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/Assembly/Writer.h"
67 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
68 #include "llvm/Transforms/Utils/Local.h"
69 #include "llvm/ADT/SmallBitVector.h"
70 #include "llvm/ADT/SetVector.h"
71 #include "llvm/ADT/DenseSet.h"
72 #include "llvm/Support/Debug.h"
73 #include "llvm/Support/CommandLine.h"
74 #include "llvm/Support/ValueHandle.h"
75 #include "llvm/Support/raw_ostream.h"
76 #include "llvm/Target/TargetLowering.h"
80 /// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for
81 /// bail out. This threshold is far beyond the number of users that LSR can
82 /// conceivably solve, so it should not affect generated code, but catches the
83 /// worst cases before LSR burns too much compile time and stack space.
84 static const unsigned MaxIVUsers = 200;
86 // Temporary flag to cleanup congruent phis after LSR phi expansion.
87 // It's currently disabled until we can determine whether it's truly useful or
88 // not. The flag should be removed after the v3.0 release.
89 // This is now needed for ivchains.
90 static cl::opt<bool> EnablePhiElim(
91 "enable-lsr-phielim", cl::Hidden, cl::init(true),
92 cl::desc("Enable LSR phi elimination"));
95 // Stress test IV chain generation.
96 static cl::opt<bool> StressIVChain(
97 "stress-ivchain", cl::Hidden, cl::init(false),
98 cl::desc("Stress test LSR IV chains"));
100 static bool StressIVChain = false;
105 /// RegSortData - This class holds data which is used to order reuse candidates.
108 /// UsedByIndices - This represents the set of LSRUse indices which reference
109 /// a particular register.
110 SmallBitVector UsedByIndices;
114 void print(raw_ostream &OS) const;
120 void RegSortData::print(raw_ostream &OS) const {
121 OS << "[NumUses=" << UsedByIndices.count() << ']';
124 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
125 void RegSortData::dump() const {
126 print(errs()); errs() << '\n';
132 /// RegUseTracker - Map register candidates to information about how they are
134 class RegUseTracker {
135 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
137 RegUsesTy RegUsesMap;
138 SmallVector<const SCEV *, 16> RegSequence;
141 void CountRegister(const SCEV *Reg, size_t LUIdx);
142 void DropRegister(const SCEV *Reg, size_t LUIdx);
143 void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx);
145 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
147 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
151 typedef SmallVectorImpl<const SCEV *>::iterator iterator;
152 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
153 iterator begin() { return RegSequence.begin(); }
154 iterator end() { return RegSequence.end(); }
155 const_iterator begin() const { return RegSequence.begin(); }
156 const_iterator end() const { return RegSequence.end(); }
162 RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
163 std::pair<RegUsesTy::iterator, bool> Pair =
164 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
165 RegSortData &RSD = Pair.first->second;
167 RegSequence.push_back(Reg);
168 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
169 RSD.UsedByIndices.set(LUIdx);
173 RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) {
174 RegUsesTy::iterator It = RegUsesMap.find(Reg);
175 assert(It != RegUsesMap.end());
176 RegSortData &RSD = It->second;
177 assert(RSD.UsedByIndices.size() > LUIdx);
178 RSD.UsedByIndices.reset(LUIdx);
182 RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
183 assert(LUIdx <= LastLUIdx);
185 // Update RegUses. The data structure is not optimized for this purpose;
186 // we must iterate through it and update each of the bit vectors.
187 for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end();
189 SmallBitVector &UsedByIndices = I->second.UsedByIndices;
190 if (LUIdx < UsedByIndices.size())
191 UsedByIndices[LUIdx] =
192 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0;
193 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
198 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
199 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
200 if (I == RegUsesMap.end())
202 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
203 int i = UsedByIndices.find_first();
204 if (i == -1) return false;
205 if ((size_t)i != LUIdx) return true;
206 return UsedByIndices.find_next(i) != -1;
209 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
210 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
211 assert(I != RegUsesMap.end() && "Unknown register!");
212 return I->second.UsedByIndices;
215 void RegUseTracker::clear() {
222 /// Formula - This class holds information that describes a formula for
223 /// computing satisfying a use. It may include broken-out immediates and scaled
226 /// AM - This is used to represent complex addressing, as well as other kinds
227 /// of interesting uses.
228 TargetLowering::AddrMode AM;
230 /// BaseRegs - The list of "base" registers for this use. When this is
231 /// non-empty, AM.HasBaseReg should be set to true.
232 SmallVector<const SCEV *, 2> BaseRegs;
234 /// ScaledReg - The 'scaled' register for this use. This should be non-null
235 /// when AM.Scale is not zero.
236 const SCEV *ScaledReg;
238 /// UnfoldedOffset - An additional constant offset which added near the
239 /// use. This requires a temporary register, but the offset itself can
240 /// live in an add immediate field rather than a register.
241 int64_t UnfoldedOffset;
243 Formula() : ScaledReg(0), UnfoldedOffset(0) {}
245 void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
247 unsigned getNumRegs() const;
248 Type *getType() const;
250 void DeleteBaseReg(const SCEV *&S);
252 bool referencesReg(const SCEV *S) const;
253 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
254 const RegUseTracker &RegUses) const;
256 void print(raw_ostream &OS) const;
262 /// DoInitialMatch - Recursion helper for InitialMatch.
263 static void DoInitialMatch(const SCEV *S, Loop *L,
264 SmallVectorImpl<const SCEV *> &Good,
265 SmallVectorImpl<const SCEV *> &Bad,
266 ScalarEvolution &SE) {
267 // Collect expressions which properly dominate the loop header.
268 if (SE.properlyDominates(S, L->getHeader())) {
273 // Look at add operands.
274 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
275 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
277 DoInitialMatch(*I, L, Good, Bad, SE);
281 // Look at addrec operands.
282 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
283 if (!AR->getStart()->isZero()) {
284 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
285 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
286 AR->getStepRecurrence(SE),
287 // FIXME: AR->getNoWrapFlags()
288 AR->getLoop(), SCEV::FlagAnyWrap),
293 // Handle a multiplication by -1 (negation) if it didn't fold.
294 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
295 if (Mul->getOperand(0)->isAllOnesValue()) {
296 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
297 const SCEV *NewMul = SE.getMulExpr(Ops);
299 SmallVector<const SCEV *, 4> MyGood;
300 SmallVector<const SCEV *, 4> MyBad;
301 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
302 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
303 SE.getEffectiveSCEVType(NewMul->getType())));
304 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
305 E = MyGood.end(); I != E; ++I)
306 Good.push_back(SE.getMulExpr(NegOne, *I));
307 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
308 E = MyBad.end(); I != E; ++I)
309 Bad.push_back(SE.getMulExpr(NegOne, *I));
313 // Ok, we can't do anything interesting. Just stuff the whole thing into a
314 // register and hope for the best.
318 /// InitialMatch - Incorporate loop-variant parts of S into this Formula,
319 /// attempting to keep all loop-invariant and loop-computable values in a
320 /// single base register.
321 void Formula::InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
322 SmallVector<const SCEV *, 4> Good;
323 SmallVector<const SCEV *, 4> Bad;
324 DoInitialMatch(S, L, Good, Bad, SE);
326 const SCEV *Sum = SE.getAddExpr(Good);
328 BaseRegs.push_back(Sum);
329 AM.HasBaseReg = true;
332 const SCEV *Sum = SE.getAddExpr(Bad);
334 BaseRegs.push_back(Sum);
335 AM.HasBaseReg = true;
339 /// getNumRegs - Return the total number of register operands used by this
340 /// formula. This does not include register uses implied by non-constant
342 unsigned Formula::getNumRegs() const {
343 return !!ScaledReg + BaseRegs.size();
346 /// getType - Return the type of this formula, if it has one, or null
347 /// otherwise. This type is meaningless except for the bit size.
348 Type *Formula::getType() const {
349 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
350 ScaledReg ? ScaledReg->getType() :
351 AM.BaseGV ? AM.BaseGV->getType() :
355 /// DeleteBaseReg - Delete the given base reg from the BaseRegs list.
356 void Formula::DeleteBaseReg(const SCEV *&S) {
357 if (&S != &BaseRegs.back())
358 std::swap(S, BaseRegs.back());
362 /// referencesReg - Test if this formula references the given register.
363 bool Formula::referencesReg(const SCEV *S) const {
364 return S == ScaledReg ||
365 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
368 /// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
369 /// which are used by uses other than the use with the given index.
370 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
371 const RegUseTracker &RegUses) const {
373 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
375 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
376 E = BaseRegs.end(); I != E; ++I)
377 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
382 void Formula::print(raw_ostream &OS) const {
385 if (!First) OS << " + "; else First = false;
386 WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false);
388 if (AM.BaseOffs != 0) {
389 if (!First) OS << " + "; else First = false;
392 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
393 E = BaseRegs.end(); I != E; ++I) {
394 if (!First) OS << " + "; else First = false;
395 OS << "reg(" << **I << ')';
397 if (AM.HasBaseReg && BaseRegs.empty()) {
398 if (!First) OS << " + "; else First = false;
399 OS << "**error: HasBaseReg**";
400 } else if (!AM.HasBaseReg && !BaseRegs.empty()) {
401 if (!First) OS << " + "; else First = false;
402 OS << "**error: !HasBaseReg**";
405 if (!First) OS << " + "; else First = false;
406 OS << AM.Scale << "*reg(";
413 if (UnfoldedOffset != 0) {
414 if (!First) OS << " + "; else First = false;
415 OS << "imm(" << UnfoldedOffset << ')';
419 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
420 void Formula::dump() const {
421 print(errs()); errs() << '\n';
425 /// isAddRecSExtable - Return true if the given addrec can be sign-extended
426 /// without changing its value.
427 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
429 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
430 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
433 /// isAddSExtable - Return true if the given add can be sign-extended
434 /// without changing its value.
435 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
437 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
438 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
441 /// isMulSExtable - Return true if the given mul can be sign-extended
442 /// without changing its value.
443 static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
445 IntegerType::get(SE.getContext(),
446 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
447 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
450 /// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
451 /// and if the remainder is known to be zero, or null otherwise. If
452 /// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
453 /// to Y, ignoring that the multiplication may overflow, which is useful when
454 /// the result will be used in a context where the most significant bits are
456 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
458 bool IgnoreSignificantBits = false) {
459 // Handle the trivial case, which works for any SCEV type.
461 return SE.getConstant(LHS->getType(), 1);
463 // Handle a few RHS special cases.
464 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
466 const APInt &RA = RC->getValue()->getValue();
467 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
469 if (RA.isAllOnesValue())
470 return SE.getMulExpr(LHS, RC);
471 // Handle x /s 1 as x.
476 // Check for a division of a constant by a constant.
477 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
480 const APInt &LA = C->getValue()->getValue();
481 const APInt &RA = RC->getValue()->getValue();
482 if (LA.srem(RA) != 0)
484 return SE.getConstant(LA.sdiv(RA));
487 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
488 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
489 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
490 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
491 IgnoreSignificantBits);
493 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
494 IgnoreSignificantBits);
495 if (!Start) return 0;
496 // FlagNW is independent of the start value, step direction, and is
497 // preserved with smaller magnitude steps.
498 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
499 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
504 // Distribute the sdiv over add operands, if the add doesn't overflow.
505 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
506 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
507 SmallVector<const SCEV *, 8> Ops;
508 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
510 const SCEV *Op = getExactSDiv(*I, RHS, SE,
511 IgnoreSignificantBits);
515 return SE.getAddExpr(Ops);
520 // Check for a multiply operand that we can pull RHS out of.
521 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
522 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
523 SmallVector<const SCEV *, 4> Ops;
525 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
529 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
530 IgnoreSignificantBits)) {
536 return Found ? SE.getMulExpr(Ops) : 0;
541 // Otherwise we don't know.
545 /// ExtractImmediate - If S involves the addition of a constant integer value,
546 /// return that integer value, and mutate S to point to a new SCEV with that
548 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
549 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
550 if (C->getValue()->getValue().getMinSignedBits() <= 64) {
551 S = SE.getConstant(C->getType(), 0);
552 return C->getValue()->getSExtValue();
554 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
555 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
556 int64_t Result = ExtractImmediate(NewOps.front(), SE);
558 S = SE.getAddExpr(NewOps);
560 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
561 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
562 int64_t Result = ExtractImmediate(NewOps.front(), SE);
564 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
565 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
572 /// ExtractSymbol - If S involves the addition of a GlobalValue address,
573 /// return that symbol, and mutate S to point to a new SCEV with that
575 static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
576 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
577 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
578 S = SE.getConstant(GV->getType(), 0);
581 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
582 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
583 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
585 S = SE.getAddExpr(NewOps);
587 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
588 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
589 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
591 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
592 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
599 /// isAddressUse - Returns true if the specified instruction is using the
600 /// specified value as an address.
601 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
602 bool isAddress = isa<LoadInst>(Inst);
603 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
604 if (SI->getOperand(1) == OperandVal)
606 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
607 // Addressing modes can also be folded into prefetches and a variety
609 switch (II->getIntrinsicID()) {
611 case Intrinsic::prefetch:
612 case Intrinsic::x86_sse_storeu_ps:
613 case Intrinsic::x86_sse2_storeu_pd:
614 case Intrinsic::x86_sse2_storeu_dq:
615 case Intrinsic::x86_sse2_storel_dq:
616 if (II->getArgOperand(0) == OperandVal)
624 /// getAccessType - Return the type of the memory being accessed.
625 static Type *getAccessType(const Instruction *Inst) {
626 Type *AccessTy = Inst->getType();
627 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
628 AccessTy = SI->getOperand(0)->getType();
629 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
630 // Addressing modes can also be folded into prefetches and a variety
632 switch (II->getIntrinsicID()) {
634 case Intrinsic::x86_sse_storeu_ps:
635 case Intrinsic::x86_sse2_storeu_pd:
636 case Intrinsic::x86_sse2_storeu_dq:
637 case Intrinsic::x86_sse2_storel_dq:
638 AccessTy = II->getArgOperand(0)->getType();
643 // All pointers have the same requirements, so canonicalize them to an
644 // arbitrary pointer type to minimize variation.
645 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy))
646 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
647 PTy->getAddressSpace());
652 /// isExistingPhi - Return true if this AddRec is already a phi in its loop.
653 static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
654 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
655 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
656 if (SE.isSCEVable(PN->getType()) &&
657 (SE.getEffectiveSCEVType(PN->getType()) ==
658 SE.getEffectiveSCEVType(AR->getType())) &&
659 SE.getSCEV(PN) == AR)
665 /// Check if expanding this expression is likely to incur significant cost. This
666 /// is tricky because SCEV doesn't track which expressions are actually computed
667 /// by the current IR.
669 /// We currently allow expansion of IV increments that involve adds,
670 /// multiplication by constants, and AddRecs from existing phis.
672 /// TODO: Allow UDivExpr if we can find an existing IV increment that is an
673 /// obvious multiple of the UDivExpr.
674 static bool isHighCostExpansion(const SCEV *S,
675 SmallPtrSet<const SCEV*, 8> &Processed,
676 ScalarEvolution &SE) {
677 // Zero/One operand expressions
678 switch (S->getSCEVType()) {
683 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
686 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
689 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
693 if (!Processed.insert(S))
696 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
697 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
699 if (isHighCostExpansion(*I, Processed, SE))
705 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
706 if (Mul->getNumOperands() == 2) {
707 // Multiplication by a constant is ok
708 if (isa<SCEVConstant>(Mul->getOperand(0)))
709 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
711 // If we have the value of one operand, check if an existing
712 // multiplication already generates this expression.
713 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
714 Value *UVal = U->getValue();
715 for (Value::use_iterator UI = UVal->use_begin(), UE = UVal->use_end();
717 // If U is a constant, it may be used by a ConstantExpr.
718 Instruction *User = dyn_cast<Instruction>(*UI);
719 if (User && User->getOpcode() == Instruction::Mul
720 && SE.isSCEVable(User->getType())) {
721 return SE.getSCEV(User) == Mul;
728 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
729 if (isExistingPhi(AR, SE))
733 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
737 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
738 /// specified set are trivially dead, delete them and see if this makes any of
739 /// their operands subsequently dead.
741 DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
742 bool Changed = false;
744 while (!DeadInsts.empty()) {
745 Value *V = DeadInsts.pop_back_val();
746 Instruction *I = dyn_cast_or_null<Instruction>(V);
748 if (I == 0 || !isInstructionTriviallyDead(I))
751 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
752 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
755 DeadInsts.push_back(U);
758 I->eraseFromParent();
767 /// Cost - This class is used to measure and compare candidate formulae.
769 /// TODO: Some of these could be merged. Also, a lexical ordering
770 /// isn't always optimal.
774 unsigned NumBaseAdds;
780 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
783 bool operator<(const Cost &Other) const;
788 // Once any of the metrics loses, they must all remain losers.
