Revert "Initial implementation of sparse conditional constant propagation."

runtime/vm/flow_graph_optimizer.h

 // 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.
 
 #ifndef VM_FLOW_GRAPH_OPTIMIZER_H_
 #define VM_FLOW_GRAPH_OPTIMIZER_H_
 
 #include "vm/intermediate_language.h"
 #include "vm/flow_graph.h"
 
@@ skipping 138 matching lines @@
  public:
   static void Optimize(FlowGraph* graph);
 
  private:
   static void OptimizeRecursive(
       BlockEntryInstr* entry,
       DirectChainedHashMap<Definition*>* map);
 };
 
 
-// Sparse conditional constant propagation and unreachable code elimination.
-// Assumes that use lists are computed and preserves them.
-class ConstantPropagator : public FlowGraphVisitor {
- public:
-  explicit ConstantPropagator(FlowGraph* graph);
-
-  static void Optimize(FlowGraph* graph) {
-    ConstantPropagator cp(graph);
-    cp.Analyze();
-    cp.Transform();
-  }
-
-  // Used to initialize the abstract value of definitions.
-  static RawObject* Unknown() { return Object::transition_sentinel(); }
-
- private:
-  void Analyze();
-  void Transform();
-
-  void SetReachable(BlockEntryInstr* block);
-  void SetValue(Definition* definition, const Object& value);
-
-  // Assign the join (least upper bound) of a pair of abstract values to the
-  // first one.
-  void Join(Object* left, const Object& right);
-
-  bool IsUnknown(const Object& value) {
-    return value.raw() == unknown_.raw();
-  }
-  bool IsNonConstant(const Object& value) {
-    return value.raw() == non_constant_.raw();
-  }
-  bool IsConstant(const Object& value) {
-    return !IsNonConstant(value) && !IsUnknown(value);
-  }
-
-  virtual void VisitBlocks() { UNREACHABLE(); }
-
-#define DECLARE_VISIT(type) virtual void Visit##type(type##Instr* instr);
-  FOR_EACH_INSTRUCTION(DECLARE_VISIT)
-#undef DECLARE_VISIT
-
-  FlowGraph* graph_;
-
-  // Sentinels for unknown constant and non-constant values.
-  const Object& unknown_;
-  const Object& non_constant_;
-
-  // Analysis results. For each block, a reachability bit.  Indexed by
-  // preorder number.
-  BitVector* reachable_;
-
-  // Definitions can move up the lattice twice, so we use a mark bit to
-  // indicate that they are already on the worklist in order to avoid adding
-  // them again.  Indexed by SSA temp index.
-  BitVector* definition_marks_;
-
-  // Worklists of blocks and definitions.
-  GrowableArray<BlockEntryInstr*> block_worklist_;
-  GrowableArray<Definition*> definition_worklist_;
-};
-
-
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_OPTIMIZER_H_