Subzero: Allow delaying Phi lowering until after register allocation.

src/IceLiveness.cpp

 //===- subzero/src/IceLiveness.cpp - Liveness analysis implementation -----===//
 //
 //                        The Subzero Code Generator
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file provides some of the support for the Liveness class.  In
@@ skipping 35 matching lines @@
       SizeT Index = VMetadata->getLocalUseNode(Var)->getIndex();
       ++Nodes[Index].NumLocals;
     }
   }
 
   // Resize each LivenessNode::LiveToVarMap, and the global
   // LiveToVarMap.  Reset the counts to 0.
   for (SizeT i = 0; i < NumNodes; ++i) {
     Nodes[i].LiveToVarMap.assign(Nodes[i].NumLocals, NULL);
     Nodes[i].NumLocals = 0;
+    Nodes[i].NumNonDeadPhis = 0;
   }
   LiveToVarMap.assign(NumGlobals, NULL);
 
   // Sort each variable into the appropriate LiveToVarMap.  Also set
   // VarToLiveMap.
   SizeT TmpNumGlobals = 0;
   for (SizeT i = 0; i < NumVars; ++i) {
     Variable *Var = Func->getVariables()[i];
     SizeT VarIndex = Var->getIndex();
     SizeT LiveIndex;
@@ skipping 22 matching lines @@
 }
 
 Variable *Liveness::getVariable(SizeT LiveIndex, const CfgNode *Node) const {
   if (LiveIndex < NumGlobals)
     return LiveToVarMap[LiveIndex];
   SizeT NodeIndex = Node->getIndex();
   return Nodes[NodeIndex].LiveToVarMap[LiveIndex - NumGlobals];
 }
 
 } // end of namespace Ice