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;
110 RegUsesTy RegUsesMap;
111 SmallVector<const SCEV *, 16> RegSequence;
114 void CountRegister(const SCEV *Reg, size_t LUIdx);
115 void DropRegister(const SCEV *Reg, size_t LUIdx);
116 void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx);
118 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
120 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
124 typedef SmallVectorImpl<const SCEV *>::iterator iterator;
125 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
126 iterator begin() { return RegSequence.begin(); }
127 iterator end() { return RegSequence.end(); }
128 const_iterator begin() const { return RegSequence.begin(); }
129 const_iterator end() const { return RegSequence.end(); }
135 RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
136 std::pair<RegUsesTy::iterator, bool> Pair =
137 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
138 RegSortData &RSD = Pair.first->second;
140 RegSequence.push_back(Reg);
141 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
142 RSD.UsedByIndices.set(LUIdx);
146 RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) {
147 RegUsesTy::iterator It = RegUsesMap.find(Reg);
148 assert(It != RegUsesMap.end());
149 RegSortData &RSD = It->second;
150 assert(RSD.UsedByIndices.size() > LUIdx);
151 RSD.UsedByIndices.reset(LUIdx);
155 RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
156 assert(LUIdx <= LastLUIdx);
158 // Update RegUses. The data structure is not optimized for this purpose;
159 // we must iterate through it and update each of the bit vectors.
160 for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end();
162 SmallBitVector &UsedByIndices = I->second.UsedByIndices;
163 if (LUIdx < UsedByIndices.size())
164 UsedByIndices[LUIdx] =
165 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0;
166 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
171 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
172 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
173 if (I == RegUsesMap.end())
175 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
176 int i = UsedByIndices.find_first();
177 if (i == -1) return false;
178 if ((size_t)i != LUIdx) return true;
179 return UsedByIndices.find_next(i) != -1;
182 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
183 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
184 assert(I != RegUsesMap.end() && "Unknown register!");
185 return I->second.UsedByIndices;
188 void RegUseTracker::clear() {
195 /// Formula - This class holds information that describes a formula for
196 /// computing satisfying a use. It may include broken-out immediates and scaled
199 /// AM - This is used to represent complex addressing, as well as other kinds
200 /// of interesting uses.
201 TargetLowering::AddrMode AM;
203 /// BaseRegs - The list of "base" registers for this use. When this is
204 /// non-empty, AM.HasBaseReg should be set to true.
205 SmallVector<const SCEV *, 2> BaseRegs;
207 /// ScaledReg - The 'scaled' register for this use. This should be non-null
208 /// when AM.Scale is not zero.
209 const SCEV *ScaledReg;
211 Formula() : ScaledReg(0) {}
213 void InitialMatch(const SCEV *S, Loop *L,
214 ScalarEvolution &SE, DominatorTree &DT);
216 unsigned getNumRegs() const;
217 const Type *getType() const;
219 void DeleteBaseReg(const SCEV *&S);
221 bool referencesReg(const SCEV *S) const;
222 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
223 const RegUseTracker &RegUses) const;
225 void print(raw_ostream &OS) const;
231 /// DoInitialMatch - Recursion helper for InitialMatch.
232 static void DoInitialMatch(const SCEV *S, Loop *L,
233 SmallVectorImpl<const SCEV *> &Good,
234 SmallVectorImpl<const SCEV *> &Bad,
235 ScalarEvolution &SE, DominatorTree &DT) {
236 // Collect expressions which properly dominate the loop header.
237 if (S->properlyDominates(L->getHeader(), &DT)) {
242 // Look at add operands.
243 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
244 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
246 DoInitialMatch(*I, L, Good, Bad, SE, DT);
250 // Look at addrec operands.
251 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
252 if (!AR->getStart()->isZero()) {
253 DoInitialMatch(AR->getStart(), L, Good, Bad, SE, DT);
254 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
255 AR->getStepRecurrence(SE),
257 L, Good, Bad, SE, DT);
261 // Handle a multiplication by -1 (negation) if it didn't fold.
262 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
263 if (Mul->getOperand(0)->isAllOnesValue()) {
264 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
265 const SCEV *NewMul = SE.getMulExpr(Ops);
267 SmallVector<const SCEV *, 4> MyGood;
268 SmallVector<const SCEV *, 4> MyBad;
269 DoInitialMatch(NewMul, L, MyGood, MyBad, SE, DT);
270 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
271 SE.getEffectiveSCEVType(NewMul->getType())));
272 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
273 E = MyGood.end(); I != E; ++I)
274 Good.push_back(SE.getMulExpr(NegOne, *I));
275 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
276 E = MyBad.end(); I != E; ++I)
277 Bad.push_back(SE.getMulExpr(NegOne, *I));
281 // Ok, we can't do anything interesting. Just stuff the whole thing into a
282 // register and hope for the best.
286 /// InitialMatch - Incorporate loop-variant parts of S into this Formula,
287 /// attempting to keep all loop-invariant and loop-computable values in a
288 /// single base register.
289 void Formula::InitialMatch(const SCEV *S, Loop *L,
290 ScalarEvolution &SE, DominatorTree &DT) {
291 SmallVector<const SCEV *, 4> Good;
292 SmallVector<const SCEV *, 4> Bad;
293 DoInitialMatch(S, L, Good, Bad, SE, DT);
295 const SCEV *Sum = SE.getAddExpr(Good);
297 BaseRegs.push_back(Sum);
298 AM.HasBaseReg = true;
301 const SCEV *Sum = SE.getAddExpr(Bad);
303 BaseRegs.push_back(Sum);
304 AM.HasBaseReg = true;
308 /// getNumRegs - Return the total number of register operands used by this
309 /// formula. This does not include register uses implied by non-constant
311 unsigned Formula::getNumRegs() const {
312 return !!ScaledReg + BaseRegs.size();
315 /// getType - Return the type of this formula, if it has one, or null
316 /// otherwise. This type is meaningless except for the bit size.
317 const Type *Formula::getType() const {
318 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
319 ScaledReg ? ScaledReg->getType() :
320 AM.BaseGV ? AM.BaseGV->getType() :
324 /// DeleteBaseReg - Delete the given base reg from the BaseRegs list.
325 void Formula::DeleteBaseReg(const SCEV *&S) {
326 if (&S != &BaseRegs.back())
327 std::swap(S, BaseRegs.back());
331 /// referencesReg - Test if this formula references the given register.
332 bool Formula::referencesReg(const SCEV *S) const {
333 return S == ScaledReg ||
334 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
337 /// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
338 /// which are used by uses other than the use with the given index.
339 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
340 const RegUseTracker &RegUses) const {
342 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
344 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
345 E = BaseRegs.end(); I != E; ++I)
346 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
351 void Formula::print(raw_ostream &OS) const {
354 if (!First) OS << " + "; else First = false;
355 WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false);
357 if (AM.BaseOffs != 0) {
358 if (!First) OS << " + "; else First = false;
361 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
362 E = BaseRegs.end(); I != E; ++I) {
363 if (!First) OS << " + "; else First = false;
364 OS << "reg(" << **I << ')';
366 if (AM.HasBaseReg && BaseRegs.empty()) {
367 if (!First) OS << " + "; else First = false;
368 OS << "**error: HasBaseReg**";
369 } else if (!AM.HasBaseReg && !BaseRegs.empty()) {
370 if (!First) OS << " + "; else First = false;
371 OS << "**error: !HasBaseReg**";
374 if (!First) OS << " + "; else First = false;
375 OS << AM.Scale << "*reg(";
384 void Formula::dump() const {
385 print(errs()); errs() << '\n';
388 /// isAddRecSExtable - Return true if the given addrec can be sign-extended
389 /// without changing its value.
390 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
392 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
393 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
396 /// isAddSExtable - Return true if the given add can be sign-extended
397 /// without changing its value.
398 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
400 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
401 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
404 /// isMulSExtable - Return true if the given mul can be sign-extended
405 /// without changing its value.
406 static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
408 IntegerType::get(SE.getContext(),
409 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
410 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
413 /// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
414 /// and if the remainder is known to be zero, or null otherwise. If
415 /// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
416 /// to Y, ignoring that the multiplication may overflow, which is useful when
417 /// the result will be used in a context where the most significant bits are
419 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
421 bool IgnoreSignificantBits = false) {
422 // Handle the trivial case, which works for any SCEV type.
424 return SE.getConstant(LHS->getType(), 1);
426 // Handle a few RHS special cases.
427 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
429 const APInt &RA = RC->getValue()->getValue();
430 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
432 if (RA.isAllOnesValue())
433 return SE.getMulExpr(LHS, RC);
434 // Handle x /s 1 as x.
439 // Check for a division of a constant by a constant.
440 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
443 const APInt &LA = C->getValue()->getValue();
444 const APInt &RA = RC->getValue()->getValue();
445 if (LA.srem(RA) != 0)
447 return SE.getConstant(LA.sdiv(RA));
450 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
451 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
452 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
453 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
454 IgnoreSignificantBits);
456 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
457 IgnoreSignificantBits);
458 if (!Start) return 0;
459 return SE.getAddRecExpr(Start, Step, AR->getLoop());
464 // Distribute the sdiv over add operands, if the add doesn't overflow.
465 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
466 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
467 SmallVector<const SCEV *, 8> Ops;
468 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
470 const SCEV *Op = getExactSDiv(*I, RHS, SE,
471 IgnoreSignificantBits);
475 return SE.getAddExpr(Ops);
480 // Check for a multiply operand that we can pull RHS out of.
481 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
482 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
483 SmallVector<const SCEV *, 4> Ops;
485 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
489 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
490 IgnoreSignificantBits)) {
496 return Found ? SE.getMulExpr(Ops) : 0;
501 // Otherwise we don't know.
505 /// ExtractImmediate - If S involves the addition of a constant integer value,
506 /// return that integer value, and mutate S to point to a new SCEV with that
508 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
509 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
510 if (C->getValue()->getValue().getMinSignedBits() <= 64) {
511 S = SE.getConstant(C->getType(), 0);
512 return C->getValue()->getSExtValue();
514 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
515 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
516 int64_t Result = ExtractImmediate(NewOps.front(), SE);
518 S = SE.getAddExpr(NewOps);
520 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
521 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
522 int64_t Result = ExtractImmediate(NewOps.front(), SE);
524 S = SE.getAddRecExpr(NewOps, AR->getLoop());
530 /// ExtractSymbol - If S involves the addition of a GlobalValue address,
531 /// return that symbol, and mutate S to point to a new SCEV with that
533 static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
534 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
535 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
536 S = SE.getConstant(GV->getType(), 0);
539 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
540 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
541 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
543 S = SE.getAddExpr(NewOps);
545 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
546 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
547 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
549 S = SE.getAddRecExpr(NewOps, AR->getLoop());
555 /// isAddressUse - Returns true if the specified instruction is using the
556 /// specified value as an address.
557 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
558 bool isAddress = isa<LoadInst>(Inst);
559 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
560 if (SI->getOperand(1) == OperandVal)
562 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
563 // Addressing modes can also be folded into prefetches and a variety
565 switch (II->getIntrinsicID()) {
567 case Intrinsic::prefetch:
568 case Intrinsic::x86_sse2_loadu_dq:
569 case Intrinsic::x86_sse2_loadu_pd:
570 case Intrinsic::x86_sse_loadu_ps:
571 case Intrinsic::x86_sse_storeu_ps:
572 case Intrinsic::x86_sse2_storeu_pd:
573 case Intrinsic::x86_sse2_storeu_dq:
574 case Intrinsic::x86_sse2_storel_dq:
575 if (II->getArgOperand(0) == OperandVal)
583 /// getAccessType - Return the type of the memory being accessed.
584 static const Type *getAccessType(const Instruction *Inst) {
585 const Type *AccessTy = Inst->getType();
586 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
587 AccessTy = SI->getOperand(0)->getType();
588 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
589 // Addressing modes can also be folded into prefetches and a variety
591 switch (II->getIntrinsicID()) {
593 case Intrinsic::x86_sse_storeu_ps:
594 case Intrinsic::x86_sse2_storeu_pd:
595 case Intrinsic::x86_sse2_storeu_dq:
596 case Intrinsic::x86_sse2_storel_dq:
597 AccessTy = II->getArgOperand(0)->getType();
602 // All pointers have the same requirements, so canonicalize them to an
603 // arbitrary pointer type to minimize variation.
604 if (const PointerType *PTy = dyn_cast<PointerType>(AccessTy))
605 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
606 PTy->getAddressSpace());
611 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
612 /// specified set are trivially dead, delete them and see if this makes any of
613 /// their operands subsequently dead.
615 DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
616 bool Changed = false;
618 while (!DeadInsts.empty()) {
619 Instruction *I = dyn_cast_or_null<Instruction>(&*DeadInsts.pop_back_val());
621 if (I == 0 || !isInstructionTriviallyDead(I))
624 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
625 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
628 DeadInsts.push_back(U);
631 I->eraseFromParent();
640 /// Cost - This class is used to measure and compare candidate formulae.
642 /// TODO: Some of these could be merged. Also, a lexical ordering
643 /// isn't always optimal.
