llvm/lib/Target/Hexagon/HexagonNewValueJump.cpp

//===- HexagonNewValueJump.cpp - Hexagon Backend New Value Jump -----------===//
//
// 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 implements NewValueJump pass in Hexagon.
// Ideally, we should merge this as a Peephole pass prior to register
// allocation, but because we have a spill in between the feeder and new value
// jump instructions, we are forced to write after register allocation.
// Having said that, we should re-attempt to pull this earlier at some point
// in future.

// The basic approach looks for sequence of predicated jump, compare instruciton
// that genereates the predicate and, the feeder to the predicate. Once it finds
// all, it collapses compare and jump instruction into a new value jump
// intstructions.
//
//===----------------------------------------------------------------------===//

#include "Hexagon.h"
#include "HexagonInstrInfo.h"
#include "HexagonRegisterInfo.h"
#include "HexagonSubtarget.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineBranchProbabilityInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/TargetOpcodes.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/Pass.h"
#include "llvm/Support/BranchProbability.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdint>
#include <iterator>

using namespace llvm;

#define DEBUG_TYPE "hexagon-nvj"

STATISTIC(NumNVJGenerated, "Number of New Value Jump Instructions created");

static cl::opt<int> DbgNVJCount("nvj-count", cl::init(-1), cl::Hidden,
    cl::desc("Maximum number of predicated jumps to be converted to "
    "New Value Jump"));

static cl::opt<bool> DisableNewValueJumps("disable-nvjump", cl::Hidden,
    cl::ZeroOrMore, cl::init(false),
    cl::desc("Disable New Value Jumps"));

namespace llvm {

FunctionPass *createHexagonNewValueJump();
void initializeHexagonNewValueJumpPass(PassRegistry&);

} // end namespace llvm

namespace {

  struct HexagonNewValueJump : public MachineFunctionPass {
    static char ID;

    HexagonNewValueJump() : MachineFunctionPass(ID) {}

    void getAnalysisUsage(AnalysisUsage &AU) const override {
      AU.addRequired<MachineBranchProbabilityInfo>();
      MachineFunctionPass::getAnalysisUsage(AU);
    }

    StringRef getPassName() const override { return "Hexagon NewValueJump"; }

    bool runOnMachineFunction(MachineFunction &Fn) override;

    MachineFunctionProperties getRequiredProperties() const override {
      return MachineFunctionProperties().set(
          MachineFunctionProperties::Property::NoVRegs);
    }

  private:
    const HexagonInstrInfo *QII;
    const HexagonRegisterInfo *QRI;

    /// A handle to the branch probability pass.
    const MachineBranchProbabilityInfo *MBPI;

    bool isNewValueJumpCandidate(const MachineInstr &MI) const;
  };

} // end anonymous namespace

char HexagonNewValueJump::ID = 0;

INITIALIZE_PASS_BEGIN(HexagonNewValueJump, "hexagon-nvj",
                      "Hexagon NewValueJump", false, false)
INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
INITIALIZE_PASS_END(HexagonNewValueJump, "hexagon-nvj",
                    "Hexagon NewValueJump", false, false)

// We have identified this II could be feeder to NVJ,
// verify that it can be.
static bool canBeFeederToNewValueJump(const HexagonInstrInfo *QII,
                                      const TargetRegisterInfo *TRI,
                                      MachineBasicBlock::iterator II,
                                      MachineBasicBlock::iterator end,
                                      MachineBasicBlock::iterator skip,
                                      MachineFunction &MF) {
  // Predicated instruction can not be feeder to NVJ.
  if (QII->isPredicated(*II))
    return false;

