Hi! On Thu, Jan 16, 2020 at 05:36:52PM +0800, Kewen.Lin wrote: > As we discussed in the thread > https://gcc.gnu.org/ml/gcc-patches/2020-01/msg00196.html > Original: https://gcc.gnu.org/ml/gcc-patches/2020-01/msg00104.html, > I'm working to teach IVOPTs to consider D-form group access during unrolling. > The difference on D-form and other forms during unrolling is we can put the > stride into displacement field to avoid additional step increment. eg:
<snip> > Imagining that if the loop get unrolled by 8 times, then 3 step updates with > D-form vs. 8 step updates with X-form. Here we only need to check stride > meet D-form field requirement, since if OFF doesn't meet, we can construct > baseA' with baseA + OFF. So why doesn't the existing code do this already? Why does it make all the extra induction variables? Is the existing cost model bad, are our target costs bad, or something like that? Segher
