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Simplify UTF-16 validation Vector128 codepath - #121981
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Combine the SSE2 codepath with a more generic Vector128 algorithm. AdvSimd is handled slightly differently to avoid using Vector128 ExtractMostSignificantBits, because there is no such equivalent instruction on Arm so the performance would be very slow otherwise.
ylpoonlg
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Nov 26, 2025
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cc @dotnet/arm64-contrib @a74nh@SwapnilGaikwad@tannergooding@EgorBo |
ylpoonlg
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November 26, 2025 10:15
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tannergooding
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EgorBo
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Improvements: dotnet/perf-autofiling-issues#67360 |
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Re-attempt at #121383.
Refactor the vectorized code path by combining the SSE2 "intrinsified" path with the original Vector128 algorithm. There are still some platform specific code (for AdvSimd), as it is difficult to fully rely on Vector128 APIs without sacrificing performance too much. The main issue is the lack of an instruction for
Vector128.ExtractMostSignificantBitson Arm, so it is significantly slower when trying to force it to use the same mask format as the SSE2 algorithm. I have looked into the possibility of usingIndexOfandCountetc, but they also useExtractMostSignificantBitsso it poses the same problem.This PR tries to encapsulate this difference in a few helper methods so they can share the same code path for the main algorithm.
Performance wise, there is not as much improvements, but hopefully the code will be easier to maintain.
Arm Neoverse-V2:
Intel Sapphire Rapids: