From: Willy Tarreau <willy@w.ods.org>
To: Jamie Lokier <jamie@shareable.org>
Cc: Albert Cahalan <albert@users.sourceforge.net>,
linux-kernel mailing list <linux-kernel@vger.kernel.org>,
chip@pobox.com
Subject: Re: [PATCH] 2.4.22pre10: {,un}likely_p() macros for pointers
Date: Sat, 9 Aug 2003 10:13:46 +0200 [thread overview]
Message-ID: <20030809081346.GC29616@alpha.home.local> (raw)
In-Reply-To: <20030809002117.GB26375@mail.jlokier.co.uk>
On Sat, Aug 09, 2003 at 01:21:17AM +0100, Jamie Lokier wrote:
> Albert Cahalan wrote:
> > // tell gcc what to expect: if(unlikely(err)) die(err);
> > #define likely(x) __builtin_expect(!!(x),1)
> > #define unlikely(x) __builtin_expect(!!(x),0)
> > #define expected(x,y) __builtin_expect((x),(y))
>
> You may want to check that GCC generates the same code as for
>
> #define likely(x) __builtin_expect((x),1)
> #define unlikely(x) __builtin_expect((x),0)
>
> I tried this once, and I don't recall the precise result but I do
> recall it generating different code (i.e. not optimal for one of the
> definitions).
anyway, in __builtin_expect(!!(x),0) there is a useless conversion, because
it's totally equivalent to __builtin_expect((x),0) (how could !!x be 0 if x
isn't ?), but I'm pretty sure that the compiler will add the test.
Willy
next prev parent reply other threads:[~2003-08-09 8:14 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-08-05 12:44 [PATCH] 2.4.22pre10: {,un}likely_p() macros for pointers Albert Cahalan
2003-08-09 0:21 ` Jamie Lokier
2003-08-09 8:13 ` Willy Tarreau [this message]
2003-08-09 8:51 ` David S. Miller
2003-08-09 9:36 ` Jamie Lokier
2003-08-09 10:10 ` Herbert Xu
2003-08-09 10:42 ` Alan Cox
2003-08-09 16:23 ` Jamie Lokier
2003-08-09 17:30 ` NULL. Again. (was Re: [PATCH] 2.4.22pre10: {,un}likely_p()) Chip Salzenberg
2003-08-09 17:43 ` Sean Neakums
2003-08-11 1:04 ` Jamie Lokier
2003-08-11 23:06 ` Timothy Miller
2003-08-09 19:44 ` Jamie Lokier
-- strict thread matches above, loose matches on Subject: below --
2003-08-10 4:03 [PATCH] 2.4.22pre10: {,un}likely_p() macros for pointers Albert Cahalan
2003-08-10 7:29 ` Willy Tarreau
2003-08-10 8:02 ` Willy Tarreau
2003-08-11 1:23 ` Chip Salzenberg
2003-08-11 2:09 ` Jamie Lokier
2003-08-11 2:39 ` Chip Salzenberg
2003-08-11 4:02 ` Albert Cahalan
2003-08-11 4:30 ` Jamie Lokier
2003-08-11 5:30 ` Willy Tarreau
2003-08-11 5:42 ` Jamie Lokier
2003-08-11 13:09 ` Albert Cahalan
2003-08-11 18:55 ` Andrew Morton
2003-08-11 23:13 ` Albert Cahalan
2003-08-13 19:42 ` Jamie Lokier
2003-08-11 4:55 ` Jamie Lokier
2003-08-11 5:26 ` Willy Tarreau
2003-08-11 5:38 ` Jamie Lokier
2003-08-04 17:06 Chip Salzenberg
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=20030809081346.GC29616@alpha.home.local \
--to=willy@w.ods.org \
--cc=albert@users.sourceforge.net \
--cc=chip@pobox.com \
--cc=jamie@shareable.org \
--cc=linux-kernel@vger.kernel.org \
/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;
as well as URLs for NNTP newsgroup(s).