[PATCH] D32166: Improve LoopVectorizers estimation of scalar loops by predicting LSR behaviour

[Renato Golin via Phabricator via llvm-commits]

rengolin added reviewers: delena, qcolombet, sanjoy, craig.topper.
rengolin added a comment.

In https://reviews.llvm.org/D32166#768590, @jonpa wrote:

> I have just looked at performance. It was a while since I tried to evaluate the compile time impact of a single pass. How would you do this?


Well, if the whole compile time doesn't increase noticeably on a good number of programs and benchmarks (I'm expecting it won't), then it should be mostly fine.

One way to track compile time is using LNT. Put up a server, run vanilla, submit the results, run with the change, submit the results, compare. (http://llvm.org/docs/lnt/quickstart.html)

If the results are mostly fine, then it'd be just a matter or understanding why it was where it was and make sure everyone agrees with the move (or addition).

I'm adding a few people that have recently worked in the LSR as well as some vectoriser people.

I have seen a few comments in the LV that expect LSR to pass after it, so it might not be completely advisable to *move*, but passing before and after might have a noticeable impact.

cheers,
--renato


https://reviews.llvm.org/D32166