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Diffstat (limited to 'contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp')
| -rw-r--r-- | contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp | 5770 |
1 files changed, 0 insertions, 5770 deletions
diff --git a/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp b/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp deleted file mode 100644 index 59a387a186b8..000000000000 --- a/contrib/llvm/lib/Transforms/Scalar/LoopStrengthReduce.cpp +++ /dev/null @@ -1,5770 +0,0 @@ -//===- LoopStrengthReduce.cpp - Strength Reduce IVs in Loops --------------===// -// -// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. -// See https://llvm.org/LICENSE.txt for license information. -// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception -// -//===----------------------------------------------------------------------===// -// -// 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 the addressing mode 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. -// -//===----------------------------------------------------------------------===// - -#include "llvm/Transforms/Scalar/LoopStrengthReduce.h" -#include "llvm/ADT/APInt.h" -#include "llvm/ADT/DenseMap.h" -#include "llvm/ADT/DenseSet.h" -#include "llvm/ADT/Hashing.h" -#include "llvm/ADT/PointerIntPair.h" -#include "llvm/ADT/STLExtras.h" -#include "llvm/ADT/SetVector.h" -#include "llvm/ADT/SmallBitVector.h" -#include "llvm/ADT/SmallPtrSet.h" -#include "llvm/ADT/SmallSet.h" -#include "llvm/ADT/SmallVector.h" -#include "llvm/ADT/iterator_range.h" -#include "llvm/Analysis/IVUsers.h" -#include "llvm/Analysis/LoopAnalysisManager.h" -#include "llvm/Analysis/LoopInfo.h" -#include "llvm/Analysis/LoopPass.h" -#include "llvm/Analysis/ScalarEvolution.h" -#include "llvm/Analysis/ScalarEvolutionExpander.h" -#include "llvm/Analysis/ScalarEvolutionExpressions.h" -#include "llvm/Analysis/ScalarEvolutionNormalization.h" -#include "llvm/Analysis/TargetTransformInfo.h" -#include "llvm/Transforms/Utils/Local.h" -#include "llvm/Config/llvm-config.h" -#include "llvm/IR/BasicBlock.h" -#include "llvm/IR/Constant.h" -#include "llvm/IR/Constants.h" -#include "llvm/IR/DerivedTypes.h" -#include "llvm/IR/Dominators.h" -#include "llvm/IR/GlobalValue.h" -#include "llvm/IR/IRBuilder.h" -#include "llvm/IR/InstrTypes.h" -#include "llvm/IR/Instruction.h" -#include "llvm/IR/Instructions.h" -#include "llvm/IR/IntrinsicInst.h" -#include "llvm/IR/Intrinsics.h" -#include "llvm/IR/Module.h" -#include "llvm/IR/OperandTraits.h" -#include "llvm/IR/Operator.h" -#include "llvm/IR/PassManager.h" -#include "llvm/IR/Type.h" -#include "llvm/IR/Use.h" -#include "llvm/IR/User.h" -#include "llvm/IR/Value.h" -#include "llvm/IR/ValueHandle.h" -#include "llvm/Pass.h" -#include "llvm/Support/Casting.h" -#include "llvm/Support/CommandLine.h" -#include "llvm/Support/Compiler.h" -#include "llvm/Support/Debug.h" -#include "llvm/Support/ErrorHandling.h" -#include "llvm/Support/MathExtras.h" -#include "llvm/Support/raw_ostream.h" -#include "llvm/Transforms/Scalar.h" -#include "llvm/Transforms/Utils.h" -#include "llvm/Transforms/Utils/BasicBlockUtils.h" -#include <algorithm> -#include <cassert> -#include <cstddef> -#include <cstdint> -#include <cstdlib> -#include <iterator> -#include <limits> -#include <numeric> -#include <map> -#include <utility> - -using namespace llvm; - -#define DEBUG_TYPE "loop-reduce" - -/// MaxIVUsers is an arbitrary threshold that provides an early opportunity 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")); - -// The flag adds instruction count to solutions cost comparision. -static cl::opt<bool> InsnsCost( - "lsr-insns-cost", cl::Hidden, cl::init(true), - cl::desc("Add instruction count to a LSR cost model")); - -// Flag to choose how to narrow complex lsr solution -static cl::opt<bool> LSRExpNarrow( - "lsr-exp-narrow", cl::Hidden, cl::init(false), - cl::desc("Narrow LSR complex solution using" - " expectation of registers number")); - -// Flag to narrow search space by filtering non-optimal formulae with -// the same ScaledReg and Scale. -static cl::opt<bool> FilterSameScaledReg( - "lsr-filter-same-scaled-reg", cl::Hidden, cl::init(true), - cl::desc("Narrow LSR search space by filtering non-optimal formulae" - " with the same ScaledReg and Scale")); - -static cl::opt<bool> EnableBackedgeIndexing( - "lsr-backedge-indexing", cl::Hidden, cl::init(true), - cl::desc("Enable the generation of cross iteration indexed memops")); - -static cl::opt<unsigned> ComplexityLimit( - "lsr-complexity-limit", cl::Hidden, - cl::init(std::numeric_limits<uint16_t>::max()), - cl::desc("LSR search space complexity limit")); - -static cl::opt<unsigned> SetupCostDepthLimit( - "lsr-setupcost-depth-limit", cl::Hidden, cl::init(7), - cl::desc("The limit on recursion depth for LSRs setup cost")); - -#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 { - -struct MemAccessTy { - /// Used in situations where the accessed memory type is unknown. - static const unsigned UnknownAddressSpace = - std::numeric_limits<unsigned>::max(); - - Type *MemTy = nullptr; - unsigned AddrSpace = UnknownAddressSpace; - - MemAccessTy() = default; - MemAccessTy(Type *Ty, unsigned AS) : MemTy(Ty), AddrSpace(AS) {} - - bool operator==(MemAccessTy Other) const { - return MemTy == Other.MemTy && AddrSpace == Other.AddrSpace; - } - - bool operator!=(MemAccessTy Other) const { return !(*this == Other); } - - static MemAccessTy getUnknown(LLVMContext &Ctx, - unsigned AS = UnknownAddressSpace) { - return MemAccessTy(Type::getVoidTy(Ctx), AS); - } - - Type *getType() { return MemTy; } -}; - -/// This class holds data which is used to order reuse candidates. -class RegSortData { -public: - /// This represents the set of LSRUse indices which reference - /// a particular register. - SmallBitVector UsedByIndices; - - void print(raw_ostream &OS) const; - void dump() const; -}; - -} // end anonymous namespace - -#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) -void RegSortData::print(raw_ostream &OS) const { - OS << "[NumUses=" << UsedByIndices.count() << ']'; -} - -LLVM_DUMP_METHOD void RegSortData::dump() const { - print(errs()); errs() << '\n'; -} -#endif - -namespace { - -/// Map register candidates to information about how they are used. -class RegUseTracker { - using RegUsesTy = DenseMap<const SCEV *, RegSortData>; - - 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(); - - using iterator = SmallVectorImpl<const SCEV *>::iterator; - using const_iterator = SmallVectorImpl<const SCEV *>::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(); } -}; - -} // end anonymous namespace - -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 (auto &Pair : RegUsesMap) { - SmallBitVector &UsedByIndices = Pair.second.UsedByIndices; - if (LUIdx < UsedByIndices.size()) - UsedByIndices[LUIdx] = - LastLUIdx < UsedByIndices.size() ? UsedByIndices[LastLUIdx] : false; - 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 { - -/// This class holds information that describes a formula for computing -/// satisfying a use. It may include broken-out immediates and scaled registers. -struct Formula { - /// Global base address used for complex addressing. - GlobalValue *BaseGV = nullptr; - - /// Base offset for complex addressing. - int64_t BaseOffset = 0; - - /// Whether any complex addressing has a base register. - bool HasBaseReg = false; - - /// The scale of any complex addressing. - int64_t Scale = 0; - - /// The list of "base" registers for this use. When this is non-empty. The - /// canonical representation of a formula is - /// 1. BaseRegs.size > 1 implies ScaledReg != NULL and - /// 2. ScaledReg != NULL implies Scale != 1 || !BaseRegs.empty(). - /// 3. The reg containing recurrent expr related with currect loop in the - /// formula should be put in the ScaledReg. - /// #1 enforces that the scaled register is always used when at least two - /// registers are needed by the formula: e.g., reg1 + reg2 is reg1 + 1 * reg2. - /// #2 enforces that 1 * reg is reg. - /// #3 ensures invariant regs with respect to current loop can be combined - /// together in LSR codegen. - /// This invariant can be temporarily broken while building a formula. - /// However, every formula inserted into the LSRInstance must be in canonical - /// form. - SmallVector<const SCEV *, 4> BaseRegs; - - /// The 'scaled' register for this use. This should be non-null when Scale is - /// not zero. - const SCEV *ScaledReg = nullptr; - - /// 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 = 0; - - Formula() = default; - - void initialMatch(const SCEV *S, Loop *L, ScalarEvolution &SE); - - bool isCanonical(const Loop &L) const; - - void canonicalize(const Loop &L); - - bool unscale(); - - bool hasZeroEnd() const; - - size_t 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; -}; - -} // end anonymous namespace - -/// 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 (const SCEV *S : Add->operands()) - DoInitialMatch(S, L, Good, Bad, SE); - return; - } - - // Look at addrec operands. - if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) - if (!AR->getStart()->isZero() && AR->isAffine()) { - 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 (const SCEV *S : MyGood) - Good.push_back(SE.getMulExpr(NegOne, S)); - for (const SCEV *S : MyBad) - Bad.push_back(SE.getMulExpr(NegOne, S)); - 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); -} - -/// 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); - HasBaseReg = true; - } - if (!Bad.empty()) { - const SCEV *Sum = SE.getAddExpr(Bad); - if (!Sum->isZero()) - BaseRegs.push_back(Sum); - HasBaseReg = true; - } - canonicalize(*L); -} - -/// Check whether or not this formula satisfies the canonical -/// representation. -/// \see Formula::BaseRegs. -bool Formula::isCanonical(const Loop &L) const { - if (!ScaledReg) - return BaseRegs.size() <= 1; - - if (Scale != 1) - return true; - - if (Scale == 1 && BaseRegs.empty()) - return false; - - const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg); - if (SAR && SAR->getLoop() == &L) - return true; - - // If ScaledReg is not a recurrent expr, or it is but its loop is not current - // loop, meanwhile BaseRegs contains a recurrent expr reg related with current - // loop, we want to swap the reg in BaseRegs with ScaledReg. - auto I = - find_if(make_range(BaseRegs.begin(), BaseRegs.end()), [&](const SCEV *S) { - return isa<const SCEVAddRecExpr>(S) && - (cast<SCEVAddRecExpr>(S)->getLoop() == &L); - }); - return I == BaseRegs.end(); -} - -/// Helper method to morph a formula into its canonical representation. -/// \see Formula::BaseRegs. -/// Every formula having more than one base register, must use the ScaledReg -/// field. Otherwise, we would have to do special cases everywhere in LSR -/// to treat reg1 + reg2 + ... the same way as reg1 + 1*reg2 + ... -/// On the other hand, 1*reg should be canonicalized into reg. -void Formula::canonicalize(const Loop &L) { - if (isCanonical(L)) - return; - // So far we did not need this case. This is easy to implement but it is - // useless to maintain dead code. Beside it could hurt compile time. - assert(!BaseRegs.empty() && "1*reg => reg, should not be needed."); - - // Keep the invariant sum in BaseRegs and one of the variant sum in ScaledReg. - if (!ScaledReg) { - ScaledReg = BaseRegs.back(); - BaseRegs.pop_back(); - Scale = 1; - } - - // If ScaledReg is an invariant with respect to L, find the reg from - // BaseRegs containing the recurrent expr related with Loop L. Swap the - // reg with ScaledReg. - const SCEVAddRecExpr *SAR = dyn_cast<const SCEVAddRecExpr>(ScaledReg); - if (!SAR || SAR->getLoop() != &L) { - auto I = find_if(make_range(BaseRegs.begin(), BaseRegs.end()), - [&](const SCEV *S) { - return isa<const SCEVAddRecExpr>(S) && - (cast<SCEVAddRecExpr>(S)->getLoop() == &L); - }); - if (I != BaseRegs.end()) - std::swap(ScaledReg, *I); - } -} - -/// Get rid of the scale in the formula. -/// In other words, this method morphes reg1 + 1*reg2 into reg1 + reg2. -/// \return true if it was possible to get rid of the scale, false otherwise. -/// \note After this operation the formula may not be in the canonical form. -bool Formula::unscale() { - if (Scale != 1) - return false; - Scale = 0; - BaseRegs.push_back(ScaledReg); - ScaledReg = nullptr; - return true; -} - -bool Formula::hasZeroEnd() const { - if (UnfoldedOffset || BaseOffset) - return false; - if (BaseRegs.size() != 1 || ScaledReg) - return false; - return true; -} - -/// Return the total number of register operands used by this formula. This does -/// not include register uses implied by non-constant addrec strides. -size_t Formula::getNumRegs() const { - return !!ScaledReg + BaseRegs.size(); -} - -/// 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() : - BaseGV ? BaseGV->getType() : - nullptr; -} - -/// 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(); -} - -/// Test if this formula references the given register. -bool Formula::referencesReg(const SCEV *S) const { - return S == ScaledReg || is_contained(BaseRegs, S); -} - -/// 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 (const SCEV *BaseReg : BaseRegs) - if (RegUses.isRegUsedByUsesOtherThan(BaseReg, LUIdx)) - return true; - return false; -} - -#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) -void Formula::print(raw_ostream &OS) const { - bool First = true; - if (BaseGV) { - if (!First) OS << " + "; else First = false; - BaseGV->printAsOperand(OS, /*PrintType=*/false); - } - if (BaseOffset != 0) { - if (!First) OS << " + "; else First = false; - OS << BaseOffset; - } - for (const SCEV *BaseReg : BaseRegs) { - if (!First) OS << " + "; else First = false; - OS << "reg(" << *BaseReg << ')'; - } - if (HasBaseReg && BaseRegs.empty()) { - if (!First) OS << " + "; else First = false; - OS << "**error: HasBaseReg**"; - } else if (!HasBaseReg && !BaseRegs.empty()) { - if (!First) OS << " + "; else First = false; - OS << "**error: !HasBaseReg**"; - } - if (Scale != 0) { - if (!First) OS << " + "; else First = false; - OS << Scale << "*reg("; - if (ScaledReg) - OS << *ScaledReg; - else - OS << "<unknown>"; - OS << ')'; - } - if (UnfoldedOffset != 0) { - if (!First) OS << " + "; - OS << "imm(" << UnfoldedOffset << ')'; - } -} - -LLVM_DUMP_METHOD void Formula::dump() const { - print(errs()); errs() << '\n'; -} -#endif - -/// 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)); -} - -/// 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)); -} - -/// 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)); -} - -/// 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->getAPInt(); - // 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 nullptr; - const APInt &LA = C->getAPInt(); - const APInt &RA = RC->getAPInt(); - if (LA.srem(RA) != 0) - return nullptr; - 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)) && AR->isAffine()) { - const SCEV *Step = getExactSDiv(AR->getStepRecurrence(SE), RHS, SE, - IgnoreSignificantBits); - if (!Step) return nullptr; - const SCEV *Start = getExactSDiv(AR->getStart(), RHS, SE, - IgnoreSignificantBits); - if (!Start) return nullptr; - // 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 nullptr; - } - - // 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 (const SCEV *S : Add->operands()) { - const SCEV *Op = getExactSDiv(S, RHS, SE, IgnoreSignificantBits); - if (!Op) return nullptr; - Ops.push_back(Op); - } - return SE.getAddExpr(Ops); - } - return nullptr; - } - - // 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 (const SCEV *S : Mul->operands()) { - if (!Found) - if (const SCEV *Q = getExactSDiv(S, RHS, SE, - IgnoreSignificantBits)) { - S = Q; - Found = true; - } - Ops.push_back(S); - } - return Found ? SE.getMulExpr(Ops) : nullptr; - } - return nullptr; - } - - // Otherwise we don't know. - return nullptr; -} - -/// 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->getAPInt().