[PATCH] D45173: [InstCombine] Recognize idioms for ctpop and ctlz

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In https://reviews.llvm.org/D45173#1059921, @kparzysz wrote:

> Moving aggressive instcombine pass to before the regular instcombine, just to demonstrate the idea.


I'm curious to know, while this does sidestep the issue of having to adapt to the instcombine/earlier passes being smarter, how does this not either
a) significantly increase the amount of matching this pass needs to do (due to being in the earlier position in the pipe),  or
b) reduce the number of patterns this pass will handle?

Unless of course the only desire is to match exactly those patterns that are being tested, and exactly those patterns only...


Repository:
  rL LLVM

https://reviews.llvm.org/D45173