1 //===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation analyzes and transforms the induction variables (and
11 // computations derived from them) into forms suitable for efficient execution
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.
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:
24 // %i = phi [ 0, %entry ], [ %i.next, %latch ]
26 // %i.next = add %i, 1
27 // %c = icmp eq %i.next, %n
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.
36 // TODO: More sophistication in the way Formulae are generated and filtered.
38 // TODO: Handle multiple loops at a time.
40 // TODO: Should the addressing mode BaseGV be changed to a ConstantExpr instead
43 // TODO: When truncation is free, truncate ICmp users' operands to make it a
44 // smaller encoding (on x86 at least).
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"
54 //===----------------------------------------------------------------------===//
56 #include "llvm/Transforms/Scalar.h"
57 #include "llvm/ADT/DenseSet.h"
58 #include "llvm/ADT/Hashing.h"
59 #include "llvm/ADT/STLExtras.h"
60 #include "llvm/ADT/SetVector.h"
61 #include "llvm/ADT/SmallBitVector.h"
62 #include "llvm/Analysis/IVUsers.h"
63 #include "llvm/Analysis/LoopPass.h"
64 #include "llvm/Analysis/ScalarEvolutionExpander.h"
65 #include "llvm/Analysis/TargetTransformInfo.h"
66 #include "llvm/IR/Constants.h"
67 #include "llvm/IR/DerivedTypes.h"
68 #include "llvm/IR/Dominators.h"
69 #include "llvm/IR/Instructions.h"
70 #include "llvm/IR/IntrinsicInst.h"
71 #include "llvm/IR/Module.h"
72 #include "llvm/IR/ValueHandle.h"
73 #include "llvm/Support/CommandLine.h"
74 #include "llvm/Support/Debug.h"
75 #include "llvm/Support/raw_ostream.h"
76 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
77 #include "llvm/Transforms/Utils/Local.h"
81 #define DEBUG_TYPE "loop-reduce"
83 /// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for
84 /// bail out. This threshold is far beyond the number of users that LSR can
85 /// conceivably solve, so it should not affect generated code, but catches the
86 /// worst cases before LSR burns too much compile time and stack space.
87 static const unsigned MaxIVUsers = 200;
89 // Temporary flag to cleanup congruent phis after LSR phi expansion.
90 // It's currently disabled until we can determine whether it's truly useful or
91 // not. The flag should be removed after the v3.0 release.
92 // This is now needed for ivchains.
93 static cl::opt<bool> EnablePhiElim(
94 "enable-lsr-phielim", cl::Hidden, cl::init(true),
95 cl::desc("Enable LSR phi elimination"));
98 // Stress test IV chain generation.
99 static cl::opt<bool> StressIVChain(
100 "stress-ivchain", cl::Hidden, cl::init(false),
101 cl::desc("Stress test LSR IV chains"));
103 static bool StressIVChain = false;
108 /// RegSortData - This class holds data which is used to order reuse candidates.
111 /// UsedByIndices - This represents the set of LSRUse indices which reference
112 /// a particular register.
113 SmallBitVector UsedByIndices;
115 void print(raw_ostream &OS) const;
121 void RegSortData::print(raw_ostream &OS) const {
122 OS << "[NumUses=" << UsedByIndices.count() << ']';
125 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
126 void RegSortData::dump() const {
127 print(errs()); errs() << '\n';
133 /// RegUseTracker - Map register candidates to information about how they are
135 class RegUseTracker {
136 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
138 RegUsesTy RegUsesMap;
139 SmallVector<const SCEV *, 16> RegSequence;
142 void CountRegister(const SCEV *Reg, size_t LUIdx);
143 void DropRegister(const SCEV *Reg, size_t LUIdx);
144 void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx);
146 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
148 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
152 typedef SmallVectorImpl<const SCEV *>::iterator iterator;
153 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
154 iterator begin() { return RegSequence.begin(); }
155 iterator end() { return RegSequence.end(); }
156 const_iterator begin() const { return RegSequence.begin(); }
157 const_iterator end() const { return RegSequence.end(); }
163 RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
164 std::pair<RegUsesTy::iterator, bool> Pair =
165 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
166 RegSortData &RSD = Pair.first->second;
168 RegSequence.push_back(Reg);
169 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
170 RSD.UsedByIndices.set(LUIdx);
174 RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) {
175 RegUsesTy::iterator It = RegUsesMap.find(Reg);
176 assert(It != RegUsesMap.end());
177 RegSortData &RSD = It->second;
178 assert(RSD.UsedByIndices.size() > LUIdx);
179 RSD.UsedByIndices.reset(LUIdx);
183 RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
184 assert(LUIdx <= LastLUIdx);
186 // Update RegUses. The data structure is not optimized for this purpose;
187 // we must iterate through it and update each of the bit vectors.
188 for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end();
190 SmallBitVector &UsedByIndices = I->second.UsedByIndices;
191 if (LUIdx < UsedByIndices.size())
192 UsedByIndices[LUIdx] =
193 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0;
194 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
199 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
200 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
201 if (I == RegUsesMap.end())
203 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
204 int i = UsedByIndices.find_first();
205 if (i == -1) return false;
206 if ((size_t)i != LUIdx) return true;
207 return UsedByIndices.find_next(i) != -1;
210 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
211 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
212 assert(I != RegUsesMap.end() && "Unknown register!");
213 return I->second.UsedByIndices;
216 void RegUseTracker::clear() {
223 /// Formula - This class holds information that describes a formula for
224 /// computing satisfying a use. It may include broken-out immediates and scaled
227 /// Global base address used for complex addressing.
230 /// Base offset for complex addressing.
233 /// Whether any complex addressing has a base register.
236 /// The scale of any complex addressing.
239 /// BaseRegs - The list of "base" registers for this use. When this is
240 /// non-empty. The canonical representation of a formula is
241 /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
242 /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
243 /// #1 enforces that the scaled register is always used when at least two
244 /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
245 /// #2 enforces that 1 * reg is reg.
246 /// This invariant can be temporarly broken while building a formula.
247 /// However, every formula inserted into the LSRInstance must be in canonical
249 SmallVector<const SCEV *, 4> BaseRegs;
251 /// ScaledReg - The 'scaled' register for this use. This should be non-null
252 /// when Scale is not zero.
253 const SCEV *ScaledReg;
255 /// UnfoldedOffset - An additional constant offset which added near the
256 /// use. This requires a temporary register, but the offset itself can
257 /// live in an add immediate field rather than a register.
258 int64_t UnfoldedOffset;
261 : BaseGV(nullptr), BaseOffset(0), HasBaseReg(false), Scale(0),
262 ScaledReg(nullptr), UnfoldedOffset(0) {}
264 void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
266 bool isCanonical() const;
272 size_t getNumRegs() const;
273 Type *getType() const;
275 void DeleteBaseReg(const SCEV *&S);
277 bool referencesReg(const SCEV *S) const;
278 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
279 const RegUseTracker &RegUses) const;
281 void print(raw_ostream &OS) const;
287 /// DoInitialMatch - Recursion helper for InitialMatch.
288 static void DoInitialMatch(const SCEV *S, Loop *L,
289 SmallVectorImpl<const SCEV *> &Good,
290 SmallVectorImpl<const SCEV *> &Bad,
291 ScalarEvolution &SE) {
292 // Collect expressions which properly dominate the loop header.
293 if (SE.properlyDominates(S, L->getHeader())) {
298 // Look at add operands.
299 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
300 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
302 DoInitialMatch(*I, L, Good, Bad, SE);
306 // Look at addrec operands.
307 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
308 if (!AR->getStart()->isZero()) {
309 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
310 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
311 AR->getStepRecurrence(SE),
312 // FIXME: AR->getNoWrapFlags()
313 AR->getLoop(), SCEV::FlagAnyWrap),
318 // Handle a multiplication by -1 (negation) if it didn't fold.
319 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
320 if (Mul->getOperand(0)->isAllOnesValue()) {
321 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
322 const SCEV *NewMul = SE.getMulExpr(Ops);
324 SmallVector<const SCEV *, 4> MyGood;
325 SmallVector<const SCEV *, 4> MyBad;
326 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
327 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
328 SE.getEffectiveSCEVType(NewMul->getType())));
329 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
330 E = MyGood.end(); I != E; ++I)
331 Good.push_back(SE.getMulExpr(NegOne, *I));
332 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
333 E = MyBad.end(); I != E; ++I)
334 Bad.push_back(SE.getMulExpr(NegOne, *I));
338 // Ok, we can't do anything interesting. Just stuff the whole thing into a
339 // register and hope for the best.
343 /// InitialMatch - Incorporate loop-variant parts of S into this Formula,
344 /// attempting to keep all loop-invariant and loop-computable values in a
345 /// single base register.
346 void Formula::InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
347 SmallVector<const SCEV *, 4> Good;
348 SmallVector<const SCEV *, 4> Bad;
349 DoInitialMatch(S, L, Good, Bad, SE);
351 const SCEV *Sum = SE.getAddExpr(Good);
353 BaseRegs.push_back(Sum);
357 const SCEV *Sum = SE.getAddExpr(Bad);
359 BaseRegs.push_back(Sum);
365 /// \brief Check whether or not this formula statisfies the canonical
367 /// \see Formula::BaseRegs.
368 bool Formula::isCanonical() const {
370 return Scale != 1 || !BaseRegs.empty();
371 return BaseRegs.size() <= 1;
374 /// \brief Helper method to morph a formula into its canonical representation.
375 /// \see Formula::BaseRegs.
376 /// Every formula having more than one base register, must use the ScaledReg
377 /// field. Otherwise, we would have to do special cases everywhere in LSR
378 /// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
379 /// On the other hand, 1*reg should be canonicalized into reg.
380 void Formula::Canonicalize() {
383 // So far we did not need this case. This is easy to implement but it is
384 // useless to maintain dead code. Beside it could hurt compile time.
385 assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.");
386 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
387 ScaledReg = BaseRegs.back();
390 size_t BaseRegsSize = BaseRegs.size();
392 // If ScaledReg is an invariant, try to find a variant expression.
393 while (Try < BaseRegsSize && !isa<SCEVAddRecExpr>(ScaledReg))
394 std::swap(ScaledReg, BaseRegs[Try++]);
397 /// \brief Get rid of the scale in the formula.
398 /// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
399 /// \return true if it was possible to get rid of the scale, false otherwise.
400 /// \note After this operation the formula may not be in the canonical form.
401 bool Formula::Unscale() {
405 BaseRegs.push_back(ScaledReg);
410 /// getNumRegs - Return the total number of register operands used by this
411 /// formula. This does not include register uses implied by non-constant
413 size_t Formula::getNumRegs() const {
414 return !!ScaledReg + BaseRegs.size();
417 /// getType - Return the type of this formula, if it has one, or null
418 /// otherwise. This type is meaningless except for the bit size.
419 Type *Formula::getType() const {
420 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
421 ScaledReg ? ScaledReg->getType() :
422 BaseGV ? BaseGV->getType() :
426 /// DeleteBaseReg - Delete the given base reg from the BaseRegs list.
427 void Formula::DeleteBaseReg(const SCEV *&S) {
428 if (&S != &BaseRegs.back())
429 std::swap(S, BaseRegs.back());
433 /// referencesReg - Test if this formula references the given register.
434 bool Formula::referencesReg(const SCEV *S) const {
435 return S == ScaledReg ||
436 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
439 /// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
440 /// which are used by uses other than the use with the given index.
441 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
442 const RegUseTracker &RegUses) const {
444 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
446 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
447 E = BaseRegs.end(); I != E; ++I)
448 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
453 void Formula::print(raw_ostream &OS) const {
456 if (!First) OS << " + "; else First = false;
457 BaseGV->printAsOperand(OS, /*PrintType=*/false);
459 if (BaseOffset != 0) {
460 if (!First) OS << " + "; else First = false;
463 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
464 E = BaseRegs.end(); I != E; ++I) {
465 if (!First) OS << " + "; else First = false;
466 OS << "reg(" << **I << ')';
468 if (HasBaseReg && BaseRegs.empty()) {
469 if (!First) OS << " + "; else First = false;
470 OS << "**error: HasBaseReg**";
471 } else if (!HasBaseReg && !BaseRegs.empty()) {
472 if (!First) OS << " + "; else First = false;
473 OS << "**error: !HasBaseReg**";
476 if (!First) OS << " + "; else First = false;
477 OS << Scale << "*reg(";
484 if (UnfoldedOffset != 0) {
485 if (!First) OS << " + ";
486 OS << "imm(" << UnfoldedOffset << ')';
490 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
491 void Formula::dump() const {
492 print(errs()); errs() << '\n';
496 /// isAddRecSExtable - Return true if the given addrec can be sign-extended
497 /// without changing its value.
498 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
500 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
501 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
504 /// isAddSExtable - Return true if the given add can be sign-extended
505 /// without changing its value.
506 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
508 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
509 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
512 /// isMulSExtable - Return true if the given mul can be sign-extended
513 /// without changing its value.
514 static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
516 IntegerType::get(SE.getContext(),
517 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
518 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
521 /// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
522 /// and if the remainder is known to be zero, or null otherwise. If
523 /// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
524 /// to Y, ignoring that the multiplication may overflow, which is useful when
525 /// the result will be used in a context where the most significant bits are
527 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
529 bool IgnoreSignificantBits = false) {
530 // Handle the trivial case, which works for any SCEV type.
532 return SE.getConstant(LHS->getType(), 1);
534 // Handle a few RHS special cases.
535 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
537 const APInt &RA = RC->getValue()->getValue();
538 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
540 if (RA.isAllOnesValue())
541 return SE.getMulExpr(LHS, RC);
542 // Handle x /s 1 as x.
547 // Check for a division of a constant by a constant.
548 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
551 const APInt &LA = C->getValue()->getValue();
552 const APInt &RA = RC->getValue()->getValue();
553 if (LA.srem(RA) != 0)
555 return SE.getConstant(LA.sdiv(RA));
558 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
559 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
560 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
561 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
562 IgnoreSignificantBits);
563 if (!Step) return nullptr;
564 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
565 IgnoreSignificantBits);
566 if (!Start) return nullptr;
567 // FlagNW is independent of the start value, step direction, and is
568 // preserved with smaller magnitude steps.
569 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
570 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
575 // Distribute the sdiv over add operands, if the add doesn't overflow.
576 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
577 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
578 SmallVector<const SCEV *, 8> Ops;
579 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
581 const SCEV *Op = getExactSDiv(*I, RHS, SE,
582 IgnoreSignificantBits);
583 if (!Op) return nullptr;
586 return SE.getAddExpr(Ops);
591 // Check for a multiply operand that we can pull RHS out of.
592 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
593 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
594 SmallVector<const SCEV *, 4> Ops;
596 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
600 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
601 IgnoreSignificantBits)) {
607 return Found ? SE.getMulExpr(Ops) : nullptr;
612 // Otherwise we don't know.
616 /// ExtractImmediate - If S involves the addition of a constant integer value,
617 /// return that integer value, and mutate S to point to a new SCEV with that
619 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
620 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
621 if (C->getValue()->getValue().getMinSignedBits() <= 64) {
622 S = SE.getConstant(C->getType(), 0);
623 return C->getValue()->getSExtValue();
625 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
626 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
627 int64_t Result = ExtractImmediate(NewOps.front(), SE);
629 S = SE.getAddExpr(NewOps);
631 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
632 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
633 int64_t Result = ExtractImmediate(NewOps.front(), SE);
635 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
636 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
643 /// ExtractSymbol - If S involves the addition of a GlobalValue address,
644 /// return that symbol, and mutate S to point to a new SCEV with that
646 static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
647 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
648 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
649 S = SE.getConstant(GV->getType(), 0);
652 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
653 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
654 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
656 S = SE.getAddExpr(NewOps);
658 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
659 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
660 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
662 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
663 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
670 /// isAddressUse - Returns true if the specified instruction is using the
671 /// specified value as an address.
672 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
673 bool isAddress = isa<LoadInst>(Inst);
674 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
675 if (SI->getOperand(1) == OperandVal)
677 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
678 // Addressing modes can also be folded into prefetches and a variety
680 switch (II->getIntrinsicID()) {
682 case Intrinsic::prefetch:
683 case Intrinsic::x86_sse_storeu_ps:
684 case Intrinsic::x86_sse2_storeu_pd:
685 case Intrinsic::x86_sse2_storeu_dq:
686 case Intrinsic::x86_sse2_storel_dq:
687 if (II->getArgOperand(0) == OperandVal)
695 /// getAccessType - Return the type of the memory being accessed.
696 static Type *getAccessType(const Instruction *Inst) {
697 Type *AccessTy = Inst->getType();
698 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
699 AccessTy = SI->getOperand(0)->getType();
700 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
701 // Addressing modes can also be folded into prefetches and a variety
703 switch (II->getIntrinsicID()) {
705 case Intrinsic::x86_sse_storeu_ps:
706 case Intrinsic::x86_sse2_storeu_pd:
707 case Intrinsic::x86_sse2_storeu_dq:
708 case Intrinsic::x86_sse2_storel_dq:
709 AccessTy = II->getArgOperand(0)->getType();
714 // All pointers have the same requirements, so canonicalize them to an
715 // arbitrary pointer type to minimize variation.
716 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy))
717 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
718 PTy->getAddressSpace());
723 /// isExistingPhi - Return true if this AddRec is already a phi in its loop.
724 static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
725 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
726 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
727 if (SE.isSCEVable(PN->getType()) &&
728 (SE.getEffectiveSCEVType(PN->getType()) ==
729 SE.getEffectiveSCEVType(AR->getType())) &&
730 SE.getSCEV(PN) == AR)
736 /// Check if expanding this expression is likely to incur significant cost. This
737 /// is tricky because SCEV doesn't track which expressions are actually computed
738 /// by the current IR.
