This crate needs nightly. (for feature(asm))
OS: Ubuntu 18.04, CPU: AMD Ryzen 7 2700X, rustc 1.51.0-nightly (257becbfe 2020-12-27)
```
reference::mulmod_u64 time: [23.077 ns 23.102 ns 23.134 ns]
Found 4 outliers among 100 measurements (4.00%)
3 (3.00%) high mild
1 (1.00%) high severe
mulmod_u64 time: [10.223 ns 10.230 ns 10.236 ns]
reference::mod_u128u64 time: [36.684 ns 36.705 ns 36.727 ns]
Found 18 outliers among 100 measurements (18.00%)
16 (16.00%) high mild
2 (2.00%) high severe
mod_u128u64 time: [13.862 ns 13.869 ns 13.878 ns]
reference::powmod_u64 time: [2.2811 us 2.2840 us 2.2872 us]
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mild
powmod_u64 time: [916.39 ns 917.03 ns 917.77 ns]
Found 2 outliers among 100 measurements (2.00%)
2 (2.00%) high mild
```