// `if_op_segment` refers to the segment of IfRegions to be merged.
// `return_indices` refers to the return indices to be kept in merged IfRegion
// `new_if_op` refers to the created new IfRegion
void CreateYieldOps(
    OpBuilder& builder, llvm::SmallVector<TF::IfRegionOp, 8>& if_op_segment,
    llvm::SmallVector<llvm::SmallVector<int, 4>>& return_indices,
    TF::IfRegionOp new_if_op, TF::IfRegionOp first_if) {