790 return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds
791 | ImmCost | SetupCost) != ~0u)
792 || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds
793 & ImmCost & SetupCost) == ~0u);
798 assert(isValid() && "invalid cost");
799 return NumRegs == ~0u;
802 void RateFormula(const Formula &F,
803 SmallPtrSet<const SCEV *, 16> &Regs,
804 const DenseSet<const SCEV *> &VisitedRegs,
806 const SmallVectorImpl<int64_t> &Offsets,
807 ScalarEvolution &SE, DominatorTree &DT,
808 SmallPtrSet<const SCEV *, 16> *LoserRegs = 0);
810 void print(raw_ostream &OS) const;
814 void RateRegister(const SCEV *Reg,
815 SmallPtrSet<const SCEV *, 16> &Regs,
817 ScalarEvolution &SE, DominatorTree &DT);
818 void RatePrimaryRegister(const SCEV *Reg,
819 SmallPtrSet<const SCEV *, 16> &Regs,
821 ScalarEvolution &SE, DominatorTree &DT,
822 SmallPtrSet<const SCEV *, 16> *LoserRegs);
827 /// RateRegister - Tally up interesting quantities from the given register.
828 void Cost::RateRegister(const SCEV *Reg,
829 SmallPtrSet<const SCEV *, 16> &Regs,
831 ScalarEvolution &SE, DominatorTree &DT) {
832 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
833 // If this is an addrec for another loop, don't second-guess its addrec phi
834 // nodes. LSR isn't currently smart enough to reason about more than one
835 // loop at a time. LSR has already run on inner loops, will not run on outer
836 // loops, and cannot be expected to change sibling loops.
837 if (AR->getLoop() != L) {
838 // If the AddRec exists, consider it's register free and leave it alone.
839 if (isExistingPhi(AR, SE))
842 // Otherwise, do not consider this formula at all.
846 AddRecCost += 1; /// TODO: This should be a function of the stride.
848 // Add the step value register, if it needs one.
849 // TODO: The non-affine case isn't precisely modeled here.
850 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
851 if (!Regs.count(AR->getOperand(1))) {
852 RateRegister(AR->getOperand(1), Regs, L, SE, DT);
860 // Rough heuristic; favor registers which don't require extra setup
861 // instructions in the preheader.
862 if (!isa<SCEVUnknown>(Reg) &&
863 !isa<SCEVConstant>(Reg) &&
864 !(isa<SCEVAddRecExpr>(Reg) &&
865 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
866 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
869 NumIVMuls += isa<SCEVMulExpr>(Reg) &&
870 SE.hasComputableLoopEvolution(Reg, L);
873 /// RatePrimaryRegister - Record this register in the set. If we haven't seen it
874 /// before, rate it. Optional LoserRegs provides a way to declare any formula
875 /// that refers to one of those regs an instant loser.
876 void Cost::RatePrimaryRegister(const SCEV *Reg,
877 SmallPtrSet<const SCEV *, 16> &Regs,
879 ScalarEvolution &SE, DominatorTree &DT,
880 SmallPtrSet<const SCEV *, 16> *LoserRegs) {
881 if (LoserRegs && LoserRegs->count(Reg)) {
885 if (Regs.insert(Reg)) {
886 RateRegister(Reg, Regs, L, SE, DT);
888 LoserRegs->insert(Reg);
892 void Cost::RateFormula(const Formula &F,
893 SmallPtrSet<const SCEV *, 16> &Regs,
894 const DenseSet<const SCEV *> &VisitedRegs,
896 const SmallVectorImpl<int64_t> &Offsets,
897 ScalarEvolution &SE, DominatorTree &DT,
898 SmallPtrSet<const SCEV *, 16> *LoserRegs) {
899 // Tally up the registers.
900 if (const SCEV *ScaledReg = F.ScaledReg) {
901 if (VisitedRegs.count(ScaledReg)) {
905 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs);
909 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
910 E = F.BaseRegs.end(); I != E; ++I) {
911 const SCEV *BaseReg = *I;
912 if (VisitedRegs.count(BaseReg)) {
916 RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs);
921 // Determine how many (unfolded) adds we'll need inside the loop.
922 size_t NumBaseParts = F.BaseRegs.size() + (F.UnfoldedOffset != 0);
923 if (NumBaseParts > 1)
924 NumBaseAdds += NumBaseParts - 1;
926 // Tally up the non-zero immediates.
927 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
928 E = Offsets.end(); I != E; ++I) {
929 int64_t Offset = (uint64_t)*I + F.AM.BaseOffs;
931 ImmCost += 64; // Handle symbolic values conservatively.
932 // TODO: This should probably be the pointer size.
933 else if (Offset != 0)
934 ImmCost += APInt(64, Offset, true).getMinSignedBits();
936 assert(isValid() && "invalid cost");
939 /// Loose - Set this cost to a losing value.
949 /// operator< - Choose the lower cost.
950 bool Cost::operator<(const Cost &Other) const {
951 if (NumRegs != Other.NumRegs)
952 return NumRegs < Other.NumRegs;
953 if (AddRecCost != Other.AddRecCost)
954 return AddRecCost < Other.AddRecCost;
955 if (NumIVMuls != Other.NumIVMuls)
956 return NumIVMuls < Other.NumIVMuls;
957 if (NumBaseAdds != Other.NumBaseAdds)
958 return NumBaseAdds < Other.NumBaseAdds;
959 if (ImmCost != Other.ImmCost)
960 return ImmCost < Other.ImmCost;
961 if (SetupCost != Other.SetupCost)
962 return SetupCost < Other.SetupCost;
966 void Cost::print(raw_ostream &OS) const {
967 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
969 OS << ", with addrec cost " << AddRecCost;
971 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
972 if (NumBaseAdds != 0)
973 OS << ", plus " << NumBaseAdds << " base add"
974 << (NumBaseAdds == 1 ? "" : "s");
976 OS << ", plus " << ImmCost << " imm cost";
978 OS << ", plus " << SetupCost << " setup cost";
981 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
982 void Cost::dump() const {
983 print(errs()); errs() << '\n';
989 /// LSRFixup - An operand value in an instruction which is to be replaced
990 /// with some equivalent, possibly strength-reduced, replacement.
992 /// UserInst - The instruction which will be updated.
993 Instruction *UserInst;
995 /// OperandValToReplace - The operand of the instruction which will
996 /// be replaced. The operand may be used more than once; every instance
997 /// will be replaced.
998 Value *OperandValToReplace;
1000 /// PostIncLoops - If this user is to use the post-incremented value of an
1001 /// induction variable, this variable is non-null and holds the loop
1002 /// associated with the induction variable.
1003 PostIncLoopSet PostIncLoops;
1005 /// LUIdx - The index of the LSRUse describing the expression which
1006 /// this fixup needs, minus an offset (below).
1009 /// Offset - A constant offset to be added to the LSRUse expression.
1010 /// This allows multiple fixups to share the same LSRUse with different
1011 /// offsets, for example in an unrolled loop.
1014 bool isUseFullyOutsideLoop(const Loop *L) const;
1018 void print(raw_ostream &OS) const;
1024 LSRFixup::LSRFixup()
1025 : UserInst(0), OperandValToReplace(0), LUIdx(~size_t(0)), Offset(0) {}
1027 /// isUseFullyOutsideLoop - Test whether this fixup always uses its
1028 /// value outside of the given loop.
1029 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1030 // PHI nodes use their value in their incoming blocks.
1031 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1032 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1033 if (PN->getIncomingValue(i) == OperandValToReplace &&
1034 L->contains(PN->getIncomingBlock(i)))
1039 return !L->contains(UserInst);
1042 void LSRFixup::print(raw_ostream &OS) const {
1044 // Store is common and interesting enough to be worth special-casing.
1045 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1047 WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false);
1048 } else if (UserInst->getType()->isVoidTy())
1049 OS << UserInst->getOpcodeName();
1051 WriteAsOperand(OS, UserInst, /*PrintType=*/false);
1053 OS << ", OperandValToReplace=";
1054 WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false);
1056 for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(),
1057 E = PostIncLoops.end(); I != E; ++I) {
1058 OS << ", PostIncLoop=";
1059 WriteAsOperand(OS, (*I)->getHeader(), /*PrintType=*/false);
1062 if (LUIdx != ~size_t(0))
1063 OS << ", LUIdx=" << LUIdx;
1066 OS << ", Offset=" << Offset;
1069 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1070 void LSRFixup::dump() const {
1071 print(errs()); errs() << '\n';
1077 /// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
1078 /// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
1079 struct UniquifierDenseMapInfo {
1080 static SmallVector<const SCEV *, 2> getEmptyKey() {
1081 SmallVector<const SCEV *, 2> V;
1082 V.push_back(reinterpret_cast<const SCEV *>(-1));
1086 static SmallVector<const SCEV *, 2> getTombstoneKey() {
1087 SmallVector<const SCEV *, 2> V;
1088 V.push_back(reinterpret_cast<const SCEV *>(-2));
1092 static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) {
1093 unsigned Result = 0;
1094 for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(),
1095 E = V.end(); I != E; ++I)
1096 Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I);
1100 static bool isEqual(const SmallVector<const SCEV *, 2> &LHS,
1101 const SmallVector<const SCEV *, 2> &RHS) {
1106 /// LSRUse - This class holds the state that LSR keeps for each use in
1107 /// IVUsers, as well as uses invented by LSR itself. It includes information
1108 /// about what kinds of things can be folded into the user, information about
1109 /// the user itself, and information about how the use may be satisfied.
1110 /// TODO: Represent multiple users of the same expression in common?
1112 DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier;
1115 /// KindType - An enum for a kind of use, indicating what types of
1116 /// scaled and immediate operands it might support.
1118 Basic, ///< A normal use, with no folding.
1119 Special, ///< A special case of basic, allowing -1 scales.
1120 Address, ///< An address use; folding according to TargetLowering
1121 ICmpZero ///< An equality icmp with both operands folded into one.
1122 // TODO: Add a generic icmp too?
1128 SmallVector<int64_t, 8> Offsets;
1132 /// AllFixupsOutsideLoop - This records whether all of the fixups using this
1133 /// LSRUse are outside of the loop, in which case some special-case heuristics
1135 bool AllFixupsOutsideLoop;
1137 /// WidestFixupType - This records the widest use type for any fixup using
1138 /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different
1139 /// max fixup widths to be equivalent, because the narrower one may be relying
1140 /// on the implicit truncation to truncate away bogus bits.
1141 Type *WidestFixupType;
1143 /// Formulae - A list of ways to build a value that can satisfy this user.
1144 /// After the list is populated, one of these is selected heuristically and
1145 /// used to formulate a replacement for OperandValToReplace in UserInst.
1146 SmallVector<Formula, 12> Formulae;
1148 /// Regs - The set of register candidates used by all formulae in this LSRUse.
1149 SmallPtrSet<const SCEV *, 4> Regs;
1151 LSRUse(KindType K, Type *T) : Kind(K), AccessTy(T),
1152 MinOffset(INT64_MAX),
1153 MaxOffset(INT64_MIN),
1154 AllFixupsOutsideLoop(true),
1155 WidestFixupType(0) {}
1157 bool HasFormulaWithSameRegs(const Formula &F) const;
1158 bool InsertFormula(const Formula &F);
1159 void DeleteFormula(Formula &F);
1160 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1162 void print(raw_ostream &OS) const;
1168 /// HasFormula - Test whether this use as a formula which has the same
1169 /// registers as the given formula.
1170 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1171 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
1172 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1173 // Unstable sort by host order ok, because this is only used for uniquifying.
1174 std::sort(Key.begin(), Key.end());
1175 return Uniquifier.count(Key);
1178 /// InsertFormula - If the given formula has not yet been inserted, add it to
1179 /// the list, and return true. Return false otherwise.
1180 bool LSRUse::InsertFormula(const Formula &F) {
1181 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
1182 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1183 // Unstable sort by host order ok, because this is only used for uniquifying.
1184 std::sort(Key.begin(), Key.end());
1186 if (!Uniquifier.insert(Key).second)
1189 // Using a register to hold the value of 0 is not profitable.
1190 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1191 "Zero allocated in a scaled register!");
1193 for (SmallVectorImpl<const SCEV *>::const_iterator I =
1194 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
1195 assert(!(*I)->isZero() && "Zero allocated in a base register!");
1198 // Add the formula to the list.
1199 Formulae.push_back(F);
1201 // Record registers now being used by this use.
1202 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1207 /// DeleteFormula - Remove the given formula from this use's list.
1208 void LSRUse::DeleteFormula(Formula &F) {
1209 if (&F != &Formulae.back())
1210 std::swap(F, Formulae.back());
1211 Formulae.pop_back();
1214 /// RecomputeRegs - Recompute the Regs field, and update RegUses.
1215 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1216 // Now that we've filtered out some formulae, recompute the Regs set.
1217 SmallPtrSet<const SCEV *, 4> OldRegs = Regs;
1219 for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(),
1220 E = Formulae.end(); I != E; ++I) {
1221 const Formula &F = *I;
1222 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1223 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1226 // Update the RegTracker.
1227 for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(),
1228 E = OldRegs.end(); I != E; ++I)
1229 if (!Regs.count(*I))
1230 RegUses.DropRegister(*I, LUIdx);
1233 void LSRUse::print(raw_ostream &OS) const {
1234 OS << "LSR Use: Kind=";
1236 case Basic: OS << "Basic"; break;
1237 case Special: OS << "Special"; break;
1238 case ICmpZero: OS << "ICmpZero"; break;
1240 OS << "Address of ";
1241 if (AccessTy->isPointerTy())
1242 OS << "pointer"; // the full pointer type could be really verbose
1247 OS << ", Offsets={";
1248 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
1249 E = Offsets.end(); I != E; ++I) {
1251 if (llvm::next(I) != E)
1256 if (AllFixupsOutsideLoop)
1257 OS << ", all-fixups-outside-loop";
1259 if (WidestFixupType)
1260 OS << ", widest fixup type: " << *WidestFixupType;
1263 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1264 void LSRUse::dump() const {
1265 print(errs()); errs() << '\n';
1269 /// isLegalUse - Test whether the use described by AM is "legal", meaning it can
1270 /// be completely folded into the user instruction at isel time. This includes
1271 /// address-mode folding and special icmp tricks.
1272 static bool isLegalUse(const TargetLowering::AddrMode &AM,
1273 LSRUse::KindType Kind, Type *AccessTy,
1274 const TargetLowering *TLI) {
1276 case LSRUse::Address:
1277 // If we have low-level target information, ask the target if it can
1278 // completely fold this address.
1279 if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy);
1281 // Otherwise, just guess that reg+reg addressing is legal.
1282 return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1;
1284 case LSRUse::ICmpZero:
1285 // There's not even a target hook for querying whether it would be legal to
1286 // fold a GV into an ICmp.
1290 // ICmp only has two operands; don't allow more than two non-trivial parts.
1291 if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0)
1294 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1295 // putting the scaled register in the other operand of the icmp.
1296 if (AM.Scale != 0 && AM.Scale != -1)
1299 // If we have low-level target information, ask the target if it can fold an
1300 // integer immediate on an icmp.
1301 if (AM.BaseOffs != 0) {
1305 // ICmpZero BaseReg + Offset => ICmp BaseReg, -Offset
1306 // ICmpZero -1*ScaleReg + Offset => ICmp ScaleReg, Offset
1307 // Offs is the ICmp immediate.
1308 int64_t Offs = AM.BaseOffs;
1310 Offs = -(uint64_t)Offs; // The cast does the right thing with INT64_MIN.
1311 return TLI->isLegalICmpImmediate(Offs);
1314 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1318 // Only handle single-register values.
1319 return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
1321 case LSRUse::Special:
1322 // Special case Basic to handle -1 scales.
1323 return !AM.BaseGV && (AM.Scale == 0 || AM.Scale == -1) && AM.BaseOffs == 0;
1326 llvm_unreachable("Invalid LSRUse Kind!");
1329 static bool isLegalUse(TargetLowering::AddrMode AM,
1330 int64_t MinOffset, int64_t MaxOffset,
1331 LSRUse::KindType Kind, Type *AccessTy,
1332 const TargetLowering *TLI) {
1333 // Check for overflow.
1334 if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) !=
1337 AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset;
1338 if (isLegalUse(AM, Kind, AccessTy, TLI)) {
1339 AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset;
1340 // Check for overflow.
1341 if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) !=
1344 AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset;
1345 return isLegalUse(AM, Kind, AccessTy, TLI);
1350 static bool isAlwaysFoldable(int64_t BaseOffs,
1351 GlobalValue *BaseGV,
1353 LSRUse::KindType Kind, Type *AccessTy,
1354 const TargetLowering *TLI) {
1355 // Fast-path: zero is always foldable.
1356 if (BaseOffs == 0 && !BaseGV) return true;
1358 // Conservatively, create an address with an immediate and a
1359 // base and a scale.
