Reduce allocations in TagHelperBinder.ProcessDescriptors

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/TagHelperBinder.TagHelperSet.cs

@@ -0,0 +1,152 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Diagnostics;
+
+namespace Microsoft.AspNetCore.Razor.Language;
+
+internal sealed partial class TagHelperBinder
+{
+    /// <summary>
+    ///  Similar to <see cref="ImmutableArray{T}"/>, but optimized to store either a single value or an array of values.
+    /// </summary>
+    [DebuggerDisplay("{GetDebuggerDisplay(),nq}")]
+    [DebuggerTypeProxy(typeof(DebuggerProxy))]
+    private readonly struct TagHelperSet
+    {
+        public static readonly TagHelperSet Empty = default!;
+
+        private readonly object _valueOrArray;
+
+        public TagHelperSet(TagHelperDescriptor value)
+        {
+            _valueOrArray = value;
+        }
+
+        public TagHelperSet(TagHelperDescriptor[] array)
+        {
+            _valueOrArray = array;
+        }
+
+        public TagHelperDescriptor this[int index]
+        {
+            get
+            {
+                return _valueOrArray switch
+                {
+                    TagHelperDescriptor[] array => array[index],
+                    not null when index == 0 => (TagHelperDescriptor)_valueOrArray,
+                    _ => throw new IndexOutOfRangeException(),
+                };
+            }
+        }
+
+        public int Count
+            => _valueOrArray switch
+            {
+                TagHelperDescriptor[] array => array.Length,
+                null => 0,
+
+                // _valueOrArray can be an array, a single value, or null.
+                // So, we can avoid a type check for the single value case.
+                _ => 1
+            };
+
+        public Enumerator GetEnumerator()
+            => new(this);
+
+        public struct Enumerator
+        {
+            private readonly TagHelperSet _tagHelperSet;
+            private int _index;
+
+            internal Enumerator(TagHelperSet tagHelperSet)
+            {
+                _tagHelperSet = tagHelperSet;
+                _index = -1;
+            }
+
+            public bool MoveNext()
+            {
+                _index++;
+                return _index < _tagHelperSet.Count;
+            }
+
+            public readonly TagHelperDescriptor Current
+                => _tagHelperSet[_index];
+        }
+
+        private sealed class DebuggerProxy(TagHelperSet instance)
+        {
+            private readonly TagHelperSet _instance = instance;
+
+            [DebuggerBrowsable(DebuggerBrowsableState.RootHidden)]
+            public TagHelperDescriptor[] Items
+                => _instance._valueOrArray switch
+                {
+                    TagHelperDescriptor[] array => array,
+                    TagHelperDescriptor value => [value],
+                    _ => []
+                };
+        }
+
+        private string GetDebuggerDisplay()
+            => "Count " + Count;
+
+        /// <summary>
+        ///  This is a mutable builder for <see cref="TagHelperSet"/>. However, it works differently from
+        ///  a typical builder. First, you must call <see cref="IncreaseSize"/> to set the number of items.
+        ///  Once you've done that for each item to be added, you can call <see cref="Add(TagHelperDescriptor)"/>
+        ///  exactly that many times. This ensures that space allocated is exactly what's needed to
+        ///  produce the resulting <see cref="TagHelperSet"/>.
+        /// </summary>
+        public struct Builder
+        {
+            private object? _valueOrArray;
+            private int _index;
+            private int _size;
+
+            public void IncreaseSize()
+            {
+                Debug.Assert(_valueOrArray is null, "Cannot increase size once items have been added.");
+                _size++;
+            }
+
+            public void Add(TagHelperDescriptor item)
+            {
+                Debug.Assert(_index < _size, "Cannot add more items.");
+
+                if (_size == 1)
+                {
+                    // We only need to store a single value.
+                    _valueOrArray = item;
+                    _index = 1;
+                    return;
+                }
+
+                Debug.Assert(_valueOrArray is null or TagHelperDescriptor[]);
+
+                if (_valueOrArray is not TagHelperDescriptor[] array)
+                {
+                    array = new TagHelperDescriptor[_size];
+                    _valueOrArray = array;
+                }
+
+                array[_index++] = item;
+            }
+
+            public readonly TagHelperSet ToSet()
+            {
+                Debug.Assert(_index == _size, "Must have added all items.");
+
+                return _size switch
+                {
+                    0 => Empty,
+                    1 => new((TagHelperDescriptor)_valueOrArray!),
+                    _ => new((TagHelperDescriptor[])_valueOrArray!)
+                };
+            }
+        }
+    }
+}

src/Compiler/Microsoft.CodeAnalysis.Razor.Compiler/src/Language/TagHelperBinder.cs

