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 DropUse(size_t LUIdx);
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::DropUse(size_t LUIdx) {
156 // Remove the use index from every register's use list.
157 for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end();
159 I->second.UsedByIndices.reset(LUIdx);
163 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
164 if (!RegUsesMap.count(Reg)) return false;
165 const SmallBitVector &UsedByIndices =
166 RegUsesMap.find(Reg)->second.UsedByIndices;
167 int i = UsedByIndices.find_first();
168 if (i == -1) return false;
169 if ((size_t)i != LUIdx) return true;
170 return UsedByIndices.find_next(i) != -1;
173 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
174 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
175 assert(I != RegUsesMap.end() && "Unknown register!");
176 return I->second.UsedByIndices;
179 void RegUseTracker::clear() {
186 /// Formula - This class holds information that describes a formula for
187 /// computing satisfying a use. It may include broken-out immediates and scaled
190 /// AM - This is used to represent complex addressing, as well as other kinds
191 /// of interesting uses.
192 TargetLowering::AddrMode AM;
194 /// BaseRegs - The list of "base" registers for this use. When this is
195 /// non-empty, AM.HasBaseReg should be set to true.
196 SmallVector<const SCEV *, 2> BaseRegs;
198 /// ScaledReg - The 'scaled' register for this use. This should be non-null
199 /// when AM.Scale is not zero.
200 const SCEV *ScaledReg;
202 Formula() : ScaledReg(0) {}
204 void InitialMatch(const SCEV *S, Loop *L,
205 ScalarEvolution &SE, DominatorTree &DT);
207 unsigned getNumRegs() const;
208 const Type *getType() const;
210 void DeleteBaseReg(const SCEV *&S);
212 bool referencesReg(const SCEV *S) const;
213 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
214 const RegUseTracker &RegUses) const;
216 void print(raw_ostream &OS) const;
222 /// DoInitialMatch - Recursion helper for InitialMatch.
223 static void DoInitialMatch(const SCEV *S, Loop *L,
224 SmallVectorImpl<const SCEV *> &Good,
225 SmallVectorImpl<const SCEV *> &Bad,
226 ScalarEvolution &SE, DominatorTree &DT) {
227 // Collect expressions which properly dominate the loop header.
228 if (S->properlyDominates(L->getHeader(), &DT)) {
233 // Look at add operands.
234 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
235 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
237 DoInitialMatch(*I, L, Good, Bad, SE, DT);
241 // Look at addrec operands.
242 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
243 if (!AR->getStart()->isZero()) {
244 DoInitialMatch(AR->getStart(), L, Good, Bad, SE, DT);
245 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
246 AR->getStepRecurrence(SE),
248 L, Good, Bad, SE, DT);
252 // Handle a multiplication by -1 (negation) if it didn't fold.
253 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
254 if (Mul->getOperand(0)->isAllOnesValue()) {
255 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
256 const SCEV *NewMul = SE.getMulExpr(Ops);
258 SmallVector<const SCEV *, 4> MyGood;
259 SmallVector<const SCEV *, 4> MyBad;
260 DoInitialMatch(NewMul, L, MyGood, MyBad, SE, DT);
261 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
262 SE.getEffectiveSCEVType(NewMul->getType())));
263 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
264 E = MyGood.end(); I != E; ++I)
265 Good.push_back(SE.getMulExpr(NegOne, *I));
266 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
267 E = MyBad.end(); I != E; ++I)
268 Bad.push_back(SE.getMulExpr(NegOne, *I));
272 // Ok, we can't do anything interesting. Just stuff the whole thing into a
273 // register and hope for the best.
277 /// InitialMatch - Incorporate loop-variant parts of S into this Formula,
278 /// attempting to keep all loop-invariant and loop-computable values in a
279 /// single base register.
280 void Formula::InitialMatch(const SCEV *S, Loop *L,
281 ScalarEvolution &SE, DominatorTree &DT) {
282 SmallVector<const SCEV *, 4> Good;
283 SmallVector<const SCEV *, 4> Bad;
284 DoInitialMatch(S, L, Good, Bad, SE, DT);
286 const SCEV *Sum = SE.getAddExpr(Good);
288 BaseRegs.push_back(Sum);
289 AM.HasBaseReg = true;
292 const SCEV *Sum = SE.getAddExpr(Bad);
294 BaseRegs.push_back(Sum);
295 AM.HasBaseReg = true;
299 /// getNumRegs - Return the total number of register operands used by this
300 /// formula. This does not include register uses implied by non-constant
302 unsigned Formula::getNumRegs() const {
303 return !!ScaledReg + BaseRegs.size();
306 /// getType - Return the type of this formula, if it has one, or null
307 /// otherwise. This type is meaningless except for the bit size.
308 const Type *Formula::getType() const {
309 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
310 ScaledReg ? ScaledReg->getType() :
311 AM.BaseGV ? AM.BaseGV->getType() :
315 /// DeleteBaseReg - Delete the given base reg from the BaseRegs list.
316 void Formula::DeleteBaseReg(const SCEV *&S) {
317 if (&S != &BaseRegs.back())
318 std::swap(S, BaseRegs.back());
322 /// referencesReg - Test if this formula references the given register.
323 bool Formula::referencesReg(const SCEV *S) const {
324 return S == ScaledReg ||
325 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
328 /// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
329 /// which are used by uses other than the use with the given index.
330 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
331 const RegUseTracker &RegUses) const {
333 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
335 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
336 E = BaseRegs.end(); I != E; ++I)
337 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
342 void Formula::print(raw_ostream &OS) const {
345 if (!First) OS << " + "; else First = false;
346 WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false);
348 if (AM.BaseOffs != 0) {
349 if (!First) OS << " + "; else First = false;
352 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
353 E = BaseRegs.end(); I != E; ++I) {
354 if (!First) OS << " + "; else First = false;
355 OS << "reg(" << **I << ')';
357 if (AM.HasBaseReg && BaseRegs.empty()) {
358 if (!First) OS << " + "; else First = false;
359 OS << "**error: HasBaseReg**";
360 } else if (!AM.HasBaseReg && !BaseRegs.empty()) {
361 if (!First) OS << " + "; else First = false;
362 OS << "**error: !HasBaseReg**";
365 if (!First) OS << " + "; else First = false;
366 OS << AM.Scale << "*reg(";
375 void Formula::dump() const {
376 print(errs()); errs() << '\n';
379 /// isAddRecSExtable - Return true if the given addrec can be sign-extended
380 /// without changing its value.
381 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
383 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
384 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
387 /// isAddSExtable - Return true if the given add can be sign-extended
388 /// without changing its value.
389 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
391 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
392 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
395 /// isMulSExtable - Return true if the given add can be sign-extended
396 /// without changing its value.
397 static bool isMulSExtable(const SCEVMulExpr *A, ScalarEvolution &SE) {
399 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
400 return isa<SCEVMulExpr>(SE.getSignExtendExpr(A, WideTy));
403 /// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
404 /// and if the remainder is known to be zero, or null otherwise. If
405 /// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
406 /// to Y, ignoring that the multiplication may overflow, which is useful when
407 /// the result will be used in a context where the most significant bits are
409 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
411 bool IgnoreSignificantBits = false) {
412 // Handle the trivial case, which works for any SCEV type.
414 return SE.getConstant(LHS->getType(), 1);
416 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do some
418 if (RHS->isAllOnesValue())
419 return SE.getMulExpr(LHS, RHS);
421 // Check for a division of a constant by a constant.
422 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
423 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
426 if (C->getValue()->getValue().srem(RC->getValue()->getValue()) != 0)
428 return SE.getConstant(C->getValue()->getValue()
429 .sdiv(RC->getValue()->getValue()));
432 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
433 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
434 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
435 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
436 IgnoreSignificantBits);
437 if (!Start) return 0;
438 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
439 IgnoreSignificantBits);
441 return SE.getAddRecExpr(Start, Step, AR->getLoop());
445 // Distribute the sdiv over add operands, if the add doesn't overflow.
446 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
447 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
448 SmallVector<const SCEV *, 8> Ops;
449 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
451 const SCEV *Op = getExactSDiv(*I, RHS, SE,
452 IgnoreSignificantBits);
456 return SE.getAddExpr(Ops);
460 // Check for a multiply operand that we can pull RHS out of.
461 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS))
462 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
463 SmallVector<const SCEV *, 4> Ops;
465 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
469 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
470 IgnoreSignificantBits)) {
476 return Found ? SE.getMulExpr(Ops) : 0;
479 // Otherwise we don't know.
483 /// ExtractImmediate - If S involves the addition of a constant integer value,
484 /// return that integer value, and mutate S to point to a new SCEV with that
486 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
487 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
488 if (C->getValue()->getValue().getMinSignedBits() <= 64) {
489 S = SE.getConstant(C->getType(), 0);
490 return C->getValue()->getSExtValue();
492 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
493 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
494 int64_t Result = ExtractImmediate(NewOps.front(), SE);
495 S = SE.getAddExpr(NewOps);
497 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
498 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
499 int64_t Result = ExtractImmediate(NewOps.front(), SE);
500 S = SE.getAddRecExpr(NewOps, AR->getLoop());
506 /// ExtractSymbol - If S involves the addition of a GlobalValue address,
507 /// return that symbol, and mutate S to point to a new SCEV with that
509 static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
510 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
511 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
512 S = SE.getConstant(GV->getType(), 0);
515 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
516 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
517 GlobalValue *Result = ExtractSymbol(NewOps.back(), 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 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
523 S = SE.getAddRecExpr(NewOps, AR->getLoop());
529 /// isAddressUse - Returns true if the specified instruction is using the
530 /// specified value as an address.
531 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
532 bool isAddress = isa<LoadInst>(Inst);
533 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
534 if (SI->getOperand(1) == OperandVal)
536 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
537 // Addressing modes can also be folded into prefetches and a variety
539 switch (II->getIntrinsicID()) {
541 case Intrinsic::prefetch:
542 case Intrinsic::x86_sse2_loadu_dq:
543 case Intrinsic::x86_sse2_loadu_pd:
544 case Intrinsic::x86_sse_loadu_ps:
545 case Intrinsic::x86_sse_storeu_ps:
546 case Intrinsic::x86_sse2_storeu_pd:
547 case Intrinsic::x86_sse2_storeu_dq:
548 case Intrinsic::x86_sse2_storel_dq:
549 if (II->getOperand(1) == OperandVal)
557 /// getAccessType - Return the type of the memory being accessed.
558 static const Type *getAccessType(const Instruction *Inst) {
559 const Type *AccessTy = Inst->getType();
560 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
561 AccessTy = SI->getOperand(0)->getType();
562 else if (const 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::x86_sse_storeu_ps:
568 case Intrinsic::x86_sse2_storeu_pd:
569 case Intrinsic::x86_sse2_storeu_dq:
570 case Intrinsic::x86_sse2_storel_dq:
571 AccessTy = II->getOperand(1)->getType();
576 // All pointers have the same requirements, so canonicalize them to an
577 // arbitrary pointer type to minimize variation.
578 if (const PointerType *PTy = dyn_cast<PointerType>(AccessTy))
579 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
580 PTy->getAddressSpace());
585 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
586 /// specified set are trivially dead, delete them and see if this makes any of
587 /// their operands subsequently dead.
589 DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
590 bool Changed = false;
592 while (!DeadInsts.empty()) {
593 Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
595 if (I == 0 || !isInstructionTriviallyDead(I))
598 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
599 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
602 DeadInsts.push_back(U);
605 I->eraseFromParent();
614 /// Cost - This class is used to measure and compare candidate formulae.
616 /// TODO: Some of these could be merged. Also, a lexical ordering
617 /// isn't always optimal.
621 unsigned NumBaseAdds;
627 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
630 unsigned getNumRegs() const { return NumRegs; }
632 bool operator<(const Cost &Other) const;
636 void RateFormula(const Formula &F,
637 SmallPtrSet<const SCEV *, 16> &Regs,
638 const DenseSet<const SCEV *> &VisitedRegs,
640 const SmallVectorImpl<int64_t> &Offsets,
641 ScalarEvolution &SE, DominatorTree &DT);
643 void print(raw_ostream &OS) const;
647 void RateRegister(const SCEV *Reg,
648 SmallPtrSet<const SCEV *, 16> &Regs,
650 ScalarEvolution &SE, DominatorTree &DT);
651 void RatePrimaryRegister(const SCEV *Reg,
652 SmallPtrSet<const SCEV *, 16> &Regs,
654 ScalarEvolution &SE, DominatorTree &DT);
659 /// RateRegister - Tally up interesting quantities from the given register.
