//===- MipsRegisterInfo.cpp - MIPS Register Information -== -----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file contains the MIPS implementation of the TargetRegisterInfo class.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "mips-reg-info"

#include "Mips.h"
#include "MipsSubtarget.h"
#include "MipsRegisterInfo.h"
#include "MipsMachineFunction.h"
#include "llvm/Constants.h"
#include "llvm/Type.h"
#include "llvm/Function.h"
#include "llvm/CodeGen/ValueTypes.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineLocation.h"
#include "llvm/Target/TargetFrameLowering.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Target/TargetInstrInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/BitVector.h"
#include "llvm/ADT/STLExtras.h"

using namespace llvm;

MipsRegisterInfo::MipsRegisterInfo(const MipsSubtarget &ST,
                                   const TargetInstrInfo &tii)
  : MipsGenRegisterInfo(Mips::ADJCALLSTACKDOWN, Mips::ADJCALLSTACKUP),
    Subtarget(ST), TII(tii) {}

/// getRegisterNumbering - Given the enum value for some register, e.g.
/// Mips::RA, return the number that it corresponds to (e.g. 31).
unsigned MipsRegisterInfo::
getRegisterNumbering(unsigned RegEnum)
{
  switch (RegEnum) {
    case Mips::ZERO : case Mips::F0 : case Mips::D0 : return 0;
    case Mips::AT   : case Mips::F1 : return 1;
    case Mips::V0   : case Mips::F2 : case Mips::D1 : return 2;
    case Mips::V1   : case Mips::F3 : return 3;
    case Mips::A0   : case Mips::F4 : case Mips::D2 : return 4;
    case Mips::A1   : case Mips::F5 : return 5;
    case Mips::A2   : case Mips::F6 : case Mips::D3 : return 6;
    case Mips::A3   : case Mips::F7 : return 7;
    case Mips::T0   : case Mips::F8 : case Mips::D4 : return 8;
    case Mips::T1   : case Mips::F9 : return 9;
    case Mips::T2   : case Mips::F10: case Mips::D5: return 10;
    case Mips::T3   : case Mips::F11: return 11;
    case Mips::T4   : case Mips::F12: case Mips::D6: return 12;
    case Mips::T5   : case Mips::F13: return 13;
    case Mips::T6   : case Mips::F14: case Mips::D7: return 14;
    case Mips::T7   : case Mips::F15: return 15;
    case Mips::T8   : case Mips::F16: case Mips::D8: return 16;
    case Mips::T9   : case Mips::F17: return 17;
    case Mips::S0   : case Mips::F18: case Mips::D9: return 18;
    case Mips::S1   : case Mips::F19: return 19;
    case Mips::S2   : case Mips::F20: case Mips::D10: return 20;
    case Mips::S3   : case Mips::F21: return 21;
    case Mips::S4   : case Mips::F22: case Mips::D11: return 22;
    case Mips::S5   : case Mips::F23: return 23;
    case Mips::S6   : case Mips::F24: case Mips::D12: return 24;
    case Mips::S7   : case Mips::F25: return 25;
    case Mips::K0   : case Mips::F26: case Mips::D13: return 26;
    case Mips::K1   : case Mips::F27: return 27;
    case Mips::GP   : case Mips::F28: case Mips::D14: return 28;
    case Mips::SP   : case Mips::F29: return 29;
    case Mips::FP   : case Mips::F30: case Mips::D15: return 30;
    case Mips::RA   : case Mips::F31: return 31;
    default: llvm_unreachable("Unknown register number!");
  }
  return 0; // Not reached
}

unsigned MipsRegisterInfo::getPICCallReg() { return Mips::T9; }

//===----------------------------------------------------------------------===//
// Callee Saved Registers methods
//===----------------------------------------------------------------------===//

/// Mips Callee Saved Registers
const unsigned* MipsRegisterInfo::
getCalleeSavedRegs(const MachineFunction *MF) const
{
  // Mips callee-save register range is $16-$23, $f20-$f30
  static const unsigned SingleFloatOnlyCalleeSavedRegs[] = {
    Mips::S0, Mips::S1, Mips::S2, Mips::S3,
    Mips::S4, Mips::S5, Mips::S6, Mips::S7,
    Mips::F20, Mips::F21, Mips::F22, Mips::F23, Mips::F24, Mips::F25,
    Mips::F26, Mips::F27, Mips::F28, Mips::F29, Mips::F30, 0
  };

  static const unsigned BitMode32CalleeSavedRegs[] = {
    Mips::S0, Mips::S1, Mips::S2, Mips::S3,
    Mips::S4, Mips::S5, Mips::S6, Mips::S7,
    Mips::F20, Mips::F22, Mips::F24, Mips::F26, Mips::F28, Mips::F30, 0
  };

  if (Subtarget.isSingleFloat())
    return SingleFloatOnlyCalleeSavedRegs;
  else
    return BitMode32CalleeSavedRegs;
}

BitVector MipsRegisterInfo::
getReservedRegs(const MachineFunction &MF) const {
  BitVector Reserved(getNumRegs());
  Reserved.set(Mips::ZERO);
  Reserved.set(Mips::AT);
  Reserved.set(Mips::K0);
  Reserved.set(Mips::K1);
  Reserved.set(Mips::GP);
  Reserved.set(Mips::SP);
  Reserved.set(Mips::FP);
  Reserved.set(Mips::RA);

