Move ConstantPropagator from flow_graph_optimizer.cc/.h into separate files.

runtime/vm/flow_graph_optimizer.h

Index: runtime/vm/flow_graph_optimizer.h
===================================================================
--- runtime/vm/flow_graph_optimizer.h	(revision 42566)
+++ runtime/vm/flow_graph_optimizer.h	(working copy)
@@ -316,83 +316,6 @@
 };
 
 
-// Sparse conditional constant propagation and unreachable code elimination.
-// Assumes that use lists are computed and preserves them.
-class ConstantPropagator : public FlowGraphVisitor {
- public:
-  ConstantPropagator(FlowGraph* graph,
-                     const GrowableArray<BlockEntryInstr*>& ignored);
-
-  static void Optimize(FlowGraph* graph);
-
-  // (1) Visit branches to optimize away unreachable blocks discovered  by range
-  // analysis.
-  // (2) Eliminate branches that have the same true- and false-target: For
-  // example, this occurs after expressions like
-  //
-  // if (a == null || b == null) {
-  //   ...
-  // }
-  //
-  // where b is known to be null.
-  static void OptimizeBranches(FlowGraph* graph);
-
-  // Used to initialize the abstract value of definitions.
-  static RawObject* Unknown() { return Object::unknown_constant().raw(); }
-
- private:
-  void Analyze();
-  void Transform();
-  void EliminateRedundantBranches();
-
-  void SetReachable(BlockEntryInstr* block);
-  bool SetValue(Definition* definition, const Object& value);
-
-  Definition* UnwrapPhi(Definition* defn);
-  void MarkPhi(Definition* defn);
-
-  // 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);
-  }
-
-  void VisitBinaryIntegerOp(BinaryIntegerOpInstr* binary_op);
-
-  virtual void VisitBlocks() { UNREACHABLE(); }
-
-#define DECLARE_VISIT(type) virtual void Visit##type(type##Instr* instr);
-  FOR_EACH_INSTRUCTION(DECLARE_VISIT)
-#undef DECLARE_VISIT
-
-  Isolate* isolate() const { return graph_->isolate(); }
-
-  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_;
-
-  BitVector* marked_phis_;
-
-  // Worklists of blocks and definitions.
-  GrowableArray<BlockEntryInstr*> block_worklist_;
-  DefinitionWorklist definition_worklist_;
-};
-
-
 // Rewrite branches to eliminate materialization of boolean values after
 // inlining, and to expose other optimizations (e.g., constant folding of
 // branches, unreachable code elimination).