Remove dead phis as soon as they are discovered.

runtime/vm/flow_graph_allocator.h

 // 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.
 
 #ifndef VM_FLOW_GRAPH_ALLOCATOR_H_
 #define VM_FLOW_GRAPH_ALLOCATOR_H_
 
 #include "vm/growable_array.h"
 #include "vm/intermediate_language.h"
 
@@ skipping 36 matching lines @@
   // Build live-in and live-out sets for each block.
   void AnalyzeLiveness();
 
   // Map a virtual register number to its live range.
   LiveRange* GetLiveRange(intptr_t vreg);
 
  private:
   void CollectRepresentations();
 
   // Eliminate unnecessary environments from the IL.
-  void EliminateEnvironmentUses();
+  void EliminateEnvironments();
 
   // Compute initial values for live-out, kill and live-in sets.
   void ComputeInitialSets();
 
   // Update live-out set for the given block: live-out should contain
   // all values that are live-in for block's successors.
   // Returns true if live-out set was changed.
   bool UpdateLiveOut(const BlockEntryInstr& instr);
 
   // Update live-in set for the given block: live-in should contain
@@ skipping 589 matching lines @@
 
   AllocationFinger finger_;
 
   DISALLOW_COPY_AND_ASSIGN(LiveRange);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_ALLOCATOR_H_