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Broaden use of SearchValues in TryFindNextPossibleStartingPosition in Regex #89205

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Jul 20, 2023
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Broaden use of SearchValues in TryFindNextPossibleStartingPosition in Regex #89205

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120 changes: 67 additions & 53 deletions src/libraries/System.Text.RegularExpressions/gen/RegexGenerator.Emitter.cs
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Expand Up @@ -399,54 +399,65 @@ private static string EmitSearchValuesOrLiteral(ReadOnlySpan<char> chars, Dictio
}

/// <summary>Adds a SearchValues instance declaration to the required helpers collection.</summary>
private static string EmitSearchValues(char[] asciiChars, Dictionary<string, string[]> requiredHelpers)
private static string EmitSearchValues(char[] chars, Dictionary<string, string[]> requiredHelpers)
{
Debug.Assert(RegexCharClass.IsAscii(asciiChars));
Array.Sort(chars);

// The set of ASCII characters can be represented as a 128-bit bitmap. Use the 16-byte hex string as the key.
byte[] bitmap = new byte[16];
foreach (char c in asciiChars)
string fieldName;
if (RegexCharClass.IsAscii(chars))
{
bitmap[c >> 3] |= (byte)(1 << (c & 7));
// The set of ASCII characters can be represented as a 128-bit bitmap. Use the 16-byte hex string as the key.
var bitmap = new byte[16];
foreach (char c in chars)
{
bitmap[c >> 3] |= (byte)(1 << (c & 7));
}

string hexBitmap = BitConverter.ToString(bitmap).Replace("-", string.Empty);

fieldName = hexBitmap switch
{
"FFFFFFFF000000000000000000000080" => "s_asciiControl",
"000000000000FF030000000000000000" => "s_asciiDigits",
"0000000000000000FEFFFF07FEFFFF07" => "s_asciiLetters",
"000000000000FF03FEFFFF07FEFFFF07" => "s_asciiLettersAndDigits",
"000000000000FF037E0000007E000000" => "s_asciiHexDigits",
"000000000000FF03000000007E000000" => "s_asciiHexDigitsLower",
"000000000000FF037E00000000000000" => "s_asciiHexDigitsUpper",
"00000000EEF7008C010000B800000028" => "s_asciiPunctuation",
"00000000010000000000000000000000" => "s_asciiSeparators",
"00000000100800700000004001000050" => "s_asciiSymbols",
"003E0000010000000000000000000000" => "s_asciiWhiteSpace",
"000000000000FF03FEFFFF87FEFFFF07" => "s_asciiWordChars",

"00000000FFFFFFFFFFFFFFFFFFFFFF7F" => "s_asciiExceptControl",
"FFFFFFFFFFFF00FCFFFFFFFFFFFFFFFF" => "s_asciiExceptDigits",
"FFFFFFFFFFFFFFFF010000F8010000F8" => "s_asciiExceptLetters",
"FFFFFFFFFFFF00FC010000F8010000F8" => "s_asciiExceptLettersAndDigits",
"FFFFFFFFFFFFFFFFFFFFFFFF010000F8" => "s_asciiExceptLower",
"FFFFFFFF1108FF73FEFFFF47FFFFFFD7" => "s_asciiExceptPunctuation",
"FFFFFFFFFEFFFFFFFFFFFFFFFFFFFFFF" => "s_asciiExceptSeparators",
"FFFFFFFFEFF7FF8FFFFFFFBFFEFFFFAF" => "s_asciiExceptSymbols",
"FFFFFFFFFFFFFFFF010000F8FFFFFFFF" => "s_asciiExceptUpper",
"FFC1FFFFFEFFFFFFFFFFFFFFFFFFFFFF" => "s_asciiExceptWhiteSpace",
"FFFFFFFFFFFF00FC01000078010000F8" => "s_asciiExceptWordChars",

_ => $"s_ascii_{hexBitmap.TrimStart('0')}"
};
}

string hexBitmap = BitConverter.ToString(bitmap).Replace("-", string.Empty);

string fieldName = hexBitmap switch
else
{
"FFFFFFFF000000000000000000000080" => "s_asciiControl",
"000000000000FF030000000000000000" => "s_asciiDigits",
"0000000000000000FEFFFF07FEFFFF07" => "s_asciiLetters",
"000000000000FF03FEFFFF07FEFFFF07" => "s_asciiLettersAndDigits",
"000000000000FF037E0000007E000000" => "s_asciiHexDigits",
"000000000000FF03000000007E000000" => "s_asciiHexDigitsLower",
"000000000000FF037E00000000000000" => "s_asciiHexDigitsUpper",
"00000000EEF7008C010000B800000028" => "s_asciiPunctuation",
"00000000010000000000000000000000" => "s_asciiSeparators",
"00000000100800700000004001000050" => "s_asciiSymbols",
"003E0000010000000000000000000000" => "s_asciiWhiteSpace",
"000000000000FF03FEFFFF87FEFFFF07" => "s_asciiWordChars",

