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Fix the other half of the alignment changing issue by making sure that the 

memcpy alignment is the minimum of the incoming alignments.

Fixes PR 8266.

llvm-svn: 115305
This commit is contained in:
Eric Christopher 2010-10-01 09:02:05 +00:00
parent 3b2b1e7942
commit 3ad2f3a2f2
1 changed files with 8 additions and 3 deletions
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11
llvm/lib/Transforms/Scalar/MemCpyOptimizer.cpp
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@ -697,13 +697,18 @@ bool MemCpyOpt::processMemCpy(MemCpyInst *M) {
M->getParent()->getParent()->getParent(),
M->getIntrinsicID(), ArgTys, 3);
// Make sure to use the alignment of the source since we're changing the
// location we're reading from.
// Make sure to use the lesser of the alignment of the source and the dest
// since we're changing where we're reading from, but don't want to increase
// the alignment past what can be read from or written to.
// TODO: Is this worth it if we're creating a less aligned memcpy? For
// example we could be moving from movaps -> movq on x86.
unsigned Align = std::min(MDep->getAlignmentCst()->getZExtValue(),
M->getAlignmentCst()->getZExtValue());
LLVMContext &Context = M->getContext();
ConstantInt *AlignCI = ConstantInt::get(Type::getInt32Ty(Context), Align);
Value *Args[5] = {
M->getRawDest(), MDep->getRawSource(), M->getLength(),
MDep->getAlignmentCst(), M->getVolatileCst()
AlignCI, M->getVolatileCst()
};
CallInst *C = CallInst::Create(MemCpyFun, Args, Args+5, "", M);