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 the addressing mode BaseGV be changed to a ConstantExpr instead
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 #include "llvm/Transforms/Scalar.h"
57 #include "llvm/ADT/DenseSet.h"
58 #include "llvm/ADT/Hashing.h"
59 #include "llvm/ADT/STLExtras.h"
60 #include "llvm/ADT/SetVector.h"
61 #include "llvm/ADT/SmallBitVector.h"
62 #include "llvm/Analysis/IVUsers.h"
63 #include "llvm/Analysis/LoopPass.h"
64 #include "llvm/Analysis/ScalarEvolutionExpander.h"
65 #include "llvm/Analysis/TargetTransformInfo.h"
66 #include "llvm/IR/Constants.h"
67 #include "llvm/IR/DerivedTypes.h"
68 #include "llvm/IR/Dominators.h"
69 #include "llvm/IR/Instructions.h"
70 #include "llvm/IR/IntrinsicInst.h"
71 #include "llvm/IR/Module.h"
72 #include "llvm/IR/ValueHandle.h"
73 #include "llvm/Support/CommandLine.h"
74 #include "llvm/Support/Debug.h"
75 #include "llvm/Support/raw_ostream.h"
76 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
77 #include "llvm/Transforms/Utils/Local.h"
81 #define DEBUG_TYPE "loop-reduce"
83 /// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for
84 /// bail out. This threshold is far beyond the number of users that LSR can
85 /// conceivably solve, so it should not affect generated code, but catches the
86 /// worst cases before LSR burns too much compile time and stack space.
87 static const unsigned MaxIVUsers = 200;
89 // Temporary flag to cleanup congruent phis after LSR phi expansion.
90 // It's currently disabled until we can determine whether it's truly useful or
91 // not. The flag should be removed after the v3.0 release.
92 // This is now needed for ivchains.
93 static cl::opt<bool> EnablePhiElim(
94 "enable-lsr-phielim", cl::Hidden, cl::init(true),
95 cl::desc("Enable LSR phi elimination"));
98 // Stress test IV chain generation.
99 static cl::opt<bool> StressIVChain(
100 "stress-ivchain", cl::Hidden, cl::init(false),
101 cl::desc("Stress test LSR IV chains"));
103 static bool StressIVChain = false;
108 /// RegSortData - This class holds data which is used to order reuse candidates.
111 /// UsedByIndices - This represents the set of LSRUse indices which reference
112 /// a particular register.
113 SmallBitVector UsedByIndices;
115 void print(raw_ostream &OS) const;
121 void RegSortData::print(raw_ostream &OS) const {
122 OS << "[NumUses=" << UsedByIndices.count() << ']';
125 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
126 void RegSortData::dump() const {
127 print(errs()); errs() << '\n';
133 /// RegUseTracker - Map register candidates to information about how they are
135 class RegUseTracker {
136 typedef DenseMap<const SCEV *, RegSortData> RegUsesTy;
138 RegUsesTy RegUsesMap;
139 SmallVector<const SCEV *, 16> RegSequence;
142 void CountRegister(const SCEV *Reg, size_t LUIdx);
143 void DropRegister(const SCEV *Reg, size_t LUIdx);
144 void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx);
146 bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const;
148 const SmallBitVector &getUsedByIndices(const SCEV *Reg) const;
152 typedef SmallVectorImpl<const SCEV *>::iterator iterator;
153 typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator;
154 iterator begin() { return RegSequence.begin(); }
155 iterator end() { return RegSequence.end(); }
156 const_iterator begin() const { return RegSequence.begin(); }
157 const_iterator end() const { return RegSequence.end(); }
163 RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) {
164 std::pair<RegUsesTy::iterator, bool> Pair =
165 RegUsesMap.insert(std::make_pair(Reg, RegSortData()));
166 RegSortData &RSD = Pair.first->second;
168 RegSequence.push_back(Reg);
169 RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1));
170 RSD.UsedByIndices.set(LUIdx);
174 RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) {
175 RegUsesTy::iterator It = RegUsesMap.find(Reg);
176 assert(It != RegUsesMap.end());
177 RegSortData &RSD = It->second;
178 assert(RSD.UsedByIndices.size() > LUIdx);
179 RSD.UsedByIndices.reset(LUIdx);
183 RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) {
184 assert(LUIdx <= LastLUIdx);
186 // Update RegUses. The data structure is not optimized for this purpose;
187 // we must iterate through it and update each of the bit vectors.
188 for (auto &Pair : RegUsesMap) {
189 SmallBitVector &UsedByIndices = Pair.second.UsedByIndices;
190 if (LUIdx < UsedByIndices.size())
191 UsedByIndices[LUIdx] =
192 LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0;
193 UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx));
198 RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const {
199 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
200 if (I == RegUsesMap.end())
202 const SmallBitVector &UsedByIndices = I->second.UsedByIndices;
203 int i = UsedByIndices.find_first();
204 if (i == -1) return false;
205 if ((size_t)i != LUIdx) return true;
206 return UsedByIndices.find_next(i) != -1;
209 const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const {
210 RegUsesTy::const_iterator I = RegUsesMap.find(Reg);
211 assert(I != RegUsesMap.end() && "Unknown register!");
212 return I->second.UsedByIndices;
215 void RegUseTracker::clear() {
222 /// Formula - This class holds information that describes a formula for
223 /// computing satisfying a use. It may include broken-out immediates and scaled
226 /// Global base address used for complex addressing.
229 /// Base offset for complex addressing.
232 /// Whether any complex addressing has a base register.
235 /// The scale of any complex addressing.
238 /// BaseRegs - The list of "base" registers for this use. When this is
239 /// non-empty. The canonical representation of a formula is
240 /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and
241 /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty().
242 /// #1 enforces that the scaled register is always used when at least two
243 /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2.
244 /// #2 enforces that 1 * reg is reg.
245 /// This invariant can be temporarly broken while building a formula.
246 /// However, every formula inserted into the LSRInstance must be in canonical
248 SmallVector<const SCEV *, 4> BaseRegs;
250 /// ScaledReg - The 'scaled' register for this use. This should be non-null
251 /// when Scale is not zero.
252 const SCEV *ScaledReg;
254 /// UnfoldedOffset - An additional constant offset which added near the
255 /// use. This requires a temporary register, but the offset itself can
256 /// live in an add immediate field rather than a register.
257 int64_t UnfoldedOffset;
259 /// ZeroExtendScaledReg - This formula zero extends the scale register to
260 /// ZeroExtendType before its use.
261 bool ZeroExtendScaledReg;
263 /// ZeroExtendBaseReg - This formula zero extends all the base registers to
264 /// ZeroExtendType before their use.
265 bool ZeroExtendBaseReg;
267 /// ZeroExtendType - The destination type of the zero extension implied by
268 /// the above two booleans.
269 Type *ZeroExtendType;
272 : BaseGV(nullptr), BaseOffset(0), HasBaseReg(false), Scale(0),
273 ScaledReg(nullptr), UnfoldedOffset(0), ZeroExtendScaledReg(false),
274 ZeroExtendBaseReg(false), ZeroExtendType(nullptr) {}
276 void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE);
278 bool isCanonical() const;
284 size_t getNumRegs() const;
285 Type *getType() const;
287 void DeleteBaseReg(const SCEV *&S);
289 bool referencesReg(const SCEV *S) const;
290 bool hasRegsUsedByUsesOtherThan(size_t LUIdx,
291 const RegUseTracker &RegUses) const;
293 void print(raw_ostream &OS) const;
299 /// DoInitialMatch - Recursion helper for InitialMatch.
300 static void DoInitialMatch(const SCEV *S, Loop *L,
301 SmallVectorImpl<const SCEV *> &Good,
302 SmallVectorImpl<const SCEV *> &Bad,
303 ScalarEvolution &SE) {
304 // Collect expressions which properly dominate the loop header.
305 if (SE.properlyDominates(S, L->getHeader())) {
310 // Look at add operands.
311 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
312 for (const SCEV *S : Add->operands())
313 DoInitialMatch(S, L, Good, Bad, SE);
317 // Look at addrec operands.
318 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S))
319 if (!AR->getStart()->isZero()) {
320 DoInitialMatch(AR->getStart(), L, Good, Bad, SE);
321 DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0),
322 AR->getStepRecurrence(SE),
323 // FIXME: AR->getNoWrapFlags()
324 AR->getLoop(), SCEV::FlagAnyWrap),
329 // Handle a multiplication by -1 (negation) if it didn't fold.
330 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S))
331 if (Mul->getOperand(0)->isAllOnesValue()) {
332 SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end());
333 const SCEV *NewMul = SE.getMulExpr(Ops);
335 SmallVector<const SCEV *, 4> MyGood;
336 SmallVector<const SCEV *, 4> MyBad;
337 DoInitialMatch(NewMul, L, MyGood, MyBad, SE);
338 const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue(
339 SE.getEffectiveSCEVType(NewMul->getType())));
340 for (const SCEV *S : MyGood)
341 Good.push_back(SE.getMulExpr(NegOne, S));
342 for (const SCEV *S : MyBad)
343 Bad.push_back(SE.getMulExpr(NegOne, S));
347 // Ok, we can't do anything interesting. Just stuff the whole thing into a
348 // register and hope for the best.
352 /// InitialMatch - Incorporate loop-variant parts of S into this Formula,
353 /// attempting to keep all loop-invariant and loop-computable values in a
354 /// single base register.
355 void Formula::InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE) {
356 SmallVector<const SCEV *, 4> Good;
357 SmallVector<const SCEV *, 4> Bad;
358 DoInitialMatch(S, L, Good, Bad, SE);
360 const SCEV *Sum = SE.getAddExpr(Good);
362 BaseRegs.push_back(Sum);
366 const SCEV *Sum = SE.getAddExpr(Bad);
368 BaseRegs.push_back(Sum);
374 /// \brief Check whether or not this formula statisfies the canonical
376 /// \see Formula::BaseRegs.
377 bool Formula::isCanonical() const {
379 return Scale != 1 || !BaseRegs.empty();
380 return BaseRegs.size() <= 1;
383 /// \brief Helper method to morph a formula into its canonical representation.
384 /// \see Formula::BaseRegs.
385 /// Every formula having more than one base register, must use the ScaledReg
386 /// field. Otherwise, we would have to do special cases everywhere in LSR
387 /// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ...
388 /// On the other hand, 1*reg should be canonicalized into reg.
389 void Formula::Canonicalize() {
392 // So far we did not need this case. This is easy to implement but it is
393 // useless to maintain dead code. Beside it could hurt compile time.
394 assert(!BaseRegs.empty() && "1*reg => reg, should not be needed.");
395 // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg.
396 ScaledReg = BaseRegs.back();
399 size_t BaseRegsSize = BaseRegs.size();
401 // If ScaledReg is an invariant, try to find a variant expression.
402 while (Try < BaseRegsSize && !isa<SCEVAddRecExpr>(ScaledReg))
403 std::swap(ScaledReg, BaseRegs[Try++]);
406 /// \brief Get rid of the scale in the formula.
407 /// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2.
408 /// \return true if it was possible to get rid of the scale, false otherwise.
409 /// \note After this operation the formula may not be in the canonical form.
410 bool Formula::Unscale() {
414 BaseRegs.push_back(ScaledReg);
419 /// getNumRegs - Return the total number of register operands used by this
420 /// formula. This does not include register uses implied by non-constant
422 size_t Formula::getNumRegs() const {
423 return !!ScaledReg + BaseRegs.size();
426 /// getType - Return the type of this formula, if it has one, or null
427 /// otherwise. This type is meaningless except for the bit size.
428 Type *Formula::getType() const {
429 return ZeroExtendType
432 ? BaseRegs.front()->getType()
433 : ScaledReg ? ScaledReg->getType()
434 : BaseGV ? BaseGV->getType() : nullptr;
437 /// DeleteBaseReg - Delete the given base reg from the BaseRegs list.
438 void Formula::DeleteBaseReg(const SCEV *&S) {
439 if (&S != &BaseRegs.back())
440 std::swap(S, BaseRegs.back());
444 /// referencesReg - Test if this formula references the given register.
445 bool Formula::referencesReg(const SCEV *S) const {
446 return S == ScaledReg ||
447 std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end();
450 /// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers
451 /// which are used by uses other than the use with the given index.
452 bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx,
453 const RegUseTracker &RegUses) const {
455 if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx))
457 for (const SCEV *BaseReg : BaseRegs)
458 if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx))
463 void Formula::print(raw_ostream &OS) const {
466 if (!First) OS << " + "; else First = false;
467 BaseGV->printAsOperand(OS, /*PrintType=*/false);
469 if (BaseOffset != 0) {
470 if (!First) OS << " + "; else First = false;
473 for (const SCEV *BaseReg : BaseRegs) {
474 if (!First) OS << " + "; else First = false;
475 if (ZeroExtendBaseReg)
476 OS << "reg(zext " << *BaseReg << " to " << *ZeroExtendType << ')';
478 OS << "reg(" << *BaseReg << ')';
480 if (HasBaseReg && BaseRegs.empty()) {
481 if (!First) OS << " + "; else First = false;
482 OS << "**error: HasBaseReg**";
483 } else if (!HasBaseReg && !BaseRegs.empty()) {
484 if (!First) OS << " + "; else First = false;
485 OS << "**error: !HasBaseReg**";
488 if (!First) OS << " + "; else First = false;
489 OS << Scale << "*reg(";
491 if (ZeroExtendScaledReg)
492 OS << "(zext " << *ScaledReg << " to " << *ZeroExtendType << ')';
499 if (UnfoldedOffset != 0) {
500 if (!First) OS << " + ";
501 OS << "imm(" << UnfoldedOffset << ')';
505 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
506 void Formula::dump() const {
507 print(errs()); errs() << '\n';
511 /// isAddRecSExtable - Return true if the given addrec can be sign-extended
512 /// without changing its value.
513 static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
515 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(AR->getType()) + 1);
516 return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy));
519 /// isAddSExtable - Return true if the given add can be sign-extended
520 /// without changing its value.
521 static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) {
523 IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1);
524 return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy));
527 /// isMulSExtable - Return true if the given mul can be sign-extended
528 /// without changing its value.
529 static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) {
531 IntegerType::get(SE.getContext(),
532 SE.getTypeSizeInBits(M->getType()) * M->getNumOperands());
533 return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, WideTy));
536 /// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined
537 /// and if the remainder is known to be zero, or null otherwise. If
538 /// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified
539 /// to Y, ignoring that the multiplication may overflow, which is useful when
540 /// the result will be used in a context where the most significant bits are
542 static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS,
544 bool IgnoreSignificantBits = false) {
545 // Handle the trivial case, which works for any SCEV type.
547 return SE.getConstant(LHS->getType(), 1);
549 // Handle a few RHS special cases.
550 const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS);
552 const APInt &RA = RC->getValue()->getValue();
553 // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do
555 if (RA.isAllOnesValue())
556 return SE.getMulExpr(LHS, RC);
557 // Handle x /s 1 as x.
562 // Check for a division of a constant by a constant.
563 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) {
566 const APInt &LA = C->getValue()->getValue();
567 const APInt &RA = RC->getValue()->getValue();
568 if (LA.srem(RA) != 0)
570 return SE.getConstant(LA.sdiv(RA));
573 // Distribute the sdiv over addrec operands, if the addrec doesn't overflow.
574 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) {
575 if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) {
576 const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE,
577 IgnoreSignificantBits);
578 if (!Step) return nullptr;
579 const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE,
580 IgnoreSignificantBits);
581 if (!Start) return nullptr;
582 // FlagNW is independent of the start value, step direction, and is
583 // preserved with smaller magnitude steps.
584 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
585 return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap);
590 // Distribute the sdiv over add operands, if the add doesn't overflow.
591 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) {
592 if (IgnoreSignificantBits || isAddSExtable(Add, SE)) {
593 SmallVector<const SCEV *, 8> Ops;
594 for (const SCEV *S : Add->operands()) {
595 const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits);
596 if (!Op) return nullptr;
599 return SE.getAddExpr(Ops);
604 // Check for a multiply operand that we can pull RHS out of.
605 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) {
606 if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) {
607 SmallVector<const SCEV *, 4> Ops;
609 for (const SCEV *S : Mul->operands()) {
611 if (const SCEV *Q = getExactSDiv(S, RHS, SE,
612 IgnoreSignificantBits)) {
618 return Found ? SE.getMulExpr(Ops) : nullptr;
623 // Otherwise we don't know.
627 /// ExtractImmediate - If S involves the addition of a constant integer value,
628 /// return that integer value, and mutate S to point to a new SCEV with that
630 static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) {
631 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) {
632 if (C->getValue()->getValue().getMinSignedBits() <= 64) {
633 S = SE.getConstant(C->getType(), 0);
634 return C->getValue()->getSExtValue();
636 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
637 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
638 int64_t Result = ExtractImmediate(NewOps.front(), SE);
640 S = SE.getAddExpr(NewOps);
642 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
643 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
644 int64_t Result = ExtractImmediate(NewOps.front(), SE);
646 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
647 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
654 /// ExtractSymbol - If S involves the addition of a GlobalValue address,
655 /// return that symbol, and mutate S to point to a new SCEV with that
657 static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) {
658 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) {
659 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) {
660 S = SE.getConstant(GV->getType(), 0);
663 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
664 SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end());
665 GlobalValue *Result = ExtractSymbol(NewOps.back(), SE);
667 S = SE.getAddExpr(NewOps);
669 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
670 SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end());
671 GlobalValue *Result = ExtractSymbol(NewOps.front(), SE);
673 S = SE.getAddRecExpr(NewOps, AR->getLoop(),
674 // FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
681 /// isAddressUse - Returns true if the specified instruction is using the
682 /// specified value as an address.
683 static bool isAddressUse(Instruction *Inst, Value *OperandVal) {
684 bool isAddress = isa<LoadInst>(Inst);
685 if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
686 if (SI->getOperand(1) == OperandVal)
688 } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
689 // Addressing modes can also be folded into prefetches and a variety
691 switch (II->getIntrinsicID()) {
693 case Intrinsic::prefetch:
694 case Intrinsic::x86_sse_storeu_ps:
695 case Intrinsic::x86_sse2_storeu_pd:
696 case Intrinsic::x86_sse2_storeu_dq:
697 case Intrinsic::x86_sse2_storel_dq:
698 if (II->getArgOperand(0) == OperandVal)
706 /// getAccessType - Return the type of the memory being accessed.
707 static Type *getAccessType(const Instruction *Inst) {
708 Type *AccessTy = Inst->getType();
709 if (const StoreInst *SI = dyn_cast<StoreInst>(Inst))
710 AccessTy = SI->getOperand(0)->getType();
711 else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) {
712 // Addressing modes can also be folded into prefetches and a variety
714 switch (II->getIntrinsicID()) {
716 case Intrinsic::x86_sse_storeu_ps:
717 case Intrinsic::x86_sse2_storeu_pd:
718 case Intrinsic::x86_sse2_storeu_dq:
719 case Intrinsic::x86_sse2_storel_dq:
720 AccessTy = II->getArgOperand(0)->getType();
725 // All pointers have the same requirements, so canonicalize them to an
726 // arbitrary pointer type to minimize variation.
727 if (PointerType *PTy = dyn_cast<PointerType>(AccessTy))
728 AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1),
729 PTy->getAddressSpace());
734 /// isExistingPhi - Return true if this AddRec is already a phi in its loop.
735 static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) {
736 for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin();
737 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
738 if (SE.isSCEVable(PN->getType()) &&
739 (SE.getEffectiveSCEVType(PN->getType()) ==
740 SE.getEffectiveSCEVType(AR->getType())) &&
741 SE.getSCEV(PN) == AR)
747 /// Check if expanding this expression is likely to incur significant cost. This
748 /// is tricky because SCEV doesn't track which expressions are actually computed
749 /// by the current IR.
751 /// We currently allow expansion of IV increments that involve adds,
752 /// multiplication by constants, and AddRecs from existing phis.
754 /// TODO: Allow UDivExpr if we can find an existing IV increment that is an
755 /// obvious multiple of the UDivExpr.
