VM: Propagate non-nullness from instance calls.

runtime/vm/flow_graph_inliner.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.
 #if !defined(DART_PRECOMPILED_RUNTIME)
 #include "vm/flow_graph_inliner.h"
 
 #include "vm/aot_optimizer.h"
 #include "vm/precompiler.h"
 #include "vm/block_scheduler.h"
 #include "vm/branch_optimizer.h"
@@ skipping 140 matching lines @@
  public:
   GraphInfoCollector() : call_site_count_(0), instruction_count_(0) {}
 
   void Collect(const FlowGraph& graph) {
     call_site_count_ = 0;
     instruction_count_ = 0;
     for (BlockIterator block_it = graph.postorder_iterator(); !block_it.Done();
          block_it.Advance()) {
       for (ForwardInstructionIterator it(block_it.Current()); !it.Done();
            it.Advance()) {
+        Instruction* current = it.Current();
+        // Don't count instructions that won't generate any code.
+        if (current->IsRedefinition()) {
+          continue;
+        }
         ++instruction_count_;
-        Instruction* current = it.Current();
         if (current->IsInstanceCall() || current->IsStaticCall() ||
             current->IsClosureCall()) {
           ++call_site_count_;
           continue;
         }
         if (current->IsPolymorphicInstanceCall()) {
           PolymorphicInstanceCallInstr* call =
               current->AsPolymorphicInstanceCall();
           // These checks make sure that the number of call-sites counted does
           // not change relative to the time when the current set of inlining
@@ skipping 3646 matching lines @@
     }
 
     default:
       return false;
   }
 }
 
 
 }  // namespace dart
 #endif  // !defined(DART_PRECOMPILED_RUNTIME)