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) {
1285 if (TLI) return TLI->isLegalICmpImmediate(-(uint64_t)AM.BaseOffs);
1292 // Only handle single-register values.
1293 return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0;
1295 case LSRUse::Special:
1296 // Only handle -1 scales, or no scale.
1297 return AM.Scale == 0 || AM.Scale == -1;
1300 llvm_unreachable("Invalid LSRUse Kind!");
1303 static bool isLegalUse(TargetLowering::AddrMode AM,
1304 int64_t MinOffset, int64_t MaxOffset,
1305 LSRUse::KindType Kind, Type *AccessTy,
1306 const TargetLowering *TLI) {
1307 // Check for overflow.
1308 if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) !=
1311 AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset;
1312 if (isLegalUse(AM, Kind, AccessTy, TLI)) {
1313 AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset;
1314 // Check for overflow.
1315 if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) !=
1318 AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset;
1319 return isLegalUse(AM, Kind, AccessTy, TLI);
1324 static bool isAlwaysFoldable(int64_t BaseOffs,
1325 GlobalValue *BaseGV,
1327 LSRUse::KindType Kind, Type *AccessTy,
1328 const TargetLowering *TLI) {
1329 // Fast-path: zero is always foldable.
1330 if (BaseOffs == 0 && !BaseGV) return true;
1332 // Conservatively, create an address with an immediate and a
1333 // base and a scale.
1334 TargetLowering::AddrMode AM;
1335 AM.BaseOffs = BaseOffs;
1337 AM.HasBaseReg = HasBaseReg;
1338 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1340 // Canonicalize a scale of 1 to a base register if the formula doesn't
1341 // already have a base register.
1342 if (!AM.HasBaseReg && AM.Scale == 1) {
1344 AM.HasBaseReg = true;
1347 return isLegalUse(AM, Kind, AccessTy, TLI);
1350 static bool isAlwaysFoldable(const SCEV *S,
1351 int64_t MinOffset, int64_t MaxOffset,
1353 LSRUse::KindType Kind, Type *AccessTy,
1354 const TargetLowering *TLI,
1355 ScalarEvolution &SE) {
1356 // Fast-path: zero is always foldable.
1357 if (S->isZero()) return true;
1359 // Conservatively, create an address with an immediate and a
1360 // base and a scale.
1361 int64_t BaseOffs = ExtractImmediate(S, SE);
1362 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1364 // If there's anything else involved, it's not foldable.
1365 if (!S->isZero()) return false;
1367 // Fast-path: zero is always foldable.
1368 if (BaseOffs == 0 && !BaseGV) return true;
1370 // Conservatively, create an address with an immediate and a
1371 // base and a scale.
1372 TargetLowering::AddrMode AM;
1373 AM.BaseOffs = BaseOffs;
1375 AM.HasBaseReg = HasBaseReg;
1376 AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1378 return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI);
1383 /// UseMapDenseMapInfo - A DenseMapInfo implementation for holding
1384 /// DenseMaps and DenseSets of pairs of const SCEV* and LSRUse::Kind.
1385 struct UseMapDenseMapInfo {
1386 static std::pair<const SCEV *, LSRUse::KindType> getEmptyKey() {
1387 return std::make_pair(reinterpret_cast<const SCEV *>(-1), LSRUse::Basic);
1390 static std::pair<const SCEV *, LSRUse::KindType> getTombstoneKey() {
1391 return std::make_pair(reinterpret_cast<const SCEV *>(-2), LSRUse::Basic);
1395 getHashValue(const std::pair<const SCEV *, LSRUse::KindType> &V) {
1396 unsigned Result = DenseMapInfo<const SCEV *>::getHashValue(V.first);
1397 Result ^= DenseMapInfo<unsigned>::getHashValue(unsigned(V.second));
1401 static bool isEqual(const std::pair<const SCEV *, LSRUse::KindType> &LHS,
1402 const std::pair<const SCEV *, LSRUse::KindType> &RHS) {
1407 /// IVInc - An individual increment in a Chain of IV increments.
1408 /// Relate an IV user to an expression that computes the IV it uses from the IV
1409 /// used by the previous link in the Chain.
1411 /// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1412 /// original IVOperand. The head of the chain's IVOperand is only valid during
1413 /// chain collection, before LSR replaces IV users. During chain generation,
1414 /// IncExpr can be used to find the new IVOperand that computes the same
1417 Instruction *UserInst;
1419 const SCEV *IncExpr;
1421 IVInc(Instruction *U, Value *O, const SCEV *E):
1422 UserInst(U), IVOperand(O), IncExpr(E) {}
1425 // IVChain - The list of IV increments in program order.
1426 // We typically add the head of a chain without finding subsequent links.
1427 typedef SmallVector<IVInc,1> IVChain;
1429 /// ChainUsers - Helper for CollectChains to track multiple IV increment uses.
1430 /// Distinguish between FarUsers that definitely cross IV increments and
1431 /// NearUsers that may be used between IV increments.
1433 SmallPtrSet<Instruction*, 4> FarUsers;
1434 SmallPtrSet<Instruction*, 4> NearUsers;
1437 /// LSRInstance - This class holds state for the main loop strength reduction
1441 ScalarEvolution &SE;
1444 const TargetLowering *const TLI;
1448 /// IVIncInsertPos - This is the insert position that the current loop's
1449 /// induction variable increment should be placed. In simple loops, this is
1450 /// the latch block's terminator. But in more complicated cases, this is a
1451 /// position which will dominate all the in-loop post-increment users.
1452 Instruction *IVIncInsertPos;
1454 /// Factors - Interesting factors between use strides.
1455 SmallSetVector<int64_t, 8> Factors;
1457 /// Types - Interesting use types, to facilitate truncation reuse.
1458 SmallSetVector<Type *, 4> Types;
1460 /// Fixups - The list of operands which are to be replaced.
1461 SmallVector<LSRFixup, 16> Fixups;
1463 /// Uses - The list of interesting uses.
1464 SmallVector<LSRUse, 16> Uses;
1466 /// RegUses - Track which uses use which register candidates.
1467 RegUseTracker RegUses;
1469 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1470 // have more than a few IV increment chains in a loop. Missing a Chain falls
1471 // back to normal LSR behavior for those uses.
1472 static const unsigned MaxChains = 8;
1474 /// IVChainVec - IV users can form a chain of IV increments.
1475 SmallVector<IVChain, MaxChains> IVChainVec;
1477 /// IVIncSet - IV users that belong to profitable IVChains.
1478 SmallPtrSet<Use*, MaxChains> IVIncSet;
1480 void OptimizeShadowIV();
1481 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1482 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1483 void OptimizeLoopTermCond();
1485 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1486 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1487 void FinalizeChain(IVChain &Chain);
1488 void CollectChains();
1489 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1490 SmallVectorImpl<WeakVH> &DeadInsts);
1492 void CollectInterestingTypesAndFactors();
1493 void CollectFixupsAndInitialFormulae();
1495 LSRFixup &getNewFixup() {
1496 Fixups.push_back(LSRFixup());
1497 return Fixups.back();
1500 // Support for sharing of LSRUses between LSRFixups.
1501 typedef DenseMap<std::pair<const SCEV *, LSRUse::KindType>,
1503 UseMapDenseMapInfo> UseMapTy;
1506 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1507 LSRUse::KindType Kind, Type *AccessTy);
1509 std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1510 LSRUse::KindType Kind,
1513 void DeleteUse(LSRUse &LU, size_t LUIdx);
1515 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1517 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1518 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1519 void CountRegisters(const Formula &F, size_t LUIdx);
1520 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1522 void CollectLoopInvariantFixupsAndFormulae();
1524 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1525 unsigned Depth = 0);
1526 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1527 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1528 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1529 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1530 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1531 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1532 void GenerateCrossUseConstantOffsets();
1533 void GenerateAllReuseFormulae();
1535 void FilterOutUndesirableDedicatedRegisters();
1537 size_t EstimateSearchSpaceComplexity() const;
1538 void NarrowSearchSpaceByDetectingSupersets();
1539 void NarrowSearchSpaceByCollapsingUnrolledCode();
1540 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1541 void NarrowSearchSpaceByPickingWinnerRegs();
1542 void NarrowSearchSpaceUsingHeuristics();
1544 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1546 SmallVectorImpl<const Formula *> &Workspace,
1547 const Cost &CurCost,
1548 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1549 DenseSet<const SCEV *> &VisitedRegs) const;
1550 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1552 BasicBlock::iterator
1553 HoistInsertPosition(BasicBlock::iterator IP,
1554 const SmallVectorImpl<Instruction *> &Inputs) const;
1555 BasicBlock::iterator
1556 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1559 SCEVExpander &Rewriter) const;
1561 Value *Expand(const LSRFixup &LF,
1563 BasicBlock::iterator IP,
1564 SCEVExpander &Rewriter,
1565 SmallVectorImpl<WeakVH> &DeadInsts) const;
1566 void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
1568 SCEVExpander &Rewriter,
1569 SmallVectorImpl<WeakVH> &DeadInsts,
1571 void Rewrite(const LSRFixup &LF,
1573 SCEVExpander &Rewriter,
1574 SmallVectorImpl<WeakVH> &DeadInsts,
1576 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1580 LSRInstance(const TargetLowering *tli, Loop *l, Pass *P);
1582 bool getChanged() const { return Changed; }
1584 void print_factors_and_types(raw_ostream &OS) const;
1585 void print_fixups(raw_ostream &OS) const;
1586 void print_uses(raw_ostream &OS) const;
1587 void print(raw_ostream &OS) const;
1593 /// OptimizeShadowIV - If IV is used in a int-to-float cast
1594 /// inside the loop then try to eliminate the cast operation.
1595 void LSRInstance::OptimizeShadowIV() {
1596 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1597 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1600 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1601 UI != E; /* empty */) {
1602 IVUsers::const_iterator CandidateUI = UI;
1604 Instruction *ShadowUse = CandidateUI->getUser();
1605 Type *DestTy = NULL;
1606 bool IsSigned = false;
1608 /* If shadow use is a int->float cast then insert a second IV
1609 to eliminate this cast.
1611 for (unsigned i = 0; i < n; ++i)
1617 for (unsigned i = 0; i < n; ++i, ++d)
1620 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
1622 DestTy = UCast->getDestTy();
1624 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
1626 DestTy = SCast->getDestTy();
1628 if (!DestTy) continue;
1631 // If target does not support DestTy natively then do not apply
1632 // this transformation.
1633 EVT DVT = TLI->getValueType(DestTy);
1634 if (!TLI->isTypeLegal(DVT)) continue;
1637 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1639 if (PH->getNumIncomingValues() != 2) continue;
1641 Type *SrcTy = PH->getType();
1642 int Mantissa = DestTy->getFPMantissaWidth();
1643 if (Mantissa == -1) continue;
1644 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1647 unsigned Entry, Latch;
1648 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1656 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1657 if (!Init) continue;
1658 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
1659 (double)Init->getSExtValue() :
1660 (double)Init->getZExtValue());
1662 BinaryOperator *Incr =
1663 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1664 if (!Incr) continue;
1665 if (Incr->getOpcode() != Instruction::Add
1666 && Incr->getOpcode() != Instruction::Sub)
1669 /* Initialize new IV, double d = 0.0 in above example. */
1670 ConstantInt *C = NULL;
1671 if (Incr->getOperand(0) == PH)
1672 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1673 else if (Incr->getOperand(1) == PH)
1674 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1680 // Ignore negative constants, as the code below doesn't handle them
1681 // correctly. TODO: Remove this restriction.
1682 if (!C->getValue().isStrictlyPositive()) continue;
1684 /* Add new PHINode. */
1685 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
1687 /* create new increment. '++d' in above example. */
1688 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1689 BinaryOperator *NewIncr =
1690 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1691 Instruction::FAdd : Instruction::FSub,
1692 NewPH, CFP, "IV.S.next.", Incr);
1694 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1695 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1697 /* Remove cast operation */
1698 ShadowUse->replaceAllUsesWith(NewPH);
1699 ShadowUse->eraseFromParent();
1705 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1706 /// set the IV user and stride information and return true, otherwise return
1708 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
1709 for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1710 if (UI->getUser() == Cond) {
1711 // NOTE: we could handle setcc instructions with multiple uses here, but
1712 // InstCombine does it as well for simple uses, it's not clear that it
1713 // occurs enough in real life to handle.
1720 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
1721 /// a max computation.
1723 /// This is a narrow solution to a specific, but acute, problem. For loops
1729 /// } while (++i < n);
1731 /// the trip count isn't just 'n', because 'n' might not be positive. And
1732 /// unfortunately this can come up even for loops where the user didn't use
1733 /// a C do-while loop. For example, seemingly well-behaved top-test loops
1734 /// will commonly be lowered like this:
1740 /// } while (++i < n);
1743 /// and then it's possible for subsequent optimization to obscure the if
1744 /// test in such a way that indvars can't find it.
