When comparing two different sets of instruction counts, on
      stumbling block can be path prefixes. Callgrind includes the
      full filepath when reporting a function (as it should). However,
      this can cause issues when diffing profiles. If a key component
      such as Python or PyTorch was built in separate locations in the
      two profiles, which can result in something resembling:
     23234231 /tmp/first_build_dir/thing.c:foo(...)
      9823794 /tmp/first_build_dir/thing.c:bar(...)
       ...
        53453 .../aten/src/Aten/...:function_that_actually_changed(...)
       ...
      -9823794 /tmp/second_build_dir/thing.c:bar(...)
     -23234231 /tmp/second_build_dir/thing.c:foo(...)

  Stripping prefixes can ameliorate this issue by regularizing the
  strings and causing better cancellation of equivalent call sites
  when diffing.

  Return type:
     *CallgrindStats*

counts(*, denoise=False)