Fix a bug where we would 'promote' an allocation from one type to another

where the second has less alignment required.  If we had explicit alignment
support in the IR, we could handle this case, but we can't until we do.

llvm-svn: 23960

1 files changed, 6 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
index 09fee7cc4bd..bd85b4abd5d 100644
--- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -3795,10 +3795,14 @@ Instruction *InstCombiner::PromoteCastOfAllocation(CastInst &CI,
   const Type *AllocElTy = AI.getAllocatedType();
   const Type *CastElTy = PTy->getElementType();
   if (!AllocElTy->isSized() || !CastElTy->isSized()) return 0;
-  
+
+  unsigned AllocElTyAlign = TD->getTypeSize(AllocElTy);
+  unsigned CastElTyAlign = TD->getTypeSize(CastElTy);
+  if (CastElTyAlign < AllocElTyAlign) return 0;
+
   uint64_t AllocElTySize = TD->getTypeSize(AllocElTy);
   uint64_t CastElTySize = TD->getTypeSize(CastElTy);
-  
+
   // If the allocation is for an even multiple of the cast type size
   if (CastElTySize == 0 || AllocElTySize % CastElTySize != 0)
     return 0;