On Mon, Sep 25, 2017 at 7:14 PM, Prathamesh Kulkarni <prathamesh.kulka...@linaro.org> wrote: > On 18 September 2017 at 15:40, Prathamesh Kulkarni > <prathamesh.kulka...@linaro.org> wrote: >> On 15 September 2017 at 22:09, Marc Glisse <marc.gli...@inria.fr> wrote: >>> On Fri, 15 Sep 2017, Wilco Dijkstra wrote: >>> >>>> Marc Glisse wrote: >>>> >>>>> The question is whether, having computed c=a/b, it is cheaper to test a<b >>>>> or c!=0. >>>>> I think it is usually the second one, but not for all types on all >>>>> targets. Although since >>>>> you mention VRP, it is easier to do further optimizations using the >>>>> information a<b. >>>> >>>> >>>> No, a<b is always better. Division does have high latency and low >>>> throughput on >>>> all modern cores, so rather than having to wait until the division >>>> finishes, you can >>>> execute whatever depends on the comparison many cycles earlier. >>>> >>>> Generally you want to avoid division as much as possible and when that >>>> fails >>>> reduce any dependencies on the result of divisions. >>> >>> >>> This would indicate that we do not need to check for single-use, makes the >>> patch simpler, thanks. >>> (let's ignore -Os) >> Hi, >> Thanks for the suggestions, I have updated the patch. >> Is this OK ? >> Bootstrap+test in progress on x86_64-unknown-linux-gnu. >> I will try address the right shift by 4 case in follow up patch. >> > ping https://gcc.gnu.org/ml/gcc-patches/2017-09/msg01145.html
Ok. Thanks, Richard. > Thanks, > Prathamesh >> Thanks, >> Prathamesh >>> >>> -- >>> Marc Glisse
