[PATCH] D37236: [InstCombine] add insertelement + shuffle demanded element fold

[Craig Topper via Phabricator via llvm-commits]

craig.topper added a comment.

Why doesn't SimplifyDemandedBits drop %out012? It doesn't have multiple users.

It looks like once we evaluate %out0123 in SimplifyDemandedVectorElts, we stop the recursion right there and don't go back any further. This might have been ok if visitShuffleVectorInst had immediately returned based on SimplifyDemandedVectorElts returning non-null. If it had we would have re-added the shuffle to the worklist and reevaluated the SimplifyDemandedVectorElts again. But instead it just sets a MadeChange flag and goes on.


https://reviews.llvm.org/D37236