On 08/10/2019 11.31, Daniel Thompson wrote: > 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. >>> >> >> 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. Agreed. Do you want me to resend the series with patch 3 updated to read "For a fixed small exponent of 3, it is more efficient to simply use two explicit multiplications rather than calling the int_pow() library function: Aside from the function call overhead, its implementation using repeated squaring means it ends up doing four 64x64 multiplications." (and obviously patch 5 dropped)? Rasmus _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/dri-devel
