https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93806
--- Comment #23 from Vincent Lefèvre <vincent-gcc at vinc17 dot net> --- (In reply to Vincent Lefèvre from comment #22) > Note that if one adds "if (s == u)" (which is true, and noticed by GCC) Sorry, this is not noticed by GCC (I used an incorrect command line). Anyway, the opaque's prevent any optimization.