one and delete the others.
4185void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
4186 DenseSet<const SCEV *> VisitedRegs;
4187 SmallPtrSet<const SCEV *, 16> Regs;
4188 SmallPtrSet<const SCEV *, 16> LoserRegs;
4189#ifndef NDEBUG
4190 bool ChangedFormulae = false;
4191#endif
4192
4193 // Collect the best formula for each unique set of shared registers. This
4194 // is reset for each use.
4195 using BestFormulaeTy =
4196 DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>;
4197
4198 BestFormulaeTy BestFormulae;
4199
4200 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4201 LSRUse &LU = Uses[LUIdx];
4202 LLVM_DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
4203 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4204
4205 bool Any = false;
4206 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
4207 FIdx != NumForms; ++FIdx) {
4208 Formula &F = LU.Formulae[FIdx];
4209
4210 // Some formulas are instant losers. For example, they may depend on
4211 // nonexistent AddRecs from other loops. These need to be filtered
4212 // immediately, otherwise heuristics could choose them over others leading
4213 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
4214 // avoids the need to recompute this information across formulae using the
4215 // same bad AddRec. Passing LoserRegs is also essential unless we remove
4216 // the corresponding bad register from the Regs set.
4217 Cost CostF;
4218 Regs.clear();
4219 CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, SE, DT, LU, &LoserRegs);
4220 if (CostF.isLoser()) {
4221 // During initial formula generation, undesirable formulae are generated
4222 // by uses within other loops that have some non-trivial address mode or
4223 // use the postinc form of the IV. LSR needs to provide these formulae
4224 // as the basis of rediscovering the desired formula that uses an AddRec
4225 // corresponding to the existing phi. Once all formulae have been
4226 // generated, these initial losers may be pruned.
4227 LLVM_DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering loser "; F.print
(dbgs()); dbgs() << "\n"; } } while (false)
4228 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering loser "; F.print
(dbgs()); dbgs() << "\n"; } } while (false)
;
4229 }
4230 else {
4231 SmallVector<const SCEV *, 4> Key;
4232 for (const SCEV *Reg : F.BaseRegs) {
4233 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
4234 Key.push_back(Reg);
4235 }
4236 if (F.ScaledReg &&
4237 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
4238 Key.push_back(F.ScaledReg);
4239 // Unstable sort by host order ok, because this is only used for
4240 // uniquifying.
4241 llvm::sort(Key);
4242
4243 std::pair<BestFormulaeTy::const_iterator, bool> P =
4244 BestFormulae.insert(std::make_pair(Key, FIdx));
4245 if (P.second)
4246 continue;
4247
4248 Formula &Best = LU.Formulae[P.first->second];
4249
4250 Cost CostBest;
4251 Regs.clear();
4252 CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, SE, DT, LU);
4253 if (CostF.isLess(CostBest, TTI))
4254 std::swap(F, Best);
4255 LLVM_DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
4256 dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
4257 " in favor of formula ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
4258 Best.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
;
4259 }
4260#ifndef NDEBUG
4261 ChangedFormulae = true;
4262#endif
4263 LU.DeleteFormula(F);
4264 --FIdx;
4265 --NumForms;
4266 Any = true;
4267 }
4268
4269 // Now that we've filtered out some formulae, recompute the Regs set.
4270 if (Any)
4271 LU.RecomputeRegs(LUIdx, RegUses);
4272
4273 // Reset this to prepare for the next use.
4274 BestFormulae.clear();
4275 }
4276
4277 LLVM_DEBUG(if (ChangedFormulae) {do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
4278 dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
4279 "After filtering out undesirable candidates:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
4280 print_uses(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
4281 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4282}
4283
4284// This is a rough guess that seems to work fairly well.
4285static const size_t ComplexityLimit = std::numeric_limits<uint16_t>::max();
4286
4287/// Estimate the worst-case number of solutions the solver might have to
4288/// consider. It almost never considers this many solutions because it prune the
4289/// search space, but the pruning isn't always sufficient.
4290size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4291 size_t Power = 1;
4292 for (const LSRUse &LU : Uses) {
4293 size_t FSize = LU.Formulae.size();
4294 if (FSize >= ComplexityLimit) {
4295 Power = ComplexityLimit;
4296 break;
4297 }
4298 Power *= FSize;
4299 if (Power >= ComplexityLimit)
4300 break;
4301 }
4302 return Power;
4303}
4304
4305/// When one formula uses a superset of the registers of another formula, it
4306/// won't help reduce register pressure (though it may not necessarily hurt
4307/// register pressure); remove it to simplify the system.
4308void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4309 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4310 LLVM_DEBUG(dbgs() << "The search space is too complex.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
; } } while (false)
;
4311
4312 LLVM_DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by eliminating formulae "
"which use a superset of registers used by other " "formulae.\n"
; } } while (false)
4313 "which use a superset of registers used by other "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by eliminating formulae "
"which use a superset of registers used by other " "formulae.\n"
; } } while (false)
4314 "formulae.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by eliminating formulae "
"which use a superset of registers used by other " "formulae.\n"
; } } while (false)
;
4315
4316 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4317 LSRUse &LU = Uses[LUIdx];
4318 bool Any = false;
4319 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4320 Formula &F = LU.Formulae[i];
4321 // Look for a formula with a constant or GV in a register. If the use
4322 // also has a formula with that same value in an immediate field,
4323 // delete the one that uses a register.
4324 for (SmallVectorImpl<const SCEV *>::const_iterator
4325 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4326 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4327 Formula NewF = F;
4328 NewF.BaseOffset += C->getValue()->getSExtValue();
4329 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4330 (I - F.BaseRegs.begin()));
4331 if (LU.HasFormulaWithSameRegs(NewF)) {
4332 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4333 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4334 LU.DeleteFormula(F);
4335 --i;
4336 --e;
4337 Any = true;
4338 break;
4339 }
4340 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4341 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4342 if (!F.BaseGV) {
4343 Formula NewF = F;
4344 NewF.BaseGV = GV;
4345 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4346 (I - F.BaseRegs.begin()));
4347 if (LU.HasFormulaWithSameRegs(NewF)) {
4348 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4349 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4350 LU.DeleteFormula(F);
4351 --i;
4352 --e;
4353 Any = true;
4354 break;
4355 }
4356 }
4357 }
4358 }
4359 }
4360 if (Any)
4361 LU.RecomputeRegs(LUIdx, RegUses);
4362 }
4363
4364 LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4365 }
4366}
4367
4368/// When there are many registers for expressions like A, A+1, A+2, etc.,
4369/// allocate a single register for them.
4370void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4371 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4372 return;
4373
4374 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by assuming that uses separated "
"by a constant offset will use the same registers.\n"; } } while
(false)
4375 dbgs() << "The search space is too complex.\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by assuming that uses separated "
"by a constant offset will use the same registers.\n"; } } while
(false)
4376 "Narrowing the search space by assuming that uses separated "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by assuming that uses separated "
"by a constant offset will use the same registers.\n"; } } while
(false)
4377 "by a constant offset will use the same registers.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by assuming that uses separated "
"by a constant offset will use the same registers.\n"; } } while
(false)
;
4378
4379 // This is especially useful for unrolled loops.
