Fix range-check monotonicity for multiplication#130426
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Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 3f1f7aae-af73-4d20-8036-8fc58daa4f21
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Pull request overview
Adds a new JIT regression test under src/tests/JIT/Regression/JitBlue and wires it into the merged regression test project, covering a miscompile scenario around negative induction variables multiplied by 2.
Changes:
- Added
Runtime_130425regression test implemented as a merged-runner test using xUnit assertions. - Updated
Regression_ro_2.csprojto compile the new test source file.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/tests/JIT/Regression/Regression_ro_2.csproj | Includes the new Runtime_130425 test source in the merged regression project. |
| src/tests/JIT/Regression/JitBlue/Runtime_130425/Runtime_130425.cs | New regression test validating the expected result for the problematic loop/range-analysis scenario. |
Propagate non-negative requirements from multiplication and left shifts back to loop initial values before widening their ranges. Fixes dotnet#130425 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 3f1f7aae-af73-4d20-8036-8fc58daa4f21
EgorBo
changed the title
Conservatively stop treating multiplication and left shifts as monotonically increasing. SuperPMI benchmarks show no asm diffs from the more precise fix. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 3f1f7aae-af73-4d20-8036-8fc58daa4f21
Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>
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PTAL @dotnet/jit-contrib AI-found fix for a potential correctness issue with a repro. minimal diffs Instead of attempting to fix the monotonically-increased logic for GT_MUL, GT_LSH I just disabled it for them, left only correct GT_ADD |
jakobbotsch
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Jul 10, 2026
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Copilot-Session: 04aea4d9-a12d-4589-a2cd-426e4af339c8
jakobbotsch
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Jul 10, 2026
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/ba-g infra issues |
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Range analysis treated multiplication and left shifts as monotonically increasing even though both operations can decrease negative values. This could widen an invalid range and incorrectly fold comparisons.
Conservatively restrict monotonic widening to addition. SuperPMI
benchmarks.runshowed zero asm diffs compared with the more precise fix. Adds a regression test for the reported miscompile.Fixes #130425.