diff --git a/src/ic/arm64/handler-compiler-arm64.cc b/src/ic/arm64/handler-compiler-arm64.cc
index 84c0397..1126beb 100644
--- a/src/ic/arm64/handler-compiler-arm64.cc
+++ b/src/ic/arm64/handler-compiler-arm64.cc
@@ -110,8 +110,9 @@
     MacroAssembler* masm, Handle<JSGlobalObject> global, Handle<Name> name,
     Register scratch, Label* miss) {
   Handle<PropertyCell> cell = JSGlobalObject::EnsurePropertyCell(global, name);
-  DCHECK(cell->value()->IsTheHole());
-  Handle<WeakCell> weak_cell = masm->isolate()->factory()->NewWeakCell(cell);
+  Isolate* isolate = masm->isolate();
+  DCHECK(cell->value()->IsTheHole(isolate));
+  Handle<WeakCell> weak_cell = isolate->factory()->NewWeakCell(cell);
   __ LoadWeakValue(scratch, weak_cell, miss);
   __ Ldr(scratch, FieldMemOperand(scratch, PropertyCell::kValueOffset));
   __ JumpIfNotRoot(scratch, Heap::kTheHoleValueRootIndex, miss);
@@ -197,7 +198,7 @@
   Handle<CallHandlerInfo> api_call_info = optimization.api_call_info();
   bool call_data_undefined = false;
   // Put call data in place.
-  if (api_call_info->data()->IsUndefined()) {
+  if (api_call_info->data()->IsUndefined(isolate)) {
     call_data_undefined = true;
     __ LoadRoot(data, Heap::kUndefinedValueRootIndex);
   } else {
@@ -467,28 +468,25 @@
   DCHECK(!AreAliased(object_reg, scratch1, scratch2));
   DCHECK(!AreAliased(holder_reg, scratch1, scratch2));
 
-  if (FLAG_eliminate_prototype_chain_checks) {
-    Handle<Cell> validity_cell =
-        Map::GetOrCreatePrototypeChainValidityCell(receiver_map, isolate());
-    if (!validity_cell.is_null()) {
-      DCHECK_EQ(Smi::FromInt(Map::kPrototypeChainValid),
-                validity_cell->value());
-      __ Mov(scratch1, Operand(validity_cell));
-      __ Ldr(scratch1, FieldMemOperand(scratch1, Cell::kValueOffset));
-      __ Cmp(scratch1, Operand(Smi::FromInt(Map::kPrototypeChainValid)));
-      __ B(ne, miss);
-    }
+  Handle<Cell> validity_cell =
+      Map::GetOrCreatePrototypeChainValidityCell(receiver_map, isolate());
+  if (!validity_cell.is_null()) {
+    DCHECK_EQ(Smi::FromInt(Map::kPrototypeChainValid), validity_cell->value());
+    __ Mov(scratch1, Operand(validity_cell));
+    __ Ldr(scratch1, FieldMemOperand(scratch1, Cell::kValueOffset));
+    __ Cmp(scratch1, Operand(Smi::FromInt(Map::kPrototypeChainValid)));
+    __ B(ne, miss);
+  }
 
-    // The prototype chain of primitives (and their JSValue wrappers) depends
-    // on the native context, which can't be guarded by validity cells.
-    // |object_reg| holds the native context specific prototype in this case;
-    // we need to check its map.
-    if (check == CHECK_ALL_MAPS) {
-      __ Ldr(scratch1, FieldMemOperand(object_reg, HeapObject::kMapOffset));
-      Handle<WeakCell> cell = Map::WeakCellForMap(receiver_map);
-      __ CmpWeakValue(scratch1, cell, scratch2);
-      __ B(ne, miss);
-    }
+  // The prototype chain of primitives (and their JSValue wrappers) depends
+  // on the native context, which can't be guarded by validity cells.
+  // |object_reg| holds the native context specific prototype in this case;
+  // we need to check its map.
+  if (check == CHECK_ALL_MAPS) {
+    __ Ldr(scratch1, FieldMemOperand(object_reg, HeapObject::kMapOffset));
+    Handle<WeakCell> cell = Map::WeakCellForMap(receiver_map);
+    __ CmpWeakValue(scratch1, cell, scratch2);
+    __ B(ne, miss);
   }
 
