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PR description draft: <!-- --> When morph replaces an array-store helper with a direct store, evaluate effectful operands in array/index/value order before introducing the array null and bounds checks. Enforce this at the conversion itself: importer spills can be undone by forward substitution while the operation is still a helper call. Include ordering-only effects such as volatile reads, both in the conversion and in the existing inline array-store importer spill. Add a single-file regression covering value-expression exceptions and index-before-value exception ordering. Fixes dotnet#133860 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: ae8155d6-f240-4542-a1da-c721ba933c91
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🟡 Changes recommended
The equivalent multidimensional-array store path remains unfixed, and ordering-only behavior lacks regression coverage.
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What changed in this PR
Fixes JIT evaluation ordering when expanding reference-array stores.
Changes:
- Preserves array/index/value evaluation order during morphing.
- Includes ordering-only effects such as volatile reads.
- Adds exception-order regression coverage.
| File | Description |
|---|---|
src/coreclr/jit/morph.cpp |
Sequences operands before array checks. |
src/coreclr/jit/importer.cpp |
Recognizes observable ordering effects. |
src/tests/JIT/Regression_ro_2/Runtime_133860.cs |
Tests exception precedence. |
🧠 Review effort: Balanced
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: d844e008-f7ad-4958-ad42-de4c706fcb00
EgorBo
marked this pull request as ready for review
October 9, 2026 10:05
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PTAL @dotnet/jit-contrib |
JulieLeeMSFT
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Oct 9, 2026
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LGTM. The new flag GTF_OBS_EFFECT (observable effect) appears to combine both exception-contributing effects (GTF_EXCEPT) and ordering-only effect (GTF_ORDER_SIDEEFF), closing a gap where ordering-only effects weren't being spilled.
Old (helper call): New (direct store, optimized):
push array eval array ----+
push index eval index ----|--> temps (preserve order)
push value (may throw/order-dep) eval value ----+
call ARRADDR_ST (does checks nullcheck/boundscheck (introduced here)
array,index,value in order) store
Finalize the new spill stores without reapplying assertions to operands already morphed by fgMorphArgs. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: e8778de6-8ade-4f24-91f4-9060e1eb4744
This was referenced Oct 10, 2026
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When morph replaces an array-store helper with a direct store, evaluate effectful operands in array/index/value order before introducing the array null and bounds checks. Enforce this at the conversion itself: importer spills can be undone by forward substitution while the operation is still a helper call.
Include ordering-only effects such as volatile reads, both in the conversion and in the existing inline array-store importer spill.
Fixes #133860
Almost no diffs