https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64099
--- Comment #4 from Dominique d'Humieres <dominiq at lps dot ens.fr> --- > Ugh - -Ofast is an alias for -O3 -ffast-math. Ah, no - it also enables > --param allow-store-data-races=1 ... -Ofast Disregard strict standards compliance. -Ofast enables all -O3 optimizations. It also enables optimizations that are not valid for all standard-compliant programs. It turns on -ffast-math and the Fortran-specific -fno-protect-parens and -fstack-arrays. My guess is that -fstack-arrays makes the difference.
