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JIT: mark pseudo return buffer temp as multi-reg return - #135594
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When a call returning via a return buffer is returned from a method whose own return type is a multi-reg struct (e.g. an HFA on arm64), the temp created by impFixupStructReturnType was not marked lvIsMultiRegRet, asserting in Lowering. Let it fall through to the multi-reg handling. Fixes dotnet#134052 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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🟢 Approval recommended
The focused fix reuses established multi-register handling and includes targeted regression coverage.
0 open findings
What changed in this PR
Fixes JIT handling of pseudo return-buffer temporaries used as multi-register struct returns.
Changes:
- Allows pseudo return-buffer temps to receive multi-register return metadata.
- Adds regression coverage validating all HFA fields.
| File | Description |
|---|---|
src/coreclr/jit/importer.cpp |
Continues through existing multi-register handling. |
src/tests/JIT/Regression_ro_2/Runtime_134052.cs |
Covers return-buffer-to-HFA bit casting. |
🧠 Review effort: Balanced
This was referenced Oct 11, 2026
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PTAL @dotnet/jit-contrib, simple bug-fix, no diffs |
adamperlin
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Oct 12, 2026
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This looks reasonable to me!
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When a call returning via a return buffer is returned from a method whose own return type is a multi-reg struct (e.g. an HFA on arm64), the temp created by impFixupStructReturnType was not marked lvIsMultiRegRet, asserting in Lowering. Let it fall through to the multi-reg handling.
Fixes #134052
No diffs