1746 /// When indvars can't find the if test in loops like this, it creates a
1747 /// max expression, which allows it to give the loop a canonical
1748 /// induction variable:
1751 /// max = n < 1 ? 1 : n;
1754 /// } while (++i != max);
1756 /// Canonical induction variables are necessary because the loop passes
1757 /// are designed around them. The most obvious example of this is the
1758 /// LoopInfo analysis, which doesn't remember trip count values. It
1759 /// expects to be able to rediscover the trip count each time it is
1760 /// needed, and it does this using a simple analysis that only succeeds if
1761 /// the loop has a canonical induction variable.
1763 /// However, when it comes time to generate code, the maximum operation
1764 /// can be quite costly, especially if it's inside of an outer loop.
1766 /// This function solves this problem by detecting this type of loop and
1767 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1768 /// the instructions for the maximum computation.
1770 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1771 // Check that the loop matches the pattern we're looking for.
1772 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1773 Cond->getPredicate() != CmpInst::ICMP_NE)
1776 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
1777 if (!Sel || !Sel->hasOneUse()) return Cond;
1779 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1780 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1782 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
1784 // Add one to the backedge-taken count to get the trip count.
1785 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
1786 if (IterationCount != SE.getSCEV(Sel)) return Cond;
1788 // Check for a max calculation that matches the pattern. There's no check
1789 // for ICMP_ULE here because the comparison would be with zero, which
1790 // isn't interesting.
1791 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
1792 const SCEVNAryExpr *Max = 0;
1793 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
1794 Pred = ICmpInst::ICMP_SLE;
1796 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
1797 Pred = ICmpInst::ICMP_SLT;
1799 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
1800 Pred = ICmpInst::ICMP_ULT;
1807 // To handle a max with more than two operands, this optimization would
1808 // require additional checking and setup.
1809 if (Max->getNumOperands() != 2)
1812 const SCEV *MaxLHS = Max->getOperand(0);
1813 const SCEV *MaxRHS = Max->getOperand(1);
1815 // ScalarEvolution canonicalizes constants to the left. For < and >, look
1816 // for a comparison with 1. For <= and >=, a comparison with zero.
1818 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
1821 // Check the relevant induction variable for conformance to
1823 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
1824 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
1825 if (!AR || !AR->isAffine() ||
1826 AR->getStart() != One ||
1827 AR->getStepRecurrence(SE) != One)
1830 assert(AR->getLoop() == L &&
1831 "Loop condition operand is an addrec in a different loop!");
1833 // Check the right operand of the select, and remember it, as it will
1834 // be used in the new comparison instruction.
1836 if (ICmpInst::isTrueWhenEqual(Pred)) {
1837 // Look for n+1, and grab n.
1838 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
1839 if (isa<ConstantInt>(BO->getOperand(1)) &&
1840 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1841 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1842 NewRHS = BO->getOperand(0);
1843 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
1844 if (isa<ConstantInt>(BO->getOperand(1)) &&
1845 cast<ConstantInt>(BO->getOperand(1))->isOne() &&
1846 SE.getSCEV(BO->getOperand(0)) == MaxRHS)
1847 NewRHS = BO->getOperand(0);
1850 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
1851 NewRHS = Sel->getOperand(1);
1852 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
1853 NewRHS = Sel->getOperand(2);
1854 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
1855 NewRHS = SU->getValue();
1857 // Max doesn't match expected pattern.
1860 // Determine the new comparison opcode. It may be signed or unsigned,
1861 // and the original comparison may be either equality or inequality.
1862 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
1863 Pred = CmpInst::getInversePredicate(Pred);
1865 // Ok, everything looks ok to change the condition into an SLT or SGE and
1866 // delete the max calculation.
1868 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
1870 // Delete the max calculation instructions.
1871 Cond->replaceAllUsesWith(NewCond);
1872 CondUse->setUser(NewCond);
1873 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
1874 Cond->eraseFromParent();
1875 Sel->eraseFromParent();
1876 if (Cmp->use_empty())
1877 Cmp->eraseFromParent();
1881 /// OptimizeLoopTermCond - Change loop terminating condition to use the
1882 /// postinc iv when possible.
1884 LSRInstance::OptimizeLoopTermCond() {
1885 SmallPtrSet<Instruction *, 4> PostIncs;
1887 BasicBlock *LatchBlock = L->getLoopLatch();
1888 SmallVector<BasicBlock*, 8> ExitingBlocks;
1889 L->getExitingBlocks(ExitingBlocks);
1891 for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) {
1892 BasicBlock *ExitingBlock = ExitingBlocks[i];
1894 // Get the terminating condition for the loop if possible. If we
1895 // can, we want to change it to use a post-incremented version of its
1896 // induction variable, to allow coalescing the live ranges for the IV into
1897 // one register value.
1899 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
1902 // FIXME: Overly conservative, termination condition could be an 'or' etc..
1903 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
1906 // Search IVUsesByStride to find Cond's IVUse if there is one.
1907 IVStrideUse *CondUse = 0;
1908 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
1909 if (!FindIVUserForCond(Cond, CondUse))
1912 // If the trip count is computed in terms of a max (due to ScalarEvolution
1913 // being unable to find a sufficient guard, for example), change the loop
1914 // comparison to use SLT or ULT instead of NE.
1915 // One consequence of doing this now is that it disrupts the count-down
1916 // optimization. That's not always a bad thing though, because in such
1917 // cases it may still be worthwhile to avoid a max.
1918 Cond = OptimizeMax(Cond, CondUse);
1920 // If this exiting block dominates the latch block, it may also use
1921 // the post-inc value if it won't be shared with other uses.
1922 // Check for dominance.
1923 if (!DT.dominates(ExitingBlock, LatchBlock))
1926 // Conservatively avoid trying to use the post-inc value in non-latch
1927 // exits if there may be pre-inc users in intervening blocks.
1928 if (LatchBlock != ExitingBlock)
1929 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
1930 // Test if the use is reachable from the exiting block. This dominator
1931 // query is a conservative approximation of reachability.
1932 if (&*UI != CondUse &&
1933 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
1934 // Conservatively assume there may be reuse if the quotient of their
1935 // strides could be a legal scale.
1936 const SCEV *A = IU.getStride(*CondUse, L);
1937 const SCEV *B = IU.getStride(*UI, L);
1938 if (!A || !B) continue;
1939 if (SE.getTypeSizeInBits(A->getType()) !=
1940 SE.getTypeSizeInBits(B->getType())) {
1941 if (SE.getTypeSizeInBits(A->getType()) >
1942 SE.getTypeSizeInBits(B->getType()))
1943 B = SE.getSignExtendExpr(B, A->getType());
1945 A = SE.getSignExtendExpr(A, B->getType());
1947 if (const SCEVConstant *D =
1948 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
1949 const ConstantInt *C = D->getValue();
1950 // Stride of one or negative one can have reuse with non-addresses.
1951 if (C->isOne() || C->isAllOnesValue())
1952 goto decline_post_inc;
1953 // Avoid weird situations.
1954 if (C->getValue().getMinSignedBits() >= 64 ||
1955 C->getValue().isMinSignedValue())
1956 goto decline_post_inc;
1957 // Without TLI, assume that any stride might be valid, and so any
1958 // use might be shared.
1960 goto decline_post_inc;
1961 // Check for possible scaled-address reuse.
1962 Type *AccessTy = getAccessType(UI->getUser());
1963 TargetLowering::AddrMode AM;
1964 AM.Scale = C->getSExtValue();
1965 if (TLI->isLegalAddressingMode(AM, AccessTy))
1966 goto decline_post_inc;
1967 AM.Scale = -AM.Scale;
1968 if (TLI->isLegalAddressingMode(AM, AccessTy))
1969 goto decline_post_inc;
1973 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
1976 // It's possible for the setcc instruction to be anywhere in the loop, and
1977 // possible for it to have multiple users. If it is not immediately before
1978 // the exiting block branch, move it.
1979 if (&*++BasicBlock::iterator(Cond) != TermBr) {
1980 if (Cond->hasOneUse()) {
1981 Cond->moveBefore(TermBr);
1983 // Clone the terminating condition and insert into the loopend.
1984 ICmpInst *OldCond = Cond;
1985 Cond = cast<ICmpInst>(Cond->clone());
1986 Cond->setName(L->getHeader()->getName() + ".termcond");
1987 ExitingBlock->getInstList().insert(TermBr, Cond);
1989 // Clone the IVUse, as the old use still exists!
1990 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
1991 TermBr->replaceUsesOfWith(OldCond, Cond);
1995 // If we get to here, we know that we can transform the setcc instruction to
1996 // use the post-incremented version of the IV, allowing us to coalesce the
1997 // live ranges for the IV correctly.
1998 CondUse->transformToPostInc(L);
2001 PostIncs.insert(Cond);
2005 // Determine an insertion point for the loop induction variable increment. It
2006 // must dominate all the post-inc comparisons we just set up, and it must
2007 // dominate the loop latch edge.
2008 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2009 for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(),
2010 E = PostIncs.end(); I != E; ++I) {
2012 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2014 if (BB == (*I)->getParent())
2015 IVIncInsertPos = *I;
2016 else if (BB != IVIncInsertPos->getParent())
2017 IVIncInsertPos = BB->getTerminator();
2021 /// reconcileNewOffset - Determine if the given use can accommodate a fixup
2022 /// at the given offset and other details. If so, update the use and
2025 LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
2026 LSRUse::KindType Kind, Type *AccessTy) {
2027 int64_t NewMinOffset = LU.MinOffset;
2028 int64_t NewMaxOffset = LU.MaxOffset;
2029 Type *NewAccessTy = AccessTy;
2031 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2032 // something conservative, however this can pessimize in the case that one of
2033 // the uses will have all its uses outside the loop, for example.
2034 if (LU.Kind != Kind)
2036 // Conservatively assume HasBaseReg is true for now.
2037 if (NewOffset < LU.MinOffset) {
2038 if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, HasBaseReg,
2039 Kind, AccessTy, TLI))
2041 NewMinOffset = NewOffset;
2042 } else if (NewOffset > LU.MaxOffset) {
2043 if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg,
2044 Kind, AccessTy, TLI))
2046 NewMaxOffset = NewOffset;
2048 // Check for a mismatched access type, and fall back conservatively as needed.
2049 // TODO: Be less conservative when the type is similar and can use the same
2050 // addressing modes.
2051 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
2052 NewAccessTy = Type::getVoidTy(AccessTy->getContext());
2055 LU.MinOffset = NewMinOffset;
2056 LU.MaxOffset = NewMaxOffset;
2057 LU.AccessTy = NewAccessTy;
2058 if (NewOffset != LU.Offsets.back())
2059 LU.Offsets.push_back(NewOffset);
2063 /// getUse - Return an LSRUse index and an offset value for a fixup which
2064 /// needs the given expression, with the given kind and optional access type.
2065 /// Either reuse an existing use or create a new one, as needed.
2066 std::pair<size_t, int64_t>
2067 LSRInstance::getUse(const SCEV *&Expr,
2068 LSRUse::KindType Kind, Type *AccessTy) {
2069 const SCEV *Copy = Expr;
2070 int64_t Offset = ExtractImmediate(Expr, SE);
2072 // Basic uses can't accept any offset, for example.
2073 if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) {
2078 std::pair<UseMapTy::iterator, bool> P =
2079 UseMap.insert(std::make_pair(std::make_pair(Expr, Kind), 0));
2081 // A use already existed with this base.
2082 size_t LUIdx = P.first->second;
2083 LSRUse &LU = Uses[LUIdx];
2084 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2086 return std::make_pair(LUIdx, Offset);
2089 // Create a new use.
2090 size_t LUIdx = Uses.size();
2091 P.first->second = LUIdx;
2092 Uses.push_back(LSRUse(Kind, AccessTy));
2093 LSRUse &LU = Uses[LUIdx];
2095 // We don't need to track redundant offsets, but we don't need to go out
2096 // of our way here to avoid them.
2097 if (LU.Offsets.empty() || Offset != LU.Offsets.back())
2098 LU.Offsets.push_back(Offset);
2100 LU.MinOffset = Offset;
2101 LU.MaxOffset = Offset;
2102 return std::make_pair(LUIdx, Offset);
2105 /// DeleteUse - Delete the given use from the Uses list.
2106 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2107 if (&LU != &Uses.back())
2108 std::swap(LU, Uses.back());
2112 RegUses.SwapAndDropUse(LUIdx, Uses.size());
2115 /// FindUseWithFormula - Look for a use distinct from OrigLU which is has
2116 /// a formula that has the same registers as the given formula.
2118 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2119 const LSRUse &OrigLU) {
2120 // Search all uses for the formula. This could be more clever.
2121 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2122 LSRUse &LU = Uses[LUIdx];
2123 // Check whether this use is close enough to OrigLU, to see whether it's
2124 // worthwhile looking through its formulae.
2125 // Ignore ICmpZero uses because they may contain formulae generated by
2126 // GenerateICmpZeroScales, in which case adding fixup offsets may
2128 if (&LU != &OrigLU &&
2129 LU.Kind != LSRUse::ICmpZero &&
2130 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2131 LU.WidestFixupType == OrigLU.WidestFixupType &&
2132 LU.HasFormulaWithSameRegs(OrigF)) {
2133 // Scan through this use's formulae.