660 void Cost::RateRegister(const SCEV *Reg,
661 SmallPtrSet<const SCEV *, 16> &Regs,
663 ScalarEvolution &SE, DominatorTree &DT) {
664 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
665 if (AR->getLoop() == L)
666 AddRecCost += 1; /// TODO: This should be a function of the stride.
668 // If this is an addrec for a loop that's already been visited by LSR,
669 // don't second-guess its addrec phi nodes. LSR isn't currently smart
670 // enough to reason about more than one loop at a time. Consider these
671 // registers free and leave them alone.
672 else if (L->contains(AR->getLoop()) ||
673 (!AR->getLoop()->contains(L) &&
674 DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) {
675 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
676 PHINode *PN = dyn_cast<PHINode>(I); ++I)
677 if (SE.isSCEVable(PN->getType()) &&
678 (SE.getEffectiveSCEVType(PN->getType()) ==
679 SE.getEffectiveSCEVType(AR->getType())) &&
680 SE.getSCEV(PN) == AR)
683 // If this isn't one of the addrecs that the loop already has, it
684 // would require a costly new phi and add. TODO: This isn't
685 // precisely modeled right now.
687 if (!Regs.count(AR->getStart()))
688 RateRegister(AR->getStart(), Regs, L, SE, DT);
691 // Add the step value register, if it needs one.
692 // TODO: The non-affine case isn't precisely modeled here.
693 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
694 if (!Regs.count(AR->getStart()))
695 RateRegister(AR->getOperand(1), Regs, L, SE, DT);
699 // Rough heuristic; favor registers which don't require extra setup
700 // instructions in the preheader.
701 if (!isa<SCEVUnknown>(Reg) &&
702 !isa<SCEVConstant>(Reg) &&
703 !(isa<SCEVAddRecExpr>(Reg) &&
704 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
705 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
709 /// RatePrimaryRegister - Record this register in the set. If we haven't seen it
711 void Cost::RatePrimaryRegister(const SCEV *Reg,
712 SmallPtrSet<const SCEV *, 16> &Regs,
714 ScalarEvolution &SE, DominatorTree &DT) {
715 if (Regs.insert(Reg))
716 RateRegister(Reg, Regs, L, SE, DT);
719 void Cost::RateFormula(const Formula &F,
720 SmallPtrSet<const SCEV *, 16> &Regs,
721 const DenseSet<const SCEV *> &VisitedRegs,
723 const SmallVectorImpl<int64_t> &Offsets,
724 ScalarEvolution &SE, DominatorTree &DT) {
725 // Tally up the registers.
726 if (const SCEV *ScaledReg = F.ScaledReg) {
727 if (VisitedRegs.count(ScaledReg)) {
731 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT);
733 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
734 E = F.BaseRegs.end(); I != E; ++I) {
735 const SCEV *BaseReg = *I;
736 if (VisitedRegs.count(BaseReg)) {
740 RatePrimaryRegister(BaseReg, Regs, L, SE, DT);
742 NumIVMuls += isa<SCEVMulExpr>(BaseReg) &&
743 BaseReg->hasComputableLoopEvolution(L);
746 if (F.BaseRegs.size() > 1)
747 NumBaseAdds += F.BaseRegs.size() - 1;
749 // Tally up the non-zero immediates.
750 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
751 E = Offsets.end(); I != E; ++I) {
752 int64_t Offset = (uint64_t)*I + F.AM.BaseOffs;
754 ImmCost += 64; // Handle symbolic values conservatively.
755 // TODO: This should probably be the pointer size.
756 else if (Offset != 0)
757 ImmCost += APInt(64, Offset, true).getMinSignedBits();
761 /// Loose - Set this cost to a loosing value.
771 /// operator< - Choose the lower cost.
772 bool Cost::operator<(const Cost &Other) const {
773 if (NumRegs != Other.NumRegs)
774 return NumRegs < Other.NumRegs;
775 if (AddRecCost != Other.AddRecCost)
776 return AddRecCost < Other.AddRecCost;
777 if (NumIVMuls != Other.NumIVMuls)
778 return NumIVMuls < Other.NumIVMuls;
779 if (NumBaseAdds != Other.NumBaseAdds)
780 return NumBaseAdds < Other.NumBaseAdds;
781 if (ImmCost != Other.ImmCost)
782 return ImmCost < Other.ImmCost;
783 if (SetupCost != Other.SetupCost)
784 return SetupCost < Other.SetupCost;
788 void Cost::print(raw_ostream &OS) const {
789 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
791 OS << ", with addrec cost " << AddRecCost;
793 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
794 if (NumBaseAdds != 0)
795 OS << ", plus " << NumBaseAdds << " base add"
796 << (NumBaseAdds == 1 ? "" : "s");
798 OS << ", plus " << ImmCost << " imm cost";
800 OS << ", plus " << SetupCost << " setup cost";
803 void Cost::dump() const {
804 print(errs()); errs() << '\n';
809 /// LSRFixup - An operand value in an instruction which is to be replaced
810 /// with some equivalent, possibly strength-reduced, replacement.
812 /// UserInst - The instruction which will be updated.
813 Instruction *UserInst;
815 /// OperandValToReplace - The operand of the instruction which will
816 /// be replaced. The operand may be used more than once; every instance
817 /// will be replaced.
818 Value *OperandValToReplace;
820 /// PostIncLoops - If this user is to use the post-incremented value of an
821 /// induction variable, this variable is non-null and holds the loop
822 /// associated with the induction variable.
823 PostIncLoopSet PostIncLoops;
825 /// LUIdx - The index of the LSRUse describing the expression which
826 /// this fixup needs, minus an offset (below).
829 /// Offset - A constant offset to be added to the LSRUse expression.
830 /// This allows multiple fixups to share the same LSRUse with different
831 /// offsets, for example in an unrolled loop.
834 bool isUseFullyOutsideLoop(const Loop *L) const;
838 void print(raw_ostream &OS) const;
845 : UserInst(0), OperandValToReplace(0), LUIdx(~size_t(0)), Offset(0) {}
847 /// isUseFullyOutsideLoop - Test whether this fixup always uses its
848 /// value outside of the given loop.
849 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
850 // PHI nodes use their value in their incoming blocks.
851 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
852 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
853 if (PN->getIncomingValue(i) == OperandValToReplace &&
854 L->contains(PN->getIncomingBlock(i)))
859 return !L->contains(UserInst);
862 void LSRFixup::print(raw_ostream &OS) const {
864 // Store is common and interesting enough to be worth special-casing.
865 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
867 WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false);
868 } else if (UserInst->getType()->isVoidTy())
869 OS << UserInst->getOpcodeName();
871 WriteAsOperand(OS, UserInst, /*PrintType=*/false);
873 OS << ", OperandValToReplace=";
874 WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false);
876 for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(),
877 E = PostIncLoops.end(); I != E; ++I) {
878 OS << ", PostIncLoop=";
879 WriteAsOperand(OS, (*I)->getHeader(), /*PrintType=*/false);
882 if (LUIdx != ~size_t(0))
883 OS << ", LUIdx=" << LUIdx;
886 OS << ", Offset=" << Offset;
889 void LSRFixup::dump() const {
890 print(errs()); errs() << '\n';
895 /// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
896 /// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
897 struct UniquifierDenseMapInfo {
898 static SmallVector<const SCEV *, 2> getEmptyKey() {
899 SmallVector<const SCEV *, 2> V;
900 V.push_back(reinterpret_cast<const SCEV *>(-1));
904 static SmallVector<const SCEV *, 2> getTombstoneKey() {
905 SmallVector<const SCEV *, 2> V;
906 V.push_back(reinterpret_cast<const SCEV *>(-2));
910 static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) {
912 for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(),
913 E = V.end(); I != E; ++I)
914 Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I);
918 static bool isEqual(const SmallVector<const SCEV *, 2> &LHS,
919 const SmallVector<const SCEV *, 2> &RHS) {
924 /// LSRUse - This class holds the state that LSR keeps for each use in
925 /// IVUsers, as well as uses invented by LSR itself. It includes information
926 /// about what kinds of things can be folded into the user, information about
927 /// the user itself, and information about how the use may be satisfied.
928 /// TODO: Represent multiple users of the same expression in common?
930 DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier;
933 /// KindType - An enum for a kind of use, indicating what types of
934 /// scaled and immediate operands it might support.
936 Basic, ///< A normal use, with no folding.
937 Special, ///< A special case of basic, allowing -1 scales.
938 Address, ///< An address use; folding according to TargetLowering
939 ICmpZero ///< An equality icmp with both operands folded into one.
940 // TODO: Add a generic icmp too?
944 const Type *AccessTy;
946 SmallVector<int64_t, 8> Offsets;
950 /// AllFixupsOutsideLoop - This records whether all of the fixups using this
951 /// LSRUse are outside of the loop, in which case some special-case heuristics
953 bool AllFixupsOutsideLoop;
955 /// Formulae - A list of ways to build a value that can satisfy this user.
956 /// After the list is populated, one of these is selected heuristically and
957 /// used to formulate a replacement for OperandValToReplace in UserInst.
958 SmallVector<Formula, 12> Formulae;
960 /// Regs - The set of register candidates used by all formulae in this LSRUse.
961 SmallPtrSet<const SCEV *, 4> Regs;
963 LSRUse(KindType K, const Type *T) : Kind(K), AccessTy(T),
964 MinOffset(INT64_MAX),
965 MaxOffset(INT64_MIN),
966 AllFixupsOutsideLoop(true) {}
968 bool HasFormulaWithSameRegs(const Formula &F) const;
969 bool InsertFormula(const Formula &F);
970 void DeleteFormula(Formula &F);
971 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
975 void print(raw_ostream &OS) const;
979 /// HasFormula - Test whether this use as a formula which has the same
980 /// registers as the given formula.
981 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
982 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
983 if (F.ScaledReg) Key.push_back(F.ScaledReg);
984 // Unstable sort by host order ok, because this is only used for uniquifying.
985 std::sort(Key.begin(), Key.end());
986 return Uniquifier.count(Key);
989 /// InsertFormula - If the given formula has not yet been inserted, add it to
990 /// the list, and return true. Return false otherwise.
991 bool LSRUse::InsertFormula(const Formula &F) {
992 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
993 if (F.ScaledReg) Key.push_back(F.ScaledReg);
994 // Unstable sort by host order ok, because this is only used for uniquifying.
995 std::sort(Key.begin(), Key.end());
997 if (!Uniquifier.insert(Key).second)
1000 // Using a register to hold the value of 0 is not profitable.
1001 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1002 "Zero allocated in a scaled register!");
1004 for (SmallVectorImpl<const SCEV *>::const_iterator I =
1005 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
1006 assert(!(*I)->isZero() && "Zero allocated in a base register!");
1009 // Add the formula to the list.
1010 Formulae.push_back(F);
1012 // Record registers now being used by this use.
1013 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1014 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1019 /// DeleteFormula - Remove the given formula from this use's list.
1020 void LSRUse::DeleteFormula(Formula &F) {
1021 if (&F != &Formulae.back())
1022 std::swap(F, Formulae.back());
1023 Formulae.pop_back();
1024 assert(!Formulae.empty() && "LSRUse has no formulae left!");
1027 /// RecomputeRegs - Recompute the Regs field, and update RegUses.
1028 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1029 // Now that we've filtered out some formulae, recompute the Regs set.
1030 SmallPtrSet<const SCEV *, 4> OldRegs = Regs;
1032 for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(),
1033 E = Formulae.end(); I != E; ++I) {
1034 const Formula &F = *I;
1035 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1036 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1039 // Update the RegTracker.
1040 for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(),
1041 E = OldRegs.end(); I != E; ++I)
1042 if (!Regs.count(*I))
1043 RegUses.DropRegister(*I, LUIdx);
1046 void LSRUse::print(raw_ostream &OS) const {
1047 OS << "LSR Use: Kind=";
1049 case Basic: OS << "Basic"; break;
1050 case Special: OS << "Special"; break;
1051 case ICmpZero: OS << "ICmpZero"; break;
1053 OS << "Address of ";
1054 if (AccessTy->isPointerTy())
1055 OS << "pointer"; // the full pointer type could be really verbose
1060 OS << ", Offsets={";
1061 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
1062 E = Offsets.end(); I != E; ++I) {
1069 if (AllFixupsOutsideLoop)
1070 OS << ", all-fixups-outside-loop";
1073 void LSRUse::dump() const {
1074 print(errs()); errs() << '\n';
1077 /// isLegalUse - Test whether the use described by AM is "legal", meaning it can
1078 /// be completely folded into the user instruction at isel time. This includes
1079 /// address-mode folding and special icmp tricks.
