C++ PHINode::getBasicBlockIndex方法代码示例

/// FindReusablePredBB - Check all of the predecessors of the block DestPHI
/// lives in to see if there is a block that we can reuse as a critical edge
/// from TIBB.
static BasicBlock *FindReusablePredBB(PHINode *DestPHI, BasicBlock *TIBB) {
  BasicBlock *Dest = DestPHI->getParent();
  
  /// TIPHIValues - This array is lazily computed to determine the values of
  /// PHIs in Dest that TI would provide.
  SmallVector<Value*, 32> TIPHIValues;
  
  /// TIBBEntryNo - This is a cache to speed up pred queries for TIBB.
  unsigned TIBBEntryNo = 0;
  
  // Check to see if Dest has any blocks that can be used as a split edge for
  // this terminator.
  for (unsigned pi = 0, e = DestPHI->getNumIncomingValues(); pi != e; ++pi) {
    BasicBlock *Pred = DestPHI->getIncomingBlock(pi);
    // To be usable, the pred has to end with an uncond branch to the dest.
    BranchInst *PredBr = dyn_cast<BranchInst>(Pred->getTerminator());
    if (!PredBr || !PredBr->isUnconditional())
      continue;
    // Must be empty other than the branch and debug info.
    BasicBlock::iterator I = Pred->begin();
    while (isa<DbgInfoIntrinsic>(I))
      I++;
    if (&*I != PredBr)
      continue;
    // Cannot be the entry block; its label does not get emitted.
    if (Pred == &Dest->getParent()->getEntryBlock())
      continue;
    
    // Finally, since we know that Dest has phi nodes in it, we have to make
    // sure that jumping to Pred will have the same effect as going to Dest in
    // terms of PHI values.
    PHINode *PN;
    unsigned PHINo = 0;
    unsigned PredEntryNo = pi;
    
    bool FoundMatch = true;
    for (BasicBlock::iterator I = Dest->begin();
         (PN = dyn_cast<PHINode>(I)); ++I, ++PHINo) {
      if (PHINo == TIPHIValues.size()) {
        if (PN->getIncomingBlock(TIBBEntryNo) != TIBB)
          TIBBEntryNo = PN->getBasicBlockIndex(TIBB);
        TIPHIValues.push_back(PN->getIncomingValue(TIBBEntryNo));
      }
      
      // If the PHI entry doesn't work, we can't use this pred.
      if (PN->getIncomingBlock(PredEntryNo) != Pred)
        PredEntryNo = PN->getBasicBlockIndex(Pred);
      
      if (TIPHIValues[PHINo] != PN->getIncomingValue(PredEntryNo)) {
        FoundMatch = false;
        break;
      }
    }
    
    // If we found a workable predecessor, change TI to branch to Succ.
    if (FoundMatch)
      return Pred;
  }
  return 0;  
}

// switchConvert - Convert the switch statement into a linear scan
// through all the case values
void LowerSwitchPass::switchConvert(CaseItr begin, CaseItr end,
                                    Value* value, BasicBlock* origBlock,
                                    BasicBlock* defaultBlock)
{
    BasicBlock *curHead = defaultBlock;
    Function *F = origBlock->getParent();

    // iterate through all the cases, creating a new BasicBlock for each
    for (CaseItr it = begin; it < end; ++it) {
        BasicBlock *newBlock = BasicBlock::Create(getGlobalContext(), "NodeBlock");
        Function::iterator FI = origBlock;
        F->getBasicBlockList().insert(++FI, newBlock);

        ICmpInst *cmpInst =
            new ICmpInst(*newBlock, ICmpInst::ICMP_EQ, value, it->value, "case.cmp");
        BranchInst::Create(it->block, curHead, cmpInst, newBlock);

        // If there were any PHI nodes in this successor, rewrite one entry
        // from origBlock to come from newBlock.
        for (BasicBlock::iterator bi = it->block->begin(); isa<PHINode>(bi); ++bi) {
            PHINode* PN = cast<PHINode>(bi);

            int blockIndex = PN->getBasicBlockIndex(origBlock);
            assert(blockIndex != -1 && "Switch didn't go to this successor??");
            PN->setIncomingBlock((unsigned)blockIndex, newBlock);
        }

        curHead = newBlock;
    }

    // Branch to our shiny new if-then stuff...
    BranchInst::Create(curHead, origBlock);
}

