Bug Summary

File:lib/Transforms/Scalar/LoopStrengthReduce.cpp
Warning:line 5219, column 22
Called C++ object pointer is null

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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-eagerly-assume -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-7/lib/clang/7.0.0 -D _DEBUG -D _GNU_SOURCE -D __STDC_CONSTANT_MACROS -D __STDC_FORMAT_MACROS -D __STDC_LIMIT_MACROS -I /build/llvm-toolchain-snapshot-7~svn329677/build-llvm/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar -I /build/llvm-toolchain-snapshot-7~svn329677/build-llvm/include -I /build/llvm-toolchain-snapshot-7~svn329677/include -U NDEBUG -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/x86_64-linux-gnu/c++/7.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/x86_64-linux-gnu/c++/7.3.0 -internal-isystem /usr/lib/gcc/x86_64-linux-gnu/7.3.0/../../../../include/c++/7.3.0/backward -internal-isystem /usr/include/clang/7.0.0/include/ -internal-isystem /usr/local/include -internal-isystem /usr/lib/llvm-7/lib/clang/7.0.0/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-7~svn329677/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-checker optin.performance.Padding -analyzer-output=html -analyzer-config stable-report-filename=true -o /tmp/scan-build-2018-04-11-031539-24776-1 -x c++ /build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp
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/Analysis/Utils/Local.h"
79#include "llvm/IR/BasicBlock.h"
80#include "llvm/IR/Constant.h"
81#include "llvm/IR/Constants.h"
82#include "llvm/IR/DerivedTypes.h"
83#include "llvm/IR/Dominators.h"
84#include "llvm/IR/GlobalValue.h"
85#include "llvm/IR/IRBuilder.h"
86#include "llvm/IR/InstrTypes.h"
87#include "llvm/IR/Instruction.h"
88#include "llvm/IR/Instructions.h"
89#include "llvm/IR/IntrinsicInst.h"
90#include "llvm/IR/Intrinsics.h"
91#include "llvm/IR/Module.h"
92#include "llvm/IR/OperandTraits.h"
93#include "llvm/IR/Operator.h"
94#include "llvm/IR/PassManager.h"
95#include "llvm/IR/Type.h"
96#include "llvm/IR/Use.h"
97#include "llvm/IR/User.h"
98#include "llvm/IR/Value.h"
99#include "llvm/IR/ValueHandle.h"
100#include "llvm/Pass.h"
101#include "llvm/Support/Casting.h"
102#include "llvm/Support/CommandLine.h"
103#include "llvm/Support/Compiler.h"
104#include "llvm/Support/Debug.h"
105#include "llvm/Support/ErrorHandling.h"
106#include "llvm/Support/MathExtras.h"
107#include "llvm/Support/raw_ostream.h"
108#include "llvm/Transforms/Scalar.h"
109#include "llvm/Transforms/Utils.h"
110#include "llvm/Transforms/Utils/BasicBlockUtils.h"
111#include <algorithm>
112#include <cassert>
113#include <cstddef>
114#include <cstdint>
115#include <cstdlib>
116#include <iterator>
117#include <limits>
118#include <map>
119#include <utility>
120
121using namespace llvm;
122
123#define DEBUG_TYPE"loop-reduce" "loop-reduce"
124
125/// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for
126/// bail out. This threshold is far beyond the number of users that LSR can
127/// conceivably solve, so it should not affect generated code, but catches the
128/// worst cases before LSR burns too much compile time and stack space.
129static const unsigned MaxIVUsers = 200;
130
131// Temporary flag to cleanup congruent phis after LSR phi expansion.
132// It's currently disabled until we can determine whether it's truly useful or
133// not. The flag should be removed after the v3.0 release.
134// This is now needed for ivchains.
135static cl::opt<bool> EnablePhiElim(
136 "enable-lsr-phielim", cl::Hidden, cl::init(true),
137 cl::desc("Enable LSR phi elimination"));
138
139// The flag adds instruction count to solutions cost comparision.
140static cl::opt<bool> InsnsCost(
141 "lsr-insns-cost", cl::Hidden, cl::init(true),
142 cl::desc("Add instruction count to a LSR cost model"));
143
144// Flag to choose how to narrow complex lsr solution
145static cl::opt<bool> LSRExpNarrow(
146 "lsr-exp-narrow", cl::Hidden, cl::init(false),
147 cl::desc("Narrow LSR complex solution using"
148 " expectation of registers number"));
149
150// Flag to narrow search space by filtering non-optimal formulae with
151// the same ScaledReg and Scale.
152static cl::opt<bool> FilterSameScaledReg(
153 "lsr-filter-same-scaled-reg", cl::Hidden, cl::init(true),
154 cl::desc("Narrow LSR search space by filtering non-optimal formulae"
155 " with the same ScaledReg and Scale"));
156
157#ifndef NDEBUG
158// Stress test IV chain generation.
159static cl::opt<bool> StressIVChain(
160 "stress-ivchain", cl::Hidden, cl::init(false),
161 cl::desc("Stress test LSR IV chains"));
162#else
163static bool StressIVChain = false;
164#endif
165
166namespace {
167
168struct MemAccessTy {
169 /// Used in situations where the accessed memory type is unknown.
170 static const unsigned UnknownAddressSpace =
171 std::numeric_limits<unsigned>::max();
172
173 Type *MemTy = nullptr;
174 unsigned AddrSpace = UnknownAddressSpace;
175
176 MemAccessTy() = default;
177 MemAccessTy(Type *Ty, unsigned AS) : MemTy(Ty), AddrSpace(AS) {}
178
179 bool operator==(MemAccessTy Other) const {
180 return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace;
181 }
182
183 bool operator!=(MemAccessTy Other) const { return !(*this == Other); }
184
185 static MemAccessTy getUnknown(LLVMContext &Ctx,
186 unsigned AS = UnknownAddressSpace) {
187 return MemAccessTy(Type::getVoidTy(Ctx), AS);
188 }
189
190 Type *getType() { return MemTy; }
191};
192
193/// This class holds data which is used to order reuse candidates.
194class RegSortData {
195public:
196 /// This represents the set of LSRUse indices which reference
197 /// a particular register.
198 SmallBitVector UsedByIndices;
199
200 void print(raw_ostream &OS) const;
201 void dump() const;
202};
203
204} // end anonymous namespace
205
206#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
207void RegSortData::print(raw_ostream &OS) const {
208 OS << "[NumUses=" << UsedByIndices.count() << ']';
209}
210
211LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void RegSortData::dump() const {
212 print(errs()); errs() << '\n';
213}
214#endif
215
216namespace {
217
218/// Map register candidates to information about how they are used.
219class RegUseTracker {
220 using RegUsesTy = DenseMap<const SCEV *, RegSortData>;
221
222 RegUsesTy RegUsesMap;
223 SmallVector<const SCEV *, 16> RegSequence;
224
225public:
226 void countRegister(const SCEV *Reg, size_t LUIdx);
227 void dropRegister(const SCEV *Reg, size_t LUIdx);
228 void swapAndDropUse(size_t LUIdx, size_t LastLUIdx);
229
230 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
231
232 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
233
234 void clear();
235
236 using iterator = SmallVectorImpl<const SCEV *>::iterator;
237 using const_iterator = SmallVectorImpl<const SCEV *>::const_iterator;
238
239 iterator begin() { return RegSequence.begin(); }
240 iterator end() { return RegSequence.end(); }
241 const_iterator begin() const { return RegSequence.begin(); }
242 const_iterator end() const { return RegSequence.end(); }
243};
244
245} // end anonymous namespace
246
247void
248RegUseTracker::countRegister(const SCEV *Reg, size_t LUIdx) {
249 std::pair<RegUsesTy::iterator, bool> Pair =
250 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
251 RegSortData &RSD = Pair.first->second;
252 if (Pair.second)
253 RegSequence.push_back(Reg);
254 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
255 RSD.UsedByIndices.set(LUIdx);
256}
257
258void
259RegUseTracker::dropRegister(const SCEV *Reg, size_t LUIdx) {
260 RegUsesTy::iterator It = RegUsesMap.find(Reg);
261 assert(It != RegUsesMap.end())(static_cast <bool> (It != RegUsesMap.end()) ? void (0)
: __assert_fail ("It != RegUsesMap.end()", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 261, __extension__ __PRETTY_FUNCTION__))
;
262 RegSortData &RSD = It->second;
263 assert(RSD.UsedByIndices.size() > LUIdx)(static_cast <bool> (RSD.UsedByIndices.size() > LUIdx
) ? void (0) : __assert_fail ("RSD.UsedByIndices.size() > LUIdx"
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 263, __extension__ __PRETTY_FUNCTION__))
;
264 RSD.UsedByIndices.reset(LUIdx);
265}
266
267void
268RegUseTracker::swapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
269 assert(LUIdx <= LastLUIdx)(static_cast <bool> (LUIdx <= LastLUIdx) ? void (0) :
__assert_fail ("LUIdx <= LastLUIdx", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 269, __extension__ __PRETTY_FUNCTION__))
;
270
271 // Update RegUses. The data structure is not optimized for this purpose;
272 // we must iterate through it and update each of the bit vectors.
273 for (auto &Pair : RegUsesMap) {
274 SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
275 if (LUIdx < UsedByIndices.size())
276 UsedByIndices[LUIdx] =
277 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false;
278 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
279 }
280}
281
282bool
283RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
284 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
285 if (I == RegUsesMap.end())
286 return false;
287 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
288 int i = UsedByIndices.find_first();
289 if (i == -1) return false;
290 if ((size_t)i != LUIdx) return true;
291 return UsedByIndices.find_next(i) != -1;
292}
293
294const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
295 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
296 assert(I != RegUsesMap.end() && "Unknown register!")(static_cast <bool> (I != RegUsesMap.end() && "Unknown register!"
) ? void (0) : __assert_fail ("I != RegUsesMap.end() && \"Unknown register!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 296, __extension__ __PRETTY_FUNCTION__))
;
297 return I->second.UsedByIndices;
298}
299
300void RegUseTracker::clear() {
301 RegUsesMap.clear();
302 RegSequence.clear();
303}
304
305namespace {
306
307/// This class holds information that describes a formula for computing
308/// satisfying a use. It may include broken-out immediates and scaled registers.
309struct Formula {
310 /// Global base address used for complex addressing.
311 GlobalValue *BaseGV = nullptr;
312
313 /// Base offset for complex addressing.
314 int64_t BaseOffset = 0;
315
316 /// Whether any complex addressing has a base register.
317 bool HasBaseReg = false;
318
319 /// The scale of any complex addressing.
320 int64_t Scale = 0;
321
322 /// The list of "base" registers for this use. When this is non-empty. The
323 /// canonical representation of a formula is
324 /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
325 /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
326 /// 3. The reg containing recurrent expr related with currect loop in the
327 /// formula should be put in the ScaledReg.
328 /// #1 enforces that the scaled register is always used when at least two
329 /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
330 /// #2 enforces that 1 * reg is reg.
331 /// #3 ensures invariant regs with respect to current loop can be combined
332 /// together in LSR codegen.
333 /// This invariant can be temporarly broken while building a formula.
334 /// However, every formula inserted into the LSRInstance must be in canonical
335 /// form.
336 SmallVector<const SCEV *, 4> BaseRegs;
337
338 /// The 'scaled' register for this use. This should be non-null when Scale is
339 /// not zero.
340 const SCEV *ScaledReg = nullptr;
341
342 /// An additional constant offset which added near the use. This requires a
343 /// temporary register, but the offset itself can live in an add immediate
344 /// field rather than a register.
345 int64_t UnfoldedOffset = 0;
346
347 Formula() = default;
348
349 void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
350
351 bool isCanonical(const Loop &L) const;
352
353 void canonicalize(const Loop &L);
354
355 bool unscale();
356
357 bool hasZeroEnd() const;
358
359 size_t getNumRegs() const;
360 Type *getType() const;
361
362 void deleteBaseReg(const SCEV *&S);
363
364 bool referencesReg(const SCEV *S) const;
365 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
366 const RegUseTracker &RegUses) const;
367
368 void print(raw_ostream &OS) const;
369 void dump() const;
370};
371
372} // end anonymous namespace
373
374/// Recursion helper for initialMatch.
375static void DoInitialMatch(const SCEV *S, Loop *L,
376 SmallVectorImpl<const SCEV *> &Good,
377 SmallVectorImpl<const SCEV *> &Bad,
378 ScalarEvolution &SE) {
379 // Collect expressions which properly dominate the loop header.
380 if (SE.properlyDominates(S, L->getHeader())) {
381 Good.push_back(S);
382 return;
383 }
384
385 // Look at add operands.
386 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
387 for (const SCEV *S : Add->operands())
388 DoInitialMatch(S, L, Good, Bad, SE);
389 return;
390 }
391
392 // Look at addrec operands.
393 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
394 if (!AR->getStart()->isZero() && AR->isAffine()) {
395 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
396 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
397 AR->getStepRecurrence(SE),
398 // FIXME: AR->getNoWrapFlags()
399 AR->getLoop(), SCEV::FlagAnyWrap),
400 L, Good, Bad, SE);
401 return;
402 }
403
404 // Handle a multiplication by -1 (negation) if it didn't fold.
405 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
406 if (Mul->getOperand(0)->isAllOnesValue()) {
407 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
408 const SCEV *NewMul = SE.getMulExpr(Ops);
409
410 SmallVector<const SCEV *, 4> MyGood;
411 SmallVector<const SCEV *, 4> MyBad;
412 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
413 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
414 SE.getEffectiveSCEVType(NewMul->getType())));
415 for (const SCEV *S : MyGood)
416 Good.push_back(SE.getMulExpr(NegOne, S));
417 for (const SCEV *S : MyBad)
418 Bad.push_back(SE.getMulExpr(NegOne, S));
419 return;
420 }
421
422 // Ok, we can't do anything interesting. Just stuff the whole thing into a
423 // register and hope for the best.
424 Bad.push_back(S);
425}
426
427/// Incorporate loop-variant parts of S into this Formula, attempting to keep
428/// all loop-invariant and loop-computable values in a single base register.
429void Formula::initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
430 SmallVector<const SCEV *, 4> Good;
431 SmallVector<const SCEV *, 4> Bad;
432 DoInitialMatch(S, L, Good, Bad, SE);
433 if (!Good.empty()) {
434 const SCEV *Sum = SE.getAddExpr(Good);
435 if (!Sum->isZero())
436 BaseRegs.push_back(Sum);
437 HasBaseReg = true;
438 }
439 if (!Bad.empty()) {
440 const SCEV *Sum = SE.getAddExpr(Bad);
441 if (!Sum->isZero())
442 BaseRegs.push_back(Sum);
443 HasBaseReg = true;
444 }
445 canonicalize(*L);
446}
447
448/// \brief Check whether or not this formula satisfies the canonical
449/// representation.
450/// \see Formula::BaseRegs.
451bool Formula::isCanonical(const Loop &L) const {
452 if (!ScaledReg)
453 return BaseRegs.size() <= 1;
454
455 if (Scale != 1)
456 return true;
457
458 if (Scale == 1 && BaseRegs.empty())
459 return false;
460
461 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
462 if (SAR && SAR->getLoop() == &L)
463 return true;
464
465 // If ScaledReg is not a recurrent expr, or it is but its loop is not current
466 // loop, meanwhile BaseRegs contains a recurrent expr reg related with current
467 // loop, we want to swap the reg in BaseRegs with ScaledReg.
468 auto I =
469 find_if(make_range(BaseRegs.begin(), BaseRegs.end()), [&](const SCEV *S) {
470 return isa<const SCEVAddRecExpr>(S) &&
471 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
472 });
473 return I == BaseRegs.end();
474}
475
476/// \brief Helper method to morph a formula into its canonical representation.
477/// \see Formula::BaseRegs.
478/// Every formula having more than one base register, must use the ScaledReg
479/// field. Otherwise, we would have to do special cases everywhere in LSR
480/// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
481/// On the other hand, 1*reg should be canonicalized into reg.
482void Formula::canonicalize(const Loop &L) {
483 if (isCanonical(L))
484 return;
485 // So far we did not need this case. This is easy to implement but it is
486 // useless to maintain dead code. Beside it could hurt compile time.
487 assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.")(static_cast <bool> (!BaseRegs.empty() && "1*reg => reg, should not be needed."
) ? void (0) : __assert_fail ("!BaseRegs.empty() && \"1*reg => reg, should not be needed.\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 487, __extension__ __PRETTY_FUNCTION__))
;
488
489 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
490 if (!ScaledReg) {
491 ScaledReg = BaseRegs.back();
492 BaseRegs.pop_back();
493 Scale = 1;
494 }
495
496 // If ScaledReg is an invariant with respect to L, find the reg from
497 // BaseRegs containing the recurrent expr related with Loop L. Swap the
498 // reg with ScaledReg.
499 const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg);
500 if (!SAR || SAR->getLoop() != &L) {
501 auto I = find_if(make_range(BaseRegs.begin(), BaseRegs.end()),
502 [&](const SCEV *S) {
503 return isa<const SCEVAddRecExpr>(S) &&
504 (cast<SCEVAddRecExpr>(S)->getLoop() == &L);
505 });
506 if (I != BaseRegs.end())
507 std::swap(ScaledReg, *I);
508 }
509}
510
511/// \brief Get rid of the scale in the formula.
512/// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
513/// \return true if it was possible to get rid of the scale, false otherwise.
514/// \note After this operation the formula may not be in the canonical form.
515bool Formula::unscale() {
516 if (Scale != 1)
517 return false;
518 Scale = 0;
519 BaseRegs.push_back(ScaledReg);
520 ScaledReg = nullptr;
521 return true;
522}
523
524bool Formula::hasZeroEnd() const {
525 if (UnfoldedOffset || BaseOffset)
526 return false;
527 if (BaseRegs.size() != 1 || ScaledReg)
528 return false;
529 return true;
530}
531
532/// Return the total number of register operands used by this formula. This does
533/// not include register uses implied by non-constant addrec strides.
534size_t Formula::getNumRegs() const {
535 return !!ScaledReg + BaseRegs.size();
536}
537
538/// Return the type of this formula, if it has one, or null otherwise. This type
539/// is meaningless except for the bit size.
540Type *Formula::getType() const {
541 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
542 ScaledReg ? ScaledReg->getType() :
543 BaseGV ? BaseGV->getType() :
544 nullptr;
545}
546
547/// Delete the given base reg from the BaseRegs list.
548void Formula::deleteBaseReg(const SCEV *&S) {
549 if (&S != &BaseRegs.back())
550 std::swap(S, BaseRegs.back());
551 BaseRegs.pop_back();
552}
553
554/// Test if this formula references the given register.
555bool Formula::referencesReg(const SCEV *S) const {
556 return S == ScaledReg || is_contained(BaseRegs, S);
557}
558
559/// Test whether this formula uses registers which are used by uses other than
560/// the use with the given index.
561bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
562 const RegUseTracker &RegUses) const {
563 if (ScaledReg)
564 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
565 return true;
566 for (const SCEV *BaseReg : BaseRegs)
567 if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
568 return true;
569 return false;
570}
571
572#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
573void Formula::print(raw_ostream &OS) const {
574 bool First = true;
575 if (BaseGV) {
576 if (!First) OS << " + "; else First = false;
577 BaseGV->printAsOperand(OS, /*PrintType=*/false);
578 }
579 if (BaseOffset != 0) {
580 if (!First) OS << " + "; else First = false;
581 OS << BaseOffset;
582 }
583 for (const SCEV *BaseReg : BaseRegs) {
584 if (!First) OS << " + "; else First = false;
585 OS << "reg(" << *BaseReg << ')';
586 }
587 if (HasBaseReg && BaseRegs.empty()) {
588 if (!First) OS << " + "; else First = false;
589 OS << "**error: HasBaseReg**";
590 } else if (!HasBaseReg && !BaseRegs.empty()) {
591 if (!First) OS << " + "; else First = false;
592 OS << "**error: !HasBaseReg**";
593 }
594 if (Scale != 0) {
595 if (!First) OS << " + "; else First = false;
596 OS << Scale << "*reg(";
597 if (ScaledReg)
598 OS << *ScaledReg;
599 else
600 OS << "<unknown>";
601 OS << ')';
602 }
603 if (UnfoldedOffset != 0) {
604 if (!First) OS << " + ";
605 OS << "imm(" << UnfoldedOffset << ')';
606 }
607}
608
609LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Formula::dump() const {
610 print(errs()); errs() << '\n';
611}
612#endif
613
614/// Return true if the given addrec can be sign-extended without changing its
615/// value.
616static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
617 Type *WideTy =
618 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
619 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
620}
621
622/// Return true if the given add can be sign-extended without changing its
623/// value.
624static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
625 Type *WideTy =
626 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
627 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
628}
629
630/// Return true if the given mul can be sign-extended without changing its
631/// value.
632static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
633 Type *WideTy =
634 IntegerType::get(SE.getContext(),
635 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
636 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
637}
638
639/// Return an expression for LHS /s RHS, if it can be determined and if the
640/// remainder is known to be zero, or null otherwise. If IgnoreSignificantBits
641/// is true, expressions like (X * Y) /s Y are simplified to Y, ignoring that
642/// the multiplication may overflow, which is useful when the result will be
643/// used in a context where the most significant bits are ignored.
644static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
645 ScalarEvolution &SE,
646 bool IgnoreSignificantBits = false) {
647 // Handle the trivial case, which works for any SCEV type.
648 if (LHS == RHS)
649 return SE.getConstant(LHS->getType(), 1);
650
651 // Handle a few RHS special cases.
652 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
653 if (RC) {
654 const APInt &RA = RC->getAPInt();
655 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
656 // some folding.
657 if (RA.isAllOnesValue())
658 return SE.getMulExpr(LHS, RC);
659 // Handle x /s 1 as x.
660 if (RA == 1)
661 return LHS;
662 }
663
664 // Check for a division of a constant by a constant.
665 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
666 if (!RC)
667 return nullptr;
668 const APInt &LA = C->getAPInt();
669 const APInt &RA = RC->getAPInt();
670 if (LA.srem(RA) != 0)
671 return nullptr;
672 return SE.getConstant(LA.sdiv(RA));
673 }
674
675 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
676 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
677 if ((IgnoreSignificantBits || isAddRecSExtable(AR, SE)) && AR->isAffine()) {
678 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
679 IgnoreSignificantBits);
680 if (!Step) return nullptr;
681 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
682 IgnoreSignificantBits);
683 if (!Start) return nullptr;
684 // FlagNW is independent of the start value, step direction, and is
685 // preserved with smaller magnitude steps.
686 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
687 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
688 }
689 return nullptr;
690 }
691
692 // Distribute the sdiv over add operands, if the add doesn't overflow.
693 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
694 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
695 SmallVector<const SCEV *, 8> Ops;
696 for (const SCEV *S : Add->operands()) {
697 const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
698 if (!Op) return nullptr;
699 Ops.push_back(Op);
700 }
701 return SE.getAddExpr(Ops);
702 }
703 return nullptr;
704 }
705
706 // Check for a multiply operand that we can pull RHS out of.
707 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
708 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
709 SmallVector<const SCEV *, 4> Ops;
710 bool Found = false;
711 for (const SCEV *S : Mul->operands()) {
712 if (!Found)
713 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
714 IgnoreSignificantBits)) {
715 S = Q;
716 Found = true;
717 }
718 Ops.push_back(S);
719 }
720 return Found ? SE.getMulExpr(Ops) : nullptr;
721 }
722 return nullptr;
723 }
724
725 // Otherwise we don't know.
726 return nullptr;
727}
728
729/// If S involves the addition of a constant integer value, return that integer
730/// value, and mutate S to point to a new SCEV with that value excluded.
731static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
732 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
733 if (C->getAPInt().getMinSignedBits() <= 64) {
734 S = SE.getConstant(C->getType(), 0);
735 return C->getValue()->getSExtValue();
736 }
737 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
738 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
739 int64_t Result = ExtractImmediate(NewOps.front(), SE);
740 if (Result != 0)
741 S = SE.getAddExpr(NewOps);
742 return Result;
743 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
744 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
745 int64_t Result = ExtractImmediate(NewOps.front(), SE);
746 if (Result != 0)
747 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
748 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
749 SCEV::FlagAnyWrap);
750 return Result;
751 }
752 return 0;
753}
754
755/// If S involves the addition of a GlobalValue address, return that symbol, and
756/// mutate S to point to a new SCEV with that value excluded.
757static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
758 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
759 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
760 S = SE.getConstant(GV->getType(), 0);
761 return GV;
762 }
763 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
764 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
765 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
766 if (Result)
767 S = SE.getAddExpr(NewOps);
768 return Result;
769 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
770 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
771 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
772 if (Result)
773 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
774 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
775 SCEV::FlagAnyWrap);
776 return Result;
777 }
778 return nullptr;
779}
780
781/// Returns true if the specified instruction is using the specified value as an
782/// address.
783static bool isAddressUse(const TargetTransformInfo &TTI,
784 Instruction *Inst, Value *OperandVal) {
785 bool isAddress = isa<LoadInst>(Inst);
786 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
787 if (SI->getPointerOperand() == OperandVal)
788 isAddress = true;
789 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
790 // Addressing modes can also be folded into prefetches and a variety
791 // of intrinsics.
