You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: pass_mode.rs
    path of file: ./repos/rustc_codegen_cranelift/src/abi
    
    the code of the file until where you have to start completion: //! Argument passing

use cranelift_codegen::ir::{ArgumentExtension, ArgumentPurpose};
use rustc_target::abi::call::{
    ArgAbi, ArgAttributes, ArgExtension as RustcArgExtension, CastTarget, PassMode, Reg, RegKind,
};
use smallvec::{smallvec, SmallVec};

use c
    
    fn get_abi_return(&self, tcx: TyCtxt<'tcx>) -> (Option<AbiParam>, Vec<AbiParam>) {
        match self.mode {
            PassMode::Ignore => (None, vec![]),
            PassMode::Direct(_) => match self.layout.abi {
                Abi::Scalar(scalar) => {
                    (None, vec![AbiParam::new(scalar_to_clif_type(tcx, scalar))])
                }
                Abi::Vector { .. } => {
                    let vector_ty = crate::intrinsics::clif_vector_type(tcx, self.layout);
                    (None, vec![AbiParam::new(vector_ty)])
                }
                _ => unreachable!("{:?}", self.layout.abi),
            },
            PassMode::Pair(_, _) => match self.layout.abi {
                Abi::ScalarPair(a, b) => {
                    let a = scalar_to_clif_type(tcx, a);
                    let b = scalar_to_clif_type(tcx, b);
                    (None, vec![AbiParam::new(a), AbiParam::new(b)])
                }
                _ => unreachable!("{:?}", self.layout.abi),
            },
            PassMode::Cast { ref cast, .. } => {
                (None, cast_target_to_abi_params(cast).into_iter().collect())
            }
            PassMode::Indirect { attrs: _, meta_attrs: None, on_stack } => {
                assert!(!on_stack);
                (Some(AbiParam::special(pointer_ty(tcx), ArgumentPurpose::StructReturn)), vec![])
            }
            PassMode::Indirect { attrs: _, meta_attrs: Some(_), on_stack: _ } => {
                unreachable!("unsized return value")
            }
        }
    }