https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109276
--- Comment #17 from Uroš Bizjak <ubizjak at gmail dot com> --- (In reply to Jakub Jelinek from comment #16) > (In reply to Uroš Bizjak from comment #15) > > (In reply to Jakub Jelinek from comment #13) > > > asks for a DImode stack slot, ix86_local_alignment newly doesn't lower the > > > alignment > > > which isn't good for -mpreferred-stack-boundary=2. > > > > IIRC, DImode FILD/FIST(P) instructions execute faster when memory is aligned > > to 64 bits. *If* it is possible, 64 bit alignment is preferred. > > Well, user who uses -mpreferred-stack-boundary=2 probably doesn't care about > performance that much. I guess I could also check whether we've already > decided to dynamically reallocate the stack for some other reasons and only > use 32-bit alignment if we haven't. > But there are too many such flags, so not sure what to check. No need to complicate things too much, I agree that by using -mpreferred-stack-boundary=2 user made a compromise w.r.t. performance.
