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Tweak code gen for Guid parsing (#56210)
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* Tweak code gen for Guid parsing

* Further tweak to use nuint/nint
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@stephentoub
stephentoub authored Jul 25, 2021
1 parent d019e70 commit ce3e00b
Showing 1 changed file with 55 additions and 47 deletions.
102 changes: 55 additions & 47 deletions src/libraries/System.Private.CoreLib/src/System/Guid.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -398,25 +398,25 @@ private static bool TryParseExactD(ReadOnlySpan<char> guidString, ref GuidResult
}

Span<byte> bytes = MemoryMarshal.AsBytes(new Span<GuidResult>(ref result, 1));
uint invalidIfFF = 0;
bytes[0] = DecodeByte(guidString[6], guidString[7], ref invalidIfFF);
bytes[1] = DecodeByte(guidString[4], guidString[5], ref invalidIfFF);
bytes[2] = DecodeByte(guidString[2], guidString[3], ref invalidIfFF);
bytes[3] = DecodeByte(guidString[0], guidString[1], ref invalidIfFF);
bytes[4] = DecodeByte(guidString[11], guidString[12], ref invalidIfFF);
bytes[5] = DecodeByte(guidString[9], guidString[10], ref invalidIfFF);
bytes[6] = DecodeByte(guidString[16], guidString[17], ref invalidIfFF);
bytes[7] = DecodeByte(guidString[14], guidString[15], ref invalidIfFF);
bytes[8] = DecodeByte(guidString[19], guidString[20], ref invalidIfFF);
bytes[9] = DecodeByte(guidString[21], guidString[22], ref invalidIfFF);
bytes[10] = DecodeByte(guidString[24], guidString[25], ref invalidIfFF);
bytes[11] = DecodeByte(guidString[26], guidString[27], ref invalidIfFF);
bytes[12] = DecodeByte(guidString[28], guidString[29], ref invalidIfFF);
bytes[13] = DecodeByte(guidString[30], guidString[31], ref invalidIfFF);
bytes[14] = DecodeByte(guidString[32], guidString[33], ref invalidIfFF);
bytes[15] = DecodeByte(guidString[34], guidString[35], ref invalidIfFF);

if (invalidIfFF != 0xFF)
int invalidIfNegative = 0;
bytes[0] = DecodeByte(guidString[6], guidString[7], ref invalidIfNegative);
bytes[1] = DecodeByte(guidString[4], guidString[5], ref invalidIfNegative);
bytes[2] = DecodeByte(guidString[2], guidString[3], ref invalidIfNegative);
bytes[3] = DecodeByte(guidString[0], guidString[1], ref invalidIfNegative);
bytes[4] = DecodeByte(guidString[11], guidString[12], ref invalidIfNegative);
bytes[5] = DecodeByte(guidString[9], guidString[10], ref invalidIfNegative);
bytes[6] = DecodeByte(guidString[16], guidString[17], ref invalidIfNegative);
bytes[7] = DecodeByte(guidString[14], guidString[15], ref invalidIfNegative);
bytes[8] = DecodeByte(guidString[19], guidString[20], ref invalidIfNegative);
bytes[9] = DecodeByte(guidString[21], guidString[22], ref invalidIfNegative);
bytes[10] = DecodeByte(guidString[24], guidString[25], ref invalidIfNegative);
bytes[11] = DecodeByte(guidString[26], guidString[27], ref invalidIfNegative);
bytes[12] = DecodeByte(guidString[28], guidString[29], ref invalidIfNegative);
bytes[13] = DecodeByte(guidString[30], guidString[31], ref invalidIfNegative);
bytes[14] = DecodeByte(guidString[32], guidString[33], ref invalidIfNegative);
bytes[15] = DecodeByte(guidString[34], guidString[35], ref invalidIfNegative);

if (invalidIfNegative >= 0)
{
if (!BitConverter.IsLittleEndian)
{
Expand Down Expand Up @@ -484,25 +484,25 @@ private static bool TryParseExactN(ReadOnlySpan<char> guidString, ref GuidResult
}

