[llvm-commits] [llvm] r40667 - in /llvm/trunk/lib/Transforms/Scalar: DeadStoreElimination.cpp FastDSE.cpp
Owen Anderson
resistor at mac.com
Tue Jul 31 23:30:52 PDT 2007
Author: resistor
Date: Wed Aug 1 01:30:51 2007
New Revision: 40667
URL: http://llvm.org/viewvc/llvm-project?rev=40667&view=rev
Log:
Move FastDSE in to DeadStoreElimination.
Added:
llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
- copied unchanged from r40665, llvm/trunk/lib/Transforms/Scalar/FastDSE.cpp
Removed:
llvm/trunk/lib/Transforms/Scalar/FastDSE.cpp
Removed: llvm/trunk/lib/Transforms/Scalar/FastDSE.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/FastDSE.cpp?rev=40666&view=auto
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/FastDSE.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/FastDSE.cpp (removed)
@@ -1,387 +0,0 @@
-//===- FastDSE.cpp - Fast Dead Store Elimination --------------------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file was developed by Owen Anderson and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file implements a trivial dead store elimination that only considers
-// basic-block local redundant stores.
-//
-// FIXME: This should eventually be extended to be a post-dominator tree
-// traversal. Doing so would be pretty trivial.
-//
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "fdse"
-#include "llvm/Transforms/Scalar.h"
-#include "llvm/Constants.h"
-#include "llvm/Function.h"
-#include "llvm/Instructions.h"
-#include "llvm/Pass.h"
-#include "llvm/ADT/SetVector.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/MemoryDependenceAnalysis.h"
-#include "llvm/Target/TargetData.h"
-#include "llvm/Transforms/Utils/Local.h"
-#include "llvm/Support/Compiler.h"
-using namespace llvm;
-
-STATISTIC(NumFastStores, "Number of stores deleted");
-STATISTIC(NumFastOther , "Number of other instrs removed");
-
-namespace {
- struct VISIBILITY_HIDDEN FDSE : public FunctionPass {
- static char ID; // Pass identification, replacement for typeid
- FDSE() : FunctionPass((intptr_t)&ID) {}
-
- virtual bool runOnFunction(Function &F) {
- bool Changed = false;
- for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
- Changed |= runOnBasicBlock(*I);
- return Changed;
- }
-
- bool runOnBasicBlock(BasicBlock &BB);
- bool handleFreeWithNonTrivialDependency(FreeInst* F, Instruction* dependency,
- SetVector<Instruction*>& possiblyDead);
- bool handleEndBlock(BasicBlock& BB, SetVector<Instruction*>& possiblyDead);
- bool RemoveUndeadPointers(Value* pointer, unsigned pointerSize,
- BasicBlock::iterator& BBI,
- SmallPtrSet<AllocaInst*, 4>& deadPointers,
- SetVector<Instruction*>& possiblyDead);
- void DeleteDeadInstructionChains(Instruction *I,
- SetVector<Instruction*> &DeadInsts);
- void TranslatePointerBitCasts(Value*& v) {
- assert(isa<PointerType>(v->getType()) && "Translating a non-pointer type?");
-
- // See through pointer-to-pointer bitcasts
- while (isa<BitCastInst>(v) || isa<GetElementPtrInst>(v))
- if (BitCastInst* C = dyn_cast<BitCastInst>(v))
- v = C->getOperand(0);
- else if (GetElementPtrInst* G = dyn_cast<GetElementPtrInst>(v))
- v = G->getOperand(0);
- }
-
- // getAnalysisUsage - We require post dominance frontiers (aka Control
- // Dependence Graph)
- virtual void getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesCFG();
- AU.addRequired<TargetData>();
- AU.addRequired<AliasAnalysis>();
- AU.addRequired<MemoryDependenceAnalysis>();
- AU.addPreserved<AliasAnalysis>();
- AU.addPreserved<MemoryDependenceAnalysis>();
- }
- };
- char FDSE::ID = 0;
- RegisterPass<FDSE> X("fdse", "Fast Dead Store Elimination");
-}
-
-FunctionPass *llvm::createFastDeadStoreEliminationPass() { return new FDSE(); }
-
-bool FDSE::runOnBasicBlock(BasicBlock &BB) {
- MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
-
- // Record the last-seen store to this pointer
- DenseMap<Value*, StoreInst*> lastStore;
- // Record instructions possibly made dead by deleting a store
- SetVector<Instruction*> possiblyDead;
-
- bool MadeChange = false;
-
- // Do a top-down walk on the BB
- for (BasicBlock::iterator BBI = BB.begin(), BBE = BB.end(); BBI != BBE; ++BBI) {
- // If we find a store or a free...
