John Ericson authored Oct 19, 2019 and Marge Bot committed Jan 22, 2021

- `inversePrimOp` is renamed to `semiInversePrimOp` to indicate the
  given primop is only a right inverse, not left inverse (and
  contra-wise for the primop which we are giving rules for). This
  explains why are new usage is not incorrect.

- The removed `subsumedByPrimOp` calls were actually dead as the match
  on ill-typed code. @hsyl20 pointed this out in
  ghc/ghc!4390 (comment 311912),

Metric Decrease:
    T13701