Remove support for Object.observe

src/ic/x64/ic-x64.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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/codegen.h"
 #include "src/ic/ic.h"
 #include "src/ic/ic-compiler.h"
 #include "src/ic/stub-cache.h"
@@ skipping 501 matching lines @@
   Label array, extra, check_if_double_array, maybe_name_key, miss;
   Register receiver = StoreDescriptor::ReceiverRegister();
   Register key = StoreDescriptor::NameRegister();
   DCHECK(receiver.is(rdx));
   DCHECK(key.is(rcx));
 
   // Check that the object isn't a smi.
   __ JumpIfSmi(receiver, &slow_with_tagged_index);
   // Get the map from the receiver.
   __ movp(r9, FieldOperand(receiver, HeapObject::kMapOffset));
-  // Check that the receiver does not require access checks and is not observed.
-  // The generic stub does not perform map checks or handle observed objects.
+  // Check that the receiver does not require access checks.
+  // The generic stub does not perform map checks.
   __ testb(FieldOperand(r9, Map::kBitFieldOffset),
-           Immediate(1 << Map::kIsAccessCheckNeeded | 1 << Map::kIsObserved));
+           Immediate(1 << Map::kIsAccessCheckNeeded));
   __ j(not_zero, &slow_with_tagged_index);
   // Check that the key is a smi.
   __ JumpIfNotSmi(key, &maybe_name_key);
   __ SmiToInteger32(key, key);
 
   __ CmpInstanceType(r9, JS_ARRAY_TYPE);
   __ j(equal, &array);
   // Check that the object is some kind of JS object EXCEPT JS Value type. In
   // the case that the object is a value-wrapper object, we enter the runtime
   // system to make sure that indexing into string objects works as intended.
@@ skipping 309 matching lines @@
   Condition cc =
       (check == ENABLE_INLINED_SMI_CHECK)
           ? (*jmp_address == Assembler::kJncShortOpcode ? not_zero : zero)
           : (*jmp_address == Assembler::kJnzShortOpcode ? not_carry : carry);
   *jmp_address = static_cast<byte>(Assembler::kJccShortPrefix | cc);
 }
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64