740 /// We currently allow expansion of IV increments that involve adds,
741 /// multiplication by constants, and AddRecs from existing phis.
743 /// TODO: Allow UDivExpr if we can find an existing IV increment that is an
744 /// obvious multiple of the UDivExpr.
745 static bool isHighCostExpansion(const SCEV *S,
746 SmallPtrSetImpl<const SCEV*> &Processed,
747 ScalarEvolution &SE) {
748 // Zero/One operand expressions
749 switch (S->getSCEVType()) {
754 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
757 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
760 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
764 if (!Processed.insert(S).second)
767 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
768 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
770 if (isHighCostExpansion(*I, Processed, SE))
776 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
777 if (Mul->getNumOperands() == 2) {
778 // Multiplication by a constant is ok
779 if (isa<SCEVConstant>(Mul->getOperand(0)))
780 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
782 // If we have the value of one operand, check if an existing
783 // multiplication already generates this expression.
784 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
785 Value *UVal = U->getValue();
786 for (User *UR : UVal->users()) {
787 // If U is a constant, it may be used by a ConstantExpr.
788 Instruction *UI = dyn_cast<Instruction>(UR);
789 if (UI && UI->getOpcode() == Instruction::Mul &&
790 SE.isSCEVable(UI->getType())) {
791 return SE.getSCEV(UI) == Mul;
798 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
799 if (isExistingPhi(AR, SE))
803 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
807 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
808 /// specified set are trivially dead, delete them and see if this makes any of
809 /// their operands subsequently dead.
811 DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
812 bool Changed = false;
814 while (!DeadInsts.empty()) {
815 Value *V = DeadInsts.pop_back_val();
816 Instruction *I = dyn_cast_or_null<Instruction>(V);
818 if (!I || !isInstructionTriviallyDead(I))
821 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
822 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
825 DeadInsts.push_back(U);
828 I->eraseFromParent();
839 /// \brief Check if the addressing mode defined by \p F is completely
840 /// folded in \p LU at isel time.
841 /// This includes address-mode folding and special icmp tricks.
842 /// This function returns true if \p LU can accommodate what \p F
843 /// defines and up to 1 base + 1 scaled + offset.
844 /// In other words, if \p F has several base registers, this function may
845 /// still return true. Therefore, users still need to account for
846 /// additional base registers and/or unfolded offsets to derive an
847 /// accurate cost model.
848 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
849 const LSRUse &LU, const Formula &F);
850 // Get the cost of the scaling factor used in F for LU.
851 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
852 const LSRUse &LU, const Formula &F);
856 /// Cost - This class is used to measure and compare candidate formulae.
858 /// TODO: Some of these could be merged. Also, a lexical ordering
859 /// isn't always optimal.
863 unsigned NumBaseAdds;
870 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
871 SetupCost(0), ScaleCost(0) {}
873 bool operator<(const Cost &Other) const;
878 // Once any of the metrics loses, they must all remain losers.
880 return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds
881 | ImmCost | SetupCost | ScaleCost) != ~0u)
882 || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds
883 & ImmCost & SetupCost & ScaleCost) == ~0u);
888 assert(isValid() && "invalid cost");
889 return NumRegs == ~0u;
892 void RateFormula(const TargetTransformInfo &TTI,
894 SmallPtrSetImpl<const SCEV *> &Regs,
895 const DenseSet<const SCEV *> &VisitedRegs,
897 const SmallVectorImpl<int64_t> &Offsets,
898 ScalarEvolution &SE, DominatorTree &DT,
900 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
902 void print(raw_ostream &OS) const;
906 void RateRegister(const SCEV *Reg,
907 SmallPtrSetImpl<const SCEV *> &Regs,
909 ScalarEvolution &SE, DominatorTree &DT);
910 void RatePrimaryRegister(const SCEV *Reg,
911 SmallPtrSetImpl<const SCEV *> &Regs,
913 ScalarEvolution &SE, DominatorTree &DT,
914 SmallPtrSetImpl<const SCEV *> *LoserRegs);
919 /// RateRegister - Tally up interesting quantities from the given register.
920 void Cost::RateRegister(const SCEV *Reg,
921 SmallPtrSetImpl<const SCEV *> &Regs,
923 ScalarEvolution &SE, DominatorTree &DT) {
924 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
925 // If this is an addrec for another loop, don't second-guess its addrec phi
926 // nodes. LSR isn't currently smart enough to reason about more than one
927 // loop at a time. LSR has already run on inner loops, will not run on outer
928 // loops, and cannot be expected to change sibling loops.
929 if (AR->getLoop() != L) {
930 // If the AddRec exists, consider it's register free and leave it alone.
931 if (isExistingPhi(AR, SE))
934 // Otherwise, do not consider this formula at all.
938 AddRecCost += 1; /// TODO: This should be a function of the stride.
940 // Add the step value register, if it needs one.
941 // TODO: The non-affine case isn't precisely modeled here.
942 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
943 if (!Regs.count(AR->getOperand(1))) {
944 RateRegister(AR->getOperand(1), Regs, L, SE, DT);
952 // Rough heuristic; favor registers which don't require extra setup
953 // instructions in the preheader.
954 if (!isa<SCEVUnknown>(Reg) &&
955 !isa<SCEVConstant>(Reg) &&
956 !(isa<SCEVAddRecExpr>(Reg) &&
957 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
958 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
961 NumIVMuls += isa<SCEVMulExpr>(Reg) &&
962 SE.hasComputableLoopEvolution(Reg, L);
965 /// RatePrimaryRegister - Record this register in the set. If we haven't seen it
966 /// before, rate it. Optional LoserRegs provides a way to declare any formula
967 /// that refers to one of those regs an instant loser.
968 void Cost::RatePrimaryRegister(const SCEV *Reg,
969 SmallPtrSetImpl<const SCEV *> &Regs,
971 ScalarEvolution &SE, DominatorTree &DT,
972 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
973 if (LoserRegs && LoserRegs->count(Reg)) {
977 if (Regs.insert(Reg).second) {
978 RateRegister(Reg, Regs, L, SE, DT);
979 if (LoserRegs && isLoser())
980 LoserRegs->insert(Reg);
984 void Cost::RateFormula(const TargetTransformInfo &TTI,
986 SmallPtrSetImpl<const SCEV *> &Regs,
987 const DenseSet<const SCEV *> &VisitedRegs,
989 const SmallVectorImpl<int64_t> &Offsets,
990 ScalarEvolution &SE, DominatorTree &DT,
992 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
993 assert(F.isCanonical() && "Cost is accurate only for canonical formula");
994 // Tally up the registers.
995 if (const SCEV *ScaledReg = F.ScaledReg) {
996 if (VisitedRegs.count(ScaledReg)) {
1000 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs);
1004 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
1005 E = F.BaseRegs.end(); I != E; ++I) {
1006 const SCEV *BaseReg = *I;
1007 if (VisitedRegs.count(BaseReg)) {
1011 RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs);
1016 // Determine how many (unfolded) adds we'll need inside the loop.
1017 size_t NumBaseParts = F.getNumRegs();
1018 if (NumBaseParts > 1)
1019 // Do not count the base and a possible second register if the target
1020 // allows to fold 2 registers.
1022 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(TTI, LU, F)));
1023 NumBaseAdds += (F.UnfoldedOffset != 0);
1025 // Accumulate non-free scaling amounts.
1026 ScaleCost += getScalingFactorCost(TTI, LU, F);
1028 // Tally up the non-zero immediates.
1029 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
1030 E = Offsets.end(); I != E; ++I) {
1031 int64_t Offset = (uint64_t)*I + F.BaseOffset;
1033 ImmCost += 64; // Handle symbolic values conservatively.
1034 // TODO: This should probably be the pointer size.
1035 else if (Offset != 0)
1036 ImmCost += APInt(64, Offset, true).getMinSignedBits();
1038 assert(isValid() && "invalid cost");
1041 /// Lose - Set this cost to a losing value.
1052 /// operator< - Choose the lower cost.
1053 bool Cost::operator<(const Cost &Other) const {
1054 return std::tie(NumRegs, AddRecCost, NumIVMuls, NumBaseAdds, ScaleCost,
1055 ImmCost, SetupCost) <
1056 std::tie(Other.NumRegs, Other.AddRecCost, Other.NumIVMuls,
1057 Other.NumBaseAdds, Other.ScaleCost, Other.ImmCost,
1061 void Cost::print(raw_ostream &OS) const {
1062 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
1063 if (AddRecCost != 0)
1064 OS << ", with addrec cost " << AddRecCost;
1066 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
1067 if (NumBaseAdds != 0)
1068 OS << ", plus " << NumBaseAdds << " base add"
1069 << (NumBaseAdds == 1 ? "" : "s");
1071 OS << ", plus " << ScaleCost << " scale cost";
1073 OS << ", plus " << ImmCost << " imm cost";
1075 OS << ", plus " << SetupCost << " setup cost";
1078 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1079 void Cost::dump() const {
1080 print(errs()); errs() << '\n';
1086 /// LSRFixup - An operand value in an instruction which is to be replaced
1087 /// with some equivalent, possibly strength-reduced, replacement.
1089 /// UserInst - The instruction which will be updated.
1090 Instruction *UserInst;
1092 /// OperandValToReplace - The operand of the instruction which will
1093 /// be replaced. The operand may be used more than once; every instance
1094 /// will be replaced.
1095 Value *OperandValToReplace;
1097 /// PostIncLoops - If this user is to use the post-incremented value of an
1098 /// induction variable, this variable is non-null and holds the loop
1099 /// associated with the induction variable.
1100 PostIncLoopSet PostIncLoops;
1102 /// LUIdx - The index of the LSRUse describing the expression which
1103 /// this fixup needs, minus an offset (below).
1106 /// Offset - A constant offset to be added to the LSRUse expression.
1107 /// This allows multiple fixups to share the same LSRUse with different
1108 /// offsets, for example in an unrolled loop.
1111 bool isUseFullyOutsideLoop(const Loop *L) const;
1115 void print(raw_ostream &OS) const;
1121 LSRFixup::LSRFixup()
1122 : UserInst(nullptr), OperandValToReplace(nullptr), LUIdx(~size_t(0)),
1125 /// isUseFullyOutsideLoop - Test whether this fixup always uses its
1126 /// value outside of the given loop.
1127 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1128 // PHI nodes use their value in their incoming blocks.
1129 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1130 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1131 if (PN->getIncomingValue(i) == OperandValToReplace &&
1132 L->contains(PN->getIncomingBlock(i)))
1137 return !L->contains(UserInst);
1140 void LSRFixup::print(raw_ostream &OS) const {
1142 // Store is common and interesting enough to be worth special-casing.
1143 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1145 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1146 } else if (UserInst->getType()->isVoidTy())
1147 OS << UserInst->getOpcodeName();
1149 UserInst->printAsOperand(OS, /*PrintType=*/false);
1151 OS << ", OperandValToReplace=";
1152 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1154 for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(),
1155 E = PostIncLoops.end(); I != E; ++I) {
1156 OS << ", PostIncLoop=";
1157 (*I)->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1160 if (LUIdx != ~size_t(0))
1161 OS << ", LUIdx=" << LUIdx;
1164 OS << ", Offset=" << Offset;
1167 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1168 void LSRFixup::dump() const {
1169 print(errs()); errs() << '\n';
1175 /// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
1176 /// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
1177 struct UniquifierDenseMapInfo {
1178 static SmallVector<const SCEV *, 4> getEmptyKey() {
1179 SmallVector<const SCEV *, 4> V;
1180 V.push_back(reinterpret_cast<const SCEV *>(-1));
1184 static SmallVector<const SCEV *, 4> getTombstoneKey() {
1185 SmallVector<const SCEV *, 4> V;
1186 V.push_back(reinterpret_cast<const SCEV *>(-2));
1190 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1191 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1194 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1195 const SmallVector<const SCEV *, 4> &RHS) {
1200 /// LSRUse - This class holds the state that LSR keeps for each use in
1201 /// IVUsers, as well as uses invented by LSR itself. It includes information
1202 /// about what kinds of things can be folded into the user, information about
1203 /// the user itself, and information about how the use may be satisfied.
1204 /// TODO: Represent multiple users of the same expression in common?
1206 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1209 /// KindType - An enum for a kind of use, indicating what types of
1210 /// scaled and immediate operands it might support.
1212 Basic, ///< A normal use, with no folding.
1213 Special, ///< A special case of basic, allowing -1 scales.
1214 Address, ///< An address use; folding according to TargetLowering
1215 ICmpZero ///< An equality icmp with both operands folded into one.
1216 // TODO: Add a generic icmp too?
1219 typedef PointerIntPair<const SCEV *, 2, KindType> SCEVUseKindPair;
1224 SmallVector<int64_t, 8> Offsets;
1228 /// AllFixupsOutsideLoop - This records whether all of the fixups using this
1229 /// LSRUse are outside of the loop, in which case some special-case heuristics
1231 bool AllFixupsOutsideLoop;
1233 /// RigidFormula is set to true to guarantee that this use will be associated
1234 /// with a single formula--the one that initially matched. Some SCEV
1235 /// expressions cannot be expanded. This allows LSR to consider the registers
1236 /// used by those expressions without the need to expand them later after
1237 /// changing the formula.
1240 /// WidestFixupType - This records the widest use type for any fixup using
1241 /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different
1242 /// max fixup widths to be equivalent, because the narrower one may be relying
1243 /// on the implicit truncation to truncate away bogus bits.
1244 Type *WidestFixupType;
1246 /// Formulae - A list of ways to build a value that can satisfy this user.
1247 /// After the list is populated, one of these is selected heuristically and
1248 /// used to formulate a replacement for OperandValToReplace in UserInst.
1249 SmallVector<Formula, 12> Formulae;
1251 /// Regs - The set of register candidates used by all formulae in this LSRUse.
1252 SmallPtrSet<const SCEV *, 4> Regs;
1254 LSRUse(KindType K, Type *T) : Kind(K), AccessTy(T),
1255 MinOffset(INT64_MAX),
1256 MaxOffset(INT64_MIN),
1257 AllFixupsOutsideLoop(true),
1258 RigidFormula(false),
1259 WidestFixupType(nullptr) {}
1261 bool HasFormulaWithSameRegs(const Formula &F) const;
1262 bool InsertFormula(const Formula &F);
1263 void DeleteFormula(Formula &F);
1264 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1266 void print(raw_ostream &OS) const;
1272 /// HasFormula - Test whether this use as a formula which has the same
1273 /// registers as the given formula.
1274 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1275 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1276 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1277 // Unstable sort by host order ok, because this is only used for uniquifying.
1278 std::sort(Key.begin(), Key.end());
1279 return Uniquifier.count(Key);
1282 /// InsertFormula - If the given formula has not yet been inserted, add it to
1283 /// the list, and return true. Return false otherwise.
1284 /// The formula must be in canonical form.
1285 bool LSRUse::InsertFormula(const Formula &F) {
1286 assert(F.isCanonical() && "Invalid canonical representation");
1288 if (!Formulae.empty() && RigidFormula)
1291 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1292 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1293 // Unstable sort by host order ok, because this is only used for uniquifying.
1294 std::sort(Key.begin(), Key.end());
1296 if (!Uniquifier.insert(Key).second)
1299 // Using a register to hold the value of 0 is not profitable.
1300 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1301 "Zero allocated in a scaled register!");
1303 for (SmallVectorImpl<const SCEV *>::const_iterator I =
1304 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
1305 assert(!(*I)->isZero() && "Zero allocated in a base register!");
1308 // Add the formula to the list.
1309 Formulae.push_back(F);
1311 // Record registers now being used by this use.
1312 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1314 Regs.insert(F.ScaledReg);
1319 /// DeleteFormula - Remove the given formula from this use's list.
1320 void LSRUse::DeleteFormula(Formula &F) {
1321 if (&F != &Formulae.back())
1322 std::swap(F, Formulae.back());
1323 Formulae.pop_back();
1326 /// RecomputeRegs - Recompute the Regs field, and update RegUses.
1327 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1328 // Now that we've filtered out some formulae, recompute the Regs set.
1329 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1331 for (const Formula &F : Formulae) {
1332 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1333 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1336 // Update the RegTracker.
1337 for (const SCEV *S : OldRegs)
1339 RegUses.DropRegister(S, LUIdx);
1342 void LSRUse::print(raw_ostream &OS) const {
1343 OS << "LSR Use: Kind=";
1345 case Basic: OS << "Basic"; break;
1346 case Special: OS << "Special"; break;
1347 case ICmpZero: OS << "ICmpZero"; break;
1349 OS << "Address of ";
1350 if (AccessTy->isPointerTy())
1351 OS << "pointer"; // the full pointer type could be really verbose
1356 OS << ", Offsets={";
1357 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
1358 E = Offsets.end(); I != E; ++I) {
1360 if (std::next(I) != E)
1365 if (AllFixupsOutsideLoop)
1366 OS << ", all-fixups-outside-loop";
1368 if (WidestFixupType)
1369 OS << ", widest fixup type: " << *WidestFixupType;
1372 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1373 void LSRUse::dump() const {
1374 print(errs()); errs() << '\n';
1378 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1379 LSRUse::KindType Kind, Type *AccessTy,
1380 GlobalValue *BaseGV, int64_t BaseOffset,
1381 bool HasBaseReg, int64_t Scale) {
1383 case LSRUse::Address:
1384 return TTI.isLegalAddressingMode(AccessTy, BaseGV, BaseOffset, HasBaseReg, Scale);
1386 // Otherwise, just guess that reg+reg addressing is legal.
