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Diffstat (limited to 'contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp')
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diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp new file mode 100644 index 0000000..b14a713 --- /dev/null +++ b/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp @@ -0,0 +1,4818 @@ +//===- 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/Assembly/Writer.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/CommandLine.h" +#include "llvm/Support/ValueHandle.h" +#include "llvm/Support/raw_ostream.h" +#include "llvm/Target/TargetLowering.h" +#include <algorithm> +using namespace llvm; + +/// MaxIVUsers is an arbitrary threshold that provides an early opportunitiy for +/// bail out. This threshold is far beyond the number of users that LSR can +/// conceivably solve, so it should not affect generated code, but catches the +/// worst cases before LSR burns too much compile time and stack space. +static const unsigned MaxIVUsers = 200; + +// Temporary flag to cleanup congruent phis after LSR phi expansion. +// It's currently disabled until we can determine whether it's truly useful or +// not. The flag should be removed after the v3.0 release. +// This is now needed for ivchains. +static cl::opt<bool> EnablePhiElim( + "enable-lsr-phielim", cl::Hidden, cl::init(true), + cl::desc("Enable LSR phi elimination")); + +#ifndef NDEBUG +// Stress test IV chain generation. +static cl::opt<bool> StressIVChain( + "stress-ivchain", cl::Hidden, cl::init(false), + cl::desc("Stress test LSR IV chains")); +#else +static bool StressIVChain = false; +#endif + +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 RegUsesMap; + SmallVector<const SCEV *, 16> RegSequence; + +public: + void CountRegister(const SCEV *Reg, size_t LUIdx); + void DropRegister(const SCEV *Reg, size_t LUIdx); + void SwapAndDropUse(size_t LUIdx, size_t LastLUIdx); + + 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 = + RegUsesMap.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); +} + +void +RegUseTracker::DropRegister(const SCEV *Reg, size_t LUIdx) { + RegUsesTy::iterator It = RegUsesMap.find(Reg); + assert(It != RegUsesMap.end()); + RegSortData &RSD = It->second; + assert(RSD.UsedByIndices.size() > LUIdx); + RSD.UsedByIndices.reset(LUIdx); +} + +void +RegUseTracker::SwapAndDropUse(size_t LUIdx, size_t LastLUIdx) { + assert(LUIdx <= LastLUIdx); + + // Update RegUses. The data structure is not optimized for this purpose; + // we must iterate through it and update each of the bit vectors. + for (RegUsesTy::iterator I = RegUsesMap.begin(), E = RegUsesMap.end(); + I != E; ++I) { + SmallBitVector &UsedByIndices = I->second.UsedByIndices; + if (LUIdx < UsedByIndices.size()) + UsedByIndices[LUIdx] = + LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : 0; + UsedByIndices.resize(std::min(UsedByIndices.size(), LastLUIdx)); + } +} + +bool +RegUseTracker::isRegUsedByUsesOtherThan(const SCEV *Reg, size_t LUIdx) const { + RegUsesTy::const_iterator I = RegUsesMap.find(Reg); + if (I == RegUsesMap.end()) + return false; + const SmallBitVector &UsedByIndices = I->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 = RegUsesMap.find(Reg); + assert(I != RegUsesMap.end() && "Unknown register!"); + return I->second.UsedByIndices; +} + +void RegUseTracker::clear() { + RegUsesMap.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; + + /// UnfoldedOffset - An additional constant offset which added near the + /// use. This requires a temporary register, but the offset itself can + /// live in an add immediate field rather than a register. + int64_t UnfoldedOffset; + + Formula() : ScaledReg(0), UnfoldedOffset(0) {} + + void InitialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE); + + unsigned getNumRegs() const; + Type *getType() const; + + void DeleteBaseReg(const SCEV *&S); + + 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) { + // Collect expressions which properly dominate the loop header. + if (SE.properlyDominates(S, L->getHeader())) { + 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); + return; + } + + // Look at addrec operands. + if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) + if (!AR->getStart()->isZero()) { + DoInitialMatch(AR->getStart(), L, Good, Bad, SE); + DoInitialMatch(SE.getAddRecExpr(SE.getConstant(AR->getType(), 0), + AR->getStepRecurrence(SE), + // FIXME: AR->getNoWrapFlags() + AR->getLoop(), SCEV::FlagAnyWrap), + L, Good, Bad, SE); + 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); + 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) { + SmallVector<const SCEV *, 4> Good; + SmallVector<const SCEV *, 4> Bad; + DoInitialMatch(S, L, Good, Bad, SE); + if (!Good.empty()) { + const SCEV *Sum = SE.getAddExpr(Good); + if (!Sum->isZero()) + BaseRegs.push_back(Sum); + AM.HasBaseReg = true; + } + if (!Bad.empty()) { + const SCEV *Sum = SE.getAddExpr(Bad); + if (!Sum->isZero()) + BaseRegs.push_back(Sum); + 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. +Type *Formula::getType() const { + return !BaseRegs.empty() ? BaseRegs.front()->getType() : + ScaledReg ? ScaledReg->getType() : + AM.BaseGV ? AM.BaseGV->getType() : + 0; +} + +/// DeleteBaseReg - Delete the given base reg from the BaseRegs list. +void Formula::DeleteBaseReg(const SCEV *&S) { + if (&S != &BaseRegs.back()) + std::swap(S, BaseRegs.back()); + BaseRegs.pop_back(); +} + +/// 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.HasBaseReg && BaseRegs.empty()) { + if (!First) OS << " + "; else First = false; + OS << "**error: HasBaseReg**"; + } else if (!AM.HasBaseReg && !BaseRegs.empty()) { + if (!First) OS << " + "; else First = false; + OS << "**error: !HasBaseReg**"; + } + if (AM.Scale != 0) { + if (!First) OS << " + "; else First = false; + OS << AM.Scale << "*reg("; + if (ScaledReg) + OS << *ScaledReg; + else + OS << "<unknown>"; + OS << ')'; + } + if (UnfoldedOffset != 0) { + if (!First) OS << " + "; else First = false; + OS << "imm(" << UnfoldedOffset << ')'; + } +} + +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) { + 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) { + Type *WideTy = + IntegerType::get(SE.getContext(), SE.getTypeSizeInBits(A->getType()) + 1); + return isa<SCEVAddExpr>(SE.getSignExtendExpr(A, WideTy)); +} + +/// isMulSExtable - Return true if the given mul can be sign-extended +/// without changing its value. +static bool isMulSExtable(const SCEVMulExpr *M, ScalarEvolution &SE) { + Type *WideTy = + IntegerType::get(SE.getContext(), + SE.getTypeSizeInBits(M->getType()) * M->getNumOperands()); + return isa<SCEVMulExpr>(SE.getSignExtendExpr(M, 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.getConstant(LHS->getType(), 1); + + // Handle a few RHS special cases. + const SCEVConstant *RC = dyn_cast<SCEVConstant>(RHS); + if (RC) { + const APInt &RA = RC->getValue()->getValue(); + // Handle x /s -1 as x * -1, to give ScalarEvolution a chance to do + // some folding. + if (RA.isAllOnesValue()) + return SE.getMulExpr(LHS, RC); + // Handle x /s 1 as x. + if (RA == 1) + return LHS; + } + + // Check for a division of a constant by a constant. + if (const SCEVConstant *C = dyn_cast<SCEVConstant>(LHS)) { + if (!RC) + return 0; + const APInt &LA = C->getValue()->getValue(); + const APInt &RA = RC->getValue()->getValue(); + if (LA.srem(RA) != 0) + return 0; + return SE.getConstant(LA.sdiv(RA)); + } + + // 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 *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE, + IgnoreSignificantBits); + if (!Step) return 0; + const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE, + IgnoreSignificantBits); + if (!Start) return 0; + // FlagNW is independent of the start value, step direction, and is + // preserved with smaller magnitude steps. + // FIXME: AR->getNoWrapFlags(SCEV::FlagNW) + return SE.getAddRecExpr(Start, Step, AR->getLoop(), SCEV::FlagAnyWrap); + } + return 0; + } + + // 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); + } + return 0; + } + + // 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) { + const SCEV *S = *I; + if (!Found) + if (const SCEV *Q = getExactSDiv(S, RHS, SE, + IgnoreSignificantBits)) { + S = Q; + Found = true; + } + Ops.push_back(S); + } + return Found ? SE.getMulExpr(Ops) : 0; + } + return 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.getConstant(C->getType(), 0); + 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); + if (Result != 0) + 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); + if (Result != 0) + S = SE.getAddRecExpr(NewOps, AR->getLoop(), + // FIXME: AR->getNoWrapFlags(SCEV::FlagNW) + SCEV::FlagAnyWrap); + 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.getConstant(GV->getType(), 0); + 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); + if (Result) + 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); + if (Result) + S = SE.getAddRecExpr(NewOps, AR->getLoop(), + // FIXME: AR->getNoWrapFlags(SCEV::FlagNW) + SCEV::FlagAnyWrap); + 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_sse_storeu_ps: + case Intrinsic::x86_sse2_storeu_pd: + case Intrinsic::x86_sse2_storeu_dq: + case Intrinsic::x86_sse2_storel_dq: + if (II->getArgOperand(0) == OperandVal) + isAddress = true; + break; + } + } + return isAddress; +} + +/// getAccessType - Return the type of the memory being accessed. +static Type *getAccessType(const Instruction *Inst) { + 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->getArgOperand(0)->getType(); + break; + } + } + + // All pointers have the same requirements, so canonicalize them to an + // arbitrary pointer type to minimize variation. + if (PointerType *PTy = dyn_cast<PointerType>(AccessTy)) + AccessTy = PointerType::get(IntegerType::get(PTy->getContext(), 1), + PTy->getAddressSpace()); + + return AccessTy; +} + +/// isExistingPhi - Return true if this AddRec is already a phi in its loop. +static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) { + 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 true; + } + return false; +} + +/// Check if expanding this expression is likely to incur significant cost. This +/// is tricky because SCEV doesn't track which expressions are actually computed +/// by the current IR. +/// +/// We currently allow expansion of IV increments that involve adds, +/// multiplication by constants, and AddRecs from existing phis. +/// +/// TODO: Allow UDivExpr if we can find an existing IV increment that is an +/// obvious multiple of the UDivExpr. +static bool isHighCostExpansion(const SCEV *S, + SmallPtrSet<const SCEV*, 8> &Processed, + ScalarEvolution &SE) { + // Zero/One operand expressions + switch (S->getSCEVType()) { + case scUnknown: + case scConstant: + return false; + case scTruncate: + return isHighCostExpansion(cast<SCEVTruncateExpr>(S)->getOperand(), + Processed, SE); + case scZeroExtend: + return isHighCostExpansion(cast<SCEVZeroExtendExpr>(S)->getOperand(), + Processed, SE); + case