C++ SmallPtrSet::erase方法代码示例

/// RemoveAccessedObjects - Check to see if the specified location may alias any
/// of the stack objects in the DeadStackObjects set.  If so, they become live
/// because the location is being loaded.
void DSE::RemoveAccessedObjects(const AliasAnalysis::Location &LoadedLoc,
                                SmallPtrSet<Value*, 16> &DeadStackObjects) {
  const Value *UnderlyingPointer = LoadedLoc.Ptr->getUnderlyingObject();

  // A constant can't be in the dead pointer set.
  if (isa<Constant>(UnderlyingPointer))
    return;
  
  // If the kill pointer can be easily reduced to an alloca, don't bother doing
  // extraneous AA queries.
  if (isa<AllocaInst>(UnderlyingPointer) || isa<Argument>(UnderlyingPointer)) {
    DeadStackObjects.erase(const_cast<Value*>(UnderlyingPointer));
    return;
  }
  
  SmallVector<Value*, 16> NowLive;
  for (SmallPtrSet<Value*, 16>::iterator I = DeadStackObjects.begin(),
       E = DeadStackObjects.end(); I != E; ++I) {
    // See if the loaded location could alias the stack location.
    AliasAnalysis::Location StackLoc(*I, getPointerSize(*I, *AA));
    if (!AA->isNoAlias(StackLoc, LoadedLoc))
      NowLive.push_back(*I);
  }

  for (SmallVector<Value*, 16>::iterator I = NowLive.begin(), E = NowLive.end();
       I != E; ++I)
    DeadStackObjects.erase(*I);
}

TEST(SmallPtrSetTest, GrowthTest) {
  int i;
  int buf[8];
  for(i=0; i<8; ++i) buf[i]=0;


  SmallPtrSet<int *, 4> s;
  typedef SmallPtrSet<int *, 4>::iterator iter;
  
  s.insert(&buf[0]);
  s.insert(&buf[1]);
  s.insert(&buf[2]);
  s.insert(&buf[3]);
  EXPECT_EQ(4U, s.size());

  i = 0;
  for(iter I=s.begin(), E=s.end(); I!=E; ++I, ++i)
      (**I)++;
  EXPECT_EQ(4, i);
  for(i=0; i<8; ++i)
      EXPECT_EQ(i<4?1:0,buf[i]);

  s.insert(&buf[4]);
  s.insert(&buf[5]);
  s.insert(&buf[6]);
  s.insert(&buf[7]);

  i = 0;
  for(iter I=s.begin(), E=s.end(); I!=E; ++I, ++i)
      (**I)++;
  EXPECT_EQ(8, i);
  s.erase(&buf[4]);
  s.erase(&buf[5]);
  s.erase(&buf[6]);
  s.erase(&buf[7]);
  EXPECT_EQ(4U, s.size());

  i = 0;
  for(iter I=s.begin(), E=s.end(); I!=E; ++I, ++i)
      (**I)++;
  EXPECT_EQ(4, i);
  for(i=0; i<8; ++i)
      EXPECT_EQ(i<4?3:1,buf[i]);

  s.clear();
  for(i=0; i<8; ++i) buf[i]=0;
  for(i=0; i<128; ++i) s.insert(&buf[i%8]); // test repeated entires
  EXPECT_EQ(8U, s.size());
  for(iter I=s.begin(), E=s.end(); I!=E; ++I, ++i)
      (**I)++;
  for(i=0; i<8; ++i)
      EXPECT_EQ(1,buf[i]);
}

/// \brief Find an insertion point that dominates all uses.
Instruction *ConstantHoisting::
FindConstantInsertionPoint(Function &F, const ConstantInfo &CI) const {
  BasicBlock *Entry = &F.getEntryBlock();