1389 case LSRUse::ICmpZero:
1390 // There's not even a target hook for querying whether it would be legal to
1391 // fold a GV into an ICmp.
1395 // ICmp only has two operands; don't allow more than two non-trivial parts.
1396 if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1399 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1400 // putting the scaled register in the other operand of the icmp.
1401 if (Scale != 0 && Scale != -1)
1404 // If we have low-level target information, ask the target if it can fold an
1405 // integer immediate on an icmp.
1406 if (BaseOffset != 0) {
1408 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1409 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1410 // Offs is the ICmp immediate.
1412 // The cast does the right thing with INT64_MIN.
1413 BaseOffset = -(uint64_t)BaseOffset;
1414 return TTI.isLegalICmpImmediate(BaseOffset);
1417 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1421 // Only handle single-register values.
1422 return !BaseGV && Scale == 0 && BaseOffset == 0;
1424 case LSRUse::Special:
1425 // Special case Basic to handle -1 scales.
1426 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1429 llvm_unreachable("Invalid LSRUse Kind!");
1432 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1433 int64_t MinOffset, int64_t MaxOffset,
1434 LSRUse::KindType Kind, Type *AccessTy,
1435 GlobalValue *BaseGV, int64_t BaseOffset,
1436 bool HasBaseReg, int64_t Scale) {
1437 // Check for overflow.
1438 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1441 MinOffset = (uint64_t)BaseOffset + MinOffset;
1442 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1445 MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1447 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1448 HasBaseReg, Scale) &&
1449 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1453 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1454 int64_t MinOffset, int64_t MaxOffset,
1455 LSRUse::KindType Kind, Type *AccessTy,
1457 // For the purpose of isAMCompletelyFolded either having a canonical formula
1458 // or a scale not equal to zero is correct.
1459 // Problems may arise from non canonical formulae having a scale == 0.
1460 // Strictly speaking it would best to just rely on canonical formulae.
1461 // However, when we generate the scaled formulae, we first check that the
1462 // scaling factor is profitable before computing the actual ScaledReg for
1463 // compile time sake.
1464 assert((F.isCanonical() || F.Scale != 0));
1465 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1466 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1469 /// isLegalUse - Test whether we know how to expand the current formula.
1470 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1471 int64_t MaxOffset, LSRUse::KindType Kind, Type *AccessTy,
1472 GlobalValue *BaseGV, int64_t BaseOffset, bool HasBaseReg,
1474 // We know how to expand completely foldable formulae.
1475 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1476 BaseOffset, HasBaseReg, Scale) ||
1477 // Or formulae that use a base register produced by a sum of base
1480 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1481 BaseGV, BaseOffset, true, 0));
1484 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1485 int64_t MaxOffset, LSRUse::KindType Kind, Type *AccessTy,
1487 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1488 F.BaseOffset, F.HasBaseReg, F.Scale);
1491 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1492 const LSRUse &LU, const Formula &F) {
1493 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1494 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1498 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1499 const LSRUse &LU, const Formula &F) {
1503 // If the use is not completely folded in that instruction, we will have to
1504 // pay an extra cost only for scale != 1.
1505 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1507 return F.Scale != 1;
1510 case LSRUse::Address: {
1511 // Check the scaling factor cost with both the min and max offsets.
1512 int ScaleCostMinOffset =
1513 TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV,
1514 F.BaseOffset + LU.MinOffset,
1515 F.HasBaseReg, F.Scale);
1516 int ScaleCostMaxOffset =
1517 TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV,
1518 F.BaseOffset + LU.MaxOffset,
1519 F.HasBaseReg, F.Scale);
1521 assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&
1522 "Legal addressing mode has an illegal cost!");
1523 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1525 case LSRUse::ICmpZero:
1527 case LSRUse::Special:
1528 // The use is completely folded, i.e., everything is folded into the
1533 llvm_unreachable("Invalid LSRUse Kind!");
1536 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1537 LSRUse::KindType Kind, Type *AccessTy,
1538 GlobalValue *BaseGV, int64_t BaseOffset,
1540 // Fast-path: zero is always foldable.
1541 if (BaseOffset == 0 && !BaseGV) return true;
1543 // Conservatively, create an address with an immediate and a
1544 // base and a scale.
1545 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1547 // Canonicalize a scale of 1 to a base register if the formula doesn't
1548 // already have a base register.
1549 if (!HasBaseReg && Scale == 1) {
1554 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1558 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1559 ScalarEvolution &SE, int64_t MinOffset,
1560 int64_t MaxOffset, LSRUse::KindType Kind,
1561 Type *AccessTy, const SCEV *S, bool HasBaseReg) {
1562 // Fast-path: zero is always foldable.
1563 if (S->isZero()) return true;
1565 // Conservatively, create an address with an immediate and a
1566 // base and a scale.
1567 int64_t BaseOffset = ExtractImmediate(S, SE);
1568 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1570 // If there's anything else involved, it's not foldable.
1571 if (!S->isZero()) return false;
1573 // Fast-path: zero is always foldable.
1574 if (BaseOffset == 0 && !BaseGV) return true;
1576 // Conservatively, create an address with an immediate and a
1577 // base and a scale.
1578 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1580 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1581 BaseOffset, HasBaseReg, Scale);
1586 /// IVInc - An individual increment in a Chain of IV increments.
1587 /// Relate an IV user to an expression that computes the IV it uses from the IV
1588 /// used by the previous link in the Chain.
1590 /// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1591 /// original IVOperand. The head of the chain's IVOperand is only valid during
1592 /// chain collection, before LSR replaces IV users. During chain generation,
1593 /// IncExpr can be used to find the new IVOperand that computes the same
1596 Instruction *UserInst;
1598 const SCEV *IncExpr;
1600 IVInc(Instruction *U, Value *O, const SCEV *E):
1601 UserInst(U), IVOperand(O), IncExpr(E) {}
1604 // IVChain - The list of IV increments in program order.
1605 // We typically add the head of a chain without finding subsequent links.
1607 SmallVector<IVInc,1> Incs;
1608 const SCEV *ExprBase;
1610 IVChain() : ExprBase(nullptr) {}
1612 IVChain(const IVInc &Head, const SCEV *Base)
1613 : Incs(1, Head), ExprBase(Base) {}
1615 typedef SmallVectorImpl<IVInc>::const_iterator const_iterator;
1617 // begin - return the first increment in the chain.
1618 const_iterator begin() const {
1619 assert(!Incs.empty());
1620 return std::next(Incs.begin());
1622 const_iterator end() const {
1626 // hasIncs - Returns true if this chain contains any increments.
1627 bool hasIncs() const { return Incs.size() >= 2; }
1629 // add - Add an IVInc to the end of this chain.
1630 void add(const IVInc &X) { Incs.push_back(X); }
1632 // tailUserInst - Returns the last UserInst in the chain.
1633 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1635 // isProfitableIncrement - Returns true if IncExpr can be profitably added to
1637 bool isProfitableIncrement(const SCEV *OperExpr,
1638 const SCEV *IncExpr,
1642 /// ChainUsers - Helper for CollectChains to track multiple IV increment uses.
1643 /// Distinguish between FarUsers that definitely cross IV increments and
1644 /// NearUsers that may be used between IV increments.
1646 SmallPtrSet<Instruction*, 4> FarUsers;
1647 SmallPtrSet<Instruction*, 4> NearUsers;
1650 /// LSRInstance - This class holds state for the main loop strength reduction
1654 ScalarEvolution &SE;
1657 const TargetTransformInfo &TTI;
1661 /// IVIncInsertPos - This is the insert position that the current loop's
1662 /// induction variable increment should be placed. In simple loops, this is
1663 /// the latch block's terminator. But in more complicated cases, this is a
1664 /// position which will dominate all the in-loop post-increment users.
1665 Instruction *IVIncInsertPos;
1667 /// Factors - Interesting factors between use strides.
1668 SmallSetVector<int64_t, 8> Factors;
1670 /// Types - Interesting use types, to facilitate truncation reuse.
1671 SmallSetVector<Type *, 4> Types;
1673 /// Fixups - The list of operands which are to be replaced.
1674 SmallVector<LSRFixup, 16> Fixups;
1676 /// Uses - The list of interesting uses.
1677 SmallVector<LSRUse, 16> Uses;
1679 /// RegUses - Track which uses use which register candidates.
1680 RegUseTracker RegUses;
1682 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1683 // have more than a few IV increment chains in a loop. Missing a Chain falls
1684 // back to normal LSR behavior for those uses.
1685 static const unsigned MaxChains = 8;
1687 /// IVChainVec - IV users can form a chain of IV increments.
1688 SmallVector<IVChain, MaxChains> IVChainVec;
1690 /// IVIncSet - IV users that belong to profitable IVChains.
1691 SmallPtrSet<Use*, MaxChains> IVIncSet;
1693 void OptimizeShadowIV();
1694 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1695 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1696 void OptimizeLoopTermCond();
1698 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1699 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1700 void FinalizeChain(IVChain &Chain);
1701 void CollectChains();
1702 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1703 SmallVectorImpl<WeakVH> &DeadInsts);
1705 void CollectInterestingTypesAndFactors();
1706 void CollectFixupsAndInitialFormulae();
1708 LSRFixup &getNewFixup() {
1709 Fixups.push_back(LSRFixup());
1710 return Fixups.back();
1713 // Support for sharing of LSRUses between LSRFixups.
1714 typedef DenseMap<LSRUse::SCEVUseKindPair, size_t> UseMapTy;
1717 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1718 LSRUse::KindType Kind, Type *AccessTy);
1720 std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1721 LSRUse::KindType Kind,
1724 void DeleteUse(LSRUse &LU, size_t LUIdx);
1726 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1728 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1729 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1730 void CountRegisters(const Formula &F, size_t LUIdx);
1731 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1733 void CollectLoopInvariantFixupsAndFormulae();
1735 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1736 unsigned Depth = 0);
1738 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1739 const Formula &Base, unsigned Depth,
1740 size_t Idx, bool IsScaledReg = false);
1741 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1742 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1743 const Formula &Base, size_t Idx,
1744 bool IsScaledReg = false);
1745 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1746 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1747 const Formula &Base,
1748 const SmallVectorImpl<int64_t> &Worklist,
1749 size_t Idx, bool IsScaledReg = false);
1750 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1751 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1752 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1753 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1754 void GenerateCrossUseConstantOffsets();
1755 void GenerateAllReuseFormulae();
1757 void FilterOutUndesirableDedicatedRegisters();
1759 size_t EstimateSearchSpaceComplexity() const;
1760 void NarrowSearchSpaceByDetectingSupersets();
1761 void NarrowSearchSpaceByCollapsingUnrolledCode();
1762 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1763 void NarrowSearchSpaceByPickingWinnerRegs();
1764 void NarrowSearchSpaceUsingHeuristics();
1766 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1768 SmallVectorImpl<const Formula *> &Workspace,
1769 const Cost &CurCost,
1770 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1771 DenseSet<const SCEV *> &VisitedRegs) const;
1772 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1774 BasicBlock::iterator
1775 HoistInsertPosition(BasicBlock::iterator IP,
1776 const SmallVectorImpl<Instruction *> &Inputs) const;
1777 BasicBlock::iterator
1778 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1781 SCEVExpander &Rewriter) const;
1783 Value *Expand(const LSRFixup &LF,
1785 BasicBlock::iterator IP,
1786 SCEVExpander &Rewriter,
1787 SmallVectorImpl<WeakVH> &DeadInsts) const;
1788 void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
1790 SCEVExpander &Rewriter,
1791 SmallVectorImpl<WeakVH> &DeadInsts,
1793 void Rewrite(const LSRFixup &LF,
1795 SCEVExpander &Rewriter,
1796 SmallVectorImpl<WeakVH> &DeadInsts,
1798 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1802 LSRInstance(Loop *L, Pass *P);
1804 bool getChanged() const { return Changed; }
1806 void print_factors_and_types(raw_ostream &OS) const;
1807 void print_fixups(raw_ostream &OS) const;
1808 void print_uses(raw_ostream &OS) const;
1809 void print(raw_ostream &OS) const;
1815 /// OptimizeShadowIV - If IV is used in a int-to-float cast
1816 /// inside the loop then try to eliminate the cast operation.
1817 void LSRInstance::OptimizeShadowIV() {
1818 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1819 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1822 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1823 UI != E; /* empty */) {
1824 IVUsers::const_iterator CandidateUI = UI;
1826 Instruction *ShadowUse = CandidateUI->getUser();
1827 Type *DestTy = nullptr;
1828 bool IsSigned = false;
1830 /* If shadow use is a int->float cast then insert a second IV
1831 to eliminate this cast.
1833 for (unsigned i = 0; i < n; ++i)
1839 for (unsigned i = 0; i < n; ++i, ++d)
1842 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
1844 DestTy = UCast->getDestTy();
1846 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
1848 DestTy = SCast->getDestTy();
1850 if (!DestTy) continue;
1852 // If target does not support DestTy natively then do not apply
1853 // this transformation.
1854 if (!TTI.isTypeLegal(DestTy)) continue;
1856 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1858 if (PH->getNumIncomingValues() != 2) continue;
1860 Type *SrcTy = PH->getType();
1861 int Mantissa = DestTy->getFPMantissaWidth();
1862 if (Mantissa == -1) continue;
1863 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1866 unsigned Entry, Latch;
1867 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1875 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1876 if (!Init) continue;
1877 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
1878 (double)Init->getSExtValue() :
1879 (double)Init->getZExtValue());
1881 BinaryOperator *Incr =
1882 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1883 if (!Incr) continue;
1884 if (Incr->getOpcode() != Instruction::Add
1885 && Incr->getOpcode() != Instruction::Sub)
1888 /* Initialize new IV, double d = 0.0 in above example. */
1889 ConstantInt *C = nullptr;
1890 if (Incr->getOperand(0) == PH)
1891 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1892 else if (Incr->getOperand(1) == PH)
1893 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1899 // Ignore negative constants, as the code below doesn't handle them
1900 // correctly. TODO: Remove this restriction.
1901 if (!C->getValue().isStrictlyPositive()) continue;
1903 /* Add new PHINode. */
1904 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
1906 /* create new increment. '++d' in above example. */
1907 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1908 BinaryOperator *NewIncr =
1909 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1910 Instruction::FAdd : Instruction::FSub,
1911 NewPH, CFP, "IV.S.next.", Incr);
1913 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1914 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1916 /* Remove cast operation */
1917 ShadowUse->replaceAllUsesWith(NewPH);
1918 ShadowUse->eraseFromParent();
1924 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1925 /// set the IV user and stride information and return true, otherwise return
1927 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
1928 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1929 if (UI->getUser() == Cond) {
1930 // NOTE: we could handle setcc instructions with multiple uses here, but
1931 // InstCombine does it as well for simple uses, it's not clear that it
1932 // occurs enough in real life to handle.
1939 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
1940 /// a max computation.
1942 /// This is a narrow solution to a specific, but acute, problem. For loops
1948 /// } while (++i < n);
1950 /// the trip count isn't just 'n', because 'n' might not be positive. And
1951 /// unfortunately this can come up even for loops where the user didn't use
1952 /// a C do-while loop. For example, seemingly well-behaved top-test loops
1953 /// will commonly be lowered like this:
1959 /// } while (++i < n);
1962 /// and then it's possible for subsequent optimization to obscure the if
1963 /// test in such a way that indvars can't find it.
1965 /// When indvars can't find the if test in loops like this, it creates a
1966 /// max expression, which allows it to give the loop a canonical
1967 /// induction variable:
1970 /// max = n < 1 ? 1 : n;
1973 /// } while (++i != max);
1975 /// Canonical induction variables are necessary because the loop passes
1976 /// are designed around them. The most obvious example of this is the
1977 /// LoopInfo analysis, which doesn't remember trip count values. It
1978 /// expects to be able to rediscover the trip count each time it is
1979 /// needed, and it does this using a simple analysis that only succeeds if
1980 /// the loop has a canonical induction variable.
1982 /// However, when it comes time to generate code, the maximum operation
1983 /// can be quite costly, especially if it's inside of an outer loop.
1985 /// This function solves this problem by detecting this type of loop and
1986 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1987 /// the instructions for the maximum computation.
1989 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1990 // Check that the loop matches the pattern we're looking for.
1991 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1992 Cond->getPredicate() != CmpInst::ICMP_NE)
1995 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
1996 if (!Sel || !Sel->hasOneUse()) return Cond;
1998 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1999 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2001 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2003 // Add one to the backedge-taken count to get the trip count.
2004 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2005 if (IterationCount != SE.getSCEV(Sel)) return Cond;
2007 // Check for a max calculation that matches the pattern. There's no check
2008 // for ICMP_ULE here because the comparison would be with zero, which
2009 // isn't interesting.
2010 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2011 const SCEVNAryExpr *Max = nullptr;
2012 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2013 Pred = ICmpInst::ICMP_SLE;
2015 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2016 Pred = ICmpInst::ICMP_SLT;
2018 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2019 Pred = ICmpInst::ICMP_ULT;
2026 // To handle a max with more than two operands, this optimization would
2027 // require additional checking and setup.
2028 if (Max->getNumOperands() != 2)
2031 const SCEV *MaxLHS = Max->getOperand(0);
2032 const SCEV *MaxRHS = Max->getOperand(1);
2034 // ScalarEvolution canonicalizes constants to the left. For < and >, look
2035 // for a comparison with 1. For <= and >=, a comparison with zero.
