[release/9.0] Arm64: Use TYP_SIMD8 for AddAcross #108805
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dotnet-issue-labeler
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Tagging subscribers to this area: @JulieLeeMSFT, @jakobbotsch |
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@dotnet/jit-contrib @tannergooding |
jeffschwMSFT
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Oct 11, 2024
kunalspathak
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The failure seems to be known failure
not sure why |
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please get a code review and then we can merge |
tannergooding
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Oct 14, 2024
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Backport of #108727 to release/9.0
/cc @kunalspathak
Customer Impact
When creating
AddAcross()we were wrongly setting the wrong return type toTYP_SIMD16instead ofTYP_SIMD8. When customer useAdvSimd.Arm64.AddAcross()directly or indirectly when usingVector128.Sum()(which we translate intoAddAcross()as part of #97460). The effect might be visible when during code generation, we would wrongly produce a value in v128 register instead of v64 and take dependence on data present in upper-half of v128 because of that, which can be garbage, leading to silent codegen issues.Regression
[If yes, specify when the regression was introduced. Provide the PR or commit if known.]
Testing
Verified locally and added test cases
Risk
Low: This affects
AddAcross()intrinsic Arm64.IMPORTANT: If this backport is for a servicing release, please verify that:
The PR target branch is
release/X.0-staging, notrelease/X.0.If the change touches code that ships in a NuGet package, you have added the necessary package authoring and gotten it explicitly reviewed.