756 static bool isHighCostExpansion(const SCEV *S,
757 SmallPtrSetImpl<const SCEV*> &Processed,
758 ScalarEvolution &SE) {
759 // Zero/One operand expressions
760 switch (S->getSCEVType()) {
765 return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(),
768 return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(),
771 return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(),
775 if (!Processed.insert(S).second)
778 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
779 for (const SCEV *S : Add->operands()) {
780 if (isHighCostExpansion(S, Processed, SE))
786 if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
787 if (Mul->getNumOperands() == 2) {
788 // Multiplication by a constant is ok
789 if (isa<SCEVConstant>(Mul->getOperand(0)))
790 return isHighCostExpansion(Mul->getOperand(1), Processed, SE);
792 // If we have the value of one operand, check if an existing
793 // multiplication already generates this expression.
794 if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) {
795 Value *UVal = U->getValue();
796 for (User *UR : UVal->users()) {
797 // If U is a constant, it may be used by a ConstantExpr.
798 Instruction *UI = dyn_cast<Instruction>(UR);
799 if (UI && UI->getOpcode() == Instruction::Mul &&
800 SE.isSCEVable(UI->getType())) {
801 return SE.getSCEV(UI) == Mul;
808 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
809 if (isExistingPhi(AR, SE))
813 // Fow now, consider any other type of expression (div/mul/min/max) high cost.
817 /// DeleteTriviallyDeadInstructions - If any of the instructions is the
818 /// specified set are trivially dead, delete them and see if this makes any of
819 /// their operands subsequently dead.
821 DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) {
822 bool Changed = false;
824 while (!DeadInsts.empty()) {
825 Value *V = DeadInsts.pop_back_val();
826 Instruction *I = dyn_cast_or_null<Instruction>(V);
828 if (!I || !isInstructionTriviallyDead(I))
831 for (Use &O : I->operands())
832 if (Instruction *U = dyn_cast<Instruction>(O)) {
835 DeadInsts.emplace_back(U);
838 I->eraseFromParent();
849 /// \brief Check if the addressing mode defined by \p F is completely
850 /// folded in \p LU at isel time.
851 /// This includes address-mode folding and special icmp tricks.
852 /// This function returns true if \p LU can accommodate what \p F
853 /// defines and up to 1 base + 1 scaled + offset.
854 /// In other words, if \p F has several base registers, this function may
855 /// still return true. Therefore, users still need to account for
856 /// additional base registers and/or unfolded offsets to derive an
857 /// accurate cost model.
858 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
859 const LSRUse &LU, const Formula &F);
860 // Get the cost of the scaling factor used in F for LU.
861 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
862 const LSRUse &LU, const Formula &F);
866 /// Cost - This class is used to measure and compare candidate formulae.
868 /// TODO: Some of these could be merged. Also, a lexical ordering
869 /// isn't always optimal.
873 unsigned NumBaseAdds;
880 : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0),
881 SetupCost(0), ScaleCost(0) {}
883 bool operator<(const Cost &Other) const;
888 // Once any of the metrics loses, they must all remain losers.
890 return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds
891 | ImmCost | SetupCost | ScaleCost) != ~0u)
892 || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds
893 & ImmCost & SetupCost & ScaleCost) == ~0u);
898 assert(isValid() && "invalid cost");
899 return NumRegs == ~0u;
902 void RateFormula(const TargetTransformInfo &TTI,
904 SmallPtrSetImpl<const SCEV *> &Regs,
905 const DenseSet<const SCEV *> &VisitedRegs,
907 const SmallVectorImpl<int64_t> &Offsets,
908 ScalarEvolution &SE, DominatorTree &DT,
910 SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr);
912 void print(raw_ostream &OS) const;
916 void RateRegister(const SCEV *Reg,
917 SmallPtrSetImpl<const SCEV *> &Regs,
919 ScalarEvolution &SE, DominatorTree &DT);
920 void RatePrimaryRegister(const SCEV *Reg,
921 SmallPtrSetImpl<const SCEV *> &Regs,
923 ScalarEvolution &SE, DominatorTree &DT,
924 SmallPtrSetImpl<const SCEV *> *LoserRegs);
929 /// RateRegister - Tally up interesting quantities from the given register.
930 void Cost::RateRegister(const SCEV *Reg,
931 SmallPtrSetImpl<const SCEV *> &Regs,
933 ScalarEvolution &SE, DominatorTree &DT) {
934 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) {
935 // If this is an addrec for another loop, don't second-guess its addrec phi
936 // nodes. LSR isn't currently smart enough to reason about more than one
937 // loop at a time. LSR has already run on inner loops, will not run on outer
938 // loops, and cannot be expected to change sibling loops.
939 if (AR->getLoop() != L) {
940 // If the AddRec exists, consider it's register free and leave it alone.
941 if (isExistingPhi(AR, SE))
944 // Otherwise, do not consider this formula at all.
948 AddRecCost += 1; /// TODO: This should be a function of the stride.
950 // Add the step value register, if it needs one.
951 // TODO: The non-affine case isn't precisely modeled here.
952 if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) {
953 if (!Regs.count(AR->getOperand(1))) {
954 RateRegister(AR->getOperand(1), Regs, L, SE, DT);
962 // Rough heuristic; favor registers which don't require extra setup
963 // instructions in the preheader.
964 if (!isa<SCEVUnknown>(Reg) &&
965 !isa<SCEVConstant>(Reg) &&
966 !(isa<SCEVAddRecExpr>(Reg) &&
967 (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) ||
968 isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart()))))
971 NumIVMuls += isa<SCEVMulExpr>(Reg) &&
972 SE.hasComputableLoopEvolution(Reg, L);
975 /// RatePrimaryRegister - Record this register in the set. If we haven't seen it
976 /// before, rate it. Optional LoserRegs provides a way to declare any formula
977 /// that refers to one of those regs an instant loser.
978 void Cost::RatePrimaryRegister(const SCEV *Reg,
979 SmallPtrSetImpl<const SCEV *> &Regs,
981 ScalarEvolution &SE, DominatorTree &DT,
982 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
983 if (LoserRegs && LoserRegs->count(Reg)) {
987 if (Regs.insert(Reg).second) {
988 RateRegister(Reg, Regs, L, SE, DT);
989 if (LoserRegs && isLoser())
990 LoserRegs->insert(Reg);
994 void Cost::RateFormula(const TargetTransformInfo &TTI,
996 SmallPtrSetImpl<const SCEV *> &Regs,
997 const DenseSet<const SCEV *> &VisitedRegs,
999 const SmallVectorImpl<int64_t> &Offsets,
1000 ScalarEvolution &SE, DominatorTree &DT,
1002 SmallPtrSetImpl<const SCEV *> *LoserRegs) {
1003 assert(F.isCanonical() && "Cost is accurate only for canonical formula");
1004 // Tally up the registers.
1005 if (const SCEV *ScaledReg = F.ScaledReg) {
1006 if (VisitedRegs.count(ScaledReg)) {
1010 RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs);
1014 for (const SCEV *BaseReg : F.BaseRegs) {
1015 if (VisitedRegs.count(BaseReg)) {
1019 RatePrimaryRegister(BaseReg, Regs, L, SE, DT, LoserRegs);
1024 // Determine how many (unfolded) adds we'll need inside the loop.
1025 size_t NumBaseParts = F.getNumRegs();
1026 if (NumBaseParts > 1)
1027 // Do not count the base and a possible second register if the target
1028 // allows to fold 2 registers.
1030 NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(TTI, LU, F)));
1031 NumBaseAdds += (F.UnfoldedOffset != 0);
1033 // Accumulate non-free scaling amounts.
1034 ScaleCost += getScalingFactorCost(TTI, LU, F);
1036 // Tally up the non-zero immediates.
1037 for (int64_t O : Offsets) {
1038 int64_t Offset = (uint64_t)O + F.BaseOffset;
1040 ImmCost += 64; // Handle symbolic values conservatively.
1041 // TODO: This should probably be the pointer size.
1042 else if (Offset != 0)
1043 ImmCost += APInt(64, Offset, true).getMinSignedBits();
1045 assert(isValid() && "invalid cost");
1048 /// Lose - Set this cost to a losing value.
1059 /// operator< - Choose the lower cost.
1060 bool Cost::operator<(const Cost &Other) const {
1061 return std::tie(NumRegs, AddRecCost, NumIVMuls, NumBaseAdds, ScaleCost,
1062 ImmCost, SetupCost) <
1063 std::tie(Other.NumRegs, Other.AddRecCost, Other.NumIVMuls,
1064 Other.NumBaseAdds, Other.ScaleCost, Other.ImmCost,
1068 void Cost::print(raw_ostream &OS) const {
1069 OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s");
1070 if (AddRecCost != 0)
1071 OS << ", with addrec cost " << AddRecCost;
1073 OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s");
1074 if (NumBaseAdds != 0)
1075 OS << ", plus " << NumBaseAdds << " base add"
1076 << (NumBaseAdds == 1 ? "" : "s");
1078 OS << ", plus " << ScaleCost << " scale cost";
1080 OS << ", plus " << ImmCost << " imm cost";
1082 OS << ", plus " << SetupCost << " setup cost";
1085 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1086 void Cost::dump() const {
1087 print(errs()); errs() << '\n';
1093 /// LSRFixup - An operand value in an instruction which is to be replaced
1094 /// with some equivalent, possibly strength-reduced, replacement.
1096 /// UserInst - The instruction which will be updated.
1097 Instruction *UserInst;
1099 /// OperandValToReplace - The operand of the instruction which will
1100 /// be replaced. The operand may be used more than once; every instance
1101 /// will be replaced.
1102 Value *OperandValToReplace;
1104 /// PostIncLoops - If this user is to use the post-incremented value of an
1105 /// induction variable, this variable is non-null and holds the loop
1106 /// associated with the induction variable.
1107 PostIncLoopSet PostIncLoops;
1109 /// LUIdx - The index of the LSRUse describing the expression which
1110 /// this fixup needs, minus an offset (below).
1113 /// Offset - A constant offset to be added to the LSRUse expression.
1114 /// This allows multiple fixups to share the same LSRUse with different
1115 /// offsets, for example in an unrolled loop.
1118 bool isUseFullyOutsideLoop(const Loop *L) const;
1122 void print(raw_ostream &OS) const;
1128 LSRFixup::LSRFixup()
1129 : UserInst(nullptr), OperandValToReplace(nullptr), LUIdx(~size_t(0)),
1132 /// isUseFullyOutsideLoop - Test whether this fixup always uses its
1133 /// value outside of the given loop.
1134 bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const {
1135 // PHI nodes use their value in their incoming blocks.
1136 if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) {
1137 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
1138 if (PN->getIncomingValue(i) == OperandValToReplace &&
1139 L->contains(PN->getIncomingBlock(i)))
1144 return !L->contains(UserInst);
1147 void LSRFixup::print(raw_ostream &OS) const {
1149 // Store is common and interesting enough to be worth special-casing.
1150 if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) {
1152 Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false);
1153 } else if (UserInst->getType()->isVoidTy())
1154 OS << UserInst->getOpcodeName();
1156 UserInst->printAsOperand(OS, /*PrintType=*/false);
1158 OS << ", OperandValToReplace=";
1159 OperandValToReplace->printAsOperand(OS, /*PrintType=*/false);
1161 for (const Loop *PIL : PostIncLoops) {
1162 OS << ", PostIncLoop=";
1163 PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false);
1166 if (LUIdx != ~size_t(0))
1167 OS << ", LUIdx=" << LUIdx;
1170 OS << ", Offset=" << Offset;
1173 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1174 void LSRFixup::dump() const {
1175 print(errs()); errs() << '\n';
1181 /// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding
1182 /// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*.
1183 struct UniquifierDenseMapInfo {
1184 static SmallVector<const SCEV *, 4> getEmptyKey() {
1185 SmallVector<const SCEV *, 4> V;
1186 V.push_back(reinterpret_cast<const SCEV *>(-1));
1190 static SmallVector<const SCEV *, 4> getTombstoneKey() {
1191 SmallVector<const SCEV *, 4> V;
1192 V.push_back(reinterpret_cast<const SCEV *>(-2));
1196 static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) {
1197 return static_cast<unsigned>(hash_combine_range(V.begin(), V.end()));
1200 static bool isEqual(const SmallVector<const SCEV *, 4> &LHS,
1201 const SmallVector<const SCEV *, 4> &RHS) {
1206 /// LSRUse - This class holds the state that LSR keeps for each use in
1207 /// IVUsers, as well as uses invented by LSR itself. It includes information
1208 /// about what kinds of things can be folded into the user, information about
1209 /// the user itself, and information about how the use may be satisfied.
1210 /// TODO: Represent multiple users of the same expression in common?
1212 DenseSet<SmallVector<const SCEV *, 4>, UniquifierDenseMapInfo> Uniquifier;
1215 /// KindType - An enum for a kind of use, indicating what types of
1216 /// scaled and immediate operands it might support.
1218 Basic, ///< A normal use, with no folding.
1219 Special, ///< A special case of basic, allowing -1 scales.
1220 Address, ///< An address use; folding according to TargetLowering
1221 ICmpZero ///< An equality icmp with both operands folded into one.
1222 // TODO: Add a generic icmp too?
1225 typedef PointerIntPair<const SCEV *, 2, KindType> SCEVUseKindPair;
1230 SmallVector<int64_t, 8> Offsets;
1234 /// AllFixupsOutsideLoop - This records whether all of the fixups using this
1235 /// LSRUse are outside of the loop, in which case some special-case heuristics
1237 bool AllFixupsOutsideLoop;
1239 /// RigidFormula is set to true to guarantee that this use will be associated
1240 /// with a single formula--the one that initially matched. Some SCEV
1241 /// expressions cannot be expanded. This allows LSR to consider the registers
1242 /// used by those expressions without the need to expand them later after
1243 /// changing the formula.
1246 /// WidestFixupType - This records the widest use type for any fixup using
1247 /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different
1248 /// max fixup widths to be equivalent, because the narrower one may be relying
1249 /// on the implicit truncation to truncate away bogus bits.
1250 Type *WidestFixupType;
1252 /// Formulae - A list of ways to build a value that can satisfy this user.
1253 /// After the list is populated, one of these is selected heuristically and
1254 /// used to formulate a replacement for OperandValToReplace in UserInst.
1255 SmallVector<Formula, 12> Formulae;
1257 /// Regs - The set of register candidates used by all formulae in this LSRUse.
1258 SmallPtrSet<const SCEV *, 4> Regs;
1260 LSRUse(KindType K, Type *T) : Kind(K), AccessTy(T),
1261 MinOffset(INT64_MAX),
1262 MaxOffset(INT64_MIN),
1263 AllFixupsOutsideLoop(true),
1264 RigidFormula(false),
1265 WidestFixupType(nullptr) {}
1267 bool HasFormulaWithSameRegs(const Formula &F) const;
1268 bool InsertFormula(const Formula &F);
1269 void DeleteFormula(Formula &F);
1270 void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses);
1272 void print(raw_ostream &OS) const;
1278 /// HasFormula - Test whether this use as a formula which has the same
1279 /// registers as the given formula.
1280 bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const {
1281 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1282 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1283 // Unstable sort by host order ok, because this is only used for uniquifying.
1284 std::sort(Key.begin(), Key.end());
1285 return Uniquifier.count(Key);
1288 /// InsertFormula - If the given formula has not yet been inserted, add it to
1289 /// the list, and return true. Return false otherwise.
1290 /// The formula must be in canonical form.
1291 bool LSRUse::InsertFormula(const Formula &F) {
1292 assert(F.isCanonical() && "Invalid canonical representation");
1294 if (!Formulae.empty() && RigidFormula)
1297 SmallVector<const SCEV *, 4> Key = F.BaseRegs;
1298 if (F.ScaledReg) Key.push_back(F.ScaledReg);
1299 // Unstable sort by host order ok, because this is only used for uniquifying.
1300 std::sort(Key.begin(), Key.end());
1302 if (!Uniquifier.insert(Key).second)
1305 // Using a register to hold the value of 0 is not profitable.
1306 assert((!F.ScaledReg || !F.ScaledReg->isZero()) &&
1307 "Zero allocated in a scaled register!");
1309 for (const SCEV *BaseReg : F.BaseRegs)
1310 assert(!BaseReg->isZero() && "Zero allocated in a base register!");
1313 // Add the formula to the list.
1314 Formulae.push_back(F);
1316 // Record registers now being used by this use.
1317 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1319 Regs.insert(F.ScaledReg);
1324 /// DeleteFormula - Remove the given formula from this use's list.
1325 void LSRUse::DeleteFormula(Formula &F) {
1326 if (&F != &Formulae.back())
1327 std::swap(F, Formulae.back());
1328 Formulae.pop_back();
1331 /// RecomputeRegs - Recompute the Regs field, and update RegUses.
1332 void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) {
1333 // Now that we've filtered out some formulae, recompute the Regs set.
1334 SmallPtrSet<const SCEV *, 4> OldRegs = std::move(Regs);
1336 for (const Formula &F : Formulae) {
1337 if (F.ScaledReg) Regs.insert(F.ScaledReg);
1338 Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end());
1341 // Update the RegTracker.
1342 for (const SCEV *S : OldRegs)
1344 RegUses.DropRegister(S, LUIdx);
1347 void LSRUse::print(raw_ostream &OS) const {
1348 OS << "LSR Use: Kind=";
1350 case Basic: OS << "Basic"; break;
1351 case Special: OS << "Special"; break;
1352 case ICmpZero: OS << "ICmpZero"; break;
1354 OS << "Address of ";
1355 if (AccessTy->isPointerTy())
1356 OS << "pointer"; // the full pointer type could be really verbose
1361 OS << ", Offsets={";
1362 bool NeedComma = false;
1363 for (int64_t O : Offsets) {
1364 if (NeedComma) OS << ',';
1370 if (AllFixupsOutsideLoop)
1371 OS << ", all-fixups-outside-loop";
1373 if (WidestFixupType)
1374 OS << ", widest fixup type: " << *WidestFixupType;
1377 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
1378 void LSRUse::dump() const {
1379 print(errs()); errs() << '\n';
1383 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1384 LSRUse::KindType Kind, Type *AccessTy,
1385 GlobalValue *BaseGV, int64_t BaseOffset,
1386 bool HasBaseReg, int64_t Scale) {
1388 case LSRUse::Address:
1389 return TTI.isLegalAddressingMode(AccessTy, BaseGV, BaseOffset, HasBaseReg, Scale);
1391 case LSRUse::ICmpZero:
1392 // There's not even a target hook for querying whether it would be legal to
1393 // fold a GV into an ICmp.
1397 // ICmp only has two operands; don't allow more than two non-trivial parts.
1398 if (Scale != 0 && HasBaseReg && BaseOffset != 0)
1401 // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by
1402 // putting the scaled register in the other operand of the icmp.
1403 if (Scale != 0 && Scale != -1)
1406 // If we have low-level target information, ask the target if it can fold an
1407 // integer immediate on an icmp.
1408 if (BaseOffset != 0) {
1410 // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset
1411 // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset
1412 // Offs is the ICmp immediate.
1414 // The cast does the right thing with INT64_MIN.
1415 BaseOffset = -(uint64_t)BaseOffset;
1416 return TTI.isLegalICmpImmediate(BaseOffset);
1419 // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg
1423 // Only handle single-register values.
1424 return !BaseGV && Scale == 0 && BaseOffset == 0;
1426 case LSRUse::Special:
1427 // Special case Basic to handle -1 scales.
1428 return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0;
1431 llvm_unreachable("Invalid LSRUse Kind!");
1434 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1435 int64_t MinOffset, int64_t MaxOffset,
1436 LSRUse::KindType Kind, Type *AccessTy,
1437 GlobalValue *BaseGV, int64_t BaseOffset,
1438 bool HasBaseReg, int64_t Scale) {
1439 // Check for overflow.
1440 if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) !=
1443 MinOffset = (uint64_t)BaseOffset + MinOffset;
1444 if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) !=
1447 MaxOffset = (uint64_t)BaseOffset + MaxOffset;
1449 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset,
1450 HasBaseReg, Scale) &&
1451 isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset,
1455 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1456 int64_t MinOffset, int64_t MaxOffset,
1457 LSRUse::KindType Kind, Type *AccessTy,
1459 // For the purpose of isAMCompletelyFolded either having a canonical formula
1460 // or a scale not equal to zero is correct.
