Subzero: Improve performance of liveness analysis and live range construction.

src/IceCfgNode.h

 //===- subzero/src/IceCfgNode.h - Control flow graph node -------*- C++ -*-===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file declares the CfgNode class, which represents a single
@@ skipping 33 matching lines @@
   bool getHasReturn() const { return HasReturn; }
 
   // Access predecessor and successor edge lists.
   const NodeList &getInEdges() const { return InEdges; }
   const NodeList &getOutEdges() const { return OutEdges; }
 
   // Manage the instruction list.
   InstList &getInsts() { return Insts; }
   void appendInst(Inst *Inst);
   void renumberInstructions();
+  // Rough and generally conservative estimate of the number of
+  // instructions in the block.  It is updated when an instruction is
+  // added, but not when deleted.  It is recomputed during
+  // renumberInstructions().
+  InstNumberT getInstCountEstimate() const { return InstCountEstimate; }
 
   // Add a predecessor edge to the InEdges list for each of this
   // node's successors.
   void computePredecessors();
 
   void placePhiLoads();
   void placePhiStores();
   void deletePhis();
   void doAddressOpt();
   void doNopInsertion();
   void genCode();
   void livenessLightweight();
   bool liveness(Liveness *Liveness);
   void livenessPostprocess(LivenessMode Mode, Liveness *Liveness);
   void doBranchOpt(const CfgNode *NextNode);
   void emit(Cfg *Func) const;
   void dump(Cfg *Func) const;
 
 private:
   CfgNode(Cfg *Func, SizeT LabelIndex, IceString Name);
   CfgNode(const CfgNode &) = delete;
   CfgNode &operator=(const CfgNode &) = delete;
   Cfg *const Func;
   const SizeT Number; // label index
   IceString Name;     // for dumping only
   bool HasReturn;     // does this block need an epilog?
+  InstNumberT InstCountEstimate; // rough instruction count estimate
   NodeList InEdges;   // in no particular order
   NodeList OutEdges;  // in no particular order
   PhiList Phis;       // unordered set of phi instructions
   InstList Insts;     // ordered list of non-phi instructions
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICECFGNODE_H