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Simplify code emitted for single char repeater #62322

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merged 1 commit into from
Dec 3, 2021
Merged

Simplify code emitted for single char repeater #62322

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37 changes: 27 additions & 10 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 @@ -2483,25 +2483,42 @@ void EmitSingleCharFixedRepeater(RegexNode node, bool emitLengthCheck = true)
return;
}

// if ((uint)(textSpanPos + iterations - 1) >= (uint)textSpan.Length) goto doneLabel;
if (emitLengthCheck)
{
EmitSpanLengthCheck(iterations);
}

if (iterations <= MaxUnrollSize)
{
// if (textSpan[textSpanPos] != c1 ||
// if ((uint)(textSpanPos + iterations - 1) >= (uint)textSpan.Length ||
// textSpan[textSpanPos] != c1 ||
// textSpan[textSpanPos + 1] != c2 ||
// ...)
// goto doneLabel;
for (int i = 0; i < iterations; i++)
// {
// goto doneLabel;
// }
writer.Write($"if (");
if (emitLengthCheck)
{
EmitSingleChar(node, emitLengthCheck: false);
writer.WriteLine($"{SpanLengthCheck(iterations)} ||");
writer.Write(" ");
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As an aside comment, I've seen in some places in the emitter we just do:

writer.Indent += 4;
// .. your indented writes
writer.Indent -= 4;

And we also have few places where we just write the spaces manually. If you agree, I'm happy to put up a PR that just normalizes to always use the Indent property to be consistent.

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@stephentoub stephentoub Dec 3, 2021 •
edited
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I'm fine with whichever is more readable and maintainable. Places that currently manually indent looked subjectively better to my eyes, but it can be changed.

}
EmitSingleChar(node, emitLengthCheck: false, clauseOnly: true);
for (int i = 1; i < iterations; i++)
{
writer.WriteLine(" ||");
writer.Write(" ");
EmitSingleChar(node, emitLengthCheck: false, clauseOnly: true);
}
writer.WriteLine(")");
using (EmitBlock(writer, null))
{
writer.WriteLine($"goto {doneLabel};");
}
}
else
{
// if ((uint)(textSpanPos + iterations - 1) >= (uint)textSpan.Length) goto doneLabel;
if (emitLengthCheck)
{
EmitSpanLengthCheck(iterations);
}

string spanLocal = "slice"; // As this repeater doesn't wrap arbitrary node emits, this shouldn't conflict with anything
writer.WriteLine($"global::System.ReadOnlySpan<char> {spanLocal} = {textSpanLocal}.Slice({textSpanPos}, {iterations});");
string i = ReserveName("charrepeater_iteration");
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