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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@23960 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index 09fee7cc4bd0e6ec3f57d8046f9f6819a6476190..bd85b4abd5d0adc6839e176af64951ece6253b54 100644 (file)
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/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;