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Avoid allocations in CanWrap... methods #3711

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Oct 18, 2023
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Avoid allocations in CanWrap... methods #3711

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16c310e
Avoid allocations in CanWrap... methods
martin-strecker-sonarsource Oct 16, 2023
b5fd4b5
Remove local function
martin-strecker-sonarsource Oct 17, 2023
3386603
Revert changes for static delegate
martin-strecker-sonarsource Oct 17, 2023
12b6f93
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martin-strecker-sonarsource Oct 17, 2023
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60 changes: 36 additions & 24 deletions StyleCop.Analyzers/StyleCop.Analyzers/Lightup/LightupHelpers.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -65,18 +65,22 @@ internal static bool CanWrapObject(object obj, Type underlyingType)
return false;
}

ConcurrentDictionary<Type, bool> wrappedObject = SupportedObjectWrappers.GetOrAdd(underlyingType, _ => new ConcurrentDictionary<Type, bool>());
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Was there an actual problem with this first lookup (in each method)? I haven't dug into your IL comparison, but since no capture is needed, it seems the only possible overhead would be creating the func instance. I think I recall that lambdas are automatically detected to be static if possible, but in case that is not correct, wouldn't simply marking the lambda as static be the best change?

ConcurrentDictionary<Type, bool> wrappedObject = SupportedObjectWrappers.GetOrAdd(underlyingType, static _ => new ConcurrentDictionary<Type, bool>());

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The IL confirmed that the delegate instance is indeed cached between calls in a static field:

// Load the delegate instance from a static field  
    IL_0033: ldsfld       class System.Func`2<System.Type, ConcurrentDictionary`2<SyntaxKind, bool>> StyleCop.Analyzers.Lightup.LightupHelpers/'<>c'::'<>9__30_0'
    IL_0038: dup
// Branch if not null?
    IL_0039: brtrue.s     IL_0052
    IL_003b: pop
// ..
// Create the delegate
    IL_0047: newobj       instance void class System.Func`2<System.Type, ConcurrentDictionary`2<SyntaxKind, bool>>::.ctor(object, native int)
    IL_004c: dup
// Store it
    IL_004d: stsfld       class System.Func`2<System.Type, ConcurrentDictionary`2<SyntaxKind, bool>> StyleCop.Analyzers.Lightup.LightupHelpers/'<>c'::'<>9__30_0'
// Invoke the delegate
    IL_0052: callvirt     instance !1/*class [System.Collections.Concurrent]System.Collections.Concurrent.ConcurrentDictionary`2<valuetype [Microsoft.CodeAnalysis.CSharp]Microsoft.CodeAnalysis.CSharp.SyntaxKind, bool>*/ class [System.Collections.Concurrent]System.Collections.Concurrent.ConcurrentDictionary`2<class [System.Runtime]System.Type, class [System.Collections.Concurrent]System.Collections.Concurrent.ConcurrentDictionary`2<valuetype [Microsoft.CodeAnalysis.CSharp]Microsoft.CodeAnalysis.CSharp.SyntaxKind, bool>>::GetOrAdd(!0/*class [System.Runtime]System.Type*/, class [System.Runtime]System.Func`2<!0/*class [System.Runtime]System.Type*/, !1/*class [System.Collections.Concurrent]System.Collections.Concurrent.ConcurrentDictionary`2<valuetype [Microsoft.CodeAnalysis.CSharp]Microsoft.CodeAnalysis.CSharp.SyntaxKind, bool>*/>)

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📝 This line does not need to change.

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I just kept the static to emphasize the non-capturing semantic of the lambda.


// Avoid creating the delegate if the value already exists
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📝 This comment is sufficient for the method (it already states the complete intent, and it's just a simple bug that we didn't adhere to it)

bool canCast;
if (!wrappedObject.TryGetValue(obj.GetType(), out canCast))
if (!SupportedObjectWrappers.TryGetValue(underlyingType, out var wrappedObject))
{
canCast = wrappedObject.GetOrAdd(
obj.GetType(),
kind => underlyingType.GetTypeInfo().IsAssignableFrom(obj.GetType().GetTypeInfo()));
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📝 This line is the source of the capturing allocation (specifically, capturing a method parameter in a lambda forces the the capture to be allocated on all paths and not just the one that creates this delegate).

