GH-112354: END_FOR instruction to only pop one value. (GH-114247)

* Compiler emits END_FOR; POP_TOP instead of END_FOR. To support tier 2 side exits in loops.

Author: markshannon

Doc/library/dis.rst

@@ -546,8 +546,8 @@ operations on it as if it was a Python list. The top of the stack corresponds to
 
 .. opcode:: END_FOR
 
-   Removes the top two values from the stack.
-   Equivalent to ``POP_TOP``; ``POP_TOP``.
+   Removes the top-of-stack item.
+   Equivalent to ``POP_TOP``.
    Used to clean up at the end of loops, hence the name.
 
    .. versionadded:: 3.12

Include/internal/pycore_global_objects_fini_generated.h

@@ -276,9 +276,11 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(after_in_child)
         STRUCT_FOR_ID(after_in_parent)
         STRUCT_FOR_ID(aggregate_class)
+        STRUCT_FOR_ID(alias)
         STRUCT_FOR_ID(allow_code)
         STRUCT_FOR_ID(append)
         STRUCT_FOR_ID(argdefs)
+        STRUCT_FOR_ID(args)
         STRUCT_FOR_ID(arguments)
         STRUCT_FOR_ID(argv)
         STRUCT_FOR_ID(as_integer_ratio)
@@ -402,6 +404,8 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(errors)
         STRUCT_FOR_ID(event)
         STRUCT_FOR_ID(eventmask)
+        STRUCT_FOR_ID(exc_type)
+        STRUCT_FOR_ID(exc_value)
         STRUCT_FOR_ID(excepthook)
         STRUCT_FOR_ID(exception)
         STRUCT_FOR_ID(existing_file_name)
@@ -655,6 +659,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(seek)
         STRUCT_FOR_ID(seekable)
         STRUCT_FOR_ID(selectors)
+        STRUCT_FOR_ID(self)
         STRUCT_FOR_ID(send)
         STRUCT_FOR_ID(sep)
         STRUCT_FOR_ID(sequence)
@@ -717,6 +722,7 @@ struct _Py_global_strings {
         STRUCT_FOR_ID(timetuple)
         STRUCT_FOR_ID(top)
         STRUCT_FOR_ID(trace_callback)
+        STRUCT_FOR_ID(traceback)
         STRUCT_FOR_ID(trailers)
         STRUCT_FOR_ID(translate)
         STRUCT_FOR_ID(true)

Include/internal/pycore_global_strings.h

@@ -464,6 +464,7 @@ def _write_atomic(path, data, mode=0o666):
 #     Python 3.13a1 3565 (Oparg of YIELD_VALUE indicates whether it is in a yield-from)
 #     Python 3.13a1 3566 (Emit JUMP_NO_INTERRUPT instead of JUMP for non-loop no-lineno cases)
 #     Python 3.13a1 3567 (Reimplement line number propagation by the compiler)
+#     Python 3.13a1 3568 (Change semantics of END_FOR)
 
 #     Python 3.14 will start with 3600
 
@@ -480,7 +481,7 @@ def _write_atomic(path, data, mode=0o666):
 # Whenever MAGIC_NUMBER is changed, the ranges in the magic_values array
 # in PC/launcher.c must also be updated.
 
-MAGIC_NUMBER = (3567).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3568).to_bytes(2, 'little') + b'\r\n'
 
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
 

Include/internal/pycore_opcode_metadata.h

@@ -49,6 +49,7 @@ def test_for_loop(self):
             ('JUMP', loop_lbl),
             exit_lbl,
             ('END_FOR', None),
+            ('POP_TOP', None),
             ('LOAD_CONST', 0),
             ('RETURN_VALUE', None),
         ]