Further reduce loops around zero-width assertions #118111
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In addition to replacing the loop with an empty when it contains only a zero-width assertion and has a lower bound of 0, if it doesn't have a lower bound of 0, we can just remove the loop layer, replacing it with its child directly, since any additional iterations beyond one is redundant.
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@MihuBot regexdiff |
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Pull Request Overview
This PR optimizes regular expression compilation by further reducing redundant loops around zero-width assertions. The change expands the existing logic that already handled loops with minimum bound 0 to also handle loops with minimum bound greater than 0.
Key changes:
- Separates handling of Empty nodes from zero-width assertions for clarity
- Extends zero-width assertion loop reduction to handle cases where minimum bound > 0
- Removes the minimum bound check restriction, allowing more loop optimizations
Comments suppressed due to low confidence (1)
src/libraries/System.Text.RegularExpressions/src/System/Text/RegularExpressions/RegexNode.cs:924
- The new logic that replaces loops with minimum bound > 0 around zero-width assertions with just the child node needs test coverage to ensure it correctly handles various edge cases, such as different types of zero-width assertions and different minimum bounds.
u = u.M == 0 ? new RegexNode(RegexNodeKind.Empty, Options) : child;
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Tagging subscribers to this area: @dotnet/area-system-text-regularexpressions |
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3 out of 18857 patterns have generated source code changes. Examples of GeneratedRegex source diffs"(?<=\\b)+demi\\s+douzaine" (106 uses)[GeneratedRegex("(?<=\\b)+demi\\s+douzaine", RegexOptions.IgnoreCase | RegexOptions.Singleline)] /// <code>RegexOptions.IgnoreCase | RegexOptions.Singleline</code><br/>
/// Explanation:<br/>
/// <code>
- /// ○ Loop greedily at least once right-to-left.<br/>
- /// ○ Zero-width positive lookbehind.<br/>
- /// ○ Match if at a word boundary.<br/>
+ /// ○ Zero-width positive lookbehind.<br/>
+ /// ○ Match if at a word boundary.<br/>
/// ○ Match a character in the set [Dd].<br/>
/// ○ Match a character in the set [Ee].<br/>
/// ○ Match a character in the set [Mm].<br/>
// Any possible match is at least 13 characters.
if (pos <= inputSpan.Length - 13)
{
- // The pattern begins with a character in the set [Dd].
- // Find the next occurrence. If it can't be found, there's no match.
- int i = inputSpan.Slice(pos).IndexOfAny('D', 'd');
+ // The pattern has the literal "demi" ordinal case-insensitive at the beginning of the pattern. Find the next occurrence.
+ // If it can't be found, there's no match.
+ int i = inputSpan.Slice(pos).IndexOfAny(Utilities.s_indexOfString_demi_OrdinalIgnoreCase);
if (i >= 0)
{
base.runtextpos = pos + i;
{
int pos = base.runtextpos;
int matchStart = pos;
- int loop_iteration = 0, loop_starting_pos = 0;
- int stackpos = 0;
ReadOnlySpan<char> slice = inputSpan.Slice(pos);
- // Loop greedily at least once right-to-left.
- //{
- loop_starting_pos = pos;
- loop_iteration = 0;
-
- LoopBody:
- Utilities.StackPush(ref base.runstack!, ref stackpos, loop_starting_pos, pos);
-
- loop_starting_pos = pos;
- loop_iteration++;
-
- // Zero-width positive lookbehind.
- {
- slice = inputSpan.Slice(pos);
- int positivelookbehind_starting_pos = pos;
-
- if (Utilities.s_hasTimeout)
- {
- base.CheckTimeout();
- }
-
- // Match if at a word boundary.
- if (!Utilities.IsBoundary(inputSpan, pos))
- {
- goto LoopIterationNoMatch;
- }
-
- pos = positivelookbehind_starting_pos;
- slice = inputSpan.Slice(pos);
- }
-
-
- // The loop has a lower bound of 1 but no upper bound. Continue iterating greedily
- // if the last iteration wasn't empty (or if it was, if the lower bound hasn't yet been reached).
- if (pos != loop_starting_pos || loop_iteration == 0)
- {
- goto LoopBody;
- }
- goto LoopEnd;
-
- // The loop iteration failed. Put state back to the way it was before the iteration.
- LoopIterationNoMatch:
- if (--loop_iteration < 0)
- {
- // Unable to match the remainder of the expression after exhausting the loop.
- return false; // The input didn't match.
- }
- Utilities.StackPop(base.runstack!, ref stackpos, out pos, out loop_starting_pos);
+ // Zero-width positive lookbehind.
+ {
slice = inputSpan.Slice(pos);
- if (loop_iteration == 0)
+ int positivelookbehind_starting_pos = pos;
+
+ if (Utilities.s_hasTimeout)
+ {
+ base.CheckTimeout();
+ }
+
+ // Match if at a word boundary.