  // Bail out if feederReg is a paired register (double regs in
  // our case). One would think that we can check to see if a given
  // register cmpReg1 or cmpReg2 is a sub register of feederReg
  // using -- if (QRI->isSubRegister(feederReg, cmpReg1) logic
  // before the callsite of this function
  // But we can not as it comes in the following fashion.
  //    %d0 = Hexagon_S2_lsr_r_p killed %d0, killed %r2
  //    %r0 = KILL %r0, implicit killed %d0
  //    %p0 = CMPEQri killed %r0, 0
  // Hence, we need to check if it's a KILL instruction.
  if (II->getOpcode() == TargetOpcode::KILL)
    return false;

  if (II->isImplicitDef())
    return false;

  if (QII->isSolo(*II))
    return false;

  if (QII->isFloat(*II))
    return false;

  // Make sure that the (unique) def operand is a register from IntRegs.
  bool HadDef = false;
  for (const MachineOperand &Op : II->operands()) {
    if (!Op.isReg() || !Op.isDef())
      continue;
    if (HadDef)
      return false;
    HadDef = true;
    if (!Hexagon::IntRegsRegClass.contains(Op.getReg()))
      return false;
  }
  assert(HadDef);

  // Make sure there is no 'def' or 'use' of any of the uses of
  // feeder insn between its definition, this MI and jump, jmpInst
  // skipping compare, cmpInst.
  // Here's the example.
  //    r21=memub(r22+r24<<#0)
  //    p0 = cmp.eq(r21, #0)
  //    r4=memub(r3+r21<<#0)
  //    if (p0.new) jump:t .LBB29_45
  // Without this check, it will be converted into
  //    r4=memub(r3+r21<<#0)
  //    r21=memub(r22+r24<<#0)
  //    p0 = cmp.eq(r21, #0)
  //    if (p0.new) jump:t .LBB29_45
  // and result WAR hazards if converted to New Value Jump.
  for (unsigned i = 0; i < II->getNumOperands(); ++i) {
    if (II->getOperand(i).isReg() &&
        (II->getOperand(i).isUse() || II->getOperand(i).isDef())) {
      MachineBasicBlock::iterator localII = II;
      ++localII;
      Register Reg = II->getOperand(i).getReg();
      for (MachineBasicBlock::iterator localBegin = localII; localBegin != end;
           ++localBegin) {
        if (localBegin == skip)
          continue;
        // Check for Subregisters too.
        if (localBegin->modifiesRegister(Reg, TRI) ||
            localBegin->readsRegister(Reg, TRI))
          return false;
      }
    }
  }
  return true;
}

// These are the common checks that need to performed
// to determine if
// 1. compare instruction can be moved before jump.
// 2. feeder to the compare instruction can be moved before jump.
static bool commonChecksToProhibitNewValueJump(bool afterRA,
                          MachineBasicBlock::iterator MII) {
  // If store in path, bail out.
  if (MII->mayStore())
    return false;

  // if call in path, bail out.
  if (MII->isCall())
    return false;

  // if NVJ is running prior to RA, do the following checks.
  if (!afterRA) {
    // The following Target Opcode instructions are spurious
    // to new value jump. If they are in the path, bail out.
    // KILL sets kill flag on the opcode. It also sets up a
    // single register, out of pair.
    //    %d0 = S2_lsr_r_p killed %d0, killed %r2
    //    %r0 = KILL %r0, implicit killed %d0
    //    %p0 = C2_cmpeqi killed %r0, 0
    // PHI can be anything after RA.
    // COPY can remateriaze things in between feeder, compare and nvj.
    if (MII->getOpcode() == TargetOpcode::KILL ||
        MII->getOpcode() == TargetOpcode::PHI ||
        MII->getOpcode() == TargetOpcode::COPY)
      return false;

    // The following pseudo Hexagon instructions sets "use" and "def"
    // of registers by individual passes in the backend. At this time,
    // we don't know the scope of usage and definitions of these
    // instructions.
    if (MII->getOpcode() == Hexagon::LDriw_pred ||
        MII->getOpcode() == Hexagon::STriw_pred)
      return false;
  }

  return true;
}

static bool canCompareBeNewValueJump(const HexagonInstrInfo *QII,
                                     const TargetRegisterInfo *TRI,
                                     MachineBasicBlock::iterator II,
                                     unsigned pReg,
                                     bool secondReg,
                                     bool optLocation,
                                     MachineBasicBlock::iterator end,
                                     MachineFunction &MF) {
  MachineInstr &MI = *II;

