[PATCH] D106408: Allow rematerialization of virtual reg uses

Mon Jul 26 05:46:34 PDT 2021

luismarques added a comment.

In D106408#2903678 <https://reviews.llvm.org/D106408#2903678>, @dmgreen wrote:

> Tail predication being awkward aside - do you have performance results for this patch? Something to show it is beneficial to do over a set of benchmarks.

I had earlier benchmarked this patch for an embedded RISC-V system (Ibex simple system). Not a comprehensive set of results at all, but in case it's useful:

- For CoreMark it had negligible size impact. At Oz and Os it had a small performance benefit (+1.17% and +0.178%, respectively). At O2 <https://reviews.llvm.org/owners/package/2/> and O3 <https://reviews.llvm.org/owners/package/3/> the performance difference was negligible (-0.016% and +0.038%, respectively).
- For Embench it had no performance impact but improved size a bit, overall. The best case was O2 <https://reviews.llvm.org/owners/package/2/>, where the size was overall reduced by 440 bytes, or 0.276%. Most programs of that benchmark suite had minor differences, some positive and some negative, but for picojpeg it shaved up to 384 bytes.

(Raw results here, in a confusing format: https://gist.github.com/luismarques/01948685c6a1d16ab1c1a0229252b0f1. Please ignore the absolute performance values).

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