Add support for adding an external and a tagged pointer

src/mips64/lithium-mips64.cc

 // Copyright 2012 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"
 
 #if V8_TARGET_ARCH_MIPS64
 
@@ skipping 1612 matching lines @@
     LOperand* right = 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->IsConsistentExternalRepresentation());
     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()) {
     if (kArchVariant == kMips64r2) {
       if (instr->left()->IsMul())
         return DoMultiplyAdd(HMul::cast(instr->left()), instr->right());
 
       if (instr->right()->IsMul()) {
@@ skipping 1036 matching lines @@
   LAllocateBlockContext* result =
       new(zone()) LAllocateBlockContext(context, function);
   return MarkAsCall(DefineFixed(result, cp), instr);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_MIPS64