mirror of
https://github.com/c64scene-ar/llvm-6502.git
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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202953 91177308-0d34-0410-b5e6-96231b3b80d8
623 lines
22 KiB
C++
623 lines
22 KiB
C++
//===- EarlyCSE.cpp - Simple and fast CSE pass ----------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This pass performs a simple dominator tree walk that eliminates trivially
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// redundant instructions.
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//
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//===----------------------------------------------------------------------===//
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#define DEBUG_TYPE "early-cse"
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#include "llvm/Transforms/Scalar.h"
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#include "llvm/ADT/Hashing.h"
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#include "llvm/ADT/ScopedHashTable.h"
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#include "llvm/ADT/Statistic.h"
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#include "llvm/Analysis/InstructionSimplify.h"
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#include "llvm/IR/DataLayout.h"
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#include "llvm/IR/Dominators.h"
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#include "llvm/IR/Instructions.h"
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#include "llvm/Pass.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/RecyclingAllocator.h"
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#include "llvm/Target/TargetLibraryInfo.h"
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#include "llvm/Transforms/Utils/Local.h"
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#include <vector>
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using namespace llvm;
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STATISTIC(NumSimplify, "Number of instructions simplified or DCE'd");
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STATISTIC(NumCSE, "Number of instructions CSE'd");
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STATISTIC(NumCSELoad, "Number of load instructions CSE'd");
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STATISTIC(NumCSECall, "Number of call instructions CSE'd");
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STATISTIC(NumDSE, "Number of trivial dead stores removed");
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static unsigned getHash(const void *V) {
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return DenseMapInfo<const void*>::getHashValue(V);
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}
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//===----------------------------------------------------------------------===//
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// SimpleValue
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//===----------------------------------------------------------------------===//
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namespace {
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/// SimpleValue - Instances of this struct represent available values in the
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/// scoped hash table.
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struct SimpleValue {
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Instruction *Inst;
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SimpleValue(Instruction *I) : Inst(I) {
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assert((isSentinel() || canHandle(I)) && "Inst can't be handled!");
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}
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bool isSentinel() const {
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return Inst == DenseMapInfo<Instruction*>::getEmptyKey() ||
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Inst == DenseMapInfo<Instruction*>::getTombstoneKey();
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}
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static bool canHandle(Instruction *Inst) {
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// This can only handle non-void readnone functions.
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if (CallInst *CI = dyn_cast<CallInst>(Inst))
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return CI->doesNotAccessMemory() && !CI->getType()->isVoidTy();
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return isa<CastInst>(Inst) || isa<BinaryOperator>(Inst) ||
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isa<GetElementPtrInst>(Inst) || isa<CmpInst>(Inst) ||
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isa<SelectInst>(Inst) || isa<ExtractElementInst>(Inst) ||
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isa<InsertElementInst>(Inst) || isa<ShuffleVectorInst>(Inst) ||
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isa<ExtractValueInst>(Inst) || isa<InsertValueInst>(Inst);
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}
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};
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}
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namespace llvm {
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template<> struct DenseMapInfo<SimpleValue> {
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static inline SimpleValue getEmptyKey() {
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return DenseMapInfo<Instruction*>::getEmptyKey();
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}
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static inline SimpleValue getTombstoneKey() {
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return DenseMapInfo<Instruction*>::getTombstoneKey();
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}
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static unsigned getHashValue(SimpleValue Val);
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static bool isEqual(SimpleValue LHS, SimpleValue RHS);
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};
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}
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unsigned DenseMapInfo<SimpleValue>::getHashValue(SimpleValue Val) {
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Instruction *Inst = Val.Inst;
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// Hash in all of the operands as pointers.