- if (isa<StoreInst>(BBI) || isa<FreeInst>(BBI)) {
- Value* pointer = 0;
- if (StoreInst* S = dyn_cast<StoreInst>(BBI))
- pointer = S->getPointerOperand();
- else if (FreeInst* F = dyn_cast<FreeInst>(BBI))
- pointer = F->getPointerOperand();
-
- assert(pointer && "Not a free or a store?");
-
- StoreInst*& last = lastStore[pointer];
- bool deletedStore = false;
-
- // ... to a pointer that has been stored to before...
- if (last) {
-
- Instruction* dep = MD.getDependency(BBI);
-
- // ... and no other memory dependencies are between them....
- while (dep != MemoryDependenceAnalysis::None &&
- dep != MemoryDependenceAnalysis::NonLocal &&
- isa<StoreInst>(dep)) {
- if (dep == last) {
-
- // Remove it!
- MD.removeInstruction(last);
-
- // DCE instructions only used to calculate that store
- if (Instruction* D = dyn_cast<Instruction>(last->getOperand(0)))
- possiblyDead.insert(D);
- if (Instruction* D = dyn_cast<Instruction>(last->getOperand(1)))
- possiblyDead.insert(D);
-
- last->eraseFromParent();
- NumFastStores++;
- deletedStore = true;
- MadeChange = true;
-
- break;
- } else {
- dep = MD.getDependency(BBI, dep);
- }
- }
- }
-
- // Handle frees whose dependencies are non-trivial
- if (FreeInst* F = dyn_cast<FreeInst>(BBI))
- if (!deletedStore)
- MadeChange |= handleFreeWithNonTrivialDependency(F, MD.getDependency(F),
- possiblyDead);
-
- // Update our most-recent-store map
- if (StoreInst* S = dyn_cast<StoreInst>(BBI))
- last = S;
- else
- last = 0;
- }
- }
-
- // If this block ends in a return, unwind, unreachable, and eventually
- // tailcall, then all allocas are dead at its end.
- if (BB.getTerminator()->getNumSuccessors() == 0)
- MadeChange |= handleEndBlock(BB, possiblyDead);
-
- // Do a trivial DCE
- while (!possiblyDead.empty()) {
- Instruction *I = possiblyDead.back();
- possiblyDead.pop_back();
- DeleteDeadInstructionChains(I, possiblyDead);
- }
-
- return MadeChange;
-}
-
-/// handleFreeWithNonTrivialDependency - Handle frees of entire structures whose
-/// dependency is a store to a field of that structure
-bool FDSE::handleFreeWithNonTrivialDependency(FreeInst* F, Instruction* dep,
- SetVector<Instruction*>& possiblyDead) {
- TargetData &TD = getAnalysis<TargetData>();
- AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
- MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
-
- if (dep == MemoryDependenceAnalysis::None ||
- dep == MemoryDependenceAnalysis::NonLocal)
- return false;
-
- StoreInst* dependency = dyn_cast<StoreInst>(dep);
- if (!dependency)
- return false;
-
- Value* depPointer = dependency->getPointerOperand();
- unsigned depPointerSize = TD.getTypeSize(dependency->getOperand(0)->getType());
-
- // Check for aliasing
- AliasAnalysis::AliasResult A = AA.alias(F->getPointerOperand(), ~0UL,
- depPointer, depPointerSize);
-
- if (A == AliasAnalysis::MustAlias) {
- // Remove it!