@@ -13,10 +13,10 @@ namespace Microsoft.AspNetCore.Razor.Language;
 /// <summary>
 /// Enables retrieval of <see cref="TagHelperBinding"/>'s.
 /// </summary>
-internal sealed class TagHelperBinder
+internal sealed partial class TagHelperBinder
 {
-    private readonly ImmutableArray<TagHelperDescriptor> _catchAllDescriptors;
-    private readonly ReadOnlyDictionary<string, ImmutableArray<TagHelperDescriptor>> _tagNameToDescriptorsMap;
+    private readonly TagHelperSet _catchAllDescriptors;
+    private readonly ReadOnlyDictionary<string, TagHelperSet> _tagNameToDescriptorsMap;
 
     public string? TagNamePrefix { get; }
     public ImmutableArray<TagHelperDescriptor> Descriptors { get; }
@@ -38,52 +38,88 @@ public TagHelperBinder(string? tagNamePrefix, ImmutableArray<TagHelperDescriptor
     private static void ProcessDescriptors(
         ImmutableArray<TagHelperDescriptor> descriptors,
         string? tagNamePrefix,
-        out ReadOnlyDictionary<string, ImmutableArray<TagHelperDescriptor>> tagNameToDescriptorsMap,
-        out ImmutableArray<TagHelperDescriptor> catchAllDescriptors)
+        out ReadOnlyDictionary<string, TagHelperSet> tagNameToDescriptorsMap,
+        out TagHelperSet catchAllDescriptors)
     {
-        using var catchAllBuilder = new PooledArrayBuilder<TagHelperDescriptor>();
-        using var pooledMap = StringDictionaryPool<ImmutableArray<TagHelperDescriptor>.Builder>.OrdinalIgnoreCase.GetPooledObject(out var mapBuilder);
-        using var pooledSet = HashSetPool<TagHelperDescriptor>.GetPooledObject(out var distinctSet);
+        // Initialize a MemoryBuilder of TagHelperSet.Builders. We need a builder for each unique tag name.
+        using var builders = new MemoryBuilder<TagHelperSet.Builder>(initialCapacity: 32, clearArray: true);
+
+        // Keep track of what needs to be added in the second pass.
+        // There will be an entry for every tag matching rule.
+        // Each entry consists of an index to identify a builder and the TagHelperDescriptor to add to it.
+        using var toAdd = new MemoryBuilder<(int, TagHelperDescriptor)>(initialCapacity: descriptors.Length * 4, clearArray: true);
+
+        // Use a special TagHelperSet.Builder to track catch-all tag helpers.
+        var catchAllBuilder = new TagHelperSet.Builder();
+
+        // At most, there should only be one catch-all tag helper per descriptor.
+        using var catchAllToAdd = new MemoryBuilder<TagHelperDescriptor>(initialCapacity: descriptors.Length, clearArray: true);
 
-        // Build a map of tag name -> tag helpers.
-        foreach (var descriptor in descriptors)
+        // The builders are indexed using a map of "tag name" to the index of the builder in the array.
+        using var _1 = StringDictionaryPool<int>.OrdinalIgnoreCase.GetPooledObject(out var tagNameToBuilderIndexMap);
+        using var _2 = HashSetPool<TagHelperDescriptor>.GetPooledObject(out var tagHelperSet);
+
+#if NET
+        tagHelperSet.EnsureCapacity(descriptors.Length);
+#endif
+
+        foreach (var tagHelper in descriptors)
         {
-            if (!distinctSet.Add(descriptor))
+            if (!tagHelperSet.Add(tagHelper))
             {
-                // We're already seen this descriptor, skip it.
+                // We've already seen this tag helper. Skip.
                 continue;
             }
 
