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

[Alex Deucher]

On Fri, Jan 25, 2019 at 10:29 AM Wentland, Harry <Harry.Wentland@xxxxxxx> wrote:
>
> On 2019-01-24 7:52 p.m., ndesaulniers@xxxxxxxxxx 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@xxxxxxxxxxxxxxx # 4.19
> > Reported-by: S, Shirish <Shirish.S@xxxxxxx>
> > Reported-by: Matthias Kaehlcke <mka@xxxxxxxxxx>
> > Suggested-by: James Y Knight <jyknight@xxxxxxxxxx>
> > Suggested-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
> > Signed-off-by: Nick Desaulniers <ndesaulniers@xxxxxxxxxx>
> > Tested-by: Guenter Roeck <linux@xxxxxxxxxxxx>
>
> Reviewed-by: Harry Wentland <harry.wentland@xxxxxxx>
>
> 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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