Optimize library code using arm64 intrinsics

[BruceForstall]

The following classes/functions in the libraries have Intel x86/x64 intrinsics usage. These are where _ISA_.IsSupported() is called. This information was collected manually and might not be complete. Some of these function names represent many overloads. There are some vectorized helper methods not shown here -- where a function calls IsSupported and then calls a specific helper function to do the actual work, such as for SSE2 or AVX2 specifically. There are other cases where Vector<T> is used, but arm64 already supports that (it should be verified that the arm64 Vector<T> code is complete and performant).

When each of these has added an arm64-specific intrinsics optimization, it should be "checked off".

The sections below are ordered in the presumed priority order that they should be implemented in. (There is no assumed priority order for the individual functions in each section.)

It is expected that System.Collections.BitArray, System.Numerics, and System.SpanHelpers will be "arm64 intrinsi-fied" for .NET 5. If possible, System.Buffers and System.Text will as well, but that is not considered required.

System.Collections.BitArray #33309

• System.Collections.BitArray - constructor
• System.Collections.BitArray.And()
• System.Collections.BitArray.Or()
• System.Collections.BitArray.Xor()
• System.Collections.BitArray.Not()
• System.Collections.BitArray.CopyTo()

System.Runtime.Intrinsics #33496

Vector64

• As<T, U>()
• AsInt64()
• AsUInt64()
• AsDouble()
• CreateScalarUnsafe(int value);
• CreateScalarUnsafe(uint value);
• CreateScalarUnsafe(float value);
• CreateScalarUnsafe(byte value);
• CreateScalarUnsafe(sbyte value);
• CreateScalarUnsafe(short value);
• CreateScalarUnsafe(ushort value);
• CreateScalar(uint)
• CreateScalar(float)
• CreateScalar(sbyte)
• CreateScalar(ushort)
• CreateScalar(short)
• CreateScalar(byte)
• CreateScalar(int)
• Create(sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte)
• Create(byte, byte, byte, byte, byte, byte, byte, byte)
• Create(ushort, ushort, ushort, ushort)
• Create(short, short, short, short)
• Create(float, float)
• Create(int, int)
• Create(ulong)
• Create(uint)
• Create(uint, uint)
• Create(float)
• Create(sbyte)
• Create(long)
• Create(int)
• Create(short)
• Create(double)
• Create(byte)
• Create(ushort)
• GetElement(int index)
• ToScalar()
• ToVector128()
• ToVector128Unsafe()
• WithElement(Vector64, int, T)

Vector128

• As<T, U>()
• AsVector()
• AsVector4(Vector128)
• AsVector128(Vector)
• AsVector128(Vector4)
• CreateScalarUnsafe(int value);
• CreateScalarUnsafe(uint value);
• CreateScalarUnsafe(float value);
• CreateScalarUnsafe(long value);
• CreateScalarUnsafe(ulong value);
• CreateScalarUnsafe(double value);
• CreateScalarUnsafe(byte value);
• CreateScalarUnsafe(sbyte value);
• CreateScalarUnsafe(short value);
• CreateScalarUnsafe(ushort value);
• CreateScalar(ulong)
• CreateScalar(uint)
• CreateScalar(ushort)
• CreateScalar(sbyte)
• CreateScalar(float)
• CreateScalar(int)
• CreateScalar(short)
• CreateScalar(double)
• CreateScalar(byte)
• CreateScalar(long)
• Create(sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte, sbyte)
• Create(byte, byte, byte, byte, byte, byte, byte, byte, byte, byte, byte, byte, byte, byte, byte, byte)
• Create(ushort, ushort, ushort, ushort, ushort, ushort, ushort, ushort)
• Create(short, short, short, short, short, short, short, short)
• Create(uint, uint, uint, uint)
• Create(float, float, float, float)
• Create(int, int, int, int)
• Create(ulong, ulong)
• Create(Vector64, Vector64)
• Create(Vector64, Vector64)
• Create(Vector64, Vector64)
• Create(Vector64, Vector64)
• Create(Vector64, Vector64)
• Create(Vector64, Vector64)
• Create(Vector64, Vector64)
• Create(Vector64, Vector64)
• Create(byte)
• Create(double)
• Create(short)
• Create(int)
• Create(long)
• Create(Vector64, Vector64)
• Create(float)
• Create(sbyte)
• Create(uint)
• Create(ulong)
• Create(double, double)
• Create(long, long)
• Create(Vector64, Vector64)
• Create(ushort)
• GetElement(int index)
• GetLower()
• GetUpper()
• WithElement(Vector128, int, T)
• WithLower(Vector64)
• WithUpper(Vector64)
• ToScalar()

Vector256

• Software fallback

System.Numerics

System.Numerics.BitOperations #33495

• System.Numerics.BitOperations.LeadingZeroCount()
• System.Numerics.BitOperations.Log2()
• System.Numerics.BitOperations.PopCount()
• System.Numerics.BitOperations.TrailingZeroCount()

System.Numerics.Matrix4x4 #33565

• System.Numerics.Matrix4x4.Transpose()
• System.Numerics.Matrix4x4.Lerp()
• System.Numerics.Matrix4x4.operator-()
• System.Numerics.Matrix4x4.operator+()
• System.Numerics.Matrix4x4.operator*()
• System.Numerics.Matrix4x4.operator==()
• System.Numerics.Matrix4x4.operator!=()