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; -} - -/// 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 nullptr; -} - -/// Returns true if the specified instruction is using the specified value as an -/// address. -static bool isAddressUse(const TargetTransformInfo &TTI, - Instruction *Inst, Value *OperandVal) { - bool isAddress = isa<LoadInst>(Inst); - if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) { - if (SI->getPointerOperand() == 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()) { - case Intrinsic::memset: - case Intrinsic::prefetch: - if (II->getArgOperand(0) == OperandVal) - isAddress = true; - break; - case Intrinsic::memmove: - case Intrinsic::memcpy: - if (II->getArgOperand(0) == OperandVal || - II->getArgOperand(1) == OperandVal) - isAddress = true; - break; - default: { - MemIntrinsicInfo IntrInfo; - if (TTI.getTgtMemIntrinsic(II, IntrInfo)) { - if (IntrInfo.PtrVal == OperandVal) - isAddress = true; - } - } - } - } else if (AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) { - if (RMW->getPointerOperand() == OperandVal) - isAddress = true; - } else if (AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) { - if (CmpX->getPointerOperand() == OperandVal) - isAddress = true; - } - return isAddress; -} - -/// Return the type of the memory being accessed. -static MemAccessTy getAccessType(const TargetTransformInfo &TTI, - Instruction *Inst, Value *OperandVal) { - MemAccessTy AccessTy(Inst->getType(), MemAccessTy::UnknownAddressSpace); - if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) { - AccessTy.MemTy = SI->getOperand(0)->getType(); - AccessTy.AddrSpace = SI->getPointerAddressSpace(); - } else if (const LoadInst *LI = dyn_cast<LoadInst>(Inst)) { - AccessTy.AddrSpace = LI->getPointerAddressSpace(); - } else if (const AtomicRMWInst *RMW = dyn_cast<AtomicRMWInst>(Inst)) { - AccessTy.AddrSpace = RMW->getPointerAddressSpace(); - } else if (const AtomicCmpXchgInst *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) { - AccessTy.AddrSpace = CmpX->getPointerAddressSpace(); - } else if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(Inst)) { - switch (II->getIntrinsicID()) { - case Intrinsic::prefetch: - case Intrinsic::memset: - AccessTy.AddrSpace = II->getArgOperand(0)->getType()->getPointerAddressSpace(); - AccessTy.MemTy = OperandVal->getType(); - break; - case Intrinsic::memmove: - case Intrinsic::memcpy: - AccessTy.AddrSpace = OperandVal->getType()->getPointerAddressSpace(); - AccessTy.MemTy = OperandVal->getType(); - break; - default: { - MemIntrinsicInfo IntrInfo; - if (TTI.getTgtMemIntrinsic(II, IntrInfo) && IntrInfo.PtrVal) { - AccessTy.AddrSpace - = IntrInfo.PtrVal->getType()->getPointerAddressSpace(); - } - - 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.MemTy)) - AccessTy.MemTy = PointerType::get(IntegerType::get(PTy->getContext(), 1), - PTy->getAddressSpace()); - - return AccessTy; -} - -/// Return true if this AddRec is already a phi in its loop. -static bool isExistingPhi(const SCEVAddRecExpr *AR, ScalarEvolution &SE) { - for (PHINode &PN : AR->getLoop()->getHeader()->phis()) { - 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, - SmallPtrSetImpl<const SCEV*> &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).second) - return false; - - if (const SCEVAddExpr *Add = dyn_cast<SCEVAddExpr>(S)) { - for (const SCEV *S : Add->operands()) { - if (isHighCostExpansion(S, 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 (User *UR : UVal->users()) { - // If U is a constant, it may be used by a ConstantExpr. - Instruction *UI = dyn_cast<Instruction>(UR); - if (UI && UI->getOpcode() == Instruction::Mul && - SE.isSCEVable(UI->getType())) { - return SE.getSCEV(UI) == 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; -} - -/// If any of the instructions in the specified set are trivially dead, delete -/// them and see if this makes any of their operands subsequently dead. -static bool -DeleteTriviallyDeadInstructions(SmallVectorImpl<WeakTrackingVH> &DeadInsts) { - bool Changed = false; - - while (!DeadInsts.empty()) { - Value *V = DeadInsts.pop_back_val(); - Instruction *I = dyn_cast_or_null<Instruction>(V); - - if (!I || !isInstructionTriviallyDead(I)) - continue; - - for (Use &O : I->operands()) - if (Instruction *U = dyn_cast<Instruction>(O)) { - O = nullptr; - if (U->use_empty()) - DeadInsts.emplace_back(U); - } - - I->eraseFromParent(); - Changed = true; - } - - return Changed; -} - -namespace { - -class LSRUse; - -} // end anonymous namespace - -/// Check if the addressing mode defined by \p F is completely -/// folded in \p LU at isel time. -/// This includes address-mode folding and special icmp tricks. -/// This function returns true if \p LU can accommodate what \p F -/// defines and up to 1 base + 1 scaled + offset. -/// In other words, if \p F has several base registers, this function may -/// still return true. Therefore, users still need to account for -/// additional base registers and/or unfolded offsets to derive an -/// accurate cost model. -static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, - const LSRUse &LU, const Formula &F); - -// Get the cost of the scaling factor used in F for LU. -static unsigned getScalingFactorCost(const TargetTransformInfo &TTI, - const LSRUse &LU, const Formula &F, - const Loop &L); - -namespace { - -/// This class is used to measure and compare candidate formulae. -class Cost { - const Loop *L = nullptr; - ScalarEvolution *SE = nullptr; - const TargetTransformInfo *TTI = nullptr; - TargetTransformInfo::LSRCost C; - -public: - Cost() = delete; - Cost(const Loop *L, ScalarEvolution &SE, const TargetTransformInfo &TTI) : - L(L), SE(&SE), TTI(&TTI) { - C.Insns = 0; - C.NumRegs = 0; - C.AddRecCost = 0; - C.NumIVMuls = 0; - C.NumBaseAdds = 0; - C.ImmCost = 0; - C.SetupCost = 0; - C.ScaleCost = 0; - } - - bool isLess(Cost &Other); - - void Lose(); - -#ifndef NDEBUG - // Once any of the metrics loses, they must all remain losers. - bool isValid() { - return ((C.Insns | C.NumRegs | C.AddRecCost | C.NumIVMuls | C.NumBaseAdds - | C.ImmCost | C.SetupCost | C.ScaleCost) != ~0u) - || ((C.Insns & C.NumRegs & C.AddRecCost & C.NumIVMuls & C.NumBaseAdds - & C.ImmCost & C.SetupCost & C.ScaleCost) == ~0u); - } -#endif - - bool isLoser() { - assert(isValid() && "invalid cost"); - return C.NumRegs == ~0u; - } - - void RateFormula(const Formula &F, - SmallPtrSetImpl<const SCEV *> &Regs, - const DenseSet<const SCEV *> &VisitedRegs, - const LSRUse &LU, - SmallPtrSetImpl<const SCEV *> *LoserRegs = nullptr); - - void print(raw_ostream &OS) const; - void dump() const; - -private: - void RateRegister(const Formula &F, const SCEV *Reg, - SmallPtrSetImpl<const SCEV *> &Regs); - void RatePrimaryRegister(const Formula &F, const SCEV *Reg, - SmallPtrSetImpl<const SCEV *> &Regs, - SmallPtrSetImpl<const SCEV *> *LoserRegs); -}; - -/// An operand value in an instruction which is to be replaced with some -/// equivalent, possibly strength-reduced, replacement. -struct LSRFixup { - /// The instruction which will be updated. - Instruction *UserInst = nullptr; - - /// The operand of the instruction which will be replaced. The operand may be - /// used more than once; every instance will be replaced. - Value *OperandValToReplace = nullptr; - - /// If this user is to use the post-incremented value of an induction - /// variable, this set is non-empty and holds the loops associated with the - /// induction variable. - PostIncLoopSet PostIncLoops; - - /// 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 = 0; - - LSRFixup() = default; - - bool isUseFullyOutsideLoop(const Loop *L) const; - - void print(raw_ostream &OS) const; - void dump() const; -}; - -/// A DenseMapInfo implementation for holding DenseMaps and DenseSets of sorted -/// SmallVectors of const SCEV*. -struct UniquifierDenseMapInfo { - static SmallVector<const SCEV *, 4> getEmptyKey() { - SmallVector<const SCEV *, 4> V; - V.push_back(reinterpret_cast<const SCEV *>(-1)); - return V; - } - - static SmallVector<const SCEV *, 4> getTombstoneKey() { - SmallVector<const SCEV *, 4> V; - V.push_back(reinterpret_cast<const SCEV *>(-2)); - return V; - } - - static unsigned getHashValue(const SmallVector<const SCEV *, 4> &V) { - return static_cast<unsigned>(hash_combine_range(V.begin(), V.end())); - } - - static bool isEqual(const SmallVector<const SCEV *, 4> &LHS, - const SmallVector<const SCEV *, 4> &RHS) { - return LHS == RHS; - } -}; - -/// 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 *, 4>, UniquifierDenseMapInfo> Uniquifier; - -public: - /// 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? - }; - - using SCEVUseKindPair = PointerIntPair<const SCEV *, 2, KindType>; - - KindType Kind; - MemAccessTy AccessTy; - - /// The list of operands which are to be replaced. - SmallVector<LSRFixup, 8> Fixups; - - /// Keep track of the min and max offsets of the fixups. - int64_t MinOffset = std::numeric_limits<int64_t>::max(); - int64_t MaxOffset = std::numeric_limits<int64_t>::min(); - - /// 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 = true; - - /// RigidFormula is set to true to guarantee that this use will be associated - /// with a single formula--the one that initially matched. Some SCEV - /// expressions cannot be expanded. This allows LSR to consider the registers - /// used by those expressions without the need to expand them later after - /// changing the formula. - bool RigidFormula = false; - - /// 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 = nullptr; - - /// 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; - - /// The set of register candidates used by all formulae in this LSRUse. - SmallPtrSet<const SCEV *, 4> Regs; - - LSRUse(KindType K, MemAccessTy AT) : Kind(K), AccessTy(AT) {} - - LSRFixup &getNewFixup() { - Fixups.push_back(LSRFixup()); - return Fixups.back(); - } - - void pushFixup(LSRFixup &f) { - Fixups.push_back(f); - if (f.Offset > MaxOffset) - MaxOffset = f.Offset; - if (f.Offset < MinOffset) - MinOffset = f.Offset; - } - - bool HasFormulaWithSameRegs(const Formula &F) const; - float getNotSelectedProbability(const SCEV *Reg) const; - bool InsertFormula(const Formula &F, const Loop &L); - void DeleteFormula(Formula &F); - void RecomputeRegs(size_t LUIdx, RegUseTracker &Reguses); - - void print(raw_ostream &OS) const; - void dump() const; -}; - -} // end anonymous namespace - -static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, - LSRUse::KindType Kind, MemAccessTy AccessTy, - GlobalValue *BaseGV, int64_t BaseOffset, - bool HasBaseReg, int64_t Scale, - Instruction *Fixup = nullptr); - -static unsigned getSetupCost(const SCEV *Reg, unsigned Depth) { - if (isa<SCEVUnknown>(Reg) || isa<SCEVConstant>(Reg)) - return 1; - if (Depth == 0) - return 0; - if (const auto *S = dyn_cast<SCEVAddRecExpr>(Reg)) - return getSetupCost(S->getStart(), Depth - 1); - if (auto S = dyn_cast<SCEVCastExpr>(Reg)) - return getSetupCost(S->getOperand(), Depth - 1); - if (auto S = dyn_cast<SCEVNAryExpr>(Reg)) - return std::accumulate(S->op_begin(), S->op_end(), 0, - [&](unsigned i, const SCEV *Reg) { - return i + getSetupCost(Reg, Depth - 1); - }); - if (auto S = dyn_cast<SCEVUDivExpr>(Reg)) - return getSetupCost(S->getLHS(), Depth - 1) + - getSetupCost(S->getRHS(), Depth - 1); - return 0; -} - -/// Tally up interesting quantities from the given register. -void Cost::RateRegister(const Formula &F, const SCEV *Reg, - SmallPtrSetImpl<const SCEV *> &Regs) { - if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Reg)) { - // If this is an addrec for another loop, it should be an invariant - // with respect to L since L is the innermost loop (at least - // for now LSR only handles innermost loops). - if (AR->getLoop() != L) { - // If the AddRec exists, consider it's register free and leave it alone. - if (isExistingPhi(AR, *SE)) - return; - - // It is bad to allow LSR for current loop to add induction variables - // for its sibling loops. - if (!AR->getLoop()->contains(L)) { - Lose(); - return; - } - - // Otherwise, it will be an invariant with respect to Loop L. - ++C.NumRegs; - return; - } - - unsigned LoopCost = 1; - if (TTI->isIndexedLoadLegal(TTI->MIM_PostInc, AR->getType()) || - TTI->isIndexedStoreLegal(TTI->MIM_PostInc, AR->getType())) { - - // If the step size matches the base offset, we could use pre-indexed - // addressing. - if (TTI->shouldFavorBackedgeIndex(L)) { - if (auto *Step = dyn_cast<SCEVConstant>(AR->getStepRecurrence(*SE))) - if (Step->getAPInt() == F.BaseOffset) - LoopCost = 0; - } - - if (TTI->shouldFavorPostInc()) { - const SCEV *LoopStep = AR->getStepRecurrence(*SE); - if (isa<SCEVConstant>(LoopStep)) { - const SCEV *LoopStart = AR->getStart(); - if (!isa<SCEVConstant>(LoopStart) && - SE->isLoopInvariant(LoopStart, L)) - LoopCost = 0; - } - } - } - C.AddRecCost += LoopCost; - - // 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(F, AR->getOperand(1), Regs); - if (isLoser()) - return; - } - } - } - ++C.NumRegs; - - // Rough heuristic; favor registers which don't require extra setup - // instructions in the preheader. - C.SetupCost += getSetupCost(Reg, SetupCostDepthLimit); - // Ensure we don't, even with the recusion limit, produce invalid costs. - C.SetupCost = std::min<unsigned>(C.SetupCost, 1 << 16); - - C.NumIVMuls += isa<SCEVMulExpr>(Reg) && - SE->hasComputableLoopEvolution(Reg, L); -} - -/// 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 Formula &F, const SCEV *Reg, - SmallPtrSetImpl<const SCEV *> &Regs, - SmallPtrSetImpl<const SCEV *> *LoserRegs) { - if (LoserRegs && LoserRegs->count(Reg)) { - Lose(); - return; - } - if (Regs.insert(Reg).second) { - RateRegister(F, Reg, Regs); - if (LoserRegs && isLoser()) - LoserRegs->insert(Reg); - } -} - -void Cost::RateFormula(const Formula &F, - SmallPtrSetImpl<const SCEV *> &Regs, - const DenseSet<const SCEV *> &VisitedRegs, - const LSRUse &LU, - SmallPtrSetImpl<const SCEV *> *LoserRegs) { - assert(F.isCanonical(*L) && "Cost is accurate only for canonical formula"); - // Tally up the registers. - unsigned PrevAddRecCost = C.AddRecCost; - unsigned PrevNumRegs = C.NumRegs; - unsigned PrevNumBaseAdds = C.NumBaseAdds; - if (const SCEV *ScaledReg = F.ScaledReg) { - if (VisitedRegs.count(ScaledReg)) { - Lose(); - return; - } - RatePrimaryRegister(F, ScaledReg, Regs, LoserRegs); - if (isLoser()) - return; - } - for (const SCEV *BaseReg : F.BaseRegs) { - if (VisitedRegs.count(BaseReg)) { - Lose(); - return; - } - RatePrimaryRegister(F, BaseReg, Regs, LoserRegs); - if (isLoser()) - return; - } - - // Determine how many (unfolded) adds we'll need inside the loop. - size_t NumBaseParts = F.getNumRegs(); - if (NumBaseParts > 1) - // Do not count the base and a possible second register if the target - // allows to fold 2 registers. - C.NumBaseAdds += - NumBaseParts - (1 + (F.Scale && isAMCompletelyFolded(*TTI, LU, F))); - C.NumBaseAdds += (F.UnfoldedOffset != 0); - - // Accumulate non-free scaling amounts. - C.ScaleCost += getScalingFactorCost(*TTI, LU, F, *L); - - // Tally up the non-zero immediates. - for (const LSRFixup &Fixup : LU.Fixups) { - int64_t O = Fixup.Offset; - int64_t Offset = (uint64_t)O + F.BaseOffset; - if (F.BaseGV) - C.ImmCost += 64; // Handle symbolic values conservatively. - // TODO: This should probably be the pointer size. - else if (Offset != 0) - C.ImmCost += APInt(64, Offset, true).getMinSignedBits(); - - // Check with target if this offset with this instruction is - // specifically not supported. - if (LU.Kind == LSRUse::Address && Offset != 0 && - !isAMCompletelyFolded(*TTI, LSRUse::Address, LU.AccessTy, F.BaseGV, - Offset, F.HasBaseReg, F.Scale, Fixup.UserInst)) - C.NumBaseAdds++; - } - - // If we don't count instruction cost exit here. - if (!InsnsCost) { - assert(isValid() && "invalid cost"); - return; - } - - // Treat every new register that exceeds TTI.getNumberOfRegisters() - 1 as - // additional instruction (at least fill). - unsigned TTIRegNum = TTI->getNumberOfRegisters(false) - 1; - if (C.NumRegs > TTIRegNum) { - // Cost already exceeded TTIRegNum, then only newly added register can add - // new instructions. - if (PrevNumRegs > TTIRegNum) - C.Insns += (C.NumRegs - PrevNumRegs); - else - C.Insns += (C.NumRegs - TTIRegNum); - } - - // If ICmpZero formula ends with not 0, it could not be replaced by - // just add or sub. We'll need to compare final result of AddRec. - // That means we'll need an additional instruction. But if the target can - // macro-fuse a compare with a branch, don't count this extra instruction. - // For -10 + {0, +, 1}: - // i = i + 1; - // cmp i, 10 - // - // For {-10, +, 1}: - // i = i + 1; - if (LU.Kind == LSRUse::ICmpZero && !F.hasZeroEnd() && - !TTI->canMacroFuseCmp()) - C.Insns++; - // Each new AddRec adds 1 instruction to calculation. - C.Insns += (C.AddRecCost - PrevAddRecCost); - - // BaseAdds adds instructions for unfolded registers. - if (LU.Kind != LSRUse::ICmpZero) - C.Insns += C.NumBaseAdds - PrevNumBaseAdds; - assert(isValid() && "invalid cost"); -} - -/// Set this cost to a losing value. -void Cost::Lose() { - C.Insns = std::numeric_limits<unsigned>::max(); - C.NumRegs = std::numeric_limits<unsigned>::max(); - C.AddRecCost = std::numeric_limits<unsigned>::max(); - C.NumIVMuls = std::numeric_limits<unsigned>::max(); - C.NumBaseAdds = std::numeric_limits<unsigned>::max(); - C.ImmCost = std::numeric_limits<unsigned>::max(); - C.SetupCost = std::numeric_limits<unsigned>::max(); - C.ScaleCost = std::numeric_limits<unsigned>::max(); -} - -/// Choose the lower cost. -bool Cost::isLess(Cost &Other) { - if (InsnsCost.getNumOccurrences() > 0 && InsnsCost && - C.Insns != Other.C.Insns) - return C.Insns < Other.C.Insns; - return TTI->isLSRCostLess(C, Other.C); -} - -#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) -void Cost::print(raw_ostream &OS) const { - if (InsnsCost) - OS << C.Insns << " instruction" << (C.Insns == 1 ? " " : "s "); - OS << C.NumRegs << " reg" << (C.NumRegs == 1 ? "" : "s"); - if (C.AddRecCost != 0) - OS << ", with addrec cost " << C.AddRecCost; - if (C.NumIVMuls != 0) - OS << ", plus " << C.NumIVMuls << " IV mul" - << (C.NumIVMuls == 1 ? "" : "s"); - if (C.NumBaseAdds != 0) - OS << ", plus " << C.NumBaseAdds << " base add" - << (C.NumBaseAdds == 1 ? "" : "s"); - if (C.ScaleCost != 0) - OS << ", plus " << C.ScaleCost << " scale cost"; - if (C.ImmCost != 0) - OS << ", plus " << C.ImmCost << " imm cost"; - if (C.SetupCost != 0) - OS << ", plus " << C.SetupCost << " setup cost"; -} - -LLVM_DUMP_METHOD void Cost::dump() const { - print(errs()); errs() << '\n'; -} -#endif - -/// 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); -} - -#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) -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 "; - Store->getOperand(0)->printAsOperand(OS, /*PrintType=*/false); - } else if (UserInst->getType()->isVoidTy()) - OS << UserInst->getOpcodeName(); - else - UserInst->printAsOperand(OS, /*PrintType=*/false); - - OS << ", OperandValToReplace="; - OperandValToReplace->printAsOperand(OS, /*PrintType=*/false); - - for (const Loop *PIL : PostIncLoops) { - OS << ", PostIncLoop="; - PIL->getHeader()->printAsOperand(OS, /*PrintType=*/false); - } - - if (Offset != 0) - OS << ", Offset=" << Offset; -} - -LLVM_DUMP_METHOD void LSRFixup::dump() const { - print(errs()); errs() << '\n'; -} -#endif - -/// 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 *, 4> Key = F.BaseRegs; - if (F.ScaledReg) Key.push_back(F.ScaledReg); - // Unstable sort by host order ok, because this is only used for uniquifying. - llvm::sort(Key); - return Uniquifier.count(Key); -} - -/// The function returns a probability of selecting formula without Reg. -float LSRUse::getNotSelectedProbability(const SCEV *Reg) const { - unsigned FNum = 0; - for (const Formula &F : Formulae) - if (F.referencesReg(Reg)) - FNum++; - return ((float)(Formulae.size() - FNum)) / Formulae.size(); -} - -/// If the given formula has not yet been inserted, add it to the list, and -/// return true. Return false otherwise. The formula must be in canonical form. -bool LSRUse::InsertFormula(const Formula &F, const Loop &L) { - assert(F.isCanonical(L) && "Invalid canonical representation"); - - if (!Formulae.empty() && RigidFormula) - return false; - - SmallVector<const SCEV *, 4> Key = F.BaseRegs; - if (F.ScaledReg) Key.push_back(F.ScaledReg); - // Unstable sort by host order ok, because this is only used for uniquifying. - llvm::sort(Key); - - 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 (const SCEV *BaseReg : F.BaseRegs) - assert(!BaseReg->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()); - if (F.ScaledReg) - Regs.insert(F.ScaledReg); - - return true; -} - -/// 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(); -} - -/// 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 = std::move(Regs); - Regs.clear(); - for (const Formula &F : Formulae) { - if (F.ScaledReg) Regs.insert(F.ScaledReg); - Regs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); - } - - // Update the RegTracker. - for (const SCEV *S : OldRegs) - if (!Regs.count(S)) - RegUses.dropRegister(S, LUIdx); -} - -#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) -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.MemTy->isPointerTy()) - OS << "pointer"; // the full pointer type could be really verbose - else { - OS << *AccessTy.MemTy; - } - - OS << " in addrspace(" << AccessTy.AddrSpace << ')'; - } - - OS << ", Offsets={"; - bool NeedComma = false; - for (const LSRFixup &Fixup : Fixups) { - if (NeedComma) OS << ','; - OS << Fixup.Offset; - NeedComma = true; - } - OS << '}'; - - if (AllFixupsOutsideLoop) - OS << ", all-fixups-outside-loop"; - - if (WidestFixupType) - OS << ", widest fixup type: " << *WidestFixupType; -} - -LLVM_DUMP_METHOD void LSRUse::dump() const { - print(errs()); errs() << '\n'; -} -#endif - -static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, - LSRUse::KindType Kind, MemAccessTy AccessTy, - GlobalValue *BaseGV, int64_t BaseOffset, - bool HasBaseReg, int64_t Scale, - Instruction *Fixup/*= nullptr*/) { - switch (Kind) { - case LSRUse::Address: - return TTI.isLegalAddressingMode(AccessTy.MemTy, BaseGV, BaseOffset, - HasBaseReg, Scale, AccessTy.AddrSpace, Fixup); - - 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 (BaseGV) - return false; - - // ICmp only has two operands; don't allow more than two non-trivial parts. - if (Scale != 0 && HasBaseReg && BaseOffset != 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 (Scale != 0 && 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 (BaseOffset != 0) { - // We have one of: - // ICmpZero BaseReg + BaseOffset => ICmp BaseReg, -BaseOffset - // ICmpZero -1*ScaleReg + BaseOffset => ICmp ScaleReg, BaseOffset - // Offs is the ICmp immediate. - if (Scale == 0) - // The cast does the right thing with - // std::numeric_limits<int64_t>::min(). - BaseOffset = -(uint64_t)BaseOffset; - return TTI.isLegalICmpImmediate(BaseOffset); - } - - // ICmpZero BaseReg + -1*ScaleReg => ICmp BaseReg, ScaleReg - return true; - - case LSRUse::Basic: - // Only handle single-register values. - return !BaseGV && Scale == 0 && BaseOffset == 0; - - case LSRUse::Special: - // Special case Basic to handle -1 scales. - return !BaseGV && (Scale == 0 || Scale == -1) && BaseOffset == 0; - } - - llvm_unreachable("Invalid LSRUse Kind!"); -} - -static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, - int64_t MinOffset, int64_t MaxOffset, - LSRUse::KindType Kind, MemAccessTy AccessTy, - GlobalValue *BaseGV, int64_t BaseOffset, - bool HasBaseReg, int64_t Scale) { - // Check for overflow. - if (((int64_t)((uint64_t)BaseOffset + MinOffset) > BaseOffset) != - (MinOffset > 0)) - return false; - MinOffset = (uint64_t)BaseOffset + MinOffset; - if (((int64_t)((uint64_t)BaseOffset + MaxOffset) > BaseOffset) != - (MaxOffset > 0)) - return false; - MaxOffset = (uint64_t)BaseOffset + MaxOffset; - - return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MinOffset, - HasBaseReg, Scale) && - isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, MaxOffset, - HasBaseReg, Scale); -} - -static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, - int64_t MinOffset, int64_t MaxOffset, - LSRUse::KindType Kind, MemAccessTy AccessTy, - const Formula &F, const Loop &L) { - // For the purpose of isAMCompletelyFolded either having a canonical formula - // or a scale not equal to zero is correct. - // Problems may arise from non canonical formulae having a scale == 0. - // Strictly speaking it would best to just rely on canonical formulae. - // However, when we generate the scaled formulae, we first check that the - // scaling factor is profitable before computing the actual ScaledReg for - // compile time sake. - assert((F.isCanonical(L) || F.Scale != 0)); - return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, - F.BaseGV, F.BaseOffset, F.HasBaseReg, F.Scale); -} - -/// Test whether we know how to expand the current formula. -static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset, - int64_t MaxOffset, LSRUse::KindType Kind, - MemAccessTy AccessTy, GlobalValue *BaseGV, - int64_t BaseOffset, bool HasBaseReg, int64_t Scale) { - // We know how to expand completely foldable formulae. - return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV, - BaseOffset, HasBaseReg, Scale) || - // Or formulae that use a base register produced by a sum of base - // registers. - (Scale == 1 && - isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, - BaseGV, BaseOffset, true, 0)); -} - -static bool isLegalUse(const TargetTransformInfo &TTI, int64_t MinOffset, - int64_t MaxOffset, LSRUse::KindType Kind, - MemAccessTy AccessTy, const Formula &F) { - return isLegalUse(TTI, MinOffset, MaxOffset, Kind, AccessTy, F.BaseGV, - F.BaseOffset, F.HasBaseReg, F.Scale); -} - -static bool isAMCompletelyFolded(const TargetTransformInfo &TTI, - const LSRUse &LU, const Formula &F) { - // Target may want to look at the user instructions. - if (LU.Kind == LSRUse::Address && TTI.LSRWithInstrQueries()) { - for (const LSRFixup &Fixup : LU.Fixups) - if (!isAMCompletelyFolded(TTI, LSRUse::Address, LU.AccessTy, F.BaseGV, - (F.BaseOffset + Fixup.Offset), F.HasBaseReg, - F.Scale, Fixup.UserInst)) - return false; - return true; - } - - return isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, - LU.AccessTy, F.BaseGV, F.BaseOffset, F.HasBaseReg, - F.Scale); -} - -static unsigned getScalingFactorCost(const TargetTransformInfo &TTI, - const LSRUse &LU, const Formula &F, - const Loop &L) { - if (!F.Scale) - return 0; - - // If the use is not completely folded in that instruction, we will have to - // pay an extra cost only for scale != 1. - if (!isAMCompletelyFolded(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, - LU.AccessTy, F, L)) - return F.Scale != 1; - - switch (LU.Kind) { - case LSRUse::Address: { - // Check the scaling factor cost with both the min and max offsets. - int ScaleCostMinOffset = TTI.getScalingFactorCost( - LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MinOffset, F.HasBaseReg, - F.Scale, LU.AccessTy.AddrSpace); - int ScaleCostMaxOffset = TTI.getScalingFactorCost( - LU.AccessTy.MemTy, F.BaseGV, F.BaseOffset + LU.MaxOffset, F.HasBaseReg, - F.Scale, LU.AccessTy.AddrSpace); - - assert(ScaleCostMinOffset >= 0 && ScaleCostMaxOffset >= 0 && - "Legal addressing mode has an illegal cost!"); - return std::max(ScaleCostMinOffset, ScaleCostMaxOffset); - } - case LSRUse::ICmpZero: - case LSRUse::Basic: - case LSRUse::Special: - // The use is completely folded, i.e., everything is folded into the - // instruction. - return 0; - } - - llvm_unreachable("Invalid LSRUse Kind!"); -} - -static bool isAlwaysFoldable(const TargetTransformInfo &TTI, - LSRUse::KindType Kind, MemAccessTy AccessTy, - GlobalValue *BaseGV, int64_t BaseOffset, - bool HasBaseReg) { - // Fast-path: zero is always foldable. - if (BaseOffset == 0 && !BaseGV) return true; - - // Conservatively, create