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 TargetLowering::AddrMode::BaseGV be changed to a ConstantExpr
41 // instead of a GlobalValue?
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 #define DEBUG_TYPE "loop-reduce"
57 #include "llvm/Transforms/Scalar.h"
58 #include "llvm/Constants.h"
59 #include "llvm/Instructions.h"
60 #include "llvm/IntrinsicInst.h"
61 #include "llvm/DerivedTypes.h"
62 #include "llvm/Analysis/IVUsers.h"
63 #include "llvm/Analysis/Dominators.h"
64 #include "llvm/Analysis/LoopPass.h"
65 #include "llvm/Analysis/ScalarEvolutionExpander.h"
66 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
67 #include "llvm/Transforms/Utils/Local.h"
68 #include "llvm/ADT/SmallBitVector.h"
69 #include "llvm/ADT/SetVector.h"
70 #include "llvm/ADT/DenseSet.h"
71 #include "llvm/Support/Debug.h"
72 #include "llvm/Support/ValueHandle.h"
73 #include "llvm/Support/raw_ostream.h"
74 #include "llvm/Target/TargetLowering.h"
80 /// RegSortData - This class holds data which is used to order reuse candidates.
83 /// UsedByIndices - This represents the set of LSRUse indices which reference
84 /// a particular register.
85 SmallBitVector UsedByIndices;
89 void print(raw_ostream &OS) const;
95 void RegSortData::print(raw_ostream &OS) const {
96 OS << "[NumUses=" << UsedByIndices.count() << ']';
99 void RegSortData::dump() const {
100 print(errs()); errs() << '\n';
105 /// RegUseTracker - Map register candidates to information about how they are
107 class RegUseTracker {
108 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
111 SmallVector<const SCEV *, 16> RegSequence;
114 void CountRegister(const SCEV *Reg, size_t LUIdx);
116 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
118 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
122 typedef SmallVectorImpl<const SCEV *>::iterator iterator;
123 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
124 iterator begin() { return RegSequence.begin(); }
125 iterator end() { return RegSequence.end(); }
126 const_iterator begin() const { return RegSequence.begin(); }
127 const_iterator end() const { return RegSequence.end(); }
133 RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
134 std::pair<RegUsesTy::iterator, bool> Pair =
135 RegUses.insert(std::make_pair(Reg, RegSortData()));
136 RegSortData &RSD = Pair.first->second;
138 RegSequence.push_back(Reg);
139 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
140 RSD.UsedByIndices.set(LUIdx);
144 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
145 if (!RegUses.count(Reg)) return false;
146 const SmallBitVector &UsedByIndices =
147 RegUses.find(Reg)->second.UsedByIndices;
148 int i = UsedByIndices.find_first();
149 if (i == -1) return false;
150 if ((size_t)i != LUIdx) return true;
151 return UsedByIndices.find_next(i) != -1;
154 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
155 RegUsesTy::const_iterator I = RegUses.find(Reg);
156 assert(I != RegUses.end() && "Unknown register!");
157 return I->second.UsedByIndices;
160 void RegUseTracker::clear() {
167 /// Formula - This class holds information that describes a formula for
168 /// computing satisfying a use. It may include broken-out immediates and scaled
171 /// AM - This is used to represent complex addressing, as well as other kinds
172 /// of interesting uses.
173 TargetLowering::AddrMode AM;
175 /// BaseRegs - The list of "base" registers for this use. When this is
176 /// non-empty, AM.HasBaseReg should be set to true.
177 SmallVector<const SCEV *, 2> BaseRegs;
179 /// ScaledReg - The 'scaled' register for this use. This should be non-null
180 /// when AM.Scale is not zero.
181 const SCEV *ScaledReg;
183 Formula() : ScaledReg(0) {}
185 void InitialMatch(const SCEV *S, Loop *L,
186 ScalarEvolution &SE, DominatorTree &DT);
188 unsigned getNumRegs() const;
189 const Type *getType() const;
191 bool referencesReg(const SCEV *S) const;
192 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
193 const RegUseTracker &RegUses) const;
195 void print(raw_ostream &OS) const;
201 /// DoInitialMatch - Recurrsion helper for InitialMatch.
202 static void DoInitialMatch(const SCEV *S, Loop *L,
203 SmallVectorImpl<const SCEV *> &Good,
204 SmallVectorImpl<const SCEV *> &Bad,
205 ScalarEvolution &SE, DominatorTree &DT) {
206 // Collect expressions which properly dominate the loop header.
207 if (S->properlyDominates(L->getHeader(), &DT)) {
212 // Look at add operands.
213 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
214 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
216 DoInitialMatch(*I, L, Good, Bad, SE, DT);
220 // Look at addrec operands.
221 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
222 if (!AR->getStart()->isZero()) {
223 DoInitialMatch(AR->getStart(), L, Good, Bad, SE, DT);
224 DoInitialMatch(SE.getAddRecExpr(SE.getIntegerSCEV(0, AR->getType()),
225 AR->getStepRecurrence(SE),
227 L, Good, Bad, SE, DT);
231 // Handle a multiplication by -1 (negation) if it didn't fold.
232 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
233 if (Mul->getOperand(0)->isAllOnesValue()) {
234 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
235 const SCEV *NewMul = SE.getMulExpr(Ops);
237 SmallVector<const SCEV *, 4> MyGood;
238 SmallVector<const SCEV *, 4> MyBad;
239 DoInitialMatch(NewMul, L, MyGood, MyBad, SE, DT);
240 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
241 SE.getEffectiveSCEVType(NewMul->getType())));
242 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
243 E = MyGood.end(); I != E; ++I)
244 Good.push_back(SE.getMulExpr(NegOne, *I));
245 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
246 E = MyBad.end(); I != E; ++I)
247 Bad.push_back(SE.getMulExpr(NegOne, *I));
251 // Ok, we can't do anything interesting. Just stuff the whole thing into a
252 // register and hope for the best.
256 /// InitialMatch - Incorporate loop-variant parts of S into this Formula,
257 /// attempting to keep all loop-invariant and loop-computable values in a
258 /// single base register.
259 void Formula::InitialMatch(const SCEV *S, Loop *L,
260 ScalarEvolution &SE, DominatorTree &DT) {
261 SmallVector<const SCEV *, 4> Good;
262 SmallVector<const SCEV *, 4> Bad;
263 DoInitialMatch(S, L, Good, Bad, SE, DT);
265 BaseRegs.push_back(SE.getAddExpr(Good));
266 AM.HasBaseReg = true;
269 BaseRegs.push_back(SE.getAddExpr(Bad));
270 AM.HasBaseReg = true;
274 /// getNumRegs - Return the total number of register operands used by this
275 /// formula. This does not include register uses implied by non-constant
277 unsigned Formula::getNumRegs() const {
278 return !!ScaledReg + BaseRegs.size();
281 /// getType - Return the type of this formula, if it has one, or null
282 /// otherwise. This type is meaningless except for the bit size.
283 const Type *Formula::getType() const {
284 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
285 ScaledReg ? ScaledReg->getType() :
286 AM.BaseGV ? AM.BaseGV->getType() :
290 /// referencesReg - Test if this formula references the given register.
291 bool Formula::referencesReg(const SCEV *S) const {
292 return S == ScaledReg ||
293 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
296 /// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
297 /// which are used by uses other than the use with the given index.
298 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
299 const RegUseTracker &RegUses) const {
301 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
303 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
304 E = BaseRegs.end(); I != E; ++I)
305 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
310 void Formula::print(raw_ostream &OS) const {
313 if (!First) OS << " + "; else First = false;
314 WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false);
316 if (AM.BaseOffs != 0) {
317 if (!First) OS << " + "; else First = false;
320 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
321 E = BaseRegs.end(); I != E; ++I) {
322 if (!First) OS << " + "; else First = false;
323 OS << "reg(" << **I << ')';
326 if (!First) OS << " + "; else First = false;
327 OS << AM.Scale << "*reg(";
336 void Formula::dump() const {
337 print(errs()); errs() << '\n';
340 /// getSDiv - Return an expression for LHS /s RHS, if it can be determined,
341 /// or null otherwise. If IgnoreSignificantBits is true, expressions like
342 /// (X * Y) /s Y are simplified to Y, ignoring that the multiplication may
343 /// overflow, which is useful when the result will be used in a context where
344 /// the most significant bits are ignored.
345 static const SCEV *getSDiv(const SCEV *LHS, const SCEV *RHS,
347 bool IgnoreSignificantBits = false) {
348 // Handle the trivial case, which works for any SCEV type.
350 return SE.getIntegerSCEV(1, LHS->getType());
352 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do some
354 if (RHS->isAllOnesValue())
355 return SE.getMulExpr(LHS, RHS);
357 // Check for a division of a constant by a constant.
358 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
359 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
362 if (C->getValue()->getValue().srem(RC->getValue()->getValue()) != 0)
364 return SE.getConstant(C->getValue()->getValue()
365 .sdiv(RC->getValue()->getValue()));
368 // Distribute the sdiv over addrec operands.
369 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
370 const SCEV *Start = getSDiv(AR->getStart(), RHS, SE,
371 IgnoreSignificantBits);
372 if (!Start) return 0;
373 const SCEV *Step = getSDiv(AR->getStepRecurrence(SE), RHS, SE,
374 IgnoreSignificantBits);
376 return SE.getAddRecExpr(Start, Step, AR->getLoop());
379 // Distribute the sdiv over add operands.
380 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
381 SmallVector<const SCEV *, 8> Ops;
382 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
384 const SCEV *Op = getSDiv(*I, RHS, SE,
385 IgnoreSignificantBits);
389 return SE.getAddExpr(Ops);
392 // Check for a multiply operand that we can pull RHS out of.
393 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS))
394 if (IgnoreSignificantBits || Mul->hasNoSignedWrap()) {
395 SmallVector<const SCEV *, 4> Ops;
397 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
400 if (const SCEV *Q = getSDiv(*I, RHS, SE, IgnoreSignificantBits)) {
407 return Found ? SE.getMulExpr(Ops) : 0;
410 // Otherwise we don't know.
414 /// ExtractImmediate - If S involves the addition of a constant integer value,
415 /// return that integer value, and mutate S to point to a new SCEV with that
417 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
418 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
419 if (C->getValue()->getValue().getMinSignedBits() <= 64) {
420 S = SE.getIntegerSCEV(0, C->getType());
421 return C->getValue()->getSExtValue();
423 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
424 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
425 int64_t Result = ExtractImmediate(NewOps.front(), SE);
426 S = SE.getAddExpr(NewOps);
428 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
429 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
430 int64_t Result = ExtractImmediate(NewOps.front(), SE);
431 S = SE.getAddRecExpr(NewOps, AR->getLoop());
437 /// ExtractSymbol - If S involves the addition of a GlobalValue address,
438 /// return that symbol, and mutate S to point to a new SCEV with that
440 static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
441 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
442 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
443 S = SE.getIntegerSCEV(0, GV->getType());
446 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
447 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
448 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
449 S = SE.getAddExpr(NewOps);
451 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
452 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
453 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
454 S = SE.getAddRecExpr(NewOps, AR->getLoop());
460 /// isAddressUse - Returns true if the specified instruction is using the
461 /// specified value as an address.
462 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
463 bool isAddress = isa<LoadInst>(Inst);
464 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
465 if (SI->getOperand(1) == OperandVal)
467 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
468 // Addressing modes can also be folded into prefetches and a variety
470 switch (II->getIntrinsicID()) {
472 case Intrinsic::prefetch:
473 case Intrinsic::x86_sse2_loadu_dq:
474 case Intrinsic::x86_sse2_loadu_pd:
475 case Intrinsic::x86_sse_loadu_ps:
476 case Intrinsic::x86_sse_storeu_ps:
477 case Intrinsic::x86_sse2_storeu_pd:
478 case Intrinsic::x86_sse2_storeu_dq:
479 case Intrinsic::x86_sse2_storel_dq:
480 if (II->getOperand(1) == OperandVal)
488 /// getAccessType - Return the type of the memory being accessed.
