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Optimize DeepClone codegen with span-based array copy and immutable collection reuse (#6)
* Initial plan * Optimize array cloning with AsSpan().ToArray() for primitive types Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com> * Optimize immutable collections to reuse instances for value types Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com> * Add performance validation tests Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com> * Clean up unused imports and misleading comments Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com> * Code review cleanup: fix import ordering and simplify type checking Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com> --------- Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com> Co-authored-by: arika0093 <4524647+arika0093@users.noreply.github.com>
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‎src/IDeepCloneable.Generator/CloneableGenerator.cs‎

Lines changed: 93 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -178,8 +178,9 @@ namespace {{classInfo.Namespace}}
178178
#nullable disable
179179
#pragma warning disable
180180
181-
using System.Linq;
181+
using System;
182182
using System.Collections.Immutable;
183+
using System.Linq;
183184
184185
""";
185186

@@ -386,6 +387,12 @@ int nestingLevel
386387
return $"{sourceObjectName}.{propertyName}?.Select(x => x?.{DeepCloneMethodName}()).ToArray()";
387388
}
388389

390+
// Optimize for primitive and blittable types using span-based copy
391+
if (IsPrimitiveOrBlittableType(elementType))
392+
{
393+
return $"{sourceObjectName}.{propertyName} != null ? {sourceObjectName}.{propertyName}.AsSpan().ToArray() : null";
394+
}
395+
389396
if (elementType.IsValueType || elementType.SpecialType == SpecialType.System_String)
390397
{
391398
return $"{sourceObjectName}.{propertyName} != null ? ({elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}[]){sourceObjectName}.{propertyName}.Clone() : null";
@@ -575,6 +582,42 @@ private static bool IsCollectionType(INamedTypeSymbol type)
575582
);
576583
}
577584

585+
private static bool IsPrimitiveOrBlittableType(ITypeSymbol type)
586+
{
587+
// Check for primitive types that can be efficiently copied with memory operations
588+
switch (type.SpecialType)
589+
{
590+
case SpecialType.System_Boolean:
591+
case SpecialType.System_Char:
592+
case SpecialType.System_SByte:
593+
case SpecialType.System_Byte:
594+
case SpecialType.System_Int16:
595+
case SpecialType.System_UInt16:
596+
case SpecialType.System_Int32:
597+
case SpecialType.System_UInt32:
598+
case SpecialType.System_Int64:
599+
case SpecialType.System_UInt64:
600+
case SpecialType.System_Single:
601+
case SpecialType.System_Double:
602+
case SpecialType.System_Decimal:
603+
case SpecialType.System_IntPtr:
604+
case SpecialType.System_UIntPtr:
605+
return true;
606+
default:
607+
break;
608+
}
609+
610+
// Check for other common blittable types
611+
var fullName = type.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat);
612+
return fullName is "global::System.Guid"
613+
or "global::System.DateTime"
614+
or "global::System.TimeSpan"
615+
or "global::System.DateTimeOffset";
616+
617+
// Note: For custom structs, we would need to recursively check all fields
618+
// For now, we're conservative and only optimize known types
619+
}
620+
578621
private static string GenerateArrayDeepClone(
579622
IPropertySymbol property,
580623
IArrayTypeSymbol arrayType
@@ -606,7 +649,23 @@ IArrayTypeSymbol arrayType
606649
}
607650
}
608651

609-
if (elementType.IsValueType || elementType.SpecialType == SpecialType.System_String)
652+
// Optimize for primitive and blittable types using span-based copy
653+
if (IsPrimitiveOrBlittableType(elementType))
654+
{
655+
// Use span-based copy for better performance - this uses memory copy under the hood
656+
return $"this.{propertyName} != null ? this.{propertyName}.AsSpan().ToArray() : null";
657+
}
658+
659+
// For string arrays, use Array.Clone (strings are immutable so shallow copy is safe)
660+
if (elementType.SpecialType == SpecialType.System_String)
661+
{
662+
var arrayTypeName =
663+
$"{elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}[]";
664+
return $"this.{propertyName} != null ? ({arrayTypeName})this.{propertyName}.Clone() : null";
665+
}
666+
667+
// For other value types (structs that may contain references), use Array.Clone
668+
if (elementType.IsValueType)
610669
{
611670
var arrayTypeName =
612671
$"{elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}[]";
@@ -697,6 +756,7 @@ INamedTypeSymbol dictionaryType
697756
{
698757
return $"this.{propertyName} != null ? new System.Collections.ObjectModel.ReadOnlyDictionary<{keyType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}, {valueType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>(this.{propertyName}.ToDictionary(kvp => kvp.Key, kvp => {valueCloneExpression})) : null";
699758
}
759+
// ReadOnlyDictionary wraps a mutable dictionary, so we need to clone it even for value types
700760
return $"this.{propertyName} != null ? new System.Collections.ObjectModel.ReadOnlyDictionary<{keyType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}, {valueType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>(new System.Collections.Generic.Dictionary<{keyType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}, {valueType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>(this.{propertyName})) : null";
701761
}
702762

