Do not run validation on runtime determined types (#1357)

It doesn't seem like we validate anything for those and `IsRuntimeDeterminedSubtype` check is rather expensive.

src/coreclr/src/tools/Common/Compiler/CompilerTypeSystemContext.Validation.cs

@@ -76,14 +76,11 @@ private static TypeDesc EnsureLoadableTypeUncached(TypeDesc type)
                         ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadGeneral, type);
                     }
 
-                    if (!parameterType.IsRuntimeDeterminedSubtype)
+                    LayoutInt elementSize = parameterType.GetElementSize();
+                    if (!elementSize.IsIndeterminate && elementSize.AsInt >= ushort.MaxValue)
                     {
-                        LayoutInt elementSize = parameterType.GetElementSize();
-                        if (!elementSize.IsIndeterminate && elementSize.AsInt >= ushort.MaxValue)
-                        {
-                            // Element size over 64k can't be encoded in the GCDesc
-                            ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadValueClassTooLarge, parameterType);
-                        }
+                        // Element size over 64k can't be encoded in the GCDesc
+                        ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadValueClassTooLarge, parameterType);
                     }
 
                     if (((ArrayType)parameterizedType).Rank > 32)
@@ -105,17 +102,19 @@ private static TypeDesc EnsureLoadableTypeUncached(TypeDesc type)
             {
                 ThrowHelper.ThrowTypeLoadException(ExceptionStringID.ClassLoadGeneral, type);
             }
+#if READYTORUN
             else if (type.IsGenericParameter)
             {
                 return type;
             }
+#endif
             else
             {
                 // Validate classes, structs, enums, interfaces, and delegates
                 Debug.Assert(type.IsDefType);
 
-                // Don't validate generic definitons or runtime determined subtypes
-                if (type.IsGenericDefinition || type.IsRuntimeDeterminedSubtype)
+                // Don't validate generic definitons
+                if (type.IsGenericDefinition)
                 {
                     return type;
                 }

src/coreclr/src/tools/crossgen2/ILCompiler.ReadyToRun/Compiler/DependencyAnalysis/ReadyToRun/GenericLookupSignature.cs

@@ -46,22 +46,6 @@ public class GenericLookupSignature : Signature
             _fieldArgument = fieldArgument;
             _methodContext = methodContext;
             _signatureContext = signatureContext;
-
-            // Ensure types in signature are loadable and resolvable, otherwise we'll fail later while emitting the signature
-            if (typeArgument != null)
-            {
-                signatureContext.Resolver.CompilerContext.EnsureLoadableType(typeArgument);
-            }
-            if (fieldArgument != null)
-            {
-                signatureContext.Resolver.CompilerContext.EnsureLoadableType(fieldArgument.OwningType);
-            }
-            if (methodArgument != null)
-            {
-                signatureContext.Resolver.CompilerContext.EnsureLoadableMethod(methodArgument.Method);
-                if (methodArgument.ConstrainedType != null)
-                    signatureContext.Resolver.CompilerContext.EnsureLoadableType(methodArgument.ConstrainedType);
-            }
         }
 
         public override int ClassCode => 258608008;