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JIT: Preserve null checks in SequenceEqual VN folding - #135364
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Preserve faulting behavior for equal references with short nonempty sequences, and retain nullable calls when the length is unknown. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 7219f17d-da1f-42e0-bd7c-d9eecdba5eb6
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🟡 Changes recommended
The behavioral JIT fix lacks targeted regression coverage for null refs, length boundaries, and evaluation order.
1 open finding
What changed in this PR
Corrects JIT folding of SpanHelpers.SequenceEqual to preserve required null-check behavior.
Changes:
- Handles zero and unknown lengths safely.
- Emits null checks for short, equal-address sequences.
- Preserves argument side effects.
| File | Description |
|---|---|
src/coreclr/jit/assertionprop.cpp |
Refines equal-VN SequenceEqual folding semantics. |
🧠 Review effort: Balanced
This was referenced Oct 7, 2026
JulieLeeMSFT
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Oct 8, 2026
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/ba-g unrelated SMPT failures |
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The equal-VN fold of
SpanHelpers.SequenceEqualcan returntruefor identical null refs even when the managed implementation would dereference them and throw.Preserve
GT_NULLCHECKs for short, nonempty sequences (0 < length < sizeof(nuint)), while keeping the zero-length and long-buffer shortcuts. Retain the call when the length is unknown and the refs may be null. Argument side effects remain evaluated before the null checks.