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 email@example.com More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/