  // Collect all basic blocks.
  SmallPtrSet<BasicBlock *, 4> BBs;
  ConstantInfo::RebasedConstantListType::const_iterator RCI, RCE;
  for (RCI = CI.RebasedConstants.begin(), RCE = CI.RebasedConstants.end();
       RCI != RCE; ++RCI)
    for (SmallVectorImpl<User *>::const_iterator U = RCI->Uses.begin(),
         E = RCI->Uses.end(); U != E; ++U)
        CollectBasicBlocks(BBs, F, *U);

  if (BBs.count(Entry))
    return Entry->getFirstInsertionPt();

  while (BBs.size() >= 2) {
    BasicBlock *BB, *BB1, *BB2;
    BB1 = *BBs.begin();
    BB2 = *llvm::next(BBs.begin());
    BB = DT->findNearestCommonDominator(BB1, BB2);
    if (BB == Entry)
      return Entry->getFirstInsertionPt();
    BBs.erase(BB1);
    BBs.erase(BB2);
    BBs.insert(BB);
  }
  assert((BBs.size() == 1) && "Expected only one element.");
  return (*BBs.begin())->getFirstInsertionPt();
}

// Calculate the largest possible vregsPassed sets. These are the registers that
// can pass through an MBB live, but may not be live every time. It is assumed
// that all vregsPassed sets are empty before the call.
void MachineVerifier::calcRegsPassed() {
  // First push live-out regs to successors' vregsPassed. Remember the MBBs that
  // have any vregsPassed.
  SmallPtrSet<const MachineBasicBlock*, 8> todo;
  for (MachineFunction::const_iterator MFI = MF->begin(), MFE = MF->end();
       MFI != MFE; ++MFI) {
    const MachineBasicBlock &MBB(*MFI);
    BBInfo &MInfo = MBBInfoMap[&MBB];
    if (!MInfo.reachable)
      continue;
    for (MachineBasicBlock::const_succ_iterator SuI = MBB.succ_begin(),
           SuE = MBB.succ_end(); SuI != SuE; ++SuI) {
      BBInfo &SInfo = MBBInfoMap[*SuI];
      if (SInfo.addPassed(MInfo.regsLiveOut))
        todo.insert(*SuI);
    }
  }

  // Iteratively push vregsPassed to successors. This will converge to the same
  // final state regardless of DenseSet iteration order.
  while (!todo.empty()) {
    const MachineBasicBlock *MBB = *todo.begin();
    todo.erase(MBB);
    BBInfo &MInfo = MBBInfoMap[MBB];
    for (MachineBasicBlock::const_succ_iterator SuI = MBB->succ_begin(),
           SuE = MBB->succ_end(); SuI != SuE; ++SuI) {
      if (*SuI == MBB)
        continue;
      BBInfo &SInfo = MBBInfoMap[*SuI];
      if (SInfo.addPassed(MInfo.vregsPassed))
        todo.insert(*SuI);
    }
  }
}

// Calculate the set of virtual registers that must be passed through each basic
// block in order to satisfy the requirements of successor blocks. This is very
// similar to calcRegsPassed, only backwards.
void MachineVerifier::calcRegsRequired() {
  // First push live-in regs to predecessors' vregsRequired.
  SmallPtrSet<const MachineBasicBlock*, 8> todo;
  for (MachineFunction::const_iterator MFI = MF->begin(), MFE = MF->end();
       MFI != MFE; ++MFI) {
    const MachineBasicBlock &MBB(*MFI);
    BBInfo &MInfo = MBBInfoMap[&MBB];
    for (MachineBasicBlock::const_pred_iterator PrI = MBB.pred_begin(),
           PrE = MBB.pred_end(); PrI != PrE; ++PrI) {
      BBInfo &PInfo = MBBInfoMap[*PrI];
      if (PInfo.addRequired(MInfo.vregsLiveIn))
        todo.insert(*PrI);
    }
  }

  // Iteratively push vregsRequired to predecessors. This will converge to the
  // same final state regardless of DenseSet iteration order.
  while (!todo.empty()) {
    const MachineBasicBlock *MBB = *todo.begin();
    todo.erase(MBB);
    BBInfo &MInfo = MBBInfoMap[MBB];
    for (MachineBasicBlock::const_pred_iterator PrI = MBB->pred_begin(),
           PrE = MBB->pred_end(); PrI != PrE; ++PrI) {
      if (*PrI == MBB)
        continue;
      BBInfo &SInfo = MBBInfoMap[*PrI];
      if (SInfo.addRequired(MInfo.vregsRequired))
        todo.insert(*PrI);
    }
  }
}

