[release/9.0] Ensure that AdvSimd.Insert doesn't zero out the upper bits #107089
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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CC. @jakobbotsch, @dotnet/jit-contrib for review This is a backport of #106981 to .NET 9 |
jakobbotsch
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Aug 28, 2024
jeffschwMSFT
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Aug 28, 2024
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lgtm. we can merge when ready
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Backport of #106981 to release/9.0
/cc @tannergooding
Customer Impact
Found via Fuzzlyn: #106079
Developers who are using
AdvSimd.Insertto insert a constant floating-point value may see incorrect codegen on Arm64.Regression
This bug was introduced in .NET 5 when the API was originally added: #35030
Testing
An explicit regression test was added covering the scenario. Additional manual testing of the patterns that are known to be problematic was completed on an Arm64 device. Similar patterns were also validated on x64 and the code was audited to identify if similar issues could exist.
Risk
Low. Most user code is doing insertions via the cross platform API,
vector.WithElementinstead which uses a different intrinsic (InsertSelectedScalar) to do the insertion, which does not have this same problem.