wrappedObject = SupportedObjectWrappers.GetOrAdd(underlyingType, static _ => new ConcurrentDictionary<Type, bool>());
}

return canCast;
// Avoid creating the delegate and capture class if the value already exists
return wrappedObject.TryGetValue(obj.GetType(), out var canCast)
? canCast
: GetOrAdd(obj, underlyingType, wrappedObject);

// Don't inline this method. Otherwise a capture class is generated on each call to CanWrapObject.
static bool GetOrAdd(object obj, Type underlyingType, ConcurrentDictionary<Type, bool> wrappedObject)
=> wrappedObject.GetOrAdd(
obj.GetType(),
kind => underlyingType.GetTypeInfo().IsAssignableFrom(obj.GetType().GetTypeInfo()));
}

internal static bool CanWrapNode(SyntaxNode node, Type underlyingType)
Expand All @@ -93,18 +97,22 @@ internal static bool CanWrapNode(SyntaxNode node, Type underlyingType)
return false;
}

ConcurrentDictionary<SyntaxKind, bool> wrappedSyntax = SupportedSyntaxWrappers.GetOrAdd(underlyingType, _ => new ConcurrentDictionary<SyntaxKind, bool>());

// Avoid creating the delegate if the value already exists
bool canCast;
if (!wrappedSyntax.TryGetValue(node.Kind(), out canCast))
if (!SupportedSyntaxWrappers.TryGetValue(underlyingType, out var wrappedSyntax))
{
canCast = wrappedSyntax.GetOrAdd(
node.Kind(),
kind => underlyingType.GetTypeInfo().IsAssignableFrom(node.GetType().GetTypeInfo()));
wrappedSyntax = SupportedSyntaxWrappers.GetOrAdd(underlyingType, static _ => new ConcurrentDictionary<SyntaxKind, bool>());
}

return canCast;
// Avoid creating the delegate and capture class if the value already exists
return wrappedSyntax.TryGetValue(node.Kind(), out var canCast)
? canCast
: GetOrAdd(node, underlyingType, wrappedSyntax);

// Don't inline this method. Otherwise a capture class is generated on each call to CanWrapNode.
static bool GetOrAdd(SyntaxNode node, Type underlyingType, ConcurrentDictionary<SyntaxKind, bool> wrappedSyntax) =>
wrappedSyntax.GetOrAdd(
node.Kind(),
kind => underlyingType.GetTypeInfo().IsAssignableFrom(node.GetType().GetTypeInfo()));
}

internal static bool CanWrapOperation(IOperation operation, Type underlyingType)
Expand All @@ -121,18 +129,22 @@ internal static bool CanWrapOperation(IOperation operation, Type underlyingType)
return false;
}

ConcurrentDictionary<OperationKind, bool> wrappedSyntax = SupportedOperationWrappers.GetOrAdd(underlyingType, _ => new ConcurrentDictionary<OperationKind, bool>());

// Avoid creating the delegate if the value already exists
bool canCast;
if (!wrappedSyntax.TryGetValue(operation.Kind, out canCast))
if (!SupportedOperationWrappers.TryGetValue(underlyingType, out var wrappedSyntax))
{
canCast = wrappedSyntax.GetOrAdd(
operation.Kind,
kind => underlyingType.GetTypeInfo().IsAssignableFrom(operation.GetType().GetTypeInfo()));
wrappedSyntax = SupportedOperationWrappers.GetOrAdd(underlyingType, static _ => new ConcurrentDictionary<OperationKind, bool>());
}

return canCast;
// Avoid creating the delegate if the value already exists
return wrappedSyntax.TryGetValue(operation.Kind, out var canCast)
? canCast
: GetOrAdd(operation, underlyingType, wrappedSyntax);

// Don't inline this method. Otherwise a capture class is generated on each call to CanWrapOperation.
static bool GetOrAdd(IOperation operation, Type underlyingType, ConcurrentDictionary<OperationKind, bool> wrappedSyntax) =>
wrappedSyntax.GetOrAdd(
operation.Kind,
kind => underlyingType.GetTypeInfo().IsAssignableFrom(operation.GetType().GetTypeInfo()));
}

internal static Func<TOperation, TProperty> CreateOperationPropertyAccessor<TOperation, TProperty>(Type type, string propertyName)
Expand Down