Update use lists after eliminating redundant phis.

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2013, 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_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/cpu.h"
 #include "vm/dart_entry.h"
@@ skipping 7187 matching lines @@
 
     // At this point worklist contains pairs of equal phis. Replace the first
     // phi in the pair with the second.
     for (intptr_t i = 0; i < worklist_.length(); i += 2) {
       PhiInstr* a = worklist_[i];
       PhiInstr* b = worklist_[i + 1];
       a->ReplaceUsesWith(b);
       if (a->is_alive()) {
         a->mark_dead();
         a->block()->RemovePhi(a);
+        a->UnuseAllInputs();
       }
     }
-
     return true;
   }
 
   // Insert the given phi into the graph. Attempt to find an equal one in the
   // target block first.
   // Returns true if the phi was inserted and false if it was replaced.
   bool EmitPhi(PhiInstr* phi) {
     for (PhiIterator it(phi->block()); !it.Done(); it.Advance()) {
       if (ReplacePhiWith(phi, it.Current())) {
         return false;
       }
     }
 
     phi->mark_alive();
     phi->block()->InsertPhi(phi);
     return true;
   }
 
   // Phis have not yet been inserted into the graph but they have uses of
   // their inputs.  Insert the non-redundant ones and clear the input uses
   // of the redundant ones.
   void EmitPhis() {
     // First eliminate all redundant phis.
     for (intptr_t i = 0; i < phis_.length(); i++) {
       PhiInstr* phi = phis_[i];
       if (!phi->HasUses() || EliminateRedundantPhi(phi)) {
-        for (intptr_t j = phi->InputCount() - 1; j >= 0; --j) {
-          phi->InputAt(j)->RemoveFromUseList();
-        }
+        phi->UnuseAllInputs();
         phis_[i] = NULL;
       }
     }
 
     // Now emit phis or replace them with equal phis already present in the
     // graph.
     for (intptr_t i = 0; i < phis_.length(); i++) {
       PhiInstr* phi = phis_[i];
       if ((phi != NULL) && (!phi->HasUses() || !EmitPhi(phi))) {
-        for (intptr_t j = phi->InputCount() - 1; j >= 0; --j) {
-          phi->InputAt(j)->RemoveFromUseList();
-        }
+        phi->UnuseAllInputs();
       }
     }
   }
 
   ZoneGrowableArray<Definition*>* CreateBlockOutValues() {
     ZoneGrowableArray<Definition*>* out =
         new(isolate()) ZoneGrowableArray<Definition*>(
             aliased_set_->max_place_id());
     for (intptr_t i = 0; i < aliased_set_->max_place_id(); i++) {
       out->Add(NULL);
@@ skipping 2595 matching lines @@
   }
 
   // Insert materializations at environment uses.
   for (intptr_t i = 0; i < exits.length(); i++) {
     CreateMaterializationAt(exits[i], alloc, alloc->cls(), *slots);
   }
 }
 
 
 }  // namespace dart