647 unsigned NumBaseAdds;
653 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
656 bool operator<(const Cost &Other) const;
660 void RateFormula(const Formula &F,
661 SmallPtrSet<const SCEV *, 16> &Regs,
662 const DenseSet<const SCEV *> &VisitedRegs,
664 const SmallVectorImpl<int64_t> &Offsets,
665 ScalarEvolution &SE, DominatorTree &DT);
667 void print(raw_ostream &OS) const;
671 void RateRegister(const SCEV *Reg,
672 SmallPtrSet<const SCEV *, 16> &Regs,
674 ScalarEvolution &SE, DominatorTree &DT);
675 void RatePrimaryRegister(const SCEV *Reg,
676 SmallPtrSet<const SCEV *, 16> &Regs,
678 ScalarEvolution &SE, DominatorTree &DT);
683 /// RateRegister - Tally up interesting quantities from the given register.
684 void Cost::RateRegister(const SCEV *Reg,
685 SmallPtrSet<const SCEV *, 16> &Regs,
687 ScalarEvolution &SE, DominatorTree &DT) {
688 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
689 if (AR->getLoop() == L)
690 AddRecCost += 1; /// TODO: This should be a function of the stride.
692 // If this is an addrec for a loop that's already been visited by LSR,
693 // don't second-guess its addrec phi nodes. LSR isn't currently smart
694 // enough to reason about more than one loop at a time. Consider these
695 // registers free and leave them alone.
696 else if (L->contains(AR->getLoop()) ||
697 (!AR->getLoop()->contains(L) &&
698 DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) {
699 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
700 PHINode *PN = dyn_cast<PHINode>(I); ++I)
701 if (SE.isSCEVable(PN->getType()) &&
702 (SE.getEffectiveSCEVType(PN->getType()) ==
703 SE.getEffectiveSCEVType(AR->getType())) &&
704 SE.getSCEV(PN) == AR)
707 // If this isn't one of the addrecs that the loop already has, it
708 // would require a costly new phi and add. TODO: This isn't
709 // precisely modeled right now.
711 if (!Regs.count(AR->getStart()))
712 RateRegister(AR->getStart(), Regs, L, SE, DT);
715 // Add the step value register, if it needs one.
716 // TODO: The non-affine case isn't precisely modeled here.
717 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
718 if (!Regs.count(AR->getStart()))
719 RateRegister(AR->getOperand(1), Regs, L, SE, DT);
723 // Rough heuristic; favor registers which don't require extra setup
724 // instructions in the preheader.
725 if (!isa<SCEVUnknown>(Reg) &&
726 !isa<SCEVConstant>(Reg) &&
727 !(isa<SCEVAddRecExpr>(Reg) &&
728 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
729 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
733 /// RatePrimaryRegister - Record this register in the set. If we haven't seen it
735 void Cost::RatePrimaryRegister(const SCEV *Reg,
736 SmallPtrSet<const SCEV *, 16> &Regs,
738 ScalarEvolution &SE, DominatorTree &DT) {
739 if (Regs.insert(Reg))
740 RateRegister(Reg, Regs, L, SE, DT);
743 void Cost::RateFormula(const Formula &F,
744 SmallPtrSet<const SCEV *, 16> &Regs,
745 const DenseSet<const SCEV *> &VisitedRegs,
747 const SmallVectorImpl<int64_t> &Offsets,
748 ScalarEvolution &SE, DominatorTree &DT) {
749 // Tally up the registers.
750 if (const SCEV *ScaledReg = F.ScaledReg) {
751 if (VisitedRegs.count(ScaledReg)) {
755 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT);
757 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
758 E = F.BaseRegs.end(); I != E; ++I) {
759 const SCEV *BaseReg = *I;
760 if (VisitedRegs.count(BaseReg)) {
764 RatePrimaryRegister(BaseReg, Regs, L, SE, DT);
766 NumIVMuls += isa<SCEVMulExpr>(BaseReg) &&
767 BaseReg->hasComputableLoopEvolution(L);
770 if (F.BaseRegs.size() > 1)
771 NumBaseAdds += F.BaseRegs.size() - 1;
773 // Tally up the non-zero immediates.
774 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
775 E = Offsets.end(); I != E; ++I) {
776 int64_t Offset = (uint64_t)*I + F.AM.BaseOffs;
778 ImmCost += 64; // Handle symbolic values conservatively.
779 // TODO: This should probably be the pointer size.
780 else if (Offset != 0)
781 ImmCost += APInt(64, Offset, true).getMinSignedBits();
785 /// Loose - Set this cost to a loosing value.
795 /// operator< - Choose the lower cost.
796 bool Cost::operator<(const Cost &Other) const {
797 if (NumRegs != Other.NumRegs)
798 return NumRegs < Other.NumRegs;
799 if (AddRecCost != Other.AddRecCost)
800 return AddRecCost < Other.AddRecCost;
801 if (NumIVMuls != Other.NumIVMuls)
802 return NumIVMuls < Other.NumIVMuls;
803 if (NumBaseAdds != Other.NumBaseAdds)
804 return NumBaseAdds < Other.NumBaseAdds;
805 if (ImmCost != Other.ImmCost)
806 return ImmCost < Other.ImmCost;
807 if (SetupCost != Other.SetupCost)
808 return SetupCost < Other.SetupCost;
812 void Cost::print(raw_ostream &OS) const {
813 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
815 OS << ", with addrec cost " << AddRecCost;
817 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
818 if (NumBaseAdds != 0)
819 OS << ", plus " << NumBaseAdds << " base add"
820 << (NumBaseAdds == 1 ? "" : "s");
822 OS << ", plus " << ImmCost << " imm cost";
824 OS << ", plus " << SetupCost << " setup cost";
827 void Cost::dump() const {
828 print(errs()); errs() << '\n';
833 /// LSRFixup - An operand value in an instruction which is to be replaced
834 /// with some equivalent, possibly strength-reduced, replacement.
836 /// UserInst - The instruction which will be updated.
837 Instruction *UserInst;
839 /// OperandValToReplace - The operand of the instruction which will
840 /// be replaced. The operand may be used more than once; every instance
841 /// will be replaced.
842 Value *OperandValToReplace;
844 /// PostIncLoops - If this user is to use the post-incremented value of an
845 /// induction variable, this variable is non-null and holds the loop
846 /// associated with the induction variable.
847 PostIncLoopSet PostIncLoops;
849 /// LUIdx - The index of the LSRUse describing the expression which
850 /// this fixup needs, minus an offset (below).
853 /// Offset - A constant offset to be added to the LSRUse expression.
854 /// This allows multiple fixups to share the same LSRUse with different
855 /// offsets, for example in an unrolled loop.
858 bool isUseFullyOutsideLoop(const Loop *L) const;
862 void print(raw_ostream &OS) const;
869 : UserInst(0), OperandValToReplace(0), LUIdx(~size_t(0)), Offset(0) {}
871 /// isUseFullyOutsideLoop - Test whether this fixup always uses its
872 /// value outside of the given loop.
873 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
874 // PHI nodes use their value in their incoming blocks.
875 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
876 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
877 if (PN->getIncomingValue(i) == OperandValToReplace &&
878 L->contains(PN->getIncomingBlock(i)))
883 return !L->contains(UserInst);
886 void LSRFixup::print(raw_ostream &OS) const {
888 // Store is common and interesting enough to be worth special-casing.
889 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
891 WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false);
892 } else if (UserInst->getType()->isVoidTy())
893 OS << UserInst->getOpcodeName();
895 WriteAsOperand(OS, UserInst, /*PrintType=*/false);
897 OS << ", OperandValToReplace=";
898 WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false);
900 for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(),
901 E = PostIncLoops.end(); I != E; ++I) {
902 OS << ", PostIncLoop=";
903 WriteAsOperand(OS, (*I)->getHeader(), /*PrintType=*/false);
906 if (LUIdx != ~size_t(0))
907 OS << ", LUIdx=" << LUIdx;
910 OS << ", Offset=" << Offset;
913 void LSRFixup::dump() const {
914 print(errs()); errs() << '\n';
919 /// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
920 /// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
921 struct UniquifierDenseMapInfo {
922 static SmallVector<const SCEV *, 2> getEmptyKey() {
923 SmallVector<const SCEV *, 2> V;
924 V.push_back(reinterpret_cast<const SCEV *>(-1));
928 static SmallVector<const SCEV *, 2> getTombstoneKey() {
929 SmallVector<const SCEV *, 2> V;
930 V.push_back(reinterpret_cast<const SCEV *>(-2));
934 static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) {
936 for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(),
937 E = V.end(); I != E; ++I)
938 Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I);
942 static bool isEqual(const SmallVector<const SCEV *, 2> &LHS,
943 const SmallVector<const SCEV *, 2> &RHS) {
948 /// LSRUse - This class holds the state that LSR keeps for each use in
949 /// IVUsers, as well as uses invented by LSR itself. It includes information
950 /// about what kinds of things can be folded into the user, information about
951 /// the user itself, and information about how the use may be satisfied.
952 /// TODO: Represent multiple users of the same expression in common?
954 DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier;
957 /// KindType - An enum for a kind of use, indicating what types of
958 /// scaled and immediate operands it might support.
960 Basic, ///< A normal use, with no folding.
961 Special, ///< A special case of basic, allowing -1 scales.
962 Address, ///< An address use; folding according to TargetLowering
963 ICmpZero ///< An equality icmp with both operands folded into one.
964 // TODO: Add a generic icmp too?
968 const Type *AccessTy;
970 SmallVector<int64_t, 8> Offsets;
974 /// AllFixupsOutsideLoop - This records whether all of the fixups using this
975 /// LSRUse are outside of the loop, in which case some special-case heuristics
977 bool AllFixupsOutsideLoop;
979 /// WidestFixupType - This records the widest use type for any fixup using
980 /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different
981 /// max fixup widths to be equivalent, because the narrower one may be relying
982 /// on the implicit truncation to truncate away bogus bits.
983 const Type *WidestFixupType;
985 /// Formulae - A list of ways to build a value that can satisfy this user.
986 /// After the list is populated, one of these is selected heuristically and
987 /// used to formulate a replacement for OperandValToReplace in UserInst.
988 SmallVector<Formula, 12> Formulae;
990 /// Regs - The set of register candidates used by all formulae in this LSRUse.
991 SmallPtrSet<const SCEV *, 4> Regs;
993 LSRUse(KindType K, const Type *T) : Kind(K), AccessTy(T),
994 MinOffset(INT64_MAX),
995 MaxOffset(INT64_MIN),
996 AllFixupsOutsideLoop(true),
997 WidestFixupType(0) {}
999 bool HasFormulaWithSameRegs(const Formula &F) const;
1000 bool InsertFormula(const Formula &F);
1001 void DeleteFormula(Formula &F);
1002 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1004 void print(raw_ostream &OS) const;
1010 /// HasFormula - Test whether this use as a formula which has the same
1011 /// registers as the given formula.
1012 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1013 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
1014 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1015 // Unstable sort by host order ok, because this is only used for uniquifying.
1016 std::sort(Key.begin(), Key.end());
1017 return Uniquifier.count(Key);
1020 /// InsertFormula - If the given formula has not yet been inserted, add it to
1021 /// the list, and return true. Return false otherwise.
1022 bool LSRUse::InsertFormula(const Formula &F) {
1023 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
1024 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1025 // Unstable sort by host order ok, because this is only used for uniquifying.
1026 std::sort(Key.begin(), Key.end());
1028 if (!Uniquifier.insert(Key).second)
1031 // Using a register to hold the value of 0 is not profitable.
1032 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1033 "Zero allocated in a scaled register!");
1035 for (SmallVectorImpl<const SCEV *>::const_iterator I =
1036 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
1037 assert(!(*I)->isZero() && "Zero allocated in a base register!");
1040 // Add the formula to the list.
1041 Formulae.push_back(F);
1043 // Record registers now being used by this use.
1044 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1045 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1050 /// DeleteFormula - Remove the given formula from this use's list.
1051 void LSRUse::DeleteFormula(Formula &F) {
1052 if (&F != &Formulae.back())
1053 std::swap(F, Formulae.back());
1054 Formulae.pop_back();
1055 assert(!Formulae.empty() && "LSRUse has no formulae left!");
1058 /// RecomputeRegs - Recompute the Regs field, and update RegUses.
1059 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1060 // Now that we've filtered out some formulae, recompute the Regs set.
1061 SmallPtrSet<const SCEV *, 4> OldRegs = Regs;
1063 for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(),
1064 E = Formulae.end(); I != E; ++I) {
1065 const Formula &F = *I;
1066 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1067 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1070 // Update the RegTracker.
1071 for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(),
1072 E = OldRegs.end(); I != E; ++I)
1073 if (!Regs.count(*I))
1074 RegUses.DropRegister(*I, LUIdx);
1077 void LSRUse::print(raw_ostream &OS) const {
1078 OS << "LSR Use: Kind=";
1080 case Basic: OS << "Basic"; break;
1081 case Special: OS << "Special"; break;
1082 case ICmpZero: OS << "ICmpZero"; break;
1084 OS << "Address of ";
1085 if (AccessTy->isPointerTy())
1086 OS << "pointer"; // the full pointer type could be really verbose
1091 OS << ", Offsets={";
1092 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
1093 E = Offsets.end(); I != E; ++I) {
1095 if (llvm::next(I) != E)
1100 if (AllFixupsOutsideLoop)
1101 OS << ", all-fixups-outside-loop";
1103 if (WidestFixupType)
1104 OS << ", widest fixup type: " << *WidestFixupType;
1107 void LSRUse::dump() const {
1108 print(errs()); errs() << '\n';
1111 /// isLegalUse - Test whether the use described by AM is "legal", meaning it can
1112 /// be completely folded into the user instruction at isel time. This includes
1113 /// address-mode folding and special icmp tricks.
