// branch functions to (a) drop the ununsed return values, and (b) as a result
// if some argument becomes unused in all branches, drop that argument and the
// corresponding if/case input operand.
void EliminateUnusedResultsForIfCase(Operation *op,
                                     ArrayRef<func::FuncOp> branches) {
  // Clone branch functions if needed since we will be mutating them.
  SmallVector<func::FuncOp, 2> cloned_branches;