1080 static bool isLegalUse(const TargetLowering::AddrMode &AM,
1081 LSRUse::KindType Kind, const Type *AccessTy,
1082 const TargetLowering *TLI) {
1084 case LSRUse::Address:
1085 // If we have low-level target information, ask the target if it can
1086 // completely fold this address.
1087 if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy);
1089 // Otherwise, just guess that reg+reg addressing is legal.
1090 return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1;
1092 case LSRUse::ICmpZero:
1093 // There's not even a target hook for querying whether it would be legal to
1094 // fold a GV into an ICmp.
1098 // ICmp only has two operands; don't allow more than two non-trivial parts.
1099 if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0)
1102 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1103 // putting the scaled register in the other operand of the icmp.
1104 if (AM.Scale != 0 && AM.Scale != -1)
1107 // If we have low-level target information, ask the target if it can fold an
1108 // integer immediate on an icmp.
1109 if (AM.BaseOffs != 0) {
1110 if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs);
1117 // Only handle single-register values.
1118 return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
1120 case LSRUse::Special:
1121 // Only handle -1 scales, or no scale.
1122 return AM.Scale == 0 || AM.Scale == -1;
1128 static bool isLegalUse(TargetLowering::AddrMode AM,
1129 int64_t MinOffset, int64_t MaxOffset,
1130 LSRUse::KindType Kind, const Type *AccessTy,
1131 const TargetLowering *TLI) {
1132 // Check for overflow.
1133 if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) !=
1136 AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset;
1137 if (isLegalUse(AM, Kind, AccessTy, TLI)) {
1138 AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset;
1139 // Check for overflow.
1140 if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) !=
1143 AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset;
1144 return isLegalUse(AM, Kind, AccessTy, TLI);
1149 static bool isAlwaysFoldable(int64_t BaseOffs,
1150 GlobalValue *BaseGV,
1152 LSRUse::KindType Kind, const Type *AccessTy,
1153 const TargetLowering *TLI) {
1154 // Fast-path: zero is always foldable.
1155 if (BaseOffs == 0 && !BaseGV) return true;
1157 // Conservatively, create an address with an immediate and a
1158 // base and a scale.
1159 TargetLowering::AddrMode AM;
1160 AM.BaseOffs = BaseOffs;
1162 AM.HasBaseReg = HasBaseReg;
1163 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1165 // Canonicalize a scale of 1 to a base register if the formula doesn't
1166 // already have a base register.
1167 if (!AM.HasBaseReg && AM.Scale == 1) {
1169 AM.HasBaseReg = true;
1172 return isLegalUse(AM, Kind, AccessTy, TLI);
1175 static bool isAlwaysFoldable(const SCEV *S,
1176 int64_t MinOffset, int64_t MaxOffset,
1178 LSRUse::KindType Kind, const Type *AccessTy,
1179 const TargetLowering *TLI,
1180 ScalarEvolution &SE) {
1181 // Fast-path: zero is always foldable.
1182 if (S->isZero()) return true;
1184 // Conservatively, create an address with an immediate and a
1185 // base and a scale.
1186 int64_t BaseOffs = ExtractImmediate(S, SE);
1187 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1189 // If there's anything else involved, it's not foldable.
1190 if (!S->isZero()) return false;
1192 // Fast-path: zero is always foldable.
1193 if (BaseOffs == 0 && !BaseGV) return true;
1195 // Conservatively, create an address with an immediate and a
1196 // base and a scale.
1197 TargetLowering::AddrMode AM;
1198 AM.BaseOffs = BaseOffs;
1200 AM.HasBaseReg = HasBaseReg;
1201 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1203 return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI);
1206 /// FormulaSorter - This class implements an ordering for formulae which sorts
1207 /// the by their standalone cost.
1208 class FormulaSorter {
1209 /// These two sets are kept empty, so that we compute standalone costs.
1210 DenseSet<const SCEV *> VisitedRegs;
1211 SmallPtrSet<const SCEV *, 16> Regs;
1214 ScalarEvolution &SE;
1218 FormulaSorter(Loop *l, LSRUse &lu, ScalarEvolution &se, DominatorTree &dt)
1219 : L(l), LU(&lu), SE(se), DT(dt) {}
1221 bool operator()(const Formula &A, const Formula &B) {
1223 CostA.RateFormula(A, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
1226 CostB.RateFormula(B, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
1228 return CostA < CostB;
1232 /// LSRInstance - This class holds state for the main loop strength reduction
1236 ScalarEvolution &SE;
1239 const TargetLowering *const TLI;
1243 /// IVIncInsertPos - This is the insert position that the current loop's
1244 /// induction variable increment should be placed. In simple loops, this is
1245 /// the latch block's terminator. But in more complicated cases, this is a
1246 /// position which will dominate all the in-loop post-increment users.
1247 Instruction *IVIncInsertPos;
1249 /// Factors - Interesting factors between use strides.
1250 SmallSetVector<int64_t, 8> Factors;
1252 /// Types - Interesting use types, to facilitate truncation reuse.
1253 SmallSetVector<const Type *, 4> Types;
1255 /// Fixups - The list of operands which are to be replaced.
1256 SmallVector<LSRFixup, 16> Fixups;
1258 /// Uses - The list of interesting uses.
1259 SmallVector<LSRUse, 16> Uses;
1261 /// RegUses - Track which uses use which register candidates.
1262 RegUseTracker RegUses;
1264 void OptimizeShadowIV();
1265 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1266 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1267 void OptimizeLoopTermCond();
1269 void CollectInterestingTypesAndFactors();
1270 void CollectFixupsAndInitialFormulae();
1272 LSRFixup &getNewFixup() {
1273 Fixups.push_back(LSRFixup());
1274 return Fixups.back();
1277 // Support for sharing of LSRUses between LSRFixups.
1278 typedef DenseMap<const SCEV *, size_t> UseMapTy;
1281 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1282 LSRUse::KindType Kind, const Type *AccessTy);
1284 std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1285 LSRUse::KindType Kind,
1286 const Type *AccessTy);
1288 void DeleteUse(LSRUse &LU);
1290 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1293 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1294 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1295 void CountRegisters(const Formula &F, size_t LUIdx);
1296 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1298 void CollectLoopInvariantFixupsAndFormulae();
1300 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1301 unsigned Depth = 0);
1302 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1303 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1304 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1305 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1306 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1307 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1308 void GenerateCrossUseConstantOffsets();
1309 void GenerateAllReuseFormulae();
1311 void FilterOutUndesirableDedicatedRegisters();
1313 size_t EstimateSearchSpaceComplexity() const;
1314 void NarrowSearchSpaceUsingHeuristics();
1316 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1318 SmallVectorImpl<const Formula *> &Workspace,
1319 const Cost &CurCost,
1320 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1321 DenseSet<const SCEV *> &VisitedRegs) const;
1322 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1324 BasicBlock::iterator
1325 HoistInsertPosition(BasicBlock::iterator IP,
1326 const SmallVectorImpl<Instruction *> &Inputs) const;
1327 BasicBlock::iterator AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1329 const LSRUse &LU) const;
1331 Value *Expand(const LSRFixup &LF,
1333 BasicBlock::iterator IP,
1334 SCEVExpander &Rewriter,
1335 SmallVectorImpl<WeakVH> &DeadInsts) const;
1336 void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
1338 SCEVExpander &Rewriter,
1339 SmallVectorImpl<WeakVH> &DeadInsts,
1341 void Rewrite(const LSRFixup &LF,
1343 SCEVExpander &Rewriter,
1344 SmallVectorImpl<WeakVH> &DeadInsts,
1346 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1349 LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
1351 bool getChanged() const { return Changed; }
1353 void print_factors_and_types(raw_ostream &OS) const;
1354 void print_fixups(raw_ostream &OS) const;
1355 void print_uses(raw_ostream &OS) const;
1356 void print(raw_ostream &OS) const;
1362 /// OptimizeShadowIV - If IV is used in a int-to-float cast
1363 /// inside the loop then try to eliminate the cast operation.
1364 void LSRInstance::OptimizeShadowIV() {
1365 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1366 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1369 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1370 UI != E; /* empty */) {
1371 IVUsers::const_iterator CandidateUI = UI;
1373 Instruction *ShadowUse = CandidateUI->getUser();
1374 const Type *DestTy = NULL;
1376 /* If shadow use is a int->float cast then insert a second IV
1377 to eliminate this cast.
1379 for (unsigned i = 0; i < n; ++i)
1385 for (unsigned i = 0; i < n; ++i, ++d)
1388 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser()))
1389 DestTy = UCast->getDestTy();
1390 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser()))
1391 DestTy = SCast->getDestTy();
1392 if (!DestTy) continue;
1395 // If target does not support DestTy natively then do not apply
1396 // this transformation.
1397 EVT DVT = TLI->getValueType(DestTy);
1398 if (!TLI->isTypeLegal(DVT)) continue;
1401 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1403 if (PH->getNumIncomingValues() != 2) continue;
1405 const Type *SrcTy = PH->getType();
1406 int Mantissa = DestTy->getFPMantissaWidth();
1407 if (Mantissa == -1) continue;
1408 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1411 unsigned Entry, Latch;
1412 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1420 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1421 if (!Init) continue;
1422 Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
1424 BinaryOperator *Incr =
1425 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1426 if (!Incr) continue;
1427 if (Incr->getOpcode() != Instruction::Add
1428 && Incr->getOpcode() != Instruction::Sub)
1431 /* Initialize new IV, double d = 0.0 in above example. */
1432 ConstantInt *C = NULL;
1433 if (Incr->getOperand(0) == PH)
1434 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1435 else if (Incr->getOperand(1) == PH)
1436 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1442 // Ignore negative constants, as the code below doesn't handle them
1443 // correctly. TODO: Remove this restriction.
1444 if (!C->getValue().isStrictlyPositive()) continue;
1446 /* Add new PHINode. */
1447 PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
1449 /* create new increment. '++d' in above example. */
1450 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1451 BinaryOperator *NewIncr =
1452 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1453 Instruction::FAdd : Instruction::FSub,
1454 NewPH, CFP, "IV.S.next.", Incr);
1456 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1457 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1459 /* Remove cast operation */
1460 ShadowUse->replaceAllUsesWith(NewPH);
1461 ShadowUse->eraseFromParent();
1467 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1468 /// set the IV user and stride information and return true, otherwise return
1470 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
1471 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1472 if (UI->getUser() == Cond) {
1473 // NOTE: we could handle setcc instructions with multiple uses here, but
1474 // InstCombine does it as well for simple uses, it's not clear that it
1475 // occurs enough in real life to handle.
1482 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
1483 /// a max computation.
1485 /// This is a narrow solution to a specific, but acute, problem. For loops
1491 /// } while (++i < n);
1493 /// the trip count isn't just 'n', because 'n' might not be positive. And
1494 /// unfortunately this can come up even for loops where the user didn't use
1495 /// a C do-while loop. For example, seemingly well-behaved top-test loops
1496 /// will commonly be lowered like this:
1502 /// } while (++i < n);
1505 /// and then it's possible for subsequent optimization to obscure the if
1506 /// test in such a way that indvars can't find it.
1508 /// When indvars can't find the if test in loops like this, it creates a
1509 /// max expression, which allows it to give the loop a canonical
1510 /// induction variable:
1513 /// max = n < 1 ? 1 : n;
1516 /// } while (++i != max);
1518 /// Canonical induction variables are necessary because the loop passes
1519 /// are designed around them. The most obvious example of this is the
1520 /// LoopInfo analysis, which doesn't remember trip count values. It
1521 /// expects to be able to rediscover the trip count each time it is
1522 /// needed, and it does this using a simple analysis that only succeeds if
1523 /// the loop has a canonical induction variable.
1525 /// However, when it comes time to generate code, the maximum operation
1526 /// can be quite costly, especially if it's inside of an outer loop.
1528 /// This function solves this problem by detecting this type of loop and
1529 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1530 /// the instructions for the maximum computation.
1532 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1533 // Check that the loop matches the pattern we're looking for.
