Use Object::null_object() instead of Object::ZoneHandle() when a null object

runtime/vm/flow_graph_compiler_x64.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 574 matching lines @@
   SubtypeTestCache& test_cache = SubtypeTestCache::ZoneHandle();
   test_cache = GenerateInlineInstanceof(token_pos, type,
                                         &is_instance, &is_not_instance);
 
   // test_cache is null if there is no fall-through.
   Label done;
   if (!test_cache.IsNull()) {
     // Generate runtime call.
     __ movq(RDX, Address(RSP, 0));  // Get instantiator type arguments.
     __ movq(RCX, Address(RSP, kWordSize));  // Get instantiator.
-    __ PushObject(Object::ZoneHandle(), PP);  // Make room for the result.
+    __ PushObject(Object::null_object(), PP);  // Make room for the result.
     __ pushq(RAX);  // Push the instance.
     __ PushObject(type, PP);  // Push the type.
     __ pushq(RCX);  // TODO(srdjan): Pass instantiator instead of null.
     __ pushq(RDX);  // Instantiator type arguments.
     __ LoadObject(RAX, test_cache, PP);
     __ pushq(RAX);
     GenerateRuntimeCall(token_pos,
                         deopt_id,
                         kInstanceofRuntimeEntry,
                         5,
@@ skipping 49 matching lines @@
          (!dst_type.IsDynamicType() && !dst_type.IsObjectType()));
   __ pushq(RCX);  // Store instantiator.
   __ pushq(RDX);  // Store instantiator type arguments.
   // A null object is always assignable and is returned as result.
   Label is_assignable, runtime_call;
   __ CompareObject(RAX, Object::null_object(), PP);
   __ j(EQUAL, &is_assignable);
 
   // Generate throw new TypeError() if the type is malformed or malbounded.
   if (dst_type.IsMalformedOrMalbounded()) {
-    __ PushObject(Object::ZoneHandle(), PP);  // Make room for the result.
+    __ PushObject(Object::null_object(), PP);  // Make room for the result.
     __ pushq(RAX);  // Push the source object.
     __ PushObject(dst_name, PP);  // Push the name of the destination.
     __ PushObject(dst_type, PP);  // Push the type of the destination.
     GenerateRuntimeCall(token_pos,
                         deopt_id,
                         kBadTypeErrorRuntimeEntry,
                         3,
                         locs);
     // We should never return here.
     __ int3();
 
     __ Bind(&is_assignable);  // For a null object.
     __ popq(RDX);  // Remove pushed instantiator type arguments.
     __ popq(RCX);  // Remove pushed instantiator.
     return;
   }
 
   // Generate inline type check, linking to runtime call if not assignable.
   SubtypeTestCache& test_cache = SubtypeTestCache::ZoneHandle();
   test_cache = GenerateInlineInstanceof(token_pos, dst_type,
                                         &is_assignable, &runtime_call);
 
   __ Bind(&runtime_call);
   __ movq(RDX, Address(RSP, 0));  // Get instantiator type arguments.
   __ movq(RCX, Address(RSP, kWordSize));  // Get instantiator.
-  __ PushObject(Object::ZoneHandle(), PP);  // Make room for the result.
+  __ PushObject(Object::null_object(), PP);  // Make room for the result.
   __ pushq(RAX);  // Push the source object.
   __ PushObject(dst_type, PP);  // Push the type of the destination.
   __ pushq(RCX);  // Instantiator.
   __ pushq(RDX);  // Instantiator type arguments.
   __ PushObject(dst_name, PP);  // Push the name of the destination.
   __ LoadObject(RAX, test_cache, PP);
   __ pushq(RAX);
   GenerateRuntimeCall(token_pos, deopt_id, kTypeCheckRuntimeEntry, 6, locs);
   // Pop the parameters supplied to the runtime entry. The result of the
   // type check runtime call is the checked value.
@@ skipping 1015 matching lines @@
   __ movups(reg, Address(RSP, 0));
   __ AddImmediate(RSP, Immediate(kFpuRegisterSize), PP);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64