lkml.org 
[lkml]   [2008]   [Dec]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] fork_init: fix division by zero
On Wed, Dec 10, 2008 at 01:29:12PM +0300, Yuri Tikhonov wrote:
> On Wednesday, December 10, 2008 you wrote:
> > x * y / z is parsed as (x * y) / z, not x * (y / z).
>
> Here we believe in preprocessor: since all PAGE_SIZE, 8, and
> THREAD_SIZE are the constants we expect it will calculate this.
>
> E.g. here is the result from this line as produced by cross-gcc
> 4.2.2:
>
> lis r9,0
> rlwinm r29,r29,2,16,29
> stw r29,0(r9)
>
> As you see - only rotate-left, i.e. multiplication to the constant.

Yes, and also note that it is masking the result by 0xfffc, to preserve
the effect of any overflow in (x * y).

-Scott


\
 
 \ /
  Last update: 2008-12-10 18:27    [W:0.119 / U:0.300 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site