489 static const Type *getAccessType(const Instruction *Inst) {
490 const Type *AccessTy = Inst->getType();
491 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
492 AccessTy = SI->getOperand(0)->getType();
493 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
494 // Addressing modes can also be folded into prefetches and a variety
496 switch (II->getIntrinsicID()) {
498 case Intrinsic::x86_sse_storeu_ps:
499 case Intrinsic::x86_sse2_storeu_pd:
500 case Intrinsic::x86_sse2_storeu_dq:
501 case Intrinsic::x86_sse2_storel_dq:
502 AccessTy = II->getOperand(1)->getType();
507 // All pointers have the same requirements, so canonicalize them to an
508 // arbitrary pointer type to minimize variation.
509 if (const PointerType *PTy = dyn_cast<PointerType>(AccessTy))
510 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
511 PTy->getAddressSpace());
516 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
517 /// specified set are trivially dead, delete them and see if this makes any of
518 /// their operands subsequently dead.
520 DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
521 bool Changed = false;
523 while (!DeadInsts.empty()) {
524 Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
526 if (I == 0 || !isInstructionTriviallyDead(I))
529 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
530 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
533 DeadInsts.push_back(U);
536 I->eraseFromParent();
545 /// Cost - This class is used to measure and compare candidate formulae.
547 /// TODO: Some of these could be merged. Also, a lexical ordering
548 /// isn't always optimal.
552 unsigned NumBaseAdds;
558 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
561 unsigned getNumRegs() const { return NumRegs; }
563 bool operator<(const Cost &Other) const;
567 void RateFormula(const Formula &F,
568 SmallPtrSet<const SCEV *, 16> &Regs,
569 const DenseSet<const SCEV *> &VisitedRegs,
571 const SmallVectorImpl<int64_t> &Offsets,
572 ScalarEvolution &SE, DominatorTree &DT);
574 void print(raw_ostream &OS) const;
578 void RateRegister(const SCEV *Reg,
579 SmallPtrSet<const SCEV *, 16> &Regs,
581 ScalarEvolution &SE, DominatorTree &DT);
582 void RatePrimaryRegister(const SCEV *Reg,
583 SmallPtrSet<const SCEV *, 16> &Regs,
585 ScalarEvolution &SE, DominatorTree &DT);
590 /// RateRegister - Tally up interesting quantities from the given register.
591 void Cost::RateRegister(const SCEV *Reg,
592 SmallPtrSet<const SCEV *, 16> &Regs,
594 ScalarEvolution &SE, DominatorTree &DT) {
595 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
596 if (AR->getLoop() == L)
597 AddRecCost += 1; /// TODO: This should be a function of the stride.
599 // If this is an addrec for a loop that's already been visited by LSR,
600 // don't second-guess its addrec phi nodes. LSR isn't currently smart
601 // enough to reason about more than one loop at a time. Consider these
602 // registers free and leave them alone.
603 else if (L->contains(AR->getLoop()) ||
604 (!AR->getLoop()->contains(L) &&
605 DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) {
606 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
607 PHINode *PN = dyn_cast<PHINode>(I); ++I)
608 if (SE.isSCEVable(PN->getType()) &&
609 (SE.getEffectiveSCEVType(PN->getType()) ==
610 SE.getEffectiveSCEVType(AR->getType())) &&
611 SE.getSCEV(PN) == AR)
614 // If this isn't one of the addrecs that the loop already has, it
615 // would require a costly new phi and add. TODO: This isn't
616 // precisely modeled right now.
618 if (!Regs.count(AR->getStart()))
619 RateRegister(AR->getStart(), Regs, L, SE, DT);
622 // Add the step value register, if it needs one.
623 // TODO: The non-affine case isn't precisely modeled here.
624 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
625 if (!Regs.count(AR->getStart()))
626 RateRegister(AR->getOperand(1), Regs, L, SE, DT);
630 // Rough heuristic; favor registers which don't require extra setup
631 // instructions in the preheader.
632 if (!isa<SCEVUnknown>(Reg) &&
633 !isa<SCEVConstant>(Reg) &&
634 !(isa<SCEVAddRecExpr>(Reg) &&
635 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
636 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
640 /// RatePrimaryRegister - Record this register in the set. If we haven't seen it
642 void Cost::RatePrimaryRegister(const SCEV *Reg,
643 SmallPtrSet<const SCEV *, 16> &Regs,
645 ScalarEvolution &SE, DominatorTree &DT) {
646 if (Regs.insert(Reg))
647 RateRegister(Reg, Regs, L, SE, DT);
650 void Cost::RateFormula(const Formula &F,
651 SmallPtrSet<const SCEV *, 16> &Regs,
652 const DenseSet<const SCEV *> &VisitedRegs,
654 const SmallVectorImpl<int64_t> &Offsets,
655 ScalarEvolution &SE, DominatorTree &DT) {
656 // Tally up the registers.
657 if (const SCEV *ScaledReg = F.ScaledReg) {
658 if (VisitedRegs.count(ScaledReg)) {
662 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT);
664 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
665 E = F.BaseRegs.end(); I != E; ++I) {
666 const SCEV *BaseReg = *I;
667 if (VisitedRegs.count(BaseReg)) {
671 RatePrimaryRegister(BaseReg, Regs, L, SE, DT);
673 NumIVMuls += isa<SCEVMulExpr>(BaseReg) &&
674 BaseReg->hasComputableLoopEvolution(L);
677 if (F.BaseRegs.size() > 1)
678 NumBaseAdds += F.BaseRegs.size() - 1;
680 // Tally up the non-zero immediates.
681 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
682 E = Offsets.end(); I != E; ++I) {
683 int64_t Offset = (uint64_t)*I + F.AM.BaseOffs;
685 ImmCost += 64; // Handle symbolic values conservatively.
686 // TODO: This should probably be the pointer size.
687 else if (Offset != 0)
688 ImmCost += APInt(64, Offset, true).getMinSignedBits();
692 /// Loose - Set this cost to a loosing value.
702 /// operator< - Choose the lower cost.
703 bool Cost::operator<(const Cost &Other) const {
704 if (NumRegs != Other.NumRegs)
705 return NumRegs < Other.NumRegs;
706 if (AddRecCost != Other.AddRecCost)
707 return AddRecCost < Other.AddRecCost;
708 if (NumIVMuls != Other.NumIVMuls)
709 return NumIVMuls < Other.NumIVMuls;
710 if (NumBaseAdds != Other.NumBaseAdds)
711 return NumBaseAdds < Other.NumBaseAdds;
712 if (ImmCost != Other.ImmCost)
713 return ImmCost < Other.ImmCost;
714 if (SetupCost != Other.SetupCost)
715 return SetupCost < Other.SetupCost;
719 void Cost::print(raw_ostream &OS) const {
720 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
722 OS << ", with addrec cost " << AddRecCost;
724 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
725 if (NumBaseAdds != 0)
726 OS << ", plus " << NumBaseAdds << " base add"
727 << (NumBaseAdds == 1 ? "" : "s");
729 OS << ", plus " << ImmCost << " imm cost";
731 OS << ", plus " << SetupCost << " setup cost";
734 void Cost::dump() const {
735 print(errs()); errs() << '\n';
740 /// LSRFixup - An operand value in an instruction which is to be replaced
741 /// with some equivalent, possibly strength-reduced, replacement.
743 /// UserInst - The instruction which will be updated.
744 Instruction *UserInst;
746 /// OperandValToReplace - The operand of the instruction which will
747 /// be replaced. The operand may be used more than once; every instance
748 /// will be replaced.
749 Value *OperandValToReplace;
751 /// PostIncLoop - If this user is to use the post-incremented value of an
752 /// induction variable, this variable is non-null and holds the loop
753 /// associated with the induction variable.
754 const Loop *PostIncLoop;
756 /// LUIdx - The index of the LSRUse describing the expression which
757 /// this fixup needs, minus an offset (below).
760 /// Offset - A constant offset to be added to the LSRUse expression.
761 /// This allows multiple fixups to share the same LSRUse with different
762 /// offsets, for example in an unrolled loop.
767 void print(raw_ostream &OS) const;
774 : UserInst(0), OperandValToReplace(0), PostIncLoop(0),
775 LUIdx(~size_t(0)), Offset(0) {}
777 void LSRFixup::print(raw_ostream &OS) const {
779 // Store is common and interesting enough to be worth special-casing.
780 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
782 WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false);
783 } else if (UserInst->getType()->isVoidTy())
784 OS << UserInst->getOpcodeName();
786 WriteAsOperand(OS, UserInst, /*PrintType=*/false);
788 OS << ", OperandValToReplace=";
789 WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false);
792 OS << ", PostIncLoop=";
793 WriteAsOperand(OS, PostIncLoop->getHeader(), /*PrintType=*/false);
796 if (LUIdx != ~size_t(0))
797 OS << ", LUIdx=" << LUIdx;
800 OS << ", Offset=" << Offset;
803 void LSRFixup::dump() const {
804 print(errs()); errs() << '\n';
809 /// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
810 /// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
811 struct UniquifierDenseMapInfo {
812 static SmallVector<const SCEV *, 2> getEmptyKey() {
813 SmallVector<const SCEV *, 2> V;
814 V.push_back(reinterpret_cast<const SCEV *>(-1));
818 static SmallVector<const SCEV *, 2> getTombstoneKey() {
819 SmallVector<const SCEV *, 2> V;
820 V.push_back(reinterpret_cast<const SCEV *>(-2));
824 static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) {
826 for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(),
827 E = V.end(); I != E; ++I)
828 Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I);
832 static bool isEqual(const SmallVector<const SCEV *, 2> &LHS,
833 const SmallVector<const SCEV *, 2> &RHS) {
838 /// LSRUse - This class holds the state that LSR keeps for each use in
839 /// IVUsers, as well as uses invented by LSR itself. It includes information
840 /// about what kinds of things can be folded into the user, information about
841 /// the user itself, and information about how the use may be satisfied.
842 /// TODO: Represent multiple users of the same expression in common?
844 DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier;
847 /// KindType - An enum for a kind of use, indicating what types of
848 /// scaled and immediate operands it might support.
850 Basic, ///< A normal use, with no folding.
851 Special, ///< A special case of basic, allowing -1 scales.
852 Address, ///< An address use; folding according to TargetLowering
853 ICmpZero ///< An equality icmp with both operands folded into one.
854 // TODO: Add a generic icmp too?
858 const Type *AccessTy;
860 SmallVector<int64_t, 8> Offsets;
864 /// AllFixupsOutsideLoop - This records whether all of the fixups using this
865 /// LSRUse are outside of the loop, in which case some special-case heuristics
867 bool AllFixupsOutsideLoop;
869 /// Formulae - A list of ways to build a value that can satisfy this user.
870 /// After the list is populated, one of these is selected heuristically and
871 /// used to formulate a replacement for OperandValToReplace in UserInst.
872 SmallVector<Formula, 12> Formulae;
874 /// Regs - The set of register candidates used by all formulae in this LSRUse.
875 SmallPtrSet<const SCEV *, 4> Regs;
877 LSRUse(KindType K, const Type *T) : Kind(K), AccessTy(T),
878 MinOffset(INT64_MAX),
879 MaxOffset(INT64_MIN),
880 AllFixupsOutsideLoop(true) {}
882 bool InsertFormula(size_t LUIdx, const Formula &F);
886 void print(raw_ostream &OS) const;
890 /// InsertFormula - If the given formula has not yet been inserted, add it to
891 /// the list, and return true. Return false otherwise.
