Re: [ft-devel] Significant optimization of ft_div64by32

[Werner LEMBERG]

> I have just committed significant optimization of ft_div64by32, one
> of the more expensive calculations that we sometimes do on 32-bit
> platforms.  The trick was to do as much as we can with 32-bit
> division before embarking on bit-by-bit long division.  So we shift
> as many bits as we can into the high register, perform 32-bit
> division with modulo there, then work through the remaining bits
> with long division. This optimization is especially noticeable for
> smaller dividends that barely use the high register.

Thanks.  Do you have some numbers for you claim?  Additionally, I
wonder whether your optimization also holds for older architectures
where division and multiplication are much more expensive than
operations like shifting and ORing.


    Werner