-            foreach (var rule in descriptor.TagMatchingRules)
+            foreach (var rule in tagHelper.TagMatchingRules)
             {
-                if (rule.TagName == TagHelperMatchingConventions.ElementCatchAllName)
+                var tagName = rule.TagName;
+
+                if (tagName == TagHelperMatchingConventions.ElementCatchAllName)
                 {
-                    // This is a catch-all descriptor, we can keep track of it separately.
-                    catchAllBuilder.Add(descriptor);
+                    catchAllBuilder.IncreaseSize();
+                    catchAllToAdd.Append(tagHelper);
+                    continue;
                 }
-                else
+
+                if (!tagNameToBuilderIndexMap.TryGetValue(tagName, out var builderIndex))
                 {
-                    // This is a specific tag name, we need to add it to the map.
-                    var tagName = tagNamePrefix + rule.TagName;
-                    var builder = mapBuilder.GetOrAdd(tagName, _ => ImmutableArray.CreateBuilder<TagHelperDescriptor>());
+                    builderIndex = builders.Length;
+                    builders.Append(default(TagHelperSet.Builder));
 
-                    builder.Add(descriptor);
+                    tagNameToBuilderIndexMap.Add(tagName, builderIndex);
                 }
+
+                builders[builderIndex].IncreaseSize();
+                toAdd.Append((builderIndex, tagHelper));
             }
         }
 
-        // Build the final dictionary with immutable arrays.
-        var map = new Dictionary<string, ImmutableArray<TagHelperDescriptor>>(capacity: mapBuilder.Count, StringComparer.OrdinalIgnoreCase);
+        // Next, we walk through toAdd and add each descriptor to the appropriate builder.
+        // Because we counted first, we know that each builder will allocate exactly the
+        // space needed for the final result.
+        foreach (var (builderIndex, tagHelper) in toAdd.AsMemory().Span)
+        {
+            builders[builderIndex].Add(tagHelper);
+        }
+
+        foreach (var tagHelper in catchAllToAdd.AsMemory().Span)
+        {
+            catchAllBuilder.Add(tagHelper);
+        }
+
+        // Build the final dictionary.
+        var map = new Dictionary<string, TagHelperSet>(capacity: tagNameToBuilderIndexMap.Count, StringComparer.OrdinalIgnoreCase);
 
-        foreach (var (key, value) in mapBuilder)
+        foreach (var (tagName, builderIndex) in tagNameToBuilderIndexMap)
         {
-            map.Add(key, value.ToImmutableAndClear());
+            map.Add(tagNamePrefix + tagName, builders[builderIndex].ToSet());
         }
 
-        tagNameToDescriptorsMap = new ReadOnlyDictionary<string, ImmutableArray<TagHelperDescriptor>>(map);
+        tagNameToDescriptorsMap = new ReadOnlyDictionary<string, TagHelperSet>(map);
 
-        // Build the catch all descriptors array.
-        catchAllDescriptors = catchAllBuilder.ToImmutableAndClear();
+        // Build the "catch all" tag helpers set.
+        catchAllDescriptors = catchAllBuilder.ToSet();
     }
 
     /// <summary>
@@ -150,7 +186,7 @@ private static void ProcessDescriptors(
             : null;
 
         static void CollectBoundRulesInfo(
-            ImmutableArray<TagHelperDescriptor> descriptors,
+            TagHelperSet descriptors,
             ReadOnlySpan<char> tagName,
             ReadOnlySpan<char> parentTagName,
             ImmutableArray<KeyValuePair<string, string>> attributes,

src/Compiler/perf/Microbenchmarks/Microsoft.AspNetCore.Razor.Microbenchmarks.Compiler.csproj

