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jit: support functions with no return value - #8479

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youknowone merged 1 commit into
RustPython:mainfrom
kyokuping:codex/jit-none-return
Aug 10, 2026
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jit: support functions with no return value#8479
youknowone merged 1 commit into
RustPython:mainfrom
kyokuping:codex/jit-none-return

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@kyokuping kyokuping commented Aug 10, 2026 •
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Assisted-by: codex-5.6-sol

Summary

  • Enable no_return_value test (crates/jit/tests/misc_tests.rs).
  • Add a JitType::None variant to represent a void/None return, instead of
    overloading Option<JitType> to mean both "return type not yet inferred"
    and "unsupported value". :
    Option::None = not seen a return yet, Some(JitType::None) = confirmed
    void return, Some(Int/Float/Bool) = confirmed typed return.
  • JitType::to_cranelift now returns Option<types::Type> (None for the
    void case), and all four call sites handle it instead of unconditionally
    pushing a cranelift return param.
  • return_value compares JitTypes directly and emits return_(&[]) when
    there's no cranelift value.

Summary by CodeRabbit

  • New Features

    • Added support for JIT-compiled functions that do not return a value.
    • Void functions now invoke successfully without producing a result.
    • Functions containing only a pass operation are now supported.

  • Bug Fixes

    • Improved handling of unsupported argument and return types during JIT compilation.
    • Corrected return behavior for typed and void functions.

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Review Change Stack

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📝 Walkthrough

Walkthrough

The JIT now supports JitValue::None and void functions. Cranelift and libffi omit return values for JitType::None. Instruction return handling and tests now support empty returns.

Changes

JIT void return support

Layer / File(s) Summary
Void type and ABI integration
crates/jit/src/lib.rs		 JitType::None maps to absent Cranelift return types and libffi void values. Argument conversion rejects unsupported types, and invocation returns no value for void functions.
Instruction type and return handling
crates/jit/src/instructions.rs		 JitValue::None maps to JitType::None. Local storage validates optional Cranelift types. Return generation supports empty returns and typed zero-value returns.
Void return test
crates/jit/tests/misc_tests.rs		 The no-return-value test now executes a pass-only function and checks for Ok(()).

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant JITCompiler
  participant CraneliftSignature
  participant LibffiInvocation
  JITCompiler->>CraneliftSignature: omit return parameter for JitType::None
  JITCompiler->>LibffiInvocation: use libffi void type
  LibffiInvocation-->>JITCompiler: return no value
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Suggested reviewers: shaharnaveh

🚥 Pre-merge checks | ✅ 5
✅ Passed checks (5 passed)
Check name Status Explanation
Docstring Coverage ✅ Passed No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check ✅ Passed Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check ✅ Passed Check skipped because no linked issues were found for this pull request.
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title clearly and concisely describes the main change: JIT support for functions with no return value.
✨ Finishing Touches
🧪 Generate unit tests (beta)
  • Create PR with unit tests

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@kyokuping
kyokuping marked this pull request as ready for review August 10, 2026 09:52
@kyokuping
kyokuping marked this pull request as draft August 10, 2026 10:20
@kyokuping
kyokuping marked this pull request as ready for review August 10, 2026 10:21
@kyokuping

kyokuping commented Aug 10, 2026

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youknowone
youknowone approved these changes Aug 10, 2026
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👍

@youknowone
youknowone merged commit 365434b into RustPython:main Aug 10, 2026
27 checks passed
@kyokuping
kyokuping deleted the codex/jit-none-return branch August 10, 2026 12:25
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