Reapply "Initial implementation of on-stack replacement (OSR)."

runtime/vm/flow_graph.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_H_
 #define VM_FLOW_GRAPH_H_
 
 #include "vm/growable_array.h"
 #include "vm/intermediate_language.h"
 #include "vm/parser.h"
@@ skipping 163 matching lines @@
   // those loads that are not affected by anything in the loop and can be
   // hoisted out. Sets are computed by LoadOptimizer.
   ZoneGrowableArray<BitVector*>* loop_invariant_loads() const {
     return loop_invariant_loads_;
   }
   void set_loop_invariant_loads(
       ZoneGrowableArray<BitVector*>* loop_invariant_loads) {
     loop_invariant_loads_ = loop_invariant_loads;
   }
 
+  bool IsCompiledForOsr() const { return graph_entry()->IsCompiledForOsr(); }
+
  private:
   friend class IfConverter;
   friend class BranchSimplifier;
   friend class ConstantPropagator;
 
   // SSA transformation methods and fields.
   void ComputeDominators(GrowableArray<BitVector*>* dominance_frontier);
 
   void CompressPath(
       intptr_t start_index,
@@ skipping 148 matching lines @@
   // Per block sets of available blocks. Block A is available at the block B if
   // and only if A dominates B and all paths from A to B are free of side
   // effects.
   GrowableArray<BitVector*> available_at_;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_H_