Specialize long tail of binary operations using a table.

There is a desire to specialize the remaining binary operations (including binary subscript).
However adding more and more specialized instructions is likely to make performance worse.

This idea is to have a lookup table of types pairs and function pointers. This is less efficient than inlining the code, but more extensible.

A single instruction can then support up to 256 specializations.
This will only work for immutable classes.

struct table_entry {
    PyTypeObject *left;
    PyTypeObject *left;
    binaryfunc *func;
};

TARGET(BINARY_OP_TABLE) {
    PyObject *lhs = SECOND();
    PyObject *rhs = TOP();
    Cache *cache = GET_CACHE();
    struct table_entry* entry = &THE_TABLE[cache->table_index];
    DEOPT_IF(Py_TYPE(lhs) != entry->left);
    DEOPT_IF(Py_TYPE(rhs) != entry->right);
    PyObject *res = entry->func(lhs, rhs);
    if (res == NULL) {
        goto error;
    }
    STACK_SHRINK(1);
    Py_DECREF(lhs);
    Py_DECREF(rhs);
    SET_TOP(res);
    DISPATCH();
}

An ancillary mapping of (left, right) -> index will be needed for efficient specialization.

It is probably worth keeping the most common operations int + int, float + float, etc. inline.

We can replace BINARY_SUBSCR with BINARY_OP ([]) to allow effective specialization of BINARY_SUBSCR
E.g. subscripting array.array[int] can be handled with the registration mechanism described below.

Registering binary functions at runtime

faster-cpython/ideas#162

Linked PRs

pythongh-100239: specialize long tail of binary operations

Merge remote-tracking branch 'upstream/main' into pythongh-100239

Merge branch 'main' into pythongh-100239

gh-100239: specialize long tail of binary operations (#128722)

pythongh-100239: specialize bitwose logical binary ops

pythongh-100239: specialize bitwise logical binary ops on non-negativ…

#128722 broke repeated runs of test.test_ctypes.test_random_things.CallbackTracbackTestCase.test_FloatDivisionError, on several refleak buildbots e.g. https://buildbot.python.org/#/builders/920/builds/1287

Is it possible to fix this today?

#128722 broke repeated runs of test.test_ctypes.test_random_things.CallbackTracbackTestCase.test_FloatDivisionError, on several refleak buildbots e.g. https://buildbot.python.org/#/builders/920/builds/1287

Is it possible to fix this today?

I'll take care of it!

gh-100239: Handle NaN and zero division in guards for `BINARY_OP_EXTE…

gh-100239: specialize BINARY_OP/SUBSCR for list-slice (#132626)

gh-100239: Use ``PyFloat_AS_DOUBLE`` and `_PyLong_IsZero`` in the flo…

pythongh-100239: Use ``PyFloat_AS_DOUBLE`` and `_PyLong_IsZero`` in t…

pythongh-100239: Propagate type info through _BINARY_OP_EXTEND in tier 2

gh-100239: Propagate type info through _BINARY_OP_EXTEND in tier 2 (G…

Some additional ideas for further improvements #128956 (comment)

gh-100239: Specialize more binary operations using BINARY_OP_EXTEND (G…

pythongh-100239: expose `sq_repeat` helpers for `BINARY_OP_EXTEND`

pythongh-100239: Use ``PyFloat_AS_DOUBLE`` and `_PyLong_IsZero`` in t…

pythongh-100239: Propagate type info through _BINARY_OP_EXTEND in tie…

pythongh-100239: Specialize more binary operations using BINARY_OP_EX…

gh-100239: specialize mixed int/float inplace binary ops (GH-149413)

Merge branch 'main' into pythongh-100239/expose-sq-repeat-helpers

gh-100239: expose `sq_repeat` helpers for `BINARY_OP_EXTEND` (#148791)

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Registering binary functions at runtime

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Specialize long tail of binary operations using a table. #100239

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Registering binary functions at runtime

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encukou commented on Jan 17, 2025

Eclips4 commented on Jan 17, 2025

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eendebakpt commented on Apr 15, 2026

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