Reimplement Maps and Sets in JS

src/x64/code-stubs-x64.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 "src/v8.h"
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 2437 matching lines @@
   if (result_size() > 1) {
     DCHECK_EQ(2, result_size());
     // Read result values stored on stack. Result is stored
     // above the four argument mirror slots and the two
     // Arguments object slots.
     __ movq(rax, Operand(rsp, 6 * kRegisterSize));
     __ movq(rdx, Operand(rsp, 7 * kRegisterSize));
   }
 #endif  // _WIN64
 
-  // Runtime functions should not return 'the hole'.  Allowing it to escape may
-  // lead to crashes in the IC code later.
-  if (FLAG_debug_code) {
-    Label okay;
-    __ CompareRoot(rax, Heap::kTheHoleValueRootIndex);
-    __ j(not_equal, &okay, Label::kNear);
-    __ int3();
-    __ bind(&okay);
-  }
-
   // Check result for exception sentinel.
   Label exception_returned;
   __ CompareRoot(rax, Heap::kExceptionRootIndex);
   __ j(equal, &exception_returned);
 
   // Check that there is no pending exception, otherwise we
   // should have returned the exception sentinel.
   if (FLAG_debug_code) {
     Label okay;
     __ LoadRoot(r14, Heap::kTheHoleValueRootIndex);
@@ skipping 2667 matching lines @@
   CallApiFunctionAndReturn(masm, api_function_address, thunk_ref, getter_arg,
                            kStackSpace, nullptr, return_value_operand, NULL);
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64