linux-kernel - Re: [PATCH 6/6] [RESEND] drm/amdgpu: work around llvm bug #42576

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Message-ID: <CAKwvOdmfD-vYNw=YZKBhZhaK04BSMD9xjPJ4seqDe+keHb42_w@mail.gmail.com>
Date:   Wed, 2 Oct 2019 14:06:33 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        Hawking.Zhang@....com, David Airlie <airlied@...ux.ie>,
        "Deucher, Alexander" <alexander.deucher@....com>,
        amd-gfx@...ts.freedesktop.org,
        "Koenig, Christian" <christian.koenig@....com>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Daniel Vetter <daniel@...ll.ch>,
        dri-devel <dri-devel@...ts.freedesktop.org>, le.ma@....com,
        LKML <linux-kernel@...r.kernel.org>, ray.huang@....com
Subject: Re: [PATCH 6/6] [RESEND] drm/amdgpu: work around llvm bug #42576

On Wed, Oct 2, 2019 at 10:07 AM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> On Wed, Oct 02, 2019 at 09:51:37AM -0700, 'Nick Desaulniers' via Clang Built Linux wrote:
> > > Apparently this bug is still present in both the released clang-9
> > > and the current development version of clang-10.
> > > I was hoping we would not need a workaround in clang-9+, but
> > > it seems that we do.

Here's a fix: https://reviews.llvm.org/D68356
Can't possibly land until clang-10 though.

> >
> > I think I'd rather:
> > 1. mark AMDGPU BROKEN if CC_IS_CLANG. There are numerous other issues building
> >    a working driver here.
>
> The only reason I am not thrilled about this is we will lose out on
> warning coverage while the compiler bug gets fixed. I think the AMDGPU
> drivers have been the single biggest source of clang warnings.
>
> I think something like:
>
> depends on CC_IS_GCC || (CC_IS_CLANG && COMPILE_TEST)
>
> would end up avoiding the runtime issues and give us warning coverage.
> The only issue is that we would still need this patch...
>
> Cheers,
> Nathan



-- 
Thanks,
~Nick Desaulniers