1534 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1535 Cond->getPredicate() != CmpInst::ICMP_NE)
1538 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
1539 if (!Sel || !Sel->hasOneUse()) return Cond;
1541 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1542 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1544 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
1546 // Add one to the backedge-taken count to get the trip count.
1547 const SCEV *IterationCount = SE.getAddExpr(BackedgeTakenCount, One);
1548 if (IterationCount != SE.getSCEV(Sel)) return Cond;
1550 // Check for a max calculation that matches the pattern. There's no check
1551 // for ICMP_ULE here because the comparison would be with zero, which
1552 // isn't interesting.
1553 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
1554 const SCEVNAryExpr *Max = 0;
1555 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
1556 Pred = ICmpInst::ICMP_SLE;
1558 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
1559 Pred = ICmpInst::ICMP_SLT;
1561 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
1562 Pred = ICmpInst::ICMP_ULT;
1569 // To handle a max with more than two operands, this optimization would
1570 // require additional checking and setup.
1571 if (Max->getNumOperands() != 2)
1574 const SCEV *MaxLHS = Max->getOperand(0);
1575 const SCEV *MaxRHS = Max->getOperand(1);
1577 // ScalarEvolution canonicalizes constants to the left. For < and >, look
1578 // for a comparison with 1. For <= and >=, a comparison with zero.
1580 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
1583 // Check the relevant induction variable for conformance to
1585 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
1586 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
1587 if (!AR || !AR->isAffine() ||
1588 AR->getStart() != One ||
1589 AR->getStepRecurrence(SE) != One)
1592 assert(AR->getLoop() == L &&
1593 "Loop condition operand is an addrec in a different loop!");
1595 // Check the right operand of the select, and remember it, as it will
1596 // be used in the new comparison instruction.
1598 if (ICmpInst::isTrueWhenEqual(Pred)) {
1599 // Look for n+1, and grab n.
1600 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
1601 if (isa<ConstantInt>(BO->getOperand(1)) &&
1602 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1603 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1604 NewRHS = BO->getOperand(0);
1605 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
1606 if (isa<ConstantInt>(BO->getOperand(1)) &&
1607 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1608 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1609 NewRHS = BO->getOperand(0);
1612 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
1613 NewRHS = Sel->getOperand(1);
1614 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
1615 NewRHS = Sel->getOperand(2);
1617 llvm_unreachable("Max doesn't match expected pattern!");
1619 // Determine the new comparison opcode. It may be signed or unsigned,
1620 // and the original comparison may be either equality or inequality.
1621 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
1622 Pred = CmpInst::getInversePredicate(Pred);
1624 // Ok, everything looks ok to change the condition into an SLT or SGE and
1625 // delete the max calculation.
1627 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
1629 // Delete the max calculation instructions.
1630 Cond->replaceAllUsesWith(NewCond);
1631 CondUse->setUser(NewCond);
1632 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
1633 Cond->eraseFromParent();
1634 Sel->eraseFromParent();
1635 if (Cmp->use_empty())
1636 Cmp->eraseFromParent();
1640 /// OptimizeLoopTermCond - Change loop terminating condition to use the
1641 /// postinc iv when possible.
1643 LSRInstance::OptimizeLoopTermCond() {
1644 SmallPtrSet<Instruction *, 4> PostIncs;
1646 BasicBlock *LatchBlock = L->getLoopLatch();
1647 SmallVector<BasicBlock*, 8> ExitingBlocks;
1648 L->getExitingBlocks(ExitingBlocks);
1650 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
1651 BasicBlock *ExitingBlock = ExitingBlocks[i];
1653 // Get the terminating condition for the loop if possible. If we
1654 // can, we want to change it to use a post-incremented version of its
1655 // induction variable, to allow coalescing the live ranges for the IV into
1656 // one register value.
1658 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
1661 // FIXME: Overly conservative, termination condition could be an 'or' etc..
1662 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
1665 // Search IVUsesByStride to find Cond's IVUse if there is one.
1666 IVStrideUse *CondUse = 0;
1667 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
1668 if (!FindIVUserForCond(Cond, CondUse))
1671 // If the trip count is computed in terms of a max (due to ScalarEvolution
1672 // being unable to find a sufficient guard, for example), change the loop
1673 // comparison to use SLT or ULT instead of NE.
1674 // One consequence of doing this now is that it disrupts the count-down
1675 // optimization. That's not always a bad thing though, because in such
1676 // cases it may still be worthwhile to avoid a max.
1677 Cond = OptimizeMax(Cond, CondUse);
1679 // If this exiting block dominates the latch block, it may also use
1680 // the post-inc value if it won't be shared with other uses.
1681 // Check for dominance.
1682 if (!DT.dominates(ExitingBlock, LatchBlock))
1685 // Conservatively avoid trying to use the post-inc value in non-latch
1686 // exits if there may be pre-inc users in intervening blocks.
1687 if (LatchBlock != ExitingBlock)
1688 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1689 // Test if the use is reachable from the exiting block. This dominator
1690 // query is a conservative approximation of reachability.
1691 if (&*UI != CondUse &&
1692 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
1693 // Conservatively assume there may be reuse if the quotient of their
1694 // strides could be a legal scale.
1695 const SCEV *A = IU.getStride(*CondUse, L);
1696 const SCEV *B = IU.getStride(*UI, L);
1697 if (!A || !B) continue;
1698 if (SE.getTypeSizeInBits(A->getType()) !=
1699 SE.getTypeSizeInBits(B->getType())) {
1700 if (SE.getTypeSizeInBits(A->getType()) >
1701 SE.getTypeSizeInBits(B->getType()))
1702 B = SE.getSignExtendExpr(B, A->getType());
1704 A = SE.getSignExtendExpr(A, B->getType());
1706 if (const SCEVConstant *D =
1707 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
1708 // Stride of one or negative one can have reuse with non-addresses.
1709 if (D->getValue()->isOne() ||
1710 D->getValue()->isAllOnesValue())
1711 goto decline_post_inc;
1712 // Avoid weird situations.
1713 if (D->getValue()->getValue().getMinSignedBits() >= 64 ||
1714 D->getValue()->getValue().isMinSignedValue())
1715 goto decline_post_inc;
1716 // Without TLI, assume that any stride might be valid, and so any
1717 // use might be shared.
1719 goto decline_post_inc;
1720 // Check for possible scaled-address reuse.
1721 const Type *AccessTy = getAccessType(UI->getUser());
1722 TargetLowering::AddrMode AM;
1723 AM.Scale = D->getValue()->getSExtValue();
1724 if (TLI->isLegalAddressingMode(AM, AccessTy))
1725 goto decline_post_inc;
1726 AM.Scale = -AM.Scale;
1727 if (TLI->isLegalAddressingMode(AM, AccessTy))
1728 goto decline_post_inc;
1732 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
1735 // It's possible for the setcc instruction to be anywhere in the loop, and
1736 // possible for it to have multiple users. If it is not immediately before
1737 // the exiting block branch, move it.
1738 if (&*++BasicBlock::iterator(Cond) != TermBr) {
1739 if (Cond->hasOneUse()) {
1740 Cond->moveBefore(TermBr);
1742 // Clone the terminating condition and insert into the loopend.
1743 ICmpInst *OldCond = Cond;
1744 Cond = cast<ICmpInst>(Cond->clone());
1745 Cond->setName(L->getHeader()->getName() + ".termcond");
1746 ExitingBlock->getInstList().insert(TermBr, Cond);
1748 // Clone the IVUse, as the old use still exists!
1749 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
1750 TermBr->replaceUsesOfWith(OldCond, Cond);
1754 // If we get to here, we know that we can transform the setcc instruction to
1755 // use the post-incremented version of the IV, allowing us to coalesce the
1756 // live ranges for the IV correctly.
1757 CondUse->transformToPostInc(L);
1760 PostIncs.insert(Cond);
1764 // Determine an insertion point for the loop induction variable increment. It
1765 // must dominate all the post-inc comparisons we just set up, and it must
1766 // dominate the loop latch edge.
1767 IVIncInsertPos = L->getLoopLatch()->getTerminator();
1768 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
1769 E = PostIncs.end(); I != E; ++I) {
1771 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
1773 if (BB == (*I)->getParent())
1774 IVIncInsertPos = *I;
1775 else if (BB != IVIncInsertPos->getParent())
1776 IVIncInsertPos = BB->getTerminator();
1781 LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1782 LSRUse::KindType Kind, const Type *AccessTy) {
1783 int64_t NewMinOffset = LU.MinOffset;
1784 int64_t NewMaxOffset = LU.MaxOffset;
1785 const Type *NewAccessTy = AccessTy;
1787 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
1788 // something conservative, however this can pessimize in the case that one of
1789 // the uses will have all its uses outside the loop, for example.
1790 if (LU.Kind != Kind)
1792 // Conservatively assume HasBaseReg is true for now.
1793 if (NewOffset < LU.MinOffset) {
1794 if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg,
1795 Kind, AccessTy, TLI))
1797 NewMinOffset = NewOffset;
1798 } else if (NewOffset > LU.MaxOffset) {
1799 if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg,
1800 Kind, AccessTy, TLI))
1802 NewMaxOffset = NewOffset;
1804 // Check for a mismatched access type, and fall back conservatively as needed.
1805 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
1806 NewAccessTy = Type::getVoidTy(AccessTy->getContext());
1809 LU.MinOffset = NewMinOffset;
1810 LU.MaxOffset = NewMaxOffset;
1811 LU.AccessTy = NewAccessTy;
1812 if (NewOffset != LU.Offsets.back())
1813 LU.Offsets.push_back(NewOffset);
1817 /// getUse - Return an LSRUse index and an offset value for a fixup which
1818 /// needs the given expression, with the given kind and optional access type.
1819 /// Either reuse an existing use or create a new one, as needed.
1820 std::pair<size_t, int64_t>
1821 LSRInstance::getUse(const SCEV *&Expr,
1822 LSRUse::KindType Kind, const Type *AccessTy) {
1823 const SCEV *Copy = Expr;
1824 int64_t Offset = ExtractImmediate(Expr, SE);
1826 // Basic uses can't accept any offset, for example.
1827 if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) {
1832 std::pair<UseMapTy::iterator, bool> P =
1833 UseMap.insert(std::make_pair(Expr, 0));
1835 // A use already existed with this base.
1836 size_t LUIdx = P.first->second;
1837 LSRUse &LU = Uses[LUIdx];
1838 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
1840 return std::make_pair(LUIdx, Offset);
1843 // Create a new use.
1844 size_t LUIdx = Uses.size();
1845 P.first->second = LUIdx;
1846 Uses.push_back(LSRUse(Kind, AccessTy));
1847 LSRUse &LU = Uses[LUIdx];
1849 // We don't need to track redundant offsets, but we don't need to go out
1850 // of our way here to avoid them.
1851 if (LU.Offsets.empty() || Offset != LU.Offsets.back())
1852 LU.Offsets.push_back(Offset);
1854 LU.MinOffset = Offset;
1855 LU.MaxOffset = Offset;
1856 return std::make_pair(LUIdx, Offset);
1859 /// DeleteUse - Delete the given use from the Uses list.
1860 void LSRInstance::DeleteUse(LSRUse &LU) {
1861 if (&LU != &Uses.back())
1862 std::swap(LU, Uses.back());
1866 /// FindUseWithFormula - Look for a use distinct from OrigLU which is has
1867 /// a formula that has the same registers as the given formula.
1869 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
1870 const LSRUse &OrigLU) {
1871 // Search all uses for the formula. This could be more clever. Ignore
1872 // ICmpZero uses because they may contain formulae generated by
1873 // GenerateICmpZeroScales, in which case adding fixup offsets may
1875 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
1876 LSRUse &LU = Uses[LUIdx];
1877 if (&LU != &OrigLU &&
1878 LU.Kind != LSRUse::ICmpZero &&
1879 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
1880 LU.HasFormulaWithSameRegs(OrigF)) {
1881 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
1882 E = LU.Formulae.end(); I != E; ++I) {
1883 const Formula &F = *I;
1884 if (F.BaseRegs == OrigF.BaseRegs &&
1885 F.ScaledReg == OrigF.ScaledReg &&
1886 F.AM.BaseGV == OrigF.AM.BaseGV &&
1887 F.AM.Scale == OrigF.AM.Scale &&
1889 if (F.AM.BaseOffs == 0)
1900 void LSRInstance::CollectInterestingTypesAndFactors() {
1901 SmallSetVector<const SCEV *, 4> Strides;
1903 // Collect interesting types and strides.