// newLeafBlock - Create a new leaf block for the binary lookup tree. It
// checks if the switch's value == the case's value. If not, then it
// jumps to the default branch. At this point in the tree, the value
// can't be another valid case value, so the jump to the "default" branch
// is warranted.
//
BasicBlock* LowerSwitch::newLeafBlock(CaseRange& Leaf, Value* Val,
                                      BasicBlock* OrigBlock,
                                      BasicBlock* Default)
{
  Function* F = OrigBlock->getParent();
  BasicBlock* NewLeaf = BasicBlock::Create(Val->getContext(), "LeafBlock");
  Function::iterator FI = OrigBlock;
  F->getBasicBlockList().insert(++FI, NewLeaf);

  // Emit comparison
  ICmpInst* Comp = NULL;
  if (Leaf.Low == Leaf.High) {
    // Make the seteq instruction...
    Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_EQ, Val,
                        Leaf.Low, "SwitchLeaf");
  } else {
    // Make range comparison
    if (cast<ConstantInt>(Leaf.Low)->isMinValue(true /*isSigned*/)) {
      // Val >= Min && Val <= Hi --> Val <= Hi
      Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_SLE, Val, Leaf.High,
                          "SwitchLeaf");
    } else if (cast<ConstantInt>(Leaf.Low)->isZero()) {
      // Val >= 0 && Val <= Hi --> Val <=u Hi
      Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_ULE, Val, Leaf.High,
                          "SwitchLeaf");      
    } else {
      // Emit V-Lo <=u Hi-Lo
      Constant* NegLo = ConstantExpr::getNeg(Leaf.Low);
      Instruction* Add = BinaryOperator::CreateAdd(Val, NegLo,
                                                   Val->getName()+".off",
                                                   NewLeaf);
      Constant *UpperBound = ConstantExpr::getAdd(NegLo, Leaf.High);
      Comp = new ICmpInst(*NewLeaf, ICmpInst::ICMP_ULE, Add, UpperBound,
                          "SwitchLeaf");
    }
  }

  // Make the conditional branch...
  BasicBlock* Succ = Leaf.BB;
  BranchInst::Create(Succ, Default, Comp, NewLeaf);

  // If there were any PHI nodes in this successor, rewrite one entry
  // from OrigBlock to come from NewLeaf.
  for (BasicBlock::iterator I = Succ->begin(); isa<PHINode>(I); ++I) {
    PHINode* PN = cast<PHINode>(I);
    // Remove all but one incoming entries from the cluster
    uint64_t Range = cast<ConstantInt>(Leaf.High)->getSExtValue() -
                     cast<ConstantInt>(Leaf.Low)->getSExtValue();    
    for (uint64_t j = 0; j < Range; ++j) {
      PN->removeIncomingValue(OrigBlock);
    }
    
    int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
    assert(BlockIdx != -1 && "Switch didn't go to this successor??");
    PN->setIncomingBlock((unsigned)BlockIdx, NewLeaf);
  }

  return NewLeaf;
}

/// This splits a basic block into two at the specified
/// instruction.  Note that all instructions BEFORE the specified iterator stay
/// as part of the original basic block, an unconditional branch is added to
/// the new BB, and the rest of the instructions in the BB are moved to the new
/// BB, including the old terminator.  This invalidates the iterator.
///
/// Note that this only works on well formed basic blocks (must have a
/// terminator), and 'I' must not be the end of instruction list (which would
/// cause a degenerate basic block to be formed, having a terminator inside of
/// the basic block).
///
BasicBlock *BasicBlock::splitBasicBlock(iterator I, const Twine &BBName) {
  assert(getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
  assert(I != InstList.end() &&
         "Trying to get me to create degenerate basic block!");

  BasicBlock *InsertBefore = std::next(Function::iterator(this))
                               .getNodePtrUnchecked();
  BasicBlock *New = BasicBlock::Create(getContext(), BBName,
                                       getParent(), InsertBefore);