  // If the second operand of the compare is an imm, make sure it's in the
  // range specified by the arch.
  if (!secondReg) {
    const MachineOperand &Op2 = MI.getOperand(2);
    if (!Op2.isImm())
      return false;

    int64_t v = Op2.getImm();
    bool Valid = false;

    switch (MI.getOpcode()) {
      case Hexagon::C2_cmpeqi:
      case Hexagon::C4_cmpneqi:
      case Hexagon::C2_cmpgti:
      case Hexagon::C4_cmpltei:
        Valid = (isUInt<5>(v) || v == -1);
        break;
      case Hexagon::C2_cmpgtui:
      case Hexagon::C4_cmplteui:
        Valid = isUInt<5>(v);
        break;
      case Hexagon::S2_tstbit_i:
      case Hexagon::S4_ntstbit_i:
        Valid = (v == 0);
        break;
    }

    if (!Valid)
      return false;
  }

  unsigned cmpReg1, cmpOp2 = 0; // cmpOp2 assignment silences compiler warning.
  cmpReg1 = MI.getOperand(1).getReg();

  if (secondReg) {
    cmpOp2 = MI.getOperand(2).getReg();

    // If the same register appears as both operands, we cannot generate a new
    // value compare. Only one operand may use the .new suffix.
    if (cmpReg1 == cmpOp2)
      return false;

    // Make sure that the second register is not from COPY
    // at machine code level, we don't need this, but if we decide
    // to move new value jump prior to RA, we would be needing this.
    MachineRegisterInfo &MRI = MF.getRegInfo();
    if (secondReg && !Register::isPhysicalRegister(cmpOp2)) {
      MachineInstr *def = MRI.getVRegDef(cmpOp2);
      if (def->getOpcode() == TargetOpcode::COPY)
        return false;
    }
  }

  // Walk the instructions after the compare (predicate def) to the jump,
  // and satisfy the following conditions.
  ++II;
  for (MachineBasicBlock::iterator localII = II; localII != end; ++localII) {
    if (localII->isDebugInstr())
      continue;

    // Check 1.
    // If "common" checks fail, bail out.
    if (!commonChecksToProhibitNewValueJump(optLocation, localII))
      return false;

    // Check 2.
    // If there is a def or use of predicate (result of compare), bail out.
    if (localII->modifiesRegister(pReg, TRI) ||
        localII->readsRegister(pReg, TRI))
      return false;

    // Check 3.
    // If there is a def of any of the use of the compare (operands of compare),
    // bail out.
    // Eg.
    //    p0 = cmp.eq(r2, r0)
    //    r2 = r4
    //    if (p0.new) jump:t .LBB28_3
    if (localII->modifiesRegister(cmpReg1, TRI) ||
        (secondReg && localII->modifiesRegister(cmpOp2, TRI)))
      return false;
  }
  return true;
}

// Given a compare operator, return a matching New Value Jump compare operator.
// Make sure that MI here is included in isNewValueJumpCandidate.
static unsigned getNewValueJumpOpcode(MachineInstr *MI, int reg,
                                      bool secondRegNewified,
                                      MachineBasicBlock *jmpTarget,
                                      const MachineBranchProbabilityInfo
                                      *MBPI) {
  bool taken = false;
  MachineBasicBlock *Src = MI->getParent();
  const BranchProbability Prediction =
    MBPI->getEdgeProbability(Src, jmpTarget);

  if (Prediction >= BranchProbability(1,2))
    taken = true;

  switch (MI->getOpcode()) {
    case Hexagon::C2_cmpeq:
      return taken ? Hexagon::J4_cmpeq_t_jumpnv_t
                   : Hexagon::J4_cmpeq_t_jumpnv_nt;

