Add support for adding an external and a tagged pointer

src/arm64/lithium-arm64.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <sstream>
 
 #include "src/v8.h"
 
 #include "src/arm64/lithium-codegen-arm64.h"
 #include "src/hydrogen-osr.h"
@@ skipping 870 matching lines @@
         UseRegisterOrConstantAtStart(instr->BetterRightOperand());
     LInstruction* result = instr->representation().IsSmi() ?
         DefineAsRegister(new(zone()) LAddS(left, right)) :
         DefineAsRegister(new(zone()) LAddI(left, right));
     if (instr->CheckFlag(HValue::kCanOverflow)) {
       result = AssignEnvironment(result);
     }
     return result;
   } else if (instr->representation().IsExternal()) {
     DCHECK(instr->left()->representation().IsExternal());
-    DCHECK(instr->right()->representation().IsInteger32());
+    DCHECK(instr->right()->representation().IsInteger32() ||
+           instr->right()->representation().IsTagged());
     DCHECK(!instr->CheckFlag(HValue::kCanOverflow));
     LOperand* left = UseRegisterAtStart(instr->left());
     LOperand* right = UseRegisterOrConstantAtStart(instr->right());
     return DefineAsRegister(new(zone()) LAddE(left, right));
   } else if (instr->representation().IsDouble()) {
     return DoArithmeticD(Token::ADD, instr);
   } else {
     DCHECK(instr->representation().IsTagged());
     return DoArithmeticT(Token::ADD, instr);
   }
@@ skipping 1881 matching lines @@
   LOperand* context = UseFixed(instr->context(), cp);
   LOperand* function = UseRegisterAtStart(instr->function());
   LAllocateBlockContext* result =
       new(zone()) LAllocateBlockContext(context, function);
   return MarkAsCall(DefineFixed(result, cp), instr);
 }
 
 
 }  // namespace internal
 }  // namespace v8