2134 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
2135 E = LU.Formulae.end(); I != E; ++I) {
2136 const Formula &F = *I;
2137 // Check to see if this formula has the same registers and symbols
2139 if (F.BaseRegs == OrigF.BaseRegs &&
2140 F.ScaledReg == OrigF.ScaledReg &&
2141 F.AM.BaseGV == OrigF.AM.BaseGV &&
2142 F.AM.Scale == OrigF.AM.Scale &&
2143 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2144 if (F.AM.BaseOffs == 0)
2146 // This is the formula where all the registers and symbols matched;
2147 // there aren't going to be any others. Since we declined it, we
2148 // can skip the rest of the formulae and procede to the next LSRUse.
2155 // Nothing looked good.
2159 void LSRInstance::CollectInterestingTypesAndFactors() {
2160 SmallSetVector<const SCEV *, 4> Strides;
2162 // Collect interesting types and strides.
2163 SmallVector<const SCEV *, 4> Worklist;
2164 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2165 const SCEV *Expr = IU.getExpr(*UI);
2167 // Collect interesting types.
2168 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2170 // Add strides for mentioned loops.
2171 Worklist.push_back(Expr);
2173 const SCEV *S = Worklist.pop_back_val();
2174 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2175 if (AR->getLoop() == L)
2176 Strides.insert(AR->getStepRecurrence(SE));
2177 Worklist.push_back(AR->getStart());
2178 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2179 Worklist.append(Add->op_begin(), Add->op_end());
2181 } while (!Worklist.empty());
2184 // Compute interesting factors from the set of interesting strides.
2185 for (SmallSetVector<const SCEV *, 4>::const_iterator
2186 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2187 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2188 llvm::next(I); NewStrideIter != E; ++NewStrideIter) {
2189 const SCEV *OldStride = *I;
2190 const SCEV *NewStride = *NewStrideIter;
2192 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2193 SE.getTypeSizeInBits(NewStride->getType())) {
2194 if (SE.getTypeSizeInBits(OldStride->getType()) >
2195 SE.getTypeSizeInBits(NewStride->getType()))
2196 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2198 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2200 if (const SCEVConstant *Factor =
2201 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2203 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2204 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2205 } else if (const SCEVConstant *Factor =
2206 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2209 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2210 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2214 // If all uses use the same type, don't bother looking for truncation-based
2216 if (Types.size() == 1)
2219 DEBUG(print_factors_and_types(dbgs()));
2222 /// findIVOperand - Helper for CollectChains that finds an IV operand (computed
2223 /// by an AddRec in this loop) within [OI,OE) or returns OE. If IVUsers mapped
2224 /// Instructions to IVStrideUses, we could partially skip this.
2225 static User::op_iterator
2226 findIVOperand(User::op_iterator OI, User::op_iterator OE,
2227 Loop *L, ScalarEvolution &SE) {
2228 for(; OI != OE; ++OI) {
2229 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2230 if (!SE.isSCEVable(Oper->getType()))
2233 if (const SCEVAddRecExpr *AR =
2234 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2235 if (AR->getLoop() == L)
2243 /// getWideOperand - IVChain logic must consistenctly peek base TruncInst
2244 /// operands, so wrap it in a convenient helper.
2245 static Value *getWideOperand(Value *Oper) {
2246 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2247 return Trunc->getOperand(0);
2251 /// isCompatibleIVType - Return true if we allow an IV chain to include both
2253 static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2254 Type *LType = LVal->getType();
2255 Type *RType = RVal->getType();
2256 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy());
2259 /// getExprBase - Return an approximation of this SCEV expression's "base", or
2260 /// NULL for any constant. Returning the expression itself is
2261 /// conservative. Returning a deeper subexpression is more precise and valid as
2262 /// long as it isn't less complex than another subexpression. For expressions
2263 /// involving multiple unscaled values, we need to return the pointer-type
2264 /// SCEVUnknown. This avoids forming chains across objects, such as:
2265 /// PrevOper==a[i], IVOper==b[i], IVInc==b-a.
2267 /// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2268 /// SCEVUnknown, we simply return the rightmost SCEV operand.
2269 static const SCEV *getExprBase(const SCEV *S) {
2270 switch (S->getSCEVType()) {
2271 default: // uncluding scUnknown.
2276 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2278 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2280 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2282 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2283 // there's nothing more complex.
2284 // FIXME: not sure if we want to recognize negation.
2285 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2286 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2287 E(Add->op_begin()); I != E; ++I) {
2288 const SCEV *SubExpr = *I;
2289 if (SubExpr->getSCEVType() == scAddExpr)
2290 return getExprBase(SubExpr);
2292 if (SubExpr->getSCEVType() != scMulExpr)
2295 return S; // all operands are scaled, be conservative.
2298 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2302 /// Return true if the chain increment is profitable to expand into a loop
2303 /// invariant value, which may require its own register. A profitable chain
2304 /// increment will be an offset relative to the same base. We allow such offsets
2305 /// to potentially be used as chain increment as long as it's not obviously
2306 /// expensive to expand using real instructions.
2308 getProfitableChainIncrement(Value *NextIV, Value *PrevIV,
2309 const IVChain &Chain, Loop *L,
2310 ScalarEvolution &SE, const TargetLowering *TLI) {
2311 // Prune the solution space aggressively by checking that both IV operands
2312 // are expressions that operate on the same unscaled SCEVUnknown. This
2313 // "base" will be canceled by the subsequent getMinusSCEV call. Checking first
2314 // avoids creating extra SCEV expressions.
2315 const SCEV *OperExpr = SE.getSCEV(NextIV);
2316 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2317 if (getExprBase(OperExpr) != getExprBase(PrevExpr) && !StressIVChain)
2320 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2321 if (!SE.isLoopInvariant(IncExpr, L))
2324 // We are not able to expand an increment unless it is loop invariant,
2325 // however, the following checks are purely for profitability.
2329 // Do not replace a constant offset from IV head with a nonconstant IV
2331 if (!isa<SCEVConstant>(IncExpr)) {
2332 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Chain[0].IVOperand));
2333 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2337 SmallPtrSet<const SCEV*, 8> Processed;
2338 if (isHighCostExpansion(IncExpr, Processed, SE))
2344 /// Return true if the number of registers needed for the chain is estimated to
2345 /// be less than the number required for the individual IV users. First prohibit
2346 /// any IV users that keep the IV live across increments (the Users set should
2347 /// be empty). Next count the number and type of increments in the chain.
2349 /// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2350 /// effectively use postinc addressing modes. Only consider it profitable it the
2351 /// increments can be computed in fewer registers when chained.
2353 /// TODO: Consider IVInc free if it's already used in another chains.
2355 isProfitableChain(IVChain &Chain, SmallPtrSet<Instruction*, 4> &Users,
2356 ScalarEvolution &SE, const TargetLowering *TLI) {
2360 if (Chain.size() <= 2)
2363 if (!Users.empty()) {
2364 DEBUG(dbgs() << "Chain: " << *Chain[0].UserInst << " users:\n";
2365 for (SmallPtrSet<Instruction*, 4>::const_iterator I = Users.begin(),
2366 E = Users.end(); I != E; ++I) {
2367 dbgs() << " " << **I << "\n";
2371 assert(!Chain.empty() && "empty IV chains are not allowed");
2373 // The chain itself may require a register, so intialize cost to 1.
2376 // A complete chain likely eliminates the need for keeping the original IV in
2377 // a register. LSR does not currently know how to form a complete chain unless
2378 // the header phi already exists.
2379 if (isa<PHINode>(Chain.back().UserInst)
2380 && SE.getSCEV(Chain.back().UserInst) == Chain[0].IncExpr) {
2383 const SCEV *LastIncExpr = 0;
2384 unsigned NumConstIncrements = 0;
2385 unsigned NumVarIncrements = 0;
2386 unsigned NumReusedIncrements = 0;
2387 for (IVChain::const_iterator I = llvm::next(Chain.begin()), E = Chain.end();
2390 if (I->IncExpr->isZero())
2393 // Incrementing by zero or some constant is neutral. We assume constants can
2394 // be folded into an addressing mode or an add's immediate operand.
2395 if (isa<SCEVConstant>(I->IncExpr)) {
2396 ++NumConstIncrements;
2400 if (I->IncExpr == LastIncExpr)
2401 ++NumReusedIncrements;
2405 LastIncExpr = I->IncExpr;
2407 // An IV chain with a single increment is handled by LSR's postinc
2408 // uses. However, a chain with multiple increments requires keeping the IV's
2409 // value live longer than it needs to be if chained.
2410 if (NumConstIncrements > 1)
2413 // Materializing increment expressions in the preheader that didn't exist in
2414 // the original code may cost a register. For example, sign-extended array
2415 // indices can produce ridiculous increments like this:
2416 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2417 cost += NumVarIncrements;
2419 // Reusing variable increments likely saves a register to hold the multiple of
2421 cost -= NumReusedIncrements;
2423 DEBUG(dbgs() << "Chain: " << *Chain[0].UserInst << " Cost: " << cost << "\n");
2428 /// ChainInstruction - Add this IV user to an existing chain or make it the head
2430 void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2431 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2432 // When IVs are used as types of varying widths, they are generally converted
2433 // to a wider type with some uses remaining narrow under a (free) trunc.
2434 Value *NextIV = getWideOperand(IVOper);
2436 // Visit all existing chains. Check if its IVOper can be computed as a
2437 // profitable loop invariant increment from the last link in the Chain.
2438 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2439 const SCEV *LastIncExpr = 0;
2440 for (; ChainIdx < NChains; ++ChainIdx) {
2441 Value *PrevIV = getWideOperand(IVChainVec[ChainIdx].back().IVOperand);
2442 if (!isCompatibleIVType(PrevIV, NextIV))
2445 // A phi node terminates a chain.
2446 if (isa<PHINode>(UserInst)
2447 && isa<PHINode>(IVChainVec[ChainIdx].back().UserInst))
2450 if (const SCEV *IncExpr =
2451 getProfitableChainIncrement(NextIV, PrevIV, IVChainVec[ChainIdx],
2453 LastIncExpr = IncExpr;
2457 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2458 // bother for phi nodes, because they must be last in the chain.
2459 if (ChainIdx == NChains) {
2460 if (isa<PHINode>(UserInst))
2462 if (NChains >= MaxChains && !StressIVChain) {
2463 DEBUG(dbgs() << "IV Chain Limit\n");
2466 LastIncExpr = SE.getSCEV(NextIV);
2467 // IVUsers may have skipped over sign/zero extensions. We don't currently
2468 // attempt to form chains involving extensions unless they can be hoisted
2469 // into this loop's AddRec.
2470 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2473 IVChainVec.resize(NChains);
2474 ChainUsersVec.resize(NChains);
2475 DEBUG(dbgs() << "IV Head: (" << *UserInst << ") IV=" << *LastIncExpr
2479 DEBUG(dbgs() << "IV Inc: (" << *UserInst << ") IV+" << *LastIncExpr
2482 // Add this IV user to the end of the chain.
2483 IVChainVec[ChainIdx].push_back(IVInc(UserInst, IVOper, LastIncExpr));
2485 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2486 // This chain's NearUsers become FarUsers.
2487 if (!LastIncExpr->isZero()) {
2488 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2493 // All other uses of IVOperand become near uses of the chain.
2494 // We currently ignore intermediate values within SCEV expressions, assuming
2495 // they will eventually be used be the current chain, or can be computed
2496 // from one of the chain increments. To be more precise we could
2497 // transitively follow its user and only add leaf IV users to the set.
2498 for (Value::use_iterator UseIter = IVOper->use_begin(),
2499 UseEnd = IVOper->use_end(); UseIter != UseEnd; ++UseIter) {
2500 Instruction *OtherUse = dyn_cast<Instruction>(*UseIter);
2501 if (!OtherUse || OtherUse == UserInst)
2503 if (SE.isSCEVable(OtherUse->getType())
2504 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2505 && IU.isIVUserOrOperand(OtherUse)) {
2508 NearUsers.insert(OtherUse);
2511 // Since this user is part of the chain, it's no longer considered a use
2513 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2516 /// CollectChains - Populate the vector of Chains.
2518 /// This decreases ILP at the architecture level. Targets with ample registers,
2519 /// multiple memory ports, and no register renaming probably don't want
2520 /// this. However, such targets should probably disable LSR altogether.
2522 /// The job of LSR is to make a reasonable choice of induction variables across
2523 /// the loop. Subsequent passes can easily "unchain" computation exposing more
2524 /// ILP *within the loop* if the target wants it.
2526 /// Finding the best IV chain is potentially a scheduling problem. Since LSR
2527 /// will not reorder memory operations, it will recognize this as a chain, but
2528 /// will generate redundant IV increments. Ideally this would be corrected later
2529 /// by a smart scheduler:
2535 /// TODO: Walk the entire domtree within this loop, not just the path to the
2536 /// loop latch. This will discover chains on side paths, but requires
2537 /// maintaining multiple copies of the Chains state.
