Fix PR1921 by promoting negative indices to intptrty.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@46599 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/CodeGen/exprs.c b/test/CodeGen/exprs.c
index 9115369..16b63f8 100644
--- a/test/CodeGen/exprs.c
+++ b/test/CodeGen/exprs.c
@@ -17,3 +17,9 @@
 _Bool test2b; 
 int test2() {if (test2b);}
 
+// PR1921
+int test3() {
+  const unsigned char *bp;
+  bp -= (short)1;
+}
+