+ if (!Utilities.IsBoundary(inputSpan, pos))
{
- // All possible iterations have matched, but it's below the required minimum of 1. Fail the loop.
return false; // The input didn't match.
}
- LoopEnd:;
- //}
+ pos = positivelookbehind_starting_pos;
+ slice = inputSpan.Slice(pos);
+ }
if ((uint)slice.Length < 4 ||
!slice.StartsWith("demi", StringComparison.OrdinalIgnoreCase)) // Match the string "demi" (ordinal case-insensitive)
{
- goto LoopIterationNoMatch;
+ return false; // The input didn't match.
}
// Match a whitespace character atomically at least once.
if (iteration == 0)
{
- goto LoopIterationNoMatch;
+ return false; // The input didn't match.
}
slice = slice.Slice(iteration);
if ((uint)slice.Length < 8 ||
!slice.StartsWith("douzaine", StringComparison.OrdinalIgnoreCase)) // Match the string "douzaine" (ordinal case-insensitive)
{
- goto LoopIterationNoMatch;
+ return false; // The input didn't match.
}
// The input matched.
(WordCategoriesMask & (1 << (int)CharUnicodeInfo.GetUnicodeCategory(ch))) != 0;
}
- /// <summary>Pops 2 values from the backtracking stack.</summary>
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- internal static void StackPop(int[] stack, ref int pos, out int arg0, out int arg1)
- {
- arg0 = stack[--pos];
- arg1 = stack[--pos];
- }
-
- /// <summary>Pushes 2 values onto the backtracking stack.</summary>
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- internal static void StackPush(ref int[] stack, ref int pos, int arg0, int arg1)
- {
- // If there's space available for all 2 values, store them.
- int[] s = stack;
- int p = pos;
- if ((uint)(p + 1) < (uint)s.Length)
- {
- s[p] = arg0;
- s[p + 1] = arg1;
- pos += 2;
- return;
- }
-
- // Otherwise, resize the stack to make room and try again.
- WithResize(ref stack, ref pos, arg0, arg1);
-
- // <summary>Resize the backtracking stack array and push 2 values onto the stack.</summary>
- [MethodImpl(MethodImplOptions.NoInlining)]
- static void WithResize(ref int[] stack, ref int pos, int arg0, int arg1)
- {
- Array.Resize(ref stack, (pos + 1) * 2);
- StackPush(ref stack, ref pos, arg0, arg1);
- }
- }
+ /// <summary>Supports searching for the string "demi".</summary>
+ internal static readonly SearchValues<string> s_indexOfString_demi_OrdinalIgnoreCase = SearchValues.Create(["demi"], StringComparison.OrdinalIgnoreCase);
}
}"^((?!-)+)([a-zA-Z_-]+$).*((?<!-)+)" (57 uses)[GeneratedRegex("^((?!-)+)([a-zA-Z_-]+$).*((?<!-)+)", RegexOptions.Singleline)] /// <code>
/// ○ Match if at the beginning of the string.<br/>
/// ○ 1st capture group.<br/>
- /// ○ Loop greedily at least once.<br/>
- /// ○ Zero-width negative lookahead.<br/>
- /// ○ Match '-'.<br/>
+ /// ○ Zero-width negative lookahead.<br/>
+ /// ○ Match '-'.<br/>
/// ○ 2nd capture group.<br/>
/// ○ Match a character in the set [\-A-Z_a-z] atomically at least once.<br/>
/// ○ Match if at the end of the string or if before an ending newline.<br/>
/// ○ Match any character greedily any number of times.<br/>
/// ○ 3rd capture group.<br/>
- /// ○ Loop greedily and atomically at least once right-to-left.<br/>
- /// ○ Zero-width negative lookbehind.<br/>
- /// ○ Match '-' right-to-left.<br/>
+ /// ○ Zero-width negative lookbehind.<br/>
+ /// ○ Match '-' right-to-left.<br/>
/// </code>
/// </remarks>
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Text.RegularExpressions.Generator", "42.42.42.42")]
int capture_starting_pos2 = 0;
int charloop_capture_pos = 0;
int charloop_starting_pos = 0, charloop_ending_pos = 0;
- int loop_iteration = 0, loop_starting_pos = 0;
- int loop_iteration1 = 0, loop_starting_pos1 = 0;
- int stackpos = 0;
- int startingStackpos = 0;
ReadOnlySpan<char> slice = inputSpan.Slice(pos);
// Match if at the beginning of the string.
}
// 1st capture group.
- //{
+ {
capture_starting_pos = pos;
- // Loop greedily at least once.
- //{
- loop_starting_pos = pos;
- loop_iteration = 0;
-
- LoopBody:
- Utilities.StackPush(ref base.runstack!, ref stackpos, base.Crawlpos(), loop_starting_pos, pos);
-
- loop_starting_pos = pos;
- loop_iteration++;
-
- // Zero-width negative lookahead.