4380
4381 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4382 LSRUse &LU = Uses[LUIdx];
4383 for (const Formula &F : LU.Formulae) {
4384 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4385 continue;
4386
4387 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4388 if (!LUThatHas)
4389 continue;
4390
4391 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4392 LU.Kind, LU.AccessTy))
4393 continue;
4394
4395 LLVM_DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4396
4397 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4398
4399 // Transfer the fixups of LU to LUThatHas.
4400 for (LSRFixup &Fixup : LU.Fixups) {
4401 Fixup.Offset += F.BaseOffset;
4402 LUThatHas->pushFixup(Fixup);
4403 LLVM_DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New fixup has offset " <<
Fixup.Offset << '\n'; } } while (false)
;
4404 }
4405
4406 // Delete formulae from the new use which are no longer legal.
4407 bool Any = false;
4408 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4409 Formula &F = LUThatHas->Formulae[i];
4410 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4411 LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4412 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4413 LUThatHas->DeleteFormula(F);
4414 --i;
4415 --e;
4416 Any = true;
4417 }
4418 }
4419
4420 if (Any)
4421 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4422
4423 // Delete the old use.
4424 DeleteUse(LU, LUIdx);
4425 --LUIdx;
4426 --NumUses;
4427 break;
4428 }
4429 }
4430
4431 LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4432}
4433
4434/// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4435/// we've done more filtering, as it may be able to find more formulae to
4436/// eliminate.
4437void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4438 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4439 LLVM_DEBUG(dbgs() << "The search space is too complex.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
; } } while (false)
;
4440
4441 LLVM_DEBUG(dbgs() << "Narrowing the search space by re-filtering out "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by re-filtering out "
"undesirable dedicated registers.\n"; } } while (false)
4442 "undesirable dedicated registers.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by re-filtering out "
"undesirable dedicated registers.\n"; } } while (false)
;
4443
4444 FilterOutUndesirableDedicatedRegisters();
4445
4446 LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4447 }
4448}
4449
4450/// If a LSRUse has multiple formulae with the same ScaledReg and Scale.
4451/// Pick the best one and delete the others.
4452/// This narrowing heuristic is to keep as many formulae with different
4453/// Scale and ScaledReg pair as possible while narrowing the search space.
4454/// The benefit is that it is more likely to find out a better solution
4455/// from a formulae set with more Scale and ScaledReg variations than
4456/// a formulae set with the same Scale and ScaledReg. The picking winner
4457/// reg heuristic will often keep the formulae with the same Scale and
4458/// ScaledReg and filter others, and we want to avoid that if possible.
4459void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() {
4460 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4461 return;
4462
4463 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by choosing the best Formula " "from the Formulae with the same Scale and ScaledReg.\n"
; } } while (false)
4464 dbgs() << "The search space is too complex.\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by choosing the best Formula " "from the Formulae with the same Scale and ScaledReg.\n"
; } } while (false)
4465 "Narrowing the search space by choosing the best Formula "do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by choosing the best Formula " "from the Formulae with the same Scale and ScaledReg.\n"
; } } while (false)
4466 "from the Formulae with the same Scale and ScaledReg.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
"Narrowing the search space by choosing the best Formula " "from the Formulae with the same Scale and ScaledReg.\n"
; } } while (false)
;
4467
4468 // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse.
4469 using BestFormulaeTy = DenseMap<std::pair<const SCEV *, int64_t>, size_t>;
4470
4471 BestFormulaeTy BestFormulae;
4472#ifndef NDEBUG
4473 bool ChangedFormulae = false;
4474#endif
4475 DenseSet<const SCEV *> VisitedRegs;
4476 SmallPtrSet<const SCEV *, 16> Regs;
4477
4478 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4479 LSRUse &LU = Uses[LUIdx];
4480 LLVM_DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
4481 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4482
4483 // Return true if Formula FA is better than Formula FB.
4484 auto IsBetterThan = [&](Formula &FA, Formula &FB) {
4485 // First we will try to choose the Formula with fewer new registers.
4486 // For a register used by current Formula, the more the register is
4487 // shared among LSRUses, the less we increase the register number
4488 // counter of the formula.
4489 size_t FARegNum = 0;
4490 for (const SCEV *Reg : FA.BaseRegs) {
4491 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4492 FARegNum += (NumUses - UsedByIndices.count() + 1);
4493 }
4494 size_t FBRegNum = 0;
4495 for (const SCEV *Reg : FB.BaseRegs) {
4496 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4497 FBRegNum += (NumUses - UsedByIndices.count() + 1);
4498 }
4499 if (FARegNum != FBRegNum)
4500 return FARegNum < FBRegNum;
4501
4502 // If the new register numbers are the same, choose the Formula with
4503 // less Cost.
4504 Cost CostFA, CostFB;
4505 Regs.clear();
4506 CostFA.RateFormula(TTI, FA, Regs, VisitedRegs, L, SE, DT, LU);
4507 Regs.clear();
4508 CostFB.RateFormula(TTI, FB, Regs, VisitedRegs, L, SE, DT, LU);
4509 return CostFA.isLess(CostFB, TTI);
4510 };
4511
4512 bool Any = false;
4513 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4514 ++FIdx) {
4515 Formula &F = LU.Formulae[FIdx];
4516 if (!F.ScaledReg)
4517 continue;
4518 auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx});
4519 if (P.second)
4520 continue;
4521
4522 Formula &Best = LU.Formulae[P.first->second];
4523 if (IsBetterThan(F, Best))
4524 std::swap(F, Best);
4525 LLVM_DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
4526 dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
4527 " in favor of formula ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
4528 Best.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering out formula "
; F.print(dbgs()); dbgs() << "\n" " in favor of formula "
; Best.print(dbgs()); dbgs() << '\n'; } } while (false)
;
4529#ifndef NDEBUG
4530 ChangedFormulae = true;
4531#endif
4532 LU.DeleteFormula(F);
4533 --FIdx;
4534 --NumForms;
4535 Any = true;
4536 }
4537 if (Any)
4538 LU.RecomputeRegs(LUIdx, RegUses);
4539
4540 // Reset this to prepare for the next use.
4541 BestFormulae.clear();
4542 }
4543
4544 LLVM_DEBUG(if (ChangedFormulae) {do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
4545 dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
4546 "After filtering out undesirable candidates:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
4547 print_uses(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
4548 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4549}
4550
4551/// The function delete formulas with high registers number expectation.
4552/// Assuming we don't know the value of each formula (already delete
4553/// all inefficient), generate probability of not selecting for each
4554/// register.
4555/// For example,
4556/// Use1:
4557/// reg(a) + reg({0,+,1})
4558/// reg(a) + reg({-1,+,1}) + 1
4559/// reg({a,+,1})
4560/// Use2:
4561/// reg(b) + reg({0,+,1})
4562/// reg(b) + reg({-1,+,1}) + 1
4563/// reg({b,+,1})
4564/// Use3:
4565/// reg(c) + reg(b) + reg({0,+,1})
4566/// reg(c) + reg({b,+,1})
4567///
4568/// Probability of not selecting
4569/// Use1 Use2 Use3
4570/// reg(a) (1/3) * 1 * 1
4571/// reg(b) 1 * (1/3) * (1/2)
4572/// reg({0,+,1}) (2/3) * (2/3) * (1/2)
4573/// reg({-1,+,1}) (2/3) * (2/3) * 1
4574/// reg({a,+,1}) (2/3) * 1 * 1
4575/// reg({b,+,1}) 1 * (2/3) * (2/3)
4576/// reg(c) 1 * 1 * 0
4577///
4578/// Now count registers number mathematical expectation for each formula:
4579/// Note that for each use we exclude probability if not selecting for the use.