2037 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2040 // Check the relevant induction variable for conformance to
2042 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2043 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2044 if (!AR || !AR->isAffine() ||
2045 AR->getStart() != One ||
2046 AR->getStepRecurrence(SE) != One)
2049 assert(AR->getLoop() == L &&
2050 "Loop condition operand is an addrec in a different loop!");
2052 // Check the right operand of the select, and remember it, as it will
2053 // be used in the new comparison instruction.
2054 Value *NewRHS = nullptr;
2055 if (ICmpInst::isTrueWhenEqual(Pred)) {
2056 // Look for n+1, and grab n.
2057 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2058 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2059 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2060 NewRHS = BO->getOperand(0);
2061 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2062 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2063 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2064 NewRHS = BO->getOperand(0);
2067 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2068 NewRHS = Sel->getOperand(1);
2069 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2070 NewRHS = Sel->getOperand(2);
2071 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2072 NewRHS = SU->getValue();
2074 // Max doesn't match expected pattern.
2077 // Determine the new comparison opcode. It may be signed or unsigned,
2078 // and the original comparison may be either equality or inequality.
2079 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2080 Pred = CmpInst::getInversePredicate(Pred);
2082 // Ok, everything looks ok to change the condition into an SLT or SGE and
2083 // delete the max calculation.
2085 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2087 // Delete the max calculation instructions.
2088 Cond->replaceAllUsesWith(NewCond);
2089 CondUse->setUser(NewCond);
2090 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2091 Cond->eraseFromParent();
2092 Sel->eraseFromParent();
2093 if (Cmp->use_empty())
2094 Cmp->eraseFromParent();
2098 /// OptimizeLoopTermCond - Change loop terminating condition to use the
2099 /// postinc iv when possible.
2101 LSRInstance::OptimizeLoopTermCond() {
2102 SmallPtrSet<Instruction *, 4> PostIncs;
2104 BasicBlock *LatchBlock = L->getLoopLatch();
2105 SmallVector<BasicBlock*, 8> ExitingBlocks;
2106 L->getExitingBlocks(ExitingBlocks);
2108 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
2109 BasicBlock *ExitingBlock = ExitingBlocks[i];
2111 // Get the terminating condition for the loop if possible. If we
2112 // can, we want to change it to use a post-incremented version of its
2113 // induction variable, to allow coalescing the live ranges for the IV into
2114 // one register value.
2116 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2119 // FIXME: Overly conservative, termination condition could be an 'or' etc..
2120 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2123 // Search IVUsesByStride to find Cond's IVUse if there is one.
2124 IVStrideUse *CondUse = nullptr;
2125 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2126 if (!FindIVUserForCond(Cond, CondUse))
2129 // If the trip count is computed in terms of a max (due to ScalarEvolution
2130 // being unable to find a sufficient guard, for example), change the loop
2131 // comparison to use SLT or ULT instead of NE.
2132 // One consequence of doing this now is that it disrupts the count-down
2133 // optimization. That's not always a bad thing though, because in such
2134 // cases it may still be worthwhile to avoid a max.
2135 Cond = OptimizeMax(Cond, CondUse);
2137 // If this exiting block dominates the latch block, it may also use
2138 // the post-inc value if it won't be shared with other uses.
2139 // Check for dominance.
2140 if (!DT.dominates(ExitingBlock, LatchBlock))
2143 // Conservatively avoid trying to use the post-inc value in non-latch
2144 // exits if there may be pre-inc users in intervening blocks.
2145 if (LatchBlock != ExitingBlock)
2146 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2147 // Test if the use is reachable from the exiting block. This dominator
2148 // query is a conservative approximation of reachability.
2149 if (&*UI != CondUse &&
2150 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2151 // Conservatively assume there may be reuse if the quotient of their
2152 // strides could be a legal scale.
2153 const SCEV *A = IU.getStride(*CondUse, L);
2154 const SCEV *B = IU.getStride(*UI, L);
2155 if (!A || !B) continue;
2156 if (SE.getTypeSizeInBits(A->getType()) !=
2157 SE.getTypeSizeInBits(B->getType())) {
2158 if (SE.getTypeSizeInBits(A->getType()) >
2159 SE.getTypeSizeInBits(B->getType()))
2160 B = SE.getSignExtendExpr(B, A->getType());
2162 A = SE.getSignExtendExpr(A, B->getType());
2164 if (const SCEVConstant *D =
2165 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2166 const ConstantInt *C = D->getValue();
2167 // Stride of one or negative one can have reuse with non-addresses.
2168 if (C->isOne() || C->isAllOnesValue())
2169 goto decline_post_inc;
2170 // Avoid weird situations.
2171 if (C->getValue().getMinSignedBits() >= 64 ||
2172 C->getValue().isMinSignedValue())
2173 goto decline_post_inc;
2174 // Check for possible scaled-address reuse.
2175 Type *AccessTy = getAccessType(UI->getUser());
2176 int64_t Scale = C->getSExtValue();
2177 if (TTI.isLegalAddressingMode(AccessTy, /*BaseGV=*/ nullptr,
2179 /*HasBaseReg=*/ false, Scale))
2180 goto decline_post_inc;
2182 if (TTI.isLegalAddressingMode(AccessTy, /*BaseGV=*/ nullptr,
2184 /*HasBaseReg=*/ false, Scale))
2185 goto decline_post_inc;
2189 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
2192 // It's possible for the setcc instruction to be anywhere in the loop, and
2193 // possible for it to have multiple users. If it is not immediately before
2194 // the exiting block branch, move it.
2195 if (&*++BasicBlock::iterator(Cond) != TermBr) {
2196 if (Cond->hasOneUse()) {
2197 Cond->moveBefore(TermBr);
2199 // Clone the terminating condition and insert into the loopend.
2200 ICmpInst *OldCond = Cond;
2201 Cond = cast<ICmpInst>(Cond->clone());
2202 Cond->setName(L->getHeader()->getName() + ".termcond");
2203 ExitingBlock->getInstList().insert(TermBr, Cond);
2205 // Clone the IVUse, as the old use still exists!
2206 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2207 TermBr->replaceUsesOfWith(OldCond, Cond);
2211 // If we get to here, we know that we can transform the setcc instruction to
2212 // use the post-incremented version of the IV, allowing us to coalesce the
2213 // live ranges for the IV correctly.
2214 CondUse->transformToPostInc(L);
2217 PostIncs.insert(Cond);
2221 // Determine an insertion point for the loop induction variable increment. It
2222 // must dominate all the post-inc comparisons we just set up, and it must
2223 // dominate the loop latch edge.
2224 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2225 for (Instruction *Inst : PostIncs) {
2227 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2229 if (BB == Inst->getParent())
2230 IVIncInsertPos = Inst;
2231 else if (BB != IVIncInsertPos->getParent())
2232 IVIncInsertPos = BB->getTerminator();
2236 /// reconcileNewOffset - Determine if the given use can accommodate a fixup
2237 /// at the given offset and other details. If so, update the use and
2240 LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
2241 LSRUse::KindType Kind, Type *AccessTy) {
2242 int64_t NewMinOffset = LU.MinOffset;
2243 int64_t NewMaxOffset = LU.MaxOffset;
2244 Type *NewAccessTy = AccessTy;
2246 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2247 // something conservative, however this can pessimize in the case that one of
2248 // the uses will have all its uses outside the loop, for example.
2249 if (LU.Kind != Kind)
2252 // Check for a mismatched access type, and fall back conservatively as needed.
2253 // TODO: Be less conservative when the type is similar and can use the same
2254 // addressing modes.
2255 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
2256 NewAccessTy = Type::getVoidTy(AccessTy->getContext());
2258 // Conservatively assume HasBaseReg is true for now.
2259 if (NewOffset < LU.MinOffset) {
2260 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2261 LU.MaxOffset - NewOffset, HasBaseReg))
2263 NewMinOffset = NewOffset;
2264 } else if (NewOffset > LU.MaxOffset) {
2265 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2266 NewOffset - LU.MinOffset, HasBaseReg))
2268 NewMaxOffset = NewOffset;
2272 LU.MinOffset = NewMinOffset;
2273 LU.MaxOffset = NewMaxOffset;
2274 LU.AccessTy = NewAccessTy;
2275 if (NewOffset != LU.Offsets.back())
2276 LU.Offsets.push_back(NewOffset);
2280 /// getUse - Return an LSRUse index and an offset value for a fixup which
2281 /// needs the given expression, with the given kind and optional access type.
2282 /// Either reuse an existing use or create a new one, as needed.
2283 std::pair<size_t, int64_t>
2284 LSRInstance::getUse(const SCEV *&Expr,
2285 LSRUse::KindType Kind, Type *AccessTy) {
2286 const SCEV *Copy = Expr;
2287 int64_t Offset = ExtractImmediate(Expr, SE);
2289 // Basic uses can't accept any offset, for example.
2290 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2291 Offset, /*HasBaseReg=*/ true)) {
2296 std::pair<UseMapTy::iterator, bool> P =
2297 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2299 // A use already existed with this base.
2300 size_t LUIdx = P.first->second;
2301 LSRUse &LU = Uses[LUIdx];
2302 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2304 return std::make_pair(LUIdx, Offset);
2307 // Create a new use.
2308 size_t LUIdx = Uses.size();
2309 P.first->second = LUIdx;
2310 Uses.push_back(LSRUse(Kind, AccessTy));
2311 LSRUse &LU = Uses[LUIdx];
2313 // We don't need to track redundant offsets, but we don't need to go out
2314 // of our way here to avoid them.
2315 if (LU.Offsets.empty() || Offset != LU.Offsets.back())
2316 LU.Offsets.push_back(Offset);
2318 LU.MinOffset = Offset;
2319 LU.MaxOffset = Offset;
2320 return std::make_pair(LUIdx, Offset);
2323 /// DeleteUse - Delete the given use from the Uses list.
2324 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2325 if (&LU != &Uses.back())
2326 std::swap(LU, Uses.back());
2330 RegUses.SwapAndDropUse(LUIdx, Uses.size());
2333 /// FindUseWithFormula - Look for a use distinct from OrigLU which is has
2334 /// a formula that has the same registers as the given formula.
2336 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2337 const LSRUse &OrigLU) {
2338 // Search all uses for the formula. This could be more clever.
2339 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2340 LSRUse &LU = Uses[LUIdx];
2341 // Check whether this use is close enough to OrigLU, to see whether it's
2342 // worthwhile looking through its formulae.
2343 // Ignore ICmpZero uses because they may contain formulae generated by
2344 // GenerateICmpZeroScales, in which case adding fixup offsets may
2346 if (&LU != &OrigLU &&
2347 LU.Kind != LSRUse::ICmpZero &&
2348 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2349 LU.WidestFixupType == OrigLU.WidestFixupType &&
2350 LU.HasFormulaWithSameRegs(OrigF)) {
2351 // Scan through this use's formulae.
2352 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
2353 E = LU.Formulae.end(); I != E; ++I) {
2354 const Formula &F = *I;
2355 // Check to see if this formula has the same registers and symbols
2357 if (F.BaseRegs == OrigF.BaseRegs &&
2358 F.ScaledReg == OrigF.ScaledReg &&
2359 F.BaseGV == OrigF.BaseGV &&
2360 F.Scale == OrigF.Scale &&
2361 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2362 if (F.BaseOffset == 0)
2364 // This is the formula where all the registers and symbols matched;
2365 // there aren't going to be any others. Since we declined it, we
2366 // can skip the rest of the formulae and proceed to the next LSRUse.
2373 // Nothing looked good.
2377 void LSRInstance::CollectInterestingTypesAndFactors() {
2378 SmallSetVector<const SCEV *, 4> Strides;
2380 // Collect interesting types and strides.
2381 SmallVector<const SCEV *, 4> Worklist;
2382 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2383 const SCEV *Expr = IU.getExpr(*UI);
2385 // Collect interesting types.
2386 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2388 // Add strides for mentioned loops.
2389 Worklist.push_back(Expr);
2391 const SCEV *S = Worklist.pop_back_val();
2392 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2393 if (AR->getLoop() == L)
2394 Strides.insert(AR->getStepRecurrence(SE));
2395 Worklist.push_back(AR->getStart());
2396 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2397 Worklist.append(Add->op_begin(), Add->op_end());
2399 } while (!Worklist.empty());
2402 // Compute interesting factors from the set of interesting strides.
2403 for (SmallSetVector<const SCEV *, 4>::const_iterator
2404 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2405 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2406 std::next(I); NewStrideIter != E; ++NewStrideIter) {
2407 const SCEV *OldStride = *I;
2408 const SCEV *NewStride = *NewStrideIter;
2410 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2411 SE.getTypeSizeInBits(NewStride->getType())) {
2412 if (SE.getTypeSizeInBits(OldStride->getType()) >
2413 SE.getTypeSizeInBits(NewStride->getType()))
2414 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2416 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2418 if (const SCEVConstant *Factor =
2419 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2421 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2422 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2423 } else if (const SCEVConstant *Factor =
2424 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2427 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2428 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2432 // If all uses use the same type, don't bother looking for truncation-based
2434 if (Types.size() == 1)
2437 DEBUG(print_factors_and_types(dbgs()));
2440 /// findIVOperand - Helper for CollectChains that finds an IV operand (computed
2441 /// by an AddRec in this loop) within [OI,OE) or returns OE. If IVUsers mapped
2442 /// Instructions to IVStrideUses, we could partially skip this.
2443 static User::op_iterator
2444 findIVOperand(User::op_iterator OI, User::op_iterator OE,
2445 Loop *L, ScalarEvolution &SE) {
2446 for(; OI != OE; ++OI) {
2447 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2448 if (!SE.isSCEVable(Oper->getType()))
2451 if (const SCEVAddRecExpr *AR =
2452 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2453 if (AR->getLoop() == L)
2461 /// getWideOperand - IVChain logic must consistenctly peek base TruncInst
2462 /// operands, so wrap it in a convenient helper.
2463 static Value *getWideOperand(Value *Oper) {
2464 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2465 return Trunc->getOperand(0);
2469 /// isCompatibleIVType - Return true if we allow an IV chain to include both
2471 static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2472 Type *LType = LVal->getType();
2473 Type *RType = RVal->getType();
2474 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy());
2477 /// getExprBase - Return an approximation of this SCEV expression's "base", or
2478 /// NULL for any constant. Returning the expression itself is
2479 /// conservative. Returning a deeper subexpression is more precise and valid as
2480 /// long as it isn't less complex than another subexpression. For expressions
2481 /// involving multiple unscaled values, we need to return the pointer-type
2482 /// SCEVUnknown. This avoids forming chains across objects, such as:
2483 /// PrevOper==a[i], IVOper==b[i], IVInc==b-a.
2485 /// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2486 /// SCEVUnknown, we simply return the rightmost SCEV operand.
2487 static const SCEV *getExprBase(const SCEV *S) {
2488 switch (S->getSCEVType()) {
2489 default: // uncluding scUnknown.
2494 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2496 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2498 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2500 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2501 // there's nothing more complex.
2502 // FIXME: not sure if we want to recognize negation.
2503 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2504 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2505 E(Add->op_begin()); I != E; ++I) {
2506 const SCEV *SubExpr = *I;
2507 if (SubExpr->getSCEVType() == scAddExpr)
2508 return getExprBase(SubExpr);
2510 if (SubExpr->getSCEVType() != scMulExpr)
2513 return S; // all operands are scaled, be conservative.
2516 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2520 /// Return true if the chain increment is profitable to expand into a loop
2521 /// invariant value, which may require its own register. A profitable chain
2522 /// increment will be an offset relative to the same base. We allow such offsets
2523 /// to potentially be used as chain increment as long as it's not obviously
2524 /// expensive to expand using real instructions.
2525 bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2526 const SCEV *IncExpr,
2527 ScalarEvolution &SE) {
2528 // Aggressively form chains when -stress-ivchain.
2532 // Do not replace a constant offset from IV head with a nonconstant IV
2534 if (!isa<SCEVConstant>(IncExpr)) {
2535 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2536 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2540 SmallPtrSet<const SCEV*, 8> Processed;
2541 return !isHighCostExpansion(IncExpr, Processed, SE);
2544 /// Return true if the number of registers needed for the chain is estimated to
2545 /// be less than the number required for the individual IV users. First prohibit
2546 /// any IV users that keep the IV live across increments (the Users set should
2547 /// be empty). Next count the number and type of increments in the chain.
2549 /// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2550 /// effectively use postinc addressing modes. Only consider it profitable it the
2551 /// increments can be computed in fewer registers when chained.
2553 /// TODO: Consider IVInc free if it's already used in another chains.
2555 isProfitableChain(IVChain &Chain, SmallPtrSetImpl<Instruction*> &Users,
2556 ScalarEvolution &SE, const TargetTransformInfo &TTI) {
2560 if (!Chain.hasIncs())
2563 if (!Users.empty()) {
2564 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";
2565 for (Instruction *Inst : Users) {
2566 dbgs() << " " << *Inst << "\n";
2570 assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2572 // The chain itself may require a register, so intialize cost to 1.
2575 // A complete chain likely eliminates the need for keeping the original IV in
2576 // a register. LSR does not currently know how to form a complete chain unless
2577 // the header phi already exists.
2578 if (isa<PHINode>(Chain.tailUserInst())
2579 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2582 const SCEV *LastIncExpr = nullptr;
2583 unsigned NumConstIncrements = 0;
2584 unsigned NumVarIncrements = 0;
2585 unsigned NumReusedIncrements = 0;
2586 for (IVChain::const_iterator I = Chain.begin(), E = Chain.end();
2589 if (I->IncExpr->isZero())
2592 // Incrementing by zero or some constant is neutral. We assume constants can
2593 // be folded into an addressing mode or an add's immediate operand.