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if (BinaryOperator* BinOp = dyn_cast<BinaryOperator>(Inst)) {
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Value *LHS = BinOp->getOperand(0);
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Value *RHS = BinOp->getOperand(1);
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if (BinOp->isCommutative() && BinOp->getOperand(0) > BinOp->getOperand(1))
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std::swap(LHS, RHS);
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if (isa<OverflowingBinaryOperator>(BinOp)) {
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// Hash the overflow behavior
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unsigned Overflow =
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BinOp->hasNoSignedWrap() * OverflowingBinaryOperator::NoSignedWrap |
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BinOp->hasNoUnsignedWrap() * OverflowingBinaryOperator::NoUnsignedWrap;
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return hash_combine(BinOp->getOpcode(), Overflow, LHS, RHS);
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}
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return hash_combine(BinOp->getOpcode(), LHS, RHS);
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}
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if (CmpInst *CI = dyn_cast<CmpInst>(Inst)) {
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Value *LHS = CI->getOperand(0);
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Value *RHS = CI->getOperand(1);
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CmpInst::Predicate Pred = CI->getPredicate();
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if (Inst->getOperand(0) > Inst->getOperand(1)) {
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std::swap(LHS, RHS);
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Pred = CI->getSwappedPredicate();
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}
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return hash_combine(Inst->getOpcode(), Pred, LHS, RHS);
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}
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if (CastInst *CI = dyn_cast<CastInst>(Inst))
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return hash_combine(CI->getOpcode(), CI->getType(), CI->getOperand(0));
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if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Inst))
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return hash_combine(EVI->getOpcode(), EVI->getOperand(0),
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hash_combine_range(EVI->idx_begin(), EVI->idx_end()));
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if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(Inst))
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return hash_combine(IVI->getOpcode(), IVI->getOperand(0),
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IVI->getOperand(1),
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hash_combine_range(IVI->idx_begin(), IVI->idx_end()));
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assert((isa<CallInst>(Inst) || isa<BinaryOperator>(Inst) ||
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isa<GetElementPtrInst>(Inst) || isa<SelectInst>(Inst) ||
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isa<ExtractElementInst>(Inst) || isa<InsertElementInst>(Inst) ||
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isa<ShuffleVectorInst>(Inst)) && "Invalid/unknown instruction");
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// Mix in the opcode.
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return hash_combine(Inst->getOpcode(),
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hash_combine_range(Inst->value_op_begin(),
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Inst->value_op_end()));
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}
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bool DenseMapInfo<SimpleValue>::isEqual(SimpleValue LHS, SimpleValue RHS) {
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Instruction *LHSI = LHS.Inst, *RHSI = RHS.Inst;
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if (LHS.isSentinel() || RHS.isSentinel())
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return LHSI == RHSI;
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if (LHSI->getOpcode() != RHSI->getOpcode()) return false;
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if (LHSI->isIdenticalTo(RHSI)) return true;
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// If we're not strictly identical, we still might be a commutable instruction
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if (BinaryOperator *LHSBinOp = dyn_cast<BinaryOperator>(LHSI)) {
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if (!LHSBinOp->isCommutative())
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return false;
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assert(isa<BinaryOperator>(RHSI)
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&& "same opcode, but different instruction type?");
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BinaryOperator *RHSBinOp = cast<BinaryOperator>(RHSI);
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// Check overflow attributes
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if (isa<OverflowingBinaryOperator>(LHSBinOp)) {
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assert(isa<OverflowingBinaryOperator>(RHSBinOp)
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&& "same opcode, but different operator type?");
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if (LHSBinOp->hasNoUnsignedWrap() != RHSBinOp->hasNoUnsignedWrap() ||
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LHSBinOp->hasNoSignedWrap() != RHSBinOp->hasNoSignedWrap())
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return false;
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}
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// Commuted equality
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return LHSBinOp->getOperand(0) == RHSBinOp->getOperand(1) &&
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LHSBinOp->getOperand(1) == RHSBinOp->getOperand(0);
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}
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if (CmpInst *LHSCmp = dyn_cast<CmpInst>(LHSI)) {
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assert(isa<CmpInst>(RHSI)
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&& "same opcode, but different instruction type?");
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CmpInst *RHSCmp = cast<CmpInst>(RHSI);
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// Commuted equality
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return LHSCmp->getOperand(0) == RHSCmp->getOperand(1) &&
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LHSCmp->getOperand(1) == RHSCmp->getOperand(0) &&
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LHSCmp->getSwappedPredicate() == RHSCmp->getPredicate();
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}
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return false;
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}
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//===----------------------------------------------------------------------===//
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// CallValue
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//===----------------------------------------------------------------------===//
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namespace {
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/// CallValue - Instances of this struct represent available call values in
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/// the scoped hash table.