1360 TargetLowering::AddrMode AM;
1361 AM.BaseOffs = BaseOffs;
1363 AM.HasBaseReg = HasBaseReg;
1364 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1366 // Canonicalize a scale of 1 to a base register if the formula doesn't
1367 // already have a base register.
1368 if (!AM.HasBaseReg && AM.Scale == 1) {
1370 AM.HasBaseReg = true;
1373 return isLegalUse(AM, Kind, AccessTy, TLI);
1376 static bool isAlwaysFoldable(const SCEV *S,
1377 int64_t MinOffset, int64_t MaxOffset,
1379 LSRUse::KindType Kind, Type *AccessTy,
1380 const TargetLowering *TLI,
1381 ScalarEvolution &SE) {
1382 // Fast-path: zero is always foldable.
1383 if (S->isZero()) return true;
1385 // Conservatively, create an address with an immediate and a
1386 // base and a scale.
1387 int64_t BaseOffs = ExtractImmediate(S, SE);
1388 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1390 // If there's anything else involved, it's not foldable.
1391 if (!S->isZero()) return false;
1393 // Fast-path: zero is always foldable.
1394 if (BaseOffs == 0 && !BaseGV) return true;
1396 // Conservatively, create an address with an immediate and a
1397 // base and a scale.
1398 TargetLowering::AddrMode AM;
1399 AM.BaseOffs = BaseOffs;
1401 AM.HasBaseReg = HasBaseReg;
1402 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1404 return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI);
1409 /// UseMapDenseMapInfo - A DenseMapInfo implementation for holding
1410 /// DenseMaps and DenseSets of pairs of const SCEV* and LSRUse::Kind.
1411 struct UseMapDenseMapInfo {
1412 static std::pair<const SCEV *, LSRUse::KindType> getEmptyKey() {
1413 return std::make_pair(reinterpret_cast<const SCEV *>(-1), LSRUse::Basic);
1416 static std::pair<const SCEV *, LSRUse::KindType> getTombstoneKey() {
1417 return std::make_pair(reinterpret_cast<const SCEV *>(-2), LSRUse::Basic);
1421 getHashValue(const std::pair<const SCEV *, LSRUse::KindType> &V) {
1422 unsigned Result = DenseMapInfo<const SCEV *>::getHashValue(V.first);
1423 Result ^= DenseMapInfo<unsigned>::getHashValue(unsigned(V.second));
1427 static bool isEqual(const std::pair<const SCEV *, LSRUse::KindType> &LHS,
1428 const std::pair<const SCEV *, LSRUse::KindType> &RHS) {
1433 /// IVInc - An individual increment in a Chain of IV increments.
1434 /// Relate an IV user to an expression that computes the IV it uses from the IV
1435 /// used by the previous link in the Chain.
1437 /// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1438 /// original IVOperand. The head of the chain's IVOperand is only valid during
1439 /// chain collection, before LSR replaces IV users. During chain generation,
1440 /// IncExpr can be used to find the new IVOperand that computes the same
1443 Instruction *UserInst;
1445 const SCEV *IncExpr;
1447 IVInc(Instruction *U, Value *O, const SCEV *E):
1448 UserInst(U), IVOperand(O), IncExpr(E) {}
1451 // IVChain - The list of IV increments in program order.
1452 // We typically add the head of a chain without finding subsequent links.
1454 SmallVector<IVInc,1> Incs;
1455 const SCEV *ExprBase;
1457 IVChain() : ExprBase(0) {}
1459 IVChain(const IVInc &Head, const SCEV *Base)
1460 : Incs(1, Head), ExprBase(Base) {}
1462 typedef SmallVectorImpl<IVInc>::const_iterator const_iterator;
1464 // begin - return the first increment in the chain.
1465 const_iterator begin() const {
1466 assert(!Incs.empty());
1467 return llvm::next(Incs.begin());
1469 const_iterator end() const {
1473 // hasIncs - Returns true if this chain contains any increments.
1474 bool hasIncs() const { return Incs.size() >= 2; }
1476 // add - Add an IVInc to the end of this chain.
1477 void add(const IVInc &X) { Incs.push_back(X); }
1479 // tailUserInst - Returns the last UserInst in the chain.
1480 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1482 // isProfitableIncrement - Returns true if IncExpr can be profitably added to
1484 bool isProfitableIncrement(const SCEV *OperExpr,
1485 const SCEV *IncExpr,
1489 /// ChainUsers - Helper for CollectChains to track multiple IV increment uses.
1490 /// Distinguish between FarUsers that definitely cross IV increments and
1491 /// NearUsers that may be used between IV increments.
1493 SmallPtrSet<Instruction*, 4> FarUsers;
1494 SmallPtrSet<Instruction*, 4> NearUsers;
1497 /// LSRInstance - This class holds state for the main loop strength reduction
1501 ScalarEvolution &SE;
1504 const TargetLowering *const TLI;
1508 /// IVIncInsertPos - This is the insert position that the current loop's
1509 /// induction variable increment should be placed. In simple loops, this is
1510 /// the latch block's terminator. But in more complicated cases, this is a
1511 /// position which will dominate all the in-loop post-increment users.
1512 Instruction *IVIncInsertPos;
1514 /// Factors - Interesting factors between use strides.
1515 SmallSetVector<int64_t, 8> Factors;
1517 /// Types - Interesting use types, to facilitate truncation reuse.
1518 SmallSetVector<Type *, 4> Types;
1520 /// Fixups - The list of operands which are to be replaced.
1521 SmallVector<LSRFixup, 16> Fixups;
1523 /// Uses - The list of interesting uses.
1524 SmallVector<LSRUse, 16> Uses;
1526 /// RegUses - Track which uses use which register candidates.
1527 RegUseTracker RegUses;
1529 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1530 // have more than a few IV increment chains in a loop. Missing a Chain falls
1531 // back to normal LSR behavior for those uses.
1532 static const unsigned MaxChains = 8;
1534 /// IVChainVec - IV users can form a chain of IV increments.
1535 SmallVector<IVChain, MaxChains> IVChainVec;
1537 /// IVIncSet - IV users that belong to profitable IVChains.
1538 SmallPtrSet<Use*, MaxChains> IVIncSet;
1540 void OptimizeShadowIV();
1541 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1542 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1543 void OptimizeLoopTermCond();
1545 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1546 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1547 void FinalizeChain(IVChain &Chain);
1548 void CollectChains();
1549 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1550 SmallVectorImpl<WeakVH> &DeadInsts);
1552 void CollectInterestingTypesAndFactors();
1553 void CollectFixupsAndInitialFormulae();
1555 LSRFixup &getNewFixup() {
1556 Fixups.push_back(LSRFixup());
1557 return Fixups.back();
1560 // Support for sharing of LSRUses between LSRFixups.
1561 typedef DenseMap<std::pair<const SCEV *, LSRUse::KindType>,
1563 UseMapDenseMapInfo> UseMapTy;
1566 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1567 LSRUse::KindType Kind, Type *AccessTy);
1569 std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1570 LSRUse::KindType Kind,
1573 void DeleteUse(LSRUse &LU, size_t LUIdx);
1575 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1577 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1578 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1579 void CountRegisters(const Formula &F, size_t LUIdx);
1580 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1582 void CollectLoopInvariantFixupsAndFormulae();
1584 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1585 unsigned Depth = 0);
1586 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1587 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1588 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1589 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1590 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1591 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1592 void GenerateCrossUseConstantOffsets();
1593 void GenerateAllReuseFormulae();
1595 void FilterOutUndesirableDedicatedRegisters();
1597 size_t EstimateSearchSpaceComplexity() const;
1598 void NarrowSearchSpaceByDetectingSupersets();
1599 void NarrowSearchSpaceByCollapsingUnrolledCode();
1600 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1601 void NarrowSearchSpaceByPickingWinnerRegs();
1602 void NarrowSearchSpaceUsingHeuristics();
1604 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1606 SmallVectorImpl<const Formula *> &Workspace,
1607 const Cost &CurCost,
1608 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1609 DenseSet<const SCEV *> &VisitedRegs) const;
1610 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1612 BasicBlock::iterator
1613 HoistInsertPosition(BasicBlock::iterator IP,
1614 const SmallVectorImpl<Instruction *> &Inputs) const;
1615 BasicBlock::iterator
1616 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1619 SCEVExpander &Rewriter) const;
1621 Value *Expand(const LSRFixup &LF,
1623 BasicBlock::iterator IP,
1624 SCEVExpander &Rewriter,
1625 SmallVectorImpl<WeakVH> &DeadInsts) const;
1626 void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
1628 SCEVExpander &Rewriter,
1629 SmallVectorImpl<WeakVH> &DeadInsts,
1631 void Rewrite(const LSRFixup &LF,
1633 SCEVExpander &Rewriter,
1634 SmallVectorImpl<WeakVH> &DeadInsts,
1636 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1640 LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
1642 bool getChanged() const { return Changed; }
1644 void print_factors_and_types(raw_ostream &OS) const;
1645 void print_fixups(raw_ostream &OS) const;
1646 void print_uses(raw_ostream &OS) const;
1647 void print(raw_ostream &OS) const;
1653 /// OptimizeShadowIV - If IV is used in a int-to-float cast
1654 /// inside the loop then try to eliminate the cast operation.
1655 void LSRInstance::OptimizeShadowIV() {
1656 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1657 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1660 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1661 UI != E; /* empty */) {
1662 IVUsers::const_iterator CandidateUI = UI;
1664 Instruction *ShadowUse = CandidateUI->getUser();
1665 Type *DestTy = NULL;
1666 bool IsSigned = false;
1668 /* If shadow use is a int->float cast then insert a second IV
1669 to eliminate this cast.
1671 for (unsigned i = 0; i < n; ++i)
1677 for (unsigned i = 0; i < n; ++i, ++d)
1680 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
1682 DestTy = UCast->getDestTy();
1684 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
1686 DestTy = SCast->getDestTy();
1688 if (!DestTy) continue;
1691 // If target does not support DestTy natively then do not apply
1692 // this transformation.
1693 EVT DVT = TLI->getValueType(DestTy);
1694 if (!TLI->isTypeLegal(DVT)) continue;
1697 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1699 if (PH->getNumIncomingValues() != 2) continue;
1701 Type *SrcTy = PH->getType();
1702 int Mantissa = DestTy->getFPMantissaWidth();
1703 if (Mantissa == -1) continue;
1704 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1707 unsigned Entry, Latch;
1708 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1716 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1717 if (!Init) continue;
1718 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
1719 (double)Init->getSExtValue() :
1720 (double)Init->getZExtValue());
1722 BinaryOperator *Incr =
1723 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1724 if (!Incr) continue;
1725 if (Incr->getOpcode() != Instruction::Add
1726 && Incr->getOpcode() != Instruction::Sub)
1729 /* Initialize new IV, double d = 0.0 in above example. */
1730 ConstantInt *C = NULL;
1731 if (Incr->getOperand(0) == PH)
1732 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1733 else if (Incr->getOperand(1) == PH)
1734 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1740 // Ignore negative constants, as the code below doesn't handle them
1741 // correctly. TODO: Remove this restriction.
1742 if (!C->getValue().isStrictlyPositive()) continue;
1744 /* Add new PHINode. */
1745 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
1747 /* create new increment. '++d' in above example. */
1748 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1749 BinaryOperator *NewIncr =
1750 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1751 Instruction::FAdd : Instruction::FSub,
1752 NewPH, CFP, "IV.S.next.", Incr);
1754 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1755 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1757 /* Remove cast operation */
1758 ShadowUse->replaceAllUsesWith(NewPH);
1759 ShadowUse->eraseFromParent();
1765 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1766 /// set the IV user and stride information and return true, otherwise return
1768 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
1769 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1770 if (UI->getUser() == Cond) {
1771 // NOTE: we could handle setcc instructions with multiple uses here, but
1772 // InstCombine does it as well for simple uses, it's not clear that it
1773 // occurs enough in real life to handle.
1780 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
1781 /// a max computation.
1783 /// This is a narrow solution to a specific, but acute, problem. For loops
1789 /// } while (++i < n);
1791 /// the trip count isn't just 'n', because 'n' might not be positive. And
1792 /// unfortunately this can come up even for loops where the user didn't use
1793 /// a C do-while loop. For example, seemingly well-behaved top-test loops
1794 /// will commonly be lowered like this:
1800 /// } while (++i < n);
1803 /// and then it's possible for subsequent optimization to obscure the if
1804 /// test in such a way that indvars can't find it.
1806 /// When indvars can't find the if test in loops like this, it creates a
1807 /// max expression, which allows it to give the loop a canonical
1808 /// induction variable:
1811 /// max = n < 1 ? 1 : n;
1814 /// } while (++i != max);
1816 /// Canonical induction variables are necessary because the loop passes
1817 /// are designed around them. The most obvious example of this is the
1818 /// LoopInfo analysis, which doesn't remember trip count values. It
1819 /// expects to be able to rediscover the trip count each time it is
1820 /// needed, and it does this using a simple analysis that only succeeds if
1821 /// the loop has a canonical induction variable.
1823 /// However, when it comes time to generate code, the maximum operation
1824 /// can be quite costly, especially if it's inside of an outer loop.
1826 /// This function solves this problem by detecting this type of loop and
1827 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1828 /// the instructions for the maximum computation.
1830 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1831 // Check that the loop matches the pattern we're looking for.
1832 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1833 Cond->getPredicate() != CmpInst::ICMP_NE)
1836 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
1837 if (!Sel || !Sel->hasOneUse()) return Cond;
1839 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1840 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1842 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
1844 // Add one to the backedge-taken count to get the trip count.
1845 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
1846 if (IterationCount != SE.getSCEV(Sel)) return Cond;
1848 // Check for a max calculation that matches the pattern. There's no check
1849 // for ICMP_ULE here because the comparison would be with zero, which
1850 // isn't interesting.
1851 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
1852 const SCEVNAryExpr *Max = 0;
1853 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
1854 Pred = ICmpInst::ICMP_SLE;
1856 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
1857 Pred = ICmpInst::ICMP_SLT;
1859 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
1860 Pred = ICmpInst::ICMP_ULT;
1867 // To handle a max with more than two operands, this optimization would
1868 // require additional checking and setup.
1869 if (Max->getNumOperands() != 2)
1872 const SCEV *MaxLHS = Max->getOperand(0);
1873 const SCEV *MaxRHS = Max->getOperand(1);
1875 // ScalarEvolution canonicalizes constants to the left. For < and >, look
1876 // for a comparison with 1. For <= and >=, a comparison with zero.
1878 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
1881 // Check the relevant induction variable for conformance to
1883 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
1884 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
1885 if (!AR || !AR->isAffine() ||
1886 AR->getStart() != One ||
1887 AR->getStepRecurrence(SE) != One)
1890 assert(AR->getLoop() == L &&
1891 "Loop condition operand is an addrec in a different loop!");
1893 // Check the right operand of the select, and remember it, as it will
1894 // be used in the new comparison instruction.
1896 if (ICmpInst::isTrueWhenEqual(Pred)) {
1897 // Look for n+1, and grab n.
1898 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
1899 if (isa<ConstantInt>(BO->getOperand(1)) &&
1900 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1901 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1902 NewRHS = BO->getOperand(0);
1903 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
1904 if (isa<ConstantInt>(BO->getOperand(1)) &&
1905 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1906 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1907 NewRHS = BO->getOperand(0);
1910 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
1911 NewRHS = Sel->getOperand(1);
1912 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
1913 NewRHS = Sel->getOperand(2);
1914 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
1915 NewRHS = SU->getValue();
1917 // Max doesn't match expected pattern.
1920 // Determine the new comparison opcode. It may be signed or unsigned,
1921 // and the original comparison may be either equality or inequality.
1922 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
1923 Pred = CmpInst::getInversePredicate(Pred);
1925 // Ok, everything looks ok to change the condition into an SLT or SGE and
1926 // delete the max calculation.
1928 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
1930 // Delete the max calculation instructions.
1931 Cond->replaceAllUsesWith(NewCond);
1932 CondUse->setUser(NewCond);
1933 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
1934 Cond->eraseFromParent();
1935 Sel->eraseFromParent();
1936 if (Cmp->use_empty())
1937 Cmp->eraseFromParent();
1941 /// OptimizeLoopTermCond - Change loop terminating condition to use the
1942 /// postinc iv when possible.
1944 LSRInstance::OptimizeLoopTermCond() {
1945 SmallPtrSet<Instruction *, 4> PostIncs;
1947 BasicBlock *LatchBlock = L->getLoopLatch();
1948 SmallVector<BasicBlock*, 8> ExitingBlocks;
1949 L->getExitingBlocks(ExitingBlocks);
1951 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
1952 BasicBlock *ExitingBlock = ExitingBlocks[i];
1954 // Get the terminating condition for the loop if possible. If we
1955 // can, we want to change it to use a post-incremented version of its
1956 // induction variable, to allow coalescing the live ranges for the IV into
1957 // one register value.
1959 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
1962 // FIXME: Overly conservative, termination condition could be an 'or' etc..
