llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp

//===----- HexagonPacketizer.cpp - vliw packetizer ---------------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This implements a simple VLIW packetizer using DFA. The packetizer works on
// machine basic blocks. For each instruction I in BB, the packetizer consults
// the DFA to see if machine resources are available to execute I. If so, the
// packetizer checks if I depends on any instruction J in the current packet.
// If no dependency is found, I is added to current packet and machine resource
// is marked as taken. If any dependency is found, a target API call is made to
// prune the dependence.
//
//===----------------------------------------------------------------------===//
#include "HexagonRegisterInfo.h"
#include "HexagonSubtarget.h"
#include "HexagonTargetMachine.h"
#include "HexagonVLIWPacketizer.h"
#include "llvm/Analysis/AliasAnalysis.h"
#include "llvm/CodeGen/MachineDominators.h"
#include "llvm/CodeGen/MachineFunctionAnalysis.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineLoopInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include <map>
#include <vector>

using namespace llvm;

#define DEBUG_TYPE "packets"

static cl::opt<bool> DisablePacketizer("disable-packetizer", cl::Hidden,
  cl::ZeroOrMore, cl::init(false),
  cl::desc("Disable Hexagon packetizer pass"));

static cl::opt<bool> PacketizeVolatiles("hexagon-packetize-volatiles",
  cl::ZeroOrMore, cl::Hidden, cl::init(true),
  cl::desc("Allow non-solo packetization of volatile memory references"));

static cl::opt<bool> EnableGenAllInsnClass("enable-gen-insn", cl::init(false),
  cl::Hidden, cl::ZeroOrMore, cl::desc("Generate all instruction with TC"));

static cl::opt<bool> DisableVecDblNVStores("disable-vecdbl-nv-stores",
  cl::init(false), cl::Hidden, cl::ZeroOrMore,
  cl::desc("Disable vector double new-value-stores"));

extern cl::opt<bool> ScheduleInlineAsm;

namespace llvm {
  FunctionPass *createHexagonPacketizer();
  void initializeHexagonPacketizerPass(PassRegistry&);
}


namespace {
  class HexagonPacketizer : public MachineFunctionPass {
  public:
    static char ID;
    HexagonPacketizer() : MachineFunctionPass(ID) {
      initializeHexagonPacketizerPass(*PassRegistry::getPassRegistry());
    }

    void getAnalysisUsage(AnalysisUsage &AU) const override {
      AU.setPreservesCFG();
      AU.addRequired<AAResultsWrapperPass>();
      AU.addRequired<MachineBranchProbabilityInfo>();
      AU.addRequired<MachineDominatorTree>();
      AU.addRequired<MachineLoopInfo>();
      AU.addPreserved<MachineDominatorTree>();
      AU.addPreserved<MachineLoopInfo>();
      MachineFunctionPass::getAnalysisUsage(AU);
    }
    const char *getPassName() const override {
      return "Hexagon Packetizer";
    }
    bool runOnMachineFunction(MachineFunction &Fn) override;

  private:
    const HexagonInstrInfo *HII;
    const HexagonRegisterInfo *HRI;
  };

  char HexagonPacketizer::ID = 0;
}

INITIALIZE_PASS_BEGIN(HexagonPacketizer, "packets", "Hexagon Packetizer",
                      false, false)
INITIALIZE_PASS_DEPENDENCY(MachineDominatorTree)
INITIALIZE_PASS_DEPENDENCY(MachineBranchProbabilityInfo)
INITIALIZE_PASS_DEPENDENCY(MachineLoopInfo)
INITIALIZE_PASS_DEPENDENCY(AAResultsWrapperPass)
INITIALIZE_PASS_END(HexagonPacketizer, "packets", "Hexagon Packetizer",
                    false, false)


HexagonPacketizerList::HexagonPacketizerList(MachineFunction &MF,
      MachineLoopInfo &MLI, AliasAnalysis *AA,
      const MachineBranchProbabilityInfo *MBPI)
    : VLIWPacketizerList(MF, MLI, AA), MBPI(MBPI), MLI(&MLI) {
  HII = MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
  HRI = MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();
}

// Check if FirstI modifies a register that SecondI reads.
static bool hasWriteToReadDep(const MachineInstr *FirstI,
      const MachineInstr *SecondI, const TargetRegisterInfo *TRI) {
  for (auto &MO : FirstI->operands()) {
    if (!MO.isReg() || !MO.isDef())
      continue;
    unsigned R = MO.getReg();
    if (SecondI->readsRegister(R, TRI))
      return true;
  }
  return false;
}


static MachineBasicBlock::iterator moveInstrOut(MachineInstr *MI,
      MachineBasicBlock::iterator BundleIt, bool Before) {
  MachineBasicBlock::instr_iterator InsertPt;
  if (Before)
    InsertPt = BundleIt.getInstrIterator();
  else
    InsertPt = std::next(BundleIt).getInstrIterator();

  MachineBasicBlock &B = *MI->getParent();
  // The instruction should at least be bundled with the preceding instruction
  // (there will always be one, i.e. BUNDLE, if nothing else).
  assert(MI->isBundledWithPred());
  if (MI->isBundledWithSucc()) {
    MI->clearFlag(MachineInstr::BundledSucc);
    MI->clearFlag(MachineInstr::BundledPred);
  } else {
    // If it's not bundled with the successor (i.e. it is the last one
    // in the bundle), then we can simply unbundle it from the predecessor,
    // which will take care of updating the predecessor's flag.
    MI->unbundleFromPred();
  }
  B.splice(InsertPt, &B, MI);

  // Get the size of the bundle without asserting.
  MachineBasicBlock::const_instr_iterator I(BundleIt);
  MachineBasicBlock::const_instr_iterator E = B.instr_end();
  unsigned Size = 0;
  for (++I; I != E && I->isBundledWithPred(); ++I)
    ++Size;

  // If there are still two or more instructions, then there is nothing
  // else to be done.
  if (Size > 1)
    return BundleIt;

  // Otherwise, extract the single instruction out and delete the bundle.
  MachineBasicBlock::iterator NextIt = std::next(BundleIt);
  MachineInstr *SingleI = BundleIt->getNextNode();
  SingleI->unbundleFromPred();
  assert(!SingleI->isBundledWithSucc());
  BundleIt->eraseFromParent();
  return NextIt;
}


bool HexagonPacketizer::runOnMachineFunction(MachineFunction &MF) {
  if (DisablePacketizer)
    return false;

  HII = MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
  HRI = MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();
  auto &MLI = getAnalysis<MachineLoopInfo>();
  auto *AA = &getAnalysis<AAResultsWrapperPass>().getAAResults();
  auto *MBPI = &getAnalysis<MachineBranchProbabilityInfo>();

  if (EnableGenAllInsnClass)
    HII->genAllInsnTimingClasses(MF);

  // Instantiate the packetizer.
  HexagonPacketizerList Packetizer(MF, MLI, AA, MBPI);

  // DFA state table should not be empty.
  assert(Packetizer.getResourceTracker() && "Empty DFA table!");

  //
  // Loop over all basic blocks and remove KILL pseudo-instructions
  // These instructions confuse the dependence analysis. Consider:
  // D0 = ...   (Insn 0)
  // R0 = KILL R0, D0 (Insn 1)
  // R0 = ... (Insn 2)
  // Here, Insn 1 will result in the dependence graph not emitting an output
  // dependence between Insn 0 and Insn 2. This can lead to incorrect
  // packetization
  //
  for (auto &MB : MF) {
    auto End = MB.end();
    auto MI = MB.begin();
    while (MI != End) {
      auto NextI = std::next(MI);
      if (MI->isKill()) {
        MB.erase(MI);
        End = MB.end();
      }
      MI = NextI;
    }
  }

