Don't inline slow path functions in the interpreter loop
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- Python
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Description
Feature or enhancement
Proposal:
I was looking at the IPA inlining dump as part of investigating the root cause of gh-132295 and noticed that we're inlining a number of slow path functions related to specialization, instrumentation, and error handling in the interpreter loop when performing LTO (full list here):
_Py_Specialize_CallKw
_Py_Specialize_CompareOp
_Py_Specialize_ContainsOp
_Py_Specialize_ForIter
_Py_Specialize_LoadGlobal
_Py_Specialize_LoadSuperAttr
_Py_Specialize_Send
_Py_Specialize_StoreAttr
_Py_Specialize_StoreSubscr
_Py_Specialize_ToBool
_Py_Specialize_UnpackSequence
_Py_call_instrumentation
_Py_call_instrumentation_instruction
_Py_call_instrumentation_line
get_exception_handler
I suspect these are being inlined because we use unit tests for collecting PGO data. These should be executed relatively infrequently for "normal" Python code. We should mark them as noinline.
Has this already been discussed elsewhere?
No response given
Links to previous discussion of this feature:
No response
Linked PRs
- gh-132337
- gh-132424
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Review the IPA inlining dump and the listed slow-path entry points, including the Py_Specialize* functions, instrumentation helpers, and get_exception_handler. Check the discussions or changes in gh-132337 and gh-132424 first; done means these functions are no longer inlined during LTO while normal interpreter behavior remains unchanged.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- compilers, performance
- Issue type
- Feature
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 30/100