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gh-131798: constant fold classmethod and staticmethod in JIT by kumaraditya303 · Pull Request #148331 · python/cpython · GitHub

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gh-131798: constant fold classmethod and staticmethod in JIT - #148331

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kumaraditya303 wants to merge 7 commits into
python:mainfrom
kumaraditya303:jit-classmethod
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gh-131798: constant fold classmethod and staticmethod in JIT#148331
kumaraditya303 wants to merge 7 commits into
python:mainfrom
kumaraditya303:jit-classmethod

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kumaraditya303 commented Apr 10, 2026 •
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Script used for benchmark:

"""Benchmark for classmethod/staticmethod JIT optimization."""

import time

LOOPS = 10_000_000


class MyClass:
    @classmethod
    def class_method(cls):
        return cls

    @staticmethod
    def static_method():
        return 42

    def regular_method(self):
        return self


obj = MyClass()


def bench_classmethod():
    o = obj
    for _ in range(LOOPS):
        o.class_method()
        o.class_method()
        o.class_method()
        o.class_method()
        o.class_method()


def bench_staticmethod():
    o = obj
    for _ in range(LOOPS):
        o.static_method()
        o.static_method()
        o.static_method()
        o.static_method()
        o.static_method()


benchmarks = [
    ("classmethod", bench_classmethod),
    ("staticmethod", bench_staticmethod),
]

for name, func in benchmarks:
    t0 = time.perf_counter()
    func()
    dt = time.perf_counter() - t0
    print(f"{name:20s} {dt:.3f}s")
Benchmark main PR Speedup
classmethod 1.000s 0.572s 1.75x faster
staticmethod 0.860s 0.482s 1.78x faster

bedevere-app Bot mentioned this pull request Apr 10, 2026
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kumaraditya303 marked this pull request as ready for review April 10, 2026 14:01

kumaraditya303 commented Apr 11, 2026

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This can be done for class lookups as well so things like Foo.bar() where bar is a classmethod gets constant folded.

Fidget-Spinner commented Apr 12, 2026

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I don't see any change in deltablue, but that's because it's using cls.classmethod() instead of self.classmethod(). Would you like to add that to this PR as well? https://github.com/python/pyperformance/blob/main/pyperformance/data-files/benchmarks/bm_deltablue/run_benchmark.py#L234

Fidget-Spinner commented Apr 12, 2026

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I don't see any change in deltablue, but that's because it's using cls.classmethod() instead of self.classmethod(). Would you like to add that to this PR as well? https://github.com/python/pyperformance/blob/main/pyperformance/data-files/benchmarks/bm_deltablue/run_benchmark.py#L234

This turned out to be harder than I thought, because it would fold the classmethod descriptor into a unbound method lookup rather than a bound one, which changes the following CALL_BOUND_METHOD_EXACT_ARGS in the trace.

NekoAsakura commented Apr 13, 2026

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The outer else doesn't set self_or_null[0], intentional?

markshannon reviewed Apr 15, 2026
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Comment thread Python/optimizer_bytecodes.c Outdated

markshannon commented Apr 15, 2026

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I don't see any change in deltablue, but that's because it's using cls.classmethod() instead of self.classmethod(). Would you like to add that to this PR as well? https://github.com/python/pyperformance/blob/main/pyperformance/data-files/benchmarks/bm_deltablue/run_benchmark.py#L234

This turned out to be harder than I thought, because it would fold the classmethod descriptor into a unbound method lookup rather than a bound one, which changes the following CALL_BOUND_METHOD_EXACT_ARGS in the trace.

That shouldn't be a problem for staticmethod though, as self_or_null is always NULL.

It would make sense for LOAD_ATTR 1 for classmethod to be leaving func cls on the stack.

If we special case classmethod in _PyObject_GetMethodStackRef, it should add negligible overhead in the interpreter (possibly speeding things up if classmethods are common) and will enable this optimization in the JIT.

Fidget-Spinner commented Apr 15, 2026

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If we special case classmethod in _PyObject_GetMethodStackRef, it should add negligible overhead in the interpreter (possibly speeding things up if classmethods are common) and will enable this optimization in the JIT.

Working on that.

github-actions Bot commented May 18, 2026

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This PR is stale because it has been open for 30 days with no activity.

github-actions Bot added the stale Stale PR or inactive for long period of time. label May 18, 2026

ambv commented Oct 20, 2026

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This PR is superseded by #157011, a newer open pull request for the same issue (gh-131798), and it no longer merges cleanly. Closing to cull the number of open pull requests. Do not reopen this pull request without getting a go-ahead from a triager or core developer.

ambv closed this Oct 20, 2026
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tomasr8 Awaiting requested review from tomasr8 tomasr8 is a code owner
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savannahostrowski Awaiting requested review from savannahostrowski
markshannon Awaiting requested review from markshannon markshannon is a code owner

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