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Use JIT intrinsic for UTF8 encoding in Utf8.TryWrite's AppendLiteral #89376

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Merged
merged 2 commits into from
Jul 24, 2023
Merged

Use JIT intrinsic for UTF8 encoding in Utf8.TryWrite's AppendLiteral #89376

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ed7158d
Use JIT intrinsic for UTF8 encoding in Utf8.TryWrite's AppendLiteral
stephentoub Jul 24, 2023
4325e67
Remove IsKnownConstant
stephentoub Jul 24, 2023
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1 change: 1 addition & 0 deletions src/libraries/System.Private.CoreLib/src/System/Text/UTF8Encoding.Sealed.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -155,6 +155,7 @@ public override bool TryGetBytes(ReadOnlySpan<char> chars, Span<byte> bytes, out
return base.TryGetBytes(chars, bytes, out bytesWritten);
}

/// <summary>Same as Encoding.UTF8.TryGetBytes, except with refs, returning the number of bytes written (or -1 if the operation fails), and optimized for a constant input.</summary>
[MethodImpl(MethodImplOptions.NoInlining)]
[Intrinsic] // Can be unrolled by JIT
internal static unsafe int ReadUtf8(ref char input, int inputLength, ref byte output, int outputLength)
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31 changes: 22 additions & 9 deletions src/libraries/System.Private.CoreLib/src/System/Text/Unicode/Utf8.cs
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Expand Up @@ -410,15 +410,28 @@ public TryWriteInterpolatedStringHandler(int literalLength, int formattedCount,
/// <summary>Writes the specified string to the handler.</summary>
/// <param name="value">The string to write.</param>
/// <returns>true if the value could be formatted to the span; otherwise, false.</returns>
public bool AppendLiteral(string value) => AppendFormatted(value.AsSpan());

// TODO https://github.com/dotnet/csharplang/issues/7072:
// Add this if/when C# supports u8 literals with string interpolation.
// If that happens prior to this type being released, the above AppendLiteral(string)
// should also be removed. If that doesn't happen, we should look into ways to optimize
// the above AppendLiteral, such as by making the underlying encoding operation a JIT
// intrinsic that can emit substitute a "abc"u8 equivalent for an "abc" string literal.
//public bool AppendLiteral(scoped ReadOnlySpan<byte> value) => AppendFormatted(value);
[MethodImpl(MethodImplOptions.AggressiveInlining)] // we want 'value' exposed to the JIT as a constant
public bool AppendLiteral(string value)
{
if (value is not null)
{
Span<byte> dest = _destination.Slice(_pos);

// The 99.999% for AppendLiteral is to be called with a const string.
// ReadUtf8 is a JIT intrinsic that can do the UTF8 encoding at JIT time.
int bytesWritten = UTF8Encoding.UTF8EncodingSealed.ReadUtf8(
ref value.GetRawStringData(), value.Length,
ref MemoryMarshal.GetReference(dest), dest.Length);
if (bytesWritten < 0)
{
return Fail();
}

_pos += bytesWritten;
}

return true;
}

/// <summary>Writes the specified value to the handler.</summary>
/// <param name="value">The value to write.</param>
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