2538 void LSRInstance::CollectChains() {
2539 SmallVector<ChainUsers, 8> ChainUsersVec;
2541 SmallVector<BasicBlock *,8> LatchPath;
2542 BasicBlock *LoopHeader = L->getHeader();
2543 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
2544 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
2545 LatchPath.push_back(Rung->getBlock());
2547 LatchPath.push_back(LoopHeader);
2549 // Walk the instruction stream from the loop header to the loop latch.
2550 for (SmallVectorImpl<BasicBlock *>::reverse_iterator
2551 BBIter = LatchPath.rbegin(), BBEnd = LatchPath.rend();
2552 BBIter != BBEnd; ++BBIter) {
2553 for (BasicBlock::iterator I = (*BBIter)->begin(), E = (*BBIter)->end();
2555 // Skip instructions that weren't seen by IVUsers analysis.
2556 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(I))
2559 // Ignore users that are part of a SCEV expression. This way we only
2560 // consider leaf IV Users. This effectively rediscovers a portion of
2561 // IVUsers analysis but in program order this time.
2562 if (SE.isSCEVable(I->getType()) && !isa<SCEVUnknown>(SE.getSCEV(I)))
2565 // Remove this instruction from any NearUsers set it may be in.
2566 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
2567 ChainIdx < NChains; ++ChainIdx) {
2568 ChainUsersVec[ChainIdx].NearUsers.erase(I);
2570 // Search for operands that can be chained.
2571 SmallPtrSet<Instruction*, 4> UniqueOperands;
2572 User::op_iterator IVOpEnd = I->op_end();
2573 User::op_iterator IVOpIter = findIVOperand(I->op_begin(), IVOpEnd, L, SE);
2574 while (IVOpIter != IVOpEnd) {
2575 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
2576 if (UniqueOperands.insert(IVOpInst))
2577 ChainInstruction(I, IVOpInst, ChainUsersVec);
2578 IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE);
2580 } // Continue walking down the instructions.
2581 } // Continue walking down the domtree.
2582 // Visit phi backedges to determine if the chain can generate the IV postinc.
2583 for (BasicBlock::iterator I = L->getHeader()->begin();
2584 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
2585 if (!SE.isSCEVable(PN->getType()))
2589 dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch()));
2591 ChainInstruction(PN, IncV, ChainUsersVec);
2593 // Remove any unprofitable chains.
2594 unsigned ChainIdx = 0;
2595 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
2596 UsersIdx < NChains; ++UsersIdx) {
2597 if (!isProfitableChain(IVChainVec[UsersIdx],
2598 ChainUsersVec[UsersIdx].FarUsers, SE, TLI))
2600 // Preserve the chain at UsesIdx.
2601 if (ChainIdx != UsersIdx)
2602 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
2603 FinalizeChain(IVChainVec[ChainIdx]);
2606 IVChainVec.resize(ChainIdx);
2609 void LSRInstance::FinalizeChain(IVChain &Chain) {
2610 assert(!Chain.empty() && "empty IV chains are not allowed");
2611 DEBUG(dbgs() << "Final Chain: " << *Chain[0].UserInst << "\n");
2613 for (IVChain::const_iterator I = llvm::next(Chain.begin()), E = Chain.end();
2615 DEBUG(dbgs() << " Inc: " << *I->UserInst << "\n");
2616 User::op_iterator UseI =
2617 std::find(I->UserInst->op_begin(), I->UserInst->op_end(), I->IVOperand);
2618 assert(UseI != I->UserInst->op_end() && "cannot find IV operand");
2619 IVIncSet.insert(UseI);
2623 /// Return true if the IVInc can be folded into an addressing mode.
2624 static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
2625 Value *Operand, const TargetLowering *TLI) {
2626 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
2627 if (!IncConst || !isAddressUse(UserInst, Operand))
2630 if (IncConst->getValue()->getValue().getMinSignedBits() > 64)
2633 int64_t IncOffset = IncConst->getValue()->getSExtValue();
2634 if (!isAlwaysFoldable(IncOffset, /*BaseGV=*/0, /*HaseBaseReg=*/false,
2635 LSRUse::Address, getAccessType(UserInst), TLI))
2641 /// GenerateIVChains - Generate an add or subtract for each IVInc in a chain to
2642 /// materialize the IV user's operand from the previous IV user's operand.
2643 void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
2644 SmallVectorImpl<WeakVH> &DeadInsts) {
2645 // Find the new IVOperand for the head of the chain. It may have been replaced
2647 const IVInc &Head = Chain[0];
2648 User::op_iterator IVOpEnd = Head.UserInst->op_end();
2649 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
2652 while (IVOpIter != IVOpEnd) {
2653 IVSrc = getWideOperand(*IVOpIter);
2655 // If this operand computes the expression that the chain needs, we may use
2656 // it. (Check this after setting IVSrc which is used below.)
2658 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
2659 // narrow for the chain, so we can no longer use it. We do allow using a
2660 // wider phi, assuming the LSR checked for free truncation. In that case we
2661 // should already have a truncate on this operand such that
2662 // getSCEV(IVSrc) == IncExpr.
2663 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
2664 || SE.getSCEV(IVSrc) == Head.IncExpr) {
2667 IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE);
2669 if (IVOpIter == IVOpEnd) {
2670 // Gracefully give up on this chain.
2671 DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
2675 DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
2676 Type *IVTy = IVSrc->getType();
2677 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
2678 const SCEV *LeftOverExpr = 0;
2679 for (IVChain::const_iterator IncI = llvm::next(Chain.begin()),
2680 IncE = Chain.end(); IncI != IncE; ++IncI) {
2682 Instruction *InsertPt = IncI->UserInst;
2683 if (isa<PHINode>(InsertPt))
2684 InsertPt = L->getLoopLatch()->getTerminator();
2686 // IVOper will replace the current IV User's operand. IVSrc is the IV
2687 // value currently held in a register.
2688 Value *IVOper = IVSrc;
2689 if (!IncI->IncExpr->isZero()) {
2690 // IncExpr was the result of subtraction of two narrow values, so must
2692 const SCEV *IncExpr = SE.getNoopOrSignExtend(IncI->IncExpr, IntTy);
2693 LeftOverExpr = LeftOverExpr ?
2694 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
2696 if (LeftOverExpr && !LeftOverExpr->isZero()) {
2697 // Expand the IV increment.
2698 Rewriter.clearPostInc();
2699 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
2700 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
2701 SE.getUnknown(IncV));
2702 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
2704 // If an IV increment can't be folded, use it as the next IV value.
2705 if (!canFoldIVIncExpr(LeftOverExpr, IncI->UserInst, IncI->IVOperand,
2707 assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
2712 Type *OperTy = IncI->IVOperand->getType();
2713 if (IVTy != OperTy) {
2714 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
2715 "cannot extend a chained IV");
2716 IRBuilder<> Builder(InsertPt);
2717 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
2719 IncI->UserInst->replaceUsesOfWith(IncI->IVOperand, IVOper);
2720 DeadInsts.push_back(IncI->IVOperand);
2722 // If LSR created a new, wider phi, we may also replace its postinc. We only
2723 // do this if we also found a wide value for the head of the chain.
2724 if (isa<PHINode>(Chain.back().UserInst)) {
2725 for (BasicBlock::iterator I = L->getHeader()->begin();
2726 PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
2727 if (!isCompatibleIVType(Phi, IVSrc))
2729 Instruction *PostIncV = dyn_cast<Instruction>(
2730 Phi->getIncomingValueForBlock(L->getLoopLatch()));
2731 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
2733 Value *IVOper = IVSrc;
2734 Type *PostIncTy = PostIncV->getType();
2735 if (IVTy != PostIncTy) {
2736 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
2737 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
2738 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
2739 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
2741 Phi->replaceUsesOfWith(PostIncV, IVOper);
2742 DeadInsts.push_back(PostIncV);
2747 void LSRInstance::CollectFixupsAndInitialFormulae() {
2748 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) {
2749 Instruction *UserInst = UI->getUser();
2750 // Skip IV users that are part of profitable IV Chains.
2751 User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(),
2752 UI->getOperandValToReplace());
2753 assert(UseI != UserInst->op_end() && "cannot find IV operand");
2754 if (IVIncSet.count(UseI))
2758 LSRFixup &LF = getNewFixup();
2759 LF.UserInst = UserInst;
2760 LF.OperandValToReplace = UI->getOperandValToReplace();
2761 LF.PostIncLoops = UI->getPostIncLoops();
2763 LSRUse::KindType Kind = LSRUse::Basic;
2765 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
2766 Kind = LSRUse::Address;
2767 AccessTy = getAccessType(LF.UserInst);
2770 const SCEV *S = IU.getExpr(*UI);
2772 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
2773 // (N - i == 0), and this allows (N - i) to be the expression that we work
2774 // with rather than just N or i, so we can consider the register
2775 // requirements for both N and i at the same time. Limiting this code to
2776 // equality icmps is not a problem because all interesting loops use
2777 // equality icmps, thanks to IndVarSimplify.
2778 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
2779 if (CI->isEquality()) {
2780 // Swap the operands if needed to put the OperandValToReplace on the
2781 // left, for consistency.
2782 Value *NV = CI->getOperand(1);
2783 if (NV == LF.OperandValToReplace) {
2784 CI->setOperand(1, CI->getOperand(0));
2785 CI->setOperand(0, NV);
2786 NV = CI->getOperand(1);
2790 // x == y --> x - y == 0
2791 const SCEV *N = SE.getSCEV(NV);
2792 if (SE.isLoopInvariant(N, L)) {
2793 // S is normalized, so normalize N before folding it into S
2794 // to keep the result normalized.
2795 N = TransformForPostIncUse(Normalize, N, CI, 0,
2796 LF.PostIncLoops, SE, DT);
2797 Kind = LSRUse::ICmpZero;
2798 S = SE.getMinusSCEV(N, S);
2801 // -1 and the negations of all interesting strides (except the negation
2802 // of -1) are now also interesting.
2803 for (size_t i = 0, e = Factors.size(); i != e; ++i)
2804 if (Factors[i] != -1)
2805 Factors.insert(-(uint64_t)Factors[i]);
2809 // Set up the initial formula for this use.
2810 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
2812 LF.Offset = P.second;
2813 LSRUse &LU = Uses[LF.LUIdx];
2814 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
2815 if (!LU.WidestFixupType ||
2816 SE.getTypeSizeInBits(LU.WidestFixupType) <
2817 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
2818 LU.WidestFixupType = LF.OperandValToReplace->getType();
2820 // If this is the first use of this LSRUse, give it a formula.
2821 if (LU.Formulae.empty()) {
2822 InsertInitialFormula(S, LU, LF.LUIdx);
2823 CountRegisters(LU.Formulae.back(), LF.LUIdx);
2827 DEBUG(print_fixups(dbgs()));
2830 /// InsertInitialFormula - Insert a formula for the given expression into
2831 /// the given use, separating out loop-variant portions from loop-invariant
2832 /// and loop-computable portions.
2834 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
2836 F.InitialMatch(S, L, SE);
2837 bool Inserted = InsertFormula(LU, LUIdx, F);
2838 assert(Inserted && "Initial formula already exists!"); (void)Inserted;
2841 /// InsertSupplementalFormula - Insert a simple single-register formula for
2842 /// the given expression into the given use.
2844 LSRInstance::InsertSupplementalFormula(const SCEV *S,
2845 LSRUse &LU, size_t LUIdx) {
2847 F.BaseRegs.push_back(S);
2848 F.AM.HasBaseReg = true;
2849 bool Inserted = InsertFormula(LU, LUIdx, F);
2850 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
2853 /// CountRegisters - Note which registers are used by the given formula,
2854 /// updating RegUses.
2855 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
2857 RegUses.CountRegister(F.ScaledReg, LUIdx);
2858 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
2859 E = F.BaseRegs.end(); I != E; ++I)
2860 RegUses.CountRegister(*I, LUIdx);
2863 /// InsertFormula - If the given formula has not yet been inserted, add it to
2864 /// the list, and return true. Return false otherwise.
2865 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
2866 if (!LU.InsertFormula(F))
2869 CountRegisters(F, LUIdx);
2873 /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
2874 /// loop-invariant values which we're tracking. These other uses will pin these
2875 /// values in registers, making them less profitable for elimination.
2876 /// TODO: This currently misses non-constant addrec step registers.
2877 /// TODO: Should this give more weight to users inside the loop?
2879 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
2880 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
2881 SmallPtrSet<const SCEV *, 8> Inserted;
2883 while (!Worklist.empty()) {
2884 const SCEV *S = Worklist.pop_back_val();
2886 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
2887 Worklist.append(N->op_begin(), N->op_end());
2888 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
2889 Worklist.push_back(C->getOperand());
2890 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
2891 Worklist.push_back(D->getLHS());
2892 Worklist.push_back(D->getRHS());
2893 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
2894 if (!Inserted.insert(U)) continue;
2895 const Value *V = U->getValue();
2896 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
2897 // Look for instructions defined outside the loop.