"00000000FFFFFFFFFFFFFFFFFFFFFF7F" => "s_asciiExceptControl",
"FFFFFFFFFFFF00FCFFFFFFFFFFFFFFFF" => "s_asciiExceptDigits",
"FFFFFFFFFFFFFFFF010000F8010000F8" => "s_asciiExceptLetters",
"FFFFFFFFFFFF00FC010000F8010000F8" => "s_asciiExceptLettersAndDigits",
"FFFFFFFFFFFFFFFFFFFFFFFF010000F8" => "s_asciiExceptLower",
"FFFFFFFF1108FF73FEFFFF47FFFFFFD7" => "s_asciiExceptPunctuation",
"FFFFFFFFFEFFFFFFFFFFFFFFFFFFFFFF" => "s_asciiExceptSeparators",
"FFFFFFFFEFF7FF8FFFFFFFBFFEFFFFAF" => "s_asciiExceptSymbols",
"FFFFFFFFFFFFFFFF010000F8FFFFFFFF" => "s_asciiExceptUpper",
"FFC1FFFFFEFFFFFFFFFFFFFFFFFFFFFF" => "s_asciiExceptWhiteSpace",
"FFFFFFFFFFFF00FC01000078010000F8" => "s_asciiExceptWordChars",

_ => $"s_ascii_{hexBitmap.TrimStart('0')}"
};
using (SHA256 sha = SHA256.Create())
{
#pragma warning disable CA1850 // SHA256.HashData isn't available on netstandard2.0
fieldName = $"s_nonAscii_{BitConverter.ToString(sha.ComputeHash(Encoding.UTF8.GetBytes(chars))).Replace("-", "")}";
#pragma warning restore CA1850
}
}

if (!requiredHelpers.ContainsKey(fieldName))
{
Array.Sort(asciiChars);

string setLiteral = Literal(new string(asciiChars));
string setLiteral = Literal(new string(chars));

requiredHelpers.Add(fieldName, new string[]
{
Expand All @@ -465,12 +476,12 @@ private static string EmitIndexOfAnyCustomHelper(string set, Dictionary<string,
// a sequential walk). In order to do that search, we actually build up a set for all of the ASCII
// characters _not_ contained in the set, and then do a search for the inverse of that, which will be
// all of the target ASCII characters and all of non-ASCII.
var asciiChars = new List<char>();
var excludedAsciiChars = new List<char>();
for (int i = 0; i < 128; i++)
{
if (!RegexCharClass.CharInClass((char)i, set))
{
asciiChars.Add((char)i);
excludedAsciiChars.Add((char)i);
}
}

Expand Down Expand Up @@ -538,9 +549,9 @@ private static string EmitIndexOfAnyCustomHelper(string set, Dictionary<string,
lines.Add($"internal static int {helperName}(this ReadOnlySpan<char> span)");
lines.Add($"{{");
int uncheckedStart = lines.Count;
lines.Add(asciiChars.Count == 128 ?
lines.Add(excludedAsciiChars.Count == 128 ?
$" int i = span.IndexOfAnyExceptInRange('\0', '\u007f');" :
$" int i = span.IndexOfAnyExcept({EmitSearchValues(asciiChars.ToArray(), requiredHelpers)});");
$" int i = span.IndexOfAnyExcept({EmitSearchValues(excludedAsciiChars.ToArray(), requiredHelpers)});");
lines.Add($" if ((uint)i < (uint)span.Length)");
lines.Add($" {{");
lines.Add($" if (char.IsAscii(span[i]))");
Expand Down Expand Up @@ -1067,6 +1078,8 @@ void EmitFixedSet_LeftToRight()
string indexOf;
if (primarySet.Chars is not null)
{
Debug.Assert(primarySet.Chars.Length > 0);