@@ -848,6 +908,7 @@ bool isCloneable
848908
{
849909
return $"this.{propertyName} != null ? new System.Collections.ObjectModel.ReadOnlyCollection<{elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>(this.{propertyName}.Select(x => x?.{DeepCloneMethodName}()).ToList()) : null";
850910
}
911+
// ReadOnlyCollection wraps a mutable list, so we need to clone it even for value types
851912
return $"this.{propertyName} != null ? new System.Collections.ObjectModel.ReadOnlyCollection<{elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>(this.{propertyName}.ToList()) : null";
852913
}
853914

@@ -861,6 +922,12 @@ bool isCloneable
861922
{
862923
return $"this.{propertyName}?.Select(x => x?.{DeepCloneMethodName}()).ToImmutableList()";
863924
}
925+
// For value types and strings in immutable collections, we can safely reuse the same collection
926+
// since both the collection and elements are immutable
927+
if (elementType.IsValueType || elementType.SpecialType == SpecialType.System_String)
928+
{
929+
return $"this.{propertyName}";
930+
}
864931
return $"this.{propertyName}?.ToImmutableList()";
865932
}
866933

@@ -874,6 +941,12 @@ bool isCloneable
874941
{
875942
return $"this.{propertyName}.IsDefault ? default : this.{propertyName}.Select(x => x?.{DeepCloneMethodName}()).ToImmutableArray()";
876943
}
944+
// For value types and strings in immutable arrays, we can safely reuse the same array
945+
// since both the array and elements are immutable
946+
if (elementType.IsValueType || elementType.SpecialType == SpecialType.System_String)
947+
{
948+
return $"this.{propertyName}";
949+
}
877950
return $"this.{propertyName}.IsDefault ? default : this.{propertyName}.ToImmutableArray()";
878951
}
879952

@@ -887,6 +960,12 @@ bool isCloneable
887960
{
888961
return $"this.{propertyName}?.Select(x => x?.{DeepCloneMethodName}()).ToImmutableHashSet()";
889962
}
963+
// For value types and strings in immutable collections, we can safely reuse the same collection
964+
// since both the collection and elements are immutable
965+
if (elementType.IsValueType || elementType.SpecialType == SpecialType.System_String)
966+
{
967+
return $"this.{propertyName}";
968+
}
890969
return $"this.{propertyName}?.ToImmutableHashSet()";
891970
}
892971

@@ -900,6 +979,11 @@ bool isCloneable
900979
{
901980
return $"this.{propertyName} == null ? System.Collections.Immutable.ImmutableQueue<{elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>.Empty : System.Collections.Immutable.ImmutableQueue.CreateRange(this.{propertyName}.Select(x => x?.{DeepCloneMethodName}()))";
902981
}
982+
// For value types and strings in immutable collections, we can safely reuse the same collection
983+
if (elementType.IsValueType || elementType.SpecialType == SpecialType.System_String)
984+
{
985+
return $"this.{propertyName}";
986+
}
903987
return $"this.{propertyName} == null ? System.Collections.Immutable.ImmutableQueue<{elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>.Empty : System.Collections.Immutable.ImmutableQueue.CreateRange(this.{propertyName})";
904988
}
905989

@@ -913,6 +997,11 @@ bool isCloneable
913997
{
914998
return $"this.{propertyName} == null ? System.Collections.Immutable.ImmutableStack<{elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>.Empty : System.Collections.Immutable.ImmutableStack.CreateRange(this.{propertyName}.Select(x => x?.{DeepCloneMethodName}()))";
915999
}
1000+
// For value types and strings in immutable collections, we can safely reuse the same collection
1001+
if (elementType.IsValueType || elementType.SpecialType == SpecialType.System_String)
1002+
{
1003+
return $"this.{propertyName}";
1004+
}
9161005
return $"this.{propertyName} == null ? System.Collections.Immutable.ImmutableStack<{elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>.Empty : System.Collections.Immutable.ImmutableStack.CreateRange(this.{propertyName})";
9171006
}
9181007

@@ -957,6 +1046,8 @@ elementType is INamedTypeSymbol namedElementTypeRef
9571046
}
9581047
}
9591048

1049+
// For value types including primitives and strings, the List constructor is already optimized
1050+
// and will use Array.Copy internally which is very efficient
9601051
return $"this.{propertyName} != null ? new System.Collections.Generic.List<{elementType.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)}>(this.{propertyName}) : null";
9611052
}
9621053

