linux-kernel - Re: [PATCH] arm: memset: zero out upper bytes in r1

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Message-id: <536B3946.9070106@samsung.com>
Date:	Thu, 08 May 2014 11:59:02 +0400
From:	Andrey Ryabinin <a.ryabinin@...sung.com>
To:	Afzal Mohammed <afzal.mohd.ma@...il.com>
Cc:	linux@....linux.org.uk, open list <linux-kernel@...r.kernel.org>,
	"moderated list:ARM PORT" <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] arm: memset: zero out upper bytes in r1

On 05/08/14 03:42, Afzal Mohammed wrote:
> 
> int is to be converted to unsigned char in memset, would having above
> change immediately upon entry to memset rather than at a place where it
> won't always execute make intention clearer ? (although it doesn't make
> difference)
> 

I think it's better to keep it near other manipulations with r1.
Plus this will save us from executing extra instruction on 'memset -> 6 -> 5 -> return'
path (memset for size <= 3).


> ubfx r1, r1, #0, #8 would have given the needed typecasting, but seems
> it is available only on ARMv6T2 & above.
> 

Indeed. It might be wrapped it with #if #else, but it will be a bit ugly,
probably not worth to do.




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