TBAA: fix PR17620.

We can have a struct type with a single field and the field does not start
with 0. In that case, we should correctly update the offset.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@193137 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 5 insertions, 1 deletions

diff --git a/lib/Analysis/TypeBasedAliasAnalysis.cpp b/lib/Analysis/TypeBasedAliasAnalysis.cpp
index 9026dc9..6791d4b 100644
--- a/lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ b/lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -231,8 +231,12 @@ namespace {
       if (Node->getNumOperands() < 2)
         return TBAAStructTypeNode();
 
-      // Special handling for a scalar type node. 
+      // Fast path for a scalar type node and a struct type node with a single
+      // field.
       if (Node->getNumOperands() <= 3) {
+        uint64_t Cur = Node->getNumOperands() == 2 ? 0 :
+                       cast<ConstantInt>(Node->getOperand(2))->getZExtValue();
+        Offset -= Cur;
         MDNode *P = dyn_cast_or_null<MDNode>(Node->getOperand(1));
         if (!P)
           return TBAAStructTypeNode();