lkml.org 
[lkml]   [2004]   [Oct]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: Semaphore assembly-code bug


On Fri, 29 Oct 2004, Linus Torvalds wrote:
>
> Here's a totally untested patch to make the semaphores use "fastcall"
> instead of "asmlinkage"

Ok, I tested it, looked through the assembly code, and did a general size
comparison. Everything looks good, and it should fix the problem that
caused this discussion. Checked in.

The patch actually improves code generation by moving the failure case
argument generation _into_ the failure case: this makes the inline asm one
instruction longer, but it means that the fastpath is often one
instruction shorter. In fact, the fastpath is usually improved even _more_
than that, because gcc does sucketh at generating code that uses fixed
registers (ie the old code often caused gcc to first generate the value
into another register, and then _move_ it into %eax, rather than just
generating it into %eax in the first place).

My test-kernel shrunk by a whopping 2kB in size from this change.

Linus
-
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: 2009-11-18 23:46    [W:2.110 / U:0.540 seconds]
©2003-2017 Jasper Spaans. hosted at Digital OceanAdvertise on this site