Hi,
On Thu, 17 Nov 2016, Bin.Cheng wrote:
> B) Depending on ilp, I think below test strings fail for long time with
> haswell:
> ! { dg-final { scan-tree-dump-times "Executing predictive commoning
> without unrolling" 1 "pcom" { target lp64 } } }
> ! { dg-final { scan-tree-dump-times "Executing predictive commoning
> without unrolling" 2 "pcom" { target ia32 } } }
> Because vectorizer choose vf==4 in this case, and there is no
> predictive commoning opportunities at all.
> Also the newly added test string fails in this case too because the
> prolog peeled iterates more than 1 times.
Btw, this probably means that on haswell (or other archs with vf==4) mgrid
is slower than necessary. On mgrid you really really want predictive
commoning to happen. Vectorization isn't that interesting there.
Ciao,
Michael.