/// \brief Find an insertion point that dominates all uses.
Instruction *ConstantHoistingPass::findConstantInsertionPoint(
    const ConstantInfo &ConstInfo) const {
  assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
  // Collect all basic blocks.
  SmallPtrSet<BasicBlock *, 8> BBs;
  for (auto const &RCI : ConstInfo.RebasedConstants)
    for (auto const &U : RCI.Uses)
      BBs.insert(findMatInsertPt(U.Inst, U.OpndIdx)->getParent());

  if (BBs.count(Entry))
    return &Entry->front();

  while (BBs.size() >= 2) {
    BasicBlock *BB, *BB1, *BB2;
    BB1 = *BBs.begin();
    BB2 = *std::next(BBs.begin());
    BB = DT->findNearestCommonDominator(BB1, BB2);
    if (BB == Entry)
      return &Entry->front();
    BBs.erase(BB1);
    BBs.erase(BB2);
    BBs.insert(BB);
  }
  assert((BBs.size() == 1) && "Expected only one element.");
  Instruction &FirstInst = (*BBs.begin())->front();
  return findMatInsertPt(&FirstInst);
}

void GlobalDCEPass::UpdateGVDependencies(GlobalValue &GV) {
  SmallPtrSet<GlobalValue *, 8> Deps;
  for (User *User : GV.users())
    ComputeDependencies(User, Deps);
  Deps.erase(&GV); // Remove self-reference.
  for (GlobalValue *GVU : Deps) {
    GVDependencies.insert(std::make_pair(GVU, &GV));
  }
}

/// Find an insertion point that dominates all uses.
SmallPtrSet<Instruction *, 8> ConstantHoistingPass::findConstantInsertionPoint(
    const ConstantInfo &ConstInfo) const {
  assert(!ConstInfo.RebasedConstants.empty() && "Invalid constant info entry.");
  // Collect all basic blocks.
  SmallPtrSet<BasicBlock *, 8> BBs;
  SmallPtrSet<Instruction *, 8> InsertPts;
  for (auto const &RCI : ConstInfo.RebasedConstants)
    for (auto const &U : RCI.Uses)
      BBs.insert(findMatInsertPt(U.Inst, U.OpndIdx)->getParent());

  if (BBs.count(Entry)) {
    InsertPts.insert(&Entry->front());
    return InsertPts;
  }

  if (BFI) {
    findBestInsertionSet(*DT, *BFI, Entry, BBs);
    for (auto BB : BBs) {
      BasicBlock::iterator InsertPt = BB->begin();
      for (; isa<PHINode>(InsertPt) || InsertPt->isEHPad(); ++InsertPt)
        ;
      InsertPts.insert(&*InsertPt);
    }
    return InsertPts;
  }

  while (BBs.size() >= 2) {
    BasicBlock *BB, *BB1, *BB2;
    BB1 = *BBs.begin();
    BB2 = *std::next(BBs.begin());
    BB = DT->findNearestCommonDominator(BB1, BB2);
    if (BB == Entry) {
      InsertPts.insert(&Entry->front());
      return InsertPts;
    }
    BBs.erase(BB1);
    BBs.erase(BB2);
    BBs.insert(BB);
  }
  assert((BBs.size() == 1) && "Expected only one element.");
  Instruction &FirstInst = (*BBs.begin())->front();
  InsertPts.insert(findMatInsertPt(&FirstInst));
  return InsertPts;
}

