[InstCombine] Fix assertion when bitcast is converted to gep

When an aggregate contains an opaque type its size cannot be
determined. This triggers an "Invalid GetElementPtrInst indices for type" assert
in function checkGEPType. The fix suppresses the conversion in this case.

http://reviews.llvm.org/D20319

llvm-svn: 270479

1 files changed, 7 insertions, 0 deletions

diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index 80b138e8c36..dddcd0183b3 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1922,6 +1922,13 @@ Instruction *InstCombiner::visitBitCast(BitCastInst &CI) {
       if (Instruction *V = PromoteCastOfAllocation(CI, *AI))
         return V;
 
+    // When the type pointed to is not sized the cast cannot be
+    // turned into a gep.
+    Type *PointeeType =
+        cast<PointerType>(Src->getType()->getScalarType())->getElementType();
+    if (!PointeeType->isSized())
+      return nullptr;
+
     // If the source and destination are pointers, and this cast is equivalent
     // to a getelementptr X, 0, 0, 0...  turn it into the appropriate gep.
     // This can enhance SROA and other transforms that want type-safe pointers.