bpo-17611: Move unwinding of stack from interpreter to compiler

Doc/library/dis.rst

@@ -335,6 +335,14 @@ The Python compiler currently generates the following bytecode instructions.
    three.
 
 
+.. opcode:: ROT_FOUR
+
+   Lifts second, third and forth stack items one position up, moves top down
+   to position four.
+
+   .. versionadded:: 3.7
+
+
 .. opcode:: DUP_TOP
 
    Duplicates the reference on top of the stack.
@@ -576,11 +584,10 @@ the original TOS1.
    Resolves ``__aenter__`` and ``__aexit__`` from the object on top of the
    stack.  Pushes ``__aexit__`` and result of ``__aenter__()`` to the stack.
 
-
 .. opcode:: SETUP_ASYNC_WITH
 
-   Creates a new frame object.
-
+   Pushes a new frame block on the block stack.  The top of stack value
+   is moved to after the new block.
 
 
 **Miscellaneous opcodes**
@@ -592,17 +599,6 @@ the original TOS1.
    is terminated with :opcode:`POP_TOP`.
 
 
-.. opcode:: BREAK_LOOP
-
-   Terminates a loop due to a :keyword:`break` statement.
-
-
-.. opcode:: CONTINUE_LOOP (target)
-
-   Continues a loop due to a :keyword:`continue` statement.  *target* is the
-   address to jump to (which should be a :opcode:`FOR_ITER` instruction).
-
-
 .. opcode:: SET_ADD (i)
 
    Calls ``set.add(TOS1[-i], TOS)``.  Used to implement set comprehensions.
@@ -649,6 +645,7 @@ iterations of the loop.
 
    .. versionadded:: 3.6
 
+
 .. opcode:: IMPORT_STAR
 
    Loads all symbols not starting with ``'_'`` directly from the module TOS to
@@ -659,7 +656,7 @@ iterations of the loop.
 .. opcode:: POP_BLOCK
 
    Removes one block from the block stack.  Per frame, there is a stack of
-   blocks, denoting nested loops, try statements, and such.
+   blocks, denoting :keyword:`try` statements, and such.
 
 
 .. opcode:: POP_EXCEPT
@@ -670,11 +667,28 @@ iterations of the loop.
    popped values are used to restore the exception state.
 
 
-.. opcode:: END_FINALLY
+.. opcode:: PUSH_NO_EXCEPT
+
+   Push NULL on the stack.  This signals to exception handling opcodes that no
+   exception occurred.
+
+   .. versionadded:: 3.7
+
 
-   Terminates a :keyword:`finally` clause.  The interpreter recalls whether the
-   exception has to be re-raised, or whether the function returns, and continues
-   with the outer-next block.
+.. opcode:: POP_NO_EXCEPT
+
+   Clear the current exception.  Pop exception info from the stack and the
+   block stack.
+
+   .. versionadded:: 3.7
+
+
+.. opcode:: RERAISE
+
+   If a finally block was entered with an exception, re-raise the exception.
+   Otherwise, exit the finally block normally.
+
+   .. versionadded:: 3.7
 
 
 .. opcode:: LOAD_BUILD_CLASS
@@ -694,33 +708,34 @@ iterations of the loop.
    store it in (a) variable(s) (:opcode:`STORE_FAST`, :opcode:`STORE_NAME`, or
    :opcode:`UNPACK_SEQUENCE`).
 
-
 .. opcode:: WITH_CLEANUP_START
 
-   Cleans up the stack when a :keyword:`with` statement block exits.  TOS is the
-   context manager's :meth:`__exit__` bound method. Below TOS are 1--3 values
-   indicating how/why the finally clause was entered:
+   Starts cleaning up the stack when a :keyword:`with` statement block exits.
 
-   * SECOND = ``None``
-   * (SECOND, THIRD) = (``WHY_{RETURN,CONTINUE}``), retval
-   * SECOND = ``WHY_*``; no retval below it
-   * (SECOND, THIRD, FOURTH) = exc_info()
+   At the top of the stack are either ``NULL`` (pushed by
+   :opcode:`BEGIN_FINALLY`), or 6 values pushed if an exception has been
+   raised in the with block.  Below is the context manager's
+   :meth:`~object.__exit__` bound method.
 
