JIT: fix overlap check in store coalescing#128587
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Ensure the new store fully overlaps the old. Fixes dotnet#128566.
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@jakobbotsch PTAL Should have minimal diffs. |
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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Pull request overview
This PR tightens JIT store-coalescing’s “remove previous store” fast-path so it only fires when the current store fully overwrites the previous store, and adds a regression test reproducing the async/runtime-async miscompile.
Changes:
- Update
LowerStoreCoalescingto requirecurrData.accessSize >= prevData.accessSize(in addition to same offset and type) before deleting the previous store. - Add a new async regression test project/source pair for issue
128566.
Reviewed changes
Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| src/coreclr/jit/lower.cpp | Fixes the overlap/overwrite check so prior stores aren’t removed unless fully covered by the later store. |
| src/tests/async/regression/128566.csproj | Adds the test project entry for the new regression. |
| src/tests/async/regression/128566.cs | Adds the regression test asserting the struct field is properly zero-initialized. |
jakobbotsch
approved these changes
May 26, 2026
jakobbotsch
reviewed
May 26, 2026
This was referenced May 26, 2026
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This is hitting the CS8032 error (dotnet/sdk#54350) |
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/ba-g sporadic analyzer error |
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Ensure the new store fully overlaps the old.
Fixes #128566.