1461 // Problems may arise from non canonical formulae having a scale == 0.
1462 // Strictly speaking it would best to just rely on canonical formulae.
1463 // However, when we generate the scaled formulae, we first check that the
1464 // scaling factor is profitable before computing the actual ScaledReg for
1465 // compile time sake.
1466 assert((F.isCanonical() || F.Scale != 0));
1467 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1468 F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale);
1471 /// isLegalUse - Test whether we know how to expand the current formula.
1472 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1473 int64_t MaxOffset, LSRUse::KindType Kind, Type *AccessTy,
1474 GlobalValue *BaseGV, int64_t BaseOffset, bool HasBaseReg,
1476 // We know how to expand completely foldable formulae.
1477 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1478 BaseOffset, HasBaseReg, Scale) ||
1479 // Or formulae that use a base register produced by a sum of base
1482 isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy,
1483 BaseGV, BaseOffset, true, 0));
1486 static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset,
1487 int64_t MaxOffset, LSRUse::KindType Kind, Type *AccessTy,
1489 return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV,
1490 F.BaseOffset, F.HasBaseReg, F.Scale);
1493 static bool isAMCompletelyFolded(const TargetTransformInfo &TTI,
1494 const LSRUse &LU, const Formula &F) {
1495 return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1496 LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg,
1500 static unsigned getScalingFactorCost(const TargetTransformInfo &TTI,
1501 const LSRUse &LU, const Formula &F) {
1505 // If the use is not completely folded in that instruction, we will have to
1506 // pay an extra cost only for scale != 1.
1507 if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind,
1509 return F.Scale != 1;
1512 case LSRUse::Address: {
1513 // Check the scaling factor cost with both the min and max offsets.
1514 int ScaleCostMinOffset =
1515 TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV,
1516 F.BaseOffset + LU.MinOffset,
1517 F.HasBaseReg, F.Scale);
1518 int ScaleCostMaxOffset =
1519 TTI.getScalingFactorCost(LU.AccessTy, F.BaseGV,
1520 F.BaseOffset + LU.MaxOffset,
1521 F.HasBaseReg, F.Scale);
1523 assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 &&
1524 "Legal addressing mode has an illegal cost!");
1525 return std::max(ScaleCostMinOffset, ScaleCostMaxOffset);
1527 case LSRUse::ICmpZero:
1529 case LSRUse::Special:
1530 // The use is completely folded, i.e., everything is folded into the
1535 llvm_unreachable("Invalid LSRUse Kind!");
1538 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1539 LSRUse::KindType Kind, Type *AccessTy,
1540 GlobalValue *BaseGV, int64_t BaseOffset,
1542 // Fast-path: zero is always foldable.
1543 if (BaseOffset == 0 && !BaseGV) return true;
1545 // Conservatively, create an address with an immediate and a
1546 // base and a scale.
1547 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1549 // Canonicalize a scale of 1 to a base register if the formula doesn't
1550 // already have a base register.
1551 if (!HasBaseReg && Scale == 1) {
1556 return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset,
1560 static bool isAlwaysFoldable(const TargetTransformInfo &TTI,
1561 ScalarEvolution &SE, int64_t MinOffset,
1562 int64_t MaxOffset, LSRUse::KindType Kind,
1563 Type *AccessTy, const SCEV *S, bool HasBaseReg) {
1564 // Fast-path: zero is always foldable.
1565 if (S->isZero()) return true;
1567 // Conservatively, create an address with an immediate and a
1568 // base and a scale.
1569 int64_t BaseOffset = ExtractImmediate(S, SE);
1570 GlobalValue *BaseGV = ExtractSymbol(S, SE);
1572 // If there's anything else involved, it's not foldable.
1573 if (!S->isZero()) return false;
1575 // Fast-path: zero is always foldable.
1576 if (BaseOffset == 0 && !BaseGV) return true;
1578 // Conservatively, create an address with an immediate and a
1579 // base and a scale.
1580 int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1;
1582 return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV,
1583 BaseOffset, HasBaseReg, Scale);
1588 /// IVInc - An individual increment in a Chain of IV increments.
1589 /// Relate an IV user to an expression that computes the IV it uses from the IV
1590 /// used by the previous link in the Chain.
1592 /// For the head of a chain, IncExpr holds the absolute SCEV expression for the
1593 /// original IVOperand. The head of the chain's IVOperand is only valid during
1594 /// chain collection, before LSR replaces IV users. During chain generation,
1595 /// IncExpr can be used to find the new IVOperand that computes the same
1598 Instruction *UserInst;
1600 const SCEV *IncExpr;
1602 IVInc(Instruction *U, Value *O, const SCEV *E):
1603 UserInst(U), IVOperand(O), IncExpr(E) {}
1606 // IVChain - The list of IV increments in program order.
1607 // We typically add the head of a chain without finding subsequent links.
1609 SmallVector<IVInc,1> Incs;
1610 const SCEV *ExprBase;
1612 IVChain() : ExprBase(nullptr) {}
1614 IVChain(const IVInc &Head, const SCEV *Base)
1615 : Incs(1, Head), ExprBase(Base) {}
1617 typedef SmallVectorImpl<IVInc>::const_iterator const_iterator;
1619 // begin - return the first increment in the chain.
1620 const_iterator begin() const {
1621 assert(!Incs.empty());
1622 return std::next(Incs.begin());
1624 const_iterator end() const {
1628 // hasIncs - Returns true if this chain contains any increments.
1629 bool hasIncs() const { return Incs.size() >= 2; }
1631 // add - Add an IVInc to the end of this chain.
1632 void add(const IVInc &X) { Incs.push_back(X); }
1634 // tailUserInst - Returns the last UserInst in the chain.
1635 Instruction *tailUserInst() const { return Incs.back().UserInst; }
1637 // isProfitableIncrement - Returns true if IncExpr can be profitably added to
1639 bool isProfitableIncrement(const SCEV *OperExpr,
1640 const SCEV *IncExpr,
1644 /// ChainUsers - Helper for CollectChains to track multiple IV increment uses.
1645 /// Distinguish between FarUsers that definitely cross IV increments and
1646 /// NearUsers that may be used between IV increments.
1648 SmallPtrSet<Instruction*, 4> FarUsers;
1649 SmallPtrSet<Instruction*, 4> NearUsers;
1652 /// LSRInstance - This class holds state for the main loop strength reduction
1656 ScalarEvolution &SE;
1659 const TargetTransformInfo &TTI;
1663 /// IVIncInsertPos - This is the insert position that the current loop's
1664 /// induction variable increment should be placed. In simple loops, this is
1665 /// the latch block's terminator. But in more complicated cases, this is a
1666 /// position which will dominate all the in-loop post-increment users.
1667 Instruction *IVIncInsertPos;
1669 /// Factors - Interesting factors between use strides.
1670 SmallSetVector<int64_t, 8> Factors;
1672 /// Types - Interesting use types, to facilitate truncation reuse.
1673 SmallSetVector<Type *, 4> Types;
1675 /// Fixups - The list of operands which are to be replaced.
1676 SmallVector<LSRFixup, 16> Fixups;
1678 /// Uses - The list of interesting uses.
1679 SmallVector<LSRUse, 16> Uses;
1681 /// RegUses - Track which uses use which register candidates.
1682 RegUseTracker RegUses;
1684 // Limit the number of chains to avoid quadratic behavior. We don't expect to
1685 // have more than a few IV increment chains in a loop. Missing a Chain falls
1686 // back to normal LSR behavior for those uses.
1687 static const unsigned MaxChains = 8;
1689 /// IVChainVec - IV users can form a chain of IV increments.
1690 SmallVector<IVChain, MaxChains> IVChainVec;
1692 /// IVIncSet - IV users that belong to profitable IVChains.
1693 SmallPtrSet<Use*, MaxChains> IVIncSet;
1695 void OptimizeShadowIV();
1696 bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse);
1697 ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse);
1698 void OptimizeLoopTermCond();
1700 void ChainInstruction(Instruction *UserInst, Instruction *IVOper,
1701 SmallVectorImpl<ChainUsers> &ChainUsersVec);
1702 void FinalizeChain(IVChain &Chain);
1703 void CollectChains();
1704 void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
1705 SmallVectorImpl<WeakVH> &DeadInsts);
1707 void CollectInterestingTypesAndFactors();
1708 void CollectFixupsAndInitialFormulae();
1710 LSRFixup &getNewFixup() {
1711 Fixups.push_back(LSRFixup());
1712 return Fixups.back();
1715 // Support for sharing of LSRUses between LSRFixups.
1716 typedef DenseMap<LSRUse::SCEVUseKindPair, size_t> UseMapTy;
1719 bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
1720 LSRUse::KindType Kind, Type *AccessTy);
1722 std::pair<size_t, int64_t> getUse(const SCEV *&Expr,
1723 LSRUse::KindType Kind,
1726 void DeleteUse(LSRUse &LU, size_t LUIdx);
1728 LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU);
1730 void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1731 void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx);
1732 void CountRegisters(const Formula &F, size_t LUIdx);
1733 bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F);
1735 void CollectLoopInvariantFixupsAndFormulae();
1737 void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base,
1738 unsigned Depth = 0);
1740 void GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
1741 const Formula &Base, unsigned Depth,
1742 size_t Idx, bool IsScaledReg = false);
1743 void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base);
1744 void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1745 const Formula &Base, size_t Idx,
1746 bool IsScaledReg = false);
1747 void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1748 void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx,
1749 const Formula &Base,
1750 const SmallVectorImpl<int64_t> &Worklist,
1751 size_t Idx, bool IsScaledReg = false);
1752 void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base);
1753 void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1754 void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base);
1755 void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base);
1756 void GenerateZExts(LSRUse &LU, unsigned LUIdx, Formula Base);
1757 void GenerateCrossUseConstantOffsets();
1758 void GenerateAllReuseFormulae();
1760 void FilterOutUndesirableDedicatedRegisters();
1762 size_t EstimateSearchSpaceComplexity() const;
1763 void NarrowSearchSpaceByDetectingSupersets();
1764 void NarrowSearchSpaceByCollapsingUnrolledCode();
1765 void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
1766 void NarrowSearchSpaceByPickingWinnerRegs();
1767 void NarrowSearchSpaceUsingHeuristics();
1769 void SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
1771 SmallVectorImpl<const Formula *> &Workspace,
1772 const Cost &CurCost,
1773 const SmallPtrSet<const SCEV *, 16> &CurRegs,
1774 DenseSet<const SCEV *> &VisitedRegs) const;
1775 void Solve(SmallVectorImpl<const Formula *> &Solution) const;
1777 BasicBlock::iterator
1778 HoistInsertPosition(BasicBlock::iterator IP,
1779 const SmallVectorImpl<Instruction *> &Inputs) const;
1780 BasicBlock::iterator
1781 AdjustInsertPositionForExpand(BasicBlock::iterator IP,
1784 SCEVExpander &Rewriter) const;
1786 Value *Expand(const LSRFixup &LF,
1788 BasicBlock::iterator IP,
1789 SCEVExpander &Rewriter,
1790 SmallVectorImpl<WeakVH> &DeadInsts) const;
1791 void RewriteForPHI(PHINode *PN, const LSRFixup &LF,
1793 SCEVExpander &Rewriter,
1794 SmallVectorImpl<WeakVH> &DeadInsts,
1796 void Rewrite(const LSRFixup &LF,
1798 SCEVExpander &Rewriter,
1799 SmallVectorImpl<WeakVH> &DeadInsts,
1801 void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
1805 LSRInstance(Loop *L, Pass *P);
1807 bool getChanged() const { return Changed; }
1809 void print_factors_and_types(raw_ostream &OS) const;
1810 void print_fixups(raw_ostream &OS) const;
1811 void print_uses(raw_ostream &OS) const;
1812 void print(raw_ostream &OS) const;
1818 /// OptimizeShadowIV - If IV is used in a int-to-float cast
1819 /// inside the loop then try to eliminate the cast operation.
1820 void LSRInstance::OptimizeShadowIV() {
1821 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
1822 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
1825 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end();
1826 UI != E; /* empty */) {
1827 IVUsers::const_iterator CandidateUI = UI;
1829 Instruction *ShadowUse = CandidateUI->getUser();
1830 Type *DestTy = nullptr;
1831 bool IsSigned = false;
1833 /* If shadow use is a int->float cast then insert a second IV
1834 to eliminate this cast.
1836 for (unsigned i = 0; i < n; ++i)
1842 for (unsigned i = 0; i < n; ++i, ++d)
1845 if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) {
1847 DestTy = UCast->getDestTy();
1849 else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) {
1851 DestTy = SCast->getDestTy();
1853 if (!DestTy) continue;
1855 // If target does not support DestTy natively then do not apply
1856 // this transformation.
1857 if (!TTI.isTypeLegal(DestTy)) continue;
1859 PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0));
1861 if (PH->getNumIncomingValues() != 2) continue;
1863 Type *SrcTy = PH->getType();
1864 int Mantissa = DestTy->getFPMantissaWidth();
1865 if (Mantissa == -1) continue;
1866 if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa)
1869 unsigned Entry, Latch;
1870 if (PH->getIncomingBlock(0) == L->getLoopPreheader()) {
1878 ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry));
1879 if (!Init) continue;
1880 Constant *NewInit = ConstantFP::get(DestTy, IsSigned ?
1881 (double)Init->getSExtValue() :
1882 (double)Init->getZExtValue());
1884 BinaryOperator *Incr =
1885 dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch));
1886 if (!Incr) continue;
1887 if (Incr->getOpcode() != Instruction::Add
1888 && Incr->getOpcode() != Instruction::Sub)
1891 /* Initialize new IV, double d = 0.0 in above example. */
1892 ConstantInt *C = nullptr;
1893 if (Incr->getOperand(0) == PH)
1894 C = dyn_cast<ConstantInt>(Incr->getOperand(1));
1895 else if (Incr->getOperand(1) == PH)
1896 C = dyn_cast<ConstantInt>(Incr->getOperand(0));
1902 // Ignore negative constants, as the code below doesn't handle them
1903 // correctly. TODO: Remove this restriction.
1904 if (!C->getValue().isStrictlyPositive()) continue;
1906 /* Add new PHINode. */
1907 PHINode *NewPH = PHINode::Create(DestTy, 2, "IV.S.", PH);
1909 /* create new increment. '++d' in above example. */
1910 Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue());
1911 BinaryOperator *NewIncr =
1912 BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ?
1913 Instruction::FAdd : Instruction::FSub,
1914 NewPH, CFP, "IV.S.next.", Incr);
1916 NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry));
1917 NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch));
1919 /* Remove cast operation */
1920 ShadowUse->replaceAllUsesWith(NewPH);
1921 ShadowUse->eraseFromParent();
1927 /// FindIVUserForCond - If Cond has an operand that is an expression of an IV,
1928 /// set the IV user and stride information and return true, otherwise return
1930 bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse) {
1931 for (IVStrideUse &U : IU)
1932 if (U.getUser() == Cond) {
1933 // NOTE: we could handle setcc instructions with multiple uses here, but
1934 // InstCombine does it as well for simple uses, it's not clear that it
1935 // occurs enough in real life to handle.
1942 /// OptimizeMax - Rewrite the loop's terminating condition if it uses
1943 /// a max computation.
1945 /// This is a narrow solution to a specific, but acute, problem. For loops
1951 /// } while (++i < n);
1953 /// the trip count isn't just 'n', because 'n' might not be positive. And
1954 /// unfortunately this can come up even for loops where the user didn't use
1955 /// a C do-while loop. For example, seemingly well-behaved top-test loops
1956 /// will commonly be lowered like this:
1962 /// } while (++i < n);
1965 /// and then it's possible for subsequent optimization to obscure the if
1966 /// test in such a way that indvars can't find it.
1968 /// When indvars can't find the if test in loops like this, it creates a
1969 /// max expression, which allows it to give the loop a canonical
1970 /// induction variable:
1973 /// max = n < 1 ? 1 : n;
1976 /// } while (++i != max);
1978 /// Canonical induction variables are necessary because the loop passes
1979 /// are designed around them. The most obvious example of this is the
1980 /// LoopInfo analysis, which doesn't remember trip count values. It
1981 /// expects to be able to rediscover the trip count each time it is
1982 /// needed, and it does this using a simple analysis that only succeeds if
1983 /// the loop has a canonical induction variable.
1985 /// However, when it comes time to generate code, the maximum operation
1986 /// can be quite costly, especially if it's inside of an outer loop.
1988 /// This function solves this problem by detecting this type of loop and
1989 /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting
1990 /// the instructions for the maximum computation.
1992 ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) {
1993 // Check that the loop matches the pattern we're looking for.
1994 if (Cond->getPredicate() != CmpInst::ICMP_EQ &&
1995 Cond->getPredicate() != CmpInst::ICMP_NE)
1998 SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1));
1999 if (!Sel || !Sel->hasOneUse()) return Cond;
2001 const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L);
2002 if (isa<SCEVCouldNotCompute>(BackedgeTakenCount))
2004 const SCEV *One = SE.getConstant(BackedgeTakenCount->getType(), 1);
2006 // Add one to the backedge-taken count to get the trip count.
2007 const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount);
2008 if (IterationCount != SE.getSCEV(Sel)) return Cond;
2010 // Check for a max calculation that matches the pattern. There's no check
2011 // for ICMP_ULE here because the comparison would be with zero, which
2012 // isn't interesting.
2013 CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE;
2014 const SCEVNAryExpr *Max = nullptr;
2015 if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) {
2016 Pred = ICmpInst::ICMP_SLE;
2018 } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) {
2019 Pred = ICmpInst::ICMP_SLT;
2021 } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) {
2022 Pred = ICmpInst::ICMP_ULT;
2029 // To handle a max with more than two operands, this optimization would
2030 // require additional checking and setup.
2031 if (Max->getNumOperands() != 2)
2034 const SCEV *MaxLHS = Max->getOperand(0);
2035 const SCEV *MaxRHS = Max->getOperand(1);
2037 // ScalarEvolution canonicalizes constants to the left. For < and >, look
2038 // for a comparison with 1. For <= and >=, a comparison with zero.
2040 (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (MaxLHS != One)))
2043 // Check the relevant induction variable for conformance to
2045 const SCEV *IV = SE.getSCEV(Cond->getOperand(0));
2046 const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV);
2047 if (!AR || !AR->isAffine() ||
2048 AR->getStart() != One ||
2049 AR->getStepRecurrence(SE) != One)
2052 assert(AR->getLoop() == L &&
2053 "Loop condition operand is an addrec in a different loop!");
2055 // Check the right operand of the select, and remember it, as it will
2056 // be used in the new comparison instruction.
2057 Value *NewRHS = nullptr;
2058 if (ICmpInst::isTrueWhenEqual(Pred)) {
2059 // Look for n+1, and grab n.
2060 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1)))
2061 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2062 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2063 NewRHS = BO->getOperand(0);
2064 if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2)))
2065 if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1)))
2066 if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS)
2067 NewRHS = BO->getOperand(0);
2070 } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS)
2071 NewRHS = Sel->getOperand(1);
2072 else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS)
2073 NewRHS = Sel->getOperand(2);
2074 else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS))
2075 NewRHS = SU->getValue();
2077 // Max doesn't match expected pattern.
2080 // Determine the new comparison opcode. It may be signed or unsigned,
2081 // and the original comparison may be either equality or inequality.
2082 if (Cond->getPredicate() == CmpInst::ICMP_EQ)
2083 Pred = CmpInst::getInversePredicate(Pred);
2085 // Ok, everything looks ok to change the condition into an SLT or SGE and
2086 // delete the max calculation.
2088 new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp");
2090 // Delete the max calculation instructions.
