On Tue, Feb 11, 2020 at 02:58:47PM +0100, Richard Biener wrote: > On Tue, 11 Feb 2020, Roman Zhuykov wrote: > > 11.02.2020 11:01, Richard Biener wrote: > > Sound good, but IMHO modulo scheduler is not the best choice to be the > > first step implementing such a concept. > > True ;) But since the context of this thread is unrolling ... > Not sure how you'd figure the unroll factor to apply if you want > to do unrolling within a classical scheduling framework? Maybe > unroll as much as you can fill slots until the last instruction > of the first iteration retires?
That will be terrible on register-rich architectures: it *already* is problematic how often some things are unrolled, blindly unrolling more would make things worse. We need to unroll more where it helps, but less where it does not. For that we need a good cost/benefit estimate. Segher