2594 if (isa<SCEVConstant>(I->IncExpr)) {
2595 ++NumConstIncrements;
2599 if (I->IncExpr == LastIncExpr)
2600 ++NumReusedIncrements;
2604 LastIncExpr = I->IncExpr;
2606 // An IV chain with a single increment is handled by LSR's postinc
2607 // uses. However, a chain with multiple increments requires keeping the IV's
2608 // value live longer than it needs to be if chained.
2609 if (NumConstIncrements > 1)
2612 // Materializing increment expressions in the preheader that didn't exist in
2613 // the original code may cost a register. For example, sign-extended array
2614 // indices can produce ridiculous increments like this:
2615 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2616 cost += NumVarIncrements;
2618 // Reusing variable increments likely saves a register to hold the multiple of
2620 cost -= NumReusedIncrements;
2622 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost
2628 /// ChainInstruction - Add this IV user to an existing chain or make it the head
2630 void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2631 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2632 // When IVs are used as types of varying widths, they are generally converted
2633 // to a wider type with some uses remaining narrow under a (free) trunc.
2634 Value *const NextIV = getWideOperand(IVOper);
2635 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2636 const SCEV *const OperExprBase = getExprBase(OperExpr);
2638 // Visit all existing chains. Check if its IVOper can be computed as a
2639 // profitable loop invariant increment from the last link in the Chain.
2640 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2641 const SCEV *LastIncExpr = nullptr;
2642 for (; ChainIdx < NChains; ++ChainIdx) {
2643 IVChain &Chain = IVChainVec[ChainIdx];
2645 // Prune the solution space aggressively by checking that both IV operands
2646 // are expressions that operate on the same unscaled SCEVUnknown. This
2647 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2648 // first avoids creating extra SCEV expressions.
2649 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2652 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2653 if (!isCompatibleIVType(PrevIV, NextIV))
2656 // A phi node terminates a chain.
2657 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2660 // The increment must be loop-invariant so it can be kept in a register.
2661 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2662 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2663 if (!SE.isLoopInvariant(IncExpr, L))
2666 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2667 LastIncExpr = IncExpr;
2671 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2672 // bother for phi nodes, because they must be last in the chain.
2673 if (ChainIdx == NChains) {
2674 if (isa<PHINode>(UserInst))
2676 if (NChains >= MaxChains && !StressIVChain) {
2677 DEBUG(dbgs() << "IV Chain Limit\n");
2680 LastIncExpr = OperExpr;
2681 // IVUsers may have skipped over sign/zero extensions. We don't currently
2682 // attempt to form chains involving extensions unless they can be hoisted
2683 // into this loop's AddRec.
2684 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2687 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2689 ChainUsersVec.resize(NChains);
2690 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst
2691 << ") IV=" << *LastIncExpr << "\n");
2693 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst
2694 << ") IV+" << *LastIncExpr << "\n");
2695 // Add this IV user to the end of the chain.
2696 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2698 IVChain &Chain = IVChainVec[ChainIdx];
2700 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2701 // This chain's NearUsers become FarUsers.
2702 if (!LastIncExpr->isZero()) {
2703 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2708 // All other uses of IVOperand become near uses of the chain.
2709 // We currently ignore intermediate values within SCEV expressions, assuming
2710 // they will eventually be used be the current chain, or can be computed
2711 // from one of the chain increments. To be more precise we could
2712 // transitively follow its user and only add leaf IV users to the set.
2713 for (User *U : IVOper->users()) {
2714 Instruction *OtherUse = dyn_cast<Instruction>(U);
2717 // Uses in the chain will no longer be uses if the chain is formed.
2718 // Include the head of the chain in this iteration (not Chain.begin()).
2719 IVChain::const_iterator IncIter = Chain.Incs.begin();
2720 IVChain::const_iterator IncEnd = Chain.Incs.end();
2721 for( ; IncIter != IncEnd; ++IncIter) {
2722 if (IncIter->UserInst == OtherUse)
2725 if (IncIter != IncEnd)
2728 if (SE.isSCEVable(OtherUse->getType())
2729 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2730 && IU.isIVUserOrOperand(OtherUse)) {
2733 NearUsers.insert(OtherUse);
2736 // Since this user is part of the chain, it's no longer considered a use
2738 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2741 /// CollectChains - Populate the vector of Chains.
2743 /// This decreases ILP at the architecture level. Targets with ample registers,
2744 /// multiple memory ports, and no register renaming probably don't want
2745 /// this. However, such targets should probably disable LSR altogether.
2747 /// The job of LSR is to make a reasonable choice of induction variables across
2748 /// the loop. Subsequent passes can easily "unchain" computation exposing more
2749 /// ILP *within the loop* if the target wants it.
2751 /// Finding the best IV chain is potentially a scheduling problem. Since LSR
2752 /// will not reorder memory operations, it will recognize this as a chain, but
2753 /// will generate redundant IV increments. Ideally this would be corrected later
2754 /// by a smart scheduler:
2760 /// TODO: Walk the entire domtree within this loop, not just the path to the
2761 /// loop latch. This will discover chains on side paths, but requires
2762 /// maintaining multiple copies of the Chains state.
2763 void LSRInstance::CollectChains() {
2764 DEBUG(dbgs() << "Collecting IV Chains.\n");
2765 SmallVector<ChainUsers, 8> ChainUsersVec;
2767 SmallVector<BasicBlock *,8> LatchPath;
2768 BasicBlock *LoopHeader = L->getHeader();
2769 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
2770 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
2771 LatchPath.push_back(Rung->getBlock());
2773 LatchPath.push_back(LoopHeader);
2775 // Walk the instruction stream from the loop header to the loop latch.
2776 for (SmallVectorImpl<BasicBlock *>::reverse_iterator
2777 BBIter = LatchPath.rbegin(), BBEnd = LatchPath.rend();
2778 BBIter != BBEnd; ++BBIter) {
2779 for (BasicBlock::iterator I = (*BBIter)->begin(), E = (*BBIter)->end();
2781 // Skip instructions that weren't seen by IVUsers analysis.
2782 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(I))
2785 // Ignore users that are part of a SCEV expression. This way we only
2786 // consider leaf IV Users. This effectively rediscovers a portion of
2787 // IVUsers analysis but in program order this time.
2788 if (SE.isSCEVable(I->getType()) && !isa<SCEVUnknown>(SE.getSCEV(I)))
2791 // Remove this instruction from any NearUsers set it may be in.
2792 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
2793 ChainIdx < NChains; ++ChainIdx) {
2794 ChainUsersVec[ChainIdx].NearUsers.erase(I);
2796 // Search for operands that can be chained.
2797 SmallPtrSet<Instruction*, 4> UniqueOperands;
2798 User::op_iterator IVOpEnd = I->op_end();
2799 User::op_iterator IVOpIter = findIVOperand(I->op_begin(), IVOpEnd, L, SE);
2800 while (IVOpIter != IVOpEnd) {
2801 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
2802 if (UniqueOperands.insert(IVOpInst).second)
2803 ChainInstruction(I, IVOpInst, ChainUsersVec);
2804 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
2806 } // Continue walking down the instructions.
2807 } // Continue walking down the domtree.
2808 // Visit phi backedges to determine if the chain can generate the IV postinc.
2809 for (BasicBlock::iterator I = L->getHeader()->begin();
2810 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
2811 if (!SE.isSCEVable(PN->getType()))
2815 dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch()));
2817 ChainInstruction(PN, IncV, ChainUsersVec);
2819 // Remove any unprofitable chains.
2820 unsigned ChainIdx = 0;
2821 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
2822 UsersIdx < NChains; ++UsersIdx) {
2823 if (!isProfitableChain(IVChainVec[UsersIdx],
2824 ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
2826 // Preserve the chain at UsesIdx.
2827 if (ChainIdx != UsersIdx)
2828 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
2829 FinalizeChain(IVChainVec[ChainIdx]);
2832 IVChainVec.resize(ChainIdx);
2835 void LSRInstance::FinalizeChain(IVChain &Chain) {
2836 assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2837 DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n");
2839 for (IVChain::const_iterator I = Chain.begin(), E = Chain.end();
2841 DEBUG(dbgs() << " Inc: " << *I->UserInst << "\n");
2842 User::op_iterator UseI =
2843 std::find(I->UserInst->op_begin(), I->UserInst->op_end(), I->IVOperand);
2844 assert(UseI != I->UserInst->op_end() && "cannot find IV operand");
2845 IVIncSet.insert(UseI);
2849 /// Return true if the IVInc can be folded into an addressing mode.
2850 static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
2851 Value *Operand, const TargetTransformInfo &TTI) {
2852 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
2853 if (!IncConst || !isAddressUse(UserInst, Operand))
2856 if (IncConst->getValue()->getValue().getMinSignedBits() > 64)
2859 int64_t IncOffset = IncConst->getValue()->getSExtValue();
2860 if (!isAlwaysFoldable(TTI, LSRUse::Address,
2861 getAccessType(UserInst), /*BaseGV=*/ nullptr,
2862 IncOffset, /*HaseBaseReg=*/ false))
2868 /// GenerateIVChains - Generate an add or subtract for each IVInc in a chain to
2869 /// materialize the IV user's operand from the previous IV user's operand.
2870 void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
2871 SmallVectorImpl<WeakVH> &DeadInsts) {
2872 // Find the new IVOperand for the head of the chain. It may have been replaced
2874 const IVInc &Head = Chain.Incs[0];
2875 User::op_iterator IVOpEnd = Head.UserInst->op_end();
2876 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
2877 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
2879 Value *IVSrc = nullptr;
2880 while (IVOpIter != IVOpEnd) {
2881 IVSrc = getWideOperand(*IVOpIter);
2883 // If this operand computes the expression that the chain needs, we may use
2884 // it. (Check this after setting IVSrc which is used below.)
2886 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
2887 // narrow for the chain, so we can no longer use it. We do allow using a
2888 // wider phi, assuming the LSR checked for free truncation. In that case we
2889 // should already have a truncate on this operand such that
2890 // getSCEV(IVSrc) == IncExpr.
2891 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
2892 || SE.getSCEV(IVSrc) == Head.IncExpr) {
2895 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
2897 if (IVOpIter == IVOpEnd) {
2898 // Gracefully give up on this chain.
2899 DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
2903 DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
2904 Type *IVTy = IVSrc->getType();
2905 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
2906 const SCEV *LeftOverExpr = nullptr;
2907 for (IVChain::const_iterator IncI = Chain.begin(),
2908 IncE = Chain.end(); IncI != IncE; ++IncI) {
2910 Instruction *InsertPt = IncI->UserInst;
2911 if (isa<PHINode>(InsertPt))
2912 InsertPt = L->getLoopLatch()->getTerminator();
2914 // IVOper will replace the current IV User's operand. IVSrc is the IV
2915 // value currently held in a register.
2916 Value *IVOper = IVSrc;
2917 if (!IncI->IncExpr->isZero()) {
2918 // IncExpr was the result of subtraction of two narrow values, so must
2920 const SCEV *IncExpr = SE.getNoopOrSignExtend(IncI->IncExpr, IntTy);
2921 LeftOverExpr = LeftOverExpr ?
2922 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
2924 if (LeftOverExpr && !LeftOverExpr->isZero()) {
2925 // Expand the IV increment.
2926 Rewriter.clearPostInc();
2927 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
2928 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
2929 SE.getUnknown(IncV));
2930 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
2932 // If an IV increment can't be folded, use it as the next IV value.
2933 if (!canFoldIVIncExpr(LeftOverExpr, IncI->UserInst, IncI->IVOperand,
2935 assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
2937 LeftOverExpr = nullptr;
2940 Type *OperTy = IncI->IVOperand->getType();
2941 if (IVTy != OperTy) {
2942 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
2943 "cannot extend a chained IV");
2944 IRBuilder<> Builder(InsertPt);
2945 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
2947 IncI->UserInst->replaceUsesOfWith(IncI->IVOperand, IVOper);
2948 DeadInsts.push_back(IncI->IVOperand);
2950 // If LSR created a new, wider phi, we may also replace its postinc. We only
2951 // do this if we also found a wide value for the head of the chain.
2952 if (isa<PHINode>(Chain.tailUserInst())) {
2953 for (BasicBlock::iterator I = L->getHeader()->begin();
2954 PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
2955 if (!isCompatibleIVType(Phi, IVSrc))
2957 Instruction *PostIncV = dyn_cast<Instruction>(
2958 Phi->getIncomingValueForBlock(L->getLoopLatch()));
2959 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
2961 Value *IVOper = IVSrc;
2962 Type *PostIncTy = PostIncV->getType();
2963 if (IVTy != PostIncTy) {
2964 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
2965 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
2966 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
2967 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
2969 Phi->replaceUsesOfWith(PostIncV, IVOper);
2970 DeadInsts.push_back(PostIncV);
2975 void LSRInstance::CollectFixupsAndInitialFormulae() {
2976 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2977 Instruction *UserInst = UI->getUser();
2978 // Skip IV users that are part of profitable IV Chains.
2979 User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(),
2980 UI->getOperandValToReplace());
2981 assert(UseI != UserInst->op_end() && "cannot find IV operand");
2982 if (IVIncSet.count(UseI))
2986 LSRFixup &LF = getNewFixup();
2987 LF.UserInst = UserInst;
2988 LF.OperandValToReplace = UI->getOperandValToReplace();
2989 LF.PostIncLoops = UI->getPostIncLoops();
2991 LSRUse::KindType Kind = LSRUse::Basic;
2992 Type *AccessTy = nullptr;
2993 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
2994 Kind = LSRUse::Address;
2995 AccessTy = getAccessType(LF.UserInst);
2998 const SCEV *S = IU.getExpr(*UI);
3000 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
3001 // (N - i == 0), and this allows (N - i) to be the expression that we work
3002 // with rather than just N or i, so we can consider the register
3003 // requirements for both N and i at the same time. Limiting this code to
3004 // equality icmps is not a problem because all interesting loops use
3005 // equality icmps, thanks to IndVarSimplify.
3006 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
3007 if (CI->isEquality()) {
3008 // Swap the operands if needed to put the OperandValToReplace on the
3009 // left, for consistency.
3010 Value *NV = CI->getOperand(1);
3011 if (NV == LF.OperandValToReplace) {
3012 CI->setOperand(1, CI->getOperand(0));
3013 CI->setOperand(0, NV);
3014 NV = CI->getOperand(1);
3018 // x == y --> x - y == 0
3019 const SCEV *N = SE.getSCEV(NV);
3020 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3021 // S is normalized, so normalize N before folding it into S
3022 // to keep the result normalized.
3023 N = TransformForPostIncUse(Normalize, N, CI, nullptr,
3024 LF.PostIncLoops, SE, DT);
3025 Kind = LSRUse::ICmpZero;
3026 S = SE.getMinusSCEV(N, S);
3029 // -1 and the negations of all interesting strides (except the negation
3030 // of -1) are now also interesting.
3031 for (size_t i = 0, e = Factors.size(); i != e; ++i)
3032 if (Factors[i] != -1)
3033 Factors.insert(-(uint64_t)Factors[i]);
3037 // Set up the initial formula for this use.
3038 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3040 LF.Offset = P.second;
3041 LSRUse &LU = Uses[LF.LUIdx];
3042 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3043 if (!LU.WidestFixupType ||
3044 SE.getTypeSizeInBits(LU.WidestFixupType) <
3045 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3046 LU.WidestFixupType = LF.OperandValToReplace->getType();
3048 // If this is the first use of this LSRUse, give it a formula.
3049 if (LU.Formulae.empty()) {
3050 InsertInitialFormula(S, LU, LF.LUIdx);
3051 CountRegisters(LU.Formulae.back(), LF.LUIdx);
3055 DEBUG(print_fixups(dbgs()));
3058 /// InsertInitialFormula - Insert a formula for the given expression into
3059 /// the given use, separating out loop-variant portions from loop-invariant
3060 /// and loop-computable portions.
3062 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3063 // Mark uses whose expressions cannot be expanded.
3064 if (!isSafeToExpand(S, SE))
3065 LU.RigidFormula = true;
3068 F.InitialMatch(S, L, SE);
3069 bool Inserted = InsertFormula(LU, LUIdx, F);
3070 assert(Inserted && "Initial formula already exists!"); (void)Inserted;
3073 /// InsertSupplementalFormula - Insert a simple single-register formula for
3074 /// the given expression into the given use.
3076 LSRInstance::InsertSupplementalFormula(const SCEV *S,
3077 LSRUse &LU, size_t LUIdx) {
3079 F.BaseRegs.push_back(S);
3080 F.HasBaseReg = true;
3081 bool Inserted = InsertFormula(LU, LUIdx, F);
3082 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
3085 /// CountRegisters - Note which registers are used by the given formula,
3086 /// updating RegUses.
3087 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3089 RegUses.CountRegister(F.ScaledReg, LUIdx);
3090 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
3091 E = F.BaseRegs.end(); I != E; ++I)
3092 RegUses.CountRegister(*I, LUIdx);
3095 /// InsertFormula - If the given formula has not yet been inserted, add it to
3096 /// the list, and return true. Return false otherwise.
3097 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3098 // Do not insert formula that we will not be able to expand.
3099 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&
3100 "Formula is illegal");
3101 if (!LU.InsertFormula(F))
3104 CountRegisters(F, LUIdx);
3108 /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
3109 /// loop-invariant values which we're tracking. These other uses will pin these
3110 /// values in registers, making them less profitable for elimination.
3111 /// TODO: This currently misses non-constant addrec step registers.
3112 /// TODO: Should this give more weight to users inside the loop?
