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 // Temporary flag to cleanup congruent phis after LSR phi expansion.
81 // It's currently disabled until we can determine whether it's truly useful or
82 // not. The flag should be removed after the v3.0 release.
83 // This is now needed for ivchains.
84 static cl::opt<bool> EnablePhiElim(
85 "enable-lsr-phielim", cl::Hidden, cl::init(true),
86 cl::desc("Enable LSR phi elimination"));
89 // Stress test IV chain generation.
90 static cl::opt<bool> StressIVChain(
91 "stress-ivchain", cl::Hidden, cl::init(false),
92 cl::desc("Stress test LSR IV chains"));
94 static bool StressIVChain = false;
99 /// RegSortData - This class holds data which is used to order reuse candidates.
102 /// UsedByIndices - This represents the set of LSRUse indices which reference
103 /// a particular register.
104 SmallBitVector UsedByIndices;
108 void print(raw_ostream &OS) const;
114 void RegSortData::print(raw_ostream &OS) const {
115 OS << "[NumUses=" << UsedByIndices.count() << ']';
118 void RegSortData::dump() const {
119 print(errs()); errs() << '\n';
124 /// RegUseTracker - Map register candidates to information about how they are
126 class RegUseTracker {
127 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
129 RegUsesTy RegUsesMap;
130 SmallVector<const SCEV *, 16> RegSequence;
133 void CountRegister(const SCEV *Reg, size_t LUIdx);
134 void DropRegister(const SCEV *Reg, size_t LUIdx);
135 void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx);
137 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
139 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
143 typedef SmallVectorImpl<const SCEV *>::iterator iterator;
144 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
145 iterator begin() { return RegSequence.begin(); }
146 iterator end() { return RegSequence.end(); }
147 const_iterator begin() const { return RegSequence.begin(); }
148 const_iterator end() const { return RegSequence.end(); }
154 RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
155 std::pair<RegUsesTy::iterator, bool> Pair =
156 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
157 RegSortData &RSD = Pair.first->second;
159 RegSequence.push_back(Reg);
160 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
161 RSD.UsedByIndices.set(LUIdx);
165 RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) {
166 RegUsesTy::iterator It = RegUsesMap.find(Reg);
167 assert(It != RegUsesMap.end());
168 RegSortData &RSD = It->second;
169 assert(RSD.UsedByIndices.size() > LUIdx);
170 RSD.UsedByIndices.reset(LUIdx);
174 RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
175 assert(LUIdx <= LastLUIdx);
177 // Update RegUses. The data structure is not optimized for this purpose;
178 // we must iterate through it and update each of the bit vectors.
179 for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end();
181 SmallBitVector &UsedByIndices = I->second.UsedByIndices;
182 if (LUIdx < UsedByIndices.size())
183 UsedByIndices[LUIdx] =
184 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0;
185 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
190 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
191 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
192 if (I == RegUsesMap.end())
194 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
195 int i = UsedByIndices.find_first();
196 if (i == -1) return false;
197 if ((size_t)i != LUIdx) return true;
198 return UsedByIndices.find_next(i) != -1;
201 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
202 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
203 assert(I != RegUsesMap.end() && "Unknown register!");
204 return I->second.UsedByIndices;
207 void RegUseTracker::clear() {
214 /// Formula - This class holds information that describes a formula for
215 /// computing satisfying a use. It may include broken-out immediates and scaled
218 /// AM - This is used to represent complex addressing, as well as other kinds
219 /// of interesting uses.
220 TargetLowering::AddrMode AM;
222 /// BaseRegs - The list of "base" registers for this use. When this is
223 /// non-empty, AM.HasBaseReg should be set to true.
224 SmallVector<const SCEV *, 2> BaseRegs;
226 /// ScaledReg - The 'scaled' register for this use. This should be non-null
227 /// when AM.Scale is not zero.
228 const SCEV *ScaledReg;
230 /// UnfoldedOffset - An additional constant offset which added near the
231 /// use. This requires a temporary register, but the offset itself can
232 /// live in an add immediate field rather than a register.
233 int64_t UnfoldedOffset;
235 Formula() : ScaledReg(0), UnfoldedOffset(0) {}
237 void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
239 unsigned getNumRegs() const;
240 Type *getType() const;
242 void DeleteBaseReg(const SCEV *&S);
244 bool referencesReg(const SCEV *S) const;
245 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
246 const RegUseTracker &RegUses) const;
248 void print(raw_ostream &OS) const;
254 /// DoInitialMatch - Recursion helper for InitialMatch.
255 static void DoInitialMatch(const SCEV *S, Loop *L,
256 SmallVectorImpl<const SCEV *> &Good,
257 SmallVectorImpl<const SCEV *> &Bad,
258 ScalarEvolution &SE) {
259 // Collect expressions which properly dominate the loop header.
260 if (SE.properlyDominates(S, L->getHeader())) {
265 // Look at add operands.
266 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
267 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
269 DoInitialMatch(*I, L, Good, Bad, SE);
273 // Look at addrec operands.
274 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
275 if (!AR->getStart()->isZero()) {
276 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
277 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
278 AR->getStepRecurrence(SE),
279 // FIXME: AR->getNoWrapFlags()
280 AR->getLoop(), SCEV::FlagAnyWrap),
285 // Handle a multiplication by -1 (negation) if it didn't fold.
286 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
287 if (Mul->getOperand(0)->isAllOnesValue()) {
288 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
289 const SCEV *NewMul = SE.getMulExpr(Ops);
291 SmallVector<const SCEV *, 4> MyGood;
292 SmallVector<const SCEV *, 4> MyBad;
293 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
294 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
295 SE.getEffectiveSCEVType(NewMul->getType())));
296 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(),
297 E = MyGood.end(); I != E; ++I)
298 Good.push_back(SE.getMulExpr(NegOne, *I));
299 for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(),
300 E = MyBad.end(); I != E; ++I)
301 Bad.push_back(SE.getMulExpr(NegOne, *I));
305 // Ok, we can't do anything interesting. Just stuff the whole thing into a
306 // register and hope for the best.
310 /// InitialMatch - Incorporate loop-variant parts of S into this Formula,
311 /// attempting to keep all loop-invariant and loop-computable values in a
312 /// single base register.
313 void Formula::InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
314 SmallVector<const SCEV *, 4> Good;
315 SmallVector<const SCEV *, 4> Bad;
316 DoInitialMatch(S, L, Good, Bad, SE);
318 const SCEV *Sum = SE.getAddExpr(Good);
320 BaseRegs.push_back(Sum);
321 AM.HasBaseReg = true;
324 const SCEV *Sum = SE.getAddExpr(Bad);
326 BaseRegs.push_back(Sum);
327 AM.HasBaseReg = true;
331 /// getNumRegs - Return the total number of register operands used by this
332 /// formula. This does not include register uses implied by non-constant
334 unsigned Formula::getNumRegs() const {
335 return !!ScaledReg + BaseRegs.size();
338 /// getType - Return the type of this formula, if it has one, or null
339 /// otherwise. This type is meaningless except for the bit size.
340 Type *Formula::getType() const {
341 return !BaseRegs.empty() ? BaseRegs.front()->getType() :
342 ScaledReg ? ScaledReg->getType() :
343 AM.BaseGV ? AM.BaseGV->getType() :
347 /// DeleteBaseReg - Delete the given base reg from the BaseRegs list.
348 void Formula::DeleteBaseReg(const SCEV *&S) {
349 if (&S != &BaseRegs.back())
350 std::swap(S, BaseRegs.back());
354 /// referencesReg - Test if this formula references the given register.
355 bool Formula::referencesReg(const SCEV *S) const {
356 return S == ScaledReg ||
357 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
360 /// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
361 /// which are used by uses other than the use with the given index.
362 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
363 const RegUseTracker &RegUses) const {
365 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
367 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
368 E = BaseRegs.end(); I != E; ++I)
369 if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx))
374 void Formula::print(raw_ostream &OS) const {
377 if (!First) OS << " + "; else First = false;
378 WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false);
380 if (AM.BaseOffs != 0) {
381 if (!First) OS << " + "; else First = false;
384 for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(),
385 E = BaseRegs.end(); I != E; ++I) {
386 if (!First) OS << " + "; else First = false;
387 OS << "reg(" << **I << ')';
389 if (AM.HasBaseReg && BaseRegs.empty()) {
390 if (!First) OS << " + "; else First = false;
391 OS << "**error: HasBaseReg**";
392 } else if (!AM.HasBaseReg && !BaseRegs.empty()) {
393 if (!First) OS << " + "; else First = false;
394 OS << "**error: !HasBaseReg**";
397 if (!First) OS << " + "; else First = false;
398 OS << AM.Scale << "*reg(";
405 if (UnfoldedOffset != 0) {
406 if (!First) OS << " + "; else First = false;
407 OS << "imm(" << UnfoldedOffset << ')';
411 void Formula::dump() const {
412 print(errs()); errs() << '\n';
415 /// isAddRecSExtable - Return true if the given addrec can be sign-extended
416 /// without changing its value.
417 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
419 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
420 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
423 /// isAddSExtable - Return true if the given add can be sign-extended
424 /// without changing its value.
425 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
427 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
428 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
431 /// isMulSExtable - Return true if the given mul can be sign-extended
432 /// without changing its value.
433 static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
435 IntegerType::get(SE.getContext(),
436 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
437 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
440 /// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
441 /// and if the remainder is known to be zero, or null otherwise. If
442 /// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
443 /// to Y, ignoring that the multiplication may overflow, which is useful when
444 /// the result will be used in a context where the most significant bits are
446 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
448 bool IgnoreSignificantBits = false) {
449 // Handle the trivial case, which works for any SCEV type.
451 return SE.getConstant(LHS->getType(), 1);
453 // Handle a few RHS special cases.
454 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
456 const APInt &RA = RC->getValue()->getValue();
457 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
459 if (RA.isAllOnesValue())
460 return SE.getMulExpr(LHS, RC);
461 // Handle x /s 1 as x.
466 // Check for a division of a constant by a constant.
467 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
470 const APInt &LA = C->getValue()->getValue();
471 const APInt &RA = RC->getValue()->getValue();
472 if (LA.srem(RA) != 0)
474 return SE.getConstant(LA.sdiv(RA));
477 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
478 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
479 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
480 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
481 IgnoreSignificantBits);
483 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
484 IgnoreSignificantBits);
485 if (!Start) return 0;
486 // FlagNW is independent of the start value, step direction, and is
487 // preserved with smaller magnitude steps.
488 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
489 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
494 // Distribute the sdiv over add operands, if the add doesn't overflow.
495 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
496 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
497 SmallVector<const SCEV *, 8> Ops;
498 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
500 const SCEV *Op = getExactSDiv(*I, RHS, SE,
501 IgnoreSignificantBits);
505 return SE.getAddExpr(Ops);
510 // Check for a multiply operand that we can pull RHS out of.
511 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
512 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
513 SmallVector<const SCEV *, 4> Ops;
515 for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end();
519 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
520 IgnoreSignificantBits)) {
526 return Found ? SE.getMulExpr(Ops) : 0;
531 // Otherwise we don't know.
535 /// ExtractImmediate - If S involves the addition of a constant integer value,
536 /// return that integer value, and mutate S to point to a new SCEV with that
538 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
539 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
540 if (C->getValue()->getValue().getMinSignedBits() <= 64) {
541 S = SE.getConstant(C->getType(), 0);
542 return C->getValue()->getSExtValue();
544 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
545 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
546 int64_t Result = ExtractImmediate(NewOps.front(), SE);
548 S = SE.getAddExpr(NewOps);
550 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
551 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
552 int64_t Result = ExtractImmediate(NewOps.front(), SE);
554 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
555 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
562 /// ExtractSymbol - If S involves the addition of a GlobalValue address,
563 /// return that symbol, and mutate S to point to a new SCEV with that
565 static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
566 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
567 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
568 S = SE.getConstant(GV->getType(), 0);
571 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
572 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
573 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
575 S = SE.getAddExpr(NewOps);
577 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
578 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
579 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
581 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
582 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
589 /// isAddressUse - Returns true if the specified instruction is using the
590 /// specified value as an address.
591 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
592 bool isAddress = isa<LoadInst>(Inst);
593 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
594 if (SI->getOperand(1) == OperandVal)
596 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
597 // Addressing modes can also be folded into prefetches and a variety
599 switch (II->getIntrinsicID()) {
601 case Intrinsic::prefetch:
602 case Intrinsic::x86_sse_storeu_ps:
603 case Intrinsic::x86_sse2_storeu_pd:
604 case Intrinsic::x86_sse2_storeu_dq:
605 case Intrinsic::x86_sse2_storel_dq:
606 if (II->getArgOperand(0) == OperandVal)
614 /// getAccessType - Return the type of the memory being accessed.
615 static Type *getAccessType(const Instruction *Inst) {
616 Type *AccessTy = Inst->getType();
617 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
618 AccessTy = SI->getOperand(0)->getType();
619 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
620 // Addressing modes can also be folded into prefetches and a variety
622 switch (II->getIntrinsicID()) {
624 case Intrinsic::x86_sse_storeu_ps:
625 case Intrinsic::x86_sse2_storeu_pd:
626 case Intrinsic::x86_sse2_storeu_dq:
627 case Intrinsic::x86_sse2_storel_dq:
628 AccessTy = II->getArgOperand(0)->getType();
633 // All pointers have the same requirements, so canonicalize them to an
634 // arbitrary pointer type to minimize variation.
635 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy))
636 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
637 PTy->getAddressSpace());
642 /// isExistingPhi - Return true if this AddRec is already a phi in its loop.
643 static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
644 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
645 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
646 if (SE.isSCEVable(PN->getType()) &&
647 (SE.getEffectiveSCEVType(PN->getType()) ==
648 SE.getEffectiveSCEVType(AR->getType())) &&
649 SE.getSCEV(PN) == AR)
655 /// Check if expanding this expression is likely to incur significant cost. This
656 /// is tricky because SCEV doesn't track which expressions are actually computed
657 /// by the current IR.
659 /// We currently allow expansion of IV increments that involve adds,
660 /// multiplication by constants, and AddRecs from existing phis.
662 /// TODO: Allow UDivExpr if we can find an existing IV increment that is an
663 /// obvious multiple of the UDivExpr.
664 static bool isHighCostExpansion(const SCEV *S,
665 SmallPtrSet<const SCEV*, 8> &Processed,
666 ScalarEvolution &SE) {
667 // Zero/One operand expressions
668 switch (S->getSCEVType()) {
673 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
676 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
679 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
683 if (!Processed.insert(S))
686 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
687 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
689 if (isHighCostExpansion(*I, Processed, SE))
695 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
696 if (Mul->getNumOperands() == 2) {
697 // Multiplication by a constant is ok
698 if (isa<SCEVConstant>(Mul->getOperand(0)))
699 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
701 // If we have the value of one operand, check if an existing
702 // multiplication already generates this expression.
703 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
704 Value *UVal = U->getValue();
705 for (Value::use_iterator UI = UVal->use_begin(), UE = UVal->use_end();
707 // If U is a constant, it may be used by a ConstantExpr.
708 Instruction *User = dyn_cast<Instruction>(*UI);
709 if (User && User->getOpcode() == Instruction::Mul
710 && SE.isSCEVable(User->getType())) {
711 return SE.getSCEV(User) == Mul;
718 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
719 if (isExistingPhi(AR, SE))
723 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
727 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
728 /// specified set are trivially dead, delete them and see if this makes any of
729 /// their operands subsequently dead.
731 DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
732 bool Changed = false;
734 while (!DeadInsts.empty()) {
735 Instruction *I = dyn_cast_or_null<Instruction>(&*DeadInsts.pop_back_val());
737 if (I == 0 || !isInstructionTriviallyDead(I))
740 for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI)
741 if (Instruction *U = dyn_cast<Instruction>(*OI)) {
744 DeadInsts.push_back(U);
747 I->eraseFromParent();
756 /// Cost - This class is used to measure and compare candidate formulae.
758 /// TODO: Some of these could be merged. Also, a lexical ordering
759 /// isn't always optimal.
763 unsigned NumBaseAdds;
769 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
772 bool operator<(const Cost &Other) const;
777 // Once any of the metrics loses, they must all remain losers.
