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# JIT hooks in PyPy

There are several hooks in the `pypyjit` module that may help you with understanding what’s pypy’s JIT doing while running your program. There are three functions related to that coming from the `pypyjit` module:

`set_optimize_hook`(callable)

  Set a compiling hook that will be called each time a loop is optimized, but before assembler compilation. This allows adding additional optimizations on Python level.

  The callable will be called with the `pypyjit.JitLoopInfo` object. Refer to it’s documentation for details.

  Result value will be the resulting list of operations, or None

`set_compile_hook`(callable)

  Set a compiling hook that will be called each time a loop is compiled.

  The callable will be called with the `pypyjit.JitLoopInfo` object. Refer to it’s documentation for details.

  Note that jit hook is not reentrant. It means that if the code inside the jit hook is itself jitted, it will get compiled, but the jit hook won’t be called for that.

`set_abort_hook`(hook)

  Set a hook (callable) that will be called each time there is tracing aborted due to some reason.

  The hook will be invoked with the siagnture: `hook(jitdriver_name, greenkey, reason)`

  Reason is a string, the meaning of other arguments is the same as attributes on JitLoopInfo object

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