Function insert_opcode

cranelift/fuzzgen/src/function_generator.rs:31–73

(
    fgen: &mut FunctionGenerator,
    builder: &mut FunctionBuilder,
    opcode: Opcode,
    args: &[Type],
    rets: &[Type],
)

type BlockSignature = Vec<Type>;

fn insert_opcode(
    fgen: &mut FunctionGenerator,
    builder: &mut FunctionBuilder,
    opcode: Opcode,
    args: &[Type],
    rets: &[Type],
) -> Result<()> {
    let mut vals = Vec::with_capacity(args.len());
    for &arg in args.into_iter() {
        let var = fgen.get_variable_of_type(arg)?;
        let val = builder.use_var(var);
        vals.push(val);
    }

    // Some opcodes require us to look at their input arguments to determine the
    // controlling type. This is not the general case, but we can neatly check this
    // using `requires_typevar_operand`.
    let ctrl_type = if opcode.constraints().requires_typevar_operand() {
        args.first()
    } else {
        rets.first()
    }
    .copied()
    .unwrap_or(INVALID);

    // Choose the appropriate instruction format for this opcode
    let (inst, dfg) = match opcode.format() {
        InstructionFormat::NullAry => builder.ins().NullAry(opcode, ctrl_type),
        InstructionFormat::Unary => builder.ins().Unary(opcode, ctrl_type, vals[0]),
        InstructionFormat::Binary => builder.ins().Binary(opcode, ctrl_type, vals[0], vals[1]),
        InstructionFormat::Ternary => builder
            .ins()
            .Ternary(opcode, ctrl_type, vals[0], vals[1], vals[2]),
        _ => unimplemented!(),
    };
    let results = dfg.inst_results(inst).to_vec();

    for (val, &ty) in results.into_iter().zip(rets) {
        let var = fgen.get_variable_of_type(ty)?;
        builder.def_var(var, val);
    }
    Ok(())
}

fn insert_call_to_function(
    fgen: &mut FunctionGenerator,