3114 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3115 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3116 SmallPtrSet<const SCEV *, 32> Visited;
3118 while (!Worklist.empty()) {
3119 const SCEV *S = Worklist.pop_back_val();
3121 // Don't process the same SCEV twice
3122 if (!Visited.insert(S).second)
3125 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3126 Worklist.append(N->op_begin(), N->op_end());
3127 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3128 Worklist.push_back(C->getOperand());
3129 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3130 Worklist.push_back(D->getLHS());
3131 Worklist.push_back(D->getRHS());
3132 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3133 const Value *V = US->getValue();
3134 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3135 // Look for instructions defined outside the loop.
3136 if (L->contains(Inst)) continue;
3137 } else if (isa<UndefValue>(V))
3138 // Undef doesn't have a live range, so it doesn't matter.
3140 for (const Use &U : V->uses()) {
3141 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3142 // Ignore non-instructions.
3145 // Ignore instructions in other functions (as can happen with
3147 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3149 // Ignore instructions not dominated by the loop.
3150 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3151 UserInst->getParent() :
3152 cast<PHINode>(UserInst)->getIncomingBlock(
3153 PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3154 if (!DT.dominates(L->getHeader(), UseBB))
3156 // Ignore uses which are part of other SCEV expressions, to avoid
3157 // analyzing them multiple times.
3158 if (SE.isSCEVable(UserInst->getType())) {
3159 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3160 // If the user is a no-op, look through to its uses.
3161 if (!isa<SCEVUnknown>(UserS))
3165 SE.getUnknown(const_cast<Instruction *>(UserInst)));
3169 // Ignore icmp instructions which are already being analyzed.
3170 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3171 unsigned OtherIdx = !U.getOperandNo();
3172 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3173 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3177 LSRFixup &LF = getNewFixup();
3178 LF.UserInst = const_cast<Instruction *>(UserInst);
3179 LF.OperandValToReplace = U;
3180 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, nullptr);
3182 LF.Offset = P.second;
3183 LSRUse &LU = Uses[LF.LUIdx];
3184 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3185 if (!LU.WidestFixupType ||
3186 SE.getTypeSizeInBits(LU.WidestFixupType) <
3187 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3188 LU.WidestFixupType = LF.OperandValToReplace->getType();
3189 InsertSupplementalFormula(US, LU, LF.LUIdx);
3190 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3197 /// CollectSubexprs - Split S into subexpressions which can be pulled out into
3198 /// separate registers. If C is non-null, multiply each subexpression by C.
3200 /// Return remainder expression after factoring the subexpressions captured by
3201 /// Ops. If Ops is complete, return NULL.
3202 static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3203 SmallVectorImpl<const SCEV *> &Ops,
3205 ScalarEvolution &SE,
3206 unsigned Depth = 0) {
3207 // Arbitrarily cap recursion to protect compile time.
3211 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3212 // Break out add operands.
3213 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
3215 const SCEV *Remainder = CollectSubexprs(*I, C, Ops, L, SE, Depth+1);
3217 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3220 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3221 // Split a non-zero base out of an addrec.
3222 if (AR->getStart()->isZero())
3225 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3226 C, Ops, L, SE, Depth+1);
3227 // Split the non-zero AddRec unless it is part of a nested recurrence that
3228 // does not pertain to this loop.
3229 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3230 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3231 Remainder = nullptr;
3233 if (Remainder != AR->getStart()) {
3235 Remainder = SE.getConstant(AR->getType(), 0);
3236 return SE.getAddRecExpr(Remainder,
3237 AR->getStepRecurrence(SE),
3239 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3242 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3243 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3244 if (Mul->getNumOperands() != 2)
3246 if (const SCEVConstant *Op0 =
3247 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3248 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3249 const SCEV *Remainder =
3250 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3252 Ops.push_back(SE.getMulExpr(C, Remainder));
3259 /// \brief Helper function for LSRInstance::GenerateReassociations.
3260 void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3261 const Formula &Base,
3262 unsigned Depth, size_t Idx,
3264 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3265 SmallVector<const SCEV *, 8> AddOps;
3266 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3268 AddOps.push_back(Remainder);
3270 if (AddOps.size() == 1)
3273 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3277 // Loop-variant "unknown" values are uninteresting; we won't be able to
3278 // do anything meaningful with them.
3279 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3282 // Don't pull a constant into a register if the constant could be folded
3283 // into an immediate field.
3284 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3285 LU.AccessTy, *J, Base.getNumRegs() > 1))
3288 // Collect all operands except *J.
3289 SmallVector<const SCEV *, 8> InnerAddOps(
3290 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3291 InnerAddOps.append(std::next(J),
3292 ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3294 // Don't leave just a constant behind in a register if the constant could
3295 // be folded into an immediate field.
3296 if (InnerAddOps.size() == 1 &&
3297 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3298 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3301 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3302 if (InnerSum->isZero())
3306 // Add the remaining pieces of the add back into the new formula.
3307 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3308 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3309 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3310 InnerSumSC->getValue()->getZExtValue())) {
3312 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3314 F.ScaledReg = nullptr;
3316 F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3317 } else if (IsScaledReg)
3318 F.ScaledReg = InnerSum;
3320 F.BaseRegs[Idx] = InnerSum;
3322 // Add J as its own register, or an unfolded immediate.
3323 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3324 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3325 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3326 SC->getValue()->getZExtValue()))
3328 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3330 F.BaseRegs.push_back(*J);
3331 // We may have changed the number of register in base regs, adjust the
3332 // formula accordingly.
3335 if (InsertFormula(LU, LUIdx, F))
3336 // If that formula hadn't been seen before, recurse to find more like
3338 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth + 1);
3342 /// GenerateReassociations - Split out subexpressions from adds and the bases of
3344 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3345 Formula Base, unsigned Depth) {
3346 assert(Base.isCanonical() && "Input must be in the canonical form");
3347 // Arbitrarily cap recursion to protect compile time.
3351 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3352 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3354 if (Base.Scale == 1)
3355 GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3356 /* Idx */ -1, /* IsScaledReg */ true);
3359 /// GenerateCombinations - Generate a formula consisting of all of the
3360 /// loop-dominating registers added into a single register.
3361 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3363 // This method is only interesting on a plurality of registers.
3364 if (Base.BaseRegs.size() + (Base.Scale == 1) <= 1)
3367 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3368 // processing the formula.
3372 SmallVector<const SCEV *, 4> Ops;
3373 for (SmallVectorImpl<const SCEV *>::const_iterator
3374 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
3375 const SCEV *BaseReg = *I;
3376 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3377 !SE.hasComputableLoopEvolution(BaseReg, L))
3378 Ops.push_back(BaseReg);
3380 F.BaseRegs.push_back(BaseReg);
3382 if (Ops.size() > 1) {
3383 const SCEV *Sum = SE.getAddExpr(Ops);
3384 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3385 // opportunity to fold something. For now, just ignore such cases
3386 // rather than proceed with zero in a register.
3387 if (!Sum->isZero()) {
3388 F.BaseRegs.push_back(Sum);
3390 (void)InsertFormula(LU, LUIdx, F);
3395 /// \brief Helper function for LSRInstance::GenerateSymbolicOffsets.
3396 void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3397 const Formula &Base, size_t Idx,
3399 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3400 GlobalValue *GV = ExtractSymbol(G, SE);
3401 if (G->isZero() || !GV)
3405 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3410 F.BaseRegs[Idx] = G;
3411 (void)InsertFormula(LU, LUIdx, F);
3414 /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
3415 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3417 // We can't add a symbolic offset if the address already contains one.
3418 if (Base.BaseGV) return;
3420 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3421 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3422 if (Base.Scale == 1)
3423 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3424 /* IsScaledReg */ true);
3427 /// \brief Helper function for LSRInstance::GenerateConstantOffsets.
3428 void LSRInstance::GenerateConstantOffsetsImpl(
3429 LSRUse &LU, unsigned LUIdx, const Formula &Base,
3430 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3431 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3432 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
3436 F.BaseOffset = (uint64_t)Base.BaseOffset - *I;
3437 if (isLegalUse(TTI, LU.MinOffset - *I, LU.MaxOffset - *I, LU.Kind,
3439 // Add the offset to the base register.
3440 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G);
3441 // If it cancelled out, drop the base register, otherwise update it.
3442 if (NewG->isZero()) {
3445 F.ScaledReg = nullptr;
3447 F.DeleteBaseReg(F.BaseRegs[Idx]);
3449 } else if (IsScaledReg)
3452 F.BaseRegs[Idx] = NewG;
3454 (void)InsertFormula(LU, LUIdx, F);
3458 int64_t Imm = ExtractImmediate(G, SE);
3459 if (G->isZero() || Imm == 0)
3462 F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3463 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3468 F.BaseRegs[Idx] = G;
3469 (void)InsertFormula(LU, LUIdx, F);
3472 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3473 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3475 // TODO: For now, just add the min and max offset, because it usually isn't
3476 // worthwhile looking at everything inbetween.
3477 SmallVector<int64_t, 2> Worklist;
3478 Worklist.push_back(LU.MinOffset);
3479 if (LU.MaxOffset != LU.MinOffset)
3480 Worklist.push_back(LU.MaxOffset);
3482 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3483 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3484 if (Base.Scale == 1)
3485 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3486 /* IsScaledReg */ true);
3489 /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
3490 /// the comparison. For example, x == y -> x*c == y*c.
3491 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3493 if (LU.Kind != LSRUse::ICmpZero) return;
3495 // Determine the integer type for the base formula.
3496 Type *IntTy = Base.getType();
3498 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3500 // Don't do this if there is more than one offset.
3501 if (LU.MinOffset != LU.MaxOffset) return;
3503 assert(!Base.BaseGV && "ICmpZero use is not legal!");
3505 // Check each interesting stride.
3506 for (SmallSetVector<int64_t, 8>::const_iterator
3507 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3508 int64_t Factor = *I;
3510 // Check that the multiplication doesn't overflow.
3511 if (Base.BaseOffset == INT64_MIN && Factor == -1)
3513 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3514 if (NewBaseOffset / Factor != Base.BaseOffset)
3516 // If the offset will be truncated at this use, check that it is in bounds.
3517 if (!IntTy->isPointerTy() &&
3518 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3521 // Check that multiplying with the use offset doesn't overflow.
3522 int64_t Offset = LU.MinOffset;
3523 if (Offset == INT64_MIN && Factor == -1)
3525 Offset = (uint64_t)Offset * Factor;
3526 if (Offset / Factor != LU.MinOffset)
3528 // If the offset will be truncated at this use, check that it is in bounds.
3529 if (!IntTy->isPointerTy() &&
3530 !ConstantInt::isValueValidForType(IntTy, Offset))
3534 F.BaseOffset = NewBaseOffset;
3536 // Check that this scale is legal.
3537 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3540 // Compensate for the use having MinOffset built into it.
3541 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3543 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3545 // Check that multiplying with each base register doesn't overflow.
3546 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3547 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3548 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3552 // Check that multiplying with the scaled register doesn't overflow.
3554 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3555 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3559 // Check that multiplying with the unfolded offset doesn't overflow.
3560 if (F.UnfoldedOffset != 0) {
3561 if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
3563 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3564 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3566 // If the offset will be truncated, check that it is in bounds.
3567 if (!IntTy->isPointerTy() &&
3568 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3572 // If we make it here and it's legal, add it.
3573 (void)InsertFormula(LU, LUIdx, F);
3578 /// GenerateScales - Generate stride factor reuse formulae by making use of
3579 /// scaled-offset address modes, for example.
3580 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3581 // Determine the integer type for the base formula.
3582 Type *IntTy = Base.getType();
3585 // If this Formula already has a scaled register, we can't add another one.
3586 // Try to unscale the formula to generate a better scale.
3587 if (Base.Scale != 0 && !Base.Unscale())
3590 assert(Base.Scale == 0 && "Unscale did not did its job!");
3592 // Check each interesting stride.
3593 for (SmallSetVector<int64_t, 8>::const_iterator
3594 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3595 int64_t Factor = *I;
3597 Base.Scale = Factor;
3598 Base.HasBaseReg = Base.BaseRegs.size() > 1;
3599 // Check whether this scale is going to be legal.
3600 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3602 // As a special-case, handle special out-of-loop Basic users specially.
3603 // TODO: Reconsider this special case.
3604 if (LU.Kind == LSRUse::Basic &&
3605 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3606 LU.AccessTy, Base) &&
3607 LU.AllFixupsOutsideLoop)
3608 LU.Kind = LSRUse::Special;
3612 // For an ICmpZero, negating a solitary base register won't lead to
3614 if (LU.Kind == LSRUse::ICmpZero &&
3615 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3617 // For each addrec base reg, apply the scale, if possible.
3618 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3619 if (const SCEVAddRecExpr *AR =
3620 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
3621 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3622 if (FactorS->isZero())
3624 // Divide out the factor, ignoring high bits, since we'll be
3625 // scaling the value back up in the end.
3626 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3627 // TODO: This could be optimized to avoid all the copying.
3629 F.ScaledReg = Quotient;
3630 F.DeleteBaseReg(F.BaseRegs[i]);
3631 // The canonical representation of 1*reg is reg, which is already in
3632 // Base. In that case, do not try to insert the formula, it will be
3634 if (F.Scale == 1 && F.BaseRegs.empty())
3636 (void)InsertFormula(LU, LUIdx, F);
3642 /// GenerateTruncates - Generate reuse formulae from different IV types.
3643 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3644 // Don't bother truncating symbolic values.
3645 if (Base.BaseGV) return;
3647 // Determine the integer type for the base formula.
3648 Type *DstTy = Base.getType();
3650 DstTy = SE.getEffectiveSCEVType(DstTy);
3652 for (SmallSetVector<Type *, 4>::const_iterator
3653 I = Types.begin(), E = Types.end(); I != E; ++I) {
3655 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
3658 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
3659 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
3660 JE = F.BaseRegs.end(); J != JE; ++J)
3661 *J = SE.getAnyExtendExpr(*J, SrcTy);
3663 // TODO: This assumes we've done basic processing on all uses and
3664 // have an idea what the register usage is.
3665 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3668 (void)InsertFormula(LU, LUIdx, F);
3675 /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
3676 /// defer modifications so that the search phase doesn't have to worry about
3677 /// the data structures moving underneath it.
3681 const SCEV *OrigReg;
3683 WorkItem(size_t LI, int64_t I, const SCEV *R)
3684 : LUIdx(LI), Imm(I), OrigReg(R) {}
3686 void print(raw_ostream &OS) const;
3692 void WorkItem::print(raw_ostream &OS) const {
3693 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3694 << " , add offset " << Imm;
3697 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
3698 void WorkItem::dump() const {
3699 print(errs()); errs() << '\n';
3703 /// GenerateCrossUseConstantOffsets - Look for registers which are a constant
3704 /// distance apart and try to form reuse opportunities between them.
3705 void LSRInstance::GenerateCrossUseConstantOffsets() {
3706 // Group the registers by their value without any added constant offset.
3707 typedef std::map<int64_t, const SCEV *> ImmMapTy;
3708 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
3710 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3711 SmallVector<const SCEV *, 8> Sequence;
3712 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
3714 const SCEV *Reg = *I;
3715 int64_t Imm = ExtractImmediate(Reg, SE);
3716 std::pair<RegMapTy::iterator, bool> Pair =
3717 Map.insert(std::make_pair(Reg, ImmMapTy()));
3719 Sequence.push_back(Reg);
3720 Pair.first->second.insert(std::make_pair(Imm, *I));
3721 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
3724 // Now examine each set of registers with the same base value. Build up
3725 // a list of work to do and do the work in a separate step so that we're
3726 // not adding formulae and register counts while we're searching.
3727 SmallVector<WorkItem, 32> WorkItems;
3728 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3729 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
3730 E = Sequence.end(); I != E; ++I) {
3731 const SCEV *Reg = *I;
3732 const ImmMapTy &Imms = Map.find(Reg)->second;
3734 // It's not worthwhile looking for reuse if there's only one offset.
3735 if (Imms.size() == 1)
3738 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
3739 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3741 dbgs() << ' ' << J->first;
3744 // Examine each offset.
3745 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3747 const SCEV *OrigReg = J->second;
3749 int64_t JImm = J->first;
3750 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
3752 if (!isa<SCEVConstant>(OrigReg) &&
3753 UsedByIndicesMap[Reg].count() == 1) {
3754 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
3758 // Conservatively examine offsets between this orig reg a few selected
3760 ImmMapTy::const_iterator OtherImms[] = {
3761 Imms.begin(), std::prev(Imms.end()),
3762 Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) /
3765 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
3766 ImmMapTy::const_iterator M = OtherImms[i];
3767 if (M == J || M == JE) continue;
3769 // Compute the difference between the two.
3770 int64_t Imm = (uint64_t)JImm - M->first;
3771 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
3772 LUIdx = UsedByIndices.find_next(LUIdx))
3773 // Make a memo of this use, offset, and register tuple.
3774 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
3775 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
3782 UsedByIndicesMap.clear();
3783 UniqueItems.clear();
3785 // Now iterate through the worklist and add new formulae.
3786 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
3787 E = WorkItems.end(); I != E; ++I) {
3788 const WorkItem &WI = *I;
3789 size_t LUIdx = WI.LUIdx;
3790 LSRUse &LU = Uses[LUIdx];
3791 int64_t Imm = WI.Imm;
3792 const SCEV *OrigReg = WI.OrigReg;
3794 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
3795 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
3796 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
3798 // TODO: Use a more targeted data structure.
3799 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
3800 Formula F = LU.Formulae[L];
3801 // FIXME: The code for the scaled and unscaled registers looks
3802 // very similar but slightly different. Investigate if they
3803 // could be merged. That way, we would not have to unscale the
3806 // Use the immediate in the scaled register.