    case Hexagon::C2_cmpeqi:
      if (reg >= 0)
        return taken ? Hexagon::J4_cmpeqi_t_jumpnv_t
                     : Hexagon::J4_cmpeqi_t_jumpnv_nt;
      return taken ? Hexagon::J4_cmpeqn1_t_jumpnv_t
                   : Hexagon::J4_cmpeqn1_t_jumpnv_nt;

    case Hexagon::C4_cmpneqi:
      if (reg >= 0)
        return taken ? Hexagon::J4_cmpeqi_f_jumpnv_t
                     : Hexagon::J4_cmpeqi_f_jumpnv_nt;
      return taken ? Hexagon::J4_cmpeqn1_f_jumpnv_t :
                     Hexagon::J4_cmpeqn1_f_jumpnv_nt;

    case Hexagon::C2_cmpgt:
      if (secondRegNewified)
        return taken ? Hexagon::J4_cmplt_t_jumpnv_t
                     : Hexagon::J4_cmplt_t_jumpnv_nt;
      return taken ? Hexagon::J4_cmpgt_t_jumpnv_t
                   : Hexagon::J4_cmpgt_t_jumpnv_nt;

    case Hexagon::C2_cmpgti:
      if (reg >= 0)
        return taken ? Hexagon::J4_cmpgti_t_jumpnv_t
                     : Hexagon::J4_cmpgti_t_jumpnv_nt;
      return taken ? Hexagon::J4_cmpgtn1_t_jumpnv_t
                   : Hexagon::J4_cmpgtn1_t_jumpnv_nt;

    case Hexagon::C2_cmpgtu:
      if (secondRegNewified)
        return taken ? Hexagon::J4_cmpltu_t_jumpnv_t
                     : Hexagon::J4_cmpltu_t_jumpnv_nt;
      return taken ? Hexagon::J4_cmpgtu_t_jumpnv_t
                   : Hexagon::J4_cmpgtu_t_jumpnv_nt;

    case Hexagon::C2_cmpgtui:
      return taken ? Hexagon::J4_cmpgtui_t_jumpnv_t
                   : Hexagon::J4_cmpgtui_t_jumpnv_nt;

    case Hexagon::C4_cmpneq:
      return taken ? Hexagon::J4_cmpeq_f_jumpnv_t
                   : Hexagon::J4_cmpeq_f_jumpnv_nt;

    case Hexagon::C4_cmplte:
      if (secondRegNewified)
        return taken ? Hexagon::J4_cmplt_f_jumpnv_t
                     : Hexagon::J4_cmplt_f_jumpnv_nt;
      return taken ? Hexagon::J4_cmpgt_f_jumpnv_t
                   : Hexagon::J4_cmpgt_f_jumpnv_nt;

    case Hexagon::C4_cmplteu:
      if (secondRegNewified)
        return taken ? Hexagon::J4_cmpltu_f_jumpnv_t
                     : Hexagon::J4_cmpltu_f_jumpnv_nt;
      return taken ? Hexagon::J4_cmpgtu_f_jumpnv_t
                   : Hexagon::J4_cmpgtu_f_jumpnv_nt;

    case Hexagon::C4_cmpltei:
      if (reg >= 0)
        return taken ? Hexagon::J4_cmpgti_f_jumpnv_t
                     : Hexagon::J4_cmpgti_f_jumpnv_nt;
      return taken ? Hexagon::J4_cmpgtn1_f_jumpnv_t
                   : Hexagon::J4_cmpgtn1_f_jumpnv_nt;

    case Hexagon::C4_cmplteui:
      return taken ? Hexagon::J4_cmpgtui_f_jumpnv_t
                   : Hexagon::J4_cmpgtui_f_jumpnv_nt;

    default:
       llvm_unreachable("Could not find matching New Value Jump instruction.");
  }
  // return *some value* to avoid compiler warning
  return 0;
}