- {
- slice = inputSpan.Slice(pos);
- int negativelookahead__starting_pos = pos;
- if (Utilities.s_hasTimeout)
- {
- base.CheckTimeout();
- }
-
- // Match '-'.
- if (slice.IsEmpty || slice[0] != '-')
- {
- goto NegativeLookaroundMatch;
- }
-
- goto LoopIterationNoMatch;
-
- NegativeLookaroundMatch:
- pos = negativelookahead__starting_pos;
- slice = inputSpan.Slice(pos);
- }
-
-
- // The loop has a lower bound of 1 but no upper bound. Continue iterating greedily
- // if the last iteration wasn't empty (or if it was, if the lower bound hasn't yet been reached).
- if (pos != loop_starting_pos || loop_iteration == 0)
- {
- goto LoopBody;
- }
- goto LoopEnd;
-
- // The loop iteration failed. Put state back to the way it was before the iteration.
- LoopIterationNoMatch:
- if (--loop_iteration < 0)
- {
- // Unable to match the remainder of the expression after exhausting the loop.
- UncaptureUntil(0);
- return false; // The input didn't match.
- }
- Utilities.StackPop(base.runstack!, ref stackpos, out pos, out loop_starting_pos);
- UncaptureUntil(base.runstack![--stackpos]);
+ // Zero-width negative lookahead.
+ {
slice = inputSpan.Slice(pos);
- if (loop_iteration == 0)
+ int negativelookahead__starting_pos = pos;
+ if (Utilities.s_hasTimeout)
{
- // All possible iterations have matched, but it's below the required minimum of 1. Fail the loop.
- UncaptureUntil(0);
- return false; // The input didn't match.
+ base.CheckTimeout();
}
- LoopEnd:;
- //}
+ // Match '-'.
+ if (slice.IsEmpty || slice[0] != '-')
+ {
+ goto NegativeLookaroundMatch;
+ }
+
+ UncaptureUntil(0);
+ return false; // The input didn't match.
+
+ NegativeLookaroundMatch:
+ pos = negativelookahead__starting_pos;
+ slice = inputSpan.Slice(pos);
+ }
base.Capture(1, capture_starting_pos, pos);
-
- goto CaptureSkipBacktrack;
-
- CaptureBacktrack:
- goto LoopIterationNoMatch;
-
- CaptureSkipBacktrack:;
- //}
+ }
// 2nd capture group.
{
if (iteration == 0)
{
- goto CaptureBacktrack;
+ UncaptureUntil(0);
+ return false; // The input didn't match.
}
slice = slice.Slice(iteration);
// Match if at the end of the string or if before an ending newline.
if (pos < inputSpan.Length - 1 || ((uint)pos < (uint)inputSpan.Length && inputSpan[pos] != '\n'))
{
- goto CaptureBacktrack;
+ UncaptureUntil(0);
+ return false; // The input didn't match.
}
base.Capture(2, capture_starting_pos1, pos);
if (charloop_starting_pos >= charloop_ending_pos)
{
- goto CaptureBacktrack;
+ UncaptureUntil(0);
+ return false; // The input didn't match.
}
pos = --charloop_ending_pos;
slice = inputSpan.Slice(pos);
{
capture_starting_pos2 = pos;
- // Loop greedily and atomically at least once right-to-left.
+ // Zero-width negative lookbehind.
{
- startingStackpos = stackpos;
- loop_starting_pos1 = pos;
- loop_iteration1 = 0;
-
- LoopBody1:
- Utilities.StackPush(ref base.runstack!, ref stackpos, base.Crawlpos(), loop_starting_pos1, pos);
-
- loop_starting_pos1 = pos;
- loop_iteration1++;
-
- // Zero-width negative lookbehind.
- {
- slice = inputSpan.Slice(pos);
- int negativelookbehind__starting_pos = pos;
- if (Utilities.s_hasTimeout)
- {
- base.CheckTimeout();
- }
-
- // Match '-' right-to-left.
- if ((uint)(pos - 1) >= inputSpan.Length || inputSpan[pos - 1] != '-')
- {
- goto NegativeLookaroundMatch1;
- }
- pos--;
-
- goto LoopIterationNoMatch1;
-
- NegativeLookaroundMatch1:
- pos = negativelookbehind__starting_pos;
- slice = inputSpan.Slice(pos);
- }
-
-
- // The loop has a lower bound of 1 but no upper bound. Continue iterating greedily
- // if the last iteration wasn't empty (or if it was, if the lower bound hasn't yet been reached).
- if (pos != loop_starting_pos1 || loop_iteration1 == 0)
- {
- goto LoopBody1;
- }
- goto LoopEnd1;
-
- // The loop iteration failed. Put state back to the way it was before the iteration.