4580/// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding
4581/// probabilty 1/3 of not selecting for Use1).
4582/// Use1:
4583/// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted
4584/// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted
4585/// reg({a,+,1}) 1
4586/// Use2:
4587/// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted
4588/// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted
4589/// reg({b,+,1}) 2/3
4590/// Use3:
4591/// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted
4592/// reg(c) + reg({b,+,1}) 1 + 2/3
4593void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() {
4594 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4595 return;
4596 // Ok, we have too many of formulae on our hands to conveniently handle.
4597 // Use a rough heuristic to thin out the list.
4598
4599 // Set of Regs wich will be 100% used in final solution.
4600 // Used in each formula of a solution (in example above this is reg(c)).
4601 // We can skip them in calculations.
4602 SmallPtrSet<const SCEV *, 4> UniqRegs;
4603 LLVM_DEBUG(dbgs() << "The search space is too complex.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
; } } while (false)
;
4604
4605 // Map each register to probability of not selecting
4606 DenseMap <const SCEV *, float> RegNumMap;
4607 for (const SCEV *Reg : RegUses) {
4608 if (UniqRegs.count(Reg))
4609 continue;
4610 float PNotSel = 1;
4611 for (const LSRUse &LU : Uses) {
4612 if (!LU.Regs.count(Reg))
4613 continue;
4614 float P = LU.getNotSelectedProbability(Reg);
4615 if (P != 0.0)
4616 PNotSel *= P;
4617 else
4618 UniqRegs.insert(Reg);
4619 }
4620 RegNumMap.insert(std::make_pair(Reg, PNotSel));
4621 }
4622
4623 LLVM_DEBUG(do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by deleting costly formulas\n"
; } } while (false)
4624 dbgs() << "Narrowing the search space by deleting costly formulas\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by deleting costly formulas\n"
; } } while (false)
;
4625
4626 // Delete formulas where registers number expectation is high.
4627 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4628 LSRUse &LU = Uses[LUIdx];
4629 // If nothing to delete - continue.
4630 if (LU.Formulae.size() < 2)
4631 continue;
4632 // This is temporary solution to test performance. Float should be
4633 // replaced with round independent type (based on integers) to avoid
4634 // different results for different target builds.
4635 float FMinRegNum = LU.Formulae[0].getNumRegs();
4636 float FMinARegNum = LU.Formulae[0].getNumRegs();
4637 size_t MinIdx = 0;
4638 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4639 Formula &F = LU.Formulae[i];
4640 float FRegNum = 0;
4641 float FARegNum = 0;
4642 for (const SCEV *BaseReg : F.BaseRegs) {
4643 if (UniqRegs.count(BaseReg))
4644 continue;
4645 FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4646 if (isa<SCEVAddRecExpr>(BaseReg))
4647 FARegNum +=
4648 RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4649 }
4650 if (const SCEV *ScaledReg = F.ScaledReg) {
4651 if (!UniqRegs.count(ScaledReg)) {
4652 FRegNum +=
4653 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4654 if (isa<SCEVAddRecExpr>(ScaledReg))
4655 FARegNum +=
4656 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4657 }
4658 }
4659 if (FMinRegNum > FRegNum ||
4660 (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) {
4661 FMinRegNum = FRegNum;
4662 FMinARegNum = FARegNum;
4663 MinIdx = i;
4664 }
4665 }
4666 LLVM_DEBUG(dbgs() << " The formula "; LU.Formulae[MinIdx].print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " The formula "; LU.Formulae
[MinIdx].print(dbgs()); dbgs() << " with min reg num " <<
FMinRegNum << '\n'; } } while (false)
4667 dbgs() << " with min reg num " << FMinRegNum << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " The formula "; LU.Formulae
[MinIdx].print(dbgs()); dbgs() << " with min reg num " <<
FMinRegNum << '\n'; } } while (false)
;
4668 if (MinIdx != 0)
4669 std::swap(LU.Formulae[MinIdx], LU.Formulae[0]);
4670 while (LU.Formulae.size() != 1) {
4671 LLVM_DEBUG(dbgs() << " Deleting "; LU.Formulae.back().print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; LU.Formulae
.back().print(dbgs()); dbgs() << '\n'; } } while (false
)
4672 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; LU.Formulae
.back().print(dbgs()); dbgs() << '\n'; } } while (false
)
;
4673 LU.Formulae.pop_back();
4674 }
4675 LU.RecomputeRegs(LUIdx, RegUses);
4676 assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula")((LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula"
) ? static_cast<void> (0) : __assert_fail ("LU.Formulae.size() == 1 && \"Should be exactly 1 min regs formula\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4676, __PRETTY_FUNCTION__))
;
4677 Formula &F = LU.Formulae[0];
4678 LLVM_DEBUG(dbgs() << " Leaving only "; F.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Leaving only "; F.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4679 // When we choose the formula, the regs become unique.
4680 UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
4681 if (F.ScaledReg)
4682 UniqRegs.insert(F.ScaledReg);
4683 }
4684 LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4685}
4686
4687/// Pick a register which seems likely to be profitable, and then in any use
4688/// which has any reference to that register, delete all formulae which do not
4689/// reference that register.
4690void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4691 // With all other options exhausted, loop until the system is simple
4692 // enough to handle.
4693 SmallPtrSet<const SCEV *, 4> Taken;
4694 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
19
Assuming the condition is true
20
Loop condition is true. Entering loop body
4695 // Ok, we have too many of formulae on our hands to conveniently handle.
4696 // Use a rough heuristic to thin out the list.
4697 LLVM_DEBUG(dbgs() << "The search space is too complex.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "The search space is too complex.\n"
; } } while (false)
;
4698
4699 // Pick the register which is used by the most LSRUses, which is likely
4700 // to be a good reuse register candidate.
4701 const SCEV *Best = nullptr;
21
'Best' initialized to a null pointer value
4702 unsigned BestNum = 0;
4703 for (const SCEV *Reg : RegUses) {
22
Assuming '__begin2' is equal to '__end2'
4704 if (Taken.count(Reg))
4705 continue;
4706 if (!Best) {
4707 Best = Reg;
4708 BestNum = RegUses.getUsedByIndices(Reg).count();
4709 } else {
4710 unsigned Count = RegUses.getUsedByIndices(Reg).count();
4711 if (Count > BestNum) {
4712 Best = Reg;
4713 BestNum = Count;
4714 }
4715 }
4716 }
4717
4718 LLVM_DEBUG(dbgs() << "Narrowing the search space by assuming " << *Bestdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by assuming "
<< *Best << " will yield profitable reuse.\n"; }
} while (false)
23
Within the expansion of the macro 'LLVM_DEBUG':
a
Assuming 'DebugFlag' is not equal to 0
b
Assuming the condition is true
c
Forming reference to null pointer
4719 << " will yield profitable reuse.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Narrowing the search space by assuming "
<< *Best << " will yield profitable reuse.\n"; }
} while (false)
;
4720 Taken.insert(Best);
4721
4722 // In any use with formulae which references this register, delete formulae
4723 // which don't reference it.