1114 static bool isLegalUse(const TargetLowering::AddrMode &AM,
1115 LSRUse::KindType Kind, const Type *AccessTy,
1116 const TargetLowering *TLI) {
1118 case LSRUse::Address:
1119 // If we have low-level target information, ask the target if it can
1120 // completely fold this address.
1121 if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy);
1123 // Otherwise, just guess that reg+reg addressing is legal.
1124 return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1;
1126 case LSRUse::ICmpZero:
1127 // There's not even a target hook for querying whether it would be legal to
1128 // fold a GV into an ICmp.
1132 // ICmp only has two operands; don't allow more than two non-trivial parts.
1133 if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0)
1136 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1137 // putting the scaled register in the other operand of the icmp.
1138 if (AM.Scale != 0 && AM.Scale != -1)
1141 // If we have low-level target information, ask the target if it can fold an
1142 // integer immediate on an icmp.
1143 if (AM.BaseOffs != 0) {
1144 if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs);
1151 // Only handle single-register values.
1152 return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
1154 case LSRUse::Special:
1155 // Only handle -1 scales, or no scale.
1156 return AM.Scale == 0 || AM.Scale == -1;
1162 static bool isLegalUse(TargetLowering::AddrMode AM,
1163 int64_t MinOffset, int64_t MaxOffset,
1164 LSRUse::KindType Kind, const Type *AccessTy,
1165 const TargetLowering *TLI) {
1166 // Check for overflow.
1167 if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) !=
1170 AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset;
1171 if (isLegalUse(AM, Kind, AccessTy, TLI)) {
1172 AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset;
1173 // Check for overflow.
1174 if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) !=
1177 AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset;
1178 return isLegalUse(AM, Kind, AccessTy, TLI);
1183 static bool isAlwaysFoldable(int64_t BaseOffs,
1184 GlobalValue *BaseGV,
1186 LSRUse::KindType Kind, const Type *AccessTy,
1187 const TargetLowering *TLI) {
1188 // Fast-path: zero is always foldable.
1189 if (BaseOffs == 0 && !BaseGV) return true;
1191 // Conservatively, create an address with an immediate and a
1192 // base and a scale.
1193 TargetLowering::AddrMode AM;
1194 AM.BaseOffs = BaseOffs;
1196 AM.HasBaseReg = HasBaseReg;
1197 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1199 // Canonicalize a scale of 1 to a base register if the formula doesn't
1200 // already have a base register.
1201 if (!AM.HasBaseReg && AM.Scale == 1) {
1203 AM.HasBaseReg = true;
1206 return isLegalUse(AM, Kind, AccessTy, TLI);
1209 static bool isAlwaysFoldable(const SCEV *S,
1210 int64_t MinOffset, int64_t MaxOffset,
1212 LSRUse::KindType Kind, const Type *AccessTy,
1213 const TargetLowering *TLI,
1214 ScalarEvolution &SE) {
1215 // Fast-path: zero is always foldable.
1216 if (S->isZero()) return true;
1218 // Conservatively, create an address with an immediate and a
1219 // base and a scale.
1220 int64_t BaseOffs = ExtractImmediate(S, SE);
1221 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1223 // If there's anything else involved, it's not foldable.
1224 if (!S->isZero()) return false;
1226 // Fast-path: zero is always foldable.
1227 if (BaseOffs == 0 && !BaseGV) return true;
1229 // Conservatively, create an address with an immediate and a
1230 // base and a scale.
1231 TargetLowering::AddrMode AM;
1232 AM.BaseOffs = BaseOffs;
1234 AM.HasBaseReg = HasBaseReg;
1235 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1237 return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI);
1242 /// UseMapDenseMapInfo - A DenseMapInfo implementation for holding
1243 /// DenseMaps and DenseSets of pairs of const SCEV* and LSRUse::Kind.
1244 struct UseMapDenseMapInfo {
1245 static std::pair<const SCEV *, LSRUse::KindType> getEmptyKey() {
1246 return std::make_pair(reinterpret_cast<const SCEV *>(-1), LSRUse::Basic);
1249 static std::pair<const SCEV *, LSRUse::KindType> getTombstoneKey() {
1250 return std::make_pair(reinterpret_cast<const SCEV *>(-2), LSRUse::Basic);
1254 getHashValue(const std::pair<const SCEV *, LSRUse::KindType> &V) {
1255 unsigned Result = DenseMapInfo<const SCEV *>::getHashValue(V.first);
1256 Result ^= DenseMapInfo<unsigned>::getHashValue(unsigned(V.second));
1260 static bool isEqual(const std::pair<const SCEV *, LSRUse::KindType> &LHS,
1261 const std::pair<const SCEV *, LSRUse::KindType> &RHS) {
1266 /// FormulaSorter - This class implements an ordering for formulae which sorts
1267 /// the by their standalone cost.
1268 class FormulaSorter {
1269 /// These two sets are kept empty, so that we compute standalone costs.
1270 DenseSet<const SCEV *> VisitedRegs;
1271 SmallPtrSet<const SCEV *, 16> Regs;
1274 ScalarEvolution &SE;
1278 FormulaSorter(Loop *l, LSRUse &lu, ScalarEvolution &se, DominatorTree &dt)
1279 : L(l), LU(&lu), SE(se), DT(dt) {}
1281 bool operator()(const Formula &A, const Formula &B) {
1283 CostA.RateFormula(A, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
1286 CostB.RateFormula(B, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
1288 return CostA < CostB;
1292 /// LSRInstance - This class holds state for the main loop strength reduction
1296 ScalarEvolution &SE;
1299 const TargetLowering *const TLI;
1303 /// IVIncInsertPos - This is the insert position that the current loop's
1304 /// induction variable increment should be placed. In simple loops, this is
1305 /// the latch block's terminator. But in more complicated cases, this is a
1306 /// position which will dominate all the in-loop post-increment users.
1307 Instruction *IVIncInsertPos;
1309 /// Factors - Interesting factors between use strides.
1310 SmallSetVector<int64_t, 8> Factors;
1312 /// Types - Interesting use types, to facilitate truncation reuse.
1313 SmallSetVector<const Type *, 4> Types;
1315 /// Fixups - The list of operands which are to be replaced.
1316 SmallVector<LSRFixup, 16> Fixups;
1318 /// Uses - The list of interesting uses.
1319 SmallVector<LSRUse, 16> Uses;
1321 /// RegUses - Track which uses use which register candidates.
1322 RegUseTracker RegUses;
1324 void OptimizeShadowIV();
1325 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1326 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1327 void OptimizeLoopTermCond();
1329 void CollectInterestingTypesAndFactors();
1330 void CollectFixupsAndInitialFormulae();
1332 LSRFixup &getNewFixup() {
1333 Fixups.push_back(LSRFixup());
1334 return Fixups.back();
1337 // Support for sharing of LSRUses between LSRFixups.
1338 typedef DenseMap<std::pair<const SCEV *, LSRUse::KindType>,
1340 UseMapDenseMapInfo> UseMapTy;
1343 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1344 LSRUse::KindType Kind, const Type *AccessTy);
1346 std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1347 LSRUse::KindType Kind,
1348 const Type *AccessTy);
1350 void DeleteUse(LSRUse &LU, size_t LUIdx);
1352 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1355 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1356 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1357 void CountRegisters(const Formula &F, size_t LUIdx);
1358 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1360 void CollectLoopInvariantFixupsAndFormulae();
1362 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1363 unsigned Depth = 0);
1364 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1365 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1366 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1367 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1368 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1369 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1370 void GenerateCrossUseConstantOffsets();
1371 void GenerateAllReuseFormulae();
1373 void FilterOutUndesirableDedicatedRegisters();
1375 size_t EstimateSearchSpaceComplexity() const;
1376 void NarrowSearchSpaceByDetectingSupersets();
1377 void NarrowSearchSpaceByCollapsingUnrolledCode();
1378 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1379 void NarrowSearchSpaceByPickingWinnerRegs();
1380 void NarrowSearchSpaceUsingHeuristics();
1382 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1384 SmallVectorImpl<const Formula *> &Workspace,
1385 const Cost &CurCost,
1386 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1387 DenseSet<const SCEV *> &VisitedRegs) const;
1388 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1390 BasicBlock::iterator
1391 HoistInsertPosition(BasicBlock::iterator IP,
1392 const SmallVectorImpl<Instruction *> &Inputs) const;
1393 BasicBlock::iterator AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1395 const LSRUse &LU) const;
1397 Value *Expand(const LSRFixup &LF,
1399 BasicBlock::iterator IP,
1400 SCEVExpander &Rewriter,
1401 SmallVectorImpl<WeakVH> &DeadInsts) const;
1402 void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
1404 SCEVExpander &Rewriter,
1405 SmallVectorImpl<WeakVH> &DeadInsts,
1407 void Rewrite(const LSRFixup &LF,
1409 SCEVExpander &Rewriter,
1410 SmallVectorImpl<WeakVH> &DeadInsts,
1412 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1415 LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
1417 bool getChanged() const { return Changed; }
1419 void print_factors_and_types(raw_ostream &OS) const;
1420 void print_fixups(raw_ostream &OS) const;
1421 void print_uses(raw_ostream &OS) const;
1422 void print(raw_ostream &OS) const;
1428 /// OptimizeShadowIV - If IV is used in a int-to-float cast
1429 /// inside the loop then try to eliminate the cast operation.
1430 void LSRInstance::OptimizeShadowIV() {
1431 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1432 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1435 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1436 UI != E; /* empty */) {
1437 IVUsers::const_iterator CandidateUI = UI;
1439 Instruction *ShadowUse = CandidateUI->getUser();
1440 const Type *DestTy = NULL;
1442 /* If shadow use is a int->float cast then insert a second IV
1443 to eliminate this cast.
1445 for (unsigned i = 0; i < n; ++i)
1451 for (unsigned i = 0; i < n; ++i, ++d)
1454 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser()))
1455 DestTy = UCast->getDestTy();
1456 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser()))
1457 DestTy = SCast->getDestTy();
1458 if (!DestTy) continue;
1461 // If target does not support DestTy natively then do not apply
1462 // this transformation.
1463 EVT DVT = TLI->getValueType(DestTy);
1464 if (!TLI->isTypeLegal(DVT)) continue;
1467 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1469 if (PH->getNumIncomingValues() != 2) continue;
1471 const Type *SrcTy = PH->getType();
1472 int Mantissa = DestTy->getFPMantissaWidth();
1473 if (Mantissa == -1) continue;
1474 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1477 unsigned Entry, Latch;
1478 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1486 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1487 if (!Init) continue;
1488 Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
1490 BinaryOperator *Incr =
1491 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1492 if (!Incr) continue;
1493 if (Incr->getOpcode() != Instruction::Add
1494 && Incr->getOpcode() != Instruction::Sub)
1497 /* Initialize new IV, double d = 0.0 in above example. */
1498 ConstantInt *C = NULL;
1499 if (Incr->getOperand(0) == PH)
1500 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1501 else if (Incr->getOperand(1) == PH)
1502 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1508 // Ignore negative constants, as the code below doesn't handle them
1509 // correctly. TODO: Remove this restriction.
1510 if (!C->getValue().isStrictlyPositive()) continue;
1512 /* Add new PHINode. */
1513 PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
1515 /* create new increment. '++d' in above example. */
1516 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1517 BinaryOperator *NewIncr =
1518 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1519 Instruction::FAdd : Instruction::FSub,
1520 NewPH, CFP, "IV.S.next.", Incr);
1522 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1523 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1525 /* Remove cast operation */
1526 ShadowUse->replaceAllUsesWith(NewPH);
1527 ShadowUse->eraseFromParent();
1533 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1534 /// set the IV user and stride information and return true, otherwise return
1536 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
1537 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1538 if (UI->getUser() == Cond) {
1539 // NOTE: we could handle setcc instructions with multiple uses here, but
1540 // InstCombine does it as well for simple uses, it's not clear that it
1541 // occurs enough in real life to handle.
1548 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
1549 /// a max computation.
1551 /// This is a narrow solution to a specific, but acute, problem. For loops
1557 /// } while (++i < n);
1559 /// the trip count isn't just 'n', because 'n' might not be positive. And
1560 /// unfortunately this can come up even for loops where the user didn't use
1561 /// a C do-while loop. For example, seemingly well-behaved top-test loops
1562 /// will commonly be lowered like this:
1568 /// } while (++i < n);
1571 /// and then it's possible for subsequent optimization to obscure the if
1572 /// test in such a way that indvars can't find it.