/// Return a set of basic blocks to insert sinked instructions.
///
/// The returned set of basic blocks (BBsToSinkInto) should satisfy:
///
/// * Inside the loop \p L
/// * For each UseBB in \p UseBBs, there is at least one BB in BBsToSinkInto
///   that domintates the UseBB
/// * Has minimum total frequency that is no greater than preheader frequency
///
/// The purpose of the function is to find the optimal sinking points to
/// minimize execution cost, which is defined as "sum of frequency of
/// BBsToSinkInto".
/// As a result, the returned BBsToSinkInto needs to have minimum total
/// frequency.
/// Additionally, if the total frequency of BBsToSinkInto exceeds preheader
/// frequency, the optimal solution is not sinking (return empty set).
///
/// \p ColdLoopBBs is used to help find the optimal sinking locations.
/// It stores a list of BBs that is:
///
/// * Inside the loop \p L
/// * Has a frequency no larger than the loop's preheader
/// * Sorted by BB frequency
///
/// The complexity of the function is O(UseBBs.size() * ColdLoopBBs.size()).
/// To avoid expensive computation, we cap the maximum UseBBs.size() in its
/// caller.
static SmallPtrSet<BasicBlock *, 2>
findBBsToSinkInto(const Loop &L, const SmallPtrSetImpl<BasicBlock *> &UseBBs,
                  const SmallVectorImpl<BasicBlock *> &ColdLoopBBs,
                  DominatorTree &DT, BlockFrequencyInfo &BFI) {
  SmallPtrSet<BasicBlock *, 2> BBsToSinkInto;
  if (UseBBs.size() == 0)
    return BBsToSinkInto;

  BBsToSinkInto.insert(UseBBs.begin(), UseBBs.end());
  SmallPtrSet<BasicBlock *, 2> BBsDominatedByColdestBB;

  // For every iteration:
  //   * Pick the ColdestBB from ColdLoopBBs
  //   * Find the set BBsDominatedByColdestBB that satisfy:
  //     - BBsDominatedByColdestBB is a subset of BBsToSinkInto
  //     - Every BB in BBsDominatedByColdestBB is dominated by ColdestBB
  //   * If Freq(ColdestBB) < Freq(BBsDominatedByColdestBB), remove
  //     BBsDominatedByColdestBB from BBsToSinkInto, add ColdestBB to
  //     BBsToSinkInto
  for (BasicBlock *ColdestBB : ColdLoopBBs) {
    BBsDominatedByColdestBB.clear();
    for (BasicBlock *SinkedBB : BBsToSinkInto)
      if (DT.dominates(ColdestBB, SinkedBB))
        BBsDominatedByColdestBB.insert(SinkedBB);
    if (BBsDominatedByColdestBB.size() == 0)
      continue;
    if (adjustedSumFreq(BBsDominatedByColdestBB, BFI) >
        BFI.getBlockFreq(ColdestBB)) {
      for (BasicBlock *DominatedBB : BBsDominatedByColdestBB) {
        BBsToSinkInto.erase(DominatedBB);
      }
      BBsToSinkInto.insert(ColdestBB);
    }
  }

  // If the total frequency of BBsToSinkInto is larger than preheader frequency,
  // do not sink.
  if (adjustedSumFreq(BBsToSinkInto, BFI) >
      BFI.getBlockFreq(L.getLoopPreheader()))
    BBsToSinkInto.clear();
  return BBsToSinkInto;
}

/// computeDFS - Computes the DFS-in and DFS-out numbers of the dominator tree
/// of the given MachineFunction.  These numbers are then used in other parts
/// of the PHI elimination process.
void StrongPHIElimination::computeDFS(MachineFunction& MF) {
  SmallPtrSet<MachineDomTreeNode*, 8> frontier;
  SmallPtrSet<MachineDomTreeNode*, 8> visited;
  
  unsigned time = 0;
  
  MachineDominatorTree& DT = getAnalysis<MachineDominatorTree>();
  
  MachineDomTreeNode* node = DT.getRootNode();
  
  std::vector<MachineDomTreeNode*> worklist;
  worklist.push_back(node);
  
  while (!worklist.empty()) {
    MachineDomTreeNode* currNode = worklist.back();
    
    if (!frontier.count(currNode)) {
      frontier.insert(currNode);
      ++time;
      preorder.insert(std::make_pair(currNode->getBlock(), time));
    }
    
    bool inserted = false;
    for (MachineDomTreeNode::iterator I = currNode->begin(), E = currNode->end();
         I != E; ++I)
      if (!frontier.count(*I) && !visited.count(*I)) {
        worklist.push_back(*I);
        inserted = true;
        break;
      }
    
