1 //===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation analyzes and transforms the induction variables (and
11 // computations derived from them) into forms suitable for efficient execution
14 // This pass performs a strength reduction on array references inside loops that
15 // have as one or more of their components the loop induction variable, it
16 // rewrites expressions to take advantage of scaled-index addressing modes
17 // available on the target, and it performs a variety of other optimizations
18 // related to loop induction variables.
20 // Terminology note: this code has a lot of handling for "post-increment" or
21 // "post-inc" users. This is not talking about post-increment addressing modes;
22 // it is instead talking about code like this:
24 // %i = phi [ 0, %entry ], [ %i.next, %latch ]
26 // %i.next = add %i, 1
27 // %c = icmp eq %i.next, %n
29 // The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however
30 // it's useful to think about these as the same register, with some uses using
31 // the value of the register before the add and some using // it after. In this
32 // example, the icmp is a post-increment user, since it uses %i.next, which is
33 // the value of the induction variable after the increment. The other common
34 // case of post-increment users is users outside the loop.
36 // TODO: More sophistication in the way Formulae are generated and filtered.
38 // TODO: Handle multiple loops at a time.
40 // TODO: Should TargetLowering::AddrMode::BaseGV be changed to a ConstantExpr
41 // instead of a GlobalValue?
43 // TODO: When truncation is free, truncate ICmp users' operands to make it a
44 // smaller encoding (on x86 at least).
46 // TODO: When a negated register is used by an add (such as in a list of
47 // multiple base registers, or as the increment expression in an addrec),
48 // we may not actually need both reg and (-1 * reg) in registers; the
49 // negation can be implemented by using a sub instead of an add. The
50 // lack of support for taking this into consideration when making
51 // register pressure decisions is partly worked around by the "Special"
54 //===----------------------------------------------------------------------===//
56 #define DEBUG_TYPE "loop-reduce"
57 #include "llvm/Transforms/Scalar.h"
58 #include "llvm/Constants.h"
59 #include "llvm/Instructions.h"
60 #include "llvm/IntrinsicInst.h"
61 #include "llvm/DerivedTypes.h"
62 #include "llvm/Analysis/IVUsers.h"
63 #include "llvm/Analysis/Dominators.h"
64 #include "llvm/Analysis/LoopPass.h"
65 #include "llvm/Analysis/ScalarEvolutionExpander.h"
66 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
67 #include "llvm/Transforms/Utils/Local.h"
68 #include "llvm/ADT/SmallBitVector.h"
69 #include "llvm/ADT/SetVector.h"
70 #include "llvm/ADT/DenseSet.h"
71 #include "llvm/Support/Debug.h"
72 #include "llvm/Support/ValueHandle.h"
73 #include "llvm/Support/raw_ostream.h"
74 #include "llvm/Target/TargetLowering.h"
80 /// RegSortData - This class holds data which is used to order reuse candidates.
83 /// UsedByIndices - This represents the set of LSRUse indices which reference
84 /// a particular register.
85 SmallBitVector UsedByIndices;
89 void print(raw_ostream &OS) const;
95 void RegSortData::print(raw_ostream &OS) const {
96 OS << "[NumUses=" << UsedByIndices.count() << ']';
99 void RegSortData::dump() const {
100 print(errs()); errs() << '\n';
105 /// RegUseTracker - Map register candidates to information about how they are
107 class RegUseTracker {
108 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
111 SmallVector<const SCEV *, 16> RegSequence;
114 void CountRegister(const SCEV *Reg, size_t LUIdx);
116 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
118 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
122 typedef SmallVectorImpl<const SCEV *>::iterator iterator;
123 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
124 iterator begin() { return RegSequence.begin(); }
125 iterator end() { return RegSequence.end(); }
126 const_iterator begin() const { return RegSequence.begin(); }
127 const_iterator end() const { return RegSequence.end(); }
133 RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
134 std::pair<RegUsesTy::iterator, bool> Pair =
135 RegUses.insert(std::make_pair(Reg, RegSortData()));
136 RegSortData &RSD = Pair.first->second;
138 RegSequence.push_back(Reg);
139 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
140 RSD.UsedByIndices.set(LUIdx);
144 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
145 if (!RegUses.count(Reg)) return false;
146 const SmallBitVector &UsedByIndices =
147 RegUses.find(Reg)->second.UsedByIndices;
148 int i = UsedByIndices.find_first();
149 if (i == -1) return false;
150 if ((size_t)i != LUIdx) return true;
151 return UsedByIndices.find_next(i) != -1;
154 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
155 RegUsesTy::const_iterator I = RegUses.find(Reg);
156 assert(I != RegUses.end() && "Unknown register!");
157 return I->second.UsedByIndices;
160 void RegUseTracker::clear() {
167 /// Formula - This class holds information that describes a formula for
168 /// computing satisfying a use. It may include broken-out immediates and scaled
171 /// AM - This is used to represent complex addressing, as well as other kinds
172 /// of interesting uses.
173 TargetLowering::AddrMode AM;
175 /// BaseRegs - The list of "base" registers for this use. When this is
176 /// non-empty, AM.HasBaseReg should be set to true.
177 SmallVector<const SCEV *, 2> BaseRegs;
179 /// ScaledReg - The 'scaled' register for this use. This should be non-null
180 /// when AM.Scale is not zero.
181 const SCEV *ScaledReg;
183 Formula() : ScaledReg(0) {}
185 void InitialMatch(const SCEV *S, Loop *L,
186 ScalarEvolution &SE, DominatorTree &DT);
188 unsigned getNumRegs() const;
189 const Type *getType() const;
191 bool referencesReg(const SCEV *S) const;
192 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
193 const RegUseTracker &RegUses) const;
195 void print(raw_ostream &OS) const;
201 /// DoInitialMatch - Recursion helper for InitialMatch.
202 static void DoInitialMatch(const SCEV *S, Loop *L,
203 SmallVectorImpl<const SCEV *> &Good,
204 SmallVectorImpl<const SCEV *> &Bad,
205 ScalarEvolution &SE, DominatorTree &DT) {
206 // Collect expressions which properly dominate the loop header.
207 if (S->properlyDominates(L->getHeader(), &DT)) {
212 // Look at add operands.
213 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
214 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
216 DoInitialMatch(*I, L, Good, Bad, SE, DT);
220 // Look at addrec operands.
221 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
222 if (!AR->getStart()->isZero()) {
223 DoInitialMatch(AR->getStart(), L, Good, Bad, SE, DT);
224 DoInitialMatch(SE.getAddRecExpr(SE.getIntegerSCEV(0, AR->getType()),
225 AR->getStepRecurrence(SE),
227 L, Good, Bad, SE, DT);
231 // Handle a multiplication by -1 (negation) if it didn't fold.
232 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
233 if (Mul->getOperand(0)->isAllOnesValue()) {
234 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
235 const SCEV *NewMul = SE.getMulExpr(Ops);
237 SmallVector<const SCEV *, 4> MyGood;
238 SmallVector<const SCEV *, 4> MyBad;
239 DoInitialMatch(NewMul, L, MyGood, MyBad, SE, DT);
240 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
241 SE.getEffectiveSCEVType(NewMul->getType())));
242 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
243 E = MyGood.end(); I != E; ++I)
244 Good.push_back(SE.getMulExpr(NegOne, *I));
245 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
246 E = MyBad.end(); I != E; ++I)
247 Bad.push_back(SE.getMulExpr(NegOne, *I));
251 // Ok, we can't do anything interesting. Just stuff the whole thing into a
252 // register and hope for the best.
256 /// InitialMatch - Incorporate loop-variant parts of S into this Formula,
257 /// attempting to keep all loop-invariant and loop-computable values in a
258 /// single base register.
259 void Formula::InitialMatch(const SCEV *S, Loop *L,
260 ScalarEvolution &SE, DominatorTree &DT) {
261 SmallVector<const SCEV *, 4> Good;
262 SmallVector<const SCEV *, 4> Bad;
263 DoInitialMatch(S, L, Good, Bad, SE, DT);
265 BaseRegs.push_back(SE.getAddExpr(Good));
266 AM.HasBaseReg = true;
269 BaseRegs.push_back(SE.getAddExpr(Bad));
270 AM.HasBaseReg = true;
274 /// getNumRegs - Return the total number of register operands used by this
275 /// formula. This does not include register uses implied by non-constant
277 unsigned Formula::getNumRegs() const {
278 return !!ScaledReg + BaseRegs.size();
281 /// getType - Return the type of this formula, if it has one, or null
282 /// otherwise. This type is meaningless except for the bit size.
283 const Type *Formula::getType() const {
284 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
285 ScaledReg ? ScaledReg->getType() :
286 AM.BaseGV ? AM.BaseGV->getType() :
290 /// referencesReg - Test if this formula references the given register.
291 bool Formula::referencesReg(const SCEV *S) const {
292 return S == ScaledReg ||
293 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
296 /// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
297 /// which are used by uses other than the use with the given index.
298 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
299 const RegUseTracker &RegUses) const {
301 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
303 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
304 E = BaseRegs.end(); I != E; ++I)
305 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
310 void Formula::print(raw_ostream &OS) const {
313 if (!First) OS << " + "; else First = false;
314 WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false);
316 if (AM.BaseOffs != 0) {
317 if (!First) OS << " + "; else First = false;
320 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
321 E = BaseRegs.end(); I != E; ++I) {
322 if (!First) OS << " + "; else First = false;
323 OS << "reg(" << **I << ')';
326 if (!First) OS << " + "; else First = false;
327 OS << AM.Scale << "*reg(";
336 void Formula::dump() const {
337 print(errs()); errs() << '\n';
340 /// isAddRecSExtable - Return true if the given addrec can be sign-extended
341 /// without changing its value.
342 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
344 IntegerType::get(SE.getContext(),
345 SE.getTypeSizeInBits(AR->getType()) + 1);
346 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
349 /// isAddSExtable - Return true if the given add can be sign-extended
350 /// without changing its value.
351 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
353 IntegerType::get(SE.getContext(),
354 SE.getTypeSizeInBits(A->getType()) + 1);
355 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
358 /// isMulSExtable - Return true if the given add can be sign-extended
359 /// without changing its value.
360 static bool isMulSExtable(const SCEVMulExpr *A, ScalarEvolution &SE) {
362 IntegerType::get(SE.getContext(),
363 SE.getTypeSizeInBits(A->getType()) + 1);
364 return isa<SCEVMulExpr>(SE.getSignExtendExpr(A, WideTy));
367 /// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
368 /// and if the remainder is known to be zero, or null otherwise. If
369 /// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
370 /// to Y, ignoring that the multiplication may overflow, which is useful when
371 /// the result will be used in a context where the most significant bits are
373 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
375 bool IgnoreSignificantBits = false) {
376 // Handle the trivial case, which works for any SCEV type.
378 return SE.getIntegerSCEV(1, LHS->getType());
380 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do some
382 if (RHS->isAllOnesValue())
383 return SE.getMulExpr(LHS, RHS);
385 // Check for a division of a constant by a constant.
386 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
387 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
390 if (C->getValue()->getValue().srem(RC->getValue()->getValue()) != 0)
392 return SE.getConstant(C->getValue()->getValue()
393 .sdiv(RC->getValue()->getValue()));
396 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
397 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
398 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
399 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
400 IgnoreSignificantBits);
401 if (!Start) return 0;
402 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
403 IgnoreSignificantBits);
405 return SE.getAddRecExpr(Start, Step, AR->getLoop());
409 // Distribute the sdiv over add operands, if the add doesn't overflow.
410 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
411 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
412 SmallVector<const SCEV *, 8> Ops;
413 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
415 const SCEV *Op = getExactSDiv(*I, RHS, SE,
416 IgnoreSignificantBits);
420 return SE.getAddExpr(Ops);
424 // Check for a multiply operand that we can pull RHS out of.
