Further restrict MetatypeInst constant folding to not constant fold classes

Author: kubamracek

SwiftCompilerSources/Sources/Optimizer/Utilities/OptUtils.swift

@@ -464,9 +464,10 @@ extension Instruction {
       return context.canMakeStaticObjectReadOnly(objectType: gvi.type)
 
     // Metatypes (and upcasts of them to existentials) can be used as static initializers for SE-0492, as long as they
-    // are not generic or resilient
+    // do not require an accessor to reference the metadata (i.e. are not generic, not resilient and not a class).
     case let mti as MetatypeInst:
       if !mti.type.isGenericAtAnyLevel,
+        !mti.type.canonicalType.instanceTypeOfMetatype.isClass,
         let nominal = mti.type.canonicalType.instanceTypeOfMetatype.nominal,
         !nominal.isGenericAtAnyLevel,
         !nominal.isResilient(in: mti.parentFunction) {

test/SILOptimizer/static_init_metatypes2.swift

@@ -0,0 +1,38 @@
+// RUN: %empty-directory(%t)
+// RUN: %{python} %utils/split_file.py -o %t %s
+
+// RUN: %target-swift-frontend -parse-as-library -emit-module -o %t/MyModule.swiftmodule %t/MyModule.swift -O
+// XXX: %target-swift-frontend -parse-as-library -I %t %t/Main.swift -O -emit-sil | %FileCheck %s --check-prefix SIL
+// RUN: %target-swift-frontend -parse-as-library -I %t %t/Main.swift -O -emit-ir | %FileCheck %s --check-prefix IR
+
+// BEGIN MyModule.swift
+
+public class MyClass {}
+public struct MyStruct {}
+
+// BEGIN Main.swift
+
+import MyModule
+
+public let classMetatype: Any.Type = MyClass.self
+public let classMetatypeArray: [Any.Type] = [classMetatype]
+
+public let structMetatype: Any.Type = MyStruct.self
+public let structMetatypeArray: [Any.Type] = [structMetatype]
+
+// SIL:       sil_global [let] @$s4Main13classMetatypeypXpvp : $@thick any Any.Type
+// SIL-EMPTY: 
+// SIL:       sil_global [let] @$s4Main18classMetatypeArraySayypXpGvp : $Array<any Any.Type>
+// SIL-EMPTY: 
+// SIL:       sil_global [let] @$s4Main14structMetatypeypXpvp : $@thick any Any.Type = {
+// SIL-NEXT:    %0 = metatype $@thick MyStruct.Type
+// SIL-NEXT:   %initval = init_existential_metatype %0, $@thick any Any.Type
+// SIL-NEXT:  }
+// SIL:       sil_global [let] @$s4Main19structMetatypeArraySayypXpGvp : $Array<any Any.Type>
+// SIL-EMPTY:
+
+// IR: @"$s4Main13classMetatypeypXpvp" = {{.*}}global { ptr } zeroinitializer
+// IR: @"$s4Main18classMetatypeArraySayypXpGvp" = {{.*}}global %TSa zeroinitializer
+// IR: @"$s8MyModule0A6StructVN" = {{.*}}global %swift.type
+// IR: @"$s4Main14structMetatypeypXpvp" = {{.*}}constant ptr @"$s8MyModule0A6StructVN"
+// IR: @"$s4Main19structMetatypeArraySayypXpGvp" = {{.*}}global %TSa zeroinitializer