‎tests/IDeepCloneable.Tests/PerformanceTests.cs‎

Lines changed: 137 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,137 @@
1+
using System;
2+
using System.Collections.Immutable;
3+
using System.Diagnostics;
4+
using System.Linq;
5+
using IDeepCloneable;
6+
7+
namespace IDeepCloneable.Tests;
8+
9+
/// <summary>
10+
/// Performance validation tests to ensure optimizations are working.
11+
/// These are not strict benchmarks but help validate that optimizations don't cause regressions.
12+
/// </summary>
13+
public class PerformanceTests
14+
{
15+
[Fact]
16+
public void DeepClone_LargeIntArray_IsFast()
17+
{
18+
// Create a large array of primitive values
19+
var original = new ClassWithLargeArray
20+
{
21+
Name = "Test",
22+
Numbers = Enumerable.Range(0, 100000).ToArray()
23+
};
24+
25+
// Warm up
26+
_ = original.DeepClone();
27+
28+
// Measure
29+
var sw = Stopwatch.StartNew();
30+
var clone = original.DeepClone();
31+
sw.Stop();
32+
33+
// Verify correctness
34+
clone.ShouldNotBeSameAs(original);
35+
clone.Numbers.ShouldNotBeNull();
36+
clone.Numbers.ShouldNotBeSameAs(original.Numbers);
37+
clone.Numbers.Length.ShouldBe(100000);
38+
39+
// Performance check: Should be fast (< 10ms for 100k integers)
40+
// This validates that we're using efficient memory copy, not element-by-element
41+
sw.ElapsedMilliseconds.ShouldBeLessThan(10);
42+
}
43+
44+
[Fact]
45+
public void DeepClone_ImmutableCollectionOfValueTypes_ReusesSameInstance()
46+
{
47+
var list = ImmutableList.Create(1, 2, 3, 4, 5);
48+
var original = new ClassWithImmutableIntList
49+
{
50+
Name = "Test",
51+
Items = list
52+
};
53+
54+
var clone = original.DeepClone();
55+
56+
// Verify that the immutable collection is reused (same instance)
57+
clone.Items.ShouldBeSameAs(original.Items);
58+
59+
// But the parent object is cloned
60+
clone.ShouldNotBeSameAs(original);
61+
}
62+
63+
[Fact]
64+
public void DeepClone_ImmutableArrayOfValueTypes_ReusesSameInstance()
65+
{
66+
var array = ImmutableArray.Create(1, 2, 3, 4, 5);
67+
var original = new ClassWithImmutableIntArray
68+
{
69+
Name = "Test",
70+
Items = array
71+
};
72+
73+
var clone = original.DeepClone();
74+
75+
// For immutable arrays of value types, the exact same array should be used
76+
// This is safe because both the array and its elements are immutable
77+
clone.Items.ShouldBe(original.Items); // Same values
78+
79+
// Verify parent is cloned
80+
clone.ShouldNotBeSameAs(original);
81+
}
82+
83+
[Fact]
84+
public void DeepClone_SpanBasedArrayCopy_IsFasterThanClone()
85+
{
86+
// This test validates that AsSpan().ToArray() is being used
87+
// by checking it's faster than reflection-based approaches would be
88+
89+
var original = new ClassWithMultipleArrays
90+
{
91+
Integers = Enumerable.Range(0, 50000).ToArray(),
92+
Doubles = Enumerable.Range(0, 50000).Select(x => (double)x).ToArray(),
93+
Booleans = Enumerable.Range(0, 50000).Select(x => x % 2 == 0).ToArray()
94+
};
95+
96+
// Warm up
97+
_ = original.DeepClone();
98+
99+
// Measure
100+
var sw = Stopwatch.StartNew();
101+
var clone = original.DeepClone();
102+
sw.Stop();
103+
104+
// Verify correctness
105+
clone.Integers.ShouldNotBeSameAs(original.Integers);
106+
clone.Doubles.ShouldNotBeSameAs(original.Doubles);
107+
clone.Booleans.ShouldNotBeSameAs(original.Booleans);
108+
109+
// Should be very fast (< 15ms for 150k total elements across 3 arrays)
110+
sw.ElapsedMilliseconds.ShouldBeLessThan(15);
111+
}
112+
}
113+
114+
public partial class ClassWithLargeArray : IDeepCloneable<ClassWithLargeArray>
115+
{
116+
public string Name { get; set; } = string.Empty;
117+
public int[]? Numbers { get; set; }
118+
}
119+
120+
public partial class ClassWithImmutableIntList : IDeepCloneable<ClassWithImmutableIntList>
121+
{
122+
public string Name { get; set; } = string.Empty;
123+
public ImmutableList<int>? Items { get; set; }
124+
}
125+
126+
public partial class ClassWithImmutableIntArray : IDeepCloneable<ClassWithImmutableIntArray>
127+
{
128+
public string Name { get; set; } = string.Empty;
129+
public ImmutableArray<int> Items { get; set; }
130+
}
131+
132+
public partial class ClassWithMultipleArrays : IDeepCloneable<ClassWithMultipleArrays>
133+
{
134+
public int[] Integers { get; set; } = Array.Empty<int>();
135+
public double[] Doubles { get; set; } = Array.Empty<double>();
136+
public bool[] Booleans { get; set; } = Array.Empty<bool>();
137+
}

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