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Several improvements / simplifications in Regex #100315

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Apr 3, 2024
Merged

Several improvements / simplifications in Regex #100315

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fc50653
Several improvements / simplifications in Regex
stephentoub Mar 26, 2024
dc4ddc7
Update src/libraries/System.Text.RegularExpressions/gen/RegexGenerato…
stephentoub Mar 29, 2024
e1cde36
Merge branch 'main' into regextweaks
stephentoub Apr 3, 2024
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52 changes: 15 additions & 37 deletions src/libraries/System.Text.RegularExpressions/gen/RegexGenerator.Emitter.cs
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Expand Up @@ -391,11 +391,13 @@ private static void AddIsECMABoundaryHelper(Dictionary<string, string[]> require
/// <summary>Adds a SearchValues instance declaration to the required helpers collection if the chars are ASCII.</summary>
private static string EmitSearchValuesOrLiteral(ReadOnlySpan<char> chars, Dictionary<string, string[]> requiredHelpers)
{
// SearchValues<char> is faster than a regular IndexOfAny("abcd") for sets of 4/5 values iff they are ASCII.
// Only emit SearchValues instances when we know they'll be faster to avoid increasing the startup cost too much.
Debug.Assert(chars.Length is 4 or 5);
Debug.Assert(chars.Length > 3);

return RegexCharClass.IsAscii(chars)
// IndexOfAny(SearchValues) is faster than a regular IndexOfAny("abcd") if:
// - There are more than 5 characters in the needle, or
// - There are only 4 or 5 characters in the needle and they're all ASCII.

return (chars.Length > 5 || (chars.Length > 3 && RegexCharClass.IsAscii(chars)))
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? EmitSearchValues(chars.ToArray(), requiredHelpers)
: Literal(chars.ToString());
}
Expand Down Expand Up @@ -3510,11 +3512,10 @@ void EmitSingleCharLazy(RegexNode node, RegexNode? subsequent = null, bool emitL
{
if (iterationCount is null &&
node.Kind is RegexNodeKind.Notonelazy &&
subsequent?.FindStartingLiteral(4) is RegexNode.StartingLiteralData literal && // 5 == max efficiently optimized by IndexOfAny, and we need to reserve 1 for node.Ch
subsequent?.FindStartingLiteral() is RegexNode.StartingLiteralData literal &&
!literal.Negated && // not negated; can't search for both the node.Ch and a negated subsequent char with an IndexOf* method
(literal.String is not null ||
literal.SetChars is not null ||
(literal.AsciiChars is not null && node.Ch < 128) || // for ASCII sets, only allow when the target can be efficiently included in the set
literal.Range.LowInclusive == literal.Range.HighInclusive ||
(literal.Range.LowInclusive <= node.Ch && node.Ch <= literal.Range.HighInclusive))) // for ranges, only allow when the range overlaps with the target, since there's no accelerated way to search for the union
{
Expand Down Expand Up @@ -3546,18 +3547,6 @@ literal.SetChars is not null ||
(false, _) => $"{startingPos} = {sliceSpan}.IndexOfAny({EmitSearchValuesOrLiteral($"{node.Ch}{literal.SetChars}".AsSpan(), requiredHelpers)});",
});
}
else if (literal.AsciiChars is not null) // set of only ASCII characters
{
char[] asciiChars = literal.AsciiChars;
overlap = asciiChars.Contains(node.Ch);
if (!overlap)
{
Debug.Assert(node.Ch < 128);
Array.Resize(ref asciiChars, asciiChars.Length + 1);
asciiChars[asciiChars.Length - 1] = node.Ch;
}
writer.WriteLine($"{startingPos} = {sliceSpan}.IndexOfAny({EmitSearchValues(asciiChars, requiredHelpers)});");
}
else if (literal.Range.LowInclusive == literal.Range.HighInclusive) // single char from a RegexNode.One
{
overlap = literal.Range.LowInclusive == node.Ch;
Expand Down Expand Up @@ -4928,11 +4917,10 @@ private static bool TryEmitIndexOf(
{
bool negated = RegexCharClass.IsNegated(node.Str) ^ negate;

Span<char> setChars = stackalloc char[5]; // current max that's vectorized
int setCharsCount = RegexCharClass.GetSetChars(node.Str, setChars);