  // SRV4 requires that odd register can't be used.
  if (!Subtarget.isSingleFloat())
    for (unsigned FReg=(Mips::F0)+1; FReg < Mips::F30; FReg+=2)
      Reserved.set(FReg);

  return Reserved;
}

// This function eliminate ADJCALLSTACKDOWN,
// ADJCALLSTACKUP pseudo instructions
void MipsRegisterInfo::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator I) const {
  // Simply discard ADJCALLSTACKDOWN, ADJCALLSTACKUP instructions.
  MBB.erase(I);
}

// FrameIndex represent objects inside a abstract stack.
// We must replace FrameIndex with an stack/frame pointer
// direct reference.
void MipsRegisterInfo::
eliminateFrameIndex(MachineBasicBlock::iterator II, int SPAdj,
                    RegScavenger *RS) const {
  MachineInstr &MI = *II;
  MachineFunction &MF = *MI.getParent()->getParent();

  unsigned i = 0;
  while (!MI.getOperand(i).isFI()) {
    ++i;
    assert(i < MI.getNumOperands() &&
           "Instr doesn't have FrameIndex operand!");
  }

  DEBUG(errs() << "\nFunction : " << MF.getFunction()->getName() << "\n";
        errs() << "<--------->\n" << MI);

  int FrameIndex = MI.getOperand(i).getIndex();
  int stackSize  = MF.getFrameInfo()->getStackSize();
  int spOffset   = MF.getFrameInfo()->getObjectOffset(FrameIndex);

  DEBUG(errs() << "FrameIndex : " << FrameIndex << "\n"
               << "spOffset   : " << spOffset << "\n"
               << "stackSize  : " << stackSize << "\n");

  // as explained on LowerFormalArguments, detect negative offsets
  // and adjust SPOffsets considering the final stack size.
  int Offset = ((spOffset < 0) ? (stackSize + (-(spOffset+4))) : (spOffset));
  Offset    += MI.getOperand(i-1).getImm();

  DEBUG(errs() << "Offset     : " << Offset << "\n" << "<--------->\n");

  unsigned NewReg = 0;
  int NewImm = 0;
  MachineBasicBlock &MBB = *MI.getParent();
  bool ATUsed;
  unsigned OrigReg = getFrameRegister(MF);
  int OrigImm = Offset;

// OrigImm fits in the 16-bit field
  if (OrigImm < 0x8000 && OrigImm >= -0x8000) {
    NewReg = OrigReg;
    NewImm = OrigImm;
    ATUsed = false;
  }
  else {
    const TargetInstrInfo *TII = MF.getTarget().getInstrInfo();
    DebugLoc DL = II->getDebugLoc();
    int ImmLo = OrigImm & 0xffff;
    int ImmHi = (((unsigned)OrigImm & 0xffff0000) >> 16) + ((OrigImm & 0x8000) != 0);

    // FIXME: change this when mips goes MC".
    BuildMI(MBB, II, DL, TII->get(Mips::NOAT));
    BuildMI(MBB, II, DL, TII->get(Mips::LUi), Mips::AT).addImm(ImmHi);
    BuildMI(MBB, II, DL, TII->get(Mips::ADDu), Mips::AT).addReg(OrigReg).addReg(Mips::AT);
    NewReg = Mips::AT;
    NewImm = ImmLo;
    
    ATUsed = true;
  }

  // FIXME: change this when mips goes MC".
  if (ATUsed)
    BuildMI(MBB, ++II, MI.getDebugLoc(), TII.get(Mips::ATMACRO));

  MI.getOperand(i).ChangeToRegister(NewReg, false);
  MI.getOperand(i-1).ChangeToImmediate(NewImm);
}

void MipsRegisterInfo::
processFunctionBeforeFrameFinalized(MachineFunction &MF) const {
  // Set the stack offset where GP must be saved/loaded from.
  MachineFrameInfo *MFI = MF.getFrameInfo();
  MipsFunctionInfo *MipsFI = MF.getInfo<MipsFunctionInfo>();
  if (MipsFI->needGPSaveRestore())
    MFI->setObjectOffset(MipsFI->getGPFI(), MipsFI->getGPStackOffset());
}

unsigned MipsRegisterInfo::
getRARegister() const {
  return Mips::RA;
}

unsigned MipsRegisterInfo::
getFrameRegister(const MachineFunction &MF) const {
  const TargetFrameLowering *TFI = MF.getTarget().getFrameLowering();

  return TFI->hasFP(MF) ? Mips::FP : Mips::SP;
}

unsigned MipsRegisterInfo::
getEHExceptionRegister() const {
  llvm_unreachable("What is the exception register");
  return 0;
}

unsigned MipsRegisterInfo::
getEHHandlerRegister() const {
  llvm_unreachable("What is the exception handler register");
  return 0;
}

int MipsRegisterInfo::
getDwarfRegNum(unsigned RegNum, bool isEH) const {
  llvm_unreachable("What is the dwarf register number");
  return -1;
}

#include "MipsGenRegisterInfo.inc"