@@ -21,6 +21,13 @@
     <None Include="$(SharedFilesRoot)Compiler\MSN.cshtml" CopyToOutputDirectory="PreserveNewest" />
     <None Include="$(SharedFilesRoot)Compiler\BlazorServerTagHelpers.razor" CopyToOutputDirectory="PreserveNewest" />
     <None Include="$(SharedFilesRoot)Compiler\taghelpers.json" CopyToOutputDirectory="PreserveNewest" />
+
+    <Compile Remove="Resources\**\*.*" />
+    <None Remove="Resources\**\*.*" />
+
+    <EmbeddedResource Include="Resources\**\*.*" />
+    <EmbeddedResource Include="$(SharedFilesRoot)\Tooling\**\*.*" Link="Resources\%(RecursiveDir)%(Filename)%(Extension)" />
+    <EmbeddedResource Include="$(SharedFilesRoot)\Compiler\MSN.cshtml" Link="Resources\%(FileName)%(Extension)" />
   </ItemGroup>
 
   <Import Project="..\..\..\Shared\Microsoft.AspNetCore.Razor.Serialization.Json\Microsoft.AspNetCore.Razor.Serialization.Json.projitems" Label="Shared" />

src/Compiler/perf/Microbenchmarks/Program.cs

@@ -4,7 +4,13 @@
 using System;
 using System.Diagnostics;
 using System.Linq;
+using BenchmarkDotNet.Columns;
 using BenchmarkDotNet.Configs;
+using BenchmarkDotNet.Diagnosers;
+using BenchmarkDotNet.Exporters;
+using BenchmarkDotNet.Exporters.Json;
+using BenchmarkDotNet.Loggers;
+using BenchmarkDotNet.Reports;
 using BenchmarkDotNet.Running;
 
 namespace Microsoft.AspNetCore.BenchmarkDotNet.Runner;
@@ -13,9 +19,7 @@ partial class Program
 {
     private static int Main(string[] args)
     {
-        IConfig config = Debugger.IsAttached
-            ? new DebugInProcessConfig()
-            : ManualConfig.CreateEmpty();
+        var config = GetConfig();
 
         var summaries = BenchmarkSwitcher.FromAssembly(typeof(Program).Assembly)
             .Run(args, config);
@@ -54,4 +58,36 @@ private static int Fail(object o, string message)
         Console.Error.WriteLine("'{0}' failed, reason: '{1}'", o, message);
         return 1;
     }
+
+    private static IConfig GetConfig()
+    {
+        if (Debugger.IsAttached)
+        {
+            return new DebugInProcessConfig();
+        }
+
+        return ManualConfig.CreateEmpty()
+            .WithBuildTimeout(TimeSpan.FromMinutes(15)) // for slow machines
+            .AddLogger(ConsoleLogger.Default) // log output to console
+            .AddValidator(DefaultConfig.Instance.GetValidators().ToArray()) // copy default validators
+            .AddAnalyser(DefaultConfig.Instance.GetAnalysers().ToArray()) // copy default analysers
+            .AddExporter(MarkdownExporter.GitHub) // export to GitHub markdown
+            .AddColumnProvider(DefaultColumnProviders.Instance) // display default columns (method name, args etc)
+            .AddDiagnoser(MemoryDiagnoser.Default)
+            .AddExporter(JsonExporter.Full)
+            .AddColumn(StatisticColumn.Median, StatisticColumn.Min, StatisticColumn.Max)
+            .WithSummaryStyle(SummaryStyle.Default.WithMaxParameterColumnWidth(36)) // the default is 20 and trims too aggressively some benchmark results
+            .AddDiagnoser(CreateDisassembler());
+    }
+
+    private static DisassemblyDiagnoser CreateDisassembler()
+        => new(new DisassemblyDiagnoserConfig(
+            maxDepth: 1, // TODO: is depth == 1 enough?
+            syntax: DisassemblySyntax.Masm, // TODO: enable diffable format
+            printSource: false, // we are not interested in getting C#
+            printInstructionAddresses: false, // would make the diffing hard, however could be useful to determine alignment
+            exportGithubMarkdown: false,
+            exportHtml: false,
+            exportCombinedDisassemblyReport: false,
+            exportDiff: false));
 }