  // Save DebugLoc of split point before invalidating iterator.
  DebugLoc Loc = I->getDebugLoc();
  // Move all of the specified instructions from the original basic block into
  // the new basic block.
  New->getInstList().splice(New->end(), this->getInstList(), I, end());

  // Add a branch instruction to the newly formed basic block.
  BranchInst *BI = BranchInst::Create(New, this);
  BI->setDebugLoc(Loc);

  // Now we must loop through all of the successors of the New block (which
  // _were_ the successors of the 'this' block), and update any PHI nodes in
  // successors.  If there were PHI nodes in the successors, then they need to
  // know that incoming branches will be from New, not from Old.
  //
  for (succ_iterator I = succ_begin(New), E = succ_end(New); I != E; ++I) {
    // Loop over any phi nodes in the basic block, updating the BB field of
    // incoming values...
    BasicBlock *Successor = *I;
    PHINode *PN;
    for (BasicBlock::iterator II = Successor->begin();
         (PN = dyn_cast<PHINode>(II)); ++II) {
      int IDX = PN->getBasicBlockIndex(this);
      while (IDX != -1) {
        PN->setIncomingBlock((unsigned)IDX, New);
        IDX = PN->getBasicBlockIndex(this);
      }
    }
  }
  return New;
}

// This is basically the split basic block function but it does not create
// a new basic block.
void Decompiler::splitBasicBlockIntoBlock(Function::iterator Src,
  BasicBlock::iterator FirstInst, BasicBlock *Tgt) {
  assert(Src->getTerminator() && "Can't use splitBasicBlock on degenerate BB!");
  assert(FirstInst != Src->end() &&
         "Trying to get me to create degenerate basic block!");

  Tgt->moveAfter(Src);

  // Move all of the specified instructions from the original basic block into
  // the new basic block.
  Tgt->getInstList().splice(Tgt->end(), Src->getInstList(),
    FirstInst, Src->end());

  // Add a branch instruction to the newly formed basic block.
  BranchInst *BI = BranchInst::Create(Tgt, Src);
  // Set debugLoc to the instruction before the terminator's DebugLoc.
  // Note the pre-inc which can confuse folks.
  BI->setDebugLoc((++Src->rbegin())->getDebugLoc());

  // Now we must loop through all of the successors of the New block (which
  // _were_ the successors of the 'this' block), and update any PHI nodes in
  // successors.  If there were PHI nodes in the successors, then they need to
  // know that incoming branches will be from New, not from Old.
  //
  for (succ_iterator I = succ_begin(Tgt), E = succ_end(Tgt); I != E; ++I) {
    // Loop over any phi nodes in the basic block, updating the BB field of
    // incoming values...
    BasicBlock *Successor = *I;
    PHINode *PN;
    for (BasicBlock::iterator II = Successor->begin();
         (PN = dyn_cast<PHINode>(II)); ++II) {
      int IDX = PN->getBasicBlockIndex(Src);
      while (IDX != -1) {
        PN->setIncomingBlock((unsigned)IDX, Tgt);
        IDX = PN->getBasicBlockIndex(Src);
      }
    }
  }
}

/// UpdatePHINodes - Update the PHI nodes in OrigBB to include the values coming
/// from NewBB. This also updates AliasAnalysis, if available.
static void UpdatePHINodes(BasicBlock *OrigBB, BasicBlock *NewBB,
                           ArrayRef<BasicBlock*> Preds, BranchInst *BI,
                           Pass *P, bool HasLoopExit) {
  // Otherwise, create a new PHI node in NewBB for each PHI node in OrigBB.
  AliasAnalysis *AA = P ? P->getAnalysisIfAvailable<AliasAnalysis>() : 0;
  for (BasicBlock::iterator I = OrigBB->begin(); isa<PHINode>(I); ) {
    PHINode *PN = cast<PHINode>(I++);