792 switch (II->getIntrinsicID()) {
793 case Intrinsic::memset:
794 case Intrinsic::prefetch:
795 if (II->getArgOperand(0) == OperandVal)
796 isAddress = true;
797 break;
798 case Intrinsic::memmove:
799 case Intrinsic::memcpy:
800 if (II->getArgOperand(0) == OperandVal ||
801 II->getArgOperand(1) == OperandVal)
802 isAddress = true;
803 break;
804 default: {
805 MemIntrinsicInfo IntrInfo;
806 if (TTI.getTgtMemIntrinsic(II, IntrInfo)) {
807 if (IntrInfo.PtrVal == OperandVal)
808 isAddress = true;
809 }
810 }
811 }
812 } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
813 if (RMW->getPointerOperand() == OperandVal)
814 isAddress = true;
815 } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
816 if (CmpX->getPointerOperand() == OperandVal)
817 isAddress = true;
818 }
819 return isAddress;
820}
821
822/// Return the type of the memory being accessed.
823static MemAccessTy getAccessType(const TargetTransformInfo &TTI,
824 Instruction *Inst) {
825 MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace);
826 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
827 AccessTy.MemTy = SI->getOperand(0)->getType();
828 AccessTy.AddrSpace = SI->getPointerAddressSpace();
829 } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
830 AccessTy.AddrSpace = LI->getPointerAddressSpace();
831 } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) {
832 AccessTy.AddrSpace = RMW->getPointerAddressSpace();
833 } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
834 AccessTy.AddrSpace = CmpX->getPointerAddressSpace();
835 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
836 switch (II->getIntrinsicID()) {
837 case Intrinsic::prefetch:
838 AccessTy.AddrSpace = II->getArgOperand(0)->getType()->getPointerAddressSpace();
839 break;
840 default: {
841 MemIntrinsicInfo IntrInfo;
842 if (TTI.getTgtMemIntrinsic(II, IntrInfo) && IntrInfo.PtrVal) {
843 AccessTy.AddrSpace
844 = IntrInfo.PtrVal->getType()->getPointerAddressSpace();
845 }
846
847 break;
848 }
849 }
850 }
851
852 // All pointers have the same requirements, so canonicalize them to an
853 // arbitrary pointer type to minimize variation.
854 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy.MemTy))
855 AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
856 PTy->getAddressSpace());
857
858 return AccessTy;
859}
860
861/// Return true if this AddRec is already a phi in its loop.
862static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
863 for (PHINode &PN : AR->getLoop()->getHeader()->phis()) {
864 if (SE.isSCEVable(PN.getType()) &&
865 (SE.getEffectiveSCEVType(PN.getType()) ==
866 SE.getEffectiveSCEVType(AR->getType())) &&
867 SE.getSCEV(&PN) == AR)
868 return true;
869 }
870 return false;
871}
872
873/// Check if expanding this expression is likely to incur significant cost. This
874/// is tricky because SCEV doesn't track which expressions are actually computed
875/// by the current IR.
876///
877/// We currently allow expansion of IV increments that involve adds,
878/// multiplication by constants, and AddRecs from existing phis.
879///
880/// TODO: Allow UDivExpr if we can find an existing IV increment that is an
881/// obvious multiple of the UDivExpr.
882static bool isHighCostExpansion(const SCEV *S,
883 SmallPtrSetImpl<const SCEV*> &Processed,
884 ScalarEvolution &SE) {
885 // Zero/One operand expressions
886 switch (S->getSCEVType()) {
887 case scUnknown:
888 case scConstant:
889 return false;
890 case scTruncate:
891 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
892 Processed, SE);
893 case scZeroExtend:
894 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
895 Processed, SE);
896 case scSignExtend:
897 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
898 Processed, SE);
899 }
900
901 if (!Processed.insert(S).second)
902 return false;
903
904 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
905 for (const SCEV *S : Add->operands()) {
906 if (isHighCostExpansion(S, Processed, SE))
907 return true;
908 }
909 return false;
910 }
911
912 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
913 if (Mul->getNumOperands() == 2) {
914 // Multiplication by a constant is ok
915 if (isa<SCEVConstant>(Mul->getOperand(0)))
916 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
917
918 // If we have the value of one operand, check if an existing
919 // multiplication already generates this expression.
920 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
921 Value *UVal = U->getValue();
922 for (User *UR : UVal->users()) {
923 // If U is a constant, it may be used by a ConstantExpr.
924 Instruction *UI = dyn_cast<Instruction>(UR);
925 if (UI && UI->getOpcode() == Instruction::Mul &&
926 SE.isSCEVable(UI->getType())) {
927 return SE.getSCEV(UI) == Mul;
928 }
929 }
930 }
931 }
932 }
933
934 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
935 if (isExistingPhi(AR, SE))
936 return false;
937 }
938
939 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
940 return true;
941}
942
943/// If any of the instructions in the specified set are trivially dead, delete
944/// them and see if this makes any of their operands subsequently dead.
945static bool
946DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
947 bool Changed = false;
948
949 while (!DeadInsts.empty()) {
950 Value *V = DeadInsts.pop_back_val();
951 Instruction *I = dyn_cast_or_null<Instruction>(V);
952
953 if (!I || !isInstructionTriviallyDead(I))
954 continue;
955
956 for (Use &O : I->operands())
957 if (Instruction *U = dyn_cast<Instruction>(O)) {
958 O = nullptr;
959 if (U->use_empty())
960 DeadInsts.emplace_back(U);
961 }
962
963 I->eraseFromParent();
964 Changed = true;
965 }
966
967 return Changed;
968}
969
970namespace {
971
972class LSRUse;
973
974} // end anonymous namespace
975
976/// \brief Check if the addressing mode defined by \p F is completely
977/// folded in \p LU at isel time.
978/// This includes address-mode folding and special icmp tricks.
979/// This function returns true if \p LU can accommodate what \p F
980/// defines and up to 1 base + 1 scaled + offset.
981/// In other words, if \p F has several base registers, this function may
982/// still return true. Therefore, users still need to account for
983/// additional base registers and/or unfolded offsets to derive an
984/// accurate cost model.
985static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
986 const LSRUse &LU, const Formula &F);
987
988// Get the cost of the scaling factor used in F for LU.
989static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
990 const LSRUse &LU, const Formula &F,
991 const Loop &L);
992
993namespace {
994
995/// This class is used to measure and compare candidate formulae.
996class Cost {
997 TargetTransformInfo::LSRCost C;
998
999public:
1000 Cost() {
1001 C.Insns = 0;
1002 C.NumRegs = 0;
1003 C.AddRecCost = 0;
1004 C.NumIVMuls = 0;
1005 C.NumBaseAdds = 0;
1006 C.ImmCost = 0;
1007 C.SetupCost = 0;
1008 C.ScaleCost = 0;
1009 }
1010
1011 bool isLess(Cost &Other, const TargetTransformInfo &TTI);
1012
1013 void Lose();
1014
1015#ifndef NDEBUG
1016 // Once any of the metrics loses, they must all remain losers.
1017 bool isValid() {
1018 return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds
1019 | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u)
1020 || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds
1021 & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u);
1022 }
1023#endif
1024
1025 bool isLoser() {
1026 assert(isValid() && "invalid cost")(static_cast <bool> (isValid() && "invalid cost"
) ? void (0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1026, __extension__ __PRETTY_FUNCTION__))
;
1027 return C.NumRegs == ~0u;
1028 }
1029
1030 void RateFormula(const TargetTransformInfo &TTI,
1031 const Formula &F,
1032 SmallPtrSetImpl<const SCEV *> &Regs,
1033 const DenseSet<const SCEV *> &VisitedRegs,
1034 const Loop *L,
1035 ScalarEvolution &SE, DominatorTree &DT,
1036 const LSRUse &LU,
1037 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
1038
1039 void print(raw_ostream &OS) const;
1040 void dump() const;
1041
1042private:
1043 void RateRegister(const SCEV *Reg,
1044 SmallPtrSetImpl<const SCEV *> &Regs,
1045 const Loop *L,
1046 ScalarEvolution &SE, DominatorTree &DT,
1047 const TargetTransformInfo &TTI);
1048 void RatePrimaryRegister(const SCEV *Reg,
1049 SmallPtrSetImpl<const SCEV *> &Regs,
1050 const Loop *L,
1051 ScalarEvolution &SE, DominatorTree &DT,
1052 SmallPtrSetImpl<const SCEV *> *LoserRegs,
1053 const TargetTransformInfo &TTI);
1054};
1055
1056/// An operand value in an instruction which is to be replaced with some
1057/// equivalent, possibly strength-reduced, replacement.
1058struct LSRFixup {
1059 /// The instruction which will be updated.
1060 Instruction *UserInst = nullptr;
1061
1062 /// The operand of the instruction which will be replaced. The operand may be
1063 /// used more than once; every instance will be replaced.
1064 Value *OperandValToReplace = nullptr;
1065
1066 /// If this user is to use the post-incremented value of an induction
1067 /// variable, this set is non-empty and holds the loops associated with the
1068 /// induction variable.
1069 PostIncLoopSet PostIncLoops;
1070
1071 /// A constant offset to be added to the LSRUse expression. This allows
1072 /// multiple fixups to share the same LSRUse with different offsets, for
1073 /// example in an unrolled loop.
1074 int64_t Offset = 0;
1075
1076 LSRFixup() = default;
1077
1078 bool isUseFullyOutsideLoop(const Loop *L) const;
1079
1080 void print(raw_ostream &OS) const;
1081 void dump() const;
1082};
1083
1084/// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted
1085/// SmallVectors of const SCEV*.
1086struct UniquifierDenseMapInfo {
1087 static SmallVector<const SCEV *, 4> getEmptyKey() {
1088 SmallVector<const SCEV *, 4> V;
1089 V.push_back(reinterpret_cast<const SCEV *>(-1));
1090 return V;
1091 }
1092
1093 static SmallVector<const SCEV *, 4> getTombstoneKey() {
1094 SmallVector<const SCEV *, 4> V;
1095 V.push_back(reinterpret_cast<const SCEV *>(-2));
1096 return V;
1097 }
1098
1099 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1100 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1101 }
1102
1103 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1104 const SmallVector<const SCEV *, 4> &RHS) {
1105 return LHS == RHS;
1106 }
1107};
1108
1109/// This class holds the state that LSR keeps for each use in IVUsers, as well
1110/// as uses invented by LSR itself. It includes information about what kinds of
1111/// things can be folded into the user, information about the user itself, and
1112/// information about how the use may be satisfied. TODO: Represent multiple
1113/// users of the same expression in common?
1114class LSRUse {
1115 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1116
1117public:
1118 /// An enum for a kind of use, indicating what types of scaled and immediate
1119 /// operands it might support.
1120 enum KindType {
1121 Basic, ///< A normal use, with no folding.
1122 Special, ///< A special case of basic, allowing -1 scales.
1123 Address, ///< An address use; folding according to TargetLowering
1124 ICmpZero ///< An equality icmp with both operands folded into one.
1125 // TODO: Add a generic icmp too?
1126 };
1127
1128 using SCEVUseKindPair = PointerIntPair<const SCEV *, 2, KindType>;
1129
1130 KindType Kind;
1131 MemAccessTy AccessTy;
1132
1133 /// The list of operands which are to be replaced.
1134 SmallVector<LSRFixup, 8> Fixups;
1135
1136 /// Keep track of the min and max offsets of the fixups.
1137 int64_t MinOffset = std::numeric_limits<int64_t>::max();
1138 int64_t MaxOffset = std::numeric_limits<int64_t>::min();
1139
1140 /// This records whether all of the fixups using this LSRUse are outside of
1141 /// the loop, in which case some special-case heuristics may be used.
1142 bool AllFixupsOutsideLoop = true;
1143
1144 /// RigidFormula is set to true to guarantee that this use will be associated
1145 /// with a single formula--the one that initially matched. Some SCEV
1146 /// expressions cannot be expanded. This allows LSR to consider the registers
1147 /// used by those expressions without the need to expand them later after
1148 /// changing the formula.
1149 bool RigidFormula = false;
1150
1151 /// This records the widest use type for any fixup using this
1152 /// LSRUse. FindUseWithSimilarFormula can't consider uses with different max
1153 /// fixup widths to be equivalent, because the narrower one may be relying on
1154 /// the implicit truncation to truncate away bogus bits.
1155 Type *WidestFixupType = nullptr;
1156
1157 /// A list of ways to build a value that can satisfy this user. After the
1158 /// list is populated, one of these is selected heuristically and used to
1159 /// formulate a replacement for OperandValToReplace in UserInst.
1160 SmallVector<Formula, 12> Formulae;
1161
1162 /// The set of register candidates used by all formulae in this LSRUse.
1163 SmallPtrSet<const SCEV *, 4> Regs;
1164
1165 LSRUse(KindType K, MemAccessTy AT) : Kind(K), AccessTy(AT) {}
1166
1167 LSRFixup &getNewFixup() {
1168 Fixups.push_back(LSRFixup());
1169 return Fixups.back();
1170 }
1171
1172 void pushFixup(LSRFixup &f) {
1173 Fixups.push_back(f);
1174 if (f.Offset > MaxOffset)
1175 MaxOffset = f.Offset;
1176 if (f.Offset < MinOffset)
1177 MinOffset = f.Offset;
1178 }
1179
1180 bool HasFormulaWithSameRegs(const Formula &F) const;
1181 float getNotSelectedProbability(const SCEV *Reg) const;
1182 bool InsertFormula(const Formula &F, const Loop &L);
1183 void DeleteFormula(Formula &F);
1184 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1185
1186 void print(raw_ostream &OS) const;
1187 void dump() const;
1188};
1189
1190} // end anonymous namespace
1191
1192static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1193 LSRUse::KindType Kind, MemAccessTy AccessTy,
1194 GlobalValue *BaseGV, int64_t BaseOffset,
1195 bool HasBaseReg, int64_t Scale,
1196 Instruction *Fixup = nullptr);
1197
1198/// Tally up interesting quantities from the given register.
1199void Cost::RateRegister(const SCEV *Reg,
1200 SmallPtrSetImpl<const SCEV *> &Regs,
1201 const Loop *L,
1202 ScalarEvolution &SE, DominatorTree &DT,
1203 const TargetTransformInfo &TTI) {
1204 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
1205 // If this is an addrec for another loop, it should be an invariant
1206 // with respect to L since L is the innermost loop (at least
1207 // for now LSR only handles innermost loops).
1208 if (AR->getLoop() != L) {
1209 // If the AddRec exists, consider it's register free and leave it alone.
1210 if (isExistingPhi(AR, SE))
1211 return;
1212
1213 // It is bad to allow LSR for current loop to add induction variables
1214 // for its sibling loops.
1215 if (!AR->getLoop()->contains(L)) {
1216 Lose();
1217 return;
1218 }
1219
1220 // Otherwise, it will be an invariant with respect to Loop L.
1221 ++C.NumRegs;
1222 return;
1223 }
1224
1225 unsigned LoopCost = 1;
1226 if (TTI.shouldFavorPostInc()) {
1227 const SCEV *LoopStep = AR->getStepRecurrence(SE);
1228 if (isa<SCEVConstant>(LoopStep)) {
1229 // Check if a post-indexed load/store can be used.
1230 if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) ||
1231 TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) {
1232 const SCEV *LoopStart = AR->getStart();
1233 if (!isa<SCEVConstant>(LoopStart) &&
1234 SE.isLoopInvariant(LoopStart, L))
1235 LoopCost = 0;
1236 }
1237 }
1238 }
1239 C.AddRecCost += LoopCost;
1240
1241 // Add the step value register, if it needs one.
1242 // TODO: The non-affine case isn't precisely modeled here.
1243 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
1244 if (!Regs.count(AR->getOperand(1))) {
1245 RateRegister(AR->getOperand(1), Regs, L, SE, DT, TTI);
1246 if (isLoser())
1247 return;
1248 }
1249 }
1250 }
1251 ++C.NumRegs;
1252
1253 // Rough heuristic; favor registers which don't require extra setup
1254 // instructions in the preheader.
1255 if (!isa<SCEVUnknown>(Reg) &&
1256 !isa<SCEVConstant>(Reg) &&
1257 !(isa<SCEVAddRecExpr>(Reg) &&
1258 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
1259 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
1260 ++C.SetupCost;
1261
1262 C.NumIVMuls += isa<SCEVMulExpr>(Reg) &&
1263 SE.hasComputableLoopEvolution(Reg, L);
1264}
1265
1266/// Record this register in the set. If we haven't seen it before, rate
1267/// it. Optional LoserRegs provides a way to declare any formula that refers to
1268/// one of those regs an instant loser.
1269void Cost::RatePrimaryRegister(const SCEV *Reg,
1270 SmallPtrSetImpl<const SCEV *> &Regs,
1271 const Loop *L,
1272 ScalarEvolution &SE, DominatorTree &DT,
1273 SmallPtrSetImpl<const SCEV *> *LoserRegs,
1274 const TargetTransformInfo &TTI) {
1275 if (LoserRegs && LoserRegs->count(Reg)) {
1276 Lose();
1277 return;
1278 }
1279 if (Regs.insert(Reg).second) {
1280 RateRegister(Reg, Regs, L, SE, DT, TTI);
1281 if (LoserRegs && isLoser())
1282 LoserRegs->insert(Reg);
1283 }
1284}
1285
1286void Cost::RateFormula(const TargetTransformInfo &TTI,
1287 const Formula &F,
1288 SmallPtrSetImpl<const SCEV *> &Regs,
1289 const DenseSet<const SCEV *> &VisitedRegs,
1290 const Loop *L,
1291 ScalarEvolution &SE, DominatorTree &DT,
1292 const LSRUse &LU,
1293 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1294 assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula")(static_cast <bool> (F.isCanonical(*L) && "Cost is accurate only for canonical formula"
) ? void (0) : __assert_fail ("F.isCanonical(*L) && \"Cost is accurate only for canonical formula\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1294, __extension__ __PRETTY_FUNCTION__))
;
1295 // Tally up the registers.
1296 unsigned PrevAddRecCost = C.AddRecCost;
1297 unsigned PrevNumRegs = C.NumRegs;
1298 unsigned PrevNumBaseAdds = C.NumBaseAdds;
1299 if (const SCEV *ScaledReg = F.ScaledReg) {
1300 if (VisitedRegs.count(ScaledReg)) {
1301 Lose();
1302 return;
1303 }
1304 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs, TTI);
1305 if (isLoser())
1306 return;
1307 }
1308 for (const SCEV *BaseReg : F.BaseRegs) {
1309 if (VisitedRegs.count(BaseReg)) {
1310 Lose();
1311 return;
1312 }
1313 RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs, TTI);
1314 if (isLoser())
1315 return;
1316 }
1317
1318 // Determine how many (unfolded) adds we'll need inside the loop.
1319 size_t NumBaseParts = F.getNumRegs();
1320 if (NumBaseParts > 1)
1321 // Do not count the base and a possible second register if the target
1322 // allows to fold 2 registers.
1323 C.NumBaseAdds +=
1324 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(TTI, LU, F)));
1325 C.NumBaseAdds += (F.UnfoldedOffset != 0);
1326
1327 // Accumulate non-free scaling amounts.
1328 C.ScaleCost += getScalingFactorCost(TTI, LU, F, *L);
1329
1330 // Tally up the non-zero immediates.
1331 for (const LSRFixup &Fixup : LU.Fixups) {
1332 int64_t O = Fixup.Offset;
1333 int64_t Offset = (uint64_t)O + F.BaseOffset;
1334 if (F.BaseGV)
1335 C.ImmCost += 64; // Handle symbolic values conservatively.
1336 // TODO: This should probably be the pointer size.
1337 else if (Offset != 0)
1338 C.ImmCost += APInt(64, Offset, true).getMinSignedBits();
1339
1340 // Check with target if this offset with this instruction is
1341 // specifically not supported.
1342 if (LU.Kind == LSRUse::Address && Offset != 0 &&
1343 !isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1344 Offset, F.HasBaseReg, F.Scale, Fixup.UserInst))
1345 C.NumBaseAdds++;
1346 }
1347
1348 // If we don't count instruction cost exit here.
1349 if (!InsnsCost) {
1350 assert(isValid() && "invalid cost")(static_cast <bool> (isValid() && "invalid cost"
) ? void (0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1350, __extension__ __PRETTY_FUNCTION__))
;
1351 return;
1352 }
1353
1354 // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as
1355 // additional instruction (at least fill).
1356 unsigned TTIRegNum = TTI.getNumberOfRegisters(false) - 1;
1357 if (C.NumRegs > TTIRegNum) {
1358 // Cost already exceeded TTIRegNum, then only newly added register can add
1359 // new instructions.
1360 if (PrevNumRegs > TTIRegNum)
1361 C.Insns += (C.NumRegs - PrevNumRegs);
1362 else
1363 C.Insns += (C.NumRegs - TTIRegNum);
1364 }
1365
1366 // If ICmpZero formula ends with not 0, it could not be replaced by
1367 // just add or sub. We'll need to compare final result of AddRec.
1368 // That means we'll need an additional instruction. But if the target can
1369 // macro-fuse a compare with a branch, don't count this extra instruction.
1370 // For -10 + {0, +, 1}:
1371 // i = i + 1;
1372 // cmp i, 10
1373 //
1374 // For {-10, +, 1}:
1375 // i = i + 1;
1376 if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd() && !TTI.canMacroFuseCmp())
1377 C.Insns++;
1378 // Each new AddRec adds 1 instruction to calculation.
1379 C.Insns += (C.AddRecCost - PrevAddRecCost);
1380
1381 // BaseAdds adds instructions for unfolded registers.
1382 if (LU.Kind != LSRUse::ICmpZero)
1383 C.Insns += C.NumBaseAdds - PrevNumBaseAdds;
1384 assert(isValid() && "invalid cost")(static_cast <bool> (isValid() && "invalid cost"
) ? void (0) : __assert_fail ("isValid() && \"invalid cost\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1384, __extension__ __PRETTY_FUNCTION__))
;
1385}
1386
1387/// Set this cost to a losing value.
1388void Cost::Lose() {
1389 C.Insns = std::numeric_limits<unsigned>::max();
1390 C.NumRegs = std::numeric_limits<unsigned>::max();
1391 C.AddRecCost = std::numeric_limits<unsigned>::max();
1392 C.NumIVMuls = std::numeric_limits<unsigned>::max();
1393 C.NumBaseAdds = std::numeric_limits<unsigned>::max();
1394 C.ImmCost = std::numeric_limits<unsigned>::max();
1395 C.SetupCost = std::numeric_limits<unsigned>::max();
1396 C.ScaleCost = std::numeric_limits<unsigned>::max();
1397}
1398
1399/// Choose the lower cost.
1400bool Cost::isLess(Cost &Other, const TargetTransformInfo &TTI) {
1401 if (InsnsCost.getNumOccurrences() > 0 && InsnsCost &&
1402 C.Insns != Other.C.Insns)
1403 return C.Insns < Other.C.Insns;
1404 return TTI.isLSRCostLess(C, Other.C);
1405}
1406
1407#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1408void Cost::print(raw_ostream &OS) const {
1409 if (InsnsCost)
1410 OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s ");
1411 OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s");
1412 if (C.AddRecCost != 0)
1413 OS << ", with addrec cost " << C.AddRecCost;
1414 if (C.NumIVMuls != 0)
1415 OS << ", plus " << C.NumIVMuls << " IV mul"
1416 << (C.NumIVMuls == 1 ? "" : "s");
1417 if (C.NumBaseAdds != 0)
1418 OS << ", plus " << C.NumBaseAdds << " base add"
1419 << (C.NumBaseAdds == 1 ? "" : "s");
1420 if (C.ScaleCost != 0)
1421 OS << ", plus " << C.ScaleCost << " scale cost";
1422 if (C.ImmCost != 0)
1423 OS << ", plus " << C.ImmCost << " imm cost";
1424 if (C.SetupCost != 0)
1425 OS << ", plus " << C.SetupCost << " setup cost";
1426}
1427
1428LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void Cost::dump() const {
1429 print(errs()); errs() << '\n';
1430}
1431#endif
1432
1433/// Test whether this fixup always uses its value outside of the given loop.
1434bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1435 // PHI nodes use their value in their incoming blocks.
1436 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1437 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1438 if (PN->getIncomingValue(i) == OperandValToReplace &&
1439 L->contains(PN->getIncomingBlock(i)))
1440 return false;
1441 return true;
1442 }
1443
1444 return !L->contains(UserInst);
1445}
1446
1447#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1448void LSRFixup::print(raw_ostream &OS) const {
1449 OS << "UserInst=";
1450 // Store is common and interesting enough to be worth special-casing.
1451 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1452 OS << "store ";
1453 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1454 } else if (UserInst->getType()->isVoidTy())
1455 OS << UserInst->getOpcodeName();
1456 else
1457 UserInst->printAsOperand(OS, /*PrintType=*/false);
1458
1459 OS << ", OperandValToReplace=";
1460 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1461
1462 for (const Loop *PIL : PostIncLoops) {
1463 OS << ", PostIncLoop=";
1464 PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1465 }
1466
1467 if (Offset != 0)
1468 OS << ", Offset=" << Offset;
1469}
1470
1471LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRFixup::dump() const {
1472 print(errs()); errs() << '\n';
1473}
1474#endif
1475
1476/// Test whether this use as a formula which has the same registers as the given
1477/// formula.
1478bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1479 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1480 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1481 // Unstable sort by host order ok, because this is only used for uniquifying.
1482 std::sort(Key.begin(), Key.end());
1483 return Uniquifier.count(Key);
1484}
1485
1486/// The function returns a probability of selecting formula without Reg.
1487float LSRUse::getNotSelectedProbability(const SCEV *Reg) const {
1488 unsigned FNum = 0;
1489 for (const Formula &F : Formulae)
1490 if (F.referencesReg(Reg))
1491 FNum++;
1492 return ((float)(Formulae.size() - FNum)) / Formulae.size();
1493}
1494
1495/// If the given formula has not yet been inserted, add it to the list, and
1496/// return true. Return false otherwise. The formula must be in canonical form.