an address with an immediate and a - // base and a scale. - int64_t 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 (!HasBaseReg && Scale == 1) { - Scale = 0; - HasBaseReg = true; - } - - return isAMCompletelyFolded(TTI, Kind, AccessTy, BaseGV, BaseOffset, - HasBaseReg, Scale); -} - -static bool isAlwaysFoldable(const TargetTransformInfo &TTI, - ScalarEvolution &SE, int64_t MinOffset, - int64_t MaxOffset, LSRUse::KindType Kind, - MemAccessTy AccessTy, const SCEV *S, - bool HasBaseReg) { - // 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 BaseOffset = 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 (BaseOffset == 0 && !BaseGV) return true; - - // Conservatively, create an address with an immediate and a - // base and a scale. - int64_t Scale = Kind == LSRUse::ICmpZero ? -1 : 1; - - return isAMCompletelyFolded(TTI, MinOffset, MaxOffset, Kind, AccessTy, BaseGV, - BaseOffset, HasBaseReg, Scale); -} - -namespace { - -/// 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) {} -}; - -// 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 = nullptr; - - IVChain() = default; - IVChain(const IVInc &Head, const SCEV *Base) - : Incs(1, Head), ExprBase(Base) {} - - using const_iterator = SmallVectorImpl<IVInc>::const_iterator; - - // Return the first increment in the chain. - const_iterator begin() const { - assert(!Incs.empty()); - return std::next(Incs.begin()); - } - const_iterator end() const { - return Incs.end(); - } - - // Returns true if this chain contains any increments. - bool hasIncs() const { return Incs.size() >= 2; } - - // Add an IVInc to the end of this chain. - void add(const IVInc &X) { Incs.push_back(X); } - - // Returns the last UserInst in the chain. - Instruction *tailUserInst() const { return Incs.back().UserInst; } - - // Returns true if IncExpr can be profitably added to this chain. - bool isProfitableIncrement(const SCEV *OperExpr, - const SCEV *IncExpr, - ScalarEvolution&); -}; - -/// 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; -}; - -/// This class holds state for the main loop strength reduction logic. -class LSRInstance { - IVUsers &IU; - ScalarEvolution &SE; - DominatorTree &DT; - LoopInfo &LI; - AssumptionCache &AC; - TargetLibraryInfo &LibInfo; - const TargetTransformInfo &TTI; - Loop *const L; - bool FavorBackedgeIndex = false; - bool Changed = false; - - /// 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 = nullptr; - - /// Interesting factors between use strides. - /// - /// We explicitly use a SetVector which contains a SmallSet, instead of the - /// default, a SmallDenseSet, because we need to use the full range of - /// int64_ts, and there's currently no good way of doing that with - /// SmallDenseSet. - SetVector<int64_t, SmallVector<int64_t, 8>, SmallSet<int64_t, 8>> Factors; - - /// Interesting use types, to facilitate truncation reuse. - SmallSetVector<Type *, 4> Types; - - /// The list of interesting uses. - mutable SmallVector<LSRUse, 16> Uses; - - /// 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; - - /// IV users can form a chain of IV increments. - SmallVector<IVChain, MaxChains> IVChainVec; - - /// 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<WeakTrackingVH> &DeadInsts); - - void CollectInterestingTypesAndFactors(); - void CollectFixupsAndInitialFormulae(); - - // Support for sharing of LSRUses between LSRFixups. - using UseMapTy = DenseMap<LSRUse::SCEVUseKindPair, size_t>; - UseMapTy UseMap; - - bool reconcileNewOffset(LSRUse &LU, int64_t NewOffset, bool HasBaseReg, - LSRUse::KindType Kind, MemAccessTy AccessTy); - - std::pair<size_t, int64_t> getUse(const SCEV *&Expr, LSRUse::KindType Kind, - MemAccessTy 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 GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx, - const Formula &Base, unsigned Depth, - size_t Idx, bool IsScaledReg = false); - void GenerateCombinations(LSRUse &LU, unsigned LUIdx, Formula Base); - void GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx, - const Formula &Base, size_t Idx, - bool IsScaledReg = false); - void GenerateSymbolicOffsets(LSRUse &LU, unsigned LUIdx, Formula Base); - void GenerateConstantOffsetsImpl(LSRUse &LU, unsigned LUIdx, - const Formula &Base, - const SmallVectorImpl<int64_t> &Worklist, - size_t Idx, bool IsScaledReg = false); - 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 NarrowSearchSpaceByFilterFormulaWithSameScaledReg(); - void NarrowSearchSpaceByDeletingCostlyFormulas(); - 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 LSRUse &LU, const LSRFixup &LF, const Formula &F, - BasicBlock::iterator IP, SCEVExpander &Rewriter, - SmallVectorImpl<WeakTrackingVH> &DeadInsts) const; - void RewriteForPHI(PHINode *PN, const LSRUse &LU, const LSRFixup &LF, - const Formula &F, SCEVExpander &Rewriter, - SmallVectorImpl<WeakTrackingVH> &DeadInsts) const; - void Rewrite(const LSRUse &LU, const LSRFixup &LF, const Formula &F, - SCEVExpander &Rewriter, - SmallVectorImpl<WeakTrackingVH> &DeadInsts) const; - void ImplementSolution(const SmallVectorImpl<const Formula *> &Solution); - -public: - LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, DominatorTree &DT, - LoopInfo &LI, const TargetTransformInfo &TTI, AssumptionCache &AC, - TargetLibraryInfo &LibInfo); - - 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; -}; - -} // end anonymous namespace - -/// 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 = nullptr; - 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 target does not support DestTy natively then do not apply - // this transformation. - if (!TTI.isTypeLegal(DestTy)) continue; - - PHINode *PH = dyn_cast<PHINode>(ShadowUse->getOperand(0)); - if (!PH) continue; - if (PH->getNumIncomingValues() != 2) continue; - - // If the calculation in integers overflows, the result in FP type will - // differ. So we only can do this transformation if we are guaranteed to not - // deal with overflowing values - const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(SE.getSCEV(PH)); - if (!AR) continue; - if (IsSigned && !AR->hasNoSignedWrap()) continue; - if (!IsSigned && !AR->hasNoUnsignedWrap()) 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 = nullptr; - 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; - } -} - -/// 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 (IVStrideUse &U : IU) - if (U.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 = &U; - return true; - } - return false; -} - -/// 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 = nullptr; - 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 = nullptr; - if (ICmpInst::isTrueWhenEqual(Pred)) { - // Look for n+1, and grab n. - if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(1))) - if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1))) - if (BO1->isOne() && SE.getSCEV(BO->getOperand(0)) == MaxRHS) - NewRHS = BO->getOperand(0); - if (AddOperator *BO = dyn_cast<AddOperator>(Sel->getOperand(2))) - if (ConstantInt *BO1 = dyn_cast<ConstantInt>(BO->getOperand(1))) - if (BO1->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; -} - -/// Change loop terminating condition to use the postinc iv when possible. -void -LSRInstance::OptimizeLoopTermCond() { - SmallPtrSet<Instruction *, 4> PostIncs; - - // We need a different set of heuristics for rotated and non-rotated loops. - // If a loop is rotated then the latch is also the backedge, so inserting - // post-inc expressions just before the latch is ideal. To reduce live ranges - // it also makes sense to rewrite terminating conditions to use post-inc - // expressions. - // - // If the loop is not rotated then the latch is not a backedge; the latch - // check is done in the loop head. Adding post-inc expressions before the - // latch will cause overlapping live-ranges of pre-inc and post-inc expressions - // in the loop body. In this case we do *not* want to use post-inc expressions - // in the latch check, and we want to insert post-inc expressions before - // the backedge. - BasicBlock *LatchBlock = L->getLoopLatch(); - SmallVector<BasicBlock*, 8> ExitingBlocks; - L->getExitingBlocks(ExitingBlocks); - if (llvm::all_of(ExitingBlocks, [&LatchBlock](const BasicBlock *BB) { - return LatchBlock != BB; - })) { - // The backedge doesn't exit the loop; treat this as a head-tested loop. - IVIncInsertPos = LatchBlock->getTerminator(); - return; - } - - // Otherwise treat this as a rotated loop. - for (BasicBlock *ExitingBlock : ExitingBlocks) { - // 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 = nullptr; - 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->isMinusOne()) - goto decline_post_inc; - // Avoid weird situations. - if (C->getValue().getMinSignedBits() >= 64 || - C->getValue().isMinSignedValue()) - goto decline_post_inc; - // Check for possible scaled-address reuse. - if (isAddressUse(TTI, UI->getUser(), UI->getOperandValToReplace())) { - MemAccessTy AccessTy = getAccessType( - TTI, UI->getUser(), UI->getOperandValToReplace()); - int64_t Scale = C->getSExtValue(); - if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr, - /*BaseOffset=*/0, - /*HasBaseReg=*/false, Scale, - AccessTy.AddrSpace)) - goto decline_post_inc; - Scale = -Scale; - if (TTI.isLegalAddressingMode(AccessTy.MemTy, /*BaseGV=*/nullptr, - /*BaseOffset=*/0, - /*HasBaseReg=*/false, Scale, - AccessTy.AddrSpace)) - goto decline_post_inc; - } - } - } - - LLVM_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->getIterator(), 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 (Instruction *Inst : PostIncs) { - BasicBlock *BB = - DT.findNearestCommonDominator(IVIncInsertPos->getParent(), - Inst->getParent()); - if (BB == Inst->getParent()) - IVIncInsertPos = Inst; - else if (BB != IVIncInsertPos->getParent()) - IVIncInsertPos = BB->getTerminator(); - } -} - -/// 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, - MemAccessTy AccessTy) { - int64_t NewMinOffset = LU.MinOffset; - int64_t NewMaxOffset = LU.MaxOffset; - MemAccessTy 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; - - // 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) { - if (AccessTy.MemTy != LU.AccessTy.MemTy) { - NewAccessTy = MemAccessTy::getUnknown(AccessTy.MemTy->getContext(), - AccessTy.AddrSpace); - } - } - - // Conservatively assume HasBaseReg is true for now. - if (NewOffset < LU.MinOffset) { - if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr, - LU.MaxOffset - NewOffset, HasBaseReg)) - return false; - NewMinOffset = NewOffset; - } else if (NewOffset > LU.MaxOffset) { - if (!isAlwaysFoldable(TTI, Kind, NewAccessTy, /*BaseGV=*/nullptr, - NewOffset - LU.MinOffset, HasBaseReg)) - return false; - NewMaxOffset = NewOffset; - } - - // Update the use. - LU.MinOffset = NewMinOffset; - LU.MaxOffset = NewMaxOffset; - LU.AccessTy = NewAccessTy; - return true; -} - -/// 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, - MemAccessTy AccessTy) { - const SCEV *Copy = Expr; - int64_t Offset = ExtractImmediate(Expr, SE); - - // Basic uses can't accept any offset, for example. - if (!isAlwaysFoldable(TTI, Kind, AccessTy, /*BaseGV=*/ nullptr, - Offset, /*HasBaseReg=*/ true)) { - Expr = Copy; - Offset = 0; - } - - std::pair<UseMapTy::iterator, bool> P = - UseMap.insert(std::make_pair(LSRUse::SCEVUseKindPair(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]; - - LU.MinOffset = Offset; - LU.MaxOffset = Offset; - return std::make_pair(LUIdx, Offset); -} - -/// 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()); -} - -/// 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 (const Formula &F : LU.Formulae) { - // Check to see if this formula has the same registers and symbols - // as OrigF. - if (F.BaseRegs == OrigF.BaseRegs && - F.ScaledReg == OrigF.ScaledReg && - F.BaseGV == OrigF.BaseGV && - F.Scale == OrigF.Scale && - F.UnfoldedOffset == OrigF.UnfoldedOffset) { - if (F.BaseOffset == 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 nullptr; -} - -void LSRInstance::CollectInterestingTypesAndFactors() { - SmallSetVector<const SCEV *, 4> Strides; - - // Collect interesting types and strides. - SmallVector<const SCEV *, 4> Worklist; - for (const IVStrideUse &U : IU) { - const SCEV *Expr = IU.getExpr(U); - - // 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 = - std::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->getAPInt().getMinSignedBits() <= 64) - Factors.insert(Factor->getAPInt().getSExtValue()); - } else if (const SCEVConstant *Factor = - dyn_cast_or_null<SCEVConstant>(getExactSDiv(OldStride, - NewStride, - SE, true))) { - if (Factor->getAPInt().getMinSignedBits() <= 64) - Factors.insert(Factor->getAPInt().getSExtValue()); - } - } - - // If all uses use the same type, don't bother looking for truncation-based - // reuse. - if (Types.size() == 1) - Types.clear(); - - LLVM_DEBUG(print_factors_and_types(dbgs())); -} - -/// 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; -} - -/// IVChain logic must consistently 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; -} - -/// 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() && - // Different address spaces means (possibly) - // different types of the pointer implementation, - // e.g. i16 vs i32 so disallow that. - (LType->getPointerAddressSpace() == - RType->getPointerAddressSpace())); -} - -/// 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 nullptr; - 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 false; - } - - 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, SmallPtrSetImpl<Instruction*> &Users, - ScalarEvolution &SE) { - if (StressIVChain) - return true; - - if (!Chain.hasIncs()) - return false; - - if (!Users.empty()) { - LLVM_DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " users:\n"; - for (Instruction *Inst - : Users) { dbgs() << " " << *Inst << "\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 = nullptr; - unsigned NumConstIncrements = 0; - unsigned NumVarIncrements = 0; - unsigned NumReusedIncrements = 0; - for (const IVInc &Inc : Chain) { - if (Inc.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>(Inc.IncExpr)) { - ++NumConstIncrements; - continue; - } - - if (Inc.IncExpr == LastIncExpr) - ++NumReusedIncrements; - else - ++NumVarIncrements; - - LastIncExpr = Inc.