[runtime] Remove _swift_getSuperclass(). (#12988)

There are too many superclass-lookup functions.
This one does not pull its own weight.

Author: Greg Parker

stdlib/public/runtime/Casting.cpp

@@ -259,7 +259,7 @@ _dynamicCastClassMetatype(const ClassMetadata *sourceType,
     if (sourceType == targetType) {
       return sourceType;
     }
-    sourceType = _swift_getSuperclass(sourceType);
+    sourceType = sourceType->SuperClass;
   } while (sourceType);
 
   return nullptr;

stdlib/public/runtime/Private.h

@@ -116,11 +116,6 @@ namespace swift {
   LLVM_LIBRARY_VISIBILITY
   const ClassMetadata *_swift_getClass(const void *object);
 
-  static inline
-  const ClassMetadata *_swift_getSuperclass(const ClassMetadata *theClass) {
-    return theClass->SuperClass;
-  }
-
   LLVM_LIBRARY_VISIBILITY
   bool usesNativeSwiftReferenceCounting(const ClassMetadata *theClass);
 

stdlib/public/runtime/Reflection.mm

@@ -761,14 +761,14 @@ void swift_ClassMirror_subscript(String *outString,
 intptr_t swift_ObjCMirror_count(HeapObject *owner,
                                 const OpaqueValue *value,
                                 const Metadata *type) {
-  auto isa = (Class)type;
+  auto isa = (const ClassMetadata *)type;
 
   unsigned count = 0;
   // ObjC makes no guarantees about the state of ivars, so we can't safely
   // introspect them in the general case.
 
   // The superobject counts as a child.
-  if (_swift_getSuperclass((const ClassMetadata*) isa))
+  if (isa->SuperClass)
     count += 1;
 
   swift_release(owner);
@@ -790,7 +790,7 @@ void swift_ObjCMirror_subscript(String *outString,
   auto isa = (Class)type;
 
   // If there's a superclass, it becomes the first child.
-  if (auto sup = (Class) _swift_getSuperclass((const ClassMetadata*) isa)) {
+  if (auto sup = class_getSuperclass(isa)) {
     if (i == 0) {
       const char *supName = class_getName(sup);
       new (outString) String(supName, strlen(supName));

stdlib/public/runtime/SwiftObject.mm

@@ -198,15 +198,14 @@ - (Class)class {
   return _swift_getObjCClassOfAllocated(self);
 }
 + (Class)superclass {
-  return class_const_cast(_swift_getSuperclass((const ClassMetadata*) self));
+  return (Class)((const ClassMetadata*) self)->SuperClass;
 }
 - (Class)superclass {
-  return
-    class_const_cast(_swift_getSuperclass(_swift_getClassOfAllocated(self)));
+  return (Class)_swift_getClassOfAllocated(self)->SuperClass;
 }
 
 + (BOOL)isMemberOfClass:(Class)cls {
-  return cls ==  _swift_getObjCClassOfAllocated(self);
+  return cls == _swift_getObjCClassOfAllocated(self);
 }
 
 - (BOOL)isMemberOfClass:(Class)cls {
@@ -293,7 +292,7 @@ - (void)dealloc {
 
 - (BOOL)isKindOfClass:(Class)someClass {
   for (auto cls = _swift_getClassOfAllocated(self); cls != nullptr;
-       cls = _swift_getSuperclass(cls))
+       cls = cls->SuperClass)
     if (cls == (const ClassMetadata*) someClass)
       return YES;
 
@@ -302,7 +301,7 @@ - (BOOL)isKindOfClass:(Class)someClass {
 
 + (BOOL)isSubclassOfClass:(Class)someClass {
   for (auto cls = (const ClassMetadata*) self; cls != nullptr;
-       cls = _swift_getSuperclass(cls))
+       cls = cls->SuperClass)
     if (cls == (const ClassMetadata*) someClass)
       return YES;