Span<byte> bytes = MemoryMarshal.AsBytes(new Span<GuidResult>(ref result, 1));
uint invalidIfFF = 0;
bytes[0] = DecodeByte(guidString[6], guidString[7], ref invalidIfFF);
bytes[1] = DecodeByte(guidString[4], guidString[5], ref invalidIfFF);
bytes[2] = DecodeByte(guidString[2], guidString[3], ref invalidIfFF);
bytes[3] = DecodeByte(guidString[0], guidString[1], ref invalidIfFF);
bytes[4] = DecodeByte(guidString[10], guidString[11], ref invalidIfFF);
bytes[5] = DecodeByte(guidString[8], guidString[9], ref invalidIfFF);
bytes[6] = DecodeByte(guidString[14], guidString[15], ref invalidIfFF);
bytes[7] = DecodeByte(guidString[12], guidString[13], ref invalidIfFF);
bytes[8] = DecodeByte(guidString[16], guidString[17], ref invalidIfFF);
bytes[9] = DecodeByte(guidString[18], guidString[19], ref invalidIfFF);
bytes[10] = DecodeByte(guidString[20], guidString[21], ref invalidIfFF);
bytes[11] = DecodeByte(guidString[22], guidString[23], ref invalidIfFF);
bytes[12] = DecodeByte(guidString[24], guidString[25], ref invalidIfFF);
bytes[13] = DecodeByte(guidString[26], guidString[27], ref invalidIfFF);
bytes[14] = DecodeByte(guidString[28], guidString[29], ref invalidIfFF);
bytes[15] = DecodeByte(guidString[30], guidString[31], ref invalidIfFF);

if (invalidIfFF != 0xFF)
int invalidIfNegative = 0;
bytes[0] = DecodeByte(guidString[6], guidString[7], ref invalidIfNegative);
bytes[1] = DecodeByte(guidString[4], guidString[5], ref invalidIfNegative);
bytes[2] = DecodeByte(guidString[2], guidString[3], ref invalidIfNegative);
bytes[3] = DecodeByte(guidString[0], guidString[1], ref invalidIfNegative);
bytes[4] = DecodeByte(guidString[10], guidString[11], ref invalidIfNegative);
bytes[5] = DecodeByte(guidString[8], guidString[9], ref invalidIfNegative);
bytes[6] = DecodeByte(guidString[14], guidString[15], ref invalidIfNegative);
bytes[7] = DecodeByte(guidString[12], guidString[13], ref invalidIfNegative);
bytes[8] = DecodeByte(guidString[16], guidString[17], ref invalidIfNegative);
bytes[9] = DecodeByte(guidString[18], guidString[19], ref invalidIfNegative);
bytes[10] = DecodeByte(guidString[20], guidString[21], ref invalidIfNegative);
bytes[11] = DecodeByte(guidString[22], guidString[23], ref invalidIfNegative);
bytes[12] = DecodeByte(guidString[24], guidString[25], ref invalidIfNegative);
bytes[13] = DecodeByte(guidString[26], guidString[27], ref invalidIfNegative);
bytes[14] = DecodeByte(guidString[28], guidString[29], ref invalidIfNegative);
bytes[15] = DecodeByte(guidString[30], guidString[31], ref invalidIfNegative);

if (invalidIfNegative >= 0)
{
if (!BitConverter.IsLittleEndian)
{
Expand Down Expand Up @@ -695,21 +695,29 @@ private static bool TryParseExactX(ReadOnlySpan<char> guidString, ref GuidResult
}

[MethodImpl(MethodImplOptions.AggressiveInlining)]
private static byte DecodeByte(char ch1, char ch2, ref uint invalidIfFF)
private static byte DecodeByte(nuint ch1, nuint ch2, ref int invalidIfNegative)
{
// TODO https://github.com/dotnet/runtime/issues/13464:
// Replace the Unsafe.Add with HexConverter.FromChar once the bounds checks are eliminated.

uint h1 = 0xFF;
if (ch1 < HexConverter.CharToHexLookup.Length)
h1 = Unsafe.Add(ref MemoryMarshal.GetReference(HexConverter.CharToHexLookup), ch1);
ReadOnlySpan<byte> lookup = HexConverter.CharToHexLookup;

uint h2 = 0xFF;
if (ch2 < HexConverter.CharToHexLookup.Length)
h2 = Unsafe.Add(ref MemoryMarshal.GetReference(HexConverter.CharToHexLookup), ch2);
int h1 = -1;
if (ch1 < (nuint)lookup.Length)
{
h1 = (sbyte)Unsafe.Add(ref MemoryMarshal.GetReference(lookup), (nint)ch1);
}
h1 <<= 4;

int h2 = -1;
if (ch2 < (nuint)lookup.Length)
{
h2 = (sbyte)Unsafe.Add(ref MemoryMarshal.GetReference(lookup), (nint)ch2);
}

invalidIfFF |= h1 | h2;
return (byte)(h1 << 4 | h2);
int result = h1 | h2;
invalidIfNegative |= result;
return (byte)result;
}

private static bool TryParseHex(ReadOnlySpan<char> guidString, out ushort result, ref bool overflow)
Expand Down

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