  // Loop over all of the basic blocks.
  for (auto &MB : MF) {
    auto Begin = MB.begin(), End = MB.end();
    while (Begin != End) {
      // First the first non-boundary starting from the end of the last
      // scheduling region.
      MachineBasicBlock::iterator RB = Begin;
      while (RB != End && HII->isSchedulingBoundary(RB, &MB, MF))
        ++RB;
      // First the first boundary starting from the beginning of the new
      // region.
      MachineBasicBlock::iterator RE = RB;
      while (RE != End && !HII->isSchedulingBoundary(RE, &MB, MF))
        ++RE;
      // Add the scheduling boundary if it's not block end.
      if (RE != End)
        ++RE;
      // If RB == End, then RE == End.
      if (RB != End)
        Packetizer.PacketizeMIs(&MB, RB, RE);

      Begin = RE;
    }
  }

  Packetizer.unpacketizeSoloInstrs(MF);
  return true;
}


// Reserve resources for a constant extender. Trigger an assertion if the
// reservation fails.
void HexagonPacketizerList::reserveResourcesForConstExt() {
  if (!tryAllocateResourcesForConstExt(true))
    llvm_unreachable("Resources not available");
}

bool HexagonPacketizerList::canReserveResourcesForConstExt() {
  return tryAllocateResourcesForConstExt(false);
}

// Allocate resources (i.e. 4 bytes) for constant extender. If succeeded,
// return true, otherwise, return false.
bool HexagonPacketizerList::tryAllocateResourcesForConstExt(bool Reserve) {
  auto *ExtMI = MF.CreateMachineInstr(HII->get(Hexagon::A4_ext), DebugLoc());
  bool Avail = ResourceTracker->canReserveResources(ExtMI);
  if (Reserve && Avail)
    ResourceTracker->reserveResources(ExtMI);
  MF.DeleteMachineInstr(ExtMI);
  return Avail;
}


bool HexagonPacketizerList::isCallDependent(const MachineInstr* MI,
      SDep::Kind DepType, unsigned DepReg) {
  // Check for LR dependence.
  if (DepReg == HRI->getRARegister())
    return true;

  if (HII->isDeallocRet(MI))
    if (DepReg == HRI->getFrameRegister() || DepReg == HRI->getStackRegister())
      return true;

  // Check if this is a predicate dependence.
  const TargetRegisterClass* RC = HRI->getMinimalPhysRegClass(DepReg);
  if (RC == &Hexagon::PredRegsRegClass)
    return true;

  // Assumes that the first operand of the CALLr is the function address.
  if (HII->isIndirectCall(MI) && (DepType == SDep::Data)) {
    MachineOperand MO = MI->getOperand(0);
    if (MO.isReg() && MO.isUse() && (MO.getReg() == DepReg))
      return true;
  }

  return false;
}

static bool isRegDependence(const SDep::Kind DepType) {
  return DepType == SDep::Data || DepType == SDep::Anti ||
         DepType == SDep::Output;
}

static bool isDirectJump(const MachineInstr* MI) {
  return MI->getOpcode() == Hexagon::J2_jump;
}

static bool isSchedBarrier(const MachineInstr* MI) {
  switch (MI->getOpcode()) {
  case Hexagon::Y2_barrier:
    return true;
  }
  return false;
}

static bool isControlFlow(const MachineInstr* MI) {
  return (MI->getDesc().isTerminator() || MI->getDesc().isCall());
}


/// Returns true if the instruction modifies a callee-saved register.
static bool doesModifyCalleeSavedReg(const MachineInstr *MI,
                                     const TargetRegisterInfo *TRI) {
  const MachineFunction &MF = *MI->getParent()->getParent();
  for (auto *CSR = TRI->getCalleeSavedRegs(&MF); CSR && *CSR; ++CSR)
    if (MI->modifiesRegister(*CSR, TRI))
      return true;
  return false;
}

// TODO: MI->isIndirectBranch() and IsRegisterJump(MI)
// Returns true if an instruction can be promoted to .new predicate or
// new-value store.
bool HexagonPacketizerList::isNewifiable(const MachineInstr* MI) {
  return HII->isCondInst(MI) || MI->isReturn() || HII->mayBeNewStore(MI);
}

// Promote an instructiont to its .cur form.
// At this time, we have already made a call to canPromoteToDotCur and made
// sure that it can *indeed* be promoted.
bool HexagonPacketizerList::promoteToDotCur(MachineInstr* MI,
      SDep::Kind DepType, MachineBasicBlock::iterator &MII,
      const TargetRegisterClass* RC) {
  assert(DepType == SDep::Data);
  int CurOpcode = HII->getDotCurOp(MI);
  MI->setDesc(HII->get(CurOpcode));
  return true;
}

void HexagonPacketizerList::cleanUpDotCur() {
  MachineInstr *MI = NULL;
  for (auto BI : CurrentPacketMIs) {
    DEBUG(dbgs() << "Cleanup packet has "; BI->dump(););
    if (BI->getOpcode() == Hexagon::V6_vL32b_cur_ai) {
      MI = BI;
      continue;
    }
    if (MI) {
      for (auto &MO : BI->operands())
        if (MO.isReg() && MO.getReg() == MI->getOperand(0).getReg())
          return;
    }
  }
  if (!MI)
    return;
  // We did not find a use of the CUR, so de-cur it.
  MI->setDesc(HII->get(Hexagon::V6_vL32b_ai));
  DEBUG(dbgs() << "Demoted CUR "; MI->dump(););
}

// Check to see if an instruction can be dot cur.
bool HexagonPacketizerList::canPromoteToDotCur(const MachineInstr *MI,
      const SUnit *PacketSU, unsigned DepReg, MachineBasicBlock::iterator &MII,
      const TargetRegisterClass *RC) {
  if (!HII->isV60VectorInstruction(MI))
    return false;
  if (!HII->isV60VectorInstruction(MII))
    return false;

  // Already a dot new instruction.
  if (HII->isDotCurInst(MI) && !HII->mayBeCurLoad(MI))
    return false;

  if (!HII->mayBeCurLoad(MI))
    return false;

  // The "cur value" cannot come from inline asm.
  if (PacketSU->getInstr()->isInlineAsm())
    return false;

  // Make sure candidate instruction uses cur.
  DEBUG(dbgs() << "Can we DOT Cur Vector MI\n";
        MI->dump();
        dbgs() << "in packet\n";);
  MachineInstr *MJ = MII;
  DEBUG(dbgs() << "Checking CUR against "; MJ->dump(););
  unsigned DestReg = MI->getOperand(0).getReg();
  bool FoundMatch = false;
  for (auto &MO : MJ->operands())
    if (MO.isReg() && MO.getReg() == DestReg)
      FoundMatch = true;
  if (!FoundMatch)
    return false;

  // Check for existing uses of a vector register within the packet which
  // would be affected by converting a vector load into .cur formt.
  for (auto BI : CurrentPacketMIs) {
    DEBUG(dbgs() << "packet has "; BI->dump(););
    if (BI->readsRegister(DepReg, MF.getSubtarget().getRegisterInfo()))
      return false;
  }

  DEBUG(dbgs() << "Can Dot CUR MI\n"; MI->dump(););
  // We can convert the opcode into a .cur.
  return true;
}