779 return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds
780 | ImmCost | SetupCost) != ~0u)
781 || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds
782 & ImmCost & SetupCost) == ~0u);
787 assert(isValid() && "invalid cost");
788 return NumRegs == ~0u;
791 void RateFormula(const Formula &F,
792 SmallPtrSet<const SCEV *, 16> &Regs,
793 const DenseSet<const SCEV *> &VisitedRegs,
795 const SmallVectorImpl<int64_t> &Offsets,
796 ScalarEvolution &SE, DominatorTree &DT,
797 SmallPtrSet<const SCEV *, 16> *LoserRegs = 0);
799 void print(raw_ostream &OS) const;
803 void RateRegister(const SCEV *Reg,
804 SmallPtrSet<const SCEV *, 16> &Regs,
806 ScalarEvolution &SE, DominatorTree &DT);
807 void RatePrimaryRegister(const SCEV *Reg,
808 SmallPtrSet<const SCEV *, 16> &Regs,
810 ScalarEvolution &SE, DominatorTree &DT,
811 SmallPtrSet<const SCEV *, 16> *LoserRegs);
816 /// RateRegister - Tally up interesting quantities from the given register.
817 void Cost::RateRegister(const SCEV *Reg,
818 SmallPtrSet<const SCEV *, 16> &Regs,
820 ScalarEvolution &SE, DominatorTree &DT) {
821 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
822 // If this is an addrec for another loop, don't second-guess its addrec phi
823 // nodes. LSR isn't currently smart enough to reason about more than one
824 // loop at a time. LSR has already run on inner loops, will not run on outer
825 // loops, and cannot be expected to change sibling loops.
826 if (AR->getLoop() != L) {
827 // If the AddRec exists, consider it's register free and leave it alone.
828 if (isExistingPhi(AR, SE))
831 // Otherwise, do not consider this formula at all.
835 AddRecCost += 1; /// TODO: This should be a function of the stride.
837 // Add the step value register, if it needs one.
838 // TODO: The non-affine case isn't precisely modeled here.
839 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
840 if (!Regs.count(AR->getOperand(1))) {
841 RateRegister(AR->getOperand(1), Regs, L, SE, DT);
849 // Rough heuristic; favor registers which don't require extra setup
850 // instructions in the preheader.
851 if (!isa<SCEVUnknown>(Reg) &&
852 !isa<SCEVConstant>(Reg) &&
853 !(isa<SCEVAddRecExpr>(Reg) &&
854 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
855 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
858 NumIVMuls += isa<SCEVMulExpr>(Reg) &&
859 SE.hasComputableLoopEvolution(Reg, L);
862 /// RatePrimaryRegister - Record this register in the set. If we haven't seen it
863 /// before, rate it. Optional LoserRegs provides a way to declare any formula
864 /// that refers to one of those regs an instant loser.
865 void Cost::RatePrimaryRegister(const SCEV *Reg,
866 SmallPtrSet<const SCEV *, 16> &Regs,
868 ScalarEvolution &SE, DominatorTree &DT,
869 SmallPtrSet<const SCEV *, 16> *LoserRegs) {
870 if (LoserRegs && LoserRegs->count(Reg)) {
874 if (Regs.insert(Reg)) {
875 RateRegister(Reg, Regs, L, SE, DT);
877 LoserRegs->insert(Reg);
881 void Cost::RateFormula(const Formula &F,
882 SmallPtrSet<const SCEV *, 16> &Regs,
883 const DenseSet<const SCEV *> &VisitedRegs,
885 const SmallVectorImpl<int64_t> &Offsets,
886 ScalarEvolution &SE, DominatorTree &DT,
887 SmallPtrSet<const SCEV *, 16> *LoserRegs) {
888 // Tally up the registers.
889 if (const SCEV *ScaledReg = F.ScaledReg) {
890 if (VisitedRegs.count(ScaledReg)) {
894 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs);
898 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
899 E = F.BaseRegs.end(); I != E; ++I) {
900 const SCEV *BaseReg = *I;
901 if (VisitedRegs.count(BaseReg)) {
905 RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs);
910 // Determine how many (unfolded) adds we'll need inside the loop.
911 size_t NumBaseParts = F.BaseRegs.size() + (F.UnfoldedOffset != 0);
912 if (NumBaseParts > 1)
913 NumBaseAdds += NumBaseParts - 1;
915 // Tally up the non-zero immediates.
916 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
917 E = Offsets.end(); I != E; ++I) {
918 int64_t Offset = (uint64_t)*I + F.AM.BaseOffs;
920 ImmCost += 64; // Handle symbolic values conservatively.
921 // TODO: This should probably be the pointer size.
922 else if (Offset != 0)
923 ImmCost += APInt(64, Offset, true).getMinSignedBits();
925 assert(isValid() && "invalid cost");
928 /// Loose - Set this cost to a losing value.
938 /// operator< - Choose the lower cost.
939 bool Cost::operator<(const Cost &Other) const {
940 if (NumRegs != Other.NumRegs)
941 return NumRegs < Other.NumRegs;
942 if (AddRecCost != Other.AddRecCost)
943 return AddRecCost < Other.AddRecCost;
944 if (NumIVMuls != Other.NumIVMuls)
945 return NumIVMuls < Other.NumIVMuls;
946 if (NumBaseAdds != Other.NumBaseAdds)
947 return NumBaseAdds < Other.NumBaseAdds;
948 if (ImmCost != Other.ImmCost)
949 return ImmCost < Other.ImmCost;
950 if (SetupCost != Other.SetupCost)
951 return SetupCost < Other.SetupCost;
955 void Cost::print(raw_ostream &OS) const {
956 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
958 OS << ", with addrec cost " << AddRecCost;
960 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
961 if (NumBaseAdds != 0)
962 OS << ", plus " << NumBaseAdds << " base add"
963 << (NumBaseAdds == 1 ? "" : "s");
965 OS << ", plus " << ImmCost << " imm cost";
967 OS << ", plus " << SetupCost << " setup cost";
970 void Cost::dump() const {
971 print(errs()); errs() << '\n';
976 /// LSRFixup - An operand value in an instruction which is to be replaced
977 /// with some equivalent, possibly strength-reduced, replacement.
979 /// UserInst - The instruction which will be updated.
980 Instruction *UserInst;
982 /// OperandValToReplace - The operand of the instruction which will
983 /// be replaced. The operand may be used more than once; every instance
984 /// will be replaced.
985 Value *OperandValToReplace;
987 /// PostIncLoops - If this user is to use the post-incremented value of an
988 /// induction variable, this variable is non-null and holds the loop
989 /// associated with the induction variable.
990 PostIncLoopSet PostIncLoops;
992 /// LUIdx - The index of the LSRUse describing the expression which
993 /// this fixup needs, minus an offset (below).
996 /// Offset - A constant offset to be added to the LSRUse expression.
997 /// This allows multiple fixups to share the same LSRUse with different
998 /// offsets, for example in an unrolled loop.
1001 bool isUseFullyOutsideLoop(const Loop *L) const;
1005 void print(raw_ostream &OS) const;
1011 LSRFixup::LSRFixup()
1012 : UserInst(0), OperandValToReplace(0), LUIdx(~size_t(0)), Offset(0) {}
1014 /// isUseFullyOutsideLoop - Test whether this fixup always uses its
1015 /// value outside of the given loop.
1016 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1017 // PHI nodes use their value in their incoming blocks.
1018 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1019 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1020 if (PN->getIncomingValue(i) == OperandValToReplace &&
1021 L->contains(PN->getIncomingBlock(i)))
1026 return !L->contains(UserInst);
1029 void LSRFixup::print(raw_ostream &OS) const {
1031 // Store is common and interesting enough to be worth special-casing.
1032 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1034 WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false);
1035 } else if (UserInst->getType()->isVoidTy())
1036 OS << UserInst->getOpcodeName();
1038 WriteAsOperand(OS, UserInst, /*PrintType=*/false);
1040 OS << ", OperandValToReplace=";
1041 WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false);
1043 for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(),
1044 E = PostIncLoops.end(); I != E; ++I) {
1045 OS << ", PostIncLoop=";
1046 WriteAsOperand(OS, (*I)->getHeader(), /*PrintType=*/false);
1049 if (LUIdx != ~size_t(0))
1050 OS << ", LUIdx=" << LUIdx;
1053 OS << ", Offset=" << Offset;
1056 void LSRFixup::dump() const {
1057 print(errs()); errs() << '\n';
1062 /// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
1063 /// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
1064 struct UniquifierDenseMapInfo {
1065 static SmallVector<const SCEV *, 2> getEmptyKey() {
1066 SmallVector<const SCEV *, 2> V;
1067 V.push_back(reinterpret_cast<const SCEV *>(-1));
1071 static SmallVector<const SCEV *, 2> getTombstoneKey() {
1072 SmallVector<const SCEV *, 2> V;
1073 V.push_back(reinterpret_cast<const SCEV *>(-2));
1077 static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) {
1078 unsigned Result = 0;
1079 for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(),
1080 E = V.end(); I != E; ++I)
1081 Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I);
1085 static bool isEqual(const SmallVector<const SCEV *, 2> &LHS,
1086 const SmallVector<const SCEV *, 2> &RHS) {
1091 /// LSRUse - This class holds the state that LSR keeps for each use in
1092 /// IVUsers, as well as uses invented by LSR itself. It includes information
1093 /// about what kinds of things can be folded into the user, information about
1094 /// the user itself, and information about how the use may be satisfied.
1095 /// TODO: Represent multiple users of the same expression in common?
1097 DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier;
1100 /// KindType - An enum for a kind of use, indicating what types of
1101 /// scaled and immediate operands it might support.
1103 Basic, ///< A normal use, with no folding.
1104 Special, ///< A special case of basic, allowing -1 scales.
1105 Address, ///< An address use; folding according to TargetLowering
1106 ICmpZero ///< An equality icmp with both operands folded into one.
1107 // TODO: Add a generic icmp too?
1113 SmallVector<int64_t, 8> Offsets;
1117 /// AllFixupsOutsideLoop - This records whether all of the fixups using this
1118 /// LSRUse are outside of the loop, in which case some special-case heuristics
1120 bool AllFixupsOutsideLoop;
1122 /// WidestFixupType - This records the widest use type for any fixup using
1123 /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different
1124 /// max fixup widths to be equivalent, because the narrower one may be relying
1125 /// on the implicit truncation to truncate away bogus bits.
1126 Type *WidestFixupType;
1128 /// Formulae - A list of ways to build a value that can satisfy this user.
1129 /// After the list is populated, one of these is selected heuristically and
1130 /// used to formulate a replacement for OperandValToReplace in UserInst.
1131 SmallVector<Formula, 12> Formulae;
1133 /// Regs - The set of register candidates used by all formulae in this LSRUse.
1134 SmallPtrSet<const SCEV *, 4> Regs;
1136 LSRUse(KindType K, Type *T) : Kind(K), AccessTy(T),
1137 MinOffset(INT64_MAX),
1138 MaxOffset(INT64_MIN),
1139 AllFixupsOutsideLoop(true),
1140 WidestFixupType(0) {}
1142 bool HasFormulaWithSameRegs(const Formula &F) const;
1143 bool InsertFormula(const Formula &F);
1144 void DeleteFormula(Formula &F);
1145 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1147 void print(raw_ostream &OS) const;
1153 /// HasFormula - Test whether this use as a formula which has the same
1154 /// registers as the given formula.
1155 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1156 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
1157 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1158 // Unstable sort by host order ok, because this is only used for uniquifying.
1159 std::sort(Key.begin(), Key.end());
1160 return Uniquifier.count(Key);
1163 /// InsertFormula - If the given formula has not yet been inserted, add it to
1164 /// the list, and return true. Return false otherwise.
1165 bool LSRUse::InsertFormula(const Formula &F) {
1166 SmallVector<const SCEV *, 2> Key = F.BaseRegs;
1167 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1168 // Unstable sort by host order ok, because this is only used for uniquifying.
1169 std::sort(Key.begin(), Key.end());
1171 if (!Uniquifier.insert(Key).second)
1174 // Using a register to hold the value of 0 is not profitable.
1175 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1176 "Zero allocated in a scaled register!");
1178 for (SmallVectorImpl<const SCEV *>::const_iterator I =
1179 F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I)
1180 assert(!(*I)->isZero() && "Zero allocated in a base register!");
1183 // Add the formula to the list.
1184 Formulae.push_back(F);
1186 // Record registers now being used by this use.
1187 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1192 /// DeleteFormula - Remove the given formula from this use's list.
1193 void LSRUse::DeleteFormula(Formula &F) {
1194 if (&F != &Formulae.back())
1195 std::swap(F, Formulae.back());
1196 Formulae.pop_back();
1199 /// RecomputeRegs - Recompute the Regs field, and update RegUses.
1200 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1201 // Now that we've filtered out some formulae, recompute the Regs set.
1202 SmallPtrSet<const SCEV *, 4> OldRegs = Regs;
1204 for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(),
1205 E = Formulae.end(); I != E; ++I) {
1206 const Formula &F = *I;
1207 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1208 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1211 // Update the RegTracker.
1212 for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(),
1213 E = OldRegs.end(); I != E; ++I)
1214 if (!Regs.count(*I))
1215 RegUses.DropRegister(*I, LUIdx);
1218 void LSRUse::print(raw_ostream &OS) const {
1219 OS << "LSR Use: Kind=";
1221 case Basic: OS << "Basic"; break;
1222 case Special: OS << "Special"; break;
1223 case ICmpZero: OS << "ICmpZero"; break;
1225 OS << "Address of ";
1226 if (AccessTy->isPointerTy())
1227 OS << "pointer"; // the full pointer type could be really verbose
1232 OS << ", Offsets={";
1233 for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(),
1234 E = Offsets.end(); I != E; ++I) {
1236 if (llvm::next(I) != E)
1241 if (AllFixupsOutsideLoop)
1242 OS << ", all-fixups-outside-loop";
1244 if (WidestFixupType)
1245 OS << ", widest fixup type: " << *WidestFixupType;
1248 void LSRUse::dump() const {
1249 print(errs()); errs() << '\n';
1252 /// isLegalUse - Test whether the use described by AM is "legal", meaning it can
1253 /// be completely folded into the user instruction at isel time. This includes
1254 /// address-mode folding and special icmp tricks.
1255 static bool isLegalUse(const TargetLowering::AddrMode &AM,
1256 LSRUse::KindType Kind, Type *AccessTy,
1257 const TargetLowering *TLI) {
1259 case LSRUse::Address:
1260 // If we have low-level target information, ask the target if it can
1261 // completely fold this address.
1262 if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy);
1264 // Otherwise, just guess that reg+reg addressing is legal.
1265 return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1;
1267 case LSRUse::ICmpZero:
1268 // There's not even a target hook for querying whether it would be legal to
1269 // fold a GV into an ICmp.
1273 // ICmp only has two operands; don't allow more than two non-trivial parts.
1274 if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0)
1277 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1278 // putting the scaled register in the other operand of the icmp.
1279 if (AM.Scale != 0 && AM.Scale != -1)
1282 // If we have low-level target information, ask the target if it can fold an
1283 // integer immediate on an icmp.
1284 if (AM.BaseOffs != 0) {
1288 // ICmpZero BaseReg + Offset => ICmp BaseReg, -Offset
1289 // ICmpZero -1*ScaleReg + Offset => ICmp ScaleReg, Offset
1290 // Offs is the ICmp immediate.
1291 int64_t Offs = AM.BaseOffs;
1293 Offs = -(uint64_t)Offs; // The cast does the right thing with INT64_MIN.
1294 return TLI->isLegalICmpImmediate(Offs);
1297 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1301 // Only handle single-register values.
1302 return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
1304 case LSRUse::Special:
1305 // Only handle -1 scales, or no scale.
1306 return AM.Scale == 0 || AM.Scale == -1;
1309 llvm_unreachable("Invalid LSRUse Kind!");
1312 static bool isLegalUse(TargetLowering::AddrMode AM,
1313 int64_t MinOffset, int64_t MaxOffset,
1314 LSRUse::KindType Kind, Type *AccessTy,
1315 const TargetLowering *TLI) {
1316 // Check for overflow.
1317 if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) !=
1320 AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset;
1321 if (isLegalUse(AM, Kind, AccessTy, TLI)) {
1322 AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset;
1323 // Check for overflow.
1324 if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) !=
1327 AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset;
1328 return isLegalUse(AM, Kind, AccessTy, TLI);
1333 static bool isAlwaysFoldable(int64_t BaseOffs,
1334 GlobalValue *BaseGV,
1336 LSRUse::KindType Kind, Type *AccessTy,
1337 const TargetLowering *TLI) {
1338 // Fast-path: zero is always foldable.
1339 if (BaseOffs == 0 && !BaseGV) return true;
1341 // Conservatively, create an address with an immediate and a
1342 // base and a scale.
1343 TargetLowering::AddrMode AM;
1344 AM.BaseOffs = BaseOffs;
1346 AM.HasBaseReg = HasBaseReg;
1347 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1349 // Canonicalize a scale of 1 to a base register if the formula doesn't
1350 // already have a base register.