1574 /// When indvars can't find the if test in loops like this, it creates a
1575 /// max expression, which allows it to give the loop a canonical
1576 /// induction variable:
1579 /// max = n < 1 ? 1 : n;
1582 /// } while (++i != max);
1584 /// Canonical induction variables are necessary because the loop passes
1585 /// are designed around them. The most obvious example of this is the
1586 /// LoopInfo analysis, which doesn't remember trip count values. It
1587 /// expects to be able to rediscover the trip count each time it is
1588 /// needed, and it does this using a simple analysis that only succeeds if
1589 /// the loop has a canonical induction variable.
1591 /// However, when it comes time to generate code, the maximum operation
1592 /// can be quite costly, especially if it's inside of an outer loop.
1594 /// This function solves this problem by detecting this type of loop and
1595 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1596 /// the instructions for the maximum computation.
1598 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1599 // Check that the loop matches the pattern we're looking for.
1600 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1601 Cond->getPredicate() != CmpInst::ICMP_NE)
1604 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
1605 if (!Sel || !Sel->hasOneUse()) return Cond;
1607 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1608 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1610 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
1612 // Add one to the backedge-taken count to get the trip count.
1613 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
1614 if (IterationCount != SE.getSCEV(Sel)) return Cond;
1616 // Check for a max calculation that matches the pattern. There's no check
1617 // for ICMP_ULE here because the comparison would be with zero, which
1618 // isn't interesting.
1619 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
1620 const SCEVNAryExpr *Max = 0;
1621 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
1622 Pred = ICmpInst::ICMP_SLE;
1624 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
1625 Pred = ICmpInst::ICMP_SLT;
1627 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
1628 Pred = ICmpInst::ICMP_ULT;
1635 // To handle a max with more than two operands, this optimization would
1636 // require additional checking and setup.
1637 if (Max->getNumOperands() != 2)
1640 const SCEV *MaxLHS = Max->getOperand(0);
1641 const SCEV *MaxRHS = Max->getOperand(1);
1643 // ScalarEvolution canonicalizes constants to the left. For < and >, look
1644 // for a comparison with 1. For <= and >=, a comparison with zero.
1646 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
1649 // Check the relevant induction variable for conformance to
1651 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
1652 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
1653 if (!AR || !AR->isAffine() ||
1654 AR->getStart() != One ||
1655 AR->getStepRecurrence(SE) != One)
1658 assert(AR->getLoop() == L &&
1659 "Loop condition operand is an addrec in a different loop!");
1661 // Check the right operand of the select, and remember it, as it will
1662 // be used in the new comparison instruction.
1664 if (ICmpInst::isTrueWhenEqual(Pred)) {
1665 // Look for n+1, and grab n.
1666 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
1667 if (isa<ConstantInt>(BO->getOperand(1)) &&
1668 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1669 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1670 NewRHS = BO->getOperand(0);
1671 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
1672 if (isa<ConstantInt>(BO->getOperand(1)) &&
1673 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1674 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1675 NewRHS = BO->getOperand(0);
1678 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
1679 NewRHS = Sel->getOperand(1);
1680 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
1681 NewRHS = Sel->getOperand(2);
1682 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
1683 NewRHS = SU->getValue();
1685 // Max doesn't match expected pattern.
1688 // Determine the new comparison opcode. It may be signed or unsigned,
1689 // and the original comparison may be either equality or inequality.
1690 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
1691 Pred = CmpInst::getInversePredicate(Pred);
1693 // Ok, everything looks ok to change the condition into an SLT or SGE and
1694 // delete the max calculation.
1696 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
1698 // Delete the max calculation instructions.
1699 Cond->replaceAllUsesWith(NewCond);
1700 CondUse->setUser(NewCond);
1701 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
1702 Cond->eraseFromParent();
1703 Sel->eraseFromParent();
1704 if (Cmp->use_empty())
1705 Cmp->eraseFromParent();
1709 /// OptimizeLoopTermCond - Change loop terminating condition to use the
1710 /// postinc iv when possible.
1712 LSRInstance::OptimizeLoopTermCond() {
1713 SmallPtrSet<Instruction *, 4> PostIncs;
1715 BasicBlock *LatchBlock = L->getLoopLatch();
1716 SmallVector<BasicBlock*, 8> ExitingBlocks;
1717 L->getExitingBlocks(ExitingBlocks);
1719 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
1720 BasicBlock *ExitingBlock = ExitingBlocks[i];
1722 // Get the terminating condition for the loop if possible. If we
1723 // can, we want to change it to use a post-incremented version of its
1724 // induction variable, to allow coalescing the live ranges for the IV into
1725 // one register value.
1727 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
1730 // FIXME: Overly conservative, termination condition could be an 'or' etc..
1731 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
1734 // Search IVUsesByStride to find Cond's IVUse if there is one.
1735 IVStrideUse *CondUse = 0;
1736 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
1737 if (!FindIVUserForCond(Cond, CondUse))
1740 // If the trip count is computed in terms of a max (due to ScalarEvolution
1741 // being unable to find a sufficient guard, for example), change the loop
1742 // comparison to use SLT or ULT instead of NE.
1743 // One consequence of doing this now is that it disrupts the count-down
1744 // optimization. That's not always a bad thing though, because in such
1745 // cases it may still be worthwhile to avoid a max.
1746 Cond = OptimizeMax(Cond, CondUse);
1748 // If this exiting block dominates the latch block, it may also use
1749 // the post-inc value if it won't be shared with other uses.
1750 // Check for dominance.
1751 if (!DT.dominates(ExitingBlock, LatchBlock))
1754 // Conservatively avoid trying to use the post-inc value in non-latch
1755 // exits if there may be pre-inc users in intervening blocks.
1756 if (LatchBlock != ExitingBlock)
1757 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1758 // Test if the use is reachable from the exiting block. This dominator
1759 // query is a conservative approximation of reachability.
1760 if (&*UI != CondUse &&
1761 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
1762 // Conservatively assume there may be reuse if the quotient of their
1763 // strides could be a legal scale.
1764 const SCEV *A = IU.getStride(*CondUse, L);
1765 const SCEV *B = IU.getStride(*UI, L);
1766 if (!A || !B) continue;
1767 if (SE.getTypeSizeInBits(A->getType()) !=
1768 SE.getTypeSizeInBits(B->getType())) {
1769 if (SE.getTypeSizeInBits(A->getType()) >
1770 SE.getTypeSizeInBits(B->getType()))
1771 B = SE.getSignExtendExpr(B, A->getType());
1773 A = SE.getSignExtendExpr(A, B->getType());
1775 if (const SCEVConstant *D =
1776 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
1777 const ConstantInt *C = D->getValue();
1778 // Stride of one or negative one can have reuse with non-addresses.
1779 if (C->isOne() || C->isAllOnesValue())
1780 goto decline_post_inc;
1781 // Avoid weird situations.
1782 if (C->getValue().getMinSignedBits() >= 64 ||
1783 C->getValue().isMinSignedValue())
1784 goto decline_post_inc;
1785 // Without TLI, assume that any stride might be valid, and so any
1786 // use might be shared.
1788 goto decline_post_inc;
1789 // Check for possible scaled-address reuse.
1790 const Type *AccessTy = getAccessType(UI->getUser());
1791 TargetLowering::AddrMode AM;
1792 AM.Scale = C->getSExtValue();
1793 if (TLI->isLegalAddressingMode(AM, AccessTy))
1794 goto decline_post_inc;
1795 AM.Scale = -AM.Scale;
1796 if (TLI->isLegalAddressingMode(AM, AccessTy))
1797 goto decline_post_inc;
1801 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
1804 // It's possible for the setcc instruction to be anywhere in the loop, and
1805 // possible for it to have multiple users. If it is not immediately before
1806 // the exiting block branch, move it.
1807 if (&*++BasicBlock::iterator(Cond) != TermBr) {
1808 if (Cond->hasOneUse()) {
1809 Cond->moveBefore(TermBr);
1811 // Clone the terminating condition and insert into the loopend.
1812 ICmpInst *OldCond = Cond;
1813 Cond = cast<ICmpInst>(Cond->clone());
1814 Cond->setName(L->getHeader()->getName() + ".termcond");
1815 ExitingBlock->getInstList().insert(TermBr, Cond);
1817 // Clone the IVUse, as the old use still exists!
1818 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
1819 TermBr->replaceUsesOfWith(OldCond, Cond);
1823 // If we get to here, we know that we can transform the setcc instruction to
1824 // use the post-incremented version of the IV, allowing us to coalesce the
1825 // live ranges for the IV correctly.
1826 CondUse->transformToPostInc(L);
1829 PostIncs.insert(Cond);
1833 // Determine an insertion point for the loop induction variable increment. It
1834 // must dominate all the post-inc comparisons we just set up, and it must
1835 // dominate the loop latch edge.
1836 IVIncInsertPos = L->getLoopLatch()->getTerminator();
1837 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
1838 E = PostIncs.end(); I != E; ++I) {
1840 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
1842 if (BB == (*I)->getParent())
1843 IVIncInsertPos = *I;
1844 else if (BB != IVIncInsertPos->getParent())
1845 IVIncInsertPos = BB->getTerminator();
1849 /// reconcileNewOffset - Determine if the given use can accomodate a fixup
1850 /// at the given offset and other details. If so, update the use and
1853 LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1854 LSRUse::KindType Kind, const Type *AccessTy) {
1855 int64_t NewMinOffset = LU.MinOffset;
1856 int64_t NewMaxOffset = LU.MaxOffset;
1857 const Type *NewAccessTy = AccessTy;
1859 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
1860 // something conservative, however this can pessimize in the case that one of
1861 // the uses will have all its uses outside the loop, for example.
1862 if (LU.Kind != Kind)
1864 // Conservatively assume HasBaseReg is true for now.
1865 if (NewOffset < LU.MinOffset) {
1866 if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg,
1867 Kind, AccessTy, TLI))
1869 NewMinOffset = NewOffset;
1870 } else if (NewOffset > LU.MaxOffset) {
1871 if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg,
1872 Kind, AccessTy, TLI))
1874 NewMaxOffset = NewOffset;
1876 // Check for a mismatched access type, and fall back conservatively as needed.
1877 // TODO: Be less conservative when the type is similar and can use the same
1878 // addressing modes.
1879 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
1880 NewAccessTy = Type::getVoidTy(AccessTy->getContext());
1883 LU.MinOffset = NewMinOffset;
1884 LU.MaxOffset = NewMaxOffset;
1885 LU.AccessTy = NewAccessTy;
1886 if (NewOffset != LU.Offsets.back())
1887 LU.Offsets.push_back(NewOffset);
1891 /// getUse - Return an LSRUse index and an offset value for a fixup which
1892 /// needs the given expression, with the given kind and optional access type.
1893 /// Either reuse an existing use or create a new one, as needed.
1894 std::pair<size_t, int64_t>
1895 LSRInstance::getUse(const SCEV *&Expr,
1896 LSRUse::KindType Kind, const Type *AccessTy) {
1897 const SCEV *Copy = Expr;
1898 int64_t Offset = ExtractImmediate(Expr, SE);
1900 // Basic uses can't accept any offset, for example.
1901 if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) {
1906 std::pair<UseMapTy::iterator, bool> P =
1907 UseMap.insert(std::make_pair(std::make_pair(Expr, Kind), 0));
1909 // A use already existed with this base.
1910 size_t LUIdx = P.first->second;
1911 LSRUse &LU = Uses[LUIdx];
1912 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
1914 return std::make_pair(LUIdx, Offset);
1917 // Create a new use.
1918 size_t LUIdx = Uses.size();
1919 P.first->second = LUIdx;
1920 Uses.push_back(LSRUse(Kind, AccessTy));
1921 LSRUse &LU = Uses[LUIdx];
1923 // We don't need to track redundant offsets, but we don't need to go out
1924 // of our way here to avoid them.
1925 if (LU.Offsets.empty() || Offset != LU.Offsets.back())
1926 LU.Offsets.push_back(Offset);
1928 LU.MinOffset = Offset;
1929 LU.MaxOffset = Offset;
1930 return std::make_pair(LUIdx, Offset);
1933 /// DeleteUse - Delete the given use from the Uses list.
1934 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
1935 if (&LU != &Uses.back())
1936 std::swap(LU, Uses.back());
1940 RegUses.SwapAndDropUse(LUIdx, Uses.size());
1943 /// FindUseWithFormula - Look for a use distinct from OrigLU which is has
1944 /// a formula that has the same registers as the given formula.
1946 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
1947 const LSRUse &OrigLU) {
1948 // Search all uses for the formula. This could be more clever.
1949 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
1950 LSRUse &LU = Uses[LUIdx];
1951 // Check whether this use is close enough to OrigLU, to see whether it's
1952 // worthwhile looking through its formulae.
1953 // Ignore ICmpZero uses because they may contain formulae generated by
1954 // GenerateICmpZeroScales, in which case adding fixup offsets may
1956 if (&LU != &OrigLU &&
1957 LU.Kind != LSRUse::ICmpZero &&
1958 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
1959 LU.WidestFixupType == OrigLU.WidestFixupType &&
1960 LU.HasFormulaWithSameRegs(OrigF)) {
1961 // Scan through this use's formulae.