    // Check to see if all of the values coming in are the same.  If so, we
    // don't need to create a new PHI node, unless it's needed for LCSSA.
    Value *InVal = 0;
    if (!HasLoopExit) {
      InVal = PN->getIncomingValueForBlock(Preds[0]);
      for (unsigned i = 1, e = Preds.size(); i != e; ++i)
        if (InVal != PN->getIncomingValueForBlock(Preds[i])) {
          InVal = 0;
          break;
        }
    }

    if (InVal) {
      // If all incoming values for the new PHI would be the same, just don't
      // make a new PHI.  Instead, just remove the incoming values from the old
      // PHI.
      for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
        // Explicitly check the BB index here to handle duplicates in Preds.
        int Idx = PN->getBasicBlockIndex(Preds[i]);
        if (Idx >= 0)
          PN->removeIncomingValue(Idx, false);
      }
    } else {
      // If the values coming into the block are not the same, we need a PHI.
      // Create the new PHI node, insert it into NewBB at the end of the block
      PHINode *NewPHI =
        PHINode::Create(PN->getType(), Preds.size(), PN->getName() + ".ph", BI);
      if (AA) AA->copyValue(PN, NewPHI);

      // Move all of the PHI values for 'Preds' to the new PHI.
      for (unsigned i = 0, e = Preds.size(); i != e; ++i) {
        Value *V = PN->removeIncomingValue(Preds[i], false);
        NewPHI->addIncoming(V, Preds[i]);
      }

      InVal = NewPHI;
    }

    // Add an incoming value to the PHI node in the loop for the preheader
    // edge.
    PN->addIncoming(InVal, NewBB);
  }
}

// processSwitchInst - Replace the specified switch instruction with a sequence
// of chained if-then instructions.
//
void LowerSwitchPass::processSwitchInst(SwitchInst *SI) {
  BasicBlock *origBlock = SI->getParent();
  BasicBlock *defaultBlock = SI->getDefaultDest();
  Function *F = origBlock->getParent();
  Value *switchValue = SI->getCondition();

  // Create a new, empty default block so that the new hierarchy of
  // if-then statements go to this and the PHI nodes are happy.
  BasicBlock* newDefault = BasicBlock::Create(getGlobalContext(), "newDefault");

#if LLVM_VERSION_CODE >= LLVM_VERSION(3, 8)
  F->getBasicBlockList().insert(defaultBlock->getIterator(), newDefault);
#else
  F->getBasicBlockList().insert(defaultBlock, newDefault);
#endif
  BranchInst::Create(defaultBlock, newDefault);

  // If there is an entry in any PHI nodes for the default edge, make sure
  // to update them as well.
  for (BasicBlock::iterator I = defaultBlock->begin(); isa<PHINode>(I); ++I) {
    PHINode *PN = cast<PHINode>(I);
    int BlockIdx = PN->getBasicBlockIndex(origBlock);
    assert(BlockIdx != -1 && "Switch didn't go to this successor??");
    PN->setIncomingBlock((unsigned)BlockIdx, newDefault);
  }
  
  CaseVector cases;
  
#if LLVM_VERSION_CODE >= LLVM_VERSION(3, 1)
  for (SwitchInst::CaseIt i = SI->case_begin(), e = SI->case_end(); i != e; ++i)
    cases.push_back(SwitchCase(i.getCaseValue(),
                               i.getCaseSuccessor()));
#else
  for (unsigned i = 1; i < SI->getNumSuccessors(); ++i)  
    cases.push_back(SwitchCase(SI->getSuccessorValue(i),
                               SI->getSuccessor(i)));
#endif
  
  // reverse cases, as switchConvert constructs a chain of
  //   basic blocks by appending to the front. if we reverse,
  //   the if comparisons will happen in the same order
  //   as the cases appear in the switch
  std::reverse(cases.begin(), cases.end());
  
  switchConvert(cases.begin(), cases.end(), switchValue, origBlock, newDefault);

  // We are now done with the switch instruction, so delete it
  origBlock->getInstList().erase(SI);
}

// processSwitchInst - Replace the specified switch instruction with a sequence
// of chained if-then insts in a balanced binary search.
//
void LowerSwitch::processSwitchInst(SwitchInst *SI) {
  BasicBlock *CurBlock = SI->getParent();
  BasicBlock *OrigBlock = CurBlock;
  Function *F = CurBlock->getParent();
  Value *Val = SI->getOperand(0);  // The value we are switching on...
  BasicBlock* Default = SI->getDefaultDest();