-   In the last case, ``TOS(SECOND, THIRD, FOURTH)`` is called, otherwise
-   ``TOS(None, None, None)``.  Pushes SECOND and result of the call
-   to the stack.
+   If TOS is ``NULL``, calls ``SECOND(None, None, None)``, otherwise calls
+   ``SEVENTH(TOP, SECOND, THIRD)``.  Pushes result of the call and TOS to the
+   stack.
 
 
 .. opcode:: WITH_CLEANUP_FINISH
 
-   Pops exception type and result of 'exit' function call from the stack.
+   Finishes cleaning up the stack when a :keyword:`with` statement block exits.
 
-   If the stack represents an exception, *and* the function call returns a
-   'true' value, this information is "zapped" and replaced with a single
-   ``WHY_SILENCED`` to prevent :opcode:`END_FINALLY` from re-raising the
-   exception.  (But non-local gotos will still be resumed.)
+   TOS is result of ``__exit__()`` function call pushed by
+   :opcode:`WITH_CLEANUP_START`.  SECOND indicates the action.
 
-   .. XXX explain the WHY stuff!
+   * If SECOND is ``NULL`` (pushed by :opcode:`BEGIN_FINALLY`) continue from
+     the next instruction.  4 values are popped from the stack.
+   * If SECOND is an exception type (pushed when an exception has been raised)
+     re-raise the exception and restore ``sys.exc_info()``. 9 values are
+     popped from the stack.
+
+   .. versionchanged:: 3.7
 
 
 All of the following opcodes use their arguments.
@@ -960,22 +975,10 @@ All of the following opcodes use their arguments.
    Loads the global named ``co_names[namei]`` onto the stack.
 
 
-.. opcode:: SETUP_LOOP (delta)
-
-   Pushes a block for a loop onto the block stack.  The block spans from the
-   current instruction with a size of *delta* bytes.
-
-
-.. opcode:: SETUP_EXCEPT (delta)
-
-   Pushes a try block from a try-except clause onto the block stack. *delta*
-   points to the first except block.
-
-
 .. opcode:: SETUP_FINALLY (delta)
 
-   Pushes a try block from a try-except clause onto the block stack. *delta*
-   points to the finally block.
+   Pushes a try block from a try-finally or try-except clause onto the block
+   stack.  *delta* points to the finally block or the first except block.
 
 
 .. opcode:: LOAD_FAST (var_num)

Include/opcode.h

@@ -12,6 +12,7 @@ extern "C" {
 #define ROT_THREE                 3
 #define DUP_TOP                   4
 #define DUP_TOP_TWO               5
+#define ROT_FOUR                  6
 #define NOP                       9
 #define UNARY_POSITIVE           10
 #define UNARY_NEGATIVE           11
@@ -29,6 +30,8 @@ extern "C" {
 #define BINARY_TRUE_DIVIDE       27
 #define INPLACE_FLOOR_DIVIDE     28
 #define INPLACE_TRUE_DIVIDE      29
+#define WITH_CLEANUP_START       40
+#define WITH_CLEANUP_FINISH      41
 #define GET_AITER                50
 #define GET_ANEXT                51
 #define BEFORE_ASYNC_WITH        52
@@ -55,15 +58,14 @@ extern "C" {
 #define INPLACE_AND              77
 #define INPLACE_XOR              78
 #define INPLACE_OR               79
-#define BREAK_LOOP               80
-#define WITH_CLEANUP_START       81
-#define WITH_CLEANUP_FINISH      82
+#define RERAISE                  80
+#define POP_NO_EXCEPT            81
 #define RETURN_VALUE             83
 #define IMPORT_STAR              84
 #define SETUP_ANNOTATIONS        85
 #define YIELD_VALUE              86
 #define POP_BLOCK                87
-#define END_FINALLY              88
+#define PUSH_NO_EXCEPT           88
 #define POP_EXCEPT               89
 #define HAVE_ARGUMENT            90
 #define STORE_NAME               90
@@ -92,8 +94,6 @@ extern "C" {
 #define POP_JUMP_IF_FALSE       114
 #define POP_JUMP_IF_TRUE        115
 #define LOAD_GLOBAL             116
-#define CONTINUE_LOOP           119
-#define SETUP_LOOP              120
 #define SETUP_EXCEPT            121
 #define SETUP_FINALLY           122
 #define LOAD_FAST               124