1497bool LSRUse::InsertFormula(const Formula &F, const Loop &L) {
1498 assert(F.isCanonical(L) && "Invalid canonical representation")(static_cast <bool> (F.isCanonical(L) && "Invalid canonical representation"
) ? void (0) : __assert_fail ("F.isCanonical(L) && \"Invalid canonical representation\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1498, __extension__ __PRETTY_FUNCTION__))
;
1499
1500 if (!Formulae.empty() && RigidFormula)
1501 return false;
1502
1503 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1504 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1505 // Unstable sort by host order ok, because this is only used for uniquifying.
1506 std::sort(Key.begin(), Key.end());
1507
1508 if (!Uniquifier.insert(Key).second)
1509 return false;
1510
1511 // Using a register to hold the value of 0 is not profitable.
1512 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&(static_cast <bool> ((!F.ScaledReg || !F.ScaledReg->
isZero()) && "Zero allocated in a scaled register!") ?
void (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1513, __extension__ __PRETTY_FUNCTION__))
1513 "Zero allocated in a scaled register!")(static_cast <bool> ((!F.ScaledReg || !F.ScaledReg->
isZero()) && "Zero allocated in a scaled register!") ?
void (0) : __assert_fail ("(!F.ScaledReg || !F.ScaledReg->isZero()) && \"Zero allocated in a scaled register!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1513, __extension__ __PRETTY_FUNCTION__))
;
1514#ifndef NDEBUG
1515 for (const SCEV *BaseReg : F.BaseRegs)
1516 assert(!BaseReg->isZero() && "Zero allocated in a base register!")(static_cast <bool> (!BaseReg->isZero() && "Zero allocated in a base register!"
) ? void (0) : __assert_fail ("!BaseReg->isZero() && \"Zero allocated in a base register!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1516, __extension__ __PRETTY_FUNCTION__))
;
1517#endif
1518
1519 // Add the formula to the list.
1520 Formulae.push_back(F);
1521
1522 // Record registers now being used by this use.
1523 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1524 if (F.ScaledReg)
1525 Regs.insert(F.ScaledReg);
1526
1527 return true;
1528}
1529
1530/// Remove the given formula from this use's list.
1531void LSRUse::DeleteFormula(Formula &F) {
1532 if (&F != &Formulae.back())
1533 std::swap(F, Formulae.back());
1534 Formulae.pop_back();
1535}
1536
1537/// Recompute the Regs field, and update RegUses.
1538void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1539 // Now that we've filtered out some formulae, recompute the Regs set.
1540 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1541 Regs.clear();
1542 for (const Formula &F : Formulae) {
1543 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1544 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1545 }
1546
1547 // Update the RegTracker.
1548 for (const SCEV *S : OldRegs)
1549 if (!Regs.count(S))
1550 RegUses.dropRegister(S, LUIdx);
1551}
1552
1553#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1554void LSRUse::print(raw_ostream &OS) const {
1555 OS << "LSR Use: Kind=";
1556 switch (Kind) {
1557 case Basic: OS << "Basic"; break;
1558 case Special: OS << "Special"; break;
1559 case ICmpZero: OS << "ICmpZero"; break;
1560 case Address:
1561 OS << "Address of ";
1562 if (AccessTy.MemTy->isPointerTy())
1563 OS << "pointer"; // the full pointer type could be really verbose
1564 else {
1565 OS << *AccessTy.MemTy;
1566 }
1567
1568 OS << " in addrspace(" << AccessTy.AddrSpace << ')';
1569 }
1570
1571 OS << ", Offsets={";
1572 bool NeedComma = false;
1573 for (const LSRFixup &Fixup : Fixups) {
1574 if (NeedComma) OS << ',';
1575 OS << Fixup.Offset;
1576 NeedComma = true;
1577 }
1578 OS << '}';
1579
1580 if (AllFixupsOutsideLoop)
1581 OS << ", all-fixups-outside-loop";
1582
1583 if (WidestFixupType)
1584 OS << ", widest fixup type: " << *WidestFixupType;
1585}
1586
1587LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRUse::dump() const {
1588 print(errs()); errs() << '\n';
1589}
1590#endif
1591
1592static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1593 LSRUse::KindType Kind, MemAccessTy AccessTy,
1594 GlobalValue *BaseGV, int64_t BaseOffset,
1595 bool HasBaseReg, int64_t Scale,
1596 Instruction *Fixup/*= nullptr*/) {
1597 switch (Kind) {
1598 case LSRUse::Address:
1599 return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset,
1600 HasBaseReg, Scale, AccessTy.AddrSpace, Fixup);
1601
1602 case LSRUse::ICmpZero:
1603 // There's not even a target hook for querying whether it would be legal to
1604 // fold a GV into an ICmp.
1605 if (BaseGV)
1606 return false;
1607
1608 // ICmp only has two operands; don't allow more than two non-trivial parts.
1609 if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1610 return false;
1611
1612 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1613 // putting the scaled register in the other operand of the icmp.
1614 if (Scale != 0 && Scale != -1)
1615 return false;
1616
1617 // If we have low-level target information, ask the target if it can fold an
1618 // integer immediate on an icmp.
1619 if (BaseOffset != 0) {
1620 // We have one of:
1621 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1622 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1623 // Offs is the ICmp immediate.
1624 if (Scale == 0)
1625 // The cast does the right thing with
1626 // std::numeric_limits<int64_t>::min().
1627 BaseOffset = -(uint64_t)BaseOffset;
1628 return TTI.isLegalICmpImmediate(BaseOffset);
1629 }
1630
1631 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1632 return true;
1633
1634 case LSRUse::Basic:
1635 // Only handle single-register values.
1636 return !BaseGV && Scale == 0 && BaseOffset == 0;
1637
1638 case LSRUse::Special:
1639 // Special case Basic to handle -1 scales.
1640 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1641 }
1642
1643 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1643)
;
1644}
1645
1646static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1647 int64_t MinOffset, int64_t MaxOffset,
1648 LSRUse::KindType Kind, MemAccessTy AccessTy,
1649 GlobalValue *BaseGV, int64_t BaseOffset,
1650 bool HasBaseReg, int64_t Scale) {
1651 // Check for overflow.
1652 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1653 (MinOffset > 0))
1654 return false;
1655 MinOffset = (uint64_t)BaseOffset + MinOffset;
1656 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1657 (MaxOffset > 0))
1658 return false;
1659 MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1660
1661 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1662 HasBaseReg, Scale) &&
1663 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1664 HasBaseReg, Scale);
1665}
1666
1667static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1668 int64_t MinOffset, int64_t MaxOffset,
1669 LSRUse::KindType Kind, MemAccessTy AccessTy,
1670 const Formula &F, const Loop &L) {
1671 // For the purpose of isAMCompletelyFolded either having a canonical formula
1672 // or a scale not equal to zero is correct.
1673 // Problems may arise from non canonical formulae having a scale == 0.
1674 // Strictly speaking it would best to just rely on canonical formulae.
1675 // However, when we generate the scaled formulae, we first check that the
1676 // scaling factor is profitable before computing the actual ScaledReg for
1677 // compile time sake.
1678 assert((F.isCanonical(L) || F.Scale != 0))(static_cast <bool> ((F.isCanonical(L) || F.Scale != 0)
) ? void (0) : __assert_fail ("(F.isCanonical(L) || F.Scale != 0)"
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1678, __extension__ __PRETTY_FUNCTION__))
;
1679 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1680 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1681}
1682
1683/// Test whether we know how to expand the current formula.
1684static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1685 int64_t MaxOffset, LSRUse::KindType Kind,
1686 MemAccessTy AccessTy, GlobalValue *BaseGV,
1687 int64_t BaseOffset, bool HasBaseReg, int64_t Scale) {
1688 // We know how to expand completely foldable formulae.
1689 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1690 BaseOffset, HasBaseReg, Scale) ||
1691 // Or formulae that use a base register produced by a sum of base
1692 // registers.
1693 (Scale == 1 &&
1694 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1695 BaseGV, BaseOffset, true, 0));
1696}
1697
1698static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1699 int64_t MaxOffset, LSRUse::KindType Kind,
1700 MemAccessTy AccessTy, const Formula &F) {
1701 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1702 F.BaseOffset, F.HasBaseReg, F.Scale);
1703}
1704
1705static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1706 const LSRUse &LU, const Formula &F) {
1707 // Target may want to look at the user instructions.
1708 if (LU.Kind == LSRUse::Address && TTI.LSRWithInstrQueries()) {
1709 for (const LSRFixup &Fixup : LU.Fixups)
1710 if (!isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV,
1711 (F.BaseOffset + Fixup.Offset), F.HasBaseReg,
1712 F.Scale, Fixup.UserInst))
1713 return false;
1714 return true;
1715 }
1716
1717 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1718 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1719 F.Scale);
1720}
1721
1722static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1723 const LSRUse &LU, const Formula &F,
1724 const Loop &L) {
1725 if (!F.Scale)
1726 return 0;
1727
1728 // If the use is not completely folded in that instruction, we will have to
1729 // pay an extra cost only for scale != 1.
1730 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1731 LU.AccessTy, F, L))
1732 return F.Scale != 1;
1733
1734 switch (LU.Kind) {
1735 case LSRUse::Address: {
1736 // Check the scaling factor cost with both the min and max offsets.
1737 int ScaleCostMinOffset = TTI.getScalingFactorCost(
1738 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg,
1739 F.Scale, LU.AccessTy.AddrSpace);
1740 int ScaleCostMaxOffset = TTI.getScalingFactorCost(
1741 LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg,
1742 F.Scale, LU.AccessTy.AddrSpace);
1743
1744 assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&(static_cast <bool> (ScaleCostMinOffset >= 0 &&
ScaleCostMaxOffset >= 0 && "Legal addressing mode has an illegal cost!"
) ? void (0) : __assert_fail ("ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && \"Legal addressing mode has an illegal cost!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1745, __extension__ __PRETTY_FUNCTION__))
1745 "Legal addressing mode has an illegal cost!")(static_cast <bool> (ScaleCostMinOffset >= 0 &&
ScaleCostMaxOffset >= 0 && "Legal addressing mode has an illegal cost!"
) ? void (0) : __assert_fail ("ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && \"Legal addressing mode has an illegal cost!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1745, __extension__ __PRETTY_FUNCTION__))
;
1746 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1747 }
1748 case LSRUse::ICmpZero:
1749 case LSRUse::Basic:
1750 case LSRUse::Special:
1751 // The use is completely folded, i.e., everything is folded into the
1752 // instruction.
1753 return 0;
1754 }
1755
1756 llvm_unreachable("Invalid LSRUse Kind!")::llvm::llvm_unreachable_internal("Invalid LSRUse Kind!", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1756)
;
1757}
1758
1759static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1760 LSRUse::KindType Kind, MemAccessTy AccessTy,
1761 GlobalValue *BaseGV, int64_t BaseOffset,
1762 bool HasBaseReg) {
1763 // Fast-path: zero is always foldable.
1764 if (BaseOffset == 0 && !BaseGV) return true;
1765
1766 // Conservatively, create an address with an immediate and a
1767 // base and a scale.
1768 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1769
1770 // Canonicalize a scale of 1 to a base register if the formula doesn't
1771 // already have a base register.
1772 if (!HasBaseReg && Scale == 1) {
1773 Scale = 0;
1774 HasBaseReg = true;
1775 }
1776
1777 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1778 HasBaseReg, Scale);
1779}
1780
1781static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1782 ScalarEvolution &SE, int64_t MinOffset,
1783 int64_t MaxOffset, LSRUse::KindType Kind,
1784 MemAccessTy AccessTy, const SCEV *S,
1785 bool HasBaseReg) {
1786 // Fast-path: zero is always foldable.
1787 if (S->isZero()) return true;
1788
1789 // Conservatively, create an address with an immediate and a
1790 // base and a scale.
1791 int64_t BaseOffset = ExtractImmediate(S, SE);
1792 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1793
1794 // If there's anything else involved, it's not foldable.
1795 if (!S->isZero()) return false;
1796
1797 // Fast-path: zero is always foldable.
1798 if (BaseOffset == 0 && !BaseGV) return true;
1799
1800 // Conservatively, create an address with an immediate and a
1801 // base and a scale.
1802 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1803
1804 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1805 BaseOffset, HasBaseReg, Scale);
1806}
1807
1808namespace {
1809
1810/// An individual increment in a Chain of IV increments. Relate an IV user to
1811/// an expression that computes the IV it uses from the IV used by the previous
1812/// link in the Chain.
1813///
1814/// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1815/// original IVOperand. The head of the chain's IVOperand is only valid during
1816/// chain collection, before LSR replaces IV users. During chain generation,
1817/// IncExpr can be used to find the new IVOperand that computes the same
1818/// expression.
1819struct IVInc {
1820 Instruction *UserInst;
1821 Value* IVOperand;
1822 const SCEV *IncExpr;
1823
1824 IVInc(Instruction *U, Value *O, const SCEV *E)
1825 : UserInst(U), IVOperand(O), IncExpr(E) {}
1826};
1827
1828// The list of IV increments in program order. We typically add the head of a
1829// chain without finding subsequent links.
1830struct IVChain {
1831 SmallVector<IVInc, 1> Incs;
1832 const SCEV *ExprBase = nullptr;
1833
1834 IVChain() = default;
1835 IVChain(const IVInc &Head, const SCEV *Base)
1836 : Incs(1, Head), ExprBase(Base) {}
1837
1838 using const_iterator = SmallVectorImpl<IVInc>::const_iterator;
1839
1840 // Return the first increment in the chain.
1841 const_iterator begin() const {
1842 assert(!Incs.empty())(static_cast <bool> (!Incs.empty()) ? void (0) : __assert_fail
("!Incs.empty()", "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 1842, __extension__ __PRETTY_FUNCTION__))
;
1843 return std::next(Incs.begin());
1844 }
1845 const_iterator end() const {
1846 return Incs.end();
1847 }
1848
1849 // Returns true if this chain contains any increments.
1850 bool hasIncs() const { return Incs.size() >= 2; }
1851
1852 // Add an IVInc to the end of this chain.
1853 void add(const IVInc &X) { Incs.push_back(X); }
1854
1855 // Returns the last UserInst in the chain.
1856 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1857
1858 // Returns true if IncExpr can be profitably added to this chain.
1859 bool isProfitableIncrement(const SCEV *OperExpr,
1860 const SCEV *IncExpr,
1861 ScalarEvolution&);
1862};
1863
1864/// Helper for CollectChains to track multiple IV increment uses. Distinguish
1865/// between FarUsers that definitely cross IV increments and NearUsers that may
1866/// be used between IV increments.
1867struct ChainUsers {
1868 SmallPtrSet<Instruction*, 4> FarUsers;
1869 SmallPtrSet<Instruction*, 4> NearUsers;
1870};
1871
1872/// This class holds state for the main loop strength reduction logic.
1873class LSRInstance {
1874 IVUsers &IU;
1875 ScalarEvolution &SE;
1876 DominatorTree &DT;
1877 LoopInfo &LI;
1878 const TargetTransformInfo &TTI;
1879 Loop *const L;
1880 bool Changed = false;
1881
1882 /// This is the insert position that the current loop's induction variable
1883 /// increment should be placed. In simple loops, this is the latch block's
1884 /// terminator. But in more complicated cases, this is a position which will
1885 /// dominate all the in-loop post-increment users.
1886 Instruction *IVIncInsertPos = nullptr;
1887
1888 /// Interesting factors between use strides.
1889 ///
1890 /// We explicitly use a SetVector which contains a SmallSet, instead of the
1891 /// default, a SmallDenseSet, because we need to use the full range of
1892 /// int64_ts, and there's currently no good way of doing that with
1893 /// SmallDenseSet.
1894 SetVector<int64_t, SmallVector<int64_t, 8>, SmallSet<int64_t, 8>> Factors;
1895
1896 /// Interesting use types, to facilitate truncation reuse.
1897 SmallSetVector<Type *, 4> Types;
1898
1899 /// The list of interesting uses.
1900 SmallVector<LSRUse, 16> Uses;
1901
1902 /// Track which uses use which register candidates.
1903 RegUseTracker RegUses;
1904
1905 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1906 // have more than a few IV increment chains in a loop. Missing a Chain falls
1907 // back to normal LSR behavior for those uses.
1908 static const unsigned MaxChains = 8;
1909
1910 /// IV users can form a chain of IV increments.
1911 SmallVector<IVChain, MaxChains> IVChainVec;
1912
1913 /// IV users that belong to profitable IVChains.
1914 SmallPtrSet<Use*, MaxChains> IVIncSet;
1915
1916 void OptimizeShadowIV();
1917 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1918 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1919 void OptimizeLoopTermCond();
1920
1921 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1922 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1923 void FinalizeChain(IVChain &Chain);
1924 void CollectChains();
1925 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1926 SmallVectorImpl<WeakTrackingVH> &DeadInsts);
1927
1928 void CollectInterestingTypesAndFactors();
1929 void CollectFixupsAndInitialFormulae();
1930
1931 // Support for sharing of LSRUses between LSRFixups.
1932 using UseMapTy = DenseMap<LSRUse::SCEVUseKindPair, size_t>;
1933 UseMapTy UseMap;
1934
1935 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1936 LSRUse::KindType Kind, MemAccessTy AccessTy);
1937
1938 std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind,
1939 MemAccessTy AccessTy);
1940
1941 void DeleteUse(LSRUse &LU, size_t LUIdx);
1942
1943 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1944
1945 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1946 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1947 void CountRegisters(const Formula &F, size_t LUIdx);
1948 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1949
1950 void CollectLoopInvariantFixupsAndFormulae();
1951
1952 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1953 unsigned Depth = 0);
1954
1955 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1956 const Formula &Base, unsigned Depth,
1957 size_t Idx, bool IsScaledReg = false);
1958 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1959 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1960 const Formula &Base, size_t Idx,
1961 bool IsScaledReg = false);
1962 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1963 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1964 const Formula &Base,
1965 const SmallVectorImpl<int64_t> &Worklist,
1966 size_t Idx, bool IsScaledReg = false);
1967 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1968 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1969 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1970 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1971 void GenerateCrossUseConstantOffsets();
1972 void GenerateAllReuseFormulae();
1973
1974 void FilterOutUndesirableDedicatedRegisters();
1975
1976 size_t EstimateSearchSpaceComplexity() const;
1977 void NarrowSearchSpaceByDetectingSupersets();
1978 void NarrowSearchSpaceByCollapsingUnrolledCode();
1979 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1980 void NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
1981 void NarrowSearchSpaceByDeletingCostlyFormulas();
1982 void NarrowSearchSpaceByPickingWinnerRegs();
1983 void NarrowSearchSpaceUsingHeuristics();
1984
1985 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1986 Cost &SolutionCost,
1987 SmallVectorImpl<const Formula *> &Workspace,
1988 const Cost &CurCost,
1989 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1990 DenseSet<const SCEV *> &VisitedRegs) const;
1991 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1992
1993 BasicBlock::iterator
1994 HoistInsertPosition(BasicBlock::iterator IP,
1995 const SmallVectorImpl<Instruction *> &Inputs) const;
1996 BasicBlock::iterator
1997 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1998 const LSRFixup &LF,
1999 const LSRUse &LU,
2000 SCEVExpander &Rewriter) const;
2001
2002 Value *Expand(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2003 BasicBlock::iterator IP, SCEVExpander &Rewriter,
2004 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2005 void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF,
2006 const Formula &F, SCEVExpander &Rewriter,
2007 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2008 void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F,
2009 SCEVExpander &Rewriter,
2010 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const;
2011 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution);
2012
2013public:
2014 LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT,
2015 LoopInfo &LI, const TargetTransformInfo &TTI);
2016
2017 bool getChanged() const { return Changed; }
2018
2019 void print_factors_and_types(raw_ostream &OS) const;
2020 void print_fixups(raw_ostream &OS) const;
2021 void print_uses(raw_ostream &OS) const;
2022 void print(raw_ostream &OS) const;
2023 void dump() const;
2024};
2025
2026} // end anonymous namespace
2027
2028/// If IV is used in a int-to-float cast inside the loop then try to eliminate
2029/// the cast operation.
2030void LSRInstance::OptimizeShadowIV() {
2031 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2032 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2033 return;
2034
2035 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
2036 UI != E; /* empty */) {
2037 IVUsers::const_iterator CandidateUI = UI;
2038 ++UI;
2039 Instruction *ShadowUse = CandidateUI->getUser();
2040 Type *DestTy = nullptr;
2041 bool IsSigned = false;
2042
2043 /* If shadow use is a int->float cast then insert a second IV
2044 to eliminate this cast.
2045
2046 for (unsigned i = 0; i < n; ++i)
2047 foo((double)i);
2048
2049 is transformed into
2050
2051 double d = 0.0;
2052 for (unsigned i = 0; i < n; ++i, ++d)
2053 foo(d);
2054 */
2055 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
2056 IsSigned = false;
2057 DestTy = UCast->getDestTy();
2058 }
2059 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
2060 IsSigned = true;
2061 DestTy = SCast->getDestTy();
2062 }
2063 if (!DestTy) continue;
2064
2065 // If target does not support DestTy natively then do not apply
2066 // this transformation.
2067 if (!TTI.isTypeLegal(DestTy)) continue;
2068
2069 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
2070 if (!PH) continue;
2071 if (PH->getNumIncomingValues() != 2) continue;
2072
2073 // If the calculation in integers overflows, the result in FP type will
2074 // differ. So we only can do this transformation if we are guaranteed to not
2075 // deal with overflowing values
2076 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PH));
2077 if (!AR) continue;
2078 if (IsSigned && !AR->hasNoSignedWrap()) continue;
2079 if (!IsSigned && !AR->hasNoUnsignedWrap()) continue;
2080
2081 Type *SrcTy = PH->getType();
2082 int Mantissa = DestTy->getFPMantissaWidth();
2083 if (Mantissa == -1) continue;
2084 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
2085 continue;
2086
2087 unsigned Entry, Latch;
2088 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
2089 Entry = 0;
2090 Latch = 1;
2091 } else {
2092 Entry = 1;
2093 Latch = 0;
2094 }
2095
2096 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
2097 if (!Init) continue;
2098 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
2099 (double)Init->getSExtValue() :
2100 (double)Init->getZExtValue());
2101
2102 BinaryOperator *Incr =
2103 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
2104 if (!Incr) continue;
2105 if (Incr->getOpcode() != Instruction::Add
2106 && Incr->getOpcode() != Instruction::Sub)
2107 continue;
2108
2109 /* Initialize new IV, double d = 0.0 in above example. */
2110 ConstantInt *C = nullptr;
2111 if (Incr->getOperand(0) == PH)
2112 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
2113 else if (Incr->getOperand(1) == PH)
2114 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
2115 else
2116 continue;
2117
2118 if (!C) continue;
2119
2120 // Ignore negative constants, as the code below doesn't handle them
2121 // correctly. TODO: Remove this restriction.
2122 if (!C->getValue().isStrictlyPositive()) continue;
2123
2124 /* Add new PHINode. */
2125 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
2126
2127 /* create new increment. '++d' in above example. */
2128 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
2129 BinaryOperator *NewIncr =
2130 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
2131 Instruction::FAdd : Instruction::FSub,
2132 NewPH, CFP, "IV.S.next.", Incr);
2133
2134 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
2135 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
2136
2137 /* Remove cast operation */
2138 ShadowUse->replaceAllUsesWith(NewPH);
2139 ShadowUse->eraseFromParent();
2140 Changed = true;
2141 break;
2142 }
2143}
2144
2145/// If Cond has an operand that is an expression of an IV, set the IV user and
2146/// stride information and return true, otherwise return false.
2147bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
2148 for (IVStrideUse &U : IU)
2149 if (U.getUser() == Cond) {
2150 // NOTE: we could handle setcc instructions with multiple uses here, but
2151 // InstCombine does it as well for simple uses, it's not clear that it
2152 // occurs enough in real life to handle.
2153 CondUse = &U;
2154 return true;
2155 }
2156 return false;
2157}
2158
2159/// Rewrite the loop's terminating condition if it uses a max computation.
2160///
2161/// This is a narrow solution to a specific, but acute, problem. For loops
2162/// like this:
2163///
2164/// i = 0;
2165/// do {
2166/// p[i] = 0.0;
2167/// } while (++i < n);
2168///
2169/// the trip count isn't just 'n', because 'n' might not be positive. And
2170/// unfortunately this can come up even for loops where the user didn't use
2171/// a C do-while loop. For example, seemingly well-behaved top-test loops
2172/// will commonly be lowered like this:
2173///
2174/// if (n > 0) {
2175/// i = 0;
2176/// do {
2177/// p[i] = 0.0;
2178/// } while (++i < n);
2179/// }
2180///
2181/// and then it's possible for subsequent optimization to obscure the if
2182/// test in such a way that indvars can't find it.
2183///
2184/// When indvars can't find the if test in loops like this, it creates a
2185/// max expression, which allows it to give the loop a canonical
2186/// induction variable:
2187///
2188/// i = 0;
2189/// max = n < 1 ? 1 : n;
2190/// do {
2191/// p[i] = 0.0;
2192/// } while (++i != max);
2193///
2194/// Canonical induction variables are necessary because the loop passes
2195/// are designed around them. The most obvious example of this is the
2196/// LoopInfo analysis, which doesn't remember trip count values. It
2197/// expects to be able to rediscover the trip count each time it is
2198/// needed, and it does this using a simple analysis that only succeeds if
2199/// the loop has a canonical induction variable.
2200///
2201/// However, when it comes time to generate code, the maximum operation
2202/// can be quite costly, especially if it's inside of an outer loop.
2203///
2204/// This function solves this problem by detecting this type of loop and
2205/// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
2206/// the instructions for the maximum computation.
2207ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
2208 // Check that the loop matches the pattern we're looking for.
