[PATCH] D47428: [InstCombine] PR37603: low bit mask canonicalization

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri added a comment.

In https://reviews.llvm.org/D47428#1117675, @spatel wrote:

> This is a good IR canonicalization regardless of what happens in the backend because a 'not' is better for bit-tracking analysis and other transforms than an 'add'.


Yep, i thought so too..

> I don't understand the nuw question:
>  https://rise4fun.com/Alive/ydD
> 
> We're missing this in instsimplify?

I think we do? https://godbolt.org/g/rT3k7v
But i was only thinking about replacing `and nuw` with `xor` there.


Repository:
  rL LLVM

https://reviews.llvm.org/D47428