Function type_suffix

cranelift/codegen/src/write.rs:287–315

Should `inst` be printed with a type suffix? Polymorphic instructions may need a suffix indicating the value of the controlling type variable if it can't be trivially inferred.

(func: &Function, inst: Inst)

// if it can't be trivially inferred.
//
fn type_suffix(func: &Function, inst: Inst) -> Option<Type> {
    let inst_data = &func.dfg.insts[inst];
    let constraints = inst_data.opcode().constraints();

    if !constraints.is_polymorphic() {
        return None;
    }

    // If the controlling type variable can be inferred from the type of the designated value input
    // operand, we don't need the type suffix.
    if constraints.use_typevar_operand() {
        let ctrl_var = inst_data.typevar_operand(&func.dfg.value_lists).unwrap();
        let def_block = match func.dfg.value_def(ctrl_var) {
            ValueDef::Result(instr, _) => func.layout.inst_block(instr),
            ValueDef::Param(block, _) => Some(block),
            ValueDef::Union(..) => None,
        };
        if def_block.is_some() && def_block == func.layout.inst_block(inst) {
            return None;
        }
    }

    let rtype = func.dfg.ctrl_typevar(inst);
    assert!(
        !rtype.is_invalid(),
        "Polymorphic instruction must produce a result"
    );
    Some(rtype)
}

/// Write out any aliases to the given target, including indirect aliases
fn write_value_aliases(