2209 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
2210 Cond->getPredicate() != CmpInst::ICMP_NE)
2211 return Cond;
2212
2213 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
2214 if (!Sel || !Sel->hasOneUse()) return Cond;
2215
2216 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2217 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2218 return Cond;
2219 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2220
2221 // Add one to the backedge-taken count to get the trip count.
2222 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2223 if (IterationCount != SE.getSCEV(Sel)) return Cond;
2224
2225 // Check for a max calculation that matches the pattern. There's no check
2226 // for ICMP_ULE here because the comparison would be with zero, which
2227 // isn't interesting.
2228 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2229 const SCEVNAryExpr *Max = nullptr;
2230 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2231 Pred = ICmpInst::ICMP_SLE;
2232 Max = S;
2233 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2234 Pred = ICmpInst::ICMP_SLT;
2235 Max = S;
2236 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2237 Pred = ICmpInst::ICMP_ULT;
2238 Max = U;
2239 } else {
2240 // No match; bail.
2241 return Cond;
2242 }
2243
2244 // To handle a max with more than two operands, this optimization would
2245 // require additional checking and setup.
2246 if (Max->getNumOperands() != 2)
2247 return Cond;
2248
2249 const SCEV *MaxLHS = Max->getOperand(0);
2250 const SCEV *MaxRHS = Max->getOperand(1);
2251
2252 // ScalarEvolution canonicalizes constants to the left. For < and >, look
2253 // for a comparison with 1. For <= and >=, a comparison with zero.
2254 if (!MaxLHS ||
2255 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2256 return Cond;
2257
2258 // Check the relevant induction variable for conformance to
2259 // the pattern.
2260 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2261 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2262 if (!AR || !AR->isAffine() ||
2263 AR->getStart() != One ||
2264 AR->getStepRecurrence(SE) != One)
2265 return Cond;
2266
2267 assert(AR->getLoop() == L &&(static_cast <bool> (AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? void (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2268, __extension__ __PRETTY_FUNCTION__))
2268 "Loop condition operand is an addrec in a different loop!")(static_cast <bool> (AR->getLoop() == L && "Loop condition operand is an addrec in a different loop!"
) ? void (0) : __assert_fail ("AR->getLoop() == L && \"Loop condition operand is an addrec in a different loop!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2268, __extension__ __PRETTY_FUNCTION__))
;
2269
2270 // Check the right operand of the select, and remember it, as it will
2271 // be used in the new comparison instruction.
2272 Value *NewRHS = nullptr;
2273 if (ICmpInst::isTrueWhenEqual(Pred)) {
2274 // Look for n+1, and grab n.
2275 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2276 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2277 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2278 NewRHS = BO->getOperand(0);
2279 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2280 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2281 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2282 NewRHS = BO->getOperand(0);
2283 if (!NewRHS)
2284 return Cond;
2285 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2286 NewRHS = Sel->getOperand(1);
2287 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2288 NewRHS = Sel->getOperand(2);
2289 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2290 NewRHS = SU->getValue();
2291 else
2292 // Max doesn't match expected pattern.
2293 return Cond;
2294
2295 // Determine the new comparison opcode. It may be signed or unsigned,
2296 // and the original comparison may be either equality or inequality.
2297 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2298 Pred = CmpInst::getInversePredicate(Pred);
2299
2300 // Ok, everything looks ok to change the condition into an SLT or SGE and
2301 // delete the max calculation.
2302 ICmpInst *NewCond =
2303 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2304
2305 // Delete the max calculation instructions.
2306 Cond->replaceAllUsesWith(NewCond);
2307 CondUse->setUser(NewCond);
2308 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2309 Cond->eraseFromParent();
2310 Sel->eraseFromParent();
2311 if (Cmp->use_empty())
2312 Cmp->eraseFromParent();
2313 return NewCond;
2314}
2315
2316/// Change loop terminating condition to use the postinc iv when possible.
2317void
2318LSRInstance::OptimizeLoopTermCond() {
2319 SmallPtrSet<Instruction *, 4> PostIncs;
2320
2321 // We need a different set of heuristics for rotated and non-rotated loops.
2322 // If a loop is rotated then the latch is also the backedge, so inserting
2323 // post-inc expressions just before the latch is ideal. To reduce live ranges
2324 // it also makes sense to rewrite terminating conditions to use post-inc
2325 // expressions.
2326 //
2327 // If the loop is not rotated then the latch is not a backedge; the latch
2328 // check is done in the loop head. Adding post-inc expressions before the
2329 // latch will cause overlapping live-ranges of pre-inc and post-inc expressions
2330 // in the loop body. In this case we do *not* want to use post-inc expressions
2331 // in the latch check, and we want to insert post-inc expressions before
2332 // the backedge.
2333 BasicBlock *LatchBlock = L->getLoopLatch();
2334 SmallVector<BasicBlock*, 8> ExitingBlocks;
2335 L->getExitingBlocks(ExitingBlocks);
2336 if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) {
2337 return LatchBlock != BB;
2338 })) {
2339 // The backedge doesn't exit the loop; treat this as a head-tested loop.
2340 IVIncInsertPos = LatchBlock->getTerminator();
2341 return;
2342 }
2343
2344 // Otherwise treat this as a rotated loop.
2345 for (BasicBlock *ExitingBlock : ExitingBlocks) {
2346 // Get the terminating condition for the loop if possible. If we
2347 // can, we want to change it to use a post-incremented version of its
2348 // induction variable, to allow coalescing the live ranges for the IV into
2349 // one register value.
2350
2351 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2352 if (!TermBr)
2353 continue;
2354 // FIXME: Overly conservative, termination condition could be an 'or' etc..
2355 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2356 continue;
2357
2358 // Search IVUsesByStride to find Cond's IVUse if there is one.
2359 IVStrideUse *CondUse = nullptr;
2360 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2361 if (!FindIVUserForCond(Cond, CondUse))
2362 continue;
2363
2364 // If the trip count is computed in terms of a max (due to ScalarEvolution
2365 // being unable to find a sufficient guard, for example), change the loop
2366 // comparison to use SLT or ULT instead of NE.
2367 // One consequence of doing this now is that it disrupts the count-down
2368 // optimization. That's not always a bad thing though, because in such
2369 // cases it may still be worthwhile to avoid a max.
2370 Cond = OptimizeMax(Cond, CondUse);
2371
2372 // If this exiting block dominates the latch block, it may also use
2373 // the post-inc value if it won't be shared with other uses.
2374 // Check for dominance.
2375 if (!DT.dominates(ExitingBlock, LatchBlock))
2376 continue;
2377
2378 // Conservatively avoid trying to use the post-inc value in non-latch
2379 // exits if there may be pre-inc users in intervening blocks.
2380 if (LatchBlock != ExitingBlock)
2381 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2382 // Test if the use is reachable from the exiting block. This dominator
2383 // query is a conservative approximation of reachability.
2384 if (&*UI != CondUse &&
2385 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2386 // Conservatively assume there may be reuse if the quotient of their
2387 // strides could be a legal scale.
2388 const SCEV *A = IU.getStride(*CondUse, L);
2389 const SCEV *B = IU.getStride(*UI, L);
2390 if (!A || !B) continue;
2391 if (SE.getTypeSizeInBits(A->getType()) !=
2392 SE.getTypeSizeInBits(B->getType())) {
2393 if (SE.getTypeSizeInBits(A->getType()) >
2394 SE.getTypeSizeInBits(B->getType()))
2395 B = SE.getSignExtendExpr(B, A->getType());
2396 else
2397 A = SE.getSignExtendExpr(A, B->getType());
2398 }
2399 if (const SCEVConstant *D =
2400 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2401 const ConstantInt *C = D->getValue();
2402 // Stride of one or negative one can have reuse with non-addresses.
2403 if (C->isOne() || C->isMinusOne())
2404 goto decline_post_inc;
2405 // Avoid weird situations.
2406 if (C->getValue().getMinSignedBits() >= 64 ||
2407 C->getValue().isMinSignedValue())
2408 goto decline_post_inc;
2409 // Check for possible scaled-address reuse.
2410 MemAccessTy AccessTy = getAccessType(TTI, UI->getUser());
2411 int64_t Scale = C->getSExtValue();
2412 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2413 /*BaseOffset=*/0,
2414 /*HasBaseReg=*/false, Scale,
2415 AccessTy.AddrSpace))
2416 goto decline_post_inc;
2417 Scale = -Scale;
2418 if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr,
2419 /*BaseOffset=*/0,
2420 /*HasBaseReg=*/false, Scale,
2421 AccessTy.AddrSpace))
2422 goto decline_post_inc;
2423 }
2424 }
2425
2426 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)
2427 << *Cond << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Change loop exiting icmp to use postinc iv: "
<< *Cond << '\n'; } } while (false)
;
2428
2429 // It's possible for the setcc instruction to be anywhere in the loop, and
2430 // possible for it to have multiple users. If it is not immediately before
2431 // the exiting block branch, move it.
2432 if (&*++BasicBlock::iterator(Cond) != TermBr) {
2433 if (Cond->hasOneUse()) {
2434 Cond->moveBefore(TermBr);
2435 } else {
2436 // Clone the terminating condition and insert into the loopend.
2437 ICmpInst *OldCond = Cond;
2438 Cond = cast<ICmpInst>(Cond->clone());
2439 Cond->setName(L->getHeader()->getName() + ".termcond");
2440 ExitingBlock->getInstList().insert(TermBr->getIterator(), Cond);
2441
2442 // Clone the IVUse, as the old use still exists!
2443 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2444 TermBr->replaceUsesOfWith(OldCond, Cond);
2445 }
2446 }
2447
2448 // If we get to here, we know that we can transform the setcc instruction to
2449 // use the post-incremented version of the IV, allowing us to coalesce the
2450 // live ranges for the IV correctly.
2451 CondUse->transformToPostInc(L);
2452 Changed = true;
2453
2454 PostIncs.insert(Cond);
2455 decline_post_inc:;
2456 }
2457
2458 // Determine an insertion point for the loop induction variable increment. It
2459 // must dominate all the post-inc comparisons we just set up, and it must
2460 // dominate the loop latch edge.
2461 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2462 for (Instruction *Inst : PostIncs) {
2463 BasicBlock *BB =
2464 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2465 Inst->getParent());
2466 if (BB == Inst->getParent())
2467 IVIncInsertPos = Inst;
2468 else if (BB != IVIncInsertPos->getParent())
2469 IVIncInsertPos = BB->getTerminator();
2470 }
2471}
2472
2473/// Determine if the given use can accommodate a fixup at the given offset and
2474/// other details. If so, update the use and return true.
2475bool LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
2476 bool HasBaseReg, LSRUse::KindType Kind,
2477 MemAccessTy AccessTy) {
2478 int64_t NewMinOffset = LU.MinOffset;
2479 int64_t NewMaxOffset = LU.MaxOffset;
2480 MemAccessTy NewAccessTy = AccessTy;
2481
2482 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2483 // something conservative, however this can pessimize in the case that one of
2484 // the uses will have all its uses outside the loop, for example.
2485 if (LU.Kind != Kind)
2486 return false;
2487
2488 // Check for a mismatched access type, and fall back conservatively as needed.
2489 // TODO: Be less conservative when the type is similar and can use the same
2490 // addressing modes.
2491 if (Kind == LSRUse::Address) {
2492 if (AccessTy.MemTy != LU.AccessTy.MemTy) {
2493 NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(),
2494 AccessTy.AddrSpace);
2495 }
2496 }
2497
2498 // Conservatively assume HasBaseReg is true for now.
2499 if (NewOffset < LU.MinOffset) {
2500 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2501 LU.MaxOffset - NewOffset, HasBaseReg))
2502 return false;
2503 NewMinOffset = NewOffset;
2504 } else if (NewOffset > LU.MaxOffset) {
2505 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2506 NewOffset - LU.MinOffset, HasBaseReg))
2507 return false;
2508 NewMaxOffset = NewOffset;
2509 }
2510
2511 // Update the use.
2512 LU.MinOffset = NewMinOffset;
2513 LU.MaxOffset = NewMaxOffset;
2514 LU.AccessTy = NewAccessTy;
2515 return true;
2516}
2517
2518/// Return an LSRUse index and an offset value for a fixup which needs the given
2519/// expression, with the given kind and optional access type. Either reuse an
2520/// existing use or create a new one, as needed.
2521std::pair<size_t, int64_t> LSRInstance::getUse(const SCEV *&Expr,
2522 LSRUse::KindType Kind,
2523 MemAccessTy AccessTy) {
2524 const SCEV *Copy = Expr;
2525 int64_t Offset = ExtractImmediate(Expr, SE);
2526
2527 // Basic uses can't accept any offset, for example.
2528 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2529 Offset, /*HasBaseReg=*/ true)) {
2530 Expr = Copy;
2531 Offset = 0;
2532 }
2533
2534 std::pair<UseMapTy::iterator, bool> P =
2535 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2536 if (!P.second) {
2537 // A use already existed with this base.
2538 size_t LUIdx = P.first->second;
2539 LSRUse &LU = Uses[LUIdx];
2540 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2541 // Reuse this use.
2542 return std::make_pair(LUIdx, Offset);
2543 }
2544
2545 // Create a new use.
2546 size_t LUIdx = Uses.size();
2547 P.first->second = LUIdx;
2548 Uses.push_back(LSRUse(Kind, AccessTy));
2549 LSRUse &LU = Uses[LUIdx];
2550
2551 LU.MinOffset = Offset;
2552 LU.MaxOffset = Offset;
2553 return std::make_pair(LUIdx, Offset);
2554}
2555
2556/// Delete the given use from the Uses list.
2557void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2558 if (&LU != &Uses.back())
2559 std::swap(LU, Uses.back());
2560 Uses.pop_back();
2561
2562 // Update RegUses.
2563 RegUses.swapAndDropUse(LUIdx, Uses.size());
2564}
2565
2566/// Look for a use distinct from OrigLU which is has a formula that has the same
2567/// registers as the given formula.
2568LSRUse *
2569LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2570 const LSRUse &OrigLU) {
2571 // Search all uses for the formula. This could be more clever.
2572 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2573 LSRUse &LU = Uses[LUIdx];
2574 // Check whether this use is close enough to OrigLU, to see whether it's
2575 // worthwhile looking through its formulae.
2576 // Ignore ICmpZero uses because they may contain formulae generated by
2577 // GenerateICmpZeroScales, in which case adding fixup offsets may
2578 // be invalid.
2579 if (&LU != &OrigLU &&
2580 LU.Kind != LSRUse::ICmpZero &&
2581 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2582 LU.WidestFixupType == OrigLU.WidestFixupType &&
2583 LU.HasFormulaWithSameRegs(OrigF)) {
2584 // Scan through this use's formulae.
2585 for (const Formula &F : LU.Formulae) {
2586 // Check to see if this formula has the same registers and symbols
2587 // as OrigF.
2588 if (F.BaseRegs == OrigF.BaseRegs &&
2589 F.ScaledReg == OrigF.ScaledReg &&
2590 F.BaseGV == OrigF.BaseGV &&
2591 F.Scale == OrigF.Scale &&
2592 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2593 if (F.BaseOffset == 0)
2594 return &LU;
2595 // This is the formula where all the registers and symbols matched;
2596 // there aren't going to be any others. Since we declined it, we
2597 // can skip the rest of the formulae and proceed to the next LSRUse.
2598 break;
2599 }
2600 }
2601 }
2602 }
2603
2604 // Nothing looked good.
2605 return nullptr;
2606}
2607
2608void LSRInstance::CollectInterestingTypesAndFactors() {
2609 SmallSetVector<const SCEV *, 4> Strides;
2610
2611 // Collect interesting types and strides.
2612 SmallVector<const SCEV *, 4> Worklist;
2613 for (const IVStrideUse &U : IU) {
2614 const SCEV *Expr = IU.getExpr(U);
2615
2616 // Collect interesting types.
2617 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2618
2619 // Add strides for mentioned loops.
2620 Worklist.push_back(Expr);
2621 do {
2622 const SCEV *S = Worklist.pop_back_val();
2623 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2624 if (AR->getLoop() == L)
2625 Strides.insert(AR->getStepRecurrence(SE));
2626 Worklist.push_back(AR->getStart());
2627 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2628 Worklist.append(Add->op_begin(), Add->op_end());
2629 }
2630 } while (!Worklist.empty());
2631 }
2632
2633 // Compute interesting factors from the set of interesting strides.
2634 for (SmallSetVector<const SCEV *, 4>::const_iterator
2635 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2636 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2637 std::next(I); NewStrideIter != E; ++NewStrideIter) {
2638 const SCEV *OldStride = *I;
2639 const SCEV *NewStride = *NewStrideIter;
2640
2641 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2642 SE.getTypeSizeInBits(NewStride->getType())) {
2643 if (SE.getTypeSizeInBits(OldStride->getType()) >
2644 SE.getTypeSizeInBits(NewStride->getType()))
2645 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2646 else
2647 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2648 }
2649 if (const SCEVConstant *Factor =
2650 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2651 SE, true))) {
2652 if (Factor->getAPInt().getMinSignedBits() <= 64)
2653 Factors.insert(Factor->getAPInt().getSExtValue());
2654 } else if (const SCEVConstant *Factor =
2655 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2656 NewStride,
2657 SE, true))) {
2658 if (Factor->getAPInt().getMinSignedBits() <= 64)
2659 Factors.insert(Factor->getAPInt().getSExtValue());
2660 }
2661 }
2662
2663 // If all uses use the same type, don't bother looking for truncation-based
2664 // reuse.
2665 if (Types.size() == 1)
2666 Types.clear();
2667
2668 DEBUG(print_factors_and_types(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_factors_and_types(dbgs()); } } while
(false)
;
2669}
2670
2671/// Helper for CollectChains that finds an IV operand (computed by an AddRec in
2672/// this loop) within [OI,OE) or returns OE. If IVUsers mapped Instructions to
2673/// IVStrideUses, we could partially skip this.
2674static User::op_iterator
2675findIVOperand(User::op_iterator OI, User::op_iterator OE,
2676 Loop *L, ScalarEvolution &SE) {
2677 for(; OI != OE; ++OI) {
2678 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2679 if (!SE.isSCEVable(Oper->getType()))
2680 continue;
2681
2682 if (const SCEVAddRecExpr *AR =
2683 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2684 if (AR->getLoop() == L)
2685 break;
2686 }
2687 }
2688 }
2689 return OI;
2690}
2691
2692/// IVChain logic must consistenctly peek base TruncInst operands, so wrap it in
2693/// a convenient helper.
2694static Value *getWideOperand(Value *Oper) {
2695 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2696 return Trunc->getOperand(0);
2697 return Oper;
2698}
2699
2700/// Return true if we allow an IV chain to include both types.
2701static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2702 Type *LType = LVal->getType();
2703 Type *RType = RVal->getType();
2704 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy() &&
2705 // Different address spaces means (possibly)
2706 // different types of the pointer implementation,
2707 // e.g. i16 vs i32 so disallow that.
2708 (LType->getPointerAddressSpace() ==
2709 RType->getPointerAddressSpace()));
2710}
2711
2712/// Return an approximation of this SCEV expression's "base", or NULL for any
2713/// constant. Returning the expression itself is conservative. Returning a
2714/// deeper subexpression is more precise and valid as long as it isn't less
2715/// complex than another subexpression. For expressions involving multiple
2716/// unscaled values, we need to return the pointer-type SCEVUnknown. This avoids
2717/// forming chains across objects, such as: PrevOper==a[i], IVOper==b[i],
2718/// IVInc==b-a.
2719///
2720/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2721/// SCEVUnknown, we simply return the rightmost SCEV operand.
2722static const SCEV *getExprBase(const SCEV *S) {
2723 switch (S->getSCEVType()) {
2724 default: // uncluding scUnknown.
2725 return S;
2726 case scConstant:
2727 return nullptr;
2728 case scTruncate:
2729 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2730 case scZeroExtend:
2731 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2732 case scSignExtend:
2733 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2734 case scAddExpr: {
2735 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2736 // there's nothing more complex.
2737 // FIXME: not sure if we want to recognize negation.
2738 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2739 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2740 E(Add->op_begin()); I != E; ++I) {
2741 const SCEV *SubExpr = *I;
2742 if (SubExpr->getSCEVType() == scAddExpr)
2743 return getExprBase(SubExpr);
2744
2745 if (SubExpr->getSCEVType() != scMulExpr)
2746 return SubExpr;
2747 }
2748 return S; // all operands are scaled, be conservative.
2749 }
2750 case scAddRecExpr:
2751 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2752 }
2753}
2754
2755/// Return true if the chain increment is profitable to expand into a loop
2756/// invariant value, which may require its own register. A profitable chain
2757/// increment will be an offset relative to the same base. We allow such offsets
2758/// to potentially be used as chain increment as long as it's not obviously
2759/// expensive to expand using real instructions.
2760bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2761 const SCEV *IncExpr,
2762 ScalarEvolution &SE) {
2763 // Aggressively form chains when -stress-ivchain.
2764 if (StressIVChain)
2765 return true;
2766
2767 // Do not replace a constant offset from IV head with a nonconstant IV
2768 // increment.
2769 if (!isa<SCEVConstant>(IncExpr)) {
2770 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2771 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2772 return false;
2773 }
2774
2775 SmallPtrSet<const SCEV*, 8> Processed;
2776 return !isHighCostExpansion(IncExpr, Processed, SE);
2777}
2778
2779/// Return true if the number of registers needed for the chain is estimated to
2780/// be less than the number required for the individual IV users. First prohibit
2781/// any IV users that keep the IV live across increments (the Users set should
2782/// be empty). Next count the number and type of increments in the chain.
2783///
2784/// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2785/// effectively use postinc addressing modes. Only consider it profitable it the
2786/// increments can be computed in fewer registers when chained.
2787///
2788/// TODO: Consider IVInc free if it's already used in another chains.
2789static bool
2790isProfitableChain(IVChain &Chain, SmallPtrSetImpl<Instruction*> &Users,
2791 ScalarEvolution &SE, const TargetTransformInfo &TTI) {
2792 if (StressIVChain)
2793 return true;
2794
2795 if (!Chain.hasIncs())
2796 return false;
2797
2798 if (!Users.empty()) {
2799 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)
2800 for (Instruction *Inst : Users) {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)
2801 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)
2802 })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)
;
2803 return false;
2804 }
2805 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")(static_cast <bool> (!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? void (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 2805, __extension__ __PRETTY_FUNCTION__))
;
2806
2807 // The chain itself may require a register, so intialize cost to 1.
2808 int cost = 1;
2809
2810 // A complete chain likely eliminates the need for keeping the original IV in
2811 // a register. LSR does not currently know how to form a complete chain unless
2812 // the header phi already exists.
2813 if (isa<PHINode>(Chain.tailUserInst())
2814 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2815 --cost;
2816 }
2817 const SCEV *LastIncExpr = nullptr;
2818 unsigned NumConstIncrements = 0;
2819 unsigned NumVarIncrements = 0;
2820 unsigned NumReusedIncrements = 0;
2821 for (const IVInc &Inc : Chain) {
2822 if (Inc.IncExpr->isZero())
2823 continue;
2824
2825 // Incrementing by zero or some constant is neutral. We assume constants can
2826 // be folded into an addressing mode or an add's immediate operand.
2827 if (isa<SCEVConstant>(Inc.IncExpr)) {
2828 ++NumConstIncrements;
2829 continue;
2830 }
2831
2832 if (Inc.IncExpr == LastIncExpr)
2833 ++NumReusedIncrements;
2834 else
2835 ++NumVarIncrements;
2836
2837 LastIncExpr = Inc.IncExpr;
2838 }
2839 // An IV chain with a single increment is handled by LSR's postinc
2840 // uses. However, a chain with multiple increments requires keeping the IV's
2841 // value live longer than it needs to be if chained.
2842 if (NumConstIncrements > 1)
2843 --cost;
2844
2845 // Materializing increment expressions in the preheader that didn't exist in
2846 // the original code may cost a register. For example, sign-extended array
2847 // indices can produce ridiculous increments like this:
2848 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2849 cost += NumVarIncrements;
2850
2851 // Reusing variable increments likely saves a register to hold the multiple of
2852 // the stride.
2853 cost -= NumReusedIncrements;
2854
2855 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)
2856 << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Chain: " << *Chain.
Incs[0].UserInst << " Cost: " << cost << "\n"
; } } while (false)
;
2857
2858 return cost < 0;
2859}
2860
2861/// Add this IV user to an existing chain or make it the head of a new chain.
2862void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2863 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2864 // When IVs are used as types of varying widths, they are generally converted
2865 // to a wider type with some uses remaining narrow under a (free) trunc.
2866 Value *const NextIV = getWideOperand(IVOper);
2867 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2868 const SCEV *const OperExprBase = getExprBase(OperExpr);
2869
2870 // Visit all existing chains. Check if its IVOper can be computed as a
2871 // profitable loop invariant increment from the last link in the Chain.
2872 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2873 const SCEV *LastIncExpr = nullptr;
2874 for (; ChainIdx < NChains; ++ChainIdx) {
2875 IVChain &Chain = IVChainVec[ChainIdx];
2876
2877 // Prune the solution space aggressively by checking that both IV operands
2878 // are expressions that operate on the same unscaled SCEVUnknown. This
2879 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2880 // first avoids creating extra SCEV expressions.
2881 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2882 continue;
2883
2884 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2885 if (!isCompatibleIVType(PrevIV, NextIV))
2886 continue;
2887
2888 // A phi node terminates a chain.
2889 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2890 continue;
2891
2892 // The increment must be loop-invariant so it can be kept in a register.
