Subzero: Don't store std::string objects inside Variable.

src/IceCfg.h

 //===- subzero/src/IceCfg.h - Control flow graph ----------------*- 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 Cfg class, which represents the control flow
@@ skipping 44 matching lines @@
   bool hasError() const { return HasError; }
   IceString getError() const { return ErrorMessage; }
 
   // Manage nodes (a.k.a. basic blocks, CfgNodes).
   void setEntryNode(CfgNode *EntryNode) { Entry = EntryNode; }
   CfgNode *getEntryNode() const { return Entry; }
   // Create a node and append it to the end of the linearized list.
   CfgNode *makeNode();
   SizeT getNumNodes() const { return Nodes.size(); }
   const NodeList &getNodes() const { return Nodes; }
+
+  typedef int32_t IdentifierIndexType;
   // Adds a name to the list and returns its index, suitable for the
-  // argument to getNodeName().  No checking for duplicates is done.
-  int32_t addNodeName(const IceString &Name) {
-    int32_t Index = NodeNames.size();
-    NodeNames.push_back(Name);
+  // argument to getIdentifierName().  No checking for duplicates is
+  // done.  This is generally used for node names and variable names
+  // to avoid embedding a std::string inside an arena-allocated
+  // object.
+  IdentifierIndexType addIdentifierName(const IceString &Name) {
+    IdentifierIndexType Index = IdentifierNames.size();
+    IdentifierNames.push_back(Name);
     return Index;
   }
-  const IceString &getNodeName(int32_t Index) const { return NodeNames[Index]; }
+  const IceString &getIdentifierName(IdentifierIndexType Index) const {
+    return IdentifierNames[Index];
+  }
+  enum {
+    IdentifierIndexInvalid = -1
+  };
 
   // Manage instruction numbering.
   InstNumberT newInstNumber() { return NextInstNumber++; }
   InstNumberT getNextInstNumber() const { return NextInstNumber; }
 
   // Manage Variables.
   // Create a new Variable with a particular type and an optional
   // name.  The Node argument is the node where the variable is defined.
-  template <typename T = Variable>
-  T *makeVariable(Type Ty, const IceString &Name = "") {
+  template <typename T = Variable> T *makeVariable(Type Ty) {
     SizeT Index = Variables.size();
-    T *Var = T::create(this, Ty, Index, Name);
+    T *Var = T::create(this, Ty, Index);
     Variables.push_back(Var);
     return Var;
   }
   SizeT getNumVariables() const { return Variables.size(); }
   const VarList &getVariables() const { return Variables; }
 
   // Manage arguments to the function.
   void addArg(Variable *Arg);
   const VarList &getArgs() const { return Args; }
   VarList &getArgs() { return Args; }
@@ skipping 81 matching lines @@
 
   GlobalContext *Ctx;
   IceString FunctionName;
   Type ReturnType;
   bool IsInternalLinkage;
   bool HasError;
   bool FocusedTiming;
   IceString ErrorMessage;
   CfgNode *Entry; // entry basic block
   NodeList Nodes; // linearized node list; Entry should be first
-  std::vector<IceString> NodeNames;
+  std::vector<IceString> IdentifierNames;
   InstNumberT NextInstNumber;
   VarList Variables;
   VarList Args; // subset of Variables, in argument order
   VarList ImplicitArgs; // subset of Variables
   std::unique_ptr<Liveness> Live;
   std::unique_ptr<TargetLowering> Target;
   std::unique_ptr<VariablesMetadata> VMetadata;
   std::unique_ptr<Assembler> TargetAssembler;
 
   // CurrentNode is maintained during dumping/emitting just for
   // validating Variable::DefNode.  Normally, a traversal over
   // CfgNodes maintains this, but before global operations like
   // register allocation, resetCurrentNode() should be called to avoid
   // spurious validation failures.
   const CfgNode *CurrentNode;
 };
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICECFG_H