[Bug tree-optimization/65712] pthread_self prints wrong result when used with ucontext

[albertnetymk at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65712

--- Comment #2 from Albert Netymk <albertnetymk at gmail dot com> ---
@Andrew Pinski Could you provide the ref for const and pure attribute? It's not
mentioned in the
[spec](http://pubs.opengroup.org/onlinepubs/009695399/functions/pthread_self.html),
or the source code of
[glibc](https://github.com/lattera/glibc/blob/master/nptl/pthread_self.c)