// Prefer IndexOfAnyInRange over IndexOfAny for sets of 3-5 values that fit in a single range.
if (setCharsCount is not (1 or 2) && RegexCharClass.TryGetSingleRange(node.Str, out char lowInclusive, out char highInclusive))
// IndexOfAny{Except}InRange
// Prefer IndexOfAnyInRange over IndexOfAny, except for tiny ranges (1 or 2 items) that IndexOfAny handles more efficiently
if (RegexCharClass.TryGetSingleRange(node.Str, out char lowInclusive, out char highInclusive) &&
(highInclusive - lowInclusive) > 1)
{
string indexOfAnyInRangeName = !negated ?
"IndexOfAnyInRange" :
Expand All @@ -4944,13 +4932,15 @@ private static bool TryEmitIndexOf(
return true;
}

if (setCharsCount > 0)
// IndexOfAny{Except}(ch1, ...)
Span<char> setChars = stackalloc char[128];
setChars = setChars.Slice(0, RegexCharClass.GetSetChars(node.Str, setChars));
if (!setChars.IsEmpty)
{
(string indexOfName, string indexOfAnyName) = !negated ?
("IndexOf", "IndexOfAny") :
("IndexOfAnyExcept", "IndexOfAnyExcept");

setChars = setChars.Slice(0, setCharsCount);
indexOfExpr = setChars.Length switch
{
1 => $"{last}{indexOfName}({Literal(setChars[0])})",
Expand All @@ -4962,18 +4952,6 @@ private static bool TryEmitIndexOf(
literalLength = 1;
return true;
}

if (RegexCharClass.TryGetAsciiSetChars(node.Str, out char[]? asciiChars))
{
string indexOfAnyName = !negated ?
"IndexOfAny" :
"IndexOfAnyExcept";

indexOfExpr = $"{last}{indexOfAnyName}({EmitSearchValues(asciiChars, requiredHelpers)})";

literalLength = 1;
return true;
}
}

indexOfExpr = null;
Expand Down
2 changes: 1 addition & 1 deletion ...raries/System.Text.RegularExpressions/gen/System.Text.RegularExpressions.Generator.csproj
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Expand Up @@ -11,7 +11,7 @@
<EnableDefaultEmbeddedResourceItems>false</EnableDefaultEmbeddedResourceItems>
<UsingToolXliff>true</UsingToolXliff>
<CLSCompliant>false</CLSCompliant>
<NoWarn>$(NoWarn);CS0436;CS0649</NoWarn>
<NoWarn>$(NoWarn);CS0436;CS0649;CA1872</NoWarn>
<AllowUnsafeBlocks>true</AllowUnsafeBlocks>
<AnalyzerLanguage>cs</AnalyzerLanguage>
</PropertyGroup>
Expand Down
51 changes: 27 additions & 24 deletions ...aries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexCharClass.cs
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Expand Up @@ -815,17 +815,23 @@ public static bool TryGetDoubleRange(
/// If 0 is returned, no assumptions can be made about the characters.
/// </returns>
/// <remarks>
/// Only considers character classes that only contain sets (no categories)
/// and no subtraction... just simple sets containing starting/ending pairs.
/// The returned characters may be negated: if IsNegated(set) is false, then
/// the returned characters are the only ones that match; if it returns true,
/// then the returned characters are the only ones that don't match.
/// Only considers character classes that only contain sets (no categories),
/// just simple sets containing starting/ending pairs (subtraction from those pairs
/// is factored in, however).The returned characters may be negated: if IsNegated(set)
/// is false, then the returned characters are the only ones that match; if it returns
/// true, then the returned characters are the only ones that don't match.
/// </remarks>
public static int GetSetChars(string set, Span<char> chars)
{
// We get the characters by enumerating the set portion, so we validate that it's
// set up to enable that, e.g. no categories.
if (!CanEasilyEnumerateSetContents(set))
if (!CanEasilyEnumerateSetContents(set, out bool hasSubtraction))
{
return 0;
}

// Negation with subtraction is too cumbersome to reason about efficiently.
if (hasSubtraction && IsNegated(set))
{
return 0;
}
Expand All @@ -837,40 +843,37 @@ public static int GetSetChars(string set, Span<char> chars)
// based on it a) complicating things, and b) it being really unlikely to
// be part of a small set.
int setLength = set[SetLengthIndex];
int count = 0;
int count = 0, evaluated = 0;
for (int i = SetStartIndex; i < SetStartIndex + setLength; i += 2)
{
int curSetEnd = set[i + 1];
for (int c = set[i]; c < curSetEnd; c++)
{
if (count >= chars.Length)
// Keep track of how many characters we've checked. This could work
// just comparing count rather than evaluated, but we also want to
// limit how much work is done here, which we can do by constraining
// the number of checks to the size of the storage provided.
if (++evaluated > chars.Length)
{
return 0;
}

