From: Adhemerval Zanella <adhemerval.zanella@linaro.org>
To: Wilco Dijkstra <Wilco.Dijkstra@arm.com>,
"libc-alpha@sourceware.org" <libc-alpha@sourceware.org>
Cc: nd <nd@arm.com>
Subject: Re: [PATCH] Improve strtok(_r) performance
Date: Mon, 14 Nov 2016 12:26:00 -0000 [thread overview]
Message-ID: <fa025578-1b1e-35b0-6477-fc109fa62e67@linaro.org> (raw)
In-Reply-To: <AM5PR0802MB261081079A9A4BC050B185E483BC0@AM5PR0802MB2610.eurprd08.prod.outlook.com>
https://sourceware.org/ml/libc-alpha/2016-11/msg00150.html
On 14/11/2016 10:20, Wilco Dijkstra wrote:
>
> ping
>
> From: Wilco Dijkstra
> Sent: 28 October 2016 12:35
> To: libc-alpha@sourceware.org
> Cc: nd
> Subject: [PATCH] Improve strtok(_r) performance
>
> Improve strtok(_r) performance. Instead of calling strpbrk which calls
> strcspn, call strcspn directly so we get the end of the token without
> an extra call to rawmemchr. Also avoid an unnecessary call to strcspn after
> the last token by adding an early exit for an empty string. The result
> is a ~2x speedup of strtok on most inputs in bench-strtok.
>
> Passes regression tests, OK for commit?
>
> ChangeLog:
> 2015-10-28 Wilco Dijkstra <wdijkstr@arm.com>
>
> * string/strtok.c (STRTOK): Optimize for performance.
> * string/strtok_r.c (__strtok_r): Likewise.
> --
>
> diff --git a/string/strtok.c b/string/strtok.c
> index 7a4574db5c80501e47d045ad4347e8a287b32191..b1ed48c24c8d20706b7d05481a138b18a01ff802 100644
> --- a/string/strtok.c
> +++ b/string/strtok.c
> @@ -38,11 +38,18 @@ static char *olds;
> char *
> STRTOK (char *s, const char *delim)
> {
> - char *token;
> + char *end;
>
> if (s == NULL)
> s = olds;
>
> + /* Return immediately at end of string. */
> + if (*s == '\0')
> + {
> + olds = s;
> + return NULL;
> + }
> +
> /* Scan leading delimiters. */
> s += strspn (s, delim);
> if (*s == '\0')
> @@ -52,16 +59,15 @@ STRTOK (char *s, const char *delim)
> }
>
> /* Find the end of the token. */
> - token = s;
> - s = strpbrk (token, delim);
> - if (s == NULL)
> - /* This token finishes the string. */
> - olds = __rawmemchr (token, '\0');
> - else
> + end = s + strcspn (s, delim);
> + if (*end == '\0')
> {
> - /* Terminate the token and make OLDS point past it. */
> - *s = '\0';
> - olds = s + 1;
> + olds = end;
> + return s;
> }
> - return token;
> +
> + /* Terminate the token and make OLDS point past it. */
> + *end = '\0';
> + olds = end + 1;
> + return s;
> }
> diff --git a/string/strtok_r.c b/string/strtok_r.c
> index f351304766108dad2c1cff881ad3bebae821b2a0..e049a5c82e026a3b6c1ba5da16ce81743717805e 100644
> --- a/string/strtok_r.c
> +++ b/string/strtok_r.c
> @@ -45,11 +45,17 @@
> char *
> __strtok_r (char *s, const char *delim, char **save_ptr)
> {
> - char *token;
> + char *end;
>
> if (s == NULL)
> s = *save_ptr;
>
> + if (*s == '\0')
> + {
> + *save_ptr = s;
> + return NULL;
> + }
> +
> /* Scan leading delimiters. */
> s += strspn (s, delim);
> if (*s == '\0')
> @@ -59,18 +65,17 @@ __strtok_r (char *s, const char *delim, char **save_ptr)
> }
>
> /* Find the end of the token. */
> - token = s;
> - s = strpbrk (token, delim);
> - if (s == NULL)
> - /* This token finishes the string. */
> - *save_ptr = __rawmemchr (token, '\0');
> - else
> + end = s + strcspn (s, delim);
> + if (*end == '\0')
> {
> - /* Terminate the token and make *SAVE_PTR point past it. */
> - *s = '\0';
> - *save_ptr = s + 1;
> + *save_ptr = end;
> + return s;
> }
> - return token;
> +
> + /* Terminate the token and make *SAVE_PTR point past it. */
> + *end = '\0';
> + *save_ptr = end + 1;
> + return s;
> }
> #ifdef weak_alias
> libc_hidden_def (__strtok_r)
>
>
next prev parent reply other threads:[~2016-11-14 12:26 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-28 11:35 Wilco Dijkstra
2016-11-04 12:55 ` Adhemerval Zanella
2016-11-14 12:21 ` Wilco Dijkstra
2016-11-14 12:26 ` Adhemerval Zanella [this message]
2016-11-14 12:50 ` Wilco Dijkstra
2016-11-14 12:57 ` Adhemerval Zanella
2016-11-16 17:06 ` [PATCH v2] " Wilco Dijkstra
2016-11-16 18:07 ` Andreas Schwab
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