1963 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
1966 // Search IVUsesByStride to find Cond's IVUse if there is one.
1967 IVStrideUse *CondUse = 0;
1968 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
1969 if (!FindIVUserForCond(Cond, CondUse))
1972 // If the trip count is computed in terms of a max (due to ScalarEvolution
1973 // being unable to find a sufficient guard, for example), change the loop
1974 // comparison to use SLT or ULT instead of NE.
1975 // One consequence of doing this now is that it disrupts the count-down
1976 // optimization. That's not always a bad thing though, because in such
1977 // cases it may still be worthwhile to avoid a max.
1978 Cond = OptimizeMax(Cond, CondUse);
1980 // If this exiting block dominates the latch block, it may also use
1981 // the post-inc value if it won't be shared with other uses.
1982 // Check for dominance.
1983 if (!DT.dominates(ExitingBlock, LatchBlock))
1986 // Conservatively avoid trying to use the post-inc value in non-latch
1987 // exits if there may be pre-inc users in intervening blocks.
1988 if (LatchBlock != ExitingBlock)
1989 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1990 // Test if the use is reachable from the exiting block. This dominator
1991 // query is a conservative approximation of reachability.
1992 if (&*UI != CondUse &&
1993 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
1994 // Conservatively assume there may be reuse if the quotient of their
1995 // strides could be a legal scale.
1996 const SCEV *A = IU.getStride(*CondUse, L);
1997 const SCEV *B = IU.getStride(*UI, L);
1998 if (!A || !B) continue;
1999 if (SE.getTypeSizeInBits(A->getType()) !=
2000 SE.getTypeSizeInBits(B->getType())) {
2001 if (SE.getTypeSizeInBits(A->getType()) >
2002 SE.getTypeSizeInBits(B->getType()))
2003 B = SE.getSignExtendExpr(B, A->getType());
2005 A = SE.getSignExtendExpr(A, B->getType());
2007 if (const SCEVConstant *D =
2008 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2009 const ConstantInt *C = D->getValue();
2010 // Stride of one or negative one can have reuse with non-addresses.
2011 if (C->isOne() || C->isAllOnesValue())
2012 goto decline_post_inc;
2013 // Avoid weird situations.
2014 if (C->getValue().getMinSignedBits() >= 64 ||
2015 C->getValue().isMinSignedValue())
2016 goto decline_post_inc;
2017 // Without TLI, assume that any stride might be valid, and so any
2018 // use might be shared.
2020 goto decline_post_inc;
2021 // Check for possible scaled-address reuse.
2022 Type *AccessTy = getAccessType(UI->getUser());
2023 TargetLowering::AddrMode AM;
2024 AM.Scale = C->getSExtValue();
2025 if (TLI->isLegalAddressingMode(AM, AccessTy))
2026 goto decline_post_inc;
2027 AM.Scale = -AM.Scale;
2028 if (TLI->isLegalAddressingMode(AM, AccessTy))
2029 goto decline_post_inc;
2033 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
2036 // It's possible for the setcc instruction to be anywhere in the loop, and
2037 // possible for it to have multiple users. If it is not immediately before
2038 // the exiting block branch, move it.
2039 if (&*++BasicBlock::iterator(Cond) != TermBr) {
2040 if (Cond->hasOneUse()) {
2041 Cond->moveBefore(TermBr);
2043 // Clone the terminating condition and insert into the loopend.
2044 ICmpInst *OldCond = Cond;
2045 Cond = cast<ICmpInst>(Cond->clone());
2046 Cond->setName(L->getHeader()->getName() + ".termcond");
2047 ExitingBlock->getInstList().insert(TermBr, Cond);
2049 // Clone the IVUse, as the old use still exists!
2050 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2051 TermBr->replaceUsesOfWith(OldCond, Cond);
2055 // If we get to here, we know that we can transform the setcc instruction to
2056 // use the post-incremented version of the IV, allowing us to coalesce the
2057 // live ranges for the IV correctly.
2058 CondUse->transformToPostInc(L);
2061 PostIncs.insert(Cond);
2065 // Determine an insertion point for the loop induction variable increment. It
2066 // must dominate all the post-inc comparisons we just set up, and it must
2067 // dominate the loop latch edge.
2068 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2069 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
2070 E = PostIncs.end(); I != E; ++I) {
2072 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2074 if (BB == (*I)->getParent())
2075 IVIncInsertPos = *I;
2076 else if (BB != IVIncInsertPos->getParent())
2077 IVIncInsertPos = BB->getTerminator();
2081 /// reconcileNewOffset - Determine if the given use can accommodate a fixup
2082 /// at the given offset and other details. If so, update the use and
2085 LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
2086 LSRUse::KindType Kind, Type *AccessTy) {
2087 int64_t NewMinOffset = LU.MinOffset;
2088 int64_t NewMaxOffset = LU.MaxOffset;
2089 Type *NewAccessTy = AccessTy;
2091 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2092 // something conservative, however this can pessimize in the case that one of
2093 // the uses will have all its uses outside the loop, for example.
2094 if (LU.Kind != Kind)
2096 // Conservatively assume HasBaseReg is true for now.
2097 if (NewOffset < LU.MinOffset) {
2098 if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg,
2099 Kind, AccessTy, TLI))
2101 NewMinOffset = NewOffset;
2102 } else if (NewOffset > LU.MaxOffset) {
2103 if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg,
2104 Kind, AccessTy, TLI))
2106 NewMaxOffset = NewOffset;
2108 // Check for a mismatched access type, and fall back conservatively as needed.
2109 // TODO: Be less conservative when the type is similar and can use the same
2110 // addressing modes.
2111 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
2112 NewAccessTy = Type::getVoidTy(AccessTy->getContext());
2115 LU.MinOffset = NewMinOffset;
2116 LU.MaxOffset = NewMaxOffset;
2117 LU.AccessTy = NewAccessTy;
2118 if (NewOffset != LU.Offsets.back())
2119 LU.Offsets.push_back(NewOffset);
2123 /// getUse - Return an LSRUse index and an offset value for a fixup which
2124 /// needs the given expression, with the given kind and optional access type.
2125 /// Either reuse an existing use or create a new one, as needed.
2126 std::pair<size_t, int64_t>
2127 LSRInstance::getUse(const SCEV *&Expr,
2128 LSRUse::KindType Kind, Type *AccessTy) {
2129 const SCEV *Copy = Expr;
2130 int64_t Offset = ExtractImmediate(Expr, SE);
2132 // Basic uses can't accept any offset, for example.
2133 if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) {
2138 std::pair<UseMapTy::iterator, bool> P =
2139 UseMap.insert(std::make_pair(std::make_pair(Expr, Kind), 0));
2141 // A use already existed with this base.
2142 size_t LUIdx = P.first->second;
2143 LSRUse &LU = Uses[LUIdx];
2144 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2146 return std::make_pair(LUIdx, Offset);
2149 // Create a new use.
2150 size_t LUIdx = Uses.size();
2151 P.first->second = LUIdx;
2152 Uses.push_back(LSRUse(Kind, AccessTy));
2153 LSRUse &LU = Uses[LUIdx];
2155 // We don't need to track redundant offsets, but we don't need to go out
2156 // of our way here to avoid them.
2157 if (LU.Offsets.empty() || Offset != LU.Offsets.back())
2158 LU.Offsets.push_back(Offset);
2160 LU.MinOffset = Offset;
2161 LU.MaxOffset = Offset;
2162 return std::make_pair(LUIdx, Offset);
2165 /// DeleteUse - Delete the given use from the Uses list.
2166 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2167 if (&LU != &Uses.back())
2168 std::swap(LU, Uses.back());
2172 RegUses.SwapAndDropUse(LUIdx, Uses.size());
2175 /// FindUseWithFormula - Look for a use distinct from OrigLU which is has
2176 /// a formula that has the same registers as the given formula.
2178 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2179 const LSRUse &OrigLU) {
2180 // Search all uses for the formula. This could be more clever.
2181 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2182 LSRUse &LU = Uses[LUIdx];
2183 // Check whether this use is close enough to OrigLU, to see whether it's
2184 // worthwhile looking through its formulae.
2185 // Ignore ICmpZero uses because they may contain formulae generated by
2186 // GenerateICmpZeroScales, in which case adding fixup offsets may
2188 if (&LU != &OrigLU &&
2189 LU.Kind != LSRUse::ICmpZero &&
2190 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2191 LU.WidestFixupType == OrigLU.WidestFixupType &&
2192 LU.HasFormulaWithSameRegs(OrigF)) {
2193 // Scan through this use's formulae.
2194 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
2195 E = LU.Formulae.end(); I != E; ++I) {
2196 const Formula &F = *I;
2197 // Check to see if this formula has the same registers and symbols
2199 if (F.BaseRegs == OrigF.BaseRegs &&
2200 F.ScaledReg == OrigF.ScaledReg &&
2201 F.AM.BaseGV == OrigF.AM.BaseGV &&
2202 F.AM.Scale == OrigF.AM.Scale &&
2203 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2204 if (F.AM.BaseOffs == 0)
2206 // This is the formula where all the registers and symbols matched;
2207 // there aren't going to be any others. Since we declined it, we
2208 // can skip the rest of the formulae and proceed to the next LSRUse.
2215 // Nothing looked good.
2219 void LSRInstance::CollectInterestingTypesAndFactors() {
2220 SmallSetVector<const SCEV *, 4> Strides;
2222 // Collect interesting types and strides.
2223 SmallVector<const SCEV *, 4> Worklist;
2224 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2225 const SCEV *Expr = IU.getExpr(*UI);
2227 // Collect interesting types.
2228 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2230 // Add strides for mentioned loops.
2231 Worklist.push_back(Expr);
2233 const SCEV *S = Worklist.pop_back_val();
2234 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2235 if (AR->getLoop() == L)
2236 Strides.insert(AR->getStepRecurrence(SE));
2237 Worklist.push_back(AR->getStart());
2238 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2239 Worklist.append(Add->op_begin(), Add->op_end());
2241 } while (!Worklist.empty());
2244 // Compute interesting factors from the set of interesting strides.
2245 for (SmallSetVector<const SCEV *, 4>::const_iterator
2246 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2247 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2248 llvm::next(I); NewStrideIter != E; ++NewStrideIter) {
2249 const SCEV *OldStride = *I;
2250 const SCEV *NewStride = *NewStrideIter;
2252 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2253 SE.getTypeSizeInBits(NewStride->getType())) {
2254 if (SE.getTypeSizeInBits(OldStride->getType()) >
2255 SE.getTypeSizeInBits(NewStride->getType()))
2256 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2258 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2260 if (const SCEVConstant *Factor =
2261 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2263 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2264 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2265 } else if (const SCEVConstant *Factor =
2266 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2269 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2270 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2274 // If all uses use the same type, don't bother looking for truncation-based
2276 if (Types.size() == 1)
2279 DEBUG(print_factors_and_types(dbgs()));
2282 /// findIVOperand - Helper for CollectChains that finds an IV operand (computed
2283 /// by an AddRec in this loop) within [OI,OE) or returns OE. If IVUsers mapped
2284 /// Instructions to IVStrideUses, we could partially skip this.
2285 static User::op_iterator
2286 findIVOperand(User::op_iterator OI, User::op_iterator OE,
2287 Loop *L, ScalarEvolution &SE) {
2288 for(; OI != OE; ++OI) {
2289 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2290 if (!SE.isSCEVable(Oper->getType()))
2293 if (const SCEVAddRecExpr *AR =
2294 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2295 if (AR->getLoop() == L)
2303 /// getWideOperand - IVChain logic must consistenctly peek base TruncInst
2304 /// operands, so wrap it in a convenient helper.
2305 static Value *getWideOperand(Value *Oper) {
2306 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2307 return Trunc->getOperand(0);
2311 /// isCompatibleIVType - Return true if we allow an IV chain to include both
2313 static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2314 Type *LType = LVal->getType();
2315 Type *RType = RVal->getType();
2316 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy());
2319 /// getExprBase - Return an approximation of this SCEV expression's "base", or
2320 /// NULL for any constant. Returning the expression itself is
2321 /// conservative. Returning a deeper subexpression is more precise and valid as
2322 /// long as it isn't less complex than another subexpression. For expressions
2323 /// involving multiple unscaled values, we need to return the pointer-type
2324 /// SCEVUnknown. This avoids forming chains across objects, such as:
2325 /// PrevOper==a[i], IVOper==b[i], IVInc==b-a.
2327 /// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2328 /// SCEVUnknown, we simply return the rightmost SCEV operand.
2329 static const SCEV *getExprBase(const SCEV *S) {
2330 switch (S->getSCEVType()) {
2331 default: // uncluding scUnknown.
2336 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2338 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2340 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2342 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2343 // there's nothing more complex.
2344 // FIXME: not sure if we want to recognize negation.
2345 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2346 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2347 E(Add->op_begin()); I != E; ++I) {
2348 const SCEV *SubExpr = *I;
2349 if (SubExpr->getSCEVType() == scAddExpr)
2350 return getExprBase(SubExpr);
2352 if (SubExpr->getSCEVType() != scMulExpr)
2355 return S; // all operands are scaled, be conservative.
2358 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2362 /// Return true if the chain increment is profitable to expand into a loop
2363 /// invariant value, which may require its own register. A profitable chain
2364 /// increment will be an offset relative to the same base. We allow such offsets
2365 /// to potentially be used as chain increment as long as it's not obviously
2366 /// expensive to expand using real instructions.
2367 bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2368 const SCEV *IncExpr,
2369 ScalarEvolution &SE) {
2370 // Aggressively form chains when -stress-ivchain.
2374 // Do not replace a constant offset from IV head with a nonconstant IV
2376 if (!isa<SCEVConstant>(IncExpr)) {
2377 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2378 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2382 SmallPtrSet<const SCEV*, 8> Processed;
2383 return !isHighCostExpansion(IncExpr, Processed, SE);
2386 /// Return true if the number of registers needed for the chain is estimated to
2387 /// be less than the number required for the individual IV users. First prohibit
2388 /// any IV users that keep the IV live across increments (the Users set should
2389 /// be empty). Next count the number and type of increments in the chain.
2391 /// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2392 /// effectively use postinc addressing modes. Only consider it profitable it the
2393 /// increments can be computed in fewer registers when chained.
2395 /// TODO: Consider IVInc free if it's already used in another chains.
2397 isProfitableChain(IVChain &Chain, SmallPtrSet<Instruction*, 4> &Users,
2398 ScalarEvolution &SE, const TargetLowering *TLI) {
2402 if (!Chain.hasIncs())
2405 if (!Users.empty()) {
2406 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";
2407 for (SmallPtrSet<Instruction*, 4>::const_iterator I = Users.begin(),
2408 E = Users.end(); I != E; ++I) {
2409 dbgs() << " " << **I << "\n";
2413 assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2415 // The chain itself may require a register, so intialize cost to 1.
2418 // A complete chain likely eliminates the need for keeping the original IV in
2419 // a register. LSR does not currently know how to form a complete chain unless
2420 // the header phi already exists.
2421 if (isa<PHINode>(Chain.tailUserInst())
2422 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2425 const SCEV *LastIncExpr = 0;
2426 unsigned NumConstIncrements = 0;
2427 unsigned NumVarIncrements = 0;
2428 unsigned NumReusedIncrements = 0;
2429 for (IVChain::const_iterator I = Chain.begin(), E = Chain.end();
2432 if (I->IncExpr->isZero())
2435 // Incrementing by zero or some constant is neutral. We assume constants can
2436 // be folded into an addressing mode or an add's immediate operand.
2437 if (isa<SCEVConstant>(I->IncExpr)) {
2438 ++NumConstIncrements;
2442 if (I->IncExpr == LastIncExpr)
2443 ++NumReusedIncrements;
2447 LastIncExpr = I->IncExpr;
2449 // An IV chain with a single increment is handled by LSR's postinc
2450 // uses. However, a chain with multiple increments requires keeping the IV's
2451 // value live longer than it needs to be if chained.
2452 if (NumConstIncrements > 1)
2455 // Materializing increment expressions in the preheader that didn't exist in
2456 // the original code may cost a register. For example, sign-extended array
2457 // indices can produce ridiculous increments like this:
2458 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2459 cost += NumVarIncrements;
2461 // Reusing variable increments likely saves a register to hold the multiple of
2463 cost -= NumReusedIncrements;
2465 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost
2471 /// ChainInstruction - Add this IV user to an existing chain or make it the head
2473 void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2474 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2475 // When IVs are used as types of varying widths, they are generally converted
2476 // to a wider type with some uses remaining narrow under a (free) trunc.
2477 Value *const NextIV = getWideOperand(IVOper);
2478 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2479 const SCEV *const OperExprBase = getExprBase(OperExpr);
2481 // Visit all existing chains. Check if its IVOper can be computed as a
2482 // profitable loop invariant increment from the last link in the Chain.