425 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS))
426 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
427 SmallVector<const SCEV *, 4> Ops;
429 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
432 if (const SCEV *Q = getExactSDiv(*I, RHS, SE,
433 IgnoreSignificantBits)) {
440 return Found ? SE.getMulExpr(Ops) : 0;
443 // Otherwise we don't know.
447 /// ExtractImmediate - If S involves the addition of a constant integer value,
448 /// return that integer value, and mutate S to point to a new SCEV with that
450 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
451 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
452 if (C->getValue()->getValue().getMinSignedBits() <= 64) {
453 S = SE.getIntegerSCEV(0, C->getType());
454 return C->getValue()->getSExtValue();
456 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
457 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
458 int64_t Result = ExtractImmediate(NewOps.front(), SE);
459 S = SE.getAddExpr(NewOps);
461 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
462 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
463 int64_t Result = ExtractImmediate(NewOps.front(), SE);
464 S = SE.getAddRecExpr(NewOps, AR->getLoop());
470 /// ExtractSymbol - If S involves the addition of a GlobalValue address,
471 /// return that symbol, and mutate S to point to a new SCEV with that
473 static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
474 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
475 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
476 S = SE.getIntegerSCEV(0, GV->getType());
479 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
480 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
481 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
482 S = SE.getAddExpr(NewOps);
484 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
485 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
486 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
487 S = SE.getAddRecExpr(NewOps, AR->getLoop());
493 /// isAddressUse - Returns true if the specified instruction is using the
494 /// specified value as an address.
495 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
496 bool isAddress = isa<LoadInst>(Inst);
497 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
498 if (SI->getOperand(1) == OperandVal)
500 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
501 // Addressing modes can also be folded into prefetches and a variety
503 switch (II->getIntrinsicID()) {
505 case Intrinsic::prefetch:
506 case Intrinsic::x86_sse2_loadu_dq:
507 case Intrinsic::x86_sse2_loadu_pd:
508 case Intrinsic::x86_sse_loadu_ps:
509 case Intrinsic::x86_sse_storeu_ps:
510 case Intrinsic::x86_sse2_storeu_pd:
511 case Intrinsic::x86_sse2_storeu_dq:
512 case Intrinsic::x86_sse2_storel_dq:
513 if (II->getOperand(1) == OperandVal)
521 /// getAccessType - Return the type of the memory being accessed.
522 static const Type *getAccessType(const Instruction *Inst) {
523 const Type *AccessTy = Inst->getType();
524 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
525 AccessTy = SI->getOperand(0)->getType();
526 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
527 // Addressing modes can also be folded into prefetches and a variety
529 switch (II->getIntrinsicID()) {
531 case Intrinsic::x86_sse_storeu_ps:
532 case Intrinsic::x86_sse2_storeu_pd:
533 case Intrinsic::x86_sse2_storeu_dq:
534 case Intrinsic::x86_sse2_storel_dq:
535 AccessTy = II->getOperand(1)->getType();
540 // All pointers have the same requirements, so canonicalize them to an
541 // arbitrary pointer type to minimize variation.
542 if (const PointerType *PTy = dyn_cast<PointerType>(AccessTy))
543 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
544 PTy->getAddressSpace());
549 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
550 /// specified set are trivially dead, delete them and see if this makes any of
551 /// their operands subsequently dead.
553 DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
554 bool Changed = false;
556 while (!DeadInsts.empty()) {
557 Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val());
559 if (I == 0 || !isInstructionTriviallyDead(I))
562 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
563 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
566 DeadInsts.push_back(U);
569 I->eraseFromParent();
578 /// Cost - This class is used to measure and compare candidate formulae.
580 /// TODO: Some of these could be merged. Also, a lexical ordering
581 /// isn't always optimal.
585 unsigned NumBaseAdds;
591 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
594 unsigned getNumRegs() const { return NumRegs; }
596 bool operator<(const Cost &Other) const;
600 void RateFormula(const Formula &F,
601 SmallPtrSet<const SCEV *, 16> &Regs,
602 const DenseSet<const SCEV *> &VisitedRegs,
604 const SmallVectorImpl<int64_t> &Offsets,
605 ScalarEvolution &SE, DominatorTree &DT);
607 void print(raw_ostream &OS) const;
611 void RateRegister(const SCEV *Reg,
612 SmallPtrSet<const SCEV *, 16> &Regs,
614 ScalarEvolution &SE, DominatorTree &DT);
615 void RatePrimaryRegister(const SCEV *Reg,
616 SmallPtrSet<const SCEV *, 16> &Regs,
618 ScalarEvolution &SE, DominatorTree &DT);
623 /// RateRegister - Tally up interesting quantities from the given register.
624 void Cost::RateRegister(const SCEV *Reg,
625 SmallPtrSet<const SCEV *, 16> &Regs,
627 ScalarEvolution &SE, DominatorTree &DT) {
628 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
629 if (AR->getLoop() == L)
630 AddRecCost += 1; /// TODO: This should be a function of the stride.
632 // If this is an addrec for a loop that's already been visited by LSR,
633 // don't second-guess its addrec phi nodes. LSR isn't currently smart
634 // enough to reason about more than one loop at a time. Consider these
635 // registers free and leave them alone.
636 else if (L->contains(AR->getLoop()) ||
637 (!AR->getLoop()->contains(L) &&
638 DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) {
639 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
640 PHINode *PN = dyn_cast<PHINode>(I); ++I)
641 if (SE.isSCEVable(PN->getType()) &&
642 (SE.getEffectiveSCEVType(PN->getType()) ==
643 SE.getEffectiveSCEVType(AR->getType())) &&
644 SE.getSCEV(PN) == AR)
647 // If this isn't one of the addrecs that the loop already has, it
648 // would require a costly new phi and add. TODO: This isn't
649 // precisely modeled right now.
651 if (!Regs.count(AR->getStart()))
652 RateRegister(AR->getStart(), Regs, L, SE, DT);
655 // Add the step value register, if it needs one.
656 // TODO: The non-affine case isn't precisely modeled here.
657 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1)))
658 if (!Regs.count(AR->getStart()))
659 RateRegister(AR->getOperand(1), Regs, L, SE, DT);
663 // Rough heuristic; favor registers which don't require extra setup
664 // instructions in the preheader.
665 if (!isa<SCEVUnknown>(Reg) &&
666 !isa<SCEVConstant>(Reg) &&
667 !(isa<SCEVAddRecExpr>(Reg) &&
668 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
669 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
673 /// RatePrimaryRegister - Record this register in the set. If we haven't seen it
675 void Cost::RatePrimaryRegister(const SCEV *Reg,
676 SmallPtrSet<const SCEV *, 16> &Regs,
678 ScalarEvolution &SE, DominatorTree &DT) {
679 if (Regs.insert(Reg))
680 RateRegister(Reg, Regs, L, SE, DT);
683 void Cost::RateFormula(const Formula &F,
684 SmallPtrSet<const SCEV *, 16> &Regs,
685 const DenseSet<const SCEV *> &VisitedRegs,
687 const SmallVectorImpl<int64_t> &Offsets,
688 ScalarEvolution &SE, DominatorTree &DT) {
689 // Tally up the registers.
690 if (const SCEV *ScaledReg = F.ScaledReg) {
691 if (VisitedRegs.count(ScaledReg)) {
695 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT);
697 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
698 E = F.BaseRegs.end(); I != E; ++I) {
699 const SCEV *BaseReg = *I;
700 if (VisitedRegs.count(BaseReg)) {
704 RatePrimaryRegister(BaseReg, Regs, L, SE, DT);
706 NumIVMuls += isa<SCEVMulExpr>(BaseReg) &&
707 BaseReg->hasComputableLoopEvolution(L);
710 if (F.BaseRegs.size() > 1)
711 NumBaseAdds += F.BaseRegs.size() - 1;
713 // Tally up the non-zero immediates.
714 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
715 E = Offsets.end(); I != E; ++I) {
716 int64_t Offset = (uint64_t)*I + F.AM.BaseOffs;
718 ImmCost += 64; // Handle symbolic values conservatively.
719 // TODO: This should probably be the pointer size.
720 else if (Offset != 0)
721 ImmCost += APInt(64, Offset, true).getMinSignedBits();
725 /// Loose - Set this cost to a loosing value.
735 /// operator< - Choose the lower cost.
736 bool Cost::operator<(const Cost &Other) const {
737 if (NumRegs != Other.NumRegs)
738 return NumRegs < Other.NumRegs;
739 if (AddRecCost != Other.AddRecCost)
740 return AddRecCost < Other.AddRecCost;
741 if (NumIVMuls != Other.NumIVMuls)
742 return NumIVMuls < Other.NumIVMuls;
743 if (NumBaseAdds != Other.NumBaseAdds)
744 return NumBaseAdds < Other.NumBaseAdds;
745 if (ImmCost != Other.ImmCost)
746 return ImmCost < Other.ImmCost;
747 if (SetupCost != Other.SetupCost)
748 return SetupCost < Other.SetupCost;
752 void Cost::print(raw_ostream &OS) const {
753 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
755 OS << ", with addrec cost " << AddRecCost;
757 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
758 if (NumBaseAdds != 0)
759 OS << ", plus " << NumBaseAdds << " base add"
760 << (NumBaseAdds == 1 ? "" : "s");
762 OS << ", plus " << ImmCost << " imm cost";
764 OS << ", plus " << SetupCost << " setup cost";
767 void Cost::dump() const {
768 print(errs()); errs() << '\n';
773 /// LSRFixup - An operand value in an instruction which is to be replaced
774 /// with some equivalent, possibly strength-reduced, replacement.
776 /// UserInst - The instruction which will be updated.
777 Instruction *UserInst;
779 /// OperandValToReplace - The operand of the instruction which will
780 /// be replaced. The operand may be used more than once; every instance
781 /// will be replaced.
782 Value *OperandValToReplace;
784 /// PostIncLoop - If this user is to use the post-incremented value of an
785 /// induction variable, this variable is non-null and holds the loop
786 /// associated with the induction variable.
787 const Loop *PostIncLoop;
789 /// LUIdx - The index of the LSRUse describing the expression which
790 /// this fixup needs, minus an offset (below).
793 /// Offset - A constant offset to be added to the LSRUse expression.
794 /// This allows multiple fixups to share the same LSRUse with different
795 /// offsets, for example in an unrolled loop.
800 void print(raw_ostream &OS) const;
807 : UserInst(0), OperandValToReplace(0), PostIncLoop(0),
808 LUIdx(~size_t(0)), Offset(0) {}
810 void LSRFixup::print(raw_ostream &OS) const {
812 // Store is common and interesting enough to be worth special-casing.
813 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
815 WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false);
816 } else if (UserInst->getType()->isVoidTy())
817 OS << UserInst->getOpcodeName();
819 WriteAsOperand(OS, UserInst, /*PrintType=*/false);
821 OS << ", OperandValToReplace=";
822 WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false);
825 OS << ", PostIncLoop=";
826 WriteAsOperand(OS, PostIncLoop->getHeader(), /*PrintType=*/false);
829 if (LUIdx != ~size_t(0))
830 OS << ", LUIdx=" << LUIdx;
833 OS << ", Offset=" << Offset;
836 void LSRFixup::dump() const {
837 print(errs()); errs() << '\n';
842 /// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
843 /// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
844 struct UniquifierDenseMapInfo {
845 static SmallVector<const SCEV *, 2> getEmptyKey() {
846 SmallVector<const SCEV *, 2> V;
847 V.push_back(reinterpret_cast<const SCEV *>(-1));
851 static SmallVector<const SCEV *, 2> getTombstoneKey() {
852 SmallVector<const SCEV *, 2> V;
853 V.push_back(reinterpret_cast<const SCEV *>(-2));
857 static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) {
859 for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(),
860 E = V.end(); I != E; ++I)
861 Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I);
865 static bool isEqual(const SmallVector<const SCEV *, 2> &LHS,
866 const SmallVector<const SCEV *, 2> &RHS) {
871 /// LSRUse - This class holds the state that LSR keeps for each use in
872 /// IVUsers, as well as uses invented by LSR itself. It includes information
873 /// about what kinds of things can be folded into the user, information about
874 /// the user itself, and information about how the use may be satisfied.
