Feature Requests item #1764638, was opened at 2007-07-31 17:12
Message generated for change (Tracker Item Submitted) made by Item Submitter
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=355470&aid=1764638&group_id=5470
Please note that this message will contain a full copy of the comment thread,
including the initial issue submission, for this request,
not just the latest update.
Category: Parser/Compiler
Group: Python 2.6
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: Paul Pogonyshev (doublep)
Assigned to: Nobody/Anonymous (nobody)
Summary: add new bytecodes: JUMP_IF_{FALSE|TRUE}_AND_POP
Initial Comment:
In disassembled code of Python functions I often see stuff like this:
421 JUMP_IF_FALSE 14 (to 438)
424 POP_TOP
1178 ...
435 JUMP_FORWARD 1 (to 439)
>> 438 POP_TOP
>> 439 END_FINALLY
Note how both branches of execution after JUMP_IF_FALSE do POP_TOP. This
causes the true-branch add JUMP_FORWARD, the only purpose of which is to bypass
the POP_TOP command.
I propose adding two new bytecodes, JUMP_IF_FALSE_AND_POP and
JUMP_IF_TRUE_AND_POP. Their semantics would be the same as that of existing
JUMP_IF_FALSE/JUMP_IF_TRUE except the commands would also pop the stack once,
after checking whether to jump. This would simplify the above code to just
421 JUMP_IF_FALSE_AND_POP 14 (to 438)
1178 ...
>> 438 END_FINALLY
This shortens bytecode by 5 bytes and both execution branches, by 1 and 2
commands correspondingly.
I'm willing to create a patch, if this sounds like a worthwile improvement.
Maybe it is better to skip 2.6 and target it for 3000 instead.
----------------------------------------------------------------------
You can respond by visiting:
https://sourceforge.net/tracker/?func=detail&atid=355470&aid=1764638&group_id=5470
_______________________________________________
Python-bugs-list mailing list
Unsubscribe:
http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