    if (!inserted) {
      frontier.erase(currNode);
      visited.insert(currNode);
      maxpreorder.insert(std::make_pair(currNode->getBlock(), time));
      
      worklist.pop_back();
    }
  }
}

/// \brief Find nearest common dominator of all uses.
/// FIXME: Replace this with NearestCommonDominator once it is in common code.
BasicBlock *
ConstantHoisting::findIDomOfAllUses(const ConstantUseListType &Uses) const {
  // Collect all basic blocks.
  SmallPtrSet<BasicBlock *, 8> BBs;
  for (auto const &U : Uses)
    BBs.insert(findMatInsertPt(U.Inst, U.OpndIdx)->getParent());

  if (BBs.count(Entry))
    return Entry;

  while (BBs.size() >= 2) {
    BasicBlock *BB, *BB1, *BB2;
    BB1 = *BBs.begin();
    BB2 = *std::next(BBs.begin());
    BB = DT->findNearestCommonDominator(BB1, BB2);
    if (BB == Entry)
      return Entry;
    BBs.erase(BB1);
    BBs.erase(BB2);
    BBs.insert(BB);
  }
  assert((BBs.size() == 1) && "Expected only one element.");
  return *BBs.begin();
}

const CodeGenRegister::SubRegMap &
CodeGenRegister::getSubRegs(CodeGenRegBank &RegBank) {
  // Only compute this map once.
  if (SubRegsComplete)
    return SubRegs;
  SubRegsComplete = true;

  std::vector<Record*> SubList = TheDef->getValueAsListOfDefs("SubRegs");
  std::vector<Record*> IdxList = TheDef->getValueAsListOfDefs("SubRegIndices");
  if (SubList.size() != IdxList.size())
    throw TGError(TheDef->getLoc(), "Register " + getName() +
                  " SubRegIndices doesn't match SubRegs");

  // First insert the direct subregs and make sure they are fully indexed.
  SmallVector<CodeGenSubRegIndex*, 8> Indices;
  for (unsigned i = 0, e = SubList.size(); i != e; ++i) {
    CodeGenRegister *SR = RegBank.getReg(SubList[i]);
    CodeGenSubRegIndex *Idx = RegBank.getSubRegIdx(IdxList[i]);
    Indices.push_back(Idx);
    if (!SubRegs.insert(std::make_pair(Idx, SR)).second)
      throw TGError(TheDef->getLoc(), "SubRegIndex " + Idx->getName() +
                    " appears twice in Register " + getName());
  }

  // Keep track of inherited subregs and how they can be reached.
  SmallPtrSet<CodeGenRegister*, 8> Orphans;

  // Clone inherited subregs and place duplicate entries in Orphans.
  // Here the order is important - earlier subregs take precedence.
  for (unsigned i = 0, e = SubList.size(); i != e; ++i) {
    CodeGenRegister *SR = RegBank.getReg(SubList[i]);
    const SubRegMap &Map = SR->getSubRegs(RegBank);

    // Add this as a super-register of SR now all sub-registers are in the list.
    // This creates a topological ordering, the exact order depends on the
    // order getSubRegs is called on all registers.
    SR->SuperRegs.push_back(this);

    for (SubRegMap::const_iterator SI = Map.begin(), SE = Map.end(); SI != SE;
         ++SI) {
      if (!SubRegs.insert(*SI).second)
        Orphans.insert(SI->second);

      // Noop sub-register indexes are possible, so avoid duplicates.
      if (SI->second != SR)
        SI->second->SuperRegs.push_back(this);
    }
  }

  // Expand any composed subreg indices.
  // If dsub_2 has ComposedOf = [qsub_1, dsub_0], and this register has a
  // qsub_1 subreg, add a dsub_2 subreg.  Keep growing Indices and process
  // expanded subreg indices recursively.
  for (unsigned i = 0; i != Indices.size(); ++i) {
    CodeGenSubRegIndex *Idx = Indices[i];
    const CodeGenSubRegIndex::CompMap &Comps = Idx->getComposites();
    CodeGenRegister *SR = SubRegs[Idx];
    const SubRegMap &Map = SR->getSubRegs(RegBank);