1962 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
1963 E = LU.Formulae.end(); I != E; ++I) {
1964 const Formula &F = *I;
1965 // Check to see if this formula has the same registers and symbols
1967 if (F.BaseRegs == OrigF.BaseRegs &&
1968 F.ScaledReg == OrigF.ScaledReg &&
1969 F.AM.BaseGV == OrigF.AM.BaseGV &&
1970 F.AM.Scale == OrigF.AM.Scale) {
1971 if (F.AM.BaseOffs == 0)
1973 // This is the formula where all the registers and symbols matched;
1974 // there aren't going to be any others. Since we declined it, we
1975 // can skip the rest of the formulae and procede to the next LSRUse.
1982 // Nothing looked good.
1986 void LSRInstance::CollectInterestingTypesAndFactors() {
1987 SmallSetVector<const SCEV *, 4> Strides;
1989 // Collect interesting types and strides.
1990 SmallVector<const SCEV *, 4> Worklist;
1991 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
1992 const SCEV *Expr = IU.getExpr(*UI);
1994 // Collect interesting types.
1995 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
1997 // Add strides for mentioned loops.
1998 Worklist.push_back(Expr);
2000 const SCEV *S = Worklist.pop_back_val();
2001 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2002 Strides.insert(AR->getStepRecurrence(SE));
2003 Worklist.push_back(AR->getStart());
2004 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2005 Worklist.append(Add->op_begin(), Add->op_end());
2007 } while (!Worklist.empty());
2010 // Compute interesting factors from the set of interesting strides.
2011 for (SmallSetVector<const SCEV *, 4>::const_iterator
2012 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2013 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2014 llvm::next(I); NewStrideIter != E; ++NewStrideIter) {
2015 const SCEV *OldStride = *I;
2016 const SCEV *NewStride = *NewStrideIter;
2018 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2019 SE.getTypeSizeInBits(NewStride->getType())) {
2020 if (SE.getTypeSizeInBits(OldStride->getType()) >
2021 SE.getTypeSizeInBits(NewStride->getType()))
2022 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2024 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2026 if (const SCEVConstant *Factor =
2027 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2029 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2030 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2031 } else if (const SCEVConstant *Factor =
2032 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2035 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2036 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2040 // If all uses use the same type, don't bother looking for truncation-based
2042 if (Types.size() == 1)
2045 DEBUG(print_factors_and_types(dbgs()));
2048 void LSRInstance::CollectFixupsAndInitialFormulae() {
2049 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2051 LSRFixup &LF = getNewFixup();
2052 LF.UserInst = UI->getUser();
2053 LF.OperandValToReplace = UI->getOperandValToReplace();
2054 LF.PostIncLoops = UI->getPostIncLoops();
2056 LSRUse::KindType Kind = LSRUse::Basic;
2057 const Type *AccessTy = 0;
2058 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
2059 Kind = LSRUse::Address;
2060 AccessTy = getAccessType(LF.UserInst);
2063 const SCEV *S = IU.getExpr(*UI);
2065 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
2066 // (N - i == 0), and this allows (N - i) to be the expression that we work
2067 // with rather than just N or i, so we can consider the register
2068 // requirements for both N and i at the same time. Limiting this code to
2069 // equality icmps is not a problem because all interesting loops use
2070 // equality icmps, thanks to IndVarSimplify.
2071 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
2072 if (CI->isEquality()) {
2073 // Swap the operands if needed to put the OperandValToReplace on the
2074 // left, for consistency.
2075 Value *NV = CI->getOperand(1);
2076 if (NV == LF.OperandValToReplace) {
2077 CI->setOperand(1, CI->getOperand(0));
2078 CI->setOperand(0, NV);
2079 NV = CI->getOperand(1);
2083 // x == y --> x - y == 0
2084 const SCEV *N = SE.getSCEV(NV);
2085 if (N->isLoopInvariant(L)) {
2086 Kind = LSRUse::ICmpZero;
2087 S = SE.getMinusSCEV(N, S);
2090 // -1 and the negations of all interesting strides (except the negation
2091 // of -1) are now also interesting.
2092 for (size_t i = 0, e = Factors.size(); i != e; ++i)
2093 if (Factors[i] != -1)
2094 Factors.insert(-(uint64_t)Factors[i]);
2098 // Set up the initial formula for this use.
2099 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
2101 LF.Offset = P.second;
2102 LSRUse &LU = Uses[LF.LUIdx];
2103 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
2104 if (!LU.WidestFixupType ||
2105 SE.getTypeSizeInBits(LU.WidestFixupType) <
2106 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
2107 LU.WidestFixupType = LF.OperandValToReplace->getType();
2109 // If this is the first use of this LSRUse, give it a formula.
2110 if (LU.Formulae.empty()) {
2111 InsertInitialFormula(S, LU, LF.LUIdx);
2112 CountRegisters(LU.Formulae.back(), LF.LUIdx);
2116 DEBUG(print_fixups(dbgs()));
2119 /// InsertInitialFormula - Insert a formula for the given expression into
2120 /// the given use, separating out loop-variant portions from loop-invariant
2121 /// and loop-computable portions.
2123 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
2125 F.InitialMatch(S, L, SE, DT);
2126 bool Inserted = InsertFormula(LU, LUIdx, F);
2127 assert(Inserted && "Initial formula already exists!"); (void)Inserted;
2130 /// InsertSupplementalFormula - Insert a simple single-register formula for
2131 /// the given expression into the given use.
2133 LSRInstance::InsertSupplementalFormula(const SCEV *S,
2134 LSRUse &LU, size_t LUIdx) {
2136 F.BaseRegs.push_back(S);
2137 F.AM.HasBaseReg = true;
2138 bool Inserted = InsertFormula(LU, LUIdx, F);
2139 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
2142 /// CountRegisters - Note which registers are used by the given formula,
2143 /// updating RegUses.
2144 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
2146 RegUses.CountRegister(F.ScaledReg, LUIdx);
2147 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
2148 E = F.BaseRegs.end(); I != E; ++I)
2149 RegUses.CountRegister(*I, LUIdx);
2152 /// InsertFormula - If the given formula has not yet been inserted, add it to
2153 /// the list, and return true. Return false otherwise.
2154 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
2155 if (!LU.InsertFormula(F))
2158 CountRegisters(F, LUIdx);
2162 /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
2163 /// loop-invariant values which we're tracking. These other uses will pin these
2164 /// values in registers, making them less profitable for elimination.
2165 /// TODO: This currently misses non-constant addrec step registers.
2166 /// TODO: Should this give more weight to users inside the loop?
2168 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
2169 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
2170 SmallPtrSet<const SCEV *, 8> Inserted;
2172 while (!Worklist.empty()) {
2173 const SCEV *S = Worklist.pop_back_val();
2175 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
2176 Worklist.append(N->op_begin(), N->op_end());
2177 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
2178 Worklist.push_back(C->getOperand());
2179 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
2180 Worklist.push_back(D->getLHS());
2181 Worklist.push_back(D->getRHS());
2182 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2183 if (!Inserted.insert(U)) continue;
2184 const Value *V = U->getValue();
2185 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
2186 // Look for instructions defined outside the loop.
2187 if (L->contains(Inst)) continue;
2188 } else if (isa<UndefValue>(V))
2189 // Undef doesn't have a live range, so it doesn't matter.
2191 for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
2193 const Instruction *UserInst = dyn_cast<Instruction>(*UI);
2194 // Ignore non-instructions.
2197 // Ignore instructions in other functions (as can happen with
2199 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
2201 // Ignore instructions not dominated by the loop.
2202 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
2203 UserInst->getParent() :
2204 cast<PHINode>(UserInst)->getIncomingBlock(
2205 PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
2206 if (!DT.dominates(L->getHeader(), UseBB))
2208 // Ignore uses which are part of other SCEV expressions, to avoid
2209 // analyzing them multiple times.
2210 if (SE.isSCEVable(UserInst->getType())) {
2211 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
2212 // If the user is a no-op, look through to its uses.
2213 if (!isa<SCEVUnknown>(UserS))
2217 SE.getUnknown(const_cast<Instruction *>(UserInst)));
2221 // Ignore icmp instructions which are already being analyzed.
2222 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
2223 unsigned OtherIdx = !UI.getOperandNo();
2224 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
2225 if (SE.getSCEV(OtherOp)->hasComputableLoopEvolution(L))
2229 LSRFixup &LF = getNewFixup();
2230 LF.UserInst = const_cast<Instruction *>(UserInst);
2231 LF.OperandValToReplace = UI.getUse();
2232 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0);
2234 LF.Offset = P.second;
2235 LSRUse &LU = Uses[LF.LUIdx];
2236 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
2237 if (!LU.WidestFixupType ||
2238 SE.getTypeSizeInBits(LU.WidestFixupType) <
2239 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
2240 LU.WidestFixupType = LF.OperandValToReplace->getType();
2241 InsertSupplementalFormula(U, LU, LF.LUIdx);
2242 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
2249 /// CollectSubexprs - Split S into subexpressions which can be pulled out into
2250 /// separate registers. If C is non-null, multiply each subexpression by C.
2251 static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
2252 SmallVectorImpl<const SCEV *> &Ops,
2254 ScalarEvolution &SE) {
2255 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2256 // Break out add operands.
2257 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
2259 CollectSubexprs(*I, C, Ops, L, SE);
2261 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2262 // Split a non-zero base out of an addrec.
2263 if (!AR->getStart()->isZero()) {
2264 CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
2265 AR->getStepRecurrence(SE),
2268 CollectSubexprs(AR->getStart(), C, Ops, L, SE);
2271 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
2272 // Break (C * (a + b + c)) into C*a + C*b + C*c.
2273 if (Mul->getNumOperands() == 2)
2274 if (const SCEVConstant *Op0 =
2275 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2276 CollectSubexprs(Mul->getOperand(1),
2277 C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
2283 // Otherwise use the value itself, optionally with a scale applied.
2284 Ops.push_back(C ? SE.getMulExpr(C, S) : S);
2287 /// GenerateReassociations - Split out subexpressions from adds and the bases of
2289 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
2292 // Arbitrarily cap recursion to protect compile time.
2293 if (Depth >= 3) return;
2295 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2296 const SCEV *BaseReg = Base.BaseRegs[i];
2298 SmallVector<const SCEV *, 8> AddOps;
2299 CollectSubexprs(BaseReg, 0, AddOps, L, SE);
2301 if (AddOps.size() == 1) continue;
2303 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
2304 JE = AddOps.end(); J != JE; ++J) {
2306 // Loop-variant "unknown" values are uninteresting; we won't be able to
2307 // do anything meaningful with them.
2308 if (isa<SCEVUnknown>(*J) && !(*J)->isLoopInvariant(L))
2311 // Don't pull a constant into a register if the constant could be folded
2312 // into an immediate field.
2313 if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,
2314 Base.getNumRegs() > 1,
2315 LU.Kind, LU.AccessTy, TLI, SE))
2318 // Collect all operands except *J.
2319 SmallVector<const SCEV *, 8> InnerAddOps
2320 (((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
2322 (llvm::next(J), ((const SmallVector<const SCEV *, 8> &)AddOps).end());
2324 // Don't leave just a constant behind in a register if the constant could
2325 // be folded into an immediate field.
2326 if (InnerAddOps.size() == 1 &&
2327 isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset,
2328 Base.getNumRegs() > 1,
2329 LU.Kind, LU.AccessTy, TLI, SE))
2332 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
2333 if (InnerSum->isZero())
2336 F.BaseRegs[i] = InnerSum;
2337 F.BaseRegs.push_back(*J);
2338 if (InsertFormula(LU, LUIdx, F))
2339 // If that formula hadn't been seen before, recurse to find more like
2341 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1);
2346 /// GenerateCombinations - Generate a formula consisting of all of the
2347 /// loop-dominating registers added into a single register.
2348 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
2350 // This method is only interesting on a plurality of registers.
2351 if (Base.BaseRegs.size() <= 1) return;
2355 SmallVector<const SCEV *, 4> Ops;
2356 for (SmallVectorImpl<const SCEV *>::const_iterator
2357 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
2358 const SCEV *BaseReg = *I;
2359 if (BaseReg->properlyDominates(L->getHeader(), &DT) &&
2360 !BaseReg->hasComputableLoopEvolution(L))
2361 Ops.push_back(BaseReg);
2363 F.BaseRegs.push_back(BaseReg);
2365 if (Ops.size() > 1) {
2366 const SCEV *Sum = SE.getAddExpr(Ops);
2367 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
2368 // opportunity to fold something. For now, just ignore such cases
2369 // rather than proceed with zero in a register.
2370 if (!Sum->isZero()) {
2371 F.BaseRegs.push_back(Sum);
2372 (void)InsertFormula(LU, LUIdx, F);
2377 /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
2378 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
2380 // We can't add a symbolic offset if the address already contains one.
2381 if (Base.AM.BaseGV) return;
2383 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2384 const SCEV *G = Base.BaseRegs[i];
2385 GlobalValue *GV = ExtractSymbol(G, SE);
2386 if (G->isZero() || !GV)
2390 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
2391 LU.Kind, LU.AccessTy, TLI))
2394 (void)InsertFormula(LU, LUIdx, F);
2398 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
2399 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
2401 // TODO: For now, just add the min and max offset, because it usually isn't
2402 // worthwhile looking at everything inbetween.