2893 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2894 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2895 if (!SE.isLoopInvariant(IncExpr, L))
2896 continue;
2897
2898 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2899 LastIncExpr = IncExpr;
2900 break;
2901 }
2902 }
2903 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2904 // bother for phi nodes, because they must be last in the chain.
2905 if (ChainIdx == NChains) {
2906 if (isa<PHINode>(UserInst))
2907 return;
2908 if (NChains >= MaxChains && !StressIVChain) {
2909 DEBUG(dbgs() << "IV Chain Limit\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain Limit\n"; } } while
(false)
;
2910 return;
2911 }
2912 LastIncExpr = OperExpr;
2913 // IVUsers may have skipped over sign/zero extensions. We don't currently
2914 // attempt to form chains involving extensions unless they can be hoisted
2915 // into this loop's AddRec.
2916 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2917 return;
2918 ++NChains;
2919 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2920 OperExprBase));
2921 ChainUsersVec.resize(NChains);
2922 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)
2923 << ") IV=" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Head: (" << *UserInst << ") IV=" <<
*LastIncExpr << "\n"; } } while (false)
;
2924 } else {
2925 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)
2926 << ") IV+" << *LastIncExpr << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "IV Chain#" << ChainIdx
<< " Inc: (" << *UserInst << ") IV+" <<
*LastIncExpr << "\n"; } } while (false)
;
2927 // Add this IV user to the end of the chain.
2928 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2929 }
2930 IVChain &Chain = IVChainVec[ChainIdx];
2931
2932 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2933 // This chain's NearUsers become FarUsers.
2934 if (!LastIncExpr->isZero()) {
2935 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2936 NearUsers.end());
2937 NearUsers.clear();
2938 }
2939
2940 // All other uses of IVOperand become near uses of the chain.
2941 // We currently ignore intermediate values within SCEV expressions, assuming
2942 // they will eventually be used be the current chain, or can be computed
2943 // from one of the chain increments. To be more precise we could
2944 // transitively follow its user and only add leaf IV users to the set.
2945 for (User *U : IVOper->users()) {
2946 Instruction *OtherUse = dyn_cast<Instruction>(U);
2947 if (!OtherUse)
2948 continue;
2949 // Uses in the chain will no longer be uses if the chain is formed.
2950 // Include the head of the chain in this iteration (not Chain.begin()).
2951 IVChain::const_iterator IncIter = Chain.Incs.begin();
2952 IVChain::const_iterator IncEnd = Chain.Incs.end();
2953 for( ; IncIter != IncEnd; ++IncIter) {
2954 if (IncIter->UserInst == OtherUse)
2955 break;
2956 }
2957 if (IncIter != IncEnd)
2958 continue;
2959
2960 if (SE.isSCEVable(OtherUse->getType())
2961 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2962 && IU.isIVUserOrOperand(OtherUse)) {
2963 continue;
2964 }
2965 NearUsers.insert(OtherUse);
2966 }
2967
2968 // Since this user is part of the chain, it's no longer considered a use
2969 // of the chain.
2970 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2971}
2972
2973/// Populate the vector of Chains.
2974///
2975/// This decreases ILP at the architecture level. Targets with ample registers,
2976/// multiple memory ports, and no register renaming probably don't want
2977/// this. However, such targets should probably disable LSR altogether.
2978///
2979/// The job of LSR is to make a reasonable choice of induction variables across
2980/// the loop. Subsequent passes can easily "unchain" computation exposing more
2981/// ILP *within the loop* if the target wants it.
2982///
2983/// Finding the best IV chain is potentially a scheduling problem. Since LSR
2984/// will not reorder memory operations, it will recognize this as a chain, but
2985/// will generate redundant IV increments. Ideally this would be corrected later
2986/// by a smart scheduler:
2987/// = A[i]
2988/// = A[i+x]
2989/// A[i] =
2990/// A[i+x] =
2991///
2992/// TODO: Walk the entire domtree within this loop, not just the path to the
2993/// loop latch. This will discover chains on side paths, but requires
2994/// maintaining multiple copies of the Chains state.
2995void LSRInstance::CollectChains() {
2996 DEBUG(dbgs() << "Collecting IV Chains.\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Collecting IV Chains.\n";
} } while (false)
;
2997 SmallVector<ChainUsers, 8> ChainUsersVec;
2998
2999 SmallVector<BasicBlock *,8> LatchPath;
3000 BasicBlock *LoopHeader = L->getHeader();
3001 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
3002 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
3003 LatchPath.push_back(Rung->getBlock());
3004 }
3005 LatchPath.push_back(LoopHeader);
3006
3007 // Walk the instruction stream from the loop header to the loop latch.
3008 for (BasicBlock *BB : reverse(LatchPath)) {
3009 for (Instruction &I : *BB) {
3010 // Skip instructions that weren't seen by IVUsers analysis.
3011 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(&I))
3012 continue;
3013
3014 // Ignore users that are part of a SCEV expression. This way we only
3015 // consider leaf IV Users. This effectively rediscovers a portion of
3016 // IVUsers analysis but in program order this time.
3017 if (SE.isSCEVable(I.getType()) && !isa<SCEVUnknown>(SE.getSCEV(&I)))
3018 continue;
3019
3020 // Remove this instruction from any NearUsers set it may be in.
3021 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
3022 ChainIdx < NChains; ++ChainIdx) {
3023 ChainUsersVec[ChainIdx].NearUsers.erase(&I);
3024 }
3025 // Search for operands that can be chained.
3026 SmallPtrSet<Instruction*, 4> UniqueOperands;
3027 User::op_iterator IVOpEnd = I.op_end();
3028 User::op_iterator IVOpIter = findIVOperand(I.op_begin(), IVOpEnd, L, SE);
3029 while (IVOpIter != IVOpEnd) {
3030 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
3031 if (UniqueOperands.insert(IVOpInst).second)
3032 ChainInstruction(&I, IVOpInst, ChainUsersVec);
3033 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3034 }
3035 } // Continue walking down the instructions.
3036 } // Continue walking down the domtree.
3037 // Visit phi backedges to determine if the chain can generate the IV postinc.
3038 for (PHINode &PN : L->getHeader()->phis()) {
3039 if (!SE.isSCEVable(PN.getType()))
3040 continue;
3041
3042 Instruction *IncV =
3043 dyn_cast<Instruction>(PN.getIncomingValueForBlock(L->getLoopLatch()));
3044 if (IncV)
3045 ChainInstruction(&PN, IncV, ChainUsersVec);
3046 }
3047 // Remove any unprofitable chains.
3048 unsigned ChainIdx = 0;
3049 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
3050 UsersIdx < NChains; ++UsersIdx) {
3051 if (!isProfitableChain(IVChainVec[UsersIdx],
3052 ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
3053 continue;
3054 // Preserve the chain at UsesIdx.
3055 if (ChainIdx != UsersIdx)
3056 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
3057 FinalizeChain(IVChainVec[ChainIdx]);
3058 ++ChainIdx;
3059 }
3060 IVChainVec.resize(ChainIdx);
3061}
3062
3063void LSRInstance::FinalizeChain(IVChain &Chain) {
3064 assert(!Chain.Incs.empty() && "empty IV chains are not allowed")(static_cast <bool> (!Chain.Incs.empty() && "empty IV chains are not allowed"
) ? void (0) : __assert_fail ("!Chain.Incs.empty() && \"empty IV chains are not allowed\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3064, __extension__ __PRETTY_FUNCTION__))
;
3065 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)
;
3066
3067 for (const IVInc &Inc : Chain) {
3068 DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Inc: " << *
Inc.UserInst << "\n"; } } while (false)
;
3069 auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand);
3070 assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand")(static_cast <bool> (UseI != Inc.UserInst->op_end() &&
"cannot find IV operand") ? void (0) : __assert_fail ("UseI != Inc.UserInst->op_end() && \"cannot find IV operand\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3070, __extension__ __PRETTY_FUNCTION__))
;
3071 IVIncSet.insert(UseI);
3072 }
3073}
3074
3075/// Return true if the IVInc can be folded into an addressing mode.
3076static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
3077 Value *Operand, const TargetTransformInfo &TTI) {
3078 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
3079 if (!IncConst || !isAddressUse(TTI, UserInst, Operand))
3080 return false;
3081
3082 if (IncConst->getAPInt().getMinSignedBits() > 64)
3083 return false;
3084
3085 MemAccessTy AccessTy = getAccessType(TTI, UserInst);
3086 int64_t IncOffset = IncConst->getValue()->getSExtValue();
3087 if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr,
3088 IncOffset, /*HaseBaseReg=*/false))
3089 return false;
3090
3091 return true;
3092}
3093
3094/// Generate an add or subtract for each IVInc in a chain to materialize the IV
3095/// user's operand from the previous IV user's operand.
3096void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
3097 SmallVectorImpl<WeakTrackingVH> &DeadInsts) {
3098 // Find the new IVOperand for the head of the chain. It may have been replaced
3099 // by LSR.
3100 const IVInc &Head = Chain.Incs[0];
3101 User::op_iterator IVOpEnd = Head.UserInst->op_end();
3102 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
3103 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
3104 IVOpEnd, L, SE);
3105 Value *IVSrc = nullptr;
3106 while (IVOpIter != IVOpEnd) {
3107 IVSrc = getWideOperand(*IVOpIter);
3108
3109 // If this operand computes the expression that the chain needs, we may use
3110 // it. (Check this after setting IVSrc which is used below.)
3111 //
3112 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
3113 // narrow for the chain, so we can no longer use it. We do allow using a
3114 // wider phi, assuming the LSR checked for free truncation. In that case we
3115 // should already have a truncate on this operand such that
3116 // getSCEV(IVSrc) == IncExpr.
3117 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
3118 || SE.getSCEV(IVSrc) == Head.IncExpr) {
3119 break;
3120 }
3121 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
3122 }
3123 if (IVOpIter == IVOpEnd) {
3124 // Gracefully give up on this chain.
3125 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)
;
3126 return;
3127 }
3128
3129 DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Generate chain at: " <<
*IVSrc << "\n"; } } while (false)
;
3130 Type *IVTy = IVSrc->getType();
3131 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
3132 const SCEV *LeftOverExpr = nullptr;
3133 for (const IVInc &Inc : Chain) {
3134 Instruction *InsertPt = Inc.UserInst;
3135 if (isa<PHINode>(InsertPt))
3136 InsertPt = L->getLoopLatch()->getTerminator();
3137
3138 // IVOper will replace the current IV User's operand. IVSrc is the IV
3139 // value currently held in a register.
3140 Value *IVOper = IVSrc;
3141 if (!Inc.IncExpr->isZero()) {
3142 // IncExpr was the result of subtraction of two narrow values, so must
3143 // be signed.
3144 const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
3145 LeftOverExpr = LeftOverExpr ?
3146 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
3147 }
3148 if (LeftOverExpr && !LeftOverExpr->isZero()) {
3149 // Expand the IV increment.
3150 Rewriter.clearPostInc();
3151 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
3152 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
3153 SE.getUnknown(IncV));
3154 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
3155
3156 // If an IV increment can't be folded, use it as the next IV value.
3157 if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
3158 assert(IVTy == IVOper->getType() && "inconsistent IV increment type")(static_cast <bool> (IVTy == IVOper->getType() &&
"inconsistent IV increment type") ? void (0) : __assert_fail
("IVTy == IVOper->getType() && \"inconsistent IV increment type\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3158, __extension__ __PRETTY_FUNCTION__))
;
3159 IVSrc = IVOper;
3160 LeftOverExpr = nullptr;
3161 }
3162 }
3163 Type *OperTy = Inc.IVOperand->getType();
3164 if (IVTy != OperTy) {
3165 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&(static_cast <bool> (SE.getTypeSizeInBits(IVTy) >= SE
.getTypeSizeInBits(OperTy) && "cannot extend a chained IV"
) ? void (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3166, __extension__ __PRETTY_FUNCTION__))
3166 "cannot extend a chained IV")(static_cast <bool> (SE.getTypeSizeInBits(IVTy) >= SE
.getTypeSizeInBits(OperTy) && "cannot extend a chained IV"
) ? void (0) : __assert_fail ("SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && \"cannot extend a chained IV\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3166, __extension__ __PRETTY_FUNCTION__))
;
3167 IRBuilder<> Builder(InsertPt);
3168 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
3169 }
3170 Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
3171 DeadInsts.emplace_back(Inc.IVOperand);
3172 }
3173 // If LSR created a new, wider phi, we may also replace its postinc. We only
3174 // do this if we also found a wide value for the head of the chain.
3175 if (isa<PHINode>(Chain.tailUserInst())) {
3176 for (PHINode &Phi : L->getHeader()->phis()) {
3177 if (!isCompatibleIVType(&Phi, IVSrc))
3178 continue;
3179 Instruction *PostIncV = dyn_cast<Instruction>(
3180 Phi.getIncomingValueForBlock(L->getLoopLatch()));
3181 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
3182 continue;
3183 Value *IVOper = IVSrc;
3184 Type *PostIncTy = PostIncV->getType();
3185 if (IVTy != PostIncTy) {
3186 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types")(static_cast <bool> (PostIncTy->isPointerTy() &&
"mixing int/ptr IV types") ? void (0) : __assert_fail ("PostIncTy->isPointerTy() && \"mixing int/ptr IV types\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3186, __extension__ __PRETTY_FUNCTION__))
;
3187 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
3188 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
3189 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
3190 }
3191 Phi.replaceUsesOfWith(PostIncV, IVOper);
3192 DeadInsts.emplace_back(PostIncV);
3193 }
3194 }
3195}
3196
3197void LSRInstance::CollectFixupsAndInitialFormulae() {
3198 for (const IVStrideUse &U : IU) {
3199 Instruction *UserInst = U.getUser();
3200 // Skip IV users that are part of profitable IV Chains.
3201 User::op_iterator UseI =
3202 find(UserInst->operands(), U.getOperandValToReplace());
3203 assert(UseI != UserInst->op_end() && "cannot find IV operand")(static_cast <bool> (UseI != UserInst->op_end() &&
"cannot find IV operand") ? void (0) : __assert_fail ("UseI != UserInst->op_end() && \"cannot find IV operand\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3203, __extension__ __PRETTY_FUNCTION__))
;
3204 if (IVIncSet.count(UseI)) {
3205 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)
;
3206 continue;
3207 }
3208
3209 LSRUse::KindType Kind = LSRUse::Basic;
3210 MemAccessTy AccessTy;
3211 if (isAddressUse(TTI, UserInst, U.getOperandValToReplace())) {
3212 Kind = LSRUse::Address;
3213 AccessTy = getAccessType(TTI, UserInst);
3214 }
3215
3216 const SCEV *S = IU.getExpr(U);
3217 PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops();
3218
3219 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3220 // (N - i == 0), and this allows (N - i) to be the expression that we work
3221 // with rather than just N or i, so we can consider the register
3222 // requirements for both N and i at the same time. Limiting this code to
3223 // equality icmps is not a problem because all interesting loops use
3224 // equality icmps, thanks to IndVarSimplify.
3225 if (ICmpInst *CI = dyn_cast<ICmpInst>(UserInst))
3226 if (CI->isEquality()) {
3227 // Swap the operands if needed to put the OperandValToReplace on the
3228 // left, for consistency.
3229 Value *NV = CI->getOperand(1);
3230 if (NV == U.getOperandValToReplace()) {
3231 CI->setOperand(1, CI->getOperand(0));
3232 CI->setOperand(0, NV);
3233 NV = CI->getOperand(1);
3234 Changed = true;
3235 }
3236
3237 // x == y --> x - y == 0
3238 const SCEV *N = SE.getSCEV(NV);
3239 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3240 // S is normalized, so normalize N before folding it into S
3241 // to keep the result normalized.
3242 N = normalizeForPostIncUse(N, TmpPostIncLoops, SE);
3243 Kind = LSRUse::ICmpZero;
3244 S = SE.getMinusSCEV(N, S);
3245 }
3246
3247 // -1 and the negations of all interesting strides (except the negation
3248 // of -1) are now also interesting.
3249 for (size_t i = 0, e = Factors.size(); i != e; ++i)
3250 if (Factors[i] != -1)
3251 Factors.insert(-(uint64_t)Factors[i]);
3252 Factors.insert(-1);
3253 }
3254
3255 // Get or create an LSRUse.
3256 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3257 size_t LUIdx = P.first;
3258 int64_t Offset = P.second;
3259 LSRUse &LU = Uses[LUIdx];
3260
3261 // Record the fixup.
3262 LSRFixup &LF = LU.getNewFixup();
3263 LF.UserInst = UserInst;
3264 LF.OperandValToReplace = U.getOperandValToReplace();
3265 LF.PostIncLoops = TmpPostIncLoops;
3266 LF.Offset = Offset;
3267 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3268
3269 if (!LU.WidestFixupType ||
3270 SE.getTypeSizeInBits(LU.WidestFixupType) <
3271 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3272 LU.WidestFixupType = LF.OperandValToReplace->getType();
3273
3274 // If this is the first use of this LSRUse, give it a formula.
3275 if (LU.Formulae.empty()) {
3276 InsertInitialFormula(S, LU, LUIdx);
3277 CountRegisters(LU.Formulae.back(), LUIdx);
3278 }
3279 }
3280
3281 DEBUG(print_fixups(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { print_fixups(dbgs()); } } while (false)
;
3282}
3283
3284/// Insert a formula for the given expression into the given use, separating out
3285/// loop-variant portions from loop-invariant and loop-computable portions.
3286void
3287LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3288 // Mark uses whose expressions cannot be expanded.
3289 if (!isSafeToExpand(S, SE))
3290 LU.RigidFormula = true;
3291
3292 Formula F;
3293 F.initialMatch(S, L, SE);
3294 bool Inserted = InsertFormula(LU, LUIdx, F);
3295 assert(Inserted && "Initial formula already exists!")(static_cast <bool> (Inserted && "Initial formula already exists!"
) ? void (0) : __assert_fail ("Inserted && \"Initial formula already exists!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3295, __extension__ __PRETTY_FUNCTION__))
; (void)Inserted;
3296}
3297
3298/// Insert a simple single-register formula for the given expression into the
3299/// given use.
3300void
3301LSRInstance::InsertSupplementalFormula(const SCEV *S,
3302 LSRUse &LU, size_t LUIdx) {
3303 Formula F;
3304 F.BaseRegs.push_back(S);
3305 F.HasBaseReg = true;
3306 bool Inserted = InsertFormula(LU, LUIdx, F);
3307 assert(Inserted && "Supplemental formula already exists!")(static_cast <bool> (Inserted && "Supplemental formula already exists!"
) ? void (0) : __assert_fail ("Inserted && \"Supplemental formula already exists!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3307, __extension__ __PRETTY_FUNCTION__))
; (void)Inserted;
3308}
3309
3310/// Note which registers are used by the given formula, updating RegUses.
3311void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3312 if (F.ScaledReg)
3313 RegUses.countRegister(F.ScaledReg, LUIdx);
3314 for (const SCEV *BaseReg : F.BaseRegs)
3315 RegUses.countRegister(BaseReg, LUIdx);
3316}
3317
3318/// If the given formula has not yet been inserted, add it to the list, and
3319/// return true. Return false otherwise.
3320bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3321 // Do not insert formula that we will not be able to expand.
3322 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&(static_cast <bool> (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset
, LU.Kind, LU.AccessTy, F) && "Formula is illegal") ?
void (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3323, __extension__ __PRETTY_FUNCTION__))
3323 "Formula is illegal")(static_cast <bool> (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset
, LU.Kind, LU.AccessTy, F) && "Formula is illegal") ?
void (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Formula is illegal\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3323, __extension__ __PRETTY_FUNCTION__))
;
3324
3325 if (!LU.InsertFormula(F, *L))
3326 return false;
3327
3328 CountRegisters(F, LUIdx);
3329 return true;
3330}
3331
3332/// Check for other uses of loop-invariant values which we're tracking. These
3333/// other uses will pin these values in registers, making them less profitable
3334/// for elimination.
3335/// TODO: This currently misses non-constant addrec step registers.
3336/// TODO: Should this give more weight to users inside the loop?
3337void
3338LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3339 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3340 SmallPtrSet<const SCEV *, 32> Visited;
3341
3342 while (!Worklist.empty()) {
3343 const SCEV *S = Worklist.pop_back_val();
3344
3345 // Don't process the same SCEV twice
3346 if (!Visited.insert(S).second)
3347 continue;
3348
3349 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3350 Worklist.append(N->op_begin(), N->op_end());
3351 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3352 Worklist.push_back(C->getOperand());
3353 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3354 Worklist.push_back(D->getLHS());
3355 Worklist.push_back(D->getRHS());
3356 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3357 const Value *V = US->getValue();
3358 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3359 // Look for instructions defined outside the loop.
3360 if (L->contains(Inst)) continue;
3361 } else if (isa<UndefValue>(V))
3362 // Undef doesn't have a live range, so it doesn't matter.
3363 continue;
3364 for (const Use &U : V->uses()) {
3365 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3366 // Ignore non-instructions.
3367 if (!UserInst)
3368 continue;
3369 // Ignore instructions in other functions (as can happen with
3370 // Constants).
3371 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3372 continue;
3373 // Ignore instructions not dominated by the loop.
3374 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3375 UserInst->getParent() :
3376 cast<PHINode>(UserInst)->getIncomingBlock(
3377 PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3378 if (!DT.dominates(L->getHeader(), UseBB))
3379 continue;
3380 // Don't bother if the instruction is in a BB which ends in an EHPad.
3381 if (UseBB->getTerminator()->isEHPad())
3382 continue;
3383 // Don't bother rewriting PHIs in catchswitch blocks.
3384 if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator()))
3385 continue;
3386 // Ignore uses which are part of other SCEV expressions, to avoid
3387 // analyzing them multiple times.
3388 if (SE.isSCEVable(UserInst->getType())) {
3389 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3390 // If the user is a no-op, look through to its uses.
3391 if (!isa<SCEVUnknown>(UserS))
3392 continue;
3393 if (UserS == US) {
3394 Worklist.push_back(
3395 SE.getUnknown(const_cast<Instruction *>(UserInst)));
3396 continue;
3397 }
3398 }
3399 // Ignore icmp instructions which are already being analyzed.
3400 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3401 unsigned OtherIdx = !U.getOperandNo();
3402 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3403 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3404 continue;
3405 }
3406
3407 std::pair<size_t, int64_t> P = getUse(
3408 S, LSRUse::Basic, MemAccessTy());
3409 size_t LUIdx = P.first;
3410 int64_t Offset = P.second;
3411 LSRUse &LU = Uses[LUIdx];
3412 LSRFixup &LF = LU.getNewFixup();
3413 LF.UserInst = const_cast<Instruction *>(UserInst);
3414 LF.OperandValToReplace = U;
3415 LF.Offset = Offset;
3416 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3417 if (!LU.WidestFixupType ||
3418 SE.getTypeSizeInBits(LU.WidestFixupType) <
3419 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3420 LU.WidestFixupType = LF.OperandValToReplace->getType();
3421 InsertSupplementalFormula(US, LU, LUIdx);
3422 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3423 break;
3424 }
3425 }
3426 }
3427}
3428
3429/// Split S into subexpressions which can be pulled out into separate
3430/// registers. If C is non-null, multiply each subexpression by C.
3431///
3432/// Return remainder expression after factoring the subexpressions captured by
3433/// Ops. If Ops is complete, return NULL.
3434static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3435 SmallVectorImpl<const SCEV *> &Ops,
3436 const Loop *L,
3437 ScalarEvolution &SE,
3438 unsigned Depth = 0) {
3439 // Arbitrarily cap recursion to protect compile time.
3440 if (Depth >= 3)
3441 return S;
3442
3443 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3444 // Break out add operands.
3445 for (const SCEV *S : Add->operands()) {
3446 const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3447 if (Remainder)
3448 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3449 }
3450 return nullptr;
3451 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3452 // Split a non-zero base out of an addrec.
3453 if (AR->getStart()->isZero() || !AR->isAffine())
3454 return S;
3455
3456 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3457 C, Ops, L, SE, Depth+1);
3458 // Split the non-zero AddRec unless it is part of a nested recurrence that
3459 // does not pertain to this loop.
3460 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3461 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3462 Remainder = nullptr;
3463 }
3464 if (Remainder != AR->getStart()) {
3465 if (!Remainder)
3466 Remainder = SE.getConstant(AR->getType(), 0);
3467 return SE.getAddRecExpr(Remainder,
3468 AR->getStepRecurrence(SE),
3469 AR->getLoop(),
3470 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3471 SCEV::FlagAnyWrap);
3472 }
3473 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3474 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3475 if (Mul->getNumOperands() != 2)
3476 return S;
3477 if (const SCEVConstant *Op0 =
3478 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3479 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3480 const SCEV *Remainder =
3481 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3482 if (Remainder)
3483 Ops.push_back(SE.getMulExpr(C, Remainder));
3484 return nullptr;
3485 }
3486 }
3487 return S;
3488}
3489
3490/// Return true if the SCEV represents a value that may end up as a
3491/// post-increment operation.
3492static bool mayUsePostIncMode(const TargetTransformInfo &TTI,
3493 LSRUse &LU, const SCEV *S, const Loop *L,
3494 ScalarEvolution &SE) {
3495 if (LU.Kind != LSRUse::Address ||
3496 !LU.AccessTy.getType()->isIntOrIntVectorTy())
3497 return false;
3498 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S);
3499 if (!AR)
3500 return false;
3501 const SCEV *LoopStep = AR->getStepRecurrence(SE);
3502 if (!isa<SCEVConstant>(LoopStep))
3503 return false;
3504 if (LU.AccessTy.getType()->getScalarSizeInBits() !=
3505 LoopStep->getType()->getScalarSizeInBits())
3506 return false;
3507 // Check if a post-indexed load/store can be used.
