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GeezerVison is showing github.com — gh-143414: Implement unique reference tracking for JIT, optimize unpacking of such tuples by reidenong · Pull Request #144300 · python/cpython

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@reidenong

@reidenong 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

  • Issue: JIT: Implement unique reference tracking in Tier 2 for reference count optimizations #143414

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@reidenong
Add unique reference tracking to JIT, optimize tuple unpacking
e4b7f51
@reidenong
reidenong requested review from Fidget-Spinner, markshannon, savannahostrowski and tomasr8 as code owners January 28, 2026 12:57
@bedevere-app bedevere-app Bot mentioned this pull request Jan 28, 2026
JIT: Implement unique reference tracking in Tier 2 for reference count optimizations #143414
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@bedevere-app bedevere-app Bot added the awaiting review label Jan 28, 2026
reidenong and others added 2 commits January 28, 2026 20:58
@reidenong
Merge branch 'main' into branch-unique-reference-tracking
b32a8e2
@reidenong
Regenerate cases
7aeac0e
cocolato
cocolato reviewed Jan 28, 2026
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Comment thread Python/optimizer_bytecodes.c Resolved

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@reidenong
Fix unique tuple unpacking checks
f8b7e4e
@reidenong

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
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@reidenong
reidenong marked this pull request as draft January 28, 2026 18:38
@bedevere-app bedevere-app Bot removed the awaiting review label Jan 28, 2026
reidenong added 2 commits January 29, 2026 18:47
@reidenong
Implement _PyTuple_ExactDealloc
37d7c4b
@reidenong
Rename symbol
7df2176
@reidenong
reidenong marked this pull request as ready for review January 29, 2026 11:04
@bedevere-app bedevere-app Bot added the awaiting review label Jan 29, 2026
@Fidget-Spinner

Fidget-Spinner commented Jan 29, 2026

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Windows Ci failure looks possibly related, can you please look into it?
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reidenong and others added 4 commits January 30, 2026 10:59
@reidenong
Merge branch 'main' into branch-unique-reference-tracking
6f66c56
@reidenong
Merge branch 'main' into branch-unique-reference-tracking
b251825
@reidenong
Regenerate cases
bcd5654
@reidenong
Add alignment checking
acfa737
@reidenong
reidenong marked this pull request as draft January 31, 2026 06:39
@bedevere-app bedevere-app Bot removed the awaiting review label Jan 31, 2026
reidenong and others added 2 commits January 31, 2026 23:11
@reidenong
Change JIT reference tags to 2 bit scheme
a0fd9e2
@blurb-it
📜🤖 Added by blurb_it.
645776a
@reidenong
reidenong marked this pull request as ready for review January 31, 2026 16:36
@bedevere-app bedevere-app Bot added the awaiting review label Jan 31, 2026
Fidget-Spinner
Fidget-Spinner reviewed Jan 31, 2026
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This is excellent. Just 2 comments, then I think it's safe to merge.

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Comment thread Include/internal/pycore_optimizer.h Resolved

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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 Fidget-Spinner Jan 31, 2026

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

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@reidenong reidenong Feb 1, 2026

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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.

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@Fidget-Spinner Fidget-Spinner Feb 1, 2026

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Sounds good, thanks!

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reidenong and others added 2 commits February 21, 2026 12:52
@reidenong
Regen cases
0b07ac4
@reidenong
Merge branch 'main' into branch-unique-reference-tracking
14e5d3d
@reidenong

reidenong commented Feb 21, 2026

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I have made the requested changes; please review again. Thanks!
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@bedevere-app bedevere-app Bot added awaiting change review and removed awaiting changes labels Feb 21, 2026
@bedevere-app

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.
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@bedevere-app
bedevere-app Bot requested a review from markshannon February 21, 2026 05:18
reidenong and others added 3 commits March 9, 2026 21:31
@reidenong
Merge branch 'main' into branch-unique-reference-tracking
8506038
@reidenong
Regen cases
d67617f
@reidenong
Merge branch 'main' into branch-unique-reference-tracking
100eeb5
@reidenong

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!
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reidenong added 2 commits March 11, 2026 21:30
@reidenong
Merge branch 'main' into branch-unique-reference-tracking
e476061
@reidenong
Merge branch 'main' into branch-unique-reference-tracking
06a9ec1
@markshannon markshannon mentioned this pull request Mar 13, 2026
Convert more uops to leave their inputs on the stack to be cleaned up by _POP_TOP #145866
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@Fidget-Spinner

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.
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Fidget-Spinner added 3 commits March 22, 2026 22:42
@Fidget-Spinner
Merge remote-tracking branch 'upstream/main' into pr/144300
6bce6b4
@Fidget-Spinner
Mark unique tuple freeing as non-escaping
89dc467
@Fidget-Spinner
fix a bugs in _COPY_FREE_VARS and frame creation
4e6c792
Fidget-Spinner
Fidget-Spinner approved these changes Mar 22, 2026
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Nice!

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@bedevere-app bedevere-app Bot added awaiting merge and removed awaiting change review labels Mar 22, 2026
@Fidget-Spinner
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
Fidget-Spinner merged commit e36f8db into python:main Mar 22, 2026
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@bedevere-app bedevere-app Bot removed the awaiting merge label Mar 22, 2026
@eendebakpt eendebakpt mentioned this pull request Mar 22, 2026
Optimize float operations by mutating uniquely-referenced operands in place (JIT only) #146306
Closed
CuriousLearner added a commit to CuriousLearner/cpython that referenced this pull request Mar 23, 2026
@CuriousLearner
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

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
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@pablogsal pablogsal mentioned this pull request Apr 4, 2026
gh-130273: Fix traceback color output with unicode characters #142529
Merged
ljfp pushed a commit to ljfp/cpython that referenced this pull request Apr 25, 2026
@reidenong @Fidget-Spinner @ljfp
pythongh-143414: Implement unique reference tracking for JIT, optimiz…
8d05049 
…e unpacking of such tuples (pythonGH-144300)

Co-authored-by: Ken Jin <[email protected]>
@reidenong
reidenong deleted the branch-unique-reference-tracking branch September 2, 2026 04:20
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@cocolato cocolato cocolato left review comments
@Fidget-Spinner Fidget-Spinner Fidget-Spinner approved these changes
@tomasr8 tomasr8 Awaiting requested review from tomasr8 tomasr8 is a code owner
@savannahostrowski savannahostrowski Awaiting requested review from savannahostrowski
@markshannon markshannon Awaiting requested review from markshannon markshannon is a code owner

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@reidenong @Fidget-Spinner @eendebakpt @markshannon @cocolato
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