3807 if (F.ScaledReg == OrigReg) {
3808 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
3809 // Don't create 50 + reg(-50).
3810 if (F.referencesReg(SE.getSCEV(
3811 ConstantInt::get(IntTy, -(uint64_t)Offset))))
3814 NewF.BaseOffset = Offset;
3815 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3818 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
3820 // If the new scale is a constant in a register, and adding the constant
3821 // value to the immediate would produce a value closer to zero than the
3822 // immediate itself, then the formula isn't worthwhile.
3823 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
3824 if (C->getValue()->isNegative() !=
3825 (NewF.BaseOffset < 0) &&
3826 (C->getValue()->getValue().abs() * APInt(BitWidth, F.Scale))
3827 .ule(std::abs(NewF.BaseOffset)))
3831 NewF.Canonicalize();
3832 (void)InsertFormula(LU, LUIdx, NewF);
3834 // Use the immediate in a base register.
3835 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
3836 const SCEV *BaseReg = F.BaseRegs[N];
3837 if (BaseReg != OrigReg)
3840 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
3841 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
3842 LU.Kind, LU.AccessTy, NewF)) {
3843 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
3846 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
3848 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
3850 // If the new formula has a constant in a register, and adding the
3851 // constant value to the immediate would produce a value closer to
3852 // zero than the immediate itself, then the formula isn't worthwhile.
3853 for (SmallVectorImpl<const SCEV *>::const_iterator
3854 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
3856 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
3857 if ((C->getValue()->getValue() + NewF.BaseOffset).abs().slt(
3858 std::abs(NewF.BaseOffset)) &&
3859 (C->getValue()->getValue() +
3860 NewF.BaseOffset).countTrailingZeros() >=
3861 countTrailingZeros<uint64_t>(NewF.BaseOffset))
3865 NewF.Canonicalize();
3866 (void)InsertFormula(LU, LUIdx, NewF);
3875 /// GenerateAllReuseFormulae - Generate formulae for each use.
3877 LSRInstance::GenerateAllReuseFormulae() {
3878 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
3879 // queries are more precise.
3880 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3881 LSRUse &LU = Uses[LUIdx];
3882 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3883 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
3884 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3885 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
3887 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3888 LSRUse &LU = Uses[LUIdx];
3889 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3890 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
3891 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3892 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
3893 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3894 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
3895 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3896 GenerateScales(LU, LUIdx, LU.Formulae[i]);
3898 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3899 LSRUse &LU = Uses[LUIdx];
3900 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3901 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
3904 GenerateCrossUseConstantOffsets();
3906 DEBUG(dbgs() << "\n"
3907 "After generating reuse formulae:\n";
3908 print_uses(dbgs()));
3911 /// If there are multiple formulae with the same set of registers used
3912 /// by other uses, pick the best one and delete the others.
3913 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
3914 DenseSet<const SCEV *> VisitedRegs;
3915 SmallPtrSet<const SCEV *, 16> Regs;
3916 SmallPtrSet<const SCEV *, 16> LoserRegs;
3918 bool ChangedFormulae = false;
3921 // Collect the best formula for each unique set of shared registers. This
3922 // is reset for each use.
3923 typedef DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>
3925 BestFormulaeTy BestFormulae;
3927 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3928 LSRUse &LU = Uses[LUIdx];
3929 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
3932 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
3933 FIdx != NumForms; ++FIdx) {
3934 Formula &F = LU.Formulae[FIdx];
3936 // Some formulas are instant losers. For example, they may depend on
3937 // nonexistent AddRecs from other loops. These need to be filtered
3938 // immediately, otherwise heuristics could choose them over others leading
3939 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
3940 // avoids the need to recompute this information across formulae using the
3941 // same bad AddRec. Passing LoserRegs is also essential unless we remove
3942 // the corresponding bad register from the Regs set.
3945 CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, LU.Offsets, SE, DT, LU,
3947 if (CostF.isLoser()) {
3948 // During initial formula generation, undesirable formulae are generated
3949 // by uses within other loops that have some non-trivial address mode or
3950 // use the postinc form of the IV. LSR needs to provide these formulae
3951 // as the basis of rediscovering the desired formula that uses an AddRec
3952 // corresponding to the existing phi. Once all formulae have been
3953 // generated, these initial losers may be pruned.
3954 DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());
3958 SmallVector<const SCEV *, 4> Key;
3959 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
3960 JE = F.BaseRegs.end(); J != JE; ++J) {
3961 const SCEV *Reg = *J;
3962 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
3966 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
3967 Key.push_back(F.ScaledReg);
3968 // Unstable sort by host order ok, because this is only used for
3970 std::sort(Key.begin(), Key.end());
3972 std::pair<BestFormulaeTy::const_iterator, bool> P =
3973 BestFormulae.insert(std::make_pair(Key, FIdx));
3977 Formula &Best = LU.Formulae[P.first->second];
3981 CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, LU.Offsets, SE,
3983 if (CostF < CostBest)
3985 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
3987 " in favor of formula "; Best.print(dbgs());
3991 ChangedFormulae = true;
3993 LU.DeleteFormula(F);
3999 // Now that we've filtered out some formulae, recompute the Regs set.
4001 LU.RecomputeRegs(LUIdx, RegUses);
4003 // Reset this to prepare for the next use.
4004 BestFormulae.clear();
4007 DEBUG(if (ChangedFormulae) {
4009 "After filtering out undesirable candidates:\n";
4014 // This is a rough guess that seems to work fairly well.
4015 static const size_t ComplexityLimit = UINT16_MAX;
4017 /// EstimateSearchSpaceComplexity - Estimate the worst-case number of
4018 /// solutions the solver might have to consider. It almost never considers
4019 /// this many solutions because it prune the search space, but the pruning
4020 /// isn't always sufficient.
4021 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4023 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
4024 E = Uses.end(); I != E; ++I) {
4025 size_t FSize = I->Formulae.size();
4026 if (FSize >= ComplexityLimit) {
4027 Power = ComplexityLimit;
4031 if (Power >= ComplexityLimit)
4037 /// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset
4038 /// of the registers of another formula, it won't help reduce register
4039 /// pressure (though it may not necessarily hurt register pressure); remove
4040 /// it to simplify the system.
4041 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4042 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4043 DEBUG(dbgs() << "The search space is too complex.\n");
4045 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
4046 "which use a superset of registers used by other "
4049 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4050 LSRUse &LU = Uses[LUIdx];
4052 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4053 Formula &F = LU.Formulae[i];
4054 // Look for a formula with a constant or GV in a register. If the use
4055 // also has a formula with that same value in an immediate field,
4056 // delete the one that uses a register.
4057 for (SmallVectorImpl<const SCEV *>::const_iterator
4058 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4059 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4061 NewF.BaseOffset += C->getValue()->getSExtValue();
4062 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4063 (I - F.BaseRegs.begin()));
4064 if (LU.HasFormulaWithSameRegs(NewF)) {
4065 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4066 LU.DeleteFormula(F);
4072 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4073 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4077 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4078 (I - F.BaseRegs.begin()));
4079 if (LU.HasFormulaWithSameRegs(NewF)) {
4080 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4082 LU.DeleteFormula(F);
4093 LU.RecomputeRegs(LUIdx, RegUses);
4096 DEBUG(dbgs() << "After pre-selection:\n";
4097 print_uses(dbgs()));
4101 /// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers
4102 /// for expressions like A, A+1, A+2, etc., allocate a single register for
4104 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4105 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4108 DEBUG(dbgs() << "The search space is too complex.\n"
4109 "Narrowing the search space by assuming that uses separated "
4110 "by a constant offset will use the same registers.\n");
4112 // This is especially useful for unrolled loops.
4114 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4115 LSRUse &LU = Uses[LUIdx];
4116 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
4117 E = LU.Formulae.end(); I != E; ++I) {
4118 const Formula &F = *I;
4119 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4122 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4126 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4127 LU.Kind, LU.AccessTy))
4130 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n');
4132 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4134 // Update the relocs to reference the new use.
4135 for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
4136 E = Fixups.end(); I != E; ++I) {
4137 LSRFixup &Fixup = *I;
4138 if (Fixup.LUIdx == LUIdx) {
4139 Fixup.LUIdx = LUThatHas - &Uses.front();
4140 Fixup.Offset += F.BaseOffset;
4141 // Add the new offset to LUThatHas' offset list.
4142 if (LUThatHas->Offsets.back() != Fixup.Offset) {
4143 LUThatHas->Offsets.push_back(Fixup.Offset);
4144 if (Fixup.Offset > LUThatHas->MaxOffset)
4145 LUThatHas->MaxOffset = Fixup.Offset;
4146 if (Fixup.Offset < LUThatHas->MinOffset)
4147 LUThatHas->MinOffset = Fixup.Offset;
4149 DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n');
4151 if (Fixup.LUIdx == NumUses-1)
4152 Fixup.LUIdx = LUIdx;
4155 // Delete formulae from the new use which are no longer legal.
4157 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4158 Formula &F = LUThatHas->Formulae[i];
4159 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4160 LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4161 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4163 LUThatHas->DeleteFormula(F);
4171 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4173 // Delete the old use.
4174 DeleteUse(LU, LUIdx);
4181 DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4184 /// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call
4185 /// FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4186 /// we've done more filtering, as it may be able to find more formulae to
4188 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4189 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4190 DEBUG(dbgs() << "The search space is too complex.\n");
4192 DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
4193 "undesirable dedicated registers.\n");
4195 FilterOutUndesirableDedicatedRegisters();
4197 DEBUG(dbgs() << "After pre-selection:\n";
4198 print_uses(dbgs()));
4202 /// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely
4203 /// to be profitable, and then in any use which has any reference to that
4204 /// register, delete all formulae which do not reference that register.
4205 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4206 // With all other options exhausted, loop until the system is simple
4207 // enough to handle.
4208 SmallPtrSet<const SCEV *, 4> Taken;
4209 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4210 // Ok, we have too many of formulae on our hands to conveniently handle.
4211 // Use a rough heuristic to thin out the list.
4212 DEBUG(dbgs() << "The search space is too complex.\n");
4214 // Pick the register which is used by the most LSRUses, which is likely
4215 // to be a good reuse register candidate.
4216 const SCEV *Best = nullptr;
4217 unsigned BestNum = 0;
4218 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
4220 const SCEV *Reg = *I;
4221 if (Taken.count(Reg))
4226 unsigned Count = RegUses.getUsedByIndices(Reg).count();
4227 if (Count > BestNum) {
4234 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
4235 << " will yield profitable reuse.\n");
4238 // In any use with formulae which references this register, delete formulae
4239 // which don't reference it.
4240 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4241 LSRUse &LU = Uses[LUIdx];
4242 if (!LU.Regs.count(Best)) continue;
4245 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4246 Formula &F = LU.Formulae[i];
4247 if (!F.referencesReg(Best)) {
4248 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4249 LU.DeleteFormula(F);
4253 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
4259 LU.RecomputeRegs(LUIdx, RegUses);
4262 DEBUG(dbgs() << "After pre-selection:\n";
4263 print_uses(dbgs()));
4267 /// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
4268 /// formulae to choose from, use some rough heuristics to prune down the number
4269 /// of formulae. This keeps the main solver from taking an extraordinary amount
4270 /// of time in some worst-case scenarios.
4271 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4272 NarrowSearchSpaceByDetectingSupersets();
4273 NarrowSearchSpaceByCollapsingUnrolledCode();
4274 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4275 NarrowSearchSpaceByPickingWinnerRegs();
4278 /// SolveRecurse - This is the recursive solver.
4279 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4281 SmallVectorImpl<const Formula *> &Workspace,
4282 const Cost &CurCost,
4283 const SmallPtrSet<const SCEV *, 16> &CurRegs,
4284 DenseSet<const SCEV *> &VisitedRegs) const {
4287 // - use more aggressive filtering
4288 // - sort the formula so that the most profitable solutions are found first
4289 // - sort the uses too
4291 // - don't compute a cost, and then compare. compare while computing a cost
4293 // - track register sets with SmallBitVector
4295 const LSRUse &LU = Uses[Workspace.size()];
4297 // If this use references any register that's already a part of the
4298 // in-progress solution, consider it a requirement that a formula must
4299 // reference that register in order to be considered. This prunes out
4300 // unprofitable searching.
4301 SmallSetVector<const SCEV *, 4> ReqRegs;
4302 for (const SCEV *S : CurRegs)
4303 if (LU.Regs.count(S))
4306 SmallPtrSet<const SCEV *, 16> NewRegs;
4308 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
4309 E = LU.Formulae.end(); I != E; ++I) {
4310 const Formula &F = *I;
4312 // Ignore formulae which may not be ideal in terms of register reuse of
4313 // ReqRegs. The formula should use all required registers before
4314 // introducing new ones.
4315 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4316 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
4317 JE = ReqRegs.end(); J != JE; ++J) {
4318 const SCEV *Reg = *J;
4319 if ((F.ScaledReg && F.ScaledReg == Reg) ||
4320 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) !=
4323 if (NumReqRegsToFind == 0)
4327 if (NumReqRegsToFind != 0) {
4328 // If none of the formulae satisfied the required registers, then we could
4329 // clear ReqRegs and try again. Currently, we simply give up in this case.
4333 // Evaluate the cost of the current formula. If it's already worse than
4334 // the current best, prune the search at that point.
4337 NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT,
4339 if (NewCost < SolutionCost) {
4340 Workspace.push_back(&F);
4341 if (Workspace.size() != Uses.size()) {
4342 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4343 NewRegs, VisitedRegs);
4344 if (F.getNumRegs() == 1 && Workspace.size() == 1)
4345 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4347 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
4348 dbgs() << ".\n Regs:";
4349 for (const SCEV *S : NewRegs)
4350 dbgs() << ' ' << *S;
4353 SolutionCost = NewCost;
4354 Solution = Workspace;
4356 Workspace.pop_back();
4361 /// Solve - Choose one formula from each use. Return the results in the given
4362 /// Solution vector.
4363 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4364 SmallVector<const Formula *, 8> Workspace;
4366 SolutionCost.Lose();
4368 SmallPtrSet<const SCEV *, 16> CurRegs;
4369 DenseSet<const SCEV *> VisitedRegs;
4370 Workspace.reserve(Uses.size());
4372 // SolveRecurse does all the work.
4373 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4374 CurRegs, VisitedRegs);
4375 if (Solution.empty()) {
4376 DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
4380 // Ok, we've now made all our decisions.
4381 DEBUG(dbgs() << "\n"
4382 "The chosen solution requires "; SolutionCost.print(dbgs());
4384 for (size_t i = 0, e = Uses.size(); i != e; ++i) {
4386 Uses[i].print(dbgs());
4389 Solution[i]->print(dbgs());
4393 assert(Solution.size() == Uses.size() && "Malformed solution!");
4396 /// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
4397 /// the dominator tree far as we can go while still being dominated by the
4398 /// input positions. This helps canonicalize the insert position, which
4399 /// encourages sharing.
4400 BasicBlock::iterator
4401 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4402 const SmallVectorImpl<Instruction *> &Inputs)
4405 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4406 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4409 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4410 if (!Rung) return IP;
4411 Rung = Rung->getIDom();
4412 if (!Rung) return IP;
4413 IDom = Rung->getBlock();
4415 // Don't climb into a loop though.
4416 const Loop *IDomLoop = LI.getLoopFor(IDom);
4417 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4418 if (IDomDepth <= IPLoopDepth &&
4419 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4423 bool AllDominate = true;
4424 Instruction *BetterPos = nullptr;
4425 Instruction *Tentative = IDom->getTerminator();
4426 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
4427 E = Inputs.end(); I != E; ++I) {
4428 Instruction *Inst = *I;
4429 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4430 AllDominate = false;
4433 // Attempt to find an insert position in the middle of the block,
4434 // instead of at the end, so that it can be used for other expansions.
4435 if (IDom == Inst->getParent() &&
4436 (!BetterPos || !DT.dominates(Inst, BetterPos)))
4437 BetterPos = std::next(BasicBlock::iterator(Inst));
4450 /// AdjustInsertPositionForExpand - Determine an input position which will be
4451 /// dominated by the operands and which will dominate the result.
4452 BasicBlock::iterator
4453 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4456 SCEVExpander &Rewriter) const {
4457 // Collect some instructions which must be dominated by the
4458 // expanding replacement. These must be dominated by any operands that
4459 // will be required in the expansion.
4460 SmallVector<Instruction *, 4> Inputs;
4461 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4462 Inputs.push_back(I);
4463 if (LU.Kind == LSRUse::ICmpZero)
4464 if (Instruction *I =
4465 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4466 Inputs.push_back(I);
4467 if (LF.PostIncLoops.count(L)) {
4468 if (LF.isUseFullyOutsideLoop(L))
4469 Inputs.push_back(L->getLoopLatch()->getTerminator());
4471 Inputs.push_back(IVIncInsertPos);
4473 // The expansion must also be dominated by the increment positions of any
4474 // loops it for which it is using post-inc mode.
4475 for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(),
4476 E = LF.PostIncLoops.end(); I != E; ++I) {
4477 const Loop *PIL = *I;
4478 if (PIL == L) continue;
4480 // Be dominated by the loop exit.
4481 SmallVector<BasicBlock *, 4> ExitingBlocks;
4482 PIL->getExitingBlocks(ExitingBlocks);
4483 if (!ExitingBlocks.empty()) {
4484 BasicBlock *BB = ExitingBlocks[0];
4485 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4486 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4487 Inputs.push_back(BB->getTerminator());
4491 assert(!isa<PHINode>(LowestIP) && !isa<LandingPadInst>(LowestIP)
4492 && !isa<DbgInfoIntrinsic>(LowestIP) &&
4493 "Insertion point must be a normal instruction");
4495 // Then, climb up the immediate dominator tree as far as we can go while
4496 // still being dominated by the input positions.
