Use the instruction iterator rather than an explicit loop in more places.

runtime/vm/il_printer.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/il_printer.h"
 
 #include "vm/intermediate_language.h"
 #include "vm/os.h"
 
 namespace dart {
@@ skipping 513 matching lines @@
         }
         END("states");
       }
 
       {
         BEGIN("HIR");
         // Print the block entry.
         Print("0 0 ");  // Required fields "bci" and "use". Unused.
         PrintInstruction(block_order_[i]);
         // And all the successors until an exit, branch, or a block entry.
-        Instruction* current = block_order_[i];
-        for (ForwardInstructionIterator it(current->AsBlockEntry());
-             !it.Done();
-             it.Advance()) {
+        BlockEntryInstr* entry = block_order_[i];
+        Instruction* current = entry;
+        for (ForwardInstructionIterator it(entry); !it.Done(); it.Advance()) {
           current = it.Current();
           Print("0 0 ");
           PrintInstruction(current);
         }
         if (current->next() != NULL) {
           ASSERT(current->next()->IsBlockEntry());
           Print("0 0 _ Goto B%d <|@\n",
                 current->next()->AsBlockEntry()->block_id());
         }
         END("HIR");
@@ skipping 118 matching lines @@
 void Environment::PrintTo(BufferFormatter* f) const {
   f->Print(" env={ ");
   for (intptr_t i = 0; i < values_.length(); ++i) {
     if (i > 0) f->Print(", ");
     values_[i]->PrintTo(f);
   }
   f->Print(" }");
 }
 
 }  // namespace dart