- LoopIterationNoMatch1:
- if (--loop_iteration1 < 0)
- {
- // Unable to match the remainder of the expression after exhausting the loop.
- goto CharLoopBacktrack;
- }
- Utilities.StackPop(base.runstack!, ref stackpos, out pos, out loop_starting_pos1);
- UncaptureUntil(base.runstack![--stackpos]);
slice = inputSpan.Slice(pos);
- if (loop_iteration1 == 0)
+ int negativelookbehind__starting_pos = pos;
+ if (Utilities.s_hasTimeout)
{
- // All possible iterations have matched, but it's below the required minimum of 1. Fail the loop.
- goto CharLoopBacktrack;
+ base.CheckTimeout();
}
- LoopEnd1:
- stackpos = startingStackpos; // Ensure any remaining backtracking state is removed.
+ // Match '-' right-to-left.
+ if ((uint)(pos - 1) >= inputSpan.Length || inputSpan[pos - 1] != '-')
+ {
+ goto NegativeLookaroundMatch1;
+ }
+ pos--;
+
+ goto CharLoopBacktrack;
+
+ NegativeLookaroundMatch1:
+ pos = negativelookbehind__starting_pos;
+ slice = inputSpan.Slice(pos);
}
base.Capture(3, capture_starting_pos2, pos);
/// <summary>Whether <see cref="s_defaultTimeout"/> is non-infinite.</summary>
internal static readonly bool s_hasTimeout = s_defaultTimeout != Regex.InfiniteMatchTimeout;
- /// <summary>Pops 2 values from the backtracking stack.</summary>
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- internal static void StackPop(int[] stack, ref int pos, out int arg0, out int arg1)
- {
- arg0 = stack[--pos];
- arg1 = stack[--pos];
- }
-
- /// <summary>Pushes 3 values onto the backtracking stack.</summary>
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- internal static void StackPush(ref int[] stack, ref int pos, int arg0, int arg1, int arg2)
- {
- // If there's space available for all 3 values, store them.
- int[] s = stack;
- int p = pos;
- if ((uint)(p + 2) < (uint)s.Length)
- {
- s[p] = arg0;
- s[p + 1] = arg1;
- s[p + 2] = arg2;
- pos += 3;
- return;
- }
-
- // Otherwise, resize the stack to make room and try again.
- WithResize(ref stack, ref pos, arg0, arg1, arg2);
-
- // <summary>Resize the backtracking stack array and push 3 values onto the stack.</summary>
- [MethodImpl(MethodImplOptions.NoInlining)]
- static void WithResize(ref int[] stack, ref int pos, int arg0, int arg1, int arg2)
- {
- Array.Resize(ref stack, (pos + 2) * 2);
- StackPush(ref stack, ref pos, arg0, arg1, arg2);
- }
- }
-
/// <summary>Supports searching for characters in or not in "-ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz".</summary>
internal static readonly SearchValues<char> s_ascii_200000FEFFFF87FEFFFF07 = SearchValues.Create("-ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz");
}For more diff examples, see https://gist.github.com/MihuBot/a15ee2958fd2e1688755cccbc6104e54 JIT assembly changesFor a list of JIT diff regressions, see Regressions.md Sample source code for further analysisconst string JsonPath = "RegexResults-1306.json";
if (!File.Exists(JsonPath))
{
await using var archiveStream = await new HttpClient().GetStreamAsync("https://mihubot.xyz/r/E2r7wB2A");
using var archive = new ZipArchive(archiveStream, ZipArchiveMode.Read);
archive.Entries.First(e => e.Name == "Results.json").ExtractToFile(JsonPath);
}
using FileStream jsonFileStream = File.OpenRead(JsonPath);
RegexEntry[] entries = JsonSerializer.Deserialize<RegexEntry[]>(jsonFileStream, new JsonSerializerOptions { IncludeFields = true })!;
Console.WriteLine($"Working with {entries.Length} patterns");
record KnownPattern(string Pattern, RegexOptions Options, int Count);
sealed class RegexEntry
{
public required KnownPattern Regex { get; set; }
public required string MainSource { get; set; }
public required string PrSource { get; set; }
public string? FullDiff { get; set; }
public string? ShortDiff { get; set; }
public (string Name, string Values)[]? SearchValuesOfChar { get; set; }
public (string[] Values, StringComparison ComparisonType)[]? SearchValuesOfString { get; set; }
} |
MihaZupan
approved these changes
Jul 28, 2025
|
@MihuBot regexdiff |
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9 out of 18857 patterns have generated source code changes. Examples of GeneratedRegex source diffs"(?<=\\b)+demi\\s+douzaine" (106 uses)[GeneratedRegex("(?<=\\b)+demi\\s+douzaine", RegexOptions.IgnoreCase | RegexOptions.Singleline)] /// <code>RegexOptions.IgnoreCase | RegexOptions.Singleline</code><br/>
/// Explanation:<br/>
/// <code>
- /// ○ Loop greedily at least once right-to-left.<br/>
- /// ○ Zero-width positive lookbehind.<br/>
- /// ○ Match if at a word boundary.<br/>
+ /// ○ Zero-width positive lookbehind.<br/>
+ /// ○ Match if at a word boundary.<br/>
/// ○ Match a character in the set [Dd].<br/>
/// ○ Match a character in the set [Ee].<br/>
/// ○ Match a character in the set [Mm].<br/>
// Any possible match is at least 13 characters.
if (pos <= inputSpan.Length - 13)
{
- // The pattern begins with a character in the set [Dd].
