gh-132775: Add _PyCode_ReturnsOnlyNone() (gh-132981)

The function indicates whether or not the function has a return statement.

This is used by a later change related treating some functions like scripts.

Include/internal/pycore_code.h

@@ -561,6 +561,10 @@ extern void _Py_ClearTLBCIndex(_PyThreadStateImpl *tstate);
 extern int _Py_ClearUnusedTLBC(PyInterpreterState *interp);
 #endif
 
+
+PyAPI_FUNC(int) _PyCode_ReturnsOnlyNone(PyCodeObject *);
+
+
 #ifdef __cplusplus
 }
 #endif

Include/internal/pycore_opcode_utils.h

@@ -54,6 +54,9 @@ extern "C" {
          (opcode) == RAISE_VARARGS || \
          (opcode) == RERAISE)
 
+#define IS_RETURN_OPCODE(opcode) \
+        (opcode == RETURN_VALUE)
+
 
 /* Flags used in the oparg for MAKE_FUNCTION */
 #define MAKE_FUNCTION_DEFAULTS    0x01