linux-kernel - Re: [PATCH 0/1] vsprintf: optimize decimal conversion (again)

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Date:	Wed, 28 Mar 2012 13:20:07 +0200
From:	Denys Vlasenko <vda.linux@...glemail.com>
To:	roma1390 <roma1390@...il.com>
Cc:	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Douglas W Jones <jones@...uiowa.edu>,
	Michal Nazarewicz <mnazarewicz@...gle.com>
Subject: Re: [PATCH 0/1] vsprintf: optimize decimal conversion (again)

On Wednesday 28 March 2012 12:39, roma1390 wrote:
> On 2012.03.28 13:33, Denys Vlasenko wrote:
> > On Wednesday 28 March 2012 12:24, roma1390 wrote:
> >> On 2012.03.28 13:13, Denys Vlasenko wrote:
> >>> Second: run
> >>> arm-linux-gnueabi-gcc -O2 -Wall test_{org,new}.c -S
> >>> and email me resulting test_{org,new}.s files.
> >>
> >> test_{org,new}.s attached.
> >
> >
> > Bingo.
> >
> >          bl      __aeabi_uidivmod
> >
> > Not good. Your gcc did not optimize division by constant.
> >
> > Can you add  "noinline_for_stack":
> >
> > static noinline_for_stack<=== HERE
> > char *put_dec(char *buf, unsigned long long n)
> >
> > amd regenerate and resend the test_new.s?
> >
> 
> Hello,
> 
> Your requested asm are attached.

Asm looks good: there are only three long multiplies in the
put_dec + put_dec_full4, and no divisions at all.

Please speed-test this version.

-- 
vda
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