- // Find the next occurrence. If it can't be found, there's no match.
- int i = inputSpan.Slice(pos).IndexOfAny('D', 'd');
+ // The pattern has the literal "demi" ordinal case-insensitive at the beginning of the pattern. Find the next occurrence.
+ // If it can't be found, there's no match.
+ int i = inputSpan.Slice(pos).IndexOfAny(Utilities.s_indexOfString_demi_OrdinalIgnoreCase);
if (i >= 0)
{
base.runtextpos = pos + i;
{
int pos = base.runtextpos;
int matchStart = pos;
- int loop_iteration = 0, loop_starting_pos = 0;
- int stackpos = 0;
ReadOnlySpan<char> slice = inputSpan.Slice(pos);
- // Loop greedily at least once right-to-left.
- //{
- loop_starting_pos = pos;
- loop_iteration = 0;
-
- LoopBody:
- Utilities.StackPush(ref base.runstack!, ref stackpos, loop_starting_pos, pos);
-
- loop_starting_pos = pos;
- loop_iteration++;
-
- // Zero-width positive lookbehind.
- {
- slice = inputSpan.Slice(pos);
- int positivelookbehind_starting_pos = pos;
-
- if (Utilities.s_hasTimeout)
- {
- base.CheckTimeout();
- }
-
- // Match if at a word boundary.
- if (!Utilities.IsBoundary(inputSpan, pos))
- {
- goto LoopIterationNoMatch;
- }
-
- pos = positivelookbehind_starting_pos;
- slice = inputSpan.Slice(pos);
- }
-
-
- // The loop has a lower bound of 1 but no upper bound. Continue iterating greedily
- // if the last iteration wasn't empty (or if it was, if the lower bound hasn't yet been reached).
- if (pos != loop_starting_pos || loop_iteration == 0)
- {
- goto LoopBody;
- }
- goto LoopEnd;
-
- // The loop iteration failed. Put state back to the way it was before the iteration.
- LoopIterationNoMatch:
- if (--loop_iteration < 0)
- {
- // Unable to match the remainder of the expression after exhausting the loop.
- return false; // The input didn't match.
- }
- Utilities.StackPop(base.runstack!, ref stackpos, out pos, out loop_starting_pos);
+ // Zero-width positive lookbehind.
+ {
slice = inputSpan.Slice(pos);
- if (loop_iteration == 0)
+ int positivelookbehind_starting_pos = pos;
+
+ if (Utilities.s_hasTimeout)
+ {
+ base.CheckTimeout();
+ }
+
+ // Match if at a word boundary.
+ if (!Utilities.IsBoundary(inputSpan, pos))
{
- // All possible iterations have matched, but it's below the required minimum of 1. Fail the loop.
return false; // The input didn't match.
}
- LoopEnd:;
- //}
+ pos = positivelookbehind_starting_pos;
+ slice = inputSpan.Slice(pos);
+ }
if ((uint)slice.Length < 4 ||
!slice.StartsWith("demi", StringComparison.OrdinalIgnoreCase)) // Match the string "demi" (ordinal case-insensitive)
{
- goto LoopIterationNoMatch;
+ return false; // The input didn't match.
}
// Match a whitespace character atomically at least once.
if (iteration == 0)
{
- goto LoopIterationNoMatch;
+ return false; // The input didn't match.
}
slice = slice.Slice(iteration);
if ((uint)slice.Length < 8 ||
!slice.StartsWith("douzaine", StringComparison.OrdinalIgnoreCase)) // Match the string "douzaine" (ordinal case-insensitive)
{
- goto LoopIterationNoMatch;
+ return false; // The input didn't match.
}
// The input matched.
(WordCategoriesMask & (1 << (int)CharUnicodeInfo.GetUnicodeCategory(ch))) != 0;
}
- /// <summary>Pops 2 values from the backtracking stack.</summary>
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- internal static void StackPop(int[] stack, ref int pos, out int arg0, out int arg1)
- {
- arg0 = stack[--pos];
- arg1 = stack[--pos];
- }
-
- /// <summary>Pushes 2 values onto the backtracking stack.</summary>
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- internal static void StackPush(ref int[] stack, ref int pos, int arg0, int arg1)
- {
- // If there's space available for all 2 values, store them.
