Method of_opcode

cranelift/codegen/src/egraph/cost.rs:67–114

Return the cost of an opcode.

(op: Opcode)

    /// Return the cost of an opcode.
    fn of_opcode(op: Opcode) -> Cost {
        match op {
            // Constants.
            Opcode::Iconst | Opcode::F32const | Opcode::F64const => Cost::new(1),

            // Extends/reduces.
            Opcode::Uextend
            | Opcode::Sextend
            | Opcode::Ireduce
            | Opcode::Iconcat
            | Opcode::Isplit => Cost::new(1),

            // "Simple" arithmetic.
            Opcode::Iadd
            | Opcode::Isub
            | Opcode::Band
            | Opcode::Bor
            | Opcode::Bxor
            | Opcode::Bnot
            | Opcode::Ishl
            | Opcode::Ushr
            | Opcode::Sshr => Cost::new(3),

            // "Expensive" arithmetic.
            Opcode::Imul => Cost::new(10),

            // Everything else.
            _ => {
                // By default, be slightly more expensive than "simple"
                // arithmetic.
                let mut c = Cost::new(4);

                // And then get more expensive as the opcode does more side
                // effects.
                if op.can_trap() || op.other_side_effects() {
                    c = c + Cost::new(10);
                }
                if op.can_load() {
                    c = c + Cost::new(20);
                }
                if op.can_store() {
                    c = c + Cost::new(50);
                }

                c
            }
        }
    }

    /// Compute the cost of the operation and its given operands.
    ///