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.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@115305 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Transforms/Scalar/MemCpyOptimizer.cpp b/lib/Transforms/Scalar/MemCpyOptimizer.cpp
index f94c9e2..4172b34 100644
--- a/lib/Transforms/Scalar/MemCpyOptimizer.cpp
+++ b/lib/Transforms/Scalar/MemCpyOptimizer.cpp
@@ -697,13 +697,18 @@
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);