[SROA] Use NewOffsetBegin in the unsplit case for memset merely for

consistency with memcpy rewriting, and fix a latent bug in the alignment
management for memset.

The alignment issue is that getAdjustedAllocaPtr is computing the
*relative* offset into the new alloca, but the alignment isn't being set
to the relative offset, it was using the the absolute offset which is
into the old alloca.

I don't think its possible to write a test case that actually reaches
this code where the resulting alignment would be observably different,
but the intent was clearly to use the relative offset within the new
alloca.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@202229 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/SROA.cpp b/lib/Transforms/Scalar/SROA.cpp
index 2ecc517d485bb17cf3c3aa225e3b63d083a97689..d0f2561dd337ddf09ceb06478675af33b8daf274 100644 (file)
--- a/lib/Transforms/Scalar/SROA.cpp
+++ b/lib/Transforms/Scalar/SROA.cpp
@@ -2393,10 +2393,11 @@ private:
     // pointer to the new alloca.
     if (!isa<Constant>(II.getLength())) {
       assert(!IsSplit);
-      assert(BeginOffset >= NewAllocaBeginOffset);
-      II.setDest(getAdjustedAllocaPtr(IRB, BeginOffset, OldPtr->getType()));
+      assert(NewBeginOffset == BeginOffset);
+      II.setDest(getAdjustedAllocaPtr(IRB, NewBeginOffset, OldPtr->getType()));
       Type *CstTy = II.getAlignmentCst()->getType();
-      II.setAlignment(ConstantInt::get(CstTy, getOffsetAlign(BeginOffset)));
+      II.setAlignment(ConstantInt::get(
+          CstTy, getOffsetAlign(NewBeginOffset - NewAllocaBeginOffset)));
 
       deleteIfTriviallyDead(OldPtr);
       return false;