ES6 symbols: Implement Symbol intrinsic and basic functionality

src/x64/stub-cache-x64.cc

 // Copyright 2012 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 2244 matching lines @@
         CheckPrototypes(
             Handle<JSObject>(JSObject::cast(object->GetPrototype())),
             rax, holder, rbx, rdx, rdi, name, &miss);
       } else {
         // Calling non-strict non-builtins with a value as the receiver
         // requires boxing.
         __ jmp(&miss);
       }
       break;
 
+    case SYMBOL_CHECK:
+      // Check that the object is a symbol.
+      __ CmpObjectType(rdx, SYMBOL_TYPE, rax);
+      __ j(not_equal, &miss);
+      break;
+
     case NUMBER_CHECK:
       if (function->IsBuiltin() || !function->shared()->is_classic_mode()) {
         Label fast;
         // Check that the object is a smi or a heap number.
         __ JumpIfSmi(rdx, &fast);
         __ CmpObjectType(rdx, HEAP_NUMBER_TYPE, rax);
         __ j(not_equal, &miss);
         __ bind(&fast);
         // Check that the maps starting from the prototype haven't changed.
         GenerateDirectLoadGlobalFunctionPrototype(
@@ skipping 1417 matching lines @@
     __ jmp(ic_slow, RelocInfo::CODE_TARGET);
   }
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64