// Promote an instruction to its .new form. At this time, we have already
// made a call to canPromoteToDotNew and made sure that it can *indeed* be
// promoted.
bool HexagonPacketizerList::promoteToDotNew(MachineInstr* MI,
      SDep::Kind DepType, MachineBasicBlock::iterator &MII,
      const TargetRegisterClass* RC) {
  assert (DepType == SDep::Data);
  int NewOpcode;
  if (RC == &Hexagon::PredRegsRegClass)
    NewOpcode = HII->getDotNewPredOp(MI, MBPI);
  else
    NewOpcode = HII->getDotNewOp(MI);
  MI->setDesc(HII->get(NewOpcode));
  return true;
}

bool HexagonPacketizerList::demoteToDotOld(MachineInstr* MI) {
  int NewOpcode = HII->getDotOldOp(MI->getOpcode());
  MI->setDesc(HII->get(NewOpcode));
  return true;
}

enum PredicateKind {
  PK_False,
  PK_True,
  PK_Unknown
};

/// Returns true if an instruction is predicated on p0 and false if it's
/// predicated on !p0.
static PredicateKind getPredicateSense(const MachineInstr &MI,
                                       const HexagonInstrInfo *HII) {
  if (!HII->isPredicated(MI))
    return PK_Unknown;
  if (HII->isPredicatedTrue(MI))
    return PK_True;
  return PK_False;
}

static const MachineOperand &getPostIncrementOperand(const MachineInstr *MI,
      const HexagonInstrInfo *HII) {
  assert(HII->isPostIncrement(MI) && "Not a post increment operation.");
#ifndef NDEBUG
  // Post Increment means duplicates. Use dense map to find duplicates in the
  // list. Caution: Densemap initializes with the minimum of 64 buckets,
  // whereas there are at most 5 operands in the post increment.
  DenseSet<unsigned> DefRegsSet;
  for (auto &MO : MI->operands())
    if (MO.isReg() && MO.isDef())
      DefRegsSet.insert(MO.getReg());

  for (auto &MO : MI->operands())
    if (MO.isReg() && MO.isUse() && DefRegsSet.count(MO.getReg()))
      return MO;
#else
  if (MI->mayLoad()) {
    const MachineOperand &Op1 = MI->getOperand(1);
    // The 2nd operand is always the post increment operand in load.
    assert(Op1.isReg() && "Post increment operand has be to a register.");
    return Op1;
  }
  if (MI->getDesc().mayStore()) {
    const MachineOperand &Op0 = MI->getOperand(0);
    // The 1st operand is always the post increment operand in store.
    assert(Op0.isReg() && "Post increment operand has be to a register.");
    return Op0;
  }
#endif
  // we should never come here.
  llvm_unreachable("mayLoad or mayStore not set for Post Increment operation");
}

// Get the value being stored.
static const MachineOperand& getStoreValueOperand(const MachineInstr *MI) {
  // value being stored is always the last operand.
  return MI->getOperand(MI->getNumOperands()-1);
}

static bool isLoadAbsSet(const MachineInstr *MI) {
  unsigned Opc = MI->getOpcode();
  switch (Opc) {
    case Hexagon::L4_loadrd_ap:
    case Hexagon::L4_loadrb_ap:
    case Hexagon::L4_loadrh_ap:
    case Hexagon::L4_loadrub_ap:
    case Hexagon::L4_loadruh_ap:
    case Hexagon::L4_loadri_ap:
      return true;
  }
  return false;
}

static const MachineOperand &getAbsSetOperand(const MachineInstr *MI) {
  assert(isLoadAbsSet(MI));
  return MI->getOperand(1);
}


// Can be new value store?
// Following restrictions are to be respected in convert a store into
// a new value store.
// 1. If an instruction uses auto-increment, its address register cannot
//    be a new-value register. Arch Spec 5.4.2.1
// 2. If an instruction uses absolute-set addressing mode, its address
//    register cannot be a new-value register. Arch Spec 5.4.2.1.
// 3. If an instruction produces a 64-bit result, its registers cannot be used
//    as new-value registers. Arch Spec 5.4.2.2.
// 4. If the instruction that sets the new-value register is conditional, then
//    the instruction that uses the new-value register must also be conditional,
//    and both must always have their predicates evaluate identically.
//    Arch Spec 5.4.2.3.
// 5. There is an implied restriction that a packet cannot have another store,
//    if there is a new value store in the packet. Corollary: if there is
//    already a store in a packet, there can not be a new value store.
//    Arch Spec: 3.4.4.2
bool HexagonPacketizerList::canPromoteToNewValueStore(const MachineInstr *MI,
      const MachineInstr *PacketMI, unsigned DepReg) {
  // Make sure we are looking at the store, that can be promoted.
  if (!HII->mayBeNewStore(MI))
    return false;

  // Make sure there is dependency and can be new value'd.
  const MachineOperand &Val = getStoreValueOperand(MI);
  if (Val.isReg() && Val.getReg() != DepReg)
    return false;

  const MCInstrDesc& MCID = PacketMI->getDesc();

  // First operand is always the result.
  const TargetRegisterClass *PacketRC = HII->getRegClass(MCID, 0, HRI, MF);
  // Double regs can not feed into new value store: PRM section: 5.4.2.2.
  if (PacketRC == &Hexagon::DoubleRegsRegClass)
    return false;

  // New-value stores are of class NV (slot 0), dual stores require class ST
  // in slot 0 (PRM 5.5).
  for (auto I : CurrentPacketMIs) {
    SUnit *PacketSU = MIToSUnit.find(I)->second;
    if (PacketSU->getInstr()->mayStore())
      return false;
  }

  // Make sure it's NOT the post increment register that we are going to
  // new value.
  if (HII->isPostIncrement(MI) &&
      getPostIncrementOperand(MI, HII).getReg() == DepReg) {
    return false;
  }

  if (HII->isPostIncrement(PacketMI) && PacketMI->mayLoad() &&
      getPostIncrementOperand(PacketMI, HII).getReg() == DepReg) {
    // If source is post_inc, or absolute-set addressing, it can not feed
    // into new value store
    //   r3 = memw(r2++#4)
    //   memw(r30 + #-1404) = r2.new -> can not be new value store
    // arch spec section: 5.4.2.1.
    return false;
  }

  if (isLoadAbsSet(PacketMI) && getAbsSetOperand(PacketMI).getReg() == DepReg)
    return false;

  // If the source that feeds the store is predicated, new value store must
  // also be predicated.
  if (HII->isPredicated(*PacketMI)) {
    if (!HII->isPredicated(*MI))
      return false;

    // Check to make sure that they both will have their predicates
    // evaluate identically.
    unsigned predRegNumSrc = 0;
    unsigned predRegNumDst = 0;
    const TargetRegisterClass* predRegClass = nullptr;

    // Get predicate register used in the source instruction.
    for (auto &MO : PacketMI->operands()) {
      if (!MO.isReg())
        continue;
      predRegNumSrc = MO.getReg();
      predRegClass = HRI->getMinimalPhysRegClass(predRegNumSrc);
      if (predRegClass == &Hexagon::PredRegsRegClass)
        break;
    }
    assert((predRegClass == &Hexagon::PredRegsRegClass) &&
        "predicate register not found in a predicated PacketMI instruction");

    // Get predicate register used in new-value store instruction.
    for (auto &MO : MI->operands()) {
      if (!MO.isReg())
        continue;
      predRegNumDst = MO.getReg();
      predRegClass = HRI->getMinimalPhysRegClass(predRegNumDst);
      if (predRegClass == &Hexagon::PredRegsRegClass)
        break;
    }
    assert((predRegClass == &Hexagon::PredRegsRegClass) &&
           "predicate register not found in a predicated MI instruction");

