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

[Michael Zolotukhin via Phabricator via llvm-commits]

mzolotukhin added a comment.

> Could you point us to the benchmarks you observed regression after boosting fully unroll threshold?

I ran the standard LLVM testsuite in the past and I think I observed several runtime regressions. However my memory might play tricks on me, so if you've just remeasured it, you can ignore this.

> What do you mean by "guaranteed benefit"?

I meant that while some compiletime/runtime tradeoff might be acceptable, we definitely need to be aware of it before we land such changes, and we do have to have numbers at hand for that. Ideally, that would be pure win (runtime performance improves, compile time and code size is the same), but yeah, unfortunately it's unfeasible.

> update the data to remove the trip count logic and merely boost the fully unroll tripcount by 2X

What option do you mean by fully unroll tripcount threshold? `-unroll-threshold`?


https://reviews.llvm.org/D28368