https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95237
--- Comment #11 from rguenther at suse dot de <rguenther at suse dot de> --- On Tue, 2 Jun 2020, hjl.tools at gmail dot com wrote: > https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95237 > > --- Comment #10 from H.J. Lu <hjl.tools at gmail dot com> --- > (In reply to rguent...@suse.de from comment #9) > > > > The i386 psABI specifies 4 byte alignment for long long. But we want to > > > use 8 byte alignment if there is no ABI implication and no stack > > > realignment > > > is needed. Will ROUND_TYPE_ALIGN always align long long to 8 bytes? > > > > So what we want here is RTL expansion pad out stack slots if they know > > to be aligned but not adjust DECL_ALIGN. Not sure if there's already > > a target hook to pad out variables, if not this may be the way to get > > what you desire here. > > > > I guess the actual reason is crossing of cache-lines? > > If the incoming stack is 4 byte aligned, we can't align long long to > 8 bytes without stack realignment. I understand. But if the stack is 4 byte aligned only and we don't to stack realignment we may not claim long long is 8 bytes aligned.