1351 if (!AM.HasBaseReg && AM.Scale == 1) {
1353 AM.HasBaseReg = true;
1356 return isLegalUse(AM, Kind, AccessTy, TLI);
1359 static bool isAlwaysFoldable(const SCEV *S,
1360 int64_t MinOffset, int64_t MaxOffset,
1362 LSRUse::KindType Kind, Type *AccessTy,
1363 const TargetLowering *TLI,
1364 ScalarEvolution &SE) {
1365 // Fast-path: zero is always foldable.
1366 if (S->isZero()) return true;
1368 // Conservatively, create an address with an immediate and a
1369 // base and a scale.
1370 int64_t BaseOffs = ExtractImmediate(S, SE);
1371 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1373 // If there's anything else involved, it's not foldable.
1374 if (!S->isZero()) return false;
1376 // Fast-path: zero is always foldable.
1377 if (BaseOffs == 0 && !BaseGV) return true;
1379 // Conservatively, create an address with an immediate and a
1380 // base and a scale.
1381 TargetLowering::AddrMode AM;
1382 AM.BaseOffs = BaseOffs;
1384 AM.HasBaseReg = HasBaseReg;
1385 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1387 return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI);
1392 /// UseMapDenseMapInfo - A DenseMapInfo implementation for holding
1393 /// DenseMaps and DenseSets of pairs of const SCEV* and LSRUse::Kind.
1394 struct UseMapDenseMapInfo {
1395 static std::pair<const SCEV *, LSRUse::KindType> getEmptyKey() {
1396 return std::make_pair(reinterpret_cast<const SCEV *>(-1), LSRUse::Basic);
1399 static std::pair<const SCEV *, LSRUse::KindType> getTombstoneKey() {
1400 return std::make_pair(reinterpret_cast<const SCEV *>(-2), LSRUse::Basic);
1404 getHashValue(const std::pair<const SCEV *, LSRUse::KindType> &V) {
1405 unsigned Result = DenseMapInfo<const SCEV *>::getHashValue(V.first);
1406 Result ^= DenseMapInfo<unsigned>::getHashValue(unsigned(V.second));
1410 static bool isEqual(const std::pair<const SCEV *, LSRUse::KindType> &LHS,
1411 const std::pair<const SCEV *, LSRUse::KindType> &RHS) {
1416 /// IVInc - An individual increment in a Chain of IV increments.
1417 /// Relate an IV user to an expression that computes the IV it uses from the IV
1418 /// used by the previous link in the Chain.
1420 /// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1421 /// original IVOperand. The head of the chain's IVOperand is only valid during
1422 /// chain collection, before LSR replaces IV users. During chain generation,
1423 /// IncExpr can be used to find the new IVOperand that computes the same
1426 Instruction *UserInst;
1428 const SCEV *IncExpr;
1430 IVInc(Instruction *U, Value *O, const SCEV *E):
1431 UserInst(U), IVOperand(O), IncExpr(E) {}
1434 // IVChain - The list of IV increments in program order.
1435 // We typically add the head of a chain without finding subsequent links.
1436 typedef SmallVector<IVInc,1> IVChain;
1438 /// ChainUsers - Helper for CollectChains to track multiple IV increment uses.
1439 /// Distinguish between FarUsers that definitely cross IV increments and
1440 /// NearUsers that may be used between IV increments.
1442 SmallPtrSet<Instruction*, 4> FarUsers;
1443 SmallPtrSet<Instruction*, 4> NearUsers;
1446 /// LSRInstance - This class holds state for the main loop strength reduction
1450 ScalarEvolution &SE;
1453 const TargetLowering *const TLI;
1457 /// IVIncInsertPos - This is the insert position that the current loop's
1458 /// induction variable increment should be placed. In simple loops, this is
1459 /// the latch block's terminator. But in more complicated cases, this is a
1460 /// position which will dominate all the in-loop post-increment users.
1461 Instruction *IVIncInsertPos;
1463 /// Factors - Interesting factors between use strides.
1464 SmallSetVector<int64_t, 8> Factors;
1466 /// Types - Interesting use types, to facilitate truncation reuse.
1467 SmallSetVector<Type *, 4> Types;
1469 /// Fixups - The list of operands which are to be replaced.
1470 SmallVector<LSRFixup, 16> Fixups;
1472 /// Uses - The list of interesting uses.
1473 SmallVector<LSRUse, 16> Uses;
1475 /// RegUses - Track which uses use which register candidates.
1476 RegUseTracker RegUses;
1478 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1479 // have more than a few IV increment chains in a loop. Missing a Chain falls
1480 // back to normal LSR behavior for those uses.
1481 static const unsigned MaxChains = 8;
1483 /// IVChainVec - IV users can form a chain of IV increments.
1484 SmallVector<IVChain, MaxChains> IVChainVec;
1486 /// IVIncSet - IV users that belong to profitable IVChains.
1487 SmallPtrSet<Use*, MaxChains> IVIncSet;
1489 void OptimizeShadowIV();
1490 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1491 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1492 void OptimizeLoopTermCond();
1494 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1495 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1496 void FinalizeChain(IVChain &Chain);
1497 void CollectChains();
1498 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1499 SmallVectorImpl<WeakVH> &DeadInsts);
1501 void CollectInterestingTypesAndFactors();
1502 void CollectFixupsAndInitialFormulae();
1504 LSRFixup &getNewFixup() {
1505 Fixups.push_back(LSRFixup());
1506 return Fixups.back();
1509 // Support for sharing of LSRUses between LSRFixups.
1510 typedef DenseMap<std::pair<const SCEV *, LSRUse::KindType>,
1512 UseMapDenseMapInfo> UseMapTy;
1515 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1516 LSRUse::KindType Kind, Type *AccessTy);
1518 std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1519 LSRUse::KindType Kind,
1522 void DeleteUse(LSRUse &LU, size_t LUIdx);
1524 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1526 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1527 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1528 void CountRegisters(const Formula &F, size_t LUIdx);
1529 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1531 void CollectLoopInvariantFixupsAndFormulae();
1533 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1534 unsigned Depth = 0);
1535 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1536 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1537 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1538 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1539 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1540 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1541 void GenerateCrossUseConstantOffsets();
1542 void GenerateAllReuseFormulae();
1544 void FilterOutUndesirableDedicatedRegisters();
1546 size_t EstimateSearchSpaceComplexity() const;
1547 void NarrowSearchSpaceByDetectingSupersets();
1548 void NarrowSearchSpaceByCollapsingUnrolledCode();
1549 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1550 void NarrowSearchSpaceByPickingWinnerRegs();
1551 void NarrowSearchSpaceUsingHeuristics();
1553 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1555 SmallVectorImpl<const Formula *> &Workspace,
1556 const Cost &CurCost,
1557 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1558 DenseSet<const SCEV *> &VisitedRegs) const;
1559 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1561 BasicBlock::iterator
1562 HoistInsertPosition(BasicBlock::iterator IP,
1563 const SmallVectorImpl<Instruction *> &Inputs) const;
1564 BasicBlock::iterator
1565 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1568 SCEVExpander &Rewriter) const;
1570 Value *Expand(const LSRFixup &LF,
1572 BasicBlock::iterator IP,
1573 SCEVExpander &Rewriter,
1574 SmallVectorImpl<WeakVH> &DeadInsts) const;
1575 void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
1577 SCEVExpander &Rewriter,
1578 SmallVectorImpl<WeakVH> &DeadInsts,
1580 void Rewrite(const LSRFixup &LF,
1582 SCEVExpander &Rewriter,
1583 SmallVectorImpl<WeakVH> &DeadInsts,
1585 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1589 LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
1591 bool getChanged() const { return Changed; }
1593 void print_factors_and_types(raw_ostream &OS) const;
1594 void print_fixups(raw_ostream &OS) const;
1595 void print_uses(raw_ostream &OS) const;
1596 void print(raw_ostream &OS) const;
1602 /// OptimizeShadowIV - If IV is used in a int-to-float cast
1603 /// inside the loop then try to eliminate the cast operation.
1604 void LSRInstance::OptimizeShadowIV() {
1605 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1606 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1609 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1610 UI != E; /* empty */) {
1611 IVUsers::const_iterator CandidateUI = UI;
1613 Instruction *ShadowUse = CandidateUI->getUser();
1614 Type *DestTy = NULL;
1615 bool IsSigned = false;
1617 /* If shadow use is a int->float cast then insert a second IV
1618 to eliminate this cast.
1620 for (unsigned i = 0; i < n; ++i)
1626 for (unsigned i = 0; i < n; ++i, ++d)
1629 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
1631 DestTy = UCast->getDestTy();
1633 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
1635 DestTy = SCast->getDestTy();
1637 if (!DestTy) continue;
1640 // If target does not support DestTy natively then do not apply
1641 // this transformation.
1642 EVT DVT = TLI->getValueType(DestTy);
1643 if (!TLI->isTypeLegal(DVT)) continue;
1646 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1648 if (PH->getNumIncomingValues() != 2) continue;
1650 Type *SrcTy = PH->getType();
1651 int Mantissa = DestTy->getFPMantissaWidth();
1652 if (Mantissa == -1) continue;
1653 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1656 unsigned Entry, Latch;
1657 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1665 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1666 if (!Init) continue;
1667 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
1668 (double)Init->getSExtValue() :
1669 (double)Init->getZExtValue());
1671 BinaryOperator *Incr =
1672 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1673 if (!Incr) continue;
1674 if (Incr->getOpcode() != Instruction::Add
1675 && Incr->getOpcode() != Instruction::Sub)
1678 /* Initialize new IV, double d = 0.0 in above example. */
1679 ConstantInt *C = NULL;
1680 if (Incr->getOperand(0) == PH)
1681 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1682 else if (Incr->getOperand(1) == PH)
1683 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1689 // Ignore negative constants, as the code below doesn't handle them
1690 // correctly. TODO: Remove this restriction.
1691 if (!C->getValue().isStrictlyPositive()) continue;
1693 /* Add new PHINode. */
1694 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
1696 /* create new increment. '++d' in above example. */
1697 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1698 BinaryOperator *NewIncr =
1699 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1700 Instruction::FAdd : Instruction::FSub,
1701 NewPH, CFP, "IV.S.next.", Incr);
1703 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1704 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1706 /* Remove cast operation */
1707 ShadowUse->replaceAllUsesWith(NewPH);
1708 ShadowUse->eraseFromParent();
1714 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1715 /// set the IV user and stride information and return true, otherwise return
1717 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
1718 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1719 if (UI->getUser() == Cond) {
1720 // NOTE: we could handle setcc instructions with multiple uses here, but
1721 // InstCombine does it as well for simple uses, it's not clear that it
1722 // occurs enough in real life to handle.
1729 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
1730 /// a max computation.
1732 /// This is a narrow solution to a specific, but acute, problem. For loops
1738 /// } while (++i < n);
1740 /// the trip count isn't just 'n', because 'n' might not be positive. And
1741 /// unfortunately this can come up even for loops where the user didn't use
1742 /// a C do-while loop. For example, seemingly well-behaved top-test loops
1743 /// will commonly be lowered like this:
1749 /// } while (++i < n);
1752 /// and then it's possible for subsequent optimization to obscure the if
1753 /// test in such a way that indvars can't find it.
1755 /// When indvars can't find the if test in loops like this, it creates a
1756 /// max expression, which allows it to give the loop a canonical
1757 /// induction variable:
1760 /// max = n < 1 ? 1 : n;
1763 /// } while (++i != max);
1765 /// Canonical induction variables are necessary because the loop passes
1766 /// are designed around them. The most obvious example of this is the
1767 /// LoopInfo analysis, which doesn't remember trip count values. It
1768 /// expects to be able to rediscover the trip count each time it is
1769 /// needed, and it does this using a simple analysis that only succeeds if
1770 /// the loop has a canonical induction variable.
1772 /// However, when it comes time to generate code, the maximum operation
1773 /// can be quite costly, especially if it's inside of an outer loop.
1775 /// This function solves this problem by detecting this type of loop and
1776 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1777 /// the instructions for the maximum computation.
1779 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1780 // Check that the loop matches the pattern we're looking for.
1781 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1782 Cond->getPredicate() != CmpInst::ICMP_NE)
1785 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
1786 if (!Sel || !Sel->hasOneUse()) return Cond;
1788 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1789 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1791 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
1793 // Add one to the backedge-taken count to get the trip count.
1794 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
1795 if (IterationCount != SE.getSCEV(Sel)) return Cond;
1797 // Check for a max calculation that matches the pattern. There's no check
1798 // for ICMP_ULE here because the comparison would be with zero, which
1799 // isn't interesting.
1800 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
1801 const SCEVNAryExpr *Max = 0;
1802 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
1803 Pred = ICmpInst::ICMP_SLE;
1805 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
1806 Pred = ICmpInst::ICMP_SLT;
1808 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
1809 Pred = ICmpInst::ICMP_ULT;
1816 // To handle a max with more than two operands, this optimization would
1817 // require additional checking and setup.
1818 if (Max->getNumOperands() != 2)
1821 const SCEV *MaxLHS = Max->getOperand(0);
1822 const SCEV *MaxRHS = Max->getOperand(1);
1824 // ScalarEvolution canonicalizes constants to the left. For < and >, look
1825 // for a comparison with 1. For <= and >=, a comparison with zero.
1827 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
1830 // Check the relevant induction variable for conformance to
1832 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
1833 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
1834 if (!AR || !AR->isAffine() ||
1835 AR->getStart() != One ||
1836 AR->getStepRecurrence(SE) != One)
1839 assert(AR->getLoop() == L &&
1840 "Loop condition operand is an addrec in a different loop!");
1842 // Check the right operand of the select, and remember it, as it will
1843 // be used in the new comparison instruction.
1845 if (ICmpInst::isTrueWhenEqual(Pred)) {
1846 // Look for n+1, and grab n.
1847 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
1848 if (isa<ConstantInt>(BO->getOperand(1)) &&
1849 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1850 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1851 NewRHS = BO->getOperand(0);
1852 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
1853 if (isa<ConstantInt>(BO->getOperand(1)) &&
1854 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1855 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1856 NewRHS = BO->getOperand(0);
1859 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
1860 NewRHS = Sel->getOperand(1);
1861 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
1862 NewRHS = Sel->getOperand(2);
1863 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
1864 NewRHS = SU->getValue();
1866 // Max doesn't match expected pattern.
1869 // Determine the new comparison opcode. It may be signed or unsigned,
1870 // and the original comparison may be either equality or inequality.
1871 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
1872 Pred = CmpInst::getInversePredicate(Pred);
1874 // Ok, everything looks ok to change the condition into an SLT or SGE and
1875 // delete the max calculation.
1877 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
1879 // Delete the max calculation instructions.
1880 Cond->replaceAllUsesWith(NewCond);
1881 CondUse->setUser(NewCond);
1882 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
1883 Cond->eraseFromParent();
1884 Sel->eraseFromParent();
1885 if (Cmp->use_empty())
1886 Cmp->eraseFromParent();
1890 /// OptimizeLoopTermCond - Change loop terminating condition to use the
1891 /// postinc iv when possible.
1893 LSRInstance::OptimizeLoopTermCond() {
1894 SmallPtrSet<Instruction *, 4> PostIncs;
1896 BasicBlock *LatchBlock = L->getLoopLatch();
1897 SmallVector<BasicBlock*, 8> ExitingBlocks;
1898 L->getExitingBlocks(ExitingBlocks);
1900 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
1901 BasicBlock *ExitingBlock = ExitingBlocks[i];
1903 // Get the terminating condition for the loop if possible. If we
1904 // can, we want to change it to use a post-incremented version of its
1905 // induction variable, to allow coalescing the live ranges for the IV into
1906 // one register value.
1908 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
1911 // FIXME: Overly conservative, termination condition could be an 'or' etc..
1912 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
1915 // Search IVUsesByStride to find Cond's IVUse if there is one.
1916 IVStrideUse *CondUse = 0;
1917 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
1918 if (!FindIVUserForCond(Cond, CondUse))
1921 // If the trip count is computed in terms of a max (due to ScalarEvolution
1922 // being unable to find a sufficient guard, for example), change the loop
1923 // comparison to use SLT or ULT instead of NE.
1924 // One consequence of doing this now is that it disrupts the count-down
1925 // optimization. That's not always a bad thing though, because in such
1926 // cases it may still be worthwhile to avoid a max.
1927 Cond = OptimizeMax(Cond, CondUse);
1929 // If this exiting block dominates the latch block, it may also use
1930 // the post-inc value if it won't be shared with other uses.
1931 // Check for dominance.
1932 if (!DT.dominates(ExitingBlock, LatchBlock))
1935 // Conservatively avoid trying to use the post-inc value in non-latch
1936 // exits if there may be pre-inc users in intervening blocks.
1937 if (LatchBlock != ExitingBlock)
1938 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1939 // Test if the use is reachable from the exiting block. This dominator
1940 // query is a conservative approximation of reachability.