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; - - LLVM_DEBUG(dbgs() << "Chain: " << *Chain.Incs[0].UserInst << " Cost: " << cost - << "\n"); - - return cost < 0; -} - -/// 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 = nullptr; - 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) { - LLVM_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); - LLVM_DEBUG(dbgs() << "IV Chain#" << ChainIdx << " Head: (" << *UserInst - << ") IV=" << *LastIncExpr << "\n"); - } else { - LLVM_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)); - } - IVChain &Chain = IVChainVec[ChainIdx]; - - 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 (User *U : IVOper->users()) { - Instruction *OtherUse = dyn_cast<Instruction>(U); - if (!OtherUse) - continue; - // Uses in the chain will no longer be uses if the chain is formed. - // Include the head of the chain in this iteration (not Chain.begin()). - IVChain::const_iterator IncIter = Chain.Incs.begin(); - IVChain::const_iterator IncEnd = Chain.Incs.end(); - for( ; IncIter != IncEnd; ++IncIter) { - if (IncIter->UserInst == OtherUse) - break; - } - if (IncIter != IncEnd) - 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); -} - -/// 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() { - LLVM_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 (BasicBlock *BB : reverse(LatchPath)) { - for (Instruction &I : *BB) { - // 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).second) - ChainInstruction(&I, IVOpInst, ChainUsersVec); - IVOpIter = findIVOperand(std::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 (PHINode &PN : L->getHeader()->phis()) { - 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)) - 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"); - LLVM_DEBUG(dbgs() << "Final Chain: " << *Chain.Incs[0].UserInst << "\n"); - - for (const IVInc &Inc : Chain) { - LLVM_DEBUG(dbgs() << " Inc: " << *Inc.UserInst << "\n"); - auto UseI = find(Inc.UserInst->operands(), Inc.IVOperand); - assert(UseI != Inc.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 TargetTransformInfo &TTI) { - const SCEVConstant *IncConst = dyn_cast<SCEVConstant>(IncExpr); - if (!IncConst || !isAddressUse(TTI, UserInst, Operand)) - return false; - - if (IncConst->getAPInt().getMinSignedBits() > 64) - return false; - - MemAccessTy AccessTy = getAccessType(TTI, UserInst, Operand); - int64_t IncOffset = IncConst->getValue()->getSExtValue(); - if (!isAlwaysFoldable(TTI, LSRUse::Address, AccessTy, /*BaseGV=*/nullptr, - IncOffset, /*HasBaseReg=*/false)) - return false; - - return true; -} - -/// 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<WeakTrackingVH> &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(); - // findIVOperand returns IVOpEnd if it can no longer find a valid IV user. - User::op_iterator IVOpIter = findIVOperand(Head.UserInst->op_begin(), - IVOpEnd, L, SE); - Value *IVSrc = nullptr; - 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(std::next(IVOpIter), IVOpEnd, L, SE); - } - if (IVOpIter == IVOpEnd) { - // Gracefully give up on this chain. - LLVM_DEBUG(dbgs() << "Concealed chain head: " << *Head.UserInst << "\n"); - return; - } - - LLVM_DEBUG(dbgs() << "Generate chain at: " << *IVSrc << "\n"); - Type *IVTy = IVSrc->getType(); - Type *IntTy = SE.getEffectiveSCEVType(IVTy); - const SCEV *LeftOverExpr = nullptr; - for (const IVInc &Inc : Chain) { - Instruction *InsertPt = Inc.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 (!Inc.IncExpr->isZero()) { - // IncExpr was the result of subtraction of two narrow values, so must - // be signed. - const SCEV *IncExpr = SE.getNoopOrSignExtend(Inc.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, Inc.UserInst, Inc.IVOperand, TTI)) { - assert(IVTy == IVOper->getType() && "inconsistent IV increment type"); - IVSrc = IVOper; - LeftOverExpr = nullptr; - } - } - Type *OperTy = Inc.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"); - } - Inc.UserInst->replaceUsesOfWith(Inc.IVOperand, IVOper); - DeadInsts.emplace_back(Inc.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 (PHINode &Phi : L->getHeader()->phis()) { - 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.emplace_back(PostIncV); - } - } -} - -void LSRInstance::CollectFixupsAndInitialFormulae() { - BranchInst *ExitBranch = nullptr; - bool SaveCmp = TTI.canSaveCmp(L, &ExitBranch, &SE, &LI, &DT, &AC, &LibInfo); - - for (const IVStrideUse &U : IU) { - Instruction *UserInst = U.getUser(); - // Skip IV users that are part of profitable IV Chains. - User::op_iterator UseI = - find(UserInst->operands(), U.getOperandValToReplace()); - assert(UseI != UserInst->op_end() && "cannot find IV operand"); - if (IVIncSet.count(UseI)) { - LLVM_DEBUG(dbgs() << "Use is in profitable chain: " << **UseI << '\n'); - continue; - } - - LSRUse::KindType Kind = LSRUse::Basic; - MemAccessTy AccessTy; - if (isAddressUse(TTI, UserInst, U.getOperandValToReplace())) { - Kind = LSRUse::Address; - AccessTy = getAccessType(TTI, UserInst, U.getOperandValToReplace()); - } - - const SCEV *S = IU.getExpr(U); - PostIncLoopSet TmpPostIncLoops = U.getPostIncLoops(); - - // 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>(UserInst)) - if (CI->isEquality()) { - // If CI can be saved in some target, like replaced inside hardware loop - // in PowerPC, no need to generate initial formulae for it. - if (SaveCmp && CI == dyn_cast<ICmpInst>(ExitBranch->getCondition())) - continue; - // Swap the operands if needed to put the OperandValToReplace on the - // left, for consistency. - Value *NV = CI->getOperand(1); - if (NV == U.getOperandValToReplace()) { - 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, SE)) { - // S is normalized, so normalize N before folding it into S - // to keep the result normalized. - N = normalizeForPostIncUse(N, TmpPostIncLoops, SE); - 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); - } - - // Get or create an LSRUse. - std::pair<size_t, int64_t> P = getUse(S, Kind, AccessTy); - size_t LUIdx = P.first; - int64_t Offset = P.second; - LSRUse &LU = Uses[LUIdx]; - - // Record the fixup. - LSRFixup &LF = LU.getNewFixup(); - LF.UserInst = UserInst; - LF.OperandValToReplace = U.getOperandValToReplace(); - LF.PostIncLoops = TmpPostIncLoops; - LF.Offset = Offset; - 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, LUIdx); - CountRegisters(LU.Formulae.back(), LUIdx); - } - } - - LLVM_DEBUG(print_fixups(dbgs())); -} - -/// 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) { - // Mark uses whose expressions cannot be expanded. - if (!isSafeToExpand(S, SE)) - LU.RigidFormula = true; - - Formula F; - F.initialMatch(S, L, SE); - bool Inserted = InsertFormula(LU, LUIdx, F); - assert(Inserted && "Initial formula already exists!"); (void)Inserted; -} - -/// 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.HasBaseReg = true; - bool Inserted = InsertFormula(LU, LUIdx, F); - assert(Inserted && "Supplemental formula already exists!"); (void)Inserted; -} - -/// 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 (const SCEV *BaseReg : F.BaseRegs) - RegUses.countRegister(BaseReg, LUIdx); -} - -/// 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) { - // Do not insert formula that we will not be able to expand. - assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F) && - "Formula is illegal"); - - if (!LU.InsertFormula(F, *L)) - return false; - - CountRegisters(F, LUIdx); - return true; -} - -/// 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 *, 32> Visited; - - while (!Worklist.empty()) { - const SCEV *S = Worklist.pop_back_val(); - - // Don't process the same SCEV twice - if (!Visited.insert(S).second) - continue; - - 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 *US = dyn_cast<SCEVUnknown>(S)) { - const Value *V = US->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 (const Use &U : V->uses()) { - const Instruction *UserInst = dyn_cast<Instruction>(U.getUser()); - // 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(U.getOperandNo())); - if (!DT.dominates(L->getHeader(), UseBB)) - continue; - // Don't bother if the instruction is in a BB which ends in an EHPad. - if (UseBB->getTerminator()->isEHPad()) - continue; - // Don't bother rewriting PHIs in catchswitch blocks. - if (isa<CatchSwitchInst>(UserInst->getParent()->getTerminator())) - 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 == US) { - 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 = !U.getOperandNo(); - Value *OtherOp = const_cast<Value *>(ICI->getOperand(OtherIdx)); - if (SE.hasComputableLoopEvolution(SE.getSCEV(OtherOp), L)) - continue; - } - - std::pair<size_t, int64_t> P = getUse( - S, LSRUse::Basic, MemAccessTy()); - size_t LUIdx = P.first; - int64_t Offset = P.second; - LSRUse &LU = Uses[LUIdx]; - LSRFixup &LF = LU.getNewFixup(); - LF.UserInst = const_cast<Instruction *>(UserInst); - LF.OperandValToReplace = U; - LF.Offset = Offset; - LU.AllFixupsOutsideLoop &= LF.isUseFullyOutsideLoop(L); - if (!LU.WidestFixupType || - SE.getTypeSizeInBits(LU.WidestFixupType) < - SE.getTypeSizeInBits(LF.OperandValToReplace->getType())) - LU.WidestFixupType = LF.OperandValToReplace->getType(); - InsertSupplementalFormula(US, LU, LUIdx); - CountRegisters(LU.Formulae.back(), Uses.size() - 1); - break; - } - } - } -} - -/// 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 (const SCEV *S : Add->operands()) { - const SCEV *Remainder = CollectSubexprs(S, C, Ops, L, SE, Depth+1); - if (Remainder) - Ops.push_back(C ? SE.getMulExpr(C, Remainder) : Remainder); - } - return nullptr; - } else if (const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S)) { - // Split a non-zero base out of an addrec. - if (AR->getStart()->isZero() || !AR->isAffine()) - 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 = nullptr; - } - 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 nullptr; - } - } - return S; -} - -/// Return true if the SCEV represents a value that may end up as a -/// post-increment operation. -static bool mayUsePostIncMode(const TargetTransformInfo &TTI, - LSRUse &LU, const SCEV *S, const Loop *L, - ScalarEvolution &SE) { - if (LU.Kind != LSRUse::Address || - !LU.AccessTy.getType()->isIntOrIntVectorTy()) - return false; - const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(S); - if (!AR) - return false; - const SCEV *LoopStep = AR->getStepRecurrence(SE); - if (!isa<SCEVConstant>(LoopStep)) - return false; - if (LU.AccessTy.getType()->getScalarSizeInBits() != - LoopStep->getType()->getScalarSizeInBits()) - return false; - // Check if a post-indexed load/store can be used. - if (TTI.isIndexedLoadLegal(TTI.MIM_PostInc, AR->getType()) || - TTI.isIndexedStoreLegal(TTI.MIM_PostInc, AR->getType())) { - const SCEV *LoopStart = AR->getStart(); - if (!isa<SCEVConstant>(LoopStart) && SE.isLoopInvariant(LoopStart, L)) - return true; - } - return false; -} - -/// Helper function for LSRInstance::GenerateReassociations. -void LSRInstance::GenerateReassociationsImpl(LSRUse &LU, unsigned LUIdx, - const Formula &Base, - unsigned Depth, size_t Idx, - bool IsScaledReg) { - const SCEV *BaseReg = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx]; - // Don't generate reassociations for the base register of a value that - // may generate a post-increment operator. The reason is that the - // reassociations cause extra base+register formula to be created, - // and possibly chosen, but the post-increment is more efficient. - if (TTI.shouldFavorPostInc() && mayUsePostIncMode(TTI, LU, BaseReg, L, SE)) - return; - SmallVector<const SCEV *, 8> AddOps; - const SCEV *Remainder = CollectSubexprs(BaseReg, nullptr, AddOps, L, SE); - if (Remainder) - AddOps.push_back(Remainder); - - if (AddOps.size() == 1) - return; - - 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(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind, - LU.AccessTy, *J, Base.getNumRegs() > 1)) - continue; - - // Collect all operands except *J. - SmallVector<const SCEV *, 8> InnerAddOps( - ((const SmallVector<const SCEV *, 8> &)AddOps).begin(), J); - InnerAddOps.append(std::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(TTI, SE, LU.MinOffset, LU.MaxOffset, LU.Kind, - LU.AccessTy, InnerAddOps[0], Base.getNumRegs() > 1)) - 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 (InnerSumSC && SE.getTypeSizeInBits(InnerSumSC->getType()) <= 64 && - TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset + - InnerSumSC->getValue()->getZExtValue())) { - F.UnfoldedOffset = - (uint64_t)F.UnfoldedOffset + InnerSumSC->getValue()->getZExtValue(); - if (IsScaledReg) - F.ScaledReg = nullptr; - else - F.BaseRegs.erase(F.BaseRegs.begin() + Idx); - } else if (IsScaledReg) - F.ScaledReg = InnerSum; - else - F.BaseRegs[Idx] = InnerSum; - - // Add J as its own register, or an unfolded immediate. - const SCEVConstant *SC = dyn_cast<SCEVConstant>(*J); - if (SC && SE.getTypeSizeInBits(SC->getType()) <= 64 && - TTI.isLegalAddImmediate((uint64_t)F.UnfoldedOffset + - SC->getValue()->getZExtValue())) - F.UnfoldedOffset = - (uint64_t)F.UnfoldedOffset + SC->getValue()->getZExtValue(); - else - F.BaseRegs.push_back(*J); - // We may have changed the number of register in base regs, adjust the - // formula accordingly. - F.canonicalize(*L); - - if (InsertFormula(LU, LUIdx, F)) - // If that formula hadn't been seen before, recurse to find more like - // it. - // Add check on Log16(AddOps.size()) - same as Log2_32(AddOps.size()) >> 2) - // Because just Depth is not enough to bound compile time. - // This means that every time AddOps.size() is greater 16^x we will add - // x to Depth. - GenerateReassociations(LU, LUIdx, LU.Formulae.back(), - Depth + 1 + (Log2_32(AddOps.size()) >> 2)); - } -} - -/// Split out subexpressions from adds and the bases of addrecs. -void LSRInstance::GenerateReassociations(LSRUse &LU, unsigned LUIdx, - Formula Base, unsigned Depth) { - assert(Base.isCanonical(*L) && "Input must be in the canonical form"); - // Arbitrarily cap recursion to protect compile time. - if (Depth >= 3) - return; - - for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) - GenerateReassociationsImpl(LU, LUIdx, Base, Depth, i); - - if (Base.Scale == 1) - GenerateReassociationsImpl(LU, LUIdx, Base, Depth, - /* Idx */ -1, /* IsScaledReg */ true); -} - -/// 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() + (Base.Scale == 1) + - (Base.UnfoldedOffset != 0) <= 1) - return; - - // Flatten the representation, i.e., reg1 + 1*reg2 => reg1 + reg2, before - // processing the formula. - Base.unscale(); - SmallVector<const SCEV *, 4> Ops; - Formula NewBase = Base; - NewBase.BaseRegs.clear(); - Type *CombinedIntegerType = nullptr; - for (const SCEV *BaseReg : Base.BaseRegs) { - if (SE.properlyDominates(BaseReg, L->getHeader()) && - !SE.hasComputableLoopEvolution(BaseReg, L)) { - if (!CombinedIntegerType) - CombinedIntegerType = SE.getEffectiveSCEVType(BaseReg->getType()); - Ops.push_back(BaseReg); - } - else - NewBase.BaseRegs.push_back(BaseReg); - } - - // If no register is relevant, we're done. - if (Ops.size() == 0) - return; - - // Utility function for