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bpo-46329: Avoid PUSH_NULL when followed by LOAD_GLOBAL#31933

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markshannon merged 1 commit into
python:mainfrom
faster-cpython:merge-push-null-load-global
Mar 17, 2022
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bpo-46329: Avoid PUSH_NULL when followed by LOAD_GLOBAL#31933
markshannon merged 1 commit into
python:mainfrom
faster-cpython:merge-push-null-load-global

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@markshannon

@markshannon markshannon commented Mar 16, 2022 •
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Uses the low bit of LOAD_GLOBAL's oparg to indicate whether it should push a NULL first.

len(alist)

now compiles to

LOAD_GLOBAL              1 (NULL + len)
LOAD_FAST                0 (alist)
PRECALL                  1
CALL                     1

This reduces the total number of VM instructions executed by ~2%.

The benchmark results show an unlikely 3% speedup, probably just one of those random build variations.

https://bugs.python.org/issue46329

@markshannon markshannon added the 🔨 test-with-buildbots Test PR w/ buildbots; report in status section label Mar 17, 2022
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bedevere-bot commented Mar 17, 2022

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🤖 New build scheduled with the buildbot fleet by @markshannon for commit 198517e 🤖

If you want to schedule another build, you need to add the ":hammer: test-with-buildbots" label again.

@bedevere-bot bedevere-bot removed the 🔨 test-with-buildbots Test PR w/ buildbots; report in status section label Mar 17, 2022
@markshannon

markshannon commented Mar 17, 2022

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Buildbot failures seem unrelated to this PR: 2 pre-existing failures and one asyncio timeout.

@markshannon markshannon merged commit 3011a09 into python:main Mar 17, 2022
@MatthieuDartiailh

MatthieuDartiailh commented Mar 18, 2022

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I may be missing something but shouldn't the computation for the stack effect of LOAD_GLOBAL be also adjusted since it can now push 2 elements on the stack ?

@terryjreedy terryjreedy mentioned this pull request Jul 17, 2022
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@markshannon markshannon deleted the merge-push-null-load-global branch September 26, 2023 12:54
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@markshannon @bedevere-bot @MatthieuDartiailh @the-knights-who-say-ni