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struct CallValue {
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Instruction *Inst;
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CallValue(Instruction *I) : Inst(I) {
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assert((isSentinel() || canHandle(I)) && "Inst can't be handled!");
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}
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bool isSentinel() const {
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return Inst == DenseMapInfo<Instruction*>::getEmptyKey() ||
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Inst == DenseMapInfo<Instruction*>::getTombstoneKey();
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}
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static bool canHandle(Instruction *Inst) {
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// Don't value number anything that returns void.
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if (Inst->getType()->isVoidTy())
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return false;
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CallInst *CI = dyn_cast<CallInst>(Inst);
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if (CI == 0 || !CI->onlyReadsMemory())
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return false;
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return true;
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}
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};
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}
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namespace llvm {
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template<> struct DenseMapInfo<CallValue> {
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static inline CallValue getEmptyKey() {
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return DenseMapInfo<Instruction*>::getEmptyKey();
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}
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static inline CallValue getTombstoneKey() {
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return DenseMapInfo<Instruction*>::getTombstoneKey();
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}
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static unsigned getHashValue(CallValue Val);
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static bool isEqual(CallValue LHS, CallValue RHS);
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};
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}
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unsigned DenseMapInfo<CallValue>::getHashValue(CallValue Val) {
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Instruction *Inst = Val.Inst;
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// Hash in all of the operands as pointers.
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unsigned Res = 0;
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for (unsigned i = 0, e = Inst->getNumOperands(); i != e; ++i) {
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assert(!Inst->getOperand(i)->getType()->isMetadataTy() &&
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"Cannot value number calls with metadata operands");
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Res ^= getHash(Inst->getOperand(i)) << (i & 0xF);
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}
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// Mix in the opcode.
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return (Res << 1) ^ Inst->getOpcode();
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}
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bool DenseMapInfo<CallValue>::isEqual(CallValue LHS, CallValue RHS) {
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Instruction *LHSI = LHS.Inst, *RHSI = RHS.Inst;
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if (LHS.isSentinel() || RHS.isSentinel())
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return LHSI == RHSI;
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return LHSI->isIdenticalTo(RHSI);
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}
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//===----------------------------------------------------------------------===//
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// EarlyCSE pass.
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//===----------------------------------------------------------------------===//
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namespace {
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/// EarlyCSE - This pass does a simple depth-first walk over the dominator
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/// tree, eliminating trivially redundant instructions and using instsimplify
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/// to canonicalize things as it goes. It is intended to be fast and catch
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/// obvious cases so that instcombine and other passes are more effective. It
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/// is expected that a later pass of GVN will catch the interesting/hard
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/// cases.
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class EarlyCSE : public FunctionPass {
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public:
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const DataLayout *DL;
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const TargetLibraryInfo *TLI;
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DominatorTree *DT;
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typedef RecyclingAllocator<BumpPtrAllocator,
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ScopedHashTableVal<SimpleValue, Value*> > AllocatorTy;
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typedef ScopedHashTable<SimpleValue, Value*, DenseMapInfo<SimpleValue>,
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AllocatorTy> ScopedHTType;
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/// AvailableValues - This scoped hash table contains the current values of
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/// all of our simple scalar expressions. As we walk down the domtree, we
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/// look to see if instructions are in this: if so, we replace them with what
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/// we find, otherwise we insert them so that dominated values can succeed in
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/// their lookup.
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ScopedHTType *AvailableValues;
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/// AvailableLoads - This scoped hash table contains the current values
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/// of loads. This allows us to get efficient access to dominating loads when
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/// we have a fully redundant load. In addition to the most recent load, we
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/// keep track of a generation count of the read, which is compared against
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/// the current generation count. The current generation count is
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/// incremented after every possibly writing memory operation, which ensures
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/// that we only CSE loads with other loads that have no intervening store.
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typedef RecyclingAllocator<BumpPtrAllocator,
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ScopedHashTableVal<Value*, std::pair<Value*, unsigned> > > LoadMapAllocator;
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typedef ScopedHashTable<Value*, std::pair<Value*, unsigned>,
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DenseMapInfo<Value*>, LoadMapAllocator> LoadHTType;
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LoadHTType *AvailableLoads;
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/// AvailableCalls - This scoped hash table contains the current values
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/// of read-only call values. It uses the same generation count as loads.
