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Date:   Tue, 25 Jan 2022 21:19:48 +0000
From:   "Jiaxun Yang" <jiaxun.yang@flygoat.com>
To:     "Nathan Chancellor" <nathan@kernel.org>
Cc:     "Nick Desaulniers" <ndesaulniers@google.com>,
        "Thomas Bogendoerfer" <tsbogend@alpha.franken.de>,
        "Huacai Chen" <chenhuacai@kernel.org>,
        "linux-mips@vger.kernel.org" <linux-mips@vger.kernel.org>,
        linux-kernel@vger.kernel.org, llvm@lists.linux.dev
Subject: Re: [PATCH 1/2] MIPS: Loongson64: Clean up use of cc-ifversion
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=E5=9C=A82022=E5=B9=B41=E6=9C=8825=E6=97=A5=E4=B8=80=E6=9C=88 =E4=B8=8A=E5=
=8D=881:25=EF=BC=8CNathan Chancellor=E5=86=99=E9=81=93=EF=BC=9A
[...]
>
> So something like this (completely untested)?

Yep, tested with multiple GCC toolchains and it works :-)

Thanks.

>
> diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/Plat=
form
> index 3e660d6d3c2b..36ab2fe00835 100644
> --- a/arch/mips/loongson64/Platform
> +++ b/arch/mips/loongson64/Platform
> @@ -5,24 +5,9 @@
>=20
>  cflags-$(CONFIG_CPU_LOONGSON64)	+=3D -Wa,--trap
>=20
> -#
> -# binutils from v2.25 on and gcc starting from v4.9.0 treat=20
> -march=3Dloongson3a
> -# as MIPS64 R2; older versions as just R1.  This leaves the=20
> possibility open
> -# that GCC might generate R2 code for -march=3Dloongson3a which then =
is=20
> rejected
> -# by GAS.  The cc-option can't probe for this behaviour so=20
> -march=3Dloongson3a
> -# can't easily be used safely within the kbuild framework.
> -#
> -ifeq ($(call cc-ifversion, -ge, 0409, y), y)
> -  ifeq ($(call ld-ifversion, -ge, 22500, y), y)
> -    cflags-$(CONFIG_CPU_LOONGSON64)  +=3D \
> -      $(call cc-option,-march=3Dloongson3a -U_MIPS_ISA=20
> -D_MIPS_ISA=3D_MIPS_ISA_MIPS64)
> -  else
> -    cflags-$(CONFIG_CPU_LOONGSON64)  +=3D \
> -      $(call cc-option,-march=3Dmips64r2,-mips64r2 -U_MIPS_ISA=20
> -D_MIPS_ISA=3D_MIPS_ISA_MIPS64)
> -  endif
> -else
> -    cflags-$(CONFIG_CPU_LOONGSON64)  +=3D \
> -      $(call cc-option,-march=3Dmips64r2,-mips64r2 -U_MIPS_ISA=20
> -D_MIPS_ISA=3D_MIPS_ISA_MIPS64)
> +ifdef CONFIG_CPU_LOONGSON64
> +cflags-$(CONFIG_CC_IS_CLANG) +=3D -march=3Dmips64r2
> +cflags-$(CONFIG_CC_IS_GCC) +=3D -march=3Dloongson3a
>  endif
>=20
>  # Some -march=3D flags enable MMI instructions, and GCC complains abo=
ut that
>
>> >
>> > Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
>> >
>> >> ---
>> >>  arch/mips/loongson64/Platform | 13 +++----------
>> >>  1 file changed, 3 insertions(+), 10 deletions(-)
>> >>
>> >> diff --git a/arch/mips/loongson64/Platform b/arch/mips/loongson64/=
Platform
>> >> index 3e660d6d3c2b..981d3abc150e 100644
>> >> --- a/arch/mips/loongson64/Platform
>> >> +++ b/arch/mips/loongson64/Platform
>> >> @@ -12,17 +12,10 @@ cflags-$(CONFIG_CPU_LOONGSON64)     +=3D -Wa,-=
-trap
>> >>  # by GAS.  The cc-option can't probe for this behaviour so -march=
=3Dloongson3a
>> >>  # can't easily be used safely within the kbuild framework.
>> >>  #
>> >> -ifeq ($(call cc-ifversion, -ge, 0409, y), y)
>> >> -  ifeq ($(call ld-ifversion, -ge, 22500, y), y)
>> >> -    cflags-$(CONFIG_CPU_LOONGSON64)  +=3D \
>> >> -      $(call cc-option,-march=3Dloongson3a -U_MIPS_ISA -D_MIPS_IS=
A=3D_MIPS_ISA_MIPS64)
>> >> -  else
>> >> -    cflags-$(CONFIG_CPU_LOONGSON64)  +=3D \
>> >> -      $(call cc-option,-march=3Dmips64r2,-mips64r2 -U_MIPS_ISA -D=
_MIPS_ISA=3D_MIPS_ISA_MIPS64)
>> >> -  endif
>> >> +ifeq ($(CONFIG_CC_IS_GCC)$(call ld-ifversion, -ge, 22500, y), yy)
>> >> +  cflags-$(CONFIG_CPU_LOONGSON64) +=3D -march=3Dloongson3a -U_MIP=
S_ISA -D_MIPS_ISA=3D_MIPS_ISA_MIPS64
>> >>  else
>> >> -    cflags-$(CONFIG_CPU_LOONGSON64)  +=3D \
>> >> -      $(call cc-option,-march=3Dmips64r2,-mips64r2 -U_MIPS_ISA -D=
_MIPS_ISA=3D_MIPS_ISA_MIPS64)
>> >> +  cflags-$(CONFIG_CPU_LOONGSON64) +=3D -march=3Dmips64r2
>> >>  endif
>> >>
>> >>  # Some -march=3D flags enable MMI instructions, and GCC complains=
 about that
>> >>
>> >> base-commit: 2c271fe77d52a0555161926c232cd5bc07178b39
>> >> --
>> >> 2.34.1
>> >>
>> >
>> >
>> > --=20
>> > Thanks,
>> > ~Nick Desaulniers
>>=20
>> --=20
>> - Jiaxun

--=20
- Jiaxun