1904 SmallVector<const SCEV *, 4> Worklist;
1905 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
1906 const SCEV *Expr = IU.getExpr(*UI);
1908 // Collect interesting types.
1909 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
1911 // Add strides for mentioned loops.
1912 Worklist.push_back(Expr);
1914 const SCEV *S = Worklist.pop_back_val();
1915 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
1916 Strides.insert(AR->getStepRecurrence(SE));
1917 Worklist.push_back(AR->getStart());
1918 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
1919 Worklist.insert(Worklist.end(), Add->op_begin(), Add->op_end());
1921 } while (!Worklist.empty());
1924 // Compute interesting factors from the set of interesting strides.
1925 for (SmallSetVector<const SCEV *, 4>::const_iterator
1926 I = Strides.begin(), E = Strides.end(); I != E; ++I)
1927 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
1928 next(I); NewStrideIter != E; ++NewStrideIter) {
1929 const SCEV *OldStride = *I;
1930 const SCEV *NewStride = *NewStrideIter;
1932 if (SE.getTypeSizeInBits(OldStride->getType()) !=
1933 SE.getTypeSizeInBits(NewStride->getType())) {
1934 if (SE.getTypeSizeInBits(OldStride->getType()) >
1935 SE.getTypeSizeInBits(NewStride->getType()))
1936 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
1938 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
1940 if (const SCEVConstant *Factor =
1941 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
1943 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
1944 Factors.insert(Factor->getValue()->getValue().getSExtValue());
1945 } else if (const SCEVConstant *Factor =
1946 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
1949 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
1950 Factors.insert(Factor->getValue()->getValue().getSExtValue());
1954 // If all uses use the same type, don't bother looking for truncation-based
1956 if (Types.size() == 1)
1959 DEBUG(print_factors_and_types(dbgs()));
1962 void LSRInstance::CollectFixupsAndInitialFormulae() {
1963 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
1965 LSRFixup &LF = getNewFixup();
1966 LF.UserInst = UI->getUser();
1967 LF.OperandValToReplace = UI->getOperandValToReplace();
1968 LF.PostIncLoops = UI->getPostIncLoops();
1970 LSRUse::KindType Kind = LSRUse::Basic;
1971 const Type *AccessTy = 0;
1972 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
1973 Kind = LSRUse::Address;
1974 AccessTy = getAccessType(LF.UserInst);
1977 const SCEV *S = IU.getExpr(*UI);
1979 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
1980 // (N - i == 0), and this allows (N - i) to be the expression that we work
1981 // with rather than just N or i, so we can consider the register
1982 // requirements for both N and i at the same time. Limiting this code to
1983 // equality icmps is not a problem because all interesting loops use
1984 // equality icmps, thanks to IndVarSimplify.
1985 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
1986 if (CI->isEquality()) {
1987 // Swap the operands if needed to put the OperandValToReplace on the
1988 // left, for consistency.
1989 Value *NV = CI->getOperand(1);
1990 if (NV == LF.OperandValToReplace) {
1991 CI->setOperand(1, CI->getOperand(0));
1992 CI->setOperand(0, NV);
1993 NV = CI->getOperand(1);
1997 // x == y --> x - y == 0
1998 const SCEV *N = SE.getSCEV(NV);
1999 if (N->isLoopInvariant(L)) {
2000 Kind = LSRUse::ICmpZero;
2001 S = SE.getMinusSCEV(N, S);
2004 // -1 and the negations of all interesting strides (except the negation
2005 // of -1) are now also interesting.
2006 for (size_t i = 0, e = Factors.size(); i != e; ++i)
2007 if (Factors[i] != -1)
2008 Factors.insert(-(uint64_t)Factors[i]);
2012 // Set up the initial formula for this use.
2013 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
2015 LF.Offset = P.second;
2016 LSRUse &LU = Uses[LF.LUIdx];
2017 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
2019 // If this is the first use of this LSRUse, give it a formula.
2020 if (LU.Formulae.empty()) {
2021 InsertInitialFormula(S, LU, LF.LUIdx);
2022 CountRegisters(LU.Formulae.back(), LF.LUIdx);
2026 DEBUG(print_fixups(dbgs()));
2030 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
2032 F.InitialMatch(S, L, SE, DT);
2033 bool Inserted = InsertFormula(LU, LUIdx, F);
2034 assert(Inserted && "Initial formula already exists!"); (void)Inserted;
2038 LSRInstance::InsertSupplementalFormula(const SCEV *S,
2039 LSRUse &LU, size_t LUIdx) {
2041 F.BaseRegs.push_back(S);
2042 F.AM.HasBaseReg = true;
2043 bool Inserted = InsertFormula(LU, LUIdx, F);
2044 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
2047 /// CountRegisters - Note which registers are used by the given formula,
2048 /// updating RegUses.
2049 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
2051 RegUses.CountRegister(F.ScaledReg, LUIdx);
2052 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
2053 E = F.BaseRegs.end(); I != E; ++I)
2054 RegUses.CountRegister(*I, LUIdx);
2057 /// InsertFormula - If the given formula has not yet been inserted, add it to
2058 /// the list, and return true. Return false otherwise.
2059 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
2060 if (!LU.InsertFormula(F))
2063 CountRegisters(F, LUIdx);
2067 /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
2068 /// loop-invariant values which we're tracking. These other uses will pin these
2069 /// values in registers, making them less profitable for elimination.
2070 /// TODO: This currently misses non-constant addrec step registers.
2071 /// TODO: Should this give more weight to users inside the loop?
2073 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
2074 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
2075 SmallPtrSet<const SCEV *, 8> Inserted;
2077 while (!Worklist.empty()) {
2078 const SCEV *S = Worklist.pop_back_val();
2080 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
2081 Worklist.insert(Worklist.end(), N->op_begin(), N->op_end());
2082 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
2083 Worklist.push_back(C->getOperand());
2084 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
2085 Worklist.push_back(D->getLHS());
2086 Worklist.push_back(D->getRHS());
2087 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2088 if (!Inserted.insert(U)) continue;
2089 const Value *V = U->getValue();
2090 if (const Instruction *Inst = dyn_cast<Instruction>(V))
2091 if (L->contains(Inst)) continue;
2092 for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
2094 const Instruction *UserInst = dyn_cast<Instruction>(*UI);
2095 // Ignore non-instructions.
2098 // Ignore instructions in other functions (as can happen with
2100 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
2102 // Ignore instructions not dominated by the loop.
2103 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
2104 UserInst->getParent() :
2105 cast<PHINode>(UserInst)->getIncomingBlock(
2106 PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
2107 if (!DT.dominates(L->getHeader(), UseBB))
2109 // Ignore uses which are part of other SCEV expressions, to avoid
2110 // analyzing them multiple times.
2111 if (SE.isSCEVable(UserInst->getType())) {
2112 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
2113 // If the user is a no-op, look through to its uses.
2114 if (!isa<SCEVUnknown>(UserS))
2118 SE.getUnknown(const_cast<Instruction *>(UserInst)));
2122 // Ignore icmp instructions which are already being analyzed.
2123 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
2124 unsigned OtherIdx = !UI.getOperandNo();
2125 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
2126 if (SE.getSCEV(OtherOp)->hasComputableLoopEvolution(L))
2130 LSRFixup &LF = getNewFixup();
2131 LF.UserInst = const_cast<Instruction *>(UserInst);
2132 LF.OperandValToReplace = UI.getUse();
2133 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0);
2135 LF.Offset = P.second;
2136 LSRUse &LU = Uses[LF.LUIdx];
2137 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
2138 InsertSupplementalFormula(U, LU, LF.LUIdx);
2139 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
2146 /// CollectSubexprs - Split S into subexpressions which can be pulled out into
2147 /// separate registers. If C is non-null, multiply each subexpression by C.
2148 static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
2149 SmallVectorImpl<const SCEV *> &Ops,
2150 ScalarEvolution &SE) {
2151 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2152 // Break out add operands.
2153 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
2155 CollectSubexprs(*I, C, Ops, SE);
2157 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2158 // Split a non-zero base out of an addrec.
2159 if (!AR->getStart()->isZero()) {
2160 CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
2161 AR->getStepRecurrence(SE),
2162 AR->getLoop()), C, Ops, SE);
2163 CollectSubexprs(AR->getStart(), C, Ops, SE);
2166 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
2167 // Break (C * (a + b + c)) into C*a + C*b + C*c.
2168 if (Mul->getNumOperands() == 2)
2169 if (const SCEVConstant *Op0 =
2170 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2171 CollectSubexprs(Mul->getOperand(1),
2172 C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
2178 // Otherwise use the value itself.
2179 Ops.push_back(C ? SE.getMulExpr(C, S) : S);
2182 /// GenerateReassociations - Split out subexpressions from adds and the bases of
2184 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
2187 // Arbitrarily cap recursion to protect compile time.
2188 if (Depth >= 3) return;
2190 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2191 const SCEV *BaseReg = Base.BaseRegs[i];
2193 SmallVector<const SCEV *, 8> AddOps;
2194 CollectSubexprs(BaseReg, 0, AddOps, SE);
2195 if (AddOps.size() == 1) continue;
2197 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
2198 JE = AddOps.end(); J != JE; ++J) {
2199 // Don't pull a constant into a register if the constant could be folded
2200 // into an immediate field.
2201 if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,
2202 Base.getNumRegs() > 1,
2203 LU.Kind, LU.AccessTy, TLI, SE))
2206 // Collect all operands except *J.
2207 SmallVector<const SCEV *, 8> InnerAddOps;
2208 for (SmallVectorImpl<const SCEV *>::const_iterator K = AddOps.begin(),
2209 KE = AddOps.end(); K != KE; ++K)
2211 InnerAddOps.push_back(*K);
2213 // Don't leave just a constant behind in a register if the constant could
2214 // be folded into an immediate field.
2215 if (InnerAddOps.size() == 1 &&
2216 isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset,
2217 Base.getNumRegs() > 1,
2218 LU.Kind, LU.AccessTy, TLI, SE))
2221 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
2222 if (InnerSum->isZero())
2225 F.BaseRegs[i] = InnerSum;
2226 F.BaseRegs.push_back(*J);
2227 if (InsertFormula(LU, LUIdx, F))
2228 // If that formula hadn't been seen before, recurse to find more like
2230 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1);
2235 /// GenerateCombinations - Generate a formula consisting of all of the
2236 /// loop-dominating registers added into a single register.
2237 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
2239 // This method is only interesting on a plurality of registers.
2240 if (Base.BaseRegs.size() <= 1) return;
2244 SmallVector<const SCEV *, 4> Ops;
2245 for (SmallVectorImpl<const SCEV *>::const_iterator
2246 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
2247 const SCEV *BaseReg = *I;
2248 if (BaseReg->properlyDominates(L->getHeader(), &DT) &&
2249 !BaseReg->hasComputableLoopEvolution(L))
2250 Ops.push_back(BaseReg);
2252 F.BaseRegs.push_back(BaseReg);
2254 if (Ops.size() > 1) {
2255 const SCEV *Sum = SE.getAddExpr(Ops);
2256 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
2257 // opportunity to fold something. For now, just ignore such cases
2258 // rather than proceed with zero in a register.
2259 if (!Sum->isZero()) {
2260 F.BaseRegs.push_back(Sum);
2261 (void)InsertFormula(LU, LUIdx, F);
2266 /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
2267 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
2269 // We can't add a symbolic offset if the address already contains one.
2270 if (Base.AM.BaseGV) return;
2272 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2273 const SCEV *G = Base.BaseRegs[i];
2274 GlobalValue *GV = ExtractSymbol(G, SE);
2275 if (G->isZero() || !GV)
2279 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
2280 LU.Kind, LU.AccessTy, TLI))
2283 (void)InsertFormula(LU, LUIdx, F);
2287 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
2288 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
2290 // TODO: For now, just add the min and max offset, because it usually isn't
2291 // worthwhile looking at everything inbetween.
2292 SmallVector<int64_t, 4> Worklist;
2293 Worklist.push_back(LU.MinOffset);
2294 if (LU.MaxOffset != LU.MinOffset)
2295 Worklist.push_back(LU.MaxOffset);
2297 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2298 const SCEV *G = Base.BaseRegs[i];
2300 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
2301 E = Worklist.end(); I != E; ++I) {
2303 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I;
2304 if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I,
2305 LU.Kind, LU.AccessTy, TLI)) {
2306 F.BaseRegs[i] = SE.getAddExpr(G, SE.getConstant(G->getType(), *I));
2308 (void)InsertFormula(LU, LUIdx, F);
2312 int64_t Imm = ExtractImmediate(G, SE);
2313 if (G->isZero() || Imm == 0)
2316 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm;
2317 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
2318 LU.Kind, LU.AccessTy, TLI))
2321 (void)InsertFormula(LU, LUIdx, F);
2325 /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
2326 /// the comparison. For example, x == y -> x*c == y*c.