3508 if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) ||
3509 TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) {
3510 const SCEV *LoopStart = AR->getStart();
3511 if (!isa<SCEVConstant>(LoopStart) && SE.isLoopInvariant(LoopStart, L))
3512 return true;
3513 }
3514 return false;
3515}
3516
3517/// \brief Helper function for LSRInstance::GenerateReassociations.
3518void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3519 const Formula &Base,
3520 unsigned Depth, size_t Idx,
3521 bool IsScaledReg) {
3522 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3523 // Don't generate reassociations for the base register of a value that
3524 // may generate a post-increment operator. The reason is that the
3525 // reassociations cause extra base+register formula to be created,
3526 // and possibly chosen, but the post-increment is more efficient.
3527 if (TTI.shouldFavorPostInc() && mayUsePostIncMode(TTI, LU, BaseReg, L, SE))
3528 return;
3529 SmallVector<const SCEV *, 8> AddOps;
3530 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3531 if (Remainder)
3532 AddOps.push_back(Remainder);
3533
3534 if (AddOps.size() == 1)
3535 return;
3536
3537 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3538 JE = AddOps.end();
3539 J != JE; ++J) {
3540 // Loop-variant "unknown" values are uninteresting; we won't be able to
3541 // do anything meaningful with them.
3542 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3543 continue;
3544
3545 // Don't pull a constant into a register if the constant could be folded
3546 // into an immediate field.
3547 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3548 LU.AccessTy, *J, Base.getNumRegs() > 1))
3549 continue;
3550
3551 // Collect all operands except *J.
3552 SmallVector<const SCEV *, 8> InnerAddOps(
3553 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3554 InnerAddOps.append(std::next(J),
3555 ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3556
3557 // Don't leave just a constant behind in a register if the constant could
3558 // be folded into an immediate field.
3559 if (InnerAddOps.size() == 1 &&
3560 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3561 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3562 continue;
3563
3564 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3565 if (InnerSum->isZero())
3566 continue;
3567 Formula F = Base;
3568
3569 // Add the remaining pieces of the add back into the new formula.
3570 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3571 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3572 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3573 InnerSumSC->getValue()->getZExtValue())) {
3574 F.UnfoldedOffset =
3575 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3576 if (IsScaledReg)
3577 F.ScaledReg = nullptr;
3578 else
3579 F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3580 } else if (IsScaledReg)
3581 F.ScaledReg = InnerSum;
3582 else
3583 F.BaseRegs[Idx] = InnerSum;
3584
3585 // Add J as its own register, or an unfolded immediate.
3586 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3587 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3588 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3589 SC->getValue()->getZExtValue()))
3590 F.UnfoldedOffset =
3591 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3592 else
3593 F.BaseRegs.push_back(*J);
3594 // We may have changed the number of register in base regs, adjust the
3595 // formula accordingly.
3596 F.canonicalize(*L);
3597
3598 if (InsertFormula(LU, LUIdx, F))
3599 // If that formula hadn't been seen before, recurse to find more like
3600 // it.
3601 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth + 1);
3602 }
3603}
3604
3605/// Split out subexpressions from adds and the bases of addrecs.
3606void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3607 Formula Base, unsigned Depth) {
3608 assert(Base.isCanonical(*L) && "Input must be in the canonical form")(static_cast <bool> (Base.isCanonical(*L) && "Input must be in the canonical form"
) ? void (0) : __assert_fail ("Base.isCanonical(*L) && \"Input must be in the canonical form\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3608, __extension__ __PRETTY_FUNCTION__))
;
3609 // Arbitrarily cap recursion to protect compile time.
3610 if (Depth >= 3)
3611 return;
3612
3613 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3614 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3615
3616 if (Base.Scale == 1)
3617 GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3618 /* Idx */ -1, /* IsScaledReg */ true);
3619}
3620
3621/// Generate a formula consisting of all of the loop-dominating registers added
3622/// into a single register.
3623void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3624 Formula Base) {
3625 // This method is only interesting on a plurality of registers.
3626 if (Base.BaseRegs.size() + (Base.Scale == 1) <= 1)
3627 return;
3628
3629 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3630 // processing the formula.
3631 Base.unscale();
3632 Formula F = Base;
3633 F.BaseRegs.clear();
3634 SmallVector<const SCEV *, 4> Ops;
3635 for (const SCEV *BaseReg : Base.BaseRegs) {
3636 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3637 !SE.hasComputableLoopEvolution(BaseReg, L))
3638 Ops.push_back(BaseReg);
3639 else
3640 F.BaseRegs.push_back(BaseReg);
3641 }
3642 if (Ops.size() > 1) {
3643 const SCEV *Sum = SE.getAddExpr(Ops);
3644 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3645 // opportunity to fold something. For now, just ignore such cases
3646 // rather than proceed with zero in a register.
3647 if (!Sum->isZero()) {
3648 F.BaseRegs.push_back(Sum);
3649 F.canonicalize(*L);
3650 (void)InsertFormula(LU, LUIdx, F);
3651 }
3652 }
3653}
3654
3655/// \brief Helper function for LSRInstance::GenerateSymbolicOffsets.
3656void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3657 const Formula &Base, size_t Idx,
3658 bool IsScaledReg) {
3659 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3660 GlobalValue *GV = ExtractSymbol(G, SE);
3661 if (G->isZero() || !GV)
3662 return;
3663 Formula F = Base;
3664 F.BaseGV = GV;
3665 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3666 return;
3667 if (IsScaledReg)
3668 F.ScaledReg = G;
3669 else
3670 F.BaseRegs[Idx] = G;
3671 (void)InsertFormula(LU, LUIdx, F);
3672}
3673
3674/// Generate reuse formulae using symbolic offsets.
3675void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3676 Formula Base) {
3677 // We can't add a symbolic offset if the address already contains one.
3678 if (Base.BaseGV) return;
3679
3680 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3681 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3682 if (Base.Scale == 1)
3683 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3684 /* IsScaledReg */ true);
3685}
3686
3687/// \brief Helper function for LSRInstance::GenerateConstantOffsets.
3688void LSRInstance::GenerateConstantOffsetsImpl(
3689 LSRUse &LU, unsigned LUIdx, const Formula &Base,
3690 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3691 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3692 for (int64_t Offset : Worklist) {
3693 Formula F = Base;
3694 F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3695 if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind,
3696 LU.AccessTy, F)) {
3697 // Add the offset to the base register.
3698 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3699 // If it cancelled out, drop the base register, otherwise update it.
3700 if (NewG->isZero()) {
3701 if (IsScaledReg) {
3702 F.Scale = 0;
3703 F.ScaledReg = nullptr;
3704 } else
3705 F.deleteBaseReg(F.BaseRegs[Idx]);
3706 F.canonicalize(*L);
3707 } else if (IsScaledReg)
3708 F.ScaledReg = NewG;
3709 else
3710 F.BaseRegs[Idx] = NewG;
3711
3712 (void)InsertFormula(LU, LUIdx, F);
3713 }
3714 }
3715
3716 int64_t Imm = ExtractImmediate(G, SE);
3717 if (G->isZero() || Imm == 0)
3718 return;
3719 Formula F = Base;
3720 F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3721 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3722 return;
3723 if (IsScaledReg)
3724 F.ScaledReg = G;
3725 else
3726 F.BaseRegs[Idx] = G;
3727 (void)InsertFormula(LU, LUIdx, F);
3728}
3729
3730/// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3731void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3732 Formula Base) {
3733 // TODO: For now, just add the min and max offset, because it usually isn't
3734 // worthwhile looking at everything inbetween.
3735 SmallVector<int64_t, 2> Worklist;
3736 Worklist.push_back(LU.MinOffset);
3737 if (LU.MaxOffset != LU.MinOffset)
3738 Worklist.push_back(LU.MaxOffset);
3739
3740 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3741 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3742 if (Base.Scale == 1)
3743 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3744 /* IsScaledReg */ true);
3745}
3746
3747/// For ICmpZero, check to see if we can scale up the comparison. For example, x
3748/// == y -> x*c == y*c.
3749void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3750 Formula Base) {
3751 if (LU.Kind != LSRUse::ICmpZero) return;
3752
3753 // Determine the integer type for the base formula.
3754 Type *IntTy = Base.getType();
3755 if (!IntTy) return;
3756 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3757
3758 // Don't do this if there is more than one offset.
3759 if (LU.MinOffset != LU.MaxOffset) return;
3760
3761 // Check if transformation is valid. It is illegal to multiply pointer.
3762 if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy())
3763 return;
3764 for (const SCEV *BaseReg : Base.BaseRegs)
3765 if (BaseReg->getType()->isPointerTy())
3766 return;
3767 assert(!Base.BaseGV && "ICmpZero use is not legal!")(static_cast <bool> (!Base.BaseGV && "ICmpZero use is not legal!"
) ? void (0) : __assert_fail ("!Base.BaseGV && \"ICmpZero use is not legal!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3767, __extension__ __PRETTY_FUNCTION__))
;
3768
3769 // Check each interesting stride.
3770 for (int64_t Factor : Factors) {
3771 // Check that the multiplication doesn't overflow.
3772 if (Base.BaseOffset == std::numeric_limits<int64_t>::min() && Factor == -1)
3773 continue;
3774 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3775 if (NewBaseOffset / Factor != Base.BaseOffset)
3776 continue;
3777 // If the offset will be truncated at this use, check that it is in bounds.
3778 if (!IntTy->isPointerTy() &&
3779 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3780 continue;
3781
3782 // Check that multiplying with the use offset doesn't overflow.
3783 int64_t Offset = LU.MinOffset;
3784 if (Offset == std::numeric_limits<int64_t>::min() && Factor == -1)
3785 continue;
3786 Offset = (uint64_t)Offset * Factor;
3787 if (Offset / Factor != LU.MinOffset)
3788 continue;
3789 // If the offset will be truncated at this use, check that it is in bounds.
3790 if (!IntTy->isPointerTy() &&
3791 !ConstantInt::isValueValidForType(IntTy, Offset))
3792 continue;
3793
3794 Formula F = Base;
3795 F.BaseOffset = NewBaseOffset;
3796
3797 // Check that this scale is legal.
3798 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3799 continue;
3800
3801 // Compensate for the use having MinOffset built into it.
3802 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3803
3804 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3805
3806 // Check that multiplying with each base register doesn't overflow.
3807 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3808 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3809 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3810 goto next;
3811 }
3812
3813 // Check that multiplying with the scaled register doesn't overflow.
3814 if (F.ScaledReg) {
3815 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3816 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3817 continue;
3818 }
3819
3820 // Check that multiplying with the unfolded offset doesn't overflow.
3821 if (F.UnfoldedOffset != 0) {
3822 if (F.UnfoldedOffset == std::numeric_limits<int64_t>::min() &&
3823 Factor == -1)
3824 continue;
3825 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3826 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3827 continue;
3828 // If the offset will be truncated, check that it is in bounds.
3829 if (!IntTy->isPointerTy() &&
3830 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3831 continue;
3832 }
3833
3834 // If we make it here and it's legal, add it.
3835 (void)InsertFormula(LU, LUIdx, F);
3836 next:;
3837 }
3838}
3839
3840/// Generate stride factor reuse formulae by making use of scaled-offset address
3841/// modes, for example.
3842void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3843 // Determine the integer type for the base formula.
3844 Type *IntTy = Base.getType();
3845 if (!IntTy) return;
3846
3847 // If this Formula already has a scaled register, we can't add another one.
3848 // Try to unscale the formula to generate a better scale.
3849 if (Base.Scale != 0 && !Base.unscale())
3850 return;
3851
3852 assert(Base.Scale == 0 && "unscale did not did its job!")(static_cast <bool> (Base.Scale == 0 && "unscale did not did its job!"
) ? void (0) : __assert_fail ("Base.Scale == 0 && \"unscale did not did its job!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 3852, __extension__ __PRETTY_FUNCTION__))
;
3853
3854 // Check each interesting stride.
3855 for (int64_t Factor : Factors) {
3856 Base.Scale = Factor;
3857 Base.HasBaseReg = Base.BaseRegs.size() > 1;
3858 // Check whether this scale is going to be legal.
3859 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3860 Base)) {
3861 // As a special-case, handle special out-of-loop Basic users specially.
3862 // TODO: Reconsider this special case.
3863 if (LU.Kind == LSRUse::Basic &&
3864 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3865 LU.AccessTy, Base) &&
3866 LU.AllFixupsOutsideLoop)
3867 LU.Kind = LSRUse::Special;
3868 else
3869 continue;
3870 }
3871 // For an ICmpZero, negating a solitary base register won't lead to
3872 // new solutions.
3873 if (LU.Kind == LSRUse::ICmpZero &&
3874 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3875 continue;
3876 // For each addrec base reg, if its loop is current loop, apply the scale.
3877 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3878 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]);
3879 if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) {
3880 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3881 if (FactorS->isZero())
3882 continue;
3883 // Divide out the factor, ignoring high bits, since we'll be
3884 // scaling the value back up in the end.
3885 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3886 // TODO: This could be optimized to avoid all the copying.
3887 Formula F = Base;
3888 F.ScaledReg = Quotient;
3889 F.deleteBaseReg(F.BaseRegs[i]);
3890 // The canonical representation of 1*reg is reg, which is already in
3891 // Base. In that case, do not try to insert the formula, it will be
3892 // rejected anyway.
3893 if (F.Scale == 1 && (F.BaseRegs.empty() ||
3894 (AR->getLoop() != L && LU.AllFixupsOutsideLoop)))
3895 continue;
3896 // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate
3897 // non canonical Formula with ScaledReg's loop not being L.
3898 if (F.Scale == 1 && LU.AllFixupsOutsideLoop)
3899 F.canonicalize(*L);
3900 (void)InsertFormula(LU, LUIdx, F);
3901 }
3902 }
3903 }
3904 }
3905}
3906
3907/// Generate reuse formulae from different IV types.
3908void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3909 // Don't bother truncating symbolic values.
3910 if (Base.BaseGV) return;
3911
3912 // Determine the integer type for the base formula.
3913 Type *DstTy = Base.getType();
3914 if (!DstTy) return;
3915 DstTy = SE.getEffectiveSCEVType(DstTy);
3916
3917 for (Type *SrcTy : Types) {
3918 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
3919 Formula F = Base;
3920
3921 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
3922 for (const SCEV *&BaseReg : F.BaseRegs)
3923 BaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
3924
3925 // TODO: This assumes we've done basic processing on all uses and
3926 // have an idea what the register usage is.
3927 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3928 continue;
3929
3930 F.canonicalize(*L);
3931 (void)InsertFormula(LU, LUIdx, F);
3932 }
3933 }
3934}
3935
3936namespace {
3937
3938/// Helper class for GenerateCrossUseConstantOffsets. It's used to defer
3939/// modifications so that the search phase doesn't have to worry about the data
3940/// structures moving underneath it.
3941struct WorkItem {
3942 size_t LUIdx;
3943 int64_t Imm;
3944 const SCEV *OrigReg;
3945
3946 WorkItem(size_t LI, int64_t I, const SCEV *R)
3947 : LUIdx(LI), Imm(I), OrigReg(R) {}
3948
3949 void print(raw_ostream &OS) const;
3950 void dump() const;
3951};
3952
3953} // end anonymous namespace
3954
3955#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
3956void WorkItem::print(raw_ostream &OS) const {
3957 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3958 << " , add offset " << Imm;
3959}
3960
3961LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void WorkItem::dump() const {
3962 print(errs()); errs() << '\n';
3963}
3964#endif
3965
3966/// Look for registers which are a constant distance apart and try to form reuse
3967/// opportunities between them.
3968void LSRInstance::GenerateCrossUseConstantOffsets() {
3969 // Group the registers by their value without any added constant offset.
3970 using ImmMapTy = std::map<int64_t, const SCEV *>;
3971
3972 DenseMap<const SCEV *, ImmMapTy> Map;
3973 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3974 SmallVector<const SCEV *, 8> Sequence;
3975 for (const SCEV *Use : RegUses) {
3976 const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
3977 int64_t Imm = ExtractImmediate(Reg, SE);
3978 auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
3979 if (Pair.second)
3980 Sequence.push_back(Reg);
3981 Pair.first->second.insert(std::make_pair(Imm, Use));
3982 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
3983 }
3984
3985 // Now examine each set of registers with the same base value. Build up
3986 // a list of work to do and do the work in a separate step so that we're
3987 // not adding formulae and register counts while we're searching.
3988 SmallVector<WorkItem, 32> WorkItems;
3989 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3990 for (const SCEV *Reg : Sequence) {
3991 const ImmMapTy &Imms = Map.find(Reg)->second;
3992
3993 // It's not worthwhile looking for reuse if there's only one offset.
3994 if (Imms.size() == 1)
3995 continue;
3996
3997 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)
3998 for (const auto &Entry : Imms)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)
3999 dbgs() << ' ' << 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)
4000 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)
;
4001
4002 // Examine each offset.
4003 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
4004 J != JE; ++J) {
4005 const SCEV *OrigReg = J->second;
4006
4007 int64_t JImm = J->first;
4008 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
4009
4010 if (!isa<SCEVConstant>(OrigReg) &&
4011 UsedByIndicesMap[Reg].count() == 1) {
4012 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Skipping cross-use reuse for "
<< *OrigReg << '\n'; } } while (false)
;
4013 continue;
4014 }
4015
4016 // Conservatively examine offsets between this orig reg a few selected
4017 // other orig regs.
4018 ImmMapTy::const_iterator OtherImms[] = {
4019 Imms.begin(), std::prev(Imms.end()),
4020 Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) /
4021 2)
4022 };
4023 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
4024 ImmMapTy::const_iterator M = OtherImms[i];
4025 if (M == J || M == JE) continue;
4026
4027 // Compute the difference between the two.
4028 int64_t Imm = (uint64_t)JImm - M->first;
4029 for (unsigned LUIdx : UsedByIndices.set_bits())
4030 // Make a memo of this use, offset, and register tuple.
4031 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
4032 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
4033 }
4034 }
4035 }
4036
4037 Map.clear();
4038 Sequence.clear();
4039 UsedByIndicesMap.clear();
4040 UniqueItems.clear();
4041
4042 // Now iterate through the worklist and add new formulae.
4043 for (const WorkItem &WI : WorkItems) {
4044 size_t LUIdx = WI.LUIdx;
4045 LSRUse &LU = Uses[LUIdx];
4046 int64_t Imm = WI.Imm;
4047 const SCEV *OrigReg = WI.OrigReg;
4048
4049 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
4050 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
4051 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
4052
4053 // TODO: Use a more targeted data structure.
4054 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
4055 Formula F = LU.Formulae[L];
4056 // FIXME: The code for the scaled and unscaled registers looks
4057 // very similar but slightly different. Investigate if they
4058 // could be merged. That way, we would not have to unscale the
4059 // Formula.
4060 F.unscale();
4061 // Use the immediate in the scaled register.
4062 if (F.ScaledReg == OrigReg) {
4063 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
4064 // Don't create 50 + reg(-50).
4065 if (F.referencesReg(SE.getSCEV(
4066 ConstantInt::get(IntTy, -(uint64_t)Offset))))
4067 continue;
4068 Formula NewF = F;
4069 NewF.BaseOffset = Offset;
4070 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4071 NewF))
4072 continue;
4073 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
4074
4075 // If the new scale is a constant in a register, and adding the constant
4076 // value to the immediate would produce a value closer to zero than the
4077 // immediate itself, then the formula isn't worthwhile.
4078 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
4079 if (C->getValue()->isNegative() != (NewF.BaseOffset < 0) &&
4080 (C->getAPInt().abs() * APInt(BitWidth, F.Scale))
4081 .ule(std::abs(NewF.BaseOffset)))
4082 continue;
4083
4084 // OK, looks good.
4085 NewF.canonicalize(*this->L);
4086 (void)InsertFormula(LU, LUIdx, NewF);
4087 } else {
4088 // Use the immediate in a base register.
4089 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
4090 const SCEV *BaseReg = F.BaseRegs[N];
4091 if (BaseReg != OrigReg)
4092 continue;
4093 Formula NewF = F;
4094 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
4095 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
4096 LU.Kind, LU.AccessTy, NewF)) {
4097 if (TTI.shouldFavorPostInc() &&
4098 mayUsePostIncMode(TTI, LU, OrigReg, this->L, SE))
4099 continue;
4100 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
4101 continue;
4102 NewF = F;
4103 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
4104 }
4105 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
4106
4107 // If the new formula has a constant in a register, and adding the
4108 // constant value to the immediate would produce a value closer to
4109 // zero than the immediate itself, then the formula isn't worthwhile.
4110 for (const SCEV *NewReg : NewF.BaseRegs)
4111 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
4112 if ((C->getAPInt() + NewF.BaseOffset)
4113 .abs()
4114 .slt(std::abs(NewF.BaseOffset)) &&
4115 (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >=
4116 countTrailingZeros<uint64_t>(NewF.BaseOffset))
4117 goto skip_formula;
4118
4119 // Ok, looks good.
4120 NewF.canonicalize(*this->L);
4121 (void)InsertFormula(LU, LUIdx, NewF);
4122 break;
4123 skip_formula:;
4124 }
4125 }
4126 }
4127 }
4128}
4129
4130/// Generate formulae for each use.
4131void
4132LSRInstance::GenerateAllReuseFormulae() {
4133 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
4134 // queries are more precise.
4135 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4136 LSRUse &LU = Uses[LUIdx];
4137 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4138 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
4139 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4140 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
4141 }
4142 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4143 LSRUse &LU = Uses[LUIdx];
4144 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4145 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
4146 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4147 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
4148 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4149 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
4150 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4151 GenerateScales(LU, LUIdx, LU.Formulae[i]);
4152 }
4153 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4154 LSRUse &LU = Uses[LUIdx];
4155 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
4156 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
4157 }
4158
4159 GenerateCrossUseConstantOffsets();
4160
4161 DEBUG(dbgs() << "\n"do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
4162 "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)
4163 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\n" "After generating reuse formulae:\n"
; print_uses(dbgs()); } } while (false)
;
4164}
4165
4166/// If there are multiple formulae with the same set of registers used
4167/// by other uses, pick the best one and delete the others.
4168void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
4169 DenseSet<const SCEV *> VisitedRegs;
4170 SmallPtrSet<const SCEV *, 16> Regs;
4171 SmallPtrSet<const SCEV *, 16> LoserRegs;
4172#ifndef NDEBUG
4173 bool ChangedFormulae = false;
4174#endif
4175
4176 // Collect the best formula for each unique set of shared registers. This
4177 // is reset for each use.
4178 using BestFormulaeTy =
4179 DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>;
4180
4181 BestFormulaeTy BestFormulae;
4182
4183 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4184 LSRUse &LU = Uses[LUIdx];
4185 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4186
4187 bool Any = false;
4188 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
4189 FIdx != NumForms; ++FIdx) {
4190 Formula &F = LU.Formulae[FIdx];
4191
4192 // Some formulas are instant losers. For example, they may depend on
4193 // nonexistent AddRecs from other loops. These need to be filtered
4194 // immediately, otherwise heuristics could choose them over others leading
4195 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
4196 // avoids the need to recompute this information across formulae using the
4197 // same bad AddRec. Passing LoserRegs is also essential unless we remove
4198 // the corresponding bad register from the Regs set.
4199 Cost CostF;
4200 Regs.clear();
4201 CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, SE, DT, LU, &LoserRegs);
4202 if (CostF.isLoser()) {
4203 // During initial formula generation, undesirable formulae are generated
4204 // by uses within other loops that have some non-trivial address mode or
4205 // use the postinc form of the IV. LSR needs to provide these formulae
4206 // as the basis of rediscovering the desired formula that uses an AddRec
4207 // corresponding to the existing phi. Once all formulae have been
4208 // generated, these initial losers may be pruned.
4209 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)
4210 dbgs() << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Filtering loser "; F.print
(dbgs()); dbgs() << "\n"; } } while (false)
;
4211 }
4212 else {
4213 SmallVector<const SCEV *, 4> Key;
4214 for (const SCEV *Reg : F.BaseRegs) {
4215 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
4216 Key.push_back(Reg);
4217 }
4218 if (F.ScaledReg &&
4219 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
4220 Key.push_back(F.ScaledReg);
4221 // Unstable sort by host order ok, because this is only used for
4222 // uniquifying.
4223 std::sort(Key.begin(), Key.end());
4224
4225 std::pair<BestFormulaeTy::const_iterator, bool> P =
4226 BestFormulae.insert(std::make_pair(Key, FIdx));
4227 if (P.second)
4228 continue;
4229
4230 Formula &Best = LU.Formulae[P.first->second];
4231
4232 Cost CostBest;
4233 Regs.clear();
4234 CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, SE, DT, LU);
4235 if (CostF.isLess(CostBest, TTI))
4236 std::swap(F, Best);
4237 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)
4238 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)
4239 " in favor of formula "; Best.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)
4240 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)
;
4241 }
4242#ifndef NDEBUG
4243 ChangedFormulae = true;
4244#endif
4245 LU.DeleteFormula(F);
4246 --FIdx;
4247 --NumForms;
4248 Any = true;
4249 }
4250
4251 // Now that we've filtered out some formulae, recompute the Regs set.
4252 if (Any)
4253 LU.RecomputeRegs(LUIdx, RegUses);
4254
4255 // Reset this to prepare for the next use.
4256 BestFormulae.clear();
4257 }
4258
4259 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)
4260 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)
4261 "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)
4262 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)
4263 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4264}
4265
4266// This is a rough guess that seems to work fairly well.
4267static const size_t ComplexityLimit = std::numeric_limits<uint16_t>::max();
4268
4269/// Estimate the worst-case number of solutions the solver might have to
4270/// consider. It almost never considers this many solutions because it prune the
4271/// search space, but the pruning isn't always sufficient.