2091 Cond->replaceAllUsesWith(NewCond);
2092 CondUse->setUser(NewCond);
2093 Instruction *Cmp = cast<Instruction>(Sel->getOperand(0));
2094 Cond->eraseFromParent();
2095 Sel->eraseFromParent();
2096 if (Cmp->use_empty())
2097 Cmp->eraseFromParent();
2101 /// OptimizeLoopTermCond - Change loop terminating condition to use the
2102 /// postinc iv when possible.
2104 LSRInstance::OptimizeLoopTermCond() {
2105 SmallPtrSet<Instruction *, 4> PostIncs;
2107 BasicBlock *LatchBlock = L->getLoopLatch();
2108 SmallVector<BasicBlock*, 8> ExitingBlocks;
2109 L->getExitingBlocks(ExitingBlocks);
2111 for (BasicBlock *ExitingBlock : ExitingBlocks) {
2113 // Get the terminating condition for the loop if possible. If we
2114 // can, we want to change it to use a post-incremented version of its
2115 // induction variable, to allow coalescing the live ranges for the IV into
2116 // one register value.
2118 BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator());
2121 // FIXME: Overly conservative, termination condition could be an 'or' etc..
2122 if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition()))
2125 // Search IVUsesByStride to find Cond's IVUse if there is one.
2126 IVStrideUse *CondUse = nullptr;
2127 ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition());
2128 if (!FindIVUserForCond(Cond, CondUse))
2131 // If the trip count is computed in terms of a max (due to ScalarEvolution
2132 // being unable to find a sufficient guard, for example), change the loop
2133 // comparison to use SLT or ULT instead of NE.
2134 // One consequence of doing this now is that it disrupts the count-down
2135 // optimization. That's not always a bad thing though, because in such
2136 // cases it may still be worthwhile to avoid a max.
2137 Cond = OptimizeMax(Cond, CondUse);
2139 // If this exiting block dominates the latch block, it may also use
2140 // the post-inc value if it won't be shared with other uses.
2141 // Check for dominance.
2142 if (!DT.dominates(ExitingBlock, LatchBlock))
2145 // Conservatively avoid trying to use the post-inc value in non-latch
2146 // exits if there may be pre-inc users in intervening blocks.
2147 if (LatchBlock != ExitingBlock)
2148 for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI)
2149 // Test if the use is reachable from the exiting block. This dominator
2150 // query is a conservative approximation of reachability.
2151 if (&*UI != CondUse &&
2152 !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) {
2153 // Conservatively assume there may be reuse if the quotient of their
2154 // strides could be a legal scale.
2155 const SCEV *A = IU.getStride(*CondUse, L);
2156 const SCEV *B = IU.getStride(*UI, L);
2157 if (!A || !B) continue;
2158 if (SE.getTypeSizeInBits(A->getType()) !=
2159 SE.getTypeSizeInBits(B->getType())) {
2160 if (SE.getTypeSizeInBits(A->getType()) >
2161 SE.getTypeSizeInBits(B->getType()))
2162 B = SE.getSignExtendExpr(B, A->getType());
2164 A = SE.getSignExtendExpr(A, B->getType());
2166 if (const SCEVConstant *D =
2167 dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) {
2168 const ConstantInt *C = D->getValue();
2169 // Stride of one or negative one can have reuse with non-addresses.
2170 if (C->isOne() || C->isAllOnesValue())
2171 goto decline_post_inc;
2172 // Avoid weird situations.
2173 if (C->getValue().getMinSignedBits() >= 64 ||
2174 C->getValue().isMinSignedValue())
2175 goto decline_post_inc;
2176 // Check for possible scaled-address reuse.
2177 Type *AccessTy = getAccessType(UI->getUser());
2178 int64_t Scale = C->getSExtValue();
2179 if (TTI.isLegalAddressingMode(AccessTy, /*BaseGV=*/ nullptr,
2181 /*HasBaseReg=*/ false, Scale))
2182 goto decline_post_inc;
2184 if (TTI.isLegalAddressingMode(AccessTy, /*BaseGV=*/ nullptr,
2186 /*HasBaseReg=*/ false, Scale))
2187 goto decline_post_inc;
2191 DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: "
2194 // It's possible for the setcc instruction to be anywhere in the loop, and
2195 // possible for it to have multiple users. If it is not immediately before
2196 // the exiting block branch, move it.
2197 if (&*++BasicBlock::iterator(Cond) != TermBr) {
2198 if (Cond->hasOneUse()) {
2199 Cond->moveBefore(TermBr);
2201 // Clone the terminating condition and insert into the loopend.
2202 ICmpInst *OldCond = Cond;
2203 Cond = cast<ICmpInst>(Cond->clone());
2204 Cond->setName(L->getHeader()->getName() + ".termcond");
2205 ExitingBlock->getInstList().insert(TermBr, Cond);
2207 // Clone the IVUse, as the old use still exists!
2208 CondUse = &IU.AddUser(Cond, CondUse->getOperandValToReplace());
2209 TermBr->replaceUsesOfWith(OldCond, Cond);
2213 // If we get to here, we know that we can transform the setcc instruction to
2214 // use the post-incremented version of the IV, allowing us to coalesce the
2215 // live ranges for the IV correctly.
2216 CondUse->transformToPostInc(L);
2219 PostIncs.insert(Cond);
2223 // Determine an insertion point for the loop induction variable increment. It
2224 // must dominate all the post-inc comparisons we just set up, and it must
2225 // dominate the loop latch edge.
2226 IVIncInsertPos = L->getLoopLatch()->getTerminator();
2227 for (Instruction *Inst : PostIncs) {
2229 DT.findNearestCommonDominator(IVIncInsertPos->getParent(),
2231 if (BB == Inst->getParent())
2232 IVIncInsertPos = Inst;
2233 else if (BB != IVIncInsertPos->getParent())
2234 IVIncInsertPos = BB->getTerminator();
2238 /// reconcileNewOffset - Determine if the given use can accommodate a fixup
2239 /// at the given offset and other details. If so, update the use and
2242 LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg,
2243 LSRUse::KindType Kind, Type *AccessTy) {
2244 int64_t NewMinOffset = LU.MinOffset;
2245 int64_t NewMaxOffset = LU.MaxOffset;
2246 Type *NewAccessTy = AccessTy;
2248 // Check for a mismatched kind. It's tempting to collapse mismatched kinds to
2249 // something conservative, however this can pessimize in the case that one of
2250 // the uses will have all its uses outside the loop, for example.
2251 if (LU.Kind != Kind)
2254 // Check for a mismatched access type, and fall back conservatively as needed.
2255 // TODO: Be less conservative when the type is similar and can use the same
2256 // addressing modes.
2257 if (Kind == LSRUse::Address && AccessTy != LU.AccessTy)
2258 NewAccessTy = Type::getVoidTy(AccessTy->getContext());
2260 // Conservatively assume HasBaseReg is true for now.
2261 if (NewOffset < LU.MinOffset) {
2262 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2263 LU.MaxOffset - NewOffset, HasBaseReg))
2265 NewMinOffset = NewOffset;
2266 } else if (NewOffset > LU.MaxOffset) {
2267 if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr,
2268 NewOffset - LU.MinOffset, HasBaseReg))
2270 NewMaxOffset = NewOffset;
2274 LU.MinOffset = NewMinOffset;
2275 LU.MaxOffset = NewMaxOffset;
2276 LU.AccessTy = NewAccessTy;
2277 if (NewOffset != LU.Offsets.back())
2278 LU.Offsets.push_back(NewOffset);
2282 /// getUse - Return an LSRUse index and an offset value for a fixup which
2283 /// needs the given expression, with the given kind and optional access type.
2284 /// Either reuse an existing use or create a new one, as needed.
2285 std::pair<size_t, int64_t>
2286 LSRInstance::getUse(const SCEV *&Expr,
2287 LSRUse::KindType Kind, Type *AccessTy) {
2288 const SCEV *Copy = Expr;
2289 int64_t Offset = ExtractImmediate(Expr, SE);
2291 // Basic uses can't accept any offset, for example.
2292 if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr,
2293 Offset, /*HasBaseReg=*/ true)) {
2298 std::pair<UseMapTy::iterator, bool> P =
2299 UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(Expr, Kind), 0));
2301 // A use already existed with this base.
2302 size_t LUIdx = P.first->second;
2303 LSRUse &LU = Uses[LUIdx];
2304 if (reconcileNewOffset(LU, Offset, /*HasBaseReg=*/true, Kind, AccessTy))
2306 return std::make_pair(LUIdx, Offset);
2309 // Create a new use.
2310 size_t LUIdx = Uses.size();
2311 P.first->second = LUIdx;
2312 Uses.push_back(LSRUse(Kind, AccessTy));
2313 LSRUse &LU = Uses[LUIdx];
2315 // We don't need to track redundant offsets, but we don't need to go out
2316 // of our way here to avoid them.
2317 if (LU.Offsets.empty() || Offset != LU.Offsets.back())
2318 LU.Offsets.push_back(Offset);
2320 LU.MinOffset = Offset;
2321 LU.MaxOffset = Offset;
2322 return std::make_pair(LUIdx, Offset);
2325 /// DeleteUse - Delete the given use from the Uses list.
2326 void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) {
2327 if (&LU != &Uses.back())
2328 std::swap(LU, Uses.back());
2332 RegUses.SwapAndDropUse(LUIdx, Uses.size());
2335 /// FindUseWithFormula - Look for a use distinct from OrigLU which is has
2336 /// a formula that has the same registers as the given formula.
2338 LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF,
2339 const LSRUse &OrigLU) {
2340 // Search all uses for the formula. This could be more clever.
2341 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
2342 LSRUse &LU = Uses[LUIdx];
2343 // Check whether this use is close enough to OrigLU, to see whether it's
2344 // worthwhile looking through its formulae.
2345 // Ignore ICmpZero uses because they may contain formulae generated by
2346 // GenerateICmpZeroScales, in which case adding fixup offsets may
2348 if (&LU != &OrigLU &&
2349 LU.Kind != LSRUse::ICmpZero &&
2350 LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy &&
2351 LU.WidestFixupType == OrigLU.WidestFixupType &&
2352 LU.HasFormulaWithSameRegs(OrigF)) {
2353 // Scan through this use's formulae.
2354 for (const Formula &F : LU.Formulae) {
2355 // Check to see if this formula has the same registers and symbols
2357 if (F.BaseRegs == OrigF.BaseRegs &&
2358 F.ScaledReg == OrigF.ScaledReg &&
2359 F.BaseGV == OrigF.BaseGV &&
2360 F.Scale == OrigF.Scale &&
2361 F.UnfoldedOffset == OrigF.UnfoldedOffset) {
2362 if (F.BaseOffset == 0)
2364 // This is the formula where all the registers and symbols matched;
2365 // there aren't going to be any others. Since we declined it, we
2366 // can skip the rest of the formulae and proceed to the next LSRUse.
2373 // Nothing looked good.
2377 void LSRInstance::CollectInterestingTypesAndFactors() {
2378 SmallSetVector<const SCEV *, 4> Strides;
2380 // Collect interesting types and strides.
2381 SmallVector<const SCEV *, 4> Worklist;
2382 for (const IVStrideUse &U : IU) {
2383 const SCEV *Expr = IU.getExpr(U);
2385 // Collect interesting types.
2386 Types.insert(SE.getEffectiveSCEVType(Expr->getType()));
2388 // Add strides for mentioned loops.
2389 Worklist.push_back(Expr);
2391 const SCEV *S = Worklist.pop_back_val();
2392 if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
2393 if (AR->getLoop() == L)
2394 Strides.insert(AR->getStepRecurrence(SE));
2395 Worklist.push_back(AR->getStart());
2396 } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
2397 Worklist.append(Add->op_begin(), Add->op_end());
2399 } while (!Worklist.empty());
2402 // Compute interesting factors from the set of interesting strides.
2403 for (SmallSetVector<const SCEV *, 4>::const_iterator
2404 I = Strides.begin(), E = Strides.end(); I != E; ++I)
2405 for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter =
2406 std::next(I); NewStrideIter != E; ++NewStrideIter) {
2407 const SCEV *OldStride = *I;
2408 const SCEV *NewStride = *NewStrideIter;
2410 if (SE.getTypeSizeInBits(OldStride->getType()) !=
2411 SE.getTypeSizeInBits(NewStride->getType())) {
2412 if (SE.getTypeSizeInBits(OldStride->getType()) >
2413 SE.getTypeSizeInBits(NewStride->getType()))
2414 NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType());
2416 OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType());
2418 if (const SCEVConstant *Factor =
2419 dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride,
2421 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2422 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2423 } else if (const SCEVConstant *Factor =
2424 dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride,
2427 if (Factor->getValue()->getValue().getMinSignedBits() <= 64)
2428 Factors.insert(Factor->getValue()->getValue().getSExtValue());
2432 // If all uses use the same type, don't bother looking for truncation-based
2434 if (Types.size() == 1)
2437 DEBUG(print_factors_and_types(dbgs()));
2440 /// findIVOperand - Helper for CollectChains that finds an IV operand (computed
2441 /// by an AddRec in this loop) within [OI,OE) or returns OE. If IVUsers mapped
2442 /// Instructions to IVStrideUses, we could partially skip this.
2443 static User::op_iterator
2444 findIVOperand(User::op_iterator OI, User::op_iterator OE,
2445 Loop *L, ScalarEvolution &SE) {
2446 for(; OI != OE; ++OI) {
2447 if (Instruction *Oper = dyn_cast<Instruction>(*OI)) {
2448 if (!SE.isSCEVable(Oper->getType()))
2451 if (const SCEVAddRecExpr *AR =
2452 dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) {
2453 if (AR->getLoop() == L)
2461 /// getWideOperand - IVChain logic must consistenctly peek base TruncInst
2462 /// operands, so wrap it in a convenient helper.
2463 static Value *getWideOperand(Value *Oper) {
2464 if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper))
2465 return Trunc->getOperand(0);
2469 /// isCompatibleIVType - Return true if we allow an IV chain to include both
2471 static bool isCompatibleIVType(Value *LVal, Value *RVal) {
2472 Type *LType = LVal->getType();
2473 Type *RType = RVal->getType();
2474 return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy());
2477 /// getExprBase - Return an approximation of this SCEV expression's "base", or
2478 /// NULL for any constant. Returning the expression itself is
2479 /// conservative. Returning a deeper subexpression is more precise and valid as
2480 /// long as it isn't less complex than another subexpression. For expressions
2481 /// involving multiple unscaled values, we need to return the pointer-type
2482 /// SCEVUnknown. This avoids forming chains across objects, such as:
2483 /// PrevOper==a[i], IVOper==b[i], IVInc==b-a.
2485 /// Since SCEVUnknown is the rightmost type, and pointers are the rightmost
2486 /// SCEVUnknown, we simply return the rightmost SCEV operand.
2487 static const SCEV *getExprBase(const SCEV *S) {
2488 switch (S->getSCEVType()) {
2489 default: // uncluding scUnknown.
2494 return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand());
2496 return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand());
2498 return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand());
2500 // Skip over scaled operands (scMulExpr) to follow add operands as long as
2501 // there's nothing more complex.
2502 // FIXME: not sure if we want to recognize negation.
2503 const SCEVAddExpr *Add = cast<SCEVAddExpr>(S);
2504 for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()),
2505 E(Add->op_begin()); I != E; ++I) {
2506 const SCEV *SubExpr = *I;
2507 if (SubExpr->getSCEVType() == scAddExpr)
2508 return getExprBase(SubExpr);
2510 if (SubExpr->getSCEVType() != scMulExpr)
2513 return S; // all operands are scaled, be conservative.
2516 return getExprBase(cast<SCEVAddRecExpr>(S)->getStart());
2520 /// Return true if the chain increment is profitable to expand into a loop
2521 /// invariant value, which may require its own register. A profitable chain
2522 /// increment will be an offset relative to the same base. We allow such offsets
2523 /// to potentially be used as chain increment as long as it's not obviously
2524 /// expensive to expand using real instructions.
2525 bool IVChain::isProfitableIncrement(const SCEV *OperExpr,
2526 const SCEV *IncExpr,
2527 ScalarEvolution &SE) {
2528 // Aggressively form chains when -stress-ivchain.
2532 // Do not replace a constant offset from IV head with a nonconstant IV
2534 if (!isa<SCEVConstant>(IncExpr)) {
2535 const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand));
2536 if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr)))
2540 SmallPtrSet<const SCEV*, 8> Processed;
2541 return !isHighCostExpansion(IncExpr, Processed, SE);
2544 /// Return true if the number of registers needed for the chain is estimated to
2545 /// be less than the number required for the individual IV users. First prohibit
2546 /// any IV users that keep the IV live across increments (the Users set should
2547 /// be empty). Next count the number and type of increments in the chain.
2549 /// Chaining IVs can lead to considerable code bloat if ISEL doesn't
2550 /// effectively use postinc addressing modes. Only consider it profitable it the
2551 /// increments can be computed in fewer registers when chained.
2553 /// TODO: Consider IVInc free if it's already used in another chains.
2555 isProfitableChain(IVChain &Chain, SmallPtrSetImpl<Instruction*> &Users,
2556 ScalarEvolution &SE, const TargetTransformInfo &TTI) {
2560 if (!Chain.hasIncs())
2563 if (!Users.empty()) {
2564 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n";
2565 for (Instruction *Inst : Users) {
2566 dbgs() << " " << *Inst << "\n";
2570 assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2572 // The chain itself may require a register, so intialize cost to 1.
2575 // A complete chain likely eliminates the need for keeping the original IV in
2576 // a register. LSR does not currently know how to form a complete chain unless
2577 // the header phi already exists.
2578 if (isa<PHINode>(Chain.tailUserInst())
2579 && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) {
2582 const SCEV *LastIncExpr = nullptr;
2583 unsigned NumConstIncrements = 0;
2584 unsigned NumVarIncrements = 0;
2585 unsigned NumReusedIncrements = 0;
2586 for (const IVInc &Inc : Chain) {
2587 if (Inc.IncExpr->isZero())
2590 // Incrementing by zero or some constant is neutral. We assume constants can
2591 // be folded into an addressing mode or an add's immediate operand.
2592 if (isa<SCEVConstant>(Inc.IncExpr)) {
2593 ++NumConstIncrements;
2597 if (Inc.IncExpr == LastIncExpr)
2598 ++NumReusedIncrements;
2602 LastIncExpr = Inc.IncExpr;
2604 // An IV chain with a single increment is handled by LSR's postinc
2605 // uses. However, a chain with multiple increments requires keeping the IV's
2606 // value live longer than it needs to be if chained.
2607 if (NumConstIncrements > 1)
2610 // Materializing increment expressions in the preheader that didn't exist in
2611 // the original code may cost a register. For example, sign-extended array
2612 // indices can produce ridiculous increments like this:
2613 // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64)))
2614 cost += NumVarIncrements;
2616 // Reusing variable increments likely saves a register to hold the multiple of
2618 cost -= NumReusedIncrements;
2620 DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost
2626 /// ChainInstruction - Add this IV user to an existing chain or make it the head
2628 void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper,
2629 SmallVectorImpl<ChainUsers> &ChainUsersVec) {
2630 // When IVs are used as types of varying widths, they are generally converted
2631 // to a wider type with some uses remaining narrow under a (free) trunc.
2632 Value *const NextIV = getWideOperand(IVOper);
2633 const SCEV *const OperExpr = SE.getSCEV(NextIV);
2634 const SCEV *const OperExprBase = getExprBase(OperExpr);
2636 // Visit all existing chains. Check if its IVOper can be computed as a
2637 // profitable loop invariant increment from the last link in the Chain.
2638 unsigned ChainIdx = 0, NChains = IVChainVec.size();
2639 const SCEV *LastIncExpr = nullptr;
2640 for (; ChainIdx < NChains; ++ChainIdx) {
2641 IVChain &Chain = IVChainVec[ChainIdx];
2643 // Prune the solution space aggressively by checking that both IV operands
2644 // are expressions that operate on the same unscaled SCEVUnknown. This
2645 // "base" will be canceled by the subsequent getMinusSCEV call. Checking
2646 // first avoids creating extra SCEV expressions.
2647 if (!StressIVChain && Chain.ExprBase != OperExprBase)
2650 Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand);
2651 if (!isCompatibleIVType(PrevIV, NextIV))
2654 // A phi node terminates a chain.
