linux-kernel - Re: [PATCH] drm/amd/display: add -msse2 to prevent Clang from emitting libcalls to undefined SW FP routines

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Message-ID: <CADnq5_OuSD7Bmeg3CP0Y6JTo9Xso2FTZ3tKk-u1C+-B32eUGmQ@mail.gmail.com>
Date:   Tue, 29 Jan 2019 10:30:31 -0500
From:   Alex Deucher <alexdeucher@...il.com>
To:     "Wentland, Harry" <Harry.Wentland@....com>
Cc:     "ndesaulniers@...gle.com" <ndesaulniers@...gle.com>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "daniel@...ll.ch" <daniel@...ll.ch>, "S@...gle.com" <S@...gle.com>,
        "Laktyushkin, Dmytro" <Dmytro.Laktyushkin@....com>,
        "Zhou, David(ChunMing)" <David1.Zhou@....com>,
        "Li, Sun peng (Leo)" <Sunpeng.Li@....com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        "Daenzer, Michel" <Michel.Daenzer@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "S, Shirish" <Shirish.S@....com>,
        Matthias Kaehlcke <mka@...gle.com>,
        Matthias Kaehlcke <mka@...omium.org>,
        "amd-gfx@...ts.freedesktop.org" <amd-gfx@...ts.freedesktop.org>,
        James Y Knight <jyknight@...gle.com>,
        "Deucher, Alexander" <Alexander.Deucher@....com>,
        Nathan Chancellor <natechancellor@...il.com>,
        "Cheng, Tony" <Tony.Cheng@....com>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        Guenter Roeck <linux@...ck-us.net>
Subject: Re: [PATCH] drm/amd/display: add -msse2 to prevent Clang from
 emitting libcalls to undefined SW FP routines

On Fri, Jan 25, 2019 at 10:29 AM Wentland, Harry <Harry.Wentland@....com> wrote:
>
> On 2019-01-24 7:52 p.m., ndesaulniers@...gle.com wrote:
> > arch/x86/Makefile disables SSE and SSE2 for the whole kernel.  The
> > AMDGPU drivers modified in this patch re-enable SSE but not SSE2.  Turn
> > on SSE2 to support emitting double precision floating point instructions
> > rather than calls to non-existent (usually available from gcc_s or
> > compiler_rt) floating point helper routines.
> >
> > Link: https://gcc.gnu.org/onlinedocs/gccint/Soft-float-library-routines.html
> > Link: https://github.com/ClangBuiltLinux/linux/issues/327
> > Cc: stable@...r.kernel.org # 4.19
> > Reported-by: S, Shirish <Shirish.S@....com>
> > Reported-by: Matthias Kaehlcke <mka@...gle.com>
> > Suggested-by: James Y Knight <jyknight@...gle.com>
> > Suggested-by: Nathan Chancellor <natechancellor@...il.com>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
> > Tested-by: Guenter Roeck <linux@...ck-us.net>
>
> Reviewed-by: Harry Wentland <harry.wentland@....com>
>
> and applied.
>

This patch causes a segfault:
https://bugs.freedesktop.org/show_bug.cgi?id=109487

Any ideas?

Alex

> Harry
>
> > ---
> >  drivers/gpu/drm/amd/display/dc/calcs/Makefile | 2 +-
> >  drivers/gpu/drm/amd/display/dc/dml/Makefile   | 2 +-
> >  2 files changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/display/dc/calcs/Makefile b/drivers/gpu/drm/amd/display/dc/calcs/Makefile
> > index 95f332ee3e7e..dc85a3c088af 100644
> > --- a/drivers/gpu/drm/amd/display/dc/calcs/Makefile
> > +++ b/drivers/gpu/drm/amd/display/dc/calcs/Makefile
> > @@ -30,7 +30,7 @@ else ifneq ($(call cc-option, -mstack-alignment=16),)
> >       cc_stack_align := -mstack-alignment=16
> >  endif
> >
> > -calcs_ccflags := -mhard-float -msse $(cc_stack_align)
> > +calcs_ccflags := -mhard-float -msse -msse2 $(cc_stack_align)
> >
> >  CFLAGS_dcn_calcs.o := $(calcs_ccflags)
> >  CFLAGS_dcn_calc_auto.o := $(calcs_ccflags)
> > diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> > index d97ca6528f9d..33c7d7588712 100644
> > --- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
> > +++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> > @@ -30,7 +30,7 @@ else ifneq ($(call cc-option, -mstack-alignment=16),)
> >       cc_stack_align := -mstack-alignment=16
> >  endif
> >
> > -dml_ccflags := -mhard-float -msse $(cc_stack_align)
> > +dml_ccflags := -mhard-float -msse -msse2 $(cc_stack_align)
> >
> >  CFLAGS_display_mode_lib.o := $(dml_ccflags)
> >  CFLAGS_display_pipe_clocks.o := $(dml_ccflags)
> >
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@...ts.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

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