This recommits the following patches now that D85684 has landed
1cf6f210a2e [IR] Disable select ? C : undef -> C fold in ConstantFoldSelectInstruction unless we know C isn't poison. 469da663f2d [InstSimplify] Re-enable select ?, undef, X -> X transform when X is provably not poison 122b0640fc9 [InstSimplify] Don't fold vectors of partial undef in SimplifySelectInst if the non-undef element value might produce poison ac0af12ed2f [InstSimplify] Add test cases for opportunities to fold select ?, X, undef -> X when we can prove X isn't poison 9b1e95329af [InstSimplify] Remove select ?, undef, X -> X and select ?, X, undef -> X transforms
Does the lowering for these intrinsics need to be adjusted in some way? This looks a bit odd and is possibly not what was intended with this fold gone. @dmgreen