[PATCH] D30446: [IndVars] Do not branch on poison

[Andrew Trick via Phabricator via llvm-commits]

atrick added a comment.

When I talk about creating or removing an IV, I'm talking about the strongly connected phi cycle. I'm not referring to any "derived IV" stemming from values that depend on the IV.

I found the dependent patches and roughly figured out what's hapenning here. It seems like we could leave the original IV's `nw` flags in place and simply introduce an `add` without the `nuw` flags for the branch's post-increment. Maybe that's what Eli is suggesting? I think that would result in a nicely canonical form, but it may require adjusting downstream passes. I think the risk of interfering with downstream passes could be reduced by moving all of LFTR into LSR.


https://reviews.llvm.org/D30446