| //===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // This transformation analyzes and transforms the induction variables (and |
| // computations derived from them) into forms suitable for efficient execution |
| // on the target. |
| // |
| // This pass performs a strength reduction on array references inside loops that |
| // have as one or more of their components the loop induction variable, it |
| // rewrites expressions to take advantage of scaled-index addressing modes |
| // available on the target, and it performs a variety of other optimizations |
| // related to loop induction variables. |
| // |
| // Terminology note: this code has a lot of handling for "post-increment" or |
| // "post-inc" users. This is not talking about post-increment addressing modes; |
| // it is instead talking about code like this: |
| // |
| // %i = phi [ 0, %entry ], [ %i.next, %latch ] |
| // ... |
| // %i.next = add %i, 1 |
| // %c = icmp eq %i.next, %n |
| // |
| // The SCEV for %i is {0,+,1}<%L>. The SCEV for %i.next is {1,+,1}<%L>, however |
| // it's useful to think about these as the same register, with some uses using |
| // the value of the register before the add and some using // it after. In this |
| // example, the icmp is a post-increment user, since it uses %i.next, which is |
| // the value of the induction variable after the increment. The other common |
| // case of post-increment users is users outside the loop. |
| // |
| // TODO: More sophistication in the way Formulae are generated and filtered. |
| // |
| // TODO: Handle multiple loops at a time. |
| // |
| // TODO: Should TargetLowering::AddrMode::BaseGV be changed to a ConstantExpr |
| // instead of a GlobalValue? |
| // |
| // TODO: When truncation is free, truncate ICmp users' operands to make it a |
| // smaller encoding (on x86 at least). |
| // |
| // TODO: When a negated register is used by an add (such as in a list of |
| // multiple base registers, or as the increment expression in an addrec), |
| // we may not actually need both reg and (-1 * reg) in registers; the |
| // negation can be implemented by using a sub instead of an add. The |
| // lack of support for taking this into consideration when making |
| // register pressure decisions is partly worked around by the "Special" |
| // use kind. |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #define DEBUG_TYPE "loop-reduce" |
| #include "llvm/Transforms/Scalar.h" |
| #include "llvm/Constants.h" |
| #include "llvm/Instructions.h" |
| #include "llvm/IntrinsicInst.h" |
| #include "llvm/DerivedTypes.h" |
| #include "llvm/Analysis/IVUsers.h" |
| #include "llvm/Analysis/Dominators.h" |
| #include "llvm/Analysis/LoopPass.h" |
| #include "llvm/Analysis/ScalarEvolutionExpander.h" |
| #include "llvm/Transforms/Utils/BasicBlockUtils.h" |
| #include "llvm/Transforms/Utils/Local.h" |
| #include "llvm/ADT/SmallBitVector.h" |
| #include "llvm/ADT/SetVector.h" |
| #include "llvm/ADT/DenseSet.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/ValueHandle.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/Target/TargetLowering.h" |
| #include <algorithm> |
| using namespace llvm; |
| |
| namespace { |
| |
| /// RegSortData - This class holds data which is used to order reuse candidates. |
| class RegSortData { |
| public: |
| /// UsedByIndices - This represents the set of LSRUse indices which reference |
| /// a particular register. |
| SmallBitVector UsedByIndices; |
| |
| RegSortData() {} |
| |
| void print(raw_ostream &OS) const; |
| void dump() const; |
| }; |
| |
| } |
| |
| void RegSortData::print(raw_ostream &OS) const { |
| OS << "[NumUses=" << UsedByIndices.count() << ']'; |
| } |
| |
| void RegSortData::dump() const { |
| print(errs()); errs() << '\n'; |
| } |
| |
| namespace { |
| |
| /// RegUseTracker - Map register candidates to information about how they are |
| /// used. |
| class RegUseTracker { |
| typedef DenseMap<const SCEV *, RegSortData> RegUsesTy; |
| |
| RegUsesTy RegUses; |
| SmallVector<const SCEV *, 16> RegSequence; |
| |
| public: |
| void CountRegister(const SCEV *Reg, size_t LUIdx); |
| |
| bool isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const; |
| |
| const SmallBitVector &getUsedByIndices(const SCEV *Reg) const; |
| |
| void clear(); |
| |
| typedef SmallVectorImpl<const SCEV *>::iterator iterator; |
| typedef SmallVectorImpl<const SCEV *>::const_iterator const_iterator; |
| iterator begin() { return RegSequence.begin(); } |
| iterator end() { return RegSequence.end(); } |
| const_iterator begin() const { return RegSequence.begin(); } |
| const_iterator end() const { return RegSequence.end(); } |
| }; |
| |
| } |
| |
| void |
| RegUseTracker::CountRegister(const SCEV *Reg, size_t LUIdx) { |
| std::pair<RegUsesTy::iterator, bool> Pair = |
| RegUses.insert(std::make_pair(Reg, RegSortData())); |
| RegSortData &RSD = Pair.first->second; |
| if (Pair.second) |
| RegSequence.push_back(Reg); |
| RSD.UsedByIndices.resize(std::max(RSD.UsedByIndices.size(), LUIdx + 1)); |
| RSD.UsedByIndices.set(LUIdx); |
| } |
| |
| bool |
| RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const { |
| if (!RegUses.count(Reg)) return false; |
| const SmallBitVector &UsedByIndices = |
| RegUses.find(Reg)->second.UsedByIndices; |
| int i = UsedByIndices.find_first(); |
| if (i == -1) return false; |
| if ((size_t)i != LUIdx) return true; |
| return UsedByIndices.find_next(i) != -1; |
| } |
| |
| const SmallBitVector &RegUseTracker::getUsedByIndices(const SCEV *Reg) const { |
| RegUsesTy::const_iterator I = RegUses.find(Reg); |
| assert(I != RegUses.end() && "Unknown register!"); |
| return I->second.UsedByIndices; |
| } |
| |
| void RegUseTracker::clear() { |
| RegUses.clear(); |
| RegSequence.clear(); |
| } |
| |
| namespace { |
| |
| /// Formula - This class holds information that describes a formula for |
| /// computing satisfying a use. It may include broken-out immediates and scaled |
| /// registers. |
| struct Formula { |
| /// AM - This is used to represent complex addressing, as well as other kinds |
| /// of interesting uses. |
| TargetLowering::AddrMode AM; |
| |
| /// BaseRegs - The list of "base" registers for this use. When this is |
| /// non-empty, AM.HasBaseReg should be set to true. |
| SmallVector<const SCEV *, 2> BaseRegs; |
| |
| /// ScaledReg - The 'scaled' register for this use. This should be non-null |
| /// when AM.Scale is not zero. |
| const SCEV *ScaledReg; |
| |
| Formula() : ScaledReg(0) {} |
| |
| void InitialMatch(const SCEV *S, Loop *L, |
| ScalarEvolution &SE, DominatorTree &DT); |
| |
| unsigned getNumRegs() const; |
| const Type *getType() const; |
| |
| bool referencesReg(const SCEV *S) const; |
| bool hasRegsUsedByUsesOtherThan(size_t LUIdx, |
| const RegUseTracker &RegUses) const; |
| |
| void print(raw_ostream &OS) const; |
| void dump() const; |
| }; |
| |
| } |
| |
| /// DoInitialMatch - Recursion helper for InitialMatch. |
| static void DoInitialMatch(const SCEV *S, Loop *L, |
| SmallVectorImpl<const SCEV *> &Good, |
| SmallVectorImpl<const SCEV *> &Bad, |
| ScalarEvolution &SE, DominatorTree &DT) { |
| // Collect expressions which properly dominate the loop header. |
| if (S->properlyDominates(L->getHeader(), &DT)) { |
| Good.push_back(S); |
| return; |
| } |
| |
| // Look at add operands. |
| if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { |
| for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); |
| I != E; ++I) |
| DoInitialMatch(*I, L, Good, Bad, SE, DT); |
| return; |
| } |
| |
| // Look at addrec operands. |
| if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) |
| if (!AR->getStart()->isZero()) { |
| DoInitialMatch(AR->getStart(), L, Good, Bad, SE, DT); |
| DoInitialMatch(SE.getAddRecExpr(SE.getIntegerSCEV(0, AR->getType()), |
| AR->getStepRecurrence(SE), |
| AR->getLoop()), |
| L, Good, Bad, SE, DT); |
| return; |
| } |
| |
| // Handle a multiplication by -1 (negation) if it didn't fold. |
| if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) |
| if (Mul->getOperand(0)->isAllOnesValue()) { |
| SmallVector<const SCEV *, 4> Ops(Mul->op_begin()+1, Mul->op_end()); |
| const SCEV *NewMul = SE.getMulExpr(Ops); |
| |
| SmallVector<const SCEV *, 4> MyGood; |
| SmallVector<const SCEV *, 4> MyBad; |
| DoInitialMatch(NewMul, L, MyGood, MyBad, SE, DT); |
| const SCEV *NegOne = SE.getSCEV(ConstantInt::getAllOnesValue( |
| SE.getEffectiveSCEVType(NewMul->getType()))); |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = MyGood.begin(), |
| E = MyGood.end(); I != E; ++I) |
| Good.push_back(SE.getMulExpr(NegOne, *I)); |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = MyBad.begin(), |
| E = MyBad.end(); I != E; ++I) |
| Bad.push_back(SE.getMulExpr(NegOne, *I)); |
| return; |
| } |
| |
| // Ok, we can't do anything interesting. Just stuff the whole thing into a |
| // register and hope for the best. |
| Bad.push_back(S); |
| } |
| |
| /// InitialMatch - Incorporate loop-variant parts of S into this Formula, |
| /// attempting to keep all loop-invariant and loop-computable values in a |
| /// single base register. |
| void Formula::InitialMatch(const SCEV *S, Loop *L, |
| ScalarEvolution &SE, DominatorTree &DT) { |
| SmallVector<const SCEV *, 4> Good; |
| SmallVector<const SCEV *, 4> Bad; |
| DoInitialMatch(S, L, Good, Bad, SE, DT); |
| if (!Good.empty()) { |
| BaseRegs.push_back(SE.getAddExpr(Good)); |
| AM.HasBaseReg = true; |
| } |
| if (!Bad.empty()) { |
| BaseRegs.push_back(SE.getAddExpr(Bad)); |
| AM.HasBaseReg = true; |
| } |
| } |
| |
| /// getNumRegs - Return the total number of register operands used by this |
| /// formula. This does not include register uses implied by non-constant |
| /// addrec strides. |
| unsigned Formula::getNumRegs() const { |
| return !!ScaledReg + BaseRegs.size(); |
| } |
| |
| /// getType - Return the type of this formula, if it has one, or null |
| /// otherwise. This type is meaningless except for the bit size. |
| const Type *Formula::getType() const { |
| return !BaseRegs.empty() ? BaseRegs.front()->getType() : |
| ScaledReg ? ScaledReg->getType() : |
| AM.BaseGV ? AM.BaseGV->getType() : |
| 0; |
| } |
| |
| /// referencesReg - Test if this formula references the given register. |
| bool Formula::referencesReg(const SCEV *S) const { |
| return S == ScaledReg || |
| std::find(BaseRegs.begin(), BaseRegs.end(), S) != BaseRegs.end(); |
| } |
| |
| /// hasRegsUsedByUsesOtherThan - Test whether this formula uses registers |
| /// which are used by uses other than the use with the given index. |
| bool Formula::hasRegsUsedByUsesOtherThan(size_t LUIdx, |
| const RegUseTracker &RegUses) const { |
| if (ScaledReg) |
| if (RegUses.isRegUsedByUsesOtherThan(ScaledReg, LUIdx)) |
| return true; |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(), |
| E = BaseRegs.end(); I != E; ++I) |
| if (RegUses.isRegUsedByUsesOtherThan(*I, LUIdx)) |
| return true; |
| return false; |
| } |
| |
| void Formula::print(raw_ostream &OS) const { |
| bool First = true; |
| if (AM.BaseGV) { |
| if (!First) OS << " + "; else First = false; |
| WriteAsOperand(OS, AM.BaseGV, /*PrintType=*/false); |
| } |
| if (AM.BaseOffs != 0) { |
| if (!First) OS << " + "; else First = false; |
| OS << AM.BaseOffs; |
| } |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = BaseRegs.begin(), |
| E = BaseRegs.end(); I != E; ++I) { |
| if (!First) OS << " + "; else First = false; |
| OS << "reg(" << **I << ')'; |
| } |
| if (AM.Scale != 0) { |
| if (!First) OS << " + "; else First = false; |
| OS << AM.Scale << "*reg("; |
| if (ScaledReg) |
| OS << *ScaledReg; |
| else |
| OS << "<unknown>"; |
| OS << ')'; |
| } |
| } |
| |
| void Formula::dump() const { |
| print(errs()); errs() << '\n'; |
| } |
| |
| /// isAddRecSExtable - Return true if the given addrec can be sign-extended |
| /// without changing its value. |
| static bool isAddRecSExtable(const SCEVAddRecExpr *AR, ScalarEvolution &SE) { |
| const Type *WideTy = |
| IntegerType::get(SE.getContext(), |
| SE.getTypeSizeInBits(AR->getType()) + 1); |
| return isa<SCEVAddRecExpr>(SE.getSignExtendExpr(AR, WideTy)); |
| } |
| |
| /// isAddSExtable - Return true if the given add can be sign-extended |
| /// without changing its value. |
| static bool isAddSExtable(const SCEVAddExpr *A, ScalarEvolution &SE) { |
| const Type *WideTy = |
| IntegerType::get(SE.getContext(), |
| SE.getTypeSizeInBits(A->getType()) + 1); |
| return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy)); |
| } |
| |
| /// isMulSExtable - Return true if the given add can be sign-extended |
| /// without changing its value. |
| static bool isMulSExtable(const SCEVMulExpr *A, ScalarEvolution &SE) { |
| const Type *WideTy = |
| IntegerType::get(SE.getContext(), |
| SE.getTypeSizeInBits(A->getType()) + 1); |
| return isa<SCEVMulExpr>(SE.getSignExtendExpr(A, WideTy)); |
| } |
| |
| /// getExactSDiv - Return an expression for LHS /s RHS, if it can be determined |
| /// and if the remainder is known to be zero, or null otherwise. If |
| /// IgnoreSignificantBits is true, expressions like (X * Y) /s Y are simplified |
| /// to Y, ignoring that the multiplication may overflow, which is useful when |
| /// the result will be used in a context where the most significant bits are |
| /// ignored. |
| static const SCEV *getExactSDiv(const SCEV *LHS, const SCEV *RHS, |
| ScalarEvolution &SE, |
| bool IgnoreSignificantBits = false) { |
| // Handle the trivial case, which works for any SCEV type. |
| if (LHS == RHS) |
| return SE.getIntegerSCEV(1, LHS->getType()); |
| |
| // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do some |
| // folding. |
| if (RHS->isAllOnesValue()) |
| return SE.getMulExpr(LHS, RHS); |
| |
| // Check for a division of a constant by a constant. |
| if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) { |
| const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS); |
| if (!RC) |
| return 0; |
| if (C->getValue()->getValue().srem(RC->getValue()->getValue()) != 0) |
| return 0; |
| return SE.getConstant(C->getValue()->getValue() |
| .sdiv(RC->getValue()->getValue())); |
| } |
| |
| // Distribute the sdiv over addrec operands, if the addrec doesn't overflow. |
| if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(LHS)) { |
| if (IgnoreSignificantBits || isAddRecSExtable(AR, SE)) { |
| const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE, |
| IgnoreSignificantBits); |
| if (!Start) return 0; |
| const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE, |
| IgnoreSignificantBits); |
| if (!Step) return 0; |
| return SE.getAddRecExpr(Start, Step, AR->getLoop()); |