- MD.removeInstruction(dependency);
-
- // DCE instructions only used to calculate that store
- if (Instruction* D = dyn_cast<Instruction>(dependency->getOperand(0)))
- possiblyDead.insert(D);
- if (Instruction* D = dyn_cast<Instruction>(dependency->getOperand(1)))
- possiblyDead.insert(D);
-
- dependency->eraseFromParent();
- NumFastStores++;
- return true;
- }
-
- return false;
-}
-
-/// handleEndBlock - Remove dead stores to stack-allocated locations in the function
-/// end block
-bool FDSE::handleEndBlock(BasicBlock& BB, SetVector<Instruction*>& possiblyDead) {
- TargetData &TD = getAnalysis<TargetData>();
- AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
- MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
-
- bool MadeChange = false;
-
- // Pointers alloca'd in this function are dead in the end block
- SmallPtrSet<AllocaInst*, 4> deadPointers;
-
- // Find all of the alloca'd pointers in the entry block
- BasicBlock *Entry = BB.getParent()->begin();
- for (BasicBlock::iterator I = Entry->begin(), E = Entry->end(); I != E; ++I)
- if (AllocaInst *AI = dyn_cast<AllocaInst>(I))
- deadPointers.insert(AI);
-
- // Scan the basic block backwards
- for (BasicBlock::iterator BBI = BB.end(); BBI != BB.begin(); ){
- --BBI;
-
- if (deadPointers.empty())
- break;
-
- Value* killPointer = 0;
- unsigned killPointerSize = 0;
-
- // If we find a store whose pointer is dead...
- if (StoreInst* S = dyn_cast<StoreInst>(BBI)) {
- Value* pointerOperand = S->getPointerOperand();
- // See through pointer-to-pointer bitcasts
- TranslatePointerBitCasts(pointerOperand);
-
- if (deadPointers.count(pointerOperand)){
- // Remove it!
- MD.removeInstruction(S);
-
- // DCE instructions only used to calculate that store
- if (Instruction* D = dyn_cast<Instruction>(S->getOperand(0)))
- possiblyDead.insert(D);
- if (Instruction* D = dyn_cast<Instruction>(S->getOperand(1)))
- possiblyDead.insert(D);
-
- BBI++;
- S->eraseFromParent();
- NumFastStores++;
- MadeChange = true;
- }
-
- // If we encounter a use of the pointer, it is no longer considered dead
- } else if (LoadInst* L = dyn_cast<LoadInst>(BBI)) {
- killPointer = L->getPointerOperand();
- killPointerSize = TD.getTypeSize(L->getType());
- } else if (VAArgInst* V = dyn_cast<VAArgInst>(BBI)) {
- killPointer = V->getOperand(0);
- killPointerSize = TD.getTypeSize(V->getType());
- } else if (FreeInst* F = dyn_cast<FreeInst>(BBI)) {
- killPointer = F->getPointerOperand();
- killPointerSize = ~0UL;
- } else if (AllocaInst* A = dyn_cast<AllocaInst>(BBI)) {
- deadPointers.erase(A);
- continue;
- } else if (CallSite::get(BBI).getInstruction() != 0) {
- // Remove any pointers made undead by the call from the dead set
- std::vector<Instruction*> dead;
- for (SmallPtrSet<AllocaInst*, 4>::iterator I = deadPointers.begin(),
- E = deadPointers.end(); I != E; ++I) {
- // Get size information for the alloca
- unsigned pointerSize = ~0UL;
- if (ConstantInt* C = dyn_cast<ConstantInt>((*I)->getArraySize()))
- pointerSize = C->getZExtValue() * TD.getTypeSize((*I)->getAllocatedType());
-
