C++ PHINode::removeIncomingValue方法代码示例

/// 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);
  }
}

// \brief Update the first occurrence of the "switch statement" BB in the PHI
// node with the "new" BB. The other occurrences will:
//
// 1) Be updated by subsequent calls to this function.  Switch statements may
// have more than one outcoming edge into the same BB if they all have the same
// value. When the switch statement is converted these incoming edges are now
// coming from multiple BBs.
// 2) Removed if subsequent incoming values now share the same case, i.e.,
// multiple outcome edges are condensed into one. This is necessary to keep the
// number of phi values equal to the number of branches to SuccBB.
static void fixPhis(BasicBlock *SuccBB, BasicBlock *OrigBB, BasicBlock *NewBB,
                    unsigned NumMergedCases) {
  for (BasicBlock::iterator I = SuccBB->begin(), IE = SuccBB->getFirstNonPHI();
       I != IE; ++I) {
    PHINode *PN = cast<PHINode>(I);

    // Only update the first occurence.
    unsigned Idx = 0, E = PN->getNumIncomingValues();
    unsigned LocalNumMergedCases = NumMergedCases;
    for (; Idx != E; ++Idx) {
      if (PN->getIncomingBlock(Idx) == OrigBB) {
        PN->setIncomingBlock(Idx, NewBB);
        break;
      }
    }

    // Remove additional occurences coming from condensed cases and keep the
    // number of incoming values equal to the number of branches to SuccBB.
    SmallVector<unsigned, 8> Indices;
    for (++Idx; LocalNumMergedCases > 0 && Idx < E; ++Idx)
      if (PN->getIncomingBlock(Idx) == OrigBB) {
        Indices.push_back(Idx);
        LocalNumMergedCases--;
      }
    // Remove incoming values in the reverse order to prevent invalidating
    // *successive* index.
    for (auto III = Indices.rbegin(), IIE = Indices.rend(); III != IIE; ++III)
      PN->removeIncomingValue(*III);
  }
}

// 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;
}

void CheckInserter::insertCycleChecks(Function &F) {
  IdentifyBackEdges &IBE = getAnalysis<IdentifyBackEdges>();

  for (Function::iterator B1 = F.begin(); B1 != F.end(); ++B1) {
    TerminatorInst *TI = B1->getTerminator();
    for (unsigned j = 0; j < TI->getNumSuccessors(); ++j) {
      BasicBlock *B2 = TI->getSuccessor(j);
      unsigned BackEdgeID = IBE.getID(B1, B2);
      if (BackEdgeID != (unsigned)-1) {
        assert(BackEdgeID < MaxNumBackEdges);
        BasicBlock *BackEdgeBlock = BasicBlock::Create(
            F.getContext(),
            "backedge_" + B1->getName() + "_" + B2->getName(),
            &F);
        CallInst::Create(CycleCheck,
                         ConstantInt::get(IntType, BackEdgeID),
                         "",
                         BackEdgeBlock);
        // BackEdgeBlock -> B2
        // Fix the PHINodes in B2.
        BranchInst::Create(B2, BackEdgeBlock);
        for (BasicBlock::iterator I = B2->begin();
             B2->getFirstNonPHI() != I;
             ++I) {
          PHINode *PHI = cast<PHINode>(I);
          // Note: If B2 has multiple incoming edges from B1 (e.g. B1 terminates
          // with a SelectInst), its PHINodes must also have multiple incoming
          // edges from B1. However, after adding BackEdgeBlock and essentially
          // merging the multiple incoming edges from B1, there will be only one
          // edge from BackEdgeBlock to B2. Therefore, we need to remove the
          // redundant incoming edges from B2's PHINodes.
          bool FirstIncomingFromB1 = true;
          for (unsigned k = 0; k < PHI->getNumIncomingValues(); ++k) {
            if (PHI->getIncomingBlock(k) == B1) {
              if (FirstIncomingFromB1) {
                FirstIncomingFromB1 = false;
                PHI->setIncomingBlock(k, BackEdgeBlock);
              } else {
                PHI->removeIncomingValue(k, false);
                --k;
              }
            }
          }
        }
        // B1 -> BackEdgeBlock
        // There might be multiple back edges from B1 to B2. Need to replace
        // them all.
        for (unsigned j2 = j; j2 < TI->getNumSuccessors(); ++j2) {
          if (TI->getSuccessor(j2) == B2) {
            TI->setSuccessor(j2, BackEdgeBlock);
          }
        }
      }
    }
  }
}