// We have a chars array, so we can use IndexOf{Any}{Except} to search for it. Choose the best overload.
string indexOfName = "IndexOf", indexOfAnyName = "IndexOfAny";
if (primarySet.Negated)
Expand All @@ -1076,18 +1089,19 @@ void EmitFixedSet_LeftToRight()

indexOf = primarySet.Chars.Length switch
{
// 1, 2, 3 have dedicated optimized IndexOfAny overloads
1 => $"{span}.{indexOfName}({Literal(primarySet.Chars[0])})",
2 => $"{span}.{indexOfAnyName}({Literal(primarySet.Chars[0])}, {Literal(primarySet.Chars[1])})",
3 => $"{span}.{indexOfAnyName}({Literal(primarySet.Chars[0])}, {Literal(primarySet.Chars[1])}, {Literal(primarySet.Chars[2])})",
_ => $"{span}.{indexOfAnyName}({EmitSearchValuesOrLiteral(primarySet.Chars, requiredHelpers)})",

// 4, 5 have dedicated optimized IndexOfAny overloads accessible via the ReadOnlySpan<char> overload,
// but can also be handled via SearchValues
4 or 5 => $"{span}.{indexOfAnyName}({EmitSearchValuesOrLiteral(primarySet.Chars, requiredHelpers)})",

// > 5 can only be handled efficiently via SearchValues
_ => $"{span}.{indexOfAnyName}({EmitSearchValues(primarySet.Chars, requiredHelpers)})",
};
}
else if (primarySet.AsciiSet is not null)
{
// We have a set of ASCII chars, so we can use IndexOfAny(SearchValues) to search for it.
Debug.Assert(!primarySet.Negated);
indexOf = $"{span}.IndexOfAny({EmitSearchValues(primarySet.AsciiSet, requiredHelpers)})";
}
else if (primarySet.Range is not null)
{
// We have a range, so we can use IndexOfAny{Except}InRange to search for it. In the corner case,
Expand All @@ -1102,8 +1116,8 @@ void EmitFixedSet_LeftToRight()
}
else
{
// We have an arbitrary set of characters that includes at least one non-ASCII char. We use a custom IndexOfAny helper that
// will perform the search as efficiently as possible.
// We have an arbitrary set of characters that's really large or otherwise not enumerable.
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// We use a custom IndexOfAny helper that will perform the search as efficiently as possible.
indexOf = $"{span}.{EmitIndexOfAnyCustomHelper(primarySet.Set, requiredHelpers, checkOverflow)}()";
}

Expand Down
19 changes: 12 additions & 7 deletions ...raries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexCompiler.cs
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Expand Up @@ -903,6 +903,7 @@ void EmitFixedSet_LeftToRight()

if (primarySet.Chars is not null)
{
Debug.Assert(primarySet.Chars.Length > 0);
switch (primarySet.Chars.Length)
{
case 1:
Expand All @@ -926,19 +927,23 @@ void EmitFixedSet_LeftToRight()
Call(primarySet.Negated ? s_spanIndexOfAnyExceptCharCharChar : s_spanIndexOfAnyCharCharChar);
break;

default:
case 4 or 5:
// tmp = ...IndexOfAny("abcd");
// Note that this case differs slightly from the source generator, where it might choose to use
// SearchValues instead of a literal, but there's extra cost to doing so for RegexCompiler so
// it just always uses IndexOfAny(span).
Ldstr(new string(primarySet.Chars));
Call(s_stringAsSpanMethod);
Call(primarySet.Negated ? s_spanIndexOfAnyExceptSpan : s_spanIndexOfAnySpan);
break;

default:
// tmp = ...IndexOfAny(s_searchValues);
LoadSearchValues(primarySet.Chars);
Call(primarySet.Negated ? s_spanIndexOfAnyExceptSearchValues : s_spanIndexOfAnySearchValues);
break;
}
}
else if (primarySet.AsciiSet is not null)
{
Debug.Assert(!primarySet.Negated);
LoadSearchValues(primarySet.AsciiSet);
Call(s_spanIndexOfAnySearchValues);
}
else if (primarySet.Range is not null)
{
if (primarySet.Range.Value.LowInclusive == primarySet.Range.Value.HighInclusive)
Expand Down
6 changes: 2 additions & 4 deletions ...stem.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexFindOptimizations.cs
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Expand Up @@ -271,8 +271,6 @@ public FixedDistanceSet(char[]? chars, string set, int distance)
public int Distance;
/// <summary>As an alternative to <see cref="Chars"/>, a description of the single range the set represents, if it does.</summary>
public (char LowInclusive, char HighInclusive)? Range;
/// <summary>As an alternative to <see cref="Chars"/>, a description of the set of ASCII characters it represents, if it does.</summary>
public char[]? AsciiSet;
}

