ES6 symbols: Implement Symbol intrinsic and basic functionality

src/ia32/lithium-codegen-ia32.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 5885 matching lines @@
     __ j(equal, true_label);
     __ CmpInstanceType(input, JS_FUNCTION_PROXY_TYPE);
     final_branch_condition = equal;
 
   } else if (type_name->Equals(heap()->object_string())) {
     __ JumpIfSmi(input, false_label);
     if (!FLAG_harmony_typeof) {
       __ cmp(input, factory()->null_value());
       __ j(equal, true_label);
     }
-    __ CmpObjectType(input, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE, input);
+    if (FLAG_harmony_symbols) {
+      __ CmpObjectType(input, SYMBOL_TYPE, input);
+      __ j(equal, true_label);
+      __ CmpInstanceType(input, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE);
+    } else {
+      __ CmpObjectType(input, FIRST_NONCALLABLE_SPEC_OBJECT_TYPE, input);
+    }
     __ j(below, false_label);
     __ CmpInstanceType(input, LAST_NONCALLABLE_SPEC_OBJECT_TYPE);
     __ j(above, false_label);
     // Check for undetectable objects => false.
     __ test_b(FieldOperand(input, Map::kBitFieldOffset),
               1 << Map::kIsUndetectable);
     final_branch_condition = zero;
 
   } else {
     __ jmp(false_label);
@@ skipping 261 matching lines @@
                               FixedArray::kHeaderSize - kPointerSize));
   __ bind(&done);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_IA32