bool HexagonNewValueJump::isNewValueJumpCandidate(
    const MachineInstr &MI) const {
  switch (MI.getOpcode()) {
  case Hexagon::C2_cmpeq:
  case Hexagon::C2_cmpeqi:
  case Hexagon::C2_cmpgt:
  case Hexagon::C2_cmpgti:
  case Hexagon::C2_cmpgtu:
  case Hexagon::C2_cmpgtui:
  case Hexagon::C4_cmpneq:
  case Hexagon::C4_cmpneqi:
  case Hexagon::C4_cmplte:
  case Hexagon::C4_cmplteu:
  case Hexagon::C4_cmpltei:
  case Hexagon::C4_cmplteui:
    return true;

  default:
    return false;
  }
}

bool HexagonNewValueJump::runOnMachineFunction(MachineFunction &MF) {
  LLVM_DEBUG(dbgs() << "********** Hexagon New Value Jump **********\n"
                    << "********** Function: " << MF.getName() << "\n");

  if (skipFunction(MF.getFunction()))
    return false;

  // If we move NewValueJump before register allocation we'll need live variable
  // analysis here too.

  QII = static_cast<const HexagonInstrInfo *>(MF.getSubtarget().getInstrInfo());
  QRI = static_cast<const HexagonRegisterInfo *>(
      MF.getSubtarget().getRegisterInfo());
  MBPI = &getAnalysis<MachineBranchProbabilityInfo>();

  if (DisableNewValueJumps ||
      !MF.getSubtarget<HexagonSubtarget>().useNewValueJumps())
    return false;

  int nvjCount = DbgNVJCount;
  int nvjGenerated = 0;

  // Loop through all the bb's of the function
  for (MachineFunction::iterator MBBb = MF.begin(), MBBe = MF.end();
       MBBb != MBBe; ++MBBb) {
    MachineBasicBlock *MBB = &*MBBb;

    LLVM_DEBUG(dbgs() << "** dumping bb ** " << MBB->getNumber() << "\n");
    LLVM_DEBUG(MBB->dump());
    LLVM_DEBUG(dbgs() << "\n"
                      << "********** dumping instr bottom up **********\n");
    bool foundJump    = false;
    bool foundCompare = false;
    bool invertPredicate = false;
    unsigned predReg = 0; // predicate reg of the jump.
    unsigned cmpReg1 = 0;
    int cmpOp2 = 0;
    MachineBasicBlock::iterator jmpPos;
    MachineBasicBlock::iterator cmpPos;
    MachineInstr *cmpInstr = nullptr, *jmpInstr = nullptr;
    MachineBasicBlock *jmpTarget = nullptr;
    bool afterRA = false;
    bool isSecondOpReg = false;
    bool isSecondOpNewified = false;
    // Traverse the basic block - bottom up
    for (MachineBasicBlock::iterator MII = MBB->end(), E = MBB->begin();
         MII != E;) {
      MachineInstr &MI = *--MII;
      if (MI.isDebugInstr()) {
        continue;
      }

      if ((nvjCount == 0) || (nvjCount > -1 && nvjCount <= nvjGenerated))
        break;

      LLVM_DEBUG(dbgs() << "Instr: "; MI.dump(); dbgs() << "\n");

      if (!foundJump && (MI.getOpcode() == Hexagon::J2_jumpt ||
                         MI.getOpcode() == Hexagon::J2_jumptpt ||
                         MI.getOpcode() == Hexagon::J2_jumpf ||
                         MI.getOpcode() == Hexagon::J2_jumpfpt ||
                         MI.getOpcode() == Hexagon::J2_jumptnewpt ||
                         MI.getOpcode() == Hexagon::J2_jumptnew ||
                         MI.getOpcode() == Hexagon::J2_jumpfnewpt ||
                         MI.getOpcode() == Hexagon::J2_jumpfnew)) {
        // This is where you would insert your compare and
        // instr that feeds compare
        jmpPos = MII;
        jmpInstr = &MI;
        predReg = MI.getOperand(0).getReg();
        afterRA = Register::isPhysicalRegister(predReg);

