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Remove some unnecessary slicing from generated Regex code #61701

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Merged
stephentoub merged 2 commits into from
Nov 17, 2021
Merged

Remove some unnecessary slicing from generated Regex code #61701

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01d6577
Remove some unnecessary slicing from generated Regex code
stephentoub Nov 16, 2021
e5f319e
Address PR feedback
stephentoub Nov 17, 2021
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Remove some unnecessary slicing from generated Regex code 
When we're outputting code to match a "multi" (a sequence of multiple characters), we're currently issuing a Slice for the known tracked offset even if that offset is 0.  We can skip that nop.
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@stephentoub
stephentoub committed Nov 16, 2021
commit 01d65771c6802e80b17dd53f870170df51599458
9 changes: 6 additions & 3 deletions src/libraries/System.Text.RegularExpressions/gen/RegexGenerator.Emitter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1529,15 +1529,17 @@ void EmitOr()
while (byteStr.Length >= sizeof(ulong))
{
EmitOr();
writer.Write($"global::System.Buffers.Binary.BinaryPrimitives.ReadUInt64LittleEndian(byteSpan.Slice({textSpanPos * sizeof(char)})) != 0x{BinaryPrimitives.ReadUInt64LittleEndian(byteStr):X}ul");
string byteSpan = textSpanPos > 0 ? $"byteSpan.Slice({textSpanPos * sizeof(char)})" : "byteSpan";
writer.Write($"global::System.Buffers.Binary.BinaryPrimitives.ReadUInt64LittleEndian({byteSpan}) != 0x{BinaryPrimitives.ReadUInt64LittleEndian(byteStr):X}ul");
textSpanPos += sizeof(ulong) / sizeof(char);
byteStr = byteStr.Slice(sizeof(ulong));
}

while (byteStr.Length >= sizeof(uint))
{
EmitOr();
writer.Write($"global::System.Buffers.Binary.BinaryPrimitives.ReadUInt32LittleEndian(byteSpan.Slice({textSpanPos * sizeof(char)})) != 0x{BinaryPrimitives.ReadUInt32LittleEndian(byteStr):X}u");
string byteSpan = textSpanPos > 0 ? $"byteSpan.Slice({textSpanPos * sizeof(char)})" : "byteSpan";
writer.Write($"global::System.Buffers.Binary.BinaryPrimitives.ReadUInt32LittleEndian({byteSpan}) != 0x{BinaryPrimitives.ReadUInt32LittleEndian(byteStr):X}u");
textSpanPos += sizeof(uint) / sizeof(char);
byteStr = byteStr.Slice(sizeof(uint));
}
Expand Down Expand Up @@ -1565,7 +1567,8 @@ void EmitOr()
// character-by-character while respecting the culture.
if (!caseInsensitive)
{
using (EmitBlock(writer, $"if (!global::System.MemoryExtensions.StartsWith({textSpanLocal}.Slice({textSpanPos}), {Literal(node.Str)}))"))
string sourceSpan = textSpanPos > 0 ? $"{textSpanLocal}.Slice({textSpanPos})" : textSpanLocal;
using (EmitBlock(writer, $"if (!global::System.MemoryExtensions.StartsWith({sourceSpan}, {Literal(node.Str)}))"))
{
writer.WriteLine($"goto {doneLabel};");
}
Expand Down