Index: include/llvm/InitializePasses.h =================================================================== --- include/llvm/InitializePasses.h +++ include/llvm/InitializePasses.h @@ -88,7 +88,7 @@ void initializeCallGraphViewerPass(PassRegistry&); void initializeCallGraphWrapperPassPass(PassRegistry &); void initializeCodeGenPreparePass(PassRegistry&); -void initializeConstantHoistingPass(PassRegistry&); +void initializeConstantHoistingLegacyPassPass(PassRegistry&); void initializeConstantMergeLegacyPassPass(PassRegistry &); void initializeConstantPropagationPass(PassRegistry&); void initializeCorrelatedValuePropagationPass(PassRegistry&); Index: include/llvm/Transforms/Scalar/ConstantHoisting.h =================================================================== --- include/llvm/Transforms/Scalar/ConstantHoisting.h +++ include/llvm/Transforms/Scalar/ConstantHoisting.h @@ -0,0 +1,146 @@ +//===-- ConstantHoisting.h - Prepare code for expensive constants ---------===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// +// +// This pass identifies expensive constants to hoist and coalesces them to +// better prepare it for SelectionDAG-based code generation. This works around +// the limitations of the basic-block-at-a-time approach. +// +// First it scans all instructions for integer constants and calculates its +// cost. If the constant can be folded into the instruction (the cost is +// TCC_Free) or the cost is just a simple operation (TCC_BASIC), then we don't +// consider it expensive and leave it alone. This is the default behavior and +// the default implementation of getIntImmCost will always return TCC_Free. +// +// If the cost is more than TCC_BASIC, then the integer constant can't be folded +// into the instruction and it might be beneficial to hoist the constant. +// Similar constants are coalesced to reduce register pressure and +// materialization code. +// +// When a constant is hoisted, it is also hidden behind a bitcast to force it to +// be live-out of the basic block. Otherwise the constant would be just +// duplicated and each basic block would have its own copy in the SelectionDAG. +// The SelectionDAG recognizes such constants as opaque and doesn't perform +// certain transformations on them, which would create a new expensive constant. +// +// This optimization is only applied to integer constants in instructions and +// simple (this means not nested) constant cast expressions. For example: +// %0 = load i64* inttoptr (i64 big_constant to i64*) +//===----------------------------------------------------------------------===// + +#ifndef LLVM_TRANSFORMS_SCALAR_CONSTANTHOISTING_H +#define LLVM_TRANSFORMS_SCALAR_CONSTANTHOISTING_H + +#include "llvm/Analysis/TargetTransformInfo.h" +#include "llvm/IR/Dominators.h" +#include "llvm/IR/PassManager.h" + +namespace llvm { + +/// A private "module" namespace for types and utilities used by +/// ConstantHoisting. These are implementation details and should not be used by +/// clients. +namespace consthoist { +/// \brief Keeps track of the user of a constant and the operand index where the +/// constant is used. +struct ConstantUser { + Instruction *Inst; + unsigned OpndIdx; + + ConstantUser(Instruction *Inst, unsigned Idx) : Inst(Inst), OpndIdx(Idx) { } +}; + +typedef SmallVector ConstantUseListType; + +/// \brief Keeps track of a constant candidate and its uses. +struct ConstantCandidate { + ConstantUseListType Uses; + ConstantInt *ConstInt; + unsigned CumulativeCost; + + ConstantCandidate(ConstantInt *ConstInt) + : ConstInt(ConstInt), CumulativeCost(0) { } + + /// \brief Add the user to the use list and update the cost. + void addUser(Instruction *Inst, unsigned Idx, unsigned Cost) { + CumulativeCost += Cost; + Uses.push_back(ConstantUser(Inst, Idx)); + } +}; + +/// \brief This represents a