Re: [PATCH] drm/amdgpu/dc: don't pass -mhard-float to clang

From: Nick Desaulniers <ndesaulniers@google.com>
To: Arnd Bergmann <arnd@arndb.de>
Cc: clang-built-linux <clang-built-linux@googlegroups.com>,
	"Masahiro Yamada" <yamada.masahiro@socionext.com>,
	"Leo Li" <sunpeng.li@amd.com>, "Marc Zyngier" <maz@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	"amd-gfx list" <amd-gfx@lists.freedesktop.org>,
	"Bhawanpreet Lakha" <Bhawanpreet.Lakha@amd.com>,
	"David Airlie" <airlied@linux.ie>,
	"Timothy Pearson" <tpearson@raptorengineering.com>,
	dri-devel <dri-devel@lists.freedesktop.org>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Charlene Liu" <charlene.liu@amd.com>,
	"Christian König" <christian.koenig@amd.com>,
	"Anthony Koo" <Anthony.Koo@amd.com>
Subject: Re: [PATCH] drm/amdgpu/dc: don't pass -mhard-float to clang
Date: Tue, 5 May 2020 08:48:36 -0700	[thread overview]
Message-ID: <CAKwvOdnBqYs1qJPm4apkGeHUgEZ+ZKe0j0h=eXWy9ACF+OS_HA@mail.gmail.com> (raw)
In-Reply-To: <20200505142519.1138945-1-arnd@arndb.de>

On Tue, May 5, 2020 at 7:25 AM Arnd Bergmann <arnd@arndb.de> wrote:
>
> Clang does not appear to care, and instead prints a warning:
>
> clang: warning: argument unused during compilation: '-mhard-float' [-Wunused-command-line-argument]
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

I want to be super careful here, this part of the build has been super
tricky in the past.  Just noting before this potentially gets merged
without any testing; we should verify the generated code does not
change with Clang.  In the past, this code compiled but would GPF
sometimes when called into via userspace (see my previous commits
here).

> ---
>  drivers/gpu/drm/amd/display/dc/calcs/Makefile | 5 +++--
>  drivers/gpu/drm/amd/display/dc/dcn20/Makefile | 5 +++--
>  drivers/gpu/drm/amd/display/dc/dcn21/Makefile | 5 +++--
>  drivers/gpu/drm/amd/display/dc/dml/Makefile   | 5 +++--
>  drivers/gpu/drm/amd/display/dc/dsc/Makefile   | 5 +++--
>  5 files changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/calcs/Makefile b/drivers/gpu/drm/amd/display/dc/calcs/Makefile
> index 4674aca8f206..64195cacf6fc 100644
> --- a/drivers/gpu/drm/amd/display/dc/calcs/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/calcs/Makefile
> @@ -26,14 +26,15 @@
>  #
>
>  ifdef CONFIG_X86
> -calcs_ccflags := -mhard-float -msse
> +calcs_ccflags := -msse
>  endif
>
>  ifdef CONFIG_PPC64
> -calcs_ccflags := -mhard-float -maltivec
> +calcs_ccflags := -maltivec
>  endif
>
>  ifdef CONFIG_CC_IS_GCC
> +calcs_ccflags += -mhard-float
>  ifeq ($(call cc-ifversion, -lt, 0701, y), y)
>  IS_OLD_GCC = 1
>  endif
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn20/Makefile b/drivers/gpu/drm/amd/display/dc/dcn20/Makefile
> index 5fcaf78334ff..0d3ce716c753 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn20/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn20/Makefile
> @@ -10,14 +10,15 @@ DCN20 = dcn20_resource.o dcn20_init.o dcn20_hwseq.o dcn20_dpp.o dcn20_dpp_cm.o d
>  DCN20 += dcn20_dsc.o
>
>  ifdef CONFIG_X86
> -CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o := -mhard-float -msse
> +CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o := -msse
>  endif
>
>  ifdef CONFIG_PPC64
> -CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o := -mhard-float -maltivec
> +CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o := -maltivec
>  endif
>
>  ifdef CONFIG_CC_IS_GCC
> +CFLAGS_$(AMDDALPATH)/dc/dcn20/dcn20_resource.o += -mhard-float
>  ifeq ($(call cc-ifversion, -lt, 0701, y), y)
>  IS_OLD_GCC = 1
>  endif
> diff --git a/drivers/gpu/drm/amd/display/dc/dcn21/Makefile b/drivers/gpu/drm/amd/display/dc/dcn21/Makefile
> index 07684d3e375a..fd209d1cf6bb 100644
> --- a/drivers/gpu/drm/amd/display/dc/dcn21/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dcn21/Makefile
> @@ -6,14 +6,15 @@ DCN21 = dcn21_init.o dcn21_hubp.o dcn21_hubbub.o dcn21_resource.o \
>          dcn21_hwseq.o dcn21_link_encoder.o
>
>  ifdef CONFIG_X86
> -CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o := -mhard-float -msse
> +CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o := -msse
>  endif
>
>  ifdef CONFIG_PPC64
> -CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o := -mhard-float -maltivec
> +CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o := -maltivec
>  endif
>
>  ifdef CONFIG_CC_IS_GCC
> +CFLAGS_$(AMDDALPATH)/dc/dcn21/dcn21_resource.o += -mhard-float
>  ifeq ($(call cc-ifversion, -lt, 0701, y), y)
>  IS_OLD_GCC = 1
>  endif
> diff --git a/drivers/gpu/drm/amd/display/dc/dml/Makefile b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> index 7ee8b8460a9b..fb74e79e15a2 100644
> --- a/drivers/gpu/drm/amd/display/dc/dml/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dml/Makefile
> @@ -26,14 +26,15 @@
>  # subcomponents.
>
>  ifdef CONFIG_X86
> -dml_ccflags := -mhard-float -msse
> +dml_ccflags := -msse
>  endif
>
>  ifdef CONFIG_PPC64
> -dml_ccflags := -mhard-float -maltivec
> +dml_ccflags := -maltivec
>  endif
>
>  ifdef CONFIG_CC_IS_GCC
> +dml_ccflags += -mhard-float
>  ifeq ($(call cc-ifversion, -lt, 0701, y), y)
>  IS_OLD_GCC = 1
>  endif
> diff --git a/drivers/gpu/drm/amd/display/dc/dsc/Makefile b/drivers/gpu/drm/amd/display/dc/dsc/Makefile
> index 3f66868df171..b0077f5c318d 100644
> --- a/drivers/gpu/drm/amd/display/dc/dsc/Makefile
> +++ b/drivers/gpu/drm/amd/display/dc/dsc/Makefile
> @@ -3,14 +3,15 @@
>  # Makefile for the 'dsc' sub-component of DAL.
>
>  ifdef CONFIG_X86
> -dsc_ccflags := -mhard-float -msse
> +dsc_ccflags := -msse
>  endif
>
>  ifdef CONFIG_PPC64
> -dsc_ccflags := -mhard-float -maltivec
> +dsc_ccflags := -maltivec
>  endif
>
>  ifdef CONFIG_CC_IS_GCC
> +dsc_ccflags += -mhard-float
>  ifeq ($(call cc-ifversion, -lt, 0701, y), y)
>  IS_OLD_GCC = 1
>  endif
> --
> 2.26.0
>

-- 
Thanks,
~Nick Desaulniers
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