LiveIntervalAnalysis.cpp

    // Loop over all slots overlapping this segment.
    while (*SlotI < LiveI->end) {
      // *SlotI overlaps LI. Collect mask bits.
      if (!Found) {
        // This is the first overlap. Initialize UsableRegs to all ones.
        UsableRegs.clear();
        UsableRegs.resize(TRI->getNumRegs(), true);
        Found = true;
      }
      // Remove usable registers clobbered by this mask.
      UsableRegs.clearBitsNotInMask(Bits[SlotI-Slots.begin()]);
      if (++SlotI == SlotE)
        return Found;
    }
    // *SlotI is beyond the current LI segment.
    LiveI = LI.advanceTo(LiveI, *SlotI);
    if (LiveI == LiveE)
      return Found;
    // Advance SlotI until it overlaps.
    while (*SlotI < LiveI->start)
      if (++SlotI == SlotE)
        return Found;
  }
}

//===----------------------------------------------------------------------===//
//                         IntervalUpdate class.
//===----------------------------------------------------------------------===//

// HMEditor is a toolkit used by handleMove to trim or extend live intervals.
class LiveIntervals::HMEditor {
private:
  LiveIntervals& LIS;
  const MachineRegisterInfo& MRI;
  const TargetRegisterInfo& TRI;
  SlotIndex NewIdx;

  typedef std::pair<LiveInterval*, LiveRange*> IntRangePair;
  typedef DenseSet<IntRangePair> RangeSet;

  struct RegRanges {
    LiveRange* Use;
    LiveRange* EC;
    LiveRange* Dead;
    LiveRange* Def;
    RegRanges() : Use(0), EC(0), Dead(0), Def(0) {}
  };
  typedef DenseMap<unsigned, RegRanges> BundleRanges;

public:
  HMEditor(LiveIntervals& LIS, const MachineRegisterInfo& MRI,
           const TargetRegisterInfo& TRI, SlotIndex NewIdx)
    : LIS(LIS), MRI(MRI), TRI(TRI), NewIdx(NewIdx) {}

  // Update intervals for all operands of MI from OldIdx to NewIdx.
  // This assumes that MI used to be at OldIdx, and now resides at
  // NewIdx.
  void moveAllRangesFrom(MachineInstr* MI, SlotIndex OldIdx) {
    assert(NewIdx != OldIdx && "No-op move? That's a bit strange.");

    // Collect the operands.
    RangeSet Entering, Internal, Exiting;
    bool hasRegMaskOp = false;
    collectRanges(MI, Entering, Internal, Exiting, hasRegMaskOp, OldIdx);

    // To keep the LiveRanges valid within an interval, move the ranges closest
    // to the destination first. This prevents ranges from overlapping, to that
    // APIs like removeRange still work.
    if (NewIdx < OldIdx) {
      moveAllEnteringFrom(OldIdx, Entering);
      moveAllInternalFrom(OldIdx, Internal);
      moveAllExitingFrom(OldIdx, Exiting);
    }
    else {
      moveAllExitingFrom(OldIdx, Exiting);
      moveAllInternalFrom(OldIdx, Internal);
      moveAllEnteringFrom(OldIdx, Entering);
    }

    if (hasRegMaskOp)
      updateRegMaskSlots(OldIdx);

#ifndef NDEBUG
    LIValidator validator;
    validator = std::for_each(Entering.begin(), Entering.end(), validator);
    validator = std::for_each(Internal.begin(), Internal.end(), validator);
    validator = std::for_each(Exiting.begin(), Exiting.end(), validator);
    assert(validator.rangesOk() && "moveAllOperandsFrom broke liveness.");
#endif

  }

  // Update intervals for all operands of MI to refer to BundleStart's
  // SlotIndex.
  void moveAllRangesInto(MachineInstr* MI, MachineInstr* BundleStart) {
    if (MI == BundleStart)
      return; // Bundling instr with itself - nothing to do.