4724 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4725 LSRUse &LU = Uses[LUIdx];
4726 if (!LU.Regs.count(Best)) continue;
4727
4728 bool Any = false;
4729 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4730 Formula &F = LU.Formulae[i];
4731 if (!F.referencesReg(Best)) {
4732 LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4733 LU.DeleteFormula(F);
4734 --e;
4735 --i;
4736 Any = true;
4737 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?")((e != 0 && "Use has no formulae left! Is Regs inconsistent?"
) ? static_cast<void> (0) : __assert_fail ("e != 0 && \"Use has no formulae left! Is Regs inconsistent?\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4737, __PRETTY_FUNCTION__))
;
4738 continue;
4739 }
4740 }
4741
4742 if (Any)
4743 LU.RecomputeRegs(LUIdx, RegUses);
4744 }
4745
4746 LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4747 }
4748}
4749
4750/// If there are an extraordinary number of formulae to choose from, use some
4751/// rough heuristics to prune down the number of formulae. This keeps the main
4752/// solver from taking an extraordinary amount of time in some worst-case
4753/// scenarios.
4754void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4755 NarrowSearchSpaceByDetectingSupersets();
4756 NarrowSearchSpaceByCollapsingUnrolledCode();
4757 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4758 if (FilterSameScaledReg)
14
Assuming the condition is false
15
Taking false branch
4759 NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
4760 if (LSRExpNarrow)
16
Assuming the condition is false
17
Taking false branch
4761 NarrowSearchSpaceByDeletingCostlyFormulas();
4762 else
4763 NarrowSearchSpaceByPickingWinnerRegs();
18
Calling 'LSRInstance::NarrowSearchSpaceByPickingWinnerRegs'
4764}
4765
4766/// This is the recursive solver.
4767void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4768 Cost &SolutionCost,
4769 SmallVectorImpl<const Formula *> &Workspace,
4770 const Cost &CurCost,
4771 const SmallPtrSet<const SCEV *, 16> &CurRegs,
4772 DenseSet<const SCEV *> &VisitedRegs) const {
4773 // Some ideas:
4774 // - prune more:
4775 // - use more aggressive filtering
4776 // - sort the formula so that the most profitable solutions are found first
4777 // - sort the uses too
4778 // - search faster:
4779 // - don't compute a cost, and then compare. compare while computing a cost
4780 // and bail early.
4781 // - track register sets with SmallBitVector
4782
4783 const LSRUse &LU = Uses[Workspace.size()];
4784
4785 // If this use references any register that's already a part of the
4786 // in-progress solution, consider it a requirement that a formula must
4787 // reference that register in order to be considered. This prunes out
4788 // unprofitable searching.
4789 SmallSetVector<const SCEV *, 4> ReqRegs;
4790 for (const SCEV *S : CurRegs)
4791 if (LU.Regs.count(S))
4792 ReqRegs.insert(S);
4793
4794 SmallPtrSet<const SCEV *, 16> NewRegs;
4795 Cost NewCost;
4796 for (const Formula &F : LU.Formulae) {
4797 // Ignore formulae which may not be ideal in terms of register reuse of
4798 // ReqRegs. The formula should use all required registers before
4799 // introducing new ones.
4800 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4801 for (const SCEV *Reg : ReqRegs) {
4802 if ((F.ScaledReg && F.ScaledReg == Reg) ||
4803 is_contained(F.BaseRegs, Reg)) {
4804 --NumReqRegsToFind;
4805 if (NumReqRegsToFind == 0)
4806 break;
4807 }
4808 }
4809 if (NumReqRegsToFind != 0) {
4810 // If none of the formulae satisfied the required registers, then we could
4811 // clear ReqRegs and try again. Currently, we simply give up in this case.
4812 continue;
4813 }
4814
4815 // Evaluate the cost of the current formula. If it's already worse than
4816 // the current best, prune the search at that point.
4817 NewCost = CurCost;
4818 NewRegs = CurRegs;
4819 NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, SE, DT, LU);
4820 if (NewCost.isLess(SolutionCost, TTI)) {
4821 Workspace.push_back(&F);
4822 if (Workspace.size() != Uses.size()) {
4823 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4824 NewRegs, VisitedRegs);
4825 if (F.getNumRegs() == 1 && Workspace.size() == 1)
4826 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4827 } else {
4828 LLVM_DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
4829 dbgs() << ".\n Regs:"; for (const SCEV *Sdo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
4830 : NewRegs) dbgs()do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
4831 << ' ' << *S;do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
4832 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "New best at "; NewCost.print
(dbgs()); dbgs() << ".\n Regs:"; for (const SCEV *S : NewRegs
) dbgs() << ' ' << *S; dbgs() << '\n'; } } while
(false)
;
4833
4834 SolutionCost = NewCost;
4835 Solution = Workspace;
4836 }
4837 Workspace.pop_back();
4838 }
4839 }
4840}
4841
4842/// Choose one formula from each use. Return the results in the given Solution
4843/// vector.
4844void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4845 SmallVector<const Formula *, 8> Workspace;
4846 Cost SolutionCost;
4847 SolutionCost.Lose();
4848 Cost CurCost;
4849 SmallPtrSet<const SCEV *, 16> CurRegs;
4850 DenseSet<const SCEV *> VisitedRegs;
4851 Workspace.reserve(Uses.size());
4852
4853 // SolveRecurse does all the work.
4854 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4855 CurRegs, VisitedRegs);
4856 if (Solution.empty()) {
4857 LLVM_DEBUG(dbgs() << "\nNo Satisfactory Solution\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nNo Satisfactory Solution\n"
; } } while (false)
;
4858 return;
4859 }
4860
4861 // Ok, we've now made all our decisions.
4862 LLVM_DEBUG(dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4863 "The chosen solution requires ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4864 SolutionCost.print(dbgs()); dbgs() << ":\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4865 for (size_t i = 0, e = Uses.size(); i != e; ++i) {do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4866 dbgs() << " ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4867 Uses[i].print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4868 dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4869 " ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4870 Solution[i]->print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4871 dbgs() << '\n';do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
4872 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "The chosen solution requires "
; SolutionCost.print(dbgs()); dbgs() << ":\n"; for (size_t
i = 0, e = Uses.size(); i != e; ++i) { dbgs() << " ";
Uses[i].print(dbgs()); dbgs() << "\n" " "; Solution
[i]->print(dbgs()); dbgs() << '\n'; }; } } while (false
)
;
4873
4874 assert(Solution.size() == Uses.size() && "Malformed solution!")((Solution.size() == Uses.size() && "Malformed solution!"
) ? static_cast<void> (0) : __assert_fail ("Solution.size() == Uses.size() && \"Malformed solution!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4874, __PRETTY_FUNCTION__))
;
4875}
4876
4877/// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
4878/// we can go while still being dominated by the input positions. This helps
4879/// canonicalize the insert position, which encourages sharing.
4880BasicBlock::iterator
4881LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4882 const SmallVectorImpl<Instruction *> &Inputs)
4883 const {
4884 Instruction *Tentative = &*IP;
4885 while (true) {
4886 bool AllDominate = true;
4887 Instruction *BetterPos = nullptr;
4888 // Don't bother attempting to insert before a catchswitch, their basic block
4889 // cannot have other non-PHI instructions.
4890 if (isa<CatchSwitchInst>(Tentative))
4891 return IP;
4892
4893 for (Instruction *Inst : Inputs) {
4894 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4895 AllDominate = false;
4896 break;
4897 }
4898 // Attempt to find an insert position in the middle of the block,
4899 // instead of at the end, so that it can be used for other expansions.