| } |
| } |
| |
| // Distribute the sdiv over add operands, if the add doesn't overflow. |
| if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(LHS)) { |
| if (IgnoreSignificantBits || isAddSExtable(Add, SE)) { |
| SmallVector<const SCEV *, 8> Ops; |
| for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); |
| I != E; ++I) { |
| const SCEV *Op = getExactSDiv(*I, RHS, SE, |
| IgnoreSignificantBits); |
| if (!Op) return 0; |
| Ops.push_back(Op); |
| } |
| return SE.getAddExpr(Ops); |
| } |
| } |
| |
| // Check for a multiply operand that we can pull RHS out of. |
| if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(LHS)) |
| if (IgnoreSignificantBits || isMulSExtable(Mul, SE)) { |
| SmallVector<const SCEV *, 4> Ops; |
| bool Found = false; |
| for (SCEVMulExpr::op_iterator I = Mul->op_begin(), E = Mul->op_end(); |
| I != E; ++I) { |
| if (!Found) |
| if (const SCEV *Q = getExactSDiv(*I, RHS, SE, |
| IgnoreSignificantBits)) { |
| Ops.push_back(Q); |
| Found = true; |
| continue; |
| } |
| Ops.push_back(*I); |
| } |
| return Found ? SE.getMulExpr(Ops) : 0; |
| } |
| |
| // Otherwise we don't know. |
| return 0; |
| } |
| |
| /// ExtractImmediate - If S involves the addition of a constant integer value, |
| /// return that integer value, and mutate S to point to a new SCEV with that |
| /// value excluded. |
| static int64_t ExtractImmediate(const SCEV *&S, ScalarEvolution &SE) { |
| if (const SCEVConstant *C = dyn_cast<SCEVConstant>(S)) { |
| if (C->getValue()->getValue().getMinSignedBits() <= 64) { |
| S = SE.getIntegerSCEV(0, C->getType()); |
| return C->getValue()->getSExtValue(); |
| } |
| } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { |
| SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); |
| int64_t Result = ExtractImmediate(NewOps.front(), SE); |
| S = SE.getAddExpr(NewOps); |
| return Result; |
| } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { |
| SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); |
| int64_t Result = ExtractImmediate(NewOps.front(), SE); |
| S = SE.getAddRecExpr(NewOps, AR->getLoop()); |
| return Result; |
| } |
| return 0; |
| } |
| |
| /// ExtractSymbol - If S involves the addition of a GlobalValue address, |
| /// return that symbol, and mutate S to point to a new SCEV with that |
| /// value excluded. |
| static GlobalValue *ExtractSymbol(const SCEV *&S, ScalarEvolution &SE) { |
| if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { |
| if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) { |
| S = SE.getIntegerSCEV(0, GV->getType()); |
| return GV; |
| } |
| } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { |
| SmallVector<const SCEV *, 8> NewOps(Add->op_begin(), Add->op_end()); |
| GlobalValue *Result = ExtractSymbol(NewOps.back(), SE); |
| S = SE.getAddExpr(NewOps); |
| return Result; |
| } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { |
| SmallVector<const SCEV *, 8> NewOps(AR->op_begin(), AR->op_end()); |
| GlobalValue *Result = ExtractSymbol(NewOps.front(), SE); |
| S = SE.getAddRecExpr(NewOps, AR->getLoop()); |
| return Result; |
| } |
| return 0; |
| } |
| |
| /// isAddressUse - Returns true if the specified instruction is using the |
| /// specified value as an address. |
| static bool isAddressUse(Instruction *Inst, Value *OperandVal) { |
| bool isAddress = isa<LoadInst>(Inst); |
| if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { |
| if (SI->getOperand(1) == OperandVal) |
| isAddress = true; |
| } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { |
| // Addressing modes can also be folded into prefetches and a variety |
| // of intrinsics. |
| switch (II->getIntrinsicID()) { |
| default: break; |
| case Intrinsic::prefetch: |
| case Intrinsic::x86_sse2_loadu_dq: |
| case Intrinsic::x86_sse2_loadu_pd: |
| case Intrinsic::x86_sse_loadu_ps: |
| case Intrinsic::x86_sse_storeu_ps: |
| case Intrinsic::x86_sse2_storeu_pd: |
| case Intrinsic::x86_sse2_storeu_dq: |
| case Intrinsic::x86_sse2_storel_dq: |
| if (II->getOperand(1) == OperandVal) |
| isAddress = true; |
| break; |
| } |
| } |
| return isAddress; |
| } |
| |
| /// getAccessType - Return the type of the memory being accessed. |
| static const Type *getAccessType(const Instruction *Inst) { |
| const Type *AccessTy = Inst->getType(); |
| if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) |
| AccessTy = SI->getOperand(0)->getType(); |
| else if (const IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { |
| // Addressing modes can also be folded into prefetches and a variety |
| // of intrinsics. |
| switch (II->getIntrinsicID()) { |
| default: break; |
| case Intrinsic::x86_sse_storeu_ps: |
| case Intrinsic::x86_sse2_storeu_pd: |
| case Intrinsic::x86_sse2_storeu_dq: |
| case Intrinsic::x86_sse2_storel_dq: |
| AccessTy = II->getOperand(1)->getType(); |
| break; |
| } |
| } |
| |
| // All pointers have the same requirements, so canonicalize them to an |
| // arbitrary pointer type to minimize variation. |
| if (const PointerType *PTy = dyn_cast<PointerType>(AccessTy)) |
| AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1), |
| PTy->getAddressSpace()); |
| |
| return AccessTy; |
| } |
| |
| /// DeleteTriviallyDeadInstructions - If any of the instructions is the |
| /// specified set are trivially dead, delete them and see if this makes any of |
| /// their operands subsequently dead. |
| static bool |
| DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakVH> &DeadInsts) { |
| bool Changed = false; |
| |
| while (!DeadInsts.empty()) { |
| Instruction *I = dyn_cast_or_null<Instruction>(DeadInsts.pop_back_val()); |
| |
| if (I == 0 || !isInstructionTriviallyDead(I)) |
| continue; |
| |
| for (User::op_iterator OI = I->op_begin(), E = I->op_end(); OI != E; ++OI) |
| if (Instruction *U = dyn_cast<Instruction>(*OI)) { |
| *OI = 0; |
| if (U->use_empty()) |
| DeadInsts.push_back(U); |
| } |
| |
| I->eraseFromParent(); |
| Changed = true; |
| } |
| |
| return Changed; |
| } |
| |
| namespace { |
| |
| /// Cost - This class is used to measure and compare candidate formulae. |
| class Cost { |
| /// TODO: Some of these could be merged. Also, a lexical ordering |
| /// isn't always optimal. |
| unsigned NumRegs; |
| unsigned AddRecCost; |
| unsigned NumIVMuls; |
| unsigned NumBaseAdds; |
| unsigned ImmCost; |
| unsigned SetupCost; |
| |
| public: |
| Cost() |
| : NumRegs(0), AddRecCost(0), NumIVMuls(0), NumBaseAdds(0), ImmCost(0), |
| SetupCost(0) {} |
| |
| unsigned getNumRegs() const { return NumRegs; } |
| |
| bool operator<(const Cost &Other) const; |
| |
| void Loose(); |
| |
| void RateFormula(const Formula &F, |
| SmallPtrSet<const SCEV *, 16> &Regs, |
| const DenseSet<const SCEV *> &VisitedRegs, |
| const Loop *L, |
| const SmallVectorImpl<int64_t> &Offsets, |
| ScalarEvolution &SE, DominatorTree &DT); |
| |
| void print(raw_ostream &OS) const; |
| void dump() const; |
| |
| private: |
| void RateRegister(const SCEV *Reg, |
| SmallPtrSet<const SCEV *, 16> &Regs, |
| const Loop *L, |
| ScalarEvolution &SE, DominatorTree &DT); |
| void RatePrimaryRegister(const SCEV *Reg, |
| SmallPtrSet<const SCEV *, 16> &Regs, |
| const Loop *L, |
| ScalarEvolution &SE, DominatorTree &DT); |
| }; |
| |
| } |
| |
| /// RateRegister - Tally up interesting quantities from the given register. |
| void Cost::RateRegister(const SCEV *Reg, |
| SmallPtrSet<const SCEV *, 16> &Regs, |
| const Loop *L, |
| ScalarEvolution &SE, DominatorTree &DT) { |
| if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) { |
| if (AR->getLoop() == L) |
| AddRecCost += 1; /// TODO: This should be a function of the stride. |
| |
| // If this is an addrec for a loop that's already been visited by LSR, |
| // don't second-guess its addrec phi nodes. LSR isn't currently smart |
| // enough to reason about more than one loop at a time. Consider these |
| // registers free and leave them alone. |
| else if (L->contains(AR->getLoop()) || |
| (!AR->getLoop()->contains(L) && |
| DT.dominates(L->getHeader(), AR->getLoop()->getHeader()))) { |
| for (BasicBlock::iterator I = AR->getLoop()->getHeader()->begin(); |
| PHINode *PN = dyn_cast<PHINode>(I); ++I) |
| if (SE.isSCEVable(PN->getType()) && |
| (SE.getEffectiveSCEVType(PN->getType()) == |
| SE.getEffectiveSCEVType(AR->getType())) && |
| SE.getSCEV(PN) == AR) |
| return; |
| |
| // If this isn't one of the addrecs that the loop already has, it |
| // would require a costly new phi and add. TODO: This isn't |
| // precisely modeled right now. |
| ++NumBaseAdds; |
| if (!Regs.count(AR->getStart())) |
| RateRegister(AR->getStart(), Regs, L, SE, DT); |
| } |
| |
| // Add the step value register, if it needs one. |
| // TODO: The non-affine case isn't precisely modeled here. |
| if (!AR->isAffine() || !isa<SCEVConstant>(AR->getOperand(1))) |
| if (!Regs.count(AR->getStart())) |
| RateRegister(AR->getOperand(1), Regs, L, SE, DT); |
| } |
| ++NumRegs; |
| |
| // Rough heuristic; favor registers which don't require extra setup |
| // instructions in the preheader. |
| if (!isa<SCEVUnknown>(Reg) && |
| !isa<SCEVConstant>(Reg) && |
| !(isa<SCEVAddRecExpr>(Reg) && |
| (isa<SCEVUnknown>(cast<SCEVAddRecExpr>(Reg)->getStart()) || |
| isa<SCEVConstant>(cast<SCEVAddRecExpr>(Reg)->getStart())))) |
| ++SetupCost; |
| } |
| |
| /// RatePrimaryRegister - Record this register in the set. If we haven't seen it |
| /// before, rate it. |
| void Cost::RatePrimaryRegister(const SCEV *Reg, |
| SmallPtrSet<const SCEV *, 16> &Regs, |
| const Loop *L, |
| ScalarEvolution &SE, DominatorTree &DT) { |
| if (Regs.insert(Reg)) |
| RateRegister(Reg, Regs, L, SE, DT); |
| } |
| |
| void Cost::RateFormula(const Formula &F, |
| SmallPtrSet<const SCEV *, 16> &Regs, |
| const DenseSet<const SCEV *> &VisitedRegs, |
| const Loop *L, |
| const SmallVectorImpl<int64_t> &Offsets, |
| ScalarEvolution &SE, DominatorTree &DT) { |
| // Tally up the registers. |
| if (const SCEV *ScaledReg = F.ScaledReg) { |
| if (VisitedRegs.count(ScaledReg)) { |
| Loose(); |
| return; |
| } |
| RatePrimaryRegister(ScaledReg, Regs, L, SE, DT); |
| } |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), |
| E = F.BaseRegs.end(); I != E; ++I) { |
| const SCEV *BaseReg = *I; |
| if (VisitedRegs.count(BaseReg)) { |
| Loose(); |
| return; |
| } |
| RatePrimaryRegister(BaseReg, Regs, L, SE, DT); |
| |
| NumIVMuls += isa<SCEVMulExpr>(BaseReg) && |
| BaseReg->hasComputableLoopEvolution(L); |
| } |
| |
| if (F.BaseRegs.size() > 1) |
| NumBaseAdds += F.BaseRegs.size() - 1; |
| |
| // Tally up the non-zero immediates. |
| for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(), |
| E = Offsets.end(); I != E; ++I) { |
| int64_t Offset = (uint64_t)*I + F.AM.BaseOffs; |
| if (F.AM.BaseGV) |
| ImmCost += 64; // Handle symbolic values conservatively. |
| // TODO: This should probably be the pointer size. |
| else if (Offset != 0) |
| ImmCost += APInt(64, Offset, true).getMinSignedBits(); |
| } |
| } |
| |
| /// Loose - Set this cost to a loosing value. |
| void Cost::Loose() { |
| NumRegs = ~0u; |
| AddRecCost = ~0u; |
| NumIVMuls = ~0u; |
| NumBaseAdds = ~0u; |
| ImmCost = ~0u; |
| SetupCost = ~0u; |
| } |
| |
| /// operator< - Choose the lower cost. |
| bool Cost::operator<(const Cost &Other) const { |
| if (NumRegs != Other.NumRegs) |
| return NumRegs < Other.NumRegs; |
| if (AddRecCost != Other.AddRecCost) |
| return AddRecCost < Other.AddRecCost; |
| if (NumIVMuls != Other.NumIVMuls) |
| return NumIVMuls < Other.NumIVMuls; |
| if (NumBaseAdds != Other.NumBaseAdds) |
| return NumBaseAdds < Other.NumBaseAdds; |
| if (ImmCost != Other.ImmCost) |
| return ImmCost < Other.ImmCost; |
| if (SetupCost != Other.SetupCost) |
| return SetupCost < Other.SetupCost; |
| return false; |
| } |
| |
| void Cost::print(raw_ostream &OS) const { |
| OS << NumRegs << " reg" << (NumRegs == 1 ? "" : "s"); |
| if (AddRecCost != 0) |
| OS << ", with addrec cost " << AddRecCost; |
| if (NumIVMuls != 0) |
| OS << ", plus " << NumIVMuls << " IV mul" << (NumIVMuls == 1 ? "" : "s"); |
| if (NumBaseAdds != 0) |
| OS << ", plus " << NumBaseAdds << " base add" |
| << (NumBaseAdds == 1 ? "" : "s"); |
| if (ImmCost != 0) |
| OS << ", plus " << ImmCost << " imm cost"; |
| if (SetupCost != 0) |
| OS << ", plus " << SetupCost << " setup cost"; |
| } |
| |
| void Cost::dump() const { |
| print(errs()); errs() << '\n'; |
| } |
| |
| namespace { |
| |
| /// LSRFixup - An operand value in an instruction which is to be replaced |
| /// with some equivalent, possibly strength-reduced, replacement. |
| struct LSRFixup { |
| /// UserInst - The instruction which will be updated. |
| Instruction *UserInst; |
| |
| /// OperandValToReplace - The operand of the instruction which will |
| /// be replaced. The operand may be used more than once; every instance |
| /// will be replaced. |
| Value *OperandValToReplace; |
| |
| /// PostIncLoop - If this user is to use the post-incremented value of an |
| /// induction variable, this variable is non-null and holds the loop |
| /// associated with the induction variable. |
| const Loop *PostIncLoop; |
| |
| /// LUIdx - The index of the LSRUse describing the expression which |
| /// this fixup needs, minus an offset (below). |
| size_t LUIdx; |
| |
| /// Offset - A constant offset to be added to the LSRUse expression. |
| /// This allows multiple fixups to share the same LSRUse with different |
| /// offsets, for example in an unrolled loop. |
| int64_t Offset; |
| |
| LSRFixup(); |
| |
| void print(raw_ostream &OS) const; |
| void dump() const; |
| }; |
| |
| } |
| |
| LSRFixup::LSRFixup() |
| : UserInst(0), OperandValToReplace(0), PostIncLoop(0), |
| LUIdx(~size_t(0)), Offset(0) {} |
| |
| void LSRFixup::print(raw_ostream &OS) const { |
| OS << "UserInst="; |
| // Store is common and interesting enough to be worth special-casing. |
| if (StoreInst *Store = dyn_cast<StoreInst>(UserInst)) { |
| OS << "store "; |
| WriteAsOperand(OS, Store->getOperand(0), /*PrintType=*/false); |
| } else if (UserInst->getType()->isVoidTy()) |
| OS << UserInst->getOpcodeName(); |
| else |
| WriteAsOperand(OS, UserInst, /*PrintType=*/false); |
| |
| OS << ", OperandValToReplace="; |
| WriteAsOperand(OS, OperandValToReplace, /*PrintType=*/false); |
| |
| if (PostIncLoop) { |
| OS << ", PostIncLoop="; |
| WriteAsOperand(OS, PostIncLoop->getHeader(), /*PrintType=*/false); |
| } |
| |
| if (LUIdx != ~size_t(0)) |
| OS << ", LUIdx=" << LUIdx; |
| |
| if (Offset != 0) |
| OS << ", Offset=" << Offset; |
| } |
| |
| void LSRFixup::dump() const { |
| print(errs()); errs() << '\n'; |
| } |
| |
| namespace { |
| |
| /// UniquifierDenseMapInfo - A DenseMapInfo implementation for holding |
