Eliminate class UseVal.

runtime/vm/flow_graph_compiler.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/globals.h"  // Needed here to get TARGET_ARCH_XXX.
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/dart_entry.h"
 #include "vm/debugger.h"
@@ skipping 32 matching lines @@
   intptr_t slot_ix = 0;
   builder.AddReturnAddress(function, deopt_id_, slot_ix++);
 
   // All locals between TOS and PC-marker.
   const GrowableArray<Value*>& values = deoptimization_env_->values();
 
   // Assign locations to values pushed above spill slots with PushArgument.
   intptr_t height = compiler->StackSize();
   for (intptr_t i = 0; i < values.length(); i++) {
     if (deoptimization_env_->LocationAt(i).IsInvalid()) {
-      ASSERT(values[i]->AsUse()->definition()->IsPushArgument());
+      ASSERT(values[i]->definition()->IsPushArgument());
       *deoptimization_env_->LocationSlotAt(i) = Location::StackSlot(height++);
     }
   }
 
   for (intptr_t i = values.length() - 1; i >= fixed_parameter_count; i--) {
     builder.AddCopy(deoptimization_env_->LocationAt(i), *values[i], slot_ix++);
   }
 
   // PC marker, caller-fp, caller-pc.
   builder.AddPcMarker(function, slot_ix++);
@@ skipping 682 matching lines @@
       return;
     }
   }
 
   // This move is not blocked.
   EmitMove(index);
 }
 
 
 }  // namespace dart