improve support for uniontype and ConstantUnion, patch by Tim Northover!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@98656 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 0 deletions

diff --git a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
index 3d9a4d523b..11293e47f6 100644
--- a/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
+++ b/lib/CodeGen/SelectionDAG/SelectionDAGBuilder.cpp
@@ -2592,6 +2592,11 @@ void SelectionDAGBuilder::visitGetElementPtr(User &I) {
       }
 
       Ty = StTy->getElementType(Field);
+    } else if (const UnionType *UnTy = dyn_cast<UnionType>(Ty)) {
+      unsigned Field = cast<ConstantInt>(Idx)->getZExtValue();
+      
+      // Offset canonically 0 for unions, but type changes
+      Ty = UnTy->getElementType(Field);
     } else {
       Ty = cast<SequentialType>(Ty)->getElementType();