http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58806
--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> --- You cannot find the PR because it's already implemented via the "fn spec" attribute (conveniently not user-accessible because bike-shedding about whether separate attributes are required). The documentation resides in gimple.c:gimple_call_arg_flags, and I _think_ it doesn't quite provide what you want as it was designed to help the context and flow-insensitive points-to analysis which doesn't benefit from "this call does not clobber or read from escaped memory". But what it provides is "the argument to this function does not escape" which is important.
