perf(longobject): add freelist for 2-digit PyLong objects

Non-compact (2-digit) int results previously bypassed the freelist and called PyObject_Malloc directly. Add an `ints2` freelist alongside the existing `ints` (1-digit) freelist.

- `long_alloc(2)` checks `ints2` before `PyObject_Malloc`
- `_PyLong_ExactDealloc` and `long_dealloc` recycle exact 2-digit ints to `ints2` instead of immediately freeing them
- `_PyObject_ClearFreeLists` clears `ints2` the same way as `ints`

Author: KRRT7

Include/internal/pycore_freelist_state.h

@@ -18,6 +18,7 @@ extern "C" {
 #  define Py_floats_MAXFREELIST 100
 #  define Py_complexes_MAXFREELIST 100
 #  define Py_ints_MAXFREELIST 100
+#  define Py_ints2_MAXFREELIST 100
 #  define Py_slices_MAXFREELIST 1
 #  define Py_ranges_MAXFREELIST 6
 #  define Py_range_iters_MAXFREELIST 6
@@ -47,6 +48,7 @@ struct _Py_freelists {
     struct _Py_freelist floats;
     struct _Py_freelist complexes;
     struct _Py_freelist ints;
+    struct _Py_freelist ints2;
     struct _Py_freelist tuples[PyTuple_MAXSAVESIZE];
     struct _Py_freelist lists;
     struct _Py_freelist list_iters;

Objects/longobject.c

@@ -172,6 +172,9 @@ long_alloc(Py_ssize_t size)
     if (ndigits == 1) {
         result = (PyLongObject *)_Py_FREELIST_POP(PyLongObject, ints);
     }
+    else if (ndigits == 2) {
+        result = (PyLongObject *)_Py_FREELIST_POP(PyLongObject, ints2);
+    }
     if (result == NULL) {
         /* Number of bytes needed is: offsetof(PyLongObject, ob_digit) +
         sizeof(digit)*size.  Previous incarnations of this code used
@@ -3644,6 +3647,10 @@ _PyLong_ExactDealloc(PyObject *self)
         _Py_FREELIST_FREE(ints, self, PyObject_Free);
         return;
     }
+    if (_PyLong_DigitCount((PyLongObject *)self) == 2) {
+        _Py_FREELIST_FREE(ints2, self, PyObject_Free);
+        return;
+    }
     PyObject_Free(self);
 }
 
@@ -3664,6 +3671,10 @@ long_dealloc(PyObject *self)
         _Py_FREELIST_FREE(ints, self, PyObject_Free);
         return;
     }
+    if (PyLong_CheckExact(self) && _PyLong_DigitCount((PyLongObject *)self) == 2) {
+        _Py_FREELIST_FREE(ints2, self, PyObject_Free);
+        return;
+    }
     Py_TYPE(self)->tp_free(self);
 }
 

Objects/object.c

@@ -952,6 +952,7 @@ _PyObject_ClearFreeLists(struct _Py_freelists *freelists, int is_finalization)
     clear_freelist(&freelists->unicode_writers, is_finalization, PyMem_Free);
     clear_freelist(&freelists->bytes_writers, is_finalization, PyMem_Free);
     clear_freelist(&freelists->ints, is_finalization, free_object);
+    clear_freelist(&freelists->ints2, is_finalization, free_object);
     clear_freelist(&freelists->pycfunctionobject, is_finalization, PyObject_GC_Del);
     clear_freelist(&freelists->pycmethodobject, is_finalization, PyObject_GC_Del);
     clear_freelist(&freelists->pymethodobjects, is_finalization, free_object);