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Modify MergedNamespaceDeclaration.MakeChildren to to allocate less #74698

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merged 2 commits into from
Aug 13, 2024
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Modify MergedNamespaceDeclaration.MakeChildren to to allocate less #74698

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68d0d23
Modify MergedNamespaceDeclaration.MakeChildrento to allocate less
ToddGrun Aug 9, 2024
3342d8d
Add comment, don't use Values collection on Dictionary
ToddGrun Aug 9, 2024
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108 changes: 84 additions & 24 deletions src/Compilers/CSharp/Portable/Declarations/MergedNamespaceDeclaration.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@

#nullable disable

using System.Collections.Generic;
using System.Collections.Immutable;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.PooledObjects;
Expand Down Expand Up @@ -139,43 +140,102 @@ private ImmutableArray<MergedNamespaceOrTypeDeclaration> MakeChildren()

var children = ArrayBuilder<MergedNamespaceOrTypeDeclaration>.GetInstance();

if (namespaces != null)
addNamespacesToChildren(namespaces, allNamespacesHaveSameName, children);
addTypesToChildren(types, allTypesHaveSameIdentity, children);

return children.ToImmutableAndFree();

static void addNamespacesToChildren(ArrayBuilder<SingleNamespaceDeclaration> namespaces, bool allNamespacesHaveSameName, ArrayBuilder<MergedNamespaceOrTypeDeclaration> children)
{
if (allNamespacesHaveSameName)
{
children.Add(MergedNamespaceDeclaration.Create(namespaces.ToImmutableAndFree()));
}
else
if (namespaces != null)
{
var namespaceGroups = namespaces.ToDictionary(n => n.Name, StringOrdinalComparer.Instance);
namespaces.Free();

foreach (var namespaceGroup in namespaceGroups.Values)
if (allNamespacesHaveSameName)
{
children.Add(MergedNamespaceDeclaration.Create(namespaces.ToImmutableAndFree()));
}
else
{
children.Add(MergedNamespaceDeclaration.Create(namespaceGroup));
// PERF: Don't use ArrayBuilder.ToDictionary directly as it requires an extra dictionary allocation. Other options such
// as MultiDictionary<string, SingleNamespaceDeclaration> and Dictionary<string, OneOrMany<SingleNamespaceDeclaration>>
// are even less appealing as they don't perform well when their value sets grow to contain a large number of items,
// as typically happens when processing the namespaces.
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var namespaceGroups = new Dictionary<string, ArrayBuilder<SingleNamespaceDeclaration>>(StringOrdinalComparer.Instance);
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foreach (var n in namespaces)
{
var builder = namespaceGroups.GetOrAdd(n.Name, static () => ArrayBuilder<SingleNamespaceDeclaration>.GetInstance());

builder.Add(n);
}

namespaces.Free();

foreach (var (_, namespaceGroup) in namespaceGroups)
{
children.Add(MergedNamespaceDeclaration.Create(namespaceGroup.ToImmutableAndFree()));
}
}
}
}

if (types != null)
static void addTypesToChildren(ArrayBuilder<SingleTypeDeclaration> types, bool allTypesHaveSameIdentity, ArrayBuilder<MergedNamespaceOrTypeDeclaration> children)
{
if (allTypesHaveSameIdentity)
{
children.Add(new MergedTypeDeclaration(types.ToImmutableAndFree()));
}
else
if (types != null)
{
var typeGroups = types.ToDictionary(t => t.Identity);
types.Free();

foreach (var typeGroup in typeGroups.Values)
if (allTypesHaveSameIdentity)
{
children.Add(new MergedTypeDeclaration(types.ToImmutableAndFree()));
}
else
{
children.Add(new MergedTypeDeclaration(typeGroup));
// PERF: Use object as the value in this dictionary to efficiently represent single item collections.
// If only a single object has been seen with a given identity, the value will be a SingleTypeDeclaration,
// otherwise, the value will be an ArrayBuilder<SingleTypeDeclaration>. This code differs from
// addNamespacesToChildren intentionally as the vast majority of identities are represented by only a
// single item in the types collection.
var typeGroups = PooledDictionary<SingleTypeDeclaration.TypeDeclarationIdentity, object>.GetInstance();

foreach (var t in types)
{
var id = t.Identity;

if (typeGroups.TryGetValue(id, out var existingValue))
{
if (existingValue is not ArrayBuilder<SingleTypeDeclaration> builder)
{
builder = ArrayBuilder<SingleTypeDeclaration>.GetInstance();
builder.Add((SingleTypeDeclaration)existingValue);
typeGroups[id] = builder;
}

builder.Add(t);
}
else
{
typeGroups.Add(id, t);
}
}

foreach (var (_, typeGroup) in typeGroups)
{
if (typeGroup is SingleTypeDeclaration t)
{
children.Add(new MergedTypeDeclaration([t]));
}
else
{
var builder = (ArrayBuilder<SingleTypeDeclaration>)typeGroup;
children.Add(new MergedTypeDeclaration(builder.ToImmutableAndFree()));
}
}

types.Free();

// ArrayBuilder values were freed above.
typeGroups.Free();
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}
}
}

return children.ToImmutableAndFree();
}

public new ImmutableArray<MergedNamespaceOrTypeDeclaration> Children
Expand Down
23 changes: 23 additions & 0 deletions src/Compilers/Core/Portable/Collections/DictionaryExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,6 +2,7 @@
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using Microsoft.CodeAnalysis.Collections;
Expand Down Expand Up @@ -36,6 +37,28 @@ public static TValue GetOrAdd<TKey, TValue>(
}
}

/// <summary>
/// If the given key is not found in the dictionary, add it with the result of invoking getValue and return the value.
/// Otherwise return the existing value associated with that key.
/// </summary>
public static TValue GetOrAdd<TKey, TValue>(
this Dictionary<TKey, TValue> dictionary,
TKey key,
Func<TValue> getValue)
where TKey : notnull
{
if (dictionary.TryGetValue(key, out var existingValue))
{
return existingValue;
}
else
{
var value = getValue();
dictionary.Add(key, value);
return value;
}
}

#if !NETCOREAPP
public static bool TryAdd<TKey, TValue>(
this Dictionary<TKey, TValue> dictionary,
Expand Down