Don't flag idempotent '+' or '-' warnings for pointer arithmetic (typically false positives).

Fixes <rdar://problem/8601243>.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@117635 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Analysis/idempotent-operations.c b/test/Analysis/idempotent-operations.c
index c673f00..197357f 100644
--- a/test/Analysis/idempotent-operations.c
+++ b/test/Analysis/idempotent-operations.c
@@ -224,3 +224,13 @@
   return pred;
 }
 
+// <rdar://problem/8601243> - Don't warn on pointer arithmetic.  This
+// is often idiomatic.
+unsigned rdar8601243_aux(unsigned n);
+void rdar8601243() {
+  char arr[100];
+  char *start = arr;
+  start = start + rdar8601243_aux(sizeof(arr) - (arr - start)); // no-warning
+  (void) start;
+}
+