On Mon, Oct 07, 2019 at 08:43:31PM +0200, Rasmus Villemoes wrote: > On 07/10/2019 17.28, Daniel Thompson wrote: > > On Thu, Sep 19, 2019 at 04:06:18PM +0200, Rasmus Villemoes wrote: > > > > It feels like there is some rationale missing in the description here. > > > > What is the benefit of replacing the explicit int_pow() with the > > implicit multiplications? > > > > > > Daniel. > > > > > >> > >> We could (and a following patch will) change to use a power-of-2 scale, > >> but for a fixed small exponent of 3, there's no advantage in using > >> repeated squaring. > > ^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > > Apart from the function call overhead (and resulting register pressure > etc.), using int_pow is less efficient (for an exponent of 3, it ends up > doing four 64x64 multiplications instead of just two). But feel free to > drop it, I'm not going to pursue it further - it just seemed like a > sensible thing to do while I was optimizing the code anyway. > > [At the time I wrote the patch, this was also the only user of int_pow > in the tree, so it also allowed removing int_pow altogether.] To be honest the change is fine but the patch description doesn't make sense if the only current purpose of the patch is as a optimization. Daniel. _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