    // New-value register producer and user (store) need to satisfy these
    // constraints:
    // 1) Both instructions should be predicated on the same register.
    // 2) If producer of the new-value register is .new predicated then store
    // should also be .new predicated and if producer is not .new predicated
    // then store should not be .new predicated.
    // 3) Both new-value register producer and user should have same predicate
    // sense, i.e, either both should be negated or both should be non-negated.
    if (predRegNumDst != predRegNumSrc ||
        HII->isDotNewInst(PacketMI) != HII->isDotNewInst(MI) ||
        getPredicateSense(*MI, HII) != getPredicateSense(*PacketMI, HII))
      return false;
  }

  // Make sure that other than the new-value register no other store instruction
  // register has been modified in the same packet. Predicate registers can be
  // modified by they should not be modified between the producer and the store
  // instruction as it will make them both conditional on different values.
  // We already know this to be true for all the instructions before and
  // including PacketMI. Howerver, we need to perform the check for the
  // remaining instructions in the packet.

  unsigned StartCheck = 0;

  for (auto I : CurrentPacketMIs) {
    SUnit *TempSU = MIToSUnit.find(I)->second;
    MachineInstr* TempMI = TempSU->getInstr();

    // Following condition is true for all the instructions until PacketMI is
    // reached (StartCheck is set to 0 before the for loop).
    // StartCheck flag is 1 for all the instructions after PacketMI.
    if (TempMI != PacketMI && !StartCheck) // Start processing only after
      continue;                            // encountering PacketMI.

    StartCheck = 1;
    if (TempMI == PacketMI) // We don't want to check PacketMI for dependence.
      continue;

    for (auto &MO : MI->operands())
      if (MO.isReg() && TempSU->getInstr()->modifiesRegister(MO.getReg(), HRI))
        return false;
  }

  // Make sure that for non-POST_INC stores:
  // 1. The only use of reg is DepReg and no other registers.
  //    This handles V4 base+index registers.
  //    The following store can not be dot new.
  //    Eg.   r0 = add(r0, #3)
  //          memw(r1+r0<<#2) = r0
  if (!HII->isPostIncrement(MI)) {
    for (unsigned opNum = 0; opNum < MI->getNumOperands()-1; opNum++) {
      const MachineOperand &MO = MI->getOperand(opNum);
      if (MO.isReg() && MO.getReg() == DepReg)
        return false;
    }
  }

  // If data definition is because of implicit definition of the register,
  // do not newify the store. Eg.
  // %R9<def> = ZXTH %R12, %D6<imp-use>, %R12<imp-def>
  // S2_storerh_io %R8, 2, %R12<kill>; mem:ST2[%scevgep343]
  for (auto &MO : PacketMI->operands()) {
    if (!MO.isReg() || !MO.isDef() || !MO.isImplicit())
      continue;
    unsigned R = MO.getReg();
    if (R == DepReg || HRI->isSuperRegister(DepReg, R))
      return false;
  }

  // Handle imp-use of super reg case. There is a target independent side
  // change that should prevent this situation but I am handling it for
  // just-in-case. For example, we cannot newify R2 in the following case:
  // %R3<def> = A2_tfrsi 0;
  // S2_storeri_io %R0<kill>, 0, %R2<kill>, %D1<imp-use,kill>;
  for (auto &MO : MI->operands()) {
    if (MO.isReg() && MO.isUse() && MO.isImplicit() && MO.getReg() == DepReg)
      return false;
  }

  // Can be dot new store.
  return true;
}

// Can this MI to promoted to either new value store or new value jump.
bool HexagonPacketizerList::canPromoteToNewValue(const MachineInstr *MI,
      const SUnit *PacketSU, unsigned DepReg,
      MachineBasicBlock::iterator &MII) {
  if (!HII->mayBeNewStore(MI))
    return false;

  // Check to see the store can be new value'ed.
  MachineInstr *PacketMI = PacketSU->getInstr();
  if (canPromoteToNewValueStore(MI, PacketMI, DepReg))
    return true;

  // Check to see the compare/jump can be new value'ed.
  // This is done as a pass on its own. Don't need to check it here.
  return false;
}

static bool isImplicitDependency(const MachineInstr *I, unsigned DepReg) {
  for (auto &MO : I->operands())
    if (MO.isReg() && MO.isDef() && (MO.getReg() == DepReg) && MO.isImplicit())
      return true;
  return false;
}

// Check to see if an instruction can be dot new
// There are three kinds.
// 1. dot new on predicate - V2/V3/V4
// 2. dot new on stores NV/ST - V4
// 3. dot new on jump NV/J - V4 -- This is generated in a pass.
bool HexagonPacketizerList::canPromoteToDotNew(const MachineInstr *MI,
      const SUnit *PacketSU, unsigned DepReg, MachineBasicBlock::iterator &MII,
      const TargetRegisterClass* RC) {
  // Already a dot new instruction.
  if (HII->isDotNewInst(MI) && !HII->mayBeNewStore(MI))
    return false;

  if (!isNewifiable(MI))
    return false;

  const MachineInstr *PI = PacketSU->getInstr();

  // The "new value" cannot come from inline asm.
  if (PI->isInlineAsm())
    return false;

  // IMPLICIT_DEFs won't materialize as real instructions, so .new makes no
  // sense.
  if (PI->isImplicitDef())
    return false;

  // If dependency is trough an implicitly defined register, we should not
  // newify the use.
  if (isImplicitDependency(PI, DepReg))
    return false;

  const MCInstrDesc& MCID = PI->getDesc();
  const TargetRegisterClass *VecRC = HII->getRegClass(MCID, 0, HRI, MF);
  if (DisableVecDblNVStores && VecRC == &Hexagon::VecDblRegsRegClass)
    return false;

  // predicate .new
  // bug 5670: until that is fixed
  // TODO: MI->isIndirectBranch() and IsRegisterJump(MI)
  if (RC == &Hexagon::PredRegsRegClass)
    if (HII->isCondInst(MI) || MI->isReturn())
      return HII->predCanBeUsedAsDotNew(PI, DepReg);

  if (RC != &Hexagon::PredRegsRegClass && !HII->mayBeNewStore(MI))
    return false;

  // Create a dot new machine instruction to see if resources can be
  // allocated. If not, bail out now.
  int NewOpcode = HII->getDotNewOp(MI);
  const MCInstrDesc &D = HII->get(NewOpcode);
  MachineInstr *NewMI = MF.CreateMachineInstr(D, DebugLoc());
  bool ResourcesAvailable = ResourceTracker->canReserveResources(NewMI);
  MF.DeleteMachineInstr(NewMI);
  if (!ResourcesAvailable)
    return false;

  // New Value Store only. New Value Jump generated as a separate pass.
  if (!canPromoteToNewValue(MI, PacketSU, DepReg, MII))
    return false;

  return true;
}

// Go through the packet instructions and search for an anti dependency between
// them and DepReg from MI. Consider this case:
// Trying to add
// a) %R1<def> = TFRI_cdNotPt %P3, 2
// to this packet:
// {
//   b) %P0<def> = C2_or %P3<kill>, %P0<kill>
//   c) %P3<def> = C2_tfrrp %R23
//   d) %R1<def> = C2_cmovenewit %P3, 4
//  }
// The P3 from a) and d) will be complements after
// a)'s P3 is converted to .new form
// Anti-dep between c) and b) is irrelevant for this case
bool HexagonPacketizerList::restrictingDepExistInPacket(MachineInstr* MI,
                                                        unsigned DepReg) {
  SUnit *PacketSUDep = MIToSUnit.find(MI)->second;

  for (auto I : CurrentPacketMIs) {
    // We only care for dependencies to predicated instructions
    if (!HII->isPredicated(*I))
      continue;

