From: Michal Nazarewicz <mpn@google.com>
To: George Spelvin <linux@horizon.com>,
linux@horizon.com, vda.linux@googlemail.com
Cc: hughd@google.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/4] lib: vsprintf: Optimize division by 10000
Date: Mon, 24 Sep 2012 14:41:32 +0200 [thread overview]
Message-ID: <xa1tfw67d24j.fsf@mina86.com> (raw)
In-Reply-To: <20120924121614.5422.qmail@science.horizon.com>
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On Mon, Sep 24 2012, George Spelvin wrote:
>> You are using a 64-bit multiply in a path that is designed for 32-bit
>> processors, which makes me feel that it will be slower.
>
> Slower than the divide it's replacing?
OK, granted, it might be faster after all. ;) Still, I'd love to see
some benchmark.
> The following 32-bit processors have 32x32->64-bit multiply:
>
> x86
> ARM (as of ARMv4 = ARM7TDMI, the lowest version in common use)
> SPARCv7, SPARCv8
Didn't some SPARCs have 32x32->32 multiply? I remember reading some
rant from a GMP developer about how SPARC is broken that way.
> MIPS32
> MC68020
> PA-RISC 1.1 (XMPYU)
> avr32
> PowerPC (MULHWU)
> VAX (EMUL)
> I could do some Kconfig hacking and make the code path
> architecture-dependent. Do you think it's worth it?
Definitely not.
--
Best regards, _ _
.o. | Liege of Serenely Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michał “mina86” Nazarewicz (o o)
ooo +----<email/xmpp: mpn@google.com>--------------ooO--(_)--Ooo--
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next prev parent reply other threads:[~2012-09-24 12:41 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-08-03 5:21 [PATCH 1/4] lib: vsprintf: Optimize division by 10 for small integers George Spelvin
2012-08-03 5:21 ` [PATCH 2/4] lib: vsprintf: Optimize division by 10000 George Spelvin
2012-09-23 17:30 ` Michal Nazarewicz
2012-09-24 12:16 ` George Spelvin
2012-09-24 12:41 ` Michal Nazarewicz [this message]
2012-09-24 13:56 ` George Spelvin
2012-09-24 15:14 ` Geert Uytterhoeven
2012-09-24 15:48 ` George Spelvin
2012-09-24 9:03 ` Denys Vlasenko
2012-09-24 12:35 ` George Spelvin
2012-09-24 15:02 ` Denys Vlasenko
2012-08-03 5:21 ` [PATCH 3/4] lib: vsprintf: Optimize put_dec_trunc8 George Spelvin
2012-09-23 14:18 ` Rabin Vincent
2012-09-24 11:13 ` George Spelvin
2012-09-24 14:33 ` George Spelvin
2012-09-24 14:53 ` Michal Nazarewicz
2012-09-24 14:57 ` Michal Nazarewicz
2012-09-23 18:22 ` Michal Nazarewicz
2012-09-24 11:46 ` George Spelvin
2012-09-24 12:29 ` Michal Nazarewicz
2012-09-24 13:49 ` George Spelvin
2012-09-24 15:06 ` Michal Nazarewicz
2012-09-25 11:44 ` George Spelvin
2012-09-25 13:00 ` Denys Vlasenko
2012-08-03 5:21 ` [PATCH 4/4] lib: vsprintf: Fix broken comments George Spelvin
2012-09-23 17:22 ` [PATCH 1/4] lib: vsprintf: Optimize division by 10 for small integers Michal Nazarewicz
2012-09-24 14:18 ` George Spelvin
2012-09-24 9:06 ` Denys Vlasenko
2012-09-24 11:27 ` George Spelvin
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