--- /dev/null
+//===- 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;
+}
+++ /dev/null
-//===- 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;
-}
projects / oota-llvm.git / commitdiff