C++ LiveRange::addSegment方法代码示例

bool LiveRange::overlapsInst(InstNumberT OtherBegin, bool UseTrimmed) const {
  bool Result = false;
  for (auto I = (UseTrimmed ? TrimmedBegin : Range.begin()), E = Range.end();
       I != E; ++I) {
    if (OtherBegin < I->first) {
      Result = false;
      break;
    }
    if (OtherBegin < I->second) {
      Result = true;
      break;
    }
  }
  // This is an equivalent but less inefficient implementation. It's expensive
  // enough that we wouldn't want to run it under any build, but it could be
  // enabled if e.g. the LiveRange implementation changes and extra testing is
  // needed.
  if (BuildDefs::extraValidation()) {
    LiveRange Temp;
    Temp.addSegment(OtherBegin, OtherBegin + 1);
    bool Validation = overlaps(Temp);
    (void)Validation;
    assert(Result == Validation);
  }
  return Result;
}

static void createSegmentsForValues(LiveRange &LR,
      iterator_range<LiveInterval::vni_iterator> VNIs) {
  for (auto VNI : VNIs) {
    if (VNI->isUnused())
      continue;
    SlotIndex Def = VNI->def;
    LR.addSegment(LiveRange::Segment(Def, Def.getDeadSlot(), VNI));
  }
}

static void extendSegmentsToUses(LiveRange &LR, const SlotIndexes &Indexes,
                                 ShrinkToUsesWorkList &WorkList,
                                 const LiveRange &OldRange) {
  // Keep track of the PHIs that are in use.
  SmallPtrSet<VNInfo*, 8> UsedPHIs;
  // Blocks that have already been added to WorkList as live-out.
  SmallPtrSet<MachineBasicBlock*, 16> LiveOut;

  // Extend intervals to reach all uses in WorkList.
  while (!WorkList.empty()) {
    SlotIndex Idx = WorkList.back().first;
    VNInfo *VNI = WorkList.back().second;
    WorkList.pop_back();
    const MachineBasicBlock *MBB = Indexes.getMBBFromIndex(Idx.getPrevSlot());
    SlotIndex BlockStart = Indexes.getMBBStartIdx(MBB);

    // Extend the live range for VNI to be live at Idx.
    if (VNInfo *ExtVNI = LR.extendInBlock(BlockStart, Idx)) {
      assert(ExtVNI == VNI && "Unexpected existing value number");
      (void)ExtVNI;
      // Is this a PHIDef we haven't seen before?
      if (!VNI->isPHIDef() || VNI->def != BlockStart ||
          !UsedPHIs.insert(VNI).second)
        continue;
      // The PHI is live, make sure the predecessors are live-out.
      for (auto &Pred : MBB->predecessors()) {
        if (!LiveOut.insert(Pred).second)
          continue;
        SlotIndex Stop = Indexes.getMBBEndIdx(Pred);
        // A predecessor is not required to have a live-out value for a PHI.
        if (VNInfo *PVNI = OldRange.getVNInfoBefore(Stop))
          WorkList.push_back(std::make_pair(Stop, PVNI));
      }
      continue;
    }

    // VNI is live-in to MBB.
    DEBUG(dbgs() << " live-in at " << BlockStart << '\n');
    LR.addSegment(LiveRange::Segment(BlockStart, Idx, VNI));

    // Make sure VNI is live-out from the predecessors.
    for (auto &Pred : MBB->predecessors()) {
      if (!LiveOut.insert(Pred).second)
        continue;
      SlotIndex Stop = Indexes.getMBBEndIdx(Pred);
      assert(OldRange.getVNInfoBefore(Stop) == VNI &&
             "Wrong value out of predecessor");
      WorkList.push_back(std::make_pair(Stop, VNI));
    }
  }
}

/// shrinkToUses - After removing some uses of a register, shrink its live
/// range to just the remaining uses. This method does not compute reaching
/// defs for new uses, and it doesn't remove dead defs.
bool LiveIntervals::shrinkToUses(LiveInterval *li,
                                 SmallVectorImpl<MachineInstr*> *dead) {
    DEBUG(dbgs() << "Shrink: " << *li << '\n');
    assert(TargetRegisterInfo::isVirtualRegister(li->reg)
           && "Can only shrink virtual registers");
    // Find all the values used, including PHI kills.
    SmallVector<std::pair<SlotIndex, VNInfo*>, 16> WorkList;

