https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99520
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Consider e.g. unsigned foo (unsigned x) { return (x<<24) + ((x<<8)&0xff0000) + ((x>>8)&0xff00) + (x>>24) + (((x&0xff00)<<16)>>8); } as example that should not be optimized into __builtin_bswap32 (but should be with | instead of +).