875 /// TODO: Represent multiple users of the same expression in common?
877 DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier;
880 /// KindType - An enum for a kind of use, indicating what types of
881 /// scaled and immediate operands it might support.
883 Basic, ///< A normal use, with no folding.
884 Special, ///< A special case of basic, allowing -1 scales.
885 Address, ///< An address use; folding according to TargetLowering
886 ICmpZero ///< An equality icmp with both operands folded into one.
887 // TODO: Add a generic icmp too?
891 const Type *AccessTy;
893 SmallVector<int64_t, 8> Offsets;
897 /// AllFixupsOutsideLoop - This records whether all of the fixups using this
898 /// LSRUse are outside of the loop, in which case some special-case heuristics
900 bool AllFixupsOutsideLoop;
902 /// Formulae - A list of ways to build a value that can satisfy this user.
903 /// After the list is populated, one of these is selected heuristically and
904 /// used to formulate a replacement for OperandValToReplace in UserInst.
905 SmallVector<Formula, 12> Formulae;
907 /// Regs - The set of register candidates used by all formulae in this LSRUse.
908 SmallPtrSet<const SCEV *, 4> Regs;
910 LSRUse(KindType K, const Type *T) : Kind(K), AccessTy(T),
911 MinOffset(INT64_MAX),
912 MaxOffset(INT64_MIN),
913 AllFixupsOutsideLoop(true) {}
915 bool InsertFormula(const Formula &F);
919 void print(raw_ostream &OS) const;
923 /// InsertFormula - If the given formula has not yet been inserted, add it to
924 /// the list, and return true. Return false otherwise.
925 bool LSRUse::InsertFormula(const Formula &F) {
926 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
927 if (F.ScaledReg) Key.push_back(F.ScaledReg);
928 // Unstable sort by host order ok, because this is only used for uniquifying.
929 std::sort(Key.begin(), Key.end());
931 if (!Uniquifier.insert(Key).second)
934 // Using a register to hold the value of 0 is not profitable.
935 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
936 "Zero allocated in a scaled register!");
938 for (SmallVectorImpl<const SCEV *>::const_iterator I =
939 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
940 assert(!(*I)->isZero() && "Zero allocated in a base register!");
943 // Add the formula to the list.
944 Formulae.push_back(F);
946 // Record registers now being used by this use.
947 if (F.ScaledReg) Regs.insert(F.ScaledReg);
948 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
953 void LSRUse::print(raw_ostream &OS) const {
954 OS << "LSR Use: Kind=";
956 case Basic: OS << "Basic"; break;
957 case Special: OS << "Special"; break;
958 case ICmpZero: OS << "ICmpZero"; break;
961 if (AccessTy->isPointerTy())
962 OS << "pointer"; // the full pointer type could be really verbose
968 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
969 E = Offsets.end(); I != E; ++I) {
976 if (AllFixupsOutsideLoop)
977 OS << ", all-fixups-outside-loop";
980 void LSRUse::dump() const {
981 print(errs()); errs() << '\n';
984 /// isLegalUse - Test whether the use described by AM is "legal", meaning it can
985 /// be completely folded into the user instruction at isel time. This includes
986 /// address-mode folding and special icmp tricks.
987 static bool isLegalUse(const TargetLowering::AddrMode &AM,
988 LSRUse::KindType Kind, const Type *AccessTy,
989 const TargetLowering *TLI) {
991 case LSRUse::Address:
992 // If we have low-level target information, ask the target if it can
993 // completely fold this address.
994 if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy);
996 // Otherwise, just guess that reg+reg addressing is legal.
997 return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1;
999 case LSRUse::ICmpZero:
1000 // There's not even a target hook for querying whether it would be legal to
1001 // fold a GV into an ICmp.
1005 // ICmp only has two operands; don't allow more than two non-trivial parts.
1006 if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0)
1009 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1010 // putting the scaled register in the other operand of the icmp.
1011 if (AM.Scale != 0 && AM.Scale != -1)
1014 // If we have low-level target information, ask the target if it can fold an
1015 // integer immediate on an icmp.
1016 if (AM.BaseOffs != 0) {
1017 if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs);
1024 // Only handle single-register values.
1025 return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
1027 case LSRUse::Special:
1028 // Only handle -1 scales, or no scale.
1029 return AM.Scale == 0 || AM.Scale == -1;
1035 static bool isLegalUse(TargetLowering::AddrMode AM,
1036 int64_t MinOffset, int64_t MaxOffset,
1037 LSRUse::KindType Kind, const Type *AccessTy,
1038 const TargetLowering *TLI) {
1039 // Check for overflow.
1040 if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) !=
1043 AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset;
1044 if (isLegalUse(AM, Kind, AccessTy, TLI)) {
1045 AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset;
1046 // Check for overflow.
1047 if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) !=
1050 AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset;
1051 return isLegalUse(AM, Kind, AccessTy, TLI);
1056 static bool isAlwaysFoldable(int64_t BaseOffs,
1057 GlobalValue *BaseGV,
1059 LSRUse::KindType Kind, const Type *AccessTy,
1060 const TargetLowering *TLI) {
1061 // Fast-path: zero is always foldable.
1062 if (BaseOffs == 0 && !BaseGV) return true;
1064 // Conservatively, create an address with an immediate and a
1065 // base and a scale.
1066 TargetLowering::AddrMode AM;
1067 AM.BaseOffs = BaseOffs;
1069 AM.HasBaseReg = HasBaseReg;
1070 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1072 return isLegalUse(AM, Kind, AccessTy, TLI);
1075 static bool isAlwaysFoldable(const SCEV *S,
1076 int64_t MinOffset, int64_t MaxOffset,
1078 LSRUse::KindType Kind, const Type *AccessTy,
1079 const TargetLowering *TLI,
1080 ScalarEvolution &SE) {
1081 // Fast-path: zero is always foldable.
1082 if (S->isZero()) return true;
1084 // Conservatively, create an address with an immediate and a
1085 // base and a scale.
1086 int64_t BaseOffs = ExtractImmediate(S, SE);
1087 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1089 // If there's anything else involved, it's not foldable.
1090 if (!S->isZero()) return false;
1092 // Fast-path: zero is always foldable.
1093 if (BaseOffs == 0 && !BaseGV) return true;
1095 // Conservatively, create an address with an immediate and a
1096 // base and a scale.
1097 TargetLowering::AddrMode AM;
1098 AM.BaseOffs = BaseOffs;
1100 AM.HasBaseReg = HasBaseReg;
1101 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1103 return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI);
1106 /// FormulaSorter - This class implements an ordering for formulae which sorts
1107 /// the by their standalone cost.
1108 class FormulaSorter {
1109 /// These two sets are kept empty, so that we compute standalone costs.
1110 DenseSet<const SCEV *> VisitedRegs;
1111 SmallPtrSet<const SCEV *, 16> Regs;
1114 ScalarEvolution &SE;
1118 FormulaSorter(Loop *l, LSRUse &lu, ScalarEvolution &se, DominatorTree &dt)
1119 : L(l), LU(&lu), SE(se), DT(dt) {}
1121 bool operator()(const Formula &A, const Formula &B) {
1123 CostA.RateFormula(A, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
1126 CostB.RateFormula(B, Regs, VisitedRegs, L, LU->Offsets, SE, DT);
1128 return CostA < CostB;
1132 /// LSRInstance - This class holds state for the main loop strength reduction
1136 ScalarEvolution &SE;
1138 const TargetLowering *const TLI;
1142 /// IVIncInsertPos - This is the insert position that the current loop's
1143 /// induction variable increment should be placed. In simple loops, this is
1144 /// the latch block's terminator. But in more complicated cases, this is a
1145 /// position which will dominate all the in-loop post-increment users.
1146 Instruction *IVIncInsertPos;
1148 /// Factors - Interesting factors between use strides.
1149 SmallSetVector<int64_t, 8> Factors;
1151 /// Types - Interesting use types, to facilitate truncation reuse.
1152 SmallSetVector<const Type *, 4> Types;
1154 /// Fixups - The list of operands which are to be replaced.
1155 SmallVector<LSRFixup, 16> Fixups;
1157 /// Uses - The list of interesting uses.
1158 SmallVector<LSRUse, 16> Uses;
1160 /// RegUses - Track which uses use which register candidates.
1161 RegUseTracker RegUses;
1163 void OptimizeShadowIV();
1164 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1165 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1166 bool OptimizeLoopTermCond();
1168 void CollectInterestingTypesAndFactors();
1169 void CollectFixupsAndInitialFormulae();
1171 LSRFixup &getNewFixup() {
1172 Fixups.push_back(LSRFixup());
1173 return Fixups.back();
1176 // Support for sharing of LSRUses between LSRFixups.
1177 typedef DenseMap<const SCEV *, size_t> UseMapTy;
1180 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
1181 LSRUse::KindType Kind, const Type *AccessTy);
1183 std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1184 LSRUse::KindType Kind,
1185 const Type *AccessTy);
1188 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1189 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1190 void CountRegisters(const Formula &F, size_t LUIdx);
1191 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1193 void CollectLoopInvariantFixupsAndFormulae();
1195 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1196 unsigned Depth = 0);
1197 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1198 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1199 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1200 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1201 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1202 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1203 void GenerateCrossUseConstantOffsets();
1204 void GenerateAllReuseFormulae();
1206 void FilterOutUndesirableDedicatedRegisters();
1207 void NarrowSearchSpaceUsingHeuristics();
1209 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1211 SmallVectorImpl<const Formula *> &Workspace,
1212 const Cost &CurCost,
1213 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1214 DenseSet<const SCEV *> &VisitedRegs) const;
1215 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1217 Value *Expand(const LSRFixup &LF,
1219 BasicBlock::iterator IP,
1220 SCEVExpander &Rewriter,
1221 SmallVectorImpl<WeakVH> &DeadInsts) const;
1222 void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
1224 SCEVExpander &Rewriter,
1225 SmallVectorImpl<WeakVH> &DeadInsts,
1227 void Rewrite(const LSRFixup &LF,
1229 SCEVExpander &Rewriter,
1230 SmallVectorImpl<WeakVH> &DeadInsts,
1232 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1235 LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
1237 bool getChanged() const { return Changed; }
1239 void print_factors_and_types(raw_ostream &OS) const;
1240 void print_fixups(raw_ostream &OS) const;
1241 void print_uses(raw_ostream &OS) const;
1242 void print(raw_ostream &OS) const;
1248 /// OptimizeShadowIV - If IV is used in a int-to-float cast
1249 /// inside the loop then try to eliminate the cast operation.
1250 void LSRInstance::OptimizeShadowIV() {
1251 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1252 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1255 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1256 UI != E; /* empty */) {
1257 IVUsers::const_iterator CandidateUI = UI;
1259 Instruction *ShadowUse = CandidateUI->getUser();
1260 const Type *DestTy = NULL;
1262 /* If shadow use is a int->float cast then insert a second IV
1263 to eliminate this cast.
1265 for (unsigned i = 0; i < n; ++i)
1271 for (unsigned i = 0; i < n; ++i, ++d)
1274 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser()))
1275 DestTy = UCast->getDestTy();
1276 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser()))
1277 DestTy = SCast->getDestTy();
1278 if (!DestTy) continue;
1281 // If target does not support DestTy natively then do not apply
1282 // this transformation.
1283 EVT DVT = TLI->getValueType(DestTy);
1284 if (!TLI->isTypeLegal(DVT)) continue;
1287 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1289 if (PH->getNumIncomingValues() != 2) continue;
1291 const Type *SrcTy = PH->getType();
1292 int Mantissa = DestTy->getFPMantissaWidth();
1293 if (Mantissa == -1) continue;
1294 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1297 unsigned Entry, Latch;
1298 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1306 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1307 if (!Init) continue;
1308 Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue());
1310 BinaryOperator *Incr =
1311 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1312 if (!Incr) continue;
1313 if (Incr->getOpcode() != Instruction::Add
1314 && Incr->getOpcode() != Instruction::Sub)
1317 /* Initialize new IV, double d = 0.0 in above example. */
1318 ConstantInt *C = NULL;
1319 if (Incr->getOperand(0) == PH)
1320 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1321 else if (Incr->getOperand(1) == PH)
1322 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1328 // Ignore negative constants, as the code below doesn't handle them
1329 // correctly. TODO: Remove this restriction.
