[PATCH] D103788: [InstCombine] Eliminate casts to optimize ctlz operation

[Datta Nagraj via Phabricator via llvm-commits]

datta.nagraj added a comment.

@lebedev.ri In this opt: ctlz(zext(A)) --> add(ctlz(A), (bitwidth(zext(A))-bitwidth(A))

I think we require to look at the trunc because, the ctlz in the LHS is operating on higher datatype and the one on RHS is operating on a lower datatype.
If we pass the output of RHS to trunc, that would be wrong, as the datatype of ADD operation and trunc operation would be same. So, we do need to remove the trunc, isn't it.

Am I missing something here, please suggest?


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D103788/new/

https://reviews.llvm.org/D103788