| /// DenseMaps and DenseSets of sorted SmallVectors of const SCEV*. |
| struct UniquifierDenseMapInfo { |
| static SmallVector<const SCEV *, 2> getEmptyKey() { |
| SmallVector<const SCEV *, 2> V; |
| V.push_back(reinterpret_cast<const SCEV *>(-1)); |
| return V; |
| } |
| |
| static SmallVector<const SCEV *, 2> getTombstoneKey() { |
| SmallVector<const SCEV *, 2> V; |
| V.push_back(reinterpret_cast<const SCEV *>(-2)); |
| return V; |
| } |
| |
| static unsigned getHashValue(const SmallVector<const SCEV *, 2> &V) { |
| unsigned Result = 0; |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = V.begin(), |
| E = V.end(); I != E; ++I) |
| Result ^= DenseMapInfo<const SCEV *>::getHashValue(*I); |
| return Result; |
| } |
| |
| static bool isEqual(const SmallVector<const SCEV *, 2> &LHS, |
| const SmallVector<const SCEV *, 2> &RHS) { |
| return LHS == RHS; |
| } |
| }; |
| |
| /// LSRUse - This class holds the state that LSR keeps for each use in |
| /// IVUsers, as well as uses invented by LSR itself. It includes information |
| /// about what kinds of things can be folded into the user, information about |
| /// the user itself, and information about how the use may be satisfied. |
| /// TODO: Represent multiple users of the same expression in common? |
| class LSRUse { |
| DenseSet<SmallVector<const SCEV *, 2>, UniquifierDenseMapInfo> Uniquifier; |
| |
| public: |
| /// KindType - An enum for a kind of use, indicating what types of |
| /// scaled and immediate operands it might support. |
| enum KindType { |
| Basic, ///< A normal use, with no folding. |
| Special, ///< A special case of basic, allowing -1 scales. |
| Address, ///< An address use; folding according to TargetLowering |
| ICmpZero ///< An equality icmp with both operands folded into one. |
| // TODO: Add a generic icmp too? |
| }; |
| |
| KindType Kind; |
| const Type *AccessTy; |
| |
| SmallVector<int64_t, 8> Offsets; |
| int64_t MinOffset; |
| int64_t MaxOffset; |
| |
| /// AllFixupsOutsideLoop - This records whether all of the fixups using this |
| /// LSRUse are outside of the loop, in which case some special-case heuristics |
| /// may be used. |
| bool AllFixupsOutsideLoop; |
| |
| /// Formulae - A list of ways to build a value that can satisfy this user. |
| /// After the list is populated, one of these is selected heuristically and |
| /// used to formulate a replacement for OperandValToReplace in UserInst. |
| SmallVector<Formula, 12> Formulae; |
| |
| /// Regs - The set of register candidates used by all formulae in this LSRUse. |
| SmallPtrSet<const SCEV *, 4> Regs; |
| |
| LSRUse(KindType K, const Type *T) : Kind(K), AccessTy(T), |
| MinOffset(INT64_MAX), |
| MaxOffset(INT64_MIN), |
| AllFixupsOutsideLoop(true) {} |
| |
| bool InsertFormula(const Formula &F); |
| |
| void check() const; |
| |
| void print(raw_ostream &OS) const; |
| void dump() const; |
| }; |
| |
| /// InsertFormula - If the given formula has not yet been inserted, add it to |
| /// the list, and return true. Return false otherwise. |
| bool LSRUse::InsertFormula(const Formula &F) { |
| SmallVector<const SCEV *, 2> Key = F.BaseRegs; |
| if (F.ScaledReg) Key.push_back(F.ScaledReg); |
| // Unstable sort by host order ok, because this is only used for uniquifying. |
| std::sort(Key.begin(), Key.end()); |
| |
| if (!Uniquifier.insert(Key).second) |
| return false; |
| |
| // Using a register to hold the value of 0 is not profitable. |
| assert((!F.ScaledReg || !F.ScaledReg->isZero()) && |
| "Zero allocated in a scaled register!"); |
| #ifndef NDEBUG |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = |
| F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) |
| assert(!(*I)->isZero() && "Zero allocated in a base register!"); |
| #endif |
| |
| // Add the formula to the list. |
| Formulae.push_back(F); |
| |
| // Record registers now being used by this use. |
| if (F.ScaledReg) Regs.insert(F.ScaledReg); |
| Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); |
| |
| return true; |
| } |
| |
| void LSRUse::print(raw_ostream &OS) const { |
| OS << "LSR Use: Kind="; |
| switch (Kind) { |
| case Basic: OS << "Basic"; break; |
| case Special: OS << "Special"; break; |
| case ICmpZero: OS << "ICmpZero"; break; |
| case Address: |
| OS << "Address of "; |
| if (AccessTy->isPointerTy()) |
| OS << "pointer"; // the full pointer type could be really verbose |
| else |
| OS << *AccessTy; |
| } |
| |
| OS << ", Offsets={"; |
| for (SmallVectorImpl<int64_t>::const_iterator I = Offsets.begin(), |
| E = Offsets.end(); I != E; ++I) { |
| OS << *I; |
| if (next(I) != E) |
| OS << ','; |
| } |
| OS << '}'; |
| |
| if (AllFixupsOutsideLoop) |
| OS << ", all-fixups-outside-loop"; |
| } |
| |
| void LSRUse::dump() const { |
| print(errs()); errs() << '\n'; |
| } |
| |
| /// isLegalUse - Test whether the use described by AM is "legal", meaning it can |
| /// be completely folded into the user instruction at isel time. This includes |
| /// address-mode folding and special icmp tricks. |
| static bool isLegalUse(const TargetLowering::AddrMode &AM, |
| LSRUse::KindType Kind, const Type *AccessTy, |
| const TargetLowering *TLI) { |
| switch (Kind) { |
| case LSRUse::Address: |
| // If we have low-level target information, ask the target if it can |
| // completely fold this address. |
| if (TLI) return TLI->isLegalAddressingMode(AM, AccessTy); |
| |
| // Otherwise, just guess that reg+reg addressing is legal. |
| return !AM.BaseGV && AM.BaseOffs == 0 && AM.Scale <= 1; |
| |
| case LSRUse::ICmpZero: |
| // There's not even a target hook for querying whether it would be legal to |
| // fold a GV into an ICmp. |
| if (AM.BaseGV) |
| return false; |
| |
| // ICmp only has two operands; don't allow more than two non-trivial parts. |
| if (AM.Scale != 0 && AM.HasBaseReg && AM.BaseOffs != 0) |
| return false; |
| |
| // ICmp only supports no scale or a -1 scale, as we can "fold" a -1 scale by |
| // putting the scaled register in the other operand of the icmp. |
| if (AM.Scale != 0 && AM.Scale != -1) |
| return false; |
| |
| // If we have low-level target information, ask the target if it can fold an |
| // integer immediate on an icmp. |
| if (AM.BaseOffs != 0) { |
| if (TLI) return TLI->isLegalICmpImmediate(-AM.BaseOffs); |
| return false; |
| } |
| |
| return true; |
| |
| case LSRUse::Basic: |
| // Only handle single-register values. |
| return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0; |
| |
| case LSRUse::Special: |
| // Only handle -1 scales, or no scale. |
| return AM.Scale == 0 || AM.Scale == -1; |
| } |
| |
| return false; |
| } |
| |
| static bool isLegalUse(TargetLowering::AddrMode AM, |
| int64_t MinOffset, int64_t MaxOffset, |
| LSRUse::KindType Kind, const Type *AccessTy, |
| const TargetLowering *TLI) { |
| // Check for overflow. |
| if (((int64_t)((uint64_t)AM.BaseOffs + MinOffset) > AM.BaseOffs) != |
| (MinOffset > 0)) |
| return false; |
| AM.BaseOffs = (uint64_t)AM.BaseOffs + MinOffset; |
| if (isLegalUse(AM, Kind, AccessTy, TLI)) { |
| AM.BaseOffs = (uint64_t)AM.BaseOffs - MinOffset; |
| // Check for overflow. |
| if (((int64_t)((uint64_t)AM.BaseOffs + MaxOffset) > AM.BaseOffs) != |
| (MaxOffset > 0)) |
| return false; |
| AM.BaseOffs = (uint64_t)AM.BaseOffs + MaxOffset; |
| return isLegalUse(AM, Kind, AccessTy, TLI); |
| } |
| return false; |
| } |
| |
| static bool isAlwaysFoldable(int64_t BaseOffs, |
| GlobalValue *BaseGV, |
| bool HasBaseReg, |
| LSRUse::KindType Kind, const Type *AccessTy, |
| const TargetLowering *TLI) { |
| // Fast-path: zero is always foldable. |
| if (BaseOffs == 0 && !BaseGV) return true; |
| |
| // Conservatively, create an address with an immediate and a |
| // base and a scale. |
| TargetLowering::AddrMode AM; |
| AM.BaseOffs = BaseOffs; |
| AM.BaseGV = BaseGV; |
| AM.HasBaseReg = HasBaseReg; |
| AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1; |
| |
| return isLegalUse(AM, Kind, AccessTy, TLI); |
| } |
| |
| static bool isAlwaysFoldable(const SCEV *S, |
| int64_t MinOffset, int64_t MaxOffset, |
| bool HasBaseReg, |
| LSRUse::KindType Kind, const Type *AccessTy, |
| const TargetLowering *TLI, |
| ScalarEvolution &SE) { |
| // Fast-path: zero is always foldable. |
| if (S->isZero()) return true; |
| |
| // Conservatively, create an address with an immediate and a |
| // base and a scale. |
| int64_t BaseOffs = ExtractImmediate(S, SE); |
| GlobalValue *BaseGV = ExtractSymbol(S, SE); |
| |
| // If there's anything else involved, it's not foldable. |
| if (!S->isZero()) return false; |
| |
| // Fast-path: zero is always foldable. |
| if (BaseOffs == 0 && !BaseGV) return true; |
| |
| // Conservatively, create an address with an immediate and a |
| // base and a scale. |
| TargetLowering::AddrMode AM; |
| AM.BaseOffs = BaseOffs; |
| AM.BaseGV = BaseGV; |
| AM.HasBaseReg = HasBaseReg; |
| AM.Scale = Kind == LSRUse::ICmpZero ? -1 : 1; |
| |
| return isLegalUse(AM, MinOffset, MaxOffset, Kind, AccessTy, TLI); |
| } |
| |
| /// FormulaSorter - This class implements an ordering for formulae which sorts |
| /// the by their standalone cost. |
| class FormulaSorter { |
| /// These two sets are kept empty, so that we compute standalone costs. |
| DenseSet<const SCEV *> VisitedRegs; |
| SmallPtrSet<const SCEV *, 16> Regs; |
| Loop *L; |
| LSRUse *LU; |
| ScalarEvolution &SE; |
| DominatorTree &DT; |
| |
| public: |
| FormulaSorter(Loop *l, LSRUse &lu, ScalarEvolution &se, DominatorTree &dt) |
| : L(l), LU(&lu), SE(se), DT(dt) {} |
| |
| bool operator()(const Formula &A, const Formula &B) { |
| Cost CostA; |
| CostA.RateFormula(A, Regs, VisitedRegs, L, LU->Offsets, SE, DT); |
| Regs.clear(); |
| Cost CostB; |
| CostB.RateFormula(B, Regs, VisitedRegs, L, LU->Offsets, SE, DT); |
| Regs.clear(); |
| return CostA < CostB; |
| } |
| }; |
| |
| /// LSRInstance - This class holds state for the main loop strength reduction |
| /// logic. |
| class LSRInstance { |
| IVUsers &IU; |
| ScalarEvolution &SE; |
| DominatorTree &DT; |
| const TargetLowering *const TLI; |
| Loop *const L; |
| bool Changed; |
| |
| /// IVIncInsertPos - This is the insert position that the current loop's |
| /// induction variable increment should be placed. In simple loops, this is |
| /// the latch block's terminator. But in more complicated cases, this is a |
| /// position which will dominate all the in-loop post-increment users. |
| Instruction *IVIncInsertPos; |
| |
| /// Factors - Interesting factors between use strides. |
| SmallSetVector<int64_t, 8> Factors; |
| |
| /// Types - Interesting use types, to facilitate truncation reuse. |
| SmallSetVector<const Type *, 4> Types; |
| |
| /// Fixups - The list of operands which are to be replaced. |
| SmallVector<LSRFixup, 16> Fixups; |
| |
| /// Uses - The list of interesting uses. |
| SmallVector<LSRUse, 16> Uses; |
| |
| /// RegUses - Track which uses use which register candidates. |
| RegUseTracker RegUses; |
| |
| void OptimizeShadowIV(); |
| bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse); |
| ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse); |
| bool OptimizeLoopTermCond(); |
| |
| void CollectInterestingTypesAndFactors(); |
| void CollectFixupsAndInitialFormulae(); |
| |
| LSRFixup &getNewFixup() { |
| Fixups.push_back(LSRFixup()); |
| return Fixups.back(); |
| } |
| |
| // Support for sharing of LSRUses between LSRFixups. |
| typedef DenseMap<const SCEV *, size_t> UseMapTy; |
| UseMapTy UseMap; |
| |
| bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, |
| LSRUse::KindType Kind, const Type *AccessTy); |
| |
| std::pair<size_t, int64_t> getUse(const SCEV *&Expr, |
| LSRUse::KindType Kind, |
| const Type *AccessTy); |
| |
| public: |
| void InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); |
| void InsertSupplementalFormula(const SCEV *S, LSRUse &LU, size_t LUIdx); |
| void CountRegisters(const Formula &F, size_t LUIdx); |
| bool InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F); |
| |
| void CollectLoopInvariantFixupsAndFormulae(); |
| |
| void GenerateReassociations(LSRUse &LU, unsigned LUIdx, Formula Base, |
| unsigned Depth = 0); |
| void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base); |
| void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); |
| void GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); |
| void GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, Formula Base); |
| void GenerateScales(LSRUse &LU, unsigned LUIdx, Formula Base); |
| void GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base); |
| void GenerateCrossUseConstantOffsets(); |
| void GenerateAllReuseFormulae(); |
| |
| void FilterOutUndesirableDedicatedRegisters(); |
| void NarrowSearchSpaceUsingHeuristics(); |
| |
| void SolveRecurse(SmallVectorImpl<const Formula *> &Solution, |
| Cost &SolutionCost, |
| SmallVectorImpl<const Formula *> &Workspace, |
| const Cost &CurCost, |
| const SmallPtrSet<const SCEV *, 16> &CurRegs, |
| DenseSet<const SCEV *> &VisitedRegs) const; |
| void Solve(SmallVectorImpl<const Formula *> &Solution) const; |
| |
| Value *Expand(const LSRFixup &LF, |
| const Formula &F, |
| BasicBlock::iterator IP, |
| SCEVExpander &Rewriter, |
| SmallVectorImpl<WeakVH> &DeadInsts) const; |
| void RewriteForPHI(PHINode *PN, const LSRFixup &LF, |
| const Formula &F, |
| SCEVExpander &Rewriter, |
| SmallVectorImpl<WeakVH> &DeadInsts, |
| Pass *P) const; |
| void Rewrite(const LSRFixup &LF, |
| const Formula &F, |
| SCEVExpander &Rewriter, |
| SmallVectorImpl<WeakVH> &DeadInsts, |
| Pass *P) const; |
| void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution, |
| Pass *P); |
| |
| LSRInstance(const TargetLowering *tli, Loop *l, Pass *P); |
| |
| bool getChanged() const { return Changed; } |
| |
| void print_factors_and_types(raw_ostream &OS) const; |
| void print_fixups(raw_ostream &OS) const; |
| void print_uses(raw_ostream &OS) const; |
| void print(raw_ostream &OS) const; |
| void dump() const; |
| }; |
| |
| } |
| |
| /// OptimizeShadowIV - If IV is used in a int-to-float cast |
| /// inside the loop then try to eliminate the cast operation. |
| void LSRInstance::OptimizeShadowIV() { |
| const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); |
| if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) |
| return; |
| |
| for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); |
| UI != E; /* empty */) { |
| IVUsers::const_iterator CandidateUI = UI; |
| ++UI; |
| Instruction *ShadowUse = CandidateUI->getUser(); |
| const Type *DestTy = NULL; |
| |
| /* If shadow use is a int->float cast then insert a second IV |
