Speed up RuntimeType.GetHashCode

src/coreclr/System.Private.CoreLib/src/System/RuntimeType.CoreCLR.cs

@@ -2341,6 +2341,22 @@ private static bool FilterApplyMethodBase(
 
         #endregion
 
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public override int GetHashCode()
+        {
+            // CLSID types share the __ComObject handle, so preserve their identity hashes.
+            if (IsGenericCOMObjectImpl())
+                return RuntimeHelpers.GetHashCode(this);
+
+            // Fibonacci hashing moves the entropy in aligned handles into the high bits.
+#if TARGET_64BIT
+            return (int)(((ulong)(nuint)m_handle * 0x9E3779B97F4A7C15UL) >> 32);
+#else
+            uint hash = (uint)(nuint)m_handle * 0x9E3779B9U;
+            return (int)(hash ^ (hash >> 16));
+#endif
+        }
+
         #region Private\Internal Members
 
         internal unsafe TypeHandle GetNativeTypeHandle()
@@ -3318,8 +3334,7 @@ public override unsafe Guid GUID
                 Guid result;
 #if FEATURE_COMINTEROP
                 Debug.Assert(OperatingSystem.IsWindows());
-                // The fully qualified name is needed since the RuntimeType has a TypeHandle property.
-                if (System.Runtime.CompilerServices.TypeHandle.AreSameType(th, System.Runtime.CompilerServices.TypeHandle.TypeHandleOf<__ComObject>()))
+                if (IsGenericCOMObjectImpl())
                 {
                     GetComObjectGuidWorker(this, &result);
                 }
@@ -4045,7 +4060,8 @@ internal void CallDefaultStructConstructor(ref byte data)
         protected override bool IsCOMObjectImpl() => RuntimeTypeHandle.CanCastTo(this, (RuntimeType)typeof(__ComObject));
 
         // We need to check the type handle values - not the instances - to determine if the runtime type is a generic ComObject.
-        internal bool IsGenericCOMObjectImpl() => TypeHandle.Value == typeof(__ComObject).TypeHandle.Value;
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        internal bool IsGenericCOMObjectImpl() => m_handle == RuntimeTypeHandle.ToIntPtr(typeof(__ComObject).TypeHandle);
 #else
         protected override bool IsCOMObjectImpl() => false;
 

src/coreclr/nativeaot/System.Private.CoreLib/src/System/RuntimeType.NativeAot.cs

@@ -212,7 +212,15 @@ public override int GetHashCode()
         {
             MethodTable* pEEType = _pUnderlyingEEType;
             if (pEEType != null)
-                return ((nuint)pEEType).GetHashCode();
+            {
+                // Fibonacci hashing moves the entropy in aligned handles into the high bits.
+#if TARGET_64BIT
+                return (int)(((ulong)(nuint)pEEType * 0x9E3779B97F4A7C15UL) >> 32);
+#else
+                uint hash = (uint)(nuint)pEEType * 0x9E3779B9U;
+                return (int)(hash ^ (hash >> 16));
+#endif
+            }
             return RuntimeHelpers.GetHashCode(this);
         }
 

src/libraries/System.Private.CoreLib/src/System/Collections/Generic/EqualityComparer.cs

@@ -153,7 +153,7 @@ public override bool Equals(T? x, T? y)
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public override int GetHashCode([DisallowNull] T obj) =>
-            obj?.GetHashCode() ?? 0;
+            obj is null ? 0 : obj.GetHashCode();
 
         // Equals method for the comparer itself.
         public override bool Equals([NotNullWhen(true)] object? obj) =>
@@ -222,7 +222,7 @@ public override bool Equals(T? x, T? y)
 
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public override int GetHashCode([DisallowNull] T obj) =>
-            obj?.GetHashCode() ?? 0;
+            obj is null ? 0 : obj.GetHashCode();
 
         // Equals method for the comparer itself.
         public override bool Equals([NotNullWhen(true)] object? obj) =>
@@ -320,7 +320,7 @@ void ISerializable.GetObjectData(SerializationInfo info, StreamingContext contex
 
         public override bool Equals(string? x, string? y) => string.Equals(x, y);
 
-        public override int GetHashCode([DisallowNull] string obj) => obj?.GetHashCode() ?? 0;
+        public override int GetHashCode([DisallowNull] string obj) => obj is null ? 0 : obj.GetHashCode();
 
         public bool Equals(ReadOnlySpan<char> span, string target)
         {

src/libraries/System.Private.CoreLib/src/System/RuntimeType.cs

@@ -184,8 +184,6 @@ public override Type GetEnumUnderlyingType()
             return Enum.InternalGetUnderlyingType(this);
         }
 
-        public override int GetHashCode() => RuntimeHelpers.GetHashCode(this);
-
         internal RuntimeModule GetRuntimeModule() => RuntimeTypeHandle.GetModule(this);
 
         protected override TypeCode GetTypeCodeImpl()

src/mono/System.Private.CoreLib/src/System/RuntimeType.Mono.cs

@@ -1486,6 +1486,8 @@ public override int GenericParameterPosition
 
         #endregion
 
+        public override int GetHashCode() => RuntimeHelpers.GetHashCode(this);
+
         public static bool operator ==(RuntimeType? left, RuntimeType? right)
         {
             return ReferenceEquals(left, right);