2655 if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst()))
2658 // The increment must be loop-invariant so it can be kept in a register.
2659 const SCEV *PrevExpr = SE.getSCEV(PrevIV);
2660 const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr);
2661 if (!SE.isLoopInvariant(IncExpr, L))
2664 if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) {
2665 LastIncExpr = IncExpr;
2669 // If we haven't found a chain, create a new one, unless we hit the max. Don't
2670 // bother for phi nodes, because they must be last in the chain.
2671 if (ChainIdx == NChains) {
2672 if (isa<PHINode>(UserInst))
2674 if (NChains >= MaxChains && !StressIVChain) {
2675 DEBUG(dbgs() << "IV Chain Limit\n");
2678 LastIncExpr = OperExpr;
2679 // IVUsers may have skipped over sign/zero extensions. We don't currently
2680 // attempt to form chains involving extensions unless they can be hoisted
2681 // into this loop's AddRec.
2682 if (!isa<SCEVAddRecExpr>(LastIncExpr))
2685 IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr),
2687 ChainUsersVec.resize(NChains);
2688 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst
2689 << ") IV=" << *LastIncExpr << "\n");
2691 DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst
2692 << ") IV+" << *LastIncExpr << "\n");
2693 // Add this IV user to the end of the chain.
2694 IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr));
2696 IVChain &Chain = IVChainVec[ChainIdx];
2698 SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers;
2699 // This chain's NearUsers become FarUsers.
2700 if (!LastIncExpr->isZero()) {
2701 ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(),
2706 // All other uses of IVOperand become near uses of the chain.
2707 // We currently ignore intermediate values within SCEV expressions, assuming
2708 // they will eventually be used be the current chain, or can be computed
2709 // from one of the chain increments. To be more precise we could
2710 // transitively follow its user and only add leaf IV users to the set.
2711 for (User *U : IVOper->users()) {
2712 Instruction *OtherUse = dyn_cast<Instruction>(U);
2715 // Uses in the chain will no longer be uses if the chain is formed.
2716 // Include the head of the chain in this iteration (not Chain.begin()).
2717 IVChain::const_iterator IncIter = Chain.Incs.begin();
2718 IVChain::const_iterator IncEnd = Chain.Incs.end();
2719 for( ; IncIter != IncEnd; ++IncIter) {
2720 if (IncIter->UserInst == OtherUse)
2723 if (IncIter != IncEnd)
2726 if (SE.isSCEVable(OtherUse->getType())
2727 && !isa<SCEVUnknown>(SE.getSCEV(OtherUse))
2728 && IU.isIVUserOrOperand(OtherUse)) {
2731 NearUsers.insert(OtherUse);
2734 // Since this user is part of the chain, it's no longer considered a use
2736 ChainUsersVec[ChainIdx].FarUsers.erase(UserInst);
2739 /// CollectChains - Populate the vector of Chains.
2741 /// This decreases ILP at the architecture level. Targets with ample registers,
2742 /// multiple memory ports, and no register renaming probably don't want
2743 /// this. However, such targets should probably disable LSR altogether.
2745 /// The job of LSR is to make a reasonable choice of induction variables across
2746 /// the loop. Subsequent passes can easily "unchain" computation exposing more
2747 /// ILP *within the loop* if the target wants it.
2749 /// Finding the best IV chain is potentially a scheduling problem. Since LSR
2750 /// will not reorder memory operations, it will recognize this as a chain, but
2751 /// will generate redundant IV increments. Ideally this would be corrected later
2752 /// by a smart scheduler:
2758 /// TODO: Walk the entire domtree within this loop, not just the path to the
2759 /// loop latch. This will discover chains on side paths, but requires
2760 /// maintaining multiple copies of the Chains state.
2761 void LSRInstance::CollectChains() {
2762 DEBUG(dbgs() << "Collecting IV Chains.\n");
2763 SmallVector<ChainUsers, 8> ChainUsersVec;
2765 SmallVector<BasicBlock *,8> LatchPath;
2766 BasicBlock *LoopHeader = L->getHeader();
2767 for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch());
2768 Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) {
2769 LatchPath.push_back(Rung->getBlock());
2771 LatchPath.push_back(LoopHeader);
2773 // Walk the instruction stream from the loop header to the loop latch.
2774 for (SmallVectorImpl<BasicBlock *>::reverse_iterator
2775 BBIter = LatchPath.rbegin(), BBEnd = LatchPath.rend();
2776 BBIter != BBEnd; ++BBIter) {
2777 for (BasicBlock::iterator I = (*BBIter)->begin(), E = (*BBIter)->end();
2779 // Skip instructions that weren't seen by IVUsers analysis.
2780 if (isa<PHINode>(I) || !IU.isIVUserOrOperand(I))
2783 // Ignore users that are part of a SCEV expression. This way we only
2784 // consider leaf IV Users. This effectively rediscovers a portion of
2785 // IVUsers analysis but in program order this time.
2786 if (SE.isSCEVable(I->getType()) && !isa<SCEVUnknown>(SE.getSCEV(I)))
2789 // Remove this instruction from any NearUsers set it may be in.
2790 for (unsigned ChainIdx = 0, NChains = IVChainVec.size();
2791 ChainIdx < NChains; ++ChainIdx) {
2792 ChainUsersVec[ChainIdx].NearUsers.erase(I);
2794 // Search for operands that can be chained.
2795 SmallPtrSet<Instruction*, 4> UniqueOperands;
2796 User::op_iterator IVOpEnd = I->op_end();
2797 User::op_iterator IVOpIter = findIVOperand(I->op_begin(), IVOpEnd, L, SE);
2798 while (IVOpIter != IVOpEnd) {
2799 Instruction *IVOpInst = cast<Instruction>(*IVOpIter);
2800 if (UniqueOperands.insert(IVOpInst).second)
2801 ChainInstruction(I, IVOpInst, ChainUsersVec);
2802 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
2804 } // Continue walking down the instructions.
2805 } // Continue walking down the domtree.
2806 // Visit phi backedges to determine if the chain can generate the IV postinc.
2807 for (BasicBlock::iterator I = L->getHeader()->begin();
2808 PHINode *PN = dyn_cast<PHINode>(I); ++I) {
2809 if (!SE.isSCEVable(PN->getType()))
2813 dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch()));
2815 ChainInstruction(PN, IncV, ChainUsersVec);
2817 // Remove any unprofitable chains.
2818 unsigned ChainIdx = 0;
2819 for (unsigned UsersIdx = 0, NChains = IVChainVec.size();
2820 UsersIdx < NChains; ++UsersIdx) {
2821 if (!isProfitableChain(IVChainVec[UsersIdx],
2822 ChainUsersVec[UsersIdx].FarUsers, SE, TTI))
2824 // Preserve the chain at UsesIdx.
2825 if (ChainIdx != UsersIdx)
2826 IVChainVec[ChainIdx] = IVChainVec[UsersIdx];
2827 FinalizeChain(IVChainVec[ChainIdx]);
2830 IVChainVec.resize(ChainIdx);
2833 void LSRInstance::FinalizeChain(IVChain &Chain) {
2834 assert(!Chain.Incs.empty() && "empty IV chains are not allowed");
2835 DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n");
2837 for (const IVInc &Inc : Chain) {
2838 DEBUG(dbgs() << " Inc: " << Inc.UserInst << "\n");
2839 auto UseI = std::find(Inc.UserInst->op_begin(), Inc.UserInst->op_end(),
2841 assert(UseI != Inc.UserInst->op_end() && "cannot find IV operand");
2842 IVIncSet.insert(UseI);
2846 /// Return true if the IVInc can be folded into an addressing mode.
2847 static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst,
2848 Value *Operand, const TargetTransformInfo &TTI) {
2849 const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr);
2850 if (!IncConst || !isAddressUse(UserInst, Operand))
2853 if (IncConst->getValue()->getValue().getMinSignedBits() > 64)
2856 int64_t IncOffset = IncConst->getValue()->getSExtValue();
2857 if (!isAlwaysFoldable(TTI, LSRUse::Address,
2858 getAccessType(UserInst), /*BaseGV=*/ nullptr,
2859 IncOffset, /*HaseBaseReg=*/ false))
2865 /// GenerateIVChains - Generate an add or subtract for each IVInc in a chain to
2866 /// materialize the IV user's operand from the previous IV user's operand.
2867 void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter,
2868 SmallVectorImpl<WeakVH> &DeadInsts) {
2869 // Find the new IVOperand for the head of the chain. It may have been replaced
2871 const IVInc &Head = Chain.Incs[0];
2872 User::op_iterator IVOpEnd = Head.UserInst->op_end();
2873 // findIVOperand returns IVOpEnd if it can no longer find a valid IV user.
2874 User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(),
2876 Value *IVSrc = nullptr;
2877 while (IVOpIter != IVOpEnd) {
2878 IVSrc = getWideOperand(*IVOpIter);
2880 // If this operand computes the expression that the chain needs, we may use
2881 // it. (Check this after setting IVSrc which is used below.)
2883 // Note that if Head.IncExpr is wider than IVSrc, then this phi is too
2884 // narrow for the chain, so we can no longer use it. We do allow using a
2885 // wider phi, assuming the LSR checked for free truncation. In that case we
2886 // should already have a truncate on this operand such that
2887 // getSCEV(IVSrc) == IncExpr.
2888 if (SE.getSCEV(*IVOpIter) == Head.IncExpr
2889 || SE.getSCEV(IVSrc) == Head.IncExpr) {
2892 IVOpIter = findIVOperand(std::next(IVOpIter), IVOpEnd, L, SE);
2894 if (IVOpIter == IVOpEnd) {
2895 // Gracefully give up on this chain.
2896 DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n");
2900 DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n");
2901 Type *IVTy = IVSrc->getType();
2902 Type *IntTy = SE.getEffectiveSCEVType(IVTy);
2903 const SCEV *LeftOverExpr = nullptr;
2904 for (const IVInc &Inc : Chain) {
2905 Instruction *InsertPt = Inc.UserInst;
2906 if (isa<PHINode>(InsertPt))
2907 InsertPt = L->getLoopLatch()->getTerminator();
2909 // IVOper will replace the current IV User's operand. IVSrc is the IV
2910 // value currently held in a register.
2911 Value *IVOper = IVSrc;
2912 if (!Inc.IncExpr->isZero()) {
2913 // IncExpr was the result of subtraction of two narrow values, so must
2915 const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.IncExpr, IntTy);
2916 LeftOverExpr = LeftOverExpr ?
2917 SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr;
2919 if (LeftOverExpr && !LeftOverExpr->isZero()) {
2920 // Expand the IV increment.
2921 Rewriter.clearPostInc();
2922 Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt);
2923 const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc),
2924 SE.getUnknown(IncV));
2925 IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt);
2927 // If an IV increment can't be folded, use it as the next IV value.
2928 if (!canFoldIVIncExpr(LeftOverExpr, Inc.UserInst, Inc.IVOperand, TTI)) {
2929 assert(IVTy == IVOper->getType() && "inconsistent IV increment type");
2931 LeftOverExpr = nullptr;
2934 Type *OperTy = Inc.IVOperand->getType();
2935 if (IVTy != OperTy) {
2936 assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) &&
2937 "cannot extend a chained IV");
2938 IRBuilder<> Builder(InsertPt);
2939 IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain");
2941 Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper);
2942 DeadInsts.emplace_back(Inc.IVOperand);
2944 // If LSR created a new, wider phi, we may also replace its postinc. We only
2945 // do this if we also found a wide value for the head of the chain.
2946 if (isa<PHINode>(Chain.tailUserInst())) {
2947 for (BasicBlock::iterator I = L->getHeader()->begin();
2948 PHINode *Phi = dyn_cast<PHINode>(I); ++I) {
2949 if (!isCompatibleIVType(Phi, IVSrc))
2951 Instruction *PostIncV = dyn_cast<Instruction>(
2952 Phi->getIncomingValueForBlock(L->getLoopLatch()));
2953 if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc)))
2955 Value *IVOper = IVSrc;
2956 Type *PostIncTy = PostIncV->getType();
2957 if (IVTy != PostIncTy) {
2958 assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types");
2959 IRBuilder<> Builder(L->getLoopLatch()->getTerminator());
2960 Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc());
2961 IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain");
2963 Phi->replaceUsesOfWith(PostIncV, IVOper);
2964 DeadInsts.emplace_back(PostIncV);
2969 void LSRInstance::CollectFixupsAndInitialFormulae() {
2970 for (const IVStrideUse &U : IU) {
2971 Instruction *UserInst = U.getUser();
2972 // Skip IV users that are part of profitable IV Chains.
2973 User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(),
2974 U.getOperandValToReplace());
2975 assert(UseI != UserInst->op_end() && "cannot find IV operand");
2976 if (IVIncSet.count(UseI))
2980 LSRFixup &LF = getNewFixup();
2981 LF.UserInst = UserInst;
2982 LF.OperandValToReplace = U.getOperandValToReplace();
2983 LF.PostIncLoops = U.getPostIncLoops();
2985 LSRUse::KindType Kind = LSRUse::Basic;
2986 Type *AccessTy = nullptr;
2987 if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) {
2988 Kind = LSRUse::Address;
2989 AccessTy = getAccessType(LF.UserInst);
2992 const SCEV *S = IU.getExpr(U);
2994 // Equality (== and !=) ICmps are special. We can rewrite (i == N) as
2995 // (N - i == 0), and this allows (N - i) to be the expression that we work
2996 // with rather than just N or i, so we can consider the register
2997 // requirements for both N and i at the same time. Limiting this code to
2998 // equality icmps is not a problem because all interesting loops use
2999 // equality icmps, thanks to IndVarSimplify.
3000 if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst))
3001 if (CI->isEquality()) {
3002 // Swap the operands if needed to put the OperandValToReplace on the
3003 // left, for consistency.
3004 Value *NV = CI->getOperand(1);
3005 if (NV == LF.OperandValToReplace) {
3006 CI->setOperand(1, CI->getOperand(0));
3007 CI->setOperand(0, NV);
3008 NV = CI->getOperand(1);
3012 // x == y --> x - y == 0
3013 const SCEV *N = SE.getSCEV(NV);
3014 if (SE.isLoopInvariant(N, L) && isSafeToExpand(N, SE)) {
3015 // S is normalized, so normalize N before folding it into S
3016 // to keep the result normalized.
3017 N = TransformForPostIncUse(Normalize, N, CI, nullptr,
3018 LF.PostIncLoops, SE, DT);
3019 Kind = LSRUse::ICmpZero;
3020 S = SE.getMinusSCEV(N, S);
3023 // -1 and the negations of all interesting strides (except the negation
3024 // of -1) are now also interesting.
3025 for (size_t i = 0, e = Factors.size(); i != e; ++i)
3026 if (Factors[i] != -1)
3027 Factors.insert(-(uint64_t)Factors[i]);
3031 // Set up the initial formula for this use.
3032 std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy);
3034 LF.Offset = P.second;
3035 LSRUse &LU = Uses[LF.LUIdx];
3036 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3037 if (!LU.WidestFixupType ||
3038 SE.getTypeSizeInBits(LU.WidestFixupType) <
3039 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3040 LU.WidestFixupType = LF.OperandValToReplace->getType();
3042 // If this is the first use of this LSRUse, give it a formula.
3043 if (LU.Formulae.empty()) {
3044 InsertInitialFormula(S, LU, LF.LUIdx);
3045 CountRegisters(LU.Formulae.back(), LF.LUIdx);
3049 DEBUG(print_fixups(dbgs()));
3052 /// InsertInitialFormula - Insert a formula for the given expression into
3053 /// the given use, separating out loop-variant portions from loop-invariant
3054 /// and loop-computable portions.
3056 LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) {
3057 // Mark uses whose expressions cannot be expanded.
3058 if (!isSafeToExpand(S, SE))
3059 LU.RigidFormula = true;
3062 F.InitialMatch(S, L, SE);
3063 bool Inserted = InsertFormula(LU, LUIdx, F);
3064 assert(Inserted && "Initial formula already exists!"); (void)Inserted;
3067 /// InsertSupplementalFormula - Insert a simple single-register formula for
3068 /// the given expression into the given use.
3070 LSRInstance::InsertSupplementalFormula(const SCEV *S,
3071 LSRUse &LU, size_t LUIdx) {
3073 F.BaseRegs.push_back(S);
3074 F.HasBaseReg = true;
3075 bool Inserted = InsertFormula(LU, LUIdx, F);
3076 assert(Inserted && "Supplemental formula already exists!"); (void)Inserted;
3079 /// CountRegisters - Note which registers are used by the given formula,
3080 /// updating RegUses.
3081 void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) {
3083 RegUses.CountRegister(F.ScaledReg, LUIdx);
3084 for (const SCEV *BaseReg : F.BaseRegs)
3085 RegUses.CountRegister(BaseReg, LUIdx);
3088 /// InsertFormula - If the given formula has not yet been inserted, add it to
3089 /// the list, and return true. Return false otherwise.
3090 bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) {
3091 // Do not insert formula that we will not be able to expand.
3092 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) &&
3093 "Formula is illegal");
3094 if (!LU.InsertFormula(F))
3097 CountRegisters(F, LUIdx);
3101 /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of
3102 /// loop-invariant values which we're tracking. These other uses will pin these
3103 /// values in registers, making them less profitable for elimination.
3104 /// TODO: This currently misses non-constant addrec step registers.
3105 /// TODO: Should this give more weight to users inside the loop?
3107 LSRInstance::CollectLoopInvariantFixupsAndFormulae() {
3108 SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end());
3109 SmallPtrSet<const SCEV *, 32> Visited;
3111 while (!Worklist.empty()) {
3112 const SCEV *S = Worklist.pop_back_val();
3114 // Don't process the same SCEV twice
3115 if (!Visited.insert(S).second)
3118 if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S))
3119 Worklist.append(N->op_begin(), N->op_end());
3120 else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S))
3121 Worklist.push_back(C->getOperand());
3122 else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) {
3123 Worklist.push_back(D->getLHS());
3124 Worklist.push_back(D->getRHS());
3125 } else if (const SCEVUnknown *US = dyn_cast<SCEVUnknown>(S)) {
3126 const Value *V = US->getValue();
3127 if (const Instruction *Inst = dyn_cast<Instruction>(V)) {
3128 // Look for instructions defined outside the loop.
3129 if (L->contains(Inst)) continue;
3130 } else if (isa<UndefValue>(V))
3131 // Undef doesn't have a live range, so it doesn't matter.
3133 for (const Use &U : V->uses()) {
3134 const Instruction *UserInst = dyn_cast<Instruction>(U.getUser());
3135 // Ignore non-instructions.
3138 // Ignore instructions in other functions (as can happen with
3140 if (UserInst->getParent()->getParent() != L->getHeader()->getParent())
3142 // Ignore instructions not dominated by the loop.
3143 const BasicBlock *UseBB = !isa<PHINode>(UserInst) ?
3144 UserInst->getParent() :
3145 cast<PHINode>(UserInst)->getIncomingBlock(
3146 PHINode::getIncomingValueNumForOperand(U.getOperandNo()));
3147 if (!DT.dominates(L->getHeader(), UseBB))
3149 // Ignore uses which are part of other SCEV expressions, to avoid
3150 // analyzing them multiple times.
3151 if (SE.isSCEVable(UserInst->getType())) {
3152 const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst));
3153 // If the user is a no-op, look through to its uses.
3154 if (!isa<SCEVUnknown>(UserS))
3158 SE.getUnknown(const_cast<Instruction *>(UserInst)));
3162 // Ignore icmp instructions which are already being analyzed.
3163 if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) {
3164 unsigned OtherIdx = !U.getOperandNo();
3165 Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx));
3166 if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L))
3170 LSRFixup &LF = getNewFixup();
3171 LF.UserInst = const_cast<Instruction *>(UserInst);
3172 LF.OperandValToReplace = U;
3173 std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, nullptr);
3175 LF.Offset = P.second;
3176 LSRUse &LU = Uses[LF.LUIdx];
3177 LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L);
3178 if (!LU.WidestFixupType ||
3179 SE.getTypeSizeInBits(LU.WidestFixupType) <
3180 SE.getTypeSizeInBits(LF.OperandValToReplace->getType()))
3181 LU.WidestFixupType = LF.OperandValToReplace->getType();
3182 InsertSupplementalFormula(US, LU, LF.LUIdx);
3183 CountRegisters(LU.Formulae.back(), Uses.size() - 1);
3190 /// CollectSubexprs - Split S into subexpressions which can be pulled out into
3191 /// separate registers. If C is non-null, multiply each subexpression by C.