constant that has been rebased with respect to a +/// base constant. The difference to the base constant is recorded in Offset. +struct RebasedConstantInfo { + ConstantUseListType Uses; + Constant *Offset; + + RebasedConstantInfo(ConstantUseListType &&Uses, Constant *Offset) + : Uses(std::move(Uses)), Offset(Offset) { } +}; + +typedef SmallVector RebasedConstantListType; + +/// \brief A base constant and all its rebased constants. +struct ConstantInfo { + ConstantInt *BaseConstant; + RebasedConstantListType RebasedConstants; +}; +} + +class ConstantHoistingPass : public PassInfoMixin { +public: + PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM); + + // Glue for old PM. + bool runImpl(Function &F, TargetTransformInfo &RunTTI, DominatorTree &RunDT, + BasicBlock &RunEntry); + + void releaseMemory() { + ConstantVec.clear(); + ClonedCastMap.clear(); + ConstCandVec.clear(); + } + +private: + typedef DenseMap ConstCandMapType; + typedef std::vector ConstCandVecType; + + const TargetTransformInfo *TTI; + DominatorTree *DT; + BasicBlock *Entry; + + /// Keeps track of constant candidates found in the function. + ConstCandVecType ConstCandVec; + + /// Keep track of cast instructions we already cloned. + SmallDenseMap ClonedCastMap; + + /// These are the final constants we decided to hoist. + SmallVector ConstantVec; + + Instruction *findMatInsertPt(Instruction *Inst, unsigned Idx = ~0U) const; + Instruction *findConstantInsertionPoint( + const consthoist::ConstantInfo &ConstInfo) const; + void collectConstantCandidates(ConstCandMapType &ConstCandMap, + Instruction *Inst, unsigned Idx, + ConstantInt *ConstInt); + void collectConstantCandidates(ConstCandMapType &ConstCandMap, + Instruction *Inst); + void collectConstantCandidates(Function &Fn); + void findAndMakeBaseConstant(ConstCandVecType::iterator S, + ConstCandVecType::iterator E); + void findBaseConstants(); + void emitBaseConstants(Instruction *Base, Constant *Offset, + const consthoist::ConstantUser &ConstUser); + bool emitBaseConstants(); + void deleteDeadCastInst() const; + bool optimizeConstants(Function &Fn); +}; +} + +#endif // LLVM_TRANSFORMS_SCALAR_CONSTANTHOISTING_H Index: lib/Passes/PassBuilder.cpp =================================================================== --- lib/Passes/PassBuilder.cpp +++ lib/Passes/PassBuilder.cpp @@ -74,6 +74,7 @@ #include "llvm/Transforms/Scalar/AlignmentFromAssumptions.h" #include "llvm/Transforms/Scalar/BDCE.h" #include "llvm/Transforms/Scalar/DCE.h" +#include "llvm/Transforms/Scalar/ConstantHoisting.h" #include "llvm/Transforms/Scalar/DeadStoreElimination.h" #include "llvm/Transforms/Scalar/EarlyCSE.h" #include "llvm/Transforms/Scalar/Float2Int.h" Index: lib/Passes/PassRegistry.def =================================================================== --- lib/Passes/PassRegistry.def +++ lib/Passes/PassRegistry.def @@ -125,6 +125,7 @@ FUNCTION_PASS("add-discriminators", AddDiscriminatorsPass()) FUNCTION_PASS("alignment-from-assumptions", AlignmentFromAssumptionsPass()) FUNCTION_PASS("bdce", BDCEPass()) +FUNCTION_PASS("consthoist", ConstantHoistingPass()) FUNCTION_PASS("dce", DCEPass()) FUNCTION_PASS("dse", DSEPass()) FUNCTION_PASS("early-cse", EarlyCSEPass()) Index: lib/Transforms/Scalar/ConstantHoisting.cpp =================================================================== --- lib/Transforms/Scalar/ConstantHoisting.cpp +++ lib/Transforms/Scalar/ConstantHoisting.cpp @@ -33,20 +33,20 @@ // %0 = load i64* inttoptr (i64 big_constant to i64*) //===----------------------------------------------------------------------===// -#include "llvm/Transforms/Scalar.h" +#include "llvm/Transforms/Scalar/ConstantHoisting.h" #include "llvm/ADT/SmallSet.