4272size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4273 size_t Power = 1;
4274 for (const LSRUse &LU : Uses) {
4275 size_t FSize = LU.Formulae.size();
4276 if (FSize >= ComplexityLimit) {
4277 Power = ComplexityLimit;
4278 break;
4279 }
4280 Power *= FSize;
4281 if (Power >= ComplexityLimit)
4282 break;
4283 }
4284 return Power;
4285}
4286
4287/// When one formula uses a superset of the registers of another formula, it
4288/// won't help reduce register pressure (though it may not necessarily hurt
4289/// register pressure); remove it to simplify the system.
4290void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4291 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4292 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)
;
4293
4294 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)
4295 "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)
4296 "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)
;
4297
4298 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4299 LSRUse &LU = Uses[LUIdx];
4300 bool Any = false;
4301 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4302 Formula &F = LU.Formulae[i];
4303 // Look for a formula with a constant or GV in a register. If the use
4304 // also has a formula with that same value in an immediate field,
4305 // delete the one that uses a register.
4306 for (SmallVectorImpl<const SCEV *>::const_iterator
4307 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4308 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4309 Formula NewF = F;
4310 NewF.BaseOffset += C->getValue()->getSExtValue();
4311 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4312 (I - F.BaseRegs.begin()));
4313 if (LU.HasFormulaWithSameRegs(NewF)) {
4314 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)
;
4315 LU.DeleteFormula(F);
4316 --i;
4317 --e;
4318 Any = true;
4319 break;
4320 }
4321 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4322 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4323 if (!F.BaseGV) {
4324 Formula NewF = F;
4325 NewF.BaseGV = GV;
4326 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4327 (I - F.BaseRegs.begin()));
4328 if (LU.HasFormulaWithSameRegs(NewF)) {
4329 DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4330 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4331 LU.DeleteFormula(F);
4332 --i;
4333 --e;
4334 Any = true;
4335 break;
4336 }
4337 }
4338 }
4339 }
4340 }
4341 if (Any)
4342 LU.RecomputeRegs(LUIdx, RegUses);
4343 }
4344
4345 DEBUG(dbgs() << "After pre-selection:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
4346 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4347 }
4348}
4349
4350/// When there are many registers for expressions like A, A+1, A+2, etc.,
4351/// allocate a single register for them.
4352void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4353 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4354 return;
4355
4356 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"
"Narrowing the search space by assuming that uses separated "
"by a constant offset will use the same registers.\n"; } } while
(false)
4357 "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)
4358 "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)
;
4359
4360 // This is especially useful for unrolled loops.
4361
4362 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4363 LSRUse &LU = Uses[LUIdx];
4364 for (const Formula &F : LU.Formulae) {
4365 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4366 continue;
4367
4368 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4369 if (!LUThatHas)
4370 continue;
4371
4372 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4373 LU.Kind, LU.AccessTy))
4374 continue;
4375
4376 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)
;
4377
4378 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4379
4380 // Transfer the fixups of LU to LUThatHas.
4381 for (LSRFixup &Fixup : LU.Fixups) {
4382 Fixup.Offset += F.BaseOffset;
4383 LUThatHas->pushFixup(Fixup);
4384 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)
;
4385 }
4386
4387 // Delete formulae from the new use which are no longer legal.
4388 bool Any = false;
4389 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4390 Formula &F = LUThatHas->Formulae[i];
4391 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4392 LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4393 DEBUG(dbgs() << " Deleting "; F.print(dbgs());do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
4394 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; F.print(dbgs
()); dbgs() << '\n'; } } while (false)
;
4395 LUThatHas->DeleteFormula(F);
4396 --i;
4397 --e;
4398 Any = true;
4399 }
4400 }
4401
4402 if (Any)
4403 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4404
4405 // Delete the old use.
4406 DeleteUse(LU, LUIdx);
4407 --LUIdx;
4408 --NumUses;
4409 break;
4410 }
4411 }
4412
4413 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)
;
4414}
4415
4416/// Call FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4417/// we've done more filtering, as it may be able to find more formulae to
4418/// eliminate.
4419void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4420 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4421 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)
;
4422
4423 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)
4424 "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)
;
4425
4426 FilterOutUndesirableDedicatedRegisters();
4427
4428 DEBUG(dbgs() << "After pre-selection:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
4429 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4430 }
4431}
4432
4433/// If a LSRUse has multiple formulae with the same ScaledReg and Scale.
4434/// Pick the best one and delete the others.
4435/// This narrowing heuristic is to keep as many formulae with different
4436/// Scale and ScaledReg pair as possible while narrowing the search space.
4437/// The benefit is that it is more likely to find out a better solution
4438/// from a formulae set with more Scale and ScaledReg variations than
4439/// a formulae set with the same Scale and ScaledReg. The picking winner
4440/// reg heurstic will often keep the formulae with the same Scale and
4441/// ScaledReg and filter others, and we want to avoid that if possible.
4442void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() {
4443 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4444 return;
4445
4446 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"
"Narrowing the search space by choosing the best Formula " "from the Formulae with the same Scale and ScaledReg.\n"
; } } while (false)
4447 "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)
4448 "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)
;
4449
4450 // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse.
4451 using BestFormulaeTy = DenseMap<std::pair<const SCEV *, int64_t>, size_t>;
4452
4453 BestFormulaeTy BestFormulae;
4454#ifndef NDEBUG
4455 bool ChangedFormulae = false;
4456#endif
4457 DenseSet<const SCEV *> VisitedRegs;
4458 SmallPtrSet<const SCEV *, 16> Regs;
4459
4460 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4461 LSRUse &LU = Uses[LUIdx];
4462 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "Filtering for use "; LU.print
(dbgs()); dbgs() << '\n'; } } while (false)
;
4463
4464 // Return true if Formula FA is better than Formula FB.
4465 auto IsBetterThan = [&](Formula &FA, Formula &FB) {
4466 // First we will try to choose the Formula with fewer new registers.
4467 // For a register used by current Formula, the more the register is
4468 // shared among LSRUses, the less we increase the register number
4469 // counter of the formula.
4470 size_t FARegNum = 0;
4471 for (const SCEV *Reg : FA.BaseRegs) {
4472 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4473 FARegNum += (NumUses - UsedByIndices.count() + 1);
4474 }
4475 size_t FBRegNum = 0;
4476 for (const SCEV *Reg : FB.BaseRegs) {
4477 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg);
4478 FBRegNum += (NumUses - UsedByIndices.count() + 1);
4479 }
4480 if (FARegNum != FBRegNum)
4481 return FARegNum < FBRegNum;
4482
4483 // If the new register numbers are the same, choose the Formula with
4484 // less Cost.
4485 Cost CostFA, CostFB;
4486 Regs.clear();
4487 CostFA.RateFormula(TTI, FA, Regs, VisitedRegs, L, SE, DT, LU);
4488 Regs.clear();
4489 CostFB.RateFormula(TTI, FB, Regs, VisitedRegs, L, SE, DT, LU);
4490 return CostFA.isLess(CostFB, TTI);
4491 };
4492
4493 bool Any = false;
4494 for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms;
4495 ++FIdx) {
4496 Formula &F = LU.Formulae[FIdx];
4497 if (!F.ScaledReg)
4498 continue;
4499 auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx});
4500 if (P.second)
4501 continue;
4502
4503 Formula &Best = LU.Formulae[P.first->second];
4504 if (IsBetterThan(F, Best))
4505 std::swap(F, Best);
4506 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)
4507 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)
4508 " 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)
4509 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)
;
4510#ifndef NDEBUG
4511 ChangedFormulae = true;
4512#endif
4513 LU.DeleteFormula(F);
4514 --FIdx;
4515 --NumForms;
4516 Any = true;
4517 }
4518 if (Any)
4519 LU.RecomputeRegs(LUIdx, RegUses);
4520
4521 // Reset this to prepare for the next use.
4522 BestFormulae.clear();
4523 }
4524
4525 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)
4526 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)
4527 "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)
4528 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)
4529 })do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { if (ChangedFormulae) { dbgs() << "\n"
"After filtering out undesirable candidates:\n"; print_uses(
dbgs()); }; } } while (false)
;
4530}
4531
4532/// The function delete formulas with high registers number expectation.
4533/// Assuming we don't know the value of each formula (already delete
4534/// all inefficient), generate probability of not selecting for each
4535/// register.
4536/// For example,
4537/// Use1:
4538/// reg(a) + reg({0,+,1})
4539/// reg(a) + reg({-1,+,1}) + 1
4540/// reg({a,+,1})
4541/// Use2:
4542/// reg(b) + reg({0,+,1})
4543/// reg(b) + reg({-1,+,1}) + 1
4544/// reg({b,+,1})
4545/// Use3:
4546/// reg(c) + reg(b) + reg({0,+,1})
4547/// reg(c) + reg({b,+,1})
4548///
4549/// Probability of not selecting
4550/// Use1 Use2 Use3
4551/// reg(a) (1/3) * 1 * 1
4552/// reg(b) 1 * (1/3) * (1/2)
4553/// reg({0,+,1}) (2/3) * (2/3) * (1/2)
4554/// reg({-1,+,1}) (2/3) * (2/3) * 1
4555/// reg({a,+,1}) (2/3) * 1 * 1
4556/// reg({b,+,1}) 1 * (2/3) * (2/3)
4557/// reg(c) 1 * 1 * 0
4558///
4559/// Now count registers number mathematical expectation for each formula:
4560/// Note that for each use we exclude probability if not selecting for the use.
4561/// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding
4562/// probabilty 1/3 of not selecting for Use1).
4563/// Use1:
4564/// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted
4565/// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted
4566/// reg({a,+,1}) 1
4567/// Use2:
4568/// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted
4569/// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted
4570/// reg({b,+,1}) 2/3
4571/// Use3:
4572/// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted
4573/// reg(c) + reg({b,+,1}) 1 + 2/3
4574void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() {
4575 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4576 return;
4577 // Ok, we have too many of formulae on our hands to conveniently handle.
4578 // Use a rough heuristic to thin out the list.
4579
4580 // Set of Regs wich will be 100% used in final solution.
4581 // Used in each formula of a solution (in example above this is reg(c)).
4582 // We can skip them in calculations.
4583 SmallPtrSet<const SCEV *, 4> UniqRegs;
4584 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)
;
4585
4586 // Map each register to probability of not selecting
4587 DenseMap <const SCEV *, float> RegNumMap;
4588 for (const SCEV *Reg : RegUses) {
4589 if (UniqRegs.count(Reg))
4590 continue;
4591 float PNotSel = 1;
4592 for (const LSRUse &LU : Uses) {
4593 if (!LU.Regs.count(Reg))
4594 continue;
4595 float P = LU.getNotSelectedProbability(Reg);
4596 if (P != 0.0)
4597 PNotSel *= P;
4598 else
4599 UniqRegs.insert(Reg);
4600 }
4601 RegNumMap.insert(std::make_pair(Reg, PNotSel));
4602 }
4603
4604 DEBUG(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)
;
4605
4606 // Delete formulas where registers number expectation is high.
4607 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4608 LSRUse &LU = Uses[LUIdx];
4609 // If nothing to delete - continue.
4610 if (LU.Formulae.size() < 2)
4611 continue;
4612 // This is temporary solution to test performance. Float should be
4613 // replaced with round independent type (based on integers) to avoid
4614 // different results for different target builds.
4615 float FMinRegNum = LU.Formulae[0].getNumRegs();
4616 float FMinARegNum = LU.Formulae[0].getNumRegs();
4617 size_t MinIdx = 0;
4618 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4619 Formula &F = LU.Formulae[i];
4620 float FRegNum = 0;
4621 float FARegNum = 0;
4622 for (const SCEV *BaseReg : F.BaseRegs) {
4623 if (UniqRegs.count(BaseReg))
4624 continue;
4625 FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4626 if (isa<SCEVAddRecExpr>(BaseReg))
4627 FARegNum +=
4628 RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg);
4629 }
4630 if (const SCEV *ScaledReg = F.ScaledReg) {
4631 if (!UniqRegs.count(ScaledReg)) {
4632 FRegNum +=
4633 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4634 if (isa<SCEVAddRecExpr>(ScaledReg))
4635 FARegNum +=
4636 RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg);
4637 }
4638 }
4639 if (FMinRegNum > FRegNum ||
4640 (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) {
4641 FMinRegNum = FRegNum;
4642 FMinARegNum = FARegNum;
4643 MinIdx = i;
4644 }
4645 }
4646 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)
4647 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)
;
4648 if (MinIdx != 0)
4649 std::swap(LU.Formulae[MinIdx], LU.Formulae[0]);
4650 while (LU.Formulae.size() != 1) {
4651 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
)
4652 dbgs() << '\n')do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << " Deleting "; LU.Formulae
.back().print(dbgs()); dbgs() << '\n'; } } while (false
)
;
4653 LU.Formulae.pop_back();
4654 }
4655 LU.RecomputeRegs(LUIdx, RegUses);
4656 assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula")(static_cast <bool> (LU.Formulae.size() == 1 &&
"Should be exactly 1 min regs formula") ? void (0) : __assert_fail
("LU.Formulae.size() == 1 && \"Should be exactly 1 min regs formula\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4656, __extension__ __PRETTY_FUNCTION__))
;
4657 Formula &F = LU.Formulae[0];
4658 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)
;
4659 // When we choose the formula, the regs become unique.
4660 UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
4661 if (F.ScaledReg)
4662 UniqRegs.insert(F.ScaledReg);
4663 }
4664 DEBUG(dbgs() << "After pre-selection:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
4665 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4666}
4667
4668/// Pick a register which seems likely to be profitable, and then in any use
4669/// which has any reference to that register, delete all formulae which do not
4670/// reference that register.
4671void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4672 // With all other options exhausted, loop until the system is simple
4673 // enough to handle.
4674 SmallPtrSet<const SCEV *, 4> Taken;
4675 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4676 // Ok, we have too many of formulae on our hands to conveniently handle.
4677 // Use a rough heuristic to thin out the list.
4678 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)
;
4679
4680 // Pick the register which is used by the most LSRUses, which is likely
4681 // to be a good reuse register candidate.
4682 const SCEV *Best = nullptr;
4683 unsigned BestNum = 0;
4684 for (const SCEV *Reg : RegUses) {
4685 if (Taken.count(Reg))
4686 continue;
4687 if (!Best) {
4688 Best = Reg;
4689 BestNum = RegUses.getUsedByIndices(Reg).count();
4690 } else {
4691 unsigned Count = RegUses.getUsedByIndices(Reg).count();
4692 if (Count > BestNum) {
4693 Best = Reg;
4694 BestNum = Count;
4695 }
4696 }
4697 }
4698
4699 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)
4700 << " 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)
;
4701 Taken.insert(Best);
4702
4703 // In any use with formulae which references this register, delete formulae
4704 // which don't reference it.
4705 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4706 LSRUse &LU = Uses[LUIdx];
4707 if (!LU.Regs.count(Best)) continue;
4708
4709 bool Any = false;
4710 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4711 Formula &F = LU.Formulae[i];
4712 if (!F.referencesReg(Best)) {
4713 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)
;
4714 LU.DeleteFormula(F);
4715 --e;
4716 --i;
4717 Any = true;
4718 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?")(static_cast <bool> (e != 0 && "Use has no formulae left! Is Regs inconsistent?"
) ? void (0) : __assert_fail ("e != 0 && \"Use has no formulae left! Is Regs inconsistent?\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4718, __extension__ __PRETTY_FUNCTION__))
;
4719 continue;
4720 }
4721 }
4722
4723 if (Any)
4724 LU.RecomputeRegs(LUIdx, RegUses);
4725 }
4726
4727 DEBUG(dbgs() << "After pre-selection:\n";do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
4728 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "After pre-selection:\n"; print_uses
(dbgs()); } } while (false)
;
4729 }
4730}
4731
4732/// If there are an extraordinary number of formulae to choose from, use some
4733/// rough heuristics to prune down the number of formulae. This keeps the main
4734/// solver from taking an extraordinary amount of time in some worst-case
4735/// scenarios.
4736void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4737 NarrowSearchSpaceByDetectingSupersets();
4738 NarrowSearchSpaceByCollapsingUnrolledCode();
4739 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4740 if (FilterSameScaledReg)
4741 NarrowSearchSpaceByFilterFormulaWithSameScaledReg();
4742 if (LSRExpNarrow)
4743 NarrowSearchSpaceByDeletingCostlyFormulas();
4744 else
4745 NarrowSearchSpaceByPickingWinnerRegs();
4746}
4747
4748/// This is the recursive solver.
4749void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4750 Cost &SolutionCost,
4751 SmallVectorImpl<const Formula *> &Workspace,
4752 const Cost &CurCost,
4753 const SmallPtrSet<const SCEV *, 16> &CurRegs,
4754 DenseSet<const SCEV *> &VisitedRegs) const {
4755 // Some ideas:
4756 // - prune more:
4757 // - use more aggressive filtering
4758 // - sort the formula so that the most profitable solutions are found first
4759 // - sort the uses too
4760 // - search faster:
4761 // - don't compute a cost, and then compare. compare while computing a cost
4762 // and bail early.
4763 // - track register sets with SmallBitVector
4764
4765 const LSRUse &LU = Uses[Workspace.size()];
4766
4767 // If this use references any register that's already a part of the
4768 // in-progress solution, consider it a requirement that a formula must
4769 // reference that register in order to be considered. This prunes out
4770 // unprofitable searching.
4771 SmallSetVector<const SCEV *, 4> ReqRegs;
4772 for (const SCEV *S : CurRegs)
4773 if (LU.Regs.count(S))
4774 ReqRegs.insert(S);
4775
4776 SmallPtrSet<const SCEV *, 16> NewRegs;
4777 Cost NewCost;
4778 for (const Formula &F : LU.Formulae) {
4779 // Ignore formulae which may not be ideal in terms of register reuse of
4780 // ReqRegs. The formula should use all required registers before
4781 // introducing new ones.
4782 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4783 for (const SCEV *Reg : ReqRegs) {
4784 if ((F.ScaledReg && F.ScaledReg == Reg) ||
4785 is_contained(F.BaseRegs, Reg)) {
4786 --NumReqRegsToFind;
4787 if (NumReqRegsToFind == 0)
4788 break;
4789 }
4790 }
4791 if (NumReqRegsToFind != 0) {
4792 // If none of the formulae satisfied the required registers, then we could
4793 // clear ReqRegs and try again. Currently, we simply give up in this case.
4794 continue;
4795 }
4796
4797 // Evaluate the cost of the current formula. If it's already worse than
4798 // the current best, prune the search at that point.
4799 NewCost = CurCost;
4800 NewRegs = CurRegs;
4801 NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, SE, DT, LU);
4802 if (NewCost.isLess(SolutionCost, TTI)) {
4803 Workspace.push_back(&F);
4804 if (Workspace.size() != Uses.size()) {
4805 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4806 NewRegs, VisitedRegs);
4807 if (F.getNumRegs() == 1 && Workspace.size() == 1)
4808 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4809 } else {
4810 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)
4811 dbgs() << ".\n Regs:";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)
4812 for (const SCEV *S : NewRegs)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)
4813 dbgs() << ' ' << *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)
4814 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)
;
4815
4816 SolutionCost = NewCost;
4817 Solution = Workspace;
4818 }
4819 Workspace.pop_back();
4820 }
4821 }
4822}
4823
4824/// Choose one formula from each use. Return the results in the given Solution
4825/// vector.
4826void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4827 SmallVector<const Formula *, 8> Workspace;
4828 Cost SolutionCost;
4829 SolutionCost.Lose();
4830 Cost CurCost;
4831 SmallPtrSet<const SCEV *, 16> CurRegs;
4832 DenseSet<const SCEV *> VisitedRegs;
4833 Workspace.reserve(Uses.size());
4834
4835 // SolveRecurse does all the work.
4836 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4837 CurRegs, VisitedRegs);
4838 if (Solution.empty()) {
4839 DEBUG(dbgs() << "\nNo Satisfactory Solution\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nNo Satisfactory Solution\n"
; } } while (false)
;
4840 return;
4841 }
4842
4843 // Ok, we've now made all our decisions.
4844 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
)
4845 "The chosen solution requires "; SolutionCost.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
)
4846 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
)
4847 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
)
4848 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
)
4849 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
)
4850 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
)
4851 " ";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
)
4852 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
)
4853 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
)
4854 })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
)
;
4855
4856 assert(Solution.size() == Uses.size() && "Malformed solution!")(static_cast <bool> (Solution.size() == Uses.size() &&
"Malformed solution!") ? void (0) : __assert_fail ("Solution.size() == Uses.size() && \"Malformed solution!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4856, __extension__ __PRETTY_FUNCTION__))
;
4857}
4858
4859/// Helper for AdjustInsertPositionForExpand. Climb up the dominator tree far as
4860/// we can go while still being dominated by the input positions. This helps
4861/// canonicalize the insert position, which encourages sharing.
4862BasicBlock::iterator
4863LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4864 const SmallVectorImpl<Instruction *> &Inputs)
4865 const {
4866 Instruction *Tentative = &*IP;
4867 while (true) {
4868 bool AllDominate = true;
4869 Instruction *BetterPos = nullptr;
4870 // Don't bother attempting to insert before a catchswitch, their basic block
4871 // cannot have other non-PHI instructions.
4872 if (isa<CatchSwitchInst>(Tentative))
4873 return IP;
4874
4875 for (Instruction *Inst : Inputs) {
4876 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4877 AllDominate = false;
4878 break;
4879 }
4880 // Attempt to find an insert position in the middle of the block,
4881 // instead of at the end, so that it can be used for other expansions.
4882 if (Tentative->getParent() == Inst->getParent() &&
4883 (!BetterPos || !DT.dominates(Inst, BetterPos)))
4884 BetterPos = &*std::next(BasicBlock::iterator(Inst));
4885 }
4886 if (!AllDominate)
4887 break;
4888 if (BetterPos)
4889 IP = BetterPos->getIterator();
4890 else
4891 IP = Tentative->getIterator();
4892
4893 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4894 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4895
4896 BasicBlock *IDom;
4897 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4898 if (!Rung) return IP;
4899 Rung = Rung->getIDom();
4900 if (!Rung) return IP;
4901 IDom = Rung->getBlock();
4902
4903 // Don't climb into a loop though.
4904 const Loop *IDomLoop = LI.getLoopFor(IDom);
4905 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4906 if (IDomDepth <= IPLoopDepth &&
4907 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4908 break;
4909 }
4910
4911 Tentative = IDom->getTerminator();
4912 }
4913
4914 return IP;
4915}
4916
4917/// Determine an input position which will be dominated by the operands and
4918/// which will dominate the result.
4919BasicBlock::iterator
4920LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4921 const LSRFixup &LF,
4922 const LSRUse &LU,
4923 SCEVExpander &Rewriter) const {
4924 // Collect some instructions which must be dominated by the
4925 // expanding replacement. These must be dominated by any operands that
4926 // will be required in the expansion.
4927 SmallVector<Instruction *, 4> Inputs;
4928 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4929 Inputs.push_back(I);
4930 if (LU.Kind == LSRUse::ICmpZero)
4931 if (Instruction *I =
4932 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4933 Inputs.push_back(I);
4934 if (LF.PostIncLoops.count(L)) {
4935 if (LF.isUseFullyOutsideLoop(L))
4936 Inputs.push_back(L->getLoopLatch()->getTerminator());
4937 else
4938 Inputs.push_back(IVIncInsertPos);
4939 }
4940 // The expansion must also be dominated by the increment positions of any
4941 // loops it for which it is using post-inc mode.
4942 for (const Loop *PIL : LF.PostIncLoops) {
4943 if (PIL == L) continue;
4944
4945 // Be dominated by the loop exit.
4946 SmallVector<BasicBlock *, 4> ExitingBlocks;
4947 PIL->getExitingBlocks(ExitingBlocks);
4948 if (!ExitingBlocks.empty()) {
4949 BasicBlock *BB = ExitingBlocks[0];
4950 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4951 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4952 Inputs.push_back(BB->getTerminator());
4953 }
4954 }
4955
4956 assert(!isa<PHINode>(LowestIP) && !LowestIP->isEHPad()(static_cast <bool> (!isa<PHINode>(LowestIP) &&
!LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>
(LowestIP) && "Insertion point must be a normal instruction"
) ? void (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4958, __extension__ __PRETTY_FUNCTION__))
4957 && !isa<DbgInfoIntrinsic>(LowestIP) &&(static_cast <bool> (!isa<PHINode>(LowestIP) &&
!LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>
(LowestIP) && "Insertion point must be a normal instruction"
) ? void (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4958, __extension__ __PRETTY_FUNCTION__))
4958 "Insertion point must be a normal instruction")(static_cast <bool> (!isa<PHINode>(LowestIP) &&
!LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>
(LowestIP) && "Insertion point must be a normal instruction"
) ? void (0) : __assert_fail ("!isa<PHINode>(LowestIP) && !LowestIP->isEHPad() && !isa<DbgInfoIntrinsic>(LowestIP) && \"Insertion point must be a normal instruction\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 4958, __extension__ __PRETTY_FUNCTION__))
;
4959
4960 // Then, climb up the immediate dominator tree as far as we can go while
4961 // still being dominated by the input positions.
4962 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4963
4964 // Don't insert instructions before PHI nodes.
4965 while (isa<PHINode>(IP)) ++IP;
4966
4967 // Ignore landingpad instructions.
4968 while (IP->isEHPad()) ++IP;
4969
4970 // Ignore debug intrinsics.
4971 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4972
4973 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4974 // IP consistent across expansions and allows the previously inserted
4975 // instructions to be reused by subsequent expansion.
