From: Jeff King <peff@peff.net>
To: Alex Riesen <raa.lkml@gmail.com>
Cc: David Kastrup <dak@gnu.org>, git@vger.kernel.org
Subject: Re: [PATCH] Make strbuf_cmp inline, constify its arguments and optimize it a bit
Date: Sun, 7 Oct 2007 22:19:45 -0400 [thread overview]
Message-ID: <20071008021945.GC20050@coredump.intra.peff.net> (raw)
In-Reply-To: <20071007215749.GD2765@steel.home>
On Sun, Oct 07, 2007 at 11:57:49PM +0200, Alex Riesen wrote:
> > > Can't the result of the expression be reused in compiled?
> > > Isn't it a common expression?
> >
> > No, since the call to memcmp might change a->len or b->len. A
>
> Huh?! How's that? It is not even given them!
But they are non-local variables (they are part of structs passed in as
pointers), so that translation unit has no idea how they are allocated.
They could be globals that memcmp mucks with as a side effect.
That being said, standards-conforming compilers _can_ realize that
memcmp is a special, standards-defined function with no side effects and
act accordingly. gcc provides the 'pure' function attribute for this
purpose, which is used by glibc.
-Peff
prev parent reply other threads:[~2007-10-08 2:20 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-09-24 9:25 mini-refactor in rerere.c Pierre Habouzit
[not found] ` <1190625904-22808-2-git-send-email-madcoder@debian.org>
[not found] ` <1190625904-22808-3-git-send-email-madcoder@debian.org>
2007-09-24 10:38 ` [PATCH 2/2] Make builtin-rerere use of strbuf nicer and more efficient Johannes Schindelin
2007-09-26 0:31 ` Junio C Hamano
2007-09-26 8:41 ` Pierre Habouzit
2007-10-07 14:00 ` [PATCH] Make strbuf_cmp inline, constify its arguments and optimize it a bit Alex Riesen
2007-10-07 14:24 ` Timo Hirvonen
2007-10-07 14:39 ` Pierre Habouzit
2007-10-07 15:46 ` Miles Bader
2007-10-07 16:07 ` David Kastrup
2007-10-07 21:54 ` Alex Riesen
2007-10-07 22:12 ` Wincent Colaiuta
2007-10-07 22:31 ` Alex Riesen
2007-10-08 1:45 ` Miles Bader
2007-10-08 7:23 ` Pierre Habouzit
2007-10-08 8:54 ` Florian Weimer
2007-10-08 18:51 ` Alex Riesen
2007-10-07 16:11 ` Johannes Schindelin
2007-10-07 16:18 ` Timo Hirvonen
2007-10-07 18:25 ` Johannes Schindelin
2007-10-07 16:54 ` Pierre Habouzit
2007-10-07 14:24 ` David Kastrup
2007-10-07 16:10 ` Alex Riesen
2007-10-07 16:27 ` David Kastrup
2007-10-07 21:57 ` Alex Riesen
2007-10-08 2:19 ` Jeff King [this message]
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