AlphaRegisterInfo.cpp

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//===- AlphaRegisterInfo.cpp - Alpha 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 Alpha implementation of the TargetRegisterInfo class.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "reginfo"
#include "Alpha.h"
#include "AlphaRegisterInfo.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/TargetFrameInfo.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/ADT/BitVector.h"
#include "llvm/ADT/STLExtras.h"
#include <cstdlib>
using namespace llvm;

//These describe LDAx
static const int IMM_LOW  = -32768;
static const int IMM_HIGH = 32767;
static const int IMM_MULT = 65536;

static long getUpper16(long l)
{
  long y = l / IMM_MULT;
  if (l % IMM_MULT > IMM_HIGH)
    ++y;
  return y;
}

static long getLower16(long l)
{
  long h = getUpper16(l);
  return l - h * IMM_MULT;
}

AlphaRegisterInfo::AlphaRegisterInfo(const TargetInstrInfo &tii)
  : AlphaGenRegisterInfo(Alpha::ADJUSTSTACKDOWN, Alpha::ADJUSTSTACKUP),
    TII(tii)
{
}

const unsigned* AlphaRegisterInfo::getCalleeSavedRegs(const MachineFunction *MF)
                                                                         const {
  static const unsigned CalleeSavedRegs[] = {
    Alpha::R9, Alpha::R10,
    Alpha::R11, Alpha::R12,
    Alpha::R13, Alpha::R14,
    Alpha::F2, Alpha::F3,
    Alpha::F4, Alpha::F5,
    Alpha::F6, Alpha::F7,
    Alpha::F8, Alpha::F9,  0
  };
  return CalleeSavedRegs;
}

const TargetRegisterClass* const*
AlphaRegisterInfo::getCalleeSavedRegClasses(const MachineFunction *MF) const {
  static const TargetRegisterClass * const CalleeSavedRegClasses[] = {
    &Alpha::GPRCRegClass, &Alpha::GPRCRegClass,
    &Alpha::GPRCRegClass, &Alpha::GPRCRegClass,
    &Alpha::GPRCRegClass, &Alpha::GPRCRegClass,
    &Alpha::F8RCRegClass, &Alpha::F8RCRegClass,
    &Alpha::F8RCRegClass, &Alpha::F8RCRegClass,
    &Alpha::F8RCRegClass, &Alpha::F8RCRegClass,
    &Alpha::F8RCRegClass, &Alpha::F8RCRegClass,  0
  };
  return CalleeSavedRegClasses;
}

BitVector AlphaRegisterInfo::getReservedRegs(const MachineFunction &MF) const {
  BitVector Reserved(getNumRegs());
  Reserved.set(Alpha::R15);
  Reserved.set(Alpha::R30);
  Reserved.set(Alpha::R31);
  return Reserved;
}

//===----------------------------------------------------------------------===//
// Stack Frame Processing methods
//===----------------------------------------------------------------------===//

// hasFP - Return true if the specified function should have a dedicated frame
// pointer register.  This is true if the function has variable sized allocas or
// if frame pointer elimination is disabled.
//
bool AlphaRegisterInfo::hasFP(const MachineFunction &MF) const {
  const MachineFrameInfo *MFI = MF.getFrameInfo();
  return MFI->hasVarSizedObjects();
}

void AlphaRegisterInfo::
eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                              MachineBasicBlock::iterator I) const {
  if (hasFP(MF)) {
    // If we have a frame pointer, turn the adjcallstackup instruction into a
    // 'sub ESP, <amt>' and the adjcallstackdown instruction into 'add ESP,
    // <amt>'
    MachineInstr *Old = I;
    uint64_t Amount = Old->getOperand(0).getImm();
    if (Amount != 0) {
      // We need to keep the stack aligned properly.  To do this, we round the
      // amount of space needed for the outgoing arguments up to the next
      // alignment boundary.
      unsigned Align = MF.getTarget().getFrameInfo()->getStackAlignment();
      Amount = (Amount+Align-1)/Align*Align;