        // If ifconverter had not messed up with the kill flags of the
        // operands, the following check on the kill flag would suffice.
        // if(!jmpInstr->getOperand(0).isKill()) break;

        // This predicate register is live out of BB
        // this would only work if we can actually use Live
        // variable analysis on phy regs - but LLVM does not
        // provide LV analysis on phys regs.
        //if(LVs.isLiveOut(predReg, *MBB)) break;

        // Get all the successors of this block - which will always
        // be 2. Check if the predicate register is live-in in those
        // successor. If yes, we can not delete the predicate -
        // I am doing this only because LLVM does not provide LiveOut
        // at the BB level.
        bool predLive = false;
        for (MachineBasicBlock::const_succ_iterator SI = MBB->succ_begin(),
                                                    SIE = MBB->succ_end();
             SI != SIE; ++SI) {
          MachineBasicBlock *succMBB = *SI;
          if (succMBB->isLiveIn(predReg))
            predLive = true;
        }
        if (predLive)
          break;

        if (!MI.getOperand(1).isMBB())
          continue;
        jmpTarget = MI.getOperand(1).getMBB();
        foundJump = true;
        if (MI.getOpcode() == Hexagon::J2_jumpf ||
            MI.getOpcode() == Hexagon::J2_jumpfnewpt ||
            MI.getOpcode() == Hexagon::J2_jumpfnew) {
          invertPredicate = true;
        }
        continue;
      }

      // No new value jump if there is a barrier. A barrier has to be in its
      // own packet. A barrier has zero operands. We conservatively bail out
      // here if we see any instruction with zero operands.
      if (foundJump && MI.getNumOperands() == 0)
        break;

      if (foundJump && !foundCompare && MI.getOperand(0).isReg() &&
          MI.getOperand(0).getReg() == predReg) {
        // Not all compares can be new value compare. Arch Spec: 7.6.1.1
        if (isNewValueJumpCandidate(MI)) {
          assert(
              (MI.getDesc().isCompare()) &&
              "Only compare instruction can be collapsed into New Value Jump");
          isSecondOpReg = MI.getOperand(2).isReg();

          if (!canCompareBeNewValueJump(QII, QRI, MII, predReg, isSecondOpReg,
                                        afterRA, jmpPos, MF))
            break;

          cmpInstr = &MI;
          cmpPos = MII;
          foundCompare = true;

          // We need cmpReg1 and cmpOp2(imm or reg) while building
          // new value jump instruction.
          cmpReg1 = MI.getOperand(1).getReg();

          if (isSecondOpReg)
            cmpOp2 = MI.getOperand(2).getReg();
          else
            cmpOp2 = MI.getOperand(2).getImm();
          continue;
        }
      }

      if (foundCompare && foundJump) {
        // If "common" checks fail, bail out on this BB.
        if (!commonChecksToProhibitNewValueJump(afterRA, MII))
          break;

        bool foundFeeder = false;
        MachineBasicBlock::iterator feederPos = MII;
        if (MI.getOperand(0).isReg() && MI.getOperand(0).isDef() &&
            (MI.getOperand(0).getReg() == cmpReg1 ||
             (isSecondOpReg &&
              MI.getOperand(0).getReg() == (unsigned)cmpOp2))) {

          Register feederReg = MI.getOperand(0).getReg();

          // First try to see if we can get the feeder from the first operand
          // of the compare. If we can not, and if secondOpReg is true
          // (second operand of the compare is also register), try that one.
          // TODO: Try to come up with some heuristic to figure out which
          // feeder would benefit.