1330 if (!C->getValue().isStrictlyPositive()) continue;
1332 /* Add new PHINode. */
1333 PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH);
1335 /* create new increment. '++d' in above example. */
1336 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1337 BinaryOperator *NewIncr =
1338 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1339 Instruction::FAdd : Instruction::FSub,
1340 NewPH, CFP, "IV.S.next.", Incr);
1342 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1343 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1345 /* Remove cast operation */
1346 ShadowUse->replaceAllUsesWith(NewPH);
1347 ShadowUse->eraseFromParent();
1352 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1353 /// set the IV user and stride information and return true, otherwise return
1355 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond,
1356 IVStrideUse *&CondUse) {
1357 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1358 if (UI->getUser() == Cond) {
1359 // NOTE: we could handle setcc instructions with multiple uses here, but
1360 // InstCombine does it as well for simple uses, it's not clear that it
1361 // occurs enough in real life to handle.
1368 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
1369 /// a max computation.
1371 /// This is a narrow solution to a specific, but acute, problem. For loops
1377 /// } while (++i < n);
1379 /// the trip count isn't just 'n', because 'n' might not be positive. And
1380 /// unfortunately this can come up even for loops where the user didn't use
1381 /// a C do-while loop. For example, seemingly well-behaved top-test loops
1382 /// will commonly be lowered like this:
1388 /// } while (++i < n);
1391 /// and then it's possible for subsequent optimization to obscure the if
1392 /// test in such a way that indvars can't find it.
1394 /// When indvars can't find the if test in loops like this, it creates a
1395 /// max expression, which allows it to give the loop a canonical
1396 /// induction variable:
1399 /// max = n < 1 ? 1 : n;
1402 /// } while (++i != max);
1404 /// Canonical induction variables are necessary because the loop passes
1405 /// are designed around them. The most obvious example of this is the
1406 /// LoopInfo analysis, which doesn't remember trip count values. It
1407 /// expects to be able to rediscover the trip count each time it is
1408 /// needed, and it does this using a simple analysis that only succeeds if
1409 /// the loop has a canonical induction variable.
1411 /// However, when it comes time to generate code, the maximum operation
1412 /// can be quite costly, especially if it's inside of an outer loop.
1414 /// This function solves this problem by detecting this type of loop and
1415 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1416 /// the instructions for the maximum computation.
1418 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1419 // Check that the loop matches the pattern we're looking for.
1420 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1421 Cond->getPredicate() != CmpInst::ICMP_NE)
1424 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
1425 if (!Sel || !Sel->hasOneUse()) return Cond;
1427 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1428 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1430 const SCEV *One = SE.getIntegerSCEV(1, BackedgeTakenCount->getType());
1432 // Add one to the backedge-taken count to get the trip count.
1433 const SCEV *IterationCount = SE.getAddExpr(BackedgeTakenCount, One);
1435 // Check for a max calculation that matches the pattern.
1436 if (!isa<SCEVSMaxExpr>(IterationCount) && !isa<SCEVUMaxExpr>(IterationCount))
1438 const SCEVNAryExpr *Max = cast<SCEVNAryExpr>(IterationCount);
1439 if (Max != SE.getSCEV(Sel)) return Cond;
1441 // To handle a max with more than two operands, this optimization would
1442 // require additional checking and setup.
1443 if (Max->getNumOperands() != 2)
1446 const SCEV *MaxLHS = Max->getOperand(0);
1447 const SCEV *MaxRHS = Max->getOperand(1);
1448 if (!MaxLHS || MaxLHS != One) return Cond;
1449 // Check the relevant induction variable for conformance to
1451 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
1452 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
1453 if (!AR || !AR->isAffine() ||
1454 AR->getStart() != One ||
1455 AR->getStepRecurrence(SE) != One)
1458 assert(AR->getLoop() == L &&
1459 "Loop condition operand is an addrec in a different loop!");
1461 // Check the right operand of the select, and remember it, as it will
1462 // be used in the new comparison instruction.
1464 if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
1465 NewRHS = Sel->getOperand(1);
1466 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
1467 NewRHS = Sel->getOperand(2);
1468 if (!NewRHS) return Cond;
1470 // Determine the new comparison opcode. It may be signed or unsigned,
1471 // and the original comparison may be either equality or inequality.
1472 CmpInst::Predicate Pred =
1473 isa<SCEVSMaxExpr>(Max) ? CmpInst::ICMP_SLT : CmpInst::ICMP_ULT;
1474 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
1475 Pred = CmpInst::getInversePredicate(Pred);
1477 // Ok, everything looks ok to change the condition into an SLT or SGE and
1478 // delete the max calculation.
1480 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
1482 // Delete the max calculation instructions.
1483 Cond->replaceAllUsesWith(NewCond);
1484 CondUse->setUser(NewCond);
1485 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
1486 Cond->eraseFromParent();
1487 Sel->eraseFromParent();
1488 if (Cmp->use_empty())
1489 Cmp->eraseFromParent();
1493 /// OptimizeLoopTermCond - Change loop terminating condition to use the
1494 /// postinc iv when possible.
1496 LSRInstance::OptimizeLoopTermCond() {
1497 SmallPtrSet<Instruction *, 4> PostIncs;
1499 BasicBlock *LatchBlock = L->getLoopLatch();
1500 SmallVector<BasicBlock*, 8> ExitingBlocks;
1501 L->getExitingBlocks(ExitingBlocks);
1503 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
1504 BasicBlock *ExitingBlock = ExitingBlocks[i];
1506 // Get the terminating condition for the loop if possible. If we
1507 // can, we want to change it to use a post-incremented version of its
1508 // induction variable, to allow coalescing the live ranges for the IV into
1509 // one register value.
1511 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
1514 // FIXME: Overly conservative, termination condition could be an 'or' etc..
1515 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
1518 // Search IVUsesByStride to find Cond's IVUse if there is one.
1519 IVStrideUse *CondUse = 0;
1520 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
1521 if (!FindIVUserForCond(Cond, CondUse))
1524 // If the trip count is computed in terms of a max (due to ScalarEvolution
1525 // being unable to find a sufficient guard, for example), change the loop
1526 // comparison to use SLT or ULT instead of NE.
1527 // One consequence of doing this now is that it disrupts the count-down
1528 // optimization. That's not always a bad thing though, because in such
1529 // cases it may still be worthwhile to avoid a max.
1530 Cond = OptimizeMax(Cond, CondUse);
1532 // If this exiting block dominates the latch block, it may also use
1533 // the post-inc value if it won't be shared with other uses.
1534 // Check for dominance.
1535 if (!DT.dominates(ExitingBlock, LatchBlock))
1538 // Conservatively avoid trying to use the post-inc value in non-latch
1539 // exits if there may be pre-inc users in intervening blocks.
1540 if (LatchBlock != ExitingBlock)
1541 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1542 // Test if the use is reachable from the exiting block. This dominator
1543 // query is a conservative approximation of reachability.
1544 if (&*UI != CondUse &&
1545 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
1546 // Conservatively assume there may be reuse if the quotient of their
1547 // strides could be a legal scale.
1548 const SCEV *A = CondUse->getStride();
1549 const SCEV *B = UI->getStride();
1550 if (SE.getTypeSizeInBits(A->getType()) !=
1551 SE.getTypeSizeInBits(B->getType())) {
1552 if (SE.getTypeSizeInBits(A->getType()) >
1553 SE.getTypeSizeInBits(B->getType()))
1554 B = SE.getSignExtendExpr(B, A->getType());
1556 A = SE.getSignExtendExpr(A, B->getType());
1558 if (const SCEVConstant *D =
1559 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
1560 // Stride of one or negative one can have reuse with non-addresses.
1561 if (D->getValue()->isOne() ||
1562 D->getValue()->isAllOnesValue())
1563 goto decline_post_inc;
1564 // Avoid weird situations.
1565 if (D->getValue()->getValue().getMinSignedBits() >= 64 ||
1566 D->getValue()->getValue().isMinSignedValue())
1567 goto decline_post_inc;
1568 // Without TLI, assume that any stride might be valid, and so any
1569 // use might be shared.
1571 goto decline_post_inc;
1572 // Check for possible scaled-address reuse.
1573 const Type *AccessTy = getAccessType(UI->getUser());
1574 TargetLowering::AddrMode AM;
1575 AM.Scale = D->getValue()->getSExtValue();
1576 if (TLI->isLegalAddressingMode(AM, AccessTy))
1577 goto decline_post_inc;
1578 AM.Scale = -AM.Scale;
1579 if (TLI->isLegalAddressingMode(AM, AccessTy))
1580 goto decline_post_inc;
1584 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
1587 // It's possible for the setcc instruction to be anywhere in the loop, and
1588 // possible for it to have multiple users. If it is not immediately before
1589 // the exiting block branch, move it.
1590 if (&*++BasicBlock::iterator(Cond) != TermBr) {
1591 if (Cond->hasOneUse()) {
1592 Cond->moveBefore(TermBr);
1594 // Clone the terminating condition and insert into the loopend.
1595 ICmpInst *OldCond = Cond;
1596 Cond = cast<ICmpInst>(Cond->clone());
1597 Cond->setName(L->getHeader()->getName() + ".termcond");
1598 ExitingBlock->getInstList().insert(TermBr, Cond);
1600 // Clone the IVUse, as the old use still exists!
1601 CondUse = &IU.AddUser(CondUse->getStride(), CondUse->getOffset(),
1602 Cond, CondUse->getOperandValToReplace());
1603 TermBr->replaceUsesOfWith(OldCond, Cond);
1607 // If we get to here, we know that we can transform the setcc instruction to
1608 // use the post-incremented version of the IV, allowing us to coalesce the
1609 // live ranges for the IV correctly.
1610 CondUse->setOffset(SE.getMinusSCEV(CondUse->getOffset(),
1611 CondUse->getStride()));
1612 CondUse->setIsUseOfPostIncrementedValue(true);
1615 PostIncs.insert(Cond);
1619 // Determine an insertion point for the loop induction variable increment. It
1620 // must dominate all the post-inc comparisons we just set up, and it must
1621 // dominate the loop latch edge.
1622 IVIncInsertPos = L->getLoopLatch()->getTerminator();
1623 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
1624 E = PostIncs.end(); I != E; ++I) {
1626 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
1628 if (BB == (*I)->getParent())
1629 IVIncInsertPos = *I;
1630 else if (BB != IVIncInsertPos->getParent())
1631 IVIncInsertPos = BB->getTerminator();
1638 LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset,
1639 LSRUse::KindType Kind, const Type *AccessTy) {
1640 int64_t NewMinOffset = LU.MinOffset;
1641 int64_t NewMaxOffset = LU.MaxOffset;
1642 const Type *NewAccessTy = AccessTy;
1644 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
1645 // something conservative, however this can pessimize in the case that one of
1646 // the uses will have all its uses outside the loop, for example.
1647 if (LU.Kind != Kind)
1649 // Conservatively assume HasBaseReg is true for now.
1650 if (NewOffset < LU.MinOffset) {
1651 if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, /*HasBaseReg=*/true,
1652 Kind, AccessTy, TLI))
1654 NewMinOffset = NewOffset;
1655 } else if (NewOffset > LU.MaxOffset) {
1656 if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, /*HasBaseReg=*/true,
1657 Kind, AccessTy, TLI))
1659 NewMaxOffset = NewOffset;
1661 // Check for a mismatched access type, and fall back conservatively as needed.
