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Optimize byte variants of IndexOfAny() #37934

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Jun 16, 2020
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Optimize byte variants of IndexOfAny() #37934

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91 changes: 88 additions & 3 deletions src/libraries/System.Private.CoreLib/src/System/SpanHelpers.Byte.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,7 @@ public static int IndexOf(ref byte searchSpace, int searchSpaceLength, ref byte
break; // The unsearched portion is now shorter than the sequence we're looking for. So it can't be there.

// Found the first element of "value". See if the tail matches.
if (SequenceEqual(ref Unsafe.Add(ref searchSpace, offset + 1), ref valueTail, (nuint)valueTailLength)) // The (nunit)-cast is necessary to pick the correct overload
if (SequenceEqual(ref Unsafe.Add(ref searchSpace, offset + 1), ref valueTail, (nuint)valueTailLength)) // The (nuint)-cast is necessary to pick the correct overload
return offset; // The tail matched. Return a successful find.

remainingSearchSpaceLength--;
Expand Down Expand Up @@ -601,7 +601,7 @@ public static int IndexOfAny(ref byte searchSpace, byte value0, byte value1, int
nuint offset = 0; // Use nuint for arithmetic to avoid unnecessary 64->32->64 truncations
nuint lengthToExamine = (nuint)(uint)length;

if (Sse2.IsSupported)
if (Sse2.IsSupported || AdvSimd.Arm64.IsSupported)
{
// Avx2 branch also operates on Sse2 sizes, so check is combined.
if (length >= Vector128<byte>.Count * 2)
Expand Down Expand Up @@ -780,6 +780,47 @@ public static int IndexOfAny(ref byte searchSpace, byte value0, byte value1, int
}
}
}
else if (AdvSimd.Arm64.IsSupported)
{
if (offset < (nuint)(uint)length)
{
lengthToExamine = GetByteVector128SpanLength(offset, length);

// Mask to help find the first lane in compareResult that is set.
// LSB 0x01 corresponds to lane 0, 0x10 - to lane 1, and so on.
Vector128<byte> mask = Vector128.Create((ushort)0x1001).AsByte();
int matchedLane = 0;

Vector128<byte> values0 = Vector128.Create(value0);
Vector128<byte> values1 = Vector128.Create(value1);

while (lengthToExamine > offset)
{
Vector128<byte> search = LoadVector128(ref searchSpace, offset);

// Same method as above
Vector128<byte> compareResult = AdvSimd.Or(
AdvSimd.CompareEqual(values0, search),
AdvSimd.CompareEqual(values1, search));

if (!TryFindFirstMatchedLane(mask, compareResult, ref matchedLane))
{
// Zero flags set so no matches
offset += (nuint)Vector128<byte>.Count;
continue;
}

// Find bitflag offset of first match and add to current offset
return (int)(offset + (uint)matchedLane);
}

if (offset < (nuint)(uint)length)
{
lengthToExamine = ((nuint)(uint)length - offset);
goto SequentialScan;
}
}
}
else if (Vector.IsHardwareAccelerated)
{
if (offset < (nuint)(uint)length)
Expand Down Expand Up @@ -842,7 +883,7 @@ public static int IndexOfAny(ref byte searchSpace, byte value0, byte value1, byt
nuint offset = 0; // Use nuint for arithmetic to avoid unnecessary 64->32->64 truncations
nuint lengthToExamine = (nuint)(uint)length;

if (Sse2.IsSupported)
if (Sse2.IsSupported || AdvSimd.Arm64.IsSupported)
{
// Avx2 branch also operates on Sse2 sizes, so check is combined.
if (length >= Vector128<byte>.Count * 2)
Expand Down Expand Up @@ -1025,6 +1066,50 @@ public static int IndexOfAny(ref byte searchSpace, byte value0, byte value1, byt
}
}
}
else if (AdvSimd.Arm64.IsSupported)
{
if (offset < (nuint)(uint)length)
{
lengthToExamine = GetByteVector128SpanLength(offset, length);

// Mask to help find the first lane in compareResult that is set.
// LSB 0x01 corresponds to lane 0, 0x10 - to lane 1, and so on.
Vector128<byte> mask = Vector128.Create((ushort)0x1001).AsByte();
int matchedLane = 0;

Vector128<byte> values0 = Vector128.Create(value0);
Vector128<byte> values1 = Vector128.Create(value1);
Vector128<byte> values2 = Vector128.Create(value2);

while (lengthToExamine > offset)
{
Vector128<byte> search = LoadVector128(ref searchSpace, offset);

// Same method as above
Vector128<byte> matches0 = AdvSimd.CompareEqual(values0, search);
Vector128<byte> matches1 = AdvSimd.CompareEqual(values1, search);
Vector128<byte> matches2 = AdvSimd.CompareEqual(values2, search);

Vector128<byte> compareResult = AdvSimd.Or(AdvSimd.Or(matches0, matches1), matches2);

if (!TryFindFirstMatchedLane(mask, compareResult, ref matchedLane))
{
// Zero flags set so no matches
offset += (nuint)Vector128<byte>.Count;
continue;
}

// Find bitflag offset of first match and add to current offset
return (int)(offset + (uint)matchedLane);
}

if (offset < (nuint)(uint)length)
{
lengthToExamine = ((nuint)(uint)length - offset);
goto SequentialScan;
}
}
}
else if (Vector.IsHardwareAccelerated)
{
if (offset < (nuint)(uint)length)
Expand Down