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Add back optimization of Encode using arm64 load/store/vectortablelookup #98719

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Merged
kunalspathak merged 2 commits into from
Feb 22, 2024
Merged

Add back optimization of Encode using arm64 load/store/vectortablelookup #98719

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4ab1ff4
Add back optimization of Encode using arm64 load/store/vectortablelookup
kunalspathak Feb 20, 2024
b8eae56
Merge remote-tracking branch 'origin/main' into load_store_enable
kunalspathak Feb 21, 2024
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67 changes: 67 additions & 0 deletions src/libraries/System.Private.CoreLib/src/System/Buffers/Text/Base64Encoder.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,15 @@ public static unsafe OperationStatus EncodeToUtf8(ReadOnlySpan<byte> bytes, Span
goto DoneExit;
}

end = srcMax - 48;
if (AdvSimd.Arm64.IsSupported && (end >= src))
{
AdvSimdEncode(ref src, ref dest, end, maxSrcLength, destLength, srcBytes, destBytes);

if (src == srcEnd)
goto DoneExit;
}

end = srcMax - 16;
if ((Ssse3.IsSupported || AdvSimd.Arm64.IsSupported) && BitConverter.IsLittleEndian && (end >= src))
{
Expand Down Expand Up @@ -480,6 +489,64 @@ private static unsafe void Avx2Encode(ref byte* srcBytes, ref byte* destBytes, b
destBytes = dest;
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
[CompExactlyDependsOn(typeof(AdvSimd.Arm64))]
private static unsafe void AdvSimdEncode(ref byte* srcBytes, ref byte* destBytes, byte* srcEnd, int sourceLength, int destLength, byte* srcStart, byte* destStart)
{
// C# implementation of https://github.com/aklomp/base64/blob/3a5add8652076612a8407627a42c768736a4263f/lib/arch/neon64/enc_loop.c
Vector128<byte> str1;
Vector128<byte> str2;
Vector128<byte> str3;
Vector128<byte> res1;
Vector128<byte> res2;
Vector128<byte> res3;
Vector128<byte> res4;
Vector128<byte> tblEnc1 = Vector128.Create("ABCDEFGHIJKLMNOP"u8).AsByte();
Vector128<byte> tblEnc2 = Vector128.Create("QRSTUVWXYZabcdef"u8).AsByte();
Vector128<byte> tblEnc3 = Vector128.Create("ghijklmnopqrstuv"u8).AsByte();
Vector128<byte> tblEnc4 = Vector128.Create("wxyz0123456789+/"u8).AsByte();
byte* src = srcBytes;
byte* dest = destBytes;

// If we have Neon support, pick off 48 bytes at a time for as long as we can.
do
{
// Load 48 bytes and deinterleave:
AssertRead<Vector128<byte>>(src, srcStart, sourceLength);
(str1, str2, str3) = AdvSimd.Arm64.LoadVector128x3AndUnzip(src);

// Divide bits of three input bytes over four output bytes:
res1 = AdvSimd.ShiftRightLogical(str1, 2);
res2 = AdvSimd.ShiftRightLogical(str2, 4);
res3 = AdvSimd.ShiftRightLogical(str3, 6);
res2 = AdvSimd.ShiftLeftAndInsert(res2, str1, 4);
res3 = AdvSimd.ShiftLeftAndInsert(res3, str2, 2);

// Clear top two bits:
res2 &= AdvSimd.DuplicateToVector128((byte)0x3F);
res3 &= AdvSimd.DuplicateToVector128((byte)0x3F);
res4 = str3 & AdvSimd.DuplicateToVector128((byte)0x3F);

// The bits have now been shifted to the right locations;
// translate their values 0..63 to the Base64 alphabet.
// Use a 64-byte table lookup:
res1 = AdvSimd.Arm64.VectorTableLookup((tblEnc1, tblEnc2, tblEnc3, tblEnc4), res1);
res2 = AdvSimd.Arm64.VectorTableLookup((tblEnc1, tblEnc2, tblEnc3, tblEnc4), res2);
res3 = AdvSimd.Arm64.VectorTableLookup((tblEnc1, tblEnc2, tblEnc3, tblEnc4), res3);
res4 = AdvSimd.Arm64.VectorTableLookup((tblEnc1, tblEnc2, tblEnc3, tblEnc4), res4);

// Interleave and store result:
AssertWrite<Vector128<byte>>(dest, destStart, destLength);
AdvSimd.Arm64.StoreVector128x4AndZip(dest, (res1, res2, res3, res4));

src += 48;
dest += 64;
} while (src <= srcEnd);

srcBytes = src;
destBytes = dest;
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
[CompExactlyDependsOn(typeof(Ssse3))]
[CompExactlyDependsOn(typeof(AdvSimd.Arm64))]
Expand Down