[release/8.0] JIT: remove incorrect type deduction for an Unsafe.As case #93703
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Thanks to @SingleAccretion for the fix. The JIT was assuming that an indirectly accessed value type field had the type of the field, but that might not be the case if the field was accessed via `Unsafe.As`. Fix this by limiting type deduction from these indirectly accessed fields to only ref type fields. Closes #93650.
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch Issue DetailsBackport of #93694 to release/8.0 /cc @AndyAyersMS Customer ImpactTestingRiskIMPORTANT: If this backport is for a servicing release, please verify that:
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@jakobbotsch PTAL Would like to consider this for .NET 8. |
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Failure unrelated - test timeout: |
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Backport of #93694 to release/8.0
/cc @AndyAyersMS
Customer Impact
Regression from prior releases, reported by @pentp in #93650.
In some uncommon cases using
Unsafe.Ason a reference to a value class struct field, the JIT may use the type of the field as the type, instead of the cast-to type.Testing
Verified repro case is now fixed, no diffs in SPMI.
Risk
Low. This is a fairly surgical fix and makes the JIT more conservative.