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

From: Alex Deucher <alexdeucher@gmail.com>
To: "Wentland, Harry" <Harry.Wentland@amd.com>
Cc: "ndesaulniers@google.com" <ndesaulniers@google.com>,
	"airlied@linux.ie" <airlied@linux.ie>,
	"daniel@ffwll.ch" <daniel@ffwll.ch>,
	"S@google.com" <S@google.com>,
	"Laktyushkin, Dmytro" <Dmytro.Laktyushkin@amd.com>,
	"Zhou, David(ChunMing)" <David1.Zhou@amd.com>,
	"Li, Sun peng (Leo)" <Sunpeng.Li@amd.com>,
	"dri-devel@lists.freedesktop.org"
	<dri-devel@lists.freedesktop.org>,
	"Daenzer, Michel" <Michel.Daenzer@amd.com>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"S, Shirish" <Shirish.S@amd.com>,
	Matthias Kaehlcke <mka@google.com>,
	Matthias Kaehlcke <mka@chromium.org>,
	"amd-gfx@lists.freedesktop.org" <amd-gfx@lists.freedesktop.org>,
	James Y Knight <jyknight@google.com>,
	"Deucher, Alexander" <Alexander.Deucher@amd.com>,
	Nathan Chancellor <natechancellor@gmail.com>,
	"Cheng, Tony" <Tony.Cheng@amd.com>,
	"Koenig, Christian" <Christian.Koenig@amd.com>,
	Guenter Roeck <linux@roeck-us.net>
Subject: Re: [PATCH] drm/amd/display: add -msse2 to prevent Clang from emitting libcalls to undefined SW FP routines
Date: Tue, 29 Jan 2019 10:30:31 -0500	[thread overview]
Message-ID: <CADnq5_OuSD7Bmeg3CP0Y6JTo9Xso2FTZ3tKk-u1C+-B32eUGmQ@mail.gmail.com> (raw)
In-Reply-To: <04bc6844-2a3b-2de8-60a7-a027149709fd@amd.com>

On Fri, Jan 25, 2019 at 10:29 AM Wentland, Harry <Harry.Wentland@amd.com> wrote:
>
> On 2019-01-24 7:52 p.m., ndesaulniers@google.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@vger.kernel.org # 4.19
> > Reported-by: S, Shirish <Shirish.S@amd.com>
> > Reported-by: Matthias Kaehlcke <mka@google.com>
> > Suggested-by: James Y Knight <jyknight@google.com>
> > Suggested-by: Nathan Chancellor <natechancellor@gmail.com>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
> > Tested-by: Guenter Roeck <linux@roeck-us.net>
>
> Reviewed-by: Harry Wentland <harry.wentland@amd.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)
> >
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