| to eliminate this cast. |
| |
| for (unsigned i = 0; i < n; ++i) |
| foo((double)i); |
| |
| is transformed into |
| |
| double d = 0.0; |
| for (unsigned i = 0; i < n; ++i, ++d) |
| foo(d); |
| */ |
| if (UIToFPInst *UCast = dyn_cast<UIToFPInst>(CandidateUI->getUser())) |
| DestTy = UCast->getDestTy(); |
| else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) |
| DestTy = SCast->getDestTy(); |
| if (!DestTy) continue; |
| |
| if (TLI) { |
| // If target does not support DestTy natively then do not apply |
| // this transformation. |
| EVT DVT = TLI->getValueType(DestTy); |
| if (!TLI->isTypeLegal(DVT)) continue; |
| } |
| |
| PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0)); |
| if (!PH) continue; |
| if (PH->getNumIncomingValues() != 2) continue; |
| |
| const Type *SrcTy = PH->getType(); |
| int Mantissa = DestTy->getFPMantissaWidth(); |
| if (Mantissa == -1) continue; |
| if ((int)SE.getTypeSizeInBits(SrcTy) > Mantissa) |
| continue; |
| |
| unsigned Entry, Latch; |
| if (PH->getIncomingBlock(0) == L->getLoopPreheader()) { |
| Entry = 0; |
| Latch = 1; |
| } else { |
| Entry = 1; |
| Latch = 0; |
| } |
| |
| ConstantInt *Init = dyn_cast<ConstantInt>(PH->getIncomingValue(Entry)); |
| if (!Init) continue; |
| Constant *NewInit = ConstantFP::get(DestTy, Init->getZExtValue()); |
| |
| BinaryOperator *Incr = |
| dyn_cast<BinaryOperator>(PH->getIncomingValue(Latch)); |
| if (!Incr) continue; |
| if (Incr->getOpcode() != Instruction::Add |
| && Incr->getOpcode() != Instruction::Sub) |
| continue; |
| |
| /* Initialize new IV, double d = 0.0 in above example. */ |
| ConstantInt *C = NULL; |
| if (Incr->getOperand(0) == PH) |
| C = dyn_cast<ConstantInt>(Incr->getOperand(1)); |
| else if (Incr->getOperand(1) == PH) |
| C = dyn_cast<ConstantInt>(Incr->getOperand(0)); |
| else |
| continue; |
| |
| if (!C) continue; |
| |
| // Ignore negative constants, as the code below doesn't handle them |
| // correctly. TODO: Remove this restriction. |
| if (!C->getValue().isStrictlyPositive()) continue; |
| |
| /* Add new PHINode. */ |
| PHINode *NewPH = PHINode::Create(DestTy, "IV.S.", PH); |
| |
| /* create new increment. '++d' in above example. */ |
| Constant *CFP = ConstantFP::get(DestTy, C->getZExtValue()); |
| BinaryOperator *NewIncr = |
| BinaryOperator::Create(Incr->getOpcode() == Instruction::Add ? |
| Instruction::FAdd : Instruction::FSub, |
| NewPH, CFP, "IV.S.next.", Incr); |
| |
| NewPH->addIncoming(NewInit, PH->getIncomingBlock(Entry)); |
| NewPH->addIncoming(NewIncr, PH->getIncomingBlock(Latch)); |
| |
| /* Remove cast operation */ |
| ShadowUse->replaceAllUsesWith(NewPH); |
| ShadowUse->eraseFromParent(); |
| break; |
| } |
| } |
| |
| /// FindIVUserForCond - If Cond has an operand that is an expression of an IV, |
| /// set the IV user and stride information and return true, otherwise return |
| /// false. |
| bool LSRInstance::FindIVUserForCond(ICmpInst *Cond, |
| IVStrideUse *&CondUse) { |
| for (IVUsers::iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) |
| if (UI->getUser() == Cond) { |
| // NOTE: we could handle setcc instructions with multiple uses here, but |
| // InstCombine does it as well for simple uses, it's not clear that it |
| // occurs enough in real life to handle. |
| CondUse = UI; |
| return true; |
| } |
| return false; |
| } |
| |
| /// OptimizeMax - Rewrite the loop's terminating condition if it uses |
| /// a max computation. |
| /// |
| /// This is a narrow solution to a specific, but acute, problem. For loops |
| /// like this: |
| /// |
| /// i = 0; |
| /// do { |
| /// p[i] = 0.0; |
| /// } while (++i < n); |
| /// |
| /// the trip count isn't just 'n', because 'n' might not be positive. And |
| /// unfortunately this can come up even for loops where the user didn't use |
| /// a C do-while loop. For example, seemingly well-behaved top-test loops |
| /// will commonly be lowered like this: |
| // |
| /// if (n > 0) { |
| /// i = 0; |
| /// do { |
| /// p[i] = 0.0; |
| /// } while (++i < n); |
| /// } |
| /// |
| /// and then it's possible for subsequent optimization to obscure the if |
| /// test in such a way that indvars can't find it. |
| /// |
| /// When indvars can't find the if test in loops like this, it creates a |
| /// max expression, which allows it to give the loop a canonical |
| /// induction variable: |
| /// |
| /// i = 0; |
| /// max = n < 1 ? 1 : n; |
| /// do { |
| /// p[i] = 0.0; |
| /// } while (++i != max); |
| /// |
| /// Canonical induction variables are necessary because the loop passes |
| /// are designed around them. The most obvious example of this is the |
| /// LoopInfo analysis, which doesn't remember trip count values. It |
| /// expects to be able to rediscover the trip count each time it is |
| /// needed, and it does this using a simple analysis that only succeeds if |
| /// the loop has a canonical induction variable. |
| /// |
| /// However, when it comes time to generate code, the maximum operation |
| /// can be quite costly, especially if it's inside of an outer loop. |
| /// |
| /// This function solves this problem by detecting this type of loop and |
| /// rewriting their conditions from ICMP_NE back to ICMP_SLT, and deleting |
| /// the instructions for the maximum computation. |
| /// |
| ICmpInst *LSRInstance::OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse) { |
| // Check that the loop matches the pattern we're looking for. |
| if (Cond->getPredicate() != CmpInst::ICMP_EQ && |
| Cond->getPredicate() != CmpInst::ICMP_NE) |
| return Cond; |
| |
| SelectInst *Sel = dyn_cast<SelectInst>(Cond->getOperand(1)); |
| if (!Sel || !Sel->hasOneUse()) return Cond; |
| |
| const SCEV *BackedgeTakenCount = SE.getBackedgeTakenCount(L); |
| if (isa<SCEVCouldNotCompute>(BackedgeTakenCount)) |
| return Cond; |
| const SCEV *One = SE.getIntegerSCEV(1, BackedgeTakenCount->getType()); |
| |
| // Add one to the backedge-taken count to get the trip count. |
| const SCEV *IterationCount = SE.getAddExpr(BackedgeTakenCount, One); |
| |
| // Check for a max calculation that matches the pattern. |
| if (!isa<SCEVSMaxExpr>(IterationCount) && !isa<SCEVUMaxExpr>(IterationCount)) |
| return Cond; |
| const SCEVNAryExpr *Max = cast<SCEVNAryExpr>(IterationCount); |
| if (Max != SE.getSCEV(Sel)) return Cond; |
| |
| // To handle a max with more than two operands, this optimization would |
| // require additional checking and setup. |
| if (Max->getNumOperands() != 2) |
| return Cond; |
| |
| const SCEV *MaxLHS = Max->getOperand(0); |
| const SCEV *MaxRHS = Max->getOperand(1); |
| if (!MaxLHS || MaxLHS != One) return Cond; |
| // Check the relevant induction variable for conformance to |
| // the pattern. |
| const SCEV *IV = SE.getSCEV(Cond->getOperand(0)); |
| const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(IV); |
| if (!AR || !AR->isAffine() || |
| AR->getStart() != One || |
| AR->getStepRecurrence(SE) != One) |
| return Cond; |
| |
| assert(AR->getLoop() == L && |
| "Loop condition operand is an addrec in a different loop!"); |
| |
| // Check the right operand of the select, and remember it, as it will |
| // be used in the new comparison instruction. |
| Value *NewRHS = 0; |
| if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS) |
| NewRHS = Sel->getOperand(1); |
| else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS) |
| NewRHS = Sel->getOperand(2); |
| if (!NewRHS) return Cond; |
| |
| // Determine the new comparison opcode. It may be signed or unsigned, |
| // and the original comparison may be either equality or inequality. |
| CmpInst::Predicate Pred = |
| isa<SCEVSMaxExpr>(Max) ? CmpInst::ICMP_SLT : CmpInst::ICMP_ULT; |
| if (Cond->getPredicate() == CmpInst::ICMP_EQ) |
| Pred = CmpInst::getInversePredicate(Pred); |
| |
| // Ok, everything looks ok to change the condition into an SLT or SGE and |
| // delete the max calculation. |
| ICmpInst *NewCond = |
| new ICmpInst(Cond, Pred, Cond->getOperand(0), NewRHS, "scmp"); |
| |
| // Delete the max calculation instructions. |
| Cond->replaceAllUsesWith(NewCond); |
| CondUse->setUser(NewCond); |
| Instruction *Cmp = cast<Instruction>(Sel->getOperand(0)); |
| Cond->eraseFromParent(); |
| Sel->eraseFromParent(); |
| if (Cmp->use_empty()) |
| Cmp->eraseFromParent(); |
| return NewCond; |
| } |
| |
| /// OptimizeLoopTermCond - Change loop terminating condition to use the |
| /// postinc iv when possible. |
| bool |
| LSRInstance::OptimizeLoopTermCond() { |
| SmallPtrSet<Instruction *, 4> PostIncs; |
| |
| BasicBlock *LatchBlock = L->getLoopLatch(); |
| SmallVector<BasicBlock*, 8> ExitingBlocks; |
| L->getExitingBlocks(ExitingBlocks); |
| |
| for (unsigned i = 0, e = ExitingBlocks.size(); i != e; ++i) { |
| BasicBlock *ExitingBlock = ExitingBlocks[i]; |
| |
| // Get the terminating condition for the loop if possible. If we |
| // can, we want to change it to use a post-incremented version of its |
| // induction variable, to allow coalescing the live ranges for the IV into |
| // one register value. |
| |
| BranchInst *TermBr = dyn_cast<BranchInst>(ExitingBlock->getTerminator()); |
| if (!TermBr) |
| continue; |
| // FIXME: Overly conservative, termination condition could be an 'or' etc.. |
| if (TermBr->isUnconditional() || !isa<ICmpInst>(TermBr->getCondition())) |
| continue; |
| |
| // Search IVUsesByStride to find Cond's IVUse if there is one. |
| IVStrideUse *CondUse = 0; |
| ICmpInst *Cond = cast<ICmpInst>(TermBr->getCondition()); |
| if (!FindIVUserForCond(Cond, CondUse)) |
| continue; |
| |
| // If the trip count is computed in terms of a max (due to ScalarEvolution |
| // being unable to find a sufficient guard, for example), change the loop |
| // comparison to use SLT or ULT instead of NE. |
| // One consequence of doing this now is that it disrupts the count-down |
| // optimization. That's not always a bad thing though, because in such |
| // cases it may still be worthwhile to avoid a max. |
| Cond = OptimizeMax(Cond, CondUse); |
| |
| // If this exiting block dominates the latch block, it may also use |
| // the post-inc value if it won't be shared with other uses. |
| // Check for dominance. |
| if (!DT.dominates(ExitingBlock, LatchBlock)) |
| continue; |
| |
| // Conservatively avoid trying to use the post-inc value in non-latch |
| // exits if there may be pre-inc users in intervening blocks. |
| if (LatchBlock != ExitingBlock) |
| for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) |
| // Test if the use is reachable from the exiting block. This dominator |
| // query is a conservative approximation of reachability. |
| if (&*UI != CondUse && |
| !DT.properlyDominates(UI->getUser()->getParent(), ExitingBlock)) { |
| // Conservatively assume there may be reuse if the quotient of their |
| // strides could be a legal scale. |
| const SCEV *A = CondUse->getStride(); |
| const SCEV *B = UI->getStride(); |
| if (SE.getTypeSizeInBits(A->getType()) != |
| SE.getTypeSizeInBits(B->getType())) { |
| if (SE.getTypeSizeInBits(A->getType()) > |
| SE.getTypeSizeInBits(B->getType())) |
| B = SE.getSignExtendExpr(B, A->getType()); |
| else |
| A = SE.getSignExtendExpr(A, B->getType()); |
| } |
| if (const SCEVConstant *D = |
| dyn_cast_or_null<SCEVConstant>(getExactSDiv(B, A, SE))) { |
| // Stride of one or negative one can have reuse with non-addresses. |
| if (D->getValue()->isOne() || |
| D->getValue()->isAllOnesValue()) |
| goto decline_post_inc; |
| // Avoid weird situations. |
| if (D->getValue()->getValue().getMinSignedBits() >= 64 || |
| D->getValue()->getValue().isMinSignedValue()) |
| goto decline_post_inc; |
| // Without TLI, assume that any stride might be valid, and so any |
| // use might be shared. |
| if (!TLI) |
| goto decline_post_inc; |
| // Check for possible scaled-address reuse. |
| const Type *AccessTy = getAccessType(UI->getUser()); |
| TargetLowering::AddrMode AM; |
| AM.Scale = D->getValue()->getSExtValue(); |
| if (TLI->isLegalAddressingMode(AM, AccessTy)) |
| goto decline_post_inc; |
| AM.Scale = -AM.Scale; |
| if (TLI->isLegalAddressingMode(AM, AccessTy)) |
| goto decline_post_inc; |
| } |
| } |
| |
| DEBUG(dbgs() << " Change loop exiting icmp to use postinc iv: " |
| << *Cond << '\n'); |
| |
| // It's possible for the setcc instruction to be anywhere in the loop, and |
| // possible for it to have multiple users. If it is not immediately before |
| // the exiting block branch, move it. |
| if (&*++BasicBlock::iterator(Cond) != TermBr) { |
| if (Cond->hasOneUse()) { |
| Cond->moveBefore(TermBr); |
| } else { |
| // Clone the terminating condition and insert into the loopend. |
| ICmpInst *OldCond = Cond; |
| Cond = cast<ICmpInst>(Cond->clone()); |
| Cond->setName(L->getHeader()->getName() + ".termcond"); |
| ExitingBlock->getInstList().insert(TermBr, Cond); |
| |
| // Clone the IVUse, as the old use still exists! |
| CondUse = &IU.AddUser(CondUse->getStride(), CondUse->getOffset(), |
| Cond, CondUse->getOperandValToReplace()); |
| TermBr->replaceUsesOfWith(OldCond, Cond); |
| } |
| } |
| |
| // If we get to here, we know that we can transform the setcc instruction to |
| // use the post-incremented version of the IV, allowing us to coalesce the |
| // live ranges for the IV correctly. |
| CondUse->setOffset(SE.getMinusSCEV(CondUse->getOffset(), |
| CondUse->getStride())); |
| CondUse->setIsUseOfPostIncrementedValue(true); |
| Changed = true; |
| |
| PostIncs.insert(Cond); |
| decline_post_inc:; |
| } |
| |
| // Determine an insertion point for the loop induction variable increment. It |
| // must dominate all the post-inc comparisons we just set up, and it must |
| // dominate the loop latch edge. |
| IVIncInsertPos = L->getLoopLatch()->getTerminator(); |
| for (SmallPtrSet<Instruction *, 4>::const_iterator I = PostIncs.begin(), |
| E = PostIncs.end(); I != E; ++I) { |
| BasicBlock *BB = |
| DT.findNearestCommonDominator(IVIncInsertPos->getParent(), |
| (*I)->getParent()); |
| if (BB == (*I)->getParent()) |
| IVIncInsertPos = *I; |
| else if (BB != IVIncInsertPos->getParent()) |
| IVIncInsertPos = BB->getTerminator(); |
| } |
| |
| return Changed; |
| } |
| |
| bool |
| LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, |
| LSRUse::KindType Kind, const Type *AccessTy) { |
| int64_t NewMinOffset = LU.MinOffset; |
| int64_t NewMaxOffset = LU.MaxOffset; |
| const Type *NewAccessTy = AccessTy; |
| |
| // Check for a mismatched kind. It's tempting to collapse mismatched kinds to |
| // something conservative, however this can pessimize in the case that one of |
| // the uses will have all its uses outside the loop, for example. |
| if (LU.Kind != Kind) |