892 bool LSRUse::InsertFormula(size_t LUIdx, const Formula &F) {
893 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
894 if (F.ScaledReg) Key.push_back(F.ScaledReg);
895 // Unstable sort by host order ok, because this is only used for uniquifying.
896 std::sort(Key.begin(), Key.end());
898 if (!Uniquifier.insert(Key).second)
901 // Using a register to hold the value of 0 is not profitable.
902 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
903 "Zero allocated in a scaled register!");
905 for (SmallVectorImpl<const SCEV *>::const_iterator I =
906 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
907 assert(!(*I)->isZero() && "Zero allocated in a base register!");
910 // Add the formula to the list.
911 Formulae.push_back(F);
913 // Record registers now being used by this use.
914 if (F.ScaledReg) Regs.insert(F.ScaledReg);
915 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
920 void LSRUse::print(raw_ostream &OS) const {
921 OS << "LSR Use: Kind=";
923 case Basic: OS << "Basic"; break;
924 case Special: OS << "Special"; break;
925 case ICmpZero: OS << "ICmpZero"; break;
928 if (AccessTy->isPointerTy())
929 OS << "pointer"; // the full pointer type could be really verbose
935 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
936 E = Offsets.end(); I != E; ++I) {
943 if (AllFixupsOutsideLoop)
944 OS << ", all-fixups-outside-loop";
947 void LSRUse::dump() const {
948 print(errs()); errs() << '\n';
951 /// isLegalUse - Test whether the use described by AM is "legal", meaning it can
952 /// be completely folded into the user instruction at isel time. This includes
953 /// address-mode folding and special icmp tricks.
954 static bool isLegalUse(const TargetLowering::AddrMode &AM,
955 LSRUse::KindType Kind, const Type *AccessTy,
956 const TargetLowering *TLI) {
958 case LSRUse::Address:
959 // If we have low-level target information, ask the target if it can
960 // completely fold this address.
961 if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy);
963 // Otherwise, just guess that reg+reg addressing is legal.
964 return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1;
966 case LSRUse::ICmpZero:
967 // There's not even a target hook for querying whether it would be legal to
968 // fold a GV into an ICmp.
972 // ICmp only has two operands; don't allow more than two non-trivial parts.
973 if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0)
976 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
977 // putting the scaled register in the other operand of the icmp.
978 if (AM.Scale != 0 && AM.Scale != -1)
981 // If we have low-level target information, ask the target if it can fold an
982 // integer immediate on an icmp.
983 if (AM.BaseOffs != 0) {
984 if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs);
991 // Only handle single-register values.
992 return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
994 case LSRUse::Special:
995 // Only handle -1 scales, or no scale.
996 return AM.Scale == 0 || AM.Scale == -1;
1002 static bool isLegalUse(TargetLowering::AddrMode AM,
1003 int64_t MinOffset, int64_t MaxOffset,
1004 LSRUse::KindType Kind, const Type *AccessTy,
1005 const TargetLowering *TLI) {
1006 // Check for overflow.
1007 if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) !=
1010 AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset;
1011 if (isLegalUse(AM, Kind, AccessTy, TLI)) {
1012 AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset;
1013 // Check for overflow.
1014 if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) !=
1017 AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset;
1018 return isLegalUse(AM, Kind, AccessTy, TLI);
1023 static bool isAlwaysFoldable(int64_t BaseOffs,
1024 GlobalValue *BaseGV,
1026 LSRUse::KindType Kind, const Type *AccessTy,
1027 const TargetLowering *TLI,
1028 ScalarEvolution &SE) {
1029 // Fast-path: zero is always foldable.
1030 if (BaseOffs == 0 && !BaseGV) return true;
1032 // Conservatively, create an address with an immediate and a
1033 // base and a scale.
1034 TargetLowering::AddrMode AM;
1035 AM.BaseOffs = BaseOffs;
1037 AM.HasBaseReg = HasBaseReg;
1038 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1040 return isLegalUse(AM, Kind, AccessTy, TLI);
1043 static bool isAlwaysFoldable(const SCEV *S,
1044 int64_t MinOffset, int64_t MaxOffset,
1046 LSRUse::KindType Kind, const Type *AccessTy,
1047 const TargetLowering *TLI,
1048 ScalarEvolution &SE) {
1049 // Fast-path: zero is always foldable.
1050 if (S->isZero()) return true;
1052 // Conservatively, create an address with an immediate and a
1053 // base and a scale.
1054 int64_t BaseOffs = ExtractImmediate(S, SE);
1055 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1057 // If there's anything else involved, it's not foldable.
1058 if (!S->isZero()) return false;
1060 // Fast-path: zero is always foldable.
1061 if (BaseOffs == 0 && !BaseGV) return true;
1063 // Conservatively, create an address with an immediate and a
1064 // base and a scale.
1065 TargetLowering::AddrMode AM;
1066 AM.BaseOffs = BaseOffs;
1068 AM.HasBaseReg = HasBaseReg;
1069 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1071 return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI);
1074 /// FormulaSorter - This class implements an ordering for formulae which sorts
1075 /// the by their standalone cost.
1076 class FormulaSorter {
1077 /// These two sets are kept empty, so that we compute standalone costs.
1078 DenseSet<const SCEV *> VisitedRegs;
1079 SmallPtrSet<const SCEV *, 16> Regs;
1082 ScalarEvolution &SE;
1086 FormulaSorter(Loop *l, LSRUse &lu, ScalarEvolution &se, DominatorTree &dt)
1087 : L(l), LU(&lu), SE(se), DT(dt) {}
1089 bool operator()(const Formula &A, const Formula &B) {
1091 CostA.RateFormula(A, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
1094 CostB.RateFormula(B, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
1096 return CostA < CostB;
1100 /// LSRInstance - This class holds state for the main loop strength reduction
1104 ScalarEvolution &SE;
1106 const TargetLowering *const TLI;
1110 /// IVIncInsertPos - This is the insert position that the current loop's
1111 /// induction variable increment should be placed. In simple loops, this is
1112 /// the latch block's terminator. But in more complicated cases, this is a
1113 /// position which will dominate all the in-loop post-increment users.
1114 Instruction *IVIncInsertPos;
1116 /// Factors - Interesting factors between use strides.
1117 SmallSetVector<int64_t, 8> Factors;
1119 /// Types - Interesting use types, to facilitate truncation reuse.
1120 SmallSetVector<const Type *, 4> Types;
1122 /// Fixups - The list of operands which are to be replaced.
1123 SmallVector<LSRFixup, 16> Fixups;
1125 /// Uses - The list of interesting uses.
1126 SmallVector<LSRUse, 16> Uses;
1128 /// RegUses - Track which uses use which register candidates.
1129 RegUseTracker RegUses;
1131 void OptimizeShadowIV();
1132 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1133 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1134 bool OptimizeLoopTermCond();
1136 void CollectInterestingTypesAndFactors();
1137 void CollectFixupsAndInitialFormulae();
1139 LSRFixup &getNewFixup() {
1140 Fixups.push_back(LSRFixup());
1141 return Fixups.back();
1144 // Support for sharing of LSRUses between LSRFixups.
1145 typedef DenseMap<const SCEV *, size_t> UseMapTy;
1148 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
1149 LSRUse::KindType Kind, const Type *AccessTy);
1151 std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1152 LSRUse::KindType Kind,
1153 const Type *AccessTy);
1156 void InsertInitialFormula(const SCEV *S, Loop *L, LSRUse &LU, size_t LUIdx);
1157 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1158 void CountRegisters(const Formula &F, size_t LUIdx);
1159 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1161 void CollectLoopInvariantFixupsAndFormulae();
1163 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1164 unsigned Depth = 0);
1165 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1166 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1167 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1168 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1169 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1170 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1171 void GenerateCrossUseConstantOffsets();
1172 void GenerateAllReuseFormulae();
1174 void FilterOutUndesirableDedicatedRegisters();
1175 void NarrowSearchSpaceUsingHeuristics();
1177 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1179 SmallVectorImpl<const Formula *> &Workspace,
1180 const Cost &CurCost,
1181 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1182 DenseSet<const SCEV *> &VisitedRegs) const;
1183 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1185 Value *Expand(const LSRFixup &LF,
1187 BasicBlock::iterator IP, Loop *L, Instruction *IVIncInsertPos,
1188 SCEVExpander &Rewriter,
1189 SmallVectorImpl<WeakVH> &DeadInsts,
1190 ScalarEvolution &SE, DominatorTree &DT) const;
1191 void Rewrite(const LSRFixup &LF,
1193 Loop *L, Instruction *IVIncInsertPos,
1194 SCEVExpander &Rewriter,
1195 SmallVectorImpl<WeakVH> &DeadInsts,
1196 ScalarEvolution &SE, DominatorTree &DT,
1198 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1201 LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
1203 bool getChanged() const { return Changed; }
1205 void print_factors_and_types(raw_ostream &OS) const;
1206 void print_fixups(raw_ostream &OS) const;
1207 void print_uses(raw_ostream &OS) const;
1208 void print(raw_ostream &OS) const;
1214 /// OptimizeShadowIV - If IV is used in a int-to-float cast
1215 /// inside the loop then try to eliminate the cast opeation.
1216 void LSRInstance::OptimizeShadowIV() {
1217 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1218 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1221 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1222 UI != E; /* empty */) {
1223 IVUsers::const_iterator CandidateUI = UI;
1225 Instruction *ShadowUse = CandidateUI->getUser();
1226 const Type *DestTy = NULL;
1228 /* If shadow use is a int->float cast then insert a second IV
1229 to eliminate this cast.
1231 for (unsigned i = 0; i < n; ++i)
1237 for (unsigned i = 0; i < n; ++i, ++d)
1240 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser()))
1241 DestTy = UCast->getDestTy();
1242 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser()))
1243 DestTy = SCast->getDestTy();
1244 if (!DestTy) continue;
1247 // If target does not support DestTy natively then do not apply
1248 // this transformation.
1249 EVT DVT = TLI->getValueType(DestTy);
1250 if (!TLI->isTypeLegal(DVT)) continue;
1253 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1255 if (PH->getNumIncomingValues() != 2) continue;
1257 const Type *SrcTy = PH->getType();
1258 int Mantissa = DestTy->getFPMantissaWidth();
1259 if (Mantissa == -1) continue;
1260 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1263 unsigned Entry, Latch;
1264 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1272 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1273 if (!Init) continue;
1274 Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
1276 BinaryOperator *Incr =
1277 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1278 if (!Incr) continue;
1279 if (Incr->getOpcode() != Instruction::Add
1280 && Incr->getOpcode() != Instruction::Sub)
1283 /* Initialize new IV, double d = 0.0 in above example. */
1284 ConstantInt *C = NULL;
1285 if (Incr->getOperand(0) == PH)
1286 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1287 else if (Incr->getOperand(1) == PH)
1288 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1294 // Ignore negative constants, as the code below doesn't handle them
1295 // correctly. TODO: Remove this restriction.
1296 if (!C->getValue().isStrictlyPositive()) continue;
1298 /* Add new PHINode. */
1299 PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
1301 /* create new increment. '++d' in above example. */
1302 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1303 BinaryOperator *NewIncr =
1304 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1305 Instruction::FAdd : Instruction::FSub,
1306 NewPH, CFP, "IV.S.next.", Incr);
1308 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1309 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1311 /* Remove cast operation */
1312 ShadowUse->replaceAllUsesWith(NewPH);
1313 ShadowUse->eraseFromParent();
1318 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1319 /// set the IV user and stride information and return true, otherwise return
1321 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond,
1322 IVStrideUse *&CondUse) {
1323 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1324 if (UI->getUser() == Cond) {
1325 // NOTE: we could handle setcc instructions with multiple uses here, but
1326 // InstCombine does it as well for simple uses, it's not clear that it
1327 // occurs enough in real life to handle.
