Ensure that embedded broadcast is correctly checking for EVEX support before use#105659
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tannergooding merged 2 commits intodotnet:release/8.0-stagingfrom Jul 30, 2024
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CC. @AndyAyersMS, the backport just needed to be 1 line here. All the other callsites were correctly filtering based on whether the JIT supported AVX512 already. |
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CC. @jeffschwMSFT |
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lgtm. we will take for consideration in 8.0.x
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Customer Impact
This resolves #96156
.NET 8 introduced support for the new AVX512 instruction set and this brought along support for several optimizations when the underlying hardware supported this feature. However, one such place was missing the check for said hardware support and would cause incorrect codegen on older hardware which could lead to incorrect results and behavior.
Regression
This is a regression as it impacts existing code and hardware when run on the .NET 8 runtime.
Testing
An explicit test was added covering the regression and additional validation was done against other callsites checking
OperIsEmbBroadcastCompatibleto ensure that they were all correctly validating that the target hardware is AVX512 capable.Risk
Low. The failure here is well understood and has had a fix in the .NET 9 previews for almost 2 months now.