   // Keep track of the current object in register reg.
@@ -525,8 +523,10 @@
            !current_map->is_access_check_needed());
 
     prototype = handle(JSObject::cast(current_map->prototype()));
-    if (current_map->is_dictionary_map() &&
-        !current_map->IsJSGlobalObjectMap()) {
+    if (current_map->IsJSGlobalObjectMap()) {
+      GenerateCheckPropertyCell(masm(), Handle<JSGlobalObject>::cast(current),
+                                name, scratch2, miss);
+    } else if (current_map->is_dictionary_map()) {
       DCHECK(!current_map->IsJSGlobalProxyMap());  // Proxy maps are fast.
       if (!name->IsUniqueName()) {
         DCHECK(name->IsString());
@@ -535,34 +535,12 @@
       DCHECK(current.is_null() || (current->property_dictionary()->FindEntry(
                                        name) == NameDictionary::kNotFound));
 
-      if (FLAG_eliminate_prototype_chain_checks && depth > 1) {
+      if (depth > 1) {
         // TODO(jkummerow): Cache and re-use weak cell.
         __ LoadWeakValue(reg, isolate()->factory()->NewWeakCell(current), miss);
       }
       GenerateDictionaryNegativeLookup(masm(), miss, reg, name, scratch1,
                                        scratch2);
-
-      if (!FLAG_eliminate_prototype_chain_checks) {
-        __ Ldr(scratch1, FieldMemOperand(reg, HeapObject::kMapOffset));
-        __ Ldr(holder_reg, FieldMemOperand(scratch1, Map::kPrototypeOffset));
-      }
-    } else {
-      Register map_reg = scratch1;
-      if (!FLAG_eliminate_prototype_chain_checks) {
-        __ Ldr(map_reg, FieldMemOperand(reg, HeapObject::kMapOffset));
-      }
-      if (current_map->IsJSGlobalObjectMap()) {
-        GenerateCheckPropertyCell(masm(), Handle<JSGlobalObject>::cast(current),
-                                  name, scratch2, miss);
-      } else if (!FLAG_eliminate_prototype_chain_checks &&
-                 (depth != 1 || check == CHECK_ALL_MAPS)) {
-        Handle<WeakCell> cell = Map::WeakCellForMap(current_map);
-        __ CmpWeakValue(map_reg, cell, scratch2);
-        __ B(ne, miss);
-      }
-      if (!FLAG_eliminate_prototype_chain_checks) {
-        __ Ldr(holder_reg, FieldMemOperand(map_reg, Map::kPrototypeOffset));
-      }
     }
 
     reg = holder_reg;  // From now on the object will be in holder_reg.
@@ -576,17 +554,8 @@
   // Log the check depth.
   LOG(isolate(), IntEvent("check-maps-depth", depth + 1));
 
-  if (!FLAG_eliminate_prototype_chain_checks &&
-      (depth != 0 || check == CHECK_ALL_MAPS)) {
-    // Check the holder map.
-    __ Ldr(scratch1, FieldMemOperand(reg, HeapObject::kMapOffset));
-    Handle<WeakCell> cell = Map::WeakCellForMap(current_map);
-    __ CmpWeakValue(scratch1, cell, scratch2);
-    __ B(ne, miss);
-  }
-
   bool return_holder = return_what == RETURN_HOLDER;
-  if (FLAG_eliminate_prototype_chain_checks && return_holder && depth != 0) {
+  if (return_holder && depth != 0) {
     __ LoadWeakValue(reg, isolate()->factory()->NewWeakCell(current), miss);
   }
 
@@ -637,7 +606,7 @@
   DCHECK(!AreAliased(receiver(), this->name(), scratch1(), scratch2(),
                      scratch3()));
   DCHECK(holder()->HasNamedInterceptor());
-  DCHECK(!holder()->GetNamedInterceptor()->getter()->IsUndefined());
+  DCHECK(!holder()->GetNamedInterceptor()->getter()->IsUndefined(isolate()));
 
   // Compile the interceptor call, followed by inline code to load the
   // property from further up the prototype chain if the call fails.
@@ -696,7 +665,7 @@
 void NamedLoadHandlerCompiler::GenerateLoadInterceptor(Register holder_reg) {
   // Call the runtime system to load the interceptor.
   DCHECK(holder()->HasNamedInterceptor());
-  DCHECK(!holder()->GetNamedInterceptor()->getter()->IsUndefined());
+  DCHECK(!holder()->GetNamedInterceptor()->getter()->IsUndefined(isolate()));
   PushInterceptorArguments(masm(), receiver(), holder_reg, this->name(),
                            holder());
 
@@ -718,7 +687,7 @@
   DCHECK(!AreAliased(holder_reg, scratch1(), scratch2(), value()));
   // If the callback cannot leak, then push the callback directly,
   // otherwise wrap it in a weak cell.
-  if (callback->data()->IsUndefined() || callback->data()->IsSmi()) {
+  if (callback->data()->IsUndefined(isolate()) || callback->data()->IsSmi()) {
     __ Mov(scratch1(), Operand(callback));
   } else {
     Handle<WeakCell> cell = isolate()->factory()->NewWeakCell(callback);