generating the required variants of the combined - // registers. - auto GenerateFormula = [&](const SCEV *Sum) { - Formula F = NewBase; - - // 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()) - return; - - F.BaseRegs.push_back(Sum); - F.canonicalize(*L); - (void)InsertFormula(LU, LUIdx, F); - }; - - // If we collected at least two registers, generate a formula combining them. - if (Ops.size() > 1) { - SmallVector<const SCEV *, 4> OpsCopy(Ops); // Don't let SE modify Ops. - GenerateFormula(SE.getAddExpr(OpsCopy)); - } - - // If we have an unfolded offset, generate a formula combining it with the - // registers collected. - if (NewBase.UnfoldedOffset) { - assert(CombinedIntegerType && "Missing a type for the unfolded offset"); - Ops.push_back(SE.getConstant(CombinedIntegerType, NewBase.UnfoldedOffset, - true)); - NewBase.UnfoldedOffset = 0; - GenerateFormula(SE.getAddExpr(Ops)); - } -} - -/// Helper function for LSRInstance::GenerateSymbolicOffsets. -void LSRInstance::GenerateSymbolicOffsetsImpl(LSRUse &LU, unsigned LUIdx, - const Formula &Base, size_t Idx, - bool IsScaledReg) { - const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx]; - GlobalValue *GV = ExtractSymbol(G, SE); - if (G->isZero() || !GV) - return; - Formula F = Base; - F.BaseGV = GV; - if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F)) - return; - if (IsScaledReg) - F.ScaledReg = G; - else - F.BaseRegs[Idx] = G; - (void)InsertFormula(LU, LUIdx, F); -} - -/// 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.BaseGV) return; - - for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) - GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, i); - if (Base.Scale == 1) - GenerateSymbolicOffsetsImpl(LU, LUIdx, Base, /* Idx */ -1, - /* IsScaledReg */ true); -} - -/// Helper function for LSRInstance::GenerateConstantOffsets. -void LSRInstance::GenerateConstantOffsetsImpl( - LSRUse &LU, unsigned LUIdx, const Formula &Base, - const SmallVectorImpl<int64_t> &Worklist, size_t Idx, bool IsScaledReg) { - - auto GenerateOffset = [&](const SCEV *G, int64_t Offset) { - Formula F = Base; - F.BaseOffset = (uint64_t)Base.BaseOffset - Offset; - - if (isLegalUse(TTI, LU.MinOffset - Offset, LU.MaxOffset - Offset, LU.Kind, - LU.AccessTy, F)) { - // Add the offset to the base register. - const SCEV *NewG = SE.getAddExpr(SE.getConstant(G->getType(), Offset), G); - // If it cancelled out, drop the base register, otherwise update it. - if (NewG->isZero()) { - if (IsScaledReg) { - F.Scale = 0; - F.ScaledReg = nullptr; - } else - F.deleteBaseReg(F.BaseRegs[Idx]); - F.canonicalize(*L); - } else if (IsScaledReg) - F.ScaledReg = NewG; - else - F.BaseRegs[Idx] = NewG; - - (void)InsertFormula(LU, LUIdx, F); - } - }; - - const SCEV *G = IsScaledReg ? Base.ScaledReg : Base.BaseRegs[Idx]; - - // With constant offsets and constant steps, we can generate pre-inc - // accesses by having the offset equal the step. So, for access #0 with a - // step of 8, we generate a G - 8 base which would require the first access - // to be ((G - 8) + 8),+,8. The pre-indexed access then updates the pointer - // for itself and hopefully becomes the base for other accesses. This means - // means that a single pre-indexed access can be generated to become the new - // base pointer for each iteration of the loop, resulting in no extra add/sub - // instructions for pointer updating. - if (FavorBackedgeIndex && LU.Kind == LSRUse::Address) { - if (auto *GAR = dyn_cast<SCEVAddRecExpr>(G)) { - if (auto *StepRec = - dyn_cast<SCEVConstant>(GAR->getStepRecurrence(SE))) { - const APInt &StepInt = StepRec->getAPInt(); - int64_t Step = StepInt.isNegative() ? - StepInt.getSExtValue() : StepInt.getZExtValue(); - - for (int64_t Offset : Worklist) { - Offset -= Step; - GenerateOffset(G, Offset); - } - } - } - } - for (int64_t Offset : Worklist) - GenerateOffset(G, Offset); - - int64_t Imm = ExtractImmediate(G, SE); - if (G->isZero() || Imm == 0) - return; - Formula F = Base; - F.BaseOffset = (uint64_t)F.BaseOffset + Imm; - if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, F)) - return; - if (IsScaledReg) - F.ScaledReg = G; - else - F.BaseRegs[Idx] = 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) - GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, i); - if (Base.Scale == 1) - GenerateConstantOffsetsImpl(LU, LUIdx, Base, Worklist, /* Idx */ -1, - /* IsScaledReg */ true); -} - -/// 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; - - // Check if transformation is valid. It is illegal to multiply pointer. - if (Base.ScaledReg && Base.ScaledReg->getType()->isPointerTy()) - return; - for (const SCEV *BaseReg : Base.BaseRegs) - if (BaseReg->getType()->isPointerTy()) - return; - assert(!Base.BaseGV && "ICmpZero use is not legal!"); - - // Check each interesting stride. - for (int64_t Factor : Factors) { - // Check that the multiplication doesn't overflow. - if (Base.BaseOffset == std::numeric_limits<int64_t>::min() && Factor == -1) - continue; - int64_t NewBaseOffset = (uint64_t)Base.BaseOffset * Factor; - if (NewBaseOffset / Factor != Base.BaseOffset) - continue; - // If the offset will be truncated at this use, check that it is in bounds. - if (!IntTy->isPointerTy() && - !ConstantInt::isValueValidForType(IntTy, NewBaseOffset)) - continue; - - // Check that multiplying with the use offset doesn't overflow. - int64_t Offset = LU.MinOffset; - if (Offset == std::numeric_limits<int64_t>::min() && Factor == -1) - continue; - Offset = (uint64_t)Offset * Factor; - if (Offset / Factor != LU.MinOffset) - continue; - // If the offset will be truncated at this use, check that it is in bounds. - if (!IntTy->isPointerTy() && - !ConstantInt::isValueValidForType(IntTy, Offset)) - continue; - - Formula F = Base; - F.BaseOffset = NewBaseOffset; - - // Check that this scale is legal. - if (!isLegalUse(TTI, Offset, Offset, LU.Kind, LU.AccessTy, F)) - continue; - - // Compensate for the use having MinOffset built into it. - F.BaseOffset = (uint64_t)F.BaseOffset + 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 == std::numeric_limits<int64_t>::min() && - Factor == -1) - continue; - F.UnfoldedOffset = (uint64_t)F.UnfoldedOffset * Factor; - if (F.UnfoldedOffset / Factor != Base.UnfoldedOffset) - continue; - // If the offset will be truncated, check that it is in bounds. - if (!IntTy->isPointerTy() && - !ConstantInt::isValueValidForType(IntTy, F.UnfoldedOffset)) - continue; - } - - // If we make it here and it's legal, add it. - (void)InsertFormula(LU, LUIdx, F); - next:; - } -} - -/// 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. - // Try to unscale the formula to generate a better scale. - if (Base.Scale != 0 && !Base.unscale()) - return; - - assert(Base.Scale == 0 && "unscale did not did its job!"); - - // Check each interesting stride. - for (int64_t Factor : Factors) { - Base.Scale = Factor; - Base.HasBaseReg = Base.BaseRegs.size() > 1; - // Check whether this scale is going to be legal. - if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, - Base)) { - // As a special-case, handle special out-of-loop Basic users specially. - // TODO: Reconsider this special case. - if (LU.Kind == LSRUse::Basic && - isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LSRUse::Special, - LU.AccessTy, Base) && - 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.HasBaseReg && Base.BaseOffset == 0 && !Base.BaseGV) - continue; - // For each addrec base reg, if its loop is current loop, apply the scale. - for (size_t i = 0, e = Base.BaseRegs.size(); i != e; ++i) { - const SCEVAddRecExpr *AR = dyn_cast<SCEVAddRecExpr>(Base.BaseRegs[i]); - if (AR && (AR->getLoop() == L || LU.AllFixupsOutsideLoop)) { - 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]); - // The canonical representation of 1*reg is reg, which is already in - // Base. In that case, do not try to insert the formula, it will be - // rejected anyway. - if (F.Scale == 1 && (F.BaseRegs.empty() || - (AR->getLoop() != L && LU.AllFixupsOutsideLoop))) - continue; - // If AllFixupsOutsideLoop is true and F.Scale is 1, we may generate - // non canonical Formula with ScaledReg's loop not being L. - if (F.Scale == 1 && LU.AllFixupsOutsideLoop) - F.canonicalize(*L); - (void)InsertFormula(LU, LUIdx, F); - } - } - } - } -} - -/// Generate reuse formulae from different IV types. -void LSRInstance::GenerateTruncates(LSRUse &LU, unsigned LUIdx, Formula Base) { - // Don't bother truncating symbolic values. - if (Base.BaseGV) return; - - // Determine the integer type for the base formula. - Type *DstTy = Base.getType(); - if (!DstTy) return; - DstTy = SE.getEffectiveSCEVType(DstTy); - - for (Type *SrcTy : Types) { - if (SrcTy != DstTy && TTI.isTruncateFree(SrcTy, DstTy)) { - Formula F = Base; - - // Sometimes SCEV is able to prove zero during ext transform. It may - // happen if SCEV did not do all possible transforms while creating the - // initial node (maybe due to depth limitations), but it can do them while - // taking ext. - if (F.ScaledReg) { - const SCEV *NewScaledReg = SE.getAnyExtendExpr(F.ScaledReg, SrcTy); - if (NewScaledReg->isZero()) - continue; - F.ScaledReg = NewScaledReg; - } - bool HasZeroBaseReg = false; - for (const SCEV *&BaseReg : F.BaseRegs) { - const SCEV *NewBaseReg = SE.getAnyExtendExpr(BaseReg, SrcTy); - if (NewBaseReg->isZero()) { - HasZeroBaseReg = true; - break; - } - BaseReg = NewBaseReg; - } - if (HasZeroBaseReg) - continue; - - // 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; - - F.canonicalize(*L); - (void)InsertFormula(LU, LUIdx, F); - } - } -} - -namespace { - -/// 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; -}; - -} // end anonymous namespace - -#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) -void WorkItem::print(raw_ostream &OS) const { - OS << "in formulae referencing " << *OrigReg << " in use " << LUIdx - << " , add offset " << Imm; -} - -LLVM_DUMP_METHOD void WorkItem::dump() const { - print(errs()); errs() << '\n'; -} -#endif - -/// 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. - using ImmMapTy = std::map<int64_t, const SCEV *>; - - DenseMap<const SCEV *, ImmMapTy> Map; - DenseMap<const SCEV *, SmallBitVector> UsedByIndicesMap; - SmallVector<const SCEV *, 8> Sequence; - for (const SCEV *Use : RegUses) { - const SCEV *Reg = Use; // Make a copy for ExtractImmediate to modify. - int64_t Imm = ExtractImmediate(Reg, SE); - auto Pair = Map.insert(std::make_pair(Reg, ImmMapTy())); - if (Pair.second) - Sequence.push_back(Reg); - Pair.first->second.insert(std::make_pair(Imm, Use)); - UsedByIndicesMap[Reg] |= RegUses.getUsedByIndices(Use); - } - - // 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 (const SCEV *Reg : Sequence) { - 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; - - LLVM_DEBUG(dbgs() << "Generating cross-use offsets for " << *Reg << ':'; - for (const auto &Entry - : Imms) dbgs() - << ' ' << Entry.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) { - LLVM_DEBUG(dbgs() << "Skipping cross-use reuse for " << *OrigReg - << '\n'); - continue; - } - - // Conservatively examine offsets between this orig reg a few selected - // other orig regs. - int64_t First = Imms.begin()->first; - int64_t Last = std::prev(Imms.end())->first; - // Compute (First + Last) / 2 without overflow using the fact that - // First + Last = 2 * (First + Last) + (First ^ Last). - int64_t Avg = (First & Last) + ((First ^ Last) >> 1); - // If the result is negative and First is odd and Last even (or vice versa), - // we rounded towards -inf. Add 1 in that case, to round towards 0. - Avg = Avg + ((First ^ Last) & ((uint64_t)Avg >> 63)); - ImmMapTy::const_iterator OtherImms[] = { - Imms.begin(), std::prev(Imms.end()), - Imms.lower_bound(Avg)}; - 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 (unsigned LUIdx : UsedByIndices.set_bits()) - // Make a memo of this use, offset, and register tuple. - if (UniqueItems.insert(std::make_pair(LUIdx, Imm)).second) - 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 (const WorkItem &WI : WorkItems) { - 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) { - Formula F = LU.Formulae[L]; - // FIXME: The code for the scaled and unscaled registers looks - // very similar but slightly different. Investigate if they - // could be merged. That way, we would not have to unscale the - // Formula. - F.unscale(); - // Use the immediate in the scaled register. - if (F.ScaledReg == OrigReg) { - int64_t Offset = (uint64_t)F.BaseOffset + Imm * (uint64_t)F.Scale; - // Don't create 50 + reg(-50). - if (F.referencesReg(SE.getSCEV( - ConstantInt::get(IntTy, -(uint64_t)Offset)))) - continue; - Formula NewF = F; - NewF.BaseOffset = Offset; - if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, - NewF)) - 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.BaseOffset < 0) && - (C->getAPInt().abs() * APInt(BitWidth, F.Scale)) - .ule(std::abs(NewF.BaseOffset))) - continue; - - // OK, looks good. - NewF.canonicalize(*this->L); - (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.BaseOffset = (uint64_t)NewF.BaseOffset + Imm; - if (!isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, - LU.Kind, LU.AccessTy, NewF)) { - if (TTI.shouldFavorPostInc() && - mayUsePostIncMode(TTI, LU, OrigReg, this->L, SE)) - continue; - if (!TTI.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 (const SCEV *NewReg : NewF.BaseRegs) - if (const SCEVConstant *C = dyn_cast<SCEVConstant>(NewReg)) - if ((C->getAPInt() + NewF.BaseOffset) - .abs() - .slt(std::abs(NewF.BaseOffset)) && - (C->getAPInt() + NewF.BaseOffset).countTrailingZeros() >= - countTrailingZeros<uint64_t>(NewF.BaseOffset)) - goto skip_formula; - - // Ok, looks good. - NewF.canonicalize(*this->L); - (void)InsertFormula(LU, LUIdx, NewF); - break; - skip_formula:; - } - } - } - } -} - -/// 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(); - - LLVM_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. - using BestFormulaeTy = - DenseMap<SmallVector<const SCEV *, 4>, size_t, UniquifierDenseMapInfo>; - - BestFormulaeTy BestFormulae; - - for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { - LSRUse &LU = Uses[LUIdx]; - LLVM_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(L, SE, TTI); - Regs.clear(); - CostF.RateFormula(F, Regs, VisitedRegs, LU, &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. - LLVM_DEBUG(dbgs() << " Filtering loser "; F.print(dbgs()); - dbgs() << "\n"); - } - else { - SmallVector<const SCEV *, 4> Key; - for (const SCEV *Reg : F.BaseRegs) { - 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. - llvm::sort(Key); - - 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(L, SE, TTI); - Regs.clear(); - CostBest.RateFormula(Best, Regs, VisitedRegs, LU); - if (CostF.isLess(CostBest)) - std::swap(F, Best); - LLVM_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(); - } - - LLVM_DEBUG(if (ChangedFormulae) { - dbgs() << "\n" - "After filtering out undesirable candidates:\n"; - print_uses(dbgs()); - }); -} - -/// 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 (const LSRUse &LU : Uses) { - size_t FSize = LU.Formulae.size(); - if (FSize >= ComplexityLimit) { - Power = ComplexityLimit; - break; - } - Power *= FSize; - if (Power >= ComplexityLimit) - break; - } - return Power; -} - -/// 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) { - LLVM_DEBUG(dbgs() << "The search space is too complex.