CPP Output: Do not emit an enter file marker for the main file.

 - This diverges from gcc, and confuses tools (like dtrace) which track # line
   markers as a way to determine which content is in the context of the main
   file.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@168128 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Preprocessor/line-directive-output.c b/test/Preprocessor/line-directive-output.c
index 290703a..bd3ea94 100644
--- a/test/Preprocessor/line-directive-output.c
+++ b/test/Preprocessor/line-directive-output.c
@@ -2,6 +2,10 @@
 // PR6101
 int a;
 // CHECK: # 1 "{{.*}}line-directive-output.c"
+
+// Check that we do not emit an enter marker for the main file.
+// CHECK-NOT: # 1 "{{.*}}line-directive-output.c" 1
+
 // CHECK: int a;
 
 // CHECK-NEXT: # 50 "{{.*}}line-directive-output.c"