Author: resistor
Date: Wed Aug 8 12:50:09 2007
New Revision: 40932
URL: http://llvm.org/viewvc/llvm-project?rev=40932&view=rev
Log:
Add some comments, remove a dead argument, and simplify some control flow.
No functionality change.
Modified:
llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
Modified: llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp
URL:
http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp?rev=40932&r1=40931&r2=40932&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp (original)
+++ llvm/trunk/lib/Transforms/Scalar/DeadStoreElimination.cpp Wed Aug 8
12:50:09 2007
@@ -51,9 +51,9 @@
Instruction* dependency,
SetVector<Instruction*>& possiblyDead);
bool handleEndBlock(BasicBlock& BB, SetVector<Instruction*>& possiblyDead);
- bool RemoveUndeadPointers(Value* pointer, unsigned pointerSize,
+ bool RemoveUndeadPointers(Value* pointer,
BasicBlock::iterator& BBI,
- SmallPtrSet<AllocaInst*, 4>& deadPointers,
+ SmallPtrSet<AllocaInst*, 64>& deadPointers,
SetVector<Instruction*>& possiblyDead);
void DeleteDeadInstructionChains(Instruction *I,
SetVector<Instruction*> &DeadInsts);
@@ -222,7 +222,11 @@
}
/// handleEndBlock - Remove dead stores to stack-allocated locations in the
-/// function end block
+/// function end block. Ex:
+/// %A = alloca i32
+/// ...
+/// store i32 1, i32* %A
+/// ret void
bool DSE::handleEndBlock(BasicBlock& BB,
SetVector<Instruction*>& possiblyDead) {
TargetData &TD = getAnalysis<TargetData>();
@@ -232,7 +236,7 @@
bool MadeChange = false;
// Pointers alloca'd in this function are dead in the end block
- SmallPtrSet<AllocaInst*, 4> deadPointers;
+ SmallPtrSet<AllocaInst*, 64> deadPointers;
// Find all of the alloca'd pointers in the entry block
BasicBlock *Entry = BB.getParent()->begin();
@@ -247,9 +251,6 @@
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();
@@ -271,24 +272,24 @@
NumFastStores++;
MadeChange = true;
}
+
+ continue;
+ }
+
+ Value* killPointer = 0;
// If we encounter a use of the pointer, it is no longer considered dead
- } else if (LoadInst* L = dyn_cast<LoadInst>(BBI)) {
+ 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(),
+ for (SmallPtrSet<AllocaInst*, 64>::iterator I = deadPointers.begin(),
E = deadPointers.end(); I != E; ++I) {
// Get size information for the alloca
unsigned pointerSize = ~0UL;
@@ -314,16 +315,20 @@
continue;
// Deal with undead pointers
- MadeChange |= RemoveUndeadPointers(killPointer, killPointerSize, BBI,
+ MadeChange |= RemoveUndeadPointers(killPointer, BBI,
deadPointers, possiblyDead);
}
return MadeChange;
}
-bool DSE::RemoveUndeadPointers(Value* killPointer, unsigned killPointerSize,
+/// RemoveUndeadPointers - takes an instruction and a setvector of
+/// dead instructions. If I is dead, it is erased, and its operands are
+/// checked for deadness. If they are dead, they are added to the dead
+/// setvector.
+bool DSE::RemoveUndeadPointers(Value* killPointer,
BasicBlock::iterator& BBI,
- SmallPtrSet<AllocaInst*, 4>& deadPointers,
+ SmallPtrSet<AllocaInst*, 64>& deadPointers,
SetVector<Instruction*>& possiblyDead) {
TargetData &TD = getAnalysis<TargetData>();
AliasAnalysis &AA = getAnalysis<AliasAnalysis>();
@@ -333,7 +338,7 @@
std::vector<Instruction*> undead;
- for (SmallPtrSet<AllocaInst*, 4>::iterator I = deadPointers.begin(),
+ for (SmallPtrSet<AllocaInst*, 64>::iterator I = deadPointers.begin(),
E = deadPointers.end(); I != E; ++I) {
// Get size information for the alloca
unsigned pointerSize = ~0UL;
@@ -343,7 +348,7 @@
// See if this pointer could alias it
AliasAnalysis::AliasResult A = AA.alias(*I, pointerSize,
- killPointer, killPointerSize);
+ killPointer, ~0UL);
// If it must-alias and a store, we can delete it
if (isa<StoreInst>(BBI) && A == AliasAnalysis::MustAlias) {
@@ -377,6 +382,10 @@
return MadeChange;
}
+/// DeleteDeadInstructionChains - takes an instruction and a setvector of
+/// dead instructions. If I is dead, it is erased, and its operands are
+/// checked for deadness. If they are dead, they are added to the dead
+/// setvector.
void DSE::DeleteDeadInstructionChains(Instruction *I,
SetVector<Instruction*> &DeadInsts) {
// Instruction must be dead.
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