missed peephole optimization (unnecessary jump at end of function after yield)

[NealNorwitz]

BPO	17607
Nosy	@vstinner, @ezio-melotti, @serhiy-storchaka

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

Show more details

GitHub fields:

assignee = None
closed_at = <Date 2018-01-05.19:57:12.360>
created_at = <Date 2013-04-01.04:45:51.251>
labels = ['interpreter-core', 'performance']
title = 'missed peephole optimization (unnecessary jump at end of function after yield)'
updated_at = <Date 2018-01-05.19:57:12.359>
user = 'https://bugs.python.org/NealNorwitz'

bugs.python.org fields:

activity = <Date 2018-01-05.19:57:12.359>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = True
closed_date = <Date 2018-01-05.19:57:12.360>
closer = 'serhiy.storchaka'
components = ['Interpreter Core']
creation = <Date 2013-04-01.04:45:51.251>
creator = 'Neal.Norwitz'
dependencies = []
files = []
hgrepos = []
issue_num = 17607
keywords = []
message_count = 3.0
messages = ['185708', '185859', '309519']
nosy_count = 4.0
nosy_names = ['vstinner', 'ezio.melotti', 'serhiy.storchaka', 'Neal.Norwitz']
pr_nums = []
priority = 'normal'
resolution = 'out of date'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'performance'
url = 'https://bugs.python.org/issue17607'
versions = ['Python 3.4']

[NealNorwitz]

>>> def foo():
...   if x:
...     yield None
... 
>>> dis.dis(foo)
  2           0 LOAD_GLOBAL              0 (x)
              3 POP_JUMP_IF_FALSE       14

3 6 LOAD_CONST 0 (None)
9 YIELD_VALUE
10 POP_TOP
11 JUMP_FORWARD 0 (to 14)
>> 14 LOAD_CONST 0 (None)
17 RETURN_VALUE

The JUMP_FORWARD at 11 is not necessary and is not in place with a return in the code:

>>> def foo():
...  if x:
...   return None
... 
>>> dis.dis(foo)
  2           0 LOAD_GLOBAL              0 (x)
              3 POP_JUMP_IF_FALSE       10

3 6 LOAD_CONST 0 (None)
9 RETURN_VALUE
>> 10 LOAD_CONST 0 (None)
13 RETURN_VALUE

[vstinner]

This issue is similar to bpo-17430.

[serhiy-storchaka]

This optimization already is implemented in 3.5+. Actually it is implemented as a part of code generation, not a peepholer.