    SlotIndex OldIdx = LIS.getSlotIndexes()->getInstructionIndex(MI);
    assert(LIS.getSlotIndexes()->getInstructionFromIndex(OldIdx) == MI &&
           "SlotIndex <-> Instruction mapping broken for MI");

    // Collect all ranges already in the bundle.
    MachineBasicBlock::instr_iterator BII(BundleStart);
    RangeSet Entering, Internal, Exiting;
    bool hasRegMaskOp = false;
    collectRanges(BII, Entering, Internal, Exiting, hasRegMaskOp, NewIdx);
    assert(!hasRegMaskOp && "Can't have RegMask operand in bundle.");
    for (++BII; &*BII == MI || BII->isInsideBundle(); ++BII) {
      if (&*BII == MI)
        continue;
      collectRanges(BII, Entering, Internal, Exiting, hasRegMaskOp, NewIdx);
      assert(!hasRegMaskOp && "Can't have RegMask operand in bundle.");
    }

    BundleRanges BR = createBundleRanges(Entering, Internal, Exiting);

    Entering.clear();
    Internal.clear();
    Exiting.clear();
    collectRanges(MI, Entering, Internal, Exiting, hasRegMaskOp, OldIdx);
    assert(!hasRegMaskOp && "Can't have RegMask operand in bundle.");

    DEBUG(dbgs() << "Entering: " << Entering.size() << "\n");
    DEBUG(dbgs() << "Internal: " << Internal.size() << "\n");
    DEBUG(dbgs() << "Exiting: " << Exiting.size() << "\n");

    moveAllEnteringFromInto(OldIdx, Entering, BR);
    moveAllInternalFromInto(OldIdx, Internal, BR);
    moveAllExitingFromInto(OldIdx, Exiting, BR);


#ifndef NDEBUG
    LIValidator validator;
    validator = std::for_each(Entering.begin(), Entering.end(), validator);
    validator = std::for_each(Internal.begin(), Internal.end(), validator);
    validator = std::for_each(Exiting.begin(), Exiting.end(), validator);
    assert(validator.rangesOk() && "moveAllOperandsInto broke liveness.");
#endif
  }

private:

#ifndef NDEBUG
  class LIValidator {
  private:
    DenseSet<const LiveInterval*> Checked, Bogus;
  public:
    void operator()(const IntRangePair& P) {
      const LiveInterval* LI = P.first;
      if (Checked.count(LI))
        return;
      Checked.insert(LI);
      if (LI->empty())
        return;
      SlotIndex LastEnd = LI->begin()->start;
      for (LiveInterval::const_iterator LRI = LI->begin(), LRE = LI->end();
           LRI != LRE; ++LRI) {
        const LiveRange& LR = *LRI;
        if (LastEnd > LR.start || LR.start >= LR.end)
          Bogus.insert(LI);
        LastEnd = LR.end;
      }
    }

    bool rangesOk() const {
      return Bogus.empty();
    }
  };
#endif

  // Collect IntRangePairs for all operands of MI that may need fixing.
  // Treat's MI's index as OldIdx (regardless of what it is in SlotIndexes'
  // maps).
  void collectRanges(MachineInstr* MI, RangeSet& Entering, RangeSet& Internal,
                     RangeSet& Exiting, bool& hasRegMaskOp, SlotIndex OldIdx) {
    hasRegMaskOp = false;
    for (MachineInstr::mop_iterator MOI = MI->operands_begin(),
                                    MOE = MI->operands_end();
         MOI != MOE; ++MOI) {
      const MachineOperand& MO = *MOI;

      if (MO.isRegMask()) {
        hasRegMaskOp = true;
        continue;
      }

      if (!MO.isReg() || MO.getReg() == 0)
        continue;

      unsigned Reg = MO.getReg();

      // TODO: Currently we're skipping uses that are reserved or have no
      // interval, but we're not updating their kills. This should be
      // fixed.
      if (TargetRegisterInfo::isPhysicalRegister(Reg) && LIS.isReserved(Reg))
        continue;

      // Collect ranges for register units. These live ranges are computed on
      // demand, so just skip any that haven't been computed yet.
      if (TargetRegisterInfo::isPhysicalRegister(Reg) && LIS.trackingRegUnits())
        for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units)
          if (LiveInterval *LI = LIS.getCachedRegUnit(*Units))
            collectRanges(MO, LI, Entering, Internal, Exiting, OldIdx);

      // Collect ranges for individual registers.
      if (LIS.hasInterval(Reg))
        collectRanges(MO, &LIS.getInterval(Reg),
                      Entering, Internal, Exiting, OldIdx);
    }
  }

  void collectRanges(const MachineOperand &MO, LiveInterval *LI,
                     RangeSet &Entering, RangeSet &Internal, RangeSet &Exiting,
                     SlotIndex OldIdx) {
    if (MO.readsReg()) {
      LiveRange* LR = LI->getLiveRangeContaining(OldIdx);
      if (LR != 0)
        Entering.insert(std::make_pair(LI, LR));
    }
    if (MO.isDef()) {
      LiveRange* LR = LI->getLiveRangeContaining(OldIdx.getRegSlot());
      assert(LR != 0 && "No live range for def?");
      if (LR->end > OldIdx.getDeadSlot())
        Exiting.insert(std::make_pair(LI, LR));
      else
        Internal.insert(std::make_pair(LI, LR));
    }
  }

