Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -71,6 +71,16 @@
 
 - ...
 
+Modified Compiler Flags
+-----------------------
+
+- Before Clang 6.0, we passed "#" to --autocomplete flag to indicate to enable cc1
+  flags. For example, when -cc1 or -Xclang was passed to shell, shell executed clang
+  --autocomplete=#-<flag they want to complete>. Clang 7.0 now passes all flags that
+  shell has, so that Clang can handle them internally which breaks backward compatibility
+  before Clang 6.0.
+
+
 New Pragmas in Clang
 -----------------------