    // Scheduling Unit for current insn in the packet
    SUnit *PacketSU = MIToSUnit.find(I)->second;

    // Look at dependencies between current members of the packet and
    // predicate defining instruction MI. Make sure that dependency is
    // on the exact register we care about.
    if (PacketSU->isSucc(PacketSUDep)) {
      for (unsigned i = 0; i < PacketSU->Succs.size(); ++i) {
        auto &Dep = PacketSU->Succs[i];
        if (Dep.getSUnit() == PacketSUDep && Dep.getKind() == SDep::Anti &&
            Dep.getReg() == DepReg)
          return true;
      }
    }
  }

  return false;
}


/// Gets the predicate register of a predicated instruction.
static unsigned getPredicatedRegister(MachineInstr &MI,
                                      const HexagonInstrInfo *QII) {
  /// We use the following rule: The first predicate register that is a use is
  /// the predicate register of a predicated instruction.
  assert(QII->isPredicated(MI) && "Must be predicated instruction");

  for (auto &Op : MI.operands()) {
    if (Op.isReg() && Op.getReg() && Op.isUse() &&
        Hexagon::PredRegsRegClass.contains(Op.getReg()))
      return Op.getReg();
  }

  llvm_unreachable("Unknown instruction operand layout");
  return 0;
}

// Given two predicated instructions, this function detects whether
// the predicates are complements.
bool HexagonPacketizerList::arePredicatesComplements(MachineInstr &MI1,
                                                     MachineInstr &MI2) {
  // If we don't know the predicate sense of the instructions bail out early, we
  // need it later.
  if (getPredicateSense(MI1, HII) == PK_Unknown ||
      getPredicateSense(MI2, HII) == PK_Unknown)
    return false;

  // Scheduling unit for candidate.
  SUnit *SU = MIToSUnit[&MI1];

  // One corner case deals with the following scenario:
  // Trying to add
  // a) %R24<def> = A2_tfrt %P0, %R25
  // to this packet:
  // {
  //   b) %R25<def> = A2_tfrf %P0, %R24
  //   c) %P0<def> = C2_cmpeqi %R26, 1
  // }
  //
  // On general check a) and b) are complements, but presence of c) will
  // convert a) to .new form, and then it is not a complement.
  // We attempt to detect it by analyzing existing dependencies in the packet.

  // Analyze relationships between all existing members of the packet.
  // Look for Anti dependecy on the same predicate reg as used in the
  // candidate.
  for (auto I : CurrentPacketMIs) {
    // Scheduling Unit for current insn in the packet.
    SUnit *PacketSU = MIToSUnit.find(I)->second;

    // If this instruction in the packet is succeeded by the candidate...
    if (PacketSU->isSucc(SU)) {
      for (unsigned i = 0; i < PacketSU->Succs.size(); ++i) {
        auto Dep = PacketSU->Succs[i];
        // The corner case exist when there is true data dependency between
        // candidate and one of current packet members, this dep is on
        // predicate reg, and there already exist anti dep on the same pred in
        // the packet.
        if (Dep.getSUnit() == SU && Dep.getKind() == SDep::Data &&
            Hexagon::PredRegsRegClass.contains(Dep.getReg())) {
          // Here I know that I is predicate setting instruction with true
          // data dep to candidate on the register we care about - c) in the
          // above example. Now I need to see if there is an anti dependency
          // from c) to any other instruction in the same packet on the pred
          // reg of interest.
          if (restrictingDepExistInPacket(I, Dep.getReg()))
            return false;
        }
      }
    }
  }

  // If the above case does not apply, check regular complement condition.
  // Check that the predicate register is the same and that the predicate
  // sense is different We also need to differentiate .old vs. .new: !p0
  // is not complementary to p0.new.
  unsigned PReg1 = getPredicatedRegister(MI1, HII);
  unsigned PReg2 = getPredicatedRegister(MI2, HII);
  return PReg1 == PReg2 &&
         Hexagon::PredRegsRegClass.contains(PReg1) &&
         Hexagon::PredRegsRegClass.contains(PReg2) &&
         getPredicateSense(MI1, HII) != getPredicateSense(MI2, HII) &&
         HII->isDotNewInst(&MI1) == HII->isDotNewInst(&MI2);
}

// Initialize packetizer flags.
void HexagonPacketizerList::initPacketizerState() {
  Dependence = false;
  PromotedToDotNew = false;
  GlueToNewValueJump = false;
  GlueAllocframeStore = false;
  FoundSequentialDependence = false;
}

// Ignore bundling of pseudo instructions.
bool HexagonPacketizerList::ignorePseudoInstruction(const MachineInstr *MI,
      const MachineBasicBlock*) {
  if (MI->isDebugValue())
    return true;

  if (MI->isCFIInstruction())
    return false;

  // We must print out inline assembly.
  if (MI->isInlineAsm())
    return false;

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

  // We check if MI has any functional units mapped to it. If it doesn't,
  // we ignore the instruction.
  const MCInstrDesc& TID = MI->getDesc();
  auto *IS = ResourceTracker->getInstrItins()->beginStage(TID.getSchedClass());
  unsigned FuncUnits = IS->getUnits();
  return !FuncUnits;
}

bool HexagonPacketizerList::isSoloInstruction(const MachineInstr *MI) {
  if (MI->isEHLabel() || MI->isCFIInstruction())
    return true;

  // Consider inline asm to not be a solo instruction by default.
  // Inline asm will be put in a packet temporarily, but then it will be
  // removed, and placed outside of the packet (before or after, depending
  // on dependencies).  This is to reduce the impact of inline asm as a
  // "packet splitting" instruction.
  if (MI->isInlineAsm() && !ScheduleInlineAsm)
    return true;

  // From Hexagon V4 Programmer's Reference Manual 3.4.4 Grouping constraints:
  // trap, pause, barrier, icinva, isync, and syncht are solo instructions.
  // They must not be grouped with other instructions in a packet.
  if (isSchedBarrier(MI))
    return true;

  if (HII->isSolo(MI))
    return true;

  if (MI->getOpcode() == Hexagon::A2_nop)
    return true;

  return false;
}


// Quick check if instructions MI and MJ cannot coexist in the same packet.
// Limit the tests to be "one-way", e.g.  "if MI->isBranch and MJ->isInlineAsm",
// but not the symmetric case: "if MJ->isBranch and MI->isInlineAsm".
// For full test call this function twice:
//   cannotCoexistAsymm(MI, MJ) || cannotCoexistAsymm(MJ, MI)
// Doing the test only one way saves the amount of code in this function,
// since every test would need to be repeated with the MI and MJ reversed.
static bool cannotCoexistAsymm(const MachineInstr *MI, const MachineInstr *MJ,
      const HexagonInstrInfo &HII) {
  const MachineFunction *MF = MI->getParent()->getParent();
  if (MF->getSubtarget<HexagonSubtarget>().hasV60TOpsOnly() &&
      HII.isHVXMemWithAIndirect(MI, MJ))
    return true;