1941 if (&*UI != CondUse &&
1942 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
1943 // Conservatively assume there may be reuse if the quotient of their
1944 // strides could be a legal scale.
1945 const SCEV *A = IU.getStride(*CondUse, L);
1946 const SCEV *B = IU.getStride(*UI, L);
1947 if (!A || !B) continue;
1948 if (SE.getTypeSizeInBits(A->getType()) !=
1949 SE.getTypeSizeInBits(B->getType())) {
1950 if (SE.getTypeSizeInBits(A->getType()) >
1951 SE.getTypeSizeInBits(B->getType()))
1952 B = SE.getSignExtendExpr(B, A->getType());
1954 A = SE.getSignExtendExpr(A, B->getType());
1956 if (const SCEVConstant *D =
1957 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
1958 const ConstantInt *C = D->getValue();
1959 // Stride of one or negative one can have reuse with non-addresses.
1960 if (C->isOne() || C->isAllOnesValue())
1961 goto decline_post_inc;
1962 // Avoid weird situations.
1963 if (C->getValue().getMinSignedBits() >= 64 ||
1964 C->getValue().isMinSignedValue())
1965 goto decline_post_inc;
1966 // Without TLI, assume that any stride might be valid, and so any
1967 // use might be shared.
1969 goto decline_post_inc;
1970 // Check for possible scaled-address reuse.
1971 Type *AccessTy = getAccessType(UI->getUser());
1972 TargetLowering::AddrMode AM;
1973 AM.Scale = C->getSExtValue();
1974 if (TLI->isLegalAddressingMode(AM, AccessTy))
1975 goto decline_post_inc;
1976 AM.Scale = -AM.Scale;
1977 if (TLI->isLegalAddressingMode(AM, AccessTy))
1978 goto decline_post_inc;
1982 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
1985 // It's possible for the setcc instruction to be anywhere in the loop, and
1986 // possible for it to have multiple users. If it is not immediately before
1987 // the exiting block branch, move it.
1988 if (&*++BasicBlock::iterator(Cond) != TermBr) {
1989 if (Cond->hasOneUse()) {
1990 Cond->moveBefore(TermBr);
1992 // Clone the terminating condition and insert into the loopend.
1993 ICmpInst *OldCond = Cond;
1994 Cond = cast<ICmpInst>(Cond->clone());
1995 Cond->setName(L->getHeader()->getName() + ".termcond");
1996 ExitingBlock->getInstList().insert(TermBr, Cond);
1998 // Clone the IVUse, as the old use still exists!
1999 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2000 TermBr->replaceUsesOfWith(OldCond, Cond);
2004 // If we get to here, we know that we can transform the setcc instruction to
2005 // use the post-incremented version of the IV, allowing us to coalesce the
2006 // live ranges for the IV correctly.
2007 CondUse->transformToPostInc(L);
2010 PostIncs.insert(Cond);
2014 // Determine an insertion point for the loop induction variable increment. It
2015 // must dominate all the post-inc comparisons we just set up, and it must
2016 // dominate the loop latch edge.
2017 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2018 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
2019 E = PostIncs.end(); I != E; ++I) {
2021 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2023 if (BB == (*I)->getParent())
2024 IVIncInsertPos = *I;
2025 else if (BB != IVIncInsertPos->getParent())
2026 IVIncInsertPos = BB->getTerminator();
2030 /// reconcileNewOffset - Determine if the given use can accommodate a fixup
2031 /// at the given offset and other details. If so, update the use and
2034 LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
2035 LSRUse::KindType Kind, Type *AccessTy) {
2036 int64_t NewMinOffset = LU.MinOffset;
2037 int64_t NewMaxOffset = LU.MaxOffset;
2038 Type *NewAccessTy = AccessTy;
2040 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2041 // something conservative, however this can pessimize in the case that one of
2042 // the uses will have all its uses outside the loop, for example.
2043 if (LU.Kind != Kind)
2045 // Conservatively assume HasBaseReg is true for now.
2046 if (NewOffset < LU.MinOffset) {
2047 if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg,
2048 Kind, AccessTy, TLI))
2050 NewMinOffset = NewOffset;
2051 } else if (NewOffset > LU.MaxOffset) {
2052 if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg,
2053 Kind, AccessTy, TLI))
2055 NewMaxOffset = NewOffset;
2057 // Check for a mismatched access type, and fall back conservatively as needed.
2058 // TODO: Be less conservative when the type is similar and can use the same
2059 // addressing modes.
2060 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
2061 NewAccessTy = Type::getVoidTy(AccessTy->getContext());
2064 LU.MinOffset = NewMinOffset;
2065 LU.MaxOffset = NewMaxOffset;
2066 LU.AccessTy = NewAccessTy;
2067 if (NewOffset != LU.Offsets.back())
2068 LU.Offsets.push_back(NewOffset);
2072 /// getUse - Return an LSRUse index and an offset value for a fixup which
2073 /// needs the given expression, with the given kind and optional access type.
2074 /// Either reuse an existing use or create a new one, as needed.
2075 std::pair<size_t, int64_t>
2076 LSRInstance::getUse(const SCEV *&Expr,
2077 LSRUse::KindType Kind, Type *AccessTy) {
2078 const SCEV *Copy = Expr;
2079 int64_t Offset = ExtractImmediate(Expr, SE);
2081 // Basic uses can't accept any offset, for example.
2082 if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) {
2087 std::pair<UseMapTy::iterator, bool> P =
2088 UseMap.insert(std::make_pair(std::make_pair(Expr, Kind), 0));
2090 // A use already existed with this base.
2091 size_t LUIdx = P.first->second;
2092 LSRUse &LU = Uses[LUIdx];
2093 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2095 return std::make_pair(LUIdx, Offset);
2098 // Create a new use.
2099 size_t LUIdx = Uses.size();
2100 P.first->second = LUIdx;
2101 Uses.push_back(LSRUse(Kind, AccessTy));
2102 LSRUse &LU = Uses[LUIdx];
2104 // We don't need to track redundant offsets, but we don't need to go out
2105 // of our way here to avoid them.
2106 if (LU.Offsets.empty() || Offset != LU.Offsets.back())
2107 LU.Offsets.push_back(Offset);
2109 LU.MinOffset = Offset;
2110 LU.MaxOffset = Offset;
2111 return std::make_pair(LUIdx, Offset);
2114 /// DeleteUse - Delete the given use from the Uses list.
2115 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2116 if (&LU != &Uses.back())
2117 std::swap(LU, Uses.back());
2121 RegUses.SwapAndDropUse(LUIdx, Uses.size());
2124 /// FindUseWithFormula - Look for a use distinct from OrigLU which is has
2125 /// a formula that has the same registers as the given formula.
2127 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2128 const LSRUse &OrigLU) {
2129 // Search all uses for the formula. This could be more clever.
2130 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2131 LSRUse &LU = Uses[LUIdx];
2132 // Check whether this use is close enough to OrigLU, to see whether it's
2133 // worthwhile looking through its formulae.
2134 // Ignore ICmpZero uses because they may contain formulae generated by
2135 // GenerateICmpZeroScales, in which case adding fixup offsets may
2137 if (&LU != &OrigLU &&
2138 LU.Kind != LSRUse::ICmpZero &&
2139 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2140 LU.WidestFixupType == OrigLU.WidestFixupType &&
2141 LU.HasFormulaWithSameRegs(OrigF)) {
2142 // Scan through this use's formulae.
2143 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
2144 E = LU.Formulae.end(); I != E; ++I) {
2145 const Formula &F = *I;
2146 // Check to see if this formula has the same registers and symbols
2148 if (F.BaseRegs == OrigF.BaseRegs &&
2149 F.ScaledReg == OrigF.ScaledReg &&
2150 F.AM.BaseGV == OrigF.AM.BaseGV &&
2151 F.AM.Scale == OrigF.AM.Scale &&
2152 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2153 if (F.AM.BaseOffs == 0)
2155 // This is the formula where all the registers and symbols matched;
2156 // there aren't going to be any others. Since we declined it, we
2157 // can skip the rest of the formulae and procede to the next LSRUse.
2164 // Nothing looked good.
2168 void LSRInstance::CollectInterestingTypesAndFactors() {
2169 SmallSetVector<const SCEV *, 4> Strides;
2171 // Collect interesting types and strides.
2172 SmallVector<const SCEV *, 4> Worklist;
2173 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2174 const SCEV *Expr = IU.getExpr(*UI);
2176 // Collect interesting types.
2177 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2179 // Add strides for mentioned loops.
2180 Worklist.push_back(Expr);
2182 const SCEV *S = Worklist.pop_back_val();
2183 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2184 if (AR->getLoop() == L)
2185 Strides.insert(AR->getStepRecurrence(SE));
2186 Worklist.push_back(AR->getStart());
2187 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2188 Worklist.append(Add->op_begin(), Add->op_end());
2190 } while (!Worklist.empty());
2193 // Compute interesting factors from the set of interesting strides.
2194 for (SmallSetVector<const SCEV *, 4>::const_iterator
2195 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2196 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2197 llvm::next(I); NewStrideIter != E; ++NewStrideIter) {
2198 const SCEV *OldStride = *I;
2199 const SCEV *NewStride = *NewStrideIter;
2201 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2202 SE.getTypeSizeInBits(NewStride->getType())) {
2203 if (SE.getTypeSizeInBits(OldStride->getType()) >
2204 SE.getTypeSizeInBits(NewStride->getType()))
2205 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2207 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2209 if (const SCEVConstant *Factor =
2210 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2212 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2213 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2214 } else if (const SCEVConstant *Factor =
2215 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2218 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2219 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2223 // If all uses use the same type, don't bother looking for truncation-based
2225 if (Types.size() == 1)
2228 DEBUG(print_factors_and_types(dbgs()));
2231 /// findIVOperand - Helper for CollectChains that finds an IV operand (computed
2232 /// by an AddRec in this loop) within [OI,OE) or returns OE. If IVUsers mapped
2233 /// Instructions to IVStrideUses, we could partially skip this.
2234 static User::op_iterator
2235 findIVOperand(User::op_iterator OI, User::op_iterator OE,
2236 Loop *L, ScalarEvolution &SE) {
2237 for(; OI != OE; ++OI) {
2238 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2239 if (!SE.isSCEVable(Oper->getType()))
2242 if (const SCEVAddRecExpr *AR =
2243 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2244 if (AR->getLoop() == L)
2252 /// getWideOperand - IVChain logic must consistenctly peek base TruncInst
2253 /// operands, so wrap it in a convenient helper.
2254 static Value *getWideOperand(Value *Oper) {
2255 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2256 return Trunc->getOperand(0);
2260 /// isCompatibleIVType - Return true if we allow an IV chain to include both
2262 static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2263 Type *LType = LVal->getType();
2264 Type *RType = RVal->getType();
2265 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy());
2268 /// getExprBase - Return an approximation of this SCEV expression's "base", or
2269 /// NULL for any constant. Returning the expression itself is
2270 /// conservative. Returning a deeper subexpression is more precise and valid as
2271 /// long as it isn't less complex than another subexpression. For expressions
2272 /// involving multiple unscaled values, we need to return the pointer-type
2273 /// SCEVUnknown. This avoids forming chains across objects, such as:
2274 /// PrevOper==a[i], IVOper==b[i], IVInc==b-a.
2276 /// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2277 /// SCEVUnknown, we simply return the rightmost SCEV operand.
2278 static const SCEV *getExprBase(const SCEV *S) {
2279 switch (S->getSCEVType()) {
2280 default: // uncluding scUnknown.
2285 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2287 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2289 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2291 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2292 // there's nothing more complex.
2293 // FIXME: not sure if we want to recognize negation.
2294 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2295 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2296 E(Add->op_begin()); I != E; ++I) {
2297 const SCEV *SubExpr = *I;
2298 if (SubExpr->getSCEVType() == scAddExpr)
2299 return getExprBase(SubExpr);
2301 if (SubExpr->getSCEVType() != scMulExpr)
2304 return S; // all operands are scaled, be conservative.
2307 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2311 /// Return true if the chain increment is profitable to expand into a loop
2312 /// invariant value, which may require its own register. A profitable chain
2313 /// increment will be an offset relative to the same base. We allow such offsets
2314 /// to potentially be used as chain increment as long as it's not obviously
2315 /// expensive to expand using real instructions.
2317 getProfitableChainIncrement(Value *NextIV, Value *PrevIV,
2318 const IVChain &Chain, Loop *L,
2319 ScalarEvolution &SE, const TargetLowering *TLI) {
2320 // Prune the solution space aggressively by checking that both IV operands
2321 // are expressions that operate on the same unscaled SCEVUnknown. This
2322 // "base" will be canceled by the subsequent getMinusSCEV call. Checking first
2323 // avoids creating extra SCEV expressions.
2324 const SCEV *OperExpr = SE.getSCEV(NextIV);
2325 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2326 if (getExprBase(OperExpr) != getExprBase(PrevExpr) && !StressIVChain)
2329 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2330 if (!SE.isLoopInvariant(IncExpr, L))
2333 // We are not able to expand an increment unless it is loop invariant,
2334 // however, the following checks are purely for profitability.
2338 // Do not replace a constant offset from IV head with a nonconstant IV
2340 if (!isa<SCEVConstant>(IncExpr)) {
2341 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Chain[0].IVOperand));
2342 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2346 SmallPtrSet<const SCEV*, 8> Processed;
2347 if (isHighCostExpansion(IncExpr, Processed, SE))
2353 /// Return true if the number of registers needed for the chain is estimated to
2354 /// be less than the number required for the individual IV users. First prohibit
2355 /// any IV users that keep the IV live across increments (the Users set should
2356 /// be empty). Next count the number and type of increments in the chain.
2358 /// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2359 /// effectively use postinc addressing modes. Only consider it profitable it the
2360 /// increments can be computed in fewer registers when chained.
2362 /// TODO: Consider IVInc free if it's already used in another chains.
2364 isProfitableChain(IVChain &Chain, SmallPtrSet<Instruction*, 4> &Users,
2365 ScalarEvolution &SE, const TargetLowering *TLI) {
2369 if (Chain.size() <= 2)
2372 if (!Users.empty()) {
2373 DEBUG(dbgs() << "Chain: " << *Chain[0].UserInst << " users:\n";
2374 for (SmallPtrSet<Instruction*, 4>::const_iterator I = Users.begin(),
2375 E = Users.end(); I != E; ++I) {
2376 dbgs() << " " << **I << "\n";
2380 assert(!Chain.empty() && "empty IV chains are not allowed");
2382 // The chain itself may require a register, so intialize cost to 1.
2385 // A complete chain likely eliminates the need for keeping the original IV in
2386 // a register. LSR does not currently know how to form a complete chain unless
2387 // the header phi already exists.
2388 if (isa<PHINode>(Chain.back().UserInst)
2389 && SE.getSCEV(Chain.back().UserInst) == Chain[0].IncExpr) {
2392 const SCEV *LastIncExpr = 0;
2393 unsigned NumConstIncrements = 0;
2394 unsigned NumVarIncrements = 0;
2395 unsigned NumReusedIncrements = 0;
2396 for (IVChain::const_iterator I = llvm::next(Chain.begin()), E = Chain.end();
2399 if (I->IncExpr->isZero())
2402 // Incrementing by zero or some constant is neutral. We assume constants can
2403 // be folded into an addressing mode or an add's immediate operand.
2404 if (isa<SCEVConstant>(I->IncExpr)) {
2405 ++NumConstIncrements;
2409 if (I->IncExpr == LastIncExpr)
2410 ++NumReusedIncrements;
2414 LastIncExpr = I->IncExpr;
2416 // An IV chain with a single increment is handled by LSR's postinc
2417 // uses. However, a chain with multiple increments requires keeping the IV's
2418 // value live longer than it needs to be if chained.
2419 if (NumConstIncrements > 1)
2422 // Materializing increment expressions in the preheader that didn't exist in
2423 // the original code may cost a register. For example, sign-extended array
2424 // indices can produce ridiculous increments like this:
2425 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2426 cost += NumVarIncrements;
2428 // Reusing variable increments likely saves a register to hold the multiple of
2430 cost -= NumReusedIncrements;
2432 DEBUG(dbgs() << "Chain: " << *Chain[0].UserInst << " Cost: " << cost << "\n");
2437 /// ChainInstruction - Add this IV user to an existing chain or make it the head
2439 void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2440 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2441 // When IVs are used as types of varying widths, they are generally converted
2442 // to a wider type with some uses remaining narrow under a (free) trunc.
2443 Value *NextIV = getWideOperand(IVOper);
2445 // Visit all existing chains. Check if its IVOper can be computed as a
2446 // profitable loop invariant increment from the last link in the Chain.
