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

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Date:   Thu, 24 Jan 2019 17:03:47 -0800
From:   Matthias Kaehlcke <mka@...omium.org>
To:     ndesaulniers@...gle.com
Cc:     airlied@...ux.ie, daniel@...ll.ch, stable@...r.kernel.org,
        S@...gle.com, Shirish <Shirish.S@....com>,
        James Y Knight <jyknight@...gle.com>,
        Nathan Chancellor <natechancellor@...il.com>,
        Guenter Roeck <linux@...ck-us.net>,
        Harry Wentland <harry.wentland@....com>,
        Leo Li <sunpeng.li@....com>,
        Alex Deucher <alexander.deucher@....com>,
        Christian König <christian.koenig@....com>,
        "David (ChunMing) Zhou" <David1.Zhou@....com>,
        Michel Dänzer <michel.daenzer@....com>,
        Tony Cheng <Tony.Cheng@....com>,
        Dmytro Laktyushkin <Dmytro.Laktyushkin@....com>,
        amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amd/display: add -msse2 to prevent Clang from
 emitting libcalls to undefined SW FP routines

On Thu, Jan 24, 2019 at 04:52:59PM -0800, 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>
> ---
>  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)

Tested-by:  Matthias Kaehlcke <mka@...omium.org>