  // An inline asm cannot be together with a branch, because we may not be
  // able to remove the asm out after packetizing (i.e. if the asm must be
  // moved past the bundle).  Similarly, two asms cannot be together to avoid
  // complications when determining their relative order outside of a bundle.
  if (MI->isInlineAsm())
    return MJ->isInlineAsm() || MJ->isBranch() || MJ->isBarrier() ||
           MJ->isCall() || MJ->isTerminator();

  // "False" really means that the quick check failed to determine if
  // I and J cannot coexist.
  return false;
}


// Full, symmetric check.
bool HexagonPacketizerList::cannotCoexist(const MachineInstr *MI,
      const MachineInstr *MJ) {
  return cannotCoexistAsymm(MI, MJ, *HII) || cannotCoexistAsymm(MJ, MI, *HII);
}

void HexagonPacketizerList::unpacketizeSoloInstrs(MachineFunction &MF) {
  for (auto &B : MF) {
    MachineBasicBlock::iterator BundleIt;
    MachineBasicBlock::instr_iterator NextI;
    for (auto I = B.instr_begin(), E = B.instr_end(); I != E; I = NextI) {
      NextI = std::next(I);
      MachineInstr *MI = &*I;
      if (MI->isBundle())
        BundleIt = I;
      if (!MI->isInsideBundle())
        continue;

      // Decide on where to insert the instruction that we are pulling out.
      // Debug instructions always go before the bundle, but the placement of
      // INLINE_ASM depends on potential dependencies.  By default, try to
      // put it before the bundle, but if the asm writes to a register that
      // other instructions in the bundle read, then we need to place it
      // after the bundle (to preserve the bundle semantics).
      bool InsertBeforeBundle;
      if (MI->isInlineAsm())
        InsertBeforeBundle = !hasWriteToReadDep(MI, BundleIt, HRI);
      else if (MI->isDebugValue())
        InsertBeforeBundle = true;
      else
        continue;

      BundleIt = moveInstrOut(MI, BundleIt, InsertBeforeBundle);
    }
  }
}

// Check if a given instruction is of class "system".
static bool isSystemInstr(const MachineInstr *MI) {
  unsigned Opc = MI->getOpcode();
  switch (Opc) {
    case Hexagon::Y2_barrier:
    case Hexagon::Y2_dcfetchbo:
      return true;
  }
  return false;
}

bool HexagonPacketizerList::hasDeadDependence(const MachineInstr *I,
                                              const MachineInstr *J) {
  // The dependence graph may not include edges between dead definitions,
  // so without extra checks, we could end up packetizing two instruction
  // defining the same (dead) register.
  if (I->isCall() || J->isCall())
    return false;
  if (HII->isPredicated(*I) || HII->isPredicated(*J))
    return false;

  BitVector DeadDefs(Hexagon::NUM_TARGET_REGS);
  for (auto &MO : I->operands()) {
    if (!MO.isReg() || !MO.isDef() || !MO.isDead())
      continue;
    DeadDefs[MO.getReg()] = true;
  }

  for (auto &MO : J->operands()) {
    if (!MO.isReg() || !MO.isDef() || !MO.isDead())
      continue;
    unsigned R = MO.getReg();
    if (R != Hexagon::USR_OVF && DeadDefs[R])
      return true;
  }
  return false;
}

bool HexagonPacketizerList::hasControlDependence(const MachineInstr *I,
                                                 const MachineInstr *J) {
  // A save callee-save register function call can only be in a packet
  // with instructions that don't write to the callee-save registers.
  if ((HII->isSaveCalleeSavedRegsCall(I) &&
       doesModifyCalleeSavedReg(J, HRI)) ||
      (HII->isSaveCalleeSavedRegsCall(J) &&
       doesModifyCalleeSavedReg(I, HRI)))
    return true;

  // Two control flow instructions cannot go in the same packet.
  if (isControlFlow(I) && isControlFlow(J))
    return true;

  // \ref-manual (7.3.4) A loop setup packet in loopN or spNloop0 cannot
  // contain a speculative indirect jump,
  // a new-value compare jump or a dealloc_return.
  auto isBadForLoopN = [this] (const MachineInstr *MI) -> bool {
    if (MI->isCall() || HII->isDeallocRet(MI) || HII->isNewValueJump(MI))
      return true;
    if (HII->isPredicated(*MI) && HII->isPredicatedNew(*MI) && HII->isJumpR(MI))
      return true;
    return false;
  };

  if (HII->isLoopN(I) && isBadForLoopN(J))
    return true;
  if (HII->isLoopN(J) && isBadForLoopN(I))
    return true;

  // dealloc_return cannot appear in the same packet as a conditional or
  // unconditional jump.
  return HII->isDeallocRet(I) &&
         (J->isBranch() || J->isCall() || J->isBarrier());
}

bool HexagonPacketizerList::hasV4SpecificDependence(const MachineInstr *I,
                                                    const MachineInstr *J) {
  bool SysI = isSystemInstr(I), SysJ = isSystemInstr(J);
  bool StoreI = I->mayStore(), StoreJ = J->mayStore();
  if ((SysI && StoreJ) || (SysJ && StoreI))
    return true;

  if (StoreI && StoreJ) {
    if (HII->isNewValueInst(J) || HII->isMemOp(J) || HII->isMemOp(I))
      return true;
  } else {
    // A memop cannot be in the same packet with another memop or a store.
    // Two stores can be together, but here I and J cannot both be stores.
    bool MopStI = HII->isMemOp(I) || StoreI;
    bool MopStJ = HII->isMemOp(J) || StoreJ;
    if (MopStI && MopStJ)
      return true;
  }

  return (StoreJ && HII->isDeallocRet(I)) || (StoreI && HII->isDeallocRet(J));
}

// SUI is the current instruction that is out side of the current packet.
// SUJ is the current instruction inside the current packet against which that
// SUI will be packetized.
bool HexagonPacketizerList::isLegalToPacketizeTogether(SUnit *SUI, SUnit *SUJ) {
  MachineInstr *I = SUI->getInstr();
  MachineInstr *J = SUJ->getInstr();
  assert(I && J && "Unable to packetize null instruction!");

  // Clear IgnoreDepMIs when Packet starts.
  if (CurrentPacketMIs.size() == 1)
    IgnoreDepMIs.clear();

  MachineBasicBlock::iterator II = I;
  const unsigned FrameSize = MF.getFrameInfo()->getStackSize();

  // Solo instructions cannot go in the packet.
  assert(!isSoloInstruction(I) && "Unexpected solo instr!");

  if (cannotCoexist(I, J))
    return false;

  Dependence = hasDeadDependence(I, J) || hasControlDependence(I, J);
  if (Dependence)
    return false;

  // V4 allows dual stores. It does not allow second store, if the first
  // store is not in SLOT0. New value store, new value jump, dealloc_return
  // and memop always take SLOT0. Arch spec 3.4.4.2.
  Dependence = hasV4SpecificDependence(I, J);
  if (Dependence)
    return false;

