[PATCH] D80658: [InstCombine] enhance vector demanded elements for select condition operand

Wed May 27 16:23:44 PDT 2020

spatel planned changes to this revision.
spatel added a comment.

In D80658#2058339 <https://reviews.llvm.org/D80658#2058339>, @efriedma wrote:

> I'm concerned that in some cases, the condition might be "demanded" due to poison rules, even if we don't actually care about the value.  See, for example, http://volta.cs.utah.edu:8080/z/YDSX7k

Yes, I overlooked poison in the condition operand itself. Given that, I don't see a way to salvage this approach vs. a pattern-specific fold for the motivating case (reducing a shuffle of the condition operand).
I'll leave this up for a bit in case anyone else sees a way forward.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D80658/new/

https://reviews.llvm.org/D80658