New submission from Gregory P. Smith <g...@krypto.org>:
The opcodes generated for the closure defining a class body looks like they might be suboptimal. It seems stuck using the generic LOAD_NAME and STORE_NAME opcodes rather than the LOAD_GLOBAL and STORE_FAST and friends as one would expect and as happens within a normal function closure. If true and the normal optimization pass (which I believe is done by `compiler.c` `compiler_nameop()` if i'm understanding this area of the code I don't know very well correctly...?) is not happening, it _appears_ maybe to be due to the `PyST_GetScope` call not currently having a way to represent this situation rather than being in a normal function? I tried searching for an open issue on this but was at a loss of what to search for. semi-related concepts might be found in: https://bugs.python.org/issue34750 - "locals().update doesn't work in Enum body, even though direct assignment to locals() does" https://bugs.python.org/issue10399 - "AST Optimization: inlining of function calls" https://bugs.python.org/issue9226 - "errors creating classes inside a closure" None of those is really the same though. if there are other filed issues regarding this, feel free to link to them in comments. If this can be improved as it has been for function bodies already, it should be a measurable improvement to CPython startup time and/or import time. Especially on larger programs and things with a lot of generated code full of classes. ``` >>> import dis >>> klass_def = ''' ... class Klassy: ... pinky = 'brain' ... def Funktion(castle_argh): ... __module__ = __name__ ... __qualname__ = 'not Klassy' ... pinky = 'brain' ... ''' >>> dis.dis(compile(klass_def, '<Hi mom!>', 'exec')) 2 0 LOAD_BUILD_CLASS 2 LOAD_CONST 0 (<code object Klassy at 0x7f62f4f6e3a0, file "<Hi mom!>", line 2>) 4 LOAD_CONST 1 ('Klassy') 6 MAKE_FUNCTION 0 8 LOAD_CONST 1 ('Klassy') 10 CALL_FUNCTION 2 12 STORE_NAME 0 (Klassy) 4 14 LOAD_CONST 2 (<code object Funktion at 0x7f62f4f7fa80, file "<Hi mom!>", line 4>) 16 LOAD_CONST 3 ('Funktion') 18 MAKE_FUNCTION 0 20 STORE_NAME 1 (Funktion) 22 LOAD_CONST 4 (None) 24 RETURN_VALUE Disassembly of <code object Klassy at 0x7f62f4f6e3a0, file "<Hi mom!>", line 2>: 2 0 LOAD_NAME 0 (__name__) 2 STORE_NAME 1 (__module__) 4 LOAD_CONST 0 ('Klassy') 6 STORE_NAME 2 (__qualname__) 3 8 LOAD_CONST 1 ('brain') 10 STORE_NAME 3 (pinky) 12 LOAD_CONST 2 (None) 14 RETURN_VALUE Disassembly of <code object Funktion at 0x7f62f4f7fa80, file "<Hi mom!>", line 4>: 5 0 LOAD_GLOBAL 0 (__name__) 2 STORE_FAST 1 (__module__) 6 4 LOAD_CONST 1 ('not Klassy') 6 STORE_FAST 2 (__qualname__) 7 8 LOAD_CONST 2 ('brain') 10 STORE_FAST 3 (pinky) 12 LOAD_CONST 0 (None) 14 RETURN_VALUE ``` ---------- components: Interpreter Core messages: 379839 nosy: gregory.p.smith, twouters priority: normal severity: normal stage: needs patch status: open title: class body bytecode uses less efficient *_NAME opcodes type: performance versions: Python 3.10 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue42185> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