1334 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
1335 /// a max computation.
1337 /// This is a narrow solution to a specific, but acute, problem. For loops
1343 /// } while (++i < n);
1345 /// the trip count isn't just 'n', because 'n' might not be positive. And
1346 /// unfortunately this can come up even for loops where the user didn't use
1347 /// a C do-while loop. For example, seemingly well-behaved top-test loops
1348 /// will commonly be lowered like this:
1354 /// } while (++i < n);
1357 /// and then it's possible for subsequent optimization to obscure the if
1358 /// test in such a way that indvars can't find it.
1360 /// When indvars can't find the if test in loops like this, it creates a
1361 /// max expression, which allows it to give the loop a canonical
1362 /// induction variable:
1365 /// max = n < 1 ? 1 : n;
1368 /// } while (++i != max);
1370 /// Canonical induction variables are necessary because the loop passes
1371 /// are designed around them. The most obvious example of this is the
1372 /// LoopInfo analysis, which doesn't remember trip count values. It
1373 /// expects to be able to rediscover the trip count each time it is
1374 /// needed, and it does this using a simple analysis that only succeeds if
1375 /// the loop has a canonical induction variable.
1377 /// However, when it comes time to generate code, the maximum operation
1378 /// can be quite costly, especially if it's inside of an outer loop.
1380 /// This function solves this problem by detecting this type of loop and
1381 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1382 /// the instructions for the maximum computation.
1384 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1385 // Check that the loop matches the pattern we're looking for.
1386 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1387 Cond->getPredicate() != CmpInst::ICMP_NE)
1390 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
1391 if (!Sel || !Sel->hasOneUse()) return Cond;
1393 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1394 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1396 const SCEV *One = SE.getIntegerSCEV(1, BackedgeTakenCount->getType());
1398 // Add one to the backedge-taken count to get the trip count.
1399 const SCEV *IterationCount = SE.getAddExpr(BackedgeTakenCount, One);
1401 // Check for a max calculation that matches the pattern.
1402 if (!isa<SCEVSMaxExpr>(IterationCount) && !isa<SCEVUMaxExpr>(IterationCount))
1404 const SCEVNAryExpr *Max = cast<SCEVNAryExpr>(IterationCount);
1405 if (Max != SE.getSCEV(Sel)) return Cond;
1407 // To handle a max with more than two operands, this optimization would
1408 // require additional checking and setup.
1409 if (Max->getNumOperands() != 2)
1412 const SCEV *MaxLHS = Max->getOperand(0);
1413 const SCEV *MaxRHS = Max->getOperand(1);
1414 if (!MaxLHS || MaxLHS != One) return Cond;
1415 // Check the relevant induction variable for conformance to
1417 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
1418 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
1419 if (!AR || !AR->isAffine() ||
1420 AR->getStart() != One ||
1421 AR->getStepRecurrence(SE) != One)
1424 assert(AR->getLoop() == L &&
1425 "Loop condition operand is an addrec in a different loop!");
1427 // Check the right operand of the select, and remember it, as it will
1428 // be used in the new comparison instruction.
1430 if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
1431 NewRHS = Sel->getOperand(1);
1432 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
1433 NewRHS = Sel->getOperand(2);
1434 if (!NewRHS) return Cond;
1436 // Determine the new comparison opcode. It may be signed or unsigned,
1437 // and the original comparison may be either equality or inequality.
1438 CmpInst::Predicate Pred =
1439 isa<SCEVSMaxExpr>(Max) ? CmpInst::ICMP_SLT : CmpInst::ICMP_ULT;
1440 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
1441 Pred = CmpInst::getInversePredicate(Pred);
1443 // Ok, everything looks ok to change the condition into an SLT or SGE and
1444 // delete the max calculation.
1446 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
1448 // Delete the max calculation instructions.
1449 Cond->replaceAllUsesWith(NewCond);
1450 CondUse->setUser(NewCond);
1451 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
1452 Cond->eraseFromParent();
1453 Sel->eraseFromParent();
1454 if (Cmp->use_empty())
1455 Cmp->eraseFromParent();
1459 /// OptimizeLoopTermCond - Change loop terminating condition to use the
1460 /// postinc iv when possible.
1462 LSRInstance::OptimizeLoopTermCond() {
1463 SmallPtrSet<Instruction *, 4> PostIncs;
1465 BasicBlock *LatchBlock = L->getLoopLatch();
1466 SmallVector<BasicBlock*, 8> ExitingBlocks;
1467 L->getExitingBlocks(ExitingBlocks);
1469 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
1470 BasicBlock *ExitingBlock = ExitingBlocks[i];
1472 // Get the terminating condition for the loop if possible. If we
1473 // can, we want to change it to use a post-incremented version of its
1474 // induction variable, to allow coalescing the live ranges for the IV into
1475 // one register value.
1477 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
1480 // FIXME: Overly conservative, termination condition could be an 'or' etc..
1481 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
1484 // Search IVUsesByStride to find Cond's IVUse if there is one.
1485 IVStrideUse *CondUse = 0;
1486 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
1487 if (!FindIVUserForCond(Cond, CondUse))
1490 // If the trip count is computed in terms of a max (due to ScalarEvolution
1491 // being unable to find a sufficient guard, for example), change the loop
1492 // comparison to use SLT or ULT instead of NE.
1493 // One consequence of doing this now is that it disrupts the count-down
1494 // optimization. That's not always a bad thing though, because in such
1495 // cases it may still be worthwhile to avoid a max.
1496 Cond = OptimizeMax(Cond, CondUse);
1498 // If this exiting block dominates the latch block, it may also use
1499 // the post-inc value if it won't be shared with other uses.
1500 // Check for dominance.
1501 if (!DT.dominates(ExitingBlock, LatchBlock))
1504 // Conservatively avoid trying to use the post-inc value in non-latch
1505 // exits if there may be pre-inc users in intervening blocks.
1506 if (LatchBlock != ExitingBlock)
1507 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1508 // Test if the use is reachable from the exiting block. This dominator
1509 // query is a conservative approximation of reachability.
1510 if (&*UI != CondUse &&
1511 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
1512 // Conservatively assume there may be reuse if the quotient of their
1513 // strides could be a legal scale.
1514 const SCEV *A = CondUse->getStride();
1515 const SCEV *B = UI->getStride();
1516 if (SE.getTypeSizeInBits(A->getType()) !=
1517 SE.getTypeSizeInBits(B->getType())) {
1518 if (SE.getTypeSizeInBits(A->getType()) >
1519 SE.getTypeSizeInBits(B->getType()))
1520 B = SE.getSignExtendExpr(B, A->getType());
1522 A = SE.getSignExtendExpr(A, B->getType());
1524 if (const SCEVConstant *D =
1525 dyn_cast_or_null<SCEVConstant>(getSDiv(B, A, SE))) {
1526 // Stride of one or negative one can have reuse with non-addresses.
1527 if (D->getValue()->isOne() ||
1528 D->getValue()->isAllOnesValue())
1529 goto decline_post_inc;
1530 // Avoid weird situations.
1531 if (D->getValue()->getValue().getMinSignedBits() >= 64 ||
1532 D->getValue()->getValue().isMinSignedValue())
1533 goto decline_post_inc;
1534 // Without TLI, assume that any stride might be valid, and so any
1535 // use might be shared.
1537 goto decline_post_inc;
1538 // Check for possible scaled-address reuse.
1539 const Type *AccessTy = getAccessType(UI->getUser());
1540 TargetLowering::AddrMode AM;
1541 AM.Scale = D->getValue()->getSExtValue();
1542 if (TLI->isLegalAddressingMode(AM, AccessTy))
1543 goto decline_post_inc;
1544 AM.Scale = -AM.Scale;
1545 if (TLI->isLegalAddressingMode(AM, AccessTy))
1546 goto decline_post_inc;
1550 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
1553 // It's possible for the setcc instruction to be anywhere in the loop, and
1554 // possible for it to have multiple users. If it is not immediately before
1555 // the exiting block branch, move it.
1556 if (&*++BasicBlock::iterator(Cond) != TermBr) {
1557 if (Cond->hasOneUse()) {
1558 Cond->moveBefore(TermBr);
1560 // Clone the terminating condition and insert into the loopend.
1561 ICmpInst *OldCond = Cond;
1562 Cond = cast<ICmpInst>(Cond->clone());
1563 Cond->setName(L->getHeader()->getName() + ".termcond");
1564 ExitingBlock->getInstList().insert(TermBr, Cond);
1566 // Clone the IVUse, as the old use still exists!
1567 CondUse = &IU.AddUser(CondUse->getStride(), CondUse->getOffset(),
1568 Cond, CondUse->getOperandValToReplace());
1569 TermBr->replaceUsesOfWith(OldCond, Cond);
1573 // If we get to here, we know that we can transform the setcc instruction to
1574 // use the post-incremented version of the IV, allowing us to coalesce the
1575 // live ranges for the IV correctly.
1576 CondUse->setOffset(SE.getMinusSCEV(CondUse->getOffset(),
1577 CondUse->getStride()));
1578 CondUse->setIsUseOfPostIncrementedValue(true);
1581 PostIncs.insert(Cond);
1585 // Determine an insertion point for the loop induction variable increment. It
1586 // must dominate all the post-inc comparisons we just set up, and it must
1587 // dominate the loop latch edge.
1588 IVIncInsertPos = L->getLoopLatch()->getTerminator();
1589 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
1590 E = PostIncs.end(); I != E; ++I) {
1592 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
1594 if (BB == (*I)->getParent())
1595 IVIncInsertPos = *I;
1596 else if (BB != IVIncInsertPos->getParent())
1597 IVIncInsertPos = BB->getTerminator();
1604 LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
1605 LSRUse::KindType Kind, const Type *AccessTy) {
1606 int64_t NewMinOffset = LU.MinOffset;
1607 int64_t NewMaxOffset = LU.MaxOffset;
1608 const Type *NewAccessTy = AccessTy;
1610 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
1611 // something conservative, however this can pessimize in the case that one of
1612 // the uses will have all its uses outside the loop, for example.
1613 if (LU.Kind != Kind)
1615 // Conservatively assume HasBaseReg is true for now.
1616 if (NewOffset < LU.MinOffset) {
1617 if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, /*HasBaseReg=*/true,
1618 Kind, AccessTy, TLI, SE))
1620 NewMinOffset = NewOffset;
1621 } else if (NewOffset > LU.MaxOffset) {
1622 if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, /*HasBaseReg=*/true,
1623 Kind, AccessTy, TLI, SE))
1625 NewMaxOffset = NewOffset;
1627 // Check for a mismatched access type, and fall back conservatively as needed.
1628 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
1629 NewAccessTy = Type::getVoidTy(AccessTy->getContext());
1632 LU.MinOffset = NewMinOffset;
1633 LU.MaxOffset = NewMaxOffset;
1634 LU.AccessTy = NewAccessTy;
1635 if (NewOffset != LU.Offsets.back())
1636 LU.Offsets.push_back(NewOffset);
1640 /// getUse - Return an LSRUse index and an offset value for a fixup which
1641 /// needs the given expression, with the given kind and optional access type.
1642 /// Either reuse an exisitng use or create a new one, as needed.
1643 std::pair<size_t, int64_t>
1644 LSRInstance::getUse(const SCEV *&Expr,
1645 LSRUse::KindType Kind, const Type *AccessTy) {
1646 const SCEV *Copy = Expr;
1647 int64_t Offset = ExtractImmediate(Expr, SE);
1649 // Basic uses can't accept any offset, for example.
1650 if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true,
1651 Kind, AccessTy, TLI, SE)) {
1656 std::pair<UseMapTy::iterator, bool> P =
1657 UseMap.insert(std::make_pair(Expr, 0));
1659 // A use already existed with this base.