- // See if the call site touches it
- AliasAnalysis::ModRefResult A = AA.getModRefInfo(CallSite::get(BBI),
- *I, pointerSize);
- if (A == AliasAnalysis::ModRef || A == AliasAnalysis::Ref)
- dead.push_back(*I);
- }
-
- for (std::vector<Instruction*>::iterator I = dead.begin(), E = dead.end();
- I != E; ++I)
- deadPointers.erase(*I);
-
- continue;
- }
-
- if (!killPointer)
- continue;
-
- // Deal with undead pointers
- MadeChange |= RemoveUndeadPointers(killPointer, killPointerSize, BBI,
- deadPointers, possiblyDead);
- }
-
- return MadeChange;
-}
-
-bool FDSE::RemoveUndeadPointers(Value* killPointer, unsigned killPointerSize,
- BasicBlock::iterator& BBI,
- SmallPtrSet<AllocaInst*, 4>& deadPointers,
- SetVector<Instruction*>& possiblyDead) {
- TargetData &TD = getAnalysis<TargetData>();
- AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
- MemoryDependenceAnalysis& MD = getAnalysis<MemoryDependenceAnalysis>();
-
- bool MadeChange = false;
-
- std::vector<Instruction*> undead;
-
- for (SmallPtrSet<AllocaInst*, 4>::iterator I = deadPointers.begin(),
- E = deadPointers.end(); I != E; ++I) {
- // Get size information for the alloca
- unsigned pointerSize = ~0UL;
- if (ConstantInt* C = dyn_cast<ConstantInt>((*I)->getArraySize()))
- pointerSize = C->getZExtValue() * TD.getTypeSize((*I)->getAllocatedType());
-
- // See if this pointer could alias it
- AliasAnalysis::AliasResult A = AA.alias(*I, pointerSize, killPointer, killPointerSize);
-
- // If it must-alias and a store, we can delete it
- if (isa<StoreInst>(BBI) && A == AliasAnalysis::MustAlias) {
- StoreInst* S = cast<StoreInst>(BBI);
-
- // Remove it!
- MD.removeInstruction(S);
-
- // DCE instructions only used to calculate that store
- if (Instruction* D = dyn_cast<Instruction>(S->getOperand(0)))
- possiblyDead.insert(D);
- if (Instruction* D = dyn_cast<Instruction>(S->getOperand(1)))
- possiblyDead.insert(D);
-
- BBI++;
- S->eraseFromParent();
- NumFastStores++;
- MadeChange = true;
-
- continue;
-
- // Otherwise, it is undead
- } else if (A != AliasAnalysis::NoAlias)
- undead.push_back(*I);
- }
-
- for (std::vector<Instruction*>::iterator I = undead.begin(), E = undead.end();
- I != E; ++I)
- deadPointers.erase(*I);
-
- return MadeChange;
-}
-
-void FDSE::DeleteDeadInstructionChains(Instruction *I,
- SetVector<Instruction*> &DeadInsts) {
- // Instruction must be dead.
- if (!I->use_empty() || !isInstructionTriviallyDead(I)) return;
-
- // Let the memory dependence know
- getAnalysis<MemoryDependenceAnalysis>().removeInstruction(I);
-
- // See if this made any operands dead. We do it this way in case the
- // instruction uses the same operand twice. We don't want to delete a
- // value then reference it.
- for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i) {
- if (I->getOperand(i)->hasOneUse())
- if (Instruction* Op = dyn_cast<Instruction>(I->getOperand(i)))
- DeadInsts.insert(Op); // Attempt to nuke it later.
-
- I->setOperand(i, 0); // Drop from the operand list.
- }
-
- I->eraseFromParent();
- ++NumFastOther;
-}
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