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Refactor this method a bit, and correct a test that was completely wrong but happened to work out anyways. :-)

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llvm-svn: 47321
This commit is contained in:
Owen Anderson 2008-02-19 07:07:51 +00:00
parent 99e0b1c063
commit 6196cdcb48
1 changed files with 11 additions and 7 deletions
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18
lib/Transforms/Scalar/GVN.cpp
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@ -1083,6 +1083,8 @@ static bool isReturnSlotOptznProfitable(Value* dest, MemCpyInst* cpy) {
/// rather than using memcpy
bool GVN::performReturnSlotOptzn(MemCpyInst* cpy, CallInst* C,
SmallVector<Instruction*, 4>& toErase) {
// Deliberately get the source and destination with bitcasts stripped away,
// because we'll need to do type comparisons based on the underlying type.
Value* cpyDest = cpy->getDest();
Value* cpySrc = cpy->getSource();
CallSite CS = CallSite::get(C);
@ -1097,23 +1099,25 @@ bool GVN::performReturnSlotOptzn(MemCpyInst* cpy, CallInst* C,
!CS.paramHasAttr(1, ParamAttr::NoAlias | ParamAttr::StructRet))
return false;
// We only perform the transformation if it will be profitable.
if (!isReturnSlotOptznProfitable(cpyDest, cpy))
return false;
// Check that something sneaky is not happening involving casting
// return slot types around.
if (CS.getArgument(0)->getType() != cpyDest->getType())
return false;
// sret --> pointer
const PointerType* PT = cast<PointerType>(cpyDest->getType());
// We can only perform the transformation if the size of the memcpy
// is constant and equal to the size of the structure.
if (!isa<ConstantInt>(cpy->getLength()))
ConstantInt* cpyLength = dyn_cast<ConstantInt>(cpy->getLength());
if (!cpyLength)
return false;
ConstantInt* cpyLength = cast<ConstantInt>(cpy->getLength());
TargetData& TD = getAnalysis<TargetData>();
if (TD.getTypeStoreSize(cpyDest->getType()) == cpyLength->getZExtValue())
if (TD.getTypeStoreSize(PT->getElementType()) != cpyLength->getZExtValue())
return false;
// We only perform the transformation if it will be profitable.
if (!isReturnSlotOptznProfitable(cpyDest, cpy))
return false;
// In addition to knowing that the call does not access the return slot