/// <summary>When in literal after set loop node, gets the literal to search for and the RegexNode representing the leading loop.</summary>
Expand Down Expand Up @@ -593,7 +591,7 @@ public bool TryFindNextStartingPositionLeftToRight(ReadOnlySpan<char> textSpan,
char[]? chars = primarySet.Chars;

ReadOnlySpan<char> span = textSpan.Slice(pos);
if (chars is not null)
if (chars is { Length: <= 5 }) // 5 == currently the max length efficiently handled by IndexOfAny{Except} without SearchValues
{
int i = primarySet.Negated ? span.IndexOfAnyExcept(chars) : span.IndexOfAny(chars);
if (i >= 0)
Expand Down Expand Up @@ -660,7 +658,7 @@ public bool TryFindNextStartingPositionLeftToRight(ReadOnlySpan<char> textSpan,

int endMinusRequiredLength = textSpan.Length - Math.Max(1, MinRequiredLength);

if (primarySet.Chars is not null)
if (primarySet.Chars is { Length: <= 5 }) // 5 == currently the max length efficiently handled by IndexOfAny{Except}
{
for (int inputPosition = pos; inputPosition <= endMinusRequiredLength; inputPosition++)
{
Expand Down
26 changes: 10 additions & 16 deletions .../System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexPrefixAnalyzer.cs
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Expand Up @@ -194,7 +194,7 @@ static bool Process(RegexNode node, ref ValueStringBuilder vsb)
TryFindRawFixedSets(root, results, ref distance, thorough);
#if DEBUG
results.ForEach(r => Debug.Assert(
!r.Negated && r.Chars is null && r.AsciiSet is null && r.Range is null,
!r.Negated && r.Chars is null && r.Range is null,
$"{nameof(TryFindRawFixedSets)} should have only populated {nameof(r.Set)} and {nameof(r.Distance)}"));
#endif

Expand Down Expand Up @@ -225,31 +225,25 @@ static bool Process(RegexNode node, ref ValueStringBuilder vsb)

// For every entry, try to get the chars that make up the set, if there are few enough.
// For any for which we couldn't get the small chars list, see if we can get other useful info.
Span<char> scratch = stackalloc char[5]; // max efficiently optimized by IndexOfAny today
Span<char> scratch = stackalloc char[128]; // limit based on what's currently efficiently handled by SearchValues
for (int i = 0; i < results.Count; i++)
{
RegexFindOptimizations.FixedDistanceSet result = results[i];
result.Negated = RegexCharClass.IsNegated(result.Set);

int count = RegexCharClass.GetSetChars(result.Set, scratch);

if (count > 0)
{
result.Chars = scratch.Slice(0, count).ToArray();
}

if (thorough)
// Prefer IndexOfAnyInRange over IndexOfAny for sets of 3-5 values that fit in a single range.
if (thorough &&
(result.Chars is null || result.Chars.Length > 2) &&
RegexCharClass.TryGetSingleRange(result.Set, out char lowInclusive, out char highInclusive))
{
// Prefer IndexOfAnyInRange over IndexOfAny for sets of 3-5 values that fit in a single range.
if ((result.Chars is null || count > 2) && RegexCharClass.TryGetSingleRange(result.Set, out char lowInclusive, out char highInclusive))
{
result.Chars = null;
result.Range = (lowInclusive, highInclusive);
}
else if (result.Chars is null && !result.Negated && RegexCharClass.TryGetAsciiSetChars(result.Set, out char[]? asciiChars))
{
result.AsciiSet = asciiChars;
}
result.Chars = null;
result.Range = (lowInclusive, highInclusive);
}

results[i] = result;
Expand Down Expand Up @@ -472,8 +466,8 @@ public static void SortFixedDistanceSetsByQuality(List<RegexFindOptimizations.Fi
// for the fastest and that have the best chance of matching as few false positives as possible.
results.Sort(static (s1, s2) =>
{
char[]? s1Chars = s1.Chars ?? s1.AsciiSet;
char[]? s2Chars = s2.Chars ?? s2.AsciiSet;
char[]? s1Chars = s1.Chars;
char[]? s2Chars = s2.Chars;
int s1CharsLength = s1Chars?.Length ?? 0;
int s2CharsLength = s2Chars?.Length ?? 0;
bool s1Negated = s1.Negated;
Expand Down
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