1660 size_t LUIdx = P.first->second;
1661 LSRUse &LU = Uses[LUIdx];
1662 if (reconcileNewOffset(LU, Offset, Kind, AccessTy))
1664 return std::make_pair(LUIdx, Offset);
1667 // Create a new use.
1668 size_t LUIdx = Uses.size();
1669 P.first->second = LUIdx;
1670 Uses.push_back(LSRUse(Kind, AccessTy));
1671 LSRUse &LU = Uses[LUIdx];
1673 // We don't need to track redundant offsets, but we don't need to go out
1674 // of our way here to avoid them.
1675 if (LU.Offsets.empty() || Offset != LU.Offsets.back())
1676 LU.Offsets.push_back(Offset);
1678 LU.MinOffset = Offset;
1679 LU.MaxOffset = Offset;
1680 return std::make_pair(LUIdx, Offset);
1683 void LSRInstance::CollectInterestingTypesAndFactors() {
1684 SmallSetVector<const SCEV *, 4> Strides;
1686 // Collect interesting types and factors.
1687 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
1688 const SCEV *Stride = UI->getStride();
1690 // Collect interesting types.
1691 Types.insert(SE.getEffectiveSCEVType(Stride->getType()));
1693 // Collect interesting factors.
1694 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
1695 Strides.begin(), SEnd = Strides.end(); NewStrideIter != SEnd;
1697 const SCEV *OldStride = Stride;
1698 const SCEV *NewStride = *NewStrideIter;
1699 if (OldStride == NewStride)
1702 if (SE.getTypeSizeInBits(OldStride->getType()) !=
1703 SE.getTypeSizeInBits(NewStride->getType())) {
1704 if (SE.getTypeSizeInBits(OldStride->getType()) >
1705 SE.getTypeSizeInBits(NewStride->getType()))
1706 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
1708 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
1710 if (const SCEVConstant *Factor =
1711 dyn_cast_or_null<SCEVConstant>(getSDiv(NewStride, OldStride,
1713 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
1714 Factors.insert(Factor->getValue()->getValue().getSExtValue());
1715 } else if (const SCEVConstant *Factor =
1716 dyn_cast_or_null<SCEVConstant>(getSDiv(OldStride, NewStride,
1718 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
1719 Factors.insert(Factor->getValue()->getValue().getSExtValue());
1722 Strides.insert(Stride);
1725 // If all uses use the same type, don't bother looking for truncation-based
1727 if (Types.size() == 1)
1730 DEBUG(print_factors_and_types(dbgs()));
1733 void LSRInstance::CollectFixupsAndInitialFormulae() {
1734 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
1736 LSRFixup &LF = getNewFixup();
1737 LF.UserInst = UI->getUser();
1738 LF.OperandValToReplace = UI->getOperandValToReplace();
1739 if (UI->isUseOfPostIncrementedValue())
1742 LSRUse::KindType Kind = LSRUse::Basic;
1743 const Type *AccessTy = 0;
1744 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
1745 Kind = LSRUse::Address;
1746 AccessTy = getAccessType(LF.UserInst);
1749 const SCEV *S = IU.getCanonicalExpr(*UI);
1751 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
1752 // (N - i == 0), and this allows (N - i) to be the expression that we work
1753 // with rather than just N or i, so we can consider the register
1754 // requirements for both N and i at the same time. Limiting this code to
1755 // equality icmps is not a problem because all interesting loops use
1756 // equality icmps, thanks to IndVarSimplify.
1757 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
1758 if (CI->isEquality()) {
1759 // Swap the operands if needed to put the OperandValToReplace on the
1760 // left, for consistency.
1761 Value *NV = CI->getOperand(1);
1762 if (NV == LF.OperandValToReplace) {
1763 CI->setOperand(1, CI->getOperand(0));
1764 CI->setOperand(0, NV);
1767 // x == y --> x - y == 0
1768 const SCEV *N = SE.getSCEV(NV);
1769 if (N->isLoopInvariant(L)) {
1770 Kind = LSRUse::ICmpZero;
1771 S = SE.getMinusSCEV(N, S);
1774 // -1 and the negations of all interesting strides (except the negation
1775 // of -1) are now also interesting.
1776 for (size_t i = 0, e = Factors.size(); i != e; ++i)
1777 if (Factors[i] != -1)
1778 Factors.insert(-(uint64_t)Factors[i]);
1782 // Set up the initial formula for this use.
1783 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
1785 LF.Offset = P.second;
1786 LSRUse &LU = Uses[LF.LUIdx];
1787 LU.AllFixupsOutsideLoop &= !L->contains(LF.UserInst);
1789 // If this is the first use of this LSRUse, give it a formula.
1790 if (LU.Formulae.empty()) {
1791 InsertInitialFormula(S, L, LU, LF.LUIdx);
1792 CountRegisters(LU.Formulae.back(), LF.LUIdx);
1796 DEBUG(print_fixups(dbgs()));
1800 LSRInstance::InsertInitialFormula(const SCEV *S, Loop *L,
1801 LSRUse &LU, size_t LUIdx) {
1803 F.InitialMatch(S, L, SE, DT);
1804 bool Inserted = InsertFormula(LU, LUIdx, F);
1805 assert(Inserted && "Initial formula already exists!"); (void)Inserted;
1809 LSRInstance::InsertSupplementalFormula(const SCEV *S,
1810 LSRUse &LU, size_t LUIdx) {
1812 F.BaseRegs.push_back(S);
1813 F.AM.HasBaseReg = true;
1814 bool Inserted = InsertFormula(LU, LUIdx, F);
1815 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
1818 /// CountRegisters - Note which registers are used by the given formula,
1819 /// updating RegUses.
1820 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
1822 RegUses.CountRegister(F.ScaledReg, LUIdx);
1823 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
1824 E = F.BaseRegs.end(); I != E; ++I)
1825 RegUses.CountRegister(*I, LUIdx);
1828 /// InsertFormula - If the given formula has not yet been inserted, add it to
1829 /// the list, and return true. Return false otherwise.
1830 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
1831 if (!LU.InsertFormula(LUIdx, F))
1834 CountRegisters(F, LUIdx);
1838 /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
1839 /// loop-invariant values which we're tracking. These other uses will pin these
1840 /// values in registers, making them less profitable for elimination.
1841 /// TODO: This currently misses non-constant addrec step registers.
1842 /// TODO: Should this give more weight to users inside the loop?
1844 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
1845 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
1846 SmallPtrSet<const SCEV *, 8> Inserted;
1848 while (!Worklist.empty()) {
1849 const SCEV *S = Worklist.pop_back_val();
1851 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
1852 Worklist.insert(Worklist.end(), N->op_begin(), N->op_end());
1853 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
1854 Worklist.push_back(C->getOperand());
1855 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
1856 Worklist.push_back(D->getLHS());
1857 Worklist.push_back(D->getRHS());
1858 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
1859 if (!Inserted.insert(U)) continue;
1860 const Value *V = U->getValue();
1861 if (const Instruction *Inst = dyn_cast<Instruction>(V))
1862 if (L->contains(Inst)) continue;
1863 for (Value::use_const_iterator UI = V->use_begin(), UE = V->use_end();
1865 const Instruction *UserInst = dyn_cast<Instruction>(*UI);
1866 // Ignore non-instructions.
1869 // Ignore instructions in other functions (as can happen with
1871 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
1873 // Ignore instructions not dominated by the loop.
1874 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
1875 UserInst->getParent() :
1876 cast<PHINode>(UserInst)->getIncomingBlock(
1877 PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
1878 if (!DT.dominates(L->getHeader(), UseBB))
1880 // Ignore uses which are part of other SCEV expressions, to avoid
1881 // analyzing them multiple times.
1882 if (SE.isSCEVable(UserInst->getType()) &&
1883 !isa<SCEVUnknown>(SE.getSCEV(const_cast<Instruction *>(UserInst))))
1885 // Ignore icmp instructions which are already being analyzed.
1886 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
1887 unsigned OtherIdx = !UI.getOperandNo();
1888 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
1889 if (SE.getSCEV(OtherOp)->hasComputableLoopEvolution(L))
1893 LSRFixup &LF = getNewFixup();
1894 LF.UserInst = const_cast<Instruction *>(UserInst);
1895 LF.OperandValToReplace = UI.getUse();
1896 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0);
1898 LF.Offset = P.second;
1899 LSRUse &LU = Uses[LF.LUIdx];
1900 LU.AllFixupsOutsideLoop &= L->contains(LF.UserInst);
1901 InsertSupplementalFormula(U, LU, LF.LUIdx);
1902 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
1909 /// CollectSubexprs - Split S into subexpressions which can be pulled out into
1910 /// separate registers. If C is non-null, multiply each subexpression by C.
1911 static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
1912 SmallVectorImpl<const SCEV *> &Ops,
1913 ScalarEvolution &SE) {
1914 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
1915 // Break out add operands.
1916 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
1918 CollectSubexprs(*I, C, Ops, SE);
1920 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
1921 // Split a non-zero base out of an addrec.
1922 if (!AR->getStart()->isZero()) {
1923 CollectSubexprs(SE.getAddRecExpr(SE.getIntegerSCEV(0, AR->getType()),
1924 AR->getStepRecurrence(SE),
1925 AR->getLoop()), C, Ops, SE);
1926 CollectSubexprs(AR->getStart(), C, Ops, SE);
1929 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
1930 // Break (C * (a + b + c)) into C*a + C*b + C*c.
1931 if (Mul->getNumOperands() == 2)
1932 if (const SCEVConstant *Op0 =
1933 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
1934 CollectSubexprs(Mul->getOperand(1),
1935 C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
1941 // Otherwise use the value itself.
1942 Ops.push_back(C ? SE.getMulExpr(C, S) : S);
1945 /// GenerateReassociations - Split out subexpressions from adds and the bases of
1947 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
1950 // Arbitrarily cap recursion to protect compile time.
1951 if (Depth >= 3) return;
1953 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
1954 const SCEV *BaseReg = Base.BaseRegs[i];
1956 SmallVector<const SCEV *, 8> AddOps;
1957 CollectSubexprs(BaseReg, 0, AddOps, SE);
1958 if (AddOps.size() == 1) continue;
1960 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
1961 JE = AddOps.end(); J != JE; ++J) {
1962 // Don't pull a constant into a register if the constant could be folded
1963 // into an immediate field.
1964 if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,
1965 Base.getNumRegs() > 1,
1966 LU.Kind, LU.AccessTy, TLI, SE))
1969 // Collect all operands except *J.
1970 SmallVector<const SCEV *, 8> InnerAddOps;
1971 for (SmallVectorImpl<const SCEV *>::const_iterator K = AddOps.begin(),
1972 KE = AddOps.end(); K != KE; ++K)
1974 InnerAddOps.push_back(*K);
1976 // Don't leave just a constant behind in a register if the constant could
1977 // be folded into an immediate field.
1978 if (InnerAddOps.size() == 1 &&
1979 isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset,
1980 Base.getNumRegs() > 1,
1981 LU.Kind, LU.AccessTy, TLI, SE))
1985 F.BaseRegs[i] = SE.getAddExpr(InnerAddOps);
1986 F.BaseRegs.push_back(*J);
1987 if (InsertFormula(LU, LUIdx, F))
1988 // If that formula hadn't been seen before, recurse to find more like
1990 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1);
1995 /// GenerateCombinations - Generate a formula consisting of all of the
1996 /// loop-dominating registers added into a single register.
1997 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
1999 // This method is only intersting on a plurality of registers.
