Semi-instrumenting pass: don't allow breakpoints in this function but do allow them in functions we call

[oxinabox]

Right now we have two things we can do:

• Normal (fully instrumented) case:

  • allows breakpoints and stepping though this function
  • instruments any function we call
    • unless it is marked no_instrument
      - unless it is also marked with a breakpoint)

• No instrument case:

  • no breakpoints or stepping allowed in this function
  • functions that we call are not instrumented. No break-points can occur in them either

I propose that we could have a third case:

• SemiInstrumented:
  • No breakpoints or stepping is allowed in this function
  • functions that we call are also instrumented as per their settings:
    - in particular if a function contains a break point it will be fully instrumented.

This would still have the compile-time overhead of fully instrumenting (unlike non-instrumenting),
but it would avoid the runtime overhead of checking breakpoints between each statement.
(and thus would not break SIMD etc).

[willow-ahrens]

It would be really nice to avoid calls to certain libraries. This is commonly done with libraries like MPI, so that we don't get lost in verbose library code (if we don't want to). Another instance where this would be useful would be if we wanted to avoid cassette passes.