[AliasAnalysis] Remove duplicate code in TBAA.

We have two places in TBAA that uses the class hierarchy to disambiguate types.
This commit removes one of the checks (the one that looked more ad-hock) and
keeps the check in line 540 that uses Type.isSuperclassOf.

lib/SILAnalysis/AliasAnalysis.cpp

@@ -442,38 +442,6 @@ static bool typedAccessTBAABuiltinTypesMayAlias(SILType LTy, SILType RTy,
   return false;
 }
 
-/// Return true if the type \p Parent is a parent of \p Child in the
-/// class hierarchy.
-static bool isParentClass(SILType Parent, SILType Child) {
-  SILType T = SILType();
-
-  // Walk the class hiearchy to see whether Parent and Child have a
-  // parent-child relationship.
-  T = Child;
-  do {
-    // There is a parent-child relationship.
-    if (T == Parent)
-      return true;
-
-    T = T.getSuperclass(nullptr);
-  } while(T);
-
-  return false;
-}
-
-/// Returns true if the reference types \p LTy and \pRTy may alias.
-static bool referenceTypeTBAAMayAlias(SILType LTy, SILType RTy) {
-
-  // Walk the type hiearchy to see whether LTy and RTy have a parent-child
-  // relationship.
-  if (isParentClass(LTy, RTy) ||
-      isParentClass(RTy, LTy)) {
-    return true;
-  }
-
-  return false;
-}
-
 /// \brief return True if the types \p LTy and \p RTy may alias.
 ///
 /// Currently this only implements typed access based TBAA. See the TBAA section
@@ -488,13 +456,6 @@ static bool typedAccessTBAAMayAlias(SILType LTy, SILType RTy, SILModule &Mod) {
   if (LTy == RTy)
     return true;
 
-  // If 2 reference types have no parent-child relationship, then they can
-  // not alias.
-  if (!LTy.isAddress() && !RTy.isAddress()) {
-    if (LTy.isHeapObjectReferenceType() && RTy.isHeapObjectReferenceType())
-      return referenceTypeTBAAMayAlias(LTy, RTy);
-  }
-
   // Typed access based TBAA only occurs on pointers. If we reach this point and
   // do not have a pointer, be conservative and return that the two types may
   // alias. *NOTE* This ensures we return may alias for local_storage.