[DAG] Add SimplifyDemandedVectorElts binop SimplifyMultipleUseDemandedBits…

Authored by RKSimon on May 25 2020, 4:41 AM.


[DAG] Add SimplifyDemandedVectorElts binop SimplifyMultipleUseDemandedBits handling

For the supported binops (basic arithmetic, logicals + shifts), if we fail to simplify the demanded vector elts, then call SimplifyMultipleUseDemandedBits and try to peek through ops to remove unnecessary dependencies.

This helps with PR40502.

Differential Revision: https://reviews.llvm.org/D79003