3193 /// Return remainder expression after factoring the subexpressions captured by
3194 /// Ops. If Ops is complete, return NULL.
3195 static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C,
3196 SmallVectorImpl<const SCEV *> &Ops,
3198 ScalarEvolution &SE,
3199 unsigned Depth = 0) {
3200 // Arbitrarily cap recursion to protect compile time.
3204 if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) {
3205 // Break out add operands.
3206 for (const SCEV *S : Add->operands()) {
3207 const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1);
3209 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3212 } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) {
3213 // Split a non-zero base out of an addrec.
3214 if (AR->getStart()->isZero())
3217 const SCEV *Remainder = CollectSubexprs(AR->getStart(),
3218 C, Ops, L, SE, Depth+1);
3219 // Split the non-zero AddRec unless it is part of a nested recurrence that
3220 // does not pertain to this loop.
3221 if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) {
3222 Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder);
3223 Remainder = nullptr;
3225 if (Remainder != AR->getStart()) {
3227 Remainder = SE.getConstant(AR->getType(), 0);
3228 return SE.getAddRecExpr(Remainder,
3229 AR->getStepRecurrence(SE),
3231 //FIXME: AR->getNoWrapFlags(SCEV::FlagNW)
3234 } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) {
3235 // Break (C * (a + b + c)) into C*a + C*b + C*c.
3236 if (Mul->getNumOperands() != 2)
3238 if (const SCEVConstant *Op0 =
3239 dyn_cast<SCEVConstant>(Mul->getOperand(0))) {
3240 C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0;
3241 const SCEV *Remainder =
3242 CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1);
3244 Ops.push_back(SE.getMulExpr(C, Remainder));
3251 /// \brief Helper function for LSRInstance::GenerateReassociations.
3252 void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx,
3253 const Formula &Base,
3254 unsigned Depth, size_t Idx,
3256 const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3257 SmallVector<const SCEV *, 8> AddOps;
3258 const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE);
3260 AddOps.push_back(Remainder);
3262 if (AddOps.size() == 1)
3265 for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(),
3269 // Loop-variant "unknown" values are uninteresting; we won't be able to
3270 // do anything meaningful with them.
3271 if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L))
3274 // Don't pull a constant into a register if the constant could be folded
3275 // into an immediate field.
3276 if (isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3277 LU.AccessTy, *J, Base.getNumRegs() > 1))
3280 // Collect all operands except *J.
3281 SmallVector<const SCEV *, 8> InnerAddOps(
3282 ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J);
3283 InnerAddOps.append(std::next(J),
3284 ((const SmallVector<const SCEV *, 8> &)AddOps).end());
3286 // Don't leave just a constant behind in a register if the constant could
3287 // be folded into an immediate field.
3288 if (InnerAddOps.size() == 1 &&
3289 isAlwaysFoldable(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind,
3290 LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1))
3293 const SCEV *InnerSum = SE.getAddExpr(InnerAddOps);
3294 if (InnerSum->isZero())
3298 // Add the remaining pieces of the add back into the new formula.
3299 const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum);
3300 if (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 &&
3301 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3302 InnerSumSC->getValue()->getZExtValue())) {
3304 (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue();
3306 F.ScaledReg = nullptr;
3308 F.BaseRegs.erase(F.BaseRegs.begin() + Idx);
3309 } else if (IsScaledReg)
3310 F.ScaledReg = InnerSum;
3312 F.BaseRegs[Idx] = InnerSum;
3314 // Add J as its own register, or an unfolded immediate.
3315 const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J);
3316 if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 &&
3317 TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset +
3318 SC->getValue()->getZExtValue()))
3320 (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue();
3322 F.BaseRegs.push_back(*J);
3323 // We may have changed the number of register in base regs, adjust the
3324 // formula accordingly.
3327 if (InsertFormula(LU, LUIdx, F))
3328 // If that formula hadn't been seen before, recurse to find more like
3330 GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth + 1);
3334 /// GenerateReassociations - Split out subexpressions from adds and the bases of
3336 void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx,
3337 Formula Base, unsigned Depth) {
3338 assert(Base.isCanonical() && "Input must be in the canonical form");
3339 // Arbitrarily cap recursion to protect compile time.
3343 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3344 GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i);
3346 if (Base.Scale == 1)
3347 GenerateReassociationsImpl(LU, LUIdx, Base, Depth,
3348 /* Idx */ -1, /* IsScaledReg */ true);
3351 /// GenerateCombinations - Generate a formula consisting of all of the
3352 /// loop-dominating registers added into a single register.
3353 void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx,
3355 // This method is only interesting on a plurality of registers.
3356 if (Base.BaseRegs.size() + (Base.Scale == 1) <= 1)
3359 // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before
3360 // processing the formula.
3364 SmallVector<const SCEV *, 4> Ops;
3365 for (const SCEV *BaseReg : Base.BaseRegs) {
3366 if (SE.properlyDominates(BaseReg, L->getHeader()) &&
3367 !SE.hasComputableLoopEvolution(BaseReg, L))
3368 Ops.push_back(BaseReg);
3370 F.BaseRegs.push_back(BaseReg);
3372 if (Ops.size() > 1) {
3373 const SCEV *Sum = SE.getAddExpr(Ops);
3374 // TODO: If Sum is zero, it probably means ScalarEvolution missed an
3375 // opportunity to fold something. For now, just ignore such cases
3376 // rather than proceed with zero in a register.
3377 if (!Sum->isZero()) {
3378 F.BaseRegs.push_back(Sum);
3380 (void)InsertFormula(LU, LUIdx, F);
3385 /// \brief Helper function for LSRInstance::GenerateSymbolicOffsets.
3386 void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx,
3387 const Formula &Base, size_t Idx,
3389 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3390 GlobalValue *GV = ExtractSymbol(G, SE);
3391 if (G->isZero() || !GV)
3395 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3400 F.BaseRegs[Idx] = G;
3401 (void)InsertFormula(LU, LUIdx, F);
3404 /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets.
3405 void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx,
3407 // We can't add a symbolic offset if the address already contains one.
3408 if (Base.BaseGV) return;
3410 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3411 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i);
3412 if (Base.Scale == 1)
3413 GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1,
3414 /* IsScaledReg */ true);
3417 /// \brief Helper function for LSRInstance::GenerateConstantOffsets.
3418 void LSRInstance::GenerateConstantOffsetsImpl(
3419 LSRUse &LU, unsigned LUIdx, const Formula &Base,
3420 const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) {
3421 const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx];
3422 for (int64_t Offset : Worklist) {
3424 F.BaseOffset = (uint64_t)Base.BaseOffset - Offset;
3425 if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind,
3427 // Add the offset to the base register.
3428 const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G);
3429 // If it cancelled out, drop the base register, otherwise update it.
3430 if (NewG->isZero()) {
3433 F.ScaledReg = nullptr;
3435 F.DeleteBaseReg(F.BaseRegs[Idx]);
3437 } else if (IsScaledReg)
3440 F.BaseRegs[Idx] = NewG;
3442 (void)InsertFormula(LU, LUIdx, F);
3446 int64_t Imm = ExtractImmediate(G, SE);
3447 if (G->isZero() || Imm == 0)
3450 F.BaseOffset = (uint64_t)F.BaseOffset + Imm;
3451 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3456 F.BaseRegs[Idx] = G;
3457 (void)InsertFormula(LU, LUIdx, F);
3460 /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets.
3461 void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx,
3463 // TODO: For now, just add the min and max offset, because it usually isn't
3464 // worthwhile looking at everything inbetween.
3465 SmallVector<int64_t, 2> Worklist;
3466 Worklist.push_back(LU.MinOffset);
3467 if (LU.MaxOffset != LU.MinOffset)
3468 Worklist.push_back(LU.MaxOffset);
3470 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3471 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i);
3472 if (Base.Scale == 1)
3473 GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1,
3474 /* IsScaledReg */ true);
3477 /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up
3478 /// the comparison. For example, x == y -> x*c == y*c.
3479 void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx,
3481 if (LU.Kind != LSRUse::ICmpZero) return;
3483 // Determine the integer type for the base formula.
3484 Type *IntTy = Base.getType();
3486 if (SE.getTypeSizeInBits(IntTy) > 64) return;
3488 // Don't do this if there is more than one offset.
3489 if (LU.MinOffset != LU.MaxOffset) return;
3491 assert(!Base.BaseGV && "ICmpZero use is not legal!");
3493 // Check each interesting stride.
3494 for (int64_t Factor : Factors) {
3495 // Check that the multiplication doesn't overflow.
3496 if (Base.BaseOffset == INT64_MIN && Factor == -1)
3498 int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor;
3499 if (NewBaseOffset / Factor != Base.BaseOffset)
3501 // If the offset will be truncated at this use, check that it is in bounds.
3502 if (!IntTy->isPointerTy() &&
3503 !ConstantInt::isValueValidForType(IntTy, NewBaseOffset))
3506 // Check that multiplying with the use offset doesn't overflow.
3507 int64_t Offset = LU.MinOffset;
3508 if (Offset == INT64_MIN && Factor == -1)
3510 Offset = (uint64_t)Offset * Factor;
3511 if (Offset / Factor != LU.MinOffset)
3513 // If the offset will be truncated at this use, check that it is in bounds.
3514 if (!IntTy->isPointerTy() &&
3515 !ConstantInt::isValueValidForType(IntTy, Offset))
3519 F.BaseOffset = NewBaseOffset;
3521 // Check that this scale is legal.
3522 if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F))
3525 // Compensate for the use having MinOffset built into it.
3526 F.BaseOffset = (uint64_t)F.BaseOffset + Offset - LU.MinOffset;
3528 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3530 // Check that multiplying with each base register doesn't overflow.
3531 for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) {
3532 F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS);
3533 if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i])
3537 // Check that multiplying with the scaled register doesn't overflow.
3539 F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS);
3540 if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg)
3544 // Check that multiplying with the unfolded offset doesn't overflow.
3545 if (F.UnfoldedOffset != 0) {
3546 if (F.UnfoldedOffset == INT64_MIN && Factor == -1)
3548 F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor;
3549 if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset)
3551 // If the offset will be truncated, check that it is in bounds.
3552 if (!IntTy->isPointerTy() &&
3553 !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset))
3557 // If we make it here and it's legal, add it.
3558 (void)InsertFormula(LU, LUIdx, F);
3563 /// GenerateScales - Generate stride factor reuse formulae by making use of
3564 /// scaled-offset address modes, for example.
3565 void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base) {
3566 // Determine the integer type for the base formula.
3567 Type *IntTy = Base.getType();
3570 // If this Formula already has a scaled register, we can't add another one.
3571 // Try to unscale the formula to generate a better scale.
3572 if (Base.Scale != 0 && !Base.Unscale())
3575 assert(Base.Scale == 0 && "Unscale did not did its job!");
3577 // Check each interesting stride.
3578 for (int64_t Factor : Factors) {
3579 Base.Scale = Factor;
3580 Base.HasBaseReg = Base.BaseRegs.size() > 1;
3581 // Check whether this scale is going to be legal.
3582 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3584 // As a special-case, handle special out-of-loop Basic users specially.
3585 // TODO: Reconsider this special case.
3586 if (LU.Kind == LSRUse::Basic &&
3587 isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special,
3588 LU.AccessTy, Base) &&
3589 LU.AllFixupsOutsideLoop)
3590 LU.Kind = LSRUse::Special;
3594 // For an ICmpZero, negating a solitary base register won't lead to
3596 if (LU.Kind == LSRUse::ICmpZero &&
3597 !Base.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV)
3599 // For each addrec base reg, apply the scale, if possible.
3600 for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i)
3601 if (const SCEVAddRecExpr *AR =
3602 dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) {
3603 const SCEV *FactorS = SE.getConstant(IntTy, Factor);
3604 if (FactorS->isZero())
3606 // Divide out the factor, ignoring high bits, since we'll be
3607 // scaling the value back up in the end.
3608 if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) {
3609 // TODO: This could be optimized to avoid all the copying.
3611 F.ScaledReg = Quotient;
3612 F.DeleteBaseReg(F.BaseRegs[i]);
3613 // The canonical representation of 1*reg is reg, which is already in
3614 // Base. In that case, do not try to insert the formula, it will be
3616 if (F.Scale == 1 && F.BaseRegs.empty())
3618 (void)InsertFormula(LU, LUIdx, F);
3624 /// GenerateTruncates - Generate reuse formulae from different IV types.
3625 void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) {
3626 // Don't bother truncating symbolic values.
3627 if (Base.BaseGV) return;
3629 // Determine the integer type for the base formula.
3630 Type *DstTy = Base.getType();
3632 DstTy = SE.getEffectiveSCEVType(DstTy);
3634 for (Type *SrcTy : Types) {
3635 if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) {
3638 if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy);
3639 for (const SCEV *&BaseReg : F.BaseRegs)
3640 BaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy);
3642 // TODO: This assumes we've done basic processing on all uses and
3643 // have an idea what the register usage is.
3644 if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses))
3647 (void)InsertFormula(LU, LUIdx, F);
3652 /// GenerateZExts - If a scale or a base register can be rewritten as
3653 /// "Zext({A,+,1})" then consider a formula of that form.
3654 void LSRInstance::GenerateZExts(LSRUse &LU, unsigned LUIdx, Formula Base) {
3655 // Don't bother with symbolic values.
3659 auto CanBeNarrowed = [&](const SCEV *Reg) -> const SCEV * {
3660 // Check if the register is an increment can be rewritten as zext(R) where
3661 // the zext is free.
3663 const auto *RegAR = dyn_cast_or_null<SCEVAddRecExpr>(Reg);
3667 const auto *ZExtStart = dyn_cast<SCEVZeroExtendExpr>(RegAR->getStart());
3668 const auto *ConstStep =
3669 dyn_cast<SCEVConstant>(RegAR->getStepRecurrence(SE));
3670 if (!ZExtStart || !ConstStep || ConstStep->getValue()->getValue() != 1)
3673 const SCEV *NarrowStart = ZExtStart->getOperand();
3674 if (!TTI.isZExtFree(NarrowStart->getType(), ZExtStart->getType()))
3677 const auto *NarrowAR = dyn_cast<SCEVAddRecExpr>(
3678 SE.getAddRecExpr(NarrowStart, SE.getConstant(NarrowStart->getType(), 1),
3679 RegAR->getLoop(), RegAR->getNoWrapFlags()));
3681 if (!NarrowAR || !NarrowAR->getNoWrapFlags(SCEV::FlagNUW))
3687 if (Base.ScaledReg && !Base.ZeroExtendType)
3688 if (const SCEV *S = CanBeNarrowed(Base.ScaledReg)) {
3690 F.ZeroExtendType = Base.ScaledReg->getType();
3691 F.ZeroExtendScaledReg = true;
3694 if (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3695 InsertFormula(LU, LUIdx, F);
3698 if (Base.BaseRegs.size() == 1 && !Base.ZeroExtendType)
3699 if (const SCEV *S = CanBeNarrowed(Base.BaseRegs[0])) {
3701 F.ZeroExtendType = Base.BaseRegs[0]->getType();
3702 F.ZeroExtendBaseReg = true;
3705 if (isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F))
3706 InsertFormula(LU, LUIdx, F);
3712 /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to
3713 /// defer modifications so that the search phase doesn't have to worry about
3714 /// the data structures moving underneath it.
3718 const SCEV *OrigReg;
3720 WorkItem(size_t LI, int64_t I, const SCEV *R)
3721 : LUIdx(LI), Imm(I), OrigReg(R) {}
3723 void print(raw_ostream &OS) const;
3729 void WorkItem::print(raw_ostream &OS) const {
3730 OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx
3731 << " , add offset " << Imm;
3734 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
3735 void WorkItem::dump() const {
3736 print(errs()); errs() << '\n';
3740 /// GenerateCrossUseConstantOffsets - Look for registers which are a constant
3741 /// distance apart and try to form reuse opportunities between them.
3742 void LSRInstance::GenerateCrossUseConstantOffsets() {
3743 // Group the registers by their value without any added constant offset.
3744 typedef std::map<int64_t, const SCEV *> ImmMapTy;
3745 DenseMap<const SCEV *, ImmMapTy> Map;
3746 DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap;
3747 SmallVector<const SCEV *, 8> Sequence;
3748 for (const SCEV *Use : RegUses) {
3749 const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify.
3750 int64_t Imm = ExtractImmediate(Reg, SE);
3751 auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy()));
3753 Sequence.push_back(Reg);
3754 Pair.first->second.insert(std::make_pair(Imm, Use));
3755 UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use);
3758 // Now examine each set of registers with the same base value. Build up
3759 // a list of work to do and do the work in a separate step so that we're
3760 // not adding formulae and register counts while we're searching.
3761 SmallVector<WorkItem, 32> WorkItems;
3762 SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems;
3763 for (const SCEV *Reg : Sequence) {
3764 const ImmMapTy &Imms = Map.find(Reg)->second;
3766 // It's not worthwhile looking for reuse if there's only one offset.
3767 if (Imms.size() == 1)
3770 DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':';
3771 for (const auto &Entry : Imms)
3772 dbgs() << ' ' << Entry.first;
3775 // Examine each offset.
3776 for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end();
3778 const SCEV *OrigReg = J->second;
3780 int64_t JImm = J->first;
3781 const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg);
3783 if (!isa<SCEVConstant>(OrigReg) &&
3784 UsedByIndicesMap[Reg].count() == 1) {
3785 DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n');
3789 // Conservatively examine offsets between this orig reg a few selected
3791 ImmMapTy::const_iterator OtherImms[] = {
3792 Imms.begin(), std::prev(Imms.end()),
3793 Imms.lower_bound((Imms.begin()->first + std::prev(Imms.end())->first) /
3796 for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) {
3797 ImmMapTy::const_iterator M = OtherImms[i];
3798 if (M == J || M == JE) continue;
3800 // Compute the difference between the two.
3801 int64_t Imm = (uint64_t)JImm - M->first;
3802 for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1;
3803 LUIdx = UsedByIndices.find_next(LUIdx))
3804 // Make a memo of this use, offset, and register tuple.
3805 if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second)
3806 WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg));
3813 UsedByIndicesMap.clear();
3814 UniqueItems.clear();
3816 // Now iterate through the worklist and add new formulae.
3817 for (const WorkItem &WI : WorkItems) {
3818 size_t LUIdx = WI.LUIdx;
3819 LSRUse &LU = Uses[LUIdx];
3820 int64_t Imm = WI.Imm;
3821 const SCEV *OrigReg = WI.OrigReg;
3823 Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType());
3824 const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm));
3825 unsigned BitWidth = SE.getTypeSizeInBits(IntTy);
3827 // TODO: Use a more targeted data structure.
3828 for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) {
3829 Formula F = LU.Formulae[L];
3830 // FIXME: The code for the scaled and unscaled registers looks
3831 // very similar but slightly different. Investigate if they
3832 // could be merged. That way, we would not have to unscale the
3835 // Use the immediate in the scaled register.
3836 if (F.ScaledReg == OrigReg) {
3837 int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale;
3838 // Don't create 50 + reg(-50).
3839 if (F.referencesReg(SE.getSCEV(
3840 ConstantInt::get(IntTy, -(uint64_t)Offset))))
3843 NewF.BaseOffset = Offset;
3844 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
3847 NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg);
3849 // If the new scale is a constant in a register, and adding the constant
3850 // value to the immediate would produce a value closer to zero than the
3851 // immediate itself, then the formula isn't worthwhile.
