linux-kernel - Re: [PATCH] ARC: bitops: Remove unecessary operation and value

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Date:   Thu, 5 Nov 2020 23:16:42 +0000
From:   Vineet Gupta <Vineet.Gupta1@...opsys.com>
To:     Gustavo Pimentel <Gustavo.Pimentel@...opsys.com>
CC:     Joao Pinto <Joao.Pinto@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ARC: bitops: Remove unecessary operation and value

On 10/21/20 2:12 PM, Gustavo Pimentel wrote:
> The 1-bit shift rotation to the left on x variable located on
> 4   last if statement can be removed because the computed value is will
> not be used afront.

All of constant_fls() is anyhow optimized away at compile time, so this 
won't affect any code-gen at all, still this patch is legit.

> Signed-off-by: Gustavo Pimentel <gustavo.pimentel@...opsys.com>

Added to for-curr !

Thx,
-Vineet

> ---
>   arch/arc/include/asm/bitops.h | 4 +---
>   1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/arch/arc/include/asm/bitops.h b/arch/arc/include/asm/bitops.h
> index 50eb3f6..8cddddc 100644
> --- a/arch/arc/include/asm/bitops.h
> +++ b/arch/arc/include/asm/bitops.h
> @@ -297,10 +297,8 @@ static inline int constant_fls(unsigned int x)
>   		x <<= 2;
>   		r -= 2;
>   	}
> -	if (!(x & 0x80000000u)) {
> -		x <<= 1;
> +	if (!(x & 0x80000000u))
>   		r -= 1;
> -	}
>   	return r;
>   }
>