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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
using System.Collections.Generic;
using Internal.TypeSystem;
using Debug = System.Diagnostics.Debug;
namespace Internal.IL.Stubs
{
/// <summary>
/// Intrinsic support arround EqualityComparer<T> and Comparer<T>.
/// </summary>
public static class ComparerIntrinsics
{
/// <summary>
/// Generates a specialized method body for Comparer`1.Create or returns null if no specialized body can be generated.
/// </summary>
public static MethodIL EmitComparerCreate(MethodDesc target)
{
return EmitComparerAndEqualityComparerCreateCommon(target, "Comparer", "IComparable`1");
}
/// <summary>
/// Generates a specialized method body for EqualityComparer`1.Create or returns null if no specialized body can be generated.
/// </summary>
public static MethodIL EmitEqualityComparerCreate(MethodDesc target)
{
return EmitComparerAndEqualityComparerCreateCommon(target, "EqualityComparer", "IEquatable`1");
}
/// <summary>
/// Gets the concrete type Comparer`1.Create returns or null if it's not known at compile time.
/// </summary>
public static TypeDesc GetComparerForType(TypeDesc comparand)
{
return GetComparerForType(comparand, "Comparer", "IComparable`1");
}
/// <summary>
/// Gets the concrete type EqualityComparer`1.Create returns or null if it's not known at compile time.
/// </summary>
public static TypeDesc GetEqualityComparerForType(TypeDesc comparand)
{
return GetComparerForType(comparand, "EqualityComparer", "IEquatable`1");
}
private static MethodIL EmitComparerAndEqualityComparerCreateCommon(MethodDesc methodBeingGenerated, string flavor, string interfaceName)
{
// We expect the method to be fully instantiated
Debug.Assert(!methodBeingGenerated.IsTypicalMethodDefinition);
TypeDesc owningType = methodBeingGenerated.OwningType;
TypeDesc comparedType = owningType.Instantiation[0];
// If the type is canonical, we use the default implementation provided by the class library.
// This will rely on the type loader to load the proper type at runtime.
if (comparedType.IsCanonicalSubtype(CanonicalFormKind.Any))
return null;
TypeDesc comparerType = GetComparerForType(comparedType, flavor, interfaceName);
Debug.Assert(comparerType != null);
ILEmitter emitter = new ILEmitter();
var codeStream = emitter.NewCodeStream();
FieldDesc defaultField = owningType.GetKnownField("s_default");
TypeSystemContext context = comparerType.Context;
TypeDesc objectType = context.GetWellKnownType(WellKnownType.Object);
MethodDesc compareExchangeObject = context.SystemModule.
GetKnownType("System.Threading", "Interlocked").
GetKnownMethod("CompareExchange",
new MethodSignature(
MethodSignatureFlags.Static,
genericParameterCount: 0,
returnType: objectType,
parameters: new TypeDesc[] { objectType.MakeByRefType(), objectType, objectType }));
codeStream.Emit(ILOpcode.ldsflda, emitter.NewToken(defaultField));
codeStream.Emit(ILOpcode.newobj, emitter.NewToken(comparerType.GetParameterlessConstructor()));
codeStream.Emit(ILOpcode.ldnull);
codeStream.Emit(ILOpcode.call, emitter.NewToken(compareExchangeObject));
codeStream.Emit(ILOpcode.pop);
codeStream.Emit(ILOpcode.ldsfld, emitter.NewToken(defaultField));
codeStream.Emit(ILOpcode.ret);
return emitter.Link(methodBeingGenerated);
}
/// <summary>
/// Gets the comparer type that is suitable to compare instances of <paramref name="type"/>
/// or null if such comparer cannot be determined at compile time.
/// </summary>
private static TypeDesc GetComparerForType(TypeDesc type, string flavor, string interfaceName)
{
TypeSystemContext context = type.Context;
if (context.IsCanonicalDefinitionType(type, CanonicalFormKind.Any) ||
(type.IsRuntimeDeterminedSubtype && !type.HasInstantiation))
{
// The comparer will be determined at runtime. We can't tell the exact type at compile time.
return null;
}
else if (type.IsNullable)
{
TypeDesc nullableType = type.Instantiation[0];
if (context.IsCanonicalDefinitionType(nullableType, CanonicalFormKind.Universal))
{
// We can't tell at compile time either.