2327 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
2329 if (LU.Kind != LSRUse::ICmpZero) return;
2331 // Determine the integer type for the base formula.
2332 const Type *IntTy = Base.getType();
2334 if (SE.getTypeSizeInBits(IntTy) > 64) return;
2336 // Don't do this if there is more than one offset.
2337 if (LU.MinOffset != LU.MaxOffset) return;
2339 assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
2341 // Check each interesting stride.
2342 for (SmallSetVector<int64_t, 8>::const_iterator
2343 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
2344 int64_t Factor = *I;
2347 // Check that the multiplication doesn't overflow.
2348 if (F.AM.BaseOffs == INT64_MIN && Factor == -1)
2350 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
2351 if (F.AM.BaseOffs / Factor != Base.AM.BaseOffs)
2354 // Check that multiplying with the use offset doesn't overflow.
2355 int64_t Offset = LU.MinOffset;
2356 if (Offset == INT64_MIN && Factor == -1)
2358 Offset = (uint64_t)Offset * Factor;
2359 if (Offset / Factor != LU.MinOffset)
2362 // Check that this scale is legal.
2363 if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI))
2366 // Compensate for the use having MinOffset built into it.
2367 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset;
2369 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
2371 // Check that multiplying with each base register doesn't overflow.
2372 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
2373 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
2374 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
2378 // Check that multiplying with the scaled register doesn't overflow.
2380 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
2381 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
2385 // If we make it here and it's legal, add it.
2386 (void)InsertFormula(LU, LUIdx, F);
2391 /// GenerateScales - Generate stride factor reuse formulae by making use of
2392 /// scaled-offset address modes, for example.
2393 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
2394 // Determine the integer type for the base formula.
2395 const Type *IntTy = Base.getType();
2398 // If this Formula already has a scaled register, we can't add another one.
2399 if (Base.AM.Scale != 0) return;
2401 // Check each interesting stride.
2402 for (SmallSetVector<int64_t, 8>::const_iterator
2403 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
2404 int64_t Factor = *I;
2406 Base.AM.Scale = Factor;
2407 Base.AM.HasBaseReg = Base.BaseRegs.size() > 1;
2408 // Check whether this scale is going to be legal.
2409 if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
2410 LU.Kind, LU.AccessTy, TLI)) {
2411 // As a special-case, handle special out-of-loop Basic users specially.
2412 // TODO: Reconsider this special case.
2413 if (LU.Kind == LSRUse::Basic &&
2414 isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
2415 LSRUse::Special, LU.AccessTy, TLI) &&
2416 LU.AllFixupsOutsideLoop)
2417 LU.Kind = LSRUse::Special;
2421 // For an ICmpZero, negating a solitary base register won't lead to
2423 if (LU.Kind == LSRUse::ICmpZero &&
2424 !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV)
2426 // For each addrec base reg, apply the scale, if possible.
2427 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
2428 if (const SCEVAddRecExpr *AR =
2429 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
2430 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
2431 if (FactorS->isZero())
2433 // Divide out the factor, ignoring high bits, since we'll be
2434 // scaling the value back up in the end.
2435 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
2436 // TODO: This could be optimized to avoid all the copying.
2438 F.ScaledReg = Quotient;
2439 F.DeleteBaseReg(F.BaseRegs[i]);
2440 (void)InsertFormula(LU, LUIdx, F);
2446 /// GenerateTruncates - Generate reuse formulae from different IV types.
2447 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
2448 // This requires TargetLowering to tell us which truncates are free.
2451 // Don't bother truncating symbolic values.
2452 if (Base.AM.BaseGV) return;
2454 // Determine the integer type for the base formula.
2455 const Type *DstTy = Base.getType();
2457 DstTy = SE.getEffectiveSCEVType(DstTy);
2459 for (SmallSetVector<const Type *, 4>::const_iterator
2460 I = Types.begin(), E = Types.end(); I != E; ++I) {
2461 const Type *SrcTy = *I;
2462 if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
2465 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
2466 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
2467 JE = F.BaseRegs.end(); J != JE; ++J)
2468 *J = SE.getAnyExtendExpr(*J, SrcTy);
2470 // TODO: This assumes we've done basic processing on all uses and
2471 // have an idea what the register usage is.
2472 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
2475 (void)InsertFormula(LU, LUIdx, F);
2482 /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
2483 /// defer modifications so that the search phase doesn't have to worry about
2484 /// the data structures moving underneath it.
2488 const SCEV *OrigReg;
2490 WorkItem(size_t LI, int64_t I, const SCEV *R)
2491 : LUIdx(LI), Imm(I), OrigReg(R) {}
2493 void print(raw_ostream &OS) const;
2499 void WorkItem::print(raw_ostream &OS) const {
2500 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
2501 << " , add offset " << Imm;
2504 void WorkItem::dump() const {
2505 print(errs()); errs() << '\n';
2508 /// GenerateCrossUseConstantOffsets - Look for registers which are a constant
2509 /// distance apart and try to form reuse opportunities between them.
2510 void LSRInstance::GenerateCrossUseConstantOffsets() {
2511 // Group the registers by their value without any added constant offset.
2512 typedef std::map<int64_t, const SCEV *> ImmMapTy;
2513 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
2515 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
2516 SmallVector<const SCEV *, 8> Sequence;
2517 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
2519 const SCEV *Reg = *I;
2520 int64_t Imm = ExtractImmediate(Reg, SE);
2521 std::pair<RegMapTy::iterator, bool> Pair =
2522 Map.insert(std::make_pair(Reg, ImmMapTy()));
2524 Sequence.push_back(Reg);
2525 Pair.first->second.insert(std::make_pair(Imm, *I));
2526 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
2529 // Now examine each set of registers with the same base value. Build up
2530 // a list of work to do and do the work in a separate step so that we're
2531 // not adding formulae and register counts while we're searching.
2532 SmallVector<WorkItem, 32> WorkItems;
2533 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
2534 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
2535 E = Sequence.end(); I != E; ++I) {
2536 const SCEV *Reg = *I;
2537 const ImmMapTy &Imms = Map.find(Reg)->second;
2539 // It's not worthwhile looking for reuse if there's only one offset.
2540 if (Imms.size() == 1)
2543 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
2544 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
2546 dbgs() << ' ' << J->first;
2549 // Examine each offset.
2550 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
2552 const SCEV *OrigReg = J->second;
2554 int64_t JImm = J->first;
2555 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
2557 if (!isa<SCEVConstant>(OrigReg) &&
2558 UsedByIndicesMap[Reg].count() == 1) {
2559 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
2563 // Conservatively examine offsets between this orig reg a few selected
2565 ImmMapTy::const_iterator OtherImms[] = {
2566 Imms.begin(), prior(Imms.end()),
2567 Imms.upper_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
2569 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
2570 ImmMapTy::const_iterator M = OtherImms[i];
2571 if (M == J || M == JE) continue;
2573 // Compute the difference between the two.
2574 int64_t Imm = (uint64_t)JImm - M->first;
2575 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
2576 LUIdx = UsedByIndices.find_next(LUIdx))
2577 // Make a memo of this use, offset, and register tuple.
2578 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
2579 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
2586 UsedByIndicesMap.clear();
2587 UniqueItems.clear();
2589 // Now iterate through the worklist and add new formulae.
2590 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
2591 E = WorkItems.end(); I != E; ++I) {
2592 const WorkItem &WI = *I;
2593 size_t LUIdx = WI.LUIdx;
2594 LSRUse &LU = Uses[LUIdx];
2595 int64_t Imm = WI.Imm;
2596 const SCEV *OrigReg = WI.OrigReg;
2598 const Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
2599 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
2600 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
2602 // TODO: Use a more targeted data structure.
2603 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
2604 Formula F = LU.Formulae[L];
2605 // Use the immediate in the scaled register.
2606 if (F.ScaledReg == OrigReg) {
2607 int64_t Offs = (uint64_t)F.AM.BaseOffs +
2608 Imm * (uint64_t)F.AM.Scale;
2609 // Don't create 50 + reg(-50).
2610 if (F.referencesReg(SE.getSCEV(
2611 ConstantInt::get(IntTy, -(uint64_t)Offs))))
2614 NewF.AM.BaseOffs = Offs;
2615 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
2616 LU.Kind, LU.AccessTy, TLI))
2618 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
2620 // If the new scale is a constant in a register, and adding the constant
2621 // value to the immediate would produce a value closer to zero than the
2622 // immediate itself, then the formula isn't worthwhile.
2623 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
2624 if (C->getValue()->getValue().isNegative() !=
2625 (NewF.AM.BaseOffs < 0) &&
2626 (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale))
2627 .ule(abs64(NewF.AM.BaseOffs)))
2631 (void)InsertFormula(LU, LUIdx, NewF);
2633 // Use the immediate in a base register.
2634 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
2635 const SCEV *BaseReg = F.BaseRegs[N];
2636 if (BaseReg != OrigReg)
2639 NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
2640 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
2641 LU.Kind, LU.AccessTy, TLI))
2643 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
2645 // If the new formula has a constant in a register, and adding the
2646 // constant value to the immediate would produce a value closer to
2647 // zero than the immediate itself, then the formula isn't worthwhile.
2648 for (SmallVectorImpl<const SCEV *>::const_iterator
2649 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
2651 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
2652 if ((C->getValue()->getValue() + NewF.AM.BaseOffs).abs().slt(
2653 abs64(NewF.AM.BaseOffs)) &&
2654 (C->getValue()->getValue() +
2655 NewF.AM.BaseOffs).countTrailingZeros() >=
2656 CountTrailingZeros_64(NewF.AM.BaseOffs))
2660 (void)InsertFormula(LU, LUIdx, NewF);
2669 /// GenerateAllReuseFormulae - Generate formulae for each use.
2671 LSRInstance::GenerateAllReuseFormulae() {
2672 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
2673 // queries are more precise.
2674 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2675 LSRUse &LU = Uses[LUIdx];
2676 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2677 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
2678 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2679 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
2681 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2682 LSRUse &LU = Uses[LUIdx];
2683 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2684 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
2685 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2686 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
2687 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2688 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
2689 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2690 GenerateScales(LU, LUIdx, LU.Formulae[i]);
2692 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2693 LSRUse &LU = Uses[LUIdx];
2694 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2695 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
2698 GenerateCrossUseConstantOffsets();
2701 /// If their are multiple formulae with the same set of registers used
2702 /// by other uses, pick the best one and delete the others.
2703 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
2705 bool ChangedFormulae = false;
2708 // Collect the best formula for each unique set of shared registers. This
2709 // is reset for each use.
2710 typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo>
2712 BestFormulaeTy BestFormulae;
2714 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2715 LSRUse &LU = Uses[LUIdx];
2716 FormulaSorter Sorter(L, LU, SE, DT);
2717 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
2720 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
2721 FIdx != NumForms; ++FIdx) {
2722 Formula &F = LU.Formulae[FIdx];
2724 SmallVector<const SCEV *, 2> Key;
2725 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
2726 JE = F.BaseRegs.end(); J != JE; ++J) {
2727 const SCEV *Reg = *J;
2728 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
2732 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
2733 Key.push_back(F.ScaledReg);
2734 // Unstable sort by host order ok, because this is only used for
2736 std::sort(Key.begin(), Key.end());
2738 std::pair<BestFormulaeTy::const_iterator, bool> P =
2739 BestFormulae.insert(std::make_pair(Key, FIdx));
2741 Formula &Best = LU.Formulae[P.first->second];
2742 if (Sorter.operator()(F, Best))
2744 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
2746 " in favor of formula "; Best.print(dbgs());
2749 ChangedFormulae = true;
2751 LU.DeleteFormula(F);
2759 // Now that we've filtered out some formulae, recompute the Regs set.
2761 LU.RecomputeRegs(LUIdx, RegUses);
2763 // Reset this to prepare for the next use.
2764 BestFormulae.clear();
2767 DEBUG(if (ChangedFormulae) {
2769 "After filtering out undesirable candidates:\n";
2774 // This is a rough guess that seems to work fairly well.