2898 if (L->contains(Inst)) continue;
2899 } else if (isa<UndefValue>(V))
2900 // Undef doesn't have a live range, so it doesn't matter.
2902 for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
2904 const Instruction *UserInst = dyn_cast<Instruction>(*UI);
2905 // Ignore non-instructions.
2908 // Ignore instructions in other functions (as can happen with
2910 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
2912 // Ignore instructions not dominated by the loop.
2913 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
2914 UserInst->getParent() :
2915 cast<PHINode>(UserInst)->getIncomingBlock(
2916 PHINode::getIncomingValueNumForOperand(UI.getOperandNo()));
2917 if (!DT.dominates(L->getHeader(), UseBB))
2919 // Ignore uses which are part of other SCEV expressions, to avoid
2920 // analyzing them multiple times.
2921 if (SE.isSCEVable(UserInst->getType())) {
2922 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
2923 // If the user is a no-op, look through to its uses.
2924 if (!isa<SCEVUnknown>(UserS))
2928 SE.getUnknown(const_cast<Instruction *>(UserInst)));
2932 // Ignore icmp instructions which are already being analyzed.
2933 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
2934 unsigned OtherIdx = !UI.getOperandNo();
2935 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
2936 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
2940 LSRFixup &LF = getNewFixup();
2941 LF.UserInst = const_cast<Instruction *>(UserInst);
2942 LF.OperandValToReplace = UI.getUse();
2943 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0);
2945 LF.Offset = P.second;
2946 LSRUse &LU = Uses[LF.LUIdx];
2947 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
2948 if (!LU.WidestFixupType ||
2949 SE.getTypeSizeInBits(LU.WidestFixupType) <
2950 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
2951 LU.WidestFixupType = LF.OperandValToReplace->getType();
2952 InsertSupplementalFormula(U, LU, LF.LUIdx);
2953 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
2960 /// CollectSubexprs - Split S into subexpressions which can be pulled out into
2961 /// separate registers. If C is non-null, multiply each subexpression by C.
2962 static void CollectSubexprs(const SCEV *S, const SCEVConstant *C,
2963 SmallVectorImpl<const SCEV *> &Ops,
2965 ScalarEvolution &SE) {
2966 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2967 // Break out add operands.
2968 for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end();
2970 CollectSubexprs(*I, C, Ops, L, SE);
2972 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2973 // Split a non-zero base out of an addrec.
2974 if (!AR->getStart()->isZero()) {
2975 CollectSubexprs(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
2976 AR->getStepRecurrence(SE),
2978 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
2981 CollectSubexprs(AR->getStart(), C, Ops, L, SE);
2984 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
2985 // Break (C * (a + b + c)) into C*a + C*b + C*c.
2986 if (Mul->getNumOperands() == 2)
2987 if (const SCEVConstant *Op0 =
2988 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
2989 CollectSubexprs(Mul->getOperand(1),
2990 C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0,
2996 // Otherwise use the value itself, optionally with a scale applied.
2997 Ops.push_back(C ? SE.getMulExpr(C, S) : S);
3000 /// GenerateReassociations - Split out subexpressions from adds and the bases of
3002 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3005 // Arbitrarily cap recursion to protect compile time.
3006 if (Depth >= 3) return;
3008 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3009 const SCEV *BaseReg = Base.BaseRegs[i];
3011 SmallVector<const SCEV *, 8> AddOps;
3012 CollectSubexprs(BaseReg, 0, AddOps, L, SE);
3014 if (AddOps.size() == 1) continue;
3016 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3017 JE = AddOps.end(); J != JE; ++J) {
3019 // Loop-variant "unknown" values are uninteresting; we won't be able to
3020 // do anything meaningful with them.
3021 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3024 // Don't pull a constant into a register if the constant could be folded
3025 // into an immediate field.
3026 if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset,
3027 Base.getNumRegs() > 1,
3028 LU.Kind, LU.AccessTy, TLI, SE))
3031 // Collect all operands except *J.
3032 SmallVector<const SCEV *, 8> InnerAddOps
3033 (((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3035 (llvm::next(J), ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3037 // Don't leave just a constant behind in a register if the constant could
3038 // be folded into an immediate field.
3039 if (InnerAddOps.size() == 1 &&
3040 isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset,
3041 Base.getNumRegs() > 1,
3042 LU.Kind, LU.AccessTy, TLI, SE))
3045 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3046 if (InnerSum->isZero())
3050 // Add the remaining pieces of the add back into the new formula.
3051 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3052 if (TLI && InnerSumSC &&
3053 SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3054 TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3055 InnerSumSC->getValue()->getZExtValue())) {
3056 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
3057 InnerSumSC->getValue()->getZExtValue();
3058 F.BaseRegs.erase(F.BaseRegs.begin() + i);
3060 F.BaseRegs[i] = InnerSum;
3062 // Add J as its own register, or an unfolded immediate.
3063 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3064 if (TLI && SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3065 TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3066 SC->getValue()->getZExtValue()))
3067 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset +
3068 SC->getValue()->getZExtValue();
3070 F.BaseRegs.push_back(*J);
3072 if (InsertFormula(LU, LUIdx, F))
3073 // If that formula hadn't been seen before, recurse to find more like
3075 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1);
3080 /// GenerateCombinations - Generate a formula consisting of all of the
3081 /// loop-dominating registers added into a single register.
3082 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3084 // This method is only interesting on a plurality of registers.
3085 if (Base.BaseRegs.size() <= 1) return;
3089 SmallVector<const SCEV *, 4> Ops;
3090 for (SmallVectorImpl<const SCEV *>::const_iterator
3091 I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) {
3092 const SCEV *BaseReg = *I;
3093 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3094 !SE.hasComputableLoopEvolution(BaseReg, L))
3095 Ops.push_back(BaseReg);
3097 F.BaseRegs.push_back(BaseReg);
3099 if (Ops.size() > 1) {
3100 const SCEV *Sum = SE.getAddExpr(Ops);
3101 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3102 // opportunity to fold something. For now, just ignore such cases
3103 // rather than proceed with zero in a register.
3104 if (!Sum->isZero()) {
3105 F.BaseRegs.push_back(Sum);
3106 (void)InsertFormula(LU, LUIdx, F);
3111 /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
3112 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3114 // We can't add a symbolic offset if the address already contains one.
3115 if (Base.AM.BaseGV) return;
3117 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3118 const SCEV *G = Base.BaseRegs[i];
3119 GlobalValue *GV = ExtractSymbol(G, SE);
3120 if (G->isZero() || !GV)
3124 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
3125 LU.Kind, LU.AccessTy, TLI))
3128 (void)InsertFormula(LU, LUIdx, F);
3132 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3133 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3135 // TODO: For now, just add the min and max offset, because it usually isn't
3136 // worthwhile looking at everything inbetween.
3137 SmallVector<int64_t, 2> Worklist;
3138 Worklist.push_back(LU.MinOffset);
3139 if (LU.MaxOffset != LU.MinOffset)
3140 Worklist.push_back(LU.MaxOffset);
3142 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) {
3143 const SCEV *G = Base.BaseRegs[i];
3145 for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(),
3146 E = Worklist.end(); I != E; ++I) {
3148 F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I;
3149 if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I,
3150 LU.Kind, LU.AccessTy, TLI)) {
3151 // Add the offset to the base register.
3152 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G);
3153 // If it cancelled out, drop the base register, otherwise update it.
3154 if (NewG->isZero()) {
3155 std::swap(F.BaseRegs[i], F.BaseRegs.back());
3156 F.BaseRegs.pop_back();
3158 F.BaseRegs[i] = NewG;
3160 (void)InsertFormula(LU, LUIdx, F);
3164 int64_t Imm = ExtractImmediate(G, SE);
3165 if (G->isZero() || Imm == 0)
3168 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm;
3169 if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset,
3170 LU.Kind, LU.AccessTy, TLI))
3173 (void)InsertFormula(LU, LUIdx, F);
3177 /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
3178 /// the comparison. For example, x == y -> x*c == y*c.
3179 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3181 if (LU.Kind != LSRUse::ICmpZero) return;
3183 // Determine the integer type for the base formula.
3184 Type *IntTy = Base.getType();
3186 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3188 // Don't do this if there is more than one offset.
3189 if (LU.MinOffset != LU.MaxOffset) return;
3191 assert(!Base.AM.BaseGV && "ICmpZero use is not legal!");
3193 // Check each interesting stride.
3194 for (SmallSetVector<int64_t, 8>::const_iterator
3195 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3196 int64_t Factor = *I;
3198 // Check that the multiplication doesn't overflow.
3199 if (Base.AM.BaseOffs == INT64_MIN && Factor == -1)
3201 int64_t NewBaseOffs = (uint64_t)Base.AM.BaseOffs * Factor;
3202 if (NewBaseOffs / Factor != Base.AM.BaseOffs)
3205 // Check that multiplying with the use offset doesn't overflow.
3206 int64_t Offset = LU.MinOffset;
3207 if (Offset == INT64_MIN && Factor == -1)
3209 Offset = (uint64_t)Offset * Factor;
3210 if (Offset / Factor != LU.MinOffset)
3214 F.AM.BaseOffs = NewBaseOffs;
3216 // Check that this scale is legal.
3217 if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI))
3220 // Compensate for the use having MinOffset built into it.
3221 F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset;
3223 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3225 // Check that multiplying with each base register doesn't overflow.
3226 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3227 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3228 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3232 // Check that multiplying with the scaled register doesn't overflow.
3234 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3235 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3239 // Check that multiplying with the unfolded offset doesn't overflow.
3240 if (F.UnfoldedOffset != 0) {
3241 if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
3243 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3244 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3248 // If we make it here and it's legal, add it.
3249 (void)InsertFormula(LU, LUIdx, F);
3254 /// GenerateScales - Generate stride factor reuse formulae by making use of
3255 /// scaled-offset address modes, for example.
3256 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3257 // Determine the integer type for the base formula.
3258 Type *IntTy = Base.getType();
3261 // If this Formula already has a scaled register, we can't add another one.
3262 if (Base.AM.Scale != 0) return;
3264 // Check each interesting stride.
3265 for (SmallSetVector<int64_t, 8>::const_iterator
3266 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
3267 int64_t Factor = *I;
3269 Base.AM.Scale = Factor;
3270 Base.AM.HasBaseReg = Base.BaseRegs.size() > 1;
3271 // Check whether this scale is going to be legal.
3272 if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
3273 LU.Kind, LU.AccessTy, TLI)) {
3274 // As a special-case, handle special out-of-loop Basic users specially.
3275 // TODO: Reconsider this special case.
3276 if (LU.Kind == LSRUse::Basic &&
3277 isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset,
3278 LSRUse::Special, LU.AccessTy, TLI) &&
3279 LU.AllFixupsOutsideLoop)
3280 LU.Kind = LSRUse::Special;
3284 // For an ICmpZero, negating a solitary base register won't lead to
3286 if (LU.Kind == LSRUse::ICmpZero &&
3287 !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV)
3289 // For each addrec base reg, apply the scale, if possible.
3290 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3291 if (const SCEVAddRecExpr *AR =
3292 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
3293 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3294 if (FactorS->isZero())
3296 // Divide out the factor, ignoring high bits, since we'll be
3297 // scaling the value back up in the end.
3298 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3299 // TODO: This could be optimized to avoid all the copying.
3301 F.ScaledReg = Quotient;
3302 F.DeleteBaseReg(F.BaseRegs[i]);
3303 (void)InsertFormula(LU, LUIdx, F);
3309 /// GenerateTruncates - Generate reuse formulae from different IV types.
3310 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3311 // This requires TargetLowering to tell us which truncates are free.
3314 // Don't bother truncating symbolic values.
3315 if (Base.AM.BaseGV) return;
3317 // Determine the integer type for the base formula.
3318 Type *DstTy = Base.getType();
3320 DstTy = SE.getEffectiveSCEVType(DstTy);
3322 for (SmallSetVector<Type *, 4>::const_iterator
3323 I = Types.begin(), E = Types.end(); I != E; ++I) {
3325 if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) {
3328 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I);
3329 for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(),
3330 JE = F.BaseRegs.end(); J != JE; ++J)
3331 *J = SE.getAnyExtendExpr(*J, SrcTy);
3333 // TODO: This assumes we've done basic processing on all uses and
3334 // have an idea what the register usage is.
3335 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3338 (void)InsertFormula(LU, LUIdx, F);
3345 /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
3346 /// defer modifications so that the search phase doesn't have to worry about
3347 /// the data structures moving underneath it.
3351 const SCEV *OrigReg;
3353 WorkItem(size_t LI, int64_t I, const SCEV *R)
3354 : LUIdx(LI), Imm(I), OrigReg(R) {}
3356 void print(raw_ostream &OS) const;
3362 void WorkItem::print(raw_ostream &OS) const {
3363 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3364 << " , add offset " << Imm;
3367 void WorkItem::dump() const {
3368 print(errs()); errs() << '\n';
3371 /// GenerateCrossUseConstantOffsets - Look for registers which are a constant
3372 /// distance apart and try to form reuse opportunities between them.