- int[] s = stack;
- int p = pos;
- if ((uint)(p + 1) < (uint)s.Length)
- {
- s[p] = arg0;
- s[p + 1] = arg1;
- pos += 2;
- return;
- }
-
- // Otherwise, resize the stack to make room and try again.
- WithResize(ref stack, ref pos, arg0, arg1);
-
- // <summary>Resize the backtracking stack array and push 2 values onto the stack.</summary>
- [MethodImpl(MethodImplOptions.NoInlining)]
- static void WithResize(ref int[] stack, ref int pos, int arg0, int arg1)
- {
- Array.Resize(ref stack, (pos + 1) * 2);
- StackPush(ref stack, ref pos, arg0, arg1);
- }
- }
+ /// <summary>Supports searching for the string "demi".</summary>
+ internal static readonly SearchValues<string> s_indexOfString_demi_OrdinalIgnoreCase = SearchValues.Create(["demi"], StringComparison.OrdinalIgnoreCase);
}
}"measles$/" (74 uses)[GeneratedRegex("measles$/", RegexOptions.IgnoreCase)] // Any possible match is at least 8 characters.
if (pos <= inputSpan.Length - 8)
{
- // The pattern has the literal "measles" ordinal case-insensitive at the beginning of the pattern. Find the next occurrence.
+ // The pattern has the literal "measles/" ordinal case-insensitive at the beginning of the pattern. Find the next occurrence.
// If it can't be found, there's no match.
- int i = inputSpan.Slice(pos).IndexOfAny(Utilities.s_indexOfString_measles_OrdinalIgnoreCase);
+ int i = inputSpan.Slice(pos).IndexOfAny(Utilities.s_indexOfString_5DE5CF41BC14B96979EE7612269C6B4F3E8639BAE77421938F36FC03C4D4DE27);
if (i >= 0)
{
base.runtextpos = pos + i;
/// <summary>Whether <see cref="s_defaultTimeout"/> is non-infinite.</summary>
internal static readonly bool s_hasTimeout = s_defaultTimeout != Regex.InfiniteMatchTimeout;
- /// <summary>Supports searching for the string "measles".</summary>
- internal static readonly SearchValues<string> s_indexOfString_measles_OrdinalIgnoreCase = SearchValues.Create(["measles"], StringComparison.OrdinalIgnoreCase);
+ /// <summary>Supports searching for the string "measles/".</summary>
+ internal static readonly SearchValues<string> s_indexOfString_5DE5CF41BC14B96979EE7612269C6B4F3E8639BAE77421938F36FC03C4D4DE27 = SearchValues.Create(["measles/"], StringComparison.OrdinalIgnoreCase);
}
}"^((?!-)+)([a-zA-Z_-]+$).*((?<!-)+)" (57 uses)[GeneratedRegex("^((?!-)+)([a-zA-Z_-]+$).*((?<!-)+)", RegexOptions.Singleline)] /// <code>
/// ○ Match if at the beginning of the string.<br/>
/// ○ 1st capture group.<br/>
- /// ○ Loop greedily at least once.<br/>
- /// ○ Zero-width negative lookahead.<br/>
- /// ○ Match '-'.<br/>
+ /// ○ Zero-width negative lookahead.<br/>
+ /// ○ Match '-'.<br/>
/// ○ 2nd capture group.<br/>
/// ○ Match a character in the set [\-A-Z_a-z] atomically at least once.<br/>
/// ○ Match if at the end of the string or if before an ending newline.<br/>
/// ○ Match any character greedily any number of times.<br/>
/// ○ 3rd capture group.<br/>
- /// ○ Loop greedily and atomically at least once right-to-left.<br/>
- /// ○ Zero-width negative lookbehind.<br/>
- /// ○ Match '-' right-to-left.<br/>
+ /// ○ Zero-width negative lookbehind.<br/>
+ /// ○ Match '-' right-to-left.<br/>
/// </code>
/// </remarks>
[global::System.CodeDom.Compiler.GeneratedCodeAttribute("System.Text.RegularExpressions.Generator", "42.42.42.42")]
int capture_starting_pos2 = 0;
int charloop_capture_pos = 0;
int charloop_starting_pos = 0, charloop_ending_pos = 0;
- int loop_iteration = 0, loop_starting_pos = 0;
- int loop_iteration1 = 0, loop_starting_pos1 = 0;
- int stackpos = 0;
- int startingStackpos = 0;
ReadOnlySpan<char> slice = inputSpan.Slice(pos);
// Match if at the beginning of the string.
}
// 1st capture group.
- //{
+ {
capture_starting_pos = pos;
- // Loop greedily at least once.
- //{
- loop_starting_pos = pos;
- loop_iteration = 0;
-
- LoopBody:
- Utilities.StackPush(ref base.runstack!, ref stackpos, base.Crawlpos(), loop_starting_pos, pos);
-
- loop_starting_pos = pos;
- loop_iteration++;
-
- // Zero-width negative lookahead.
- {
- slice = inputSpan.Slice(pos);
- int negativelookahead__starting_pos = pos;
- if (Utilities.s_hasTimeout)
- {
- base.CheckTimeout();
- }
-
- // Match '-'.
- if (slice.IsEmpty || slice[0] != '-')
- {
- goto NegativeLookaroundMatch;
- }
-
- goto LoopIterationNoMatch;
-
- NegativeLookaroundMatch:
- pos = negativelookahead__starting_pos;
- slice = inputSpan.Slice(pos);
- }
-
-
- // The loop has a lower bound of 1 but no upper bound. Continue iterating greedily
- // if the last iteration wasn't empty (or if it was, if the lower bound hasn't yet been reached).
- if (pos != loop_starting_pos || loop_iteration == 0)
- {
- goto LoopBody;
- }
- goto LoopEnd;
-
- // The loop iteration failed. Put state back to the way it was before the iteration.
- LoopIterationNoMatch:
- if (--loop_iteration < 0)
- {
- // Unable to match the remainder of the expression after exhausting the loop.
- UncaptureUntil(0);
- return false; // The input didn't match.
- }
- Utilities.StackPop(base.runstack!, ref stackpos, out pos, out loop_starting_pos);
- UncaptureUntil(base.runstack![--stackpos]);
+ // Zero-width negative lookahead.
+ {
slice = inputSpan.Slice(pos);
- if (loop_iteration == 0)
+ int negativelookahead__starting_pos = pos;
+ if (Utilities.s_hasTimeout)
{
- // All possible iterations have matched, but it's below the required minimum of 1. Fail the loop.
- UncaptureUntil(0);
- return false; // The input didn't match.
+ base.CheckTimeout();
}
- LoopEnd:;
- //}
+ // Match '-'.
+ if (slice.IsEmpty || slice[0] != '-')
+ {
+ goto NegativeLookaroundMatch;
+ }
+
+ UncaptureUntil(0);
+ return false; // The input didn't match.
+
+ NegativeLookaroundMatch:
+ pos = negativelookahead__starting_pos;
+ slice = inputSpan.Slice(pos);
+ }
base.Capture(1, capture_starting_pos, pos);
-
- goto CaptureSkipBacktrack;
-
- CaptureBacktrack:
- goto LoopIterationNoMatch;
-
- CaptureSkipBacktrack:;
- //}
+ }
// 2nd capture group.
{
if (iteration == 0)
{
- goto CaptureBacktrack;
+ UncaptureUntil(0);
+ return false; // The input didn't match.
}
slice = slice.Slice(iteration);
// Match if at the end of the string or if before an ending newline.
if (pos < inputSpan.Length - 1 || ((uint)pos < (uint)inputSpan.Length && inputSpan[pos] != '\n'))
{
- goto CaptureBacktrack;
+ UncaptureUntil(0);
+ return false; // The input didn't match.
}
base.Capture(2, capture_starting_pos1, pos);
if (charloop_starting_pos >= charloop_ending_pos)
{
- goto CaptureBacktrack;
+ UncaptureUntil(0);
+ return false; // The input didn't match.
}
pos = --charloop_ending_pos;
slice = inputSpan.Slice(pos);
{
capture_starting_pos2 = pos;
- // Loop greedily and atomically at least once right-to-left.
+ // Zero-width negative lookbehind.
{
- startingStackpos = stackpos;
- loop_starting_pos1 = pos;
- loop_iteration1 = 0;
-
- LoopBody1:
- Utilities.StackPush(ref base.runstack!, ref stackpos, base.Crawlpos(), loop_starting_pos1, pos);
-
- loop_starting_pos1 = pos;
- loop_iteration1++;
-
- // Zero-width negative lookbehind.
- {
- slice = inputSpan.Slice(pos);
- int negativelookbehind__starting_pos = pos;
- if (Utilities.s_hasTimeout)
- {
- base.CheckTimeout();
- }
-
- // Match '-' right-to-left.
- if ((uint)(pos - 1) >= inputSpan.Length || inputSpan[pos - 1] != '-')
- {
- goto NegativeLookaroundMatch1;
- }
- pos--;
-
- goto LoopIterationNoMatch1;
-
- NegativeLookaroundMatch1:
- pos = negativelookbehind__starting_pos;
- slice = inputSpan.Slice(pos);
- }
-
-
- // The loop has a lower bound of 1 but no upper bound. Continue iterating greedily
- // if the last iteration wasn't empty (or if it was, if the lower bound hasn't yet been reached).
- if (pos != loop_starting_pos1 || loop_iteration1 == 0)
- {
- goto LoopBody1;
- }
- goto LoopEnd1;
-
- // The loop iteration failed. Put state back to the way it was before the iteration.