4976 while (Rewriter.isInsertedInstruction(&*IP) && IP != LowestIP)
4977 ++IP;
4978
4979 return IP;
4980}
4981
4982/// Emit instructions for the leading candidate expression for this LSRUse (this
4983/// is called "expanding").
4984Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF,
4985 const Formula &F, BasicBlock::iterator IP,
4986 SCEVExpander &Rewriter,
4987 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
4988 if (LU.RigidFormula)
4989 return LF.OperandValToReplace;
4990
4991 // Determine an input position which will be dominated by the operands and
4992 // which will dominate the result.
4993 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4994 Rewriter.setInsertPoint(&*IP);
4995
4996 // Inform the Rewriter if we have a post-increment use, so that it can
4997 // perform an advantageous expansion.
4998 Rewriter.setPostInc(LF.PostIncLoops);
4999
5000 // This is the type that the user actually needs.
5001 Type *OpTy = LF.OperandValToReplace->getType();
5002 // This will be the type that we'll initially expand to.
5003 Type *Ty = F.getType();
5004 if (!Ty)
5005 // No type known; just expand directly to the ultimate type.
5006 Ty = OpTy;
5007 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
5008 // Expand directly to the ultimate type if it's the right size.
5009 Ty = OpTy;
5010 // This is the type to do integer arithmetic in.
5011 Type *IntTy = SE.getEffectiveSCEVType(Ty);
5012
5013 // Build up a list of operands to add together to form the full base.
5014 SmallVector<const SCEV *, 8> Ops;
5015
5016 // Expand the BaseRegs portion.
5017 for (const SCEV *Reg : F.BaseRegs) {
5018 assert(!Reg->isZero() && "Zero allocated in a base register!")(static_cast <bool> (!Reg->isZero() && "Zero allocated in a base register!"
) ? void (0) : __assert_fail ("!Reg->isZero() && \"Zero allocated in a base register!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5018, __extension__ __PRETTY_FUNCTION__))
;
5019
5020 // If we're expanding for a post-inc user, make the post-inc adjustment.
5021 Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE);
5022 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr)));
5023 }
5024
5025 // Expand the ScaledReg portion.
5026 Value *ICmpScaledV = nullptr;
5027 if (F.Scale != 0) {
5028 const SCEV *ScaledS = F.ScaledReg;
5029
5030 // If we're expanding for a post-inc user, make the post-inc adjustment.
5031 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
5032 ScaledS = denormalizeForPostIncUse(ScaledS, Loops, SE);
5033
5034 if (LU.Kind == LSRUse::ICmpZero) {
5035 // Expand ScaleReg as if it was part of the base regs.
5036 if (F.Scale == 1)
5037 Ops.push_back(
5038 SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)));
5039 else {
5040 // An interesting way of "folding" with an icmp is to use a negated
5041 // scale, which we'll implement by inserting it into the other operand
5042 // of the icmp.
5043 assert(F.Scale == -1 &&(static_cast <bool> (F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? void (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5044, __extension__ __PRETTY_FUNCTION__))
5044 "The only scale supported by ICmpZero uses is -1!")(static_cast <bool> (F.Scale == -1 && "The only scale supported by ICmpZero uses is -1!"
) ? void (0) : __assert_fail ("F.Scale == -1 && \"The only scale supported by ICmpZero uses is -1!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5044, __extension__ __PRETTY_FUNCTION__))
;
5045 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr);
5046 }
5047 } else {
5048 // Otherwise just expand the scaled register and an explicit scale,
5049 // which is expected to be matched as part of the address.
5050
5051 // Flush the operand list to suppress SCEVExpander hoisting address modes.
5052 // Unless the addressing mode will not be folded.
5053 if (!Ops.empty() && LU.Kind == LSRUse::Address &&
5054 isAMCompletelyFolded(TTI, LU, F)) {
5055 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), nullptr);
5056 Ops.clear();
5057 Ops.push_back(SE.getUnknown(FullV));
5058 }
5059 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr));
5060 if (F.Scale != 1)
5061 ScaledS =
5062 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
5063 Ops.push_back(ScaledS);
5064 }
5065 }
5066
5067 // Expand the GV portion.
5068 if (F.BaseGV) {
5069 // Flush the operand list to suppress SCEVExpander hoisting.
5070 if (!Ops.empty()) {
5071 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5072 Ops.clear();
5073 Ops.push_back(SE.getUnknown(FullV));
5074 }
5075 Ops.push_back(SE.getUnknown(F.BaseGV));
5076 }
5077
5078 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
5079 // unfolded offsets. LSR assumes they both live next to their uses.
5080 if (!Ops.empty()) {
5081 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty);
5082 Ops.clear();
5083 Ops.push_back(SE.getUnknown(FullV));
5084 }
5085
5086 // Expand the immediate portion.
5087 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
5088 if (Offset != 0) {
5089 if (LU.Kind == LSRUse::ICmpZero) {
5090 // The other interesting way of "folding" with an ICmpZero is to use a
5091 // negated immediate.
5092 if (!ICmpScaledV)
5093 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
5094 else {
5095 Ops.push_back(SE.getUnknown(ICmpScaledV));
5096 ICmpScaledV = ConstantInt::get(IntTy, Offset);
5097 }
5098 } else {
5099 // Just add the immediate values. These again are expected to be matched
5100 // as part of the address.
5101 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
5102 }
5103 }
5104
5105 // Expand the unfolded offset portion.
5106 int64_t UnfoldedOffset = F.UnfoldedOffset;
5107 if (UnfoldedOffset != 0) {
5108 // Just add the immediate values.
5109 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
5110 UnfoldedOffset)));
5111 }
5112
5113 // Emit instructions summing all the operands.
5114 const SCEV *FullS = Ops.empty() ?
5115 SE.getConstant(IntTy, 0) :
5116 SE.getAddExpr(Ops);
5117 Value *FullV = Rewriter.expandCodeFor(FullS, Ty);
5118
5119 // We're done expanding now, so reset the rewriter.
5120 Rewriter.clearPostInc();
5121
5122 // An ICmpZero Formula represents an ICmp which we're handling as a
5123 // comparison against zero. Now that we've expanded an expression for that
5124 // form, update the ICmp's other operand.
5125 if (LU.Kind == LSRUse::ICmpZero) {
5126 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
5127 DeadInsts.emplace_back(CI->getOperand(1));
5128 assert(!F.BaseGV && "ICmp does not support folding a global value and "(static_cast <bool> (!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? 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-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5129, __extension__ __PRETTY_FUNCTION__))
5129 "a scale at the same time!")(static_cast <bool> (!F.BaseGV && "ICmp does not support folding a global value and "
"a scale at the same time!") ? 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-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5129, __extension__ __PRETTY_FUNCTION__))
;
5130 if (F.Scale == -1) {
5131 if (ICmpScaledV->getType() != OpTy) {
5132 Instruction *Cast =
5133 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
5134 OpTy, false),
5135 ICmpScaledV, OpTy, "tmp", CI);
5136 ICmpScaledV = Cast;
5137 }
5138 CI->setOperand(1, ICmpScaledV);
5139 } else {
5140 // A scale of 1 means that the scale has been expanded as part of the
5141 // base regs.
5142 assert((F.Scale == 0 || F.Scale == 1) &&(static_cast <bool> ((F.Scale == 0 || F.Scale == 1) &&
"ICmp does not support folding a global value and " "a scale at the same time!"
) ? 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-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5144, __extension__ __PRETTY_FUNCTION__))
5143 "ICmp does not support folding a global value and "(static_cast <bool> ((F.Scale == 0 || F.Scale == 1) &&
"ICmp does not support folding a global value and " "a scale at the same time!"
) ? 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-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5144, __extension__ __PRETTY_FUNCTION__))
5144 "a scale at the same time!")(static_cast <bool> ((F.Scale == 0 || F.Scale == 1) &&
"ICmp does not support folding a global value and " "a scale at the same time!"
) ? 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-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5144, __extension__ __PRETTY_FUNCTION__))
;
5145 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
5146 -(uint64_t)Offset);
5147 if (C->getType() != OpTy)
5148 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
5149 OpTy, false),
5150 C, OpTy);
5151
5152 CI->setOperand(1, C);
5153 }
5154 }
5155
5156 return FullV;
5157}
5158
5159/// Helper for Rewrite. PHI nodes are special because the use of their operands
5160/// effectively happens in their predecessor blocks, so the expression may need
5161/// to be expanded in multiple places.
5162void LSRInstance::RewriteForPHI(
5163 PHINode *PN, const LSRUse &LU, const LSRFixup &LF, const Formula &F,
5164 SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5165 DenseMap<BasicBlock *, Value *> Inserted;
5166 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1
Assuming 'i' is not equal to 'e'
2
Loop condition is true. Entering loop body
5167 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
3
Assuming pointer value is null
4
Taking true branch
5168 BasicBlock *BB = PN->getIncomingBlock(i);
5169
5170 // If this is a critical edge, split the edge so that we do not insert
5171 // the code on all predecessor/successor paths. We do this unless this
5172 // is the canonical backedge for this loop, which complicates post-inc
5173 // users.
5174 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
5
Assuming 'e' is equal to 1
6
Taking false branch
5175 !isa<IndirectBrInst>(BB->getTerminator()) &&
5176 !isa<CatchSwitchInst>(BB->getTerminator())) {
5177 BasicBlock *Parent = PN->getParent();
5178 Loop *PNLoop = LI.getLoopFor(Parent);
5179 if (!PNLoop || Parent != PNLoop->getHeader()) {
5180 // Split the critical edge.
5181 BasicBlock *NewBB = nullptr;
5182 if (!Parent->isLandingPad()) {
5183 NewBB = SplitCriticalEdge(BB, Parent,
5184 CriticalEdgeSplittingOptions(&DT, &LI)
5185 .setMergeIdenticalEdges()
5186 .setDontDeleteUselessPHIs());
5187 } else {
5188 SmallVector<BasicBlock*, 2> NewBBs;
5189 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
5190 NewBB = NewBBs[0];
5191 }
5192 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
5193 // phi predecessors are identical. The simple thing to do is skip
5194 // splitting in this case rather than complicate the API.
5195 if (NewBB) {
5196 // If PN is outside of the loop and BB is in the loop, we want to
5197 // move the block to be immediately before the PHI block, not
5198 // immediately after BB.
5199 if (L->contains(BB) && !L->contains(PN))
5200 NewBB->moveBefore(PN->getParent());
5201
5202 // Splitting the edge can reduce the number of PHI entries we have.
5203 e = PN->getNumIncomingValues();
5204 BB = NewBB;
5205 i = PN->getBasicBlockIndex(BB);
5206 }
5207 }
5208 }
5209
5210 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
5211 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
5212 if (!Pair.second)
7
Assuming the condition is false
8
Taking false branch
5213 PN->setIncomingValue(i, Pair.first->second);
5214 else {
5215 Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(),
5216 Rewriter, DeadInsts);
5217
5218 // If this is reuse-by-noop-cast, insert the noop cast.
5219 Type *OpTy = LF.OperandValToReplace->getType();
9
Called C++ object pointer is null
5220 if (FullV->getType() != OpTy)
5221 FullV =
5222 CastInst::Create(CastInst::getCastOpcode(FullV, false,
5223 OpTy, false),
5224 FullV, LF.OperandValToReplace->getType(),
5225 "tmp", BB->getTerminator());
5226
5227 PN->setIncomingValue(i, FullV);
5228 Pair.first->second = FullV;
5229 }
5230 }
5231}
5232
5233/// Emit instructions for the leading candidate expression for this LSRUse (this
5234/// is called "expanding"), and update the UserInst to reference the newly
5235/// expanded value.
5236void LSRInstance::Rewrite(const LSRUse &LU, const LSRFixup &LF,
5237 const Formula &F, SCEVExpander &Rewriter,
5238 SmallVectorImpl<WeakTrackingVH> &DeadInsts) const {
5239 // First, find an insertion point that dominates UserInst. For PHI nodes,
5240 // find the nearest block which dominates all the relevant uses.
5241 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
5242 RewriteForPHI(PN, LU, LF, F, Rewriter, DeadInsts);
5243 } else {
5244 Value *FullV =
5245 Expand(LU, LF, F, LF.UserInst->getIterator(), Rewriter, DeadInsts);
5246
5247 // If this is reuse-by-noop-cast, insert the noop cast.
5248 Type *OpTy = LF.OperandValToReplace->getType();
5249 if (FullV->getType() != OpTy) {
5250 Instruction *Cast =
5251 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
5252 FullV, OpTy, "tmp", LF.UserInst);
5253 FullV = Cast;
5254 }
5255
5256 // Update the user. ICmpZero is handled specially here (for now) because
5257 // Expand may have updated one of the operands of the icmp already, and
5258 // its new value may happen to be equal to LF.OperandValToReplace, in
5259 // which case doing replaceUsesOfWith leads to replacing both operands
5260 // with the same value. TODO: Reorganize this.
5261 if (LU.Kind == LSRUse::ICmpZero)
5262 LF.UserInst->setOperand(0, FullV);
5263 else
5264 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
5265 }
5266
5267 DeadInsts.emplace_back(LF.OperandValToReplace);
5268}
5269
5270/// Rewrite all the fixup locations with new values, following the chosen
5271/// solution.
5272void LSRInstance::ImplementSolution(
5273 const SmallVectorImpl<const Formula *> &Solution) {
5274 // Keep track of instructions we may have made dead, so that
5275 // we can remove them after we are done working.
5276 SmallVector<WeakTrackingVH, 16> DeadInsts;
5277
5278 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(),
5279 "lsr");
5280#ifndef NDEBUG
5281 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5282#endif
5283 Rewriter.disableCanonicalMode();
5284 Rewriter.enableLSRMode();
5285 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
5286
5287 // Mark phi nodes that terminate chains so the expander tries to reuse them.
5288 for (const IVChain &Chain : IVChainVec) {
5289 if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
5290 Rewriter.setChainedPhi(PN);
5291 }
5292
5293 // Expand the new value definitions and update the users.
5294 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx)
5295 for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) {
5296 Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts);
5297 Changed = true;
5298 }
5299
5300 for (const IVChain &Chain : IVChainVec) {
5301 GenerateIVChain(Chain, Rewriter, DeadInsts);
5302 Changed = true;
5303 }
5304 // Clean up after ourselves. This must be done before deleting any
5305 // instructions.
5306 Rewriter.clear();
5307
5308 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
5309}
5310
5311LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5312 DominatorTree &DT, LoopInfo &LI,
5313 const TargetTransformInfo &TTI)
5314 : IU(IU), SE(SE), DT(DT), LI(LI), TTI(TTI), L(L) {
5315 // If LoopSimplify form is not available, stay out of trouble.
5316 if (!L->isLoopSimplifyForm())
5317 return;
5318
5319 // If there's no interesting work to be done, bail early.
5320 if (IU.empty()) return;
5321
5322 // If there's too much analysis to be done, bail early. We won't be able to
5323 // model the problem anyway.
5324 unsigned NumUsers = 0;
5325 for (const IVStrideUse &U : IU) {
5326 if (++NumUsers > MaxIVUsers) {
5327 (void)U;
5328 DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << U << "\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR skipping loop, too many IV Users in "
<< U << "\n"; } } while (false)
;
5329 return;
5330 }
5331 // Bail out if we have a PHI on an EHPad that gets a value from a
5332 // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is
5333 // no good place to stick any instructions.
5334 if (auto *PN = dyn_cast<PHINode>(U.getUser())) {
5335 auto *FirstNonPHI = PN->getParent()->getFirstNonPHI();
5336 if (isa<FuncletPadInst>(FirstNonPHI) ||
5337 isa<CatchSwitchInst>(FirstNonPHI))
5338 for (BasicBlock *PredBB : PN->blocks())
5339 if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI()))
5340 return;
5341 }
5342 }
5343
5344#ifndef NDEBUG
5345 // All dominating loops must have preheaders, or SCEVExpander may not be able
5346 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
5347 //
5348 // IVUsers analysis should only create users that are dominated by simple loop
5349 // headers. Since this loop should dominate all of its users, its user list
5350 // should be empty if this loop itself is not within a simple loop nest.
5351 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
5352 Rung; Rung = Rung->getIDom()) {
5353 BasicBlock *BB = Rung->getBlock();
5354 const Loop *DomLoop = LI.getLoopFor(BB);
5355 if (DomLoop && DomLoop->getHeader() == BB) {
5356 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest")(static_cast <bool> (DomLoop->getLoopPreheader() &&
"LSR needs a simplified loop nest") ? void (0) : __assert_fail
("DomLoop->getLoopPreheader() && \"LSR needs a simplified loop nest\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5356, __extension__ __PRETTY_FUNCTION__))
;
5357 }
5358 }
5359#endif // DEBUG
5360
5361 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)
5362 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)
5363 dbgs() << ":\n")do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "\nLSR on loop "; L->getHeader
()->printAsOperand(dbgs(), false); dbgs() << ":\n"; }
} while (false)
;
5364
5365 // First, perform some low-level loop optimizations.
5366 OptimizeShadowIV();
5367 OptimizeLoopTermCond();
5368
5369 // If loop preparation eliminates all interesting IV users, bail.
5370 if (IU.empty()) return;
5371
5372 // Skip nested loops until we can model them better with formulae.
5373 if (!L->empty()) {
5374 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)
;
5375 return;
5376 }
5377
5378 // Start collecting data and preparing for the solver.
5379 CollectChains();
5380 CollectInterestingTypesAndFactors();
5381 CollectFixupsAndInitialFormulae();
5382 CollectLoopInvariantFixupsAndFormulae();
5383
5384 assert(!Uses.empty() && "IVUsers reported at least one use")(static_cast <bool> (!Uses.empty() && "IVUsers reported at least one use"
) ? void (0) : __assert_fail ("!Uses.empty() && \"IVUsers reported at least one use\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5384, __extension__ __PRETTY_FUNCTION__))
;
5385 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
)
5386 print_uses(dbgs()))do { if (::llvm::DebugFlag && ::llvm::isCurrentDebugType
("loop-reduce")) { dbgs() << "LSR found " << Uses
.size() << " uses:\n"; print_uses(dbgs()); } } while (false
)
;
5387
5388 // Now use the reuse data to generate a bunch of interesting ways
5389 // to formulate the values needed for the uses.
5390 GenerateAllReuseFormulae();
5391
5392 FilterOutUndesirableDedicatedRegisters();
5393 NarrowSearchSpaceUsingHeuristics();
5394
5395 SmallVector<const Formula *, 8> Solution;
5396 Solve(Solution);
5397
5398 // Release memory that is no longer needed.
5399 Factors.clear();
5400 Types.clear();
5401 RegUses.clear();
5402
5403 if (Solution.empty())
5404 return;
5405
5406#ifndef NDEBUG
5407 // Formulae should be legal.
5408 for (const LSRUse &LU : Uses) {
5409 for (const Formula &F : LU.Formulae)
5410 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,(static_cast <bool> (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset
, LU.Kind, LU.AccessTy, F) && "Illegal formula generated!"
) ? void (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Illegal formula generated!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5411, __extension__ __PRETTY_FUNCTION__))
5411 F) && "Illegal formula generated!")(static_cast <bool> (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset
, LU.Kind, LU.AccessTy, F) && "Illegal formula generated!"
) ? void (0) : __assert_fail ("isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && \"Illegal formula generated!\""
, "/build/llvm-toolchain-snapshot-7~svn329677/lib/Transforms/Scalar/LoopStrengthReduce.cpp"
, 5411, __extension__ __PRETTY_FUNCTION__))
;
5412 };
5413#endif
5414
5415 // Now that we've decided what we want, make it so.
5416 ImplementSolution(Solution);
5417}
5418
5419#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5420void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
5421 if (Factors.empty() && Types.empty()) return;
5422
5423 OS << "LSR has identified the following interesting factors and types: ";
5424 bool First = true;
5425
5426 for (int64_t Factor : Factors) {
5427 if (!First) OS << ", ";
5428 First = false;
5429 OS << '*' << Factor;
5430 }
5431
5432 for (Type *Ty : Types) {
5433 if (!First) OS << ", ";
5434 First = false;
5435 OS << '(' << *Ty << ')';
5436 }
5437 OS << '\n';
5438}
5439
5440void LSRInstance::print_fixups(raw_ostream &OS) const {
5441 OS << "LSR is examining the following fixup sites:\n";
5442 for (const LSRUse &LU : Uses)
5443 for (const LSRFixup &LF : LU.Fixups) {
5444 dbgs() << " ";
5445 LF.print(OS);
5446 OS << '\n';
5447 }
5448}
5449
5450void LSRInstance::print_uses(raw_ostream &OS) const {
5451 OS << "LSR is examining the following uses:\n";
5452 for (const LSRUse &LU : Uses) {
5453 dbgs() << " ";
5454 LU.print(OS);
5455 OS << '\n';
5456 for (const Formula &F : LU.Formulae) {
5457 OS << " ";
5458 F.print(OS);
5459 OS << '\n';
5460 }
5461 }
5462}
5463
5464void LSRInstance::print(raw_ostream &OS) const {
5465 print_factors_and_types(OS);
5466 print_fixups(OS);
5467 print_uses(OS);
5468}
5469
5470LLVM_DUMP_METHOD__attribute__((noinline)) __attribute__((__used__)) void LSRInstance::dump() const {
5471 print(errs()); errs() << '\n';
5472}
5473#endif
5474
5475namespace {
5476
5477class LoopStrengthReduce : public LoopPass {
5478public:
5479 static char ID; // Pass ID, replacement for typeid
5480
5481 LoopStrengthReduce();
5482
5483private:
5484 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
5485 void getAnalysisUsage(AnalysisUsage &AU) const override;
5486};
5487
5488} // end anonymous namespace
5489
5490LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
5491 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
5492}
5493
5494void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
5495 // We split critical edges, so we change the CFG. However, we do update
5496 // many analyses if they are around.
5497 AU.addPreservedID(LoopSimplifyID);
5498
5499 AU.addRequired<LoopInfoWrapperPass>();
5500 AU.addPreserved<LoopInfoWrapperPass>();
5501 AU.addRequiredID(LoopSimplifyID);
5502 AU.addRequired<DominatorTreeWrapperPass>();
5503 AU.addPreserved<DominatorTreeWrapperPass>();
5504 AU.addRequired<ScalarEvolutionWrapperPass>();
5505 AU.addPreserved<ScalarEvolutionWrapperPass>();
5506 // Requiring LoopSimplify a second time here prevents IVUsers from running
5507 // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5508 AU.addRequiredID(LoopSimplifyID);
5509 AU.addRequired<IVUsersWrapperPass>();
5510 AU.addPreserved<IVUsersWrapperPass>();
5511 AU.addRequired<TargetTransformInfoWrapperPass>();
5512}
5513
5514static bool ReduceLoopStrength(Loop *L, IVUsers &IU, ScalarEvolution &SE,
5515 DominatorTree &DT, LoopInfo &LI,
5516 const TargetTransformInfo &TTI) {
5517 bool Changed = false;
5518
5519 // Run the main LSR transformation.
5520 Changed |= LSRInstance(L, IU, SE, DT, LI, TTI).getChanged();
5521
5522 // Remove any extra phis created by processing inner loops.
5523 Changed |= DeleteDeadPHIs(L->getHeader());
5524 if (EnablePhiElim && L->isLoopSimplifyForm()) {
5525 SmallVector<WeakTrackingVH, 16> DeadInsts;
5526 const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
5527 SCEVExpander Rewriter(SE, DL, "lsr");
5528#ifndef NDEBUG
5529 Rewriter.setDebugType(DEBUG_TYPE"loop-reduce");
5530#endif
5531 unsigned numFolded = Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, &TTI);
5532 if (numFolded) {
5533 Changed = true;
5534 DeleteTriviallyDeadInstructions(DeadInsts);
5535 DeleteDeadPHIs(L->getHeader());
5536 }
5537 }
5538 return Changed;
5539}
5540
5541bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5542 if (skipLoop(L))
5543 return false;
5544
5545 auto &IU = getAnalysis<IVUsersWrapperPass>().getIU();
5546 auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE();
5547 auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
5548 auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
5549 const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
5550 *L->getHeader()->getParent());
5551 return ReduceLoopStrength(L, IU, SE, DT, LI, TTI);
5552}
5553
5554PreservedAnalyses LoopStrengthReducePass::run(Loop &L, LoopAnalysisManager &AM,
5555 LoopStandardAnalysisResults &AR,
5556 LPMUpdater &) {
5557 if (!ReduceLoopStrength(&L, AM.getResult<IVUsersAnalysis>(L, AR), AR.SE,
5558 AR.DT, AR.LI, AR.TTI))
5559 return PreservedAnalyses::all();
5560
5561 return getLoopPassPreservedAnalyses();
5562}
5563
5564char LoopStrengthReduce::ID = 0;
5565
5566INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",static void *initializeLoopStrengthReducePassOnce(PassRegistry
&Registry) {
5567 "Loop Strength Reduction", false, false)static void *initializeLoopStrengthReducePassOnce(PassRegistry
&Registry) {
5568INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)initializeTargetTransformInfoWrapperPassPass(Registry);
5569INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)initializeDominatorTreeWrapperPassPass(Registry);
5570INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass)initializeScalarEvolutionWrapperPassPass(Registry);
5571INITIALIZE_PASS_DEPENDENCY(IVUsersWrapperPass)initializeIVUsersWrapperPassPass(Registry);
5572INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)initializeLoopInfoWrapperPassPass(Registry);
5573INITIALIZE_PASS_DEPENDENCY(LoopSimplify)initializeLoopSimplifyPass(Registry);
5574INITIALIZE_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)); }
5575 "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)); }
5576
5577Pass *llvm::createLoopStrengthReducePass() { return new LoopStrengthReduce(); }