Lib/importlib/_bootstrap_external.py

@@ -242,6 +242,7 @@ def _write_atomic(path, data, mode=0o666):
 #     Python 3.6rc1 3379 (more thorough __class__ validation #23722)
 #     Python 3.7a0  3390 (add LOAD_METHOD and CALL_METHOD opcodes)
 #     Python 3.7a0  3391 (update GET_AITER #31709)
+#     Python 3.7a0  3392 (bpo-17611: move frame block handling to compiler)
 #
 # MAGIC must change whenever the bytecode emitted by the compiler may no
 # longer be understood by older implementations of the eval loop (usually
@@ -250,7 +251,7 @@ 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 = (3391).to_bytes(2, 'little') + b'\r\n'
+MAGIC_NUMBER = (3392).to_bytes(2, 'little') + b'\r\n'
 _RAW_MAGIC_NUMBER = int.from_bytes(MAGIC_NUMBER, 'little')  # For import.c
 
 _PYCACHE = '__pycache__'

Lib/opcode.py

@@ -60,6 +60,7 @@ def jabs_op(name, op):
 def_op('ROT_THREE', 3)
 def_op('DUP_TOP', 4)
 def_op('DUP_TOP_TWO', 5)
+def_op('ROT_FOUR', 6)
 
 def_op('NOP', 9)
 def_op('UNARY_POSITIVE', 10)
@@ -83,6 +84,9 @@ def jabs_op(name, op):
 def_op('INPLACE_FLOOR_DIVIDE', 28)
 def_op('INPLACE_TRUE_DIVIDE', 29)
 
+def_op('WITH_CLEANUP_START', 40)
+def_op('WITH_CLEANUP_FINISH', 41)
+
 def_op('GET_AITER', 50)
 def_op('GET_ANEXT', 51)
 def_op('BEFORE_ASYNC_WITH', 52)
@@ -113,16 +117,15 @@ def jabs_op(name, op):
 def_op('INPLACE_AND', 77)
 def_op('INPLACE_XOR', 78)
 def_op('INPLACE_OR', 79)
-def_op('BREAK_LOOP', 80)
-def_op('WITH_CLEANUP_START', 81)
-def_op('WITH_CLEANUP_FINISH', 82)
+def_op('RERAISE', 80)
+def_op('POP_NO_EXCEPT', 81)
 
 def_op('RETURN_VALUE', 83)
 def_op('IMPORT_STAR', 84)
 def_op('SETUP_ANNOTATIONS', 85)
 def_op('YIELD_VALUE', 86)
 def_op('POP_BLOCK', 87)
-def_op('END_FINALLY', 88)
+def_op('PUSH_NO_EXCEPT', 88)
 def_op('POP_EXCEPT', 89)
 
 HAVE_ARGUMENT = 90              # Opcodes from here have an argument:
@@ -158,9 +161,7 @@ def jabs_op(name, op):
 
 name_op('LOAD_GLOBAL', 116)     # Index in name list
 
-jabs_op('CONTINUE_LOOP', 119)   # Target address
-jrel_op('SETUP_LOOP', 120)      # Distance to target address
-jrel_op('SETUP_EXCEPT', 121)    # ""
+jrel_op('SETUP_EXCEPT', 121)    # Distance to target address
 jrel_op('SETUP_FINALLY', 122)   # ""
 
 def_op('LOAD_FAST', 124)        # Local variable number
@@ -189,16 +190,16 @@ def jabs_op(name, op):
 
 jrel_op('SETUP_WITH', 143)
 
+def_op('EXTENDED_ARG', 144)
+EXTENDED_ARG = 144
+
 def_op('LIST_APPEND', 145)
 def_op('SET_ADD', 146)
 def_op('MAP_ADD', 147)
 
 def_op('LOAD_CLASSDEREF', 148)
 hasfree.append(148)
 
-def_op('EXTENDED_ARG', 144)
-EXTENDED_ARG = 144
-
 def_op('BUILD_LIST_UNPACK', 149)
 def_op('BUILD_MAP_UNPACK', 150)
 def_op('BUILD_MAP_UNPACK_WITH_CALL', 151)