// If the set is all ranges but has a subtracted class,
// validate the char is actually in the set prior to storing it:
// it might be in the subtracted range.
if (hasSubtraction && !CharInClass((char)c, set))
{
continue;
}

Debug.Assert(count <= evaluated);
chars[count++] = (char)c;
}
}

return count;
}

public static bool TryGetAsciiSetChars(string set, [NotNullWhen(true)] out char[]? asciiChars)
{
Span<char> chars = stackalloc char[128];

chars = chars.Slice(0, GetSetChars(set, chars));

if (chars.IsEmpty || !IsAscii(chars))
{
asciiChars = null;
return false;
}

asciiChars = chars.ToArray();
return true;
}

/// <summary>
/// Determines whether two sets may overlap.
/// </summary>
Expand Down
75 changes: 15 additions & 60 deletions ...raries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexCompiler.cs
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Expand Up @@ -939,7 +939,7 @@ void EmitFixedSet_LeftToRight()
default:
// tmp = ...IndexOfAny(setChars);
// tmp = ...IndexOfAny(s_searchValues);
EmitIndexOfAnyWithSearchValuesOrLiteral(new string(primarySet.Chars), except: primarySet.Negated);
EmitIndexOfAnyWithSearchValuesOrLiteral(primarySet.Chars, except: primarySet.Negated);
break;
}
}
Expand Down Expand Up @@ -3587,11 +3587,10 @@ void EmitSingleCharLazy(RegexNode node, RegexNode? subsequent = null, bool emitL
if (!rtl &&
iterationCount is null &&
node.Kind is RegexNodeKind.Notonelazy &&
subsequent?.FindStartingLiteral(4) is RegexNode.StartingLiteralData literal && // 5 == max optimized by IndexOfAny, and we need to reserve 1 for node.Ch
subsequent?.FindStartingLiteral() is RegexNode.StartingLiteralData literal &&
!literal.Negated && // not negated; can't search for both the node.Ch and a negated subsequent char with an IndexOf* method
(literal.String is not null ||
literal.SetChars is not null ||
(literal.AsciiChars is not null && node.Ch < 128) || // for ASCII sets, only allow when the target can be efficiently included in the set
literal.Range.LowInclusive == literal.Range.HighInclusive ||
(literal.Range.LowInclusive <= node.Ch && node.Ch <= literal.Range.HighInclusive))) // for ranges, only allow when the range overlaps with the target, since there's no accelerated way to search for the union
{
Expand Down Expand Up @@ -3660,18 +3659,6 @@ literal.SetChars is not null ||
break;
}
}
else if (literal.AsciiChars is not null) // set of only ASCII characters
{
char[] asciiChars = literal.AsciiChars;
overlap = asciiChars.AsSpan().Contains(node.Ch);
if (!overlap)
{
Debug.Assert(node.Ch < 128);
Array.Resize(ref asciiChars, asciiChars.Length + 1);
asciiChars[^1] = node.Ch;
}
EmitIndexOfAnyWithSearchValuesOrLiteral(new string(asciiChars));
}
else if (literal.Range.LowInclusive == literal.Range.HighInclusive) // single char from a RegexNode.One
{
overlap = literal.Range.LowInclusive == node.Ch;
Expand Down Expand Up @@ -5153,21 +5140,9 @@ bool CanEmitIndexOf(RegexNode node, out int literalLength)

if (node.IsSetFamily)
{
Span<char> setChars = stackalloc char[5]; // current max that's vectorized
int setCharsCount;
if ((setCharsCount = RegexCharClass.GetSetChars(node.Str, setChars)) > 0)
{
literalLength = 1;
return true;
}

if (RegexCharClass.TryGetSingleRange(node.Str, out char lowInclusive, out char highInclusive))
{
literalLength = 1;
return true;
}

if (RegexCharClass.TryGetAsciiSetChars(node.Str, out _))
Span<char> setChars = stackalloc char[128];
if (RegexCharClass.TryGetSingleRange(node.Str, out _, out _) ||
RegexCharClass.GetSetChars(node.Str, setChars) > 0)
{
literalLength = 1;
return true;
Expand Down Expand Up @@ -5218,26 +5193,11 @@ void EmitIndexOf(RegexNode node, bool useLast, bool negate)
{
bool negated = RegexCharClass.IsNegated(node.Str) ^ negate;

