More general dead phi elimination.

runtime/vm/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/compiler.h"
 
 #include "vm/assembler.h"
 
 #include "vm/ast_printer.h"
 #include "vm/block_scheduler.h"
@@ skipping 471 matching lines @@
         DEBUG_ASSERT(flow_graph->VerifyUseLists());
 
         // Optimize try-blocks.
         TryCatchAnalyzer::Optimize(flow_graph);
 
         // Detach environments from the instructions that can't deoptimize.
         // Do it before we attempt to perform allocation sinking to minimize
         // amount of materializations it has to perform.
         optimizer.EliminateEnvironments();
 
+        DeadCodeElimination::EliminateDeadPhis(flow_graph);
+
         // Attempt to sink allocations of temporary non-escaping objects to
         // the deoptimization path.
         AllocationSinking* sinking = NULL;
         if (FLAG_allocation_sinking &&
             (flow_graph->graph_entry()->SuccessorCount()  == 1)) {
           // TODO(fschneider): Support allocation sinking with try-catch.
           sinking = new AllocationSinking(flow_graph);
           sinking->Optimize();
         }
 
@@ skipping 465 matching lines @@
     const Object& result =
       Object::Handle(isolate->object_store()->sticky_error());
     isolate->object_store()->clear_sticky_error();
     return result.raw();
   }
   UNREACHABLE();
   return Object::null();
 }
 
 }  // namespace dart