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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;
using System.Diagnostics;
using Internal.TypeSystem;
namespace Internal.Runtime
{
internal static class UniversalGenericParameterLayout
{
private enum HasVarsInvestigationLevel
{
Parameter,
NotParameter
}
/// <summary>
/// IF THESE SEMANTICS EVER CHANGE UPDATE THE LOGIC WHICH DEFINES THIS BEHAVIOR IN
/// THE DYNAMIC TYPE LOADER AS WELL AS THE COMPILER.
/// (There is a version of this in TypeLoaderEnvironment.SignatureParsing.cs that must be kept in sync with this.)
///
/// Parameter's are considered to have type layout dependent on their generic instantiation
/// if the type of the parameter in its signature is a type variable, or if the type is a generic
/// structure which meets 2 characteristics:
/// 1. Structure size/layout is affected by the size/layout of one or more of its generic parameters
/// 2. One or more of the generic parameters is a type variable, or a generic structure which also recursively
/// would satisfy constraint 2. (Note, that in the recursion case, whether or not the structure is affected
/// by the size/layout of its generic parameters is not investigated.)
///
/// Examples parameter types, and behavior.
///
/// T = true
/// List[T] = false
/// StructNotDependentOnArgsForSize[T] = false
/// GenStructDependencyOnArgsForSize[T] = true
/// StructNotDependentOnArgsForSize[GenStructDependencyOnArgsForSize[T]] = true
/// StructNotDependentOnArgsForSize[GenStructDependencyOnArgsForSize[List[T]]]] = false
///
/// Example non-parameter type behavior
/// T = true
/// List[T] = false
/// StructNotDependentOnArgsForSize[T] = *true*
/// GenStructDependencyOnArgsForSize[T] = true
/// StructNotDependentOnArgsForSize[GenStructDependencyOnArgsForSize[T]] = true
/// StructNotDependentOnArgsForSize[GenStructDependencyOnArgsForSize[List[T]]]] = false
/// </summary>
public static bool IsLayoutDependentOnGenericInstantiation(TypeDesc type)
{
return IsLayoutDependentOnGenericInstantiation(type, HasVarsInvestigationLevel.Parameter);
}
private static bool IsLayoutDependentOnGenericInstantiation(TypeDesc type, HasVarsInvestigationLevel investigationLevel)
{
if (type.IsSignatureVariable)
{
return true;
}
else if (type.HasInstantiation && type.IsValueType)
{
foreach (TypeDesc valueTypeInstantiationParam in type.Instantiation)
{
if (IsLayoutDependentOnGenericInstantiation(valueTypeInstantiationParam, HasVarsInvestigationLevel.NotParameter))
{
if (investigationLevel == HasVarsInvestigationLevel.Parameter)
{
DefType universalCanonForm = (DefType)type.ConvertToCanonForm(CanonicalFormKind.Universal);
return universalCanonForm.InstanceFieldSize.IsIndeterminate;
}
else
{
return true;
}
}
}
return false;
}
else
{
// All other forms of type do not change their shape dependent on signature variables.
return false;
}
}
public static bool MethodSignatureHasVarsNeedingCallingConventionConverter(TypeSystem.MethodSignature methodSignature)
{
if (IsLayoutDependentOnGenericInstantiation(methodSignature.ReturnType, HasVarsInvestigationLevel.Parameter))
return true;
for (int i = 0; i < methodSignature.Length; i++)
{
if (IsLayoutDependentOnGenericInstantiation(methodSignature[i], HasVarsInvestigationLevel.Parameter))
return true;
}
return false;
}
public static bool VTableMethodRequiresCallingConventionConverter(MethodDesc method)
{
if (!MethodSignatureHasVarsNeedingCallingConventionConverter(method.GetTypicalMethodDefinition().Signature))
return false;
MethodDesc slotDecl = MetadataVirtualMethodAlgorithm.FindSlotDefiningMethodForVirtualMethod(method).GetCanonMethodTarget(CanonicalFormKind.Specific);
return slotDecl.IsCanonicalMethod(CanonicalFormKind.Universal);
}
}
}
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