Improve efficiency of PRECALL/CALL instructions

[markshannon]

BPO	46532
Nosy	@markshannon
PRs	bpo-46532: Reduce number of memory writes to update call_shape.kwnames. #31231

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = 'https://github.com/markshannon'
closed_at = None
created_at = <Date 2022-01-26.09:44:42.979>
labels = []
title = 'Improve efficiency of PRECALL/CALL instructions'
updated_at = <Date 2022-02-10.12:57:59.448>
user = 'https://github.com/markshannon'

bugs.python.org fields:

activity = <Date 2022-02-10.12:57:59.448>
actor = 'Mark.Shannon'
assignee = 'Mark.Shannon'
closed = False
closed_date = None
closer = None
components = []
creation = <Date 2022-01-26.09:44:42.979>
creator = 'Mark.Shannon'
dependencies = []
files = []
hgrepos = []
issue_num = 46532
keywords = ['patch']
message_count = 3.0
messages = ['411721', '411723', '412996']
nosy_count = 1.0
nosy_names = ['Mark.Shannon']
pr_nums = ['31231']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue46532'
versions = []

Linked PRs

• GH-90690: Mention removal of PRECALL in What's New #103910
• [3.12] GH-90690: Mention removal of PRECALL in What's New (GH-103910) #109027

[markshannon]

The PRECALL/CALL bytecode pair for calls is new (still in review at time of writing) and is not as efficient as it could be.

Some possible improvements are:

Transfer refcount of func when making a frame.

NULL call_shape.kwnames after use instead of in PRECALL, as many specialized instructions already assert that it is NULL.

Specialize the PRECALL instructions. Either for simple cases like type(arg) so we can skip the CALL, or for complex cases like PythonClass(args) where PRECALL can create object, and set up the frame so that CALL calls the init function.

[markshannon]

Possibly consider replacing the specializations for str(arg) and tuple(arg) with a more general bytecode that can be used for other objects as well.

[markshannon]

New changeset 2cea8c2 by Mark Shannon in branch 'main':
bpo-46532: Reduce number of memory writes to update call_shape.kwnames. (GH-31231)
2cea8c2

[markshannon]

As described here we can remove the PRECALL instruction entirely, shortening the call sequence for many calls.