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/Statistic.h" -#include "llvm/Analysis/TargetTransformInfo.h" #include "llvm/IR/Constants.h" -#include "llvm/IR/Dominators.h" #include "llvm/IR/IntrinsicInst.h" #include "llvm/Pass.h" #include "llvm/Support/Debug.h" #include "llvm/Support/raw_ostream.h" +#include "llvm/Transforms/Scalar.h" #include using namespace llvm; +using namespace consthoist; #define DEBUG_TYPE "consthoist" @@ -54,75 +54,12 @@ STATISTIC(NumConstantsRebased, "Number of constants rebased"); namespace { -struct ConstantUser; -struct RebasedConstantInfo; - -typedef SmallVector ConstantUseListType; -typedef SmallVector RebasedConstantListType; - -/// \brief Keeps track of the user of a constant and the operand index where the -/// constant is used. -struct ConstantUser { - Instruction *Inst; - unsigned OpndIdx; - - ConstantUser(Instruction *Inst, unsigned Idx) : Inst(Inst), OpndIdx(Idx) { } -}; - -/// \brief Keeps track of a constant candidate and its uses. -struct ConstantCandidate { - ConstantUseListType Uses; - ConstantInt *ConstInt; - unsigned CumulativeCost; - - ConstantCandidate(ConstantInt *ConstInt) - : ConstInt(ConstInt), CumulativeCost(0) { } - - /// \brief Add the user to the use list and update the cost. - void addUser(Instruction *Inst, unsigned Idx, unsigned Cost) { - CumulativeCost += Cost; - Uses.push_back(ConstantUser(Inst, Idx)); - } -}; - -/// \brief This represents a constant that has been rebased with respect to a -/// base constant. The difference to the base constant is recorded in Offset. -struct RebasedConstantInfo { - ConstantUseListType Uses; - Constant *Offset; - - RebasedConstantInfo(ConstantUseListType &&Uses, Constant *Offset) - : Uses(std::move(Uses)), Offset(Offset) { } -}; - -/// \brief A base constant and all its rebased constants. -struct ConstantInfo { - ConstantInt *BaseConstant; - RebasedConstantListType RebasedConstants; -}; - /// \brief The constant hoisting pass. -class ConstantHoisting : public FunctionPass { - typedef DenseMap ConstCandMapType; - typedef std::vector ConstCandVecType; - - const TargetTransformInfo *TTI; - DominatorTree *DT; - BasicBlock *Entry; - - /// Keeps track of constant candidates found in the function. - ConstCandVecType ConstCandVec; - - /// Keep track of cast instructions we already cloned. - SmallDenseMap ClonedCastMap; - - /// These are the final constants we decided to hoist. - SmallVector ConstantVec; +class ConstantHoistingLegacyPass : public FunctionPass { public: static char ID; // Pass identification, replacement for typeid - ConstantHoisting() : FunctionPass(ID), TTI(nullptr), DT(nullptr), - Entry(nullptr) { - initializeConstantHoistingPass(*PassRegistry::getPassRegistry()); + ConstantHoistingLegacyPass() : FunctionPass(ID) { + initializeConstantHoistingLegacyPassPass(*PassRegistry::getPassRegistry()); } bool runOnFunction(Function &Fn) override; @@ -135,67 +72,36 @@ AU.addRequired(); } + void releaseMemory() override { Impl.releaseMemory(); } + private: - /// \brief Initialize the pass. - void setup(Function &Fn) { - DT = &getAnalysis().getDomTree(); - TTI = &getAnalysis().getTTI(Fn); - Entry = &Fn.getEntryBlock(); - } - - /// \brief Cleanup. - void cleanup() { - ConstantVec.clear(); - ClonedCastMap.clear(); - ConstCandVec.clear(); - - TTI = nullptr; - DT = nullptr; - Entry = nullptr; - } - - Instruction *findMatInsertPt(Instruction *Inst, unsigned Idx = ~0U) const; - Instruction *findConstantInsertionPoint(const ConstantInfo &ConstInfo) const; - void collectConstantCandidates(ConstCandMapType &ConstCandMap, - Instruction *Inst, unsigned Idx, - ConstantInt *ConstInt); - void collectConstantCandidates(ConstCandMapType &ConstCandMap, - Instruction *Inst); - void collectConstantCandidates(Function &Fn); - void findAndMakeBaseConstant(ConstCandVecType::iterator S, - ConstCandVecType::iterator E); - void findBaseConstants(); - void emitBaseConstants(Instruction *Base, Constant *Offset, - const