From: "George Spelvin" <linux@horizon.com>
To: geert@linux-m68k.org, linux@horizon.com
Cc: hughd@google.com, linux-kernel@vger.kernel.org, mpn@google.com,
vda.linux@googlemail.com
Subject: Re: [PATCH 2/4] lib: vsprintf: Optimize division by 10000
Date: 24 Sep 2012 11:48:32 -0400 [thread overview]
Message-ID: <20120924154832.12150.qmail@science.horizon.com> (raw)
In-Reply-To: <CAMuHMdUt3WvLgt73L39BZ4D5_qDr7ZCYhTz6RDEsH4qV2vSa7g@mail.gmail.com>
Geert Uytterhoeven <geert@linux-m68k.org> wrote:
> On Mon, Sep 24, 2012 at 3:56 PM, George Spelvin <linux@horizon.com> wrote:
>> SPARCv8 UMUL puts the high half of the 64-bit result into the Y
>> register, and SPARCv7 has a multiply-step instruction (MULScc) which
>> does likewise.
>
> Early SPARCs don't even have a multiply instruction.
Are you sure we're not talking about the same thing? Early SPARCs didn't
have a *single* multiply instruction, but *did* have a multiply step
instruction, which can be iterated to produce a 32x32->64-bit multiply.
That's what I was referring to. All multiplies were slow, but widening
multiply was no slower.
And SPARCv7 had no divide support at all, so that was *really* slow.
SPARClite added a divide step, but also added an integer multiply
instruction, so again widening multiply beat the pants off divide.
next prev parent reply other threads:[~2012-09-24 15:48 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
2012-09-24 13:56 ` George Spelvin
2012-09-24 15:14 ` Geert Uytterhoeven
2012-09-24 15:48 ` George Spelvin [this message]
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20120924154832.12150.qmail@science.horizon.com \
--to=linux@horizon.com \
--cc=geert@linux-m68k.org \
--cc=hughd@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mpn@google.com \
--cc=vda.linux@googlemail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox
all inboxes | Powered by JetHome®