  BundleRanges createBundleRanges(RangeSet& Entering,
                                  RangeSet& Internal,
                                  RangeSet& Exiting) {
    BundleRanges BR;

    for (RangeSet::iterator EI = Entering.begin(), EE = Entering.end();
         EI != EE; ++EI) {
      LiveInterval* LI = EI->first;
      LiveRange* LR = EI->second;
      BR[LI->reg].Use = LR;
    }

    for (RangeSet::iterator II = Internal.begin(), IE = Internal.end();
         II != IE; ++II) {
      LiveInterval* LI = II->first;
      LiveRange* LR = II->second;
      if (LR->end.isDead()) {
        BR[LI->reg].Dead = LR;
      } else {
        BR[LI->reg].EC = LR;
      }
    }

    for (RangeSet::iterator EI = Exiting.begin(), EE = Exiting.end();
         EI != EE; ++EI) {
      LiveInterval* LI = EI->first;
      LiveRange* LR = EI->second;
      BR[LI->reg].Def = LR;
    }

    return BR;
  }

  void moveKillFlags(unsigned reg, SlotIndex OldIdx, SlotIndex newKillIdx) {
    MachineInstr* OldKillMI = LIS.getInstructionFromIndex(OldIdx);
    if (!OldKillMI->killsRegister(reg))
      return; // Bail out if we don't have kill flags on the old register.
    MachineInstr* NewKillMI = LIS.getInstructionFromIndex(newKillIdx);
    assert(OldKillMI->killsRegister(reg) && "Old 'kill' instr isn't a kill.");
    assert(!NewKillMI->killsRegister(reg) &&
           "New kill instr is already a kill.");
    OldKillMI->clearRegisterKills(reg, &TRI);
    NewKillMI->addRegisterKilled(reg, &TRI);
  }

  void updateRegMaskSlots(SlotIndex OldIdx) {
    SmallVectorImpl<SlotIndex>::iterator RI =
      std::lower_bound(LIS.RegMaskSlots.begin(), LIS.RegMaskSlots.end(),
                       OldIdx);
    assert(*RI == OldIdx && "No RegMask at OldIdx.");
    *RI = NewIdx;
    assert(*prior(RI) < *RI && *RI < *next(RI) &&
           "RegSlots out of order. Did you move one call across another?");
  }

  // Return the last use of reg between NewIdx and OldIdx.
  SlotIndex findLastUseBefore(unsigned Reg, SlotIndex OldIdx) {
    SlotIndex LastUse = NewIdx;
    for (MachineRegisterInfo::use_nodbg_iterator
           UI = MRI.use_nodbg_begin(Reg),
           UE = MRI.use_nodbg_end();
         UI != UE; UI.skipInstruction()) {
      const MachineInstr* MI = &*UI;
      SlotIndex InstSlot = LIS.getSlotIndexes()->getInstructionIndex(MI);
      if (InstSlot > LastUse && InstSlot < OldIdx)
        LastUse = InstSlot;
    }
    return LastUse;
  }

  void moveEnteringUpFrom(SlotIndex OldIdx, IntRangePair& P) {
    LiveInterval* LI = P.first;
    LiveRange* LR = P.second;
    bool LiveThrough = LR->end > OldIdx.getRegSlot();
    if (LiveThrough)
      return;
    SlotIndex LastUse = findLastUseBefore(LI->reg, OldIdx);
    if (LastUse != NewIdx)
      moveKillFlags(LI->reg, NewIdx, LastUse);
    LR->end = LastUse.getRegSlot();
  }

  void moveEnteringDownFrom(SlotIndex OldIdx, IntRangePair& P) {
    LiveInterval* LI = P.first;
    LiveRange* LR = P.second;
    // Extend the LiveRange if NewIdx is past the end.
    if (NewIdx > LR->end) {
      // Move kill flags if OldIdx was not originally the end
      // (otherwise LR->end points to an invalid slot).
      if (LR->end.getRegSlot() != OldIdx.getRegSlot()) {
        assert(LR->end > OldIdx && "LiveRange does not cover original slot");
        moveKillFlags(LI->reg, LR->end, NewIdx);
      }
      LR->end = NewIdx.getRegSlot();
    }
  }

