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JIT: sign-extend folded 32-bit RotateLeft/RotateRight constants - #135833
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impRotateHelper folds 32-bit rotates of constants into a uint32_t and passed it to gtNewIconNode, which zero-extended it on 64-bit hosts. TYP_INT constants must be sign-extended, so a result with bit 31 set (e.g. int.RotateLeft(1, 31)) was treated as +2^31 and comparisons against it were folded incorrectly. Cast the result to int32_t. Fixes dotnet#135814 Fixes dotnet#129099 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 6ec7c151-8b7f-4bf9-8b1a-8c601a2965ec
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🟡 Changes recommended
The unsigned test omits the multiple-use pattern needed to cover the reported Checked-build assertion.
1 open finding
What changed in this PR
Fixes JIT constant folding for 32-bit rotations whose results have the sign bit set.
Changes:
- Sign-extends folded results before creating integer constant nodes.
- Adds signed-comparison and unsigned-rotation regression tests.
Builds and tests were not run.
| File | Description |
|---|---|
| src/tests/JIT/Regression_ro_2/Runtime_135814.cs | Adds rotation regression coverage. |
| src/coreclr/jit/importercalls.cpp | Corrects folded constant representation. |
🧠 Review effort: Balanced
This was referenced Oct 15, 2026
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PTAL @dotnet/jit-contrib, trivial change, no diffs |
tannergooding
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Oct 15, 2026
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impRotateHelper folds 32-bit rotates of constants into a uint32_t and passed it to gtNewIconNode, which zero-extended it on 64-bit hosts. TYP_INT constants must be sign-extended, so a result with bit 31 set (e.g. int.RotateLeft(1, 31)) was treated as +2^31 and comparisons against it were folded incorrectly. Cast the result to int32_t.
Fixes #135814
Fixes #129099
No diffs