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typedef ScopedHashTable<CallValue, std::pair<Value*, unsigned> > CallHTType;
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CallHTType *AvailableCalls;
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/// CurrentGeneration - This is the current generation of the memory value.
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unsigned CurrentGeneration;
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static char ID;
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explicit EarlyCSE() : FunctionPass(ID) {
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initializeEarlyCSEPass(*PassRegistry::getPassRegistry());
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}
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bool runOnFunction(Function &F) override;
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private:
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// NodeScope - almost a POD, but needs to call the constructors for the
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// scoped hash tables so that a new scope gets pushed on. These are RAII so
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// that the scope gets popped when the NodeScope is destroyed.
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class NodeScope {
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public:
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NodeScope(ScopedHTType *availableValues,
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LoadHTType *availableLoads,
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CallHTType *availableCalls) :
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Scope(*availableValues),
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LoadScope(*availableLoads),
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CallScope(*availableCalls) {}
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private:
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NodeScope(const NodeScope&) LLVM_DELETED_FUNCTION;
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void operator=(const NodeScope&) LLVM_DELETED_FUNCTION;
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ScopedHTType::ScopeTy Scope;
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LoadHTType::ScopeTy LoadScope;
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CallHTType::ScopeTy CallScope;
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};
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// StackNode - contains all the needed information to create a stack for
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// doing a depth first tranversal of the tree. This includes scopes for
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// values, loads, and calls as well as the generation. There is a child
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// iterator so that the children do not need to be store spearately.
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class StackNode {
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public:
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StackNode(ScopedHTType *availableValues,
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LoadHTType *availableLoads,
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CallHTType *availableCalls,
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unsigned cg, DomTreeNode *n,
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DomTreeNode::iterator child, DomTreeNode::iterator end) :
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CurrentGeneration(cg), ChildGeneration(cg), Node(n),
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ChildIter(child), EndIter(end),
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Scopes(availableValues, availableLoads, availableCalls),
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Processed(false) {}
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// Accessors.
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unsigned currentGeneration() { return CurrentGeneration; }
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unsigned childGeneration() { return ChildGeneration; }
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void childGeneration(unsigned generation) { ChildGeneration = generation; }
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DomTreeNode *node() { return Node; }
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DomTreeNode::iterator childIter() { return ChildIter; }
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DomTreeNode *nextChild() {
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DomTreeNode *child = *ChildIter;
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++ChildIter;
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return child;
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}
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DomTreeNode::iterator end() { return EndIter; }
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bool isProcessed() { return Processed; }
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void process() { Processed = true; }
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private:
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StackNode(const StackNode&) LLVM_DELETED_FUNCTION;
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void operator=(const StackNode&) LLVM_DELETED_FUNCTION;
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// Members.
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unsigned CurrentGeneration;
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unsigned ChildGeneration;
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DomTreeNode *Node;
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DomTreeNode::iterator ChildIter;
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DomTreeNode::iterator EndIter;
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NodeScope Scopes;
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bool Processed;
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};
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bool processNode(DomTreeNode *Node);
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// This transformation requires dominator postdominator info
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void getAnalysisUsage(AnalysisUsage &AU) const override {
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AU.addRequired<DominatorTreeWrapperPass>();
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AU.addRequired<TargetLibraryInfo>();
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AU.setPreservesCFG();
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}
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};
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}
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char EarlyCSE::ID = 0;
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// createEarlyCSEPass - The public interface to this file.
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FunctionPass *llvm::createEarlyCSEPass() {
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return new EarlyCSE();
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}
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INITIALIZE_PASS_BEGIN(EarlyCSE, "early-cse", "Early CSE", false, false)
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INITIALIZE_PASS_DEPENDENCY(DominatorTreeWrapperPass)
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INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
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INITIALIZE_PASS_END(EarlyCSE, "early-cse", "Early CSE", false, false)
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bool EarlyCSE::processNode(DomTreeNode *Node) {
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BasicBlock *BB = Node->getBlock();
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// If this block has a single predecessor, then the predecessor is the parent
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// of the domtree node and all of the live out memory values are still current
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// in this block. If this block has multiple predecessors, then they could
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// have invalidated the live-out memory values of our parent value. For now,
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// just be conservative and invalidate memory if this block has multiple
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// predecessors.
