linux-kernel - Re: [PATCH] memchr (trivial) optimization

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <200708230213.21332.ioe-lkml@rameria.de>
Date:	Thu, 23 Aug 2007 02:13:20 +0200
From:	Ingo Oeser <ioe-lkml@...eria.de>
To:	"lode leroy" <lode_leroy@...mail.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memchr (trivial) optimization

On Wednesday 22 August 2007, lode leroy wrote:
> While profiling something completely unrelated, I noticed
> that on the workloads I used memchr for, I saw a 30%-40% improvement
> in performance, with the following trivial changes...
> (basically, it saves 3 operations for each call)

Yes, but then you could be a bit more explicit to the compiler
on what you are doing here:
 
void *memchr(const void *s, int c, size_t n)
{
	const unsigned char *p = s;

	for (; n != 0; n--, p++) {
               if ((unsigned char)c == *p) {
                       return (void *)p;
	}
	return NULL;
}

Now the compiler should see the loop more clearly.


Best Regards

Ingo Oeser
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/