2000 if (Base.BaseRegs.size() <= 1) return;
2004 SmallVector<const SCEV *, 4> Ops;
2005 for (SmallVectorImpl<const SCEV *>::const_iterator
2006 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
2007 const SCEV *BaseReg = *I;
2008 if (BaseReg->properlyDominates(L->getHeader(), &DT) &&
2009 !BaseReg->hasComputableLoopEvolution(L))
2010 Ops.push_back(BaseReg);
2012 F.BaseRegs.push_back(BaseReg);
2014 if (Ops.size() > 1) {
2015 const SCEV *Sum = SE.getAddExpr(Ops);
2016 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
2017 // opportunity to fold something. For now, just ignore such cases
2018 // rather than procede with zero in a register.
2019 if (!Sum->isZero()) {
2020 F.BaseRegs.push_back(Sum);
2021 (void)InsertFormula(LU, LUIdx, F);
2026 /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
2027 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
2029 // We can't add a symbolic offset if the address already contains one.
2030 if (Base.AM.BaseGV) return;
2032 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2033 const SCEV *G = Base.BaseRegs[i];
2034 GlobalValue *GV = ExtractSymbol(G, SE);
2035 if (G->isZero() || !GV)
2039 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
2040 LU.Kind, LU.AccessTy, TLI))
2043 (void)InsertFormula(LU, LUIdx, F);
2047 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
2048 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
2050 // TODO: For now, just add the min and max offset, because it usually isn't
2051 // worthwhile looking at everything inbetween.
2052 SmallVector<int64_t, 4> Worklist;
2053 Worklist.push_back(LU.MinOffset);
2054 if (LU.MaxOffset != LU.MinOffset)
2055 Worklist.push_back(LU.MaxOffset);
2057 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2058 const SCEV *G = Base.BaseRegs[i];
2060 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
2061 E = Worklist.end(); I != E; ++I) {
2063 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I;
2064 if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I,
2065 LU.Kind, LU.AccessTy, TLI)) {
2066 F.BaseRegs[i] = SE.getAddExpr(G, SE.getIntegerSCEV(*I, G->getType()));
2068 (void)InsertFormula(LU, LUIdx, F);
2072 int64_t Imm = ExtractImmediate(G, SE);
2073 if (G->isZero() || Imm == 0)
2076 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm;
2077 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
2078 LU.Kind, LU.AccessTy, TLI))
2081 (void)InsertFormula(LU, LUIdx, F);
2085 /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
2086 /// the comparison. For example, x == y -> x*c == y*c.
2087 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
2089 if (LU.Kind != LSRUse::ICmpZero) return;
2091 // Determine the integer type for the base formula.
2092 const Type *IntTy = Base.getType();
2094 if (SE.getTypeSizeInBits(IntTy) > 64) return;
2096 // Don't do this if there is more than one offset.
2097 if (LU.MinOffset != LU.MaxOffset) return;
2099 assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
2101 // Check each interesting stride.
2102 for (SmallSetVector<int64_t, 8>::const_iterator
2103 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
2104 int64_t Factor = *I;
2107 // Check that the multiplication doesn't overflow.
2108 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
2109 if ((int64_t)F.AM.BaseOffs / Factor != Base.AM.BaseOffs)
2112 // Check that multiplying with the use offset doesn't overflow.
2113 int64_t Offset = LU.MinOffset;
2114 Offset = (uint64_t)Offset * Factor;
2115 if ((int64_t)Offset / Factor != LU.MinOffset)
2118 // Check that this scale is legal.
2119 if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI))
2122 // Compensate for the use having MinOffset built into it.
2123 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset;
2125 const SCEV *FactorS = SE.getIntegerSCEV(Factor, IntTy);
2127 // Check that multiplying with each base register doesn't overflow.
2128 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
2129 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
2130 if (getSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
2134 // Check that multiplying with the scaled register doesn't overflow.
2136 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
2137 if (getSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
2141 // If we make it here and it's legal, add it.
2142 (void)InsertFormula(LU, LUIdx, F);
2147 /// GenerateScales - Generate stride factor reuse formulae by making use of
2148 /// scaled-offset address modes, for example.
2149 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx,
2151 // Determine the integer type for the base formula.
2152 const Type *IntTy = Base.getType();
2155 // If this Formula already has a scaled register, we can't add another one.
2156 if (Base.AM.Scale != 0) return;
2158 // Check each interesting stride.
2159 for (SmallSetVector<int64_t, 8>::const_iterator
2160 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
2161 int64_t Factor = *I;
2163 Base.AM.Scale = Factor;
2164 Base.AM.HasBaseReg = Base.BaseRegs.size() > 1;
2165 // Check whether this scale is going to be legal.
2166 if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
2167 LU.Kind, LU.AccessTy, TLI)) {
2168 // As a special-case, handle special out-of-loop Basic users specially.
2169 // TODO: Reconsider this special case.
2170 if (LU.Kind == LSRUse::Basic &&
2171 isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
2172 LSRUse::Special, LU.AccessTy, TLI) &&
2173 LU.AllFixupsOutsideLoop)
2174 LU.Kind = LSRUse::Special;
2178 // For an ICmpZero, negating a solitary base register won't lead to
2180 if (LU.Kind == LSRUse::ICmpZero &&
2181 !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV)
2183 // For each addrec base reg, apply the scale, if possible.
2184 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
2185 if (const SCEVAddRecExpr *AR =
2186 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
2187 const SCEV *FactorS = SE.getIntegerSCEV(Factor, IntTy);
2188 if (FactorS->isZero())
2190 // Divide out the factor, ignoring high bits, since we'll be
2191 // scaling the value back up in the end.
2192 if (const SCEV *Quotient = getSDiv(AR, FactorS, SE, true)) {
2193 // TODO: This could be optimized to avoid all the copying.
2195 F.ScaledReg = Quotient;
2196 std::swap(F.BaseRegs[i], F.BaseRegs.back());
2197 F.BaseRegs.pop_back();
2198 (void)InsertFormula(LU, LUIdx, F);
2204 /// GenerateTruncates - Generate reuse formulae from different IV types.
2205 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx,
2207 // This requires TargetLowering to tell us which truncates are free.
2210 // Don't bother truncating symbolic values.
2211 if (Base.AM.BaseGV) return;
2213 // Determine the integer type for the base formula.
2214 const Type *DstTy = Base.getType();
2216 DstTy = SE.getEffectiveSCEVType(DstTy);
2218 for (SmallSetVector<const Type *, 4>::const_iterator
2219 I = Types.begin(), E = Types.end(); I != E; ++I) {
2220 const Type *SrcTy = *I;
2221 if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
2224 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
2225 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
2226 JE = F.BaseRegs.end(); J != JE; ++J)
2227 *J = SE.getAnyExtendExpr(*J, SrcTy);
2229 // TODO: This assumes we've done basic processing on all uses and
2230 // have an idea what the register usage is.
2231 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
2234 (void)InsertFormula(LU, LUIdx, F);
2241 /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
2242 /// defer modifications so that the search phase doesn't have to worry about
2243 /// the data structures moving underneath it.
2247 const SCEV *OrigReg;
2249 WorkItem(size_t LI, int64_t I, const SCEV *R)
2250 : LUIdx(LI), Imm(I), OrigReg(R) {}
2252 void print(raw_ostream &OS) const;
2258 void WorkItem::print(raw_ostream &OS) const {
2259 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
2260 << " , add offset " << Imm;
2263 void WorkItem::dump() const {
2264 print(errs()); errs() << '\n';
2267 /// GenerateCrossUseConstantOffsets - Look for registers which are a constant
2268 /// distance apart and try to form reuse opportunities between them.
2269 void LSRInstance::GenerateCrossUseConstantOffsets() {
2270 // Group the registers by their value without any added constant offset.
2271 typedef std::map<int64_t, const SCEV *> ImmMapTy;
2272 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
2274 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
2275 SmallVector<const SCEV *, 8> Sequence;
2276 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
2278 const SCEV *Reg = *I;
2279 int64_t Imm = ExtractImmediate(Reg, SE);
2280 std::pair<RegMapTy::iterator, bool> Pair =
2281 Map.insert(std::make_pair(Reg, ImmMapTy()));
2283 Sequence.push_back(Reg);
2284 Pair.first->second.insert(std::make_pair(Imm, *I));
2285 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
2288 // Now examine each set of registers with the same base value. Build up
2289 // a list of work to do and do the work in a separate step so that we're
2290 // not adding formulae and register counts while we're searching.
2291 SmallVector<WorkItem, 32> WorkItems;
2292 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
2293 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
2294 E = Sequence.end(); I != E; ++I) {
2295 const SCEV *Reg = *I;
2296 const ImmMapTy &Imms = Map.find(Reg)->second;
2298 // It's not worthwhile looking for reuse if there's only one offset.
2299 if (Imms.size() == 1)
2302 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
2303 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
2305 dbgs() << ' ' << J->first;
2308 // Examine each offset.
2309 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
2311 const SCEV *OrigReg = J->second;
2313 int64_t JImm = J->first;
2314 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
2316 if (!isa<SCEVConstant>(OrigReg) &&
2317 UsedByIndicesMap[Reg].count() == 1) {
2318 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
2322 // Conservatively examine offsets between this orig reg a few selected
2324 ImmMapTy::const_iterator OtherImms[] = {
2325 Imms.begin(), prior(Imms.end()),
2326 Imms.upper_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
2328 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
2329 ImmMapTy::const_iterator M = OtherImms[i];
2330 if (M == J || M == JE) continue;
2332 // Compute the difference between the two.
2333 int64_t Imm = (uint64_t)JImm - M->first;
2334 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
2335 LUIdx = UsedByIndices.find_next(LUIdx))
2336 // Make a memo of this use, offset, and register tuple.
2337 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
2338 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
2345 UsedByIndicesMap.clear();
2346 UniqueItems.clear();
2348 // Now iterate through the worklist and add new formulae.
2349 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
2350 E = WorkItems.end(); I != E; ++I) {
2351 const WorkItem &WI = *I;
2352 size_t LUIdx = WI.LUIdx;
2353 LSRUse &LU = Uses[LUIdx];
2354 int64_t Imm = WI.Imm;
2355 const SCEV *OrigReg = WI.OrigReg;
2357 const Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
2358 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
2359 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
2361 // TODO: Use a more targetted data structure.
2362 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
2363 Formula F = LU.Formulae[L];
2364 // Use the immediate in the scaled register.
2365 if (F.ScaledReg == OrigReg) {
2366 int64_t Offs = (uint64_t)F.AM.BaseOffs +
2367 Imm * (uint64_t)F.AM.Scale;
2368 // Don't create 50 + reg(-50).
2369 if (F.referencesReg(SE.getSCEV(
2370 ConstantInt::get(IntTy, -(uint64_t)Offs))))
2373 NewF.AM.BaseOffs = Offs;
2374 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
2375 LU.Kind, LU.AccessTy, TLI))
2377 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
2379 // If the new scale is a constant in a register, and adding the constant
2380 // value to the immediate would produce a value closer to zero than the
2381 // immediate itself, then the formula isn't worthwhile.
2382 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
2383 if (C->getValue()->getValue().isNegative() !=
2384 (NewF.AM.BaseOffs < 0) &&
2385 (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale))
2386 .ule(APInt(BitWidth, NewF.AM.BaseOffs).abs()))
2390 (void)InsertFormula(LU, LUIdx, NewF);
2392 // Use the immediate in a base register.
2393 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
2394 const SCEV *BaseReg = F.BaseRegs[N];
2395 if (BaseReg != OrigReg)
2398 NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
2399 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
2400 LU.Kind, LU.AccessTy, TLI))
2402 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
2404 // If the new formula has a constant in a register, and adding the
2405 // constant value to the immediate would produce a value closer to
2406 // zero than the immediate itself, then the formula isn't worthwhile.
