[4.2] CastOptimizer: A load store to the existential box is not valid on address only types

rdar://40949457

Author: aschwaighofer

lib/SILOptimizer/Utils/CastOptimizer.cpp

@@ -1440,10 +1440,7 @@ static bool optimizeStaticallyKnownProtocolConformance(
                                                       SourceType, Conformances);
           auto Projection =
               B.createProjectExistentialBox(Loc, Src->getType(), AllocBox);
-          auto Value = B.createLoad(Loc, Src,
-                                    swift::LoadOwnershipQualifier::Unqualified);
-          B.createStore(Loc, Value, Projection,
-                        swift::StoreOwnershipQualifier::Unqualified);
+          B.createCopyAddr(Loc, Src, Projection, IsTake, IsInitialization);
           B.createStore(Loc, AllocBox, Dest,
                         swift::StoreOwnershipQualifier::Unqualified);
           break;

test/SILOptimizer/sil_combine_objc_bridge.sil

@@ -197,3 +197,28 @@ bb0(%0 : $*NSObject, %1 : $*Array<String>):
   return %7 : $()
 }
 
+enum AddressOnlyError : Error {
+  case data(Data)
+  case none
+}
+
+// CHECK-LABEL: sil @unconditional_checked_cast_addr_address_only_type
+// CHECK: alloc_stack $Error
+// CHECK: alloc_stack $AddressOnlyError
+// CHECK  copy_addr
+// CHECK: alloc_existential_box
+// CHECK: project_existential_box
+// CHECK: copy_addr
+// CHECK: store
+sil @unconditional_checked_cast_addr_address_only_type: $@convention(thin) (@in_guaranteed AddressOnlyError) -> @owned Error {
+bb0(%0 : $*AddressOnlyError):
+  %1 = alloc_stack $Error
+  %2 = alloc_stack $AddressOnlyError
+  copy_addr %0 to [initialization] %2 : $*AddressOnlyError
+  unconditional_checked_cast_addr AddressOnlyError in %2 : $*AddressOnlyError to Error in %1 : $*Error
+  dealloc_stack %2 : $*AddressOnlyError
+  %8 = tuple ()
+  %9 = load %1 : $*Error
+  dealloc_stack %1 : $*Error
+  return %9 : $Error
+}