[PATCH] D99588: [ARM] Allow v6m runtime loop unrolling

[Dave Green via Phabricator via llvm-commits]

dmgreen added a comment.

I'm not sure exactly why T1 unrolling wasn't enabled in the past. I think it was causing more trouble than it was worth, and not being a focus at the time was dropped fairly early. The extra tuning that was done for T2 after that would have helped T1 not regress too.

As with any change like this, some things are better, a few things are worse. In general the performance looks good though (I would not have suggested it if it didn't!). I've done a few minor changes elsewhere, but they were fairly generic, not v6m specific. There is more that we could probably get out of it in by tuning it in places, and I was contemplating whether to try and tune that now or to get this in and work from there. All the geomeans of the benchmarks I've ran are looking healthy though.


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https://reviews.llvm.org/D99588