1662 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
1663 NewAccessTy = Type::getVoidTy(AccessTy->getContext());
1666 LU.MinOffset = NewMinOffset;
1667 LU.MaxOffset = NewMaxOffset;
1668 LU.AccessTy = NewAccessTy;
1669 if (NewOffset != LU.Offsets.back())
1670 LU.Offsets.push_back(NewOffset);
1674 /// getUse - Return an LSRUse index and an offset value for a fixup which
1675 /// needs the given expression, with the given kind and optional access type.
1676 /// Either reuse an existing use or create a new one, as needed.
1677 std::pair<size_t, int64_t>
1678 LSRInstance::getUse(const SCEV *&Expr,
1679 LSRUse::KindType Kind, const Type *AccessTy) {
1680 const SCEV *Copy = Expr;
1681 int64_t Offset = ExtractImmediate(Expr, SE);
1683 // Basic uses can't accept any offset, for example.
1684 if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) {
1689 std::pair<UseMapTy::iterator, bool> P =
1690 UseMap.insert(std::make_pair(Expr, 0));
1692 // A use already existed with this base.
1693 size_t LUIdx = P.first->second;
1694 LSRUse &LU = Uses[LUIdx];
1695 if (reconcileNewOffset(LU, Offset, Kind, AccessTy))
1697 return std::make_pair(LUIdx, Offset);
1700 // Create a new use.
1701 size_t LUIdx = Uses.size();
1702 P.first->second = LUIdx;
1703 Uses.push_back(LSRUse(Kind, AccessTy));
1704 LSRUse &LU = Uses[LUIdx];
1706 // We don't need to track redundant offsets, but we don't need to go out
1707 // of our way here to avoid them.
1708 if (LU.Offsets.empty() || Offset != LU.Offsets.back())
1709 LU.Offsets.push_back(Offset);
1711 LU.MinOffset = Offset;
1712 LU.MaxOffset = Offset;
1713 return std::make_pair(LUIdx, Offset);
1716 void LSRInstance::CollectInterestingTypesAndFactors() {
1717 SmallSetVector<const SCEV *, 4> Strides;
1719 // Collect interesting types and strides.
1720 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
1721 const SCEV *Stride = UI->getStride();
1723 // Collect interesting types.
1724 Types.insert(SE.getEffectiveSCEVType(Stride->getType()));
1726 // Add the stride for this loop.
1727 Strides.insert(Stride);
1729 // Add strides for other mentioned loops.
1730 for (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(UI->getOffset());
1731 AR; AR = dyn_cast<SCEVAddRecExpr>(AR->getStart()))
1732 Strides.insert(AR->getStepRecurrence(SE));
1735 // Compute interesting factors from the set of interesting strides.
1736 for (SmallSetVector<const SCEV *, 4>::const_iterator
1737 I = Strides.begin(), E = Strides.end(); I != E; ++I)
1738 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
1739 next(I); NewStrideIter != E; ++NewStrideIter) {
1740 const SCEV *OldStride = *I;
1741 const SCEV *NewStride = *NewStrideIter;
1743 if (SE.getTypeSizeInBits(OldStride->getType()) !=
1744 SE.getTypeSizeInBits(NewStride->getType())) {
1745 if (SE.getTypeSizeInBits(OldStride->getType()) >
1746 SE.getTypeSizeInBits(NewStride->getType()))
1747 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
1749 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
1751 if (const SCEVConstant *Factor =
1752 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
1754 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
1755 Factors.insert(Factor->getValue()->getValue().getSExtValue());
1756 } else if (const SCEVConstant *Factor =
1757 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
1760 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
1761 Factors.insert(Factor->getValue()->getValue().getSExtValue());
1765 // If all uses use the same type, don't bother looking for truncation-based
1767 if (Types.size() == 1)
1770 DEBUG(print_factors_and_types(dbgs()));
1773 void LSRInstance::CollectFixupsAndInitialFormulae() {
1774 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
1776 LSRFixup &LF = getNewFixup();
1777 LF.UserInst = UI->getUser();
1778 LF.OperandValToReplace = UI->getOperandValToReplace();
1779 if (UI->isUseOfPostIncrementedValue())
1782 LSRUse::KindType Kind = LSRUse::Basic;
1783 const Type *AccessTy = 0;
1784 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
1785 Kind = LSRUse::Address;
1786 AccessTy = getAccessType(LF.UserInst);
1789 const SCEV *S = IU.getCanonicalExpr(*UI);
1791 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
1792 // (N - i == 0), and this allows (N - i) to be the expression that we work
1793 // with rather than just N or i, so we can consider the register
1794 // requirements for both N and i at the same time. Limiting this code to
1795 // equality icmps is not a problem because all interesting loops use
1796 // equality icmps, thanks to IndVarSimplify.
1797 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
1798 if (CI->isEquality()) {
1799 // Swap the operands if needed to put the OperandValToReplace on the
1800 // left, for consistency.
1801 Value *NV = CI->getOperand(1);
1802 if (NV == LF.OperandValToReplace) {
1803 CI->setOperand(1, CI->getOperand(0));
1804 CI->setOperand(0, NV);
1807 // x == y --> x - y == 0
1808 const SCEV *N = SE.getSCEV(NV);
1809 if (N->isLoopInvariant(L)) {
1810 Kind = LSRUse::ICmpZero;
1811 S = SE.getMinusSCEV(N, S);
1814 // -1 and the negations of all interesting strides (except the negation
1815 // of -1) are now also interesting.
1816 for (size_t i = 0, e = Factors.size(); i != e; ++i)
1817 if (Factors[i] != -1)
1818 Factors.insert(-(uint64_t)Factors[i]);
1822 // Set up the initial formula for this use.
1823 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
1825 LF.Offset = P.second;
1826 LSRUse &LU = Uses[LF.LUIdx];
1827 LU.AllFixupsOutsideLoop &= !L->contains(LF.UserInst);
1829 // If this is the first use of this LSRUse, give it a formula.
1830 if (LU.Formulae.empty()) {
1831 InsertInitialFormula(S, LU, LF.LUIdx);
1832 CountRegisters(LU.Formulae.back(), LF.LUIdx);
1836 DEBUG(print_fixups(dbgs()));
1840 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
1842 F.InitialMatch(S, L, SE, DT);
1843 bool Inserted = InsertFormula(LU, LUIdx, F);
1844 assert(Inserted && "Initial formula already exists!"); (void)Inserted;
1848 LSRInstance::InsertSupplementalFormula(const SCEV *S,
1849 LSRUse &LU, size_t LUIdx) {
1851 F.BaseRegs.push_back(S);
1852 F.AM.HasBaseReg = true;
1853 bool Inserted = InsertFormula(LU, LUIdx, F);
1854 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
1857 /// CountRegisters - Note which registers are used by the given formula,
1858 /// updating RegUses.
1859 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
1861 RegUses.CountRegister(F.ScaledReg, LUIdx);
1862 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
1863 E = F.BaseRegs.end(); I != E; ++I)
1864 RegUses.CountRegister(*I, LUIdx);
1867 /// InsertFormula - If the given formula has not yet been inserted, add it to
1868 /// the list, and return true. Return false otherwise.
1869 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
1870 if (!LU.InsertFormula(F))
1873 CountRegisters(F, LUIdx);
1877 /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
1878 /// loop-invariant values which we're tracking. These other uses will pin these
1879 /// values in registers, making them less profitable for elimination.
1880 /// TODO: This currently misses non-constant addrec step registers.
1881 /// TODO: Should this give more weight to users inside the loop?
1883 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
1884 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
1885 SmallPtrSet<const SCEV *, 8> Inserted;
1887 while (!Worklist.empty()) {
1888 const SCEV *S = Worklist.pop_back_val();
1890 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
1891 Worklist.insert(Worklist.end(), N->op_begin(), N->op_end());
1892 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
1893 Worklist.push_back(C->getOperand());
1894 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
1895 Worklist.push_back(D->getLHS());
1896 Worklist.push_back(D->getRHS());
1897 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
1898 if (!Inserted.insert(U)) continue;
1899 const Value *V = U->getValue();
1900 if (const Instruction *Inst = dyn_cast<Instruction>(V))
1901 if (L->contains(Inst)) continue;
1902 for (Value::use_const_iterator UI = V->use_begin(), UE = V->use_end();
1904 const Instruction *UserInst = dyn_cast<Instruction>(*UI);
1905 // Ignore non-instructions.
1908 // Ignore instructions in other functions (as can happen with
1910 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
1912 // Ignore instructions not dominated by the loop.
1913 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
1914 UserInst->getParent() :
1915 cast<PHINode>(UserInst)->getIncomingBlock(
1916 PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
1917 if (!DT.dominates(L->getHeader(), UseBB))
1919 // Ignore uses which are part of other SCEV expressions, to avoid
1920 // analyzing them multiple times.
1921 if (SE.isSCEVable(UserInst->getType()) &&
1922 !isa<SCEVUnknown>(SE.getSCEV(const_cast<Instruction *>(UserInst))))
1924 // Ignore icmp instructions which are already being analyzed.
1925 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
1926 unsigned OtherIdx = !UI.getOperandNo();
1927 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
1928 if (SE.getSCEV(OtherOp)->hasComputableLoopEvolution(L))
1932 LSRFixup &LF = getNewFixup();
1933 LF.UserInst = const_cast<Instruction *>(UserInst);
1934 LF.OperandValToReplace = UI.getUse();
1935 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0);
1937 LF.Offset = P.second;
1938 LSRUse &LU = Uses[LF.LUIdx];
1939 LU.AllFixupsOutsideLoop &= L->contains(LF.UserInst);
1940 InsertSupplementalFormula(U, LU, LF.LUIdx);
1941 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
1948 /// CollectSubexprs - Split S into subexpressions which can be pulled out into
1949 /// separate registers. If C is non-null, multiply each subexpression by C.
1950 static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
1951 SmallVectorImpl<const SCEV *> &Ops,
1952 ScalarEvolution &SE) {
1953 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
1954 // Break out add operands.
1955 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
1957 CollectSubexprs(*I, C, Ops, SE);
1959 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
1960 // Split a non-zero base out of an addrec.
1961 if (!AR->getStart()->isZero()) {
1962 CollectSubexprs(SE.getAddRecExpr(SE.getIntegerSCEV(0, AR->getType()),
1963 AR->getStepRecurrence(SE),
1964 AR->getLoop()), C, Ops, SE);
1965 CollectSubexprs(AR->getStart(), C, Ops, SE);
1968 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
1969 // Break (C * (a + b + c)) into C*a + C*b + C*c.
1970 if (Mul->getNumOperands() == 2)
1971 if (const SCEVConstant *Op0 =
1972 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
1973 CollectSubexprs(Mul->getOperand(1),
1974 C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
1980 // Otherwise use the value itself.
1981 Ops.push_back(C ? SE.getMulExpr(C, S) : S);
1984 /// GenerateReassociations - Split out subexpressions from adds and the bases of
1986 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
1989 // Arbitrarily cap recursion to protect compile time.
1990 if (Depth >= 3) return;
1992 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
1993 const SCEV *BaseReg = Base.BaseRegs[i];
1995 SmallVector<const SCEV *, 8> AddOps;
1996 CollectSubexprs(BaseReg, 0, AddOps, SE);
1997 if (AddOps.size() == 1) continue;
1999 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
2000 JE = AddOps.end(); J != JE; ++J) {
2001 // Don't pull a constant into a register if the constant could be folded
2002 // into an immediate field.
2003 if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,
2004 Base.getNumRegs() > 1,
2005 LU.Kind, LU.AccessTy, TLI, SE))
2008 // Collect all operands except *J.
2009 SmallVector<const SCEV *, 8> InnerAddOps;
2010 for (SmallVectorImpl<const SCEV *>::const_iterator K = AddOps.begin(),
2011 KE = AddOps.end(); K != KE; ++K)
2013 InnerAddOps.push_back(*K);
2015 // Don't leave just a constant behind in a register if the constant could
2016 // be folded into an immediate field.