return null;
}
return context.SystemModule.GetKnownType("System.Collections.Generic", $"Nullable{flavor}`1")
.MakeInstantiatedType(nullableType);
}
else if (type.IsEnum)
{
// Enums have a specialized comparer that avoids boxing
return context.SystemModule.GetKnownType("System.Collections.Generic", $"Enum{flavor}`1")
.MakeInstantiatedType(type);
}
else if (ImplementsInterfaceOfSelf(type, interfaceName))
{
return context.SystemModule.GetKnownType("System.Collections.Generic", $"Generic{flavor}`1")
.MakeInstantiatedType(type);
}
return context.SystemModule.GetKnownType("System.Collections.Generic", $"Object{flavor}`1")
.MakeInstantiatedType(type);
}
public static TypeDesc[] GetPotentialComparersForType(TypeDesc type)
{
return GetPotentialComparersForTypeCommon(type, "Comparer", "IComparable`1");
}
public static TypeDesc[] GetPotentialEqualityComparersForType(TypeDesc type)
{
return GetPotentialComparersForTypeCommon(type, "EqualityComparer", "IEquatable`1");
}
/// <summary>
/// Gets the set of template types needed to support loading comparers for the give canonical type at runtime.
/// </summary>
private static TypeDesc[] GetPotentialComparersForTypeCommon(TypeDesc type, string flavor, string interfaceName)
{
Debug.Assert(type.IsCanonicalSubtype(CanonicalFormKind.Any));
TypeDesc exactComparer = GetComparerForType(type, flavor, interfaceName);
if (exactComparer != null)
{
// If we have a comparer that is exactly known at runtime, we're done.
// This will typically be if type is a generic struct, generic enum, or a nullable.
return new TypeDesc[] { exactComparer };
}
TypeSystemContext context = type.Context;
if (context.IsCanonicalDefinitionType(type, CanonicalFormKind.Universal))
{
// This can be any of the comparers we have.
ArrayBuilder<TypeDesc> universalComparers = default(ArrayBuilder<TypeDesc>);
universalComparers.Add(context.SystemModule.GetKnownType("System.Collections.Generic", $"Nullable{flavor}`1")
.MakeInstantiatedType(type));
if (flavor == "EqualityComparer")
universalComparers.Add(context.SystemModule.GetKnownType("System.Collections.Generic", $"Enum{flavor}`1")
.MakeInstantiatedType(type));
universalComparers.Add(context.SystemModule.GetKnownType("System.Collections.Generic", $"Generic{flavor}`1")
.MakeInstantiatedType(type));
universalComparers.Add(context.SystemModule.GetKnownType("System.Collections.Generic", $"Object{flavor}`1")
.MakeInstantiatedType(type));
return universalComparers.ToArray();
}
// This mirrors exactly what GetUnknownEquatableComparer and GetUnknownComparer (in the class library)
// will need at runtime. This is the general purpose code path that can be used to compare
// anything.
if (type.IsNullable)
{
TypeDesc nullableType = type.Instantiation[0];
// This should only be reachabe for universal canon code.
// For specific canon, this should have been an exact match above.
Debug.Assert(context.IsCanonicalDefinitionType(nullableType, CanonicalFormKind.Universal));
return new TypeDesc[]
{
context.SystemModule.GetKnownType("System.Collections.Generic", $"Nullable{flavor}`1")
.MakeInstantiatedType(nullableType),
context.SystemModule.GetKnownType("System.Collections.Generic", $"Object{flavor}`1")
.MakeInstantiatedType(type),
};
}
return new TypeDesc[]
{
context.SystemModule.GetKnownType("System.Collections.Generic", $"Generic{flavor}`1")
.MakeInstantiatedType(type),
context.SystemModule.GetKnownType("System.Collections.Generic", $"Object{flavor}`1")
.MakeInstantiatedType(type),
};
}
public static bool ImplementsIEquatable(TypeDesc type)
=> ImplementsInterfaceOfSelf(type, "IEquatable`1");
private static bool ImplementsInterfaceOfSelf(TypeDesc type, string interfaceName)
{
MetadataType interfaceType = null;
foreach (TypeDesc implementedInterface in type.RuntimeInterfaces)
{
Instantiation interfaceInstantiation = implementedInterface.Instantiation;
if (interfaceInstantiation.Length == 1 &&
interfaceInstantiation[0] == type)
{
interfaceType ??= interfaceType = type.Context.SystemModule.GetKnownType("System", interfaceName);
if (implementedInterface.GetTypeDefinition() == interfaceType)
return true;
}
}
return false;
}
}
}
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