Re: [PATCH] common implementation of iterative div/mod

On Thu, 08 May 2008 16:16:41 +0100 Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:

We have a few instances of the open-coded iterative div/mod loop, used
when we don't expcet the dividend to be much bigger than the divisor.
Unfortunately modern gcc's have the tendency to strength "reduce" this
into a full mod operation, which isn't necessarily any faster, and
even if it were, doesn't exist if gcc implements it in libgcc.

The workaround is to put a dummy asm statement in the loop to prevent
gcc from performing the transformation.

This patch creates a single implementation of this loop, and uses it
to replace the open-coded versions I know about.

Believe it or not, this patch causes one of my test machines to fail to
find its disk.

good dmesg: http://userweb.kernel.org/~akpm/dmesg-t61p.txt
bad dmesg: http://userweb.kernel.org/~akpm/dmesg-t61p-dead.txt
config: http://userweb.kernel.org/~akpm/config-t61p.txt
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/