linux-kernel - Re: [PATCH] LoongArch: Select ARCH_HAS_FAST

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Date: Fri, 29 Mar 2024 10:09:46 +0800
From: Huacai Chen <chenhuacai@...nel.org>
To: Xi Ruoyao <xry111@...111.site>
Cc: WANG Xuerui <kernel@...0n.name>, loongarch@...ts.linux.dev, 
	linux-kernel@...r.kernel.org, Tiezhu Yang <yangtiezhu@...ngson.cn>
Subject: Re: [PATCH] LoongArch: Select ARCH_HAS_FAST_MULTIPLIER

Queued for loongarch-next, thanks.

Huacai

On Thu, Mar 28, 2024 at 1:18 AM Xi Ruoyao <xry111@...111.site> wrote:
>
> LA464 and LA664 can do 32-bit/64-bit integer multiplication with a
> latency of 4 cycles and a throughput of 2 ops per cycle.  It's
> comparable to mainstream x86 and arm64 cores, so select
> ARCH_HAS_FAST_MULTIPLIER like them.
>
> It speeds up __sw_hweight32 in lib/hweight.c for about 14% on LA464 and
> 11% on LA664, and __sw_hweight64 for about 30% on LA464 and 33% on
> LA664.
>
> Signed-off-by: Xi Ruoyao <xry111@...111.site>
> ---
>  arch/loongarch/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
> index 5a769bb92d7c..d52a95195e7f 100644
> --- a/arch/loongarch/Kconfig
> +++ b/arch/loongarch/Kconfig
> @@ -16,6 +16,7 @@ config LOONGARCH
>         select ARCH_HAS_ACPI_TABLE_UPGRADE      if ACPI
>         select ARCH_HAS_CPU_FINALIZE_INIT
>         select ARCH_HAS_CURRENT_STACK_POINTER
> +       select ARCH_HAS_FAST_MULTIPLIER
>         select ARCH_HAS_FORTIFY_SOURCE
>         select ARCH_HAS_KCOV
>         select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS
> --
> 2.44.0
>