[Bug target/111107] i686-w64-mingw32 does not realign stack when __attribute__((aligned)) or __attribute__((vector_size)) are used

["zfigura at codeweavers dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111107

--- Comment #4 from Zebediah Figura <zfigura at codeweavers dot com> ---
(In reply to Andrew Pinski from comment #3)
> https://inbox.sourceware.org/gcc-patches/5969976.Bvae8NF9fS@polaris/

Again, I'm not sure what you're trying to communicate here. I'm aware that
-mstackrealign exists (and its attribute equivalent). We *do* use that in Wine.

Here is, again, what I am trying to communicate: Currently i686-w64-mingw32-gcc
effectly assumes 4-byte stack alignment in some places (when -msse2 is used),
and 16-byte alignment in others (when __attribute__((aligned)) is used). I am
trying to request that it pick one or the other and stick with it.

Now, personally, I think that assuming 4-byte stack alignment makes more
*sense*. Otherwise *every* API function needs that extra alignment, which is
wasteful when comparatively little code actually uses types aligned to 8 or
more bytes. (It obviously makes more sense if you can get the whole API to
agree on 16-bytes; then you don't have to manually align anything).

But if there's a clear consensus that gcc should assume 16 bytes, and that it's
Wine's responsibility to set -mstackrealign, or -mincoming-stack-boundary=2, or
something, fine, but I'd like GCC to be consistent about that policy. Otherwise
it looks like this behaviour is a bug. That's why I reported this as a bug.