2403 SmallVector<int64_t, 2> Worklist;
2404 Worklist.push_back(LU.MinOffset);
2405 if (LU.MaxOffset != LU.MinOffset)
2406 Worklist.push_back(LU.MaxOffset);
2408 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2409 const SCEV *G = Base.BaseRegs[i];
2411 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
2412 E = Worklist.end(); I != E; ++I) {
2414 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I;
2415 if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I,
2416 LU.Kind, LU.AccessTy, TLI)) {
2417 // Add the offset to the base register.
2418 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G);
2419 // If it cancelled out, drop the base register, otherwise update it.
2420 if (NewG->isZero()) {
2421 std::swap(F.BaseRegs[i], F.BaseRegs.back());
2422 F.BaseRegs.pop_back();
2424 F.BaseRegs[i] = NewG;
2426 (void)InsertFormula(LU, LUIdx, F);
2430 int64_t Imm = ExtractImmediate(G, SE);
2431 if (G->isZero() || Imm == 0)
2434 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm;
2435 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
2436 LU.Kind, LU.AccessTy, TLI))
2439 (void)InsertFormula(LU, LUIdx, F);
2443 /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
2444 /// the comparison. For example, x == y -> x*c == y*c.
2445 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
2447 if (LU.Kind != LSRUse::ICmpZero) return;
2449 // Determine the integer type for the base formula.
2450 const Type *IntTy = Base.getType();
2452 if (SE.getTypeSizeInBits(IntTy) > 64) return;
2454 // Don't do this if there is more than one offset.
2455 if (LU.MinOffset != LU.MaxOffset) return;
2457 assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
2459 // Check each interesting stride.
2460 for (SmallSetVector<int64_t, 8>::const_iterator
2461 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
2462 int64_t Factor = *I;
2464 // Check that the multiplication doesn't overflow.
2465 if (Base.AM.BaseOffs == INT64_MIN && Factor == -1)
2467 int64_t NewBaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
2468 if (NewBaseOffs / Factor != Base.AM.BaseOffs)
2471 // Check that multiplying with the use offset doesn't overflow.
2472 int64_t Offset = LU.MinOffset;
2473 if (Offset == INT64_MIN && Factor == -1)
2475 Offset = (uint64_t)Offset * Factor;
2476 if (Offset / Factor != LU.MinOffset)
2480 F.AM.BaseOffs = NewBaseOffs;
2482 // Check that this scale is legal.
2483 if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI))
2486 // Compensate for the use having MinOffset built into it.
2487 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset;
2489 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
2491 // Check that multiplying with each base register doesn't overflow.
2492 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
2493 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
2494 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
2498 // Check that multiplying with the scaled register doesn't overflow.
2500 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
2501 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
2505 // If we make it here and it's legal, add it.
2506 (void)InsertFormula(LU, LUIdx, F);
2511 /// GenerateScales - Generate stride factor reuse formulae by making use of
2512 /// scaled-offset address modes, for example.
2513 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
2514 // Determine the integer type for the base formula.
2515 const Type *IntTy = Base.getType();
2518 // If this Formula already has a scaled register, we can't add another one.
2519 if (Base.AM.Scale != 0) return;
2521 // Check each interesting stride.
2522 for (SmallSetVector<int64_t, 8>::const_iterator
2523 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
2524 int64_t Factor = *I;
2526 Base.AM.Scale = Factor;
2527 Base.AM.HasBaseReg = Base.BaseRegs.size() > 1;
2528 // Check whether this scale is going to be legal.
2529 if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
2530 LU.Kind, LU.AccessTy, TLI)) {
2531 // As a special-case, handle special out-of-loop Basic users specially.
2532 // TODO: Reconsider this special case.
2533 if (LU.Kind == LSRUse::Basic &&
2534 isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
2535 LSRUse::Special, LU.AccessTy, TLI) &&
2536 LU.AllFixupsOutsideLoop)
2537 LU.Kind = LSRUse::Special;
2541 // For an ICmpZero, negating a solitary base register won't lead to
2543 if (LU.Kind == LSRUse::ICmpZero &&
2544 !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV)
2546 // For each addrec base reg, apply the scale, if possible.
2547 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
2548 if (const SCEVAddRecExpr *AR =
2549 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
2550 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
2551 if (FactorS->isZero())
2553 // Divide out the factor, ignoring high bits, since we'll be
2554 // scaling the value back up in the end.
2555 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
2556 // TODO: This could be optimized to avoid all the copying.
2558 F.ScaledReg = Quotient;
2559 F.DeleteBaseReg(F.BaseRegs[i]);
2560 (void)InsertFormula(LU, LUIdx, F);
2566 /// GenerateTruncates - Generate reuse formulae from different IV types.
2567 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
2568 // This requires TargetLowering to tell us which truncates are free.
2571 // Don't bother truncating symbolic values.
2572 if (Base.AM.BaseGV) return;
2574 // Determine the integer type for the base formula.
2575 const Type *DstTy = Base.getType();
2577 DstTy = SE.getEffectiveSCEVType(DstTy);
2579 for (SmallSetVector<const Type *, 4>::const_iterator
2580 I = Types.begin(), E = Types.end(); I != E; ++I) {
2581 const Type *SrcTy = *I;
2582 if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
2585 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
2586 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
2587 JE = F.BaseRegs.end(); J != JE; ++J)
2588 *J = SE.getAnyExtendExpr(*J, SrcTy);
2590 // TODO: This assumes we've done basic processing on all uses and
2591 // have an idea what the register usage is.
2592 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
2595 (void)InsertFormula(LU, LUIdx, F);
2602 /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
2603 /// defer modifications so that the search phase doesn't have to worry about
2604 /// the data structures moving underneath it.
2608 const SCEV *OrigReg;
2610 WorkItem(size_t LI, int64_t I, const SCEV *R)
2611 : LUIdx(LI), Imm(I), OrigReg(R) {}
2613 void print(raw_ostream &OS) const;
2619 void WorkItem::print(raw_ostream &OS) const {
2620 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
2621 << " , add offset " << Imm;
2624 void WorkItem::dump() const {
2625 print(errs()); errs() << '\n';
2628 /// GenerateCrossUseConstantOffsets - Look for registers which are a constant
2629 /// distance apart and try to form reuse opportunities between them.
2630 void LSRInstance::GenerateCrossUseConstantOffsets() {
2631 // Group the registers by their value without any added constant offset.
2632 typedef std::map<int64_t, const SCEV *> ImmMapTy;
2633 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
2635 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
2636 SmallVector<const SCEV *, 8> Sequence;
2637 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
2639 const SCEV *Reg = *I;
2640 int64_t Imm = ExtractImmediate(Reg, SE);
2641 std::pair<RegMapTy::iterator, bool> Pair =
2642 Map.insert(std::make_pair(Reg, ImmMapTy()));
2644 Sequence.push_back(Reg);
2645 Pair.first->second.insert(std::make_pair(Imm, *I));
2646 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
2649 // Now examine each set of registers with the same base value. Build up
2650 // a list of work to do and do the work in a separate step so that we're
2651 // not adding formulae and register counts while we're searching.
2652 SmallVector<WorkItem, 32> WorkItems;
2653 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
2654 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
2655 E = Sequence.end(); I != E; ++I) {
2656 const SCEV *Reg = *I;
2657 const ImmMapTy &Imms = Map.find(Reg)->second;
2659 // It's not worthwhile looking for reuse if there's only one offset.
2660 if (Imms.size() == 1)
2663 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
2664 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
2666 dbgs() << ' ' << J->first;
2669 // Examine each offset.
2670 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
2672 const SCEV *OrigReg = J->second;
2674 int64_t JImm = J->first;
2675 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
2677 if (!isa<SCEVConstant>(OrigReg) &&
2678 UsedByIndicesMap[Reg].count() == 1) {
2679 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
2683 // Conservatively examine offsets between this orig reg a few selected
2685 ImmMapTy::const_iterator OtherImms[] = {
2686 Imms.begin(), prior(Imms.end()),
2687 Imms.upper_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
2689 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
2690 ImmMapTy::const_iterator M = OtherImms[i];
2691 if (M == J || M == JE) continue;
2693 // Compute the difference between the two.
2694 int64_t Imm = (uint64_t)JImm - M->first;
2695 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
2696 LUIdx = UsedByIndices.find_next(LUIdx))
2697 // Make a memo of this use, offset, and register tuple.
2698 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
2699 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
2706 UsedByIndicesMap.clear();
2707 UniqueItems.clear();
2709 // Now iterate through the worklist and add new formulae.
2710 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
2711 E = WorkItems.end(); I != E; ++I) {
2712 const WorkItem &WI = *I;
2713 size_t LUIdx = WI.LUIdx;
2714 LSRUse &LU = Uses[LUIdx];
2715 int64_t Imm = WI.Imm;
2716 const SCEV *OrigReg = WI.OrigReg;
2718 const Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
2719 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
2720 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
2722 // TODO: Use a more targeted data structure.
2723 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
2724 const Formula &F = LU.Formulae[L];
2725 // Use the immediate in the scaled register.
2726 if (F.ScaledReg == OrigReg) {
2727 int64_t Offs = (uint64_t)F.AM.BaseOffs +
2728 Imm * (uint64_t)F.AM.Scale;
2729 // Don't create 50 + reg(-50).
2730 if (F.referencesReg(SE.getSCEV(
2731 ConstantInt::get(IntTy, -(uint64_t)Offs))))
2734 NewF.AM.BaseOffs = Offs;
2735 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
2736 LU.Kind, LU.AccessTy, TLI))
2738 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
2740 // If the new scale is a constant in a register, and adding the constant
2741 // value to the immediate would produce a value closer to zero than the
2742 // immediate itself, then the formula isn't worthwhile.
2743 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
2744 if (C->getValue()->getValue().isNegative() !=
2745 (NewF.AM.BaseOffs < 0) &&
2746 (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale))
2747 .ule(abs64(NewF.AM.BaseOffs)))
2751 (void)InsertFormula(LU, LUIdx, NewF);
2753 // Use the immediate in a base register.
2754 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
2755 const SCEV *BaseReg = F.BaseRegs[N];
2756 if (BaseReg != OrigReg)
2759 NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
2760 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
2761 LU.Kind, LU.AccessTy, TLI))
2763 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
2765 // If the new formula has a constant in a register, and adding the
2766 // constant value to the immediate would produce a value closer to
2767 // zero than the immediate itself, then the formula isn't worthwhile.
2768 for (SmallVectorImpl<const SCEV *>::const_iterator
2769 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
2771 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
2772 if ((C->getValue()->getValue() + NewF.AM.BaseOffs).abs().slt(
2773 abs64(NewF.AM.BaseOffs)) &&
2774 (C->getValue()->getValue() +
2775 NewF.AM.BaseOffs).countTrailingZeros() >=
2776 CountTrailingZeros_64(NewF.AM.BaseOffs))
2780 (void)InsertFormula(LU, LUIdx, NewF);
2789 /// GenerateAllReuseFormulae - Generate formulae for each use.
2791 LSRInstance::GenerateAllReuseFormulae() {
2792 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
2793 // queries are more precise.
2794 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2795 LSRUse &LU = Uses[LUIdx];
2796 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2797 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
2798 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2799 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
2801 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2802 LSRUse &LU = Uses[LUIdx];
2803 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2804 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
2805 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2806 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
2807 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2808 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
2809 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2810 GenerateScales(LU, LUIdx, LU.Formulae[i]);
2812 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2813 LSRUse &LU = Uses[LUIdx];
2814 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2815 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
2818 GenerateCrossUseConstantOffsets();
2820 DEBUG(dbgs() << "\n"
2821 "After generating reuse formulae:\n";
2822 print_uses(dbgs()));
2825 /// If their are multiple formulae with the same set of registers used
2826 /// by other uses, pick the best one and delete the others.
2827 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
2829 bool ChangedFormulae = false;
2832 // Collect the best formula for each unique set of shared registers. This
2833 // is reset for each use.
2834 typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo>
2836 BestFormulaeTy BestFormulae;
2838 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2839 LSRUse &LU = Uses[LUIdx];
2840 FormulaSorter Sorter(L, LU, SE, DT);
2841 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
2844 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
2845 FIdx != NumForms; ++FIdx) {
2846 Formula &F = LU.Formulae[FIdx];
2848 SmallVector<const SCEV *, 2> Key;
2849 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
2850 JE = F.BaseRegs.end(); J != JE; ++J) {
2851 const SCEV *Reg = *J;
2852 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
2856 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
2857 Key.push_back(F.ScaledReg);
2858 // Unstable sort by host order ok, because this is only used for
2860 std::sort(Key.begin(), Key.end());
2862 std::pair<BestFormulaeTy::const_iterator, bool> P =
2863 BestFormulae.insert(std::make_pair(Key, FIdx));
2865 Formula &Best = LU.Formulae[P.first->second];
2866 if (Sorter.operator()(F, Best))
2868 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
2870 " in favor of formula "; Best.print(dbgs());
2873 ChangedFormulae = true;
2875 LU.DeleteFormula(F);
2883 // Now that we've filtered out some formulae, recompute the Regs set.
2885 LU.RecomputeRegs(LUIdx, RegUses);
2887 // Reset this to prepare for the next use.
