> On Fri, Jun 22, 2012 at 11:15 AM, Jan Hubicka <hubi...@ucw.cz> wrote:
> >> >
> >>
> >> Here is the patch for invoke.texi. OK to install?
> >>
> >> I will prepare a similar one for news.html.
> >>
> >> Thanks.
> >>
> >> --
> >> H.J.
> >> ---
> >> diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
> >> index 029a7ab..87e0d1c 100644
> >> --- a/gcc/doc/invoke.texi
> >> +++ b/gcc/doc/invoke.texi
> >> @@ -13579,9 +13579,18 @@ the default is 4 (16 bytes or 128 bits).
> >>
> >> @strong{Warning:} When generating code for the x86-64 architecture with
> >> SSE extensions disabled, @option{-mpreferred-stack-boundary=3} can be
> >> -used to keep the stack boundary aligned to 8 byte boundary. You must
> >> -build all modules with @option{-mpreferred-stack-boundary=3}, including
> >> -any libraries. This includes the system libraries and startup modules.
> >> +used to keep the stack boundary aligned to 8 byte boundary. Since
> >> +x86-64 ABI require 16 byte stack alignment, this is ABI incompatible and
> >> +intended to be used in controlled environment where stack space is
> >> +important limitation. This option will lead to wrong code when functions
> >> +compiled with 16 byte stack alignment (such as functions from a standard
> >> +library) are called with misaligned stack. In this case, SSE
> >> +instructions may lead to misaligned memory access traps. In addition,
> >> +variable arguments will be handled incorrectly for 16 byte aligned
> >> +objects (including x87 long double and __int128), leading to wrong
> >> +results. You must build all modules with
> >> +@option{-mpreferred-stack-boundary=3}, including any libraries. This
> >> +includes the system libraries and startup modules.
> >
> > This is not true in a strict sense. One can build some part with 16 byte
> > alignment and just watch to not call from 8byte world to 16byte world, but
> > I am
> > fine with it. (I guess -mpreferred-stack-boundary=3 is something to try on
> > recursion heavy benchmarks as some in SPEC and I would also expect resulting
> > binary to just work most of time ;)
> >
> > OK, Thanks!
> > Honza
> >>
> >> @item -mincoming-stack-boundary=@var{num}
> >> @opindex mincoming-stack-boundary
>
> I am not sure if news.html is the best place for this.
> How about putting it in gcc-4.8/changes.html? Does
> it look OK?
Yes, I meant changes.html, sorry.
Just to have it documented since when this is allowed.
Thanks,
Honza
