Enable new compiler in x64 mode (bail-out all the time, but we can use automated testing).

runtime/vm/compiler.cc

 // Copyright (c) 2012, 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/compiler.h"
 
 #include "vm/assembler.h"
 #include "vm/ast_printer.h"
 #include "vm/code_generator.h"
 #include "vm/code_index_table.h"
@@ skipping 12 matching lines @@
 #include "vm/scanner.h"
 #include "vm/timer.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, disassemble, false, "Disassemble dart code.");
 DEFINE_FLAG(bool, trace_compiler, false, "Trace compiler operations.");
 DEFINE_FLAG(int, deoptimization_counter_threshold, 5,
     "How many times we allow deoptimization before we disallow"
     " certain optimizations");
+#if defined(TARGET_ARCH_X64)
+DEFINE_FLAG(bool, use_new_compiler, true,
+    "Try to use the new compiler backend.");
+#else
 DEFINE_FLAG(bool, use_new_compiler, false,
     "Try to use the new compiler backend.");
+#endif
 DEFINE_FLAG(bool, trace_bailout, false, "Print bailout from new compiler.");
 
 
 // Compile a function. Should call only if the function has not been compiled.
 //   Arg0: function object.
 DEFINE_RUNTIME_ENTRY(CompileFunction, 1) {
   ASSERT(arguments.Count() == kCompileFunctionRuntimeEntry.argument_count());
   const Function& function = Function::CheckedHandle(arguments.At(0));
   ASSERT(!function.HasCode());
   const Error& error = Error::Handle(Compiler::CompileFunction(function));
@@ skipping 311 matching lines @@
   } else {
     result = isolate->object_store()->sticky_error();
     isolate->object_store()->clear_sticky_error();
   }
   isolate->set_long_jump_base(base);
   return result.raw();
 }
 
 
 }  // namespace dart