Readd the C++ ABI alignment handling logic

include/clang/Basic/TargetCXXABI.h

 //===--- TargetCXXABI.h - C++ ABI Target Configuration ----------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
@@ skipping 128 matching lines @@
     case iOS64:
     case GenericMIPS:
       return false;
 
     case Microsoft:
       return true;
     }
     llvm_unreachable("bad ABI kind");
   }
 
+  /// \brief Are pointers to member functions differently aligned?
+  bool arePointersToMemberFunctionsAligned() const {
+    switch (getKind()) {
+    case GenericARM:
+    case GenericAArch64:
+      // TODO: ARM-style pointers to member functions put the discriminator in
+      //       the this adjustment, so they don't require functions to have any
+      //       special alignment and could therefore also return false.
+    case GenericItanium:
+    case GenericMIPS:
+    case iOS:
+    case iOS64:
+    case Microsoft:
+      return true;
+    }
+    llvm_unreachable("bad ABI kind");
+  }
+
   /// \brief Is the default C++ member function calling convention
   /// the same as the default calling convention?
   bool isMemberFunctionCCDefault() const {
     // Right now, this is always false for Microsoft.
     return !isMicrosoft();
   }
 
   /// Are arguments to a call destroyed left to right in the callee?
   /// This is a fundamental language change, since it implies that objects
   /// passed by value do *not* live to the end of the full expression.
@@ skipping 131 matching lines @@
   }
 
   friend bool operator!=(const TargetCXXABI &left, const TargetCXXABI &right) {
     return !(left == right);
   }
 };
 
 }  // end namespace clang
 
 #endif