- LoopIterationNoMatch1:
- if (--loop_iteration1 < 0)
- {
- // Unable to match the remainder of the expression after exhausting the loop.
- goto CharLoopBacktrack;
- }
- Utilities.StackPop(base.runstack!, ref stackpos, out pos, out loop_starting_pos1);
- UncaptureUntil(base.runstack![--stackpos]);
slice = inputSpan.Slice(pos);
- if (loop_iteration1 == 0)
+ int negativelookbehind__starting_pos = pos;
+ if (Utilities.s_hasTimeout)
{
- // All possible iterations have matched, but it's below the required minimum of 1. Fail the loop.
- goto CharLoopBacktrack;
+ base.CheckTimeout();
}
- LoopEnd1:
- stackpos = startingStackpos; // Ensure any remaining backtracking state is removed.
+ // Match '-' right-to-left.
+ if ((uint)(pos - 1) >= inputSpan.Length || inputSpan[pos - 1] != '-')
+ {
+ goto NegativeLookaroundMatch1;
+ }
+ pos--;
+
+ goto CharLoopBacktrack;
+
+ NegativeLookaroundMatch1:
+ pos = negativelookbehind__starting_pos;
+ slice = inputSpan.Slice(pos);
}
base.Capture(3, capture_starting_pos2, pos);
/// <summary>Whether <see cref="s_defaultTimeout"/> is non-infinite.</summary>
internal static readonly bool s_hasTimeout = s_defaultTimeout != Regex.InfiniteMatchTimeout;
- /// <summary>Pops 2 values from the backtracking stack.</summary>
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- internal static void StackPop(int[] stack, ref int pos, out int arg0, out int arg1)
- {
- arg0 = stack[--pos];
- arg1 = stack[--pos];
- }
-
- /// <summary>Pushes 3 values onto the backtracking stack.</summary>
- [MethodImpl(MethodImplOptions.AggressiveInlining)]
- internal static void StackPush(ref int[] stack, ref int pos, int arg0, int arg1, int arg2)
- {
- // If there's space available for all 3 values, store them.
- int[] s = stack;
- int p = pos;
- if ((uint)(p + 2) < (uint)s.Length)
- {
- s[p] = arg0;
- s[p + 1] = arg1;
- s[p + 2] = arg2;
- pos += 3;
- return;
- }
-
- // Otherwise, resize the stack to make room and try again.
- WithResize(ref stack, ref pos, arg0, arg1, arg2);
-
- // <summary>Resize the backtracking stack array and push 3 values onto the stack.</summary>
- [MethodImpl(MethodImplOptions.NoInlining)]
- static void WithResize(ref int[] stack, ref int pos, int arg0, int arg1, int arg2)
- {
- Array.Resize(ref stack, (pos + 2) * 2);
- StackPush(ref stack, ref pos, arg0, arg1, arg2);
- }
- }
-
/// <summary>Supports searching for characters in or not in "-ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz".</summary>
internal static readonly SearchValues<char> s_ascii_200000FEFFFF87FEFFFF07 = SearchValues.Create("-ABCDEFGHIJKLMNOPQRSTUVWXYZ_abcdefghijklmnopqrstuvwxyz");
}For more diff examples, see https://gist.github.com/MihuBot/567aa328619b6cde02f2cd78c49018bd JIT assembly changesFor a list of JIT diff regressions, see Regressions.md Sample source code for further analysisconst string JsonPath = "RegexResults-1309.json";
if (!File.Exists(JsonPath))
{
await using var archiveStream = await new HttpClient().GetStreamAsync("https://mihubot.xyz/r/E2ukaNOA");
using var archive = new ZipArchive(archiveStream, ZipArchiveMode.Read);
archive.Entries.First(e => e.Name == "Results.json").ExtractToFile(JsonPath);
}
using FileStream jsonFileStream = File.OpenRead(JsonPath);
RegexEntry[] entries = JsonSerializer.Deserialize<RegexEntry[]>(jsonFileStream, new JsonSerializerOptions { IncludeFields = true })!;
Console.WriteLine($"Working with {entries.Length} patterns");
record KnownPattern(string Pattern, RegexOptions Options, int Count);
sealed class RegexEntry
{
public required KnownPattern Regex { get; set; }
public required string MainSource { get; set; }
public required string PrSource { get; set; }
public string? FullDiff { get; set; }
public string? ShortDiff { get; set; }
public (string Name, string Values)[]? SearchValuesOfChar { get; set; }
public (string[] Values, StringComparison ComparisonType)[]? SearchValuesOfString { get; set; }
} |
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In addition to replacing the loop with an empty when it contains only a zero-width assertion and has a lower bound of 0, if it doesn't have a lower bound of 0, we can just remove the loop layer, replacing it with its child directly, since any additional iterations beyond one is redundant.