Fix bug in RangeOps::ShiftRight #123794
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Fix bug in RangeOps::ShiftRight #123794
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Tagging subscribers to this area: @JulieLeeMSFT, @dotnet/jit-contrib |
EgorBo
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Jan 30, 2026
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| // Check if the range represents a single constant value. Example: [7..7] | ||
| bool IsSingleConstValue(int* pConstVal) const |
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Two PRs introduced similar helpers, removed one of them.
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Pull request overview
Fixes an incorrect range computation in JIT range analysis for right-shift operations (RangeOps::ShiftRight), addressing #123790 and adding a regression test to prevent recurrence.
Changes:
- Add a JIT regression test for the reported shift/comparison miscompile.
- Rework
RangeOps::ShiftRightto compute bounds using opposite shift-count endpoints (lower usesr2.UpperLimit, upper usesr2.LowerLimit) when the shift-count range is constant and within[0..31]. - Remove
Range::IsSingleConstValueusage in favor of the existingRange::IsSingleValueConstant.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
| src/tests/JIT/Regression/JitBlue/Runtime_123790/Runtime_123790.cs | Adds an xUnit regression test for the miscompile scenario from #123790. |
| src/coreclr/jit/rangecheck.h | Updates range computation logic for ShiftRight and replaces IsSingleConstValue references with IsSingleValueConstant. |
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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/azp run Fuzzlyn |
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Azure Pipelines successfully started running 1 pipeline(s). |
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PTAL @jakobbotsch @dotnet/jit-contrib fix for ShiftRight (see description). No diffs. |
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Fixes #123790
For e.g.
[0..65535] >> [0..31]I didn't realize I need to swap lower and upper bound for r2, so the result should be:[0 >> 31 .. 65535 >> 0], not[0 >> 0 .. 65535 >> 31]No diffs