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GeezerVison is showing github.com — Wrong oparg is passed to trace recorder when `JUMP_BACKWARD_JIT` is preceded by `EXTENDED_ARG` · Issue #152192 · python/cpython

Wrong oparg is passed to trace recorder when JUMP_BACKWARD_JIT is preceded by EXTENDED_ARG #152192

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Wrong oparg is passed to trace recorder when JUMP_BACKWARD_JIT is preceded by EXTENDED_ARG#152192
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interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)topic-JITtype-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

Description

@markshannon
markshannon
opened on Jun 25, 2026
Issue body actions

Bug report

Bug description:

This doesn't seem to cause any failure, AFAICT, but there could be a failure mode somewhere.
Found when experimenting with a new (small) optimization.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

  • gh-152192: Fix JUMP_BACKWARD passing a truncated oparg to the jit tracer #152382

Activity

  1. markshannon
    added
    type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error
    on Jun 25, 2026
  2. StanFromIreland
    added
    interpreter-core(Objects, Python, Grammar, and Parser dirs)(Objects, Python, Grammar, and Parser dirs)
    topic-JIT
    on Jun 25, 2026

  3. markshannon commented on Jun 25, 2026

    @markshannon
    markshannon
    on Jun 25, 2026
    MemberAuthor
    More actions

    To clarify what is happening:
    The instruction made of this pair of code units: EXTENDED_ARG 1; JUMP_BACKWARD_JIT 1 has an oparg of 257, but the EXTENDED_ARG part is ignored and _PyJit_TryInitializeTracing gets passed oparg=1.

  4. markshannon commented on Jun 25, 2026

    @markshannon
    markshannon
    on Jun 25, 2026
    MemberAuthor
    More actions

    Please don't dump AI output into the issue.
    If you have a working fix, by all means open PR

  5. Codeer22 commented on Jun 25, 2026

    @Codeer22
    Codeer22
    on Jun 25, 2026
    More actions

    Deleted that

  6. deadlovelll commented on Jun 25, 2026

    @deadlovelll
    deadlovelll
    on Jun 25, 2026
    Contributor
    More actions

    To clarify what is happening: The instruction made of this pair of code units: EXTENDED_ARG 1; JUMP_BACKWARD_JIT 1 has an oparg of 257, but the EXTENDED_ARG part is ignored and _PyJit_TryInitializeTracing gets passed oparg=1.

    Hello! If you don't mind, can i try work on this?

  7. deadlovelll
    added 2 commits that reference this issue on Jun 27, 2026

    pythongh-152192: Fix JUMP_BACKWARD passing a truncated oparg to the j…

    69be5f0

    pythongh-152192: Fix JUMP_BACKWARD passing a truncated oparg to the j…

    a290969
  8. markshannon
    added a commit that references this issue on Jun 30, 2026

    gh-152192: Fix JUMP_BACKWARD passing a truncated oparg to the jit tra…

    9e10f14
  9. markshannon
    closed this as completedon Jun 30, 2026
  10. maurycy
    added a commit that references this issue on Jul 1, 2026

    Merge branch 'main' into maurycy/bye-abba

    da7d768
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