gh-146640: Optimize int operations by mutating uniquely-referenced operands in place (JIT only)

Include/internal/pycore_long.h

@@ -82,6 +82,14 @@ static inline PyObject* _PyLong_FromUnsignedChar(unsigned char i)
     return (PyObject *)&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS+i];
 }
 
+// Return a reference to the cached small int singleton.
+// The caller must ensure -_PY_NSMALLNEGINTS <= value < _PY_NSMALLPOSINTS.
+static inline PyObject* _PyLong_GetSmallInt(Py_ssize_t value)
+{
+    assert(-_PY_NSMALLNEGINTS <= value && value < _PY_NSMALLPOSINTS);
+    return (PyObject *)&_PyLong_SMALL_INTS[_PY_NSMALLNEGINTS + (int)value];
+}
+
 // _PyLong_Frexp returns a double x and an exponent e such that the
 // true value is approximately equal to x * 2**e.  x is
 // 0.0 if and only if the input is 0 (in which case, e and x are both