2775 static const size_t ComplexityLimit = UINT16_MAX;
2777 /// EstimateSearchSpaceComplexity - Estimate the worst-case number of
2778 /// solutions the solver might have to consider. It almost never considers
2779 /// this many solutions because it prune the search space, but the pruning
2780 /// isn't always sufficient.
2781 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
2783 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
2784 E = Uses.end(); I != E; ++I) {
2785 size_t FSize = I->Formulae.size();
2786 if (FSize >= ComplexityLimit) {
2787 Power = ComplexityLimit;
2791 if (Power >= ComplexityLimit)
2797 /// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
2798 /// formulae to choose from, use some rough heuristics to prune down the number
2799 /// of formulae. This keeps the main solver from taking an extraordinary amount
2800 /// of time in some worst-case scenarios.
2801 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
2802 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
2803 DEBUG(dbgs() << "The search space is too complex.\n");
2805 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
2806 "which use a superset of registers used by other "
2809 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2810 LSRUse &LU = Uses[LUIdx];
2812 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
2813 Formula &F = LU.Formulae[i];
2814 // Look for a formula with a constant or GV in a register. If the use
2815 // also has a formula with that same value in an immediate field,
2816 // delete the one that uses a register.
2817 for (SmallVectorImpl<const SCEV *>::const_iterator
2818 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
2819 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
2821 NewF.AM.BaseOffs += C->getValue()->getSExtValue();
2822 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
2823 (I - F.BaseRegs.begin()));
2824 if (LU.HasFormulaWithSameRegs(NewF)) {
2825 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
2826 LU.DeleteFormula(F);
2832 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
2833 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
2836 NewF.AM.BaseGV = GV;
2837 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
2838 (I - F.BaseRegs.begin()));
2839 if (LU.HasFormulaWithSameRegs(NewF)) {
2840 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
2842 LU.DeleteFormula(F);
2853 LU.RecomputeRegs(LUIdx, RegUses);
2856 DEBUG(dbgs() << "After pre-selection:\n";
2857 print_uses(dbgs()));
2860 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
2861 DEBUG(dbgs() << "The search space is too complex.\n");
2863 DEBUG(dbgs() << "Narrowing the search space by assuming that uses "
2864 "separated by a constant offset will use the same "
2867 // This is especially useful for unrolled loops.
2869 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2870 LSRUse &LU = Uses[LUIdx];
2871 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
2872 E = LU.Formulae.end(); I != E; ++I) {
2873 const Formula &F = *I;
2874 if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) {
2875 if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) {
2876 if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs,
2877 /*HasBaseReg=*/false,
2878 LU.Kind, LU.AccessTy)) {
2879 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs());
2882 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
2884 // Delete formulae from the new use which are no longer legal.
2886 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
2887 Formula &F = LUThatHas->Formulae[i];
2888 if (!isLegalUse(F.AM,
2889 LUThatHas->MinOffset, LUThatHas->MaxOffset,
2890 LUThatHas->Kind, LUThatHas->AccessTy, TLI)) {
2891 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
2893 LUThatHas->DeleteFormula(F);
2900 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
2902 // Update the relocs to reference the new use.
2903 for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
2904 E = Fixups.end(); I != E; ++I) {
2905 LSRFixup &Fixup = *I;
2906 if (Fixup.LUIdx == LUIdx) {
2907 Fixup.LUIdx = LUThatHas - &Uses.front();
2908 Fixup.Offset += F.AM.BaseOffs;
2909 DEBUG(errs() << "New fixup has offset "
2910 << Fixup.Offset << '\n');
2912 if (Fixup.LUIdx == NumUses-1)
2913 Fixup.LUIdx = LUIdx;
2916 // Delete the old use.
2927 DEBUG(dbgs() << "After pre-selection:\n";
2928 print_uses(dbgs()));
2931 SmallPtrSet<const SCEV *, 4> Taken;
2932 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
2933 // Ok, we have too many of formulae on our hands to conveniently handle.
2934 // Use a rough heuristic to thin out the list.
2935 DEBUG(dbgs() << "The search space is too complex.\n");
2937 // Pick the register which is used by the most LSRUses, which is likely
2938 // to be a good reuse register candidate.
2939 const SCEV *Best = 0;
2940 unsigned BestNum = 0;
2941 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
2943 const SCEV *Reg = *I;
2944 if (Taken.count(Reg))
2949 unsigned Count = RegUses.getUsedByIndices(Reg).count();
2950 if (Count > BestNum) {
2957 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
2958 << " will yield profitable reuse.\n");
2961 // In any use with formulae which references this register, delete formulae
2962 // which don't reference it.
2963 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2964 LSRUse &LU = Uses[LUIdx];
2965 if (!LU.Regs.count(Best)) continue;
2968 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
2969 Formula &F = LU.Formulae[i];
2970 if (!F.referencesReg(Best)) {
2971 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
2972 LU.DeleteFormula(F);
2976 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
2982 LU.RecomputeRegs(LUIdx, RegUses);
2985 DEBUG(dbgs() << "After pre-selection:\n";
2986 print_uses(dbgs()));
2990 /// SolveRecurse - This is the recursive solver.
2991 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
2993 SmallVectorImpl<const Formula *> &Workspace,
2994 const Cost &CurCost,
2995 const SmallPtrSet<const SCEV *, 16> &CurRegs,
2996 DenseSet<const SCEV *> &VisitedRegs) const {
2999 // - use more aggressive filtering
3000 // - sort the formula so that the most profitable solutions are found first
3001 // - sort the uses too
3003 // - don't compute a cost, and then compare. compare while computing a cost
3005 // - track register sets with SmallBitVector
3007 const LSRUse &LU = Uses[Workspace.size()];
3009 // If this use references any register that's already a part of the
3010 // in-progress solution, consider it a requirement that a formula must
3011 // reference that register in order to be considered. This prunes out
3012 // unprofitable searching.
3013 SmallSetVector<const SCEV *, 4> ReqRegs;
3014 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
3015 E = CurRegs.end(); I != E; ++I)
3016 if (LU.Regs.count(*I))
3019 bool AnySatisfiedReqRegs = false;
3020 SmallPtrSet<const SCEV *, 16> NewRegs;
3023 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
3024 E = LU.Formulae.end(); I != E; ++I) {
3025 const Formula &F = *I;
3027 // Ignore formulae which do not use any of the required registers.
3028 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
3029 JE = ReqRegs.end(); J != JE; ++J) {
3030 const SCEV *Reg = *J;
3031 if ((!F.ScaledReg || F.ScaledReg != Reg) &&
3032 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) ==
3036 AnySatisfiedReqRegs = true;
3038 // Evaluate the cost of the current formula. If it's already worse than
3039 // the current best, prune the search at that point.
3042 NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT);
3043 if (NewCost < SolutionCost) {
3044 Workspace.push_back(&F);
3045 if (Workspace.size() != Uses.size()) {
3046 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
3047 NewRegs, VisitedRegs);
3048 if (F.getNumRegs() == 1 && Workspace.size() == 1)
3049 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
3051 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
3052 dbgs() << ". Regs:";
3053 for (SmallPtrSet<const SCEV *, 16>::const_iterator
3054 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
3055 dbgs() << ' ' << **I;
3058 SolutionCost = NewCost;
3059 Solution = Workspace;
3061 Workspace.pop_back();
3066 // If none of the formulae had all of the required registers, relax the
3067 // constraint so that we don't exclude all formulae.
3068 if (!AnySatisfiedReqRegs) {
3069 assert(!ReqRegs.empty() && "Solver failed even without required registers");
3075 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
3076 SmallVector<const Formula *, 8> Workspace;
3078 SolutionCost.Loose();
3080 SmallPtrSet<const SCEV *, 16> CurRegs;
3081 DenseSet<const SCEV *> VisitedRegs;
3082 Workspace.reserve(Uses.size());
3084 // SolveRecurse does all the work.
3085 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
3086 CurRegs, VisitedRegs);
3088 // Ok, we've now made all our decisions.
3089 DEBUG(dbgs() << "\n"
3090 "The chosen solution requires "; SolutionCost.print(dbgs());
3092 for (size_t i = 0, e = Uses.size(); i != e; ++i) {
3094 Uses[i].print(dbgs());
3097 Solution[i]->print(dbgs());
3102 /// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
3103 /// the dominator tree far as we can go while still being dominated by the
3104 /// input positions. This helps canonicalize the insert position, which
3105 /// encourages sharing.
3106 BasicBlock::iterator
3107 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
3108 const SmallVectorImpl<Instruction *> &Inputs)
3111 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
3112 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
3115 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
3116 assert(Rung && "Block has no DomTreeNode!");
3117 Rung = Rung->getIDom();
3118 if (!Rung) return IP;
3119 IDom = Rung->getBlock();
3121 // Don't climb into a loop though.
3122 const Loop *IDomLoop = LI.getLoopFor(IDom);
3123 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
3124 if (IDomDepth <= IPLoopDepth &&
3125 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
3129 bool AllDominate = true;
3130 Instruction *BetterPos = 0;
3131 Instruction *Tentative = IDom->getTerminator();
3132 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
3133 E = Inputs.end(); I != E; ++I) {
3134 Instruction *Inst = *I;
3135 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
3136 AllDominate = false;
3139 // Attempt to find an insert position in the middle of the block,
3140 // instead of at the end, so that it can be used for other expansions.
3141 if (IDom == Inst->getParent() &&
3142 (!BetterPos || DT.dominates(BetterPos, Inst)))
3143 BetterPos = llvm::next(BasicBlock::iterator(Inst));
3156 /// AdjustInsertPositionForExpand - Determine an input position which will be
3157 /// dominated by the operands and which will dominate the result.
3158 BasicBlock::iterator
3159 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator IP,
3161 const LSRUse &LU) const {
3162 // Collect some instructions which must be dominated by the
3163 // expanding replacement. These must be dominated by any operands that
3164 // will be required in the expansion.
3165 SmallVector<Instruction *, 4> Inputs;
3166 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
3167 Inputs.push_back(I);
3168 if (LU.Kind == LSRUse::ICmpZero)
3169 if (Instruction *I =
3170 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
3171 Inputs.push_back(I);
3172 if (LF.PostIncLoops.count(L)) {
3173 if (LF.isUseFullyOutsideLoop(L))
3174 Inputs.push_back(L->getLoopLatch()->getTerminator());
3176 Inputs.push_back(IVIncInsertPos);
3178 // The expansion must also be dominated by the increment positions of any
3179 // loops it for which it is using post-inc mode.
3180 for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(),
3181 E = LF.PostIncLoops.end(); I != E; ++I) {
3182 const Loop *PIL = *I;
3183 if (PIL == L) continue;
3185 // Be dominated by the loop exit.
3186 SmallVector<BasicBlock *, 4> ExitingBlocks;
3187 PIL->getExitingBlocks(ExitingBlocks);
3188 if (!ExitingBlocks.empty()) {
3189 BasicBlock *BB = ExitingBlocks[0];
3190 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
3191 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
3192 Inputs.push_back(BB->getTerminator());
3196 // Then, climb up the immediate dominator tree as far as we can go while
3197 // still being dominated by the input positions.
3198 IP = HoistInsertPosition(IP, Inputs);
3200 // Don't insert instructions before PHI nodes.
3201 while (isa<PHINode>(IP)) ++IP;
3203 // Ignore debug intrinsics.
3204 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
3209 Value *LSRInstance::Expand(const LSRFixup &LF,
3211 BasicBlock::iterator IP,
3212 SCEVExpander &Rewriter,
3213 SmallVectorImpl<WeakVH> &DeadInsts) const {
3214 const LSRUse &LU = Uses[LF.LUIdx];
3216 // Determine an input position which will be dominated by the operands and
3217 // which will dominate the result.
3218 IP = AdjustInsertPositionForExpand(IP, LF, LU);
3220 // Inform the Rewriter if we have a post-increment use, so that it can
3221 // perform an advantageous expansion.
3222 Rewriter.setPostInc(LF.PostIncLoops);
3224 // This is the type that the user actually needs.
3225 const Type *OpTy = LF.OperandValToReplace->getType();
3226 // This will be the type that we'll initially expand to.
3227 const Type *Ty = F.getType();
3229 // No type known; just expand directly to the ultimate type.
3231 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
3232 // Expand directly to the ultimate type if it's the right size.
3234 // This is the type to do integer arithmetic in.
3235 const Type *IntTy = SE.getEffectiveSCEVType(Ty);
3237 // Build up a list of operands to add together to form the full base.