  // If there is only the default destination, don't bother with the code below.
  if (SI->getNumOperands() == 2) {
    BranchInst::Create(SI->getDefaultDest(), CurBlock);
    CurBlock->getInstList().erase(SI);
    return;
  }

  // Create a new, empty default block so that the new hierarchy of
  // if-then statements go to this and the PHI nodes are happy.
  BasicBlock* NewDefault = BasicBlock::Create(SI->getContext(), "NewDefault");
  F->getBasicBlockList().insert(Default, NewDefault);

  BranchInst::Create(Default, NewDefault);

  // If there is an entry in any PHI nodes for the default edge, make sure
  // to update them as well.
  for (BasicBlock::iterator I = Default->begin(); isa<PHINode>(I); ++I) {
    PHINode *PN = cast<PHINode>(I);
    int BlockIdx = PN->getBasicBlockIndex(OrigBlock);
    assert(BlockIdx != -1 && "Switch didn't go to this successor??");
    PN->setIncomingBlock((unsigned)BlockIdx, NewDefault);
  }

  // Prepare cases vector.
  CaseVector Cases;
  unsigned numCmps = Clusterify(Cases, SI);

  DEBUG(dbgs() << "Clusterify finished. Total clusters: " << Cases.size()
               << ". Total compares: " << numCmps << "\n");
  DEBUG(dbgs() << "Cases: " << Cases << "\n");
  (void)numCmps;
  
  BasicBlock* SwitchBlock = switchConvert(Cases.begin(), Cases.end(), Val,
                                          OrigBlock, NewDefault);

  // Branch to our shiny new if-then stuff...
  BranchInst::Create(SwitchBlock, OrigBlock);

  // We are now done with the switch instruction, delete it.
  CurBlock->getInstList().erase(SI);
}

/// \brief Add the real PHI value as soon as everything is set up
void StructurizeCFG::setPhiValues() {
  SSAUpdater Updater;
  for (BB2BBVecMap::iterator AI = AddedPhis.begin(), AE = AddedPhis.end();
       AI != AE; ++AI) {

    BasicBlock *To = AI->first;
    BBVector &From = AI->second;

    if (!DeletedPhis.count(To))
      continue;

    PhiMap &Map = DeletedPhis[To];
    for (PhiMap::iterator PI = Map.begin(), PE = Map.end();
         PI != PE; ++PI) {

      PHINode *Phi = PI->first;
      Value *Undef = UndefValue::get(Phi->getType());
      Updater.Initialize(Phi->getType(), "");
      Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
      Updater.AddAvailableValue(To, Undef);

      NearestCommonDominator Dominator(DT);
      Dominator.addBlock(To, false);
      for (BBValueVector::iterator VI = PI->second.begin(),
           VE = PI->second.end(); VI != VE; ++VI) {

        Updater.AddAvailableValue(VI->first, VI->second);
        Dominator.addBlock(VI->first);
      }

      if (!Dominator.wasResultExplicitMentioned())
        Updater.AddAvailableValue(Dominator.getResult(), Undef);

      for (BBVector::iterator FI = From.begin(), FE = From.end();
           FI != FE; ++FI) {

        int Idx = Phi->getBasicBlockIndex(*FI);
        assert(Idx != -1);
        Phi->setIncomingValue(Idx, Updater.GetValueAtEndOfBlock(*FI));
      }
    }