3852 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg))
3853 if (C->getValue()->isNegative() !=
3854 (NewF.BaseOffset < 0) &&
3855 (C->getValue()->getValue().abs() * APInt(BitWidth, F.Scale))
3856 .ule(std::abs(NewF.BaseOffset)))
3860 NewF.Canonicalize();
3861 (void)InsertFormula(LU, LUIdx, NewF);
3863 // Use the immediate in a base register.
3864 for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) {
3865 const SCEV *BaseReg = F.BaseRegs[N];
3866 if (BaseReg != OrigReg)
3869 NewF.BaseOffset = (uint64_t)NewF.BaseOffset + Imm;
3870 if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset,
3871 LU.Kind, LU.AccessTy, NewF)) {
3872 if (!TTI.isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm))
3875 NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm;
3877 NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg);
3879 // If the new formula has a constant in a register, and adding the
3880 // constant value to the immediate would produce a value closer to
3881 // zero than the immediate itself, then the formula isn't worthwhile.
3882 for (const SCEV *NewReg : NewF.BaseRegs)
3883 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg))
3884 if ((C->getValue()->getValue() + NewF.BaseOffset).abs().slt(
3885 std::abs(NewF.BaseOffset)) &&
3886 (C->getValue()->getValue() +
3887 NewF.BaseOffset).countTrailingZeros() >=
3888 countTrailingZeros<uint64_t>(NewF.BaseOffset))
3892 NewF.Canonicalize();
3893 (void)InsertFormula(LU, LUIdx, NewF);
3902 /// GenerateAllReuseFormulae - Generate formulae for each use.
3904 LSRInstance::GenerateAllReuseFormulae() {
3905 // This is split into multiple loops so that hasRegsUsedByUsesOtherThan
3906 // queries are more precise.
3907 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3908 LSRUse &LU = Uses[LUIdx];
3909 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3910 GenerateReassociations(LU, LUIdx, LU.Formulae[i]);
3911 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3912 GenerateCombinations(LU, LUIdx, LU.Formulae[i]);
3914 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3915 LSRUse &LU = Uses[LUIdx];
3916 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3917 GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]);
3918 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3919 GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]);
3920 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3921 GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]);
3922 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3923 GenerateScales(LU, LUIdx, LU.Formulae[i]);
3925 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3926 LSRUse &LU = Uses[LUIdx];
3927 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3928 GenerateTruncates(LU, LUIdx, LU.Formulae[i]);
3929 for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i)
3930 GenerateZExts(LU, LUIdx, LU.Formulae[i]);
3933 GenerateCrossUseConstantOffsets();
3935 DEBUG(dbgs() << "\n"
3936 "After generating reuse formulae:\n";
3937 print_uses(dbgs()));
3940 /// If there are multiple formulae with the same set of registers used
3941 /// by other uses, pick the best one and delete the others.
3942 void LSRInstance::FilterOutUndesirableDedicatedRegisters() {
3943 DenseSet<const SCEV *> VisitedRegs;
3944 SmallPtrSet<const SCEV *, 16> Regs;
3945 SmallPtrSet<const SCEV *, 16> LoserRegs;
3947 bool ChangedFormulae = false;
3950 // Collect the best formula for each unique set of shared registers. This
3951 // is reset for each use.
3952 typedef DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>
3954 BestFormulaeTy BestFormulae;
3956 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
3957 LSRUse &LU = Uses[LUIdx];
3958 DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n');
3961 for (size_t FIdx = 0, NumForms = LU.Formulae.size();
3962 FIdx != NumForms; ++FIdx) {
3963 Formula &F = LU.Formulae[FIdx];
3965 // Some formulas are instant losers. For example, they may depend on
3966 // nonexistent AddRecs from other loops. These need to be filtered
3967 // immediately, otherwise heuristics could choose them over others leading
3968 // to an unsatisfactory solution. Passing LoserRegs into RateFormula here
3969 // avoids the need to recompute this information across formulae using the
3970 // same bad AddRec. Passing LoserRegs is also essential unless we remove
3971 // the corresponding bad register from the Regs set.
3974 CostF.RateFormula(TTI, F, Regs, VisitedRegs, L, LU.Offsets, SE, DT, LU,
3976 if (CostF.isLoser()) {
3977 // During initial formula generation, undesirable formulae are generated
3978 // by uses within other loops that have some non-trivial address mode or
3979 // use the postinc form of the IV. LSR needs to provide these formulae
3980 // as the basis of rediscovering the desired formula that uses an AddRec
3981 // corresponding to the existing phi. Once all formulae have been
3982 // generated, these initial losers may be pruned.
3983 DEBUG(dbgs() << " Filtering loser "; F.print(dbgs());
3987 SmallVector<const SCEV *, 4> Key;
3988 for (const SCEV *Reg : F.BaseRegs) {
3989 if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx))
3993 RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx))
3994 Key.push_back(F.ScaledReg);
3995 // Unstable sort by host order ok, because this is only used for
3997 std::sort(Key.begin(), Key.end());
3999 std::pair<BestFormulaeTy::const_iterator, bool> P =
4000 BestFormulae.insert(std::make_pair(Key, FIdx));
4004 Formula &Best = LU.Formulae[P.first->second];
4008 CostBest.RateFormula(TTI, Best, Regs, VisitedRegs, L, LU.Offsets, SE,
4010 if (CostF < CostBest)
4012 DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs());
4014 " in favor of formula "; Best.print(dbgs());
4018 ChangedFormulae = true;
4020 LU.DeleteFormula(F);
4026 // Now that we've filtered out some formulae, recompute the Regs set.
4028 LU.RecomputeRegs(LUIdx, RegUses);
4030 // Reset this to prepare for the next use.
4031 BestFormulae.clear();
4034 DEBUG(if (ChangedFormulae) {
4036 "After filtering out undesirable candidates:\n";
4041 // This is a rough guess that seems to work fairly well.
4042 static const size_t ComplexityLimit = UINT16_MAX;
4044 /// EstimateSearchSpaceComplexity - Estimate the worst-case number of
4045 /// solutions the solver might have to consider. It almost never considers
4046 /// this many solutions because it prune the search space, but the pruning
4047 /// isn't always sufficient.
4048 size_t LSRInstance::EstimateSearchSpaceComplexity() const {
4050 for (const LSRUse &LU : Uses) {
4051 size_t FSize = LU.Formulae.size();
4052 if (FSize >= ComplexityLimit) {
4053 Power = ComplexityLimit;
4057 if (Power >= ComplexityLimit)
4063 /// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset
4064 /// of the registers of another formula, it won't help reduce register
4065 /// pressure (though it may not necessarily hurt register pressure); remove
4066 /// it to simplify the system.
4067 void LSRInstance::NarrowSearchSpaceByDetectingSupersets() {
4068 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4069 DEBUG(dbgs() << "The search space is too complex.\n");
4071 DEBUG(dbgs() << "Narrowing the search space by eliminating formulae "
4072 "which use a superset of registers used by other "
4075 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4076 LSRUse &LU = Uses[LUIdx];
4078 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4079 Formula &F = LU.Formulae[i];
4080 // Look for a formula with a constant or GV in a register. If the use
4081 // also has a formula with that same value in an immediate field,
4082 // delete the one that uses a register.
4083 for (SmallVectorImpl<const SCEV *>::const_iterator
4084 I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) {
4085 if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) {
4087 NewF.BaseOffset += C->getValue()->getSExtValue();
4088 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4089 (I - F.BaseRegs.begin()));
4090 if (LU.HasFormulaWithSameRegs(NewF)) {
4091 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4092 LU.DeleteFormula(F);
4098 } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) {
4099 if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue()))
4103 NewF.BaseRegs.erase(NewF.BaseRegs.begin() +
4104 (I - F.BaseRegs.begin()));
4105 if (LU.HasFormulaWithSameRegs(NewF)) {
4106 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4108 LU.DeleteFormula(F);
4119 LU.RecomputeRegs(LUIdx, RegUses);
4122 DEBUG(dbgs() << "After pre-selection:\n";
4123 print_uses(dbgs()));
4127 /// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers
4128 /// for expressions like A, A+1, A+2, etc., allocate a single register for
4130 void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() {
4131 if (EstimateSearchSpaceComplexity() < ComplexityLimit)
4134 DEBUG(dbgs() << "The search space is too complex.\n"
4135 "Narrowing the search space by assuming that uses separated "
4136 "by a constant offset will use the same registers.\n");
4138 // This is especially useful for unrolled loops.
4140 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4141 LSRUse &LU = Uses[LUIdx];
4142 for (const Formula &F : LU.Formulae) {
4143 if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1))
4146 LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU);
4150 if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false,
4151 LU.Kind, LU.AccessTy))
4154 DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n');
4156 LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop;
4158 // Update the relocs to reference the new use.
4159 for (LSRFixup &Fixup : Fixups) {
4160 if (Fixup.LUIdx == LUIdx) {
4161 Fixup.LUIdx = LUThatHas - &Uses.front();
4162 Fixup.Offset += F.BaseOffset;
4163 // Add the new offset to LUThatHas' offset list.
4164 if (LUThatHas->Offsets.back() != Fixup.Offset) {
4165 LUThatHas->Offsets.push_back(Fixup.Offset);
4166 if (Fixup.Offset > LUThatHas->MaxOffset)
4167 LUThatHas->MaxOffset = Fixup.Offset;
4168 if (Fixup.Offset < LUThatHas->MinOffset)
4169 LUThatHas->MinOffset = Fixup.Offset;
4171 DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n');
4173 if (Fixup.LUIdx == NumUses-1)
4174 Fixup.LUIdx = LUIdx;
4177 // Delete formulae from the new use which are no longer legal.
4179 for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) {
4180 Formula &F = LUThatHas->Formulae[i];
4181 if (!isLegalUse(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset,
4182 LUThatHas->Kind, LUThatHas->AccessTy, F)) {
4183 DEBUG(dbgs() << " Deleting "; F.print(dbgs());
4185 LUThatHas->DeleteFormula(F);
4193 LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses);
4195 // Delete the old use.
4196 DeleteUse(LU, LUIdx);
4203 DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs()));
4206 /// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call
4207 /// FilterOutUndesirableDedicatedRegisters again, if necessary, now that
4208 /// we've done more filtering, as it may be able to find more formulae to
4210 void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){
4211 if (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4212 DEBUG(dbgs() << "The search space is too complex.\n");
4214 DEBUG(dbgs() << "Narrowing the search space by re-filtering out "
4215 "undesirable dedicated registers.\n");
4217 FilterOutUndesirableDedicatedRegisters();
4219 DEBUG(dbgs() << "After pre-selection:\n";
4220 print_uses(dbgs()));
4224 /// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely
4225 /// to be profitable, and then in any use which has any reference to that
4226 /// register, delete all formulae which do not reference that register.
4227 void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() {
4228 // With all other options exhausted, loop until the system is simple
4229 // enough to handle.
4230 SmallPtrSet<const SCEV *, 4> Taken;
4231 while (EstimateSearchSpaceComplexity() >= ComplexityLimit) {
4232 // Ok, we have too many of formulae on our hands to conveniently handle.
4233 // Use a rough heuristic to thin out the list.
4234 DEBUG(dbgs() << "The search space is too complex.\n");
4236 // Pick the register which is used by the most LSRUses, which is likely
4237 // to be a good reuse register candidate.
4238 const SCEV *Best = nullptr;
4239 unsigned BestNum = 0;
4240 for (const SCEV *Reg : RegUses) {
4241 if (Taken.count(Reg))
4246 unsigned Count = RegUses.getUsedByIndices(Reg).count();
4247 if (Count > BestNum) {
4254 DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best
4255 << " will yield profitable reuse.\n");
4258 // In any use with formulae which references this register, delete formulae
4259 // which don't reference it.
4260 for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) {
4261 LSRUse &LU = Uses[LUIdx];
4262 if (!LU.Regs.count(Best)) continue;
4265 for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) {
4266 Formula &F = LU.Formulae[i];
4267 if (!F.referencesReg(Best)) {
4268 DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n');
4269 LU.DeleteFormula(F);
4273 assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?");
4279 LU.RecomputeRegs(LUIdx, RegUses);
4282 DEBUG(dbgs() << "After pre-selection:\n";
4283 print_uses(dbgs()));
4287 /// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of
4288 /// formulae to choose from, use some rough heuristics to prune down the number
4289 /// of formulae. This keeps the main solver from taking an extraordinary amount
4290 /// of time in some worst-case scenarios.
4291 void LSRInstance::NarrowSearchSpaceUsingHeuristics() {
4292 NarrowSearchSpaceByDetectingSupersets();
4293 NarrowSearchSpaceByCollapsingUnrolledCode();
4294 NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters();
4295 NarrowSearchSpaceByPickingWinnerRegs();
4298 /// SolveRecurse - This is the recursive solver.
4299 void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution,
4301 SmallVectorImpl<const Formula *> &Workspace,
4302 const Cost &CurCost,
4303 const SmallPtrSet<const SCEV *, 16> &CurRegs,
4304 DenseSet<const SCEV *> &VisitedRegs) const {
4307 // - use more aggressive filtering
4308 // - sort the formula so that the most profitable solutions are found first
4309 // - sort the uses too
4311 // - don't compute a cost, and then compare. compare while computing a cost
4313 // - track register sets with SmallBitVector
4315 const LSRUse &LU = Uses[Workspace.size()];
4317 // If this use references any register that's already a part of the
4318 // in-progress solution, consider it a requirement that a formula must
4319 // reference that register in order to be considered. This prunes out
4320 // unprofitable searching.
4321 SmallSetVector<const SCEV *, 4> ReqRegs;
4322 for (const SCEV *S : CurRegs)
4323 if (LU.Regs.count(S))
4326 SmallPtrSet<const SCEV *, 16> NewRegs;
4328 for (const Formula &F : LU.Formulae) {
4329 // Ignore formulae which may not be ideal in terms of register reuse of
4330 // ReqRegs. The formula should use all required registers before
4331 // introducing new ones.
4332 int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size());
4333 for (const SCEV *Reg : ReqRegs) {
4334 if ((F.ScaledReg && F.ScaledReg == Reg) ||
4335 std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) !=
4338 if (NumReqRegsToFind == 0)
4342 if (NumReqRegsToFind != 0) {
4343 // If none of the formulae satisfied the required registers, then we could
4344 // clear ReqRegs and try again. Currently, we simply give up in this case.
4348 // Evaluate the cost of the current formula. If it's already worse than
4349 // the current best, prune the search at that point.
4352 NewCost.RateFormula(TTI, F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT,
4354 if (NewCost < SolutionCost) {
4355 Workspace.push_back(&F);
4356 if (Workspace.size() != Uses.size()) {
4357 SolveRecurse(Solution, SolutionCost, Workspace, NewCost,
4358 NewRegs, VisitedRegs);
4359 if (F.getNumRegs() == 1 && Workspace.size() == 1)
4360 VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]);
4362 DEBUG(dbgs() << "New best at "; NewCost.print(dbgs());
4363 dbgs() << ".\n Regs:";
4364 for (const SCEV *S : NewRegs)
4365 dbgs() << ' ' << *S;
4368 SolutionCost = NewCost;
4369 Solution = Workspace;
4371 Workspace.pop_back();
4376 /// Solve - Choose one formula from each use. Return the results in the given
4377 /// Solution vector.
4378 void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const {
4379 SmallVector<const Formula *, 8> Workspace;
4381 SolutionCost.Lose();
4383 SmallPtrSet<const SCEV *, 16> CurRegs;
4384 DenseSet<const SCEV *> VisitedRegs;
4385 Workspace.reserve(Uses.size());
4387 // SolveRecurse does all the work.
4388 SolveRecurse(Solution, SolutionCost, Workspace, CurCost,
4389 CurRegs, VisitedRegs);
4390 if (Solution.empty()) {
4391 DEBUG(dbgs() << "\nNo Satisfactory Solution\n");
4395 // Ok, we've now made all our decisions.
4396 DEBUG(dbgs() << "\n"
4397 "The chosen solution requires "; SolutionCost.print(dbgs());
4399 for (size_t i = 0, e = Uses.size(); i != e; ++i) {
4401 Uses[i].print(dbgs());
4404 Solution[i]->print(dbgs());
4408 assert(Solution.size() == Uses.size() && "Malformed solution!");
4411 /// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up
4412 /// the dominator tree far as we can go while still being dominated by the
4413 /// input positions. This helps canonicalize the insert position, which
4414 /// encourages sharing.
4415 BasicBlock::iterator
4416 LSRInstance::HoistInsertPosition(BasicBlock::iterator IP,
4417 const SmallVectorImpl<Instruction *> &Inputs)
4420 const Loop *IPLoop = LI.getLoopFor(IP->getParent());
4421 unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0;
4424 for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) {
4425 if (!Rung) return IP;
4426 Rung = Rung->getIDom();
4427 if (!Rung) return IP;
4428 IDom = Rung->getBlock();
4430 // Don't climb into a loop though.
4431 const Loop *IDomLoop = LI.getLoopFor(IDom);
4432 unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0;
4433 if (IDomDepth <= IPLoopDepth &&
4434 (IDomDepth != IPLoopDepth || IDomLoop == IPLoop))
4438 bool AllDominate = true;
4439 Instruction *BetterPos = nullptr;
4440 Instruction *Tentative = IDom->getTerminator();
4441 for (Instruction *Inst : Inputs) {
4442 if (Inst == Tentative || !DT.dominates(Inst, Tentative)) {
4443 AllDominate = false;
4446 // Attempt to find an insert position in the middle of the block,
4447 // instead of at the end, so that it can be used for other expansions.
4448 if (IDom == Inst->getParent() &&
4449 (!BetterPos || !DT.dominates(Inst, BetterPos)))
4450 BetterPos = std::next(BasicBlock::iterator(Inst));
4463 /// AdjustInsertPositionForExpand - Determine an input position which will be
4464 /// dominated by the operands and which will dominate the result.
4465 BasicBlock::iterator
4466 LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP,
4469 SCEVExpander &Rewriter) const {
4470 // Collect some instructions which must be dominated by the
4471 // expanding replacement. These must be dominated by any operands that
4472 // will be required in the expansion.
4473 SmallVector<Instruction *, 4> Inputs;
4474 if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace))
4475 Inputs.push_back(I);
4476 if (LU.Kind == LSRUse::ICmpZero)
4477 if (Instruction *I =
4478 dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1)))
4479 Inputs.push_back(I);
4480 if (LF.PostIncLoops.count(L)) {
4481 if (LF.isUseFullyOutsideLoop(L))
4482 Inputs.push_back(L->getLoopLatch()->getTerminator());
4484 Inputs.push_back(IVIncInsertPos);
4486 // The expansion must also be dominated by the increment positions of any
4487 // loops it for which it is using post-inc mode.
4488 for (const Loop *PIL : LF.PostIncLoops) {
4489 if (PIL == L) continue;
4491 // Be dominated by the loop exit.
4492 SmallVector<BasicBlock *, 4> ExitingBlocks;
4493 PIL->getExitingBlocks(ExitingBlocks);
4494 if (!ExitingBlocks.empty()) {
4495 BasicBlock *BB = ExitingBlocks[0];
4496 for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i)
4497 BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]);
4498 Inputs.push_back(BB->getTerminator());
4502 assert(!isa<PHINode>(LowestIP) && !isa<LandingPadInst>(LowestIP)
4503 && !isa<DbgInfoIntrinsic>(LowestIP) &&
4504 "Insertion point must be a normal instruction");
4506 // Then, climb up the immediate dominator tree as far as we can go while
4507 // still being dominated by the input positions.
4508 BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs);
4510 // Don't insert instructions before PHI nodes.
4511 while (isa<PHINode>(IP)) ++IP;
4513 // Ignore landingpad instructions.
4514 while (isa<LandingPadInst>(IP)) ++IP;
4516 // Ignore debug intrinsics.
4517 while (isa<DbgInfoIntrinsic>(IP)) ++IP;
4519 // Set IP below instructions recently inserted by SCEVExpander. This keeps the
4520 // IP consistent across expansions and allows the previously inserted
4521 // instructions to be reused by subsequent expansion.
4522 while (Rewriter.isInsertedInstruction(IP) && IP != LowestIP) ++IP;
4527 /// Expand - Emit instructions for the leading candidate expression for this
4528 /// LSRUse (this is called "expanding").
