//=== MC/MCRegisterInfo.h - Target Register Description ---------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file describes an abstract interface used to get information about a
// target machines register file.  This information is used for a variety of
// purposed, especially register allocation.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_MC_MCREGISTERINFO_H
#define LLVM_MC_MCREGISTERINFO_H

#include <cassert>

namespace llvm {

/// MCRegisterDesc - This record contains all of the information known about
/// a particular register.  The Overlaps field contains a pointer to a zero
/// terminated array of registers that this register aliases, starting with
/// itself. This is needed for architectures like X86 which have AL alias AX
/// alias EAX. The SubRegs field is a zero terminated array of registers that
/// are sub-registers of the specific register, e.g. AL, AH are sub-registers of
/// AX. The SuperRegs field is a zero terminated array of registers that are
/// super-registers of the specific register, e.g. RAX, EAX, are super-registers
/// of AX.
///
struct MCRegisterDesc {
  const char     *Name;         // Printable name for the reg (for debugging)
  const unsigned *Overlaps;     // Overlapping registers, described above
  const unsigned *SubRegs;      // Sub-register set, described above
  const unsigned *SuperRegs;    // Super-register set, described above
};

/// MCRegisterInfo base class - We assume that the target defines a static
/// array of MCRegisterDesc objects that represent all of the machine
/// registers that the target has.  As such, we simply have to track a pointer
/// to this array so that we can turn register number into a register
/// descriptor.
///
/// Note this class is designed to be a base class of TargetRegisterInfo, which
/// is the interface used by codegen. However, specific targets *should never*
/// specialize this class. MCRegisterInfo should only contain getters to access
/// TableGen generated physical register data. It must not be extended with
/// virtual methods.
///
class MCRegisterInfo {
private:
  const MCRegisterDesc *Desc;             // Pointer to the descriptor array
  unsigned NumRegs;                       // Number of entries in the array

public:
  /// InitMCRegisterInfo - Initialize MCRegisterInfo, called by TableGen
  /// auto-generated routines. *DO NOT USE*.
  void InitMCRegisterInfo(const MCRegisterDesc *D, unsigned NR) {
    Desc = D;
    NumRegs = NR;
  }
    
  const MCRegisterDesc &operator[](unsigned RegNo) const {
    assert(RegNo < NumRegs &&
           "Attempting to access record for invalid register number!");
    return Desc[RegNo];
  }

  /// Provide a get method, equivalent to [], but more useful if we have a
  /// pointer to this object.
  ///
  const MCRegisterDesc &get(unsigned RegNo) const {
    return operator[](RegNo);
  }

  /// getAliasSet - Return the set of registers aliased by the specified
  /// register, or a null list of there are none.  The list returned is zero
  /// terminated.
  ///
  const unsigned *getAliasSet(unsigned RegNo) const {
    // The Overlaps set always begins with Reg itself.
    return get(RegNo).Overlaps + 1;
  }

  /// getOverlaps - Return a list of registers that overlap Reg, including
  /// itself. This is the same as the alias set except Reg is included in the
  /// list.
  /// These are exactly the registers in { x | regsOverlap(x, Reg) }.
  ///
  const unsigned *getOverlaps(unsigned RegNo) const {
    return get(RegNo).Overlaps;
  }

  /// getSubRegisters - Return the list of registers that are sub-registers of
  /// the specified register, or a null list of there are none. The list
  /// returned is zero terminated and sorted according to super-sub register
  /// relations. e.g. X86::RAX's sub-register list is EAX, AX, AL, AH.
  ///
  const unsigned *getSubRegisters(unsigned RegNo) const {
    return get(RegNo).SubRegs;
  }

  /// getSuperRegisters - Return the list of registers that are super-registers
  /// of the specified register, or a null list of there are none. The list
  /// returned is zero terminated and sorted according to super-sub register
  /// relations. e.g. X86::AL's super-register list is AX, EAX, RAX.
  ///
  const unsigned *getSuperRegisters(unsigned RegNo) const {
    return get(RegNo).SuperRegs;
  }

  /// getName - Return the human-readable symbolic target-specific name for the
  /// specified physical register.
  const char *getName(unsigned RegNo) const {
    return get(RegNo).Name;
  }

  /// getNumRegs - Return the number of registers this target has (useful for
  /// sizing arrays holding per register information)
  unsigned getNumRegs() const {
    return NumRegs;
  }
};
 
} // End llvm namespace

#endif