3373 void LSRInstance::GenerateCrossUseConstantOffsets() {
3374 // Group the registers by their value without any added constant offset.
3375 typedef std::map<int64_t, const SCEV *> ImmMapTy;
3376 typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy;
3378 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3379 SmallVector<const SCEV *, 8> Sequence;
3380 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
3382 const SCEV *Reg = *I;
3383 int64_t Imm = ExtractImmediate(Reg, SE);
3384 std::pair<RegMapTy::iterator, bool> Pair =
3385 Map.insert(std::make_pair(Reg, ImmMapTy()));
3387 Sequence.push_back(Reg);
3388 Pair.first->second.insert(std::make_pair(Imm, *I));
3389 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I);
3392 // Now examine each set of registers with the same base value. Build up
3393 // a list of work to do and do the work in a separate step so that we're
3394 // not adding formulae and register counts while we're searching.
3395 SmallVector<WorkItem, 32> WorkItems;
3396 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3397 for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(),
3398 E = Sequence.end(); I != E; ++I) {
3399 const SCEV *Reg = *I;
3400 const ImmMapTy &Imms = Map.find(Reg)->second;
3402 // It's not worthwhile looking for reuse if there's only one offset.
3403 if (Imms.size() == 1)
3406 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
3407 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3409 dbgs() << ' ' << J->first;
3412 // Examine each offset.
3413 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3415 const SCEV *OrigReg = J->second;
3417 int64_t JImm = J->first;
3418 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
3420 if (!isa<SCEVConstant>(OrigReg) &&
3421 UsedByIndicesMap[Reg].count() == 1) {
3422 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
3426 // Conservatively examine offsets between this orig reg a few selected
3428 ImmMapTy::const_iterator OtherImms[] = {
3429 Imms.begin(), prior(Imms.end()),
3430 Imms.lower_bound((Imms.begin()->first + prior(Imms.end())->first) / 2)
3432 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
3433 ImmMapTy::const_iterator M = OtherImms[i];
3434 if (M == J || M == JE) continue;
3436 // Compute the difference between the two.
3437 int64_t Imm = (uint64_t)JImm - M->first;
3438 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
3439 LUIdx = UsedByIndices.find_next(LUIdx))
3440 // Make a memo of this use, offset, and register tuple.
3441 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)))
3442 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
3449 UsedByIndicesMap.clear();
3450 UniqueItems.clear();
3452 // Now iterate through the worklist and add new formulae.
3453 for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(),
3454 E = WorkItems.end(); I != E; ++I) {
3455 const WorkItem &WI = *I;
3456 size_t LUIdx = WI.LUIdx;
3457 LSRUse &LU = Uses[LUIdx];
3458 int64_t Imm = WI.Imm;
3459 const SCEV *OrigReg = WI.OrigReg;
3461 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
3462 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
3463 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
3465 // TODO: Use a more targeted data structure.
3466 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
3467 const Formula &F = LU.Formulae[L];
3468 // Use the immediate in the scaled register.
3469 if (F.ScaledReg == OrigReg) {
3470 int64_t Offs = (uint64_t)F.AM.BaseOffs +
3471 Imm * (uint64_t)F.AM.Scale;
3472 // Don't create 50 + reg(-50).
3473 if (F.referencesReg(SE.getSCEV(
3474 ConstantInt::get(IntTy, -(uint64_t)Offs))))
3477 NewF.AM.BaseOffs = Offs;
3478 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
3479 LU.Kind, LU.AccessTy, TLI))
3481 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
3483 // If the new scale is a constant in a register, and adding the constant
3484 // value to the immediate would produce a value closer to zero than the
3485 // immediate itself, then the formula isn't worthwhile.
3486 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
3487 if (C->getValue()->isNegative() !=
3488 (NewF.AM.BaseOffs < 0) &&
3489 (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale))
3490 .ule(abs64(NewF.AM.BaseOffs)))
3494 (void)InsertFormula(LU, LUIdx, NewF);
3496 // Use the immediate in a base register.
3497 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
3498 const SCEV *BaseReg = F.BaseRegs[N];
3499 if (BaseReg != OrigReg)
3502 NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm;
3503 if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset,
3504 LU.Kind, LU.AccessTy, TLI)) {
3506 !TLI->isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
3509 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
3511 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
3513 // If the new formula has a constant in a register, and adding the
3514 // constant value to the immediate would produce a value closer to
3515 // zero than the immediate itself, then the formula isn't worthwhile.
3516 for (SmallVectorImpl<const SCEV *>::const_iterator
3517 J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end();
3519 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J))
3520 if ((C->getValue()->getValue() + NewF.AM.BaseOffs).abs().slt(
3521 abs64(NewF.AM.BaseOffs)) &&
3522 (C->getValue()->getValue() +
3523 NewF.AM.BaseOffs).countTrailingZeros() >=
3524 CountTrailingZeros_64(NewF.AM.BaseOffs))
3528 (void)InsertFormula(LU, LUIdx, NewF);
3537 /// GenerateAllReuseFormulae - Generate formulae for each use.
3539 LSRInstance::GenerateAllReuseFormulae() {
3540 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
3541 // queries are more precise.
3542 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3543 LSRUse &LU = Uses[LUIdx];
3544 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3545 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
3546 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3547 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
3549 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3550 LSRUse &LU = Uses[LUIdx];
3551 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3552 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
3553 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3554 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
3555 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3556 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
3557 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3558 GenerateScales(LU, LUIdx, LU.Formulae[i]);
3560 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3561 LSRUse &LU = Uses[LUIdx];
3562 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3563 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
3566 GenerateCrossUseConstantOffsets();
3568 DEBUG(dbgs() << "\n"
3569 "After generating reuse formulae:\n";
3570 print_uses(dbgs()));
3573 /// If there are multiple formulae with the same set of registers used
3574 /// by other uses, pick the best one and delete the others.
3575 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
3576 DenseSet<const SCEV *> VisitedRegs;
3577 SmallPtrSet<const SCEV *, 16> Regs;
3578 SmallPtrSet<const SCEV *, 16> LoserRegs;
3580 bool ChangedFormulae = false;
3583 // Collect the best formula for each unique set of shared registers. This
3584 // is reset for each use.
3585 typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo>
3587 BestFormulaeTy BestFormulae;
3589 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3590 LSRUse &LU = Uses[LUIdx];
3591 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
3594 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
3595 FIdx != NumForms; ++FIdx) {
3596 Formula &F = LU.Formulae[FIdx];
3598 // Some formulas are instant losers. For example, they may depend on
3599 // nonexistent AddRecs from other loops. These need to be filtered
3600 // immediately, otherwise heuristics could choose them over others leading
3601 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
3602 // avoids the need to recompute this information across formulae using the
3603 // same bad AddRec. Passing LoserRegs is also essential unless we remove
3604 // the corresponding bad register from the Regs set.
3607 CostF.RateFormula(F, Regs, VisitedRegs, L, LU.Offsets, SE, DT,
3609 if (CostF.isLoser()) {
3610 // During initial formula generation, undesirable formulae are generated
3611 // by uses within other loops that have some non-trivial address mode or
3612 // use the postinc form of the IV. LSR needs to provide these formulae
3613 // as the basis of rediscovering the desired formula that uses an AddRec
3614 // corresponding to the existing phi. Once all formulae have been
3615 // generated, these initial losers may be pruned.
3616 DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());
3620 SmallVector<const SCEV *, 2> Key;
3621 for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(),
3622 JE = F.BaseRegs.end(); J != JE; ++J) {
3623 const SCEV *Reg = *J;
3624 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
3628 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
3629 Key.push_back(F.ScaledReg);
3630 // Unstable sort by host order ok, because this is only used for
3632 std::sort(Key.begin(), Key.end());
3634 std::pair<BestFormulaeTy::const_iterator, bool> P =
3635 BestFormulae.insert(std::make_pair(Key, FIdx));
3639 Formula &Best = LU.Formulae[P.first->second];
3643 CostBest.RateFormula(Best, Regs, VisitedRegs, L, LU.Offsets, SE, DT);
3644 if (CostF < CostBest)
3646 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
3648 " in favor of formula "; Best.print(dbgs());
3652 ChangedFormulae = true;
3654 LU.DeleteFormula(F);
3660 // Now that we've filtered out some formulae, recompute the Regs set.
3662 LU.RecomputeRegs(LUIdx, RegUses);
3664 // Reset this to prepare for the next use.
3665 BestFormulae.clear();
3668 DEBUG(if (ChangedFormulae) {
3670 "After filtering out undesirable candidates:\n";
3675 // This is a rough guess that seems to work fairly well.
3676 static const size_t ComplexityLimit = UINT16_MAX;
3678 /// EstimateSearchSpaceComplexity - Estimate the worst-case number of
3679 /// solutions the solver might have to consider. It almost never considers
3680 /// this many solutions because it prune the search space, but the pruning
3681 /// isn't always sufficient.
3682 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
3684 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
3685 E = Uses.end(); I != E; ++I) {
3686 size_t FSize = I->Formulae.size();
3687 if (FSize >= ComplexityLimit) {
3688 Power = ComplexityLimit;
3692 if (Power >= ComplexityLimit)
3698 /// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset
3699 /// of the registers of another formula, it won't help reduce register
3700 /// pressure (though it may not necessarily hurt register pressure); remove
3701 /// it to simplify the system.
3702 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
3703 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3704 DEBUG(dbgs() << "The search space is too complex.\n");
3706 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
3707 "which use a superset of registers used by other "
3710 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3711 LSRUse &LU = Uses[LUIdx];
3713 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
3714 Formula &F = LU.Formulae[i];
3715 // Look for a formula with a constant or GV in a register. If the use
3716 // also has a formula with that same value in an immediate field,
3717 // delete the one that uses a register.
3718 for (SmallVectorImpl<const SCEV *>::const_iterator
3719 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
3720 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
3722 NewF.AM.BaseOffs += C->getValue()->getSExtValue();
3723 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
3724 (I - F.BaseRegs.begin()));
3725 if (LU.HasFormulaWithSameRegs(NewF)) {
3726 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
3727 LU.DeleteFormula(F);
3733 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
3734 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
3737 NewF.AM.BaseGV = GV;
3738 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
3739 (I - F.BaseRegs.begin()));
3740 if (LU.HasFormulaWithSameRegs(NewF)) {
3741 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
3743 LU.DeleteFormula(F);
3754 LU.RecomputeRegs(LUIdx, RegUses);
3757 DEBUG(dbgs() << "After pre-selection:\n";
3758 print_uses(dbgs()));
3762 /// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers
3763 /// for expressions like A, A+1, A+2, etc., allocate a single register for
3765 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
3766 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3767 DEBUG(dbgs() << "The search space is too complex.\n");
3769 DEBUG(dbgs() << "Narrowing the search space by assuming that uses "
3770 "separated by a constant offset will use the same "
3773 // This is especially useful for unrolled loops.
3775 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3776 LSRUse &LU = Uses[LUIdx];
3777 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
3778 E = LU.Formulae.end(); I != E; ++I) {
3779 const Formula &F = *I;
3780 if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) {
3781 if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) {
3782 if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs,
3783 /*HasBaseReg=*/false,
3784 LU.Kind, LU.AccessTy)) {
3785 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs());
3788 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
3790 // Update the relocs to reference the new use.
3791 for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(),
3792 E = Fixups.end(); I != E; ++I) {
3793 LSRFixup &Fixup = *I;
3794 if (Fixup.LUIdx == LUIdx) {
3795 Fixup.LUIdx = LUThatHas - &Uses.front();
3796 Fixup.Offset += F.AM.BaseOffs;
3797 // Add the new offset to LUThatHas' offset list.
3798 if (LUThatHas->Offsets.back() != Fixup.Offset) {
3799 LUThatHas->Offsets.push_back(Fixup.Offset);
3800 if (Fixup.Offset > LUThatHas->MaxOffset)
3801 LUThatHas->MaxOffset = Fixup.Offset;
3802 if (Fixup.Offset < LUThatHas->MinOffset)
3803 LUThatHas->MinOffset = Fixup.Offset;
3805 DEBUG(dbgs() << "New fixup has offset "
3806 << Fixup.Offset << '\n');
3808 if (Fixup.LUIdx == NumUses-1)
3809 Fixup.LUIdx = LUIdx;
3812 // Delete formulae from the new use which are no longer legal.
3814 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
3815 Formula &F = LUThatHas->Formulae[i];
3816 if (!isLegalUse(F.AM,
3817 LUThatHas->MinOffset, LUThatHas->MaxOffset,
3818 LUThatHas->Kind, LUThatHas->AccessTy, TLI)) {
3819 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
3821 LUThatHas->DeleteFormula(F);
3828 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
3830 // Delete the old use.
