René's URL Explorer Experiment

Title: bpo-43693: Add new internal code objects fields: co_fastlocalnames and co_fastlocalkinds. by ericsnowcurrently · Pull Request #26388 · python/cpython · GitHub

Open Graph Title: bpo-43693: Add new internal code objects fields: co_fastlocalnames and co_fastlocalkinds. by ericsnowcurrently · Pull Request #26388 · python/cpython

X Title: bpo-43693: Add new internal code objects fields: co_fastlocalnames and co_fastlocalkinds. by ericsnowcurrently · Pull Request #26388 · python/cpython

Description: A number of places in the code base (notably ceval.c and frameobject.c) rely on mapping variable names to indices in the frame "locals plus" array (AKA fast locals), and thus opargs. Currently the compiler indirectly encodes that information on the code object as the tuples co_varnames, co_cellvars, and co_freevars. At runtime the dependent code must calculate the proper mapping from those, which isn't ideal and impacts performance-sensitive sections. This is something we can easily address in the compiler instead. This PR addresses the situation by replacing internal use of co_varnames, etc. with a single combined tuple of names in locals-plus order, along with a minimal array mapping each to its kind (local vs. cell vs. free). These two new PyCodeObject fields, co_fastlocalnames and co_fastllocalkinds, are not exposed to Python code for now, but co_varnames, etc. are still available with the same values as before (though computed lazily). Aside from the (mild) performance impact, there are a number of other benefits: there's now a clear, direct relationship between locals-plus and variables code that relies on the locals-plus-to-name mapping is simpler marshaled code objects are smaller and serialize/de-serialize faster Also note that we can take this approach further by expanding the possible values in co_fastlocalkinds to include specific argument types (e.g. positional-only, kwargs). Doing so would allow further speed-ups in _PyEval_MakeFrameVector(), which is where args get unpacked into the locals-plus array. It would also allow us to shrink marshaled code objects even further. (FYI, I have a later PR that relies on having this direct mapping instead of co_varnames.) FWIW, if this PR is too big I can split it up between "add the fields" and "use the fields". However, typically in this project we keep those together in one change. https://bugs.python.org/issue43693

Open Graph Description: A number of places in the code base (notably ceval.c and frameobject.c) rely on mapping variable names to indices in the frame "locals plus" array (AKA fast locals), and thus opargs. Cur...

X Description: A number of places in the code base (notably ceval.c and frameobject.c) rely on mapping variable names to indices in the frame "locals plus" array (AKA fast locals), and thus opar...

Opengraph URL: https://github.com/python/cpython/pull/26388

X: @github

direct link

Domain: github.com

Links:

Viewport: width=device-width