  // If an instruction feeds new value jump, glue it.
  MachineBasicBlock::iterator NextMII = I;
  ++NextMII;
  if (NextMII != I->getParent()->end() && HII->isNewValueJump(NextMII)) {
    MachineInstr *NextMI = NextMII;

    bool secondRegMatch = false;
    const MachineOperand &NOp0 = NextMI->getOperand(0);
    const MachineOperand &NOp1 = NextMI->getOperand(1);

    if (NOp1.isReg() && I->getOperand(0).getReg() == NOp1.getReg())
      secondRegMatch = true;

    for (auto I : CurrentPacketMIs) {
      SUnit *PacketSU = MIToSUnit.find(I)->second;
      MachineInstr *PI = PacketSU->getInstr();
      // NVJ can not be part of the dual jump - Arch Spec: section 7.8.
      if (PI->isCall()) {
        Dependence = true;
        break;
      }
      // Validate:
      // 1. Packet does not have a store in it.
      // 2. If the first operand of the nvj is newified, and the second
      //    operand is also a reg, it (second reg) is not defined in
      //    the same packet.
      // 3. If the second operand of the nvj is newified, (which means
      //    first operand is also a reg), first reg is not defined in
      //    the same packet.
      if (PI->getOpcode() == Hexagon::S2_allocframe || PI->mayStore() ||
          HII->isLoopN(PI)) {
        Dependence = true;
        break;
      }
      // Check #2/#3.
      const MachineOperand &OpR = secondRegMatch ? NOp0 : NOp1;
      if (OpR.isReg() && PI->modifiesRegister(OpR.getReg(), HRI)) {
        Dependence = true;
        break;
      }
    }

    if (Dependence)
      return false;
    GlueToNewValueJump = true;
  }

  // There no dependency between a prolog instruction and its successor.
  if (!SUJ->isSucc(SUI))
    return true;

  for (unsigned i = 0; i < SUJ->Succs.size(); ++i) {
    if (FoundSequentialDependence)
      break;

    if (SUJ->Succs[i].getSUnit() != SUI)
      continue;

    SDep::Kind DepType = SUJ->Succs[i].getKind();
    // For direct calls:
    // Ignore register dependences for call instructions for packetization
    // purposes except for those due to r31 and predicate registers.
    //
    // For indirect calls:
    // Same as direct calls + check for true dependences to the register
    // used in the indirect call.
    //
    // We completely ignore Order dependences for call instructions.
    //
    // For returns:
    // Ignore register dependences for return instructions like jumpr,
    // dealloc return unless we have dependencies on the explicit uses
    // of the registers used by jumpr (like r31) or dealloc return
    // (like r29 or r30).
    //
    // TODO: Currently, jumpr is handling only return of r31. So, the
    // following logic (specificaly isCallDependent) is working fine.
    // We need to enable jumpr for register other than r31 and then,
    // we need to rework the last part, where it handles indirect call
    // of that (isCallDependent) function. Bug 6216 is opened for this.
    unsigned DepReg = 0;
    const TargetRegisterClass *RC = nullptr;
    if (DepType == SDep::Data) {
      DepReg = SUJ->Succs[i].getReg();
      RC = HRI->getMinimalPhysRegClass(DepReg);
    }

    if (I->isCall() || I->isReturn()) {
      if (!isRegDependence(DepType))
        continue;
      if (!isCallDependent(I, DepType, SUJ->Succs[i].getReg()))
        continue;
    }

    if (DepType == SDep::Data) {
      if (canPromoteToDotCur(J, SUJ, DepReg, II, RC))
        if (promoteToDotCur(J, DepType, II, RC))
          continue;
    }

    // Data dpendence ok if we have load.cur.
    if (DepType == SDep::Data && HII->isDotCurInst(J)) {
      if (HII->isV60VectorInstruction(I))
        continue;
    }

    // For instructions that can be promoted to dot-new, try to promote.
    if (DepType == SDep::Data) {
      if (canPromoteToDotNew(I, SUJ, DepReg, II, RC)) {
        if (promoteToDotNew(I, DepType, II, RC)) {
          PromotedToDotNew = true;
          continue;
        }
      }
      if (HII->isNewValueJump(I))
        continue;
    }

    // For predicated instructions, if the predicates are complements then
    // there can be no dependence.
    if (HII->isPredicated(*I) && HII->isPredicated(*J) &&
        arePredicatesComplements(*I, *J)) {
      // Not always safe to do this translation.
      // DAG Builder attempts to reduce dependence edges using transitive
      // nature of dependencies. Here is an example:
      //
      // r0 = tfr_pt ... (1)
      // r0 = tfr_pf ... (2)
      // r0 = tfr_pt ... (3)
      //
      // There will be an output dependence between (1)->(2) and (2)->(3).
      // However, there is no dependence edge between (1)->(3). This results
      // in all 3 instructions going in the same packet. We ignore dependce
      // only once to avoid this situation.
      auto Itr = std::find(IgnoreDepMIs.begin(), IgnoreDepMIs.end(), J);
      if (Itr != IgnoreDepMIs.end()) {
        Dependence = true;
        return false;
      }
      IgnoreDepMIs.push_back(I);
      continue;
    }

    // Ignore Order dependences between unconditional direct branches
    // and non-control-flow instructions.
    if (isDirectJump(I) && !J->isBranch() && !J->isCall() &&
        DepType == SDep::Order)
      continue;

    // Ignore all dependences for jumps except for true and output
    // dependences.
    if (I->isConditionalBranch() && DepType != SDep::Data &&
        DepType != SDep::Output)
      continue;

    // Ignore output dependences due to superregs. We can write to two
    // different subregisters of R1:0 for instance in the same cycle.

    // If neither I nor J defines DepReg, then this is a superfluous output
    // dependence. The dependence must be of the form:
    //   R0 = ...
    //   R1 = ...
    // and there is an output dependence between the two instructions with
    // DepReg = D0.
    // We want to ignore these dependences. Ideally, the dependence
    // constructor should annotate such dependences. We can then avoid this
    // relatively expensive check.
    //
    if (DepType == SDep::Output) {
      // DepReg is the register that's responsible for the dependence.
      unsigned DepReg = SUJ->Succs[i].getReg();

      // Check if I and J really defines DepReg.
      if (!I->definesRegister(DepReg) && !J->definesRegister(DepReg))
        continue;
      FoundSequentialDependence = true;
      break;
    }

    // For Order dependences:
    // 1. On V4 or later, volatile loads/stores can be packetized together,
    //    unless other rules prevent is.
    // 2. Store followed by a load is not allowed.
    // 3. Store followed by a store is only valid on V4 or later.
    // 4. Load followed by any memory operation is allowed.
    if (DepType == SDep::Order) {
      if (!PacketizeVolatiles) {
        bool OrdRefs = I->hasOrderedMemoryRef() || J->hasOrderedMemoryRef();
        if (OrdRefs) {
          FoundSequentialDependence = true;
          break;
        }
      }
      // J is first, I is second.
      bool LoadJ = J->mayLoad(), StoreJ = J->mayStore();
      bool LoadI = I->mayLoad(), StoreI = I->mayStore();
      if (StoreJ) {
        // Two stores are only allowed on V4+. Load following store is never
        // allowed.
        if (LoadI) {
          FoundSequentialDependence = true;
          break;
        }
      } else if (!LoadJ || (!LoadI && !StoreI)) {
        // If J is neither load nor store, assume a dependency.
        // If J is a load, but I is neither, also assume a dependency.
        FoundSequentialDependence = true;
        break;
      }
      // Store followed by store: not OK on V2.
      // Store followed by load: not OK on all.
      // Load followed by store: OK on all.
      // Load followed by load: OK on all.
      continue;
    }

