Remove possibility of critical edges.

runtime/vm/flow_graph_builder.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/flow_graph_builder.h"
 
 #include "vm/ast_printer.h"
 #include "vm/flags.h"
 #include "vm/intermediate_language.h"
 #include "vm/longjump.h"
@@ skipping 704 matching lines @@
   AddInstruction(join);
   join->SetSuccessor(for_body.entry());
   Instruction* body_exit = for_body.is_empty() ? join : for_body.exit();
 
   if (body_exit != NULL) {
     TargetEntryInstr* target_entry = new TargetEntryInstr();
     target_entry->SetSuccessor(for_test.entry());
     body_exit->SetSuccessor(target_entry);
   }
 
-  *for_test.true_successor_address() = join;
+  TargetEntryInstr* back_target_entry = new TargetEntryInstr();
+  *for_test.true_successor_address() = back_target_entry;
+  back_target_entry->SetSuccessor(join);
   exit_ = *for_test.false_successor_address() = new TargetEntryInstr();
 }
 
 
 void EffectGraphVisitor::VisitForNode(ForNode* node) {
   EffectGraphVisitor for_initializer(owner(), temp_index());
   node->initializer()->Visit(&for_initializer);
   Append(for_initializer);
   ASSERT(is_open());
 
@@ skipping 948 matching lines @@
   char* chars = reinterpret_cast<char*>(
       Isolate::Current()->current_zone()->Allocate(len));
   OS::SNPrint(chars, len, kFormat, function_name, reason);
   const Error& error = Error::Handle(
       LanguageError::New(String::Handle(String::New(chars))));
   Isolate::Current()->long_jump_base()->Jump(1, error);
 }
 
 
 }  // namespace dart