[release/9.0] Ensure that Arm64 correctly handles multiplication of simd by a 64-bit scalar #106972
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EgorBo
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Aug 26, 2024
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CC. @jeffschwMSFT, @JulieLeeMSFT for approval |
jeffschwMSFT
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Backport of #106839 to release/9.0
/cc @tannergooding
Customer Impact
#106838
On Arm64 hardware, multiplication of a vector containing
Int64orUInt64elements by a scalar (such asvector128 * 5UL) could produce incorrect results.Regression
64-bit vector multiplication was not accelerated in .NET 8, but support was added in .NET 9. A refactoring then later caused the
fgMakeMultiUsecall to replace the wrong node leading the second multiplication to produce incorrect results.Testing
An explicit test was added to validate the codegen was correct. The test was authored so it also validates the scenarios for other platforms as well.
Risk
Low. This is a relatively simple fix and is simply ensuring the write node is being duplicated.