Validate store-coalescing constants before modifying IR - #133976
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🟡 Changes recommended
Add the required SDK configuration so the no-HW regression builds and runs.
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Review tier: Lite
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What changed in this PR
Fixes JIT store-coalescing corruption by validating constants before mutating IR.
Changes:
- Moves scalar and SIMD validation ahead of store rewriting.
- Adds
Vector2andVector64.CreateScalarregression coverage. - Adds a hardware-intrinsics-disabled test variant.
| File | Summary |
|---|---|
src/tests/JIT/Regression_2/Runtime_133746/Runtime_133746.csproj |
Configures the primary regression test. |
src/tests/JIT/Regression_2/Runtime_133746/Runtime_133746.cs |
Adds regression coverage for affected vector cases. |
src/tests/JIT/Regression_2/Runtime_133746/Runtime_133746_nohw.csproj |
Critical: lacks the root SDK configuration, so the no-HW regression cannot run. |
src/coreclr/jit/lower.cpp |
Validates constants before store removal and widening. |
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| <Project> | |||
This was referenced Sep 15, 2026
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Fixes #133746.
LowerStoreCoalescingremoved the previous store and widened the current store before checking whether their constants could be combined. If constant extraction failed, lowering returned with the transformation only partially applied: the earlier bytes were lost and a narrow constant could be stored at the widened size without masking.Move scalar constant extraction and SIMD constant validation ahead of IR mutation. Unsupported combinations retain their original stores; supported combinations retain the existing packing and atomicity handling. This fixes the rejection path rather than special-casing
CreateScalaror disabling coalescing.Add regressions for a narrow write over a
Vector2constant and signedVector64.CreateScalarvalues, with normal and hardware-intrinsics-disabled configurations. On Windows x64, theVector2case reproduces the same invalid byte-to-long widening and fails against the baseline JIT; both variants pass with the fix. The exact reportedCreateScalarfailure did not reproduce on this host.Validation: checked Windows x64 CoreCLR, fixed JIT and cross-target JIT builds; both regression variants, AVX2-disabled execution, and 16 existing struct-promotion tests. Four existing coalescing-related methods have identical normalized disassembly before and after the fix (27, 55, 19, and 21 bytes respectively). JIT formatting passed. ARM64 execution was not performed.
Note
This PR description was drafted by GitHub Copilot.