    DeletedPhis.erase(To);
  }
  assert(DeletedPhis.empty());
}

void BasicBlock::replaceSuccessorsPhiUsesWith(BasicBlock *New) {
  TerminatorInst *TI = getTerminator();
  if (!TI)
    // Cope with being called on a BasicBlock that doesn't have a terminator
    // yet. Clang's CodeGenFunction::EmitReturnBlock() likes to do this.
    return;
  for (BasicBlock *Succ : TI->successors()) {
    // N.B. Succ might not be a complete BasicBlock, so don't assume
    // that it ends with a non-phi instruction.
    for (iterator II = Succ->begin(), IE = Succ->end(); II != IE; ++II) {
      PHINode *PN = dyn_cast<PHINode>(II);
      if (!PN)
        break;
      int i;
      while ((i = PN->getBasicBlockIndex(this)) >= 0)
        PN->setIncomingBlock(i, New);
    }
  }
}

void MemoryInstrumenter::instrumentPointerInstruction(Instruction *I) {
    BasicBlock::iterator Loc;
    if (isa<PHINode>(I)) {
        // Cannot insert hooks right after a PHI, because PHINodes have to be
        // grouped together.
        Loc = I->getParent()->getFirstNonPHI();
    } else if (!I->isTerminator()) {
        Loc = I;
        ++Loc;
    } else {
        assert(isa<InvokeInst>(I));
        InvokeInst *II = cast<InvokeInst>(I);
        BasicBlock *NormalDest = II->getNormalDest();
        // It's not always OK to insert HookTopLevel simply at the beginning of the
        // normal destination, because the normal destionation may be shared by
        // multiple InvokeInsts. In that case, we will create a critical edge block,
        // and add the HookTopLevel over there.
        if (NormalDest->getUniquePredecessor()) {
            Loc = NormalDest->getFirstNonPHI();
        } else {
            BasicBlock *CritEdge = BasicBlock::Create(I->getContext(),
                                   "crit_edge",
                                   I->getParent()->getParent());
            Loc = BranchInst::Create(NormalDest, CritEdge);
            // Now that CritEdge becomes the new predecessor of NormalDest, replace
            // all phi uses of I->getParent() with CritEdge.
            for (auto J = NormalDest->begin();
                    NormalDest->getFirstNonPHI() != J;
                    ++J) {
                PHINode *Phi = cast<PHINode>(J);
                int i;
                while ((i = Phi->getBasicBlockIndex(I->getParent())) >= 0)
                    Phi->setIncomingBlock(i, CritEdge);
            }
            II->setNormalDest(CritEdge);
        }
    }
    if (LoadInst *LI = dyn_cast<LoadInst>(I))
        instrumentPointer(I, LI->getPointerOperand(), Loc);
    else
        instrumentPointer(I, NULL, Loc);
}

/// \brief Add the real PHI value as soon as everything is set up
void StructurizeCFG::setPhiValues() {
    SSAUpdater Updater;
    for (const auto &AddedPhi : AddedPhis) {

        BasicBlock *To = AddedPhi.first;
        const BBVector &From = AddedPhi.second;

        if (!DeletedPhis.count(To))
            continue;

        PhiMap &Map = DeletedPhis[To];
        for (const auto &PI : Map) {

            PHINode *Phi = PI.first;
            Value *Undef = UndefValue::get(Phi->getType());
            Updater.Initialize(Phi->getType(), "");
            Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
            Updater.AddAvailableValue(To, Undef);

            NearestCommonDominator Dominator(DT);
            Dominator.addBlock(To, false);
            for (const auto &VI : PI.second) {

                Updater.AddAvailableValue(VI.first, VI.second);
                Dominator.addBlock(VI.first);
            }

            if (!Dominator.wasResultExplicitMentioned())
                Updater.AddAvailableValue(Dominator.getResult(), Undef);

            for (BasicBlock *FI : From) {

                int Idx = Phi->getBasicBlockIndex(FI);
                assert(Idx != -1);
                Phi->setIncomingValue(Idx, Updater.GetValueAtEndOfBlock(FI));
            }
        }

        DeletedPhis.erase(To);
    }
    assert(DeletedPhis.empty());
}

void Executor::transferToBasicBlock(BasicBlock *dst, BasicBlock *src,
                                    ExecutionState &state) {
  // Note that in general phi nodes can reuse phi values from the same
  // block but the incoming value is the eval() result *before* the
  // execution of any phi nodes. this is pathological and doesn't
  // really seem to occur, but just in case we run the PhiCleanerPass
  // which makes sure this cannot happen and so it is safe to just
  // eval things in order. The PhiCleanerPass also makes sure that all
  // incoming blocks have the same order for each PHINode so we only
  // have to compute the index once.
  //
  // With that done we simply set an index in the state so that PHI
  // instructions know which argument to eval, set the pc, and continue.