4900 if (Tentative->getParent() == Inst->getParent() &&
4901 (!BetterPos || !DT.dominates(Inst, BetterPos)))
4902 BetterPos = &*std::next(BasicBlock::iterator(Inst));
4903 }
4904 if (!AllDominate)
4905 break;
4906 if (BetterPos)
4907 IP = BetterPos->getIterator();
4908 else
4909 IP = Tentative->getIterator();
4910
4911 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4912 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4913
4914 BasicBlock *IDom;
4915 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4916 if (!Rung) return IP;
4917 Rung = Rung->getIDom();
4918 if (!Rung) return IP;
4919 IDom = Rung->getBlock();
4920
4921 // Don't climb into a loop though.
4922 const Loop *IDomLoop = LI.getLoopFor(IDom);
4923 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4924 if (IDomDepth <= IPLoopDepth &&
4925 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4926 break;
4927 }
4928
4929 Tentative = IDom->getTerminator();
4930 }
4931
4932 return IP;
4933}
4934
4935/// Determine an input position which will be dominated by the operands and
4936/// which will dominate the result.
4937BasicBlock::iterator
4938LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4939 const LSRFixup &LF,
4940 const LSRUse &LU,
4941 SCEVExpander &Rewriter) const {
4942 // Collect some instructions which must be dominated by the
4943 // expanding replacement. These must be dominated by any operands that
4944 // will be required in the expansion.
4945 SmallVector<Instruction *, 4> Inputs;
4946 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4947 Inputs.push_back(I);
4948 if (LU.Kind == LSRUse::ICmpZero)
4949 if (Instruction *I =
4950 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4951 Inputs.push_back(I);
4952 if (LF.PostIncLoops.count(L)) {
4953 if (LF.isUseFullyOutsideLoop(L))
4954 Inputs.push_back(L->getLoopLatch()->getTerminator());
4955 else
4956 Inputs.push_back(IVIncInsertPos);
4957 }
4958 // The expansion must also be dominated by the increment positions of any
4959 // loops it for which it is using post-inc mode.
4960 for (const Loop *PIL : LF.PostIncLoops) {
4961 if (PIL == L) continue;
4962
4963 // Be dominated by the loop exit.
4964 SmallVector<BasicBlock *, 4> ExitingBlocks;
4965 PIL->getExitingBlocks(ExitingBlocks);
4966 if (!ExitingBlocks.empty()) {
4967 BasicBlock *BB = ExitingBlocks[0];
4968 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4969 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4970 Inputs.push_back(BB->getTerminator());
4971 }
4972 }
4973
4974 assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad()((!isa<PHINode>(LowestIP) && !LowestIP->isEHPad
() && !isa<DbgInfoIntrinsic>(LowestIP) &&
"Insertion point must be a normal instruction") ? static_cast
<void> (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4976, __PRETTY_FUNCTION__))
4975 && !isa<DbgInfoIntrinsic>(LowestIP) &&((!isa<PHINode>(LowestIP) && !LowestIP->isEHPad
() && !isa<DbgInfoIntrinsic>(LowestIP) &&
"Insertion point must be a normal instruction") ? static_cast
<void> (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4976, __PRETTY_FUNCTION__))
4976 "Insertion point must be a normal instruction")((!isa<PHINode>(LowestIP) && !LowestIP->isEHPad
() && !isa<DbgInfoIntrinsic>(LowestIP) &&
"Insertion point must be a normal instruction") ? static_cast
<void> (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4976, __PRETTY_FUNCTION__))
;
4977
4978 // Then, climb up the immediate dominator tree as far as we can go while
4979 // still being dominated by the input positions.
4980 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4981
4982 // Don't insert instructions before PHI nodes.
4983 while (isa<PHINode>(IP)) ++IP;
4984
4985 // Ignore landingpad instructions.
4986 while (IP->isEHPad()) ++IP;
4987
4988 // Ignore debug intrinsics.
4989 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4990
4991 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4992 // IP consistent across expansions and allows the previously inserted
4993 // instructions to be reused by subsequent expansion.
4994 while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
4995 ++IP;
4996
4997 return IP;
4998}
4999
5000/// Emit instructions for the leading candidate expression for this LSRUse (this
5001/// is called "expanding").
5002Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF,
5003 const Formula &F, BasicBlock::iterator IP,
5004 SCEVExpander &Rewriter,
5005 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5006 if (LU.RigidFormula)
5007 return LF.OperandValToReplace;
5008
5009 // Determine an input position which will be dominated by the operands and
5010 // which will dominate the result.
5011 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
5012 Rewriter.setInsertPoint(&*IP);
5013
5014 // Inform the Rewriter if we have a post-increment use, so that it can
5015 // perform an advantageous expansion.
5016 Rewriter.setPostInc(LF.PostIncLoops);
5017
5018 // This is the type that the user actually needs.
5019 Type *OpTy = LF.OperandValToReplace->getType();
5020 // This will be the type that we'll initially expand to.
5021 Type *Ty = F.getType();
5022 if (!Ty)
5023 // No type known; just expand directly to the ultimate type.
5024 Ty = OpTy;
5025 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
5026 // Expand directly to the ultimate type if it's the right size.
5027 Ty = OpTy;
5028 // This is the type to do integer arithmetic in.
5029 Type *IntTy = SE.getEffectiveSCEVType(Ty);
5030
5031 // Build up a list of operands to add together to form the full base.
5032 SmallVector<const SCEV *, 8> Ops;
5033
5034 // Expand the BaseRegs portion.
5035 for (const SCEV *Reg : F.BaseRegs) {
5036 assert(!Reg->isZero() && "Zero allocated in a base register!")((!Reg->isZero() && "Zero allocated in a base register!"
) ? static_cast<void> (0) : __assert_fail ("!Reg->isZero() && \"Zero allocated in a base register!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5036, __PRETTY_FUNCTION__))
;
5037
5038 // If we're expanding for a post-inc user, make the post-inc adjustment.
5039 Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE);
5040 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
5041 }
5042
5043 // Expand the ScaledReg portion.
5044 Value *ICmpScaledV = nullptr;
5045 if (F.Scale != 0) {
5046 const SCEV *ScaledS = F.ScaledReg;
5047
5048 // If we're expanding for a post-inc user, make the post-inc adjustment.
5049 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
5050 ScaledS = denormalizeForPostIncUse(ScaledS, Loops, SE);
5051
5052 if (LU.Kind == LSRUse::ICmpZero) {
5053 // Expand ScaleReg as if it was part of the base regs.
5054 if (F.Scale == 1)
5055 Ops.push_back(
5056 SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
5057 else {
5058 // An interesting way of "folding" with an icmp is to use a negated
5059 // scale, which we'll implement by inserting it into the other operand
5060 // of the icmp.
5061 assert(F.Scale == -1 &&((F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? static_cast<void> (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5062, __PRETTY_FUNCTION__))
5062 "The only scale supported by ICmpZero uses is -1!")((F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? static_cast<void> (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5062, __PRETTY_FUNCTION__))
;
5063 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
5064 }
5065 } else {
5066 // Otherwise just expand the scaled register and an explicit scale,
5067 // which is expected to be matched as part of the address.
5068
5069 // Flush the operand list to suppress SCEVExpander hoisting address modes.
5070 // Unless the addressing mode will not be folded.