| return false; |
| // Conservatively assume HasBaseReg is true for now. |
| if (NewOffset < LU.MinOffset) { |
| if (!isAlwaysFoldable(LU.MaxOffset - NewOffset, 0, /*HasBaseReg=*/true, |
| Kind, AccessTy, TLI)) |
| return false; |
| NewMinOffset = NewOffset; |
| } else if (NewOffset > LU.MaxOffset) { |
| if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, /*HasBaseReg=*/true, |
| Kind, AccessTy, TLI)) |
| return false; |
| NewMaxOffset = NewOffset; |
| } |
| // Check for a mismatched access type, and fall back conservatively as needed. |
| if (Kind == LSRUse::Address && AccessTy != LU.AccessTy) |
| NewAccessTy = Type::getVoidTy(AccessTy->getContext()); |
| |
| // Update the use. |
| LU.MinOffset = NewMinOffset; |
| LU.MaxOffset = NewMaxOffset; |
| LU.AccessTy = NewAccessTy; |
| if (NewOffset != LU.Offsets.back()) |
| LU.Offsets.push_back(NewOffset); |
| return true; |
| } |
| |
| /// getUse - Return an LSRUse index and an offset value for a fixup which |
| /// needs the given expression, with the given kind and optional access type. |
| /// Either reuse an existing use or create a new one, as needed. |
| std::pair<size_t, int64_t> |
| LSRInstance::getUse(const SCEV *&Expr, |
| LSRUse::KindType Kind, const Type *AccessTy) { |
| const SCEV *Copy = Expr; |
| int64_t Offset = ExtractImmediate(Expr, SE); |
| |
| // Basic uses can't accept any offset, for example. |
| if (!isAlwaysFoldable(Offset, 0, /*HasBaseReg=*/true, Kind, AccessTy, TLI)) { |
| Expr = Copy; |
| Offset = 0; |
| } |
| |
| std::pair<UseMapTy::iterator, bool> P = |
| UseMap.insert(std::make_pair(Expr, 0)); |
| if (!P.second) { |
| // A use already existed with this base. |
| size_t LUIdx = P.first->second; |
| LSRUse &LU = Uses[LUIdx]; |
| if (reconcileNewOffset(LU, Offset, Kind, AccessTy)) |
| // Reuse this use. |
| return std::make_pair(LUIdx, Offset); |
| } |
| |
| // Create a new use. |
| size_t LUIdx = Uses.size(); |
| P.first->second = LUIdx; |
| Uses.push_back(LSRUse(Kind, AccessTy)); |
| LSRUse &LU = Uses[LUIdx]; |
| |
| // We don't need to track redundant offsets, but we don't need to go out |
| // of our way here to avoid them. |
| if (LU.Offsets.empty() || Offset != LU.Offsets.back()) |
| LU.Offsets.push_back(Offset); |
| |
| LU.MinOffset = Offset; |
| LU.MaxOffset = Offset; |
| return std::make_pair(LUIdx, Offset); |
| } |
| |
| void LSRInstance::CollectInterestingTypesAndFactors() { |
| SmallSetVector<const SCEV *, 4> Strides; |
| |
| // Collect interesting types and strides. |
| for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { |
| const SCEV *Stride = UI->getStride(); |
| |
| // Collect interesting types. |
| Types.insert(SE.getEffectiveSCEVType(Stride->getType())); |
| |
| // Add the stride for this loop. |
| Strides.insert(Stride); |
| |
| // Add strides for other mentioned loops. |
| for (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(UI->getOffset()); |
| AR; AR = dyn_cast<SCEVAddRecExpr>(AR->getStart())) |
| Strides.insert(AR->getStepRecurrence(SE)); |
| } |
| |
| // Compute interesting factors from the set of interesting strides. |
| for (SmallSetVector<const SCEV *, 4>::const_iterator |
| I = Strides.begin(), E = Strides.end(); I != E; ++I) |
| for (SmallSetVector<const SCEV *, 4>::const_iterator NewStrideIter = |
| next(I); NewStrideIter != E; ++NewStrideIter) { |
| const SCEV *OldStride = *I; |
| const SCEV *NewStride = *NewStrideIter; |
| |
| if (SE.getTypeSizeInBits(OldStride->getType()) != |
| SE.getTypeSizeInBits(NewStride->getType())) { |
| if (SE.getTypeSizeInBits(OldStride->getType()) > |
| SE.getTypeSizeInBits(NewStride->getType())) |
| NewStride = SE.getSignExtendExpr(NewStride, OldStride->getType()); |
| else |
| OldStride = SE.getSignExtendExpr(OldStride, NewStride->getType()); |
| } |
| if (const SCEVConstant *Factor = |
| dyn_cast_or_null<SCEVConstant>(getExactSDiv(NewStride, OldStride, |
| SE, true))) { |
| if (Factor->getValue()->getValue().getMinSignedBits() <= 64) |
| Factors.insert(Factor->getValue()->getValue().getSExtValue()); |
| } else if (const SCEVConstant *Factor = |
| dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride, |
| NewStride, |
| SE, true))) { |
| if (Factor->getValue()->getValue().getMinSignedBits() <= 64) |
| Factors.insert(Factor->getValue()->getValue().getSExtValue()); |
| } |
| } |
| |
| // If all uses use the same type, don't bother looking for truncation-based |
| // reuse. |
| if (Types.size() == 1) |
| Types.clear(); |
| |
| DEBUG(print_factors_and_types(dbgs())); |
| } |
| |
| void LSRInstance::CollectFixupsAndInitialFormulae() { |
| for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { |
| // Record the uses. |
| LSRFixup &LF = getNewFixup(); |
| LF.UserInst = UI->getUser(); |
| LF.OperandValToReplace = UI->getOperandValToReplace(); |
| if (UI->isUseOfPostIncrementedValue()) |
| LF.PostIncLoop = L; |
| |
| LSRUse::KindType Kind = LSRUse::Basic; |
| const Type *AccessTy = 0; |
| if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) { |
| Kind = LSRUse::Address; |
| AccessTy = getAccessType(LF.UserInst); |
| } |
| |
| const SCEV *S = IU.getCanonicalExpr(*UI); |
| |
| // Equality (== and !=) ICmps are special. We can rewrite (i == N) as |
| // (N - i == 0), and this allows (N - i) to be the expression that we work |
| // with rather than just N or i, so we can consider the register |
| // requirements for both N and i at the same time. Limiting this code to |
| // equality icmps is not a problem because all interesting loops use |
| // equality icmps, thanks to IndVarSimplify. |
| if (ICmpInst *CI = dyn_cast<ICmpInst>(LF.UserInst)) |
| if (CI->isEquality()) { |
| // Swap the operands if needed to put the OperandValToReplace on the |
| // left, for consistency. |
| Value *NV = CI->getOperand(1); |
| if (NV == LF.OperandValToReplace) { |
| CI->setOperand(1, CI->getOperand(0)); |
| CI->setOperand(0, NV); |
| } |
| |
| // x == y --> x - y == 0 |
| const SCEV *N = SE.getSCEV(NV); |
| if (N->isLoopInvariant(L)) { |
| Kind = LSRUse::ICmpZero; |
| S = SE.getMinusSCEV(N, S); |
| } |
| |
| // -1 and the negations of all interesting strides (except the negation |
| // of -1) are now also interesting. |
| for (size_t i = 0, e = Factors.size(); i != e; ++i) |
| if (Factors[i] != -1) |
| Factors.insert(-(uint64_t)Factors[i]); |
| Factors.insert(-1); |
| } |
| |
| // Set up the initial formula for this use. |
| std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy); |
| LF.LUIdx = P.first; |
| LF.Offset = P.second; |
| LSRUse &LU = Uses[LF.LUIdx]; |
| LU.AllFixupsOutsideLoop &= !L->contains(LF.UserInst); |
| |
| // If this is the first use of this LSRUse, give it a formula. |
| if (LU.Formulae.empty()) { |
| InsertInitialFormula(S, LU, LF.LUIdx); |
| CountRegisters(LU.Formulae.back(), LF.LUIdx); |
| } |
| } |
| |
| DEBUG(print_fixups(dbgs())); |
| } |
| |
| void |
| LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) { |
| Formula F; |
| F.InitialMatch(S, L, SE, DT); |
| bool Inserted = InsertFormula(LU, LUIdx, F); |
| assert(Inserted && "Initial formula already exists!"); (void)Inserted; |
| } |
| |
| void |
| LSRInstance::InsertSupplementalFormula(const SCEV *S, |
| LSRUse &LU, size_t LUIdx) { |
| Formula F; |
| F.BaseRegs.push_back(S); |
| F.AM.HasBaseReg = true; |
| bool Inserted = InsertFormula(LU, LUIdx, F); |
| assert(Inserted && "Supplemental formula already exists!"); (void)Inserted; |
| } |
| |
| /// CountRegisters - Note which registers are used by the given formula, |
| /// updating RegUses. |
| void LSRInstance::CountRegisters(const Formula &F, size_t LUIdx) { |
| if (F.ScaledReg) |
| RegUses.CountRegister(F.ScaledReg, LUIdx); |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), |
| E = F.BaseRegs.end(); I != E; ++I) |
| RegUses.CountRegister(*I, LUIdx); |
| } |
| |
| /// InsertFormula - If the given formula has not yet been inserted, add it to |
| /// the list, and return true. Return false otherwise. |
| bool LSRInstance::InsertFormula(LSRUse &LU, unsigned LUIdx, const Formula &F) { |
| if (!LU.InsertFormula(F)) |
| return false; |
| |
| CountRegisters(F, LUIdx); |
| return true; |
| } |
| |
| /// CollectLoopInvariantFixupsAndFormulae - Check for other uses of |
| /// loop-invariant values which we're tracking. These other uses will pin these |
| /// values in registers, making them less profitable for elimination. |
| /// TODO: This currently misses non-constant addrec step registers. |
| /// TODO: Should this give more weight to users inside the loop? |
| void |
| LSRInstance::CollectLoopInvariantFixupsAndFormulae() { |
| SmallVector<const SCEV *, 8> Worklist(RegUses.begin(), RegUses.end()); |
| SmallPtrSet<const SCEV *, 8> Inserted; |
| |
| while (!Worklist.empty()) { |
| const SCEV *S = Worklist.pop_back_val(); |
| |
| if (const SCEVNAryExpr *N = dyn_cast<SCEVNAryExpr>(S)) |
| Worklist.insert(Worklist.end(), N->op_begin(), N->op_end()); |
| else if (const SCEVCastExpr *C = dyn_cast<SCEVCastExpr>(S)) |
| Worklist.push_back(C->getOperand()); |
| else if (const SCEVUDivExpr *D = dyn_cast<SCEVUDivExpr>(S)) { |
| Worklist.push_back(D->getLHS()); |
| Worklist.push_back(D->getRHS()); |
| } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(S)) { |
| if (!Inserted.insert(U)) continue; |
| const Value *V = U->getValue(); |
| if (const Instruction *Inst = dyn_cast<Instruction>(V)) |
| if (L->contains(Inst)) continue; |
| for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end(); |
| UI != UE; ++UI) { |
| const Instruction *UserInst = dyn_cast<Instruction>(*UI); |
| // Ignore non-instructions. |
| if (!UserInst) |
| continue; |
| // Ignore instructions in other functions (as can happen with |
| // Constants). |
| if (UserInst->getParent()->getParent() != L->getHeader()->getParent()) |
| continue; |
| // Ignore instructions not dominated by the loop. |
| const BasicBlock *UseBB = !isa<PHINode>(UserInst) ? |
| UserInst->getParent() : |
| cast<PHINode>(UserInst)->getIncomingBlock( |
| PHINode::getIncomingValueNumForOperand(UI.getOperandNo())); |
| if (!DT.dominates(L->getHeader(), UseBB)) |
| continue; |
| // Ignore uses which are part of other SCEV expressions, to avoid |
| // analyzing them multiple times. |
| if (SE.isSCEVable(UserInst->getType()) && |
| !isa<SCEVUnknown>(SE.getSCEV(const_cast<Instruction *>(UserInst)))) |
| continue; |
| // Ignore icmp instructions which are already being analyzed. |
| if (const ICmpInst *ICI = dyn_cast<ICmpInst>(UserInst)) { |
| unsigned OtherIdx = !UI.getOperandNo(); |
| Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx)); |
| if (SE.getSCEV(OtherOp)->hasComputableLoopEvolution(L)) |
| continue; |
| } |
| |
| LSRFixup &LF = getNewFixup(); |
| LF.UserInst = const_cast<Instruction *>(UserInst); |
| LF.OperandValToReplace = UI.getUse(); |
| std::pair<size_t, int64_t> P = getUse(S, LSRUse::Basic, 0); |
| LF.LUIdx = P.first; |
| LF.Offset = P.second; |
| LSRUse &LU = Uses[LF.LUIdx]; |
| LU.AllFixupsOutsideLoop &= L->contains(LF.UserInst); |
| InsertSupplementalFormula(U, LU, LF.LUIdx); |
| CountRegisters(LU.Formulae.back(), Uses.size() - 1); |
| break; |
| } |
| } |
| } |
| } |
| |
| /// CollectSubexprs - Split S into subexpressions which can be pulled out into |
| /// separate registers. If C is non-null, multiply each subexpression by C. |
| static void CollectSubexprs(const SCEV *S, const SCEVConstant *C, |
| SmallVectorImpl<const SCEV *> &Ops, |
| ScalarEvolution &SE) { |
| if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { |
| // Break out add operands. |
| for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); |
| I != E; ++I) |
| CollectSubexprs(*I, C, Ops, SE); |
| return; |
| } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { |
| // Split a non-zero base out of an addrec. |
| if (!AR->getStart()->isZero()) { |
| CollectSubexprs(SE.getAddRecExpr(SE.getIntegerSCEV(0, AR->getType()), |
| AR->getStepRecurrence(SE), |
| AR->getLoop()), C, Ops, SE); |
| CollectSubexprs(AR->getStart(), C, Ops, SE); |
| return; |
| } |
| } else if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) { |
| // Break (C * (a + b + c)) into C*a + C*b + C*c. |
| if (Mul->getNumOperands() == 2) |
| if (const SCEVConstant *Op0 = |
| dyn_cast<SCEVConstant>(Mul->getOperand(0))) { |
| CollectSubexprs(Mul->getOperand(1), |
| C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0, |
| Ops, SE); |
| return; |
| } |
| } |
| |
| // Otherwise use the value itself. |
| Ops.push_back(C ? SE.getMulExpr(C, S) : S); |
| } |
| |
| /// GenerateReassociations - Split out subexpressions from adds and the bases of |
| /// addrecs. |
| void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx, |
| Formula Base, |
| unsigned Depth) { |
| // Arbitrarily cap recursion to protect compile time. |
| if (Depth >= 3) return; |
| |
| for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { |
| const SCEV *BaseReg = Base.BaseRegs[i]; |
| |
| SmallVector<const SCEV *, 8> AddOps; |
| CollectSubexprs(BaseReg, 0, AddOps, SE); |
| if (AddOps.size() == 1) continue; |
| |
| for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(), |
| JE = AddOps.end(); J != JE; ++J) { |
| // Don't pull a constant into a register if the constant could be folded |
| // into an immediate field. |
| if (isAlwaysFoldable(*J, LU.MinOffset, LU.MaxOffset, |
| Base.getNumRegs() > 1, |
| LU.Kind, LU.AccessTy, TLI, SE)) |
| continue; |
| |
| // Collect all operands except *J. |
| SmallVector<const SCEV *, 8> InnerAddOps; |
| for (SmallVectorImpl<const SCEV *>::const_iterator K = AddOps.begin(), |
| KE = AddOps.end(); K != KE; ++K) |
| if (K != J) |
| InnerAddOps.push_back(*K); |
| |
| // Don't leave just a constant behind in a register if the constant could |
| // be folded into an immediate field. |
| if (InnerAddOps.size() == 1 && |
| isAlwaysFoldable(InnerAddOps[0], LU.MinOffset, LU.MaxOffset, |
| Base.getNumRegs() > 1, |
| LU.Kind, LU.AccessTy, TLI, SE)) |
| continue; |
| |
| Formula F = Base; |
| F.BaseRegs[i] = SE.getAddExpr(InnerAddOps); |
| F.BaseRegs.push_back(*J); |
| if (InsertFormula(LU, LUIdx, F)) |
| // If that formula hadn't been seen before, recurse to find more like |
| // it. |
| GenerateReassociations(LU, LUIdx, LU.Formulae.back(), Depth+1); |
| } |
| } |
| } |
| |
| /// GenerateCombinations - Generate a formula consisting of all of the |
| /// loop-dominating registers added into a single register. |
| void LSRInstance::GenerateCombinations(LSRUse &LU, unsigned LUIdx, |
| Formula Base) { |
| // This method is only interesting on a plurality of registers. |
| if (Base.BaseRegs.size() <= 1) return; |
| |
| Formula F = Base; |
| F.BaseRegs.clear(); |