3831 DeleteUse(LU, LUIdx);
3841 DEBUG(dbgs() << "After pre-selection:\n";
3842 print_uses(dbgs()));
3846 /// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call
3847 /// FilterOutUndesirableDedicatedRegisters again, if necessary, now that
3848 /// we've done more filtering, as it may be able to find more formulae to
3850 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
3851 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3852 DEBUG(dbgs() << "The search space is too complex.\n");
3854 DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
3855 "undesirable dedicated registers.\n");
3857 FilterOutUndesirableDedicatedRegisters();
3859 DEBUG(dbgs() << "After pre-selection:\n";
3860 print_uses(dbgs()));
3864 /// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely
3865 /// to be profitable, and then in any use which has any reference to that
3866 /// register, delete all formulae which do not reference that register.
3867 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
3868 // With all other options exhausted, loop until the system is simple
3869 // enough to handle.
3870 SmallPtrSet<const SCEV *, 4> Taken;
3871 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
3872 // Ok, we have too many of formulae on our hands to conveniently handle.
3873 // Use a rough heuristic to thin out the list.
3874 DEBUG(dbgs() << "The search space is too complex.\n");
3876 // Pick the register which is used by the most LSRUses, which is likely
3877 // to be a good reuse register candidate.
3878 const SCEV *Best = 0;
3879 unsigned BestNum = 0;
3880 for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end();
3882 const SCEV *Reg = *I;
3883 if (Taken.count(Reg))
3888 unsigned Count = RegUses.getUsedByIndices(Reg).count();
3889 if (Count > BestNum) {
3896 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
3897 << " will yield profitable reuse.\n");
3900 // In any use with formulae which references this register, delete formulae
3901 // which don't reference it.
3902 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3903 LSRUse &LU = Uses[LUIdx];
3904 if (!LU.Regs.count(Best)) continue;
3907 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
3908 Formula &F = LU.Formulae[i];
3909 if (!F.referencesReg(Best)) {
3910 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
3911 LU.DeleteFormula(F);
3915 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
3921 LU.RecomputeRegs(LUIdx, RegUses);
3924 DEBUG(dbgs() << "After pre-selection:\n";
3925 print_uses(dbgs()));
3929 /// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
3930 /// formulae to choose from, use some rough heuristics to prune down the number
3931 /// of formulae. This keeps the main solver from taking an extraordinary amount
3932 /// of time in some worst-case scenarios.
3933 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
3934 NarrowSearchSpaceByDetectingSupersets();
3935 NarrowSearchSpaceByCollapsingUnrolledCode();
3936 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
3937 NarrowSearchSpaceByPickingWinnerRegs();
3940 /// SolveRecurse - This is the recursive solver.
3941 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
3943 SmallVectorImpl<const Formula *> &Workspace,
3944 const Cost &CurCost,
3945 const SmallPtrSet<const SCEV *, 16> &CurRegs,
3946 DenseSet<const SCEV *> &VisitedRegs) const {
3949 // - use more aggressive filtering
3950 // - sort the formula so that the most profitable solutions are found first
3951 // - sort the uses too
3953 // - don't compute a cost, and then compare. compare while computing a cost
3955 // - track register sets with SmallBitVector
3957 const LSRUse &LU = Uses[Workspace.size()];
3959 // If this use references any register that's already a part of the
3960 // in-progress solution, consider it a requirement that a formula must
3961 // reference that register in order to be considered. This prunes out
3962 // unprofitable searching.
3963 SmallSetVector<const SCEV *, 4> ReqRegs;
3964 for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(),
3965 E = CurRegs.end(); I != E; ++I)
3966 if (LU.Regs.count(*I))
3969 SmallPtrSet<const SCEV *, 16> NewRegs;
3971 for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(),
3972 E = LU.Formulae.end(); I != E; ++I) {
3973 const Formula &F = *I;
3975 // Ignore formulae which do not use any of the required registers.
3976 bool SatisfiedReqReg = true;
3977 for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(),
3978 JE = ReqRegs.end(); J != JE; ++J) {
3979 const SCEV *Reg = *J;
3980 if ((!F.ScaledReg || F.ScaledReg != Reg) &&
3981 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) ==
3983 SatisfiedReqReg = false;
3987 if (!SatisfiedReqReg) {
3988 // If none of the formulae satisfied the required registers, then we could
3989 // clear ReqRegs and try again. Currently, we simply give up in this case.
3993 // Evaluate the cost of the current formula. If it's already worse than
3994 // the current best, prune the search at that point.
3997 NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT);
3998 if (NewCost < SolutionCost) {
3999 Workspace.push_back(&F);
4000 if (Workspace.size() != Uses.size()) {
4001 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4002 NewRegs, VisitedRegs);
4003 if (F.getNumRegs() == 1 && Workspace.size() == 1)
4004 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4006 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
4007 dbgs() << ".\n Regs:";
4008 for (SmallPtrSet<const SCEV *, 16>::const_iterator
4009 I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I)
4010 dbgs() << ' ' << **I;
4013 SolutionCost = NewCost;
4014 Solution = Workspace;
4016 Workspace.pop_back();
4021 /// Solve - Choose one formula from each use. Return the results in the given
4022 /// Solution vector.
4023 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4024 SmallVector<const Formula *, 8> Workspace;
4026 SolutionCost.Loose();
4028 SmallPtrSet<const SCEV *, 16> CurRegs;
4029 DenseSet<const SCEV *> VisitedRegs;
4030 Workspace.reserve(Uses.size());
4032 // SolveRecurse does all the work.
4033 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4034 CurRegs, VisitedRegs);
4035 if (Solution.empty()) {
4036 DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
4040 // Ok, we've now made all our decisions.
4041 DEBUG(dbgs() << "\n"
4042 "The chosen solution requires "; SolutionCost.print(dbgs());
4044 for (size_t i = 0, e = Uses.size(); i != e; ++i) {
4046 Uses[i].print(dbgs());
4049 Solution[i]->print(dbgs());
4053 assert(Solution.size() == Uses.size() && "Malformed solution!");
4056 /// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
4057 /// the dominator tree far as we can go while still being dominated by the
4058 /// input positions. This helps canonicalize the insert position, which
4059 /// encourages sharing.
4060 BasicBlock::iterator
4061 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4062 const SmallVectorImpl<Instruction *> &Inputs)
4065 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4066 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4069 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4070 if (!Rung) return IP;
4071 Rung = Rung->getIDom();
4072 if (!Rung) return IP;
4073 IDom = Rung->getBlock();
4075 // Don't climb into a loop though.
4076 const Loop *IDomLoop = LI.getLoopFor(IDom);
4077 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4078 if (IDomDepth <= IPLoopDepth &&
4079 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4083 bool AllDominate = true;
4084 Instruction *BetterPos = 0;
4085 Instruction *Tentative = IDom->getTerminator();
4086 for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(),
4087 E = Inputs.end(); I != E; ++I) {
4088 Instruction *Inst = *I;
4089 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4090 AllDominate = false;
4093 // Attempt to find an insert position in the middle of the block,
4094 // instead of at the end, so that it can be used for other expansions.
4095 if (IDom == Inst->getParent() &&
4096 (!BetterPos || DT.dominates(BetterPos, Inst)))
4097 BetterPos = llvm::next(BasicBlock::iterator(Inst));
4110 /// AdjustInsertPositionForExpand - Determine an input position which will be
4111 /// dominated by the operands and which will dominate the result.
4112 BasicBlock::iterator
4113 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4116 SCEVExpander &Rewriter) const {
4117 // Collect some instructions which must be dominated by the
4118 // expanding replacement. These must be dominated by any operands that
4119 // will be required in the expansion.
4120 SmallVector<Instruction *, 4> Inputs;
4121 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4122 Inputs.push_back(I);
4123 if (LU.Kind == LSRUse::ICmpZero)
4124 if (Instruction *I =
4125 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4126 Inputs.push_back(I);
4127 if (LF.PostIncLoops.count(L)) {
4128 if (LF.isUseFullyOutsideLoop(L))
4129 Inputs.push_back(L->getLoopLatch()->getTerminator());
4131 Inputs.push_back(IVIncInsertPos);
4133 // The expansion must also be dominated by the increment positions of any
4134 // loops it for which it is using post-inc mode.
4135 for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(),
4136 E = LF.PostIncLoops.end(); I != E; ++I) {
4137 const Loop *PIL = *I;
4138 if (PIL == L) continue;
4140 // Be dominated by the loop exit.
4141 SmallVector<BasicBlock *, 4> ExitingBlocks;
4142 PIL->getExitingBlocks(ExitingBlocks);
4143 if (!ExitingBlocks.empty()) {
4144 BasicBlock *BB = ExitingBlocks[0];
4145 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4146 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4147 Inputs.push_back(BB->getTerminator());
4151 assert(!isa<PHINode>(LowestIP) && !isa<LandingPadInst>(LowestIP)
4152 && !isa<DbgInfoIntrinsic>(LowestIP) &&
4153 "Insertion point must be a normal instruction");
4155 // Then, climb up the immediate dominator tree as far as we can go while
4156 // still being dominated by the input positions.
4157 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4159 // Don't insert instructions before PHI nodes.
4160 while (isa<PHINode>(IP)) ++IP;
4162 // Ignore landingpad instructions.
4163 while (isa<LandingPadInst>(IP)) ++IP;
4165 // Ignore debug intrinsics.
4166 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4168 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4169 // IP consistent across expansions and allows the previously inserted
4170 // instructions to be reused by subsequent expansion.
4171 while (Rewriter.isInsertedInstruction(IP) && IP != LowestIP) ++IP;
4176 /// Expand - Emit instructions for the leading candidate expression for this
4177 /// LSRUse (this is called "expanding").
4178 Value *LSRInstance::Expand(const LSRFixup &LF,
4180 BasicBlock::iterator IP,
4181 SCEVExpander &Rewriter,
4182 SmallVectorImpl<WeakVH> &DeadInsts) const {
4183 const LSRUse &LU = Uses[LF.LUIdx];
4185 // Determine an input position which will be dominated by the operands and
4186 // which will dominate the result.
4187 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4189 // Inform the Rewriter if we have a post-increment use, so that it can
4190 // perform an advantageous expansion.
4191 Rewriter.setPostInc(LF.PostIncLoops);
4193 // This is the type that the user actually needs.
4194 Type *OpTy = LF.OperandValToReplace->getType();
4195 // This will be the type that we'll initially expand to.
4196 Type *Ty = F.getType();
4198 // No type known; just expand directly to the ultimate type.
4200 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
4201 // Expand directly to the ultimate type if it's the right size.
4203 // This is the type to do integer arithmetic in.
4204 Type *IntTy = SE.getEffectiveSCEVType(Ty);
4206 // Build up a list of operands to add together to form the full base.
4207 SmallVector<const SCEV *, 8> Ops;
4209 // Expand the BaseRegs portion.
4210 for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(),
4211 E = F.BaseRegs.end(); I != E; ++I) {
4212 const SCEV *Reg = *I;
4213 assert(!Reg->isZero() && "Zero allocated in a base register!");
4215 // If we're expanding for a post-inc user, make the post-inc adjustment.
4216 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4217 Reg = TransformForPostIncUse(Denormalize, Reg,
4218 LF.UserInst, LF.OperandValToReplace,
4221 Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP)));
4224 // Flush the operand list to suppress SCEVExpander hoisting.
4226 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4228 Ops.push_back(SE.getUnknown(FullV));
4231 // Expand the ScaledReg portion.
4232 Value *ICmpScaledV = 0;
4233 if (F.AM.Scale != 0) {
4234 const SCEV *ScaledS = F.ScaledReg;
4236 // If we're expanding for a post-inc user, make the post-inc adjustment.
4237 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4238 ScaledS = TransformForPostIncUse(Denormalize, ScaledS,
4239 LF.UserInst, LF.OperandValToReplace,
4242 if (LU.Kind == LSRUse::ICmpZero) {
4243 // An interesting way of "folding" with an icmp is to use a negated
4244 // scale, which we'll implement by inserting it into the other operand
4246 assert(F.AM.Scale == -1 &&
4247 "The only scale supported by ICmpZero uses is -1!");
4248 ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP);
4250 // Otherwise just expand the scaled register and an explicit scale,
4251 // which is expected to be matched as part of the address.
4252 ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP));
4253 ScaledS = SE.getMulExpr(ScaledS,
4254 SE.getConstant(ScaledS->getType(), F.AM.Scale));
4255 Ops.push_back(ScaledS);
4257 // Flush the operand list to suppress SCEVExpander hoisting.
4258 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4260 Ops.push_back(SE.getUnknown(FullV));
4264 // Expand the GV portion.
4266 Ops.push_back(SE.getUnknown(F.AM.BaseGV));
4268 // Flush the operand list to suppress SCEVExpander hoisting.
4269 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4271 Ops.push_back(SE.getUnknown(FullV));
4274 // Expand the immediate portion.
4275 int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset;
4277 if (LU.Kind == LSRUse::ICmpZero) {
4278 // The other interesting way of "folding" with an ICmpZero is to use a
4279 // negated immediate.