5071 if (!Ops.empty() && LU.Kind == LSRUse::Address &&
5072 isAMCompletelyFolded(TTI, LU, F)) {
5073 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), nullptr);
5074 Ops.clear();
5075 Ops.push_back(SE.getUnknown(FullV));
5076 }
5077 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
5078 if (F.Scale != 1)
5079 ScaledS =
5080 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
5081 Ops.push_back(ScaledS);
5082 }
5083 }
5084
5085 // Expand the GV portion.
5086 if (F.BaseGV) {
5087 // Flush the operand list to suppress SCEVExpander hoisting.
5088 if (!Ops.empty()) {
5089 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5090 Ops.clear();
5091 Ops.push_back(SE.getUnknown(FullV));
5092 }
5093 Ops.push_back(SE.getUnknown(F.BaseGV));
5094 }
5095
5096 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
5097 // unfolded offsets. LSR assumes they both live next to their uses.
5098 if (!Ops.empty()) {
5099 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5100 Ops.clear();
5101 Ops.push_back(SE.getUnknown(FullV));
5102 }
5103
5104 // Expand the immediate portion.
5105 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
5106 if (Offset != 0) {
5107 if (LU.Kind == LSRUse::ICmpZero) {
5108 // The other interesting way of "folding" with an ICmpZero is to use a
5109 // negated immediate.
5110 if (!ICmpScaledV)
5111 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
5112 else {
5113 Ops.push_back(SE.getUnknown(ICmpScaledV));
5114 ICmpScaledV = ConstantInt::get(IntTy, Offset);
5115 }
5116 } else {
5117 // Just add the immediate values. These again are expected to be matched
5118 // as part of the address.
5119 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
5120 }
5121 }
5122
5123 // Expand the unfolded offset portion.
5124 int64_t UnfoldedOffset = F.UnfoldedOffset;
5125 if (UnfoldedOffset != 0) {
5126 // Just add the immediate values.
5127 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
5128 UnfoldedOffset)));
5129 }
5130
5131 // Emit instructions summing all the operands.
5132 const SCEV *FullS = Ops.empty() ?
5133 SE.getConstant(IntTy, 0) :
5134 SE.getAddExpr(Ops);
5135 Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
5136
5137 // We're done expanding now, so reset the rewriter.
5138 Rewriter.clearPostInc();
5139
5140 // An ICmpZero Formula represents an ICmp which we're handling as a
5141 // comparison against zero. Now that we've expanded an expression for that
5142 // form, update the ICmp's other operand.
5143 if (LU.Kind == LSRUse::ICmpZero) {
5144 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
5145 DeadInsts.emplace_back(CI->getOperand(1));
5146 assert(!F.BaseGV && "ICmp does not support folding a global value and "((!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("!F.BaseGV && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5147, __PRETTY_FUNCTION__))
5147 "a scale at the same time!")((!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("!F.BaseGV && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5147, __PRETTY_FUNCTION__))
;
5148 if (F.Scale == -1) {
5149 if (ICmpScaledV->getType() != OpTy) {
5150 Instruction *Cast =
5151 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
5152 OpTy, false),
5153 ICmpScaledV, OpTy, "tmp", CI);
5154 ICmpScaledV = Cast;
5155 }
5156 CI->setOperand(1, ICmpScaledV);
5157 } else {
5158 // A scale of 1 means that the scale has been expanded as part of the
5159 // base regs.
5160 assert((F.Scale == 0 || F.Scale == 1) &&(((F.Scale == 0 || F.Scale == 1) && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5162, __PRETTY_FUNCTION__))
5161 "ICmp does not support folding a global value and "(((F.Scale == 0 || F.Scale == 1) && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5162, __PRETTY_FUNCTION__))
5162 "a scale at the same time!")(((F.Scale == 0 || F.Scale == 1) && "ICmp does not support folding a global value and "
"a scale at the same time!") ? static_cast<void> (0) :
__assert_fail ("(F.Scale == 0 || F.Scale == 1) && \"ICmp does not support folding a global value and \" \"a scale at the same time!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5162, __PRETTY_FUNCTION__))
;
5163 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
5164 -(uint64_t)Offset);
5165 if (C->getType() != OpTy)
5166 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
5167 OpTy, false),
5168 C, OpTy);
5169
5170 CI->setOperand(1, C);
5171 }
5172 }
5173
5174 return FullV;
5175}
5176
5177/// Helper for Rewrite. PHI nodes are special because the use of their operands
5178/// effectively happens in their predecessor blocks, so the expression may need
5179/// to be expanded in multiple places.
5180void LSRInstance::RewriteForPHI(
5181 PHINode *PN, const LSRUse &LU, const LSRFixup &LF, const Formula &F,
5182 SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5183 DenseMap<BasicBlock *, Value *> Inserted;
5184 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
5185 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
5186 BasicBlock *BB = PN->getIncomingBlock(i);
5187
5188 // If this is a critical edge, split the edge so that we do not insert
5189 // the code on all predecessor/successor paths. We do this unless this
5190 // is the canonical backedge for this loop, which complicates post-inc
5191 // users.
5192 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
5193 !isa<IndirectBrInst>(BB->getTerminator()) &&
5194 !isa<CatchSwitchInst>(BB->getTerminator())) {
5195 BasicBlock *Parent = PN->getParent();
5196 Loop *PNLoop = LI.getLoopFor(Parent);
5197 if (!PNLoop || Parent != PNLoop->getHeader()) {
5198 // Split the critical edge.
5199 BasicBlock *NewBB = nullptr;
5200 if (!Parent->isLandingPad()) {
5201 NewBB = SplitCriticalEdge(BB, Parent,
5202 CriticalEdgeSplittingOptions(&DT, &LI)
5203 .setMergeIdenticalEdges()
5204 .setDontDeleteUselessPHIs());
5205 } else {
5206 SmallVector<BasicBlock*, 2> NewBBs;
5207 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
5208 NewBB = NewBBs[0];
5209 }
5210 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
5211 // phi predecessors are identical. The simple thing to do is skip
5212 // splitting in this case rather than complicate the API.
5213 if (NewBB) {
5214 // If PN is outside of the loop and BB is in the loop, we want to
5215 // move the block to be immediately before the PHI block, not
5216 // immediately after BB.
5217 if (L->contains(BB) && !L->contains(PN))
5218 NewBB->moveBefore(PN->getParent());
5219
5220 // Splitting the edge can reduce the number of PHI entries we have.
5221 e = PN->getNumIncomingValues();
5222 BB = NewBB;
5223 i = PN->getBasicBlockIndex(BB);
5224 }
5225 }
5226 }
5227
5228 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
5229 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
5230 if (!Pair.second)
5231 PN->setIncomingValue(i, Pair.first->second);
5232 else {
5233 Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
5234 Rewriter, DeadInsts);
5235
5236 // If this is reuse-by-noop-cast, insert the noop cast.
5237 Type *OpTy = LF.OperandValToReplace->getType();
5238 if (FullV->getType() != OpTy)
5239 FullV =
5240 CastInst::Create(CastInst::getCastOpcode(FullV, false,
5241 OpTy, false),
5242 FullV, LF.OperandValToReplace->getType(),
5243 "tmp", BB->getTerminator());
5244
5245 PN->setIncomingValue(i, FullV);
5246 Pair.first->second = FullV;
5247 }
5248 }
5249}
5250
5251/// Emit instructions for the leading candidate expression for this LSRUse (this
5252/// is called "expanding"), and update the UserInst to reference the newly
5253/// expanded value.
