https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86940
--- Comment #2 from Aritz Erkiaga <aerkiaga6 at gmail dot com> --- I don't know. Somehow it does know it when the testcase is compiled without any -O flags, but it not something trivial, and so I would not be surprised if GCC were not able to get that information.