2447 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2448 const SCEV *LastIncExpr = 0;
2449 for (; ChainIdx < NChains; ++ChainIdx) {
2450 Value *PrevIV = getWideOperand(IVChainVec[ChainIdx].back().IVOperand);
2451 if (!isCompatibleIVType(PrevIV, NextIV))
2454 // A phi node terminates a chain.
2455 if (isa<PHINode>(UserInst)
2456 && isa<PHINode>(IVChainVec[ChainIdx].back().UserInst))
2459 if (const SCEV *IncExpr =
2460 getProfitableChainIncrement(NextIV, PrevIV, IVChainVec[ChainIdx],
2462 LastIncExpr = IncExpr;
2466 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2467 // bother for phi nodes, because they must be last in the chain.
2468 if (ChainIdx == NChains) {
2469 if (isa<PHINode>(UserInst))
2471 if (NChains >= MaxChains && !StressIVChain) {
2472 DEBUG(dbgs() << "IV Chain Limit\n");
2475 LastIncExpr = SE.getSCEV(NextIV);
2476 // IVUsers may have skipped over sign/zero extensions. We don't currently
2477 // attempt to form chains involving extensions unless they can be hoisted
2478 // into this loop's AddRec.
2479 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2482 IVChainVec.resize(NChains);
2483 ChainUsersVec.resize(NChains);
2484 DEBUG(dbgs() << "IV Head: (" << *UserInst << ") IV=" << *LastIncExpr
2488 DEBUG(dbgs() << "IV Inc: (" << *UserInst << ") IV+" << *LastIncExpr
2491 // Add this IV user to the end of the chain.
2492 IVChainVec[ChainIdx].push_back(IVInc(UserInst, IVOper, LastIncExpr));
2494 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2495 // This chain's NearUsers become FarUsers.
2496 if (!LastIncExpr->isZero()) {
2497 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2502 // All other uses of IVOperand become near uses of the chain.
2503 // We currently ignore intermediate values within SCEV expressions, assuming
2504 // they will eventually be used be the current chain, or can be computed
2505 // from one of the chain increments. To be more precise we could
2506 // transitively follow its user and only add leaf IV users to the set.
2507 for (Value::use_iterator UseIter = IVOper->use_begin(),
2508 UseEnd = IVOper->use_end(); UseIter != UseEnd; ++UseIter) {
2509 Instruction *OtherUse = dyn_cast<Instruction>(*UseIter);
2510 if (!OtherUse || OtherUse == UserInst)
2512 if (SE.isSCEVable(OtherUse->getType())
2513 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2514 && IU.isIVUserOrOperand(OtherUse)) {
2517 NearUsers.insert(OtherUse);
2520 // Since this user is part of the chain, it's no longer considered a use
2522 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2525 /// CollectChains - Populate the vector of Chains.
2527 /// This decreases ILP at the architecture level. Targets with ample registers,
2528 /// multiple memory ports, and no register renaming probably don't want
2529 /// this. However, such targets should probably disable LSR altogether.
2531 /// The job of LSR is to make a reasonable choice of induction variables across
2532 /// the loop. Subsequent passes can easily "unchain" computation exposing more
2533 /// ILP *within the loop* if the target wants it.
2535 /// Finding the best IV chain is potentially a scheduling problem. Since LSR
2536 /// will not reorder memory operations, it will recognize this as a chain, but
2537 /// will generate redundant IV increments. Ideally this would be corrected later
2538 /// by a smart scheduler:
2544 /// TODO: Walk the entire domtree within this loop, not just the path to the
2545 /// loop latch. This will discover chains on side paths, but requires
2546 /// maintaining multiple copies of the Chains state.
2547 void LSRInstance::CollectChains() {
2548 SmallVector<ChainUsers, 8> ChainUsersVec;
2550 SmallVector<BasicBlock *,8> LatchPath;
2551 BasicBlock *LoopHeader = L->getHeader();
2552 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
2553 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
2554 LatchPath.push_back(Rung->getBlock());
2556 LatchPath.push_back(LoopHeader);
2558 // Walk the instruction stream from the loop header to the loop latch.
2559 for (SmallVectorImpl<BasicBlock *>::reverse_iterator
2560 BBIter = LatchPath.rbegin(), BBEnd = LatchPath.rend();
2561 BBIter != BBEnd; ++BBIter) {
2562 for (BasicBlock::iterator I = (*BBIter)->begin(), E = (*BBIter)->end();
2564 // Skip instructions that weren't seen by IVUsers analysis.
2565 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(I))
2568 // Ignore users that are part of a SCEV expression. This way we only
2569 // consider leaf IV Users. This effectively rediscovers a portion of
2570 // IVUsers analysis but in program order this time.
2571 if (SE.isSCEVable(I->getType()) && !isa<SCEVUnknown>(SE.getSCEV(I)))
2574 // Remove this instruction from any NearUsers set it may be in.
2575 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
2576 ChainIdx < NChains; ++ChainIdx) {
2577 ChainUsersVec[ChainIdx].NearUsers.erase(I);
2579 // Search for operands that can be chained.
2580 SmallPtrSet<Instruction*, 4> UniqueOperands;
2581 User::op_iterator IVOpEnd = I->op_end();
2582 User::op_iterator IVOpIter = findIVOperand(I->op_begin(), IVOpEnd, L, SE);
2583 while (IVOpIter != IVOpEnd) {
2584 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
2585 if (UniqueOperands.insert(IVOpInst))
2586 ChainInstruction(I, IVOpInst, ChainUsersVec);
2587 IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE);
2589 } // Continue walking down the instructions.
2590 } // Continue walking down the domtree.
2591 // Visit phi backedges to determine if the chain can generate the IV postinc.
2592 for (BasicBlock::iterator I = L->getHeader()->begin();
2593 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
2594 if (!SE.isSCEVable(PN->getType()))
2598 dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch()));
2600 ChainInstruction(PN, IncV, ChainUsersVec);
2602 // Remove any unprofitable chains.
2603 unsigned ChainIdx = 0;
2604 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
2605 UsersIdx < NChains; ++UsersIdx) {
2606 if (!isProfitableChain(IVChainVec[UsersIdx],
2607 ChainUsersVec[UsersIdx].FarUsers, SE, TLI))
2609 // Preserve the chain at UsesIdx.
2610 if (ChainIdx != UsersIdx)
2611 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
2612 FinalizeChain(IVChainVec[ChainIdx]);
2615 IVChainVec.resize(ChainIdx);
2618 void LSRInstance::FinalizeChain(IVChain &Chain) {
2619 assert(!Chain.empty() && "empty IV chains are not allowed");
2620 DEBUG(dbgs() << "Final Chain: " << *Chain[0].UserInst << "\n");
2622 for (IVChain::const_iterator I = llvm::next(Chain.begin()), E = Chain.end();
2624 DEBUG(dbgs() << " Inc: " << *I->UserInst << "\n");
2625 User::op_iterator UseI =
2626 std::find(I->UserInst->op_begin(), I->UserInst->op_end(), I->IVOperand);
2627 assert(UseI != I->UserInst->op_end() && "cannot find IV operand");
2628 IVIncSet.insert(UseI);
2632 /// Return true if the IVInc can be folded into an addressing mode.
2633 static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
2634 Value *Operand, const TargetLowering *TLI) {
2635 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
2636 if (!IncConst || !isAddressUse(UserInst, Operand))
2639 if (IncConst->getValue()->getValue().getMinSignedBits() > 64)
2642 int64_t IncOffset = IncConst->getValue()->getSExtValue();
2643 if (!isAlwaysFoldable(IncOffset, /*BaseGV=*/0, /*HaseBaseReg=*/false,
2644 LSRUse::Address, getAccessType(UserInst), TLI))
2650 /// GenerateIVChains - Generate an add or subtract for each IVInc in a chain to
2651 /// materialize the IV user's operand from the previous IV user's operand.
2652 void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
2653 SmallVectorImpl<WeakVH> &DeadInsts) {
2654 // Find the new IVOperand for the head of the chain. It may have been replaced
2656 const IVInc &Head = Chain[0];
2657 User::op_iterator IVOpEnd = Head.UserInst->op_end();
2658 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
2661 while (IVOpIter != IVOpEnd) {
2662 IVSrc = getWideOperand(*IVOpIter);
2664 // If this operand computes the expression that the chain needs, we may use
2665 // it. (Check this after setting IVSrc which is used below.)
2667 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
2668 // narrow for the chain, so we can no longer use it. We do allow using a
2669 // wider phi, assuming the LSR checked for free truncation. In that case we
2670 // should already have a truncate on this operand such that
2671 // getSCEV(IVSrc) == IncExpr.
2672 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
2673 || SE.getSCEV(IVSrc) == Head.IncExpr) {
2676 IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE);
2678 if (IVOpIter == IVOpEnd) {
2679 // Gracefully give up on this chain.
2680 DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
2684 DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
2685 Type *IVTy = IVSrc->getType();
2686 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
2687 const SCEV *LeftOverExpr = 0;
2688 for (IVChain::const_iterator IncI = llvm::next(Chain.begin()),
2689 IncE = Chain.end(); IncI != IncE; ++IncI) {
2691 Instruction *InsertPt = IncI->UserInst;
2692 if (isa<PHINode>(InsertPt))
2693 InsertPt = L->getLoopLatch()->getTerminator();
2695 // IVOper will replace the current IV User's operand. IVSrc is the IV
2696 // value currently held in a register.
2697 Value *IVOper = IVSrc;
2698 if (!IncI->IncExpr->isZero()) {
2699 // IncExpr was the result of subtraction of two narrow values, so must
2701 const SCEV *IncExpr = SE.getNoopOrSignExtend(IncI->IncExpr, IntTy);
2702 LeftOverExpr = LeftOverExpr ?
2703 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
2705 if (LeftOverExpr && !LeftOverExpr->isZero()) {
2706 // Expand the IV increment.
2707 Rewriter.clearPostInc();
2708 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
2709 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
2710 SE.getUnknown(IncV));
2711 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
2713 // If an IV increment can't be folded, use it as the next IV value.
2714 if (!canFoldIVIncExpr(LeftOverExpr, IncI->UserInst, IncI->IVOperand,
2716 assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
2721 Type *OperTy = IncI->IVOperand->getType();
2722 if (IVTy != OperTy) {
2723 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
2724 "cannot extend a chained IV");
2725 IRBuilder<> Builder(InsertPt);
2726 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
2728 IncI->UserInst->replaceUsesOfWith(IncI->IVOperand, IVOper);
2729 DeadInsts.push_back(IncI->IVOperand);
2731 // If LSR created a new, wider phi, we may also replace its postinc. We only
2732 // do this if we also found a wide value for the head of the chain.
2733 if (isa<PHINode>(Chain.back().UserInst)) {
2734 for (BasicBlock::iterator I = L->getHeader()->begin();
2735 PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
2736 if (!isCompatibleIVType(Phi, IVSrc))
2738 Instruction *PostIncV = dyn_cast<Instruction>(
2739 Phi->getIncomingValueForBlock(L->getLoopLatch()));
2740 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
2742 Value *IVOper = IVSrc;
2743 Type *PostIncTy = PostIncV->getType();
2744 if (IVTy != PostIncTy) {
2745 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
2746 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
2747 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
2748 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
2750 Phi->replaceUsesOfWith(PostIncV, IVOper);
2751 DeadInsts.push_back(PostIncV);
2756 void LSRInstance::CollectFixupsAndInitialFormulae() {
2757 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2758 Instruction *UserInst = UI->getUser();
2759 // Skip IV users that are part of profitable IV Chains.
2760 User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(),
2761 UI->getOperandValToReplace());
2762 assert(UseI != UserInst->op_end() && "cannot find IV operand");
2763 if (IVIncSet.count(UseI))
2767 LSRFixup &LF = getNewFixup();
2768 LF.UserInst = UserInst;
2769 LF.OperandValToReplace = UI->getOperandValToReplace();
2770 LF.PostIncLoops = UI->getPostIncLoops();
2772 LSRUse::KindType Kind = LSRUse::Basic;
2774 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
2775 Kind = LSRUse::Address;
2776 AccessTy = getAccessType(LF.UserInst);
2779 const SCEV *S = IU.getExpr(*UI);
2781 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
2782 // (N - i == 0), and this allows (N - i) to be the expression that we work
2783 // with rather than just N or i, so we can consider the register
2784 // requirements for both N and i at the same time. Limiting this code to
2785 // equality icmps is not a problem because all interesting loops use
2786 // equality icmps, thanks to IndVarSimplify.
2787 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
2788 if (CI->isEquality()) {
2789 // Swap the operands if needed to put the OperandValToReplace on the
2790 // left, for consistency.
2791 Value *NV = CI->getOperand(1);
2792 if (NV == LF.OperandValToReplace) {
2793 CI->setOperand(1, CI->getOperand(0));
2794 CI->setOperand(0, NV);
2795 NV = CI->getOperand(1);
2799 // x == y --> x - y == 0
2800 const SCEV *N = SE.getSCEV(NV);
2801 if (SE.isLoopInvariant(N, L)) {
2802 // S is normalized, so normalize N before folding it into S
2803 // to keep the result normalized.
2804 N = TransformForPostIncUse(Normalize, N, CI, 0,
2805 LF.PostIncLoops, SE, DT);
2806 Kind = LSRUse::ICmpZero;
2807 S = SE.getMinusSCEV(N, S);
2810 // -1 and the negations of all interesting strides (except the negation
2811 // of -1) are now also interesting.
2812 for (size_t i = 0, e = Factors.size(); i != e; ++i)
2813 if (Factors[i] != -1)
2814 Factors.insert(-(uint64_t)Factors[i]);
2818 // Set up the initial formula for this use.
2819 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
2821 LF.Offset = P.second;
2822 LSRUse &LU = Uses[LF.LUIdx];
2823 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
2824 if (!LU.WidestFixupType ||
2825 SE.getTypeSizeInBits(LU.WidestFixupType) <
2826 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
2827 LU.WidestFixupType = LF.OperandValToReplace->getType();
2829 // If this is the first use of this LSRUse, give it a formula.
2830 if (LU.Formulae.empty()) {
2831 InsertInitialFormula(S, LU, LF.LUIdx);
2832 CountRegisters(LU.Formulae.back(), LF.LUIdx);
2836 DEBUG(print_fixups(dbgs()));
2839 /// InsertInitialFormula - Insert a formula for the given expression into
2840 /// the given use, separating out loop-variant portions from loop-invariant
2841 /// and loop-computable portions.
2843 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
2845 F.InitialMatch(S, L, SE);
2846 bool Inserted = InsertFormula(LU, LUIdx, F);
2847 assert(Inserted && "Initial formula already exists!"); (void)Inserted;
2850 /// InsertSupplementalFormula - Insert a simple single-register formula for
2851 /// the given expression into the given use.
2853 LSRInstance::InsertSupplementalFormula(const SCEV *S,
2854 LSRUse &LU, size_t LUIdx) {
2856 F.BaseRegs.push_back(S);
2857 F.AM.HasBaseReg = true;
2858 bool Inserted = InsertFormula(LU, LUIdx, F);
2859 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
2862 /// CountRegisters - Note which registers are used by the given formula,
2863 /// updating RegUses.
2864 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
2866 RegUses.CountRegister(F.ScaledReg, LUIdx);
2867 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
2868 E = F.BaseRegs.end(); I != E; ++I)
2869 RegUses.CountRegister(*I, LUIdx);
2872 /// InsertFormula - If the given formula has not yet been inserted, add it to
2873 /// the list, and return true. Return false otherwise.
2874 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
2875 if (!LU.InsertFormula(F))
2878 CountRegisters(F, LUIdx);
2882 /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
2883 /// loop-invariant values which we're tracking. These other uses will pin these
2884 /// values in registers, making them less profitable for elimination.
2885 /// TODO: This currently misses non-constant addrec step registers.
2886 /// TODO: Should this give more weight to users inside the loop?
2888 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
2889 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
2890 SmallPtrSet<const SCEV *, 8> Inserted;
2892 while (!Worklist.empty()) {
2893 const SCEV *S = Worklist.pop_back_val();
2895 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
2896 Worklist.append(N->op_begin(), N->op_end());
2897 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
2898 Worklist.push_back(C->getOperand());
2899 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
2900 Worklist.push_back(D->getLHS());
2901 Worklist.push_back(D->getRHS());
2902 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2903 if (!Inserted.insert(U)) continue;
2904 const Value *V = U->getValue();
2905 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
2906 // Look for instructions defined outside the loop.
2907 if (L->contains(Inst)) continue;
2908 } else if (isa<UndefValue>(V))
2909 // Undef doesn't have a live range, so it doesn't matter.
2911 for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
2913 const Instruction *UserInst = dyn_cast<Instruction>(*UI);
2914 // Ignore non-instructions.
2917 // Ignore instructions in other functions (as can happen with
2919 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
2921 // Ignore instructions not dominated by the loop.