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if (BB->getSinglePredecessor() == 0)
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++CurrentGeneration;
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/// LastStore - Keep track of the last non-volatile store that we saw... for
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/// as long as there in no instruction that reads memory. If we see a store
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/// to the same location, we delete the dead store. This zaps trivial dead
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/// stores which can occur in bitfield code among other things.
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StoreInst *LastStore = 0;
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bool Changed = false;
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// See if any instructions in the block can be eliminated. If so, do it. If
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// not, add them to AvailableValues.
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for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
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Instruction *Inst = I++;
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// Dead instructions should just be removed.
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if (isInstructionTriviallyDead(Inst, TLI)) {
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DEBUG(dbgs() << "EarlyCSE DCE: " << *Inst << '\n');
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Inst->eraseFromParent();
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Changed = true;
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++NumSimplify;
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continue;
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}
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// If the instruction can be simplified (e.g. X+0 = X) then replace it with
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// its simpler value.
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if (Value *V = SimplifyInstruction(Inst, DL, TLI, DT)) {
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DEBUG(dbgs() << "EarlyCSE Simplify: " << *Inst << " to: " << *V << '\n');
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Inst->replaceAllUsesWith(V);
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Inst->eraseFromParent();
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Changed = true;
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++NumSimplify;
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continue;
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}
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// If this is a simple instruction that we can value number, process it.
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if (SimpleValue::canHandle(Inst)) {
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// See if the instruction has an available value. If so, use it.
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if (Value *V = AvailableValues->lookup(Inst)) {
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DEBUG(dbgs() << "EarlyCSE CSE: " << *Inst << " to: " << *V << '\n');
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Inst->replaceAllUsesWith(V);
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Inst->eraseFromParent();
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Changed = true;
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++NumCSE;
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continue;
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}
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// Otherwise, just remember that this value is available.
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AvailableValues->insert(Inst, Inst);
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continue;
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}
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// If this is a non-volatile load, process it.
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if (LoadInst *LI = dyn_cast<LoadInst>(Inst)) {
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// Ignore volatile loads.
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if (!LI->isSimple()) {
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LastStore = 0;
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continue;
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}
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// If we have an available version of this load, and if it is the right
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// generation, replace this instruction.
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std::pair<Value*, unsigned> InVal =
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AvailableLoads->lookup(Inst->getOperand(0));
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if (InVal.first != 0 && InVal.second == CurrentGeneration) {
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DEBUG(dbgs() << "EarlyCSE CSE LOAD: " << *Inst << " to: "
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<< *InVal.first << '\n');
|
|
if (!Inst->use_empty()) Inst->replaceAllUsesWith(InVal.first);
|
|
Inst->eraseFromParent();
|
|
Changed = true;
|
|
++NumCSELoad;
|
|
continue;
|
|
}
|
|
|
|
// Otherwise, remember that we have this instruction.
|
|
AvailableLoads->insert(Inst->getOperand(0),
|
|
std::pair<Value*, unsigned>(Inst, CurrentGeneration));
|
|
LastStore = 0;
|
|
continue;
|
|
}
|
|
|
|
// If this instruction may read from memory, forget LastStore.
|
|
if (Inst->mayReadFromMemory())
|
|
LastStore = 0;
|
|
|
|
// If this is a read-only call, process it.
|
|
if (CallValue::canHandle(Inst)) {
|
|
// If we have an available version of this call, and if it is the right
|
|
// generation, replace this instruction.
|
|
std::pair<Value*, unsigned> InVal = AvailableCalls->lookup(Inst);
|
|
if (InVal.first != 0 && InVal.second == CurrentGeneration) {
|
|
DEBUG(dbgs() << "EarlyCSE CSE CALL: " << *Inst << " to: "
|
|
<< *InVal.first << '\n');
|
|
if (!Inst->use_empty()) Inst->replaceAllUsesWith(InVal.first);
|
|
Inst->eraseFromParent();
|
|
Changed = true;
|
|
++NumCSECall;
|
|
continue;
|
|
}
|
|
|
|
// Otherwise, remember that we have this instruction.
|
|
AvailableCalls->insert(Inst,
|
|
std::pair<Value*, unsigned>(Inst, CurrentGeneration));
|
|
continue;
|
|
}
|
|
|
|
// Okay, this isn't something we can CSE at all. Check to see if it is
|
|
// something that could modify memory. If so, our available memory values
|
|
// cannot be used so bump the generation count.