2017 if (InnerAddOps.size() == 1 &&
2018 isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset,
2019 Base.getNumRegs() > 1,
2020 LU.Kind, LU.AccessTy, TLI, SE))
2024 F.BaseRegs[i] = SE.getAddExpr(InnerAddOps);
2025 F.BaseRegs.push_back(*J);
2026 if (InsertFormula(LU, LUIdx, F))
2027 // If that formula hadn't been seen before, recurse to find more like
2029 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1);
2034 /// GenerateCombinations - Generate a formula consisting of all of the
2035 /// loop-dominating registers added into a single register.
2036 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
2038 // This method is only interesting on a plurality of registers.
2039 if (Base.BaseRegs.size() <= 1) return;
2043 SmallVector<const SCEV *, 4> Ops;
2044 for (SmallVectorImpl<const SCEV *>::const_iterator
2045 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
2046 const SCEV *BaseReg = *I;
2047 if (BaseReg->properlyDominates(L->getHeader(), &DT) &&
2048 !BaseReg->hasComputableLoopEvolution(L))
2049 Ops.push_back(BaseReg);
2051 F.BaseRegs.push_back(BaseReg);
2053 if (Ops.size() > 1) {
2054 const SCEV *Sum = SE.getAddExpr(Ops);
2055 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
2056 // opportunity to fold something. For now, just ignore such cases
2057 // rather than proceed with zero in a register.
2058 if (!Sum->isZero()) {
2059 F.BaseRegs.push_back(Sum);
2060 (void)InsertFormula(LU, LUIdx, F);
2065 /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
2066 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
2068 // We can't add a symbolic offset if the address already contains one.
2069 if (Base.AM.BaseGV) return;
2071 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2072 const SCEV *G = Base.BaseRegs[i];
2073 GlobalValue *GV = ExtractSymbol(G, SE);
2074 if (G->isZero() || !GV)
2078 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
2079 LU.Kind, LU.AccessTy, TLI))
2082 (void)InsertFormula(LU, LUIdx, F);
2086 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
2087 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
2089 // TODO: For now, just add the min and max offset, because it usually isn't
2090 // worthwhile looking at everything inbetween.
2091 SmallVector<int64_t, 4> Worklist;
2092 Worklist.push_back(LU.MinOffset);
2093 if (LU.MaxOffset != LU.MinOffset)
2094 Worklist.push_back(LU.MaxOffset);
2096 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
2097 const SCEV *G = Base.BaseRegs[i];
2099 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
2100 E = Worklist.end(); I != E; ++I) {
2102 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I;
2103 if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I,
2104 LU.Kind, LU.AccessTy, TLI)) {
2105 F.BaseRegs[i] = SE.getAddExpr(G, SE.getIntegerSCEV(*I, G->getType()));
2107 (void)InsertFormula(LU, LUIdx, F);
2111 int64_t Imm = ExtractImmediate(G, SE);
2112 if (G->isZero() || Imm == 0)
2115 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm;
2116 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
2117 LU.Kind, LU.AccessTy, TLI))
2120 (void)InsertFormula(LU, LUIdx, F);
2124 /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
2125 /// the comparison. For example, x == y -> x*c == y*c.
2126 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
2128 if (LU.Kind != LSRUse::ICmpZero) return;
2130 // Determine the integer type for the base formula.
2131 const Type *IntTy = Base.getType();
2133 if (SE.getTypeSizeInBits(IntTy) > 64) return;
2135 // Don't do this if there is more than one offset.
2136 if (LU.MinOffset != LU.MaxOffset) return;
2138 assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
2140 // Check each interesting stride.
2141 for (SmallSetVector<int64_t, 8>::const_iterator
2142 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
2143 int64_t Factor = *I;
2146 // Check that the multiplication doesn't overflow.
2147 if (F.AM.BaseOffs == INT64_MIN && Factor == -1)
2149 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
2150 if (F.AM.BaseOffs / Factor != Base.AM.BaseOffs)
2153 // Check that multiplying with the use offset doesn't overflow.
2154 int64_t Offset = LU.MinOffset;
2155 if (Offset == INT64_MIN && Factor == -1)
2157 Offset = (uint64_t)Offset * Factor;
2158 if (Offset / Factor != LU.MinOffset)
2161 // Check that this scale is legal.
2162 if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI))
2165 // Compensate for the use having MinOffset built into it.
2166 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset;
2168 const SCEV *FactorS = SE.getIntegerSCEV(Factor, IntTy);
2170 // Check that multiplying with each base register doesn't overflow.
2171 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
2172 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
2173 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
2177 // Check that multiplying with the scaled register doesn't overflow.
2179 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
2180 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
2184 // If we make it here and it's legal, add it.
2185 (void)InsertFormula(LU, LUIdx, F);
2190 /// GenerateScales - Generate stride factor reuse formulae by making use of
2191 /// scaled-offset address modes, for example.
2192 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx,
2194 // Determine the integer type for the base formula.
2195 const Type *IntTy = Base.getType();
2198 // If this Formula already has a scaled register, we can't add another one.
2199 if (Base.AM.Scale != 0) return;
2201 // Check each interesting stride.
2202 for (SmallSetVector<int64_t, 8>::const_iterator
2203 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
2204 int64_t Factor = *I;
2206 Base.AM.Scale = Factor;
2207 Base.AM.HasBaseReg = Base.BaseRegs.size() > 1;
2208 // Check whether this scale is going to be legal.
2209 if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
2210 LU.Kind, LU.AccessTy, TLI)) {
2211 // As a special-case, handle special out-of-loop Basic users specially.
2212 // TODO: Reconsider this special case.
2213 if (LU.Kind == LSRUse::Basic &&
2214 isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
2215 LSRUse::Special, LU.AccessTy, TLI) &&
2216 LU.AllFixupsOutsideLoop)
2217 LU.Kind = LSRUse::Special;
2221 // For an ICmpZero, negating a solitary base register won't lead to
2223 if (LU.Kind == LSRUse::ICmpZero &&
2224 !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV)
2226 // For each addrec base reg, apply the scale, if possible.
2227 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
2228 if (const SCEVAddRecExpr *AR =
2229 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
2230 const SCEV *FactorS = SE.getIntegerSCEV(Factor, IntTy);
2231 if (FactorS->isZero())
2233 // Divide out the factor, ignoring high bits, since we'll be
2234 // scaling the value back up in the end.
2235 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
2236 // TODO: This could be optimized to avoid all the copying.
2238 F.ScaledReg = Quotient;
2239 std::swap(F.BaseRegs[i], F.BaseRegs.back());
2240 F.BaseRegs.pop_back();
2241 (void)InsertFormula(LU, LUIdx, F);
2247 /// GenerateTruncates - Generate reuse formulae from different IV types.
2248 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx,
2250 // This requires TargetLowering to tell us which truncates are free.
2253 // Don't bother truncating symbolic values.
2254 if (Base.AM.BaseGV) return;
2256 // Determine the integer type for the base formula.
2257 const Type *DstTy = Base.getType();
2259 DstTy = SE.getEffectiveSCEVType(DstTy);
2261 for (SmallSetVector<const Type *, 4>::const_iterator
2262 I = Types.begin(), E = Types.end(); I != E; ++I) {
2263 const Type *SrcTy = *I;
2264 if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
2267 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
2268 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
2269 JE = F.BaseRegs.end(); J != JE; ++J)
2270 *J = SE.getAnyExtendExpr(*J, SrcTy);
2272 // TODO: This assumes we've done basic processing on all uses and
2273 // have an idea what the register usage is.
2274 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
2277 (void)InsertFormula(LU, LUIdx, F);
2284 /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
2285 /// defer modifications so that the search phase doesn't have to worry about
2286 /// the data structures moving underneath it.
2290 const SCEV *OrigReg;
2292 WorkItem(size_t LI, int64_t I, const SCEV *R)
2293 : LUIdx(LI), Imm(I), OrigReg(R) {}
2295 void print(raw_ostream &OS) const;
2301 void WorkItem::print(raw_ostream &OS) const {
2302 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
2303 << " , add offset " << Imm;
2306 void WorkItem::dump() const {
2307 print(errs()); errs() << '\n';
2310 /// GenerateCrossUseConstantOffsets - Look for registers which are a constant
2311 /// distance apart and try to form reuse opportunities between them.
2312 void LSRInstance::GenerateCrossUseConstantOffsets() {
2313 // Group the registers by their value without any added constant offset.
2314 typedef std::map<int64_t, const SCEV *> ImmMapTy;
2315 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
2317 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
2318 SmallVector<const SCEV *, 8> Sequence;
2319 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
2321 const SCEV *Reg = *I;
2322 int64_t Imm = ExtractImmediate(Reg, SE);
2323 std::pair<RegMapTy::iterator, bool> Pair =
2324 Map.insert(std::make_pair(Reg, ImmMapTy()));
2326 Sequence.push_back(Reg);
2327 Pair.first->second.insert(std::make_pair(Imm, *I));
2328 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
2331 // Now examine each set of registers with the same base value. Build up
2332 // a list of work to do and do the work in a separate step so that we're
2333 // not adding formulae and register counts while we're searching.
2334 SmallVector<WorkItem, 32> WorkItems;
2335 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
2336 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
2337 E = Sequence.end(); I != E; ++I) {
2338 const SCEV *Reg = *I;
2339 const ImmMapTy &Imms = Map.find(Reg)->second;
2341 // It's not worthwhile looking for reuse if there's only one offset.
2342 if (Imms.size() == 1)
2345 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
2346 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
2348 dbgs() << ' ' << J->first;
2351 // Examine each offset.
2352 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
2354 const SCEV *OrigReg = J->second;
2356 int64_t JImm = J->first;
2357 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
2359 if (!isa<SCEVConstant>(OrigReg) &&
2360 UsedByIndicesMap[Reg].count() == 1) {
2361 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
2365 // Conservatively examine offsets between this orig reg a few selected
2367 ImmMapTy::const_iterator OtherImms[] = {
2368 Imms.begin(), prior(Imms.end()),
2369 Imms.upper_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
2371 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
2372 ImmMapTy::const_iterator M = OtherImms[i];
2373 if (M == J || M == JE) continue;
2375 // Compute the difference between the two.
2376 int64_t Imm = (uint64_t)JImm - M->first;
2377 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
2378 LUIdx = UsedByIndices.find_next(LUIdx))
2379 // Make a memo of this use, offset, and register tuple.
2380 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
2381 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
2388 UsedByIndicesMap.clear();
2389 UniqueItems.clear();
2391 // Now iterate through the worklist and add new formulae.
2392 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
2393 E = WorkItems.end(); I != E; ++I) {
2394 const WorkItem &WI = *I;
2395 size_t LUIdx = WI.LUIdx;
2396 LSRUse &LU = Uses[LUIdx];
2397 int64_t Imm = WI.Imm;
2398 const SCEV *OrigReg = WI.OrigReg;
2400 const Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
2401 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
2402 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
2404 // TODO: Use a more targeted data structure.
2405 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
2406 Formula F = LU.Formulae[L];
2407 // Use the immediate in the scaled register.
2408 if (F.ScaledReg == OrigReg) {
2409 int64_t Offs = (uint64_t)F.AM.BaseOffs +
2410 Imm * (uint64_t)F.AM.Scale;
2411 // Don't create 50 + reg(-50).
2412 if (F.referencesReg(SE.getSCEV(
2413 ConstantInt::get(IntTy, -(uint64_t)Offs))))
2416 NewF.AM.BaseOffs = Offs;
2417 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
2418 LU.Kind, LU.AccessTy, TLI))
2420 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
2422 // If the new scale is a constant in a register, and adding the constant
2423 // value to the immediate would produce a value closer to zero than the
2424 // immediate itself, then the formula isn't worthwhile.
2425 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
2426 if (C->getValue()->getValue().isNegative() !=
2427 (NewF.AM.BaseOffs < 0) &&
2428 (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale))
2429 .ule(APInt(BitWidth, NewF.AM.BaseOffs).abs()))
2433 (void)InsertFormula(LU, LUIdx, NewF);
2435 // Use the immediate in a base register.