| SmallVector<const SCEV *, 4> Ops; |
| for (SmallVectorImpl<const SCEV *>::const_iterator |
| I = Base.BaseRegs.begin(), E = Base.BaseRegs.end(); I != E; ++I) { |
| const SCEV *BaseReg = *I; |
| if (BaseReg->properlyDominates(L->getHeader(), &DT) && |
| !BaseReg->hasComputableLoopEvolution(L)) |
| Ops.push_back(BaseReg); |
| else |
| F.BaseRegs.push_back(BaseReg); |
| } |
| if (Ops.size() > 1) { |
| const SCEV *Sum = SE.getAddExpr(Ops); |
| // TODO: If Sum is zero, it probably means ScalarEvolution missed an |
| // opportunity to fold something. For now, just ignore such cases |
| // rather than proceed with zero in a register. |
| if (!Sum->isZero()) { |
| F.BaseRegs.push_back(Sum); |
| (void)InsertFormula(LU, LUIdx, F); |
| } |
| } |
| } |
| |
| /// GenerateSymbolicOffsets - Generate reuse formulae using symbolic offsets. |
| void LSRInstance::GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, |
| Formula Base) { |
| // We can't add a symbolic offset if the address already contains one. |
| if (Base.AM.BaseGV) return; |
| |
| for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { |
| const SCEV *G = Base.BaseRegs[i]; |
| GlobalValue *GV = ExtractSymbol(G, SE); |
| if (G->isZero() || !GV) |
| continue; |
| Formula F = Base; |
| F.AM.BaseGV = GV; |
| if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset, |
| LU.Kind, LU.AccessTy, TLI)) |
| continue; |
| F.BaseRegs[i] = G; |
| (void)InsertFormula(LU, LUIdx, F); |
| } |
| } |
| |
| /// GenerateConstantOffsets - Generate reuse formulae using symbolic offsets. |
| void LSRInstance::GenerateConstantOffsets(LSRUse &LU, unsigned LUIdx, |
| Formula Base) { |
| // TODO: For now, just add the min and max offset, because it usually isn't |
| // worthwhile looking at everything inbetween. |
| SmallVector<int64_t, 4> Worklist; |
| Worklist.push_back(LU.MinOffset); |
| if (LU.MaxOffset != LU.MinOffset) |
| Worklist.push_back(LU.MaxOffset); |
| |
| for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { |
| const SCEV *G = Base.BaseRegs[i]; |
| |
| for (SmallVectorImpl<int64_t>::const_iterator I = Worklist.begin(), |
| E = Worklist.end(); I != E; ++I) { |
| Formula F = Base; |
| F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs - *I; |
| if (isLegalUse(F.AM, LU.MinOffset - *I, LU.MaxOffset - *I, |
| LU.Kind, LU.AccessTy, TLI)) { |
| F.BaseRegs[i] = SE.getAddExpr(G, SE.getIntegerSCEV(*I, G->getType())); |
| |
| (void)InsertFormula(LU, LUIdx, F); |
| } |
| } |
| |
| int64_t Imm = ExtractImmediate(G, SE); |
| if (G->isZero() || Imm == 0) |
| continue; |
| Formula F = Base; |
| F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Imm; |
| if (!isLegalUse(F.AM, LU.MinOffset, LU.MaxOffset, |
| LU.Kind, LU.AccessTy, TLI)) |
| continue; |
| F.BaseRegs[i] = G; |
| (void)InsertFormula(LU, LUIdx, F); |
| } |
| } |
| |
| /// GenerateICmpZeroScales - For ICmpZero, check to see if we can scale up |
| /// the comparison. For example, x == y -> x*c == y*c. |
| void LSRInstance::GenerateICmpZeroScales(LSRUse &LU, unsigned LUIdx, |
| Formula Base) { |
| if (LU.Kind != LSRUse::ICmpZero) return; |
| |
| // Determine the integer type for the base formula. |
| const Type *IntTy = Base.getType(); |
| if (!IntTy) return; |
| if (SE.getTypeSizeInBits(IntTy) > 64) return; |
| |
| // Don't do this if there is more than one offset. |
| if (LU.MinOffset != LU.MaxOffset) return; |
| |
| assert(!Base.AM.BaseGV && "ICmpZero use is not legal!"); |
| |
| // Check each interesting stride. |
| for (SmallSetVector<int64_t, 8>::const_iterator |
| I = Factors.begin(), E = Factors.end(); I != E; ++I) { |
| int64_t Factor = *I; |
| Formula F = Base; |
| |
| // Check that the multiplication doesn't overflow. |
| if (F.AM.BaseOffs == INT64_MIN && Factor == -1) |
| continue; |
| F.AM.BaseOffs = (uint64_t)Base.AM.BaseOffs * Factor; |
| if (F.AM.BaseOffs / Factor != Base.AM.BaseOffs) |
| continue; |
| |
| // Check that multiplying with the use offset doesn't overflow. |
| int64_t Offset = LU.MinOffset; |
| if (Offset == INT64_MIN && Factor == -1) |
| continue; |
| Offset = (uint64_t)Offset * Factor; |
| if (Offset / Factor != LU.MinOffset) |
| continue; |
| |
| // Check that this scale is legal. |
| if (!isLegalUse(F.AM, Offset, Offset, LU.Kind, LU.AccessTy, TLI)) |
| continue; |
| |
| // Compensate for the use having MinOffset built into it. |
| F.AM.BaseOffs = (uint64_t)F.AM.BaseOffs + Offset - LU.MinOffset; |
| |
| const SCEV *FactorS = SE.getIntegerSCEV(Factor, IntTy); |
| |
| // Check that multiplying with each base register doesn't overflow. |
| for (size_t i = 0, e = F.BaseRegs.size(); i != e; ++i) { |
| F.BaseRegs[i] = SE.getMulExpr(F.BaseRegs[i], FactorS); |
| if (getExactSDiv(F.BaseRegs[i], FactorS, SE) != Base.BaseRegs[i]) |
| goto next; |
| } |
| |
| // Check that multiplying with the scaled register doesn't overflow. |
| if (F.ScaledReg) { |
| F.ScaledReg = SE.getMulExpr(F.ScaledReg, FactorS); |
| if (getExactSDiv(F.ScaledReg, FactorS, SE) != Base.ScaledReg) |
| continue; |
| } |
| |
| // If we make it here and it's legal, add it. |
| (void)InsertFormula(LU, LUIdx, F); |
| next:; |
| } |
| } |
| |
| /// GenerateScales - Generate stride factor reuse formulae by making use of |
| /// scaled-offset address modes, for example. |
| void LSRInstance::GenerateScales(LSRUse &LU, unsigned LUIdx, |
| Formula Base) { |
| // Determine the integer type for the base formula. |
| const Type *IntTy = Base.getType(); |
| if (!IntTy) return; |
| |
| // If this Formula already has a scaled register, we can't add another one. |
| if (Base.AM.Scale != 0) return; |
| |
| // Check each interesting stride. |
| for (SmallSetVector<int64_t, 8>::const_iterator |
| I = Factors.begin(), E = Factors.end(); I != E; ++I) { |
| int64_t Factor = *I; |
| |
| Base.AM.Scale = Factor; |
| Base.AM.HasBaseReg = Base.BaseRegs.size() > 1; |
| // Check whether this scale is going to be legal. |
| if (!isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset, |
| LU.Kind, LU.AccessTy, TLI)) { |
| // As a special-case, handle special out-of-loop Basic users specially. |
| // TODO: Reconsider this special case. |
| if (LU.Kind == LSRUse::Basic && |
| isLegalUse(Base.AM, LU.MinOffset, LU.MaxOffset, |
| LSRUse::Special, LU.AccessTy, TLI) && |
| LU.AllFixupsOutsideLoop) |
| LU.Kind = LSRUse::Special; |
| else |
| continue; |
| } |
| // For an ICmpZero, negating a solitary base register won't lead to |
| // new solutions. |
| if (LU.Kind == LSRUse::ICmpZero && |
| !Base.AM.HasBaseReg && Base.AM.BaseOffs == 0 && !Base.AM.BaseGV) |
| continue; |
| // For each addrec base reg, apply the scale, if possible. |
| for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) |
| if (const SCEVAddRecExpr *AR = |
| dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i])) { |
| const SCEV *FactorS = SE.getIntegerSCEV(Factor, IntTy); |
| if (FactorS->isZero()) |
| continue; |
| // Divide out the factor, ignoring high bits, since we'll be |
| // scaling the value back up in the end. |
| if (const SCEV *Quotient = getExactSDiv(AR, FactorS, SE, true)) { |
| // TODO: This could be optimized to avoid all the copying. |
| Formula F = Base; |
| F.ScaledReg = Quotient; |
| std::swap(F.BaseRegs[i], F.BaseRegs.back()); |
| F.BaseRegs.pop_back(); |
| (void)InsertFormula(LU, LUIdx, F); |
| } |
| } |
| } |
| } |
| |
| /// GenerateTruncates - Generate reuse formulae from different IV types. |
| void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, |
| Formula Base) { |
| // This requires TargetLowering to tell us which truncates are free. |
| if (!TLI) return; |
| |
| // Don't bother truncating symbolic values. |
| if (Base.AM.BaseGV) return; |
| |
| // Determine the integer type for the base formula. |
| const Type *DstTy = Base.getType(); |
| if (!DstTy) return; |
| DstTy = SE.getEffectiveSCEVType(DstTy); |
| |
| for (SmallSetVector<const Type *, 4>::const_iterator |
| I = Types.begin(), E = Types.end(); I != E; ++I) { |
| const Type *SrcTy = *I; |
| if (SrcTy != DstTy && TLI->isTruncateFree(SrcTy, DstTy)) { |
| Formula F = Base; |
| |
| if (F.ScaledReg) F.ScaledReg = SE.getAnyExtendExpr(F.ScaledReg, *I); |
| for (SmallVectorImpl<const SCEV *>::iterator J = F.BaseRegs.begin(), |
| JE = F.BaseRegs.end(); J != JE; ++J) |
| *J = SE.getAnyExtendExpr(*J, SrcTy); |
| |
| // TODO: This assumes we've done basic processing on all uses and |
| // have an idea what the register usage is. |
| if (!F.hasRegsUsedByUsesOtherThan(LUIdx, RegUses)) |
| continue; |
| |
| (void)InsertFormula(LU, LUIdx, F); |
| } |
| } |
| } |
| |
| namespace { |
| |
| /// WorkItem - Helper class for GenerateCrossUseConstantOffsets. It's used to |
| /// defer modifications so that the search phase doesn't have to worry about |
| /// the data structures moving underneath it. |
| struct WorkItem { |
| size_t LUIdx; |
| int64_t Imm; |
| const SCEV *OrigReg; |
| |
| WorkItem(size_t LI, int64_t I, const SCEV *R) |
| : LUIdx(LI), Imm(I), OrigReg(R) {} |
| |
| void print(raw_ostream &OS) const; |
| void dump() const; |
| }; |
| |
| } |
| |
| void WorkItem::print(raw_ostream &OS) const { |
| OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx |
| << " , add offset " << Imm; |
| } |
| |
| void WorkItem::dump() const { |
| print(errs()); errs() << '\n'; |
| } |
| |
| /// GenerateCrossUseConstantOffsets - Look for registers which are a constant |
| /// distance apart and try to form reuse opportunities between them. |
| void LSRInstance::GenerateCrossUseConstantOffsets() { |
| // Group the registers by their value without any added constant offset. |
| typedef std::map<int64_t, const SCEV *> ImmMapTy; |
| typedef DenseMap<const SCEV *, ImmMapTy> RegMapTy; |
| RegMapTy Map; |
| DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap; |
| SmallVector<const SCEV *, 8> Sequence; |
| for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end(); |
| I != E; ++I) { |
| const SCEV *Reg = *I; |
| int64_t Imm = ExtractImmediate(Reg, SE); |
| std::pair<RegMapTy::iterator, bool> Pair = |
| Map.insert(std::make_pair(Reg, ImmMapTy())); |
| if (Pair.second) |
| Sequence.push_back(Reg); |
| Pair.first->second.insert(std::make_pair(Imm, *I)); |
| UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(*I); |
| } |
| |
| // Now examine each set of registers with the same base value. Build up |
| // a list of work to do and do the work in a separate step so that we're |
| // not adding formulae and register counts while we're searching. |
| SmallVector<WorkItem, 32> WorkItems; |
| SmallSet<std::pair<size_t, int64_t>, 32> UniqueItems; |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = Sequence.begin(), |
| E = Sequence.end(); I != E; ++I) { |
| const SCEV *Reg = *I; |
| const ImmMapTy &Imms = Map.find(Reg)->second; |
| |
| // It's not worthwhile looking for reuse if there's only one offset. |
| if (Imms.size() == 1) |
| continue; |
| |
| DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':'; |
| for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end(); |
| J != JE; ++J) |
| dbgs() << ' ' << J->first; |
| dbgs() << '\n'); |
| |
| // Examine each offset. |
| for (ImmMapTy::const_iterator J = Imms.begin(), JE = Imms.end(); |
| J != JE; ++J) { |
| const SCEV *OrigReg = J->second; |
| |
| int64_t JImm = J->first; |
| const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(OrigReg); |
| |
| if (!isa<SCEVConstant>(OrigReg) && |
| UsedByIndicesMap[Reg].count() == 1) { |
| DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg << '\n'); |
| continue; |
| } |
| |
| // Conservatively examine offsets between this orig reg a few selected |
| // other orig regs. |
| ImmMapTy::const_iterator OtherImms[] = { |
| Imms.begin(), prior(Imms.end()), |
| Imms.upper_bound((Imms.begin()->first + prior(Imms.end())->first) / 2) |
| }; |
| for (size_t i = 0, e = array_lengthof(OtherImms); i != e; ++i) { |
| ImmMapTy::const_iterator M = OtherImms[i]; |
| if (M == J || M == JE) continue; |
| |
| // Compute the difference between the two. |
| int64_t Imm = (uint64_t)JImm - M->first; |
| for (int LUIdx = UsedByIndices.find_first(); LUIdx != -1; |
| LUIdx = UsedByIndices.find_next(LUIdx)) |
| // Make a memo of this use, offset, and register tuple. |
| if (UniqueItems.insert(std::make_pair(LUIdx, Imm))) |
| WorkItems.push_back(WorkItem(LUIdx, Imm, OrigReg)); |
| } |
| } |
| } |
| |
| Map.clear(); |
| Sequence.clear(); |
| UsedByIndicesMap.clear(); |
| UniqueItems.clear(); |
| |
| // Now iterate through the worklist and add new formulae. |
| for (SmallVectorImpl<WorkItem>::const_iterator I = WorkItems.begin(), |
| E = WorkItems.end(); I != E; ++I) { |
| const WorkItem &WI = *I; |
| size_t LUIdx = WI.LUIdx; |
| LSRUse &LU = Uses[LUIdx]; |
| int64_t Imm = WI.Imm; |
| const SCEV *OrigReg = WI.OrigReg; |
| |
| const Type *IntTy = SE.getEffectiveSCEVType(OrigReg->getType()); |
| const SCEV *NegImmS = SE.getSCEV(ConstantInt::get(IntTy, -(uint64_t)Imm)); |
| unsigned BitWidth = SE.getTypeSizeInBits(IntTy); |
| |
| // TODO: Use a more targeted data structure. |
| for (size_t L = 0, LE = LU.Formulae.size(); L != LE; ++L) { |
| Formula F = LU.Formulae[L]; |
| // Use the immediate in the scaled register. |
| if (F.ScaledReg == OrigReg) { |
| int64_t Offs = (uint64_t)F.AM.BaseOffs + |
| Imm * (uint64_t)F.AM.Scale; |
| // Don't create 50 + reg(-50). |
| if (F.referencesReg(SE.getSCEV( |
| ConstantInt::get(IntTy, -(uint64_t)Offs)))) |
| continue; |
| Formula NewF = F; |
| NewF.AM.BaseOffs = Offs; |
| if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset, |
| LU.Kind, LU.AccessTy, TLI)) |
| continue; |
| NewF.ScaledReg = SE.getAddExpr(NegImmS, NewF.ScaledReg); |
| |
| // If the new scale is a constant in a register, and adding the constant |
| // value to the immediate would produce a value closer to zero than the |
| // immediate itself, then the formula isn't worthwhile. |
| if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewF.ScaledReg)) |
| if (C->getValue()->getValue().isNegative() != |
| (NewF.AM.BaseOffs < 0) && |
| (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale)) |
| .ule(APInt(BitWidth, NewF.AM.BaseOffs).abs())) |
| continue; |
| |
| // OK, looks good. |
| (void)InsertFormula(LU, LUIdx, NewF); |
| } else { |
| // Use the immediate in a base register. |
| for (size_t N = 0, NE = F.BaseRegs.size(); N != NE; ++N) { |
| const SCEV *BaseReg = F.BaseRegs[N]; |
| if (BaseReg != OrigReg) |
| continue; |
| Formula NewF = F; |
| NewF.AM.BaseOffs = (uint64_t)NewF.AM.BaseOffs + Imm; |
| if (!isLegalUse(NewF.AM, LU.MinOffset, LU.MaxOffset, |
| LU.Kind, LU.AccessTy, TLI)) |
| continue; |
| NewF.BaseRegs[N] = SE.getAddExpr(NegImmS, BaseReg); |
| |