    // Blocks that have already been added to WorkList as live-out.
    SmallPtrSet<MachineBasicBlock*, 16> LiveOut;

    // Visit all instructions reading li->reg.
    for (MachineRegisterInfo::reg_instr_iterator
            I = MRI->reg_instr_begin(li->reg), E = MRI->reg_instr_end();
            I != E; ) {
        MachineInstr *UseMI = &*(I++);
        if (UseMI->isDebugValue() || !UseMI->readsVirtualRegister(li->reg))
            continue;
        SlotIndex Idx = getInstructionIndex(UseMI).getRegSlot();
        LiveQueryResult LRQ = li->Query(Idx);
        VNInfo *VNI = LRQ.valueIn();
        if (!VNI) {
            // This shouldn't happen: readsVirtualRegister returns true, but there is
            // no live value. It is likely caused by a target getting <undef> flags
            // wrong.
            DEBUG(dbgs() << Idx << '\t' << *UseMI
                  << "Warning: Instr claims to read non-existent value in "
                  << *li << '\n');
            continue;
        }
        // Special case: An early-clobber tied operand reads and writes the
        // register one slot early.
        if (VNInfo *DefVNI = LRQ.valueDefined())
            Idx = DefVNI->def;

        WorkList.push_back(std::make_pair(Idx, VNI));
    }

    // Create new live ranges with only minimal live segments per def.
    LiveRange NewLR;
    for (LiveInterval::vni_iterator I = li->vni_begin(), E = li->vni_end();
            I != E; ++I) {
        VNInfo *VNI = *I;
        if (VNI->isUnused())
            continue;
        NewLR.addSegment(LiveRange::Segment(VNI->def, VNI->def.getDeadSlot(), VNI));
    }

    // Keep track of the PHIs that are in use.
    SmallPtrSet<VNInfo*, 8> UsedPHIs;

    // Extend intervals to reach all uses in WorkList.
    while (!WorkList.empty()) {
        SlotIndex Idx = WorkList.back().first;
        VNInfo *VNI = WorkList.back().second;
        WorkList.pop_back();
        const MachineBasicBlock *MBB = getMBBFromIndex(Idx.getPrevSlot());
        SlotIndex BlockStart = getMBBStartIdx(MBB);

        // Extend the live range for VNI to be live at Idx.
        if (VNInfo *ExtVNI = NewLR.extendInBlock(BlockStart, Idx)) {
            (void)ExtVNI;
            assert(ExtVNI == VNI && "Unexpected existing value number");
            // Is this a PHIDef we haven't seen before?
            if (!VNI->isPHIDef() || VNI->def != BlockStart || !UsedPHIs.insert(VNI))
                continue;
            // The PHI is live, make sure the predecessors are live-out.
            for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
                    PE = MBB->pred_end(); PI != PE; ++PI) {
                if (!LiveOut.insert(*PI))
                    continue;
                SlotIndex Stop = getMBBEndIdx(*PI);
                // A predecessor is not required to have a live-out value for a PHI.
                if (VNInfo *PVNI = li->getVNInfoBefore(Stop))
                    WorkList.push_back(std::make_pair(Stop, PVNI));
            }
            continue;
        }

        // VNI is live-in to MBB.
        DEBUG(dbgs() << " live-in at " << BlockStart << '\n');
        NewLR.addSegment(LiveRange::Segment(BlockStart, Idx, VNI));

        // Make sure VNI is live-out from the predecessors.
        for (MachineBasicBlock::const_pred_iterator PI = MBB->pred_begin(),
                PE = MBB->pred_end(); PI != PE; ++PI) {
            if (!LiveOut.insert(*PI))
                continue;
            SlotIndex Stop = getMBBEndIdx(*PI);
            assert(li->getVNInfoBefore(Stop) == VNI &&
                   "Wrong value out of predecessor");
            WorkList.push_back(std::make_pair(Stop, VNI));
        }
    }

    // Handle dead values.
    bool CanSeparate = false;
//.........这里部分代码省略.........