4529 Value *LSRInstance::Expand(const LSRFixup &LF,
4531 BasicBlock::iterator IP,
4532 SCEVExpander &Rewriter,
4533 SmallVectorImpl<WeakVH> &DeadInsts) const {
4534 const LSRUse &LU = Uses[LF.LUIdx];
4535 if (LU.RigidFormula)
4536 return LF.OperandValToReplace;
4538 // Determine an input position which will be dominated by the operands and
4539 // which will dominate the result.
4540 IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter);
4542 // Inform the Rewriter if we have a post-increment use, so that it can
4543 // perform an advantageous expansion.
4544 Rewriter.setPostInc(LF.PostIncLoops);
4546 // This is the type that the user actually needs.
4547 Type *OpTy = LF.OperandValToReplace->getType();
4548 // This will be the type that we'll initially expand to.
4549 Type *Ty = F.getType();
4551 // No type known; just expand directly to the ultimate type.
4553 else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy))
4554 // Expand directly to the ultimate type if it's the right size.
4556 // This is the type to do integer arithmetic in.
4557 Type *IntTy = SE.getEffectiveSCEVType(Ty);
4559 // Build up a list of operands to add together to form the full base.
4560 SmallVector<const SCEV *, 8> Ops;
4562 // Expand the BaseRegs portion.
4563 for (const SCEV *Reg : F.BaseRegs) {
4564 assert(!Reg->isZero() && "Zero allocated in a base register!");
4566 // If we're expanding for a post-inc user, make the post-inc adjustment.
4567 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4568 const SCEV *ExtendedReg =
4569 F.ZeroExtendBaseReg ? SE.getZeroExtendExpr(Reg, F.ZeroExtendType) : Reg;
4571 const SCEV *PostIncReg =
4572 TransformForPostIncUse(Denormalize, ExtendedReg, LF.UserInst,
4573 LF.OperandValToReplace, Loops, SE, DT);
4574 if (PostIncReg == ExtendedReg) {
4575 Value *Expanded = Rewriter.expandCodeFor(Reg, nullptr, IP);
4576 if (F.ZeroExtendBaseReg)
4577 Expanded = new ZExtInst(Expanded, F.ZeroExtendType, "", IP);
4578 Ops.push_back(SE.getUnknown(Expanded));
4581 SE.getUnknown(Rewriter.expandCodeFor(PostIncReg, nullptr, IP)));
4585 // Note on post-inc uses and zero extends -- since the no-wrap behavior for
4586 // the post-inc SCEV can be different from the no-wrap behavior of the pre-inc
4587 // SCEV, if a post-inc transform is required we do the zero extension on the
4588 // pre-inc expression before doing the post-inc transform.
4590 // Expand the ScaledReg portion.
4591 Value *ICmpScaledV = nullptr;
4593 const SCEV *ScaledS = F.ScaledReg;
4595 // If we're expanding for a post-inc user, make the post-inc adjustment.
4596 PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops);
4597 const SCEV *ExtendedScaleS =
4598 F.ZeroExtendScaledReg ? SE.getZeroExtendExpr(ScaledS, F.ZeroExtendType)
4600 const SCEV *PostIncScaleS =
4601 TransformForPostIncUse(Denormalize, ExtendedScaleS, LF.UserInst,
4602 LF.OperandValToReplace, Loops, SE, DT);
4604 if (LU.Kind == LSRUse::ICmpZero) {
4605 // Expand ScaleReg as if it was part of the base regs.
4606 Value *Expanded = nullptr;
4607 if (PostIncScaleS == ExtendedScaleS) {
4608 Expanded = Rewriter.expandCodeFor(ScaledS, nullptr, IP);
4609 if (F.ZeroExtendScaledReg)
4610 Expanded = new ZExtInst(Expanded, F.ZeroExtendType, "", IP);
4612 Expanded = Rewriter.expandCodeFor(PostIncScaleS, nullptr, IP);
4616 Ops.push_back(SE.getUnknown(Expanded));
4618 // An interesting way of "folding" with an icmp is to use a negated
4619 // scale, which we'll implement by inserting it into the other operand
4621 assert(F.Scale == -1 &&
4622 "The only scale supported by ICmpZero uses is -1!");
4623 ICmpScaledV = Expanded;
4626 // Otherwise just expand the scaled register and an explicit scale,
4627 // which is expected to be matched as part of the address.
4629 // Flush the operand list to suppress SCEVExpander hoisting address modes.
4630 // Unless the addressing mode will not be folded.
4631 if (!Ops.empty() && LU.Kind == LSRUse::Address &&
4632 isAMCompletelyFolded(TTI, LU, F)) {
4633 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4635 Ops.push_back(SE.getUnknown(FullV));
4638 Value *Expanded = nullptr;
4639 if (PostIncScaleS == ExtendedScaleS) {
4640 Expanded = Rewriter.expandCodeFor(ScaledS, nullptr, IP);
4641 if (F.ZeroExtendScaledReg)
4642 Expanded = new ZExtInst(Expanded, F.ZeroExtendType, "", IP);
4644 Expanded = Rewriter.expandCodeFor(PostIncScaleS, nullptr, IP);
4647 ScaledS = SE.getUnknown(Expanded);
4650 SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale));
4651 Ops.push_back(ScaledS);
4655 // Expand the GV portion.
4657 // Flush the operand list to suppress SCEVExpander hoisting.
4659 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4661 Ops.push_back(SE.getUnknown(FullV));
4663 Ops.push_back(SE.getUnknown(F.BaseGV));
4666 // Flush the operand list to suppress SCEVExpander hoisting of both folded and
4667 // unfolded offsets. LSR assumes they both live next to their uses.
4669 Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP);
4671 Ops.push_back(SE.getUnknown(FullV));
4674 // Expand the immediate portion.
4675 int64_t Offset = (uint64_t)F.BaseOffset + LF.Offset;
4677 if (LU.Kind == LSRUse::ICmpZero) {
4678 // The other interesting way of "folding" with an ICmpZero is to use a
4679 // negated immediate.
4681 ICmpScaledV = ConstantInt::get(IntTy, -(uint64_t)Offset);
4683 Ops.push_back(SE.getUnknown(ICmpScaledV));
4684 ICmpScaledV = ConstantInt::get(IntTy, Offset);
4687 // Just add the immediate values. These again are expected to be matched
4688 // as part of the address.
4689 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset)));
4693 // Expand the unfolded offset portion.
4694 int64_t UnfoldedOffset = F.UnfoldedOffset;
4695 if (UnfoldedOffset != 0) {
4696 // Just add the immediate values.
4697 Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy,
4701 // Emit instructions summing all the operands.
4702 const SCEV *FullS = Ops.empty() ?
4703 SE.getConstant(IntTy, 0) :
4705 Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP);
4707 // We're done expanding now, so reset the rewriter.
4708 Rewriter.clearPostInc();
4710 // An ICmpZero Formula represents an ICmp which we're handling as a
4711 // comparison against zero. Now that we've expanded an expression for that
4712 // form, update the ICmp's other operand.
4713 if (LU.Kind == LSRUse::ICmpZero) {
4714 ICmpInst *CI = cast<ICmpInst>(LF.UserInst);
4715 DeadInsts.emplace_back(CI->getOperand(1));
4716 assert(!F.BaseGV && "ICmp does not support folding a global value and "
4717 "a scale at the same time!");
4718 if (F.Scale == -1) {
4719 if (ICmpScaledV->getType() != OpTy) {
4721 CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false,
4723 ICmpScaledV, OpTy, "tmp", CI);
4726 CI->setOperand(1, ICmpScaledV);
4728 // A scale of 1 means that the scale has been expanded as part of the
4730 assert((F.Scale == 0 || F.Scale == 1) &&
4731 "ICmp does not support folding a global value and "
4732 "a scale at the same time!");
4733 Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy),
4735 if (C->getType() != OpTy)
4736 C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false,
4740 CI->setOperand(1, C);
4747 /// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use
4748 /// of their operands effectively happens in their predecessor blocks, so the
4749 /// expression may need to be expanded in multiple places.
4750 void LSRInstance::RewriteForPHI(PHINode *PN,
4753 SCEVExpander &Rewriter,
4754 SmallVectorImpl<WeakVH> &DeadInsts,
4756 DenseMap<BasicBlock *, Value *> Inserted;
4757 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
4758 if (PN->getIncomingValue(i) == LF.OperandValToReplace) {
4759 BasicBlock *BB = PN->getIncomingBlock(i);
4761 // If this is a critical edge, split the edge so that we do not insert
4762 // the code on all predecessor/successor paths. We do this unless this
4763 // is the canonical backedge for this loop, which complicates post-inc
4765 if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 &&
4766 !isa<IndirectBrInst>(BB->getTerminator())) {
4767 BasicBlock *Parent = PN->getParent();
4768 Loop *PNLoop = LI.getLoopFor(Parent);
4769 if (!PNLoop || Parent != PNLoop->getHeader()) {
4770 // Split the critical edge.
4771 BasicBlock *NewBB = nullptr;
4772 if (!Parent->isLandingPad()) {
4773 NewBB = SplitCriticalEdge(BB, Parent,
4774 CriticalEdgeSplittingOptions(&DT, &LI)
4775 .setMergeIdenticalEdges()
4776 .setDontDeleteUselessPHIs());
4778 SmallVector<BasicBlock*, 2> NewBBs;
4779 SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI);
4782 // If NewBB==NULL, then SplitCriticalEdge refused to split because all
4783 // phi predecessors are identical. The simple thing to do is skip
4784 // splitting in this case rather than complicate the API.
4786 // If PN is outside of the loop and BB is in the loop, we want to
4787 // move the block to be immediately before the PHI block, not
4788 // immediately after BB.
4789 if (L->contains(BB) && !L->contains(PN))
4790 NewBB->moveBefore(PN->getParent());
4792 // Splitting the edge can reduce the number of PHI entries we have.
4793 e = PN->getNumIncomingValues();
4795 i = PN->getBasicBlockIndex(BB);
4800 std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair =
4801 Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr)));
4803 PN->setIncomingValue(i, Pair.first->second);
4805 Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts);
4807 // If this is reuse-by-noop-cast, insert the noop cast.
4808 Type *OpTy = LF.OperandValToReplace->getType();
4809 if (FullV->getType() != OpTy)
4811 CastInst::Create(CastInst::getCastOpcode(FullV, false,
4813 FullV, LF.OperandValToReplace->getType(),
4814 "tmp", BB->getTerminator());
4816 PN->setIncomingValue(i, FullV);
4817 Pair.first->second = FullV;
4822 /// Rewrite - Emit instructions for the leading candidate expression for this
4823 /// LSRUse (this is called "expanding"), and update the UserInst to reference
4824 /// the newly expanded value.
4825 void LSRInstance::Rewrite(const LSRFixup &LF,
4827 SCEVExpander &Rewriter,
4828 SmallVectorImpl<WeakVH> &DeadInsts,
4830 // First, find an insertion point that dominates UserInst. For PHI nodes,
4831 // find the nearest block which dominates all the relevant uses.
4832 if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) {
4833 RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P);
4835 Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts);
4837 // If this is reuse-by-noop-cast, insert the noop cast.
4838 Type *OpTy = LF.OperandValToReplace->getType();
4839 if (FullV->getType() != OpTy) {
4841 CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false),
4842 FullV, OpTy, "tmp", LF.UserInst);
4846 // Update the user. ICmpZero is handled specially here (for now) because
4847 // Expand may have updated one of the operands of the icmp already, and
4848 // its new value may happen to be equal to LF.OperandValToReplace, in
4849 // which case doing replaceUsesOfWith leads to replacing both operands
4850 // with the same value. TODO: Reorganize this.
4851 if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero)
4852 LF.UserInst->setOperand(0, FullV);
4854 LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV);
4857 DeadInsts.emplace_back(LF.OperandValToReplace);
4860 /// ImplementSolution - Rewrite all the fixup locations with new values,
4861 /// following the chosen solution.
4863 LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution,
4865 // Keep track of instructions we may have made dead, so that
4866 // we can remove them after we are done working.
4867 SmallVector<WeakVH, 16> DeadInsts;
4869 SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(),
4872 Rewriter.setDebugType(DEBUG_TYPE);
4874 Rewriter.disableCanonicalMode();
4875 Rewriter.enableLSRMode();
4876 Rewriter.setIVIncInsertPos(L, IVIncInsertPos);
4878 // Mark phi nodes that terminate chains so the expander tries to reuse them.
4879 for (const IVChain &Chain : IVChainVec) {
4880 if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst()))
4881 Rewriter.setChainedPhi(PN);
4884 // Expand the new value definitions and update the users.
4885 for (const LSRFixup &Fixup : Fixups) {
4886 Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P);
4891 for (const IVChain &Chain : IVChainVec) {
4892 GenerateIVChain(Chain, Rewriter, DeadInsts);
4895 // Clean up after ourselves. This must be done before deleting any
4899 Changed |= DeleteTriviallyDeadInstructions(DeadInsts);
4902 LSRInstance::LSRInstance(Loop *L, Pass *P)
4903 : IU(P->getAnalysis<IVUsers>()), SE(P->getAnalysis<ScalarEvolution>()),
4904 DT(P->getAnalysis<DominatorTreeWrapperPass>().getDomTree()),
4905 LI(P->getAnalysis<LoopInfoWrapperPass>().getLoopInfo()),
4906 TTI(P->getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
4907 *L->getHeader()->getParent())),
4908 L(L), Changed(false), IVIncInsertPos(nullptr) {
4909 // If LoopSimplify form is not available, stay out of trouble.
4910 if (!L->isLoopSimplifyForm())
4913 // If there's no interesting work to be done, bail early.
4914 if (IU.empty()) return;
4916 // If there's too much analysis to be done, bail early. We won't be able to
4917 // model the problem anyway.
4918 unsigned NumUsers = 0;
4919 for (const IVStrideUse &U : IU) {
4920 if (++NumUsers > MaxIVUsers) {
4922 DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << U << "\n");
4928 // All dominating loops must have preheaders, or SCEVExpander may not be able
4929 // to materialize an AddRecExpr whose Start is an outer AddRecExpr.
4931 // IVUsers analysis should only create users that are dominated by simple loop
4932 // headers. Since this loop should dominate all of its users, its user list
4933 // should be empty if this loop itself is not within a simple loop nest.
4934 for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader());
4935 Rung; Rung = Rung->getIDom()) {
4936 BasicBlock *BB = Rung->getBlock();
4937 const Loop *DomLoop = LI.getLoopFor(BB);
4938 if (DomLoop && DomLoop->getHeader() == BB) {
4939 assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest");
4944 DEBUG(dbgs() << "\nLSR on loop ";
4945 L->getHeader()->printAsOperand(dbgs(), /*PrintType=*/false);
4948 // First, perform some low-level loop optimizations.
4950 OptimizeLoopTermCond();
4952 // If loop preparation eliminates all interesting IV users, bail.
4953 if (IU.empty()) return;
4955 // Skip nested loops until we can model them better with formulae.
4957 DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n");
4961 // Start collecting data and preparing for the solver.
4963 CollectInterestingTypesAndFactors();
4964 CollectFixupsAndInitialFormulae();
4965 CollectLoopInvariantFixupsAndFormulae();
4967 assert(!Uses.empty() && "IVUsers reported at least one use");
4968 DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n";
4969 print_uses(dbgs()));
4971 // Now use the reuse data to generate a bunch of interesting ways
4972 // to formulate the values needed for the uses.
4973 GenerateAllReuseFormulae();
4975 FilterOutUndesirableDedicatedRegisters();
4976 NarrowSearchSpaceUsingHeuristics();
4978 SmallVector<const Formula *, 8> Solution;
4981 // Release memory that is no longer needed.
4986 if (Solution.empty())
4990 // Formulae should be legal.
4991 for (const LSRUse &LU : Uses) {
4992 for (const Formula &F : LU.Formulae)
4993 assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy,
4994 F) && "Illegal formula generated!");
4998 // Now that we've decided what we want, make it so.
4999 ImplementSolution(Solution, P);
5002 void LSRInstance::print_factors_and_types(raw_ostream &OS) const {
5003 if (Factors.empty() && Types.empty()) return;
5005 OS << "LSR has identified the following interesting factors and types: ";
5008 for (int64_t Factor : Factors) {
5009 if (!First) OS << ", ";
5011 OS << '*' << Factor;
5014 for (Type *Ty : Types) {
5015 if (!First) OS << ", ";
5017 OS << '(' << *Ty << ')';
5022 void LSRInstance::print_fixups(raw_ostream &OS) const {
5023 OS << "LSR is examining the following fixup sites:\n";
5024 for (const LSRFixup &LF : Fixups) {
5031 void LSRInstance::print_uses(raw_ostream &OS) const {
5032 OS << "LSR is examining the following uses:\n";
5033 for (const LSRUse &LU : Uses) {
5037 for (const Formula &F : LU.Formulae) {
5045 void LSRInstance::print(raw_ostream &OS) const {
5046 print_factors_and_types(OS);
5051 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
5052 void LSRInstance::dump() const {
5053 print(errs()); errs() << '\n';
5059 class LoopStrengthReduce : public LoopPass {
5061 static char ID; // Pass ID, replacement for typeid
5062 LoopStrengthReduce();
5065 bool runOnLoop(Loop *L, LPPassManager &LPM) override;
5066 void getAnalysisUsage(AnalysisUsage &AU) const override;
5071 char LoopStrengthReduce::ID = 0;
5072 INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce",
5073 "Loop Strength Reduction", false, false)
5074 INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass)
5075 INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
5076 INITIALIZE_PASS_DEPENDENCY(ScalarEvolution)
5077 INITIALIZE_PASS_DEPENDENCY(IVUsers)
5078 INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass)
5079 INITIALIZE_PASS_DEPENDENCY(LoopSimplify)
5080 INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce",
5081 "Loop Strength Reduction", false, false)
5084 Pass *llvm::createLoopStrengthReducePass() {
5085 return new LoopStrengthReduce();
5088 LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) {
5089 initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry());
5092 void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const {
5093 // We split critical edges, so we change the CFG. However, we do update
5094 // many analyses if they are around.
5095 AU.addPreservedID(LoopSimplifyID);
5097 AU.addRequired<LoopInfoWrapperPass>();
5098 AU.addPreserved<LoopInfoWrapperPass>();
5099 AU.addRequiredID(LoopSimplifyID);
5100 AU.addRequired<DominatorTreeWrapperPass>();
5101 AU.addPreserved<DominatorTreeWrapperPass>();
5102 AU.addRequired<ScalarEvolution>();
5103 AU.addPreserved<ScalarEvolution>();
5104 // Requiring LoopSimplify a second time here prevents IVUsers from running
5105 // twice, since LoopSimplify was invalidated by running ScalarEvolution.
5106 AU.addRequiredID(LoopSimplifyID);
5107 AU.addRequired<IVUsers>();
5108 AU.addPreserved<IVUsers>();
5109 AU.addRequired<TargetTransformInfoWrapperPass>();
5112 bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) {
5113 if (skipOptnoneFunction(L))
5116 bool Changed = false;
5118 // Run the main LSR transformation.
5119 Changed |= LSRInstance(L, this).getChanged();
5121 // Remove any extra phis created by processing inner loops.
5122 Changed |= DeleteDeadPHIs(L->getHeader());
5123 if (EnablePhiElim && L->isLoopSimplifyForm()) {
5124 SmallVector<WeakVH, 16> DeadInsts;
5125 const DataLayout &DL = L->getHeader()->getModule()->getDataLayout();
5126 SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), DL, "lsr");
5128 Rewriter.setDebugType(DEBUG_TYPE);
5130 unsigned numFolded = Rewriter.replaceCongruentIVs(
5131 L, &getAnalysis<DominatorTreeWrapperPass>().getDomTree(), DeadInsts,
5132 &getAnalysis<TargetTransformInfoWrapperPass>().getTTI(
5133 *L->getHeader()->getParent()));
5136 DeleteTriviallyDeadInstructions(DeadInsts);
5137 DeleteDeadPHIs(L->getHeader());