Documentation: add a note that -cc1 options are not guaranteed to be stable
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@173280 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/FAQ.rst b/docs/FAQ.rst
index dc97507..d0b47d6 100644
--- a/docs/FAQ.rst
+++ b/docs/FAQ.rst
@@ -42,7 +42,8 @@
Some clang command line options are driver-only options, some are frontend-only
options. Frontend-only options are intended to be used only by developers.
-Users should not run ``clang -cc1`` directly.
+Users should not run ``clang -cc1`` directly, because ``-cc1`` options are not
+guaranteed to be stable.
If you want to use a frontend-only option ("a ``-cc1`` option"), for example
``-ast-dump``, then you need to take the ``clang -cc1`` line generated by the