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gh-143414: Implement unique reference tracking for JIT, optimize unpacking of such tuples by reidenong · Pull Request #144300 · python/cpython · GitHub

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gh-143414: Implement unique reference tracking for JIT, optimize unpacking of such tuples - #144300

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Fidget-Spinner merged 36 commits into
python:mainfrom
reidenong:branch-unique-reference-tracking
Mar 22, 2026
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gh-143414: Implement unique reference tracking for JIT, optimize unpacking of such tuples#144300
Fidget-Spinner merged 36 commits into
python:mainfrom
reidenong:branch-unique-reference-tracking

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reidenong commented Jan 28, 2026 •
edited by bedevere-app Bot
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  1. Implements unique reference tracking to references in the JIT Optimizer.
  2. Uses the unique reference tracking to eliminate unnecessary reference counting for uniquely referenced tuples. ex:
x, y, z = f()

Some notes:

  • Only implements the unique reference tracking (and relevant optimization) for tuples in _BUILD_TUPLE, to be extended to other objects in the future
  • Objects are deemed as not uniquely referenced when they are made aliases or duplicated, in uops of _LOAD_FAST_* and _COPY.

Would appreciate any feedback.
Thanks

bedevere-app Bot mentioned this pull request Jan 28, 2026
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cocolato reviewed Jan 28, 2026
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Comment thread Python/optimizer_bytecodes.c Outdated

reidenong commented Jan 28, 2026 •
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Discussed with @Fidget-Spinner, will reopen the PR after implementing PyStackRef_CLOSE_SPECIALIZED for _UNPACK_SEQUENCE_UNIQUE_TUPLE

reidenong marked this pull request as draft January 28, 2026 18:38
reidenong marked this pull request as ready for review January 29, 2026 11:04

Fidget-Spinner commented Jan 29, 2026

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Windows Ci failure looks possibly related, can you please look into it?

reidenong marked this pull request as draft January 31, 2026 06:39
reidenong marked this pull request as ready for review January 31, 2026 16:36
Fidget-Spinner reviewed Jan 31, 2026
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

This is excellent. Just 2 comments, then I think it's safe to merge.

Comment thread Include/internal/pycore_optimizer.h Outdated
Comment thread Python/optimizer_bytecodes.c Outdated

op(_COPY, (bottom, unused[oparg-1] -- bottom, unused[oparg-1], top)) {
assert(oparg > 0);
bottom = PyJitRef_IsUnique(bottom) ? PyJitRef_StripReferenceInfo(bottom) : bottom;

Fidget-Spinner Jan 31, 2026

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

We only need to strip unique info here, not the borrow info too. This way we still get refcount elimination with the borrow.

reidenong Feb 1, 2026

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

I think this is consistent with the code?

If the ref is unique, we remove the unique tag, otherwise we leave it as is. Since a ref cannot be both unique and borrowed at the same time, borrowed/invalid refs will be maintained.

Fidget-Spinner Feb 1, 2026

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Sounds good, thanks!

reidenong commented Feb 21, 2026

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I have made the requested changes; please review again. Thanks!

bedevere-app Bot commented Feb 21, 2026

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Thanks for making the requested changes!

@markshannon: please review the changes made to this pull request.

bedevere-app Bot requested a review from markshannon February 21, 2026 05:18

reidenong commented Mar 9, 2026

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@markshannon Hi mark, please take a look at this PR when you have the time. Thanks!

markshannon mentioned this pull request Mar 13, 2026
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Fidget-Spinner commented Mar 22, 2026 •
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@reidenong sorry can you please merge in main to this PR? I'll try to get this in this week.

Fidget-Spinner approved these changes Mar 22, 2026
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

Nice!

Fidget-Spinner dismissed markshannon’s stale review March 22, 2026 16:56

Mark's review has already been addressed and given 2 weeks for a response.

Fidget-Spinner merged commit e36f8db into python:main Mar 22, 2026
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eendebakpt mentioned this pull request Mar 22, 2026
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CuriousLearner added a commit to CuriousLearner/cpython that referenced this pull request Mar 23, 2026
Merge branch 'main' of github.com:python/cpython into fix-pythongh-13…
3e05fa3 
…8577

* 'main' of github.com:python/cpython:
  pythongh-146197: Run -m test.pythoninfo on the Emscripten CI (python#146332)
  pythongh-146325: Use `test.support.requires_fork` in test_fastpath_cache_cleared_in_forked_child (python#146330)
  pythongh-146197: Add Emscripten to CI (python#146198)
  pythongh-143387: Raise an exception instead of returning None when metadata file is missing. (python#146234)
  pythongh-108907: ctypes: Document _type_ codes (pythonGH-145837)
  pythongh-146175: Soft-deprecate outdated macros; convert internal usage (pythonGH-146178)
  pythongh-146056: Rework ref counting in treebuilder_handle_end() (python#146167)
  Add a warning about untrusted input to `configparser` docs (python#146276)
  pythongh-145264: Do not ignore excess Base64 data after the first padded quad (pythonGH-145267)
  pythongh-146308: Fix error handling issues in _remote_debugging module (python#146309)
  pythongh-146192: Add base32 support to binascii (pythonGH-146193)
  pythongh-135953: Properly obtain main thread identifier in Gecko Collector (python#146045)
  pythongh-143414: Implement unique reference tracking for JIT, optimize unpacking of such tuples (pythonGH-144300)
  pythongh-146261: Fix bug in `_Py_uop_sym_set_func_version` (pythonGH-146291)
  pythongh-145144: Add more tests for UserList, UserDict, etc (pythonGH-145145)
  pythongh-143959: Fix test_datetime if _datetime is unavailable (pythonGH-145248)
  pythongh-146245: Fix reference and buffer leaks via audit hook in socket module (pythonGH-146248)
  pythongh-140049: Colorize exception notes in `traceback.py` (python#140051)
  Update docs for pythongh-146056 (pythonGH-146213)

eendebakpt commented Apr 4, 2026

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FYI: Adding unique reference tracking for lists is possible in a similar way as done for tuples in this PR. A prototype is main...eendebakpt:cpython:unique_list. Performance improves, but I am not sure unique list unpacking is as relevant as tuple unpackage @Fidget-Spinner

pablogsal mentioned this pull request Apr 4, 2026
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ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026
pythongh-143414: Implement unique reference tracking for JIT, optimiz…
8d05049 
…e unpacking of such tuples (pythonGH-144300)

Co-authored-by: Ken Jin <kenjin4096@gmail.com>
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cocolato cocolato left review comments
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tomasr8 Awaiting requested review from tomasr8 tomasr8 is a code owner
savannahostrowski Awaiting requested review from savannahostrowski savannahostrowski is a code owner
markshannon Awaiting requested review from markshannon markshannon is a code owner

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