scSignExtend: + return isHighCostExpansion(cast<SCEVSignExtendExpr>(S)->getOperand(), + Processed, SE); + } + + if (!Processed.insert(S)) + return false; + + if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { + for (SCEVAddExpr::op_iterator I = Add->op_begin(), E = Add->op_end(); + I != E; ++I) { + if (isHighCostExpansion(*I, Processed, SE)) + return true; + } + return false; + } + + if (const SCEVMulExpr *Mul = dyn_cast<SCEVMulExpr>(S)) { + if (Mul->getNumOperands() == 2) { + // Multiplication by a constant is ok + if (isa<SCEVConstant>(Mul->getOperand(0))) + return isHighCostExpansion(Mul->getOperand(1), Processed, SE); + + // If we have the value of one operand, check if an existing + // multiplication already generates this expression. + if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(Mul->getOperand(1))) { + Value *UVal = U->getValue(); + for (Value::use_iterator UI = UVal->use_begin(), UE = UVal->use_end(); + UI != UE; ++UI) { + // If U is a constant, it may be used by a ConstantExpr. + Instruction *User = dyn_cast<Instruction>(*UI); + if (User && User->getOpcode() == Instruction::Mul + && SE.isSCEVable(User->getType())) { + return SE.getSCEV(User) == Mul; + } + } + } + } + } + + if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { + if (isExistingPhi(AR, SE)) + return false; + } + + // Fow now, consider any other type of expression (div/mul/min/max) high cost. + return true; +} + +/// 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) {} + + bool operator<(const Cost &Other) const; + + void Loose(); + +#ifndef NDEBUG + // Once any of the metrics loses, they must all remain losers. + bool isValid() { + return ((NumRegs | AddRecCost | NumIVMuls | NumBaseAdds + | ImmCost | SetupCost) != ~0u) + || ((NumRegs & AddRecCost & NumIVMuls & NumBaseAdds + & ImmCost & SetupCost) == ~0u); + } +#endif + + bool isLoser() { + assert(isValid() && "invalid cost"); + return NumRegs == ~0u; + } + + 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, + SmallPtrSet<const SCEV *, 16> *LoserRegs = 0); + + 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, + SmallPtrSet<const SCEV *, 16> *LoserRegs); +}; + +} + +/// 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 this is an addrec for another loop, don't second-guess its addrec phi + // nodes. LSR isn't currently smart enough to reason about more than one + // loop at a time. LSR has already run on inner loops, will not run on outer + // loops, and cannot be expected to change sibling loops. + if (AR->getLoop() != L) { + // If the AddRec exists, consider it's register free and leave it alone. + if (isExistingPhi(AR, SE)) + return; + + // Otherwise, do not consider this formula at all. + Loose(); + return; + } + AddRecCost += 1; /// TODO: This should be a function of the stride. + + // 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->getOperand(1))) { + RateRegister(AR->getOperand(1), Regs, L, SE, DT); + if (isLoser()) + return; + } + } + } + ++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; + + NumIVMuls += isa<SCEVMulExpr>(Reg) && + SE.hasComputableLoopEvolution(Reg, L); +} + +/// RatePrimaryRegister - Record this register in the set. If we haven't seen it +/// before, rate it. Optional LoserRegs provides a way to declare any formula +/// that refers to one of those regs an instant loser. +void Cost::RatePrimaryRegister(const SCEV *Reg, + SmallPtrSet<const SCEV *, 16> &Regs, + const Loop *L, + ScalarEvolution &SE, DominatorTree &DT, + SmallPtrSet<const SCEV *, 16> *LoserRegs) { + if (LoserRegs && LoserRegs->count(Reg)) { + Loose(); + return; + } + if (Regs.insert(Reg)) { + RateRegister(Reg, Regs, L, SE, DT); + if (isLoser()) + LoserRegs->insert(Reg); + } +} + +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, + SmallPtrSet<const SCEV *, 16> *LoserRegs) { + // Tally up the registers. + if (const SCEV *ScaledReg = F.ScaledReg) { + if (VisitedRegs.count(ScaledReg)) { + Loose(); + return; + } + RatePrimaryRegister(ScaledReg, Regs, L, SE, DT, LoserRegs); + if (isLoser()) + return; + } + 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, LoserRegs); + if (isLoser()) + return; + } + + // Determine how many (unfolded) adds we'll need inside the loop. + size_t NumBaseParts = F.BaseRegs.size() + (F.UnfoldedOffset != 0); + if (NumBaseParts > 1) + NumBaseAdds += NumBaseParts - 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(); + } + assert(isValid() && "invalid cost"); +} + +/// Loose - Set this cost to a losing 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; + + /// PostIncLoops - 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. + PostIncLoopSet PostIncLoops; + + /// 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; + + bool isUseFullyOutsideLoop(const Loop *L) const; + + LSRFixup(); + + void print(raw_ostream &OS) const; + void dump() const; +}; + +} + +LSRFixup::LSRFixup() + : UserInst(0), OperandValToReplace(0), LUIdx(~size_t(0)), Offset(0) {} + +/// isUseFullyOutsideLoop - Test whether this fixup always uses its +/// value outside of the given loop. +bool LSRFixup::isUseFullyOutsideLoop(const Loop *L) const { + // PHI nodes use their value in their incoming blocks. + if (const PHINode *PN = dyn_cast<PHINode>(UserInst)) { + for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) + if (PN->getIncomingValue(i) == OperandValToReplace && + L->contains(PN->getIncomingBlock(i))) + return false; + return true; + } + + return !L->contains(UserInst); +} + +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); + + for (PostIncLoopSet::const_iterator I = PostIncLoops.begin(), + E = PostIncLoops.end(); I != E; ++I) { + OS << ", PostIncLoop="; + WriteAsOperand(OS, (*I)->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; + 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; + + /// WidestFixupType - This records the widest use type for any fixup using + /// this LSRUse. FindUseWithSimilarFormula can't consider uses with different + /// max fixup widths to be equivalent, because the narrower one may be relying + /// on the implicit truncation to truncate away bogus bits. + Type *WidestFixupType; + + /// 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, Type *T) : Kind(K), AccessTy(T), + MinOffset(INT64_MAX), + MaxOffset(INT64_MIN), + AllFixupsOutsideLoop(true), + WidestFixupType(0) {} + + bool HasFormulaWithSameRegs(const Formula &F) const; + bool InsertFormula(const Formula &F); + void DeleteFormula(Formula &F); + void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses); + + void print(raw_ostream &OS) const; + void dump() const; +}; + +} + +/// HasFormula - Test whether this use as a formula which has the same +/// registers as the given formula. +bool LSRUse::HasFormulaWithSameRegs(const Formula &F) const { + 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()); + return Uniquifier.count(Key); +} + +/// 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. + Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); + + return true; +} + +/// DeleteFormula - Remove the given formula from this use's list. +void LSRUse::DeleteFormula(Formula &F) { + if (&F != &Formulae.back()) + std::swap(F, Formulae.back()); + Formulae.pop_back(); +} + +/// RecomputeRegs - Recompute the Regs field, and update RegUses. +void LSRUse::RecomputeRegs(size_t LUIdx, RegUseTracker &RegUses) { + // Now that we've filtered out some formulae, recompute the Regs set. + SmallPtrSet<const SCEV *, 4> OldRegs = Regs; + Regs.clear(); + for (SmallVectorImpl<Formula>::const_iterator I = Formulae.begin(), + E = Formulae.end(); I != E; ++I) { + const Formula &F = *I; + if (F.ScaledReg) Regs.insert(F.ScaledReg); + Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); + } + + // Update the RegTracker. + for (SmallPtrSet<const SCEV *, 4>::iterator I = OldRegs.begin(), + E = OldRegs.end(); I != E; ++I) + if (!Regs.count(*I)) + RegUses.DropRegister(*I, LUIdx); +} + +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 (llvm::next(I) != E) + OS << ','; + } + OS << '}'; + + if (AllFixupsOutsideLoop) + OS << ", all-fixups-outside-loop"; + + if (WidestFixupType) + OS << ", widest fixup type: " << *WidestFixupType; +} + +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, 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 false; + // We have one of: + // ICmpZero BaseReg + Offset => ICmp BaseReg, -Offset + // ICmpZero -1*ScaleReg + Offset => ICmp ScaleReg, Offset + // Offs is the ICmp immediate. + int64_t Offs = AM.BaseOffs; + if (AM.Scale == 0) + Offs = -(uint64_t)Offs; // The cast does the right thing with INT64_MIN. + return TLI->isLegalICmpImmediate(Offs); + } + + // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg + return true; + + case LSRUse::Basic: + // Only handle single-register values. + return !AM.BaseGV && AM.Scale == 0 && AM.BaseOffs == 0; + + case LSRUse::Special: + // Special case Basic to handle -1 scales. + return !AM.BaseGV && (AM.Scale == 0 || AM.Scale == -1) && AM.BaseOffs == 0; + } + + llvm_unreachable("Invalid LSRUse Kind!"); +} + +static bool isLegalUse(TargetLowering::AddrMode AM, + int64_t MinOffset, int64_t MaxOffset, + LSRUse::KindType Kind, 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, 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; + + // Canonicalize a scale of 1 to a base register if the formula doesn't + // already have a base register. + if (!AM.HasBaseReg && AM.Scale == 1) { + AM.Scale = 0; + AM.HasBaseReg = true; + } + + return isLegalUse(AM, Kind, AccessTy, TLI); +} + +static bool isAlwaysFoldable(const SCEV *S, + int64_t MinOffset, int64_t MaxOffset, + bool HasBaseReg, + LSRUse::KindType Kind, 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); +} + +namespace { + +/// UseMapDenseMapInfo - A DenseMapInfo implementation for holding +/// DenseMaps and DenseSets of pairs of const SCEV* and LSRUse::Kind. +struct UseMapDenseMapInfo { + static std::pair<const SCEV *, LSRUse::KindType> getEmptyKey() { + return std::make_pair(reinterpret_cast<const SCEV *>(-1), LSRUse::Basic); + } + + static std::pair<const SCEV *, LSRUse::KindType> getTombstoneKey() { + return std::make_pair(reinterpret_cast<const SCEV *>(-2), LSRUse::Basic); + } + + static unsigned + getHashValue(const std::pair<const SCEV *, LSRUse::KindType> &V) { + unsigned Result = DenseMapInfo<const SCEV *>::getHashValue(V.first); + Result ^= DenseMapInfo<unsigned>::getHashValue(unsigned(V.second)); + return Result; + } + + static bool isEqual(const std::pair<const SCEV *, LSRUse::KindType> &LHS, + const std::pair<const SCEV *, LSRUse::KindType> &RHS) { + return LHS == RHS; + } +}; + +/// IVInc - An individual increment in a Chain of IV increments. +/// Relate an IV user to an expression that computes the IV it uses from the IV +/// used by the previous link in the Chain. +/// +/// For the head of a chain, IncExpr holds the absolute SCEV expression for the +/// original IVOperand. The head of the chain's IVOperand is only valid during +/// chain collection, before LSR replaces IV users. During chain generation, +/// IncExpr can be used to find the new IVOperand that computes the same +/// expression. +struct IVInc { + Instruction *UserInst; + Value* IVOperand; + const SCEV *IncExpr; + + IVInc(Instruction *U, Value *O, const SCEV *E): + UserInst(U), IVOperand(O), IncExpr(E) {} +}; + +// IVChain - The list of IV increments in program order. +// We typically add the head of a chain without finding subsequent links. +struct IVChain { + SmallVector<IVInc,1> Incs; + const SCEV *ExprBase; + + IVChain() : ExprBase(0) {} + + IVChain(const IVInc &Head, const SCEV *Base) + : Incs(1, Head), ExprBase(Base) {} + + typedef SmallVectorImpl<IVInc>::const_iterator const_iterator; + + // begin - return the first increment in the chain. + const_iterator begin() const { + assert(!Incs.empty()); + return llvm::next(Incs.begin()); + } + const_iterator end() const { + return Incs.end(); + } + + // hasIncs - Returns true if this chain contains any increments. + bool hasIncs() const { return Incs.size() >= 2; } + + // add - Add an IVInc to the end of this chain. + void add(const IVInc &X) { Incs.push_back(X); } + + // tailUserInst - Returns the last UserInst in the chain. + Instruction *tailUserInst() const { return Incs.back().UserInst; } + + // isProfitableIncrement - Returns true if IncExpr can be profitably added to + // this chain. + bool isProfitableIncrement(const SCEV *OperExpr, + const SCEV *IncExpr, + ScalarEvolution&); +}; + +/// ChainUsers - Helper for CollectChains to track multiple IV increment uses. +/// Distinguish between FarUsers that definitely cross IV increments and +/// NearUsers that may be used between IV increments. +struct ChainUsers { + SmallPtrSet<Instruction*, 4> FarUsers; + SmallPtrSet<Instruction*, 4> NearUsers; +}; + +/// LSRInstance - This class holds state for the main loop strength reduction +/// logic. +class LSRInstance { + IVUsers &IU; + ScalarEvolution &SE; + DominatorTree &DT; + LoopInfo &LI; + 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<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; + + // Limit the number of chains to avoid quadratic behavior. We don't expect to + // have more than a few IV increment chains in a loop. Missing a Chain falls + // back to normal LSR behavior for those uses. + static const unsigned MaxChains = 8; + + /// IVChainVec - IV users can form a chain of IV increments. + SmallVector<IVChain, MaxChains> IVChainVec; + + /// IVIncSet - IV users that belong to profitable IVChains. + SmallPtrSet<Use*, MaxChains> IVIncSet; + + void OptimizeShadowIV(); + bool FindIVUserForCond(ICmpInst *Cond, IVStrideUse *&CondUse); + ICmpInst *OptimizeMax(ICmpInst *Cond, IVStrideUse* &CondUse); + void OptimizeLoopTermCond(); + + void ChainInstruction(Instruction *UserInst, Instruction *IVOper, + SmallVectorImpl<ChainUsers> &ChainUsersVec); + void FinalizeChain(IVChain &Chain); + void CollectChains(); + void GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter, + SmallVectorImpl<WeakVH> &DeadInsts); + + void CollectInterestingTypesAndFactors(); + void CollectFixupsAndInitialFormulae(); + + LSRFixup &getNewFixup() { + Fixups.push_back(LSRFixup()); + return Fixups.back(); + } + + // Support for sharing of LSRUses between LSRFixups. + typedef DenseMap<std::pair<const SCEV *, LSRUse::KindType>, + size_t, + UseMapDenseMapInfo> UseMapTy; + UseMapTy UseMap; + + bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg, + LSRUse::KindType Kind, Type *AccessTy); + + std::pair<size_t, int64_t> getUse(const SCEV *&Expr, + LSRUse::KindType Kind, + Type *AccessTy); + + void DeleteUse(LSRUse &LU, size_t LUIdx); + + LSRUse *FindUseWithSimilarFormula(const Formula &F, const LSRUse &OrigLU); + + 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(); + + size_t EstimateSearchSpaceComplexity() const; + void NarrowSearchSpaceByDetectingSupersets(); + void NarrowSearchSpaceByCollapsingUnrolledCode(); + void NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(); + void NarrowSearchSpaceByPickingWinnerRegs(); + 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; + + BasicBlock::iterator + HoistInsertPosition(BasicBlock::iterator IP, + const SmallVectorImpl<Instruction *> &Inputs) const; + BasicBlock::iterator + AdjustInsertPositionForExpand(BasicBlock::iterator IP, + const LSRFixup &LF, + const LSRUse &LU, + SCEVExpander &Rewriter) 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); + +public: + 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(); + Type *DestTy = NULL; + bool IsSigned = false; + + /* 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())) { + IsSigned = false; + DestTy = UCast->getDestTy(); + } + else if (SIToFPInst *SCast = dyn_cast<SIToFPInst>(CandidateUI->getUser())) { + IsSigned = true; + 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; + + 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, IsSigned ? + (double)Init->getSExtValue() : + (double)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, 2, "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(); + Changed = true; + 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.getConstant(BackedgeTakenCount->getType(), 1); + + // Add one to the backedge-taken count to get the trip count. + const SCEV *IterationCount = SE.getAddExpr(One, BackedgeTakenCount); + if (IterationCount != SE.getSCEV(Sel)) return Cond; + + // Check for a max calculation that matches the pattern. There's no check + // for ICMP_ULE here because the comparison would be with zero, which + // isn't interesting. + CmpInst::Predicate Pred = ICmpInst::BAD_ICMP_PREDICATE; + const SCEVNAryExpr *Max = 0; + if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(BackedgeTakenCount)) { + Pred = ICmpInst::ICMP_SLE; + Max = S; + } else if (const SCEVSMaxExpr *S = dyn_cast<SCEVSMaxExpr>(IterationCount)) { + Pred = ICmpInst::ICMP_SLT; + Max = S; + } else if (const SCEVUMaxExpr *U = dyn_cast<SCEVUMaxExpr>(IterationCount)) { + Pred = ICmpInst::ICMP_ULT; + Max = U; + } else { + // No match; bail. + 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); + + // ScalarEvolution canonicalizes constants to the left. For < and >, look + // for a comparison with 1. For <= and >=, a comparison with zero. + if (!MaxLHS || + (ICmpInst::isTrueWhenEqual(Pred) ? !MaxLHS->isZero() : (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 (ICmpInst::isTrueWhenEqual(Pred)) { + // Look for n+1, and grab n. + if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1))) + if (isa<ConstantInt>(BO->getOperand(1)) && + cast<ConstantInt>(BO->getOperand(1))->isOne() && + SE.getSCEV(BO->getOperand(0)) == MaxRHS) + NewRHS = BO->getOperand(0); + if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2))) + if (isa<ConstantInt>(BO->getOperand(1)) && + cast<ConstantInt>(BO->getOperand(1))->isOne() && + SE.getSCEV(BO->getOperand(0)) == MaxRHS) + NewRHS = BO->getOperand(0); + if (!NewRHS) + return Cond; + } else if (SE.getSCEV(Sel->getOperand(1)) == MaxRHS) + NewRHS = Sel->getOperand(1); + else if (SE.getSCEV(Sel->getOperand(2)) == MaxRHS) + NewRHS = Sel->getOperand(2); + else if (const SCEVUnknown *SU = dyn_cast<SCEVUnknown>(MaxRHS)) + NewRHS = SU->getValue(); + else + // Max doesn't match expected pattern. + return Cond; + + // Determine the new comparison opcode. It may be signed or unsigned, + // and the original comparison may be either equality or inequality. + 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. +void +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 = IU.getStride(*CondUse, L); + const SCEV *B = IU.getStride(*UI, L); + if (!A || !B) continue; + 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))) { + const ConstantInt *C = D->getValue(); + // Stride of one or negative one can have reuse with non-addresses. + if (C->isOne() || C->isAllOnesValue()) + goto decline_post_inc; + // Avoid weird situations. + if (C->getValue().getMinSignedBits() >= 64 || + C->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. + Type *AccessTy = getAccessType(UI->getUser()); + TargetLowering::AddrMode AM; + AM.Scale = C->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(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->transformToPostInc(L); + 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(); + } +} + +/// reconcileNewOffset - Determine if the given use can accommodate a fixup +/// at the given offset and other details. If so, update the use and +/// return true. +bool +LSRInstance::reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg, + LSRUse::KindType Kind, Type *AccessTy) { + int64_t NewMinOffset = LU.MinOffset; + int64_t NewMaxOffset = LU.MaxOffset; + 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, + Kind, AccessTy, TLI)) + return false; + NewMinOffset = NewOffset; + } else if (NewOffset > LU.MaxOffset) { + if (!isAlwaysFoldable(NewOffset - LU.MinOffset, 0, HasBaseReg, + Kind, AccessTy, TLI)) + return false; + NewMaxOffset = NewOffset; + } + // Check for a mismatched access type, and fall back conservatively as needed. + // TODO: Be less conservative when the type is similar and can use the same + // addressing modes. + 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, 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(std::make_pair(Expr, Kind), 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, /*HasBaseReg=*/true, 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); +} + +/// DeleteUse - Delete the given use from the Uses list. +void LSRInstance::DeleteUse(LSRUse &LU, size_t LUIdx) { + if (&LU != &Uses.back()) + std::swap(LU, Uses.back()); + Uses.pop_back(); + + // Update RegUses. + RegUses.SwapAndDropUse(LUIdx, Uses.size()); +} + +/// FindUseWithFormula - Look for a use distinct from OrigLU which is has +/// a formula that has the same registers as the given formula. +LSRUse * +LSRInstance::FindUseWithSimilarFormula(const Formula &OrigF, + const LSRUse &OrigLU) { + // Search all uses for the formula. This could be more clever. + for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { + LSRUse &LU = Uses[LUIdx]; + // Check whether this use is close enough to OrigLU, to see whether it's + // worthwhile looking through its formulae. + // Ignore ICmpZero uses because they may contain formulae generated by + // GenerateICmpZeroScales, in which case adding fixup offsets may + // be invalid. + if (&LU != &OrigLU && + LU.Kind != LSRUse::ICmpZero && + LU.Kind == OrigLU.Kind && OrigLU.AccessTy == LU.AccessTy && + LU.WidestFixupType == OrigLU.WidestFixupType && + LU.HasFormulaWithSameRegs(OrigF)) { + // Scan through this use's formulae. + for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), + E = LU.Formulae.end(); I != E; ++I) { + const Formula &F = *I; + // Check to see if this formula has the same registers and symbols + // as OrigF. + if (F.BaseRegs == OrigF.BaseRegs && + F.ScaledReg == OrigF.ScaledReg && + F.AM.BaseGV == OrigF.AM.BaseGV && + F.AM.Scale == OrigF.AM.Scale && + F.UnfoldedOffset == OrigF.UnfoldedOffset) { + if (F.AM.BaseOffs == 0) + return &LU; + // This is the formula where all the registers and symbols matched; + // there aren't going to be any others. Since we declined it, we + // can skip the rest of the formulae and proceed to the next LSRUse. + break; + } + } + } + } + + // Nothing looked good. + return 0; +} + +void LSRInstance::CollectInterestingTypesAndFactors() { + SmallSetVector<const SCEV *, 4> Strides; + + // Collect interesting types and strides. + SmallVector<const SCEV *, 4> Worklist; + for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { + const SCEV *Expr = IU.getExpr(*UI); + + // Collect interesting types. + Types.insert(SE.getEffectiveSCEVType(Expr->getType())); + + // Add strides for mentioned loops. + Worklist.push_back(Expr); + do { + const SCEV *S = Worklist.pop_back_val(); + if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { + if (AR->getLoop() == L) + Strides.insert(AR->getStepRecurrence(SE)); + Worklist.push_back(AR->getStart()); + } else if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { + Worklist.append(Add->op_begin(), Add->op_end()); + } + } while (!Worklist.empty()); + } + + // 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 = + llvm::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())); +} + +/// findIVOperand - Helper for CollectChains that finds an IV operand (computed +/// by an AddRec in this loop) within [OI,OE) or returns OE. If IVUsers mapped +/// Instructions to IVStrideUses, we could partially skip this. +static User::op_iterator +findIVOperand(User::op_iterator OI, User::op_iterator OE, + Loop *L, ScalarEvolution &SE) { + for(; OI != OE; ++OI) { + if (Instruction *Oper = dyn_cast<Instruction>(*OI)) { + if (!SE.isSCEVable(Oper->getType())) + continue; + + if (const SCEVAddRecExpr *AR = + dyn_cast<SCEVAddRecExpr>(SE.getSCEV(Oper))) { + if (AR->getLoop() == L) + break; + } + } + } + return OI; +} + +/// getWideOperand - IVChain logic must consistenctly peek base TruncInst +/// operands, so wrap it in a convenient helper. +static Value *getWideOperand(Value *Oper) { + if (TruncInst *Trunc = dyn_cast<TruncInst>(Oper)) + return Trunc->getOperand(0); + return Oper; +} + +/// isCompatibleIVType - Return true if we allow an IV chain to include both +/// types. +static bool isCompatibleIVType(Value *LVal, Value *RVal) { + Type *LType = LVal->getType(); + Type *RType = RVal->getType(); + return (LType == RType) || (LType->isPointerTy() && RType->isPointerTy()); +} + +/// getExprBase - Return an approximation of this SCEV expression's "base", or +/// NULL for any constant. Returning the expression itself is +/// conservative. Returning a deeper subexpression is more precise and valid as +/// long as it isn't less complex than another subexpression. For expressions +/// involving multiple unscaled values, we need to return the pointer-type +/// SCEVUnknown. This avoids forming chains across objects, such as: +/// PrevOper==a[i], IVOper==b[i], IVInc==b-a. +/// +/// Since SCEVUnknown is the rightmost type, and pointers are the rightmost +/// SCEVUnknown, we simply return the rightmost SCEV operand. +static const SCEV *getExprBase(const SCEV *S) { + switch (S->getSCEVType()) { + default: // uncluding scUnknown. + return S; + case scConstant: + return 0; + case scTruncate: + return getExprBase(cast<SCEVTruncateExpr>(S)->getOperand()); + case scZeroExtend: + return getExprBase(cast<SCEVZeroExtendExpr>(S)->getOperand()); + case scSignExtend: + return getExprBase(cast<SCEVSignExtendExpr>(S)->getOperand()); + case scAddExpr: { + // Skip over scaled operands (scMulExpr) to follow add operands as long as + // there's nothing more complex. + // FIXME: not sure if we want to recognize negation. + const SCEVAddExpr *Add = cast<SCEVAddExpr>(S); + for (std::reverse_iterator<SCEVAddExpr::op_iterator> I(Add->op_end()), + E(Add->op_begin()); I != E; ++I) { + const SCEV *SubExpr = *I; + if (SubExpr->getSCEVType() == scAddExpr) + return getExprBase(SubExpr); + + if (SubExpr->getSCEVType() != scMulExpr) + return SubExpr; + } + return S; // all operands are scaled, be conservative. + } + case scAddRecExpr: + return getExprBase(cast<SCEVAddRecExpr>(S)->getStart()); + } +} + +/// Return true if the chain increment is profitable to expand into a loop +/// invariant value, which may require its own register. A profitable chain +/// increment will be an offset relative to the same base. We allow such offsets +/// to potentially be used as chain increment as long as it's not obviously +/// expensive to expand using real instructions. +bool IVChain::isProfitableIncrement(const SCEV *OperExpr, + const SCEV *IncExpr, + ScalarEvolution &SE) { + // Aggressively form chains when -stress-ivchain. + if (StressIVChain) + return true; + + // Do not replace a constant offset from IV head with a nonconstant IV + // increment. + if (!isa<SCEVConstant>(IncExpr)) { + const SCEV *HeadExpr = SE.getSCEV(getWideOperand(Incs[0].IVOperand)); + if (isa<SCEVConstant>(SE.getMinusSCEV(OperExpr, HeadExpr))) + return 0; + } + + SmallPtrSet<const SCEV*, 8> Processed; + return !isHighCostExpansion(IncExpr, Processed, SE); +} + +/// Return true if the number of registers needed for the chain is estimated to +/// be less than the number required for the individual IV users. First prohibit +/// any IV users that keep the IV live across increments (the Users set should +/// be empty). Next count the number and type of increments in the chain. +/// +/// Chaining IVs can lead to considerable code bloat if ISEL doesn't +/// effectively use postinc addressing modes. Only consider it profitable it the +/// increments can be computed in fewer registers when chained. +/// +/// TODO: Consider IVInc free if it's already used in another chains. +static bool +isProfitableChain(IVChain &Chain, SmallPtrSet<Instruction*, 4> &Users, + ScalarEvolution &SE, const TargetLowering *TLI) { + if (StressIVChain) + return true; + + if (!Chain.hasIncs()) + return false; + + if (!Users.empty()) { + DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n"; + for (SmallPtrSet<Instruction*, 4>::const_iterator I = Users.begin(), + E = Users.end(); I != E; ++I) { + dbgs() << " " << **I << "\n"; + }); + return false; + } + assert(!Chain.Incs.empty() && "empty IV chains are not allowed"); + + // The chain itself may require a register, so intialize cost to 1. + int cost = 1; + + // A complete chain likely eliminates the need for keeping the original IV in + // a register. LSR does not currently know how to form a complete chain unless + // the header phi already exists. + if (isa<PHINode>(Chain.tailUserInst()) + && SE.getSCEV(Chain.tailUserInst()) == Chain.Incs[0].IncExpr) { + --cost; + } + const SCEV *LastIncExpr = 0; + unsigned NumConstIncrements = 0; + unsigned NumVarIncrements = 0; + unsigned NumReusedIncrements = 0; + for (IVChain::const_iterator I = Chain.begin(), E = Chain.end(); + I != E; ++I) { + + if (I->IncExpr->isZero()) + continue; + + // Incrementing by zero or some constant is neutral. We assume constants can + // be folded into an addressing mode or an add's immediate operand. + if (isa<SCEVConstant>(I->IncExpr)) { + ++NumConstIncrements; + continue; + } + + if (I->IncExpr == LastIncExpr) + ++NumReusedIncrements; + else + ++NumVarIncrements; + + LastIncExpr = I->IncExpr; + } + // An IV chain with a single increment is handled by LSR's postinc + // uses. However, a chain with multiple increments requires keeping the IV's + // value live longer than it needs to be if chained. + if (NumConstIncrements > 1) + --cost; + + // Materializing increment expressions in the preheader that didn't exist in + // the original code may cost a register. For example, sign-extended array + // indices can produce ridiculous increments like this: + // IV + ((sext i32 (2 * %s) to i64) + (-1 * (sext i32 %s to i64))) + cost += NumVarIncrements; + + // Reusing variable increments likely saves a register to hold the multiple of + // the stride. + cost -= NumReusedIncrements; + + DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost + << "\n"); + + return cost < 0; +} + +/// ChainInstruction - Add this IV user to an existing chain or make it the head +/// of a new chain. +void LSRInstance::ChainInstruction(Instruction *UserInst, Instruction *IVOper, + SmallVectorImpl<ChainUsers> &ChainUsersVec) { + // When IVs are used as types of varying widths, they are generally converted + // to a wider type with some uses remaining narrow under a (free) trunc. + Value *const NextIV = getWideOperand(IVOper); + const SCEV *const OperExpr = SE.getSCEV(NextIV); + const SCEV *const OperExprBase = getExprBase(OperExpr); + + // Visit all existing chains. Check if its IVOper can be computed as a + // profitable loop invariant increment from the last link in the Chain. + unsigned ChainIdx = 0, NChains = IVChainVec.size(); + const SCEV *LastIncExpr = 0; + for (; ChainIdx < NChains; ++ChainIdx) { + IVChain &Chain = IVChainVec[ChainIdx]; + + // Prune the solution space aggressively by checking that both IV operands + // are expressions that operate on the same unscaled SCEVUnknown. This + // "base" will be canceled by the subsequent getMinusSCEV call. Checking + // first avoids creating extra SCEV expressions. + if (!StressIVChain && Chain.ExprBase != OperExprBase) + continue; + + Value *PrevIV = getWideOperand(Chain.Incs.back().IVOperand); + if (!isCompatibleIVType(PrevIV, NextIV)) + continue; + + // A phi node terminates a chain. + if (isa<PHINode>(UserInst) && isa<PHINode>(Chain.tailUserInst())) + continue; + + // The increment must be loop-invariant so it can be kept in a register. + const SCEV *PrevExpr = SE.getSCEV(PrevIV); + const SCEV *IncExpr = SE.getMinusSCEV(OperExpr, PrevExpr); + if (!SE.isLoopInvariant(IncExpr, L)) + continue; + + if (Chain.isProfitableIncrement(OperExpr, IncExpr, SE)) { + LastIncExpr = IncExpr; + break; + } + } + // If we haven't found a chain, create a new one, unless we hit the max. Don't + // bother for phi nodes, because they must be last in the chain. + if (ChainIdx == NChains) { + if (isa<PHINode>(UserInst)) + return; + if (NChains >= MaxChains && !StressIVChain) { + DEBUG(dbgs() << "IV Chain Limit\n"); + return; + } + LastIncExpr = OperExpr; + // IVUsers may have skipped over sign/zero extensions. We don't currently + // attempt to form chains involving extensions unless they can be hoisted + // into this loop's AddRec. + if (!isa<SCEVAddRecExpr>(LastIncExpr)) + return; + ++NChains; + IVChainVec.push_back(IVChain(IVInc(UserInst, IVOper, LastIncExpr), + OperExprBase)); + ChainUsersVec.resize(NChains); + DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst + << ") IV=" << *LastIncExpr << "\n"); + } else { + DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Inc: (" << *UserInst + << ") IV+" << *LastIncExpr << "\n"); + // Add this IV user to the end of the chain. + IVChainVec[ChainIdx].add(IVInc(UserInst, IVOper, LastIncExpr)); + } + + SmallPtrSet<Instruction*,4> &NearUsers = ChainUsersVec[ChainIdx].NearUsers; + // This chain's NearUsers become FarUsers. + if (!LastIncExpr->isZero()) { + ChainUsersVec[ChainIdx].FarUsers.insert(NearUsers.begin(), + NearUsers.end()); + NearUsers.clear(); + } + + // All other uses of IVOperand become near uses of the chain. + // We currently ignore intermediate values within SCEV expressions, assuming + // they will eventually be used be the current chain, or can be computed + // from one of the chain increments. To be more precise we could + // transitively follow its user and only add leaf IV users to the set. + for (Value::use_iterator UseIter = IVOper->use_begin(), + UseEnd = IVOper->use_end(); UseIter != UseEnd; ++UseIter) { + Instruction *OtherUse = dyn_cast<Instruction>(*UseIter); + if (!OtherUse || OtherUse == UserInst) + continue; + if (SE.isSCEVable(OtherUse->getType()) + && !isa<SCEVUnknown>(SE.getSCEV(OtherUse)) + && IU.isIVUserOrOperand(OtherUse)) { + continue; + } + NearUsers.insert(OtherUse); + } + + // Since this user is part of the chain, it's no longer considered a use + // of the chain. + ChainUsersVec[ChainIdx].FarUsers.erase(UserInst); +} + +/// CollectChains - Populate the vector of Chains. +/// +/// This decreases ILP at the architecture level. Targets with ample registers, +/// multiple memory ports, and no register renaming probably don't want +/// this. However, such targets should probably disable LSR altogether. +/// +/// The job of LSR is to make a reasonable choice of induction variables across +/// the loop. Subsequent passes can easily "unchain" computation exposing more +/// ILP *within the loop* if the target wants it. +/// +/// Finding the best IV chain is potentially a scheduling problem. Since LSR +/// will not reorder memory operations, it will recognize this as a chain, but +/// will generate redundant IV increments. Ideally this would be corrected later +/// by a smart scheduler: +/// = A[i] +/// = A[i+x] +/// A[i] = +/// A[i+x] = +/// +/// TODO: Walk the entire domtree within this loop, not just the path to the +/// loop latch. This will discover chains on side paths, but requires +/// maintaining multiple copies of the Chains state. +void LSRInstance::CollectChains() { + DEBUG(dbgs() << "Collecting IV Chains.\n"); + SmallVector<ChainUsers, 8> ChainUsersVec; + + SmallVector<BasicBlock *,8> LatchPath; + BasicBlock *LoopHeader = L->getHeader(); + for (DomTreeNode *Rung = DT.getNode(L->getLoopLatch()); + Rung->getBlock() != LoopHeader; Rung = Rung->getIDom()) { + LatchPath.push_back(Rung->getBlock()); + } + LatchPath.push_back(LoopHeader); + + // Walk the instruction stream from the loop header to the loop latch. + for (SmallVectorImpl<BasicBlock *>::reverse_iterator + BBIter = LatchPath.rbegin(), BBEnd = LatchPath.rend(); + BBIter != BBEnd; ++BBIter) { + for (BasicBlock::iterator I = (*BBIter)->begin(), E = (*BBIter)->end(); + I != E; ++I) { + // Skip instructions that weren't seen by IVUsers analysis. + if (isa<PHINode>(I) || !IU.isIVUserOrOperand(I)) + continue; + + // Ignore users that are part of a SCEV expression. This way we only + // consider leaf IV Users. This effectively rediscovers a portion of + // IVUsers analysis but in program order this time. + if (SE.isSCEVable(I->getType()) && !isa<SCEVUnknown>(SE.getSCEV(I))) + continue; + + // Remove this instruction from any NearUsers set it may be in. + for (unsigned ChainIdx = 0, NChains = IVChainVec.size(); + ChainIdx < NChains; ++ChainIdx) { + ChainUsersVec[ChainIdx].NearUsers.erase(I); + } + // Search for operands that can be chained. + SmallPtrSet<Instruction*, 4> UniqueOperands; + User::op_iterator IVOpEnd = I->op_end(); + User::op_iterator IVOpIter = findIVOperand(I->op_begin(), IVOpEnd, L, SE); + while (IVOpIter != IVOpEnd) { + Instruction *IVOpInst = cast<Instruction>(*IVOpIter); + if (UniqueOperands.insert(IVOpInst)) + ChainInstruction(I, IVOpInst, ChainUsersVec); + IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE); + } + } // Continue walking down the instructions. + } // Continue walking down the domtree. + // Visit phi backedges to determine if the chain can generate the IV postinc. + for (BasicBlock::iterator I = L->getHeader()->begin(); + PHINode *PN = dyn_cast<PHINode>(I); ++I) { + if (!SE.isSCEVable(PN->getType())) + continue; + + Instruction *IncV = + dyn_cast<Instruction>(PN->getIncomingValueForBlock(L->getLoopLatch())); + if (IncV) + ChainInstruction(PN, IncV, ChainUsersVec); + } + // Remove any unprofitable chains. + unsigned ChainIdx = 0; + for (unsigned UsersIdx = 0, NChains = IVChainVec.size(); + UsersIdx < NChains; ++UsersIdx) { + if (!isProfitableChain(IVChainVec[UsersIdx], + ChainUsersVec[UsersIdx].FarUsers, SE, TLI)) + continue; + // Preserve the chain at UsesIdx. + if (ChainIdx != UsersIdx) + IVChainVec[ChainIdx] = IVChainVec[UsersIdx]; + FinalizeChain(IVChainVec[ChainIdx]); + ++ChainIdx; + } + IVChainVec.resize(ChainIdx); +} + +void LSRInstance::FinalizeChain(IVChain &Chain) { + assert(!Chain.Incs.empty() && "empty IV chains are not allowed"); + DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n"); + + for (IVChain::const_iterator I = Chain.begin(), E = Chain.end(); + I != E; ++I) { + DEBUG(dbgs() << " Inc: " << *I->UserInst << "\n"); + User::op_iterator UseI = + std::find(I->UserInst->op_begin(), I->UserInst->op_end(), I->IVOperand); + assert(UseI != I->UserInst->op_end() && "cannot find IV operand"); + IVIncSet.insert(UseI); + } +} + +/// Return true if the IVInc can be folded into an addressing mode. +static bool canFoldIVIncExpr(const SCEV *IncExpr, Instruction *UserInst, + Value *Operand, const TargetLowering *TLI) { + const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr); + if (!IncConst || !isAddressUse(UserInst, Operand)) + return false; + + if (IncConst->getValue()->getValue().getMinSignedBits() > 64) + return false; + + int64_t IncOffset = IncConst->getValue()->getSExtValue(); + if (!isAlwaysFoldable(IncOffset, /*BaseGV=*/0, /*HaseBaseReg=*/false, + LSRUse::Address, getAccessType(UserInst), TLI)) + return false; + + return true; +} + +/// GenerateIVChains - Generate an add or subtract for each IVInc in a chain to +/// materialize the IV user's operand from the previous IV user's operand. +void LSRInstance::GenerateIVChain(const IVChain &Chain, SCEVExpander &Rewriter, + SmallVectorImpl<WeakVH> &DeadInsts) { + // Find the new IVOperand for the head of the chain. It may have been replaced + // by LSR. + const IVInc &Head = Chain.Incs[0]; + User::op_iterator IVOpEnd = Head.UserInst->op_end(); + User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(), + IVOpEnd, L, SE); + Value *IVSrc = 0; + while (IVOpIter != IVOpEnd) { + IVSrc = getWideOperand(*IVOpIter); + + // If this operand computes the expression that the chain needs, we may use + // it. (Check this after setting IVSrc which is used below.) + // + // Note that if Head.IncExpr is wider than IVSrc, then this phi is too + // narrow for the chain, so we can no longer use it. We do allow using a + // wider phi, assuming the LSR checked for free truncation. In that case we + // should already have a truncate on this operand such that + // getSCEV(IVSrc) == IncExpr. + if (SE.getSCEV(*IVOpIter) == Head.IncExpr + || SE.getSCEV(IVSrc) == Head.IncExpr) { + break; + } + IVOpIter = findIVOperand(llvm::next(IVOpIter), IVOpEnd, L, SE); + } + if (IVOpIter == IVOpEnd) { + // Gracefully give up on this chain. + DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n"); + return; + } + + DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n"); + Type *IVTy = IVSrc->getType(); + Type *IntTy = SE.getEffectiveSCEVType(IVTy); + const SCEV *LeftOverExpr = 0; + for (IVChain::const_iterator IncI = Chain.begin(), + IncE = Chain.end(); IncI != IncE; ++IncI) { + + Instruction *InsertPt = IncI->UserInst; + if (isa<PHINode>(InsertPt)) + InsertPt = L->getLoopLatch()->getTerminator(); + + // IVOper will replace the current IV User's operand. IVSrc is the IV + // value currently held in a register. + Value *IVOper = IVSrc; + if (!IncI->IncExpr->isZero()) { + // IncExpr was the result of subtraction of two narrow values, so must + // be signed. + const SCEV *IncExpr = SE.getNoopOrSignExtend(IncI->IncExpr, IntTy); + LeftOverExpr = LeftOverExpr ? + SE.getAddExpr(LeftOverExpr, IncExpr) : IncExpr; + } + if (LeftOverExpr && !LeftOverExpr->isZero()) { + // Expand the IV increment. + Rewriter.clearPostInc(); + Value *IncV = Rewriter.expandCodeFor(LeftOverExpr, IntTy, InsertPt); + const SCEV *IVOperExpr = SE.getAddExpr(SE.getUnknown(IVSrc), + SE.getUnknown(IncV)); + IVOper = Rewriter.expandCodeFor(IVOperExpr, IVTy, InsertPt); + + // If an IV increment can't be folded, use it as the next IV value. + if (!canFoldIVIncExpr(LeftOverExpr, IncI->UserInst, IncI->IVOperand, + TLI)) { + assert(IVTy == IVOper->getType() && "inconsistent IV increment type"); + IVSrc = IVOper; + LeftOverExpr = 0; + } + } + Type *OperTy = IncI->IVOperand->getType(); + if (IVTy != OperTy) { + assert(SE.getTypeSizeInBits(IVTy) >= SE.getTypeSizeInBits(OperTy) && + "cannot extend a chained IV"); + IRBuilder<> Builder(InsertPt); + IVOper = Builder.CreateTruncOrBitCast(IVOper, OperTy, "lsr.chain"); + } + IncI->UserInst->replaceUsesOfWith(IncI->IVOperand, IVOper); + DeadInsts.push_back(IncI->IVOperand); + } + // If LSR created a new, wider phi, we may also replace its postinc. We only + // do this if we also found a wide value for the head of the chain. + if (isa<PHINode>(Chain.tailUserInst())) { + for (BasicBlock::iterator I = L->getHeader()->begin(); + PHINode *Phi = dyn_cast<PHINode>(I); ++I) { + if (!isCompatibleIVType(Phi, IVSrc)) + continue; + Instruction *PostIncV = dyn_cast<Instruction>( + Phi->getIncomingValueForBlock(L->getLoopLatch())); + if (!PostIncV || (SE.getSCEV(PostIncV) != SE.getSCEV(IVSrc))) + continue; + Value *IVOper = IVSrc; + Type *PostIncTy = PostIncV->getType(); + if (IVTy != PostIncTy) { + assert(PostIncTy->isPointerTy() && "mixing int/ptr IV types"); + IRBuilder<> Builder(L->getLoopLatch()->getTerminator()); + Builder.SetCurrentDebugLocation(PostIncV->getDebugLoc()); + IVOper = Builder.CreatePointerCast(IVSrc, PostIncTy, "lsr.chain"); + } + Phi->replaceUsesOfWith(PostIncV, IVOper); + DeadInsts.push_back(PostIncV); + } + } +} + +void LSRInstance::CollectFixupsAndInitialFormulae() { + for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { + Instruction *UserInst = UI->getUser(); + // Skip IV users that are part of profitable IV Chains. + User::op_iterator UseI = std::find(UserInst->op_begin(), UserInst->op_end(), + UI->getOperandValToReplace()); + assert(UseI != UserInst->op_end() && "cannot find IV operand"); + if (IVIncSet.count(UseI)) + continue; + + // Record the uses. + LSRFixup &LF = getNewFixup(); + LF.UserInst = UserInst; + LF.OperandValToReplace = UI->getOperandValToReplace(); + LF.PostIncLoops = UI->getPostIncLoops(); + + LSRUse::KindType Kind = LSRUse::Basic; + Type *AccessTy = 0; + if (isAddressUse(LF.UserInst, LF.OperandValToReplace)) { + Kind = LSRUse::Address; + AccessTy = getAccessType(LF.UserInst); + } + + const SCEV *S = IU.getExpr(*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); + NV = CI->getOperand(1); + Changed = true; + } + + // x == y --> x - y == 0 + const SCEV *N = SE.getSCEV(NV); + if (SE.isLoopInvariant(N, L) && isSafeToExpand(N)) { + // S is normalized, so normalize N before folding it into S + // to keep the result normalized. + N = TransformForPostIncUse(Normalize, N, CI, 0, + LF.PostIncLoops, SE, DT); + 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 &= LF.isUseFullyOutsideLoop(L); + if (!LU.WidestFixupType || + SE.getTypeSizeInBits(LU.WidestFixupType) < + SE.getTypeSizeInBits(LF.OperandValToReplace->getType())) + LU.WidestFixupType = LF.OperandValToReplace->getType(); + + // 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())); +} + +/// InsertInitialFormula - Insert a formula for the given expression into +/// the given use, separating out loop-variant portions from loop-invariant +/// and loop-computable portions. +void +LSRInstance::InsertInitialFormula(const SCEV *S, LSRUse &LU, size_t LUIdx) { + Formula F; + F.InitialMatch(S, L, SE); + bool Inserted = InsertFormula(LU, LUIdx, F); + assert(Inserted && "Initial formula already exists!"); (void)Inserted; +} + +/// InsertSupplementalFormula - Insert a simple single-register formula for +/// the given expression into the given use. +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.append(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)) { + // Look for instructions defined outside the loop. + if (L->contains(Inst)) continue; + } else if (isa<UndefValue>(V)) + // Undef doesn't have a live range, so it doesn't matter. + 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())) { + const SCEV *UserS = SE.getSCEV(const_cast<Instruction *>(UserInst)); + // If the user is a no-op, look through to its uses. + if (!isa<SCEVUnknown>(UserS)) + continue; + if (UserS == U) { + Worklist.push_back( + SE.getUnknown(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.hasComputableLoopEvolution(SE.getSCEV(OtherOp), 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 &= LF.isUseFullyOutsideLoop(L); + if (!LU.WidestFixupType || + SE.getTypeSizeInBits(LU.WidestFixupType) < + SE.getTypeSizeInBits(LF.OperandValToReplace->getType())) + LU.WidestFixupType = LF.OperandValToReplace->getType(); + 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. +/// +/// Return remainder expression after factoring the subexpressions captured by +/// Ops. If Ops is complete, return NULL. +static const SCEV *CollectSubexprs(const SCEV *S, const SCEVConstant *C, + SmallVectorImpl<const SCEV *> &Ops, + const Loop *L, + ScalarEvolution &SE, + unsigned Depth = 0) { + // Arbitrarily cap recursion to protect compile time. + if (Depth >= 3) + return S; + + 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) { + const SCEV *Remainder = CollectSubexprs(*I, C, Ops, L, SE, Depth+1); + if (Remainder) + Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder); + } + return NULL; + } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { + // Split a non-zero base out of an addrec. + if (AR->getStart()->isZero()) + return S; + + const SCEV *Remainder = CollectSubexprs(AR->getStart(), + C, Ops, L, SE, Depth+1); + // Split the non-zero AddRec unless it is part of a nested recurrence that + // does not pertain to this loop. + if (Remainder && (AR->getLoop() == L || !isa<SCEVAddRecExpr>(Remainder))) { + Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder); + Remainder = NULL; + } + if (Remainder != AR->getStart()) { + if (!Remainder) + Remainder = SE.getConstant(AR->getType(), 0); + return SE.getAddRecExpr(Remainder, + AR->getStepRecurrence(SE), + AR->getLoop(), + //FIXME: AR->getNoWrapFlags(SCEV::FlagNW) + SCEV::FlagAnyWrap); + } + } 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) + return S; + if (const SCEVConstant *Op0 = + dyn_cast<SCEVConstant>(Mul->getOperand(0))) { + C = C ? cast<SCEVConstant>(SE.getMulExpr(C, Op0)) : Op0; + const SCEV *Remainder = + CollectSubexprs(Mul->getOperand(1), C, Ops, L, SE, Depth+1); + if (Remainder) + Ops.push_back(SE.getMulExpr(C, Remainder)); + return NULL; + } + } + return 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; + const SCEV *Remainder = CollectSubexprs(BaseReg, 0, AddOps, L, SE); + if (Remainder) + AddOps.push_back(Remainder); + + if (AddOps.size() == 1) continue; + + for (SmallVectorImpl<const SCEV *>::const_iterator J = AddOps.begin(), + JE = AddOps.end(); J != JE; ++J) { + + // Loop-variant "unknown" values are uninteresting; we won't be able to + // do anything meaningful with them. + if (isa<SCEVUnknown>(*J) && !SE.isLoopInvariant(*J, L)) + continue; + + // 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 + (((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J); + InnerAddOps.append + (llvm::next(J), ((const SmallVector<const SCEV *, 8> &)AddOps).end()); + + // 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; + + const SCEV *InnerSum = SE.getAddExpr(InnerAddOps); + if (InnerSum->isZero()) + continue; + Formula F = Base; + + // Add the remaining pieces of the add back into the new formula. + const SCEVConstant *InnerSumSC = dyn_cast<SCEVConstant>(InnerSum); + if (TLI && InnerSumSC && + SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 && + TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset + + InnerSumSC->getValue()->getZExtValue())) { + F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset + + InnerSumSC->getValue()->getZExtValue(); + F.BaseRegs.erase(F.BaseRegs.begin() + i); + } else + F.BaseRegs[i] = InnerSum; + + // Add J as its own register, or an unfolded immediate. + const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J); + if (TLI && SC && SE.getTypeSizeInBits(SC->getType()) <= 64 && + TLI->isLegalAddImmediate((uint64_t)F.UnfoldedOffset + + SC->getValue()->getZExtValue())) + F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset + + SC->getValue()->getZExtValue(); + else + 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 (SE.properlyDominates(BaseReg, L->getHeader()) && + !SE.hasComputableLoopEvolution(BaseReg, 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, 2> 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)) { + // Add the offset to the base register. + const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), *I), G); + // If it cancelled out, drop the base register, otherwise update it. + if (NewG->isZero()) { + std::swap(F.BaseRegs[i], F.BaseRegs.back()); + F.BaseRegs.pop_back(); + } else + F.BaseRegs[i] = NewG; + + (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. + 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; + + // Check that the multiplication doesn't overflow. + if (Base.AM.BaseOffs == INT64_MIN && Factor == -1) + continue; + int64_t NewBaseOffs = (uint64_t)Base.AM.BaseOffs * Factor; + if (NewBaseOffs / 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; + + Formula F = Base; + F.AM.BaseOffs = NewBaseOffs; + + // 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.getConstant(IntTy, Factor); + + // 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; + } + + // Check that multiplying with the unfolded offset doesn't overflow. + if (F.UnfoldedOffset != 0) { + if (F.UnfoldedOffset == INT64_MIN && Factor == -1) + continue; + F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor; + if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset) + 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. + 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.getConstant(IntTy, Factor); + 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; + F.DeleteBaseReg(F.BaseRegs[i]); + (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. + Type *DstTy = Base.getType(); + if (!DstTy) return; + DstTy = SE.getEffectiveSCEVType(DstTy); + + for (SmallSetVector<Type *, 4>::const_iterator + I = Types.begin(), E = Types.end(); I != E; ++I) { + 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.lower_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; + + 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) { + const 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()->isNegative() != + (NewF.AM.BaseOffs < 0) && + (C->getValue()->getValue().abs() * APInt(BitWidth, F.AM.Scale)) + .ule(abs64(NewF.AM.BaseOffs))) + 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)) { + if (!TLI || + !TLI->isLegalAddImmediate((uint64_t)NewF.UnfoldedOffset + Imm)) + continue; + NewF = F; + NewF.UnfoldedOffset = (uint64_t)NewF.UnfoldedOffset + Imm; + } + 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() + NewF.AM.BaseOffs).abs().slt( + abs64(NewF.AM.BaseOffs)) && + (C->getValue()->getValue() + + NewF.AM.BaseOffs).countTrailingZeros() >= + CountTrailingZeros_64(NewF.AM.BaseOffs)) + 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(); + + DEBUG(dbgs() << "\n" + "After generating reuse formulae:\n"; + print_uses(dbgs())); +} + +/// If there are multiple formulae with the same set of registers used +/// by other uses, pick the best one and delete the others. +void LSRInstance::FilterOutUndesirableDedicatedRegisters() { + DenseSet<const SCEV *> VisitedRegs; + SmallPtrSet<const SCEV *, 16> Regs; + SmallPtrSet<const SCEV *, 16> LoserRegs; +#ifndef NDEBUG + bool ChangedFormulae = 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]; + DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); dbgs() << '\n'); + + bool Any = false; + for (size_t FIdx = 0, NumForms = LU.Formulae.size(); + FIdx != NumForms; ++FIdx) { + Formula &F = LU.Formulae[FIdx]; + + // Some formulas are instant losers. For example, they may depend on + // nonexistent AddRecs from other loops. These need to be filtered + // immediately, otherwise heuristics could choose them over others leading + // to an unsatisfactory solution. Passing LoserRegs into RateFormula here + // avoids the need to recompute this information across formulae using the + // same bad AddRec. Passing LoserRegs is also essential unless we remove + // the corresponding bad register from the Regs set. + Cost CostF; + Regs.clear(); + CostF.RateFormula(F, Regs, VisitedRegs, L, LU.Offsets, SE, DT, + &LoserRegs); + if (CostF.isLoser()) { + // During initial formula generation, undesirable formulae are generated + // by uses within other loops that have some non-trivial address mode or + // use the postinc form of the IV. LSR needs to provide these formulae + // as the basis of rediscovering the desired formula that uses an AddRec + // corresponding to the existing phi. Once all formulae have been + // generated, these initial losers may be pruned. + DEBUG(dbgs() << " Filtering loser "; F.print(dbgs()); + dbgs() << "\n"); + } + else { + 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) + continue; + + Formula &Best = LU.Formulae[P.first->second]; + + Cost