5254void LSRInstance::Rewrite(const LSRUse &LU, const LSRFixup &LF,
5255 const Formula &F, SCEVExpander &Rewriter,
5256 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5257 // First, find an insertion point that dominates UserInst. For PHI nodes,
5258 // find the nearest block which dominates all the relevant uses.
5259 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
5260 RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
5261 } else {
5262 Value *FullV =
5263 Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
5264
5265 // If this is reuse-by-noop-cast, insert the noop cast.
5266 Type *OpTy = LF.OperandValToReplace->getType();
5267 if (FullV->getType() != OpTy) {
5268 Instruction *Cast =
5269 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
5270 FullV, OpTy, "tmp", LF.UserInst);
5271 FullV = Cast;
5272 }
5273
5274 // Update the user. ICmpZero is handled specially here (for now) because
5275 // Expand may have updated one of the operands of the icmp already, and
5276 // its new value may happen to be equal to LF.OperandValToReplace, in
5277 // which case doing replaceUsesOfWith leads to replacing both operands
5278 // with the same value. TODO: Reorganize this.
5279 if (LU.Kind == LSRUse::ICmpZero)
5280 LF.UserInst->setOperand(0, FullV);
5281 else
5282 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
5283 }
5284
5285 DeadInsts.emplace_back(LF.OperandValToReplace);
5286}
5287
5288/// Rewrite all the fixup locations with new values, following the chosen
5289/// solution.
5290void LSRInstance::ImplementSolution(
5291 const SmallVectorImpl<const Formula *> &Solution) {
5292 // Keep track of instructions we may have made dead, so that
5293 // we can remove them after we are done working.
5294 SmallVector<WeakTrackingVH, 16> DeadInsts;
5295
5296 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(),
5297 "lsr");
5298#ifndef NDEBUG
5299 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5300#endif
5301 Rewriter.disableCanonicalMode();
5302 Rewriter.enableLSRMode();
5303 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
5304
5305 // Mark phi nodes that terminate chains so the expander tries to reuse them.
5306 for (const IVChain &Chain : IVChainVec) {
5307 if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
5308 Rewriter.setChainedPhi(PN);
5309 }
5310
5311 // Expand the new value definitions and update the users.
5312 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5313 for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
5314 Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
5315 Changed = true;
5316 }
5317
5318 for (const IVChain &Chain : IVChainVec) {
5319 GenerateIVChain(Chain, Rewriter, DeadInsts);
5320 Changed = true;
5321 }
5322 // Clean up after ourselves. This must be done before deleting any
5323 // instructions.
5324 Rewriter.clear();
5325
5326 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
5327}
5328
5329LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5330 DominatorTree &DT, LoopInfo &LI,
5331 const TargetTransformInfo &TTI)
5332 : IU(IU), SE(SE), DT(DT), LI(LI), TTI(TTI), L(L) {
5333 // If LoopSimplify form is not available, stay out of trouble.
5334 if (!L->isLoopSimplifyForm())
3
Assuming the condition is false
4
Taking false branch
5335 return;
5336
5337 // If there's no interesting work to be done, bail early.
5338 if (IU.empty()) return;
5
Assuming the condition is false
6
Taking false branch
5339
5340 // If there's too much analysis to be done, bail early. We won't be able to
5341 // model the problem anyway.
5342 unsigned NumUsers = 0;
5343 for (const IVStrideUse &U : IU) {
5344 if (++NumUsers > MaxIVUsers) {
5345 (void)U;
5346 LLVM_DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << Udo { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping loop, too many IV Users in "
<< U << "\n"; } } while (false)
5347 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping loop, too many IV Users in "
<< U << "\n"; } } while (false)
;
5348 return;
5349 }
5350 // Bail out if we have a PHI on an EHPad that gets a value from a
5351 // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is
5352 // no good place to stick any instructions.
5353 if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
5354 auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
5355 if (isa<FuncletPadInst>(FirstNonPHI) ||
5356 isa<CatchSwitchInst>(FirstNonPHI))
5357 for (BasicBlock *PredBB : PN->blocks())
5358 if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
5359 return;
5360 }
5361 }
5362
5363#ifndef NDEBUG
5364 // All dominating loops must have preheaders, or SCEVExpander may not be able
5365 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
5366 //
5367 // IVUsers analysis should only create users that are dominated by simple loop
5368 // headers. Since this loop should dominate all of its users, its user list
5369 // should be empty if this loop itself is not within a simple loop nest.
5370 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
7
Loop condition is false. Execution continues on line 5380
5371 Rung; Rung = Rung->getIDom()) {
5372 BasicBlock *BB = Rung->getBlock();
5373 const Loop *DomLoop = LI.getLoopFor(BB);
5374 if (DomLoop && DomLoop->getHeader() == BB) {
5375 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest")((DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest"
) ? static_cast<void> (0) : __assert_fail ("DomLoop->getLoopPreheader() && \"LSR needs a simplified loop nest\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5375, __PRETTY_FUNCTION__))
;
5376 }
5377 }
5378#endif // DEBUG
5379
5380 LLVM_DEBUG(dbgs() << "\nLSR on loop ";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
5381 L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false);do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
5382 dbgs() << ":\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
;
5383
5384 // First, perform some low-level loop optimizations.
5385 OptimizeShadowIV();
5386 OptimizeLoopTermCond();
5387
5388 // If loop preparation eliminates all interesting IV users, bail.
5389 if (IU.empty()) return;
8
Assuming the condition is false
9
Taking false branch
5390
5391 // Skip nested loops until we can model them better with formulae.
5392 if (!L->empty()) {
10
Assuming the condition is false
11
Taking false branch
5393 LLVM_DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping outer loop "
<< *L << "\n"; } } while (false)
;
5394 return;
5395 }
5396
5397 // Start collecting data and preparing for the solver.
5398 CollectChains();
5399 CollectInterestingTypesAndFactors();
5400 CollectFixupsAndInitialFormulae();
5401 CollectLoopInvariantFixupsAndFormulae();
5402
5403 if (Uses.empty())
12
Taking false branch
5404 return;
5405
5406 LLVM_DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR found " << Uses
.size() << " uses:\n"; print_uses(dbgs()); } } while (false
)
5407 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR found " << Uses
.size() << " uses:\n"; print_uses(dbgs()); } } while (false
)
;
5408
5409 // Now use the reuse data to generate a bunch of interesting ways
5410 // to formulate the values needed for the uses.
5411 GenerateAllReuseFormulae();
5412
5413 FilterOutUndesirableDedicatedRegisters();
5414 NarrowSearchSpaceUsingHeuristics();
13
Calling 'LSRInstance::NarrowSearchSpaceUsingHeuristics'
5415
5416 SmallVector<const Formula *, 8> Solution;
5417 Solve(Solution);
5418
5419 // Release memory that is no longer needed.
5420 Factors.clear();
5421 Types.clear();
5422 RegUses.clear();
5423
5424 if (Solution.empty())
5425 return;
5426
5427#ifndef NDEBUG
5428 // Formulae should be legal.
5429 for (const LSRUse &LU : Uses) {
5430 for (const Formula &F : LU.Formulae)
5431 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Illegal formula generated!") ? static_cast<
void> (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Illegal formula generated!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5432, __PRETTY_FUNCTION__))
5432 F) && "Illegal formula generated!")((isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy
, F) && "Illegal formula generated!") ? static_cast<
void> (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Illegal formula generated!\""
, "/build/llvm-toolchain-snapshot-8~svn345461/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5432, __PRETTY_FUNCTION__))
;
5433 };
5434#endif
5435
5436 // Now that we've decided what we want, make it so.