    // Look at the possible compositions of Idx.
    // They may not all be supported by SR.
    for (CodeGenSubRegIndex::CompMap::const_iterator I = Comps.begin(),
           E = Comps.end(); I != E; ++I) {
      SubRegMap::const_iterator SRI = Map.find(I->first);
      if (SRI == Map.end())
        continue; // Idx + I->first doesn't exist in SR.
      // Add I->second as a name for the subreg SRI->second, assuming it is
      // orphaned, and the name isn't already used for something else.
      if (SubRegs.count(I->second) || !Orphans.erase(SRI->second))
        continue;
      // We found a new name for the orphaned sub-register.
      SubRegs.insert(std::make_pair(I->second, SRI->second));
      Indices.push_back(I->second);
    }
  }

  // Process the composites.
  ListInit *Comps = TheDef->getValueAsListInit("CompositeIndices");
  for (unsigned i = 0, e = Comps->size(); i != e; ++i) {
    DagInit *Pat = dynamic_cast<DagInit*>(Comps->getElement(i));
    if (!Pat)
      throw TGError(TheDef->getLoc(), "Invalid dag '" +
                    Comps->getElement(i)->getAsString() +
                    "' in CompositeIndices");
    DefInit *BaseIdxInit = dynamic_cast<DefInit*>(Pat->getOperator());
    if (!BaseIdxInit || !BaseIdxInit->getDef()->isSubClassOf("SubRegIndex"))
      throw TGError(TheDef->getLoc(), "Invalid SubClassIndex in " +
                    Pat->getAsString());
    CodeGenSubRegIndex *BaseIdx = RegBank.getSubRegIdx(BaseIdxInit->getDef());

    // Resolve list of subreg indices into R2.
    CodeGenRegister *R2 = this;
    for (DagInit::const_arg_iterator di = Pat->arg_begin(),
         de = Pat->arg_end(); di != de; ++di) {
      DefInit *IdxInit = dynamic_cast<DefInit*>(*di);
      if (!IdxInit || !IdxInit->getDef()->isSubClassOf("SubRegIndex"))
        throw TGError(TheDef->getLoc(), "Invalid SubClassIndex in " +
                      Pat->getAsString());
      CodeGenSubRegIndex *Idx = RegBank.getSubRegIdx(IdxInit->getDef());
      const SubRegMap &R2Subs = R2->getSubRegs(RegBank);
//.........这里部分代码省略.........

bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
  if (DisablePeephole)
    return false;

  TM  = &MF.getTarget();
  TII = TM->getInstrInfo();
  MRI = &MF.getRegInfo();
  DT  = Aggressive ? &getAnalysis<MachineDominatorTree>() : 0;

  bool Changed = false;

  SmallPtrSet<MachineInstr*, 8> LocalMIs;
  SmallSet<unsigned, 4> ImmDefRegs;
  DenseMap<unsigned, MachineInstr*> ImmDefMIs;
  for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
    MachineBasicBlock *MBB = &*I;

    bool SeenMoveImm = false;
    LocalMIs.clear();
    ImmDefRegs.clear();
    ImmDefMIs.clear();

    bool First = true;
    MachineBasicBlock::iterator PMII;
    for (MachineBasicBlock::iterator
           MII = I->begin(), MIE = I->end(); MII != MIE; ) {
      MachineInstr *MI = &*MII;
      LocalMIs.insert(MI);

      if (MI->isLabel() || MI->isPHI() || MI->isImplicitDef() ||
          MI->isKill() || MI->isInlineAsm() || MI->isDebugValue() ||
          MI->hasUnmodeledSideEffects()) {
        ++MII;
        continue;
      }

      if (MI->isBitcast()) {
        if (optimizeBitcastInstr(MI, MBB)) {
          // MI is deleted.
          LocalMIs.erase(MI);
          Changed = true;
          MII = First ? I->begin() : llvm::next(PMII);
          continue;
        }
      } else if (MI->isCompare()) {
        if (optimizeCmpInstr(MI, MBB)) {
          // MI is deleted.
          LocalMIs.erase(MI);
          Changed = true;
          MII = First ? I->begin() : llvm::next(PMII);
          continue;
        }
      }

      if (isMoveImmediate(MI, ImmDefRegs, ImmDefMIs)) {
        SeenMoveImm = true;
      } else {
        Changed |= optimizeExtInstr(MI, MBB, LocalMIs);
        if (SeenMoveImm)
          Changed |= foldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs);
      }

