IRGen: super_method: Dynamically get superclass of static base class

After talking with @jckarter and @slavapestov we decided that getting
the superclass at runtime for super_method lookup was the right approach
if its based in the static base class and the lookup doesn't start with
  the instance pointer.

NFC for current IRGen - SILGen doesn't lead to here yet.

rdar://problem/22749732

Author: bitjammer

lib/IRGen/GenMeta.cpp

@@ -4313,9 +4313,10 @@ llvm::Value *irgen::emitVirtualMethodValue(IRGenFunction &IGF,
     if (auto metaTy = dyn_cast<MetatypeType>(baseType.getSwiftRValueType()))
       baseType = SILType::getPrimitiveObjectType(metaTy.getInstanceType());
 
-    auto superType = baseType.getSuperclass(/*resolver=*/nullptr);
-    metadata = emitClassHeapMetadataRef(IGF, superType.getSwiftRValueType(),
+    metadata = emitClassHeapMetadataRef(IGF, baseType.getSwiftRValueType(),
                                         MetadataValueType::TypeMetadata);
+    auto superField = emitAddressOfSuperclassRefInClassMetadata(IGF, metadata);
+    metadata = IGF.Builder.CreateLoad(superField);
   } else {
     if ((isa<FuncDecl>(methodDecl) && cast<FuncDecl>(methodDecl)->isStatic()) ||
         (isa<ConstructorDecl>(methodDecl) &&

test/IRGen/super_class_method.sil

@@ -47,11 +47,12 @@ sil_vtable Child {
 sil_vtable Grandchild {
   #Parent.foo!1: Grandchild_foo
 }
-
 // CHECK-LABEL: define void @Grandchild_foo(%swift.type*) #0
-// CHECK: [[CHILD_METADATA_PTR:%[0-9]+]] = call %swift.type* @_TMaC18super_class_method5Child()
-// CHECK: [[CASTED_CHILD_METADATA_PTR:%[0-9]+]] = bitcast %swift.type* [[CHILD_METADATA_PTR]] to void (%swift.type*)**
-// CHECK: [[FOO_VTABLE_SLOT:%[0-9]+]] = getelementptr inbounds void (%swift.type*)*, void (%swift.type*)** [[CASTED_CHILD_METADATA_PTR]]
-// CHECK: [[FOO_FNPTR:%[0-9]+]] = load void (%swift.type*)*, void (%swift.type*)** [[FOO_VTABLE_SLOT]]
+// CHECK: [[CHILD_METADATA_PTR:%[0-9]+]] = call %swift.type* @_TMaC18super_class_method10Grandchild()
+// CHECK: [[OPAQUE_CHILD_METADATA_PTR:%[0-9]+]] = bitcast %swift.type* [[CHILD_METADATA_PTR]] to %swift.type**
+// CHECK: [[SUPER_METADATA_PTR:%[0-9]+]] = getelementptr inbounds %swift.type*, %swift.type** [[OPAQUE_CHILD_METADATA_PTR]], i32 1
+// CHECK: [[SUPER_METADATA:%[0-9]+]] = load %swift.type*, %swift.type** [[SUPER_METADATA_PTR]]
+// CHECK: [[OPAQUE_SUPER_METADATA_PTR:%[0-9]+]] = bitcast %swift.type* [[SUPER_METADATA]] to void (%swift.type*)**
+// CHECK: [[FOO_VTABLE_SLOT:%[0-9]+]] = getelementptr inbounds void (%swift.type*)*, void (%swift.type*)** [[OPAQUE_SUPER_METADATA_PTR]]
+// CHECK: [[FOO_FN_PTR:%[0-9]+]] = load void (%swift.type*)*, void (%swift.type*)** [[FOO_VTABLE_SLOT]]
 // CHECK: call void
-

test/IRGen/super_instance_method.sil

@@ -49,9 +49,11 @@ sil_vtable Grandchild {
 }
 
 // CHECK-LABEL: define void @Grandchild_foo(%C21super_instance_method10Grandchild*)
-// CHECK: [[CHILD_METADATA_PTR:%[0-9]+]] = call %swift.type* @_TMaC21super_instance_method5Child()
-// CHECK: [[CASTED_CHILD_METADATA_PTR:%[0-9]+]] = bitcast %swift.type* [[CHILD_METADATA_PTR]] to void (%C21super_instance_method6Parent*)**
-// CHECK: [[FOO_VTABLE_SLOT:%[0-9]+]] = getelementptr inbounds void (%C21super_instance_method6Parent*)*, void (%C21super_instance_method6Parent*)** [[CASTED_CHILD_METADATA_PTR]]
+// CHECK: [[GRANDCHILD_METADATA_PTR:%[0-9]+]] = call %swift.type* @_TMaC21super_instance_method10Grandchild()
+// CHECK: [[OPAQUE_METADATA_PTR:%[0-9]+]] = bitcast %swift.type* %4 to %swift.type**
+// CHECK: [[SUPER_METADATA_PTR:%[0-9]+]] = getelementptr inbounds %swift.type*, %swift.type** [[OPAQUE_METADATA_PTR]], i32 1
+// CHECK: [[SUPER_METADATA:%[0-9]+]] = load %swift.type*, %swift.type** [[SUPER_METADATA_PTR]]
+// CHECK: [[PARENT_METADATA:%[0-9]+]] = bitcast %swift.type* [[SUPER_METADATA]] to void (%C21super_instance_method6Parent*)**
+// CHECK: [[FOO_VTABLE_SLOT:%[0-9]+]] = getelementptr inbounds void (%C21super_instance_method6Parent*)*, void (%C21super_instance_method6Parent*)** [[PARENT_METADATA]]
 // CHECK: [[FOO_FN_PTR:%[0-9]+]] = load void (%C21super_instance_method6Parent*)*, void (%C21super_instance_method6Parent*)** [[FOO_VTABLE_SLOT]]
 // CHECK: call void
-