2436 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
2437 const SCEV *BaseReg = F.BaseRegs[N];
2438 if (BaseReg != OrigReg)
2441 NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
2442 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
2443 LU.Kind, LU.AccessTy, TLI))
2445 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
2447 // If the new formula has a constant in a register, and adding the
2448 // constant value to the immediate would produce a value closer to
2449 // zero than the immediate itself, then the formula isn't worthwhile.
2450 for (SmallVectorImpl<const SCEV *>::const_iterator
2451 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
2453 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
2454 if (C->getValue()->getValue().isNegative() !=
2455 (NewF.AM.BaseOffs < 0) &&
2456 C->getValue()->getValue().abs()
2457 .ule(APInt(BitWidth, NewF.AM.BaseOffs).abs()))
2461 (void)InsertFormula(LU, LUIdx, NewF);
2470 /// GenerateAllReuseFormulae - Generate formulae for each use.
2472 LSRInstance::GenerateAllReuseFormulae() {
2473 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
2474 // queries are more precise.
2475 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2476 LSRUse &LU = Uses[LUIdx];
2477 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2478 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
2479 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2480 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
2482 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2483 LSRUse &LU = Uses[LUIdx];
2484 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2485 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
2486 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2487 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
2488 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2489 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
2490 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2491 GenerateScales(LU, LUIdx, LU.Formulae[i]);
2493 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2494 LSRUse &LU = Uses[LUIdx];
2495 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
2496 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
2499 GenerateCrossUseConstantOffsets();
2502 /// If their are multiple formulae with the same set of registers used
2503 /// by other uses, pick the best one and delete the others.
2504 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
2506 bool Changed = false;
2509 // Collect the best formula for each unique set of shared registers. This
2510 // is reset for each use.
2511 typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo>
2513 BestFormulaeTy BestFormulae;
2515 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2516 LSRUse &LU = Uses[LUIdx];
2517 FormulaSorter Sorter(L, LU, SE, DT);
2519 // Clear out the set of used regs; it will be recomputed.
2522 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
2523 FIdx != NumForms; ++FIdx) {
2524 Formula &F = LU.Formulae[FIdx];
2526 SmallVector<const SCEV *, 2> Key;
2527 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
2528 JE = F.BaseRegs.end(); J != JE; ++J) {
2529 const SCEV *Reg = *J;
2530 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
2534 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
2535 Key.push_back(F.ScaledReg);
2536 // Unstable sort by host order ok, because this is only used for
2538 std::sort(Key.begin(), Key.end());
2540 std::pair<BestFormulaeTy::const_iterator, bool> P =
2541 BestFormulae.insert(std::make_pair(Key, FIdx));
2543 Formula &Best = LU.Formulae[P.first->second];
2544 if (Sorter.operator()(F, Best))
2546 DEBUG(dbgs() << "Filtering out "; F.print(dbgs());
2548 " in favor of "; Best.print(dbgs());
2553 std::swap(F, LU.Formulae.back());
2554 LU.Formulae.pop_back();
2559 if (F.ScaledReg) LU.Regs.insert(F.ScaledReg);
2560 LU.Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
2562 BestFormulae.clear();
2565 DEBUG(if (Changed) {
2567 "After filtering out undesirable candidates:\n";
2572 /// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
2573 /// formulae to choose from, use some rough heuristics to prune down the number
2574 /// of formulae. This keeps the main solver from taking an extraordinary amount
2575 /// of time in some worst-case scenarios.
2576 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
2577 // This is a rough guess that seems to work fairly well.
2578 const size_t Limit = UINT16_MAX;
2580 SmallPtrSet<const SCEV *, 4> Taken;
2582 // Estimate the worst-case number of solutions we might consider. We almost
2583 // never consider this many solutions because we prune the search space,
2584 // but the pruning isn't always sufficient.
2586 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
2587 E = Uses.end(); I != E; ++I) {
2588 size_t FSize = I->Formulae.size();
2589 if (FSize >= Limit) {
2600 // Ok, we have too many of formulae on our hands to conveniently handle.
2601 // Use a rough heuristic to thin out the list.
2603 // Pick the register which is used by the most LSRUses, which is likely
2604 // to be a good reuse register candidate.
2605 const SCEV *Best = 0;
2606 unsigned BestNum = 0;
2607 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
2609 const SCEV *Reg = *I;
2610 if (Taken.count(Reg))
2615 unsigned Count = RegUses.getUsedByIndices(Reg).count();
2616 if (Count > BestNum) {
2623 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
2624 << " will yield profitable reuse.\n");
2627 // In any use with formulae which references this register, delete formulae
2628 // which don't reference it.
2629 for (SmallVectorImpl<LSRUse>::iterator I = Uses.begin(),
2630 E = Uses.end(); I != E; ++I) {
2632 if (!LU.Regs.count(Best)) continue;
2634 // Clear out the set of used regs; it will be recomputed.
2637 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
2638 Formula &F = LU.Formulae[i];
2639 if (!F.referencesReg(Best)) {
2640 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
2641 std::swap(LU.Formulae.back(), F);
2642 LU.Formulae.pop_back();
2648 if (F.ScaledReg) LU.Regs.insert(F.ScaledReg);
2649 LU.Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
2653 DEBUG(dbgs() << "After pre-selection:\n";
2654 print_uses(dbgs()));
2658 /// SolveRecurse - This is the recursive solver.
2659 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
2661 SmallVectorImpl<const Formula *> &Workspace,
2662 const Cost &CurCost,
2663 const SmallPtrSet<const SCEV *, 16> &CurRegs,
2664 DenseSet<const SCEV *> &VisitedRegs) const {
2667 // - use more aggressive filtering
2668 // - sort the formula so that the most profitable solutions are found first
2669 // - sort the uses too
2671 // - don't compute a cost, and then compare. compare while computing a cost
2673 // - track register sets with SmallBitVector
2675 const LSRUse &LU = Uses[Workspace.size()];
2677 // If this use references any register that's already a part of the
2678 // in-progress solution, consider it a requirement that a formula must
2679 // reference that register in order to be considered. This prunes out
2680 // unprofitable searching.
2681 SmallSetVector<const SCEV *, 4> ReqRegs;
2682 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
2683 E = CurRegs.end(); I != E; ++I)
2684 if (LU.Regs.count(*I))
2687 bool AnySatisfiedReqRegs = false;
2688 SmallPtrSet<const SCEV *, 16> NewRegs;
2691 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
2692 E = LU.Formulae.end(); I != E; ++I) {
2693 const Formula &F = *I;
2695 // Ignore formulae which do not use any of the required registers.
2696 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
2697 JE = ReqRegs.end(); J != JE; ++J) {
2698 const SCEV *Reg = *J;
2699 if ((!F.ScaledReg || F.ScaledReg != Reg) &&
2700 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) ==
2704 AnySatisfiedReqRegs = true;
2706 // Evaluate the cost of the current formula. If it's already worse than
2707 // the current best, prune the search at that point.
2710 NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT);
2711 if (NewCost < SolutionCost) {
2712 Workspace.push_back(&F);
2713 if (Workspace.size() != Uses.size()) {
2714 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
2715 NewRegs, VisitedRegs);
2716 if (F.getNumRegs() == 1 && Workspace.size() == 1)
2717 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
2719 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
2720 dbgs() << ". Regs:";
2721 for (SmallPtrSet<const SCEV *, 16>::const_iterator
2722 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
2723 dbgs() << ' ' << **I;
2726 SolutionCost = NewCost;
2727 Solution = Workspace;
2729 Workspace.pop_back();
2734 // If none of the formulae had all of the required registers, relax the
2735 // constraint so that we don't exclude all formulae.
2736 if (!AnySatisfiedReqRegs) {
2742 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
2743 SmallVector<const Formula *, 8> Workspace;
2745 SolutionCost.Loose();
2747 SmallPtrSet<const SCEV *, 16> CurRegs;
2748 DenseSet<const SCEV *> VisitedRegs;
2749 Workspace.reserve(Uses.size());
2751 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
2752 CurRegs, VisitedRegs);
2754 // Ok, we've now made all our decisions.
2755 DEBUG(dbgs() << "\n"
2756 "The chosen solution requires "; SolutionCost.print(dbgs());
2758 for (size_t i = 0, e = Uses.size(); i != e; ++i) {
2760 Uses[i].print(dbgs());
2763 Solution[i]->print(dbgs());
2768 /// getImmediateDominator - A handy utility for the specific DominatorTree
2769 /// query that we need here.
2771 static BasicBlock *getImmediateDominator(BasicBlock *BB, DominatorTree &DT) {
2772 DomTreeNode *Node = DT.getNode(BB);
2773 if (!Node) return 0;
2774 Node = Node->getIDom();
2775 if (!Node) return 0;
2776 return Node->getBlock();
2779 Value *LSRInstance::Expand(const LSRFixup &LF,
2781 BasicBlock::iterator IP,
2782 SCEVExpander &Rewriter,
2783 SmallVectorImpl<WeakVH> &DeadInsts) const {
2784 const LSRUse &LU = Uses[LF.LUIdx];
2786 // Then, collect some instructions which we will remain dominated by when
2787 // expanding the replacement. These must be dominated by any operands that
2788 // will be required in the expansion.
2789 SmallVector<Instruction *, 4> Inputs;
2790 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
2791 Inputs.push_back(I);
2792 if (LU.Kind == LSRUse::ICmpZero)
2793 if (Instruction *I =
2794 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
2795 Inputs.push_back(I);
2796 if (LF.PostIncLoop) {
2797 if (!L->contains(LF.UserInst))
2798 Inputs.push_back(L->getLoopLatch()->getTerminator());
2800 Inputs.push_back(IVIncInsertPos);
2803 // Then, climb up the immediate dominator tree as far as we can go while
2804 // still being dominated by the input positions.
2806 bool AllDominate = true;
2807 Instruction *BetterPos = 0;
2808 BasicBlock *IDom = getImmediateDominator(IP->getParent(), DT);
2810 Instruction *Tentative = IDom->getTerminator();
2811 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
2812 E = Inputs.end(); I != E; ++I) {
2813 Instruction *Inst = *I;
2814 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
2815 AllDominate = false;
2818 if (IDom == Inst->getParent() &&
2819 (!BetterPos || DT.dominates(BetterPos, Inst)))
2820 BetterPos = next(BasicBlock::iterator(Inst));
2829 while (isa<PHINode>(IP)) ++IP;
2831 // Inform the Rewriter if we have a post-increment use, so that it can
2832 // perform an advantageous expansion.
2833 Rewriter.setPostInc(LF.PostIncLoop);
2835 // This is the type that the user actually needs.
2836 const Type *OpTy = LF.OperandValToReplace->getType();
2837 // This will be the type that we'll initially expand to.
2838 const Type *Ty = F.getType();
2840 // No type known; just expand directly to the ultimate type.
2842 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
2843 // Expand directly to the ultimate type if it's the right size.
2845 // This is the type to do integer arithmetic in.
2846 const Type *IntTy = SE.getEffectiveSCEVType(Ty);
2848 // Build up a list of operands to add together to form the full base.
2849 SmallVector<const SCEV *, 8> Ops;
2851 // Expand the BaseRegs portion.
2852 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
2853 E = F.BaseRegs.end(); I != E; ++I) {
2854 const SCEV *Reg = *I;
2855 assert(!Reg->isZero() && "Zero allocated in a base register!");
2857 // If we're expanding for a post-inc user for the add-rec's loop, make the
2858 // post-inc adjustment.
2859 const SCEV *Start = Reg;
2860 while (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Start)) {
2861 if (AR->getLoop() == LF.PostIncLoop) {
2862 Reg = SE.getAddExpr(Reg, AR->getStepRecurrence(SE));
2863 // If the user is inside the loop, insert the code after the increment
2864 // so that it is dominated by its operand. If the original insert point
2865 // was already dominated by the increment, keep it, because there may
2866 // be loop-variant operands that need to be respected also.
