Optimized code debugging

[dimdin]

The mechanisms are:

1. Atomics

   const _var = @atomicLoad(@TypeOf(some_var), &some_var, .seq_cst);
   

2. doNotOptimizeAway See: How to use std.mem.doNotOptimizeAway?
3. volatile Note: Benchmarking isDigit - #17 by andrewrk