Subzero: Allow delaying Phi lowering until after register allocation.

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 28 matching lines @@
   }
   IceString getAsmName() const {
     return ".L" + Func->getFunctionName() + "$" + getName();
   }
 
   // The HasReturn flag indicates that this node contains a return
   // instruction and therefore needs an epilog.
   void setHasReturn() { HasReturn = true; }
   bool getHasReturn() const { return HasReturn; }
 
+  void setNeedsPlacement(bool Value) { NeedsPlacement = Value; }
+  bool needsPlacement() const { return NeedsPlacement; }
+
   // 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; }
   PhiList &getPhis() { return Phis; }
   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();
+  CfgNode *splitIncomingEdge(CfgNode *Pred, SizeT InEdgeIndex);
 
   void placePhiLoads();
   void placePhiStores();
   void deletePhis();
+  void advancedPhiLowering();
   void doAddressOpt();
   void doNopInsertion();
   void genCode();
   void livenessLightweight();
   bool liveness(Liveness *Liveness);
   void livenessPostprocess(LivenessMode Mode, Liveness *Liveness);
+  void contractIfEmpty();
   void doBranchOpt(const CfgNode *NextNode);
   void emit(Cfg *Func) const;
   void dump(Cfg *Func) const;
 
 private:
   CfgNode(Cfg *Func, SizeT LabelIndex, IceString Name);
   Cfg *const Func;
   const SizeT Number; // label index
   IceString Name;     // for dumping only
   bool HasReturn;     // does this block need an epilog?
+  bool NeedsPlacement;
   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