2922 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
2923 UserInst->getParent() :
2924 cast<PHINode>(UserInst)->getIncomingBlock(
2925 PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
2926 if (!DT.dominates(L->getHeader(), UseBB))
2928 // Ignore uses which are part of other SCEV expressions, to avoid
2929 // analyzing them multiple times.
2930 if (SE.isSCEVable(UserInst->getType())) {
2931 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
2932 // If the user is a no-op, look through to its uses.
2933 if (!isa<SCEVUnknown>(UserS))
2937 SE.getUnknown(const_cast<Instruction *>(UserInst)));
2941 // Ignore icmp instructions which are already being analyzed.
2942 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
2943 unsigned OtherIdx = !UI.getOperandNo();
2944 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
2945 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
2949 LSRFixup &LF = getNewFixup();
2950 LF.UserInst = const_cast<Instruction *>(UserInst);
2951 LF.OperandValToReplace = UI.getUse();
2952 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0);
2954 LF.Offset = P.second;
2955 LSRUse &LU = Uses[LF.LUIdx];
2956 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
2957 if (!LU.WidestFixupType ||
2958 SE.getTypeSizeInBits(LU.WidestFixupType) <
2959 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
2960 LU.WidestFixupType = LF.OperandValToReplace->getType();
2961 InsertSupplementalFormula(U, LU, LF.LUIdx);
2962 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
2969 /// CollectSubexprs - Split S into subexpressions which can be pulled out into
2970 /// separate registers. If C is non-null, multiply each subexpression by C.
2971 static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
2972 SmallVectorImpl<const SCEV *> &Ops,
2974 ScalarEvolution &SE) {
2975 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2976 // Break out add operands.
2977 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
2979 CollectSubexprs(*I, C, Ops, L, SE);
2981 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2982 // Split a non-zero base out of an addrec.
2983 if (!AR->getStart()->isZero()) {
2984 CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
2985 AR->getStepRecurrence(SE),
2987 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
2990 CollectSubexprs(AR->getStart(), C, Ops, L, SE);
2993 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
2994 // Break (C * (a + b + c)) into C*a + C*b + C*c.
2995 if (Mul->getNumOperands() == 2)
2996 if (const SCEVConstant *Op0 =
2997 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2998 CollectSubexprs(Mul->getOperand(1),
2999 C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
3005 // Otherwise use the value itself, optionally with a scale applied.
3006 Ops.push_back(C ? SE.getMulExpr(C, S) : S);
3009 /// GenerateReassociations - Split out subexpressions from adds and the bases of
3011 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3014 // Arbitrarily cap recursion to protect compile time.
3015 if (Depth >= 3) return;
3017 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3018 const SCEV *BaseReg = Base.BaseRegs[i];
3020 SmallVector<const SCEV *, 8> AddOps;
3021 CollectSubexprs(BaseReg, 0, AddOps, L, SE);
3023 if (AddOps.size() == 1) continue;
3025 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3026 JE = AddOps.end(); J != JE; ++J) {
3028 // Loop-variant "unknown" values are uninteresting; we won't be able to
3029 // do anything meaningful with them.
3030 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3033 // Don't pull a constant into a register if the constant could be folded
3034 // into an immediate field.
3035 if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,
3036 Base.getNumRegs() > 1,
3037 LU.Kind, LU.AccessTy, TLI, SE))
3040 // Collect all operands except *J.
3041 SmallVector<const SCEV *, 8> InnerAddOps
3042 (((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3044 (llvm::next(J), ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3046 // Don't leave just a constant behind in a register if the constant could
3047 // be folded into an immediate field.
3048 if (InnerAddOps.size() == 1 &&
3049 isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset,
3050 Base.getNumRegs() > 1,
3051 LU.Kind, LU.AccessTy, TLI, SE))
3054 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3055 if (InnerSum->isZero())
3059 // Add the remaining pieces of the add back into the new formula.
3060 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3061 if (TLI && InnerSumSC &&
3062 SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3063 TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3064 InnerSumSC->getValue()->getZExtValue())) {
3065 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
3066 InnerSumSC->getValue()->getZExtValue();
3067 F.BaseRegs.erase(F.BaseRegs.begin() + i);
3069 F.BaseRegs[i] = InnerSum;
3071 // Add J as its own register, or an unfolded immediate.
3072 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3073 if (TLI && SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3074 TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3075 SC->getValue()->getZExtValue()))
3076 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
3077 SC->getValue()->getZExtValue();
3079 F.BaseRegs.push_back(*J);
3081 if (InsertFormula(LU, LUIdx, F))
3082 // If that formula hadn't been seen before, recurse to find more like
3084 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1);
3089 /// GenerateCombinations - Generate a formula consisting of all of the
3090 /// loop-dominating registers added into a single register.
3091 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3093 // This method is only interesting on a plurality of registers.
3094 if (Base.BaseRegs.size() <= 1) return;
3098 SmallVector<const SCEV *, 4> Ops;
3099 for (SmallVectorImpl<const SCEV *>::const_iterator
3100 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
3101 const SCEV *BaseReg = *I;
3102 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3103 !SE.hasComputableLoopEvolution(BaseReg, L))
3104 Ops.push_back(BaseReg);
3106 F.BaseRegs.push_back(BaseReg);
3108 if (Ops.size() > 1) {
3109 const SCEV *Sum = SE.getAddExpr(Ops);
3110 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3111 // opportunity to fold something. For now, just ignore such cases
3112 // rather than proceed with zero in a register.
3113 if (!Sum->isZero()) {
3114 F.BaseRegs.push_back(Sum);
3115 (void)InsertFormula(LU, LUIdx, F);
3120 /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
3121 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3123 // We can't add a symbolic offset if the address already contains one.
3124 if (Base.AM.BaseGV) return;
3126 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3127 const SCEV *G = Base.BaseRegs[i];
3128 GlobalValue *GV = ExtractSymbol(G, SE);
3129 if (G->isZero() || !GV)
3133 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
3134 LU.Kind, LU.AccessTy, TLI))
3137 (void)InsertFormula(LU, LUIdx, F);
3141 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3142 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3144 // TODO: For now, just add the min and max offset, because it usually isn't
3145 // worthwhile looking at everything inbetween.
3146 SmallVector<int64_t, 2> Worklist;
3147 Worklist.push_back(LU.MinOffset);
3148 if (LU.MaxOffset != LU.MinOffset)
3149 Worklist.push_back(LU.MaxOffset);
3151 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3152 const SCEV *G = Base.BaseRegs[i];
3154 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
3155 E = Worklist.end(); I != E; ++I) {
3157 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I;
3158 if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I,
3159 LU.Kind, LU.AccessTy, TLI)) {
3160 // Add the offset to the base register.
3161 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G);
3162 // If it cancelled out, drop the base register, otherwise update it.
3163 if (NewG->isZero()) {
3164 std::swap(F.BaseRegs[i], F.BaseRegs.back());
3165 F.BaseRegs.pop_back();
3167 F.BaseRegs[i] = NewG;
3169 (void)InsertFormula(LU, LUIdx, F);
3173 int64_t Imm = ExtractImmediate(G, SE);
3174 if (G->isZero() || Imm == 0)
3177 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm;
3178 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
3179 LU.Kind, LU.AccessTy, TLI))
3182 (void)InsertFormula(LU, LUIdx, F);
3186 /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
3187 /// the comparison. For example, x == y -> x*c == y*c.
3188 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3190 if (LU.Kind != LSRUse::ICmpZero) return;
3192 // Determine the integer type for the base formula.
3193 Type *IntTy = Base.getType();
3195 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3197 // Don't do this if there is more than one offset.
3198 if (LU.MinOffset != LU.MaxOffset) return;
3200 assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
3202 // Check each interesting stride.
3203 for (SmallSetVector<int64_t, 8>::const_iterator
3204 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3205 int64_t Factor = *I;
3207 // Check that the multiplication doesn't overflow.
3208 if (Base.AM.BaseOffs == INT64_MIN && Factor == -1)
3210 int64_t NewBaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
3211 if (NewBaseOffs / Factor != Base.AM.BaseOffs)
3214 // Check that multiplying with the use offset doesn't overflow.
3215 int64_t Offset = LU.MinOffset;
3216 if (Offset == INT64_MIN && Factor == -1)
3218 Offset = (uint64_t)Offset * Factor;
3219 if (Offset / Factor != LU.MinOffset)
3223 F.AM.BaseOffs = NewBaseOffs;
3225 // Check that this scale is legal.
3226 if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI))
3229 // Compensate for the use having MinOffset built into it.
3230 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset;
3232 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3234 // Check that multiplying with each base register doesn't overflow.
3235 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3236 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3237 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3241 // Check that multiplying with the scaled register doesn't overflow.
3243 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3244 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3248 // Check that multiplying with the unfolded offset doesn't overflow.
3249 if (F.UnfoldedOffset != 0) {
3250 if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
3252 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3253 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3257 // If we make it here and it's legal, add it.
3258 (void)InsertFormula(LU, LUIdx, F);
3263 /// GenerateScales - Generate stride factor reuse formulae by making use of
3264 /// scaled-offset address modes, for example.
3265 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3266 // Determine the integer type for the base formula.
3267 Type *IntTy = Base.getType();
3270 // If this Formula already has a scaled register, we can't add another one.
3271 if (Base.AM.Scale != 0) return;
3273 // Check each interesting stride.
3274 for (SmallSetVector<int64_t, 8>::const_iterator
3275 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3276 int64_t Factor = *I;
3278 Base.AM.Scale = Factor;
3279 Base.AM.HasBaseReg = Base.BaseRegs.size() > 1;
3280 // Check whether this scale is going to be legal.
3281 if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
3282 LU.Kind, LU.AccessTy, TLI)) {
3283 // As a special-case, handle special out-of-loop Basic users specially.
3284 // TODO: Reconsider this special case.
3285 if (LU.Kind == LSRUse::Basic &&
3286 isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
3287 LSRUse::Special, LU.AccessTy, TLI) &&
3288 LU.AllFixupsOutsideLoop)
3289 LU.Kind = LSRUse::Special;
3293 // For an ICmpZero, negating a solitary base register won't lead to
3295 if (LU.Kind == LSRUse::ICmpZero &&
3296 !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV)
3298 // For each addrec base reg, apply the scale, if possible.
3299 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3300 if (const SCEVAddRecExpr *AR =
3301 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
3302 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3303 if (FactorS->isZero())
3305 // Divide out the factor, ignoring high bits, since we'll be
3306 // scaling the value back up in the end.
3307 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3308 // TODO: This could be optimized to avoid all the copying.
3310 F.ScaledReg = Quotient;
3311 F.DeleteBaseReg(F.BaseRegs[i]);
3312 (void)InsertFormula(LU, LUIdx, F);
3318 /// GenerateTruncates - Generate reuse formulae from different IV types.
3319 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3320 // This requires TargetLowering to tell us which truncates are free.
3323 // Don't bother truncating symbolic values.
3324 if (Base.AM.BaseGV) return;
3326 // Determine the integer type for the base formula.
3327 Type *DstTy = Base.getType();
3329 DstTy = SE.getEffectiveSCEVType(DstTy);
3331 for (SmallSetVector<Type *, 4>::const_iterator
3332 I = Types.begin(), E = Types.end(); I != E; ++I) {
3334 if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
3337 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
3338 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
3339 JE = F.BaseRegs.end(); J != JE; ++J)
3340 *J = SE.getAnyExtendExpr(*J, SrcTy);
3342 // TODO: This assumes we've done basic processing on all uses and
3343 // have an idea what the register usage is.
3344 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3347 (void)InsertFormula(LU, LUIdx, F);
3354 /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
3355 /// defer modifications so that the search phase doesn't have to worry about
3356 /// the data structures moving underneath it.
3360 const SCEV *OrigReg;
3362 WorkItem(size_t LI, int64_t I, const SCEV *R)
3363 : LUIdx(LI), Imm(I), OrigReg(R) {}
3365 void print(raw_ostream &OS) const;
3371 void WorkItem::print(raw_ostream &OS) const {
3372 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3373 << " , add offset " << Imm;
3376 void WorkItem::dump() const {
3377 print(errs()); errs() << '\n';
3380 /// GenerateCrossUseConstantOffsets - Look for registers which are a constant
3381 /// distance apart and try to form reuse opportunities between them.
3382 void LSRInstance::GenerateCrossUseConstantOffsets() {
3383 // Group the registers by their value without any added constant offset.
3384 typedef std::map<int64_t, const SCEV *> ImmMapTy;
3385 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
3387 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3388 SmallVector<const SCEV *, 8> Sequence;
3389 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
3391 const SCEV *Reg = *I;
3392 int64_t Imm = ExtractImmediate(Reg, SE);
3393 std::pair<RegMapTy::iterator, bool> Pair =
3394 Map.insert(std::make_pair(Reg, ImmMapTy()));
3396 Sequence.push_back(Reg);
3397 Pair.first->second.insert(std::make_pair(Imm, *I));
3398 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
3401 // Now examine each set of registers with the same base value. Build up
3402 // a list of work to do and do the work in a separate step so that we're
3403 // not adding formulae and register counts while we're searching.
3404 SmallVector<WorkItem, 32> WorkItems;
3405 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3406 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
3407 E = Sequence.end(); I != E; ++I) {
3408 const SCEV *Reg = *I;
3409 const ImmMapTy &Imms = Map.find(Reg)->second;
3411 // It's not worthwhile looking for reuse if there's only one offset.
3412 if (Imms.size() == 1)
3415 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
3416 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3418 dbgs() << ' ' << J->first;
3421 // Examine each offset.
3422 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3424 const SCEV *OrigReg = J->second;
3426 int64_t JImm = J->first;
3427 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
3429 if (!isa<SCEVConstant>(OrigReg) &&
3430 UsedByIndicesMap[Reg].count() == 1) {
3431 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
3435 // Conservatively examine offsets between this orig reg a few selected
3437 ImmMapTy::const_iterator OtherImms[] = {
3438 Imms.begin(), prior(Imms.end()),
3439 Imms.lower_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
3441 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
3442 ImmMapTy::const_iterator M = OtherImms[i];
3443 if (M == J || M == JE) continue;
3445 // Compute the difference between the two.
3446 int64_t Imm = (uint64_t)JImm - M->first;
3447 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
3448 LUIdx = UsedByIndices.find_next(LUIdx))
3449 // Make a memo of this use, offset, and register tuple.
3450 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
3451 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
3458 UsedByIndicesMap.clear();
3459 UniqueItems.clear();
3461 // Now iterate through the worklist and add new formulae.
3462 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
3463 E = WorkItems.end(); I != E; ++I) {
3464 const WorkItem &WI = *I;
3465 size_t LUIdx = WI.LUIdx;
3466 LSRUse &LU = Uses[LUIdx];
3467 int64_t Imm = WI.Imm;
3468 const SCEV *OrigReg = WI.OrigReg;
3470 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
3471 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
3472 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
3474 // TODO: Use a more targeted data structure.
3475 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
3476 const Formula &F = LU.Formulae[L];
3477 // Use the immediate in the scaled register.
3478 if (F.ScaledReg == OrigReg) {
3479 int64_t Offs = (uint64_t)F.AM.BaseOffs +
3480 Imm * (uint64_t)F.AM.Scale;
3481 // Don't create 50 + reg(-50).
3482 if (F.referencesReg(SE.getSCEV(
3483 ConstantInt::get(IntTy, -(uint64_t)Offs))))
3486 NewF.AM.BaseOffs = Offs;
3487 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
3488 LU.Kind, LU.AccessTy, TLI))
3490 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
3492 // If the new scale is a constant in a register, and adding the constant
3493 // value to the immediate would produce a value closer to zero than the
3494 // immediate itself, then the formula isn't worthwhile.
3495 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
3496 if (C->getValue()->isNegative() !=
3497 (NewF.AM.BaseOffs < 0) &&
3498 (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale))
3499 .ule(abs64(NewF.AM.BaseOffs)))
3503 (void)InsertFormula(LU, LUIdx, NewF);
3505 // Use the immediate in a base register.
3506 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
3507 const SCEV *BaseReg = F.BaseRegs[N];
3508 if (BaseReg != OrigReg)
3511 NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
3512 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
3513 LU.Kind, LU.AccessTy, TLI)) {
3515 !TLI->isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
3518 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
3520 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
3522 // If the new formula has a constant in a register, and adding the
3523 // constant value to the immediate would produce a value closer to
3524 // zero than the immediate itself, then the formula isn't worthwhile.
3525 for (SmallVectorImpl<const SCEV *>::const_iterator
3526 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
3528 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
3529 if ((C->getValue()->getValue() + NewF.AM.BaseOffs).abs().slt(
3530 abs64(NewF.AM.BaseOffs)) &&
3531 (C->getValue()->getValue() +
3532 NewF.AM.BaseOffs).countTrailingZeros() >=
3533 CountTrailingZeros_64(NewF.AM.BaseOffs))
3537 (void)InsertFormula(LU, LUIdx, NewF);
3546 /// GenerateAllReuseFormulae - Generate formulae for each use.
