From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Segher Boessenkool <segher@kernel.crashing.org>
Cc: Anton Blanchard <anton@samba.org>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Paul Mackerras <paulus@samba.org>,
acsawdey@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH 2/2] powerpc: Align hot loops of some string functions
Date: Fri, 27 May 2016 07:45:18 +0200 [thread overview]
Message-ID: <91429364-b0f4-89c2-dc92-1cc40970d3e3@c-s.fr> (raw)
In-Reply-To: <20160526193728.GA883@gate.crashing.org>
Le 26/05/2016 à 21:37, Segher Boessenkool a écrit :
> On Thu, May 26, 2016 at 09:24:51AM +0200, Christophe Leroy wrote:
>> Wouldn't it be better to add nops before the function entry in order to
>> get the hot loop aligned, instead of adding nops in the middle of the
>> function ?
> Why would that be better? The nops are executed once per function call
> in either case, there are the same number of nops in either case, and
> on most CPUs nops aren't actually executed anyway (they are decoded and
> the thrown away).
>
The idea was to not execute them:
|.balign 16 nop nop _GLOBAL(strcpy) addi r5,r3,-1 addi r4,r4,-1 1: lbzu
r0,1(r4) cmpwi 0,r0,0 stbu r0,1(r5) bne 1b blr |
Christophe
next prev parent reply other threads:[~2016-05-27 5:45 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-25 22:38 [PATCH 1/2] powerpc: Remove assembly versions of strcpy, strcat, strlen and strcmp Anton Blanchard
2016-05-25 22:39 ` [PATCH 2/2] powerpc: Align hot loops of some string functions Anton Blanchard
2016-05-26 7:24 ` Christophe Leroy
2016-05-26 19:37 ` Segher Boessenkool
2016-05-27 5:45 ` Christophe Leroy [this message]
2016-05-27 6:26 ` Segher Boessenkool
2016-06-15 12:39 ` [2/2] " Michael Ellerman
2016-06-15 12:39 ` [1/2] powerpc: Remove assembly versions of strcpy, strcat, strlen and strcmp Michael Ellerman
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