2867 if (L->contains(LF.UserInst) && !DT.dominates(IVIncInsertPos, IP))
2868 IP = IVIncInsertPos;
2871 Start = AR->getStart();
2874 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
2877 // Expand the ScaledReg portion.
2878 Value *ICmpScaledV = 0;
2879 if (F.AM.Scale != 0) {
2880 const SCEV *ScaledS = F.ScaledReg;
2882 // If we're expanding for a post-inc user for the add-rec's loop, make the
2883 // post-inc adjustment.
2884 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(ScaledS))
2885 if (AR->getLoop() == LF.PostIncLoop)
2886 ScaledS = SE.getAddExpr(ScaledS, AR->getStepRecurrence(SE));
2888 if (LU.Kind == LSRUse::ICmpZero) {
2889 // An interesting way of "folding" with an icmp is to use a negated
2890 // scale, which we'll implement by inserting it into the other operand
2892 assert(F.AM.Scale == -1 &&
2893 "The only scale supported by ICmpZero uses is -1!");
2894 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
2896 // Otherwise just expand the scaled register and an explicit scale,
2897 // which is expected to be matched as part of the address.
2898 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
2899 ScaledS = SE.getMulExpr(ScaledS,
2900 SE.getIntegerSCEV(F.AM.Scale,
2901 ScaledS->getType()));
2902 Ops.push_back(ScaledS);
2906 // Expand the immediate portions.
2908 Ops.push_back(SE.getSCEV(F.AM.BaseGV));
2909 int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset;
2911 if (LU.Kind == LSRUse::ICmpZero) {
2912 // The other interesting way of "folding" with an ICmpZero is to use a
2913 // negated immediate.
2915 ICmpScaledV = ConstantInt::get(IntTy, -Offset);
2917 Ops.push_back(SE.getUnknown(ICmpScaledV));
2918 ICmpScaledV = ConstantInt::get(IntTy, Offset);
2921 // Just add the immediate values. These again are expected to be matched
2922 // as part of the address.
2923 Ops.push_back(SE.getIntegerSCEV(Offset, IntTy));
2927 // Emit instructions summing all the operands.
2928 const SCEV *FullS = Ops.empty() ?
2929 SE.getIntegerSCEV(0, IntTy) :
2931 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
2933 // We're done expanding now, so reset the rewriter.
2934 Rewriter.setPostInc(0);
2936 // An ICmpZero Formula represents an ICmp which we're handling as a
2937 // comparison against zero. Now that we've expanded an expression for that
2938 // form, update the ICmp's other operand.
2939 if (LU.Kind == LSRUse::ICmpZero) {
2940 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
2941 DeadInsts.push_back(CI->getOperand(1));
2942 assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
2943 "a scale at the same time!");
2944 if (F.AM.Scale == -1) {
2945 if (ICmpScaledV->getType() != OpTy) {
2947 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
2949 ICmpScaledV, OpTy, "tmp", CI);
2952 CI->setOperand(1, ICmpScaledV);
2954 assert(F.AM.Scale == 0 &&
2955 "ICmp does not support folding a global value and "
2956 "a scale at the same time!");
2957 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
2959 if (C->getType() != OpTy)
2960 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
2964 CI->setOperand(1, C);
2971 /// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
2972 /// of their operands effectively happens in their predecessor blocks, so the
2973 /// expression may need to be expanded in multiple places.
2974 void LSRInstance::RewriteForPHI(PHINode *PN,
2977 SCEVExpander &Rewriter,
2978 SmallVectorImpl<WeakVH> &DeadInsts,
2980 DenseMap<BasicBlock *, Value *> Inserted;
2981 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
2982 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
2983 BasicBlock *BB = PN->getIncomingBlock(i);
2985 // If this is a critical edge, split the edge so that we do not insert
2986 // the code on all predecessor/successor paths. We do this unless this
2987 // is the canonical backedge for this loop, which complicates post-inc
2989 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
2990 !isa<IndirectBrInst>(BB->getTerminator()) &&
2991 (PN->getParent() != L->getHeader() || !L->contains(BB))) {
2992 // Split the critical edge.
2993 BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P);
2995 // If PN is outside of the loop and BB is in the loop, we want to
2996 // move the block to be immediately before the PHI block, not
2997 // immediately after BB.
2998 if (L->contains(BB) && !L->contains(PN))
2999 NewBB->moveBefore(PN->getParent());
3001 // Splitting the edge can reduce the number of PHI entries we have.
3002 e = PN->getNumIncomingValues();
3004 i = PN->getBasicBlockIndex(BB);
3007 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
3008 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
3010 PN->setIncomingValue(i, Pair.first->second);
3012 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
3014 // If this is reuse-by-noop-cast, insert the noop cast.
3015 const Type *OpTy = LF.OperandValToReplace->getType();
3016 if (FullV->getType() != OpTy)
3018 CastInst::Create(CastInst::getCastOpcode(FullV, false,
3020 FullV, LF.OperandValToReplace->getType(),
3021 "tmp", BB->getTerminator());
3023 PN->setIncomingValue(i, FullV);
3024 Pair.first->second = FullV;
3029 /// Rewrite - Emit instructions for the leading candidate expression for this
3030 /// LSRUse (this is called "expanding"), and update the UserInst to reference
3031 /// the newly expanded value.
3032 void LSRInstance::Rewrite(const LSRFixup &LF,
3034 SCEVExpander &Rewriter,
3035 SmallVectorImpl<WeakVH> &DeadInsts,
3037 // First, find an insertion point that dominates UserInst. For PHI nodes,
3038 // find the nearest block which dominates all the relevant uses.
3039 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
3040 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
3042 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
3044 // If this is reuse-by-noop-cast, insert the noop cast.
3045 const Type *OpTy = LF.OperandValToReplace->getType();
3046 if (FullV->getType() != OpTy) {
3048 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
3049 FullV, OpTy, "tmp", LF.UserInst);
3053 // Update the user. ICmpZero is handled specially here (for now) because
3054 // Expand may have updated one of the operands of the icmp already, and
3055 // its new value may happen to be equal to LF.OperandValToReplace, in
3056 // which case doing replaceUsesOfWith leads to replacing both operands
3057 // with the same value. TODO: Reorganize this.
3058 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
3059 LF.UserInst->setOperand(0, FullV);
3061 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
3064 DeadInsts.push_back(LF.OperandValToReplace);
3068 LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
3070 // Keep track of instructions we may have made dead, so that
3071 // we can remove them after we are done working.
3072 SmallVector<WeakVH, 16> DeadInsts;
3074 SCEVExpander Rewriter(SE);
3075 Rewriter.disableCanonicalMode();
3076 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
3078 // Expand the new value definitions and update the users.
3079 for (size_t i = 0, e = Fixups.size(); i != e; ++i) {
3080 size_t LUIdx = Fixups[i].LUIdx;
3082 Rewrite(Fixups[i], *Solution[LUIdx], Rewriter, DeadInsts, P);
3087 // Clean up after ourselves. This must be done before deleting any
3091 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
3094 LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
3095 : IU(P->getAnalysis<IVUsers>()),
3096 SE(P->getAnalysis<ScalarEvolution>()),
3097 DT(P->getAnalysis<DominatorTree>()),
3098 TLI(tli), L(l), Changed(false), IVIncInsertPos(0) {
3100 // If LoopSimplify form is not available, stay out of trouble.
3101 if (!L->isLoopSimplifyForm()) return;
3103 // If there's no interesting work to be done, bail early.
3104 if (IU.empty()) return;
3106 DEBUG(dbgs() << "\nLSR on loop ";
3107 WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
3110 /// OptimizeShadowIV - If IV is used in a int-to-float cast
3111 /// inside the loop then try to eliminate the cast operation.
3114 // Change loop terminating condition to use the postinc iv when possible.
3115 Changed |= OptimizeLoopTermCond();
3117 CollectInterestingTypesAndFactors();
3118 CollectFixupsAndInitialFormulae();
3119 CollectLoopInvariantFixupsAndFormulae();
3121 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
3122 print_uses(dbgs()));
3124 // Now use the reuse data to generate a bunch of interesting ways
3125 // to formulate the values needed for the uses.
3126 GenerateAllReuseFormulae();
3128 DEBUG(dbgs() << "\n"
3129 "After generating reuse formulae:\n";
3130 print_uses(dbgs()));
3132 FilterOutUndesirableDedicatedRegisters();
3133 NarrowSearchSpaceUsingHeuristics();
3135 SmallVector<const Formula *, 8> Solution;
3137 assert(Solution.size() == Uses.size() && "Malformed solution!");
3139 // Release memory that is no longer needed.
3145 // Formulae should be legal.
3146 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3147 E = Uses.end(); I != E; ++I) {
3148 const LSRUse &LU = *I;
3149 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
3150 JE = LU.Formulae.end(); J != JE; ++J)
3151 assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset,
3152 LU.Kind, LU.AccessTy, TLI) &&
3153 "Illegal formula generated!");
3157 // Now that we've decided what we want, make it so.
3158 ImplementSolution(Solution, P);
3161 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
3162 if (Factors.empty() && Types.empty()) return;
3164 OS << "LSR has identified the following interesting factors and types: ";
3167 for (SmallSetVector<int64_t, 8>::const_iterator
3168 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3169 if (!First) OS << ", ";
3174 for (SmallSetVector<const Type *, 4>::const_iterator
3175 I = Types.begin(), E = Types.end(); I != E; ++I) {
3176 if (!First) OS << ", ";
3178 OS << '(' << **I << ')';
3183 void LSRInstance::print_fixups(raw_ostream &OS) const {
3184 OS << "LSR is examining the following fixup sites:\n";
3185 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
3186 E = Fixups.end(); I != E; ++I) {
3187 const LSRFixup &LF = *I;
3194 void LSRInstance::print_uses(raw_ostream &OS) const {
3195 OS << "LSR is examining the following uses:\n";
3196 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3197 E = Uses.end(); I != E; ++I) {
3198 const LSRUse &LU = *I;
3202 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
3203 JE = LU.Formulae.end(); J != JE; ++J) {
3211 void LSRInstance::print(raw_ostream &OS) const {
3212 print_factors_and_types(OS);
3217 void LSRInstance::dump() const {
3218 print(errs()); errs() << '\n';
3223 class LoopStrengthReduce : public LoopPass {
3224 /// TLI - Keep a pointer of a TargetLowering to consult for determining
3225 /// transformation profitability.
3226 const TargetLowering *const TLI;
3229 static char ID; // Pass ID, replacement for typeid
3230 explicit LoopStrengthReduce(const TargetLowering *tli = 0);
3233 bool runOnLoop(Loop *L, LPPassManager &LPM);
3234 void getAnalysisUsage(AnalysisUsage &AU) const;
3239 char LoopStrengthReduce::ID = 0;
3240 static RegisterPass<LoopStrengthReduce>
3241 X("loop-reduce", "Loop Strength Reduction");
3243 Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
3244 return new LoopStrengthReduce(TLI);
3247 LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
3248 : LoopPass(&ID), TLI(tli) {}
3250 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
3251 // We split critical edges, so we change the CFG. However, we do update
3252 // many analyses if they are around.
3253 AU.addPreservedID(LoopSimplifyID);
3254 AU.addPreserved<LoopInfo>();
3255 AU.addPreserved("domfrontier");
3257 AU.addRequiredID(LoopSimplifyID);
3258 AU.addRequired<DominatorTree>();
3259 AU.addPreserved<DominatorTree>();
3260 AU.addRequired<ScalarEvolution>();
3261 AU.addPreserved<ScalarEvolution>();
3262 AU.addRequired<IVUsers>();
3263 AU.addPreserved<IVUsers>();
3266 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
3267 bool Changed = false;
3269 // Run the main LSR transformation.
3270 Changed |= LSRInstance(TLI, L, this).getChanged();
3272 // At this point, it is worth checking to see if any recurrence PHIs are also
3273 // dead, so that we can remove them as well.
3274 Changed |= DeleteDeadPHIs(L->getHeader());