3548 LSRInstance::GenerateAllReuseFormulae() {
3549 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
3550 // queries are more precise.
3551 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3552 LSRUse &LU = Uses[LUIdx];
3553 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3554 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
3555 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3556 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
3558 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3559 LSRUse &LU = Uses[LUIdx];
3560 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3561 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
3562 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3563 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
3564 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3565 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
3566 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3567 GenerateScales(LU, LUIdx, LU.Formulae[i]);
3569 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3570 LSRUse &LU = Uses[LUIdx];
3571 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3572 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
3575 GenerateCrossUseConstantOffsets();
3577 DEBUG(dbgs() << "\n"
3578 "After generating reuse formulae:\n";
3579 print_uses(dbgs()));
3582 /// If there are multiple formulae with the same set of registers used
3583 /// by other uses, pick the best one and delete the others.
3584 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
3585 DenseSet<const SCEV *> VisitedRegs;
3586 SmallPtrSet<const SCEV *, 16> Regs;
3587 SmallPtrSet<const SCEV *, 16> LoserRegs;
3589 bool ChangedFormulae = false;
3592 // Collect the best formula for each unique set of shared registers. This
3593 // is reset for each use.
3594 typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo>
3596 BestFormulaeTy BestFormulae;
3598 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3599 LSRUse &LU = Uses[LUIdx];
3600 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
3603 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
3604 FIdx != NumForms; ++FIdx) {
3605 Formula &F = LU.Formulae[FIdx];
3607 // Some formulas are instant losers. For example, they may depend on
3608 // nonexistent AddRecs from other loops. These need to be filtered
3609 // immediately, otherwise heuristics could choose them over others leading
3610 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
3611 // avoids the need to recompute this information across formulae using the
3612 // same bad AddRec. Passing LoserRegs is also essential unless we remove
3613 // the corresponding bad register from the Regs set.
3616 CostF.RateFormula(F, Regs, VisitedRegs, L, LU.Offsets, SE, DT,
3618 if (CostF.isLoser()) {
3619 // During initial formula generation, undesirable formulae are generated
3620 // by uses within other loops that have some non-trivial address mode or
3621 // use the postinc form of the IV. LSR needs to provide these formulae
3622 // as the basis of rediscovering the desired formula that uses an AddRec
3623 // corresponding to the existing phi. Once all formulae have been
3624 // generated, these initial losers may be pruned.
3625 DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());
3629 SmallVector<const SCEV *, 2> Key;
3630 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
3631 JE = F.BaseRegs.end(); J != JE; ++J) {
3632 const SCEV *Reg = *J;
3633 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
3637 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
3638 Key.push_back(F.ScaledReg);
3639 // Unstable sort by host order ok, because this is only used for
3641 std::sort(Key.begin(), Key.end());
3643 std::pair<BestFormulaeTy::const_iterator, bool> P =
3644 BestFormulae.insert(std::make_pair(Key, FIdx));
3648 Formula &Best = LU.Formulae[P.first->second];
3652 CostBest.RateFormula(Best, Regs, VisitedRegs, L, LU.Offsets, SE, DT);
3653 if (CostF < CostBest)
3655 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
3657 " in favor of formula "; Best.print(dbgs());
3661 ChangedFormulae = true;
3663 LU.DeleteFormula(F);
3669 // Now that we've filtered out some formulae, recompute the Regs set.
3671 LU.RecomputeRegs(LUIdx, RegUses);
3673 // Reset this to prepare for the next use.
3674 BestFormulae.clear();
3677 DEBUG(if (ChangedFormulae) {
3679 "After filtering out undesirable candidates:\n";
3684 // This is a rough guess that seems to work fairly well.
3685 static const size_t ComplexityLimit = UINT16_MAX;
3687 /// EstimateSearchSpaceComplexity - Estimate the worst-case number of
3688 /// solutions the solver might have to consider. It almost never considers
3689 /// this many solutions because it prune the search space, but the pruning
3690 /// isn't always sufficient.
3691 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
3693 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3694 E = Uses.end(); I != E; ++I) {
3695 size_t FSize = I->Formulae.size();
3696 if (FSize >= ComplexityLimit) {
3697 Power = ComplexityLimit;
3701 if (Power >= ComplexityLimit)
3707 /// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset
3708 /// of the registers of another formula, it won't help reduce register
3709 /// pressure (though it may not necessarily hurt register pressure); remove
3710 /// it to simplify the system.
3711 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
3712 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3713 DEBUG(dbgs() << "The search space is too complex.\n");
3715 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
3716 "which use a superset of registers used by other "
3719 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3720 LSRUse &LU = Uses[LUIdx];
3722 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
3723 Formula &F = LU.Formulae[i];
3724 // Look for a formula with a constant or GV in a register. If the use
3725 // also has a formula with that same value in an immediate field,
3726 // delete the one that uses a register.
3727 for (SmallVectorImpl<const SCEV *>::const_iterator
3728 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
3729 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
3731 NewF.AM.BaseOffs += C->getValue()->getSExtValue();
3732 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
3733 (I - F.BaseRegs.begin()));
3734 if (LU.HasFormulaWithSameRegs(NewF)) {
3735 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
3736 LU.DeleteFormula(F);
3742 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
3743 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
3746 NewF.AM.BaseGV = GV;
3747 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
3748 (I - F.BaseRegs.begin()));
3749 if (LU.HasFormulaWithSameRegs(NewF)) {
3750 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
3752 LU.DeleteFormula(F);
3763 LU.RecomputeRegs(LUIdx, RegUses);
3766 DEBUG(dbgs() << "After pre-selection:\n";
3767 print_uses(dbgs()));
3771 /// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers
3772 /// for expressions like A, A+1, A+2, etc., allocate a single register for
3774 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
3775 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3776 DEBUG(dbgs() << "The search space is too complex.\n");
3778 DEBUG(dbgs() << "Narrowing the search space by assuming that uses "
3779 "separated by a constant offset will use the same "
3782 // This is especially useful for unrolled loops.
3784 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3785 LSRUse &LU = Uses[LUIdx];
3786 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
3787 E = LU.Formulae.end(); I != E; ++I) {
3788 const Formula &F = *I;
3789 if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) {
3790 if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) {
3791 if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs,
3792 /*HasBaseReg=*/false,
3793 LU.Kind, LU.AccessTy)) {
3794 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs());
3797 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
3799 // Update the relocs to reference the new use.
3800 for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
3801 E = Fixups.end(); I != E; ++I) {
3802 LSRFixup &Fixup = *I;
3803 if (Fixup.LUIdx == LUIdx) {
3804 Fixup.LUIdx = LUThatHas - &Uses.front();
3805 Fixup.Offset += F.AM.BaseOffs;
3806 // Add the new offset to LUThatHas' offset list.
3807 if (LUThatHas->Offsets.back() != Fixup.Offset) {
3808 LUThatHas->Offsets.push_back(Fixup.Offset);
3809 if (Fixup.Offset > LUThatHas->MaxOffset)
3810 LUThatHas->MaxOffset = Fixup.Offset;
3811 if (Fixup.Offset < LUThatHas->MinOffset)
3812 LUThatHas->MinOffset = Fixup.Offset;
3814 DEBUG(dbgs() << "New fixup has offset "
3815 << Fixup.Offset << '\n');
3817 if (Fixup.LUIdx == NumUses-1)
3818 Fixup.LUIdx = LUIdx;
3821 // Delete formulae from the new use which are no longer legal.
3823 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
3824 Formula &F = LUThatHas->Formulae[i];
3825 if (!isLegalUse(F.AM,
3826 LUThatHas->MinOffset, LUThatHas->MaxOffset,
3827 LUThatHas->Kind, LUThatHas->AccessTy, TLI)) {
3828 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
3830 LUThatHas->DeleteFormula(F);
3837 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
3839 // Delete the old use.
3840 DeleteUse(LU, LUIdx);
3850 DEBUG(dbgs() << "After pre-selection:\n";
3851 print_uses(dbgs()));
3855 /// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call
3856 /// FilterOutUndesirableDedicatedRegisters again, if necessary, now that
3857 /// we've done more filtering, as it may be able to find more formulae to
3859 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
3860 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3861 DEBUG(dbgs() << "The search space is too complex.\n");
3863 DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
3864 "undesirable dedicated registers.\n");
3866 FilterOutUndesirableDedicatedRegisters();
3868 DEBUG(dbgs() << "After pre-selection:\n";
3869 print_uses(dbgs()));
3873 /// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely
3874 /// to be profitable, and then in any use which has any reference to that
3875 /// register, delete all formulae which do not reference that register.
3876 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
3877 // With all other options exhausted, loop until the system is simple
3878 // enough to handle.
3879 SmallPtrSet<const SCEV *, 4> Taken;
3880 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3881 // Ok, we have too many of formulae on our hands to conveniently handle.
3882 // Use a rough heuristic to thin out the list.
3883 DEBUG(dbgs() << "The search space is too complex.\n");
3885 // Pick the register which is used by the most LSRUses, which is likely
3886 // to be a good reuse register candidate.
3887 const SCEV *Best = 0;
3888 unsigned BestNum = 0;
3889 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
3891 const SCEV *Reg = *I;
3892 if (Taken.count(Reg))
3897 unsigned Count = RegUses.getUsedByIndices(Reg).count();
3898 if (Count > BestNum) {
3905 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
3906 << " will yield profitable reuse.\n");
3909 // In any use with formulae which references this register, delete formulae
3910 // which don't reference it.
3911 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3912 LSRUse &LU = Uses[LUIdx];
3913 if (!LU.Regs.count(Best)) continue;
3916 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
3917 Formula &F = LU.Formulae[i];
3918 if (!F.referencesReg(Best)) {
3919 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
3920 LU.DeleteFormula(F);
3924 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
3930 LU.RecomputeRegs(LUIdx, RegUses);
3933 DEBUG(dbgs() << "After pre-selection:\n";
3934 print_uses(dbgs()));
3938 /// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
3939 /// formulae to choose from, use some rough heuristics to prune down the number
3940 /// of formulae. This keeps the main solver from taking an extraordinary amount
3941 /// of time in some worst-case scenarios.
3942 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
3943 NarrowSearchSpaceByDetectingSupersets();
3944 NarrowSearchSpaceByCollapsingUnrolledCode();
3945 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
3946 NarrowSearchSpaceByPickingWinnerRegs();
3949 /// SolveRecurse - This is the recursive solver.
3950 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
3952 SmallVectorImpl<const Formula *> &Workspace,
3953 const Cost &CurCost,
3954 const SmallPtrSet<const SCEV *, 16> &CurRegs,
3955 DenseSet<const SCEV *> &VisitedRegs) const {
3958 // - use more aggressive filtering
3959 // - sort the formula so that the most profitable solutions are found first
3960 // - sort the uses too
3962 // - don't compute a cost, and then compare. compare while computing a cost
3964 // - track register sets with SmallBitVector
3966 const LSRUse &LU = Uses[Workspace.size()];
3968 // If this use references any register that's already a part of the
3969 // in-progress solution, consider it a requirement that a formula must
3970 // reference that register in order to be considered. This prunes out
3971 // unprofitable searching.
3972 SmallSetVector<const SCEV *, 4> ReqRegs;
3973 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
3974 E = CurRegs.end(); I != E; ++I)
3975 if (LU.Regs.count(*I))
3978 SmallPtrSet<const SCEV *, 16> NewRegs;
3980 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
3981 E = LU.Formulae.end(); I != E; ++I) {
3982 const Formula &F = *I;
3984 // Ignore formulae which do not use any of the required registers.
3985 bool SatisfiedReqReg = true;
3986 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
3987 JE = ReqRegs.end(); J != JE; ++J) {
3988 const SCEV *Reg = *J;
3989 if ((!F.ScaledReg || F.ScaledReg != Reg) &&
3990 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) ==
3992 SatisfiedReqReg = false;
3996 if (!SatisfiedReqReg) {
3997 // If none of the formulae satisfied the required registers, then we could
3998 // clear ReqRegs and try again. Currently, we simply give up in this case.
4002 // Evaluate the cost of the current formula. If it's already worse than
4003 // the current best, prune the search at that point.
4006 NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT);
4007 if (NewCost < SolutionCost) {
4008 Workspace.push_back(&F);
4009 if (Workspace.size() != Uses.size()) {
4010 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4011 NewRegs, VisitedRegs);
4012 if (F.getNumRegs() == 1 && Workspace.size() == 1)
4013 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4015 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
4016 dbgs() << ".\n Regs:";
4017 for (SmallPtrSet<const SCEV *, 16>::const_iterator
4018 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
4019 dbgs() << ' ' << **I;
4022 SolutionCost = NewCost;
4023 Solution = Workspace;
4025 Workspace.pop_back();
4030 /// Solve - Choose one formula from each use. Return the results in the given
4031 /// Solution vector.
4032 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4033 SmallVector<const Formula *, 8> Workspace;
4035 SolutionCost.Loose();
4037 SmallPtrSet<const SCEV *, 16> CurRegs;
4038 DenseSet<const SCEV *> VisitedRegs;
4039 Workspace.reserve(Uses.size());
4041 // SolveRecurse does all the work.
4042 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4043 CurRegs, VisitedRegs);
4044 if (Solution.empty()) {
4045 DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
4049 // Ok, we've now made all our decisions.
4050 DEBUG(dbgs() << "\n"
4051 "The chosen solution requires "; SolutionCost.print(dbgs());
4053 for (size_t i = 0, e = Uses.size(); i != e; ++i) {
4055 Uses[i].print(dbgs());
4058 Solution[i]->print(dbgs());
4062 assert(Solution.size() == Uses.size() && "Malformed solution!");
4065 /// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
4066 /// the dominator tree far as we can go while still being dominated by the
4067 /// input positions. This helps canonicalize the insert position, which
4068 /// encourages sharing.
4069 BasicBlock::iterator
4070 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4071 const SmallVectorImpl<Instruction *> &Inputs)
4074 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4075 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4078 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4079 if (!Rung) return IP;
4080 Rung = Rung->getIDom();
4081 if (!Rung) return IP;
4082 IDom = Rung->getBlock();
4084 // Don't climb into a loop though.
4085 const Loop *IDomLoop = LI.getLoopFor(IDom);
4086 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4087 if (IDomDepth <= IPLoopDepth &&
4088 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4092 bool AllDominate = true;
4093 Instruction *BetterPos = 0;
4094 Instruction *Tentative = IDom->getTerminator();
4095 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
4096 E = Inputs.end(); I != E; ++I) {
4097 Instruction *Inst = *I;
4098 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4099 AllDominate = false;
4102 // Attempt to find an insert position in the middle of the block,
4103 // instead of at the end, so that it can be used for other expansions.
4104 if (IDom == Inst->getParent() &&
4105 (!BetterPos || DT.dominates(BetterPos, Inst)))
4106 BetterPos = llvm::next(BasicBlock::iterator(Inst));
4119 /// AdjustInsertPositionForExpand - Determine an input position which will be
4120 /// dominated by the operands and which will dominate the result.
4121 BasicBlock::iterator
4122 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4125 SCEVExpander &Rewriter) const {
4126 // Collect some instructions which must be dominated by the
4127 // expanding replacement. These must be dominated by any operands that
4128 // will be required in the expansion.
4129 SmallVector<Instruction *, 4> Inputs;
4130 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4131 Inputs.push_back(I);
4132 if (LU.Kind == LSRUse::ICmpZero)
4133 if (Instruction *I =
4134 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4135 Inputs.push_back(I);
4136 if (LF.PostIncLoops.count(L)) {
4137 if (LF.isUseFullyOutsideLoop(L))
4138 Inputs.push_back(L->getLoopLatch()->getTerminator());
4140 Inputs.push_back(IVIncInsertPos);
4142 // The expansion must also be dominated by the increment positions of any
4143 // loops it for which it is using post-inc mode.
4144 for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(),
4145 E = LF.PostIncLoops.end(); I != E; ++I) {
4146 const Loop *PIL = *I;
4147 if (PIL == L) continue;
4149 // Be dominated by the loop exit.
4150 SmallVector<BasicBlock *, 4> ExitingBlocks;
4151 PIL->getExitingBlocks(ExitingBlocks);
4152 if (!ExitingBlocks.empty()) {
4153 BasicBlock *BB = ExitingBlocks[0];
4154 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4155 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4156 Inputs.push_back(BB->getTerminator());
4160 assert(!isa<PHINode>(LowestIP) && !isa<LandingPadInst>(LowestIP)
4161 && !isa<DbgInfoIntrinsic>(LowestIP) &&
4162 "Insertion point must be a normal instruction");
4164 // Then, climb up the immediate dominator tree as far as we can go while
4165 // still being dominated by the input positions.