2407 for (SmallVectorImpl<const SCEV *>::const_iterator
2408 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
2410 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
2411 if (C->getValue()->getValue().isNegative() !=
2412 (NewF.AM.BaseOffs < 0) &&
2413 C->getValue()->getValue().abs()
2414 .ule(APInt(BitWidth, NewF.AM.BaseOffs).abs()))
2418 (void)InsertFormula(LU, LUIdx, NewF);
2427 /// GenerateAllReuseFormulae - Generate formulae for each use.
2429 LSRInstance::GenerateAllReuseFormulae() {
2430 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
2431 // queries are more precise.
2432 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2433 LSRUse &LU = Uses[LUIdx];
2434 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2435 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
2436 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2437 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
2439 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2440 LSRUse &LU = Uses[LUIdx];
2441 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2442 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
2443 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2444 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
2445 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2446 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
2447 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2448 GenerateScales(LU, LUIdx, LU.Formulae[i]);
2450 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2451 LSRUse &LU = Uses[LUIdx];
2452 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2453 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
2456 GenerateCrossUseConstantOffsets();
2459 /// If their are multiple formulae with the same set of registers used
2460 /// by other uses, pick the best one and delete the others.
2461 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
2463 bool Changed = false;
2466 // Collect the best formula for each unique set of shared registers. This
2467 // is reset for each use.
2468 typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo>
2470 BestFormulaeTy BestFormulae;
2472 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2473 LSRUse &LU = Uses[LUIdx];
2474 FormulaSorter Sorter(L, LU, SE, DT);
2476 // Clear out the set of used regs; it will be recomputed.
2479 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
2480 FIdx != NumForms; ++FIdx) {
2481 Formula &F = LU.Formulae[FIdx];
2483 SmallVector<const SCEV *, 2> Key;
2484 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
2485 JE = F.BaseRegs.end(); J != JE; ++J) {
2486 const SCEV *Reg = *J;
2487 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
2491 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
2492 Key.push_back(F.ScaledReg);
2493 // Unstable sort by host order ok, because this is only used for
2495 std::sort(Key.begin(), Key.end());
2497 std::pair<BestFormulaeTy::const_iterator, bool> P =
2498 BestFormulae.insert(std::make_pair(Key, FIdx));
2500 Formula &Best = LU.Formulae[P.first->second];
2501 if (Sorter.operator()(F, Best))
2503 DEBUG(dbgs() << "Filtering out "; F.print(dbgs());
2505 " in favor of "; Best.print(dbgs());
2510 std::swap(F, LU.Formulae.back());
2511 LU.Formulae.pop_back();
2516 if (F.ScaledReg) LU.Regs.insert(F.ScaledReg);
2517 LU.Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
2519 BestFormulae.clear();
2522 DEBUG(if (Changed) {
2524 "After filtering out undesirable candidates:\n";
2529 /// NarrowSearchSpaceUsingHeuristics - If there are an extrordinary number of
2530 /// formulae to choose from, use some rough heuristics to prune down the number
2531 /// of formulae. This keeps the main solver from taking an extrordinary amount
2532 /// of time in some worst-case scenarios.
2533 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
2534 // This is a rough guess that seems to work fairly well.
2535 const size_t Limit = UINT16_MAX;
2537 SmallPtrSet<const SCEV *, 4> Taken;
2539 // Estimate the worst-case number of solutions we might consider. We almost
2540 // never consider this many solutions because we prune the search space,
2541 // but the pruning isn't always sufficient.
2543 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
2544 E = Uses.end(); I != E; ++I) {
2545 size_t FSize = I->Formulae.size();
2546 if (FSize >= Limit) {
2557 // Ok, we have too many of formulae on our hands to conveniently handle.
2558 // Use a rough heuristic to thin out the list.
2560 // Pick the register which is used by the most LSRUses, which is likely
2561 // to be a good reuse register candidate.
2562 const SCEV *Best = 0;
2563 unsigned BestNum = 0;
2564 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
2566 const SCEV *Reg = *I;
2567 if (Taken.count(Reg))
2572 unsigned Count = RegUses.getUsedByIndices(Reg).count();
2573 if (Count > BestNum) {
2580 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
2581 << " will yeild profitable reuse.\n");
2584 // In any use with formulae which references this register, delete formulae
2585 // which don't reference it.
2586 for (SmallVectorImpl<LSRUse>::iterator I = Uses.begin(),
2587 E = Uses.end(); I != E; ++I) {
2589 if (!LU.Regs.count(Best)) continue;
2591 // Clear out the set of used regs; it will be recomputed.
2594 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
2595 Formula &F = LU.Formulae[i];
2596 if (!F.referencesReg(Best)) {
2597 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
2598 std::swap(LU.Formulae.back(), F);
2599 LU.Formulae.pop_back();
2605 if (F.ScaledReg) LU.Regs.insert(F.ScaledReg);
2606 LU.Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
2610 DEBUG(dbgs() << "After pre-selection:\n";
2611 print_uses(dbgs()));
2615 /// SolveRecurse - This is the recursive solver.
2616 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
2618 SmallVectorImpl<const Formula *> &Workspace,
2619 const Cost &CurCost,
2620 const SmallPtrSet<const SCEV *, 16> &CurRegs,
2621 DenseSet<const SCEV *> &VisitedRegs) const {
2624 // - use more aggressive filtering
2625 // - sort the formula so that the most profitable solutions are found first
2626 // - sort the uses too
2628 // - dont compute a cost, and then compare. compare while computing a cost
2630 // - track register sets with SmallBitVector
2632 const LSRUse &LU = Uses[Workspace.size()];
2634 // If this use references any register that's already a part of the
2635 // in-progress solution, consider it a requirement that a formula must
2636 // reference that register in order to be considered. This prunes out
2637 // unprofitable searching.
2638 SmallSetVector<const SCEV *, 4> ReqRegs;
2639 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
2640 E = CurRegs.end(); I != E; ++I)
2641 if (LU.Regs.count(*I))
2644 bool AnySatisfiedReqRegs = false;
2645 SmallPtrSet<const SCEV *, 16> NewRegs;
2648 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
2649 E = LU.Formulae.end(); I != E; ++I) {
2650 const Formula &F = *I;
2652 // Ignore formulae which do not use any of the required registers.
2653 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
2654 JE = ReqRegs.end(); J != JE; ++J) {
2655 const SCEV *Reg = *J;
2656 if ((!F.ScaledReg || F.ScaledReg != Reg) &&
2657 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) ==
2661 AnySatisfiedReqRegs = true;
2663 // Evaluate the cost of the current formula. If it's already worse than
2664 // the current best, prune the search at that point.
2667 NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT);
2668 if (NewCost < SolutionCost) {
2669 Workspace.push_back(&F);
2670 if (Workspace.size() != Uses.size()) {
2671 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
2672 NewRegs, VisitedRegs);
2673 if (F.getNumRegs() == 1 && Workspace.size() == 1)
2674 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
2676 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
2677 dbgs() << ". Regs:";
2678 for (SmallPtrSet<const SCEV *, 16>::const_iterator
2679 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
2680 dbgs() << ' ' << **I;
2683 SolutionCost = NewCost;
2684 Solution = Workspace;
2686 Workspace.pop_back();
2691 // If none of the formulae had all of the required registers, relax the
2692 // constraint so that we don't exclude all formulae.
2693 if (!AnySatisfiedReqRegs) {
2699 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
2700 SmallVector<const Formula *, 8> Workspace;
2702 SolutionCost.Loose();
2704 SmallPtrSet<const SCEV *, 16> CurRegs;
2705 DenseSet<const SCEV *> VisitedRegs;
2706 Workspace.reserve(Uses.size());
2708 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
2709 CurRegs, VisitedRegs);
2711 // Ok, we've now made all our decisions.
2712 DEBUG(dbgs() << "\n"
2713 "The chosen solution requires "; SolutionCost.print(dbgs());
2715 for (size_t i = 0, e = Uses.size(); i != e; ++i) {
2717 Uses[i].print(dbgs());
2720 Solution[i]->print(dbgs());
2725 /// getImmediateDominator - A handy utility for the specific DominatorTree
2726 /// query that we need here.
2728 static BasicBlock *getImmediateDominator(BasicBlock *BB, DominatorTree &DT) {
2729 DomTreeNode *Node = DT.getNode(BB);
2730 if (!Node) return 0;
2731 Node = Node->getIDom();
2732 if (!Node) return 0;
2733 return Node->getBlock();
2736 Value *LSRInstance::Expand(const LSRFixup &LF,
2738 BasicBlock::iterator IP,
2739 Loop *L, Instruction *IVIncInsertPos,
2740 SCEVExpander &Rewriter,
2741 SmallVectorImpl<WeakVH> &DeadInsts,
2742 ScalarEvolution &SE, DominatorTree &DT) const {
2743 const LSRUse &LU = Uses[LF.LUIdx];
2745 // Then, collect some instructions which we will remain dominated by when
2746 // expanding the replacement. These must be dominated by any operands that
2747 // will be required in the expansion.
2748 SmallVector<Instruction *, 4> Inputs;
2749 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
2750 Inputs.push_back(I);
2751 if (LU.Kind == LSRUse::ICmpZero)
2752 if (Instruction *I =
2753 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
2754 Inputs.push_back(I);
2755 if (LF.PostIncLoop && !L->contains(LF.UserInst))
2756 Inputs.push_back(L->getLoopLatch()->getTerminator());
2758 // Then, climb up the immediate dominator tree as far as we can go while
2759 // still being dominated by the input positions.
2761 bool AllDominate = true;
2762 Instruction *BetterPos = 0;
2763 BasicBlock *IDom = getImmediateDominator(IP->getParent(), DT);
2765 Instruction *Tentative = IDom->getTerminator();
2766 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
2767 E = Inputs.end(); I != E; ++I) {
2768 Instruction *Inst = *I;
2769 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
2770 AllDominate = false;
2773 if (IDom == Inst->getParent() &&
2774 (!BetterPos || DT.dominates(BetterPos, Inst)))
2775 BetterPos = next(BasicBlock::iterator(Inst));
2784 while (isa<PHINode>(IP)) ++IP;
2786 // Inform the Rewriter if we have a post-increment use, so that it can
2787 // perform an advantageous expansion.
2788 Rewriter.setPostInc(LF.PostIncLoop);
2790 // This is the type that the user actually needs.
2791 const Type *OpTy = LF.OperandValToReplace->getType();
2792 // This will be the type that we'll initially expand to.
2793 const Type *Ty = F.getType();
2795 // No type known; just expand directly to the ultimate type.
2797 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
2798 // Expand directly to the ultimate type if it's the right size.
2800 // This is the type to do integer arithmetic in.
2801 const Type *IntTy = SE.getEffectiveSCEVType(Ty);
2803 // Build up a list of operands to add together to form the full base.
2804 SmallVector<const SCEV *, 8> Ops;
2806 // Expand the BaseRegs portion.
2807 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
2808 E = F.BaseRegs.end(); I != E; ++I) {
2809 const SCEV *Reg = *I;
2810 assert(!Reg->isZero() && "Zero allocated in a base register!");
2812 // If we're expanding for a post-inc user for the add-rec's loop, make the
2813 // post-inc adjustment.
2814 const SCEV *Start = Reg;
2815 while (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Start)) {
2816 if (AR->getLoop() == LF.PostIncLoop) {
2817 Reg = SE.getAddExpr(Reg, AR->getStepRecurrence(SE));
2818 // If the user is inside the loop, insert the code after the increment
2819 // so that it is dominated by its operand.
2820 if (L->contains(LF.UserInst))
2821 IP = IVIncInsertPos;
2824 Start = AR->getStart();
2827 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
2830 // Expand the ScaledReg portion.