2483 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2484 const SCEV *LastIncExpr = 0;
2485 for (; ChainIdx < NChains; ++ChainIdx) {
2486 IVChain &Chain = IVChainVec[ChainIdx];
2488 // Prune the solution space aggressively by checking that both IV operands
2489 // are expressions that operate on the same unscaled SCEVUnknown. This
2490 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2491 // first avoids creating extra SCEV expressions.
2492 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2495 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2496 if (!isCompatibleIVType(PrevIV, NextIV))
2499 // A phi node terminates a chain.
2500 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2503 // The increment must be loop-invariant so it can be kept in a register.
2504 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2505 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2506 if (!SE.isLoopInvariant(IncExpr, L))
2509 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2510 LastIncExpr = IncExpr;
2514 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2515 // bother for phi nodes, because they must be last in the chain.
2516 if (ChainIdx == NChains) {
2517 if (isa<PHINode>(UserInst))
2519 if (NChains >= MaxChains && !StressIVChain) {
2520 DEBUG(dbgs() << "IV Chain Limit\n");
2523 LastIncExpr = OperExpr;
2524 // IVUsers may have skipped over sign/zero extensions. We don't currently
2525 // attempt to form chains involving extensions unless they can be hoisted
2526 // into this loop's AddRec.
2527 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2530 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2532 ChainUsersVec.resize(NChains);
2533 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst
2534 << ") IV=" << *LastIncExpr << "\n");
2536 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst
2537 << ") IV+" << *LastIncExpr << "\n");
2538 // Add this IV user to the end of the chain.
2539 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2542 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2543 // This chain's NearUsers become FarUsers.
2544 if (!LastIncExpr->isZero()) {
2545 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2550 // All other uses of IVOperand become near uses of the chain.
2551 // We currently ignore intermediate values within SCEV expressions, assuming
2552 // they will eventually be used be the current chain, or can be computed
2553 // from one of the chain increments. To be more precise we could
2554 // transitively follow its user and only add leaf IV users to the set.
2555 for (Value::use_iterator UseIter = IVOper->use_begin(),
2556 UseEnd = IVOper->use_end(); UseIter != UseEnd; ++UseIter) {
2557 Instruction *OtherUse = dyn_cast<Instruction>(*UseIter);
2558 if (!OtherUse || OtherUse == UserInst)
2560 if (SE.isSCEVable(OtherUse->getType())
2561 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2562 && IU.isIVUserOrOperand(OtherUse)) {
2565 NearUsers.insert(OtherUse);
2568 // Since this user is part of the chain, it's no longer considered a use
2570 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2573 /// CollectChains - Populate the vector of Chains.
2575 /// This decreases ILP at the architecture level. Targets with ample registers,
2576 /// multiple memory ports, and no register renaming probably don't want
2577 /// this. However, such targets should probably disable LSR altogether.
2579 /// The job of LSR is to make a reasonable choice of induction variables across
2580 /// the loop. Subsequent passes can easily "unchain" computation exposing more
2581 /// ILP *within the loop* if the target wants it.
2583 /// Finding the best IV chain is potentially a scheduling problem. Since LSR
2584 /// will not reorder memory operations, it will recognize this as a chain, but
2585 /// will generate redundant IV increments. Ideally this would be corrected later
2586 /// by a smart scheduler:
2592 /// TODO: Walk the entire domtree within this loop, not just the path to the
2593 /// loop latch. This will discover chains on side paths, but requires
2594 /// maintaining multiple copies of the Chains state.
2595 void LSRInstance::CollectChains() {
2596 DEBUG(dbgs() << "Collecting IV Chains.\n");
2597 SmallVector<ChainUsers, 8> ChainUsersVec;
2599 SmallVector<BasicBlock *,8> LatchPath;
2600 BasicBlock *LoopHeader = L->getHeader();
2601 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
2602 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
2603 LatchPath.push_back(Rung->getBlock());
2605 LatchPath.push_back(LoopHeader);
2607 // Walk the instruction stream from the loop header to the loop latch.
2608 for (SmallVectorImpl<BasicBlock *>::reverse_iterator
2609 BBIter = LatchPath.rbegin(), BBEnd = LatchPath.rend();
2610 BBIter != BBEnd; ++BBIter) {
2611 for (BasicBlock::iterator I = (*BBIter)->begin(), E = (*BBIter)->end();
2613 // Skip instructions that weren't seen by IVUsers analysis.
2614 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(I))
2617 // Ignore users that are part of a SCEV expression. This way we only
2618 // consider leaf IV Users. This effectively rediscovers a portion of
2619 // IVUsers analysis but in program order this time.
2620 if (SE.isSCEVable(I->getType()) && !isa<SCEVUnknown>(SE.getSCEV(I)))
2623 // Remove this instruction from any NearUsers set it may be in.
2624 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
2625 ChainIdx < NChains; ++ChainIdx) {
2626 ChainUsersVec[ChainIdx].NearUsers.erase(I);
2628 // Search for operands that can be chained.
2629 SmallPtrSet<Instruction*, 4> UniqueOperands;
2630 User::op_iterator IVOpEnd = I->op_end();
2631 User::op_iterator IVOpIter = findIVOperand(I->op_begin(), IVOpEnd, L, SE);
2632 while (IVOpIter != IVOpEnd) {
2633 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
2634 if (UniqueOperands.insert(IVOpInst))
2635 ChainInstruction(I, IVOpInst, ChainUsersVec);
2636 IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE);
2638 } // Continue walking down the instructions.
2639 } // Continue walking down the domtree.
2640 // Visit phi backedges to determine if the chain can generate the IV postinc.
2641 for (BasicBlock::iterator I = L->getHeader()->begin();
2642 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
2643 if (!SE.isSCEVable(PN->getType()))
2647 dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch()));
2649 ChainInstruction(PN, IncV, ChainUsersVec);
2651 // Remove any unprofitable chains.
2652 unsigned ChainIdx = 0;
2653 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
2654 UsersIdx < NChains; ++UsersIdx) {
2655 if (!isProfitableChain(IVChainVec[UsersIdx],
2656 ChainUsersVec[UsersIdx].FarUsers, SE, TLI))
2658 // Preserve the chain at UsesIdx.
2659 if (ChainIdx != UsersIdx)
2660 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
2661 FinalizeChain(IVChainVec[ChainIdx]);
2664 IVChainVec.resize(ChainIdx);
2667 void LSRInstance::FinalizeChain(IVChain &Chain) {
2668 assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2669 DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n");
2671 for (IVChain::const_iterator I = Chain.begin(), E = Chain.end();
2673 DEBUG(dbgs() << " Inc: " << *I->UserInst << "\n");
2674 User::op_iterator UseI =
2675 std::find(I->UserInst->op_begin(), I->UserInst->op_end(), I->IVOperand);
2676 assert(UseI != I->UserInst->op_end() && "cannot find IV operand");
2677 IVIncSet.insert(UseI);
2681 /// Return true if the IVInc can be folded into an addressing mode.
2682 static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
2683 Value *Operand, const TargetLowering *TLI) {
2684 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
2685 if (!IncConst || !isAddressUse(UserInst, Operand))
2688 if (IncConst->getValue()->getValue().getMinSignedBits() > 64)
2691 int64_t IncOffset = IncConst->getValue()->getSExtValue();
2692 if (!isAlwaysFoldable(IncOffset, /*BaseGV=*/0, /*HaseBaseReg=*/false,
2693 LSRUse::Address, getAccessType(UserInst), TLI))
2699 /// GenerateIVChains - Generate an add or subtract for each IVInc in a chain to
2700 /// materialize the IV user's operand from the previous IV user's operand.
2701 void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
2702 SmallVectorImpl<WeakVH> &DeadInsts) {
2703 // Find the new IVOperand for the head of the chain. It may have been replaced
2705 const IVInc &Head = Chain.Incs[0];
2706 User::op_iterator IVOpEnd = Head.UserInst->op_end();
2707 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
2710 while (IVOpIter != IVOpEnd) {
2711 IVSrc = getWideOperand(*IVOpIter);
2713 // If this operand computes the expression that the chain needs, we may use
2714 // it. (Check this after setting IVSrc which is used below.)
2716 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
2717 // narrow for the chain, so we can no longer use it. We do allow using a
2718 // wider phi, assuming the LSR checked for free truncation. In that case we
2719 // should already have a truncate on this operand such that
2720 // getSCEV(IVSrc) == IncExpr.
2721 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
2722 || SE.getSCEV(IVSrc) == Head.IncExpr) {
2725 IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE);
2727 if (IVOpIter == IVOpEnd) {
2728 // Gracefully give up on this chain.
2729 DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
2733 DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
2734 Type *IVTy = IVSrc->getType();
2735 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
2736 const SCEV *LeftOverExpr = 0;
2737 for (IVChain::const_iterator IncI = Chain.begin(),
2738 IncE = Chain.end(); IncI != IncE; ++IncI) {
2740 Instruction *InsertPt = IncI->UserInst;
2741 if (isa<PHINode>(InsertPt))
2742 InsertPt = L->getLoopLatch()->getTerminator();
2744 // IVOper will replace the current IV User's operand. IVSrc is the IV
2745 // value currently held in a register.
2746 Value *IVOper = IVSrc;
2747 if (!IncI->IncExpr->isZero()) {
2748 // IncExpr was the result of subtraction of two narrow values, so must
2750 const SCEV *IncExpr = SE.getNoopOrSignExtend(IncI->IncExpr, IntTy);
2751 LeftOverExpr = LeftOverExpr ?
2752 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
2754 if (LeftOverExpr && !LeftOverExpr->isZero()) {
2755 // Expand the IV increment.
2756 Rewriter.clearPostInc();
2757 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
2758 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
2759 SE.getUnknown(IncV));
2760 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
2762 // If an IV increment can't be folded, use it as the next IV value.
2763 if (!canFoldIVIncExpr(LeftOverExpr, IncI->UserInst, IncI->IVOperand,
2765 assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
2770 Type *OperTy = IncI->IVOperand->getType();
2771 if (IVTy != OperTy) {
2772 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
2773 "cannot extend a chained IV");
2774 IRBuilder<> Builder(InsertPt);
2775 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
2777 IncI->UserInst->replaceUsesOfWith(IncI->IVOperand, IVOper);
2778 DeadInsts.push_back(IncI->IVOperand);
2780 // If LSR created a new, wider phi, we may also replace its postinc. We only
2781 // do this if we also found a wide value for the head of the chain.
2782 if (isa<PHINode>(Chain.tailUserInst())) {
2783 for (BasicBlock::iterator I = L->getHeader()->begin();
2784 PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
2785 if (!isCompatibleIVType(Phi, IVSrc))
2787 Instruction *PostIncV = dyn_cast<Instruction>(
2788 Phi->getIncomingValueForBlock(L->getLoopLatch()));
2789 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
2791 Value *IVOper = IVSrc;
2792 Type *PostIncTy = PostIncV->getType();
2793 if (IVTy != PostIncTy) {
2794 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
2795 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
2796 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
2797 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
2799 Phi->replaceUsesOfWith(PostIncV, IVOper);
2800 DeadInsts.push_back(PostIncV);
2805 void LSRInstance::CollectFixupsAndInitialFormulae() {
2806 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2807 Instruction *UserInst = UI->getUser();
2808 // Skip IV users that are part of profitable IV Chains.
2809 User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(),
2810 UI->getOperandValToReplace());
2811 assert(UseI != UserInst->op_end() && "cannot find IV operand");
2812 if (IVIncSet.count(UseI))
2816 LSRFixup &LF = getNewFixup();
2817 LF.UserInst = UserInst;
2818 LF.OperandValToReplace = UI->getOperandValToReplace();
2819 LF.PostIncLoops = UI->getPostIncLoops();
2821 LSRUse::KindType Kind = LSRUse::Basic;
2823 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
2824 Kind = LSRUse::Address;
2825 AccessTy = getAccessType(LF.UserInst);
2828 const SCEV *S = IU.getExpr(*UI);
2830 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
2831 // (N - i == 0), and this allows (N - i) to be the expression that we work
2832 // with rather than just N or i, so we can consider the register
2833 // requirements for both N and i at the same time. Limiting this code to
2834 // equality icmps is not a problem because all interesting loops use
2835 // equality icmps, thanks to IndVarSimplify.
2836 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
2837 if (CI->isEquality()) {
2838 // Swap the operands if needed to put the OperandValToReplace on the
2839 // left, for consistency.
2840 Value *NV = CI->getOperand(1);
2841 if (NV == LF.OperandValToReplace) {
2842 CI->setOperand(1, CI->getOperand(0));
2843 CI->setOperand(0, NV);
2844 NV = CI->getOperand(1);
2848 // x == y --> x - y == 0
2849 const SCEV *N = SE.getSCEV(NV);
2850 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N)) {
2851 // S is normalized, so normalize N before folding it into S
2852 // to keep the result normalized.
2853 N = TransformForPostIncUse(Normalize, N, CI, 0,
2854 LF.PostIncLoops, SE, DT);
2855 Kind = LSRUse::ICmpZero;
2856 S = SE.getMinusSCEV(N, S);
2859 // -1 and the negations of all interesting strides (except the negation
2860 // of -1) are now also interesting.
2861 for (size_t i = 0, e = Factors.size(); i != e; ++i)
2862 if (Factors[i] != -1)
2863 Factors.insert(-(uint64_t)Factors[i]);
2867 // Set up the initial formula for this use.
2868 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
2870 LF.Offset = P.second;
2871 LSRUse &LU = Uses[LF.LUIdx];
2872 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
2873 if (!LU.WidestFixupType ||
2874 SE.getTypeSizeInBits(LU.WidestFixupType) <
2875 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
2876 LU.WidestFixupType = LF.OperandValToReplace->getType();
2878 // If this is the first use of this LSRUse, give it a formula.
2879 if (LU.Formulae.empty()) {
2880 InsertInitialFormula(S, LU, LF.LUIdx);
2881 CountRegisters(LU.Formulae.back(), LF.LUIdx);
2885 DEBUG(print_fixups(dbgs()));
2888 /// InsertInitialFormula - Insert a formula for the given expression into
2889 /// the given use, separating out loop-variant portions from loop-invariant
2890 /// and loop-computable portions.
2892 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
2894 F.InitialMatch(S, L, SE);
2895 bool Inserted = InsertFormula(LU, LUIdx, F);
2896 assert(Inserted && "Initial formula already exists!"); (void)Inserted;
2899 /// InsertSupplementalFormula - Insert a simple single-register formula for
2900 /// the given expression into the given use.
2902 LSRInstance::InsertSupplementalFormula(const SCEV *S,
2903 LSRUse &LU, size_t LUIdx) {
2905 F.BaseRegs.push_back(S);
2906 F.AM.HasBaseReg = true;
2907 bool Inserted = InsertFormula(LU, LUIdx, F);
2908 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
2911 /// CountRegisters - Note which registers are used by the given formula,
2912 /// updating RegUses.
2913 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
2915 RegUses.CountRegister(F.ScaledReg, LUIdx);
2916 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
2917 E = F.BaseRegs.end(); I != E; ++I)
2918 RegUses.CountRegister(*I, LUIdx);
2921 /// InsertFormula - If the given formula has not yet been inserted, add it to
2922 /// the list, and return true. Return false otherwise.
2923 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
2924 if (!LU.InsertFormula(F))
2927 CountRegisters(F, LUIdx);
2931 /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
2932 /// loop-invariant values which we're tracking. These other uses will pin these
2933 /// values in registers, making them less profitable for elimination.
2934 /// TODO: This currently misses non-constant addrec step registers.
2935 /// TODO: Should this give more weight to users inside the loop?
2937 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
2938 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
2939 SmallPtrSet<const SCEV *, 8> Inserted;
2941 while (!Worklist.empty()) {
2942 const SCEV *S = Worklist.pop_back_val();
2944 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
2945 Worklist.append(N->op_begin(), N->op_end());
2946 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
2947 Worklist.push_back(C->getOperand());
2948 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
2949 Worklist.push_back(D->getLHS());
2950 Worklist.push_back(D->getRHS());
2951 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2952 if (!Inserted.insert(U)) continue;
2953 const Value *V = U->getValue();
2954 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
2955 // Look for instructions defined outside the loop.
2956 if (L->contains(Inst)) continue;
2957 } else if (isa<UndefValue>(V))
2958 // Undef doesn't have a live range, so it doesn't matter.
2960 for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
2962 const Instruction *UserInst = dyn_cast<Instruction>(*UI);
2963 // Ignore non-instructions.
2966 // Ignore instructions in other functions (as can happen with
2968 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
2970 // Ignore instructions not dominated by the loop.
2971 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
2972 UserInst->getParent() :
2973 cast<PHINode>(UserInst)->getIncomingBlock(
2974 PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
2975 if (!DT.dominates(L->getHeader(), UseBB))
2977 // Ignore uses which are part of other SCEV expressions, to avoid
2978 // analyzing them multiple times.
2979 if (SE.isSCEVable(UserInst->getType())) {
2980 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
2981 // If the user is a no-op, look through to its uses.
