[mypyc] Update vec value struct to have direct pointer to items#21420
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[mypyc] Update vec value struct to have direct pointer to items#21420
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p-sawicki
reviewed
May 6, 2026
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| def vec_load_mem_item( | ||
| builder: LowLevelIRBuilder, | ||
| ptr: Value, | ||
| item_type: RType, | ||
| line: int, | ||
| *, | ||
| can_borrow: bool = False, | ||
| ) -> Value: | ||
| """Load a vec item from storage, converting nested vec slots to RVec values.""" | ||
| return builder.load_mem(ptr, item_type, borrow=can_borrow) | ||
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| def vec_set_mem_item( | ||
| builder: LowLevelIRBuilder, ptr: Value, item_type: RType, item: Value, line: int | ||
| ) -> None: | ||
| """Store a vec item, converting RVec values to nested storage items.""" | ||
| builder.set_mem(ptr, item_type, item) |
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the line arguments are unused
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| Py_DECREF(r.f0.buf); | ||
| Py_DECREF(r.f1.buf); |
Collaborator
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shouldn't we still decref the buffer of the parent vec in r.f0?
| typedef struct _VecNestedBufItem { | ||
| Py_ssize_t len; | ||
| PyObject *buf; | ||
| CPyPtr items; |
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i think this change made AI compare/set items to 0 instead of NULL because CPyPtr is size_t. but the field is still a pointer so it's a little confusing. maybe use void * instead? or change those comparisons/assignments.
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| if (self->vec.items) { | ||
| Py_DECREF(VEC_BUF(self->vec)); | ||
| self->vec.items = NULL; | ||
| } |
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Suggested change
| if (self->vec.items) { | |
| Py_DECREF(VEC_BUF(self->vec)); | |
| self->vec.items = NULL; | |
| } | |
| VecNested_clear() |
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| if (self->vec.items) { | ||
| Py_DECREF(VEC_BUF(self->vec)); | ||
| self->vec.items = NULL; | ||
| } |
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Suggested change
| if (self->vec.items) { | |
| Py_DECREF(VEC_BUF(self->vec)); | |
| self->vec.items = NULL; | |
| } | |
| VecT_clear() |
| view->obj = (PyObject *)self; | ||
| Py_INCREF(self); | ||
| view->buf = (self->vec.buf != NULL) ? (void *)self->vec.buf->items : NULL; | ||
| view->buf = (self->vec.items != NULL) ? (void *)self->vec.items : NULL; |
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Suggested change
| view->buf = (self->vec.items != NULL) ? (void *)self->vec.items : NULL; | |
| view->buf = (void *)self->vec.items; |
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Now the second field of a
vecstruct representation points to the first data item. Previously the second field of thevecstruct representation was aPyObject *targeting the buffer object. This removes one pointer addition per get item or set item operation. Since these are often the most performance critical operations, we want them to be as efficient as possible. This should reduce the number of instructions at least on ARM, and it will reduce code size on x64 as well.Since vec is still behind a feature flag, we can still break the ABI.
Used heavy coding agent assist, but iterated until the results look good.