All of lore.kernel.org
 help / color / mirror / Atom feed
From: Matteo Croce <mcroce@linux.microsoft.com>
To: linux-kernel@vger.kernel.org, Nick Kossifidis <mick@ics.forth.gr>,
	Guo Ren <guoren@kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	David Laight <David.Laight@aculab.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Emil Renner Berthing <kernel@esmil.dk>,
	Drew Fustini <drew@beagleboard.org>
Cc: linux-arch@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-riscv@lists.infradead.org
Subject: [PATCH 2/3] lib/string: optimized memmove
Date: Fri, 25 Jun 2021 03:01:59 +0200	[thread overview]
Message-ID: <20210625010200.362755-3-mcroce@linux.microsoft.com> (raw)
In-Reply-To: <20210625010200.362755-1-mcroce@linux.microsoft.com>

From: Matteo Croce <mcroce@microsoft.com>

When the destination buffer is before the source one, or when the
buffers doesn't overlap, it's safe to use memcpy() instead, which is
optimized to use a bigger data size possible.

This "optimization" only covers a common case. In future, proper code
which does the same thing as memcpy() does but backwards can be done.

Signed-off-by: Matteo Croce <mcroce@microsoft.com>
---
 lib/string.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/lib/string.c b/lib/string.c
index 15e906f97d9e..69adec252597 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -976,19 +976,13 @@ EXPORT_SYMBOL(memcpy);
  */
 void *memmove(void *dest, const void *src, size_t count)
 {
-	char *tmp;
-	const char *s;
+	if (dest < src || src + count <= dest)
+		return memcpy(dest, src, count);
+
+	if (dest > src) {
+		const char *s = src + count;
+		char *tmp = dest + count;
 
-	if (dest <= src) {
-		tmp = dest;
-		s = src;
-		while (count--)
-			*tmp++ = *s++;
-	} else {
-		tmp = dest;
-		tmp += count;
-		s = src;
-		s += count;
 		while (count--)
 			*--tmp = *--s;
 	}
-- 
2.31.1


WARNING: multiple messages have this Message-ID (diff)
From: Matteo Croce <mcroce@linux.microsoft.com>
To: linux-kernel@vger.kernel.org, Nick Kossifidis <mick@ics.forth.gr>,
	Guo Ren <guoren@kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	David Laight <David.Laight@aculab.com>,
	Palmer Dabbelt <palmer@dabbelt.com>,
	Emil Renner Berthing <kernel@esmil.dk>,
	Drew Fustini <drew@beagleboard.org>
Cc: linux-arch@vger.kernel.org,
	Andrew Morton <akpm@linux-foundation.org>,
	Nick Desaulniers <ndesaulniers@google.com>,
	linux-riscv@lists.infradead.org
Subject: [PATCH 2/3] lib/string: optimized memmove
Date: Fri, 25 Jun 2021 03:01:59 +0200	[thread overview]
Message-ID: <20210625010200.362755-3-mcroce@linux.microsoft.com> (raw)
In-Reply-To: <20210625010200.362755-1-mcroce@linux.microsoft.com>

From: Matteo Croce <mcroce@microsoft.com>

When the destination buffer is before the source one, or when the
buffers doesn't overlap, it's safe to use memcpy() instead, which is
optimized to use a bigger data size possible.

This "optimization" only covers a common case. In future, proper code
which does the same thing as memcpy() does but backwards can be done.

Signed-off-by: Matteo Croce <mcroce@microsoft.com>
---
 lib/string.c | 18 ++++++------------
 1 file changed, 6 insertions(+), 12 deletions(-)

diff --git a/lib/string.c b/lib/string.c
index 15e906f97d9e..69adec252597 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -976,19 +976,13 @@ EXPORT_SYMBOL(memcpy);
  */
 void *memmove(void *dest, const void *src, size_t count)
 {
-	char *tmp;
-	const char *s;
+	if (dest < src || src + count <= dest)
+		return memcpy(dest, src, count);
+
+	if (dest > src) {
+		const char *s = src + count;
+		char *tmp = dest + count;
 
-	if (dest <= src) {
-		tmp = dest;
-		s = src;
-		while (count--)
-			*tmp++ = *s++;
-	} else {
-		tmp = dest;
-		tmp += count;
-		s = src;
-		s += count;
 		while (count--)
 			*--tmp = *--s;
 	}
-- 
2.31.1


_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv

  parent reply	other threads:[~2021-06-25  1:02 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-25  1:01 [PATCH 0/3] lib/string: optimized mem* functions Matteo Croce
2021-06-25  1:01 ` Matteo Croce
2021-06-25  1:01 ` [PATCH 1/3] lib/string: optimized memcpy Matteo Croce
2021-06-25  1:01   ` Matteo Croce
2021-06-25  5:01   ` kernel test robot
2021-06-25  5:01     ` kernel test robot
2021-06-25 14:41   ` kernel test robot
2021-06-25 14:41     ` kernel test robot
2021-06-25  1:01 ` Matteo Croce [this message]
2021-06-25  1:01   ` [PATCH 2/3] lib/string: optimized memmove Matteo Croce
2021-06-25  1:02 ` [PATCH 3/3] lib/string: optimized memset Matteo Croce
2021-06-25  1:02   ` Matteo Croce
2021-06-25 17:45 ` [PATCH 0/3] lib/string: optimized mem* functions Nick Desaulniers
2021-06-25 17:45   ` Nick Desaulniers
2021-06-27  0:19   ` Matteo Croce
2021-06-27  0:19     ` Matteo Croce
2021-07-01  0:29     ` Matteo Croce
2021-07-01  0:29       ` Matteo Croce

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=20210625010200.362755-3-mcroce@linux.microsoft.com \
    --to=mcroce@linux.microsoft.com \
    --cc=David.Laight@aculab.com \
    --cc=akpm@linux-foundation.org \
    --cc=drew@beagleboard.org \
    --cc=guoren@kernel.org \
    --cc=hch@infradead.org \
    --cc=kernel@esmil.dk \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-riscv@lists.infradead.org \
    --cc=mick@ics.forth.gr \
    --cc=ndesaulniers@google.com \
    --cc=palmer@dabbelt.com \
    /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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.