linux-kernel - Re: AMDGPU and 16B stack alignment

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Message-ID: <CAKwvOdmEDQ1yy0A1Z+x-8MX6taBJPaAseghpHxphrUi29wWRfA@mail.gmail.com>
Date:   Tue, 15 Oct 2019 11:11:28 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Arnd Bergmann <arnd@...db.de>, "S, Shirish" <sshankar@....com>
Cc:     "Wentland, Harry" <Harry.Wentland@....com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        "yshuiv7@...il.com" <yshuiv7@...il.com>,
        "andrew.cooper3@...rix.com" <andrew.cooper3@...rix.com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Matthias Kaehlcke <mka@...gle.com>,
        "S, Shirish" <Shirish.S@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        amd-gfx list <amd-gfx@...ts.freedesktop.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: AMDGPU and 16B stack alignment

On Tue, Oct 15, 2019 at 11:05 AM Nick Desaulniers
<ndesaulniers@...gle.com> wrote:
>
> On Tue, Oct 15, 2019 at 12:19 AM Arnd Bergmann <arnd@...db.de> wrote:
> >
> > On Tue, Oct 15, 2019 at 9:08 AM S, Shirish <sshankar@....com> wrote:
> > > On 10/15/2019 3:52 AM, Nick Desaulniers wrote:
> >
> > > My gcc build fails with below errors:
> > >
> > > dcn_calcs.c:1:0: error: -mpreferred-stack-boundary=3 is not between 4 and 12
> > >
> > > dcn_calc_math.c:1:0: error: -mpreferred-stack-boundary=3 is not between 4 and 12
>
> I was able to reproduce this failure on pre-7.1 versions of GCC.  It
> seems that when:
> 1. code is using doubles
> 2. setting -mpreferred-stack-boundary=3 -mno-sse2, ie. 8B stack alignment
> than GCC produces that error:
> https://godbolt.org/z/7T8nbH
>

Also, I suspect that very error solves the mystery of "why was 16B
stack alignment ever specified?"
-- 
Thanks,
~Nick Desaulniers