4497 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4499 // Don't insert instructions before PHI nodes.
4500 while (isa<PHINode>(IP)) ++IP;
4502 // Ignore landingpad instructions.
4503 while (isa<LandingPadInst>(IP)) ++IP;
4505 // Ignore debug intrinsics.
4506 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4508 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4509 // IP consistent across expansions and allows the previously inserted
4510 // instructions to be reused by subsequent expansion.
4511 while (Rewriter.isInsertedInstruction(IP) && IP != LowestIP) ++IP;
4516 /// Expand - Emit instructions for the leading candidate expression for this
4517 /// LSRUse (this is called "expanding").
4518 Value *LSRInstance::Expand(const LSRFixup &LF,
4520 BasicBlock::iterator IP,
4521 SCEVExpander &Rewriter,
4522 SmallVectorImpl<WeakVH> &DeadInsts) const {
4523 const LSRUse &LU = Uses[LF.LUIdx];
4524 if (LU.RigidFormula)
4525 return LF.OperandValToReplace;
4527 // Determine an input position which will be dominated by the operands and
4528 // which will dominate the result.
4529 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4531 // Inform the Rewriter if we have a post-increment use, so that it can
4532 // perform an advantageous expansion.
4533 Rewriter.setPostInc(LF.PostIncLoops);
4535 // This is the type that the user actually needs.
4536 Type *OpTy = LF.OperandValToReplace->getType();
4537 // This will be the type that we'll initially expand to.
4538 Type *Ty = F.getType();
4540 // No type known; just expand directly to the ultimate type.
4542 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
4543 // Expand directly to the ultimate type if it's the right size.
4545 // This is the type to do integer arithmetic in.
4546 Type *IntTy = SE.getEffectiveSCEVType(Ty);
4548 // Build up a list of operands to add together to form the full base.
4549 SmallVector<const SCEV *, 8> Ops;
4551 // Expand the BaseRegs portion.
4552 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
4553 E = F.BaseRegs.end(); I != E; ++I) {
4554 const SCEV *Reg = *I;
4555 assert(!Reg->isZero() && "Zero allocated in a base register!");
4557 // If we're expanding for a post-inc user, make the post-inc adjustment.
4558 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4559 Reg = TransformForPostIncUse(Denormalize, Reg,
4560 LF.UserInst, LF.OperandValToReplace,
4563 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr, IP)));
4566 // Expand the ScaledReg portion.
4567 Value *ICmpScaledV = nullptr;
4569 const SCEV *ScaledS = F.ScaledReg;
4571 // If we're expanding for a post-inc user, make the post-inc adjustment.
4572 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4573 ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
4574 LF.UserInst, LF.OperandValToReplace,
4577 if (LU.Kind == LSRUse::ICmpZero) {
4578 // Expand ScaleReg as if it was part of the base regs.
4581 SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr, IP)));
4583 // An interesting way of "folding" with an icmp is to use a negated
4584 // scale, which we'll implement by inserting it into the other operand
4586 assert(F.Scale == -1 &&
4587 "The only scale supported by ICmpZero uses is -1!");
4588 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr, IP);
4591 // Otherwise just expand the scaled register and an explicit scale,
4592 // which is expected to be matched as part of the address.
4594 // Flush the operand list to suppress SCEVExpander hoisting address modes.
4595 // Unless the addressing mode will not be folded.
4596 if (!Ops.empty() && LU.Kind == LSRUse::Address &&
4597 isAMCompletelyFolded(TTI, LU, F)) {
4598 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4600 Ops.push_back(SE.getUnknown(FullV));
4602 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr, IP));
4605 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
4606 Ops.push_back(ScaledS);
4610 // Expand the GV portion.
4612 // Flush the operand list to suppress SCEVExpander hoisting.
4614 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4616 Ops.push_back(SE.getUnknown(FullV));
4618 Ops.push_back(SE.getUnknown(F.BaseGV));
4621 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
4622 // unfolded offsets. LSR assumes they both live next to their uses.
4624 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4626 Ops.push_back(SE.getUnknown(FullV));
4629 // Expand the immediate portion.
4630 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
4632 if (LU.Kind == LSRUse::ICmpZero) {
4633 // The other interesting way of "folding" with an ICmpZero is to use a
4634 // negated immediate.
4636 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
4638 Ops.push_back(SE.getUnknown(ICmpScaledV));
4639 ICmpScaledV = ConstantInt::get(IntTy, Offset);
4642 // Just add the immediate values. These again are expected to be matched
4643 // as part of the address.
4644 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
4648 // Expand the unfolded offset portion.
4649 int64_t UnfoldedOffset = F.UnfoldedOffset;
4650 if (UnfoldedOffset != 0) {
4651 // Just add the immediate values.
4652 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
4656 // Emit instructions summing all the operands.
4657 const SCEV *FullS = Ops.empty() ?
4658 SE.getConstant(IntTy, 0) :
4660 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
4662 // We're done expanding now, so reset the rewriter.
4663 Rewriter.clearPostInc();
4665 // An ICmpZero Formula represents an ICmp which we're handling as a
4666 // comparison against zero. Now that we've expanded an expression for that
4667 // form, update the ICmp's other operand.
4668 if (LU.Kind == LSRUse::ICmpZero) {
4669 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
4670 DeadInsts.push_back(CI->getOperand(1));
4671 assert(!F.BaseGV && "ICmp does not support folding a global value and "
4672 "a scale at the same time!");
4673 if (F.Scale == -1) {
4674 if (ICmpScaledV->getType() != OpTy) {
4676 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
4678 ICmpScaledV, OpTy, "tmp", CI);
4681 CI->setOperand(1, ICmpScaledV);
4683 // A scale of 1 means that the scale has been expanded as part of the
4685 assert((F.Scale == 0 || F.Scale == 1) &&
4686 "ICmp does not support folding a global value and "
4687 "a scale at the same time!");
4688 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
4690 if (C->getType() != OpTy)
4691 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4695 CI->setOperand(1, C);
4702 /// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
4703 /// of their operands effectively happens in their predecessor blocks, so the
4704 /// expression may need to be expanded in multiple places.
4705 void LSRInstance::RewriteForPHI(PHINode *PN,
4708 SCEVExpander &Rewriter,
4709 SmallVectorImpl<WeakVH> &DeadInsts,
4711 DenseMap<BasicBlock *, Value *> Inserted;
4712 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
4713 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
4714 BasicBlock *BB = PN->getIncomingBlock(i);
4716 // If this is a critical edge, split the edge so that we do not insert
4717 // the code on all predecessor/successor paths. We do this unless this
4718 // is the canonical backedge for this loop, which complicates post-inc
4720 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
4721 !isa<IndirectBrInst>(BB->getTerminator())) {
4722 BasicBlock *Parent = PN->getParent();
4723 Loop *PNLoop = LI.getLoopFor(Parent);
4724 if (!PNLoop || Parent != PNLoop->getHeader()) {
4725 // Split the critical edge.
4726 BasicBlock *NewBB = nullptr;
4727 if (!Parent->isLandingPad()) {
4728 NewBB = SplitCriticalEdge(BB, Parent,
4729 CriticalEdgeSplittingOptions(&DT, &LI)
4730 .setMergeIdenticalEdges()
4731 .setDontDeleteUselessPHIs());
4733 SmallVector<BasicBlock*, 2> NewBBs;
4734 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs,
4735 /*AliasAnalysis*/ nullptr, &DT, &LI);
4738 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
4739 // phi predecessors are identical. The simple thing to do is skip
4740 // splitting in this case rather than complicate the API.
4742 // If PN is outside of the loop and BB is in the loop, we want to
4743 // move the block to be immediately before the PHI block, not
4744 // immediately after BB.
4745 if (L->contains(BB) && !L->contains(PN))
4746 NewBB->moveBefore(PN->getParent());
4748 // Splitting the edge can reduce the number of PHI entries we have.
4749 e = PN->getNumIncomingValues();
4751 i = PN->getBasicBlockIndex(BB);
4756 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
4757 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
4759 PN->setIncomingValue(i, Pair.first->second);
4761 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
4763 // If this is reuse-by-noop-cast, insert the noop cast.
4764 Type *OpTy = LF.OperandValToReplace->getType();
4765 if (FullV->getType() != OpTy)
4767 CastInst::Create(CastInst::getCastOpcode(FullV, false,
4769 FullV, LF.OperandValToReplace->getType(),
4770 "tmp", BB->getTerminator());
4772 PN->setIncomingValue(i, FullV);
4773 Pair.first->second = FullV;
4778 /// Rewrite - Emit instructions for the leading candidate expression for this
4779 /// LSRUse (this is called "expanding"), and update the UserInst to reference
4780 /// the newly expanded value.
4781 void LSRInstance::Rewrite(const LSRFixup &LF,
4783 SCEVExpander &Rewriter,
4784 SmallVectorImpl<WeakVH> &DeadInsts,
4786 // First, find an insertion point that dominates UserInst. For PHI nodes,
4787 // find the nearest block which dominates all the relevant uses.
4788 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
4789 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
4791 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
4793 // If this is reuse-by-noop-cast, insert the noop cast.
4794 Type *OpTy = LF.OperandValToReplace->getType();
4795 if (FullV->getType() != OpTy) {
4797 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
4798 FullV, OpTy, "tmp", LF.UserInst);
4802 // Update the user. ICmpZero is handled specially here (for now) because
4803 // Expand may have updated one of the operands of the icmp already, and
4804 // its new value may happen to be equal to LF.OperandValToReplace, in
4805 // which case doing replaceUsesOfWith leads to replacing both operands
4806 // with the same value. TODO: Reorganize this.
4807 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
4808 LF.UserInst->setOperand(0, FullV);
4810 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
4813 DeadInsts.push_back(LF.OperandValToReplace);
4816 /// ImplementSolution - Rewrite all the fixup locations with new values,
4817 /// following the chosen solution.
4819 LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
4821 // Keep track of instructions we may have made dead, so that
4822 // we can remove them after we are done working.
4823 SmallVector<WeakVH, 16> DeadInsts;
4825 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(),
4828 Rewriter.setDebugType(DEBUG_TYPE);
4830 Rewriter.disableCanonicalMode();
4831 Rewriter.enableLSRMode();
4832 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
4834 // Mark phi nodes that terminate chains so the expander tries to reuse them.
4835 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4836 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4837 if (PHINode *PN = dyn_cast<PHINode>(ChainI->tailUserInst()))
4838 Rewriter.setChainedPhi(PN);
4841 // Expand the new value definitions and update the users.
4842 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4843 E = Fixups.end(); I != E; ++I) {
4844 const LSRFixup &Fixup = *I;
4846 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
4851 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4852 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4853 GenerateIVChain(*ChainI, Rewriter, DeadInsts);
4856 // Clean up after ourselves. This must be done before deleting any
4860 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
4863 LSRInstance::LSRInstance(Loop *L, Pass *P)
4864 : IU(P->getAnalysis<IVUsers>()), SE(P->getAnalysis<ScalarEvolution>()),
4865 DT(P->getAnalysis<DominatorTreeWrapperPass>().getDomTree()),
4866 LI(P->getAnalysis<LoopInfoWrapperPass>().getLoopInfo()),
4867 TTI(P->getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
4868 *L->getHeader()->getParent())),
4869 L(L), Changed(false), IVIncInsertPos(nullptr) {
4870 // If LoopSimplify form is not available, stay out of trouble.
4871 if (!L->isLoopSimplifyForm())
4874 // If there's no interesting work to be done, bail early.
4875 if (IU.empty()) return;
4877 // If there's too much analysis to be done, bail early. We won't be able to
4878 // model the problem anyway.
4879 unsigned NumUsers = 0;
4880 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
4881 if (++NumUsers > MaxIVUsers) {
4882 DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << *L
4889 // All dominating loops must have preheaders, or SCEVExpander may not be able
4890 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
4892 // IVUsers analysis should only create users that are dominated by simple loop
4893 // headers. Since this loop should dominate all of its users, its user list
4894 // should be empty if this loop itself is not within a simple loop nest.
4895 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
4896 Rung; Rung = Rung->getIDom()) {
4897 BasicBlock *BB = Rung->getBlock();
4898 const Loop *DomLoop = LI.getLoopFor(BB);
4899 if (DomLoop && DomLoop->getHeader() == BB) {
4900 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
4905 DEBUG(dbgs() << "\nLSR on loop ";
4906 L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false);
4909 // First, perform some low-level loop optimizations.
4911 OptimizeLoopTermCond();
4913 // If loop preparation eliminates all interesting IV users, bail.
4914 if (IU.empty()) return;
4916 // Skip nested loops until we can model them better with formulae.
4918 DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
4922 // Start collecting data and preparing for the solver.
4924 CollectInterestingTypesAndFactors();
4925 CollectFixupsAndInitialFormulae();
4926 CollectLoopInvariantFixupsAndFormulae();
4928 assert(!Uses.empty() && "IVUsers reported at least one use");
4929 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
4930 print_uses(dbgs()));
4932 // Now use the reuse data to generate a bunch of interesting ways
4933 // to formulate the values needed for the uses.
4934 GenerateAllReuseFormulae();
4936 FilterOutUndesirableDedicatedRegisters();
4937 NarrowSearchSpaceUsingHeuristics();
4939 SmallVector<const Formula *, 8> Solution;
4942 // Release memory that is no longer needed.
4947 if (Solution.empty())
4951 // Formulae should be legal.
4952 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), E = Uses.end();
4954 const LSRUse &LU = *I;
4955 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
4956 JE = LU.Formulae.end();
4958 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4959 *J) && "Illegal formula generated!");
4963 // Now that we've decided what we want, make it so.
4964 ImplementSolution(Solution, P);
4967 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
4968 if (Factors.empty() && Types.empty()) return;
4970 OS << "LSR has identified the following interesting factors and types: ";
4973 for (SmallSetVector<int64_t, 8>::const_iterator
4974 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
4975 if (!First) OS << ", ";
4980 for (SmallSetVector<Type *, 4>::const_iterator
4981 I = Types.begin(), E = Types.end(); I != E; ++I) {
4982 if (!First) OS << ", ";
4984 OS << '(' << **I << ')';
4989 void LSRInstance::print_fixups(raw_ostream &OS) const {
4990 OS << "LSR is examining the following fixup sites:\n";
4991 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4992 E = Fixups.end(); I != E; ++I) {
4999 void LSRInstance::print_uses(raw_ostream &OS) const {
5000 OS << "LSR is examining the following uses:\n";
5001 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
5002 E = Uses.end(); I != E; ++I) {
5003 const LSRUse &LU = *I;
5007 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
5008 JE = LU.Formulae.end(); J != JE; ++J) {
5016 void LSRInstance::print(raw_ostream &OS) const {
5017 print_factors_and_types(OS);
5022 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5023 void LSRInstance::dump() const {
5024 print(errs()); errs() << '\n';
5030 class LoopStrengthReduce : public LoopPass {
5032 static char ID; // Pass ID, replacement for typeid
5033 LoopStrengthReduce();
5036 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
5037 void getAnalysisUsage(AnalysisUsage &AU) const override;
5042 char LoopStrengthReduce::ID = 0;
5043 INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
5044 "Loop Strength Reduction", false, false)
5045 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
5046 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
5047 INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
5048 INITIALIZE_PASS_DEPENDENCY(IVUsers)
5049 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
5050 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
5051 INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
5052 "Loop Strength Reduction", false, false)
5055 Pass *llvm::createLoopStrengthReducePass() {
5056 return new LoopStrengthReduce();
5059 LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
5060 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
5063 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
5064 // We split critical edges, so we change the CFG. However, we do update
5065 // many analyses if they are around.
5066 AU.addPreservedID(LoopSimplifyID);
5068 AU.addRequired<LoopInfoWrapperPass>();
5069 AU.addPreserved<LoopInfoWrapperPass>();
5070 AU.addRequiredID(LoopSimplifyID);
5071 AU.addRequired<DominatorTreeWrapperPass>();
5072 AU.addPreserved<DominatorTreeWrapperPass>();
5073 AU.addRequired<ScalarEvolution>();
5074 AU.addPreserved<ScalarEvolution>();
5075 // Requiring LoopSimplify a second time here prevents IVUsers from running
5076 // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5077 AU.addRequiredID(LoopSimplifyID);
5078 AU.addRequired<IVUsers>();
5079 AU.addPreserved<IVUsers>();
5080 AU.addRequired<TargetTransformInfoWrapperPass>();
5083 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5084 if (skipOptnoneFunction(L))
5087 bool Changed = false;
5089 // Run the main LSR transformation.
5090 Changed |= LSRInstance(L, this).getChanged();
5092 // Remove any extra phis created by processing inner loops.
5093 Changed |= DeleteDeadPHIs(L->getHeader());
5094 if (EnablePhiElim && L->isLoopSimplifyForm()) {
5095 SmallVector<WeakVH, 16> DeadInsts;
5096 const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
5097 SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), DL, "lsr");
5099 Rewriter.setDebugType(DEBUG_TYPE);
5101 unsigned numFolded = Rewriter.replaceCongruentIVs(
5102 L, &getAnalysis<DominatorTreeWrapperPass>().getDomTree(), DeadInsts,
5103 &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
5104 *L->getHeader()->getParent()));
5107 DeleteTriviallyDeadInstructions(DeadInsts);
5108 DeleteDeadPHIs(L->getHeader());