From: Joe Perches <joe@perches.com>
To: Alexey Dobriyan <adobriyan@gmail.com>, akpm@linux-foundation.org
Cc: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] lib/string.c: make strncmp() smaller
Date: Fri, 08 Feb 2019 01:31:49 -0800 [thread overview]
Message-ID: <061655a972b4037b5bf245a65aed937967410e61.camel@perches.com> (raw)
In-Reply-To: <20190208073403.GA19734@avx2>
On Fri, 2019-02-08 at 10:34 +0300, Alexey Dobriyan wrote:
> Space savings on x86_64:
>
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-29 (-29)
> Function old new delta
> strncmp 67 38 -29
>
> Space savings on arm:
>
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-60 (-60)
> Function old new delta
> strncmp 116 56 -60
[]
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -344,16 +344,14 @@ EXPORT_SYMBOL(strcmp);
> */
> int strncmp(const char *cs, const char *ct, size_t count)
> {
> - unsigned char c1, c2;
> + while (count--) {
> + unsigned int c1 = *(unsigned char *)cs++;
> + unsigned int c2 = *(unsigned char *)ct++;
>
> - while (count) {
> - c1 = *cs++;
> - c2 = *ct++;
> if (c1 != c2)
> - return c1 < c2 ? -1 : 1;
> + return c1 - c2;
This does change the return value for most comparisons.
Wasn't there a specific reason for -1 and 1?
next prev parent reply other threads:[~2019-02-08 9:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-08 7:34 [PATCH] lib/string.c: make strncmp() smaller Alexey Dobriyan
2019-02-08 9:31 ` Joe Perches [this message]
2019-02-09 13:02 ` Alexey Dobriyan
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=061655a972b4037b5bf245a65aed937967410e61.camel@perches.com \
--to=joe@perches.com \
--cc=adobriyan@gmail.com \
--cc=akpm@linux-foundation.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).