[PATCH] D91481: [LoopUnroll] Discount uniform instructions in cost models

Philip Reames via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Mon Nov 23 14:55:36 PST 2020

reames added a comment.

In D91481#2412365 <https://reviews.llvm.org/D91481#2412365>, @fhahn wrote:

> In D91481#2411958 <https://reviews.llvm.org/D91481#2411958>, @reames wrote:
>> In D91481#2410666 <https://reviews.llvm.org/D91481#2410666>, @samparker wrote:
>>> This looks sensible to me and a step in the right direction. Have you ran any benchmarks? Would be good to know, at least, that this isn't causing any obvious regressions.
>> I haven't.  I'm not particularly setup to do so easily either.
> It might be helpful to build llvm-test-suite and check the impact on the number of unrolled loops using statistics (-DTEST_SUITE_COLLECT_STATS)? That should give a rough idea on how broad the impact is going to be, without having actual HW for benchmarking.

This seems like overkill.  We have no reason to expect the impact from this to be high or negative for that matter.  I would strongly prefer simply landing and watching the bots.



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