From: Nicolas Pitre <nicolas.pitre@linaro.org>
To: "Alexey Brodkin" <Alexey.Brodkin@synopsys.com>,
"Måns Rullgård" <mans@mansr.com>
Cc: Arnd Bergmann <arnd@arndb.de>,
rmk+kernel@arm.linux.org.uk, linux-arch@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 0/5] 64-by-32 ddivision optimization for constant divisors on 32-bit machines
Date: Mon, 02 Nov 2015 17:33:25 -0500 [thread overview]
Message-ID: <1446503610-6942-1-git-send-email-nicolas.pitre@linaro.org> (raw)
This is a generalization of the optimization I produced for ARM a decade
ago to turn constant divisors into a multiplication by the divisor
reciprocal. Turns out that after all those years gcc is still not
optimizing things on its own for that case.
This has important performance benefits as discussed in this thread:
https://lkml.org/lkml/2015/10/28/851
This series brings the formerly ARMonly optimization to all 32-bit
architectures using C code by default. The possibility for the actual
multiplication to be implemented in assembly is provided in order to get
optimal code. The ARM version can be used as an example implementation
for other interested architectures to implement.
Nicolas
next reply other threads:[~2015-11-02 22:33 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-11-02 22:33 Nicolas Pitre [this message]
2015-11-02 22:33 ` [PATCH 0/5] 64-by-32 ddivision optimization for constant divisors on 32-bit machines Nicolas Pitre
2015-11-02 22:33 ` [PATCH 1/5] div64.h: optimize do_div() for power-of-two constant divisors Nicolas Pitre
2015-11-02 22:33 ` Nicolas Pitre
2015-11-02 22:33 ` [PATCH 2/5] do_div(): generic optimization for constant divisor on 32-bit machines Nicolas Pitre
2015-11-03 5:32 ` kbuild test robot
2015-11-03 9:15 ` Arnd Bergmann
2015-11-04 21:04 ` Nicolas Pitre
2015-11-04 21:42 ` Måns Rullgård
2015-11-04 21:42 ` Måns Rullgård
2015-11-02 22:33 ` [PATCH 3/5] __div64_const32(): abstract out the actual 128-bit cross product code Nicolas Pitre
2015-11-02 22:33 ` Nicolas Pitre
2015-11-02 22:33 ` [PATCH 4/5] __div64_32(): make it overridable at compile time Nicolas Pitre
2015-11-02 22:33 ` Nicolas Pitre
2015-11-02 22:33 ` [PATCH 5/5] ARM: asm/div64.h: adjust to generic codde Nicolas Pitre
2015-11-02 22:33 ` Nicolas Pitre
2015-11-03 1:25 ` kbuild test robot
2015-11-03 4:03 ` Nicolas Pitre
2015-11-03 21:39 ` kbuild test robot
2015-11-19 16:36 ` Måns Rullgård
2015-11-19 16:42 ` Nicolas Pitre
2015-11-19 16:44 ` Måns Rullgård
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=1446503610-6942-1-git-send-email-nicolas.pitre@linaro.org \
--to=nicolas.pitre@linaro.org \
--cc=Alexey.Brodkin@synopsys.com \
--cc=arnd@arndb.de \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mans@mansr.com \
--cc=rmk+kernel@arm.linux.org.uk \
/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