A better way to inspect the code of the benchmark loop/kernel

Doing benchmark correctly sometimes involving making sure there's no additional overhead (e.g. due to accidental use of global variables) and the operation being benchmarked isn't optimized out (most likely due to constant propagation). In additional to documenting and giving examples about different ways to supply the parameters to the benchmark, I think it'll be useful to provide a way to show the code actually running in the loop.

This is also most relevant for cheap operations...

No file, test, or entry point is named. Start by reviewing the existing benchmark parameter APIs and documentation, then determine how a user could inspect the code running in the benchmark loop or kernel. Done means documented parameter-supply examples and a way to verify that benchmarking adds no unintended overhead and that the operation is not optimized out.