lkml.org 
[lkml]   [2003]   [Jul]   [1]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
Date
SubjectRe: [PATCH] Kill div64.h dupes, parenthesize do_div() macro params
>>>>> "Bernardo" == Bernardo Innocenti <bernie@develer.com> writes:

Bernardo> On Wednesday 02 July 2003 02:36, Andrew Morton wrote:

Bernardo> If there are architectures where gcc doesn't implement
Bernardo> divisions correctly, this issue should be solved in gcc, not
Bernardo> by adding a silly macro to the kernel.

The issue is that on 32-bit platforms, 64bit divided by 32 bit is
handed off to a subroutine _udivdi3 which isn't linked into the
kernel, and which in any case does a full 64 bit by 64-bit division
(which is slow).

Using do_div() allows one to generate near-optimal code for a 64by32
bit division/remainder on platforms (e.g., IA32) which have problems,
and generating something sane for other platforms (e.g., IA64).

Platforms that never expect to deal with a 64-bit number just redefine
the macro in terms of long. Which means that printing out long longs
doesn't work properly on those architectures.


--
Dr Peter Chubb http://www.gelato.unsw.edu.au peterc AT gelato.unsw.edu.au
You are lost in a maze of BitKeeper repositories, all slightly different.
-
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: 2005-03-22 13:46    [W:1.365 / U:0.072 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site