2888 BestFormulae.clear();
2891 DEBUG(if (ChangedFormulae) {
2893 "After filtering out undesirable candidates:\n";
2898 // This is a rough guess that seems to work fairly well.
2899 static const size_t ComplexityLimit = UINT16_MAX;
2901 /// EstimateSearchSpaceComplexity - Estimate the worst-case number of
2902 /// solutions the solver might have to consider. It almost never considers
2903 /// this many solutions because it prune the search space, but the pruning
2904 /// isn't always sufficient.
2905 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
2907 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
2908 E = Uses.end(); I != E; ++I) {
2909 size_t FSize = I->Formulae.size();
2910 if (FSize >= ComplexityLimit) {
2911 Power = ComplexityLimit;
2915 if (Power >= ComplexityLimit)
2921 /// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset
2922 /// of the registers of another formula, it won't help reduce register
2923 /// pressure (though it may not necessarily hurt register pressure); remove
2924 /// it to simplify the system.
2925 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
2926 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
2927 DEBUG(dbgs() << "The search space is too complex.\n");
2929 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
2930 "which use a superset of registers used by other "
2933 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2934 LSRUse &LU = Uses[LUIdx];
2936 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
2937 Formula &F = LU.Formulae[i];
2938 // Look for a formula with a constant or GV in a register. If the use
2939 // also has a formula with that same value in an immediate field,
2940 // delete the one that uses a register.
2941 for (SmallVectorImpl<const SCEV *>::const_iterator
2942 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
2943 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
2945 NewF.AM.BaseOffs += C->getValue()->getSExtValue();
2946 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
2947 (I - F.BaseRegs.begin()));
2948 if (LU.HasFormulaWithSameRegs(NewF)) {
2949 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
2950 LU.DeleteFormula(F);
2956 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
2957 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
2960 NewF.AM.BaseGV = GV;
2961 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
2962 (I - F.BaseRegs.begin()));
2963 if (LU.HasFormulaWithSameRegs(NewF)) {
2964 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
2966 LU.DeleteFormula(F);
2977 LU.RecomputeRegs(LUIdx, RegUses);
2980 DEBUG(dbgs() << "After pre-selection:\n";
2981 print_uses(dbgs()));
2985 /// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers
2986 /// for expressions like A, A+1, A+2, etc., allocate a single register for
2988 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
2989 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
2990 DEBUG(dbgs() << "The search space is too complex.\n");
2992 DEBUG(dbgs() << "Narrowing the search space by assuming that uses "
2993 "separated by a constant offset will use the same "
2996 // This is especially useful for unrolled loops.
2998 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2999 LSRUse &LU = Uses[LUIdx];
3000 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
3001 E = LU.Formulae.end(); I != E; ++I) {
3002 const Formula &F = *I;
3003 if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) {
3004 if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) {
3005 if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs,
3006 /*HasBaseReg=*/false,
3007 LU.Kind, LU.AccessTy)) {
3008 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs());
3011 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
3013 // Delete formulae from the new use which are no longer legal.
3015 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
3016 Formula &F = LUThatHas->Formulae[i];
3017 if (!isLegalUse(F.AM,
3018 LUThatHas->MinOffset, LUThatHas->MaxOffset,
3019 LUThatHas->Kind, LUThatHas->AccessTy, TLI)) {
3020 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
3022 LUThatHas->DeleteFormula(F);
3029 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
3031 // Update the relocs to reference the new use.
3032 for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
3033 E = Fixups.end(); I != E; ++I) {
3034 LSRFixup &Fixup = *I;
3035 if (Fixup.LUIdx == LUIdx) {
3036 Fixup.LUIdx = LUThatHas - &Uses.front();
3037 Fixup.Offset += F.AM.BaseOffs;
3038 DEBUG(dbgs() << "New fixup has offset "
3039 << Fixup.Offset << '\n');
3041 if (Fixup.LUIdx == NumUses-1)
3042 Fixup.LUIdx = LUIdx;
3045 // Delete the old use.
3046 DeleteUse(LU, LUIdx);
3056 DEBUG(dbgs() << "After pre-selection:\n";
3057 print_uses(dbgs()));
3061 /// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call
3062 /// FilterOutUndesirableDedicatedRegisters again, if necessary, now that
3063 /// we've done more filtering, as it may be able to find more formulae to
3065 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
3066 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3067 DEBUG(dbgs() << "The search space is too complex.\n");
3069 DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
3070 "undesirable dedicated registers.\n");
3072 FilterOutUndesirableDedicatedRegisters();
3074 DEBUG(dbgs() << "After pre-selection:\n";
3075 print_uses(dbgs()));
3079 /// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely
3080 /// to be profitable, and then in any use which has any reference to that
3081 /// register, delete all formulae which do not reference that register.
3082 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
3083 // With all other options exhausted, loop until the system is simple
3084 // enough to handle.
3085 SmallPtrSet<const SCEV *, 4> Taken;
3086 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3087 // Ok, we have too many of formulae on our hands to conveniently handle.
3088 // Use a rough heuristic to thin out the list.
3089 DEBUG(dbgs() << "The search space is too complex.\n");
3091 // Pick the register which is used by the most LSRUses, which is likely
3092 // to be a good reuse register candidate.
3093 const SCEV *Best = 0;
3094 unsigned BestNum = 0;
3095 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
3097 const SCEV *Reg = *I;
3098 if (Taken.count(Reg))
3103 unsigned Count = RegUses.getUsedByIndices(Reg).count();
3104 if (Count > BestNum) {
3111 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
3112 << " will yield profitable reuse.\n");
3115 // In any use with formulae which references this register, delete formulae
3116 // which don't reference it.
3117 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3118 LSRUse &LU = Uses[LUIdx];
3119 if (!LU.Regs.count(Best)) continue;
3122 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
3123 Formula &F = LU.Formulae[i];
3124 if (!F.referencesReg(Best)) {
3125 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
3126 LU.DeleteFormula(F);
3130 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
3136 LU.RecomputeRegs(LUIdx, RegUses);
3139 DEBUG(dbgs() << "After pre-selection:\n";
3140 print_uses(dbgs()));
3144 /// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
3145 /// formulae to choose from, use some rough heuristics to prune down the number
3146 /// of formulae. This keeps the main solver from taking an extraordinary amount
3147 /// of time in some worst-case scenarios.
3148 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
3149 NarrowSearchSpaceByDetectingSupersets();
3150 NarrowSearchSpaceByCollapsingUnrolledCode();
3151 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
3152 NarrowSearchSpaceByPickingWinnerRegs();
3155 /// SolveRecurse - This is the recursive solver.
3156 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
3158 SmallVectorImpl<const Formula *> &Workspace,
3159 const Cost &CurCost,
3160 const SmallPtrSet<const SCEV *, 16> &CurRegs,
3161 DenseSet<const SCEV *> &VisitedRegs) const {
3164 // - use more aggressive filtering
3165 // - sort the formula so that the most profitable solutions are found first
3166 // - sort the uses too
3168 // - don't compute a cost, and then compare. compare while computing a cost
3170 // - track register sets with SmallBitVector
3172 const LSRUse &LU = Uses[Workspace.size()];
3174 // If this use references any register that's already a part of the
3175 // in-progress solution, consider it a requirement that a formula must
3176 // reference that register in order to be considered. This prunes out
3177 // unprofitable searching.
3178 SmallSetVector<const SCEV *, 4> ReqRegs;
3179 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
3180 E = CurRegs.end(); I != E; ++I)
3181 if (LU.Regs.count(*I))
3184 bool AnySatisfiedReqRegs = false;
3185 SmallPtrSet<const SCEV *, 16> NewRegs;
3188 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
3189 E = LU.Formulae.end(); I != E; ++I) {
3190 const Formula &F = *I;
3192 // Ignore formulae which do not use any of the required registers.
3193 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
3194 JE = ReqRegs.end(); J != JE; ++J) {
3195 const SCEV *Reg = *J;
3196 if ((!F.ScaledReg || F.ScaledReg != Reg) &&
3197 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) ==
3201 AnySatisfiedReqRegs = true;
3203 // Evaluate the cost of the current formula. If it's already worse than
3204 // the current best, prune the search at that point.
3207 NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT);
3208 if (NewCost < SolutionCost) {
3209 Workspace.push_back(&F);
3210 if (Workspace.size() != Uses.size()) {
3211 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
3212 NewRegs, VisitedRegs);
3213 if (F.getNumRegs() == 1 && Workspace.size() == 1)
3214 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
3216 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
3217 dbgs() << ". Regs:";
3218 for (SmallPtrSet<const SCEV *, 16>::const_iterator
3219 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
3220 dbgs() << ' ' << **I;
3223 SolutionCost = NewCost;
3224 Solution = Workspace;
3226 Workspace.pop_back();
3231 // If none of the formulae had all of the required registers, relax the
3232 // constraint so that we don't exclude all formulae.
3233 if (!AnySatisfiedReqRegs) {
3234 assert(!ReqRegs.empty() && "Solver failed even without required registers");
3240 /// Solve - Choose one formula from each use. Return the results in the given
3241 /// Solution vector.
3242 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
3243 SmallVector<const Formula *, 8> Workspace;
3245 SolutionCost.Loose();
3247 SmallPtrSet<const SCEV *, 16> CurRegs;
3248 DenseSet<const SCEV *> VisitedRegs;
3249 Workspace.reserve(Uses.size());
3251 // SolveRecurse does all the work.
3252 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
3253 CurRegs, VisitedRegs);
3255 // Ok, we've now made all our decisions.
3256 DEBUG(dbgs() << "\n"
3257 "The chosen solution requires "; SolutionCost.print(dbgs());
3259 for (size_t i = 0, e = Uses.size(); i != e; ++i) {
3261 Uses[i].print(dbgs());
3264 Solution[i]->print(dbgs());
3268 assert(Solution.size() == Uses.size() && "Malformed solution!");
3271 /// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
3272 /// the dominator tree far as we can go while still being dominated by the
3273 /// input positions. This helps canonicalize the insert position, which
3274 /// encourages sharing.
3275 BasicBlock::iterator
3276 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
3277 const SmallVectorImpl<Instruction *> &Inputs)
3280 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
3281 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
3284 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
3285 if (!Rung) return IP;
3286 Rung = Rung->getIDom();
3287 if (!Rung) return IP;
3288 IDom = Rung->getBlock();
3290 // Don't climb into a loop though.
3291 const Loop *IDomLoop = LI.getLoopFor(IDom);
3292 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
3293 if (IDomDepth <= IPLoopDepth &&
3294 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
3298 bool AllDominate = true;
3299 Instruction *BetterPos = 0;
3300 Instruction *Tentative = IDom->getTerminator();
3301 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
3302 E = Inputs.end(); I != E; ++I) {
3303 Instruction *Inst = *I;
3304 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
3305 AllDominate = false;
3308 // Attempt to find an insert position in the middle of the block,
3309 // instead of at the end, so that it can be used for other expansions.
3310 if (IDom == Inst->getParent() &&
3311 (!BetterPos || DT.dominates(BetterPos, Inst)))
3312 BetterPos = llvm::next(BasicBlock::iterator(Inst));
3325 /// AdjustInsertPositionForExpand - Determine an input position which will be
3326 /// dominated by the operands and which will dominate the result.
3327 BasicBlock::iterator
3328 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator IP,
3330 const LSRUse &LU) const {
3331 // Collect some instructions which must be dominated by the
3332 // expanding replacement. These must be dominated by any operands that
3333 // will be required in the expansion.
3334 SmallVector<Instruction *, 4> Inputs;
3335 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
3336 Inputs.push_back(I);
3337 if (LU.Kind == LSRUse::ICmpZero)
3338 if (Instruction *I =
3339 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
3340 Inputs.push_back(I);
3341 if (LF.PostIncLoops.count(L)) {
3342 if (LF.isUseFullyOutsideLoop(L))
3343 Inputs.push_back(L->getLoopLatch()->getTerminator());
3345 Inputs.push_back(IVIncInsertPos);
3347 // The expansion must also be dominated by the increment positions of any
3348 // loops it for which it is using post-inc mode.
3349 for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(),
3350 E = LF.PostIncLoops.end(); I != E; ++I) {
3351 const Loop *PIL = *I;
3352 if (PIL == L) continue;
3354 // Be dominated by the loop exit.
3355 SmallVector<BasicBlock *, 4> ExitingBlocks;
3356 PIL->getExitingBlocks(ExitingBlocks);
3357 if (!ExitingBlocks.empty()) {
3358 BasicBlock *BB = ExitingBlocks[0];
3359 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
3360 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
3361 Inputs.push_back(BB->getTerminator());
3365 // Then, climb up the immediate dominator tree as far as we can go while
3366 // still being dominated by the input positions.
3367 IP = HoistInsertPosition(IP, Inputs);
3369 // Don't insert instructions before PHI nodes.
3370 while (isa<PHINode>(IP)) ++IP;
3372 // Ignore debug intrinsics.
3373 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
3378 /// Expand - Emit instructions for the leading candidate expression for this
3379 /// LSRUse (this is called "expanding").
3380 Value *LSRInstance::Expand(const LSRFixup &LF,
3382 BasicBlock::iterator IP,
3383 SCEVExpander &Rewriter,
3384 SmallVectorImpl<WeakVH> &DeadInsts) const {
3385 const LSRUse &LU = Uses[LF.LUIdx];
3387 // Determine an input position which will be dominated by the operands and
3388 // which will dominate the result.
