llvm-project/llvm/lib/Target/ARM/Thumb1InstrInfo.cpp

//===-- Thumb1InstrInfo.cpp - Thumb-1 Instruction Information -------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file contains the Thumb-1 implementation of the TargetInstrInfo class.
//
//===----------------------------------------------------------------------===//

#include "Thumb1InstrInfo.h"
#include "ARMSubtarget.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstBuilder.h"

using namespace llvm;

Thumb1InstrInfo::Thumb1InstrInfo(const ARMSubtarget &STI)
    : ARMBaseInstrInfo(STI), RI() {}

/// Return the noop instruction to use for a noop.
MCInst Thumb1InstrInfo::getNop() const {
  return MCInstBuilder(ARM::tMOVr)
      .addReg(ARM::R8)
      .addReg(ARM::R8)
      .addImm(ARMCC::AL)
      .addReg(0);
}

unsigned Thumb1InstrInfo::getUnindexedOpcode(unsigned Opc) const {
  return 0;
}

void Thumb1InstrInfo::copyPhysReg(MachineBasicBlock &MBB,
                                  MachineBasicBlock::iterator I,
                                  const DebugLoc &DL, MCRegister DestReg,
                                  MCRegister SrcReg, bool KillSrc) const {
  // Need to check the arch.
  MachineFunction &MF = *MBB.getParent();
  const ARMSubtarget &st = MF.getSubtarget<ARMSubtarget>();

  assert(ARM::GPRRegClass.contains(DestReg, SrcReg) &&
         "Thumb1 can only copy GPR registers");

  if (st.hasV6Ops() || ARM::hGPRRegClass.contains(SrcReg)
      || !ARM::tGPRRegClass.contains(DestReg))
    BuildMI(MBB, I, DL, get(ARM::tMOVr), DestReg)
        .addReg(SrcReg, getKillRegState(KillSrc))
        .add(predOps(ARMCC::AL));
  else {
    // FIXME: Can also use 'mov hi, $src; mov $dst, hi',
    // with hi as either r10 or r11.

    const TargetRegisterInfo *RegInfo = st.getRegisterInfo();
    if (MBB.computeRegisterLiveness(RegInfo, ARM::CPSR, I)
        == MachineBasicBlock::LQR_Dead) {
      BuildMI(MBB, I, DL, get(ARM::tMOVSr), DestReg)
          .addReg(SrcReg, getKillRegState(KillSrc))
          ->addRegisterDead(ARM::CPSR, RegInfo);
      return;
    }

    // 'MOV lo, lo' is unpredictable on < v6, so use the stack to do it
    BuildMI(MBB, I, DL, get(ARM::tPUSH))
        .add(predOps(ARMCC::AL))
        .addReg(SrcReg, getKillRegState(KillSrc));
    BuildMI(MBB, I, DL, get(ARM::tPOP))
        .add(predOps(ARMCC::AL))
        .addReg(DestReg, getDefRegState(true));
  }
}

void Thumb1InstrInfo::
storeRegToStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
                    Register SrcReg, bool isKill, int FI,
                    const TargetRegisterClass *RC,
                    const TargetRegisterInfo *TRI) const {
  assert((RC == &ARM::tGPRRegClass ||
          (Register::isPhysicalRegister(SrcReg) && isARMLowRegister(SrcReg))) &&
         "Unknown regclass!");

  if (RC == &ARM::tGPRRegClass ||
      (Register::isPhysicalRegister(SrcReg) && isARMLowRegister(SrcReg))) {
    DebugLoc DL;
    if (I != MBB.end()) DL = I->getDebugLoc();

    MachineFunction &MF = *MBB.getParent();
    MachineFrameInfo &MFI = MF.getFrameInfo();
    MachineMemOperand *MMO = MF.getMachineMemOperand(
        MachinePointerInfo::getFixedStack(MF, FI), MachineMemOperand::MOStore,
        MFI.getObjectSize(FI), MFI.getObjectAlign(FI));
    BuildMI(MBB, I, DL, get(ARM::tSTRspi))
        .addReg(SrcReg, getKillRegState(isKill))
        .addFrameIndex(FI)
        .addImm(0)
        .addMemOperand(MMO)
        .add(predOps(ARMCC::AL));
  }
}

void Thumb1InstrInfo::
loadRegFromStackSlot(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
                     Register DestReg, int FI,
                     const TargetRegisterClass *RC,
                     const TargetRegisterInfo *TRI) const {
  assert(
      (RC->hasSuperClassEq(&ARM::tGPRRegClass) ||
       (Register::isPhysicalRegister(DestReg) && isARMLowRegister(DestReg))) &&
      "Unknown regclass!");

  if (RC->hasSuperClassEq(&ARM::tGPRRegClass) ||
      (Register::isPhysicalRegister(DestReg) && isARMLowRegister(DestReg))) {
    DebugLoc DL;
    if (I != MBB.end()) DL = I->getDebugLoc();

    MachineFunction &MF = *MBB.getParent();
    MachineFrameInfo &MFI = MF.getFrameInfo();
    MachineMemOperand *MMO = MF.getMachineMemOperand(
        MachinePointerInfo::getFixedStack(MF, FI), MachineMemOperand::MOLoad,
        MFI.getObjectSize(FI), MFI.getObjectAlign(FI));
    BuildMI(MBB, I, DL, get(ARM::tLDRspi), DestReg)
        .addFrameIndex(FI)
        .addImm(0)
        .addMemOperand(MMO)
        .add(predOps(ARMCC::AL));
  }
}

void Thumb1InstrInfo::expandLoadStackGuard(
    MachineBasicBlock::iterator MI) const {
  MachineFunction &MF = *MI->getParent()->getParent();
  const TargetMachine &TM = MF.getTarget();
  if (TM.isPositionIndependent())
    expandLoadStackGuardBase(MI, ARM::tLDRLIT_ga_pcrel, ARM::tLDRi);
  else
    expandLoadStackGuardBase(MI, ARM::tLDRLIT_ga_abs, ARM::tLDRi);
}

bool Thumb1InstrInfo::canCopyGluedNodeDuringSchedule(SDNode *N) const {
  // In Thumb1 the scheduler may need to schedule a cross-copy between GPRS and CPSR
  // but this is not always possible there, so allow the Scheduler to clone tADCS and tSBCS
  // even if they have glue.
  // FIXME. Actually implement the cross-copy where it is possible (post v6)
  // because these copies entail more spilling.
  unsigned Opcode = N->getMachineOpcode();
  if (Opcode == ARM::tADCS || Opcode == ARM::tSBCS)
    return true;

  return false;
}