Add test case for PR 9774, which got fixed along the way.

llvm-svn: 147479

clang/test/Sema/warn-unreachable.c

@@ -125,4 +125,10 @@ void test_assert() {
   return; // no-warning
 }
 
+// Test case for PR 9774.  Tests that dead code in macros aren't warned about.
+#define MY_MAX(a,b)     ((a) >= (b) ? (a) : (b))
+void PR9774(int *s) {
+    for (int i = 0; i < MY_MAX(2, 3); i++) // no-warning
+        s[i] = 0;
+}