From: Steven Rostedt <rostedt@goodmis.org>
To: Pekka Enberg <penberg@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Thiago Farina <tfransosi@gmail.com>,
linux-kernel@vger.kernel.org,
Alexey Dobriyan <adobriyan@gmail.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Ingo Molnar <mingo@elte.hu>,
"David S. Miller" <davem@davemloft.net>,
Al Viro <viro@zeniv.linux.org.uk>, "Ted Ts'o" <tytso@mit.edu>,
Christoph Hellwig <hch@infradead.org>
Subject: Re: [PATCH] linux/string.h: Introduce streq macro.
Date: Wed, 27 Apr 2011 15:26:22 -0400 [thread overview]
Message-ID: <1303932382.18763.104.camel@gandalf.stny.rr.com> (raw)
In-Reply-To: <1303931761.18763.101.camel@gandalf.stny.rr.com>
On Wed, 2011-04-27 at 15:16 -0400, Steven Rostedt wrote:
> On Wed, 2011-04-27 at 21:51 +0300, Pekka Enberg wrote:
> 00000000000001df <streq>:
> 1df: 55 push %rbp
> 1e0: 48 89 e5 mov %rsp,%rbp
> 1e3: 8a 07 mov (%rdi),%al
> 1e5: 8a 16 mov (%rsi),%dl
> 1e7: 48 ff c7 inc %rdi
> 1ea: 48 ff c6 inc %rsi
> 1ed: 38 d0 cmp %dl,%al
> 1ef: 75 0b jne 1fc <streq+0x1d>
> 1f1: 84 c0 test %al,%al
> 1f3: 75 ee jne 1e3 <streq+0x4>
> 1f5: b8 01 00 00 00 mov $0x1,%eax
> 1fa: eb 02 jmp 1fe <streq+0x1f>
> 1fc: 31 c0 xor %eax,%eax
> 1fe: c9 leaveq
> 1ff: c3 retq
I just noticed that 5 byte move instruction. So changing the function to
bool, makes it a little nicer:
bool streq(const char *cs, const char *ct)
{
unsigned char c1, c2;
while (1) {
c1 = *cs++;
c2 = *ct++;
if (c1 != c2)
return false;
if (!c1)
break;
}
return true;
}
00000000000001df <streq>:
1df: 55 push %rbp
1e0: 48 89 e5 mov %rsp,%rbp
1e3: 8a 07 mov (%rdi),%al
1e5: 8a 16 mov (%rsi),%dl
1e7: 48 ff c7 inc %rdi
1ea: 48 ff c6 inc %rsi
1ed: 38 d0 cmp %dl,%al
1ef: 75 08 jne 1f9 <streq+0x1a>
1f1: 84 c0 test %al,%al
1f3: 75 ee jne 1e3 <streq+0x4>
1f5: b0 01 mov $0x1,%al
1f7: eb 02 jmp 1fb <streq+0x1c>
1f9: 31 c0 xor %eax,%eax
1fb: c9 leaveq
1fc: c3 retq
-- Steve
next prev parent reply other threads:[~2011-04-27 19:26 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-26 18:49 Thiago Farina
2011-04-26 19:00 ` Steven Rostedt
2011-04-26 19:05 ` Alexey Dobriyan
2011-04-26 19:17 ` Steven Rostedt
2011-04-26 19:20 ` Alexey Dobriyan
2011-04-26 19:21 ` Thiago Farina
2011-04-26 19:37 ` Steven Rostedt
2011-04-26 19:45 ` Joe Perches
2011-04-26 19:47 ` Thiago Farina
2011-04-26 19:58 ` Steven Rostedt
2011-04-26 20:06 ` Joe Perches
2011-04-27 8:29 ` Miguel Ojeda
2011-04-27 8:42 ` Geert Uytterhoeven
2011-04-27 8:49 ` Miguel Ojeda
2011-04-27 9:04 ` Pavel Vasilyev
2011-04-26 20:00 ` Steven Rostedt
2011-04-26 19:25 ` Steven Rostedt
2011-04-26 19:45 ` Thiago Farina
2011-04-26 19:54 ` Thiago Farina
2011-04-27 17:49 ` Steven Rostedt
2011-04-27 18:33 ` H. Peter Anvin
2011-04-27 18:51 ` Pekka Enberg
2011-04-27 19:16 ` Steven Rostedt
2011-04-27 19:26 ` Steven Rostedt [this message]
2011-04-27 19:38 ` Pekka Enberg
2011-04-27 20:04 ` Steven Rostedt
2011-04-27 20:24 ` H. Peter Anvin
2011-04-27 19:01 ` Steven Rostedt
2011-04-27 23:38 ` Ted Ts'o
2011-04-28 3:30 ` Rusty Russell
2011-04-26 20:27 ` Davidlohr Bueso
2011-04-26 20:33 ` Thiago Farina
2011-04-27 0:52 ` Ted Ts'o
2011-04-27 1:32 ` Steven Rostedt
2011-04-27 6:47 ` Christoph Hellwig
2011-04-27 8:47 ` gmack
2011-04-27 14:52 ` Ted Ts'o
2011-04-27 16:04 ` Alexey Dobriyan
2011-04-27 16:26 ` Steven Rostedt
2011-04-27 8:35 ` Mike Frysinger
2011-04-27 16:46 ` Al Viro
2011-04-27 17:07 ` Steven Rostedt
2011-04-27 21:46 ` Al Viro
2011-04-27 22:17 ` Thiago Farina
2011-04-27 22:38 ` Pavel Vasilyev
2011-04-27 22:45 ` Al Viro
2011-04-28 0:05 ` Steven Rostedt
2011-04-27 22:21 ` Thiago Farina
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