      MachineInstr *New;
      if (Old->getOpcode() == Alpha::ADJUSTSTACKDOWN) {
        New=BuildMI(MF, TII.get(Alpha::LDA), Alpha::R30)
          .addImm(-Amount).addReg(Alpha::R30);
      } else {
         assert(Old->getOpcode() == Alpha::ADJUSTSTACKUP);
         New=BuildMI(MF, TII.get(Alpha::LDA), Alpha::R30)
          .addImm(Amount).addReg(Alpha::R30);
      }

      // Replace the pseudo instruction with a new instruction...
      MBB.insert(I, New);
    }
  }

  MBB.erase(I);
}

//Alpha has a slightly funny stack:
//Args
//<- incoming SP
//fixed locals (and spills, callee saved, etc)
//<- FP
//variable locals
//<- SP

void AlphaRegisterInfo::eliminateFrameIndex(MachineBasicBlock::iterator II,
                                            int SPAdj, RegScavenger *RS) const {
  assert(SPAdj == 0 && "Unexpected");

  unsigned i = 0;
  MachineInstr &MI = *II;
  MachineBasicBlock &MBB = *MI.getParent();
  MachineFunction &MF = *MBB.getParent();
  bool FP = hasFP(MF);

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

  int FrameIndex = MI.getOperand(i).getIndex();

  // Add the base register of R30 (SP) or R15 (FP).
  MI.getOperand(i + 1).ChangeToRegister(FP ? Alpha::R15 : Alpha::R30, false);

  // Now add the frame object offset to the offset from the virtual frame index.
  int Offset = MF.getFrameInfo()->getObjectOffset(FrameIndex);

  DOUT << "FI: " << FrameIndex << " Offset: " << Offset << "\n";

  Offset += MF.getFrameInfo()->getStackSize();

  DOUT << "Corrected Offset " << Offset
       << " for stack size: " << MF.getFrameInfo()->getStackSize() << "\n";

  if (Offset > IMM_HIGH || Offset < IMM_LOW) {
    DOUT << "Unconditionally using R28 for evil purposes Offset: "
         << Offset << "\n";
    //so in this case, we need to use a temporary register, and move the
    //original inst off the SP/FP
    //fix up the old:
    MI.getOperand(i + 1).ChangeToRegister(Alpha::R28, false);
    MI.getOperand(i).ChangeToImmediate(getLower16(Offset));
    //insert the new
    MachineInstr* nMI=BuildMI(MF, TII.get(Alpha::LDAH), Alpha::R28)
      .addImm(getUpper16(Offset)).addReg(FP ? Alpha::R15 : Alpha::R30);
    MBB.insert(II, nMI);
  } else {
    MI.getOperand(i).ChangeToImmediate(Offset);
  }
}


void AlphaRegisterInfo::emitPrologue(MachineFunction &MF) const {
  MachineBasicBlock &MBB = MF.front();   // Prolog goes in entry BB
  MachineBasicBlock::iterator MBBI = MBB.begin();
  MachineFrameInfo *MFI = MF.getFrameInfo();
  bool FP = hasFP(MF);

  static int curgpdist = 0;

  //handle GOP offset
  BuildMI(MBB, MBBI, TII.get(Alpha::LDAHg), Alpha::R29)
    .addGlobalAddress(const_cast<Function*>(MF.getFunction()))
    .addReg(Alpha::R27).addImm(++curgpdist);
  BuildMI(MBB, MBBI, TII.get(Alpha::LDAg), Alpha::R29)
    .addGlobalAddress(const_cast<Function*>(MF.getFunction()))
    .addReg(Alpha::R29).addImm(curgpdist);

  //evil const_cast until MO stuff setup to handle const
  BuildMI(MBB, MBBI, TII.get(Alpha::ALTENT))
    .addGlobalAddress(const_cast<Function*>(MF.getFunction()));

  // Get the number of bytes to allocate from the FrameInfo
  long NumBytes = MFI->getStackSize();

  if (FP)
    NumBytes += 8; //reserve space for the old FP

  // Do we need to allocate space on the stack?
  if (NumBytes == 0) return;

  unsigned Align = MF.getTarget().getFrameInfo()->getStackAlignment();
  NumBytes = (NumBytes+Align-1)/Align*Align;

