Test where the tipping point is

[recmo]

On 2020-09-24 @recmo wrote in f724670 “Optimize small exponents”:

Test where the tipping point is

                            (_, 0) => "0x01".to_owned(),
                            (a, 1) => a.soldity_encode(memory_layout),
                            (a, e) if *e <= 4 => {
                                format!("exp{}({})", e, a.soldity_encode(memory_layout))
                            }
                            // TODO: Test where the tipping point is
                            (a, e) if *e < 16 => {
                                format!(
                                    "small_expmod({}, {})",
                                    a.soldity_encode(memory_layout),
                                    e.to_string()

From crypto/stark/src/solidity_verifier.rs:171