  // XXX this lookup has to go ?
  KFunction *kf = state.stack().back().kf;
  unsigned entry = kf->basicBlockEntry[dst];
  state.pc() = &kf->instructions[entry];
  if (state.pc()->inst->getOpcode() == Instruction::PHI) {
    PHINode *first = static_cast<PHINode*>(state.pc()->inst);
    state.crtThread().incomingBBIndex = first->getBasicBlockIndex(src);
  }
}

/// Create a clone of the blocks in a loop and connect them together.
/// This function doesn't create a clone of the loop structure.
///
/// There are two value maps that are defined and used.  VMap is
/// for the values in the current loop instance.  LVMap contains
/// the values from the last loop instance.  We need the LVMap values
/// to update the initial values for the current loop instance.
///
static void CloneLoopBlocks(Loop *L,
                            bool FirstCopy,
                            BasicBlock *InsertTop,
                            BasicBlock *InsertBot,
                            std::vector<BasicBlock *> &NewBlocks,
                            LoopBlocksDFS &LoopBlocks,
                            ValueToValueMapTy &VMap,
                            ValueToValueMapTy &LVMap,
                            LoopInfo *LI) {

  BasicBlock *Preheader = L->getLoopPreheader();
  BasicBlock *Header = L->getHeader();
  BasicBlock *Latch = L->getLoopLatch();
  Function *F = Header->getParent();
  LoopBlocksDFS::RPOIterator BlockBegin = LoopBlocks.beginRPO();
  LoopBlocksDFS::RPOIterator BlockEnd = LoopBlocks.endRPO();
  // For each block in the original loop, create a new copy,
  // and update the value map with the newly created values.
  for (LoopBlocksDFS::RPOIterator BB = BlockBegin; BB != BlockEnd; ++BB) {
    BasicBlock *NewBB = CloneBasicBlock(*BB, VMap, ".unr", F);
    NewBlocks.push_back(NewBB);

    if (Loop *ParentLoop = L->getParentLoop())
      ParentLoop->addBasicBlockToLoop(NewBB, LI->getBase());

    VMap[*BB] = NewBB;
    if (Header == *BB) {
      // For the first block, add a CFG connection to this newly
      // created block
      InsertTop->getTerminator()->setSuccessor(0, NewBB);

      // Change the incoming values to the ones defined in the
      // previously cloned loop.
      for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
        PHINode *NewPHI = cast<PHINode>(VMap[I]);
        if (FirstCopy) {
          // We replace the first phi node with the value from the preheader
          VMap[I] = NewPHI->getIncomingValueForBlock(Preheader);
          NewBB->getInstList().erase(NewPHI);
        } else {
          // Update VMap with values from the previous block
          unsigned idx = NewPHI->getBasicBlockIndex(Latch);
          Value *InVal = NewPHI->getIncomingValue(idx);
          if (Instruction *I = dyn_cast<Instruction>(InVal))
            if (L->contains(I))
              InVal = LVMap[InVal];
          NewPHI->setIncomingValue(idx, InVal);
          NewPHI->setIncomingBlock(idx, InsertTop);
        }
      }
    }

    if (Latch == *BB) {
      VMap.erase((*BB)->getTerminator());
      NewBB->getTerminator()->eraseFromParent();
      BranchInst::Create(InsertBot, NewBB);
    }
  }
  // LastValueMap is updated with the values for the current loop
  // which are used the next time this function is called.
  for (ValueToValueMapTy::iterator VI = VMap.begin(), VE = VMap.end();
       VI != VE; ++VI) {
    LVMap[VI->first] = VI->second;
  }
}

//.........这里部分代码省略.........

  while (!Blocks.empty()) {
    BasicBlock *BB = Blocks.front();
    Blocks.pop_front();

    // First split the block and update dominance information.
    BasicBlock *BBCopy = splitBB(BB);
    BasicBlock *BBCopyIDom = repairDominance(BB, BBCopy);