2982 if (!isa<SCEVUnknown>(UserS))
2986 SE.getUnknown(const_cast<Instruction *>(UserInst)));
2990 // Ignore icmp instructions which are already being analyzed.
2991 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
2992 unsigned OtherIdx = !UI.getOperandNo();
2993 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
2994 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
2998 LSRFixup &LF = getNewFixup();
2999 LF.UserInst = const_cast<Instruction *>(UserInst);
3000 LF.OperandValToReplace = UI.getUse();
3001 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0);
3003 LF.Offset = P.second;
3004 LSRUse &LU = Uses[LF.LUIdx];
3005 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3006 if (!LU.WidestFixupType ||
3007 SE.getTypeSizeInBits(LU.WidestFixupType) <
3008 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3009 LU.WidestFixupType = LF.OperandValToReplace->getType();
3010 InsertSupplementalFormula(U, LU, LF.LUIdx);
3011 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3018 /// CollectSubexprs - Split S into subexpressions which can be pulled out into
3019 /// separate registers. If C is non-null, multiply each subexpression by C.
3021 /// Return remainder expression after factoring the subexpressions captured by
3022 /// Ops. If Ops is complete, return NULL.
3023 static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3024 SmallVectorImpl<const SCEV *> &Ops,
3026 ScalarEvolution &SE,
3027 unsigned Depth = 0) {
3028 // Arbitrarily cap recursion to protect compile time.
3032 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3033 // Break out add operands.
3034 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
3036 const SCEV *Remainder = CollectSubexprs(*I, C, Ops, L, SE, Depth+1);
3038 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3041 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3042 // Split a non-zero base out of an addrec.
3043 if (AR->getStart()->isZero())
3046 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3047 C, Ops, L, SE, Depth+1);
3048 // Split the non-zero AddRec unless it is part of a nested recurrence that
3049 // does not pertain to this loop.
3050 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3051 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3054 if (Remainder != AR->getStart()) {
3056 Remainder = SE.getConstant(AR->getType(), 0);
3057 return SE.getAddRecExpr(Remainder,
3058 AR->getStepRecurrence(SE),
3060 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3063 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3064 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3065 if (Mul->getNumOperands() != 2)
3067 if (const SCEVConstant *Op0 =
3068 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3069 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3070 const SCEV *Remainder =
3071 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3073 Ops.push_back(SE.getMulExpr(C, Remainder));
3080 /// GenerateReassociations - Split out subexpressions from adds and the bases of
3082 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3085 // Arbitrarily cap recursion to protect compile time.
3086 if (Depth >= 3) return;
3088 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3089 const SCEV *BaseReg = Base.BaseRegs[i];
3091 SmallVector<const SCEV *, 8> AddOps;
3092 const SCEV *Remainder = CollectSubexprs(BaseReg, 0, AddOps, L, SE);
3094 AddOps.push_back(Remainder);
3096 if (AddOps.size() == 1) continue;
3098 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3099 JE = AddOps.end(); J != JE; ++J) {
3101 // Loop-variant "unknown" values are uninteresting; we won't be able to
3102 // do anything meaningful with them.
3103 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3106 // Don't pull a constant into a register if the constant could be folded
3107 // into an immediate field.
3108 if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,
3109 Base.getNumRegs() > 1,
3110 LU.Kind, LU.AccessTy, TLI, SE))
3113 // Collect all operands except *J.
3114 SmallVector<const SCEV *, 8> InnerAddOps
3115 (((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3117 (llvm::next(J), ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3119 // Don't leave just a constant behind in a register if the constant could
3120 // be folded into an immediate field.
3121 if (InnerAddOps.size() == 1 &&
3122 isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset,
3123 Base.getNumRegs() > 1,
3124 LU.Kind, LU.AccessTy, TLI, SE))
3127 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3128 if (InnerSum->isZero())
3132 // Add the remaining pieces of the add back into the new formula.
3133 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3134 if (TLI && InnerSumSC &&
3135 SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3136 TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3137 InnerSumSC->getValue()->getZExtValue())) {
3138 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
3139 InnerSumSC->getValue()->getZExtValue();
3140 F.BaseRegs.erase(F.BaseRegs.begin() + i);
3142 F.BaseRegs[i] = InnerSum;
3144 // Add J as its own register, or an unfolded immediate.
3145 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3146 if (TLI && SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3147 TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3148 SC->getValue()->getZExtValue()))
3149 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
3150 SC->getValue()->getZExtValue();
3152 F.BaseRegs.push_back(*J);
3154 if (InsertFormula(LU, LUIdx, F))
3155 // If that formula hadn't been seen before, recurse to find more like
3157 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1);
3162 /// GenerateCombinations - Generate a formula consisting of all of the
3163 /// loop-dominating registers added into a single register.
3164 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3166 // This method is only interesting on a plurality of registers.
3167 if (Base.BaseRegs.size() <= 1) return;
3171 SmallVector<const SCEV *, 4> Ops;
3172 for (SmallVectorImpl<const SCEV *>::const_iterator
3173 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
3174 const SCEV *BaseReg = *I;
3175 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3176 !SE.hasComputableLoopEvolution(BaseReg, L))
3177 Ops.push_back(BaseReg);
3179 F.BaseRegs.push_back(BaseReg);
3181 if (Ops.size() > 1) {
3182 const SCEV *Sum = SE.getAddExpr(Ops);
3183 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3184 // opportunity to fold something. For now, just ignore such cases
3185 // rather than proceed with zero in a register.
3186 if (!Sum->isZero()) {
3187 F.BaseRegs.push_back(Sum);
3188 (void)InsertFormula(LU, LUIdx, F);
3193 /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
3194 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3196 // We can't add a symbolic offset if the address already contains one.
3197 if (Base.AM.BaseGV) return;
3199 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3200 const SCEV *G = Base.BaseRegs[i];
3201 GlobalValue *GV = ExtractSymbol(G, SE);
3202 if (G->isZero() || !GV)
3206 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
3207 LU.Kind, LU.AccessTy, TLI))
3210 (void)InsertFormula(LU, LUIdx, F);
3214 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3215 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3217 // TODO: For now, just add the min and max offset, because it usually isn't
3218 // worthwhile looking at everything inbetween.
3219 SmallVector<int64_t, 2> Worklist;
3220 Worklist.push_back(LU.MinOffset);
3221 if (LU.MaxOffset != LU.MinOffset)
3222 Worklist.push_back(LU.MaxOffset);
3224 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3225 const SCEV *G = Base.BaseRegs[i];
3227 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
3228 E = Worklist.end(); I != E; ++I) {
3230 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I;
3231 if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I,
3232 LU.Kind, LU.AccessTy, TLI)) {
3233 // Add the offset to the base register.
3234 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G);
3235 // If it cancelled out, drop the base register, otherwise update it.
3236 if (NewG->isZero()) {
3237 std::swap(F.BaseRegs[i], F.BaseRegs.back());
3238 F.BaseRegs.pop_back();
3240 F.BaseRegs[i] = NewG;
3242 (void)InsertFormula(LU, LUIdx, F);
3246 int64_t Imm = ExtractImmediate(G, SE);
3247 if (G->isZero() || Imm == 0)
3250 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm;
3251 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
3252 LU.Kind, LU.AccessTy, TLI))
3255 (void)InsertFormula(LU, LUIdx, F);
3259 /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
3260 /// the comparison. For example, x == y -> x*c == y*c.
3261 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3263 if (LU.Kind != LSRUse::ICmpZero) return;
3265 // Determine the integer type for the base formula.
3266 Type *IntTy = Base.getType();
3268 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3270 // Don't do this if there is more than one offset.
3271 if (LU.MinOffset != LU.MaxOffset) return;
3273 assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
3275 // Check each interesting stride.
3276 for (SmallSetVector<int64_t, 8>::const_iterator
3277 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3278 int64_t Factor = *I;
3280 // Check that the multiplication doesn't overflow.
3281 if (Base.AM.BaseOffs == INT64_MIN && Factor == -1)
3283 int64_t NewBaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
3284 if (NewBaseOffs / Factor != Base.AM.BaseOffs)
3287 // Check that multiplying with the use offset doesn't overflow.
3288 int64_t Offset = LU.MinOffset;
3289 if (Offset == INT64_MIN && Factor == -1)
3291 Offset = (uint64_t)Offset * Factor;
3292 if (Offset / Factor != LU.MinOffset)
3296 F.AM.BaseOffs = NewBaseOffs;
3298 // Check that this scale is legal.
3299 if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI))
3302 // Compensate for the use having MinOffset built into it.
3303 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset;
3305 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3307 // Check that multiplying with each base register doesn't overflow.
3308 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3309 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3310 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3314 // Check that multiplying with the scaled register doesn't overflow.
3316 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3317 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3321 // Check that multiplying with the unfolded offset doesn't overflow.
3322 if (F.UnfoldedOffset != 0) {
3323 if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
3325 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3326 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3330 // If we make it here and it's legal, add it.
3331 (void)InsertFormula(LU, LUIdx, F);
3336 /// GenerateScales - Generate stride factor reuse formulae by making use of
3337 /// scaled-offset address modes, for example.
3338 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3339 // Determine the integer type for the base formula.
3340 Type *IntTy = Base.getType();
3343 // If this Formula already has a scaled register, we can't add another one.
3344 if (Base.AM.Scale != 0) return;
3346 // Check each interesting stride.
3347 for (SmallSetVector<int64_t, 8>::const_iterator
3348 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3349 int64_t Factor = *I;
3351 Base.AM.Scale = Factor;
3352 Base.AM.HasBaseReg = Base.BaseRegs.size() > 1;
3353 // Check whether this scale is going to be legal.
3354 if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
3355 LU.Kind, LU.AccessTy, TLI)) {
3356 // As a special-case, handle special out-of-loop Basic users specially.
3357 // TODO: Reconsider this special case.
3358 if (LU.Kind == LSRUse::Basic &&
3359 isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
3360 LSRUse::Special, LU.AccessTy, TLI) &&
3361 LU.AllFixupsOutsideLoop)
3362 LU.Kind = LSRUse::Special;
3366 // For an ICmpZero, negating a solitary base register won't lead to
3368 if (LU.Kind == LSRUse::ICmpZero &&
3369 !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV)
3371 // For each addrec base reg, apply the scale, if possible.
3372 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3373 if (const SCEVAddRecExpr *AR =
3374 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
3375 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3376 if (FactorS->isZero())
3378 // Divide out the factor, ignoring high bits, since we'll be
3379 // scaling the value back up in the end.
3380 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3381 // TODO: This could be optimized to avoid all the copying.
3383 F.ScaledReg = Quotient;
3384 F.DeleteBaseReg(F.BaseRegs[i]);
3385 (void)InsertFormula(LU, LUIdx, F);
3391 /// GenerateTruncates - Generate reuse formulae from different IV types.
3392 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3393 // This requires TargetLowering to tell us which truncates are free.
3396 // Don't bother truncating symbolic values.
3397 if (Base.AM.BaseGV) return;
3399 // Determine the integer type for the base formula.
3400 Type *DstTy = Base.getType();
3402 DstTy = SE.getEffectiveSCEVType(DstTy);
3404 for (SmallSetVector<Type *, 4>::const_iterator
3405 I = Types.begin(), E = Types.end(); I != E; ++I) {
3407 if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
3410 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
3411 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
3412 JE = F.BaseRegs.end(); J != JE; ++J)
3413 *J = SE.getAnyExtendExpr(*J, SrcTy);
3415 // TODO: This assumes we've done basic processing on all uses and
3416 // have an idea what the register usage is.
3417 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3420 (void)InsertFormula(LU, LUIdx, F);
3427 /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
3428 /// defer modifications so that the search phase doesn't have to worry about
3429 /// the data structures moving underneath it.
3433 const SCEV *OrigReg;
3435 WorkItem(size_t LI, int64_t I, const SCEV *R)
3436 : LUIdx(LI), Imm(I), OrigReg(R) {}
3438 void print(raw_ostream &OS) const;
3444 void WorkItem::print(raw_ostream &OS) const {
3445 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3446 << " , add offset " << Imm;
3449 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
3450 void WorkItem::dump() const {
3451 print(errs()); errs() << '\n';
3455 /// GenerateCrossUseConstantOffsets - Look for registers which are a constant
3456 /// distance apart and try to form reuse opportunities between them.
3457 void LSRInstance::GenerateCrossUseConstantOffsets() {
3458 // Group the registers by their value without any added constant offset.
3459 typedef std::map<int64_t, const SCEV *> ImmMapTy;
3460 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
3462 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3463 SmallVector<const SCEV *, 8> Sequence;
3464 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
3466 const SCEV *Reg = *I;
3467 int64_t Imm = ExtractImmediate(Reg, SE);
3468 std::pair<RegMapTy::iterator, bool> Pair =
3469 Map.insert(std::make_pair(Reg, ImmMapTy()));
3471 Sequence.push_back(Reg);
3472 Pair.first->second.insert(std::make_pair(Imm, *I));
3473 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
3476 // Now examine each set of registers with the same base value. Build up
3477 // a list of work to do and do the work in a separate step so that we're
3478 // not adding formulae and register counts while we're searching.
3479 SmallVector<WorkItem, 32> WorkItems;
3480 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3481 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
3482 E = Sequence.end(); I != E; ++I) {
3483 const SCEV *Reg = *I;
3484 const ImmMapTy &Imms = Map.find(Reg)->second;
3486 // It's not worthwhile looking for reuse if there's only one offset.
3487 if (Imms.size() == 1)
3490 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
3491 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3493 dbgs() << ' ' << J->first;
3496 // Examine each offset.
3497 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3499 const SCEV *OrigReg = J->second;
3501 int64_t JImm = J->first;
3502 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
3504 if (!isa<SCEVConstant>(OrigReg) &&
3505 UsedByIndicesMap[Reg].count() == 1) {
3506 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
3510 // Conservatively examine offsets between this orig reg a few selected
3512 ImmMapTy::const_iterator OtherImms[] = {
3513 Imms.begin(), prior(Imms.end()),
3514 Imms.lower_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
3516 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
3517 ImmMapTy::const_iterator M = OtherImms[i];
3518 if (M == J || M == JE) continue;
3520 // Compute the difference between the two.
3521 int64_t Imm = (uint64_t)JImm - M->first;
3522 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
3523 LUIdx = UsedByIndices.find_next(LUIdx))
3524 // Make a memo of this use, offset, and register tuple.
3525 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
3526 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
3533 UsedByIndicesMap.clear();
3534 UniqueItems.clear();
3536 // Now iterate through the worklist and add new formulae.
3537 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
3538 E = WorkItems.end(); I != E; ++I) {
3539 const WorkItem &WI = *I;
3540 size_t LUIdx = WI.LUIdx;
3541 LSRUse &LU = Uses[LUIdx];
3542 int64_t Imm = WI.Imm;
3543 const SCEV *OrigReg = WI.OrigReg;
3545 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
3546 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
3547 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
3549 // TODO: Use a more targeted data structure.
3550 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
3551 const Formula &F = LU.Formulae[L];
3552 // Use the immediate in the scaled register.
3553 if (F.ScaledReg == OrigReg) {
3554 int64_t Offs = (uint64_t)F.AM.BaseOffs +
3555 Imm * (uint64_t)F.AM.Scale;
3556 // Don't create 50 + reg(-50).
3557 if (F.referencesReg(SE.getSCEV(
3558 ConstantInt::get(IntTy, -(uint64_t)Offs))))
3561 NewF.AM.BaseOffs = Offs;
3562 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
3563 LU.Kind, LU.AccessTy, TLI))
3565 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
3567 // If the new scale is a constant in a register, and adding the constant
3568 // value to the immediate would produce a value closer to zero than the
3569 // immediate itself, then the formula isn't worthwhile.
3570 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
3571 if (C->getValue()->isNegative() !=
3572 (NewF.AM.BaseOffs < 0) &&
3573 (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale))
3574 .ule(abs64(NewF.AM.BaseOffs)))
3578 (void)InsertFormula(LU, LUIdx, NewF);
3580 // Use the immediate in a base register.
3581 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
3582 const SCEV *BaseReg = F.BaseRegs[N];
3583 if (BaseReg != OrigReg)
3586 NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
3587 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
3588 LU.Kind, LU.AccessTy, TLI)) {
3590 !TLI->isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
3593 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
3595 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
3597 // If the new formula has a constant in a register, and adding the
3598 // constant value to the immediate would produce a value closer to
3599 // zero than the immediate itself, then the formula isn't worthwhile.
3600 for (SmallVectorImpl<const SCEV *>::const_iterator
3601 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
3603 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
3604 if ((C->getValue()->getValue() + NewF.AM.BaseOffs).abs().slt(
3605 abs64(NewF.AM.BaseOffs)) &&
3606 (C->getValue()->getValue() +
3607 NewF.AM.BaseOffs).countTrailingZeros() >=
3608 CountTrailingZeros_64(NewF.AM.BaseOffs))
3612 (void)InsertFormula(LU, LUIdx, NewF);
3621 /// GenerateAllReuseFormulae - Generate formulae for each use.
