[llvm] [VPlan] Don't convert VPWidenSelectRecipes to vp.select in EVL transform (PR #146695)

[Philip Reames via llvm-commits]

preames wrote:

> However we currently also convert widened selects to vp.select even though they don't necessarily use the header mask.

This bit doesn't seem to match the code.  We only iterate through the users of the headermask calling createEVLRecipe.  You are right that we don't seem to rewrite the mask operand in the expected way though.  This patch otherwise makes sense, just making sure you don't have a bad assumption on your way to this outcome.  

https://github.com/llvm/llvm-project/pull/146695