          if (feederReg == cmpReg1) {
            if (!canBeFeederToNewValueJump(QII, QRI, MII, jmpPos, cmpPos, MF)) {
              if (!isSecondOpReg)
                break;
              else
                continue;
            } else
              foundFeeder = true;
          }

          if (!foundFeeder && isSecondOpReg && feederReg == (unsigned)cmpOp2)
            if (!canBeFeederToNewValueJump(QII, QRI, MII, jmpPos, cmpPos, MF))
              break;

          if (isSecondOpReg) {
            // In case of CMPLT, or CMPLTU, or EQ with the second register
            // to newify, swap the operands.
            unsigned COp = cmpInstr->getOpcode();
            if ((COp == Hexagon::C2_cmpeq || COp == Hexagon::C4_cmpneq) &&
                (feederReg == (unsigned)cmpOp2)) {
              unsigned tmp = cmpReg1;
              cmpReg1 = cmpOp2;
              cmpOp2 = tmp;
            }

            // Now we have swapped the operands, all we need to check is,
            // if the second operand (after swap) is the feeder.
            // And if it is, make a note.
            if (feederReg == (unsigned)cmpOp2)
              isSecondOpNewified = true;
          }

          // Now that we are moving feeder close the jump,
          // make sure we are respecting the kill values of
          // the operands of the feeder.

          auto TransferKills = [jmpPos,cmpPos] (MachineInstr &MI) {
            for (MachineOperand &MO : MI.operands()) {
              if (!MO.isReg() || !MO.isUse())
                continue;
              Register UseR = MO.getReg();
              for (auto I = std::next(MI.getIterator()); I != jmpPos; ++I) {
                if (I == cmpPos)
                  continue;
                for (MachineOperand &Op : I->operands()) {
                  if (!Op.isReg() || !Op.isUse() || !Op.isKill())
                    continue;
                  if (Op.getReg() != UseR)
                    continue;
                  // We found that there is kill of a use register
                  // Set up a kill flag on the register
                  Op.setIsKill(false);
                  MO.setIsKill(true);
                  return;
                }
              }
            }
          };

          TransferKills(*feederPos);
          TransferKills(*cmpPos);
          bool MO1IsKill = cmpPos->killsRegister(cmpReg1, QRI);
          bool MO2IsKill = isSecondOpReg && cmpPos->killsRegister(cmpOp2, QRI);

          MBB->splice(jmpPos, MI.getParent(), MI);
          MBB->splice(jmpPos, MI.getParent(), cmpInstr);
          DebugLoc dl = MI.getDebugLoc();
          MachineInstr *NewMI;

          assert((isNewValueJumpCandidate(*cmpInstr)) &&
                 "This compare is not a New Value Jump candidate.");
          unsigned opc = getNewValueJumpOpcode(cmpInstr, cmpOp2,
                                               isSecondOpNewified,
                                               jmpTarget, MBPI);
          if (invertPredicate)
            opc = QII->getInvertedPredicatedOpcode(opc);

          if (isSecondOpReg)
            NewMI = BuildMI(*MBB, jmpPos, dl, QII->get(opc))
                        .addReg(cmpReg1, getKillRegState(MO1IsKill))
                        .addReg(cmpOp2, getKillRegState(MO2IsKill))
                        .addMBB(jmpTarget);

          else
            NewMI = BuildMI(*MBB, jmpPos, dl, QII->get(opc))
                        .addReg(cmpReg1, getKillRegState(MO1IsKill))
                        .addImm(cmpOp2)
                        .addMBB(jmpTarget);

          assert(NewMI && "New Value Jump Instruction Not created!");
          (void)NewMI;
          if (cmpInstr->getOperand(0).isReg() &&
              cmpInstr->getOperand(0).isKill())
            cmpInstr->getOperand(0).setIsKill(false);
          if (cmpInstr->getOperand(1).isReg() &&
              cmpInstr->getOperand(1).isKill())
            cmpInstr->getOperand(1).setIsKill(false);
          cmpInstr->eraseFromParent();
          jmpInstr->eraseFromParent();
          ++nvjGenerated;
          ++NumNVJGenerated;
          break;
        }
      }
    }
  }

  return true;
}

FunctionPass *llvm::createHexagonNewValueJump() {
  return new HexagonNewValueJump();
}