3623 LSRInstance::GenerateAllReuseFormulae() {
3624 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
3625 // queries are more precise.
3626 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3627 LSRUse &LU = Uses[LUIdx];
3628 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3629 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
3630 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3631 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
3633 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3634 LSRUse &LU = Uses[LUIdx];
3635 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3636 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
3637 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3638 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
3639 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3640 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
3641 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3642 GenerateScales(LU, LUIdx, LU.Formulae[i]);
3644 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3645 LSRUse &LU = Uses[LUIdx];
3646 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3647 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
3650 GenerateCrossUseConstantOffsets();
3652 DEBUG(dbgs() << "\n"
3653 "After generating reuse formulae:\n";
3654 print_uses(dbgs()));
3657 /// If there are multiple formulae with the same set of registers used
3658 /// by other uses, pick the best one and delete the others.
3659 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
3660 DenseSet<const SCEV *> VisitedRegs;
3661 SmallPtrSet<const SCEV *, 16> Regs;
3662 SmallPtrSet<const SCEV *, 16> LoserRegs;
3664 bool ChangedFormulae = false;
3667 // Collect the best formula for each unique set of shared registers. This
3668 // is reset for each use.
3669 typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo>
3671 BestFormulaeTy BestFormulae;
3673 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3674 LSRUse &LU = Uses[LUIdx];
3675 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
3678 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
3679 FIdx != NumForms; ++FIdx) {
3680 Formula &F = LU.Formulae[FIdx];
3682 // Some formulas are instant losers. For example, they may depend on
3683 // nonexistent AddRecs from other loops. These need to be filtered
3684 // immediately, otherwise heuristics could choose them over others leading
3685 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
3686 // avoids the need to recompute this information across formulae using the
3687 // same bad AddRec. Passing LoserRegs is also essential unless we remove
3688 // the corresponding bad register from the Regs set.
3691 CostF.RateFormula(F, Regs, VisitedRegs, L, LU.Offsets, SE, DT,
3693 if (CostF.isLoser()) {
3694 // During initial formula generation, undesirable formulae are generated
3695 // by uses within other loops that have some non-trivial address mode or
3696 // use the postinc form of the IV. LSR needs to provide these formulae
3697 // as the basis of rediscovering the desired formula that uses an AddRec
3698 // corresponding to the existing phi. Once all formulae have been
3699 // generated, these initial losers may be pruned.
3700 DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());
3704 SmallVector<const SCEV *, 2> Key;
3705 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
3706 JE = F.BaseRegs.end(); J != JE; ++J) {
3707 const SCEV *Reg = *J;
3708 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
3712 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
3713 Key.push_back(F.ScaledReg);
3714 // Unstable sort by host order ok, because this is only used for
3716 std::sort(Key.begin(), Key.end());
3718 std::pair<BestFormulaeTy::const_iterator, bool> P =
3719 BestFormulae.insert(std::make_pair(Key, FIdx));
3723 Formula &Best = LU.Formulae[P.first->second];
3727 CostBest.RateFormula(Best, Regs, VisitedRegs, L, LU.Offsets, SE, DT);
3728 if (CostF < CostBest)
3730 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
3732 " in favor of formula "; Best.print(dbgs());
3736 ChangedFormulae = true;
3738 LU.DeleteFormula(F);
3744 // Now that we've filtered out some formulae, recompute the Regs set.
3746 LU.RecomputeRegs(LUIdx, RegUses);
3748 // Reset this to prepare for the next use.
3749 BestFormulae.clear();
3752 DEBUG(if (ChangedFormulae) {
3754 "After filtering out undesirable candidates:\n";
3759 // This is a rough guess that seems to work fairly well.
3760 static const size_t ComplexityLimit = UINT16_MAX;
3762 /// EstimateSearchSpaceComplexity - Estimate the worst-case number of
3763 /// solutions the solver might have to consider. It almost never considers
3764 /// this many solutions because it prune the search space, but the pruning
3765 /// isn't always sufficient.
3766 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
3768 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3769 E = Uses.end(); I != E; ++I) {
3770 size_t FSize = I->Formulae.size();
3771 if (FSize >= ComplexityLimit) {
3772 Power = ComplexityLimit;
3776 if (Power >= ComplexityLimit)
3782 /// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset
3783 /// of the registers of another formula, it won't help reduce register
3784 /// pressure (though it may not necessarily hurt register pressure); remove
3785 /// it to simplify the system.
3786 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
3787 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3788 DEBUG(dbgs() << "The search space is too complex.\n");
3790 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
3791 "which use a superset of registers used by other "
3794 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3795 LSRUse &LU = Uses[LUIdx];
3797 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
3798 Formula &F = LU.Formulae[i];
3799 // Look for a formula with a constant or GV in a register. If the use
3800 // also has a formula with that same value in an immediate field,
3801 // delete the one that uses a register.
3802 for (SmallVectorImpl<const SCEV *>::const_iterator
3803 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
3804 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
3806 NewF.AM.BaseOffs += C->getValue()->getSExtValue();
3807 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
3808 (I - F.BaseRegs.begin()));
3809 if (LU.HasFormulaWithSameRegs(NewF)) {
3810 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
3811 LU.DeleteFormula(F);
3817 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
3818 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
3821 NewF.AM.BaseGV = GV;
3822 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
3823 (I - F.BaseRegs.begin()));
3824 if (LU.HasFormulaWithSameRegs(NewF)) {
3825 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
3827 LU.DeleteFormula(F);
3838 LU.RecomputeRegs(LUIdx, RegUses);
3841 DEBUG(dbgs() << "After pre-selection:\n";
3842 print_uses(dbgs()));
3846 /// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers
3847 /// for expressions like A, A+1, A+2, etc., allocate a single register for
3849 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
3850 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3851 DEBUG(dbgs() << "The search space is too complex.\n");
3853 DEBUG(dbgs() << "Narrowing the search space by assuming that uses "
3854 "separated by a constant offset will use the same "
3857 // This is especially useful for unrolled loops.
3859 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3860 LSRUse &LU = Uses[LUIdx];
3861 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
3862 E = LU.Formulae.end(); I != E; ++I) {
3863 const Formula &F = *I;
3864 if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) {
3865 if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) {
3866 if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs,
3867 /*HasBaseReg=*/false,
3868 LU.Kind, LU.AccessTy)) {
3869 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs());
3872 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
3874 // Update the relocs to reference the new use.
3875 for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
3876 E = Fixups.end(); I != E; ++I) {
3877 LSRFixup &Fixup = *I;
3878 if (Fixup.LUIdx == LUIdx) {
3879 Fixup.LUIdx = LUThatHas - &Uses.front();
3880 Fixup.Offset += F.AM.BaseOffs;
3881 // Add the new offset to LUThatHas' offset list.
3882 if (LUThatHas->Offsets.back() != Fixup.Offset) {
3883 LUThatHas->Offsets.push_back(Fixup.Offset);
3884 if (Fixup.Offset > LUThatHas->MaxOffset)
3885 LUThatHas->MaxOffset = Fixup.Offset;
3886 if (Fixup.Offset < LUThatHas->MinOffset)
3887 LUThatHas->MinOffset = Fixup.Offset;
3889 DEBUG(dbgs() << "New fixup has offset "
3890 << Fixup.Offset << '\n');
3892 if (Fixup.LUIdx == NumUses-1)
3893 Fixup.LUIdx = LUIdx;
3896 // Delete formulae from the new use which are no longer legal.
3898 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
3899 Formula &F = LUThatHas->Formulae[i];
3900 if (!isLegalUse(F.AM,
3901 LUThatHas->MinOffset, LUThatHas->MaxOffset,
3902 LUThatHas->Kind, LUThatHas->AccessTy, TLI)) {
3903 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
3905 LUThatHas->DeleteFormula(F);
3912 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
3914 // Delete the old use.
3915 DeleteUse(LU, LUIdx);
3925 DEBUG(dbgs() << "After pre-selection:\n";
3926 print_uses(dbgs()));
3930 /// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call
3931 /// FilterOutUndesirableDedicatedRegisters again, if necessary, now that
3932 /// we've done more filtering, as it may be able to find more formulae to
3934 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
3935 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3936 DEBUG(dbgs() << "The search space is too complex.\n");
3938 DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
3939 "undesirable dedicated registers.\n");
3941 FilterOutUndesirableDedicatedRegisters();
3943 DEBUG(dbgs() << "After pre-selection:\n";
3944 print_uses(dbgs()));
3948 /// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely
3949 /// to be profitable, and then in any use which has any reference to that
3950 /// register, delete all formulae which do not reference that register.
3951 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
3952 // With all other options exhausted, loop until the system is simple
3953 // enough to handle.
3954 SmallPtrSet<const SCEV *, 4> Taken;
3955 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3956 // Ok, we have too many of formulae on our hands to conveniently handle.
3957 // Use a rough heuristic to thin out the list.
3958 DEBUG(dbgs() << "The search space is too complex.\n");
3960 // Pick the register which is used by the most LSRUses, which is likely
3961 // to be a good reuse register candidate.
3962 const SCEV *Best = 0;
3963 unsigned BestNum = 0;
3964 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
3966 const SCEV *Reg = *I;
3967 if (Taken.count(Reg))
3972 unsigned Count = RegUses.getUsedByIndices(Reg).count();
3973 if (Count > BestNum) {
3980 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
3981 << " will yield profitable reuse.\n");
3984 // In any use with formulae which references this register, delete formulae
3985 // which don't reference it.
3986 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3987 LSRUse &LU = Uses[LUIdx];
3988 if (!LU.Regs.count(Best)) continue;
3991 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
3992 Formula &F = LU.Formulae[i];
3993 if (!F.referencesReg(Best)) {
3994 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
3995 LU.DeleteFormula(F);
3999 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
4005 LU.RecomputeRegs(LUIdx, RegUses);
4008 DEBUG(dbgs() << "After pre-selection:\n";
4009 print_uses(dbgs()));
4013 /// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
4014 /// formulae to choose from, use some rough heuristics to prune down the number
4015 /// of formulae. This keeps the main solver from taking an extraordinary amount
4016 /// of time in some worst-case scenarios.
4017 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4018 NarrowSearchSpaceByDetectingSupersets();
4019 NarrowSearchSpaceByCollapsingUnrolledCode();
4020 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4021 NarrowSearchSpaceByPickingWinnerRegs();
4024 /// SolveRecurse - This is the recursive solver.
4025 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4027 SmallVectorImpl<const Formula *> &Workspace,
4028 const Cost &CurCost,
4029 const SmallPtrSet<const SCEV *, 16> &CurRegs,
4030 DenseSet<const SCEV *> &VisitedRegs) const {
4033 // - use more aggressive filtering
4034 // - sort the formula so that the most profitable solutions are found first
4035 // - sort the uses too
4037 // - don't compute a cost, and then compare. compare while computing a cost
4039 // - track register sets with SmallBitVector
4041 const LSRUse &LU = Uses[Workspace.size()];
4043 // If this use references any register that's already a part of the
4044 // in-progress solution, consider it a requirement that a formula must
4045 // reference that register in order to be considered. This prunes out
4046 // unprofitable searching.
4047 SmallSetVector<const SCEV *, 4> ReqRegs;
4048 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
4049 E = CurRegs.end(); I != E; ++I)
4050 if (LU.Regs.count(*I))
4053 SmallPtrSet<const SCEV *, 16> NewRegs;
4055 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
4056 E = LU.Formulae.end(); I != E; ++I) {
4057 const Formula &F = *I;
4059 // Ignore formulae which do not use any of the required registers.
4060 bool SatisfiedReqReg = true;
4061 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
4062 JE = ReqRegs.end(); J != JE; ++J) {
4063 const SCEV *Reg = *J;
4064 if ((!F.ScaledReg || F.ScaledReg != Reg) &&
4065 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) ==
4067 SatisfiedReqReg = false;
4071 if (!SatisfiedReqReg) {
4072 // If none of the formulae satisfied the required registers, then we could
4073 // clear ReqRegs and try again. Currently, we simply give up in this case.
4077 // Evaluate the cost of the current formula. If it's already worse than
4078 // the current best, prune the search at that point.
4081 NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT);
4082 if (NewCost < SolutionCost) {
4083 Workspace.push_back(&F);
4084 if (Workspace.size() != Uses.size()) {
4085 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4086 NewRegs, VisitedRegs);
4087 if (F.getNumRegs() == 1 && Workspace.size() == 1)
4088 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4090 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
4091 dbgs() << ".\n Regs:";
4092 for (SmallPtrSet<const SCEV *, 16>::const_iterator
4093 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
4094 dbgs() << ' ' << **I;
4097 SolutionCost = NewCost;
4098 Solution = Workspace;
4100 Workspace.pop_back();
4105 /// Solve - Choose one formula from each use. Return the results in the given
4106 /// Solution vector.
4107 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4108 SmallVector<const Formula *, 8> Workspace;
4110 SolutionCost.Loose();
4112 SmallPtrSet<const SCEV *, 16> CurRegs;
4113 DenseSet<const SCEV *> VisitedRegs;
4114 Workspace.reserve(Uses.size());
4116 // SolveRecurse does all the work.
4117 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4118 CurRegs, VisitedRegs);
4119 if (Solution.empty()) {
4120 DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
4124 // Ok, we've now made all our decisions.
4125 DEBUG(dbgs() << "\n"
4126 "The chosen solution requires "; SolutionCost.print(dbgs());
4128 for (size_t i = 0, e = Uses.size(); i != e; ++i) {
4130 Uses[i].print(dbgs());
4133 Solution[i]->print(dbgs());
4137 assert(Solution.size() == Uses.size() && "Malformed solution!");
4140 /// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
4141 /// the dominator tree far as we can go while still being dominated by the
4142 /// input positions. This helps canonicalize the insert position, which
4143 /// encourages sharing.
4144 BasicBlock::iterator
4145 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4146 const SmallVectorImpl<Instruction *> &Inputs)
4149 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4150 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4153 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4154 if (!Rung) return IP;
4155 Rung = Rung->getIDom();
4156 if (!Rung) return IP;
4157 IDom = Rung->getBlock();
4159 // Don't climb into a loop though.
4160 const Loop *IDomLoop = LI.getLoopFor(IDom);
4161 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4162 if (IDomDepth <= IPLoopDepth &&
4163 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4167 bool AllDominate = true;
4168 Instruction *BetterPos = 0;
4169 Instruction *Tentative = IDom->getTerminator();
4170 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
4171 E = Inputs.end(); I != E; ++I) {
4172 Instruction *Inst = *I;
4173 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4174 AllDominate = false;
4177 // Attempt to find an insert position in the middle of the block,
4178 // instead of at the end, so that it can be used for other expansions.
4179 if (IDom == Inst->getParent() &&
4180 (!BetterPos || !DT.dominates(Inst, BetterPos)))
4181 BetterPos = llvm::next(BasicBlock::iterator(Inst));
4194 /// AdjustInsertPositionForExpand - Determine an input position which will be
4195 /// dominated by the operands and which will dominate the result.
4196 BasicBlock::iterator
4197 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4200 SCEVExpander &Rewriter) const {
4201 // Collect some instructions which must be dominated by the
4202 // expanding replacement. These must be dominated by any operands that
4203 // will be required in the expansion.
4204 SmallVector<Instruction *, 4> Inputs;
4205 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4206 Inputs.push_back(I);
4207 if (LU.Kind == LSRUse::ICmpZero)
4208 if (Instruction *I =
4209 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4210 Inputs.push_back(I);
4211 if (LF.PostIncLoops.count(L)) {
4212 if (LF.isUseFullyOutsideLoop(L))
4213 Inputs.push_back(L->getLoopLatch()->getTerminator());
4215 Inputs.push_back(IVIncInsertPos);
4217 // The expansion must also be dominated by the increment positions of any
4218 // loops it for which it is using post-inc mode.
4219 for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(),
4220 E = LF.PostIncLoops.end(); I != E; ++I) {
4221 const Loop *PIL = *I;
4222 if (PIL == L) continue;
4224 // Be dominated by the loop exit.
4225 SmallVector<BasicBlock *, 4> ExitingBlocks;
4226 PIL->getExitingBlocks(ExitingBlocks);
4227 if (!ExitingBlocks.empty()) {
4228 BasicBlock *BB = ExitingBlocks[0];
4229 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4230 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4231 Inputs.push_back(BB->getTerminator());
4235 assert(!isa<PHINode>(LowestIP) && !isa<LandingPadInst>(LowestIP)
4236 && !isa<DbgInfoIntrinsic>(LowestIP) &&
4237 "Insertion point must be a normal instruction");
4239 // Then, climb up the immediate dominator tree as far as we can go while
4240 // still being dominated by the input positions.
4241 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4243 // Don't insert instructions before PHI nodes.
4244 while (isa<PHINode>(IP)) ++IP;
4246 // Ignore landingpad instructions.