3238 SmallVector<const SCEV *, 8> Ops;
3240 // Expand the BaseRegs portion.
3241 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
3242 E = F.BaseRegs.end(); I != E; ++I) {
3243 const SCEV *Reg = *I;
3244 assert(!Reg->isZero() && "Zero allocated in a base register!");
3246 // If we're expanding for a post-inc user, make the post-inc adjustment.
3247 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
3248 Reg = TransformForPostIncUse(Denormalize, Reg,
3249 LF.UserInst, LF.OperandValToReplace,
3252 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
3255 // Flush the operand list to suppress SCEVExpander hoisting.
3257 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
3259 Ops.push_back(SE.getUnknown(FullV));
3262 // Expand the ScaledReg portion.
3263 Value *ICmpScaledV = 0;
3264 if (F.AM.Scale != 0) {
3265 const SCEV *ScaledS = F.ScaledReg;
3267 // If we're expanding for a post-inc user, make the post-inc adjustment.
3268 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
3269 ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
3270 LF.UserInst, LF.OperandValToReplace,
3273 if (LU.Kind == LSRUse::ICmpZero) {
3274 // An interesting way of "folding" with an icmp is to use a negated
3275 // scale, which we'll implement by inserting it into the other operand
3277 assert(F.AM.Scale == -1 &&
3278 "The only scale supported by ICmpZero uses is -1!");
3279 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
3281 // Otherwise just expand the scaled register and an explicit scale,
3282 // which is expected to be matched as part of the address.
3283 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
3284 ScaledS = SE.getMulExpr(ScaledS,
3285 SE.getConstant(ScaledS->getType(), F.AM.Scale));
3286 Ops.push_back(ScaledS);
3288 // Flush the operand list to suppress SCEVExpander hoisting.
3289 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
3291 Ops.push_back(SE.getUnknown(FullV));
3295 // Expand the GV portion.
3297 Ops.push_back(SE.getUnknown(F.AM.BaseGV));
3299 // Flush the operand list to suppress SCEVExpander hoisting.
3300 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
3302 Ops.push_back(SE.getUnknown(FullV));
3305 // Expand the immediate portion.
3306 int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset;
3308 if (LU.Kind == LSRUse::ICmpZero) {
3309 // The other interesting way of "folding" with an ICmpZero is to use a
3310 // negated immediate.
3312 ICmpScaledV = ConstantInt::get(IntTy, -Offset);
3314 Ops.push_back(SE.getUnknown(ICmpScaledV));
3315 ICmpScaledV = ConstantInt::get(IntTy, Offset);
3318 // Just add the immediate values. These again are expected to be matched
3319 // as part of the address.
3320 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
3324 // Emit instructions summing all the operands.
3325 const SCEV *FullS = Ops.empty() ?
3326 SE.getConstant(IntTy, 0) :
3328 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
3330 // We're done expanding now, so reset the rewriter.
3331 Rewriter.clearPostInc();
3333 // An ICmpZero Formula represents an ICmp which we're handling as a
3334 // comparison against zero. Now that we've expanded an expression for that
3335 // form, update the ICmp's other operand.
3336 if (LU.Kind == LSRUse::ICmpZero) {
3337 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
3338 DeadInsts.push_back(CI->getOperand(1));
3339 assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
3340 "a scale at the same time!");
3341 if (F.AM.Scale == -1) {
3342 if (ICmpScaledV->getType() != OpTy) {
3344 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
3346 ICmpScaledV, OpTy, "tmp", CI);
3349 CI->setOperand(1, ICmpScaledV);
3351 assert(F.AM.Scale == 0 &&
3352 "ICmp does not support folding a global value and "
3353 "a scale at the same time!");
3354 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
3356 if (C->getType() != OpTy)
3357 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
3361 CI->setOperand(1, C);
3368 /// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
3369 /// of their operands effectively happens in their predecessor blocks, so the
3370 /// expression may need to be expanded in multiple places.
3371 void LSRInstance::RewriteForPHI(PHINode *PN,
3374 SCEVExpander &Rewriter,
3375 SmallVectorImpl<WeakVH> &DeadInsts,
3377 DenseMap<BasicBlock *, Value *> Inserted;
3378 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
3379 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
3380 BasicBlock *BB = PN->getIncomingBlock(i);
3382 // If this is a critical edge, split the edge so that we do not insert
3383 // the code on all predecessor/successor paths. We do this unless this
3384 // is the canonical backedge for this loop, which complicates post-inc
3386 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
3387 !isa<IndirectBrInst>(BB->getTerminator()) &&
3388 (PN->getParent() != L->getHeader() || !L->contains(BB))) {
3389 // Split the critical edge.
3390 BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P);
3392 // If PN is outside of the loop and BB is in the loop, we want to
3393 // move the block to be immediately before the PHI block, not
3394 // immediately after BB.
3395 if (L->contains(BB) && !L->contains(PN))
3396 NewBB->moveBefore(PN->getParent());
3398 // Splitting the edge can reduce the number of PHI entries we have.
3399 e = PN->getNumIncomingValues();
3401 i = PN->getBasicBlockIndex(BB);
3404 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
3405 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
3407 PN->setIncomingValue(i, Pair.first->second);
3409 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
3411 // If this is reuse-by-noop-cast, insert the noop cast.
3412 const Type *OpTy = LF.OperandValToReplace->getType();
3413 if (FullV->getType() != OpTy)
3415 CastInst::Create(CastInst::getCastOpcode(FullV, false,
3417 FullV, LF.OperandValToReplace->getType(),
3418 "tmp", BB->getTerminator());
3420 PN->setIncomingValue(i, FullV);
3421 Pair.first->second = FullV;
3426 /// Rewrite - Emit instructions for the leading candidate expression for this
3427 /// LSRUse (this is called "expanding"), and update the UserInst to reference
3428 /// the newly expanded value.
3429 void LSRInstance::Rewrite(const LSRFixup &LF,
3431 SCEVExpander &Rewriter,
3432 SmallVectorImpl<WeakVH> &DeadInsts,
3434 // First, find an insertion point that dominates UserInst. For PHI nodes,
3435 // find the nearest block which dominates all the relevant uses.
3436 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
3437 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
3439 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
3441 // If this is reuse-by-noop-cast, insert the noop cast.
3442 const Type *OpTy = LF.OperandValToReplace->getType();
3443 if (FullV->getType() != OpTy) {
3445 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
3446 FullV, OpTy, "tmp", LF.UserInst);
3450 // Update the user. ICmpZero is handled specially here (for now) because
3451 // Expand may have updated one of the operands of the icmp already, and
3452 // its new value may happen to be equal to LF.OperandValToReplace, in
3453 // which case doing replaceUsesOfWith leads to replacing both operands
3454 // with the same value. TODO: Reorganize this.
3455 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
3456 LF.UserInst->setOperand(0, FullV);
3458 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
3461 DeadInsts.push_back(LF.OperandValToReplace);
3465 LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
3467 // Keep track of instructions we may have made dead, so that
3468 // we can remove them after we are done working.
3469 SmallVector<WeakVH, 16> DeadInsts;
3471 SCEVExpander Rewriter(SE);
3472 Rewriter.disableCanonicalMode();
3473 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
3475 // Expand the new value definitions and update the users.
3476 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
3477 E = Fixups.end(); I != E; ++I) {
3478 const LSRFixup &Fixup = *I;
3480 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
3485 // Clean up after ourselves. This must be done before deleting any
3489 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
3492 LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
3493 : IU(P->getAnalysis<IVUsers>()),
3494 SE(P->getAnalysis<ScalarEvolution>()),
3495 DT(P->getAnalysis<DominatorTree>()),
3496 LI(P->getAnalysis<LoopInfo>()),
3497 TLI(tli), L(l), Changed(false), IVIncInsertPos(0) {
3499 // If LoopSimplify form is not available, stay out of trouble.
3500 if (!L->isLoopSimplifyForm()) return;
3502 // If there's no interesting work to be done, bail early.
3503 if (IU.empty()) return;
3505 DEBUG(dbgs() << "\nLSR on loop ";
3506 WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
3509 // First, perform some low-level loop optimizations.
3511 OptimizeLoopTermCond();
3513 // Start collecting data and preparing for the solver.
3514 CollectInterestingTypesAndFactors();
3515 CollectFixupsAndInitialFormulae();
3516 CollectLoopInvariantFixupsAndFormulae();
3518 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
3519 print_uses(dbgs()));
3521 // Now use the reuse data to generate a bunch of interesting ways
3522 // to formulate the values needed for the uses.
3523 GenerateAllReuseFormulae();
3525 DEBUG(dbgs() << "\n"
3526 "After generating reuse formulae:\n";
3527 print_uses(dbgs()));
3529 FilterOutUndesirableDedicatedRegisters();
3530 NarrowSearchSpaceUsingHeuristics();
3532 SmallVector<const Formula *, 8> Solution;
3534 assert(Solution.size() == Uses.size() && "Malformed solution!");
3536 // Release memory that is no longer needed.
3542 // Formulae should be legal.
3543 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3544 E = Uses.end(); I != E; ++I) {
3545 const LSRUse &LU = *I;
3546 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
3547 JE = LU.Formulae.end(); J != JE; ++J)
3548 assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset,
3549 LU.Kind, LU.AccessTy, TLI) &&
3550 "Illegal formula generated!");
3554 // Now that we've decided what we want, make it so.
3555 ImplementSolution(Solution, P);
3558 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
3559 if (Factors.empty() && Types.empty()) return;
3561 OS << "LSR has identified the following interesting factors and types: ";
3564 for (SmallSetVector<int64_t, 8>::const_iterator
3565 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3566 if (!First) OS << ", ";
3571 for (SmallSetVector<const Type *, 4>::const_iterator
3572 I = Types.begin(), E = Types.end(); I != E; ++I) {
3573 if (!First) OS << ", ";
3575 OS << '(' << **I << ')';
3580 void LSRInstance::print_fixups(raw_ostream &OS) const {
3581 OS << "LSR is examining the following fixup sites:\n";
3582 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
3583 E = Fixups.end(); I != E; ++I) {
3584 const LSRFixup &LF = *I;
3591 void LSRInstance::print_uses(raw_ostream &OS) const {
3592 OS << "LSR is examining the following uses:\n";
3593 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3594 E = Uses.end(); I != E; ++I) {
3595 const LSRUse &LU = *I;
3599 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
3600 JE = LU.Formulae.end(); J != JE; ++J) {
3608 void LSRInstance::print(raw_ostream &OS) const {
3609 print_factors_and_types(OS);
3614 void LSRInstance::dump() const {
3615 print(errs()); errs() << '\n';
3620 class LoopStrengthReduce : public LoopPass {
3621 /// TLI - Keep a pointer of a TargetLowering to consult for determining
3622 /// transformation profitability.
3623 const TargetLowering *const TLI;
3626 static char ID; // Pass ID, replacement for typeid
3627 explicit LoopStrengthReduce(const TargetLowering *tli = 0);
3630 bool runOnLoop(Loop *L, LPPassManager &LPM);
3631 void getAnalysisUsage(AnalysisUsage &AU) const;
3636 char LoopStrengthReduce::ID = 0;
3637 static RegisterPass<LoopStrengthReduce>
3638 X("loop-reduce", "Loop Strength Reduction");
3640 Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
3641 return new LoopStrengthReduce(TLI);
3644 LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
3645 : LoopPass(&ID), TLI(tli) {}
3647 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
3648 // We split critical edges, so we change the CFG. However, we do update
3649 // many analyses if they are around.
3650 AU.addPreservedID(LoopSimplifyID);
3651 AU.addPreserved("domfrontier");
3653 AU.addRequired<LoopInfo>();
3654 AU.addPreserved<LoopInfo>();
3655 AU.addRequiredID(LoopSimplifyID);
3656 AU.addRequired<DominatorTree>();
3657 AU.addPreserved<DominatorTree>();
3658 AU.addRequired<ScalarEvolution>();
3659 AU.addPreserved<ScalarEvolution>();
3660 AU.addRequired<IVUsers>();
3661 AU.addPreserved<IVUsers>();
3664 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
3665 bool Changed = false;
3667 // Run the main LSR transformation.
3668 Changed |= LSRInstance(TLI, L, this).getChanged();
3670 // At this point, it is worth checking to see if any recurrence PHIs are also
3671 // dead, so that we can remove them as well.
3672 Changed |= DeleteDeadPHIs(L->getHeader());