      First = false;
      PMII = MII;
      ++MII;
    }
  }

  return Changed;
}

/// FindBackAndExitEdges - Search for back and exit edges for all blocks
/// within the function loops, calculated using loop information.
void BranchPredictionInfo::FindBackAndExitEdges(Function &F) {
  SmallPtrSet<const BasicBlock *, 64> LoopsVisited;
  SmallPtrSet<const BasicBlock *, 64> BlocksVisited;

	int count = 0;
	if(F.getName() == "hypre_SMGResidual")
		count = count + 1;
  for (LoopInfo::iterator LIT = LI->begin(), LIE = LI->end();
       LIT != LIE; ++LIT) {
    Loop *rootLoop = *LIT;
    BasicBlock *rootHeader = rootLoop->getHeader();

    // Check if we already visited this loop.
    if (LoopsVisited.count(rootHeader))
      continue;

    // Create a stack to hold loops (inner most on the top).
    SmallVectorImpl<Loop *> Stack(8);
    SmallPtrSet<const BasicBlock *, 8> InStack;

    // Put the current loop into the Stack.
    Stack.push_back(rootLoop);
    InStack.insert(rootHeader);

    do {
      Loop *loop = Stack.back();

      // Search for new inner loops.
      bool foundNew = false;
      for (Loop::iterator I = loop->begin(), E = loop->end(); I != E; ++I) {
        Loop *innerLoop = *I;
        BasicBlock *innerHeader = innerLoop->getHeader();

        // Skip visited inner loops.
        if (!LoopsVisited.count(innerHeader)) {
          Stack.push_back(innerLoop);
          InStack.insert(innerHeader);
          foundNew = true;
          break;
        }
      }

      // If a new loop is found, continue.
      // Otherwise, it is time to expand it, because it is the most inner loop
      // yet unprocessed.
      if (foundNew)
        continue;

      // The variable "loop" is now the unvisited inner most loop.
      BasicBlock *header = loop->getHeader();

      // Search for all basic blocks on the loop.
      for (Loop::block_iterator LBI = loop->block_begin(),
           LBE = loop->block_end(); LBI != LBE; ++LBI) {
        BasicBlock *lpBB = *LBI;
        if (!BlocksVisited.insert(lpBB))
          continue;

        // Set the number of back edges to this loop head (lpBB) as zero.
        BackEdgesCount[lpBB] = 0;

        // For each loop block successor, check if the block pointing is
        // outside the loop.
        TerminatorInst *TI = lpBB->getTerminator();
        for (unsigned s = 0; s < TI->getNumSuccessors(); ++s) {
          BasicBlock *successor = TI->getSuccessor(s);
          Edge edge = std::make_pair(lpBB, successor);

          // If the successor matches any loop header on the stack,
          // then it is a backedge.
          if (InStack.count(successor)) {
            listBackEdges.insert(edge);
            ++BackEdgesCount[lpBB];
          }

          // If the successor is not present in the loop block list, then it is
          // an exit edge.
          if (!loop->contains(successor))
            listExitEdges.insert(edge);
        }
      }

      // Cleaning the visited loop.
      LoopsVisited.insert(header);
      Stack.pop_back();
      InStack.erase(header);
    } while (!InStack.empty());
  }
}

bool WebAssemblyFixIrreducibleControlFlow::VisitLoop(MachineFunction &MF,
                                                     MachineLoopInfo &MLI,
                                                     MachineLoop *Loop) {
  MachineBasicBlock *Header = Loop ? Loop->getHeader() : &*MF.begin();
  SetVector<MachineBasicBlock *> RewriteSuccs;