4247 while (isa<LandingPadInst>(IP)) ++IP;
4249 // Ignore debug intrinsics.
4250 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4252 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4253 // IP consistent across expansions and allows the previously inserted
4254 // instructions to be reused by subsequent expansion.
4255 while (Rewriter.isInsertedInstruction(IP) && IP != LowestIP) ++IP;
4260 /// Expand - Emit instructions for the leading candidate expression for this
4261 /// LSRUse (this is called "expanding").
4262 Value *LSRInstance::Expand(const LSRFixup &LF,
4264 BasicBlock::iterator IP,
4265 SCEVExpander &Rewriter,
4266 SmallVectorImpl<WeakVH> &DeadInsts) const {
4267 const LSRUse &LU = Uses[LF.LUIdx];
4269 // Determine an input position which will be dominated by the operands and
4270 // which will dominate the result.
4271 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4273 // Inform the Rewriter if we have a post-increment use, so that it can
4274 // perform an advantageous expansion.
4275 Rewriter.setPostInc(LF.PostIncLoops);
4277 // This is the type that the user actually needs.
4278 Type *OpTy = LF.OperandValToReplace->getType();
4279 // This will be the type that we'll initially expand to.
4280 Type *Ty = F.getType();
4282 // No type known; just expand directly to the ultimate type.
4284 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
4285 // Expand directly to the ultimate type if it's the right size.
4287 // This is the type to do integer arithmetic in.
4288 Type *IntTy = SE.getEffectiveSCEVType(Ty);
4290 // Build up a list of operands to add together to form the full base.
4291 SmallVector<const SCEV *, 8> Ops;
4293 // Expand the BaseRegs portion.
4294 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
4295 E = F.BaseRegs.end(); I != E; ++I) {
4296 const SCEV *Reg = *I;
4297 assert(!Reg->isZero() && "Zero allocated in a base register!");
4299 // If we're expanding for a post-inc user, make the post-inc adjustment.
4300 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4301 Reg = TransformForPostIncUse(Denormalize, Reg,
4302 LF.UserInst, LF.OperandValToReplace,
4305 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
4308 // Expand the ScaledReg portion.
4309 Value *ICmpScaledV = 0;
4310 if (F.AM.Scale != 0) {
4311 const SCEV *ScaledS = F.ScaledReg;
4313 // If we're expanding for a post-inc user, make the post-inc adjustment.
4314 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4315 ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
4316 LF.UserInst, LF.OperandValToReplace,
4319 if (LU.Kind == LSRUse::ICmpZero) {
4320 // An interesting way of "folding" with an icmp is to use a negated
4321 // scale, which we'll implement by inserting it into the other operand
4323 assert(F.AM.Scale == -1 &&
4324 "The only scale supported by ICmpZero uses is -1!");
4325 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
4327 // Otherwise just expand the scaled register and an explicit scale,
4328 // which is expected to be matched as part of the address.
4330 // Flush the operand list to suppress SCEVExpander hoisting address modes.
4331 if (!Ops.empty() && LU.Kind == LSRUse::Address) {
4332 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4334 Ops.push_back(SE.getUnknown(FullV));
4336 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
4337 ScaledS = SE.getMulExpr(ScaledS,
4338 SE.getConstant(ScaledS->getType(), F.AM.Scale));
4339 Ops.push_back(ScaledS);
4343 // Expand the GV portion.
4345 // Flush the operand list to suppress SCEVExpander hoisting.
4347 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4349 Ops.push_back(SE.getUnknown(FullV));
4351 Ops.push_back(SE.getUnknown(F.AM.BaseGV));
4354 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
4355 // unfolded offsets. LSR assumes they both live next to their uses.
4357 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4359 Ops.push_back(SE.getUnknown(FullV));
4362 // Expand the immediate portion.
4363 int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset;
4365 if (LU.Kind == LSRUse::ICmpZero) {
4366 // The other interesting way of "folding" with an ICmpZero is to use a
4367 // negated immediate.
4369 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
4371 Ops.push_back(SE.getUnknown(ICmpScaledV));
4372 ICmpScaledV = ConstantInt::get(IntTy, Offset);
4375 // Just add the immediate values. These again are expected to be matched
4376 // as part of the address.
4377 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
4381 // Expand the unfolded offset portion.
4382 int64_t UnfoldedOffset = F.UnfoldedOffset;
4383 if (UnfoldedOffset != 0) {
4384 // Just add the immediate values.
4385 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
4389 // Emit instructions summing all the operands.
4390 const SCEV *FullS = Ops.empty() ?
4391 SE.getConstant(IntTy, 0) :
4393 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
4395 // We're done expanding now, so reset the rewriter.
4396 Rewriter.clearPostInc();
4398 // An ICmpZero Formula represents an ICmp which we're handling as a
4399 // comparison against zero. Now that we've expanded an expression for that
4400 // form, update the ICmp's other operand.
4401 if (LU.Kind == LSRUse::ICmpZero) {
4402 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
4403 DeadInsts.push_back(CI->getOperand(1));
4404 assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
4405 "a scale at the same time!");
4406 if (F.AM.Scale == -1) {
4407 if (ICmpScaledV->getType() != OpTy) {
4409 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
4411 ICmpScaledV, OpTy, "tmp", CI);
4414 CI->setOperand(1, ICmpScaledV);
4416 assert(F.AM.Scale == 0 &&
4417 "ICmp does not support folding a global value and "
4418 "a scale at the same time!");
4419 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
4421 if (C->getType() != OpTy)
4422 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4426 CI->setOperand(1, C);
4433 /// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
4434 /// of their operands effectively happens in their predecessor blocks, so the
4435 /// expression may need to be expanded in multiple places.
4436 void LSRInstance::RewriteForPHI(PHINode *PN,
4439 SCEVExpander &Rewriter,
4440 SmallVectorImpl<WeakVH> &DeadInsts,
4442 DenseMap<BasicBlock *, Value *> Inserted;
4443 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
4444 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
4445 BasicBlock *BB = PN->getIncomingBlock(i);
4447 // If this is a critical edge, split the edge so that we do not insert
4448 // the code on all predecessor/successor paths. We do this unless this
4449 // is the canonical backedge for this loop, which complicates post-inc
4451 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
4452 !isa<IndirectBrInst>(BB->getTerminator())) {
4453 BasicBlock *Parent = PN->getParent();
4454 Loop *PNLoop = LI.getLoopFor(Parent);
4455 if (!PNLoop || Parent != PNLoop->getHeader()) {
4456 // Split the critical edge.
4457 BasicBlock *NewBB = 0;
4458 if (!Parent->isLandingPad()) {
4459 NewBB = SplitCriticalEdge(BB, Parent, P,
4460 /*MergeIdenticalEdges=*/true,
4461 /*DontDeleteUselessPhis=*/true);
4463 SmallVector<BasicBlock*, 2> NewBBs;
4464 SplitLandingPadPredecessors(Parent, BB, "", "", P, NewBBs);
4467 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
4468 // phi predecessors are identical. The simple thing to do is skip
4469 // splitting in this case rather than complicate the API.
4471 // If PN is outside of the loop and BB is in the loop, we want to
4472 // move the block to be immediately before the PHI block, not
4473 // immediately after BB.
4474 if (L->contains(BB) && !L->contains(PN))
4475 NewBB->moveBefore(PN->getParent());
4477 // Splitting the edge can reduce the number of PHI entries we have.
4478 e = PN->getNumIncomingValues();
4480 i = PN->getBasicBlockIndex(BB);
4485 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
4486 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
4488 PN->setIncomingValue(i, Pair.first->second);
4490 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
4492 // If this is reuse-by-noop-cast, insert the noop cast.
4493 Type *OpTy = LF.OperandValToReplace->getType();
4494 if (FullV->getType() != OpTy)
4496 CastInst::Create(CastInst::getCastOpcode(FullV, false,
4498 FullV, LF.OperandValToReplace->getType(),
4499 "tmp", BB->getTerminator());
4501 PN->setIncomingValue(i, FullV);
4502 Pair.first->second = FullV;
4507 /// Rewrite - Emit instructions for the leading candidate expression for this
4508 /// LSRUse (this is called "expanding"), and update the UserInst to reference
4509 /// the newly expanded value.
4510 void LSRInstance::Rewrite(const LSRFixup &LF,
4512 SCEVExpander &Rewriter,
4513 SmallVectorImpl<WeakVH> &DeadInsts,
4515 // First, find an insertion point that dominates UserInst. For PHI nodes,
4516 // find the nearest block which dominates all the relevant uses.
4517 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
4518 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
4520 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
4522 // If this is reuse-by-noop-cast, insert the noop cast.
4523 Type *OpTy = LF.OperandValToReplace->getType();
4524 if (FullV->getType() != OpTy) {
4526 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
4527 FullV, OpTy, "tmp", LF.UserInst);
4531 // Update the user. ICmpZero is handled specially here (for now) because
4532 // Expand may have updated one of the operands of the icmp already, and
4533 // its new value may happen to be equal to LF.OperandValToReplace, in
4534 // which case doing replaceUsesOfWith leads to replacing both operands
4535 // with the same value. TODO: Reorganize this.
4536 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
4537 LF.UserInst->setOperand(0, FullV);
4539 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
4542 DeadInsts.push_back(LF.OperandValToReplace);
4545 /// ImplementSolution - Rewrite all the fixup locations with new values,
4546 /// following the chosen solution.
4548 LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
4550 // Keep track of instructions we may have made dead, so that
4551 // we can remove them after we are done working.
4552 SmallVector<WeakVH, 16> DeadInsts;
4554 SCEVExpander Rewriter(SE, "lsr");
4556 Rewriter.setDebugType(DEBUG_TYPE);
4558 Rewriter.disableCanonicalMode();
4559 Rewriter.enableLSRMode();
4560 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
4562 // Mark phi nodes that terminate chains so the expander tries to reuse them.
4563 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4564 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4565 if (PHINode *PN = dyn_cast<PHINode>(ChainI->tailUserInst()))
4566 Rewriter.setChainedPhi(PN);
4569 // Expand the new value definitions and update the users.
4570 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4571 E = Fixups.end(); I != E; ++I) {
4572 const LSRFixup &Fixup = *I;
4574 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
4579 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4580 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4581 GenerateIVChain(*ChainI, Rewriter, DeadInsts);
4584 // Clean up after ourselves. This must be done before deleting any
4588 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
4591 LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
4592 : IU(P->getAnalysis<IVUsers>()),
4593 SE(P->getAnalysis<ScalarEvolution>()),
4594 DT(P->getAnalysis<DominatorTree>()),
4595 LI(P->getAnalysis<LoopInfo>()),
4596 TLI(tli), L(l), Changed(false), IVIncInsertPos(0) {
4598 // If LoopSimplify form is not available, stay out of trouble.
4599 if (!L->isLoopSimplifyForm())
4602 // If there's no interesting work to be done, bail early.
4603 if (IU.empty()) return;
4605 // If there's too much analysis to be done, bail early. We won't be able to
4606 // model the problem anyway.
4607 unsigned NumUsers = 0;
4608 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
4609 if (++NumUsers > MaxIVUsers) {
4610 DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << *L
4617 // All dominating loops must have preheaders, or SCEVExpander may not be able
4618 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
4620 // IVUsers analysis should only create users that are dominated by simple loop
4621 // headers. Since this loop should dominate all of its users, its user list
4622 // should be empty if this loop itself is not within a simple loop nest.
4623 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
4624 Rung; Rung = Rung->getIDom()) {
4625 BasicBlock *BB = Rung->getBlock();
4626 const Loop *DomLoop = LI.getLoopFor(BB);
4627 if (DomLoop && DomLoop->getHeader() == BB) {
4628 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
4633 DEBUG(dbgs() << "\nLSR on loop ";
4634 WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
4637 // First, perform some low-level loop optimizations.
4639 OptimizeLoopTermCond();
4641 // If loop preparation eliminates all interesting IV users, bail.
4642 if (IU.empty()) return;
4644 // Skip nested loops until we can model them better with formulae.
4646 DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
4650 // Start collecting data and preparing for the solver.
4652 CollectInterestingTypesAndFactors();
4653 CollectFixupsAndInitialFormulae();
4654 CollectLoopInvariantFixupsAndFormulae();
4656 assert(!Uses.empty() && "IVUsers reported at least one use");
4657 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
4658 print_uses(dbgs()));
4660 // Now use the reuse data to generate a bunch of interesting ways
4661 // to formulate the values needed for the uses.
4662 GenerateAllReuseFormulae();
4664 FilterOutUndesirableDedicatedRegisters();
4665 NarrowSearchSpaceUsingHeuristics();
4667 SmallVector<const Formula *, 8> Solution;
4670 // Release memory that is no longer needed.
4675 if (Solution.empty())
4679 // Formulae should be legal.
4680 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
4681 E = Uses.end(); I != E; ++I) {
4682 const LSRUse &LU = *I;
4683 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
4684 JE = LU.Formulae.end(); J != JE; ++J)
4685 assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset,
4686 LU.Kind, LU.AccessTy, TLI) &&
4687 "Illegal formula generated!");
4691 // Now that we've decided what we want, make it so.
4692 ImplementSolution(Solution, P);
4695 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
4696 if (Factors.empty() && Types.empty()) return;
4698 OS << "LSR has identified the following interesting factors and types: ";
4701 for (SmallSetVector<int64_t, 8>::const_iterator
4702 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
4703 if (!First) OS << ", ";
4708 for (SmallSetVector<Type *, 4>::const_iterator
4709 I = Types.begin(), E = Types.end(); I != E; ++I) {
4710 if (!First) OS << ", ";
4712 OS << '(' << **I << ')';
4717 void LSRInstance::print_fixups(raw_ostream &OS) const {
4718 OS << "LSR is examining the following fixup sites:\n";
4719 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4720 E = Fixups.end(); I != E; ++I) {
4727 void LSRInstance::print_uses(raw_ostream &OS) const {
4728 OS << "LSR is examining the following uses:\n";
4729 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
4730 E = Uses.end(); I != E; ++I) {
4731 const LSRUse &LU = *I;
4735 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
4736 JE = LU.Formulae.end(); J != JE; ++J) {
4744 void LSRInstance::print(raw_ostream &OS) const {
4745 print_factors_and_types(OS);
4750 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
4751 void LSRInstance::dump() const {
4752 print(errs()); errs() << '\n';
4758 class LoopStrengthReduce : public LoopPass {
4759 /// TLI - Keep a pointer of a TargetLowering to consult for determining
4760 /// transformation profitability.
4761 const TargetLowering *const TLI;
4764 static char ID; // Pass ID, replacement for typeid
4765 explicit LoopStrengthReduce(const TargetLowering *tli = 0);
4768 bool runOnLoop(Loop *L, LPPassManager &LPM);
4769 void getAnalysisUsage(AnalysisUsage &AU) const;
4774 char LoopStrengthReduce::ID = 0;
4775 INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
4776 "Loop Strength Reduction", false, false)
4777 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
4778 INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
4779 INITIALIZE_PASS_DEPENDENCY(IVUsers)
4780 INITIALIZE_PASS_DEPENDENCY(LoopInfo)
4781 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
4782 INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
4783 "Loop Strength Reduction", false, false)
4786 Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
4787 return new LoopStrengthReduce(TLI);
4790 LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
4791 : LoopPass(ID), TLI(tli) {
4792 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
4795 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
4796 // We split critical edges, so we change the CFG. However, we do update
4797 // many analyses if they are around.
4798 AU.addPreservedID(LoopSimplifyID);
4800 AU.addRequired<LoopInfo>();
4801 AU.addPreserved<LoopInfo>();
4802 AU.addRequiredID(LoopSimplifyID);
4803 AU.addRequired<DominatorTree>();
4804 AU.addPreserved<DominatorTree>();
4805 AU.addRequired<ScalarEvolution>();
4806 AU.addPreserved<ScalarEvolution>();
4807 // Requiring LoopSimplify a second time here prevents IVUsers from running
4808 // twice, since LoopSimplify was invalidated by running ScalarEvolution.
4809 AU.addRequiredID(LoopSimplifyID);
4810 AU.addRequired<IVUsers>();
4811 AU.addPreserved<IVUsers>();
4814 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
4815 bool Changed = false;
4817 // Run the main LSR transformation.
4818 Changed |= LSRInstance(TLI, L, this).getChanged();
4820 // Remove any extra phis created by processing inner loops.
4821 Changed |= DeleteDeadPHIs(L->getHeader());
4822 if (EnablePhiElim) {
4823 SmallVector<WeakVH, 16> DeadInsts;
4824 SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), "lsr");
4826 Rewriter.setDebugType(DEBUG_TYPE);
4828 unsigned numFolded = Rewriter.
4829 replaceCongruentIVs(L, &getAnalysis<DominatorTree>(), DeadInsts, TLI);
4832 DeleteTriviallyDeadInstructions(DeadInsts);
4833 DeleteDeadPHIs(L->getHeader());