C++ LiveVariables::addNewBlock方法代码示例

//.........这里部分代码省略.........
      }
    }
  }

  // Fix PHI nodes in Succ so they refer to NMBB instead of this
  for (MachineBasicBlock::instr_iterator
         i = Succ->instr_begin(),e = Succ->instr_end();
       i != e && i->isPHI(); ++i)
    for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
      if (i->getOperand(ni+1).getMBB() == this)
        i->getOperand(ni+1).setMBB(NMBB);

  // Inherit live-ins from the successor
  for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(),
         E = Succ->livein_end(); I != E; ++I)
    NMBB->addLiveIn(*I);

  // Update LiveVariables.
  const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
  if (LV) {
    // Restore kills of virtual registers that were killed by the terminators.
    while (!KilledRegs.empty()) {
      unsigned Reg = KilledRegs.pop_back_val();
      for (instr_iterator I = instr_end(), E = instr_begin(); I != E;) {
        if (!(--I)->addRegisterKilled(Reg, TRI, /* addIfNotFound= */ false))
          continue;
        if (TargetRegisterInfo::isVirtualRegister(Reg))
          LV->getVarInfo(Reg).Kills.push_back(I);
        DEBUG(dbgs() << "Restored terminator kill: " << *I);
        break;
      }
    }
    // Update relevant live-through information.
    LV->addNewBlock(NMBB, this, Succ);
  }

  if (LIS) {
    // After splitting the edge and updating SlotIndexes, live intervals may be
    // in one of two situations, depending on whether this block was the last in
    // the function. If the original block was the last in the function, all live
    // intervals will end prior to the beginning of the new split block. If the
    // original block was not at the end of the function, all live intervals will
    // extend to the end of the new split block.

    bool isLastMBB =
      std::next(MachineFunction::iterator(NMBB)) == getParent()->end();

    SlotIndex StartIndex = Indexes->getMBBEndIdx(this);
    SlotIndex PrevIndex = StartIndex.getPrevSlot();
    SlotIndex EndIndex = Indexes->getMBBEndIdx(NMBB);

    // Find the registers used from NMBB in PHIs in Succ.
    SmallSet<unsigned, 8> PHISrcRegs;
    for (MachineBasicBlock::instr_iterator
         I = Succ->instr_begin(), E = Succ->instr_end();
         I != E && I->isPHI(); ++I) {
      for (unsigned ni = 1, ne = I->getNumOperands(); ni != ne; ni += 2) {
        if (I->getOperand(ni+1).getMBB() == NMBB) {
          MachineOperand &MO = I->getOperand(ni);
          unsigned Reg = MO.getReg();
          PHISrcRegs.insert(Reg);
          if (MO.isUndef())
            continue;

          LiveInterval &LI = LIS->getInterval(Reg);
          VNInfo *VNI = LI.getVNInfoAt(PrevIndex);

MachineBasicBlock *
MachineBasicBlock::SplitCriticalEdge(MachineBasicBlock *Succ, Pass *P) {
  MachineFunction *MF = getParent();
  DebugLoc dl;  // FIXME: this is nowhere

  // We may need to update this's terminator, but we can't do that if
  // AnalyzeBranch fails. If this uses a jump table, we won't touch it.
  const TargetInstrInfo *TII = MF->getTarget().getInstrInfo();
  MachineBasicBlock *TBB = 0, *FBB = 0;
  SmallVector<MachineOperand, 4> Cond;
  if (TII->AnalyzeBranch(*this, TBB, FBB, Cond))
    return NULL;

  // Avoid bugpoint weirdness: A block may end with a conditional branch but
  // jumps to the same MBB is either case. We have duplicate CFG edges in that
  // case that we can't handle. Since this never happens in properly optimized
  // code, just skip those edges.
  if (TBB && TBB == FBB) {
    DEBUG(dbgs() << "Won't split critical edge after degenerate BB#"
                 << getNumber() << '\n');
    return NULL;
  }

  MachineBasicBlock *NMBB = MF->CreateMachineBasicBlock();
  MF->insert(llvm::next(MachineFunction::iterator(this)), NMBB);
  DEBUG(dbgs() << "Splitting critical edge:"
        " BB#" << getNumber()
        << " -- BB#" << NMBB->getNumber()
        << " -- BB#" << Succ->getNumber() << '\n');

  // On some targets like Mips, branches may kill virtual registers. Make sure
  // that LiveVariables is properly updated after updateTerminator replaces the
  // terminators.
  LiveVariables *LV = P->getAnalysisIfAvailable<LiveVariables>();

  // Collect a list of virtual registers killed by the terminators.
  SmallVector<unsigned, 4> KilledRegs;
  if (LV)
    for (iterator I = getFirstTerminator(), E = end(); I != E; ++I) {
      MachineInstr *MI = I;
      for (MachineInstr::mop_iterator OI = MI->operands_begin(),
           OE = MI->operands_end(); OI != OE; ++OI) {
        if (!OI->isReg() || !OI->isUse() || !OI->isKill() || OI->isUndef())
          continue;
        unsigned Reg = OI->getReg();
        if (TargetRegisterInfo::isVirtualRegister(Reg) &&
            LV->getVarInfo(Reg).removeKill(MI)) {
          KilledRegs.push_back(Reg);
          DEBUG(dbgs() << "Removing terminator kill: " << *MI);
          OI->setIsKill(false);
        }
      }
    }

  ReplaceUsesOfBlockWith(Succ, NMBB);
  updateTerminator();

  // Insert unconditional "jump Succ" instruction in NMBB if necessary.
  NMBB->addSuccessor(Succ);
  if (!NMBB->isLayoutSuccessor(Succ)) {
    Cond.clear();
    MF->getTarget().getInstrInfo()->InsertBranch(*NMBB, Succ, NULL, Cond, dl);
  }

  // Fix PHI nodes in Succ so they refer to NMBB instead of this
  for (MachineBasicBlock::iterator i = Succ->begin(), e = Succ->end();
       i != e && i->isPHI(); ++i)
    for (unsigned ni = 1, ne = i->getNumOperands(); ni != ne; ni += 2)
      if (i->getOperand(ni+1).getMBB() == this)
        i->getOperand(ni+1).setMBB(NMBB);

  // Inherit live-ins from the successor
  for (MachineBasicBlock::livein_iterator I = Succ->livein_begin(),
	 E = Succ->livein_end(); I != E; ++I)
    NMBB->addLiveIn(*I);

  // Update LiveVariables.
  if (LV) {
    // Restore kills of virtual registers that were killed by the terminators.
    while (!KilledRegs.empty()) {
      unsigned Reg = KilledRegs.pop_back_val();
      for (iterator I = end(), E = begin(); I != E;) {
        if (!(--I)->addRegisterKilled(Reg, NULL, /* addIfNotFound= */ false))
          continue;
        LV->getVarInfo(Reg).Kills.push_back(I);
        DEBUG(dbgs() << "Restored terminator kill: " << *I);
        break;
      }
    }
    // Update relevant live-through information.
    LV->addNewBlock(NMBB, this, Succ);
  }

  if (MachineDominatorTree *MDT =
      P->getAnalysisIfAvailable<MachineDominatorTree>()) {
    // Update dominator information.
    MachineDomTreeNode *SucccDTNode = MDT->getNode(Succ);

    bool IsNewIDom = true;
    for (const_pred_iterator PI = Succ->pred_begin(), E = Succ->pred_end();
//.........这里部分代码省略.........