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Narrow four utf16 chars to ascii and write to buffer #39508

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Merged
pgovind merged 6 commits into from
Jul 29, 2020
Merged

Narrow four utf16 chars to ascii and write to buffer #39508

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Prashanth Govindarajan committed Jul 28, 2020
commit 9c2b8a7f0e9ef55a6c386f1c915c8b01f83d326d
7 changes: 2 additions & 5 deletions src/libraries/System.Private.CoreLib/src/System/Text/ASCIIUtility.cs
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Expand Up @@ -1006,14 +1006,11 @@ private static void NarrowFourUtf16CharsToAsciiAndWriteToBuffer(ref byte outputB
else if (AdvSimd.Arm64.IsSupported)
{
// Narrows a vector of words [ w0 w1 w2 w3 ] to a vector of bytes
// [ b0 b1 b2 b3 b0 b1 b2 b3 ], then writes 4 bytes (32 bits) to the destination.
// [ b0 b1 b2 b3 * * * * ], then writes 4 bytes (32 bits) to the destination.

Vector128<short> vecWide = Vector128.CreateScalarUnsafe(value).AsInt16();
Vector64<byte> lower = AdvSimd.ExtractNarrowingSaturateUnsignedLower(vecWide);
unsafe
{
AdvSimd.StoreSelectedScalar((byte*)Unsafe.AsPointer(ref outputBuffer), lower, 0);
}
Unsafe.WriteUnaligned<uint>(ref outputBuffer, lower.AsUInt32().ToScalar());
}

else
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