| // If the new formula has a constant in a register, and adding the |
| // constant value to the immediate would produce a value closer to |
| // zero than the immediate itself, then the formula isn't worthwhile. |
| for (SmallVectorImpl<const SCEV *>::const_iterator |
| J = NewF.BaseRegs.begin(), JE = NewF.BaseRegs.end(); |
| J != JE; ++J) |
| if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*J)) |
| if (C->getValue()->getValue().isNegative() != |
| (NewF.AM.BaseOffs < 0) && |
| C->getValue()->getValue().abs() |
| .ule(APInt(BitWidth, NewF.AM.BaseOffs).abs())) |
| goto skip_formula; |
| |
| // Ok, looks good. |
| (void)InsertFormula(LU, LUIdx, NewF); |
| break; |
| skip_formula:; |
| } |
| } |
| } |
| } |
| } |
| |
| /// GenerateAllReuseFormulae - Generate formulae for each use. |
| void |
| LSRInstance::GenerateAllReuseFormulae() { |
| // This is split into multiple loops so that hasRegsUsedByUsesOtherThan |
| // queries are more precise. |
| for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { |
| LSRUse &LU = Uses[LUIdx]; |
| for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) |
| GenerateReassociations(LU, LUIdx, LU.Formulae[i]); |
| for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) |
| GenerateCombinations(LU, LUIdx, LU.Formulae[i]); |
| } |
| for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { |
| LSRUse &LU = Uses[LUIdx]; |
| for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) |
| GenerateSymbolicOffsets(LU, LUIdx, LU.Formulae[i]); |
| for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) |
| GenerateConstantOffsets(LU, LUIdx, LU.Formulae[i]); |
| for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) |
| GenerateICmpZeroScales(LU, LUIdx, LU.Formulae[i]); |
| for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) |
| GenerateScales(LU, LUIdx, LU.Formulae[i]); |
| } |
| for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { |
| LSRUse &LU = Uses[LUIdx]; |
| for (size_t i = 0, f = LU.Formulae.size(); i != f; ++i) |
| GenerateTruncates(LU, LUIdx, LU.Formulae[i]); |
| } |
| |
| GenerateCrossUseConstantOffsets(); |
| } |
| |
| /// If their are multiple formulae with the same set of registers used |
| /// by other uses, pick the best one and delete the others. |
| void LSRInstance::FilterOutUndesirableDedicatedRegisters() { |
| #ifndef NDEBUG |
| bool Changed = false; |
| #endif |
| |
| // Collect the best formula for each unique set of shared registers. This |
| // is reset for each use. |
| typedef DenseMap<SmallVector<const SCEV *, 2>, size_t, UniquifierDenseMapInfo> |
| BestFormulaeTy; |
| BestFormulaeTy BestFormulae; |
| |
| for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { |
| LSRUse &LU = Uses[LUIdx]; |
| FormulaSorter Sorter(L, LU, SE, DT); |
| |
| // Clear out the set of used regs; it will be recomputed. |
| LU.Regs.clear(); |
| |
| for (size_t FIdx = 0, NumForms = LU.Formulae.size(); |
| FIdx != NumForms; ++FIdx) { |
| Formula &F = LU.Formulae[FIdx]; |
| |
| SmallVector<const SCEV *, 2> Key; |
| for (SmallVectorImpl<const SCEV *>::const_iterator J = F.BaseRegs.begin(), |
| JE = F.BaseRegs.end(); J != JE; ++J) { |
| const SCEV *Reg = *J; |
| if (RegUses.isRegUsedByUsesOtherThan(Reg, LUIdx)) |
| Key.push_back(Reg); |
| } |
| if (F.ScaledReg && |
| RegUses.isRegUsedByUsesOtherThan(F.ScaledReg, LUIdx)) |
| Key.push_back(F.ScaledReg); |
| // Unstable sort by host order ok, because this is only used for |
| // uniquifying. |
| std::sort(Key.begin(), Key.end()); |
| |
| std::pair<BestFormulaeTy::const_iterator, bool> P = |
| BestFormulae.insert(std::make_pair(Key, FIdx)); |
| if (!P.second) { |
| Formula &Best = LU.Formulae[P.first->second]; |
| if (Sorter.operator()(F, Best)) |
| std::swap(F, Best); |
| DEBUG(dbgs() << "Filtering out "; F.print(dbgs()); |
| dbgs() << "\n" |
| " in favor of "; Best.print(dbgs()); |
| dbgs() << '\n'); |
| #ifndef NDEBUG |
| Changed = true; |
| #endif |
| std::swap(F, LU.Formulae.back()); |
| LU.Formulae.pop_back(); |
| --FIdx; |
| --NumForms; |
| continue; |
| } |
| if (F.ScaledReg) LU.Regs.insert(F.ScaledReg); |
| LU.Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); |
| } |
| BestFormulae.clear(); |
| } |
| |
| DEBUG(if (Changed) { |
| dbgs() << "\n" |
| "After filtering out undesirable candidates:\n"; |
| print_uses(dbgs()); |
| }); |
| } |
| |
| /// NarrowSearchSpaceUsingHeuristics - If there are an extraordinary number of |
| /// formulae to choose from, use some rough heuristics to prune down the number |
| /// of formulae. This keeps the main solver from taking an extraordinary amount |
| /// of time in some worst-case scenarios. |
| void LSRInstance::NarrowSearchSpaceUsingHeuristics() { |
| // This is a rough guess that seems to work fairly well. |
| const size_t Limit = UINT16_MAX; |
| |
| SmallPtrSet<const SCEV *, 4> Taken; |
| for (;;) { |
| // Estimate the worst-case number of solutions we might consider. We almost |
| // never consider this many solutions because we prune the search space, |
| // but the pruning isn't always sufficient. |
| uint32_t Power = 1; |
| for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), |
| E = Uses.end(); I != E; ++I) { |
| size_t FSize = I->Formulae.size(); |
| if (FSize >= Limit) { |
| Power = Limit; |
| break; |
| } |
| Power *= FSize; |
| if (Power >= Limit) |
| break; |
| } |
| if (Power < Limit) |
| break; |
| |
| // Ok, we have too many of formulae on our hands to conveniently handle. |
| // Use a rough heuristic to thin out the list. |
| |
| // Pick the register which is used by the most LSRUses, which is likely |
| // to be a good reuse register candidate. |
| const SCEV *Best = 0; |
| unsigned BestNum = 0; |
| for (RegUseTracker::const_iterator I = RegUses.begin(), E = RegUses.end(); |
| I != E; ++I) { |
| const SCEV *Reg = *I; |
| if (Taken.count(Reg)) |
| continue; |
| if (!Best) |
| Best = Reg; |
| else { |
| unsigned Count = RegUses.getUsedByIndices(Reg).count(); |
| if (Count > BestNum) { |
| Best = Reg; |
| BestNum = Count; |
| } |
| } |
| } |
| |
| DEBUG(dbgs() << "Narrowing the search space by assuming " << *Best |
| << " will yield profitable reuse.\n"); |
| Taken.insert(Best); |
| |
| // In any use with formulae which references this register, delete formulae |
| // which don't reference it. |
| for (SmallVectorImpl<LSRUse>::iterator I = Uses.begin(), |
| E = Uses.end(); I != E; ++I) { |
| LSRUse &LU = *I; |
| if (!LU.Regs.count(Best)) continue; |
| |
| // Clear out the set of used regs; it will be recomputed. |
| LU.Regs.clear(); |
| |
| for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { |
| Formula &F = LU.Formulae[i]; |
| if (!F.referencesReg(Best)) { |
| DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); |
| std::swap(LU.Formulae.back(), F); |
| LU.Formulae.pop_back(); |
| --e; |
| --i; |
| continue; |
| } |
| |
| if (F.ScaledReg) LU.Regs.insert(F.ScaledReg); |
| LU.Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); |
| } |
| } |
| |
| DEBUG(dbgs() << "After pre-selection:\n"; |
| print_uses(dbgs())); |
| } |
| } |
| |
| /// SolveRecurse - This is the recursive solver. |
| void LSRInstance::SolveRecurse(SmallVectorImpl<const Formula *> &Solution, |
| Cost &SolutionCost, |
| SmallVectorImpl<const Formula *> &Workspace, |
| const Cost &CurCost, |
| const SmallPtrSet<const SCEV *, 16> &CurRegs, |
| DenseSet<const SCEV *> &VisitedRegs) const { |
| // Some ideas: |
| // - prune more: |
| // - use more aggressive filtering |
| // - sort the formula so that the most profitable solutions are found first |
| // - sort the uses too |
| // - search faster: |
| // - don't compute a cost, and then compare. compare while computing a cost |
| // and bail early. |
| // - track register sets with SmallBitVector |
| |
| const LSRUse &LU = Uses[Workspace.size()]; |
| |
| // If this use references any register that's already a part of the |
| // in-progress solution, consider it a requirement that a formula must |
| // reference that register in order to be considered. This prunes out |
| // unprofitable searching. |
| SmallSetVector<const SCEV *, 4> ReqRegs; |
| for (SmallPtrSet<const SCEV *, 16>::const_iterator I = CurRegs.begin(), |
| E = CurRegs.end(); I != E; ++I) |
| if (LU.Regs.count(*I)) |
| ReqRegs.insert(*I); |
| |
| bool AnySatisfiedReqRegs = false; |
| SmallPtrSet<const SCEV *, 16> NewRegs; |
| Cost NewCost; |
| retry: |
| for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), |
| E = LU.Formulae.end(); I != E; ++I) { |
| const Formula &F = *I; |
| |
| // Ignore formulae which do not use any of the required registers. |
| for (SmallSetVector<const SCEV *, 4>::const_iterator J = ReqRegs.begin(), |
| JE = ReqRegs.end(); J != JE; ++J) { |
| const SCEV *Reg = *J; |
| if ((!F.ScaledReg || F.ScaledReg != Reg) && |
| std::find(F.BaseRegs.begin(), F.BaseRegs.end(), Reg) == |
| F.BaseRegs.end()) |
| goto skip; |
| } |
| AnySatisfiedReqRegs = true; |
| |
| // Evaluate the cost of the current formula. If it's already worse than |
| // the current best, prune the search at that point. |
| NewCost = CurCost; |
| NewRegs = CurRegs; |
| NewCost.RateFormula(F, NewRegs, VisitedRegs, L, LU.Offsets, SE, DT); |
| if (NewCost < SolutionCost) { |
| Workspace.push_back(&F); |
| if (Workspace.size() != Uses.size()) { |
| SolveRecurse(Solution, SolutionCost, Workspace, NewCost, |
| NewRegs, VisitedRegs); |
| if (F.getNumRegs() == 1 && Workspace.size() == 1) |
| VisitedRegs.insert(F.ScaledReg ? F.ScaledReg : F.BaseRegs[0]); |
| } else { |
| DEBUG(dbgs() << "New best at "; NewCost.print(dbgs()); |
| dbgs() << ". Regs:"; |
| for (SmallPtrSet<const SCEV *, 16>::const_iterator |
| I = NewRegs.begin(), E = NewRegs.end(); I != E; ++I) |
| dbgs() << ' ' << **I; |
| dbgs() << '\n'); |
| |
| SolutionCost = NewCost; |
| Solution = Workspace; |
| } |
| Workspace.pop_back(); |
| } |
| skip:; |
| } |
| |
| // If none of the formulae had all of the required registers, relax the |
| // constraint so that we don't exclude all formulae. |
| if (!AnySatisfiedReqRegs) { |
| ReqRegs.clear(); |
| goto retry; |
| } |
| } |
| |
| void LSRInstance::Solve(SmallVectorImpl<const Formula *> &Solution) const { |
| SmallVector<const Formula *, 8> Workspace; |
| Cost SolutionCost; |
| SolutionCost.Loose(); |
| Cost CurCost; |
| SmallPtrSet<const SCEV *, 16> CurRegs; |
| DenseSet<const SCEV *> VisitedRegs; |
| Workspace.reserve(Uses.size()); |
| |
| SolveRecurse(Solution, SolutionCost, Workspace, CurCost, |
| CurRegs, VisitedRegs); |
| |
| // Ok, we've now made all our decisions. |
| DEBUG(dbgs() << "\n" |
| "The chosen solution requires "; SolutionCost.print(dbgs()); |
| dbgs() << ":\n"; |
| for (size_t i = 0, e = Uses.size(); i != e; ++i) { |
| dbgs() << " "; |
| Uses[i].print(dbgs()); |
| dbgs() << "\n" |
| " "; |
| Solution[i]->print(dbgs()); |
| dbgs() << '\n'; |
| }); |
| } |
| |
| /// getImmediateDominator - A handy utility for the specific DominatorTree |
| /// query that we need here. |
| /// |
| static BasicBlock *getImmediateDominator(BasicBlock *BB, DominatorTree &DT) { |
| DomTreeNode *Node = DT.getNode(BB); |
| if (!Node) return 0; |
| Node = Node->getIDom(); |
| if (!Node) return 0; |
| return Node->getBlock(); |
| } |
| |
| Value *LSRInstance::Expand(const LSRFixup &LF, |
| const Formula &F, |
| BasicBlock::iterator IP, |
| SCEVExpander &Rewriter, |
| SmallVectorImpl<WeakVH> &DeadInsts) const { |
| const LSRUse &LU = Uses[LF.LUIdx]; |
| |
| // Then, collect some instructions which we will remain dominated by when |
| // expanding the replacement. These must be dominated by any operands that |
| // will be required in the expansion. |
| SmallVector<Instruction *, 4> Inputs; |
| if (Instruction *I = dyn_cast<Instruction>(LF.OperandValToReplace)) |
| Inputs.push_back(I); |
| if (LU.Kind == LSRUse::ICmpZero) |
| if (Instruction *I = |
| dyn_cast<Instruction>(cast<ICmpInst>(LF.UserInst)->getOperand(1))) |
| Inputs.push_back(I); |
| if (LF.PostIncLoop) { |
| if (!L->contains(LF.UserInst)) |
| Inputs.push_back(L->getLoopLatch()->getTerminator()); |
| else |
| Inputs.push_back(IVIncInsertPos); |
| } |
| |
| // Then, climb up the immediate dominator tree as far as we can go while |
| // still being dominated by the input positions. |
| for (;;) { |
| bool AllDominate = true; |
| Instruction *BetterPos = 0; |
| BasicBlock *IDom = getImmediateDominator(IP->getParent(), DT); |
| if (!IDom) break; |
| Instruction *Tentative = IDom->getTerminator(); |
| for (SmallVectorImpl<Instruction *>::const_iterator I = Inputs.begin(), |
| E = Inputs.end(); I != E; ++I) { |
| Instruction *Inst = *I; |
| if (Inst == Tentative || !DT.dominates(Inst, Tentative)) { |
| AllDominate = false; |
| break; |
| } |
| if (IDom == Inst->getParent() && |
| (!BetterPos || DT.dominates(BetterPos, Inst))) |
| BetterPos = next(BasicBlock::iterator(Inst)); |
| } |
| if (!AllDominate) |
| break; |
| if (BetterPos) |
| IP = BetterPos; |
| else |
| IP = Tentative; |
| } |
| while (isa<PHINode>(IP)) ++IP; |
| |
| // Inform the Rewriter if we have a post-increment use, so that it can |
| // perform an advantageous expansion. |
| Rewriter.setPostInc(LF.PostIncLoop); |
| |
| // This is the type that the user actually needs. |
| const Type *OpTy = LF.OperandValToReplace->getType(); |
| // This will be the type that we'll initially expand to. |
| const Type *Ty = F.getType(); |
| if (!Ty) |
| // No type known; just expand directly to the ultimate type. |
| Ty = OpTy; |
| else if (SE.getEffectiveSCEVType(Ty) == SE.getEffectiveSCEVType(OpTy)) |
| // Expand directly to the ultimate type if it's the right size. |
| Ty = OpTy; |
| // This is the type to do integer arithmetic in. |
| const Type *IntTy = SE.getEffectiveSCEVType(Ty); |
| |
| // Build up a list of operands to add together to form the full base. |
| SmallVector<const SCEV *, 8> Ops; |
| |
| // Expand the BaseRegs portion. |
| for (SmallVectorImpl<const SCEV *>::const_iterator I = F.BaseRegs.begin(), |
| E = F.BaseRegs.end(); I != E; ++I) { |
| const SCEV *Reg = *I; |
| assert(!Reg->isZero() && "Zero allocated in a base register!"); |
| |
| // If we're expanding for a post-inc user for the add-rec's loop, make the |
| // post-inc adjustment. |
| const SCEV *Start = Reg; |
| while (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Start)) { |
| if (AR->getLoop() == LF.PostIncLoop) { |
| Reg = SE.getAddExpr(Reg, AR->getStepRecurrence(SE)); |
| // If the user is inside the loop, insert the code after the increment |
| // so that it is dominated by its operand. If the original insert point |
| // was already dominated by the increment, keep it, because there may |