  // Update frame info to pretend that this is part of the stack...
  MFI->setStackSize(NumBytes);

  // adjust stack pointer: r30 -= numbytes
  NumBytes = -NumBytes;
  if (NumBytes >= IMM_LOW) {
    BuildMI(MBB, MBBI, TII.get(Alpha::LDA), Alpha::R30).addImm(NumBytes)
      .addReg(Alpha::R30);
  } else if (getUpper16(NumBytes) >= IMM_LOW) {
    BuildMI(MBB, MBBI, TII.get(Alpha::LDAH), Alpha::R30).addImm(getUpper16(NumBytes))
      .addReg(Alpha::R30);
    BuildMI(MBB, MBBI, TII.get(Alpha::LDA), Alpha::R30).addImm(getLower16(NumBytes))
      .addReg(Alpha::R30);
  } else {
    cerr << "Too big a stack frame at " << NumBytes << "\n";
    abort();
  }

  //now if we need to, save the old FP and set the new
  if (FP)
  {
    BuildMI(MBB, MBBI, TII.get(Alpha::STQ))
      .addReg(Alpha::R15).addImm(0).addReg(Alpha::R30);
    //this must be the last instr in the prolog
    BuildMI(MBB, MBBI, TII.get(Alpha::BISr), Alpha::R15)
      .addReg(Alpha::R30).addReg(Alpha::R30);
  }

}

void AlphaRegisterInfo::emitEpilogue(MachineFunction &MF,
                                     MachineBasicBlock &MBB) const {
  const MachineFrameInfo *MFI = MF.getFrameInfo();
  MachineBasicBlock::iterator MBBI = prior(MBB.end());
  assert((MBBI->getOpcode() == Alpha::RETDAG ||
          MBBI->getOpcode() == Alpha::RETDAGp)
         && "Can only insert epilog into returning blocks");

  bool FP = hasFP(MF);

  // Get the number of bytes allocated from the FrameInfo...
  long NumBytes = MFI->getStackSize();

  //now if we need to, restore the old FP
  if (FP) {
    //copy the FP into the SP (discards allocas)
    BuildMI(MBB, MBBI, TII.get(Alpha::BISr), Alpha::R30).addReg(Alpha::R15)
      .addReg(Alpha::R15);
    //restore the FP
    BuildMI(MBB, MBBI, TII.get(Alpha::LDQ), Alpha::R15).addImm(0).addReg(Alpha::R15);
  }

  if (NumBytes != 0) {
    if (NumBytes <= IMM_HIGH) {
      BuildMI(MBB, MBBI, TII.get(Alpha::LDA), Alpha::R30).addImm(NumBytes)
        .addReg(Alpha::R30);
    } else if (getUpper16(NumBytes) <= IMM_HIGH) {
      BuildMI(MBB, MBBI, TII.get(Alpha::LDAH), Alpha::R30)
        .addImm(getUpper16(NumBytes)).addReg(Alpha::R30);
      BuildMI(MBB, MBBI, TII.get(Alpha::LDA), Alpha::R30)
        .addImm(getLower16(NumBytes)).addReg(Alpha::R30);
    } else {
      cerr << "Too big a stack frame at " << NumBytes << "\n";
      abort();
    }
  }
}

unsigned AlphaRegisterInfo::getRARegister() const {
  assert(0 && "What is the return address register");
  return 0;
}

unsigned AlphaRegisterInfo::getFrameRegister(MachineFunction &MF) const {
  return hasFP(MF) ? Alpha::R15 : Alpha::R30;
}

unsigned AlphaRegisterInfo::getEHExceptionRegister() const {
  assert(0 && "What is the exception register");
  return 0;
}

unsigned AlphaRegisterInfo::getEHHandlerRegister() const {
  assert(0 && "What is the exception handler register");
  return 0;
}

int AlphaRegisterInfo::getDwarfRegNum(unsigned RegNum, bool isEH) const {
  assert(0 && "What is the dwarf register number");
  return -1;
}

#include "AlphaGenRegisterInfo.inc"

std::string AlphaRegisterInfo::getPrettyName(unsigned reg)
{
  std::string s(RegisterDescriptors[reg].Name);
  return s;
}