[PATCH] D90170: [InstCombine] InstCombinerImpl::visitOr - enable bitreverse matching

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In D90170#2759102 <https://reviews.llvm.org/D90170#2759102>, @RKSimon wrote:

> In D90170#2759050 <https://reviews.llvm.org/D90170#2759050>, @lebedev.ri wrote:
>
>> LGTM, but from the llvm-xray traces of LLVM i've seen, IIRC matchBSwapOrBitReverse/collectbitparts is pretty high up in the list of cycle eaters.
>
> OK, I'm going to reduce the traversal tree depth in a separate patch first to make any nasty build time regressions due to the bitreverse matching more specific.

To be noted, i don't have any specific issues with *this* patch, just that whole transform as a whole.
I would maybe suggest to dyamically compute the `BitPartRecursionMaxDepth` based on the bitwidth,
and //maybe// change it to be a not depth-based cut-off, but a number of visited `Value`s.


Repository:
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https://reviews.llvm.org/D90170