[PATCH] D28368: Give higher full-unroll boosting when the loop iteration is small.

[Michael Zolotukhin via Phabricator via llvm-commits]

mzolotukhin added a comment.

Hi,

I don't think that a right approach for it. We already have a lot of thresholds and I'd prefer to avoid adding another one as much as possible.

In this particular case it also seems that we can express the same 'bonus' with existing thresholds. There is `unroll-max-iteration-count-to-analyze`, which you might want to play with - if your loops have higher trip-counts then this thresholds, we don't try to predict benefits of unrolling and behave conservatively. Increasing this threshold should help unrolling more loops. If for some reason you don't want to change this parameter, then you can get almost the same effect as you propose by just bumping up `unroll-threshold`.

Please also note that we already take into account the fact that unrolling removes branches: see `getUnrolledLoopSize`.

Also, please also provide results of compile time testing for such changes.

Michael


https://reviews.llvm.org/D28368