4281 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
4283 Ops.push_back(SE.getUnknown(ICmpScaledV));
4284 ICmpScaledV = ConstantInt::get(IntTy, Offset);
4287 // Just add the immediate values. These again are expected to be matched
4288 // as part of the address.
4289 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
4293 // Expand the unfolded offset portion.
4294 int64_t UnfoldedOffset = F.UnfoldedOffset;
4295 if (UnfoldedOffset != 0) {
4296 // Just add the immediate values.
4297 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
4301 // Emit instructions summing all the operands.
4302 const SCEV *FullS = Ops.empty() ?
4303 SE.getConstant(IntTy, 0) :
4305 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
4307 // We're done expanding now, so reset the rewriter.
4308 Rewriter.clearPostInc();
4310 // An ICmpZero Formula represents an ICmp which we're handling as a
4311 // comparison against zero. Now that we've expanded an expression for that
4312 // form, update the ICmp's other operand.
4313 if (LU.Kind == LSRUse::ICmpZero) {
4314 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
4315 DeadInsts.push_back(CI->getOperand(1));
4316 assert(!F.AM.BaseGV && "ICmp does not support folding a global value and "
4317 "a scale at the same time!");
4318 if (F.AM.Scale == -1) {
4319 if (ICmpScaledV->getType() != OpTy) {
4321 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
4323 ICmpScaledV, OpTy, "tmp", CI);
4326 CI->setOperand(1, ICmpScaledV);
4328 assert(F.AM.Scale == 0 &&
4329 "ICmp does not support folding a global value and "
4330 "a scale at the same time!");
4331 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
4333 if (C->getType() != OpTy)
4334 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4338 CI->setOperand(1, C);
4345 /// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
4346 /// of their operands effectively happens in their predecessor blocks, so the
4347 /// expression may need to be expanded in multiple places.
4348 void LSRInstance::RewriteForPHI(PHINode *PN,
4351 SCEVExpander &Rewriter,
4352 SmallVectorImpl<WeakVH> &DeadInsts,
4354 DenseMap<BasicBlock *, Value *> Inserted;
4355 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
4356 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
4357 BasicBlock *BB = PN->getIncomingBlock(i);
4359 // If this is a critical edge, split the edge so that we do not insert
4360 // the code on all predecessor/successor paths. We do this unless this
4361 // is the canonical backedge for this loop, which complicates post-inc
4363 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
4364 !isa<IndirectBrInst>(BB->getTerminator())) {
4365 BasicBlock *Parent = PN->getParent();
4366 Loop *PNLoop = LI.getLoopFor(Parent);
4367 if (!PNLoop || Parent != PNLoop->getHeader()) {
4368 // Split the critical edge.
4369 BasicBlock *NewBB = 0;
4370 if (!Parent->isLandingPad()) {
4371 NewBB = SplitCriticalEdge(BB, Parent, P,
4372 /*MergeIdenticalEdges=*/true,
4373 /*DontDeleteUselessPhis=*/true);
4375 SmallVector<BasicBlock*, 2> NewBBs;
4376 SplitLandingPadPredecessors(Parent, BB, "", "", P, NewBBs);
4380 // If PN is outside of the loop and BB is in the loop, we want to
4381 // move the block to be immediately before the PHI block, not
4382 // immediately after BB.
4383 if (L->contains(BB) && !L->contains(PN))
4384 NewBB->moveBefore(PN->getParent());
4386 // Splitting the edge can reduce the number of PHI entries we have.
4387 e = PN->getNumIncomingValues();
4389 i = PN->getBasicBlockIndex(BB);
4393 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
4394 Inserted.insert(std::make_pair(BB, static_cast<Value *>(0)));
4396 PN->setIncomingValue(i, Pair.first->second);
4398 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
4400 // If this is reuse-by-noop-cast, insert the noop cast.
4401 Type *OpTy = LF.OperandValToReplace->getType();
4402 if (FullV->getType() != OpTy)
4404 CastInst::Create(CastInst::getCastOpcode(FullV, false,
4406 FullV, LF.OperandValToReplace->getType(),
4407 "tmp", BB->getTerminator());
4409 PN->setIncomingValue(i, FullV);
4410 Pair.first->second = FullV;
4415 /// Rewrite - Emit instructions for the leading candidate expression for this
4416 /// LSRUse (this is called "expanding"), and update the UserInst to reference
4417 /// the newly expanded value.
4418 void LSRInstance::Rewrite(const LSRFixup &LF,
4420 SCEVExpander &Rewriter,
4421 SmallVectorImpl<WeakVH> &DeadInsts,
4423 // First, find an insertion point that dominates UserInst. For PHI nodes,
4424 // find the nearest block which dominates all the relevant uses.
4425 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
4426 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
4428 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
4430 // If this is reuse-by-noop-cast, insert the noop cast.
4431 Type *OpTy = LF.OperandValToReplace->getType();
4432 if (FullV->getType() != OpTy) {
4434 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
4435 FullV, OpTy, "tmp", LF.UserInst);
4439 // Update the user. ICmpZero is handled specially here (for now) because
4440 // Expand may have updated one of the operands of the icmp already, and
4441 // its new value may happen to be equal to LF.OperandValToReplace, in
4442 // which case doing replaceUsesOfWith leads to replacing both operands
4443 // with the same value. TODO: Reorganize this.
4444 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
4445 LF.UserInst->setOperand(0, FullV);
4447 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
4450 DeadInsts.push_back(LF.OperandValToReplace);
4453 /// ImplementSolution - Rewrite all the fixup locations with new values,
4454 /// following the chosen solution.
4456 LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
4458 // Keep track of instructions we may have made dead, so that
4459 // we can remove them after we are done working.
4460 SmallVector<WeakVH, 16> DeadInsts;
4462 SCEVExpander Rewriter(SE, "lsr");
4464 Rewriter.setDebugType(DEBUG_TYPE);
4466 Rewriter.disableCanonicalMode();
4467 Rewriter.enableLSRMode();
4468 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
4470 // Mark phi nodes that terminate chains so the expander tries to reuse them.
4471 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4472 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4473 if (PHINode *PN = dyn_cast<PHINode>(ChainI->back().UserInst))
4474 Rewriter.setChainedPhi(PN);
4477 // Expand the new value definitions and update the users.
4478 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4479 E = Fixups.end(); I != E; ++I) {
4480 const LSRFixup &Fixup = *I;
4482 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
4487 for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(),
4488 ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) {
4489 GenerateIVChain(*ChainI, Rewriter, DeadInsts);
4492 // Clean up after ourselves. This must be done before deleting any
4496 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
4499 LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P)
4500 : IU(P->getAnalysis<IVUsers>()),
4501 SE(P->getAnalysis<ScalarEvolution>()),
4502 DT(P->getAnalysis<DominatorTree>()),
4503 LI(P->getAnalysis<LoopInfo>()),
4504 TLI(tli), L(l), Changed(false), IVIncInsertPos(0) {
4506 // If LoopSimplify form is not available, stay out of trouble.
4507 if (!L->isLoopSimplifyForm())
4510 // If there's no interesting work to be done, bail early.
4511 if (IU.empty()) return;
4514 // All dominating loops must have preheaders, or SCEVExpander may not be able
4515 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
4517 // IVUsers analysis should only create users that are dominated by simple loop
4518 // headers. Since this loop should dominate all of its users, its user list
4519 // should be empty if this loop itself is not within a simple loop nest.
4520 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
4521 Rung; Rung = Rung->getIDom()) {
4522 BasicBlock *BB = Rung->getBlock();
4523 const Loop *DomLoop = LI.getLoopFor(BB);
4524 if (DomLoop && DomLoop->getHeader() == BB) {
4525 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
4530 DEBUG(dbgs() << "\nLSR on loop ";
4531 WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false);
4534 // First, perform some low-level loop optimizations.
4536 OptimizeLoopTermCond();
4538 // If loop preparation eliminates all interesting IV users, bail.
4539 if (IU.empty()) return;
4541 // Skip nested loops until we can model them better with formulae.
4543 DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
4547 // Start collecting data and preparing for the solver.
4549 CollectInterestingTypesAndFactors();
4550 CollectFixupsAndInitialFormulae();
4551 CollectLoopInvariantFixupsAndFormulae();
4553 assert(!Uses.empty() && "IVUsers reported at least one use");
4554 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
4555 print_uses(dbgs()));
4557 // Now use the reuse data to generate a bunch of interesting ways
4558 // to formulate the values needed for the uses.
4559 GenerateAllReuseFormulae();
4561 FilterOutUndesirableDedicatedRegisters();
4562 NarrowSearchSpaceUsingHeuristics();
4564 SmallVector<const Formula *, 8> Solution;
4567 // Release memory that is no longer needed.
4572 if (Solution.empty())
4576 // Formulae should be legal.
4577 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
4578 E = Uses.end(); I != E; ++I) {
4579 const LSRUse &LU = *I;
4580 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
4581 JE = LU.Formulae.end(); J != JE; ++J)
4582 assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset,
4583 LU.Kind, LU.AccessTy, TLI) &&
4584 "Illegal formula generated!");
4588 // Now that we've decided what we want, make it so.
4589 ImplementSolution(Solution, P);
4592 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
4593 if (Factors.empty() && Types.empty()) return;
4595 OS << "LSR has identified the following interesting factors and types: ";
4598 for (SmallSetVector<int64_t, 8>::const_iterator
4599 I = Factors.begin(), E = Factors.end(); I != E; ++I) {
4600 if (!First) OS << ", ";
4605 for (SmallSetVector<Type *, 4>::const_iterator
4606 I = Types.begin(), E = Types.end(); I != E; ++I) {
4607 if (!First) OS << ", ";
4609 OS << '(' << **I << ')';
4614 void LSRInstance::print_fixups(raw_ostream &OS) const {
4615 OS << "LSR is examining the following fixup sites:\n";
4616 for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(),
4617 E = Fixups.end(); I != E; ++I) {
4624 void LSRInstance::print_uses(raw_ostream &OS) const {
4625 OS << "LSR is examining the following uses:\n";
4626 for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(),
4627 E = Uses.end(); I != E; ++I) {
4628 const LSRUse &LU = *I;
4632 for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(),
4633 JE = LU.Formulae.end(); J != JE; ++J) {
4641 void LSRInstance::print(raw_ostream &OS) const {
4642 print_factors_and_types(OS);
4647 void LSRInstance::dump() const {
4648 print(errs()); errs() << '\n';
4653 class LoopStrengthReduce : public LoopPass {
4654 /// TLI - Keep a pointer of a TargetLowering to consult for determining
4655 /// transformation profitability.
4656 const TargetLowering *const TLI;
4659 static char ID; // Pass ID, replacement for typeid
4660 explicit LoopStrengthReduce(const TargetLowering *tli = 0);
4663 bool runOnLoop(Loop *L, LPPassManager &LPM);
4664 void getAnalysisUsage(AnalysisUsage &AU) const;
4669 char LoopStrengthReduce::ID = 0;
4670 INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
4671 "Loop Strength Reduction", false, false)
4672 INITIALIZE_PASS_DEPENDENCY(DominatorTree)
4673 INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
4674 INITIALIZE_PASS_DEPENDENCY(IVUsers)
4675 INITIALIZE_PASS_DEPENDENCY(LoopInfo)
4676 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
4677 INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
4678 "Loop Strength Reduction", false, false)
4681 Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) {
4682 return new LoopStrengthReduce(TLI);
4685 LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli)
4686 : LoopPass(ID), TLI(tli) {
4687 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
4690 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
4691 // We split critical edges, so we change the CFG. However, we do update
4692 // many analyses if they are around.
4693 AU.addPreservedID(LoopSimplifyID);
4695 AU.addRequired<LoopInfo>();
4696 AU.addPreserved<LoopInfo>();
4697 AU.addRequiredID(LoopSimplifyID);
4698 AU.addRequired<DominatorTree>();
4699 AU.addPreserved<DominatorTree>();
4700 AU.addRequired<ScalarEvolution>();
4701 AU.addPreserved<ScalarEvolution>();
4702 // Requiring LoopSimplify a second time here prevents IVUsers from running
4703 // twice, since LoopSimplify was invalidated by running ScalarEvolution.
4704 AU.addRequiredID(LoopSimplifyID);
4705 AU.addRequired<IVUsers>();
4706 AU.addPreserved<IVUsers>();
4709 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
4710 bool Changed = false;
4712 // Run the main LSR transformation.
4713 Changed |= LSRInstance(TLI, L, this).getChanged();
4715 // Remove any extra phis created by processing inner loops.
4716 Changed |= DeleteDeadPHIs(L->getHeader());
4717 if (EnablePhiElim) {
4718 SmallVector<WeakVH, 16> DeadInsts;
4719 SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), "lsr");
4721 Rewriter.setDebugType(DEBUG_TYPE);
4723 unsigned numFolded = Rewriter.
4724 replaceCongruentIVs(L, &getAnalysis<DominatorTree>(), DeadInsts, TLI);
4727 DeleteTriviallyDeadInstructions(DeadInsts);
4728 DeleteDeadPHIs(L->getHeader());