linux-kernel - Re: [PATCH] riscv: move GCC version check for ARCH_SUPPORTS

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Date:   Thu, 6 Sep 2018 19:45:56 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Palmer Dabbelt <palmer@...ive.com>
Cc:     aou@...s.berkeley.edu, linux-riscv@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] riscv: move GCC version check for ARCH_SUPPORTS_INT128 to Kconfig

Hi Palmer,

2018-09-06 18:45 GMT+09:00 Palmer Dabbelt <palmer@...ive.com>:
> On Fri, 24 Aug 2018 01:33:53 PDT (-0700), yamada.masahiro@...ionext.com
> wrote:
>>
>> This becomes much neater in Kconfig.
>>
>> Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>> ---
>>
>>  arch/riscv/Kconfig  | 1 +
>>  arch/riscv/Makefile | 2 --
>>  2 files changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
>> index a344980..ed81df4 100644
>> --- a/arch/riscv/Kconfig
>> +++ b/arch/riscv/Kconfig
>> @@ -112,6 +112,7 @@ config ARCH_RV32I
>>  config ARCH_RV64I
>>         bool "RV64I"
>>         select 64BIT
>> +       select ARCH_SUPPORTS_INT128 if GCC_VERSION >= 50000
>>         select HAVE_FUNCTION_TRACER
>>         select HAVE_FUNCTION_GRAPH_TRACER
>>         select HAVE_FTRACE_MCOUNT_RECORD
>> diff --git a/arch/riscv/Makefile b/arch/riscv/Makefile
>> index 61ec424..33700e4 100644
>> --- a/arch/riscv/Makefile
>> +++ b/arch/riscv/Makefile
>> @@ -25,8 +25,6 @@ ifeq ($(CONFIG_ARCH_RV64I),y)
>>
>>         KBUILD_CFLAGS += -mabi=lp64
>>         KBUILD_AFLAGS += -mabi=lp64
>> -
>> -       KBUILD_CFLAGS   += $(call cc-ifversion, -ge, 0500,
>> -DCONFIG_ARCH_SUPPORTS_INT128)
>>
>>         KBUILD_MARCH = rv64im
>>         KBUILD_LDFLAGS += -melf64lriscv
>
>
> FWIW, while there isn't an official RISC-V GCC port that old (IIRC 6 was our
> first version, but it may have been 7) there are out-of-tree ports so I
> think this is OK to leave as it stands.


It is not my point.
I would not argue the minimum GCC version for RISC-V.


My motivation:

[1] Remove (or move to Kconfig)
    $(call cc-ifversion, ...) from Makefile.

    If you test the GCC version in arch/riscv/Makefile,
    scripts/gcc-version.sh  is invoked for every incremental build.


[2] Follow the macro naming convention

    We add CONFIG_ prefix to macros defined in Kconfig.

    I know some CONFIG options are defined in Makefiles,
    but my ultimate goal is to move all CONFIG options to Kconfig.

    See arch/{arm64,x86}/Kconfig that select ARCH_SUPPORTS_INT128



If you think GCC 6 or 7 is the minimum,
please feel free to remove "if GCC_VERSION >= 50000",
but it is not my main interest here
(and it should be done as a separate work).



-- 
Best Regards
Masahiro Yamada