|
|
if (Inst->mayWriteToMemory()) {
|
|
++CurrentGeneration;
|
|
|
|
if (StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
|
|
// We do a trivial form of DSE if there are two stores to the same
|
|
// location with no intervening loads. Delete the earlier store.
|
|
if (LastStore &&
|
|
LastStore->getPointerOperand() == SI->getPointerOperand()) {
|
|
DEBUG(dbgs() << "EarlyCSE DEAD STORE: " << *LastStore << " due to: "
|
|
<< *Inst << '\n');
|
|
LastStore->eraseFromParent();
|
|
Changed = true;
|
|
++NumDSE;
|
|
LastStore = 0;
|
|
continue;
|
|
}
|
|
|
|
// Okay, we just invalidated anything we knew about loaded values. Try
|
|
// to salvage *something* by remembering that the stored value is a live
|
|
// version of the pointer. It is safe to forward from volatile stores
|
|
// to non-volatile loads, so we don't have to check for volatility of
|
|
// the store.
|
|
AvailableLoads->insert(SI->getPointerOperand(),
|
|
std::pair<Value*, unsigned>(SI->getValueOperand(), CurrentGeneration));
|
|
|
|
// Remember that this was the last store we saw for DSE.
|
|
if (SI->isSimple())
|
|
LastStore = SI;
|
|
}
|
|
}
|
|
}
|
|
|
|
return Changed;
|
|
}
|
|
|
|
|
|
bool EarlyCSE::runOnFunction(Function &F) {
|
|
if (skipOptnoneFunction(F))
|
|
return false;
|
|
|
|
std::vector<StackNode *> nodesToProcess;
|
|
|
|
DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
|
|
DL = DLP ? &DLP->getDataLayout() : 0;
|
|
TLI = &getAnalysis<TargetLibraryInfo>();
|
|
DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
|
|
|
|
// Tables that the pass uses when walking the domtree.
|
|
ScopedHTType AVTable;
|
|
AvailableValues = &AVTable;
|
|
LoadHTType LoadTable;
|
|
AvailableLoads = &LoadTable;
|
|
CallHTType CallTable;
|
|
AvailableCalls = &CallTable;
|
|
|
|
CurrentGeneration = 0;
|
|
bool Changed = false;
|
|
|
|
// Process the root node.
|
|
nodesToProcess.push_back(
|
|
new StackNode(AvailableValues, AvailableLoads, AvailableCalls,
|
|
CurrentGeneration, DT->getRootNode(),
|
|
DT->getRootNode()->begin(),
|
|
DT->getRootNode()->end()));
|
|
|
|
// Save the current generation.
|
|
unsigned LiveOutGeneration = CurrentGeneration;
|
|
|
|
// Process the stack.
|
|
while (!nodesToProcess.empty()) {
|
|
// Grab the first item off the stack. Set the current generation, remove
|
|
// the node from the stack, and process it.
|
|
StackNode *NodeToProcess = nodesToProcess.back();
|
|
|
|
// Initialize class members.
|
|
CurrentGeneration = NodeToProcess->currentGeneration();
|
|
|
|
// Check if the node needs to be processed.
|
|
if (!NodeToProcess->isProcessed()) {
|
|
// Process the node.
|
|
Changed |= processNode(NodeToProcess->node());
|
|
NodeToProcess->childGeneration(CurrentGeneration);
|
|
NodeToProcess->process();
|
|
} else if (NodeToProcess->childIter() != NodeToProcess->end()) {
|
|
// Push the next child onto the stack.
|
|
DomTreeNode *child = NodeToProcess->nextChild();
|
|
nodesToProcess.push_back(
|
|
new StackNode(AvailableValues,
|
|
AvailableLoads,
|
|
AvailableCalls,
|
|
NodeToProcess->childGeneration(), child,
|
|
child->begin(), child->end()));
|
|
} else {
|
|
// It has been processed, and there are no more children to process,
|
|
// so delete it and pop it off the stack.
|
|
delete NodeToProcess;
|
|
nodesToProcess.pop_back();
|
|
}
|
|
} // while (!nodes...)
|
|
|
|
// Reset the current generation.
|
|
CurrentGeneration = LiveOutGeneration;
|
|
|
|
return Changed;
|
|
}
|