  void moveAllEnteringFrom(SlotIndex OldIdx, RangeSet& Entering) {
    bool GoingUp = NewIdx < OldIdx;

    if (GoingUp) {
      for (RangeSet::iterator EI = Entering.begin(), EE = Entering.end();
           EI != EE; ++EI)
        moveEnteringUpFrom(OldIdx, *EI);
    } else {
      for (RangeSet::iterator EI = Entering.begin(), EE = Entering.end();
           EI != EE; ++EI)
        moveEnteringDownFrom(OldIdx, *EI);
    }
  }

  void moveInternalFrom(SlotIndex OldIdx, IntRangePair& P) {
    LiveInterval* LI = P.first;
    LiveRange* LR = P.second;
    assert(OldIdx < LR->start && LR->start < OldIdx.getDeadSlot() &&
           LR->end <= OldIdx.getDeadSlot() &&
           "Range should be internal to OldIdx.");
    LiveRange Tmp(*LR);
    Tmp.start = NewIdx.getRegSlot(LR->start.isEarlyClobber());
    Tmp.valno->def = Tmp.start;
    Tmp.end = LR->end.isDead() ? NewIdx.getDeadSlot() : NewIdx.getRegSlot();
    LI->removeRange(*LR);
    LI->addRange(Tmp);
  }

  void moveAllInternalFrom(SlotIndex OldIdx, RangeSet& Internal) {
    for (RangeSet::iterator II = Internal.begin(), IE = Internal.end();
         II != IE; ++II)
      moveInternalFrom(OldIdx, *II);
  }

  void moveExitingFrom(SlotIndex OldIdx, IntRangePair& P) {
    LiveRange* LR = P.second;
    assert(OldIdx < LR->start && LR->start < OldIdx.getDeadSlot() &&
           "Range should start in OldIdx.");
    assert(LR->end > OldIdx.getDeadSlot() && "Range should exit OldIdx.");
    SlotIndex NewStart = NewIdx.getRegSlot(LR->start.isEarlyClobber());
    LR->start = NewStart;
    LR->valno->def = NewStart;
  }

  void moveAllExitingFrom(SlotIndex OldIdx, RangeSet& Exiting) {
    for (RangeSet::iterator EI = Exiting.begin(), EE = Exiting.end();
         EI != EE; ++EI)
      moveExitingFrom(OldIdx, *EI);
  }

  void moveEnteringUpFromInto(SlotIndex OldIdx, IntRangePair& P,
                              BundleRanges& BR) {
    LiveInterval* LI = P.first;
    LiveRange* LR = P.second;
    bool LiveThrough = LR->end > OldIdx.getRegSlot();
    if (LiveThrough) {
      assert((LR->start < NewIdx || BR[LI->reg].Def == LR) &&
             "Def in bundle should be def range.");
      assert((BR[LI->reg].Use == 0 || BR[LI->reg].Use == LR) &&
             "If bundle has use for this reg it should be LR.");
      BR[LI->reg].Use = LR;
      return;
    }

    SlotIndex LastUse = findLastUseBefore(LI->reg, OldIdx);
    moveKillFlags(LI->reg, OldIdx, LastUse);

    if (LR->start < NewIdx) {
      // Becoming a new entering range.
      assert(BR[LI->reg].Dead == 0 && BR[LI->reg].Def == 0 &&
             "Bundle shouldn't be re-defining reg mid-range.");
      assert((BR[LI->reg].Use == 0 || BR[LI->reg].Use == LR) &&
             "Bundle shouldn't have different use range for same reg.");
      LR->end = LastUse.getRegSlot();
      BR[LI->reg].Use = LR;
    } else {
      // Becoming a new Dead-def.
      assert(LR->start == NewIdx.getRegSlot(LR->start.isEarlyClobber()) &&
             "Live range starting at unexpected slot.");
      assert(BR[LI->reg].Def == LR && "Reg should have def range.");
      assert(BR[LI->reg].Dead == 0 &&
               "Can't have def and dead def of same reg in a bundle.");
      LR->end = LastUse.getDeadSlot();
      BR[LI->reg].Dead = BR[LI->reg].Def;
      BR[LI->reg].Def = 0;
    }
  }

  void moveEnteringDownFromInto(SlotIndex OldIdx, IntRangePair& P,
                                BundleRanges& BR) {
    LiveInterval* LI = P.first;
    LiveRange* LR = P.second;
    if (NewIdx > LR->end) {
      // Range extended to bundle. Add to bundle uses.
      // Note: Currently adds kill flags to bundle start.
      assert(BR[LI->reg].Use == 0 &&
             "Bundle already has use range for reg.");
      moveKillFlags(LI->reg, LR->end, NewIdx);
      LR->end = NewIdx.getRegSlot();
      BR[LI->reg].Use = LR;
    } else {
      assert(BR[LI->reg].Use != 0 &&
             "Bundle should already have a use range for reg.");
    }
  }

