Subzero: Allow delaying Phi lowering until after register allocation.

src/IceOperand.h

 //===- subzero/src/IceOperand.h - High-level operands -----------*- 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 Operand class and its target-independent
@@ skipping 380 matching lines @@
   }
 
   bool getIsArg() const { return IsArgument; }
   void setIsArg(bool Val = true) { IsArgument = Val; }
   bool getIsImplicitArg() const { return IsImplicitArgument; }
   void setIsImplicitArg(bool Val = true) { IsImplicitArgument = Val; }
 
   void setIgnoreLiveness() { IgnoreLiveness = true; }
   bool getIgnoreLiveness() const { return IgnoreLiveness; }
 
+  bool needsStackSlot() const { return NeedsStackSlot; }
+  void setNeedsStackSlot() { NeedsStackSlot = true; }
   int32_t getStackOffset() const { return StackOffset; }
   void setStackOffset(int32_t Offset) { StackOffset = Offset; }
 
   static const int32_t NoRegister = -1;
   bool hasReg() const { return getRegNum() != NoRegister; }
   int32_t getRegNum() const { return RegNum; }
   void setRegNum(int32_t NewRegNum) {
     // Regnum shouldn't be set more than once.
     assert(!hasReg() || RegNum == NewRegNum);
     RegNum = NewRegNum;
@@ skipping 56 matching lines @@
     OperandKind Kind = Operand->getKind();
     return Kind >= kVariable && Kind <= kVariable_Num;
   }
 
   // The destructor is public because of the asType() method.
   ~Variable() override {}
 
 protected:
   Variable(OperandKind K, Type Ty, SizeT Index, const IceString &Name)
       : Operand(K, Ty), Number(Index), Name(Name), IsArgument(false),
-        IsImplicitArgument(false), IgnoreLiveness(false), StackOffset(0),
-        RegNum(NoRegister), RegNumTmp(NoRegister), Weight(1), LoVar(NULL),
-        HiVar(NULL) {
+        IsImplicitArgument(false), IgnoreLiveness(false), NeedsStackSlot(false),
+        StackOffset(0), RegNum(NoRegister), RegNumTmp(NoRegister), Weight(1),
+        LoVar(NULL), HiVar(NULL) {
     Vars = VarsReal;
     Vars[0] = this;
     NumVars = 1;
   }
   // Number is unique across all variables, and is used as a
   // (bit)vector index for liveness analysis.
   const SizeT Number;
   // Name is optional.
   IceString Name;
   bool IsArgument;
   bool IsImplicitArgument;
   // IgnoreLiveness means that the variable should be ignored when
   // constructing and validating live ranges.  This is usually
   // reserved for the stack pointer.
   bool IgnoreLiveness;
+  // NeedsStackSlot starts out false, and is set to true once we know
+  // for sure that the variable needs a stack slot.
+  bool NeedsStackSlot;
   // StackOffset is the canonical location on stack (only if
   // RegNum==NoRegister || IsArgument).
   int32_t StackOffset;
   // RegNum is the allocated register, or NoRegister if it isn't
   // register-allocated.
   int32_t RegNum;
   // RegNumTmp is the tentative assignment during register allocation.
   int32_t RegNumTmp;
   RegWeight Weight; // Register allocation priority
   LiveRange Live;
@@ skipping 66 matching lines @@
 // complete set of Variables.
 class VariablesMetadata {
   VariablesMetadata(const VariablesMetadata &) = delete;
   VariablesMetadata &operator=(const VariablesMetadata &) = delete;
 
 public:
   VariablesMetadata(const Cfg *Func) : Func(Func) {}
   // Initialize the state by traversing all instructions/variables in
   // the CFG.
   void init(MetadataKind TrackingKind);
+  // Add a single node.  This is called by init(), and can be called
+  // incrementally from elsewhere, e.g. after edge-splitting.
+  void addNode(CfgNode *Node);
   // Returns whether the given Variable is tracked in this object.  It
   // should only return false if changes were made to the CFG after
   // running init(), in which case the state is stale and the results
   // shouldn't be trusted (but it may be OK e.g. for dumping).
   bool isTracked(const Variable *Var) const {
     return Var->getIndex() < Metadata.size();
   }
 
   // Returns whether the given Variable has multiple definitions.
   bool isMultiDef(const Variable *Var) const;
@@ skipping 27 matching lines @@
 private:
   const Cfg *Func;
   MetadataKind Kind;
   std::vector<VariableTracking> Metadata;
   const static InstDefList NoDefinitions;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEOPERAND_H