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From: "Wang, Xiao W" <xiao.w.wang@intel.com>
To: Thorsten Blum <thorsten.blum@toblux.com>, Arnd Bergmann <arnd@arndb.de>
CC: 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-arch@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] bitops: Change function return types from long to int
Thread-Topic: [PATCH] bitops: Change function return types from long to int
Thread-Index: AQHak3OZaQtUtvzCc06TYzDBL0U7LrFzv9wQ
Date: Mon, 22 Apr 2024 05:24:39 +0000
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References: <20240420223836.241472-1-thorsten.blum@toblux.com>
In-Reply-To: <20240420223836.241472-1-thorsten.blum@toblux.com>
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> -----Original Message-----
> From: Thorsten Blum <thorsten.blum@toblux.com>
> Sent: Sunday, April 21, 2024 6:39 AM
> To: Arnd Bergmann <arnd@arndb.de>
> Cc: Wang, Xiao W <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; Thorsten Blum <thorsten.blum@toblux.com>
> Subject: [PATCH] bitops: Change function return types from long to int
>=20
> 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.
>=20
> Additionally, int aligns well with the return types of the corresponding
> __builtin_* functions, potentially reducing overall type conversions.

Could we change the return types to "int", instead of "unsigned int"?
https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html says that these __bu=
iltin_*
functions return "int".

>=20
> 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.
>=20
> Adjust some return variables to match the function return types.
>=20
> 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.

I guess your test is based on 64bit arch, right?

BRs,
Xiao