5437 ImplementSolution(Solution);
5438}
5439
5440#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5441void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
5442 if (Factors.empty() && Types.empty()) return;
5443
5444 OS << "LSR has identified the following interesting factors and types: ";
5445 bool First = true;
5446
5447 for (int64_t Factor : Factors) {
5448 if (!First) OS << ", ";
5449 First = false;
5450 OS << '*' << Factor;
5451 }
5452
5453 for (Type *Ty : Types) {
5454 if (!First) OS << ", ";
5455 First = false;
5456 OS << '(' << *Ty << ')';
5457 }
5458 OS << '\n';
5459}
5460
5461void LSRInstance::print_fixups(raw_ostream &OS) const {
5462 OS << "LSR is examining the following fixup sites:\n";
5463 for (const LSRUse &LU : Uses)
5464 for (const LSRFixup &LF : LU.Fixups) {
5465 dbgs() << " ";
5466 LF.print(OS);
5467 OS << '\n';
5468 }
5469}
5470
5471void LSRInstance::print_uses(raw_ostream &OS) const {
5472 OS << "LSR is examining the following uses:\n";
5473 for (const LSRUse &LU : Uses) {
5474 dbgs() << " ";
5475 LU.print(OS);
5476 OS << '\n';
5477 for (const Formula &F : LU.Formulae) {
5478 OS << " ";
5479 F.print(OS);
5480 OS << '\n';
5481 }
5482 }
5483}
5484
5485void LSRInstance::print(raw_ostream &OS) const {
5486 print_factors_and_types(OS);
5487 print_fixups(OS);
5488 print_uses(OS);
5489}
5490
5491LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRInstance::dump() const {
5492 print(errs()); errs() << '\n';
5493}
5494#endif
5495
5496namespace {
5497
5498class LoopStrengthReduce : public LoopPass {
5499public:
5500 static char ID; // Pass ID, replacement for typeid
5501
5502 LoopStrengthReduce();
5503
5504private:
5505 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
5506 void getAnalysisUsage(AnalysisUsage &AU) const override;
5507};
5508
5509} // end anonymous namespace
5510
5511LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
5512 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
5513}
5514
5515void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
5516 // We split critical edges, so we change the CFG. However, we do update
5517 // many analyses if they are around.
5518 AU.addPreservedID(LoopSimplifyID);
5519
5520 AU.addRequired<LoopInfoWrapperPass>();
5521 AU.addPreserved<LoopInfoWrapperPass>();
5522 AU.addRequiredID(LoopSimplifyID);
5523 AU.addRequired<DominatorTreeWrapperPass>();
5524 AU.addPreserved<DominatorTreeWrapperPass>();
5525 AU.addRequired<ScalarEvolutionWrapperPass>();
5526 AU.addPreserved<ScalarEvolutionWrapperPass>();
5527 // Requiring LoopSimplify a second time here prevents IVUsers from running
5528 // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5529 AU.addRequiredID(LoopSimplifyID);
5530 AU.addRequired<IVUsersWrapperPass>();
5531 AU.addPreserved<IVUsersWrapperPass>();
5532 AU.addRequired<TargetTransformInfoWrapperPass>();
5533}
5534
5535static bool ReduceLoopStrength(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5536 DominatorTree &DT, LoopInfo &LI,
5537 const TargetTransformInfo &TTI) {
5538 bool Changed = false;
5539
5540 // Run the main LSR transformation.
5541 Changed |= LSRInstance(L, IU, SE, DT, LI, TTI).getChanged();
2
Calling constructor for 'LSRInstance'
5542
5543 // Remove any extra phis created by processing inner loops.
5544 Changed |= DeleteDeadPHIs(L->getHeader());
5545 if (EnablePhiElim && L->isLoopSimplifyForm()) {
5546 SmallVector<WeakTrackingVH, 16> DeadInsts;
5547 const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
5548 SCEVExpander Rewriter(SE, DL, "lsr");
5549#ifndef NDEBUG
5550 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5551#endif
5552 unsigned numFolded = Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, &TTI);
5553 if (numFolded) {
5554 Changed = true;
5555 DeleteTriviallyDeadInstructions(DeadInsts);
5556 DeleteDeadPHIs(L->getHeader());
5557 }
5558 }
5559 return Changed;
5560}
5561
5562bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5563 if (skipLoop(L))
5564 return false;
5565
5566 auto &IU = getAnalysis<IVUsersWrapperPass>().getIU();
5567 auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
5568 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
5569 auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
5570 const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
5571 *L->getHeader()->getParent());
5572 return ReduceLoopStrength(L, IU, SE, DT, LI, TTI);
5573}
5574
5575PreservedAnalyses LoopStrengthReducePass::run(Loop &L, LoopAnalysisManager &AM,
5576 LoopStandardAnalysisResults &AR,
5577 LPMUpdater &) {
5578 if (!ReduceLoopStrength(&L, AM.getResult<IVUsersAnalysis>(L, AR), AR.SE,
1
Calling 'ReduceLoopStrength'
5579 AR.DT, AR.LI, AR.TTI))
5580 return PreservedAnalyses::all();
5581
5582 return getLoopPassPreservedAnalyses();
5583}
5584
5585char LoopStrengthReduce::ID = 0;
5586
5587INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",static void *initializeLoopStrengthReducePassOnce(PassRegistry
&Registry) {
5588 "Loop Strength Reduction", false, false)static void *initializeLoopStrengthReducePassOnce(PassRegistry
&Registry) {
5589INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry);
5590INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
5591INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)initializeScalarEvolutionWrapperPassPass(Registry);
5592INITIALIZE_PASS_DEPENDENCY(IVUsersWrapperPass)initializeIVUsersWrapperPassPass(Registry);
5593INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry);
5594INITIALIZE_PASS_DEPENDENCY(LoopSimplify)initializeLoopSimplifyPass(Registry);
5595INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",PassInfo *PI = new PassInfo( "Loop Strength Reduction", "loop-reduce"
, &LoopStrengthReduce::ID, PassInfo::NormalCtor_t(callDefaultCtor
<LoopStrengthReduce>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeLoopStrengthReducePassFlag
; void llvm::initializeLoopStrengthReducePass(PassRegistry &
Registry) { llvm::call_once(InitializeLoopStrengthReducePassFlag
, initializeLoopStrengthReducePassOnce, std::ref(Registry)); }
5596 "Loop Strength Reduction", false, false)PassInfo *PI = new PassInfo( "Loop Strength Reduction", "loop-reduce"
, &LoopStrengthReduce::ID, PassInfo::NormalCtor_t(callDefaultCtor
<LoopStrengthReduce>), false, false); Registry.registerPass
(*PI, true); return PI; } static llvm::once_flag InitializeLoopStrengthReducePassFlag
; void llvm::initializeLoopStrengthReducePass(PassRegistry &
Registry) { llvm::call_once(InitializeLoopStrengthReducePassFlag
, initializeLoopStrengthReducePassOnce, std::ref(Registry)); }
5597
5598Pass *llvm::createLoopStrengthReducePass() { return new LoopStrengthReduce(); }