Fix a bug introduced by the Getelementptr change

llvm-svn: 3695
diff --git a/llvm/lib/CWriter/Writer.cpp b/llvm/lib/CWriter/Writer.cpp
index bc3829f..c54af08 100644
--- a/llvm/lib/CWriter/Writer.cpp
+++ b/llvm/lib/CWriter/Writer.cpp
@@ -925,7 +925,7 @@
       printType(cast<PointerType>(Ptr->getType())->getElementType());
       Out << ")]";
     } else {
-      Out << ".field" << cast<ConstantSInt>(*I)->getValue();
+      Out << ".field" << cast<ConstantUInt>(*I)->getValue();
     }
 }