[llvm] [SelectionDAG] Deal with POISON for INSERT_VECTOR_ELT/INSERT_SUBVECTOR (PR #143102)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon commented:

What happened to the plan to to add ISD::INSERT_SUBVECTOR to the multiple operand list in visitFREEZE? With that in place much of this logic can be simplified and we just FREEZE instead of calling isGuaranteedNotToBePoison explicitly so much

https://github.com/llvm/llvm-project/pull/143102