Span<char> setChars = stackalloc char[5]; // current max that's vectorized
int setCharsCount = RegexCharClass.GetSetChars(node.Str, setChars);

// IndexOfAny{Except}InRange
// Prefer IndexOfAnyInRange over IndexOfAny for sets of 3-5 values that fit in a single range.
if (setCharsCount is not (1 or 2) && RegexCharClass.TryGetSingleRange(node.Str, out char lowInclusive, out char highInclusive))
// Prefer IndexOfAnyInRange over IndexOfAny, except for tiny ranges (1 or 2 items) that IndexOfAny handles more efficiently
if (RegexCharClass.TryGetSingleRange(node.Str, out char lowInclusive, out char highInclusive) &&
(highInclusive - lowInclusive) > 1)
{
if (lowInclusive == highInclusive)
{
Ldc(lowInclusive);
Call((useLast, negated) switch
{
(false, false) => s_spanIndexOfChar,
(false, true) => s_spanIndexOfAnyExceptChar,
(true, false) => s_spanLastIndexOfChar,
(true, true) => s_spanLastIndexOfAnyExceptChar,
});
return;
}

Ldc(lowInclusive);
Ldc(highInclusive);
Call((useLast, negated) switch
Expand All @@ -5251,6 +5211,8 @@ void EmitIndexOf(RegexNode node, bool useLast, bool negate)
}

// IndexOfAny{Except}(ch1, ...)
Span<char> setChars = stackalloc char[128]; // arbitrary cut-off that accomodates all of ASCII and doesn't take too long to compute
int setCharsCount = RegexCharClass.GetSetChars(node.Str, setChars);
if (setCharsCount > 0)
{
setChars = setChars.Slice(0, setCharsCount);
Expand Down Expand Up @@ -5293,17 +5255,10 @@ void EmitIndexOf(RegexNode node, bool useLast, bool negate)
return;

default:
EmitIndexOfAnyWithSearchValuesOrLiteral(setChars.ToString(), last: useLast, except: negated);
EmitIndexOfAnyWithSearchValuesOrLiteral(setChars, last: useLast, except: negated);
return;
}
}

// IndexOfAny{Except}(SearchValues<char>)
if (RegexCharClass.TryGetAsciiSetChars(node.Str, out char[]? asciiChars))
{
EmitIndexOfAnyWithSearchValuesOrLiteral(new string(asciiChars), last: useLast, except: negated);
return;
}
}

Debug.Fail("We should never get here. This method should only be called if CanEmitIndexOf returned true, and all of the same cases should be covered.");
Expand Down Expand Up @@ -6197,15 +6152,15 @@ private void EmitTimeoutCheckIfNeeded()
}

/// <summary>Emits a call to either IndexOfAny("abcd") or IndexOfAny(SearchValues) depending on the <paramref name="chars"/>.</summary>
private void EmitIndexOfAnyWithSearchValuesOrLiteral(string chars, bool last = false, bool except = false)
private void EmitIndexOfAnyWithSearchValuesOrLiteral(ReadOnlySpan<char> chars, bool last = false, bool except = false)
{
Debug.Assert(chars.Length > 3);
Debug.Assert(chars.Length > 3, $"chars.Length == {chars.Length}");

// SearchValues<char> is faster than a regular IndexOfAny("abcd") for sets of 4/5 values iff they are ASCII.
// Only emit SearchValues instances when we know they'll be faster to avoid increasing the startup cost too much.
if (chars.Length is 4 or 5 && !RegexCharClass.IsAscii(chars))
{
Ldstr(chars);
Ldstr(chars.ToString());
Call(s_stringAsSpanMethod);
Call((last, except) switch
{
Expand All @@ -6217,7 +6172,7 @@ private void EmitIndexOfAnyWithSearchValuesOrLiteral(string chars, bool last = f
}
else
{
LoadSearchValues(chars.ToCharArray());
LoadSearchValues(chars.ToArray());
Call((last, except) switch
{
(false, false) => s_spanIndexOfAnySearchValues,
Expand Down
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