Fix an issue where we failed to adjust the alignment constraint on

a memcpy to reflect that '0' has a different meaning when applied to
a load or store. Now we correctly use underaligned loads and stores for
the test case added.

llvm-svn: 165101

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/Scalar/SROA.cpp b/llvm/lib/Transforms/Scalar/SROA.cpp
index 58bae0971e3..f4fd8575d3a 100644
--- a/llvm/lib/Transforms/Scalar/SROA.cpp
+++ b/llvm/lib/Transforms/Scalar/SROA.cpp
@@ -2585,6 +2585,12 @@ private:
       return false;
     }
 
+    // Note that we clamp the alignment to 1 here as a 0 alignment for a memcpy
+    // is equivalent to 1, but that isn't true if we end up rewriting this as
+    // a load or store.
+    if (!Align)
+      Align = 1;
+
     Value *SrcPtr = OtherPtr;
     Value *DstPtr = &NewAI;
     if (!IsDest)