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Produce cleaner bytecode for 'with' and 'async with' by generating separate code for normal and exceptional paths. (#6641)

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Remove BEGIN_FINALLY, END_FINALLY, CALL_FINALLY and POP_FINALLY bytecodes. Implement finally blocks by code duplication.
Reimplement frame.lineno setter using line numbers rather than bytecode offsets.
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Mark Shannon 2019-11-21 09:11:43 +00:00 • committed by GitHub
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@ -706,50 +706,21 @@ iterations of the loop.
popped values are used to restore the exception state.
.. opcode:: POP_FINALLY (preserve_tos)
.. opcode:: RERAISE
Cleans up the value stack and the block stack. If *preserve_tos* is not
``0`` TOS first is popped from the stack and pushed on the stack after
performing other stack operations:
Re-raises the exception currently on top of the stack.
* If TOS is ``NULL`` or an integer (pushed by :opcode:`BEGIN_FINALLY`
or :opcode:`CALL_FINALLY`) it is popped from the stack.
* If TOS is an exception type (pushed when an exception has been raised)
6 values are popped from the stack, the last three popped values are
used to restore the exception state. An exception handler block is
removed from the block stack.
It is similar to :opcode:`END_FINALLY`, but doesn't change the bytecode
counter nor raise an exception. Used for implementing :keyword:`break`,
:keyword:`continue` and :keyword:`return` in the :keyword:`finally` block.
.. versionadded:: 3.8
.. versionadded:: 3.8
.. opcode:: BEGIN_FINALLY
.. opcode:: WITH_EXCEPT_START
Pushes ``NULL`` onto the stack for using it in :opcode:`END_FINALLY`,
:opcode:`POP_FINALLY`, :opcode:`WITH_CLEANUP_START` and
:opcode:`WITH_CLEANUP_FINISH`. Starts the :keyword:`finally` block.
Calls the function in position 7 on the stack with the top three
items on the stack as arguments.
Used to implement the call ``context_manager.__exit__(*exc_info())`` when an exception
has occurred in a :keyword:`with` statement.
.. versionadded:: 3.8
.. opcode:: END_FINALLY
Terminates a :keyword:`finally` clause. The interpreter recalls whether the
exception has to be re-raised or execution has to be continued depending on
the value of TOS.
* If TOS is ``NULL`` (pushed by :opcode:`BEGIN_FINALLY`) continue from
the next instruction. TOS is popped.
* If TOS is an integer (pushed by :opcode:`CALL_FINALLY`), sets the
bytecode counter to TOS. TOS is popped.
* If TOS is an exception type (pushed when an exception has been raised)
6 values are popped from the stack, the first three popped values are
used to re-raise the exception and the last three popped values are used
to restore the exception state. An exception handler block is removed
from the block stack.
.. versionadded:: 3.8
.. opcode:: LOAD_ASSERTION_ERROR
@ -780,35 +751,6 @@ iterations of the loop.
.. versionadded:: 3.2
.. opcode:: WITH_CLEANUP_START
Starts cleaning up the stack when a :keyword:`with` statement block exits.
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__` or :meth:`~object.__aexit__` bound method.
If TOS is ``NULL``, calls ``SECOND(None, None, None)``,
removes the function from the stack, leaving TOS, and pushes ``None``
to the stack. Otherwise calls ``SEVENTH(TOP, SECOND, THIRD)``,
shifts the bottom 3 values of the stack down, replaces the empty spot
with ``NULL`` and pushes TOS. Finally pushes the result of the call.
.. opcode:: WITH_CLEANUP_FINISH
Finishes cleaning up the stack when a :keyword:`with` statement block exits.
TOS is result of ``__exit__()`` or ``__aexit__()`` function call pushed
by :opcode:`WITH_CLEANUP_START`. SECOND is ``None`` or an exception type
(pushed when an exception has been raised).
Pops two values from the stack. If SECOND is not None and TOS is true
unwinds the EXCEPT_HANDLER block which was created when the exception
was caught and pushes ``NULL`` to the stack.
All of the following opcodes use their arguments.
.. opcode:: STORE_NAME (namei)
@ -1060,15 +1002,6 @@ All of the following opcodes use their arguments.
stack. *delta* points to the finally block or the first except block.
.. opcode:: CALL_FINALLY (delta)
Pushes the address of the next instruction onto the stack and increments
bytecode counter by *delta*. Used for calling the finally block as a
"subroutine".
.. versionadded:: 3.8
.. opcode:: LOAD_FAST (var_num)
Pushes a reference to the local ``co_varnames[var_num]`` onto the stack.