  // DFS through Loop's body, looking for for irreducible control flow. Loop is
  // natural, and we stay in its body, and we treat any nested loops
  // monolithically, so any cycles we encounter indicate irreducibility.
  SmallPtrSet<MachineBasicBlock *, 8> OnStack;
  SmallPtrSet<MachineBasicBlock *, 8> Visited;
  SmallVector<SuccessorList, 4> LoopWorklist;
  LoopWorklist.push_back(SuccessorList(Header));
  OnStack.insert(Header);
  Visited.insert(Header);
  while (!LoopWorklist.empty()) {
    SuccessorList &Top = LoopWorklist.back();
    if (Top.HasNext()) {
      MachineBasicBlock *Next = Top.Next();
      if (Next == Header || (Loop && !Loop->contains(Next)))
        continue;
      if (LLVM_LIKELY(OnStack.insert(Next).second)) {
        if (!Visited.insert(Next).second) {
          OnStack.erase(Next);
          continue;
        }
        MachineLoop *InnerLoop = MLI.getLoopFor(Next);
        if (InnerLoop != Loop)
          LoopWorklist.push_back(SuccessorList(InnerLoop));
        else
          LoopWorklist.push_back(SuccessorList(Next));
      } else {
        RewriteSuccs.insert(Top.getBlock());
      }
      continue;
    }
    OnStack.erase(Top.getBlock());
    LoopWorklist.pop_back();
  }

  // Most likely, we didn't find any irreducible control flow.
  if (LLVM_LIKELY(RewriteSuccs.empty()))
    return false;

  DEBUG(dbgs() << "Irreducible control flow detected!\n");

  // Ok. We have irreducible control flow! Create a dispatch block which will
  // contains a jump table to any block in the problematic set of blocks.
  MachineBasicBlock *Dispatch = MF.CreateMachineBasicBlock();
  MF.insert(MF.end(), Dispatch);
  MLI.changeLoopFor(Dispatch, Loop);

  // Add the jump table.
  const auto &TII = *MF.getSubtarget<WebAssemblySubtarget>().getInstrInfo();
  MachineInstrBuilder MIB = BuildMI(*Dispatch, Dispatch->end(), DebugLoc(),
                                    TII.get(WebAssembly::BR_TABLE_I32));

  // Add the register which will be used to tell the jump table which block to
  // jump to.
  MachineRegisterInfo &MRI = MF.getRegInfo();
  unsigned Reg = MRI.createVirtualRegister(&WebAssembly::I32RegClass);
  MIB.addReg(Reg);

  // Collect all the blocks which need to have their successors rewritten,
  // add the successors to the jump table, and remember their index.
  DenseMap<MachineBasicBlock *, unsigned> Indices;
  SmallVector<MachineBasicBlock *, 4> SuccWorklist(RewriteSuccs.begin(),
                                                   RewriteSuccs.end());
  while (!SuccWorklist.empty()) {
    MachineBasicBlock *MBB = SuccWorklist.pop_back_val();
    auto Pair = Indices.insert(std::make_pair(MBB, 0));
    if (!Pair.second)
      continue;

    unsigned Index = MIB.getInstr()->getNumExplicitOperands() - 1;
    DEBUG(dbgs() << printMBBReference(*MBB) << " has index " << Index << "\n");

    Pair.first->second = Index;
    for (auto Pred : MBB->predecessors())
      RewriteSuccs.insert(Pred);

    MIB.addMBB(MBB);
    Dispatch->addSuccessor(MBB);

    MetaBlock Meta(MBB);
    for (auto *Succ : Meta.successors())
      if (Succ != Header && (!Loop || Loop->contains(Succ)))
        SuccWorklist.push_back(Succ);
  }

  // Rewrite the problematic successors for every block in RewriteSuccs.
  // For simplicity, we just introduce a new block for every edge we need to
  // rewrite. Fancier things are possible.
  for (MachineBasicBlock *MBB : RewriteSuccs) {
    DenseMap<MachineBasicBlock *, MachineBasicBlock *> Map;
    for (auto *Succ : MBB->successors()) {
      if (!Indices.count(Succ))
        continue;

      MachineBasicBlock *Split = MF.CreateMachineBasicBlock();
//.........这里部分代码省略.........