CostBest; + Regs.clear(); + CostBest.RateFormula(Best, Regs, VisitedRegs, L, LU.Offsets, SE, DT); + if (CostF < CostBest) + std::swap(F, Best); + DEBUG(dbgs() << " Filtering out formula "; F.print(dbgs()); + dbgs() << "\n" + " in favor of formula "; Best.print(dbgs()); + dbgs() << '\n'); + } +#ifndef NDEBUG + ChangedFormulae = true; +#endif + LU.DeleteFormula(F); + --FIdx; + --NumForms; + Any = true; + } + + // Now that we've filtered out some formulae, recompute the Regs set. + if (Any) + LU.RecomputeRegs(LUIdx, RegUses); + + // Reset this to prepare for the next use. + BestFormulae.clear(); + } + + DEBUG(if (ChangedFormulae) { + dbgs() << "\n" + "After filtering out undesirable candidates:\n"; + print_uses(dbgs()); + }); +} + +// This is a rough guess that seems to work fairly well. +static const size_t ComplexityLimit = UINT16_MAX; + +/// EstimateSearchSpaceComplexity - Estimate the worst-case number of +/// solutions the solver might have to consider. It almost never considers +/// this many solutions because it prune the search space, but the pruning +/// isn't always sufficient. +size_t LSRInstance::EstimateSearchSpaceComplexity() const { + size_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 >= ComplexityLimit) { + Power = ComplexityLimit; + break; + } + Power *= FSize; + if (Power >= ComplexityLimit) + break; + } + return Power; +} + +/// NarrowSearchSpaceByDetectingSupersets - When one formula uses a superset +/// of the registers of another formula, it won't help reduce register +/// pressure (though it may not necessarily hurt register pressure); remove +/// it to simplify the system. +void LSRInstance::NarrowSearchSpaceByDetectingSupersets() { + if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { + DEBUG(dbgs() << "The search space is too complex.\n"); + + DEBUG(dbgs() << "Narrowing the search space by eliminating formulae " + "which use a superset of registers used by other " + "formulae.\n"); + + for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { + LSRUse &LU = Uses[LUIdx]; + bool Any = false; + for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { + Formula &F = LU.Formulae[i]; + // Look for a formula with a constant or GV in a register. If the use + // also has a formula with that same value in an immediate field, + // delete the one that uses a register. + for (SmallVectorImpl<const SCEV *>::const_iterator + I = F.BaseRegs.begin(), E = F.BaseRegs.end(); I != E; ++I) { + if (const SCEVConstant *C = dyn_cast<SCEVConstant>(*I)) { + Formula NewF = F; + NewF.AM.BaseOffs += C->getValue()->getSExtValue(); + NewF.BaseRegs.erase(NewF.BaseRegs.begin() + + (I - F.BaseRegs.begin())); + if (LU.HasFormulaWithSameRegs(NewF)) { + DEBUG(dbgs() << " Deleting "; F.print(dbgs()); dbgs() << '\n'); + LU.DeleteFormula(F); + --i; + --e; + Any = true; + break; + } + } else if (const SCEVUnknown *U = dyn_cast<SCEVUnknown>(*I)) { + if (GlobalValue *GV = dyn_cast<GlobalValue>(U->getValue())) + if (!F.AM.BaseGV) { + Formula NewF = F; + NewF.AM.BaseGV = GV; + NewF.BaseRegs.erase(NewF.BaseRegs.begin() + + (I - F.BaseRegs.begin())); + if (LU.HasFormulaWithSameRegs(NewF)) { + DEBUG(dbgs() << " Deleting "; F.print(dbgs()); + dbgs() << '\n'); + LU.DeleteFormula(F); + --i; + --e; + Any = true; + break; + } + } + } + } + } + if (Any) + LU.RecomputeRegs(LUIdx, RegUses); + } + + DEBUG(dbgs() << "After pre-selection:\n"; + print_uses(dbgs())); + } +} + +/// NarrowSearchSpaceByCollapsingUnrolledCode - When there are many registers +/// for expressions like A, A+1, A+2, etc., allocate a single register for +/// them. +void LSRInstance::NarrowSearchSpaceByCollapsingUnrolledCode() { + if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { + DEBUG(dbgs() << "The search space is too complex.\n"); + + DEBUG(dbgs() << "Narrowing the search space by assuming that uses " + "separated by a constant offset will use the same " + "registers.\n"); + + // This is especially useful for unrolled loops. + + for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { + LSRUse &LU = Uses[LUIdx]; + for (SmallVectorImpl<Formula>::const_iterator I = LU.Formulae.begin(), + E = LU.Formulae.end(); I != E; ++I) { + const Formula &F = *I; + if (F.AM.BaseOffs != 0 && F.AM.Scale == 0) { + if (LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU)) { + if (reconcileNewOffset(*LUThatHas, F.AM.BaseOffs, + /*HasBaseReg=*/false, + LU.Kind, LU.AccessTy)) { + DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); + dbgs() << '\n'); + + LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop; + + // Update the relocs to reference the new use. + for (SmallVectorImpl<LSRFixup>::iterator I = Fixups.begin(), + E = Fixups.end(); I != E; ++I) { + LSRFixup &Fixup = *I; + if (Fixup.LUIdx == LUIdx) { + Fixup.LUIdx = LUThatHas - &Uses.front(); + Fixup.Offset += F.AM.BaseOffs; + // Add the new offset to LUThatHas' offset list. + if (LUThatHas->Offsets.back() != Fixup.Offset) { + LUThatHas->Offsets.push_back(Fixup.Offset); + if (Fixup.Offset > LUThatHas->MaxOffset) + LUThatHas->MaxOffset = Fixup.Offset; + if (Fixup.Offset < LUThatHas->MinOffset) + LUThatHas->MinOffset = Fixup.Offset; + } + DEBUG(dbgs() << "New fixup has offset " + << Fixup.Offset << '\n'); + } + if (Fixup.LUIdx == NumUses-1) + Fixup.LUIdx = LUIdx; + } + + // Delete formulae from the new use which are no longer legal. + bool Any = false; + for (size_t i = 0, e = LUThatHas->Formulae.size(); i != e; ++i) { + Formula &F = LUThatHas->Formulae[i]; + if (!isLegalUse(F.AM, + LUThatHas->MinOffset, LUThatHas->MaxOffset, + LUThatHas->Kind, LUThatHas->AccessTy, TLI)) { + DEBUG(dbgs() << " Deleting "; F.print(dbgs()); + dbgs() << '\n'); + LUThatHas->DeleteFormula(F); + --i; + --e; + Any = true; + } + } + if (Any) + LUThatHas->RecomputeRegs(LUThatHas - &Uses.front(), RegUses); + + // Delete the old use. + DeleteUse(LU, LUIdx); + --LUIdx; + --NumUses; + break; + } + } + } + } + } + + DEBUG(dbgs() << "After pre-selection:\n"; + print_uses(dbgs())); + } +} + +/// NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters - Call +/// FilterOutUndesirableDedicatedRegisters again, if necessary, now that +/// we've done more filtering, as it may be able to find more formulae to +/// eliminate. +void LSRInstance::NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(){ + if (EstimateSearchSpaceComplexity() >= ComplexityLimit) { + DEBUG(dbgs() << "The search space is too complex.\n"); + + DEBUG(dbgs() << "Narrowing the search space by re-filtering out " + "undesirable dedicated registers.\n"); + + FilterOutUndesirableDedicatedRegisters(); + + DEBUG(dbgs() << "After pre-selection:\n"; + print_uses(dbgs())); + } +} + +/// NarrowSearchSpaceByPickingWinnerRegs - Pick a register which seems likely +/// to be profitable, and then in any use which has any reference to that +/// register, delete all formulae which do not reference that register. +void LSRInstance::NarrowSearchSpaceByPickingWinnerRegs() { + // With all other options exhausted, loop until the system is simple + // enough to handle. + SmallPtrSet<const SCEV *, 4> Taken; + while (EstimateSearchSpaceComplexity() >= ComplexityLimit) { + // Ok, we have too many of formulae on our hands to conveniently handle. + // Use a rough heuristic to thin out the list. + DEBUG(dbgs() << "The search space is too complex.\n"); + + // 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 (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { + LSRUse &LU = Uses[LUIdx]; + if (!LU.Regs.count(Best)) continue; + + bool Any = false; + 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'); + LU.DeleteFormula(F); + --e; + --i; + Any = true; + assert(e != 0 && "Use has no formulae left! Is Regs inconsistent?"); + continue; + } + } + + if (Any) + LU.RecomputeRegs(LUIdx, RegUses); + } + + DEBUG(dbgs() << "After pre-selection:\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() { + NarrowSearchSpaceByDetectingSupersets(); + NarrowSearchSpaceByCollapsingUnrolledCode(); + NarrowSearchSpaceByRefilteringUndesirableDedicatedRegisters(); + NarrowSearchSpaceByPickingWinnerRegs(); +} + +/// 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); + + SmallPtrSet<const SCEV *, 16> NewRegs; + Cost NewCost; + 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. + bool SatisfiedReqReg = true; + 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()) { + SatisfiedReqReg = false; + break; + } + } + if (!SatisfiedReqReg) { + // If none of the formulae satisfied the required registers, then we could + // clear ReqRegs and try again. Currently, we simply give up in this case. + continue; + } + + // 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() << ".\n 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(); + } + } +} + +/// Solve - Choose one formula from each use. Return the results in the given +/// Solution vector. +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 does all the work. + SolveRecurse(Solution, SolutionCost, Workspace, CurCost, + CurRegs, VisitedRegs); + if (Solution.empty()) { + DEBUG(dbgs() << "\nNo Satisfactory Solution\n"); + return; + } + + // 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'; + }); + + assert(Solution.size() == Uses.size() && "Malformed solution!"); +} + +/// HoistInsertPosition - Helper for AdjustInsertPositionForExpand. Climb up +/// the dominator tree far as we can go while still being dominated by the +/// input positions. This helps canonicalize the insert position, which +/// encourages sharing. +BasicBlock::iterator +LSRInstance::HoistInsertPosition(BasicBlock::iterator IP, + const SmallVectorImpl<Instruction *> &Inputs) + const { + for (;;) { + const Loop *IPLoop = LI.getLoopFor(IP->getParent()); + unsigned IPLoopDepth = IPLoop ? IPLoop->getLoopDepth() : 0; + + BasicBlock *IDom; + for (DomTreeNode *Rung = DT.getNode(IP->getParent()); ; ) { + if (!Rung) return IP; + Rung = Rung->getIDom(); + if (!Rung) return IP; + IDom = Rung->getBlock(); + + // Don't climb into a loop though. + const Loop *IDomLoop = LI.getLoopFor(IDom); + unsigned IDomDepth = IDomLoop ? IDomLoop->getLoopDepth() : 0; + if (IDomDepth <= IPLoopDepth && + (IDomDepth != IPLoopDepth || IDomLoop == IPLoop)) + break; + } + + bool AllDominate = true; + Instruction *BetterPos = 0; + 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; + } + // Attempt to find an insert position in the middle of the block, + // instead of at the end, so that it can be used for other expansions. + if (IDom == Inst->getParent() && + (!BetterPos || !DT.dominates(Inst, BetterPos))) + BetterPos = llvm::next(BasicBlock::iterator(Inst)); + } + if (!AllDominate) + break; + if (BetterPos) + IP = BetterPos; + else + IP = Tentative; + } + + return IP; +} + +/// AdjustInsertPositionForExpand - Determine an input position which will be +/// dominated by the operands and which will dominate the result. +BasicBlock::iterator +LSRInstance::AdjustInsertPositionForExpand(BasicBlock::iterator LowestIP, + const LSRFixup &LF, + const LSRUse &LU, + SCEVExpander &Rewriter) const { + // Collect some instructions which must be dominated by the + // expanding 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.PostIncLoops.count(L)) { + if (LF.isUseFullyOutsideLoop(L)) + Inputs.push_back(L->getLoopLatch()->getTerminator()); + else + Inputs.push_back(IVIncInsertPos); + } + // The expansion must also be dominated by the increment positions of any + // loops it for which it is using post-inc mode. + for (PostIncLoopSet::const_iterator I = LF.PostIncLoops.begin(), + E = LF.PostIncLoops.end(); I != E; ++I) { + const Loop *PIL = *I; + if (PIL == L) continue; + + // Be dominated by the loop exit. + SmallVector<BasicBlock *, 4> ExitingBlocks; + PIL->getExitingBlocks(ExitingBlocks); + if (!ExitingBlocks.empty()) { + BasicBlock *BB = ExitingBlocks[0]; + for (unsigned i = 1, e = ExitingBlocks.size(); i != e; ++i) + BB = DT.findNearestCommonDominator(BB, ExitingBlocks[i]); + Inputs.push_back(BB->getTerminator()); + } + } + + assert(!isa<PHINode>(LowestIP) && !isa<LandingPadInst>(LowestIP) + && !isa<DbgInfoIntrinsic>(LowestIP) && + "Insertion point must be a normal instruction"); + + // Then, climb up the immediate dominator tree as far as we can go while + // still being dominated by the input positions. + BasicBlock::iterator IP = HoistInsertPosition(LowestIP, Inputs); + + // Don't insert instructions before PHI nodes. + while (isa<PHINode>(IP)) ++IP; + + // Ignore landingpad instructions. + while (isa<LandingPadInst>(IP)) ++IP; + + // Ignore debug intrinsics. + while (isa<DbgInfoIntrinsic>(IP)) ++IP; + + // Set IP below instructions recently inserted by SCEVExpander. This keeps the + // IP consistent across expansions and allows the previously inserted + // instructions to be reused by subsequent expansion. + while (Rewriter.isInsertedInstruction(IP) && IP != LowestIP) ++IP; + + return IP; +} + +/// Expand - Emit instructions for the leading candidate expression for this +/// LSRUse (this is called "expanding"). +Value *LSRInstance::Expand(const LSRFixup &LF, + const Formula &F, + BasicBlock::iterator IP, + SCEVExpander &Rewriter, + SmallVectorImpl<WeakVH> &DeadInsts) const { + const LSRUse &LU = Uses[LF.LUIdx]; + + // Determine an input position which will be dominated by the operands and + // which will dominate the result. + IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter); + + // Inform the Rewriter if we have a post-increment use, so that it can + // perform an advantageous expansion. + Rewriter.setPostInc(LF.PostIncLoops); + + // This is the type that the user actually needs. + Type *OpTy = LF.OperandValToReplace->getType(); + // This will be the type that we'll initially expand to. + 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. + 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, make the post-inc adjustment. + PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); + Reg = TransformForPostIncUse(Denormalize, Reg, + LF.UserInst, LF.OperandValToReplace, + Loops, SE, DT); + + Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, 0, IP))); + } + + // 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, make the post-inc adjustment. + PostIncLoopSet &Loops = const_cast<PostIncLoopSet &>(LF.PostIncLoops); + ScaledS = TransformForPostIncUse(Denormalize, ScaledS, + LF.UserInst, LF.OperandValToReplace, + Loops, SE, DT); + + 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. + + // Flush the operand list to suppress SCEVExpander hoisting address modes. + if (!Ops.empty() && LU.Kind == LSRUse::Address) { + Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty, IP); + Ops.clear(); + Ops.push_back(SE.getUnknown(FullV)); + } + ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, 0, IP)); + ScaledS = SE.getMulExpr(ScaledS, + SE.getConstant(ScaledS->getType(), F.AM.Scale)); + Ops.push_back(ScaledS); + } + } + + // Expand the GV portion. + if (F.AM.BaseGV) { + // 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)); + } + Ops.push_back(SE.getUnknown(F.AM.BaseGV)); + } + + // Flush the operand list to suppress SCEVExpander hoisting of both folded and + // unfolded offsets. LSR assumes they both live next to their uses. + if (!Ops.empty()) { + 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, -(uint64_t)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))); + } + } + + // Expand the unfolded offset portion. + int64_t UnfoldedOffset = F.UnfoldedOffset; + if (UnfoldedOffset != 0) { + // Just add the immediate values. + Ops.push_back(SE.getUnknown(ConstantInt::getSigned(IntTy, + UnfoldedOffset))); + } + + // Emit instructions summing all the operands. + const SCEV *FullS = Ops.empty() ? + SE.getConstant(IntTy, 0) : + SE.getAddExpr(Ops); + Value *FullV = Rewriter.expandCodeFor(FullS, Ty, IP); + + // We're done expanding now, so reset the rewriter. + Rewriter.clearPostInc(); + + // 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())) { + BasicBlock *Parent = PN->getParent(); + Loop *PNLoop = LI.getLoopFor(Parent); + if (!PNLoop || Parent != PNLoop->getHeader()) { + // Split the critical edge. + BasicBlock *NewBB = 0; + if (!Parent->isLandingPad()) { + NewBB = SplitCriticalEdge(BB, Parent, P, + /*MergeIdenticalEdges=*/true, + /*DontDeleteUselessPhis=*/true); + } else { + SmallVector<BasicBlock*, 2> NewBBs; + SplitLandingPadPredecessors(Parent, BB, "", "", P, NewBBs); + NewBB = NewBBs[0]; + } + + // 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. + 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. + 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); +} + +/// ImplementSolution - Rewrite all the fixup locations with new values, +/// following the chosen solution. +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, "lsr"); +#ifndef NDEBUG + Rewriter.setDebugType(DEBUG_TYPE); +#endif + Rewriter.disableCanonicalMode(); + Rewriter.enableLSRMode(); + Rewriter.setIVIncInsertPos(L, IVIncInsertPos); + + // Mark phi nodes that terminate chains so the expander tries to reuse them. + for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(), + ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) { + if (PHINode *PN = dyn_cast<PHINode>(ChainI->tailUserInst())) + Rewriter.setChainedPhi(PN); + } + + // Expand the new value definitions and update the users. + for (SmallVectorImpl<LSRFixup>::const_iterator I = Fixups.begin(), + E = Fixups.end(); I != E; ++I) { + const LSRFixup &Fixup = *I; + + Rewrite(Fixup, *Solution[Fixup.LUIdx], Rewriter, DeadInsts, P); + + Changed = true; + } + + for (SmallVectorImpl<IVChain>::const_iterator ChainI = IVChainVec.begin(), + ChainE = IVChainVec.end(); ChainI != ChainE; ++ChainI) { + GenerateIVChain(*ChainI, Rewriter, DeadInsts); + 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>()), + LI(P->getAnalysis<LoopInfo>()), + 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; + + // If there's too much analysis to be done, bail early. We won't be able to + // model the problem anyway. + unsigned NumUsers = 0; + for (IVUsers::const_iterator UI = IU.begin(), E = IU.end(); UI != E; ++UI) { + if (++NumUsers > MaxIVUsers) { + DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << *L + << "\n"); + return; + } + } + +#ifndef NDEBUG + // All dominating loops must have preheaders, or SCEVExpander may not be able + // to materialize an AddRecExpr whose Start is an outer AddRecExpr. + // + // IVUsers analysis should only create users that are dominated by simple loop + // headers. Since this loop should dominate all of its users, its user list + // should be empty if this loop itself is not within a simple loop nest. + for (DomTreeNode *Rung = DT.getNode(L->getLoopPreheader()); + Rung; Rung = Rung->getIDom()) { + BasicBlock *BB = Rung->getBlock(); + const Loop *DomLoop = LI.getLoopFor(BB); + if (DomLoop && DomLoop->getHeader() == BB) { + assert(DomLoop->getLoopPreheader() && "LSR needs a simplified loop nest"); + } + } +#endif // DEBUG + + DEBUG(dbgs() << "\nLSR on loop "; + WriteAsOperand(dbgs(), L->getHeader(), /*PrintType=*/false); + dbgs() << ":\n"); + + // First, perform some low-level loop optimizations. + OptimizeShadowIV(); + OptimizeLoopTermCond(); + + // If loop preparation eliminates all interesting IV users, bail. + if (IU.empty()) return; + + // Skip nested loops until we can model them better with formulae. + if (!L->empty()) { + DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n"); + return; + } + + // Start collecting data and preparing for the solver. + CollectChains(); + CollectInterestingTypesAndFactors(); + CollectFixupsAndInitialFormulae(); + CollectLoopInvariantFixupsAndFormulae(); + + assert(!Uses.empty() && "IVUsers reported at least one use"); + 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(); + + FilterOutUndesirableDedicatedRegisters(); + NarrowSearchSpaceUsingHeuristics(); + + SmallVector<const Formula *, 8> Solution; + Solve(Solution); + + // Release memory that is no longer needed. + Factors.clear(); + Types.clear(); + RegUses.clear(); + + if (Solution.empty()) + return; + +#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<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) { + dbgs() << " "; + I->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; +INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce", + "Loop Strength Reduction", false, false) +INITIALIZE_PASS_DEPENDENCY(DominatorTree) +INITIALIZE_PASS_DEPENDENCY(ScalarEvolution) +INITIALIZE_PASS_DEPENDENCY(IVUsers) +INITIALIZE_PASS_DEPENDENCY(LoopInfo) +INITIALIZE_PASS_DEPENDENCY(LoopSimplify) +INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce", + "Loop Strength Reduction", false, false) + + +Pass *llvm::createLoopStrengthReducePass(const TargetLowering *TLI) { + return new LoopStrengthReduce(TLI); +} + +LoopStrengthReduce::LoopStrengthReduce(const TargetLowering *tli) + : LoopPass(ID), TLI(tli) { + initializeLoopStrengthReducePass(*PassRegistry::getPassRegistry()); + } + +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.addRequired<LoopInfo>(); + AU.addPreserved<LoopInfo>(); + AU.addRequiredID(LoopSimplifyID); + AU.addRequired<DominatorTree>(); + AU.addPreserved<DominatorTree>(); + AU.addRequired<ScalarEvolution>(); + AU.addPreserved<ScalarEvolution>(); + // Requiring LoopSimplify a second time here prevents IVUsers from running + // twice, since LoopSimplify was invalidated by running ScalarEvolution. + AU.addRequiredID(LoopSimplifyID); + 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(); + + // Remove any extra phis created by processing inner loops. + Changed |= DeleteDeadPHIs(L->getHeader()); + if (EnablePhiElim) { + SmallVector<WeakVH, 16> DeadInsts; + SCEVExpander Rewriter(getAnalysis<ScalarEvolution>(), "lsr"); +#ifndef NDEBUG + Rewriter.setDebugType(DEBUG_TYPE); +#endif + unsigned numFolded = Rewriter. + replaceCongruentIVs(L, &getAnalysis<DominatorTree>(), DeadInsts, TLI); + if (numFolded) { + Changed = true; + DeleteTriviallyDeadInstructions(DeadInsts); + DeleteDeadPHIs(L->getHeader()); + } + } + return Changed; +} |