ConstantUser &ConstUser); - bool emitBaseConstants(); - void deleteDeadCastInst() const; - bool optimizeConstants(Function &Fn); + ConstantHoistingPass Impl; }; } -char ConstantHoisting::ID = 0; -INITIALIZE_PASS_BEGIN(ConstantHoisting, "consthoist", "Constant Hoisting", - false, false) +char ConstantHoistingLegacyPass::ID = 0; +INITIALIZE_PASS_BEGIN(ConstantHoistingLegacyPass, "consthoist", + "Constant Hoisting", false, false) INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass) INITIALIZE_PASS_DEPENDENCY(TargetTransformInfoWrapperPass) -INITIALIZE_PASS_END(ConstantHoisting, "consthoist", "Constant Hoisting", - false, false) +INITIALIZE_PASS_END(ConstantHoistingLegacyPass, "consthoist", + "Constant Hoisting", false, false) FunctionPass *llvm::createConstantHoistingPass() { - return new ConstantHoisting(); + return new ConstantHoistingLegacyPass(); } /// \brief Perform the constant hoisting optimization for the given function. -bool ConstantHoisting::runOnFunction(Function &Fn) { +bool ConstantHoistingLegacyPass::runOnFunction(Function &Fn) { if (skipFunction(Fn)) return false; DEBUG(dbgs() << "********** Begin Constant Hoisting **********\n"); DEBUG(dbgs() << "********** Function: " << Fn.getName() << '\n'); - setup(Fn); - - bool MadeChange = optimizeConstants(Fn); + bool MadeChange = Impl.runImpl( + Fn, getAnalysis().getTTI(Fn), + getAnalysis().getDomTree(), Fn.getEntryBlock()); if (MadeChange) { DEBUG(dbgs() << "********** Function after Constant Hoisting: " @@ -204,15 +110,13 @@ } DEBUG(dbgs() << "********** End Constant Hoisting **********\n"); - cleanup(); - return MadeChange; } /// \brief Find the constant materialization insertion point. -Instruction *ConstantHoisting::findMatInsertPt(Instruction *Inst, - unsigned Idx) const { +Instruction *ConstantHoistingPass::findMatInsertPt(Instruction *Inst, + unsigned Idx) const { // If the operand is a cast instruction, then we have to materialize the // constant before the cast instruction. if (Idx != ~0U) { @@ -237,8 +141,8 @@ } /// \brief Find an insertion point that dominates all uses. -Instruction *ConstantHoisting:: -findConstantInsertionPoint(const ConstantInfo &ConstInfo) const { +Instruction *ConstantHoistingPass::findConstantInsertionPoint( + const ConstantInfo &ConstInfo) const { assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry."); // Collect all basic blocks. SmallPtrSet BBs; @@ -272,10 +176,9 @@ /// The operand at index Idx is not necessarily the constant integer itself. It /// could also be a cast instruction or a constant expression that uses the // constant integer. -void ConstantHoisting::collectConstantCandidates(ConstCandMapType &ConstCandMap, - Instruction *Inst, - unsigned Idx, - ConstantInt *ConstInt) { +void ConstantHoistingPass::collectConstantCandidates( + ConstCandMapType &ConstCandMap, Instruction *Inst, unsigned Idx, + ConstantInt *ConstInt) { unsigned Cost; // Ask the target about the cost of materializing the constant for the given // instruction and operand index. @@ -309,8 +212,8 @@ /// \brief Scan the instruction for expensive integer constants and record them /// in the constant candidate vector. -void ConstantHoisting::collectConstantCandidates(ConstCandMapType &ConstCandMap, - Instruction *Inst) { +void ConstantHoistingPass::collectConstantCandidates( + ConstCandMapType &ConstCandMap, Instruction *Inst) { // Skip all cast instructions. They are visited indirectly later on. if (Inst->isCast()) return; @@ -375,7 +278,7 @@ /// \brief Collect all integer constants in the function that cannot be folded /// into an instruction itself. -void ConstantHoisting::collectConstantCandidates(Function &Fn) { +void ConstantHoistingPass::collectConstantCandidates(Function &Fn) { ConstCandMapType ConstCandMap; for (BasicBlock &BB : Fn) for (Instruction &Inst : BB) @@ -384,8 +287,8 @@ /// \brief Find the base constant within the given range and rebase all other /// constants with respect to the base constant. -void ConstantHoisting::findAndMakeBaseConstant(ConstCandVecType::iterator S, - ConstCandVecType::iterator E) { +void ConstantHoistingPass::findAndMakeBaseConstant( + ConstCandVecType::iterator S, ConstCandVecType::iterator E) { auto MaxCostItr = S; unsigned NumUses = 0; // Use the constant that has the maximum cost as base constant. @@ -416,7 +319,7 @@ /// \brief Finds and combines constant candidates that can be easily /// rematerialized with an add from a common base constant. -void ConstantHoisting::findBaseConstants() { +void ConstantHoistingPass::findBaseConstants() { // Sort the constants by value and type. This invalidates the mapping! std::sort(ConstCandVec.begin(), ConstCandVec.end(), [](const ConstantCandidate &LHS, const ConstantCandidate &RHS) { @@ -478,8 +381,9 @@ /// \brief Emit materialization code for all rebased constants and update their /// users. -void ConstantHoisting::emitBaseConstants(Instruction *Base, Constant *Offset, - const ConstantUser &ConstUser) { +void ConstantHoistingPass::emitBaseConstants(Instruction *Base, + Constant *Offset, + const ConstantUser &ConstUser) { Instruction *Mat = Base; if (Offset) { Instruction *InsertionPt = findMatInsertPt(ConstUser.Inst, @@ -550,7 +454,7 @@ /// \brief Hoist and hide the base constant behind a bitcast and emit /// materialization code for derived constants. -bool ConstantHoisting::emitBaseConstants() { +bool ConstantHoistingPass::emitBaseConstants() { bool MadeChange = false; for (auto const &ConstInfo : ConstantVec) { // Hoist and hide the base constant behind a bitcast. @@ -584,14 +488,18 @@ /// \brief Check all cast instructions we made a copy of and remove them if they /// have no more users. -void ConstantHoisting::deleteDeadCastInst() const { +void ConstantHoistingPass::deleteDeadCastInst() const { for (auto const &I : ClonedCastMap) if (I.first->use_empty()) I.first->eraseFromParent(); } /// \brief Optimize expensive integer constants in the given function. -bool ConstantHoisting::optimizeConstants(Function &Fn) { +bool ConstantHoistingPass::runImpl(Function &Fn, TargetTransformInfo &RunTTI, + DominatorTree &RunDT, BasicBlock &RunEntry) { + TTI = &RunTTI; + DT = &RunDT; + Entry = &RunEntry; // Collect all constant candidates. collectConstantCandidates(Fn); @@ -616,3 +524,15 @@ return MadeChange; } + +PreservedAnalyses ConstantHoistingPass::run(Function &F, + FunctionAnalysisManager &AM) { + auto &DT = AM.getResult(F); + auto &TTI = AM.getResult(F); + if (!runImpl(F, TTI, DT, F.getEntryBlock())) + return PreservedAnalyses::all(); + else { + // FIXME: This should also 'preserve the CFG'. + return PreservedAnalyses::none(); + } +} Index: lib/Transforms/Scalar/Scalar.cpp =================================================================== --- lib/Transforms/Scalar/Scalar.cpp +++ lib/Transforms/Scalar/Scalar.cpp @@ -34,7 +34,7 @@ initializeADCELegacyPassPass(Registry); initializeBDCELegacyPassPass(Registry); initializeAlignmentFromAssumptionsPass(Registry); - initializeConstantHoistingPass(Registry); + initializeConstantHoistingLegacyPassPass(Registry); initializeConstantPropagationPass(Registry); initializeCorrelatedValuePropagationPass(Registry); initializeDCELegacyPassPass(Registry); Index: test/Transforms/ConstantHoisting/X86/cast-inst.ll =================================================================== --- test/Transforms/ConstantHoisting/X86/cast-inst.ll +++ test/Transforms/ConstantHoisting/X86/cast-inst.ll @@ -1,4 +1,5 @@ ; RUN: opt -S -consthoist < %s | FileCheck %s +; RUN: opt -S -passes='consthoist' < %s | FileCheck %s target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128" target triple = "x86_64-apple-macosx10.9.0"