Fix bailing out of SSA compilation and enable --use-ssa on x64 by default.

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_patcher.h"
@@ skipping 250 matching lines @@
                 function.ToFullyQualifiedCString(),
                 function.token_pos());
     }
     Parser::ParseFunction(&parsed_function);
     parsed_function.AllocateVariables();
 
     if (!CompileParsedFunctionHelper(parsed_function,
                                      optimized,
                                      FLAG_use_ssa)) {
       // Compile again using non-ssa code generation.
+      // Re-parse because of side-effects to the AST during compilation.
+      ParsedFunction parsed_function(function);
+      Parser::ParseFunction(&parsed_function);
+      parsed_function.AllocateVariables();
       CompileParsedFunctionHelper(parsed_function, optimized, false);
     }
 
     if (FLAG_trace_compiler) {
       OS::Print("--> '%s' entry: 0x%x\n",
                 function.ToFullyQualifiedCString(),
                 Code::Handle(function.CurrentCode()).EntryPoint());
     }
     if (Isolate::Current()->debugger()->IsActive()) {
       Isolate::Current()->debugger()->NotifyCompilation(function);
@@ skipping 191 matching lines @@
     isolate->object_store()->clear_sticky_error();
     isolate->set_long_jump_base(base);
     return result.raw();
   }
   UNREACHABLE();
   return Object::null();
 }
 
 
 }  // namespace dart