  void moveAllEnteringFromInto(SlotIndex OldIdx, RangeSet& Entering,
                               BundleRanges& BR) {
    bool GoingUp = NewIdx < OldIdx;

    if (GoingUp) {
      for (RangeSet::iterator EI = Entering.begin(), EE = Entering.end();
           EI != EE; ++EI)
        moveEnteringUpFromInto(OldIdx, *EI, BR);
    } else {
      for (RangeSet::iterator EI = Entering.begin(), EE = Entering.end();
           EI != EE; ++EI)
        moveEnteringDownFromInto(OldIdx, *EI, BR);
    }
  }

  void moveInternalFromInto(SlotIndex OldIdx, IntRangePair& P,
                            BundleRanges& BR) {
    // TODO: Sane rules for moving ranges into bundles.
  }

  void moveAllInternalFromInto(SlotIndex OldIdx, RangeSet& Internal,
                               BundleRanges& BR) {
    for (RangeSet::iterator II = Internal.begin(), IE = Internal.end();
         II != IE; ++II)
      moveInternalFromInto(OldIdx, *II, BR);
  }

  void moveExitingFromInto(SlotIndex OldIdx, IntRangePair& P,
                           BundleRanges& BR) {
    LiveInterval* LI = P.first;
    LiveRange* LR = P.second;

    assert(LR->start.isRegister() &&
           "Don't know how to merge exiting ECs into bundles yet.");

    if (LR->end > NewIdx.getDeadSlot()) {
      // This range is becoming an exiting range on the bundle.
      // If there was an old dead-def of this reg, delete it.
      if (BR[LI->reg].Dead != 0) {
        LI->removeRange(*BR[LI->reg].Dead);
        BR[LI->reg].Dead = 0;
      }
      assert(BR[LI->reg].Def == 0 &&
             "Can't have two defs for the same variable exiting a bundle.");
      LR->start = NewIdx.getRegSlot();
      LR->valno->def = LR->start;
      BR[LI->reg].Def = LR;
    } else {
      // This range is becoming internal to the bundle.
      assert(LR->end == NewIdx.getRegSlot() &&
             "Can't bundle def whose kill is before the bundle");
      if (BR[LI->reg].Dead || BR[LI->reg].Def) {
        // Already have a def for this. Just delete range.
        LI->removeRange(*LR);
      } else {
        // Make range dead, record.
        LR->end = NewIdx.getDeadSlot();
        BR[LI->reg].Dead = LR;
        assert(BR[LI->reg].Use == LR &&
               "Range becoming dead should currently be use.");
      }
      // In both cases the range is no longer a use on the bundle.
      BR[LI->reg].Use = 0;
    }
  }

  void moveAllExitingFromInto(SlotIndex OldIdx, RangeSet& Exiting,
                              BundleRanges& BR) {
    for (RangeSet::iterator EI = Exiting.begin(), EE = Exiting.end();
         EI != EE; ++EI)
      moveExitingFromInto(OldIdx, *EI, BR);
  }

};

void LiveIntervals::handleMove(MachineInstr* MI) {
  SlotIndex OldIndex = Indexes->getInstructionIndex(MI);
  Indexes->removeMachineInstrFromMaps(MI);
  SlotIndex NewIndex = MI->isInsideBundle() ?
                        Indexes->getInstructionIndex(MI) :
                        Indexes->insertMachineInstrInMaps(MI);
  assert(getMBBStartIdx(MI->getParent()) <= OldIndex &&
         OldIndex < getMBBEndIdx(MI->getParent()) &&
         "Cannot handle moves across basic block boundaries.");
  assert(!MI->isBundled() && "Can't handle bundled instructions yet.");

  HMEditor HME(*this, *MRI, *TRI, NewIndex);
  HME.moveAllRangesFrom(MI, OldIndex);
}

void LiveIntervals::handleMoveIntoBundle(MachineInstr* MI,
                                         MachineInstr* BundleStart) {
  SlotIndex NewIndex = Indexes->getInstructionIndex(BundleStart);
  HMEditor HME(*this, *MRI, *TRI, NewIndex);
  HME.moveAllRangesInto(MI, BundleStart);
}