    // For V4, special case ALLOCFRAME. Even though there is dependency
    // between ALLOCFRAME and subsequent store, allow it to be packetized
    // in a same packet. This implies that the store is using the caller's
    // SP. Hence, offset needs to be updated accordingly.
    if (DepType == SDep::Data && J->getOpcode() == Hexagon::S2_allocframe) {
      unsigned Opc = I->getOpcode();
      switch (Opc) {
        case Hexagon::S2_storerd_io:
        case Hexagon::S2_storeri_io:
        case Hexagon::S2_storerh_io:
        case Hexagon::S2_storerb_io:
          if (I->getOperand(0).getReg() == HRI->getStackRegister()) {
            int64_t Imm = I->getOperand(1).getImm();
            int64_t NewOff = Imm - (FrameSize + HEXAGON_LRFP_SIZE);
            if (HII->isValidOffset(Opc, NewOff)) {
              GlueAllocframeStore = true;
              // Since this store is to be glued with allocframe in the same
              // packet, it will use SP of the previous stack frame, i.e.
              // caller's SP. Therefore, we need to recalculate offset
              // according to this change.
              I->getOperand(1).setImm(NewOff);
              continue;
            }
          }
        default:
          break;
      }
    }

    // Skip over anti-dependences. Two instructions that are anti-dependent
    // can share a packet.
    if (DepType != SDep::Anti) {
      FoundSequentialDependence = true;
      break;
    }
  }

  if (FoundSequentialDependence) {
    Dependence = true;
    return false;
  }

  return true;
}

bool HexagonPacketizerList::isLegalToPruneDependencies(SUnit *SUI, SUnit *SUJ) {
  MachineInstr *I = SUI->getInstr();
  MachineInstr *J = SUJ->getInstr();
  assert(I && J && "Unable to packetize null instruction!");

  if (cannotCoexist(I, J))
    return false;

  if (!Dependence)
    return true;

  // Check if the instruction was promoted to a dot-new. If so, demote it
  // back into a dot-old.
  if (PromotedToDotNew)
    demoteToDotOld(I);

  cleanUpDotCur();
  // Check if the instruction (must be a store) was glued with an allocframe
  // instruction. If so, restore its offset to its original value, i.e. use
  // current SP instead of caller's SP.
  if (GlueAllocframeStore) {
    unsigned FrameSize = MF.getFrameInfo()->getStackSize();
    MachineOperand &MOff = I->getOperand(1);
    MOff.setImm(MOff.getImm() + FrameSize + HEXAGON_LRFP_SIZE);
  }
  return false;
}


MachineBasicBlock::iterator
HexagonPacketizerList::addToPacket(MachineInstr *MI) {
  MachineBasicBlock::iterator MII = MI;
  MachineBasicBlock *MBB = MI->getParent();
  if (MI->isImplicitDef()) {
    unsigned R = MI->getOperand(0).getReg();
    if (Hexagon::IntRegsRegClass.contains(R)) {
      MCSuperRegIterator S(R, HRI, false);
      MI->addOperand(MachineOperand::CreateReg(*S, true, true));
    }
    return MII;
  }
  assert(ResourceTracker->canReserveResources(MI));

  bool ExtMI = HII->isExtended(MI) || HII->isConstExtended(MI);
  bool Good = true;

  if (GlueToNewValueJump) {
    MachineInstr *NvjMI = ++MII;
    // We need to put both instructions in the same packet: MI and NvjMI.
    // Either of them can require a constant extender. Try to add both to
    // the current packet, and if that fails, end the packet and start a
    // new one.
    ResourceTracker->reserveResources(MI);
    if (ExtMI)
      Good = tryAllocateResourcesForConstExt(true);

    bool ExtNvjMI = HII->isExtended(NvjMI) || HII->isConstExtended(NvjMI);
    if (Good) {
      if (ResourceTracker->canReserveResources(NvjMI))
        ResourceTracker->reserveResources(NvjMI);
      else
        Good = false;
    }
    if (Good && ExtNvjMI)
      Good = tryAllocateResourcesForConstExt(true);

    if (!Good) {
      endPacket(MBB, MI);
      assert(ResourceTracker->canReserveResources(MI));
      ResourceTracker->reserveResources(MI);
      if (ExtMI) {
        assert(canReserveResourcesForConstExt());
        tryAllocateResourcesForConstExt(true);
      }
      assert(ResourceTracker->canReserveResources(NvjMI));
      ResourceTracker->reserveResources(NvjMI);
      if (ExtNvjMI) {
        assert(canReserveResourcesForConstExt());
        reserveResourcesForConstExt();
      }
    }
    CurrentPacketMIs.push_back(MI);
    CurrentPacketMIs.push_back(NvjMI);
    return MII;
  }

  ResourceTracker->reserveResources(MI);
  if (ExtMI && !tryAllocateResourcesForConstExt(true)) {
    endPacket(MBB, MI);
    if (PromotedToDotNew)
      demoteToDotOld(MI);
    ResourceTracker->reserveResources(MI);
    reserveResourcesForConstExt();
  }

  CurrentPacketMIs.push_back(MI);
  return MII;
}

void HexagonPacketizerList::endPacket(MachineBasicBlock *MBB,
      MachineInstr *MI) {
  OldPacketMIs = CurrentPacketMIs;
  VLIWPacketizerList::endPacket(MBB, MI);
}

bool HexagonPacketizerList::shouldAddToPacket(const MachineInstr *MI) {
  return !producesStall(MI);
}


// Return true when ConsMI uses a register defined by ProdMI.
static bool isDependent(const MachineInstr *ProdMI,
      const MachineInstr *ConsMI) {
  if (!ProdMI->getOperand(0).isReg())
    return false;
  unsigned DstReg = ProdMI->getOperand(0).getReg();

  for (auto &Op : ConsMI->operands())
    if (Op.isReg() && Op.isUse() && Op.getReg() == DstReg)
      // The MIs depend on each other.
      return true;

  return false;
}

// V60 forward scheduling.
bool HexagonPacketizerList::producesStall(const MachineInstr *I) {
  // Check whether the previous packet is in a different loop. If this is the
  // case, there is little point in trying to avoid a stall because that would
  // favor the rare case (loop entry) over the common case (loop iteration).
  //
  // TODO: We should really be able to check all the incoming edges if this is
  // the first packet in a basic block, so we can avoid stalls from the loop
  // backedge.
  if (!OldPacketMIs.empty()) {
    auto *OldBB = OldPacketMIs.front()->getParent();
    auto *ThisBB = I->getParent();
    if (MLI->getLoopFor(OldBB) != MLI->getLoopFor(ThisBB))
      return false;
  }

  // Check for stall between two vector instructions.
  if (HII->isV60VectorInstruction(I)) {
    for (auto J : OldPacketMIs) {
      if (!HII->isV60VectorInstruction(J))
        continue;
      if (isDependent(J, I) && !HII->isVecUsableNextPacket(J, I))
        return true;
    }
    return false;
  }

  // Check for stall between two scalar instructions. First, check that
  // there is no definition of a use in the current packet, because it
  // may be a candidate for .new.
  for (auto J : CurrentPacketMIs)
    if (!HII->isV60VectorInstruction(J) && isDependent(J, I))
      return false;

  // Check for stall between I and instructions in the previous packet.
  if (MF.getSubtarget<HexagonSubtarget>().useBSBScheduling()) {
    for (auto J : OldPacketMIs) {
      if (HII->isV60VectorInstruction(J))
        continue;
      if (!HII->isLateInstrFeedsEarlyInstr(J, I))
        continue;
      if (isDependent(J, I) && !HII->canExecuteInBundle(J, I))
        return true;
    }
  }

  return false;
}


//===----------------------------------------------------------------------===//
//                         Public Constructor Functions
//===----------------------------------------------------------------------===//

FunctionPass *llvm::createHexagonPacketizer() {
  return new HexagonPacketizer();
}