VM: Use read-only handle Object::dynamic_type() where possible.

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 443 matching lines @@
     // Load instantiator (or null) and instantiator type arguments on stack.
     __ movq(RDX, Address(RSP, 0));  // Get instantiator type arguments.
     // RDX: instantiator type arguments.
     // Check if type arguments are null, i.e. equivalent to vector of dynamic.
     __ CompareObject(RDX, Object::null_object());
     __ j(EQUAL, is_instance_lbl);
     __ movq(RDI,
         FieldAddress(RDX, TypeArguments::type_at_offset(type_param.index())));
     // RDI: Concrete type of type.
     // Check if type argument is dynamic.
-    __ CompareObject(RDI, Type::ZoneHandle(zone(), Type::DynamicType()));
+    __ CompareObject(RDI, Object::dynamic_type());
     __ j(EQUAL,  is_instance_lbl);
     const Type& object_type = Type::ZoneHandle(zone(), Type::ObjectType());
     __ CompareObject(RDI, object_type);
     __ j(EQUAL,  is_instance_lbl);
 
     // For Smi check quickly against int and num interfaces.
     Label not_smi;
     __ testq(RAX, Immediate(kSmiTagMask));  // Value is Smi?
     __ j(NOT_ZERO, &not_smi, Assembler::kNearJump);
     __ CompareObject(RDI, Type::ZoneHandle(zone(), Type::IntType()));
@@ skipping 1320 matching lines @@
   __ movups(reg, Address(RSP, 0));
   __ AddImmediate(RSP, Immediate(kFpuRegisterSize));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64