Fix compilation error on X64. Error is from r5080

src/x64/codegen-x64.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 420 matching lines @@
       // always at a function context. However it is safe to dereference be-
       // cause the function context of a function context is itself. Before
       // deleting this mov we should try to create a counter-example first,
       // though...)
       __ movq(tmp, ContextOperand(context, Context::FCONTEXT_INDEX));
       return ContextOperand(tmp, index);
     }
 
     default:
       UNREACHABLE();
-      return Operand(rax);
+      return Operand(rsp, 0);
   }
 }
 
 
 Operand CodeGenerator::ContextSlotOperandCheckExtensions(Slot* slot,
                                                          Result tmp,
                                                          JumpTarget* slow) {
   ASSERT(slot->type() == Slot::CONTEXT);
   ASSERT(tmp.is_register());
   Register context = rsi;
@@ skipping 11067 matching lines @@
   ASSERT(src.is(rsi));  // rep movs source
   ASSERT(count.is(rcx));  // rep movs count
 
   // Nothing to do for zero characters.
   Label done;
   __ testl(count, count);
   __ j(zero, &done);
 
   // Make count the number of bytes to copy.
   if (!ascii) {
-    ASSERT_EQ(2, sizeof(uc16));  // NOLINT
+    ASSERT_EQ(2, static_cast<int>(sizeof(uc16)));  // NOLINT
     __ addl(count, count);
   }
 
   // Don't enter the rep movs if there are less than 4 bytes to copy.
   Label last_bytes;
   __ testl(count, Immediate(~7));
   __ j(zero, &last_bytes);
 
   // Copy from edi to esi using rep movs instruction.
   __ movl(kScratchRegister, count);
@@ skipping 560 matching lines @@
 #undef __
 
 void RecordWriteStub::Generate(MacroAssembler* masm) {
   masm->RecordWriteHelper(object_, addr_, scratch_);
   masm->ret(0);
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64