Subzero: Assemble calls to constant addresses.

src/IceFixups.h

 //===- subzero/src/IceFixups.h - Assembler fixup kinds ----------*- 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 generic fixup types.
@@ skipping 20 matching lines @@
   AssemblerFixup() : position_(0), kind_(0), value_(nullptr) {}
   AssemblerFixup(const AssemblerFixup &) = default;
   intptr_t position() const { return position_; }
   void set_position(intptr_t Position) { position_ = Position; }
 
   FixupKind kind() const { return kind_; }
   void set_kind(FixupKind Kind) { kind_ = Kind; }
 
   RelocOffsetT offset() const;
   IceString symbol(const GlobalContext *Ctx) const;
+
+  static const Constant *NullSymbol;
+  bool isNullSymbol() const { return value_ == NullSymbol; }
+
   void set_value(const Constant *Value) { value_ = Value; }
 
   void emit(GlobalContext *Ctx) const;
 
 private:
   intptr_t position_;
   FixupKind kind_;
   const Constant *value_;
 };
 
 typedef std::vector<AssemblerFixup> FixupList;
 typedef std::vector<AssemblerFixup *> FixupRefList;
 
 } // end of namespace Ice
 
 #endif // SUBZERO_SRC_ICEFIXUPS_H