From: "Amadeusz Sławiński" <amadeuszx.slawinski@linux.intel.com>
To: Thorsten Blum <thorsten.blum@toblux.com>, Arnd Bergmann <arnd@arndb.de>
Cc: Xiao Wang <xiao.w.wang@intel.com>,
Palmer Dabbelt <palmer@rivosinc.com>,
Charlie Jenkins <charlie@rivosinc.com>,
Namhyung Kim <namhyung@kernel.org>,
Huacai Chen <chenhuacai@kernel.org>,
Youling Tang <tangyouling@loongson.cn>,
Tiezhu Yang <yangtiezhu@loongson.cn>,
Jinyang He <hejinyang@loongson.cn>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] bitops: Change function return types from long to int
Date: Mon, 22 Apr 2024 09:44:40 +0200 [thread overview]
Message-ID: <42e6a510-9000-44a4-b6bf-2bca9cf74d5e@linux.intel.com> (raw)
In-Reply-To: <20240420223836.241472-1-thorsten.blum@toblux.com>
On 4/21/2024 12:38 AM, Thorsten Blum wrote:
> Change the return types of bitops functions (ffs, fls, and fns) from
> long to int. The expected return values are in the range [0, 64], for
> which int is sufficient.
>
> Additionally, int aligns well with the return types of the corresponding
> __builtin_* functions, potentially reducing overall type conversions.
>
> Many of the existing bitops functions already return an int and don't
> need to be changed. The bitops functions in arch/ should be considered
> separately.
>
> Adjust some return variables to match the function return types.
>
> With GCC 13 and defconfig, these changes reduced the size of a test
> kernel image by 5,432 bytes on arm64 and by 248 bytes on riscv; there
> were no changes in size on x86_64, powerpc, or m68k.
>
> Signed-off-by: Thorsten Blum <thorsten.blum@toblux.com>
> ---
> include/asm-generic/bitops/__ffs.h | 4 ++--
> include/asm-generic/bitops/__fls.h | 4 ++--
> include/asm-generic/bitops/builtin-__ffs.h | 2 +-
> include/asm-generic/bitops/builtin-__fls.h | 2 +-
> include/linux/bitops.h | 6 +++---
> tools/include/asm-generic/bitops/__ffs.h | 4 ++--
> tools/include/asm-generic/bitops/__fls.h | 4 ++--
> tools/include/linux/bitops.h | 2 +-
> 8 files changed, 14 insertions(+), 14 deletions(-)
I don't mind the idea, but in the past I've send some patches trying to
align some arch specific implementations with asm-generic ones. Now you
are changing only asm-generic implementation and leaving arch specific
ones untouched (that's probably why you see no size change on some of them).
For example on x86, there is:
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/include/asm/bitops.h?id=ed30a4a51bb196781c8058073ea720133a65596f#n293
and you probably need to check all architectures for those implementations.
Thanks,
Amadeusz
next prev parent reply other threads:[~2024-04-22 7:44 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-20 22:38 [PATCH] bitops: Change function return types from long to int Thorsten Blum
2024-04-22 5:24 ` Wang, Xiao W
2024-04-22 9:15 ` Thorsten Blum
2024-04-22 7:44 ` Amadeusz Sławiński [this message]
2024-04-22 14:30 ` Thorsten Blum
2024-04-22 15:55 ` Arnd Bergmann
2024-04-23 11:45 ` Thorsten Blum
2024-05-03 14:49 ` Thorsten Blum
2024-05-03 15:05 ` Arnd Bergmann
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