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Teach DeadStoreElimination to eliminate exit-block stores with phi addresses.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@156558 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Dan Gohman
2012-05-10 18:57:38 +00:00
parent fe65d98dad
commit b401e3bd16
4 changed files with 68 additions and 3 deletions
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22
lib/Transforms/Scalar/DeadStoreElimination.cpp
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@ -731,14 +731,30 @@ bool DSE::handleEndBlock(BasicBlock &BB) {
// If we find a store, check to see if it points into a dead stack value.
if (hasMemoryWrite(BBI) && isRemovable(BBI)) {
// See through pointer-to-pointer bitcasts
Value *Pointer = GetUnderlyingObject(getStoredPointerOperand(BBI));
SmallVector<Value *, 4> Pointers;
GetUnderlyingObjects(getStoredPointerOperand(BBI), Pointers);
// Stores to stack values are valid candidates for removal.
if (DeadStackObjects.count(Pointer)) {
bool AllDead = true;
for (SmallVectorImpl<Value *>::iterator I = Pointers.begin(),
E = Pointers.end(); I != E; ++I)
if (!DeadStackObjects.count(*I)) {
AllDead = false;
break;
}
if (AllDead) {
Instruction *Dead = BBI++;
DEBUG(dbgs() << "DSE: Dead Store at End of Block:\n DEAD: "
<< *Dead << "\n Object: " << *Pointer << '\n');
<< *Dead << "\n Objects: ";
for (SmallVectorImpl<Value *>::iterator I = Pointers.begin(),
E = Pointers.end(); I != E; ++I) {
dbgs() << **I;
if (llvm::next(I) != E)
dbgs() << ", ";
}
dbgs() << '\n');
// DCE instructions only used to calculate that store.
DeleteDeadInstruction(Dead, *MD, &DeadStackObjects);