3389 IP = AdjustInsertPositionForExpand(IP, LF, LU);
3391 // Inform the Rewriter if we have a post-increment use, so that it can
3392 // perform an advantageous expansion.
3393 Rewriter.setPostInc(LF.PostIncLoops);
3395 // This is the type that the user actually needs.
3396 const Type *OpTy = LF.OperandValToReplace->getType();
3397 // This will be the type that we'll initially expand to.
3398 const Type *Ty = F.getType();
3400 // No type known; just expand directly to the ultimate type.
3402 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
3403 // Expand directly to the ultimate type if it's the right size.
3405 // This is the type to do integer arithmetic in.
3406 const Type *IntTy = SE.getEffectiveSCEVType(Ty);
3408 // Build up a list of operands to add together to form the full base.
3409 SmallVector<const SCEV *, 8> Ops;
3411 // Expand the BaseRegs portion.
3412 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
3413 E = F.BaseRegs.end(); I != E; ++I) {
3414 const SCEV *Reg = *I;
3415 assert(!Reg->isZero() && "Zero allocated in a base register!");
3417 // If we're expanding for a post-inc user, make the post-inc adjustment.
3418 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
3419 Reg = TransformForPostIncUse(Denormalize, Reg,
3420 LF.UserInst, LF.OperandValToReplace,
3423 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
3426 // Flush the operand list to suppress SCEVExpander hoisting.
3428 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
3430 Ops.push_back(SE.getUnknown(FullV));
3433 // Expand the ScaledReg portion.
3434 Value *ICmpScaledV = 0;
3435 if (F.AM.Scale != 0) {
3436 const SCEV *ScaledS = F.ScaledReg;
3438 // If we're expanding for a post-inc user, make the post-inc adjustment.
3439 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
3440 ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
3441 LF.UserInst, LF.OperandValToReplace,
3444 if (LU.Kind == LSRUse::ICmpZero) {
3445 // An interesting way of "folding" with an icmp is to use a negated
3446 // scale, which we'll implement by inserting it into the other operand
3448 assert(F.AM.Scale == -1 &&
3449 "The only scale supported by ICmpZero uses is -1!");
3450 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
3452 // Otherwise just expand the scaled register and an explicit scale,
3453 // which is expected to be matched as part of the address.
3454 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
3455 ScaledS = SE.getMulExpr(ScaledS,
3456 SE.getConstant(ScaledS->getType(), F.AM.Scale));
3457 Ops.push_back(ScaledS);
3459 // Flush the operand list to suppress SCEVExpander hoisting.
3460 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
3462 Ops.push_back(SE.getUnknown(FullV));
3466 // Expand the GV portion.
3468 Ops.push_back(SE.getUnknown(F.AM.BaseGV));
3470 // Flush the operand list to suppress SCEVExpander hoisting.
3471 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
3473 Ops.push_back(SE.getUnknown(FullV));
3476 // Expand the immediate portion.
3477 int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset;
3479 if (LU.Kind == LSRUse::ICmpZero) {
3480 // The other interesting way of "folding" with an ICmpZero is to use a
3481 // negated immediate.
3483 ICmpScaledV = ConstantInt::get(IntTy, -Offset);
3485 Ops.push_back(SE.getUnknown(ICmpScaledV));
3486 ICmpScaledV = ConstantInt::get(IntTy, Offset);
3489 // Just add the immediate values. These again are expected to be matched
3490 // as part of the address.
3491 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
3495 // Emit instructions summing all the operands.
3496 const SCEV *FullS = Ops.empty() ?
3497 SE.getConstant(IntTy, 0) :
3499 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
3501 // We're done expanding now, so reset the rewriter.
3502 Rewriter.clearPostInc();
3504 // An ICmpZero Formula represents an ICmp which we're handling as a
3505 // comparison against zero. Now that we've expanded an expression for that
3506 // form, update the ICmp's other operand.
3507 if (LU.Kind == LSRUse::ICmpZero) {
3508 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
3509 DeadInsts.push_back(CI->getOperand(1));
3510 assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
3511 "a scale at the same time!");
3512 if (F.AM.Scale == -1) {
3513 if (ICmpScaledV->getType() != OpTy) {
3515 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
3517 ICmpScaledV, OpTy, "tmp", CI);
3520 CI->setOperand(1, ICmpScaledV);
3522 assert(F.AM.Scale == 0 &&
3523 "ICmp does not support folding a global value and "
3524 "a scale at the same time!");
3525 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
3527 if (C->getType() != OpTy)
3528 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
3532 CI->setOperand(1, C);
3539 /// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
3540 /// of their operands effectively happens in their predecessor blocks, so the
3541 /// expression may need to be expanded in multiple places.
3542 void LSRInstance::RewriteForPHI(PHINode *PN,
3545 SCEVExpander &Rewriter,
3546 SmallVectorImpl<WeakVH> &DeadInsts,
3548 DenseMap<BasicBlock *, Value *> Inserted;
3549 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
3550 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
3551 BasicBlock *BB = PN->getIncomingBlock(i);
3553 // If this is a critical edge, split the edge so that we do not insert
3554 // the code on all predecessor/successor paths. We do this unless this
3555 // is the canonical backedge for this loop, which complicates post-inc
3557 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
3558 !isa<IndirectBrInst>(BB->getTerminator()) &&
3559 (PN->getParent() != L->getHeader() || !L->contains(BB))) {
3560 // Split the critical edge.
3561 BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P);
3563 // If PN is outside of the loop and BB is in the loop, we want to
3564 // move the block to be immediately before the PHI block, not
3565 // immediately after BB.
3566 if (L->contains(BB) && !L->contains(PN))
3567 NewBB->moveBefore(PN->getParent());
3569 // Splitting the edge can reduce the number of PHI entries we have.
3570 e = PN->getNumIncomingValues();
3572 i = PN->getBasicBlockIndex(BB);
3575 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
3576 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
3578 PN->setIncomingValue(i, Pair.first->second);
3580 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
3582 // If this is reuse-by-noop-cast, insert the noop cast.
3583 const Type *OpTy = LF.OperandValToReplace->getType();
3584 if (FullV->getType() != OpTy)
3586 CastInst::Create(CastInst::getCastOpcode(FullV, false,
3588 FullV, LF.OperandValToReplace->getType(),
3589 "tmp", BB->getTerminator());
3591 PN->setIncomingValue(i, FullV);
3592 Pair.first->second = FullV;
3597 /// Rewrite - Emit instructions for the leading candidate expression for this
3598 /// LSRUse (this is called "expanding"), and update the UserInst to reference
3599 /// the newly expanded value.
3600 void LSRInstance::Rewrite(const LSRFixup &LF,
3602 SCEVExpander &Rewriter,
3603 SmallVectorImpl<WeakVH> &DeadInsts,
3605 // First, find an insertion point that dominates UserInst. For PHI nodes,
3606 // find the nearest block which dominates all the relevant uses.
3607 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
3608 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
3610 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
3612 // If this is reuse-by-noop-cast, insert the noop cast.
3613 const Type *OpTy = LF.OperandValToReplace->getType();
3614 if (FullV->getType() != OpTy) {
3616 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
3617 FullV, OpTy, "tmp", LF.UserInst);
3621 // Update the user. ICmpZero is handled specially here (for now) because
3622 // Expand may have updated one of the operands of the icmp already, and
3623 // its new value may happen to be equal to LF.OperandValToReplace, in
3624 // which case doing replaceUsesOfWith leads to replacing both operands
3625 // with the same value. TODO: Reorganize this.
3626 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
3627 LF.UserInst->setOperand(0, FullV);
3629 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
3632 DeadInsts.push_back(LF.OperandValToReplace);
3635 /// ImplementSolution - Rewrite all the fixup locations with new values,
3636 /// following the chosen solution.
3638 LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
3640 // Keep track of instructions we may have made dead, so that
3641 // we can remove them after we are done working.
3642 SmallVector<WeakVH, 16> DeadInsts;
3644 SCEVExpander Rewriter(SE);
3645 Rewriter.disableCanonicalMode();
3646 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
3648 // Expand the new value definitions and update the users.
3649 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
3650 E = Fixups.end(); I != E; ++I) {
3651 const LSRFixup &Fixup = *I;
3653 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
3658 // Clean up after ourselves. This must be done before deleting any
3662 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
3665 LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
3666 : IU(P->getAnalysis<IVUsers>()),
3667 SE(P->getAnalysis<ScalarEvolution>()),
3668 DT(P->getAnalysis<DominatorTree>()),
3669 LI(P->getAnalysis<LoopInfo>()),
3670 TLI(tli), L(l), Changed(false), IVIncInsertPos(0) {
3672 // If LoopSimplify form is not available, stay out of trouble.
3673 if (!L->isLoopSimplifyForm()) return;
3675 // If there's no interesting work to be done, bail early.
3676 if (IU.empty()) return;
3678 DEBUG(dbgs() << "\nLSR on loop ";
3679 WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
3682 // First, perform some low-level loop optimizations.
3684 OptimizeLoopTermCond();
3686 // Start collecting data and preparing for the solver.
3687 CollectInterestingTypesAndFactors();
3688 CollectFixupsAndInitialFormulae();
3689 CollectLoopInvariantFixupsAndFormulae();
3691 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
3692 print_uses(dbgs()));
3694 // Now use the reuse data to generate a bunch of interesting ways
3695 // to formulate the values needed for the uses.
3696 GenerateAllReuseFormulae();
3698 FilterOutUndesirableDedicatedRegisters();
3699 NarrowSearchSpaceUsingHeuristics();
3701 SmallVector<const Formula *, 8> Solution;
3704 // Release memory that is no longer needed.
3710 // Formulae should be legal.
3711 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3712 E = Uses.end(); I != E; ++I) {
3713 const LSRUse &LU = *I;
3714 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
3715 JE = LU.Formulae.end(); J != JE; ++J)
3716 assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset,
3717 LU.Kind, LU.AccessTy, TLI) &&
3718 "Illegal formula generated!");
3722 // Now that we've decided what we want, make it so.
3723 ImplementSolution(Solution, P);
3726 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
3727 if (Factors.empty() && Types.empty()) return;
3729 OS << "LSR has identified the following interesting factors and types: ";
3732 for (SmallSetVector<int64_t, 8>::const_iterator
3733 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3734 if (!First) OS << ", ";
3739 for (SmallSetVector<const Type *, 4>::const_iterator
3740 I = Types.begin(), E = Types.end(); I != E; ++I) {
3741 if (!First) OS << ", ";
3743 OS << '(' << **I << ')';
3748 void LSRInstance::print_fixups(raw_ostream &OS) const {
3749 OS << "LSR is examining the following fixup sites:\n";
3750 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
3751 E = Fixups.end(); I != E; ++I) {
3758 void LSRInstance::print_uses(raw_ostream &OS) const {
3759 OS << "LSR is examining the following uses:\n";
3760 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3761 E = Uses.end(); I != E; ++I) {
3762 const LSRUse &LU = *I;
3766 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
3767 JE = LU.Formulae.end(); J != JE; ++J) {
3775 void LSRInstance::print(raw_ostream &OS) const {
3776 print_factors_and_types(OS);
3781 void LSRInstance::dump() const {
3782 print(errs()); errs() << '\n';
3787 class LoopStrengthReduce : public LoopPass {
3788 /// TLI - Keep a pointer of a TargetLowering to consult for determining
3789 /// transformation profitability.
3790 const TargetLowering *const TLI;
3793 static char ID; // Pass ID, replacement for typeid
3794 explicit LoopStrengthReduce(const TargetLowering *tli = 0);
3797 bool runOnLoop(Loop *L, LPPassManager &LPM);
3798 void getAnalysisUsage(AnalysisUsage &AU) const;
3803 char LoopStrengthReduce::ID = 0;
3804 INITIALIZE_PASS(LoopStrengthReduce, "loop-reduce",
3805 "Loop Strength Reduction", false, false)
3807 Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
3808 return new LoopStrengthReduce(TLI);
3811 LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
3812 : LoopPass(ID), TLI(tli) {}
3814 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
3815 // We split critical edges, so we change the CFG. However, we do update
3816 // many analyses if they are around.
3817 AU.addPreservedID(LoopSimplifyID);
3818 AU.addPreserved("domfrontier");
3820 AU.addRequired<LoopInfo>();
3821 AU.addPreserved<LoopInfo>();
3822 AU.addRequiredID(LoopSimplifyID);
3823 AU.addRequired<DominatorTree>();
3824 AU.addPreserved<DominatorTree>();
3825 AU.addRequired<ScalarEvolution>();
3826 AU.addPreserved<ScalarEvolution>();
3827 AU.addRequired<IVUsers>();
3828 AU.addPreserved<IVUsers>();
3831 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
3832 bool Changed = false;
3834 // Run the main LSR transformation.
3835 Changed |= LSRInstance(TLI, L, this).getChanged();
3837 // At this point, it is worth checking to see if any recurrence PHIs are also
3838 // dead, so that we can remove them as well.
3839 Changed |= DeleteDeadPHIs(L->getHeader());