\n"); - - LLVM_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; - //FIXME: Formulas should store bitwidth to do wrapping properly. - // See PR41034. - NewF.BaseOffset += (uint64_t)C->getValue()->getSExtValue(); - NewF.BaseRegs.erase(NewF.BaseRegs.begin() + - (I - F.BaseRegs.begin())); - if (LU.HasFormulaWithSameRegs(NewF)) { - LLVM_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.BaseGV) { - Formula NewF = F; - NewF.BaseGV = GV; - NewF.BaseRegs.erase(NewF.BaseRegs.begin() + - (I - F.BaseRegs.begin())); - if (LU.HasFormulaWithSameRegs(NewF)) { - LLVM_DEBUG(dbgs() << " Deleting "; F.print(dbgs()); - dbgs() << '\n'); - LU.DeleteFormula(F); - --i; - --e; - Any = true; - break; - } - } - } - } - } - if (Any) - LU.RecomputeRegs(LUIdx, RegUses); - } - - LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs())); - } -} - -/// 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) - return; - - LLVM_DEBUG( - dbgs() << "The search space is too complex.\n" - "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 (const Formula &F : LU.Formulae) { - if (F.BaseOffset == 0 || (F.Scale != 0 && F.Scale != 1)) - continue; - - LSRUse *LUThatHas = FindUseWithSimilarFormula(F, LU); - if (!LUThatHas) - continue; - - if (!reconcileNewOffset(*LUThatHas, F.BaseOffset, /*HasBaseReg=*/ false, - LU.Kind, LU.AccessTy)) - continue; - - LLVM_DEBUG(dbgs() << " Deleting use "; LU.print(dbgs()); dbgs() << '\n'); - - LUThatHas->AllFixupsOutsideLoop &= LU.AllFixupsOutsideLoop; - - // Transfer the fixups of LU to LUThatHas. - for (LSRFixup &Fixup : LU.Fixups) { - Fixup.Offset += F.BaseOffset; - LUThatHas->pushFixup(Fixup); - LLVM_DEBUG(dbgs() << "New fixup has offset " << Fixup.Offset << '\n'); - } - - // 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(TTI, LUThatHas->MinOffset, LUThatHas->MaxOffset, - LUThatHas->Kind, LUThatHas->AccessTy, F)) { - LLVM_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; - } - } - - LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs())); -} - -/// 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) { - LLVM_DEBUG(dbgs() << "The search space is too complex.\n"); - - LLVM_DEBUG(dbgs() << "Narrowing the search space by re-filtering out " - "undesirable dedicated registers.\n"); - - FilterOutUndesirableDedicatedRegisters(); - - LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs())); - } -} - -/// If a LSRUse has multiple formulae with the same ScaledReg and Scale. -/// Pick the best one and delete the others. -/// This narrowing heuristic is to keep as many formulae with different -/// Scale and ScaledReg pair as possible while narrowing the search space. -/// The benefit is that it is more likely to find out a better solution -/// from a formulae set with more Scale and ScaledReg variations than -/// a formulae set with the same Scale and ScaledReg. The picking winner -/// reg heuristic will often keep the formulae with the same Scale and -/// ScaledReg and filter others, and we want to avoid that if possible. -void LSRInstance::NarrowSearchSpaceByFilterFormulaWithSameScaledReg() { - if (EstimateSearchSpaceComplexity() < ComplexityLimit) - return; - - LLVM_DEBUG( - dbgs() << "The search space is too complex.\n" - "Narrowing the search space by choosing the best Formula " - "from the Formulae with the same Scale and ScaledReg.\n"); - - // Map the "Scale * ScaledReg" pair to the best formula of current LSRUse. - using BestFormulaeTy = DenseMap<std::pair<const SCEV *, int64_t>, size_t>; - - BestFormulaeTy BestFormulae; -#ifndef NDEBUG - bool ChangedFormulae = false; -#endif - DenseSet<const SCEV *> VisitedRegs; - SmallPtrSet<const SCEV *, 16> Regs; - - for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { - LSRUse &LU = Uses[LUIdx]; - LLVM_DEBUG(dbgs() << "Filtering for use "; LU.print(dbgs()); - dbgs() << '\n'); - - // Return true if Formula FA is better than Formula FB. - auto IsBetterThan = [&](Formula &FA, Formula &FB) { - // First we will try to choose the Formula with fewer new registers. - // For a register used by current Formula, the more the register is - // shared among LSRUses, the less we increase the register number - // counter of the formula. - size_t FARegNum = 0; - for (const SCEV *Reg : FA.BaseRegs) { - const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg); - FARegNum += (NumUses - UsedByIndices.count() + 1); - } - size_t FBRegNum = 0; - for (const SCEV *Reg : FB.BaseRegs) { - const SmallBitVector &UsedByIndices = RegUses.getUsedByIndices(Reg); - FBRegNum += (NumUses - UsedByIndices.count() + 1); - } - if (FARegNum != FBRegNum) - return FARegNum < FBRegNum; - - // If the new register numbers are the same, choose the Formula with - // less Cost. - Cost CostFA(L, SE, TTI); - Cost CostFB(L, SE, TTI); - Regs.clear(); - CostFA.RateFormula(FA, Regs, VisitedRegs, LU); - Regs.clear(); - CostFB.RateFormula(FB, Regs, VisitedRegs, LU); - return CostFA.isLess(CostFB); - }; - - bool Any = false; - for (size_t FIdx = 0, NumForms = LU.Formulae.size(); FIdx != NumForms; - ++FIdx) { - Formula &F = LU.Formulae[FIdx]; - if (!F.ScaledReg) - continue; - auto P = BestFormulae.insert({{F.ScaledReg, F.Scale}, FIdx}); - if (P.second) - continue; - - Formula &Best = LU.Formulae[P.first->second]; - if (IsBetterThan(F, Best)) - std::swap(F, Best); - LLVM_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; - } - if (Any) - LU.RecomputeRegs(LUIdx, RegUses); - - // Reset this to prepare for the next use. - BestFormulae.clear(); - } - - LLVM_DEBUG(if (ChangedFormulae) { - dbgs() << "\n" - "After filtering out undesirable candidates:\n"; - print_uses(dbgs()); - }); -} - -/// The function delete formulas with high registers number expectation. -/// Assuming we don't know the value of each formula (already delete -/// all inefficient), generate probability of not selecting for each -/// register. -/// For example, -/// Use1: -/// reg(a) + reg({0,+,1}) -/// reg(a) + reg({-1,+,1}) + 1 -/// reg({a,+,1}) -/// Use2: -/// reg(b) + reg({0,+,1}) -/// reg(b) + reg({-1,+,1}) + 1 -/// reg({b,+,1}) -/// Use3: -/// reg(c) + reg(b) + reg({0,+,1}) -/// reg(c) + reg({b,+,1}) -/// -/// Probability of not selecting -/// Use1 Use2 Use3 -/// reg(a) (1/3) * 1 * 1 -/// reg(b) 1 * (1/3) * (1/2) -/// reg({0,+,1}) (2/3) * (2/3) * (1/2) -/// reg({-1,+,1}) (2/3) * (2/3) * 1 -/// reg({a,+,1}) (2/3) * 1 * 1 -/// reg({b,+,1}) 1 * (2/3) * (2/3) -/// reg(c) 1 * 1 * 0 -/// -/// Now count registers number mathematical expectation for each formula: -/// Note that for each use we exclude probability if not selecting for the use. -/// For example for Use1 probability for reg(a) would be just 1 * 1 (excluding -/// probabilty 1/3 of not selecting for Use1). -/// Use1: -/// reg(a) + reg({0,+,1}) 1 + 1/3 -- to be deleted -/// reg(a) + reg({-1,+,1}) + 1 1 + 4/9 -- to be deleted -/// reg({a,+,1}) 1 -/// Use2: -/// reg(b) + reg({0,+,1}) 1/2 + 1/3 -- to be deleted -/// reg(b) + reg({-1,+,1}) + 1 1/2 + 2/3 -- to be deleted -/// reg({b,+,1}) 2/3 -/// Use3: -/// reg(c) + reg(b) + reg({0,+,1}) 1 + 1/3 + 4/9 -- to be deleted -/// reg(c) + reg({b,+,1}) 1 + 2/3 -void LSRInstance::NarrowSearchSpaceByDeletingCostlyFormulas() { - if (EstimateSearchSpaceComplexity() < ComplexityLimit) - return; - // Ok, we have too many of formulae on our hands to conveniently handle. - // Use a rough heuristic to thin out the list. - - // Set of Regs wich will be 100% used in final solution. - // Used in each formula of a solution (in example above this is reg(c)). - // We can skip them in calculations. - SmallPtrSet<const SCEV *, 4> UniqRegs; - LLVM_DEBUG(dbgs() << "The search space is too complex.\n"); - - // Map each register to probability of not selecting - DenseMap <const SCEV *, float> RegNumMap; - for (const SCEV *Reg : RegUses) { - if (UniqRegs.count(Reg)) - continue; - float PNotSel = 1; - for (const LSRUse &LU : Uses) { - if (!LU.Regs.count(Reg)) - continue; - float P = LU.getNotSelectedProbability(Reg); - if (P != 0.0) - PNotSel *= P; - else - UniqRegs.insert(Reg); - } - RegNumMap.insert(std::make_pair(Reg, PNotSel)); - } - - LLVM_DEBUG( - dbgs() << "Narrowing the search space by deleting costly formulas\n"); - - // Delete formulas where registers number expectation is high. - for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) { - LSRUse &LU = Uses[LUIdx]; - // If nothing to delete - continue. - if (LU.Formulae.size() < 2) - continue; - // This is temporary solution to test performance. Float should be - // replaced with round independent type (based on integers) to avoid - // different results for different target builds. - float FMinRegNum = LU.Formulae[0].getNumRegs(); - float FMinARegNum = LU.Formulae[0].getNumRegs(); - size_t MinIdx = 0; - for (size_t i = 0, e = LU.Formulae.size(); i != e; ++i) { - Formula &F = LU.Formulae[i]; - float FRegNum = 0; - float FARegNum = 0; - for (const SCEV *BaseReg : F.BaseRegs) { - if (UniqRegs.count(BaseReg)) - continue; - FRegNum += RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg); - if (isa<SCEVAddRecExpr>(BaseReg)) - FARegNum += - RegNumMap[BaseReg] / LU.getNotSelectedProbability(BaseReg); - } - if (const SCEV *ScaledReg = F.ScaledReg) { - if (!UniqRegs.count(ScaledReg)) { - FRegNum += - RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg); - if (isa<SCEVAddRecExpr>(ScaledReg)) - FARegNum += - RegNumMap[ScaledReg] / LU.getNotSelectedProbability(ScaledReg); - } - } - if (FMinRegNum > FRegNum || - (FMinRegNum == FRegNum && FMinARegNum > FARegNum)) { - FMinRegNum = FRegNum; - FMinARegNum = FARegNum; - MinIdx = i; - } - } - LLVM_DEBUG(dbgs() << " The formula "; LU.Formulae[MinIdx].print(dbgs()); - dbgs() << " with min reg num " << FMinRegNum << '\n'); - if (MinIdx != 0) - std::swap(LU.Formulae[MinIdx], LU.Formulae[0]); - while (LU.Formulae.size() != 1) { - LLVM_DEBUG(dbgs() << " Deleting "; LU.Formulae.back().print(dbgs()); - dbgs() << '\n'); - LU.Formulae.pop_back(); - } - LU.RecomputeRegs(LUIdx, RegUses); - assert(LU.Formulae.size() == 1 && "Should be exactly 1 min regs formula"); - Formula &F = LU.Formulae[0]; - LLVM_DEBUG(dbgs() << " Leaving only "; F.print(dbgs()); dbgs() << '\n'); - // When we choose the formula, the regs become unique. - UniqRegs.insert(F.BaseRegs.begin(), F.BaseRegs.end()); - if (F.ScaledReg) - UniqRegs.insert(F.ScaledReg); - } - LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs())); -} - -/// 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. - LLVM_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 = nullptr; - unsigned BestNum = 0; - for (const SCEV *Reg : RegUses) { - if (Taken.count(Reg)) - continue; - if (!Best) { - Best = Reg; - BestNum = RegUses.getUsedByIndices(Reg).count(); - } else { - unsigned Count = RegUses.getUsedByIndices(Reg).count(); - if (Count > BestNum) { - Best = Reg; - BestNum = Count; - } - } - } - - LLVM_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)) { - LLVM_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); - } - - LLVM_DEBUG(dbgs() << "After pre-selection:\n"; print_uses(dbgs())); - } -} - -/// 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(); - if (FilterSameScaledReg) - NarrowSearchSpaceByFilterFormulaWithSameScaledReg(); - if (LSRExpNarrow) - NarrowSearchSpaceByDeletingCostlyFormulas(); - else - NarrowSearchSpaceByPickingWinnerRegs(); -} - -/// 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 (const SCEV *S : CurRegs) - if (LU.Regs.count(S)) - ReqRegs.insert(S); - - SmallPtrSet<const SCEV *, 16> NewRegs; - Cost NewCost(L, SE, TTI); - for (const Formula &F : LU.Formulae) { - // Ignore formulae which may not be ideal in terms of register reuse of - // ReqRegs. The formula should use all required registers before - // introducing new ones. - int NumReqRegsToFind = std::min(F.getNumRegs(), ReqRegs.size()); - for (const SCEV *Reg : ReqRegs) { - if ((F.ScaledReg && F.ScaledReg == Reg) || - is_contained(F.BaseRegs, Reg)) { - --NumReqRegsToFind; - if (NumReqRegsToFind == 0) - break; - } - } - if (NumReqRegsToFind != 0) { - // 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, LU); - if (NewCost.isLess(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 { - LLVM_DEBUG(dbgs() << "New best at "; NewCost.print(dbgs()); - dbgs() << ".\nRegs:\n"; - for (const SCEV *S : NewRegs) dbgs() - << "- " << *S << "\n"; - dbgs() << '\n'); - - SolutionCost = NewCost; - Solution = Workspace; - } - Workspace.pop_back(); - } - } -} - -/// 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(L, SE, TTI); - SolutionCost.Lose(); - Cost CurCost(L, SE, TTI); - 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()) { - LLVM_DEBUG(dbgs() << "\nNo Satisfactory Solution\n"); - return; - } - - // Ok, we've now made all our decisions. - LLVM_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!"); -} - -/// 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 { - Instruction *Tentative = &*IP; - while (true) { - bool AllDominate = true; - Instruction *BetterPos = nullptr; - // Don't bother attempting to insert before a catchswitch, their basic block - // cannot have other non-PHI instructions. - if (isa<CatchSwitchInst>(Tentative)) - return IP; - - for (Instruction *Inst : Inputs) { - 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 (Tentative->getParent() == Inst->getParent() && - (!BetterPos || !DT.dominates(Inst, BetterPos))) - BetterPos = &*std::next(BasicBlock::iterator(Inst)); - } - if (!AllDominate) - break; - if (BetterPos) - IP = BetterPos->getIterator(); - else - IP = Tentative->getIterator(); - - 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; - } - - Tentative = IDom->getTerminator(); - } - - return IP; -} - -/// 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 (const Loop *PIL : LF.PostIncLoops) { - 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) && !LowestIP->isEHPad() - && !