Add forward iterator to iterate instructions inside a basic block.

vm/flow_graph_allocator.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_allocator.h"
 
 #include "vm/bit_vector.h"
 #include "vm/intermediate_language.h"
 #include "vm/flow_graph_compiler.h"
 
@@ skipping 48 matching lines @@
             const intptr_t use = ToVirtualRegister(val->AsUse()->definition());
             if (use >= 0) {
               BlockEntryInstr* pred = block->PredecessorAt(k);
               live_out_[pred->postorder_number()]->Add(use);
             }
           }
         }
       }
     }
 
-    Instruction* current = block->successor();
     // TODO(vegorov): iterate backwards.
-    while ((current != NULL) && !current->IsBlockEntry()) {
+    for (ForwardInstructionIterator it(block); !it.Done(); it.Advance()) {
+      Instruction* current = it.Current();
       for (intptr_t j = 0; j < current->InputCount(); j++) {
         Value* input = current->InputAt(j);
         if (!input->IsUse()) continue;
         const intptr_t use = ToVirtualRegister(input->AsUse()->definition());
         if ((use >= 0) && !kill->Contains(use)) live_in->Add(use);
       }
 
       const intptr_t def = ToVirtualRegister(current);
       if (def >= 0) kill->Add(def);
-
-      current = current->successor();
     }
   }
 
   // Update initial live_in sets to match live_out sets. Has to be
   // done in a separate path because of backwards branches.
   for (intptr_t i = 0; i < block_count; i++) {
     UpdateLiveIn(postorder_[i]);
   }
 }
 
@@ skipping 83 matching lines @@
     OS::Print("\n");
 
     PrintBitVector("  live out", live_out_[i]);
     PrintBitVector("  kill", kill_[i]);
     PrintBitVector("  live in", live_in_[i]);
   }
 }
 
 
 }  // namespace dart