    // In order to remap PHI nodes we store also basic block mappings.
    BlockMap[BB] = BBCopy;

    // Get the mapping for this block and initialize it with the mapping
    // available at its immediate dominator (in the new region).
    ValueMapT &RegionMap = RegionMaps[BBCopy];
    RegionMap = RegionMaps[BBCopyIDom];

    // Copy the block with the BlockGenerator.
    copyBB(Stmt, BB, BBCopy, RegionMap, GlobalMap, LTS);

    // In order to remap PHI nodes we store also basic block mappings.
    BlockMap[BB] = BBCopy;

    // Add values to incomplete PHI nodes waiting for this block to be copied.
    for (const PHINodePairTy &PHINodePair : IncompletePHINodeMap[BB])
      addOperandToPHI(Stmt, PHINodePair.first, PHINodePair.second, BB,
                      GlobalMap, LTS);
    IncompletePHINodeMap[BB].clear();

    // And continue with new successors inside the region.
    for (auto SI = succ_begin(BB), SE = succ_end(BB); SI != SE; SI++)
      if (R->contains(*SI) && SeenBlocks.insert(*SI).second)
        Blocks.push_back(*SI);
  }

  // Now create a new dedicated region exit block and add it to the region map.
  BasicBlock *ExitBBCopy =
      SplitBlock(Builder.GetInsertBlock(), Builder.GetInsertPoint(), &DT, &LI);
  ExitBBCopy->setName("polly.stmt." + R->getExit()->getName() + ".exit");
  BlockMap[R->getExit()] = ExitBBCopy;

  repairDominance(R->getExit(), ExitBBCopy);

  // As the block generator doesn't handle control flow we need to add the
  // region control flow by hand after all blocks have been copied.
  for (BasicBlock *BB : SeenBlocks) {

    BranchInst *BI = cast<BranchInst>(BB->getTerminator());

    BasicBlock *BBCopy = BlockMap[BB];
    Instruction *BICopy = BBCopy->getTerminator();

    ValueMapT &RegionMap = RegionMaps[BBCopy];
    RegionMap.insert(BlockMap.begin(), BlockMap.end());

    Builder.SetInsertPoint(BBCopy);
    copyInstScalar(Stmt, BI, RegionMap, GlobalMap, LTS);
    BICopy->eraseFromParent();
  }

  // Add counting PHI nodes to all loops in the region that can be used as
  // replacement for SCEVs refering to the old loop.
  for (BasicBlock *BB : SeenBlocks) {
    Loop *L = LI.getLoopFor(BB);
    if (L == nullptr || L->getHeader() != BB)
      continue;

    BasicBlock *BBCopy = BlockMap[BB];
    Value *NullVal = Builder.getInt32(0);
    PHINode *LoopPHI =
        PHINode::Create(Builder.getInt32Ty(), 2, "polly.subregion.iv");
    Instruction *LoopPHIInc = BinaryOperator::CreateAdd(
        LoopPHI, Builder.getInt32(1), "polly.subregion.iv.inc");
    LoopPHI->insertBefore(BBCopy->begin());
    LoopPHIInc->insertBefore(BBCopy->getTerminator());

    for (auto *PredBB : make_range(pred_begin(BB), pred_end(BB))) {
      if (!R->contains(PredBB))
        continue;
      if (L->contains(PredBB))
        LoopPHI->addIncoming(LoopPHIInc, BlockMap[PredBB]);
      else
        LoopPHI->addIncoming(NullVal, BlockMap[PredBB]);
    }

    for (auto *PredBBCopy : make_range(pred_begin(BBCopy), pred_end(BBCopy)))
      if (LoopPHI->getBasicBlockIndex(PredBBCopy) < 0)
        LoopPHI->addIncoming(NullVal, PredBBCopy);

    LTS[L] = SE.getUnknown(LoopPHI);
  }

  // Add all mappings from the region to the global map so outside uses will use
  // the copied instructions.
  for (auto &BBMap : RegionMaps)
    GlobalMap.insert(BBMap.second.begin(), BBMap.second.end());

  // Reset the old insert point for the build.
  Builder.SetInsertPoint(ExitBBCopy->begin());
}