4166 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4168 // Don't insert instructions before PHI nodes.
4169 while (isa<PHINode>(IP)) ++IP;
4171 // Ignore landingpad instructions.
4172 while (isa<LandingPadInst>(IP)) ++IP;
4174 // Ignore debug intrinsics.
4175 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4177 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4178 // IP consistent across expansions and allows the previously inserted
4179 // instructions to be reused by subsequent expansion.
4180 while (Rewriter.isInsertedInstruction(IP) && IP != LowestIP) ++IP;
4185 /// Expand - Emit instructions for the leading candidate expression for this
4186 /// LSRUse (this is called "expanding").
4187 Value *LSRInstance::Expand(const LSRFixup &LF,
4189 BasicBlock::iterator IP,
4190 SCEVExpander &Rewriter,
4191 SmallVectorImpl<WeakVH> &DeadInsts) const {
4192 const LSRUse &LU = Uses[LF.LUIdx];
4194 // Determine an input position which will be dominated by the operands and
4195 // which will dominate the result.
4196 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4198 // Inform the Rewriter if we have a post-increment use, so that it can
4199 // perform an advantageous expansion.
4200 Rewriter.setPostInc(LF.PostIncLoops);
4202 // This is the type that the user actually needs.
4203 Type *OpTy = LF.OperandValToReplace->getType();
4204 // This will be the type that we'll initially expand to.
4205 Type *Ty = F.getType();
4207 // No type known; just expand directly to the ultimate type.
4209 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
4210 // Expand directly to the ultimate type if it's the right size.
4212 // This is the type to do integer arithmetic in.
4213 Type *IntTy = SE.getEffectiveSCEVType(Ty);
4215 // Build up a list of operands to add together to form the full base.
4216 SmallVector<const SCEV *, 8> Ops;
4218 // Expand the BaseRegs portion.
4219 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
4220 E = F.BaseRegs.end(); I != E; ++I) {
4221 const SCEV *Reg = *I;
4222 assert(!Reg->isZero() && "Zero allocated in a base register!");
4224 // If we're expanding for a post-inc user, make the post-inc adjustment.
4225 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4226 Reg = TransformForPostIncUse(Denormalize, Reg,
4227 LF.UserInst, LF.OperandValToReplace,
4230 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
4233 // Flush the operand list to suppress SCEVExpander hoisting.
4235 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4237 Ops.push_back(SE.getUnknown(FullV));
4240 // Expand the ScaledReg portion.
4241 Value *ICmpScaledV = 0;
4242 if (F.AM.Scale != 0) {
4243 const SCEV *ScaledS = F.ScaledReg;
4245 // If we're expanding for a post-inc user, make the post-inc adjustment.
4246 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4247 ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
4248 LF.UserInst, LF.OperandValToReplace,
4251 if (LU.Kind == LSRUse::ICmpZero) {
4252 // An interesting way of "folding" with an icmp is to use a negated
4253 // scale, which we'll implement by inserting it into the other operand
4255 assert(F.AM.Scale == -1 &&
4256 "The only scale supported by ICmpZero uses is -1!");
4257 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
4259 // Otherwise just expand the scaled register and an explicit scale,
4260 // which is expected to be matched as part of the address.
4261 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
4262 ScaledS = SE.getMulExpr(ScaledS,
4263 SE.getConstant(ScaledS->getType(), F.AM.Scale));
4264 Ops.push_back(ScaledS);
4266 // Flush the operand list to suppress SCEVExpander hoisting.
4267 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4269 Ops.push_back(SE.getUnknown(FullV));
4273 // Expand the GV portion.
4275 Ops.push_back(SE.getUnknown(F.AM.BaseGV));
4277 // Flush the operand list to suppress SCEVExpander hoisting.
4278 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4280 Ops.push_back(SE.getUnknown(FullV));
4283 // Expand the immediate portion.
4284 int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset;
4286 if (LU.Kind == LSRUse::ICmpZero) {
4287 // The other interesting way of "folding" with an ICmpZero is to use a
4288 // negated immediate.
4290 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
4292 Ops.push_back(SE.getUnknown(ICmpScaledV));
4293 ICmpScaledV = ConstantInt::get(IntTy, Offset);
4296 // Just add the immediate values. These again are expected to be matched
4297 // as part of the address.
4298 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
4302 // Expand the unfolded offset portion.
4303 int64_t UnfoldedOffset = F.UnfoldedOffset;
4304 if (UnfoldedOffset != 0) {
4305 // Just add the immediate values.
4306 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
4310 // Emit instructions summing all the operands.
4311 const SCEV *FullS = Ops.empty() ?
4312 SE.getConstant(IntTy, 0) :
4314 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
4316 // We're done expanding now, so reset the rewriter.
4317 Rewriter.clearPostInc();
4319 // An ICmpZero Formula represents an ICmp which we're handling as a
4320 // comparison against zero. Now that we've expanded an expression for that
4321 // form, update the ICmp's other operand.
4322 if (LU.Kind == LSRUse::ICmpZero) {
4323 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
4324 DeadInsts.push_back(CI->getOperand(1));
4325 assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
4326 "a scale at the same time!");
4327 if (F.AM.Scale == -1) {
4328 if (ICmpScaledV->getType() != OpTy) {
4330 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
4332 ICmpScaledV, OpTy, "tmp", CI);
4335 CI->setOperand(1, ICmpScaledV);
4337 assert(F.AM.Scale == 0 &&
4338 "ICmp does not support folding a global value and "
4339 "a scale at the same time!");
4340 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
4342 if (C->getType() != OpTy)
4343 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4347 CI->setOperand(1, C);
4354 /// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
4355 /// of their operands effectively happens in their predecessor blocks, so the
4356 /// expression may need to be expanded in multiple places.
4357 void LSRInstance::RewriteForPHI(PHINode *PN,
4360 SCEVExpander &Rewriter,
4361 SmallVectorImpl<WeakVH> &DeadInsts,
4363 DenseMap<BasicBlock *, Value *> Inserted;
4364 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
4365 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
4366 BasicBlock *BB = PN->getIncomingBlock(i);
4368 // If this is a critical edge, split the edge so that we do not insert
4369 // the code on all predecessor/successor paths. We do this unless this
4370 // is the canonical backedge for this loop, which complicates post-inc
4372 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
4373 !isa<IndirectBrInst>(BB->getTerminator())) {
4374 BasicBlock *Parent = PN->getParent();
4375 Loop *PNLoop = LI.getLoopFor(Parent);
4376 if (!PNLoop || Parent != PNLoop->getHeader()) {
4377 // Split the critical edge.
4378 BasicBlock *NewBB = 0;
4379 if (!Parent->isLandingPad()) {
4380 NewBB = SplitCriticalEdge(BB, Parent, P,
4381 /*MergeIdenticalEdges=*/true,
4382 /*DontDeleteUselessPhis=*/true);
4384 SmallVector<BasicBlock*, 2> NewBBs;
4385 SplitLandingPadPredecessors(Parent, BB, "", "", P, NewBBs);
4389 // If PN is outside of the loop and BB is in the loop, we want to
4390 // move the block to be immediately before the PHI block, not
4391 // immediately after BB.
4392 if (L->contains(BB) && !L->contains(PN))
4393 NewBB->moveBefore(PN->getParent());
4395 // Splitting the edge can reduce the number of PHI entries we have.
4396 e = PN->getNumIncomingValues();
4398 i = PN->getBasicBlockIndex(BB);
4402 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
4403 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
4405 PN->setIncomingValue(i, Pair.first->second);
4407 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
4409 // If this is reuse-by-noop-cast, insert the noop cast.
4410 Type *OpTy = LF.OperandValToReplace->getType();
4411 if (FullV->getType() != OpTy)
4413 CastInst::Create(CastInst::getCastOpcode(FullV, false,
4415 FullV, LF.OperandValToReplace->getType(),
4416 "tmp", BB->getTerminator());
4418 PN->setIncomingValue(i, FullV);
4419 Pair.first->second = FullV;
4424 /// Rewrite - Emit instructions for the leading candidate expression for this
4425 /// LSRUse (this is called "expanding"), and update the UserInst to reference
4426 /// the newly expanded value.
4427 void LSRInstance::Rewrite(const LSRFixup &LF,
4429 SCEVExpander &Rewriter,
4430 SmallVectorImpl<WeakVH> &DeadInsts,
4432 // First, find an insertion point that dominates UserInst. For PHI nodes,
4433 // find the nearest block which dominates all the relevant uses.
4434 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
4435 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
4437 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
4439 // If this is reuse-by-noop-cast, insert the noop cast.
4440 Type *OpTy = LF.OperandValToReplace->getType();
4441 if (FullV->getType() != OpTy) {
4443 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
4444 FullV, OpTy, "tmp", LF.UserInst);
4448 // Update the user. ICmpZero is handled specially here (for now) because
4449 // Expand may have updated one of the operands of the icmp already, and
4450 // its new value may happen to be equal to LF.OperandValToReplace, in
4451 // which case doing replaceUsesOfWith leads to replacing both operands
4452 // with the same value. TODO: Reorganize this.
4453 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
4454 LF.UserInst->setOperand(0, FullV);
4456 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
4459 DeadInsts.push_back(LF.OperandValToReplace);
4462 /// ImplementSolution - Rewrite all the fixup locations with new values,
4463 /// following the chosen solution.
4465 LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
4467 // Keep track of instructions we may have made dead, so that
4468 // we can remove them after we are done working.
4469 SmallVector<WeakVH, 16> DeadInsts;
4471 SCEVExpander Rewriter(SE, "lsr");
4473 Rewriter.setDebugType(DEBUG_TYPE);
4475 Rewriter.disableCanonicalMode();
4476 Rewriter.enableLSRMode();
4477 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
4479 // Mark phi nodes that terminate chains so the expander tries to reuse them.
4480 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4481 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4482 if (PHINode *PN = dyn_cast<PHINode>(ChainI->back().UserInst))
4483 Rewriter.setChainedPhi(PN);
4486 // Expand the new value definitions and update the users.
4487 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4488 E = Fixups.end(); I != E; ++I) {
4489 const LSRFixup &Fixup = *I;
4491 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
4496 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4497 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4498 GenerateIVChain(*ChainI, Rewriter, DeadInsts);
4501 // Clean up after ourselves. This must be done before deleting any
4505 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
4508 LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
4509 : IU(P->getAnalysis<IVUsers>()),
4510 SE(P->getAnalysis<ScalarEvolution>()),
4511 DT(P->getAnalysis<DominatorTree>()),
4512 LI(P->getAnalysis<LoopInfo>()),
4513 TLI(tli), L(l), Changed(false), IVIncInsertPos(0) {
4515 // If LoopSimplify form is not available, stay out of trouble.
4516 if (!L->isLoopSimplifyForm())
4519 // If there's no interesting work to be done, bail early.
4520 if (IU.empty()) return;
4523 // All dominating loops must have preheaders, or SCEVExpander may not be able
4524 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
4526 // IVUsers analysis should only create users that are dominated by simple loop
4527 // headers. Since this loop should dominate all of its users, its user list
4528 // should be empty if this loop itself is not within a simple loop nest.
4529 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
4530 Rung; Rung = Rung->getIDom()) {
4531 BasicBlock *BB = Rung->getBlock();
4532 const Loop *DomLoop = LI.getLoopFor(BB);
4533 if (DomLoop && DomLoop->getHeader() == BB) {
4534 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
4539 DEBUG(dbgs() << "\nLSR on loop ";
4540 WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
4543 // First, perform some low-level loop optimizations.
4545 OptimizeLoopTermCond();
4547 // If loop preparation eliminates all interesting IV users, bail.
4548 if (IU.empty()) return;
4550 // Skip nested loops until we can model them better with formulae.
4552 DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
4556 // Start collecting data and preparing for the solver.
4558 CollectInterestingTypesAndFactors();
4559 CollectFixupsAndInitialFormulae();
4560 CollectLoopInvariantFixupsAndFormulae();
4562 assert(!Uses.empty() && "IVUsers reported at least one use");
4563 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
4564 print_uses(dbgs()));
4566 // Now use the reuse data to generate a bunch of interesting ways
4567 // to formulate the values needed for the uses.
4568 GenerateAllReuseFormulae();
4570 FilterOutUndesirableDedicatedRegisters();
4571 NarrowSearchSpaceUsingHeuristics();
4573 SmallVector<const Formula *, 8> Solution;
4576 // Release memory that is no longer needed.
4581 if (Solution.empty())
4585 // Formulae should be legal.
4586 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
4587 E = Uses.end(); I != E; ++I) {
4588 const LSRUse &LU = *I;
4589 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
4590 JE = LU.Formulae.end(); J != JE; ++J)
4591 assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset,
4592 LU.Kind, LU.AccessTy, TLI) &&
4593 "Illegal formula generated!");
4597 // Now that we've decided what we want, make it so.
4598 ImplementSolution(Solution, P);
4601 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
4602 if (Factors.empty() && Types.empty()) return;
4604 OS << "LSR has identified the following interesting factors and types: ";
4607 for (SmallSetVector<int64_t, 8>::const_iterator
4608 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
4609 if (!First) OS << ", ";
4614 for (SmallSetVector<Type *, 4>::const_iterator
4615 I = Types.begin(), E = Types.end(); I != E; ++I) {
4616 if (!First) OS << ", ";
4618 OS << '(' << **I << ')';
4623 void LSRInstance::print_fixups(raw_ostream &OS) const {
4624 OS << "LSR is examining the following fixup sites:\n";
4625 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4626 E = Fixups.end(); I != E; ++I) {
4633 void LSRInstance::print_uses(raw_ostream &OS) const {
4634 OS << "LSR is examining the following uses:\n";
4635 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
4636 E = Uses.end(); I != E; ++I) {
4637 const LSRUse &LU = *I;
4641 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
4642 JE = LU.Formulae.end(); J != JE; ++J) {
4650 void LSRInstance::print(raw_ostream &OS) const {
4651 print_factors_and_types(OS);
4656 void LSRInstance::dump() const {
4657 print(errs()); errs() << '\n';
4662 class LoopStrengthReduce : public LoopPass {
4663 /// TLI - Keep a pointer of a TargetLowering to consult for determining
4664 /// transformation profitability.
4665 const TargetLowering *const TLI;
4668 static char ID; // Pass ID, replacement for typeid
4669 explicit LoopStrengthReduce(const TargetLowering *tli = 0);
4672 bool runOnLoop(Loop *L, LPPassManager &LPM);
4673 void getAnalysisUsage(AnalysisUsage &AU) const;
4678 char LoopStrengthReduce::ID = 0;
4679 INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
4680 "Loop Strength Reduction", false, false)
4681 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
4682 INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
4683 INITIALIZE_PASS_DEPENDENCY(IVUsers)
4684 INITIALIZE_PASS_DEPENDENCY(LoopInfo)
4685 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
4686 INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
4687 "Loop Strength Reduction", false, false)
4690 Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
4691 return new LoopStrengthReduce(TLI);
4694 LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
4695 : LoopPass(ID), TLI(tli) {
4696 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
4699 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
4700 // We split critical edges, so we change the CFG. However, we do update
4701 // many analyses if they are around.
4702 AU.addPreservedID(LoopSimplifyID);
4704 AU.addRequired<LoopInfo>();
4705 AU.addPreserved<LoopInfo>();
4706 AU.addRequiredID(LoopSimplifyID);
4707 AU.addRequired<DominatorTree>();
4708 AU.addPreserved<DominatorTree>();
4709 AU.addRequired<ScalarEvolution>();
4710 AU.addPreserved<ScalarEvolution>();
4711 // Requiring LoopSimplify a second time here prevents IVUsers from running
4712 // twice, since LoopSimplify was invalidated by running ScalarEvolution.
4713 AU.addRequiredID(LoopSimplifyID);
4714 AU.addRequired<IVUsers>();
4715 AU.addPreserved<IVUsers>();
4718 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
4719 bool Changed = false;
4721 // Run the main LSR transformation.
4722 Changed |= LSRInstance(TLI, L, this).getChanged();
4724 // Remove any extra phis created by processing inner loops.
4725 Changed |= DeleteDeadPHIs(L->getHeader());
4726 if (EnablePhiElim) {
4727 SmallVector<WeakVH, 16> DeadInsts;
4728 SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), "lsr");
4730 Rewriter.setDebugType(DEBUG_TYPE);
4732 unsigned numFolded = Rewriter.
4733 replaceCongruentIVs(L, &getAnalysis<DominatorTree>(), DeadInsts, TLI);
4736 DeleteTriviallyDeadInstructions(DeadInsts);
4737 DeleteDeadPHIs(L->getHeader());