System.SpanHelpers #33707

• System.SpanHelpers.IndexOf(byte)
• System.SpanHelpers.IndexOf(char)
• System.SpanHelpers.IndexOfAny(byte)
  [ ] System.SpanHelpers.SequenceCompareTo(byte) (SIMD vector implementation is fast enough)
  [ ] System.SpanHelpers.SequenceEqual(byte) (SIMD vector implementation is fast enough)
  [ ] System.SpanHelpers.LocateFirstFoundByte() (Only used by SIMD version of IndexOf and IndexOfAny which are already optimized by ARM64 intrinsics)

System.Buffers #35033

(Not completed in 5.0.0; moved to 6.0.0)

• System.Buffers.Text.Base64.DecodeFromUtf8()
• System.Buffers.Text.Base64.EncodeToUtf8()

System.Text

System.Text.ASCIIUtility #35034

(Not completed in 5.0.0; #41292 contains the items moved to 6.0.0)

• System.Text.ASCIIUtility.GetIndexOfFirstNonAsciiByte()
• System.Text.ASCIIUtility.GetIndexOfFirstNonAsciiChar() - (Not completed in 5.0.0; moved to 6.0.0) - PR Get index of first non ascii char #39507
• System.Text.ASCIIUtility.NarrowFourUtf16CharsToAsciiAndWriteToBuffer()
• System.Text.ASCIIUtility.NarrowUtf16ToAscii() - (Not completed in 5.0.0; moved to 6.0.0) - PR Narrow utf16 to ascii #39509
• System.Text.ASCIIUtility.WidenAsciiToUtf16()
• System.Text.ASCIIUtility.WidenFourAsciiBytesToUtf16AndWriteToBuffer()
• System.Text.ASCIIUtility.CountNumberOfLeadingAsciiBytesFromUInt32WithSomeNonAsciiData()

System.Text.Unicode #35035

• System.Text.Unicode.Utf16Utility.GetPointerToFirstInvalidChar()
• System.Text.Unicode.Utf8Utility.TranscodeToUtf8()
• System.Text.Unicode.Utf8Utility.GetPointerToFirstInvalidByte()

System.Text.Encodings.Web #35036

• System.Text.Encodings.Web.DefaultJavaScriptEncoder.FindFirstCharacterToEncodeUtf8()
• System.Text.Encodings.Web.DefaultJavaScriptEncoderBasicLatin.FindFirstCharacterToEncode()
• System.Text.Encodings.Web.DefaultJavaScriptEncoderBasicLatin.FindFirstCharacterToEncodeUtf8()
• System.Text.Encodings.Web.TextEncoder.FindFirstCharacterToEncodeUtf8()
• System.Text.Encodings.Web.UnsafeRelaxedJavaScriptEncoder.WillEncode()
• System.Text.Encodings.Web.UnsafeRelaxedJavaScriptEncoder.FindFirstCharacterToEncodeUtf8()

[jkotas]

System.Text System.Text.ASCIIUtility, System.Text.Unicode and System.SpanHelpers are the most important ones for Web workloads.

[BruceForstall]

@jkotas It's my understanding that ASP.NET is currently not running benchmarks on arm64. Hopefully that will change, then we'd be able to see benefits from optimizing these.

[BruceForstall]

Also, BitArray is chosen to be first to implement because it's simple, has benchmarks defined, and can easily be used as a proof-of-concept of the basics of the intrinsics implementation -- not because it's the most important class.

[tannergooding]

CC. @CarolEidt, @echesakovMSFT, @GrabYourPitchforks, @TamarChristinaArm

[Gnbrkm41]

Would love to help this! Though, I remember majority of the ARM intrinsics being unavailable last time I looked up (only available via experimental NuGet package). Has this been addressed? I have seen a few API review sessions where ARM intrinsics are discussed but I don't know if they are implemented.

[Gnbrkm41]

One concern is that I can't quite run tests and benchmarks locally since I do not own an ARM machine (well, I do - but it's an RPi 3B+). I know those exist as part of CI/CD but are the perf numbers available to non-MSFT people?

[BruceForstall]

I have seen a few API review sessions where ARM intrinsics are discussed but I don't know if they are implemented.

The implementation is in progress, so there will be feature gaps.

One concern is that I can't quite run tests and benchmarks locally since I do not own an ARM machine (well, I do - but it's an RPi 3B+). I know those exist as part of CI/CD but are the perf numbers available to non-MSFT people?

That's a bigger problem. The CI will do feature testing on ARM64, but there is currently no perf testing available to non-MSFT (and minimal available internal). You probably don't want to depend on the CI to do all functional testing for you. I think it's possible to use the RPi for this if you install, say, Ubuntu 64-bit.

[CarolEidt]

I think it's possible to use the RPi for this if you install, say, Ubuntu 64-bit.

I have successfully run perf tests on a RPi 4 with Ubuntu 64-bit; I assume it would also work on the RPi 3B+.

[BruceForstall]

cc @jeffschwMSFT