https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108279
--- Comment #21 from Wilco <wilco at gcc dot gnu.org> --- (In reply to Jakub Jelinek from comment #20) > __attribute__((noinline, optimize ("rounding-math"))) static int > round_to_nearest (void) { return 1.0f - __FLT_MIN__ == 1.0f + __FLT_MIN__; } Wouldn't that always set inexact? > and > if (round_to_nearest ()) \ > _fcw = FP_RND_NEAREST; \ > else \ > __asm__ __volatile__ ("%vstmxcsr\t%0" : "=m" (_fcw)); \ > > Except that from _fcw we don't determine just the rounding mode but also > what exceptions are enabled. Yes that wouldn't work in fenv but FP emulation functions don't need to read the exception flags.