//===-- llvm/CodeGen/AllocationOrder.h - Allocation Order -*- C++ -*-------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements an allocation order for virtual registers.
//
// The preferred allocation order for a virtual register depends on allocation
// hints and target hooks. The AllocationOrder class encapsulates all of that.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_CODEGEN_ALLOCATIONORDER_H
#define LLVM_CODEGEN_ALLOCATIONORDER_H

namespace llvm {

class BitVector;
class VirtRegMap;

class AllocationOrder {
  const unsigned *Begin;
  const unsigned *End;
  const unsigned *Pos;
  const BitVector &Reserved;
  unsigned Hint;
public:

  /// AllocationOrder - Create a new AllocationOrder for VirtReg.
  /// @param VirtReg      Virtual register to allocate for.
  /// @param VRM          Virtual register map for function.
  /// @param ReservedRegs Set of reserved registers as returned by
  ///        TargetRegisterInfo::getReservedRegs().
  AllocationOrder(unsigned VirtReg,
                  const VirtRegMap &VRM,
                  const BitVector &ReservedRegs);

  /// next - Return the next physical register in the allocation order, or 0.
  /// It is safe to call next again after it returned 0.
  /// It will keep returning 0 until rewind() is called.
  unsigned next();

  /// rewind - Start over from the beginning.
  void rewind() { Pos = 0; }

  /// isHint - Return true if PhysReg is a preferred register.
  bool isHint(unsigned PhysReg) const { return PhysReg == Hint; }
};

} // end namespace llvm

#endif