2831 Value *ICmpScaledV = 0;
2832 if (F.AM.Scale != 0) {
2833 const SCEV *ScaledS = F.ScaledReg;
2835 // If we're expanding for a post-inc user for the add-rec's loop, make the
2836 // post-inc adjustment.
2837 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(ScaledS))
2838 if (AR->getLoop() == LF.PostIncLoop)
2839 ScaledS = SE.getAddExpr(ScaledS, AR->getStepRecurrence(SE));
2841 if (LU.Kind == LSRUse::ICmpZero) {
2842 // An interesting way of "folding" with an icmp is to use a negated
2843 // scale, which we'll implement by inserting it into the other operand
2845 assert(F.AM.Scale == -1 &&
2846 "The only scale supported by ICmpZero uses is -1!");
2847 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
2849 // Otherwise just expand the scaled register and an explicit scale,
2850 // which is expected to be matched as part of the address.
2851 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
2852 ScaledS = SE.getMulExpr(ScaledS,
2853 SE.getIntegerSCEV(F.AM.Scale,
2854 ScaledS->getType()));
2855 Ops.push_back(ScaledS);
2859 // Expand the immediate portions.
2861 Ops.push_back(SE.getSCEV(F.AM.BaseGV));
2862 int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset;
2864 if (LU.Kind == LSRUse::ICmpZero) {
2865 // The other interesting way of "folding" with an ICmpZero is to use a
2866 // negated immediate.
2868 ICmpScaledV = ConstantInt::get(IntTy, -Offset);
2870 Ops.push_back(SE.getUnknown(ICmpScaledV));
2871 ICmpScaledV = ConstantInt::get(IntTy, Offset);
2874 // Just add the immediate values. These again are expected to be matched
2875 // as part of the address.
2876 Ops.push_back(SE.getIntegerSCEV(Offset, IntTy));
2880 // Emit instructions summing all the operands.
2881 const SCEV *FullS = Ops.empty() ?
2882 SE.getIntegerSCEV(0, IntTy) :
2884 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
2886 // We're done expanding now, so reset the rewriter.
2887 Rewriter.setPostInc(0);
2889 // An ICmpZero Formula represents an ICmp which we're handling as a
2890 // comparison against zero. Now that we've expanded an expression for that
2891 // form, update the ICmp's other operand.
2892 if (LU.Kind == LSRUse::ICmpZero) {
2893 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
2894 DeadInsts.push_back(CI->getOperand(1));
2895 assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
2896 "a scale at the same time!");
2897 if (F.AM.Scale == -1) {
2898 if (ICmpScaledV->getType() != OpTy) {
2900 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
2902 ICmpScaledV, OpTy, "tmp", CI);
2905 CI->setOperand(1, ICmpScaledV);
2907 assert(F.AM.Scale == 0 &&
2908 "ICmp does not support folding a global value and "
2909 "a scale at the same time!");
2910 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
2912 if (C->getType() != OpTy)
2913 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
2917 CI->setOperand(1, C);
2924 /// Rewrite - Emit instructions for the leading candidate expression for this
2925 /// LSRUse (this is called "expanding"), and update the UserInst to reference
2926 /// the newly expanded value.
2927 void LSRInstance::Rewrite(const LSRFixup &LF,
2929 Loop *L, Instruction *IVIncInsertPos,
2930 SCEVExpander &Rewriter,
2931 SmallVectorImpl<WeakVH> &DeadInsts,
2932 ScalarEvolution &SE, DominatorTree &DT,
2934 const Type *OpTy = LF.OperandValToReplace->getType();
2936 // First, find an insertion point that dominates UserInst. For PHI nodes,
2937 // find the nearest block which dominates all the relevant uses.
2938 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
2939 DenseMap<BasicBlock *, Value *> Inserted;
2940 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
2941 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
2942 BasicBlock *BB = PN->getIncomingBlock(i);
2944 // If this is a critical edge, split the edge so that we do not insert
2945 // the code on all predecessor/successor paths. We do this unless this
2946 // is the canonical backedge for this loop, which complicates post-inc
2948 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
2949 !isa<IndirectBrInst>(BB->getTerminator()) &&
2950 (PN->getParent() != L->getHeader() || !L->contains(BB))) {
2951 // Split the critical edge.
2952 BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P);
2954 // If PN is outside of the loop and BB is in the loop, we want to
2955 // move the block to be immediately before the PHI block, not
2956 // immediately after BB.
2957 if (L->contains(BB) && !L->contains(PN))
2958 NewBB->moveBefore(PN->getParent());
2960 // Splitting the edge can reduce the number of PHI entries we have.
2961 e = PN->getNumIncomingValues();
2963 i = PN->getBasicBlockIndex(BB);
2966 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
2967 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
2969 PN->setIncomingValue(i, Pair.first->second);
2971 Value *FullV = Expand(LF, F, BB->getTerminator(), L, IVIncInsertPos,
2972 Rewriter, DeadInsts, SE, DT);
2974 // If this is reuse-by-noop-cast, insert the noop cast.
2975 if (FullV->getType() != OpTy)
2977 CastInst::Create(CastInst::getCastOpcode(FullV, false,
2979 FullV, LF.OperandValToReplace->getType(),
2980 "tmp", BB->getTerminator());
2982 PN->setIncomingValue(i, FullV);
2983 Pair.first->second = FullV;
2987 Value *FullV = Expand(LF, F, LF.UserInst, L, IVIncInsertPos,
2988 Rewriter, DeadInsts, SE, DT);
2990 // If this is reuse-by-noop-cast, insert the noop cast.
2991 if (FullV->getType() != OpTy) {
2993 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
2994 FullV, OpTy, "tmp", LF.UserInst);
2998 // Update the user. ICmpZero is handled specially here (for now) because
2999 // Expand may have updated one of the operands of the icmp already, and
3000 // its new value may happen to be equal to LF.OperandValToReplace, in
3001 // which case doing replaceUsesOfWith leads to replacing both operands
3002 // with the same value. TODO: Reorganize this.
3003 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
3004 LF.UserInst->setOperand(0, FullV);
3006 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
3009 DeadInsts.push_back(LF.OperandValToReplace);
3013 LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
3015 // Keep track of instructions we may have made dead, so that
3016 // we can remove them after we are done working.
3017 SmallVector<WeakVH, 16> DeadInsts;
3019 SCEVExpander Rewriter(SE);
3020 Rewriter.disableCanonicalMode();
3021 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
3023 // Expand the new value definitions and update the users.
3024 for (size_t i = 0, e = Fixups.size(); i != e; ++i) {
3025 size_t LUIdx = Fixups[i].LUIdx;
3027 Rewrite(Fixups[i], *Solution[LUIdx], L, IVIncInsertPos, Rewriter,
3028 DeadInsts, SE, DT, P);
3033 // Clean up after ourselves. This must be done before deleting any
3037 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
3040 LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
3041 : IU(P->getAnalysis<IVUsers>()),
3042 SE(P->getAnalysis<ScalarEvolution>()),
3043 DT(P->getAnalysis<DominatorTree>()),
3044 TLI(tli), L(l), Changed(false), IVIncInsertPos(0) {
3046 // If LoopSimplify form is not available, stay out of trouble.
3047 if (!L->isLoopSimplifyForm()) return;
3049 // If there's no interesting work to be done, bail early.
3050 if (IU.empty()) return;
3052 DEBUG(dbgs() << "\nLSR on loop ";
3053 WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
3056 /// OptimizeShadowIV - If IV is used in a int-to-float cast
3057 /// inside the loop then try to eliminate the cast opeation.
3060 // Change loop terminating condition to use the postinc iv when possible.
3061 Changed |= OptimizeLoopTermCond();
3063 CollectInterestingTypesAndFactors();
3064 CollectFixupsAndInitialFormulae();
3065 CollectLoopInvariantFixupsAndFormulae();
3067 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
3068 print_uses(dbgs()));
3070 // Now use the reuse data to generate a bunch of interesting ways
3071 // to formulate the values needed for the uses.
3072 GenerateAllReuseFormulae();
3074 DEBUG(dbgs() << "\n"
3075 "After generating reuse formulae:\n";
3076 print_uses(dbgs()));
3078 FilterOutUndesirableDedicatedRegisters();
3079 NarrowSearchSpaceUsingHeuristics();
3081 SmallVector<const Formula *, 8> Solution;
3083 assert(Solution.size() == Uses.size() && "Malformed solution!");
3085 // Release memory that is no longer needed.
3091 // Formulae should be legal.
3092 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3093 E = Uses.end(); I != E; ++I) {
3094 const LSRUse &LU = *I;
3095 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
3096 JE = LU.Formulae.end(); J != JE; ++J)
3097 assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset,
3098 LU.Kind, LU.AccessTy, TLI) &&
3099 "Illegal formula generated!");
3103 // Now that we've decided what we want, make it so.
3104 ImplementSolution(Solution, P);
3107 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
3108 if (Factors.empty() && Types.empty()) return;
3110 OS << "LSR has identified the following interesting factors and types: ";
3113 for (SmallSetVector<int64_t, 8>::const_iterator
3114 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3115 if (!First) OS << ", ";
3120 for (SmallSetVector<const Type *, 4>::const_iterator
3121 I = Types.begin(), E = Types.end(); I != E; ++I) {
3122 if (!First) OS << ", ";
3124 OS << '(' << **I << ')';
3129 void LSRInstance::print_fixups(raw_ostream &OS) const {
3130 OS << "LSR is examining the following fixup sites:\n";
3131 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
3132 E = Fixups.end(); I != E; ++I) {
3133 const LSRFixup &LF = *I;
3140 void LSRInstance::print_uses(raw_ostream &OS) const {
3141 OS << "LSR is examining the following uses:\n";
3142 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3143 E = Uses.end(); I != E; ++I) {
3144 const LSRUse &LU = *I;
3148 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
3149 JE = LU.Formulae.end(); J != JE; ++J) {
3157 void LSRInstance::print(raw_ostream &OS) const {
3158 print_factors_and_types(OS);
3163 void LSRInstance::dump() const {
3164 print(errs()); errs() << '\n';
3169 class LoopStrengthReduce : public LoopPass {
3170 /// TLI - Keep a pointer of a TargetLowering to consult for determining
3171 /// transformation profitability.
3172 const TargetLowering *const TLI;
3175 static char ID; // Pass ID, replacement for typeid
3176 explicit LoopStrengthReduce(const TargetLowering *tli = 0);
3179 bool runOnLoop(Loop *L, LPPassManager &LPM);
3180 void getAnalysisUsage(AnalysisUsage &AU) const;
3185 char LoopStrengthReduce::ID = 0;
3186 static RegisterPass<LoopStrengthReduce>
3187 X("loop-reduce", "Loop Strength Reduction");
3189 Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
3190 return new LoopStrengthReduce(TLI);
3193 LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
3194 : LoopPass(&ID), TLI(tli) {}
3196 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
3197 // We split critical edges, so we change the CFG. However, we do update
3198 // many analyses if they are around.
3199 AU.addPreservedID(LoopSimplifyID);
3200 AU.addPreserved<LoopInfo>();
3201 AU.addPreserved("domfrontier");
3203 AU.addRequiredID(LoopSimplifyID);
3204 AU.addRequired<DominatorTree>();
3205 AU.addPreserved<DominatorTree>();
3206 AU.addRequired<ScalarEvolution>();
3207 AU.addPreserved<ScalarEvolution>();
3208 AU.addRequired<IVUsers>();
3209 AU.addPreserved<IVUsers>();
3212 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
3213 bool Changed = false;
3215 // Run the main LSR transformation.
3216 Changed |= LSRInstance(TLI, L, this).getChanged();
3218 // At this point, it is worth checking to see if any recurrence PHIs are also
3219 // dead, so that we can remove them as well.
3220 Changed |= DeleteDeadPHIs(L->getHeader());