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 (IP->isEHPad()) ++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; -} - -/// Emit instructions for the leading candidate expression for this LSRUse (this -/// is called "expanding"). -Value *LSRInstance::Expand(const LSRUse &LU, const LSRFixup &LF, - const Formula &F, BasicBlock::iterator IP, - SCEVExpander &Rewriter, - SmallVectorImpl<WeakTrackingVH> &DeadInsts) const { - if (LU.RigidFormula) - return LF.OperandValToReplace; - - // Determine an input position which will be dominated by the operands and - // which will dominate the result. - IP = AdjustInsertPositionForExpand(IP, LF, LU, Rewriter); - Rewriter.setInsertPoint(&*IP); - - // 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 (const SCEV *Reg : F.BaseRegs) { - assert(!Reg->isZero() && "Zero allocated in a base register!"); - - // If we're expanding for a post-inc user, make the post-inc adjustment. - Reg = denormalizeForPostIncUse(Reg, LF.PostIncLoops, SE); - Ops.push_back(SE.getUnknown(Rewriter.expandCodeFor(Reg, nullptr))); - } - - // Expand the ScaledReg portion. - Value *ICmpScaledV = nullptr; - if (F.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 = denormalizeForPostIncUse(ScaledS, Loops, SE); - - if (LU.Kind == LSRUse::ICmpZero) { - // Expand ScaleReg as if it was part of the base regs. - if (F.Scale == 1) - Ops.push_back( - SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr))); - else { - // 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.Scale == -1 && - "The only scale supported by ICmpZero uses is -1!"); - ICmpScaledV = Rewriter.expandCodeFor(ScaledS, nullptr); - } - } 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. - // Unless the addressing mode will not be folded. - if (!Ops.empty() && LU.Kind == LSRUse::Address && - isAMCompletelyFolded(TTI, LU, F)) { - Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), nullptr); - Ops.clear(); - Ops.push_back(SE.getUnknown(FullV)); - } - ScaledS = SE.getUnknown(Rewriter.expandCodeFor(ScaledS, nullptr)); - if (F.Scale != 1) - ScaledS = - SE.getMulExpr(ScaledS, SE.getConstant(ScaledS->getType(), F.Scale)); - Ops.push_back(ScaledS); - } - } - - // Expand the GV portion. - if (F.BaseGV) { - // Flush the operand list to suppress SCEVExpander hoisting. - if (!Ops.empty()) { - Value *FullV = Rewriter.expandCodeFor(SE.getAddExpr(Ops), Ty); - Ops.clear(); - Ops.push_back(SE.getUnknown(FullV)); - } - Ops.push_back(SE.getUnknown(F.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); - Ops.clear(); - Ops.push_back(SE.getUnknown(FullV)); - } - - // Expand the immediate portion. - int64_t Offset = (uint64_t)F.BaseOffset + 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); - - // 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.emplace_back(CI->getOperand(1)); - assert(!F.BaseGV && "ICmp does not support folding a global value and " - "a scale at the same time!"); - if (F.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 { - // A scale of 1 means that the scale has been expanded as part of the - // base regs. - assert((F.Scale == 0 || F.Scale == 1) && - "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; -} - -/// 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 LSRUse &LU, const LSRFixup &LF, const Formula &F, - SCEVExpander &Rewriter, SmallVectorImpl<WeakTrackingVH> &DeadInsts) const { - DenseMap<BasicBlock *, Value *> Inserted; - for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) - if (PN->getIncomingValue(i) == LF.OperandValToReplace) { - bool needUpdateFixups = false; - 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()) && - !isa<CatchSwitchInst>(BB->getTerminator())) { - BasicBlock *Parent = PN->getParent(); - Loop *PNLoop = LI.getLoopFor(Parent); - if (!PNLoop || Parent != PNLoop->getHeader()) { - // Split the critical edge. - BasicBlock *NewBB = nullptr; - if (!Parent->isLandingPad()) { - NewBB = SplitCriticalEdge(BB, Parent, - CriticalEdgeSplittingOptions(&DT, &LI) - .setMergeIdenticalEdges() - .setKeepOneInputPHIs()); - } else { - SmallVector<BasicBlock*, 2> NewBBs; - SplitLandingPadPredecessors(Parent, BB, "", "", NewBBs, &DT, &LI); - NewBB = NewBBs[0]; - } - // If NewBB==NULL, then SplitCriticalEdge refused to split because all - // phi predecessors are identical. The simple thing to do is skip - // splitting in this case rather than complicate the API. - if (NewBB) { - // 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); - - needUpdateFixups = true; - } - } - } - - std::pair<DenseMap<BasicBlock *, Value *>::iterator, bool> Pair = - Inserted.insert(std::make_pair(BB, static_cast<Value *>(nullptr))); - if (!Pair.second) - PN->setIncomingValue(i, Pair.first->second); - else { - Value *FullV = Expand(LU, LF, F, BB->getTerminator()->getIterator(), - 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; - } - - // If LSR splits critical edge and phi node has other pending - // fixup operands, we need to update those pending fixups. Otherwise - // formulae will not be implemented completely and some instructions - // will not be eliminated. - if (needUpdateFixups) { - for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) - for (LSRFixup &Fixup : Uses[LUIdx].Fixups) - // If fixup is supposed to rewrite some operand in the phi - // that was just updated, it may be already moved to - // another phi node. Such fixup requires update. - if (Fixup.UserInst == PN) { - // Check if the operand we try to replace still exists in the - // original phi. - bool foundInOriginalPHI = false; - for (const auto &val : PN->incoming_values()) - if (val == Fixup.OperandValToReplace) { - foundInOriginalPHI = true; - break; - } - - // If fixup operand found in original PHI - nothing to do. - if (foundInOriginalPHI) - continue; - - // Otherwise it might be moved to another PHI and requires update. - // If fixup operand not found in any of the incoming blocks that - // means we have already rewritten it - nothing to do. - for (const auto &Block : PN->blocks()) - for (BasicBlock::iterator I = Block->begin(); isa<PHINode>(I); - ++I) { - PHINode *NewPN = cast<PHINode>(I); - for (const auto &val : NewPN->incoming_values()) - if (val == Fixup.OperandValToReplace) - Fixup.UserInst = NewPN; - } - } - } - } -} - -/// 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 LSRUse &LU, const LSRFixup &LF, - const Formula &F, SCEVExpander &Rewriter, - SmallVectorImpl<WeakTrackingVH> &DeadInsts) 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, LU, LF, F, Rewriter, DeadInsts); - } else { - Value *FullV = - Expand(LU, LF, F, LF.UserInst->getIterator(), 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 (LU.Kind == LSRUse::ICmpZero) - LF.UserInst->setOperand(0, FullV); - else - LF.UserInst->replaceUsesOfWith(LF.OperandValToReplace, FullV); - } - - DeadInsts.emplace_back(LF.OperandValToReplace); -} - -/// Rewrite all the fixup locations with new values, following the chosen -/// solution. -void LSRInstance::ImplementSolution( - const SmallVectorImpl<const Formula *> &Solution) { - // Keep track of instructions we may have made dead, so that - // we can remove them after we are done working. - SmallVector<WeakTrackingVH, 16> DeadInsts; - - SCEVExpander Rewriter(SE, L->getHeader()->getModule()->getDataLayout(), - "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 (const IVChain &Chain : IVChainVec) { - if (PHINode *PN = dyn_cast<PHINode>(Chain.tailUserInst())) - Rewriter.setChainedPhi(PN); - } - - // Expand the new value definitions and update the users. - for (size_t LUIdx = 0, NumUses = Uses.size(); LUIdx != NumUses; ++LUIdx) - for (const LSRFixup &Fixup : Uses[LUIdx].Fixups) { - Rewrite(Uses[LUIdx], Fixup, *Solution[LUIdx], Rewriter, DeadInsts); - Changed = true; - } - - for (const IVChain &Chain : IVChainVec) { - GenerateIVChain(Chain, Rewriter, DeadInsts); - Changed = true; - } - // Clean up after ourselves. This must be done before deleting any - // instructions. - Rewriter.clear(); - - Changed |= DeleteTriviallyDeadInstructions(DeadInsts); -} - -LSRInstance::LSRInstance(Loop *L, IVUsers &IU, ScalarEvolution &SE, - DominatorTree &DT, LoopInfo &LI, - const TargetTransformInfo &TTI, AssumptionCache &AC, - TargetLibraryInfo &LibInfo) - : IU(IU), SE(SE), DT(DT), LI(LI), AC(AC), LibInfo(LibInfo), TTI(TTI), L(L), - FavorBackedgeIndex(EnableBackedgeIndexing && - TTI.shouldFavorBackedgeIndex(L)) { - // 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 (const IVStrideUse &U : IU) { - if (++NumUsers > MaxIVUsers) { - (void)U; - LLVM_DEBUG(dbgs() << "LSR skipping loop, too many IV Users in " << U - << "\n"); - return; - } - // Bail out if we have a PHI on an EHPad that gets a value from a - // CatchSwitchInst. Because the CatchSwitchInst cannot be split, there is - // no good place to stick any instructions. - if (auto *PN = dyn_cast<PHINode>(U.getUser())) { - auto *FirstNonPHI = PN->getParent()->getFirstNonPHI(); - if (isa<FuncletPadInst>(FirstNonPHI) || - isa<CatchSwitchInst>(FirstNonPHI)) - for (BasicBlock *PredBB : PN->blocks()) - if (isa<CatchSwitchInst>(PredBB->getFirstNonPHI())) - 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 - - LLVM_DEBUG(dbgs() << "\nLSR on loop "; - L->getHeader()->printAsOperand(dbgs(), /*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()) { - LLVM_DEBUG(dbgs() << "LSR skipping outer loop " << *L << "\n"); - return; - } - - // Start collecting data and preparing for the solver. - CollectChains(); - CollectInterestingTypesAndFactors(); - CollectFixupsAndInitialFormulae(); - CollectLoopInvariantFixupsAndFormulae(); - - if (Uses.empty()) - return; - - LLVM_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 (const LSRUse &LU : Uses) { - for (const Formula &F : LU.Formulae) - assert(isLegalUse(TTI, LU.MinOffset, LU.MaxOffset, LU.Kind, LU.AccessTy, - F) && "Illegal formula generated!"); - }; -#endif - - // Now that we've decided what we want, make it so. - ImplementSolution(Solution); -} - -#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP) -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 (int64_t Factor : Factors) { - if (!First) OS << ", "; - First = false; - OS << '*' << Factor; - } - - for (Type *Ty : Types) { - if (!First) OS << ", "; - First = false; - OS << '(' << *Ty << ')'; - } - OS << '\n'; -} - -void LSRInstance::print_fixups(raw_ostream &OS) const { - OS << "LSR is examining the following fixup sites:\n"; - for (const LSRUse &LU : Uses) - for (const LSRFixup &LF : LU.Fixups) { - dbgs() << " "; - LF.print(OS); - OS << '\n'; - } -} - -void LSRInstance::print_uses(raw_ostream &OS) const { - OS << "LSR is examining the following uses:\n"; - for (const LSRUse &LU : Uses) { - dbgs() << " "; - LU.print(OS); - OS << '\n'; - for (const Formula &F : LU.Formulae) { - OS << " "; - F.print(OS); - OS << '\n'; - } - } -} - -void LSRInstance::print(raw_ostream &OS) const { - print_factors_and_types(OS); - print_fixups(OS); - print_uses(OS); -} - -LLVM_DUMP_METHOD void LSRInstance::dump() const { - print(errs()); errs() << '\n'; -} -#endif - -namespace { - -class LoopStrengthReduce : public LoopPass { -public: - static char ID; // Pass ID, replacement for typeid - - LoopStrengthReduce(); - -private: - bool runOnLoop(Loop *L, LPPassManager &LPM) override; - void getAnalysisUsage(AnalysisUsage &AU) const override; -}; - -} // end anonymous namespace - -LoopStrengthReduce::LoopStrengthReduce() : LoopPass(ID) { - 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<LoopInfoWrapperPass>(); - AU.addPreserved<LoopInfoWrapperPass>(); - AU.addRequiredID(LoopSimplifyID); - AU.addRequired<DominatorTreeWrapperPass>(); - AU.addPreserved<DominatorTreeWrapperPass>(); - AU.addRequired<ScalarEvolutionWrapperPass>(); - AU.addPreserved<ScalarEvolutionWrapperPass>(); - AU.addRequired<AssumptionCacheTracker>(); - AU.addRequired<TargetLibraryInfoWrapperPass>(); - // Requiring LoopSimplify a second time here prevents IVUsers from running - // twice, since LoopSimplify was invalidated by running ScalarEvolution. - AU.addRequiredID(LoopSimplifyID); - AU.addRequired<IVUsersWrapperPass>(); - AU.addPreserved<IVUsersWrapperPass>(); - AU.addRequired<TargetTransformInfoWrapperPass>(); -} - -static bool ReduceLoopStrength(Loop *L, IVUsers &IU, ScalarEvolution &SE, - DominatorTree &DT, LoopInfo &LI, - const TargetTransformInfo &TTI, - AssumptionCache &AC, - TargetLibraryInfo &LibInfo) { - - bool Changed = false; - - // Run the main LSR transformation. - Changed |= LSRInstance(L, IU, SE, DT, LI, TTI, AC, LibInfo).getChanged(); - - // Remove any extra phis created by processing inner loops. - Changed |= DeleteDeadPHIs(L->getHeader()); - if (EnablePhiElim && L->isLoopSimplifyForm()) { - SmallVector<WeakTrackingVH, 16> DeadInsts; - const DataLayout &DL = L->getHeader()->getModule()->getDataLayout(); - SCEVExpander Rewriter(SE, DL, "lsr"); -#ifndef NDEBUG - Rewriter.setDebugType(DEBUG_TYPE); -#endif - unsigned numFolded = Rewriter.replaceCongruentIVs(L, &DT, DeadInsts, &TTI); - if (numFolded) { - Changed = true; - DeleteTriviallyDeadInstructions(DeadInsts); - DeleteDeadPHIs(L->getHeader()); - } - } - return Changed; -} - -bool LoopStrengthReduce::runOnLoop(Loop *L, LPPassManager & /*LPM*/) { - if (skipLoop(L)) - return false; - - auto &IU = getAnalysis<IVUsersWrapperPass>().getIU(); - auto &SE = getAnalysis<ScalarEvolutionWrapperPass>().getSE(); - auto &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree(); - auto &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo(); - const auto &TTI = getAnalysis<TargetTransformInfoWrapperPass>().getTTI( - *L->getHeader()->getParent()); - auto &AC = getAnalysis<AssumptionCacheTracker>().getAssumptionCache( - *L->getHeader()->getParent()); - auto &LibInfo = getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(); - return ReduceLoopStrength(L, IU, SE, DT, LI, TTI, AC, LibInfo); -} - -PreservedAnalyses LoopStrengthReducePass::run(Loop &L, LoopAnalysisManager &AM, - LoopStandardAnalysisResults &AR, - LPMUpdater &) { - if (!ReduceLoopStrength(&L, AM.getResult<IVUsersAnalysis>(L, AR), AR.SE, - AR.DT, AR.LI, AR.TTI, AR.AC, AR.TLI)) - return PreservedAnalyses::all(); - - return getLoopPassPreservedAnalyses(); -} - -char LoopStrengthReduce::ID = 0; - -INITIALIZE_PASS_BEGIN(LoopStrengthReduce, "loop-reduce", - "Loop Strength Reduction", false, false) -INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) -INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) -INITIALIZE_PASS_DEPENDENCY(ScalarEvolutionWrapperPass) -INITIALIZE_PASS_DEPENDENCY(IVUsersWrapperPass) -INITIALIZE_PASS_DEPENDENCY(LoopInfoWrapperPass) -INITIALIZE_PASS_DEPENDENCY(LoopSimplify) -INITIALIZE_PASS_END(LoopStrengthReduce, "loop-reduce", - "Loop Strength Reduction", false, false) - -Pass *llvm::createLoopStrengthReducePass() { return new LoopStrengthReduce(); } |