| // be loop-variant operands that need to be respected also. |
| if (L->contains(LF.UserInst) && !DT.dominates(IVIncInsertPos, IP)) |
| IP = IVIncInsertPos; |
| break; |
| } |
| Start = AR->getStart(); |
| } |
| |
| Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP))); |
| } |
| |
| // Flush the operand list to suppress SCEVExpander hoisting. |
| if (!Ops.empty()) { |
| Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); |
| Ops.clear(); |
| Ops.push_back(SE.getUnknown(FullV)); |
| } |
| |
| // Expand the ScaledReg portion. |
| Value *ICmpScaledV = 0; |
| if (F.AM.Scale != 0) { |
| const SCEV *ScaledS = F.ScaledReg; |
| |
| // If we're expanding for a post-inc user for the add-rec's loop, make the |
| // post-inc adjustment. |
| if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(ScaledS)) |
| if (AR->getLoop() == LF.PostIncLoop) |
| ScaledS = SE.getAddExpr(ScaledS, AR->getStepRecurrence(SE)); |
| |
| if (LU.Kind == LSRUse::ICmpZero) { |
| // An interesting way of "folding" with an icmp is to use a negated |
| // scale, which we'll implement by inserting it into the other operand |
| // of the icmp. |
| assert(F.AM.Scale == -1 && |
| "The only scale supported by ICmpZero uses is -1!"); |
| ICmpScaledV = Rewriter.expandCodeFor(ScaledS, 0, IP); |
| } else { |
| // Otherwise just expand the scaled register and an explicit scale, |
| // which is expected to be matched as part of the address. |
| ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP)); |
| ScaledS = SE.getMulExpr(ScaledS, |
| SE.getIntegerSCEV(F.AM.Scale, |
| ScaledS->getType())); |
| Ops.push_back(ScaledS); |
| |
| // Flush the operand list to suppress SCEVExpander hoisting. |
| Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); |
| Ops.clear(); |
| Ops.push_back(SE.getUnknown(FullV)); |
| } |
| } |
| |
| // Expand the GV portion. |
| if (F.AM.BaseGV) { |
| Ops.push_back(SE.getUnknown(F.AM.BaseGV)); |
| |
| // Flush the operand list to suppress SCEVExpander hoisting. |
| Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); |
| Ops.clear(); |
| Ops.push_back(SE.getUnknown(FullV)); |
| } |
| |
| // Expand the immediate portion. |
| int64_t Offset = (uint64_t)F.AM.BaseOffs + LF.Offset; |
| if (Offset != 0) { |
| if (LU.Kind == LSRUse::ICmpZero) { |
| // The other interesting way of "folding" with an ICmpZero is to use a |
| // negated immediate. |
| if (!ICmpScaledV) |
| ICmpScaledV = ConstantInt::get(IntTy, -Offset); |
| else { |
| Ops.push_back(SE.getUnknown(ICmpScaledV)); |
| ICmpScaledV = ConstantInt::get(IntTy, Offset); |
| } |
| } else { |
| // Just add the immediate values. These again are expected to be matched |
| // as part of the address. |
| Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, Offset))); |
| } |
| } |
| |
| // Emit instructions summing all the operands. |
| const SCEV *FullS = Ops.empty() ? |
| SE.getIntegerSCEV(0, IntTy) : |
| SE.getAddExpr(Ops); |
| Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP); |
| |
| // We're done expanding now, so reset the rewriter. |
| Rewriter.setPostInc(0); |
| |
| // An ICmpZero Formula represents an ICmp which we're handling as a |
| // comparison against zero. Now that we've expanded an expression for that |
| // form, update the ICmp's other operand. |
| if (LU.Kind == LSRUse::ICmpZero) { |
| ICmpInst *CI = cast<ICmpInst>(LF.UserInst); |
| DeadInsts.push_back(CI->getOperand(1)); |
| assert(!F.AM.BaseGV && "ICmp does not support folding a global value and " |
| "a scale at the same time!"); |
| if (F.AM.Scale == -1) { |
| if (ICmpScaledV->getType() != OpTy) { |
| Instruction *Cast = |
| CastInst::Create(CastInst::getCastOpcode(ICmpScaledV, false, |
| OpTy, false), |
| ICmpScaledV, OpTy, "tmp", CI); |
| ICmpScaledV = Cast; |
| } |
| CI->setOperand(1, ICmpScaledV); |
| } else { |
| assert(F.AM.Scale == 0 && |
| "ICmp does not support folding a global value and " |
| "a scale at the same time!"); |
| Constant *C = ConstantInt::getSigned(SE.getEffectiveSCEVType(OpTy), |
| -(uint64_t)Offset); |
| if (C->getType() != OpTy) |
| C = ConstantExpr::getCast(CastInst::getCastOpcode(C, false, |
| OpTy, false), |
| C, OpTy); |
| |
| CI->setOperand(1, C); |
| } |
| } |
| |
| return FullV; |
| } |
| |
| /// RewriteForPHI - Helper for Rewrite. PHI nodes are special because the use |
| /// of their operands effectively happens in their predecessor blocks, so the |
| /// expression may need to be expanded in multiple places. |
| void LSRInstance::RewriteForPHI(PHINode *PN, |
| const LSRFixup &LF, |
| const Formula &F, |
| SCEVExpander &Rewriter, |
| SmallVectorImpl<WeakVH> &DeadInsts, |
| Pass *P) const { |
| DenseMap<BasicBlock *, Value *> Inserted; |
| for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) |
| if (PN->getIncomingValue(i) == LF.OperandValToReplace) { |
| BasicBlock *BB = PN->getIncomingBlock(i); |
| |
| // If this is a critical edge, split the edge so that we do not insert |
| // the code on all predecessor/successor paths. We do this unless this |
| // is the canonical backedge for this loop, which complicates post-inc |
| // users. |
| if (e != 1 && BB->getTerminator()->getNumSuccessors() > 1 && |
| !isa<IndirectBrInst>(BB->getTerminator()) && |
| (PN->getParent() != L->getHeader() || !L->contains(BB))) { |
| // Split the critical edge. |
| BasicBlock *NewBB = SplitCriticalEdge(BB, PN->getParent(), P); |
| |
| // If PN is outside of the loop and BB is in the loop, we want to |
| // move the block to be immediately before the PHI block, not |
| // immediately after BB. |
| if (L->contains(BB) && !L->contains(PN)) |
| NewBB->moveBefore(PN->getParent()); |
| |
| // Splitting the edge can reduce the number of PHI entries we have. |
| e = PN->getNumIncomingValues(); |
| BB = NewBB; |
| i = PN->getBasicBlockIndex(BB); |
| } |
| |
| std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair = |
| Inserted.insert(std::make_pair(BB, static_cast<Value *>(0))); |
| if (!Pair.second) |
| PN->setIncomingValue(i, Pair.first->second); |
| else { |
| Value *FullV = Expand(LF, F, BB->getTerminator(), Rewriter, DeadInsts); |
| |
| // If this is reuse-by-noop-cast, insert the noop cast. |
| const Type *OpTy = LF.OperandValToReplace->getType(); |
| if (FullV->getType() != OpTy) |
| FullV = |
| CastInst::Create(CastInst::getCastOpcode(FullV, false, |
| OpTy, false), |
| FullV, LF.OperandValToReplace->getType(), |
| "tmp", BB->getTerminator()); |
| |
| PN->setIncomingValue(i, FullV); |
| Pair.first->second = FullV; |
| } |
| } |
| } |
| |
| /// Rewrite - Emit instructions for the leading candidate expression for this |
| /// LSRUse (this is called "expanding"), and update the UserInst to reference |
| /// the newly expanded value. |
| void LSRInstance::Rewrite(const LSRFixup &LF, |
| const Formula &F, |
| SCEVExpander &Rewriter, |
| SmallVectorImpl<WeakVH> &DeadInsts, |
| Pass *P) const { |
| // First, find an insertion point that dominates UserInst. For PHI nodes, |
| // find the nearest block which dominates all the relevant uses. |
| if (PHINode *PN = dyn_cast<PHINode>(LF.UserInst)) { |
| RewriteForPHI(PN, LF, F, Rewriter, DeadInsts, P); |
| } else { |
| Value *FullV = Expand(LF, F, LF.UserInst, Rewriter, DeadInsts); |
| |
| // If this is reuse-by-noop-cast, insert the noop cast. |
| const Type *OpTy = LF.OperandValToReplace->getType(); |
| if (FullV->getType() != OpTy) { |
| Instruction *Cast = |
| CastInst::Create(CastInst::getCastOpcode(FullV, false, OpTy, false), |
| FullV, OpTy, "tmp", LF.UserInst); |
| FullV = Cast; |
| } |
| |
| // Update the user. ICmpZero is handled specially here (for now) because |
| // Expand may have updated one of the operands of the icmp already, and |
| // its new value may happen to be equal to LF.OperandValToReplace, in |
| // which case doing replaceUsesOfWith leads to replacing both operands |
| // with the same value. TODO: Reorganize this. |
| if (Uses[LF.LUIdx].Kind == LSRUse::ICmpZero) |
| LF.UserInst->setOperand(0, FullV); |
| else |
| LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV); |
| } |
| |
| DeadInsts.push_back(LF.OperandValToReplace); |
| } |
| |
| void |
| LSRInstance::ImplementSolution(const SmallVectorImpl<const Formula *> &Solution, |
| Pass *P) { |
| // Keep track of instructions we may have made dead, so that |
| // we can remove them after we are done working. |
| SmallVector<WeakVH, 16> DeadInsts; |
| |
| SCEVExpander Rewriter(SE); |
| Rewriter.disableCanonicalMode(); |
| Rewriter.setIVIncInsertPos(L, IVIncInsertPos); |
| |
| // Expand the new value definitions and update the users. |
| for (size_t i = 0, e = Fixups.size(); i != e; ++i) { |
| size_t LUIdx = Fixups[i].LUIdx; |
| |
| Rewrite(Fixups[i], *Solution[LUIdx], Rewriter, DeadInsts, P); |
| |
| Changed = true; |
| } |
| |
| // Clean up after ourselves. This must be done before deleting any |
| // instructions. |
| Rewriter.clear(); |
| |
| Changed |= DeleteTriviallyDeadInstructions(DeadInsts); |
| } |
| |
| LSRInstance::LSRInstance(const TargetLowering *tli, Loop *l, Pass *P) |
| : IU(P->getAnalysis<IVUsers>()), |
| SE(P->getAnalysis<ScalarEvolution>()), |
| DT(P->getAnalysis<DominatorTree>()), |
| TLI(tli), L(l), Changed(false), IVIncInsertPos(0) { |
| |
| // If LoopSimplify form is not available, stay out of trouble. |
| if (!L->isLoopSimplifyForm()) return; |
| |
| // If there's no interesting work to be done, bail early. |
| if (IU.empty()) return; |
| |
| DEBUG(dbgs() << "\nLSR on loop "; |
| WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false); |
| dbgs() << ":\n"); |
| |
| /// OptimizeShadowIV - If IV is used in a int-to-float cast |
| /// inside the loop then try to eliminate the cast operation. |
| OptimizeShadowIV(); |
| |
| // Change loop terminating condition to use the postinc iv when possible. |
| Changed |= OptimizeLoopTermCond(); |
| |
| CollectInterestingTypesAndFactors(); |
| CollectFixupsAndInitialFormulae(); |
| CollectLoopInvariantFixupsAndFormulae(); |
| |
| DEBUG(dbgs() << "LSR found " << Uses.size() << " uses:\n"; |
| print_uses(dbgs())); |
| |
| // Now use the reuse data to generate a bunch of interesting ways |
| // to formulate the values needed for the uses. |
| GenerateAllReuseFormulae(); |
| |
| DEBUG(dbgs() << "\n" |
| "After generating reuse formulae:\n"; |
| print_uses(dbgs())); |
| |
| FilterOutUndesirableDedicatedRegisters(); |
| NarrowSearchSpaceUsingHeuristics(); |
| |
| SmallVector<const Formula *, 8> Solution; |
| Solve(Solution); |
| assert(Solution.size() == Uses.size() && "Malformed solution!"); |
| |
| // Release memory that is no longer needed. |
| Factors.clear(); |
| Types.clear(); |
| RegUses.clear(); |
| |
| #ifndef NDEBUG |
| // Formulae should be legal. |
| for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), |
| E = Uses.end(); I != E; ++I) { |
| const LSRUse &LU = *I; |
| for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(), |
| JE = LU.Formulae.end(); J != JE; ++J) |
| assert(isLegalUse(J->AM, LU.MinOffset, LU.MaxOffset, |
| LU.Kind, LU.AccessTy, TLI) && |
| "Illegal formula generated!"); |
| }; |
| #endif |
| |
| // Now that we've decided what we want, make it so. |
| ImplementSolution(Solution, P); |
| } |
| |
| void LSRInstance::print_factors_and_types(raw_ostream &OS) const { |
| if (Factors.empty() && Types.empty()) return; |
| |
| OS << "LSR has identified the following interesting factors and types: "; |
| bool First = true; |
| |
| for (SmallSetVector<int64_t, 8>::const_iterator |
| I = Factors.begin(), E = Factors.end(); I != E; ++I) { |
| if (!First) OS << ", "; |
| First = false; |
| OS << '*' << *I; |
| } |
| |
| for (SmallSetVector<const Type *, 4>::const_iterator |
| I = Types.begin(), E = Types.end(); I != E; ++I) { |
| if (!First) OS << ", "; |
| First = false; |
| OS << '(' << **I << ')'; |
| } |
| OS << '\n'; |
| } |
| |
| void LSRInstance::print_fixups(raw_ostream &OS) const { |
| OS << "LSR is examining the following fixup sites:\n"; |
| for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(), |
| E = Fixups.end(); I != E; ++I) { |
| const LSRFixup &LF = *I; |
| dbgs() << " "; |
| LF.print(OS); |
| OS << '\n'; |
| } |
| } |
| |
| void LSRInstance::print_uses(raw_ostream &OS) const { |
| OS << "LSR is examining the following uses:\n"; |
| for (SmallVectorImpl<LSRUse>::const_iterator I = Uses.begin(), |
| E = Uses.end(); I != E; ++I) { |
| const LSRUse &LU = *I; |
| dbgs() << " "; |
| LU.print(OS); |
| OS << '\n'; |
| for (SmallVectorImpl<Formula>::const_iterator J = LU.Formulae.begin(), |
| JE = LU.Formulae.end(); J != JE; ++J) { |
| OS << " "; |
| J->print(OS); |
| OS << '\n'; |
| } |
| } |
| } |
| |
| void LSRInstance::print(raw_ostream &OS) const { |
| print_factors_and_types(OS); |
| print_fixups(OS); |
| print_uses(OS); |
| } |
| |
| void LSRInstance::dump() const { |
| print(errs()); errs() << '\n'; |
| } |
| |
| namespace { |
| |
| class LoopStrengthReduce : public LoopPass { |
| /// TLI - Keep a pointer of a TargetLowering to consult for determining |
| /// transformation profitability. |
| const TargetLowering *const TLI; |
| |
| public: |
| static char ID; // Pass ID, replacement for typeid |
| explicit LoopStrengthReduce(const TargetLowering *tli = 0); |
| |
| private: |
| bool runOnLoop(Loop *L, LPPassManager &LPM); |
| void getAnalysisUsage(AnalysisUsage &AU) const; |
| }; |
| |
| } |
| |
| char LoopStrengthReduce::ID = 0; |
| static RegisterPass<LoopStrengthReduce> |
| X("loop-reduce", "Loop Strength Reduction"); |
| |
| Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) { |
| return new LoopStrengthReduce(TLI); |
| } |
| |
| LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli) |
| : LoopPass(&ID), TLI(tli) {} |
| |
| void LoopStrengthReduce::getAnalysisUsage(AnalysisUsage &AU) const { |
| // We split critical edges, so we change the CFG. However, we do update |
| // many analyses if they are around. |
| AU.addPreservedID(LoopSimplifyID); |
| AU.addPreserved<LoopInfo>(); |
| AU.addPreserved("domfrontier"); |
| |
| AU.addRequiredID(LoopSimplifyID); |
| AU.addRequired<DominatorTree>(); |
| AU.addPreserved<DominatorTree>(); |
| AU.addRequired<ScalarEvolution>(); |
| AU.addPreserved<ScalarEvolution>(); |
| AU.addRequired<IVUsers>(); |
| AU.addPreserved<IVUsers>(); |
| } |
| |
| bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) { |
| bool Changed = false; |
| |
| // Run the main LSR transformation. |
| Changed |= LSRInstance(TLI, L, this).getChanged(); |
| |
| // At this point, it is worth checking to see if any recurrence PHIs are also |
| // dead, so that we can remove them as well. |
| Changed |= DeleteDeadPHIs(L->getHeader()); |
| |
| return Changed; |
| } |