lkml.org 
[lkml]   [2005]   [Sep]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] introduce setup_timer() helper
Andrew Morton wrote:
>
> Oleg Nesterov <oleg@tv-sign.ru> wrote:
> >
> > I think this can save a couple of cpu cycles. The init_timer()
> > is not inline, gcc can't reorder exprx() and init_timer() calls.
> >
> > Ok, I do not want to persist very much, I can resend this patch.
> >
> > Andrew, should I?
>
> Try both, see which one generates the shorter code?

The code:

void *expr(void);

void tst(struct timer_list *timer)
{
setup_timer(timer, expr(), 0);
}

Asm output:

1 tst:
2 pushl %ebp
3 movl %esp, %ebp
4 pushl %ebx
5 movl 8(%ebp), %ebx
6 call expr
7 movl %eax, 16(%ebx)
8 movl %ebx, %eax
9 movl $0, 20(%ebx)
10 call init_timer
11 popl %ebx
12 popl %ebp
13 ret

After the Arjan proposed change:

1 tst:
2 pushl %ebp
3 movl %esp, %ebp
4 subl $8, %esp
5 movl %ebx, (%esp)
6 movl 8(%ebp), %ebx
7 movl %esi, 4(%esp)
8 call expr
9 movl %eax, %esi
10 movl %ebx, %eax
11 call init_timer
12 movl %esi, 16(%ebx)
13 movl $0, 20(%ebx)
14 movl (%esp), %ebx
15 movl 4(%esp), %esi
16 movl %ebp, %esp
17 popl %ebp
18 ret

I don't think we'll see any difference in practice, but still...

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

\
 
 \ /
  Last update: 2005-09-19 17:03    [W:0.036 / U:1.320 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site