Subzero: Allow delaying Phi lowering until after register allocation.

src/IceLiveness.h

 //===- subzero/src/IceLiveness.h - Liveness analysis ------------*- 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 Liveness and LivenessNode classes,
@@ skipping 14 matching lines @@
 
 namespace Ice {
 
 class LivenessNode {
   // TODO: Disable these constructors when Liveness::Nodes is no
   // longer an STL container.
   // LivenessNode(const LivenessNode &) = delete;
   // LivenessNode &operator=(const LivenessNode &) = delete;
 
 public:
-  LivenessNode() : NumLocals(0) {}
+  LivenessNode() : NumLocals(0), NumNonDeadPhis(0) {}
   // NumLocals is the number of Variables local to this block.
   SizeT NumLocals;
+  // NumNonDeadPhis tracks the number of Phi instructions that
+  // Inst::liveness() identified as tentatively live.  If
+  // NumNonDeadPhis changes from the last liveness pass, then liveness
+  // has not yet converged.
+  SizeT NumNonDeadPhis;
   // LiveToVarMap maps a liveness bitvector index to a Variable.  This
   // is generally just for printing/dumping.  The index should be less
   // than NumLocals + Liveness::NumGlobals.
   std::vector<Variable *> LiveToVarMap;
   // LiveIn and LiveOut track the in- and out-liveness of the global
   // variables.  The size of each vector is
   // LivenessNode::NumGlobals.
   LivenessBV LiveIn, LiveOut;
   // LiveBegin and LiveEnd track the instruction numbers of the start
   // and end of each variable's live range within this block.  The
@@ skipping 11 matching lines @@
       : Func(Func), Mode(Mode), NumGlobals(0) {}
   void init();
   Cfg *getFunc() const { return Func; }
   LivenessMode getMode() const { return Mode; }
   Variable *getVariable(SizeT LiveIndex, const CfgNode *Node) const;
   SizeT getLiveIndex(SizeT VarIndex) const { return VarToLiveMap[VarIndex]; }
   SizeT getNumGlobalVars() const { return NumGlobals; }
   SizeT getNumVarsInNode(const CfgNode *Node) const {
     return NumGlobals + Nodes[Node->getIndex()].NumLocals;
   }
+  SizeT &getNumNonDeadPhis(const CfgNode *Node) {
+    return Nodes[Node->getIndex()].NumNonDeadPhis;
+  }
   LivenessBV &getLiveIn(const CfgNode *Node) {
-    return Nodes[Node->getIndex()].LiveIn;
+    SizeT Index = Node->getIndex();
+    resize(Index);
+    return Nodes[Index].LiveIn;
   }
   LivenessBV &getLiveOut(const CfgNode *Node) {
-    return Nodes[Node->getIndex()].LiveOut;
+    SizeT Index = Node->getIndex();
+    resize(Index);
+    return Nodes[Index].LiveOut;
   }
   LiveBeginEndMap *getLiveBegin(const CfgNode *Node) {
-    return &Nodes[Node->getIndex()].LiveBegin;
+    SizeT Index = Node->getIndex();
+    resize(Index);
+    return &Nodes[Index].LiveBegin;
   }
   LiveBeginEndMap *getLiveEnd(const CfgNode *Node) {
-    return &Nodes[Node->getIndex()].LiveEnd;
+    SizeT Index = Node->getIndex();
+    resize(Index);
+    return &Nodes[Index].LiveEnd;
   }
 
 private:
+  // Resize Nodes so that Nodes[Index] is valid.
+  void resize(SizeT Index) {
+    if (Index >= Nodes.size())
+      Nodes.resize(Index + 1);
+  }
   Cfg *Func;
   LivenessMode Mode;
   SizeT NumGlobals;
   // Size of Nodes is Cfg::Nodes.size().
   std::vector<LivenessNode> Nodes;
   // VarToLiveMap maps a Variable's Variable::Number to its live index
   // within its basic block.
   std::vector<SizeT> VarToLiveMap;
   // LiveToVarMap is analogous to LivenessNode::LiveToVarMap, but for
   // non-local variables.
   std::vector<Variable *> LiveToVarMap;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICELIVENESS_H