Message 389707 - Python tracker

Message389707

Author	Mark.Shannon
Recipients	Demur Rumed, Mark.Shannon, berker.peksag, eric.fahlgren, godaygo, python-dev, rhettinger, serhiy.storchaka, vstinner
Date	2021-03-29.15:03:36
SpamBayes Score	-1.0
Marked as misclassified	Yes
Message-id	<1617030217.04.0.57083317095.issue27129@roundup.psfhosted.org>
In-reply-to

Content
frame.f_lasti and traceback.tb_lasti are best left as byte offsets. There is no guarantee that we won't go back to variable length instructions. For example, a "LONG_JUMP" instruction which is 4 bytes long and takes a 3 byte offset might well be a worthwhile extension. However, changing bytecode offsets and the internal representation of frame.f_lasti will reduce the number of "EXTENDED_ARG"s by 60% or more and makes interpreter dispatch a tad more efficient.

Content

frame.f_lasti and traceback.tb_lasti are best left as byte offsets.
There is no guarantee that we won't go back to variable length instructions.
For example, a "LONG_JUMP" instruction which is 4 bytes long and takes a 3 byte offset might well be a worthwhile extension.

However, changing bytecode offsets and the internal representation of frame.f_lasti will reduce the number of "EXTENDED_ARG"s by 60% or more and makes interpreter dispatch a tad more efficient.

History
Date	User	Action	Args
2021-03-29 15:03:37	Mark.Shannon	set	recipients: + Mark.Shannon, rhettinger, vstinner, python-dev, berker.peksag, serhiy.storchaka, eric.fahlgren, Demur Rumed, godaygo
2021-03-29 15:03:37	Mark.Shannon	set	messageid: <1617030217.04.0.57083317095.issue27129@roundup.psfhosted.org>
2021-03-29 15:03:37	Mark.Shannon	link	issue27129 messages
2021-03-29 15:03:36	Mark.Shannon	create