/// updatePHINodes - CFG has been changed. 
/// Before 
///   - ExitBB's single predecessor was Latch
///   - Latch's second successor was Header
/// Now
///   - ExitBB's single predecessor is Header
///   - Latch's one and only successor is Header
///
/// Update ExitBB PHINodes' to reflect this change.
void LoopIndexSplit::updatePHINodes(BasicBlock *ExitBB, BasicBlock *Latch, 
                                    BasicBlock *Header,
                                    PHINode *IV, Instruction *IVIncrement,
                                    Loop *LP) {

  for (BasicBlock::iterator BI = ExitBB->begin(), BE = ExitBB->end(); 
       BI != BE; ) {
    PHINode *PN = dyn_cast<PHINode>(BI);
    ++BI;
    if (!PN)
      break;

    Value *V = PN->getIncomingValueForBlock(Latch);
    if (PHINode *PHV = dyn_cast<PHINode>(V)) {
      // PHV is in Latch. PHV has one use is in ExitBB PHINode. And one use
      // in Header which is new incoming value for PN.
      Value *NewV = NULL;
      for (Value::use_iterator UI = PHV->use_begin(), E = PHV->use_end(); 
           UI != E; ++UI) 
        if (PHINode *U = dyn_cast<PHINode>(*UI)) 
          if (LP->contains(U->getParent())) {
            NewV = U;
            break;
          }

      // Add incoming value from header only if PN has any use inside the loop.
      if (NewV)
        PN->addIncoming(NewV, Header);

    } else if (Instruction *PHI = dyn_cast<Instruction>(V)) {
      // If this instruction is IVIncrement then IV is new incoming value 
      // from header otherwise this instruction must be incoming value from 
      // header because loop is in LCSSA form.
      if (PHI == IVIncrement)
        PN->addIncoming(IV, Header);
      else
        PN->addIncoming(V, Header);
    } else
      // Otherwise this is an incoming value from header because loop is in 
      // LCSSA form.
      PN->addIncoming(V, Header);
    
    // Remove incoming value from Latch.
    PN->removeIncomingValue(Latch);
  }
}

Function* PartialInliner::unswitchFunction(Function* F) {
  // First, verify that this function is an unswitching candidate...
  BasicBlock* entryBlock = F->begin();
  BranchInst *BR = dyn_cast<BranchInst>(entryBlock->getTerminator());
  if (!BR || BR->isUnconditional())
    return 0;
  
  BasicBlock* returnBlock = 0;
  BasicBlock* nonReturnBlock = 0;
  unsigned returnCount = 0;
  for (succ_iterator SI = succ_begin(entryBlock), SE = succ_end(entryBlock);
       SI != SE; ++SI)
    if (isa<ReturnInst>((*SI)->getTerminator())) {
      returnBlock = *SI;
      returnCount++;
    } else
      nonReturnBlock = *SI;
  
  if (returnCount != 1)
    return 0;
  
  // Clone the function, so that we can hack away on it.
  ValueToValueMapTy VMap;
  Function* duplicateFunction = CloneFunction(F, VMap,
                                              /*ModuleLevelChanges=*/false);
  duplicateFunction->setLinkage(GlobalValue::InternalLinkage);
  F->getParent()->getFunctionList().push_back(duplicateFunction);
  BasicBlock* newEntryBlock = cast<BasicBlock>(VMap[entryBlock]);
  BasicBlock* newReturnBlock = cast<BasicBlock>(VMap[returnBlock]);
  BasicBlock* newNonReturnBlock = cast<BasicBlock>(VMap[nonReturnBlock]);
  
  // Go ahead and update all uses to the duplicate, so that we can just
  // use the inliner functionality when we're done hacking.
  F->replaceAllUsesWith(duplicateFunction);
  
  // Special hackery is needed with PHI nodes that have inputs from more than
  // one extracted block.  For simplicity, just split the PHIs into a two-level
  // sequence of PHIs, some of which will go in the extracted region, and some
  // of which will go outside.
  BasicBlock* preReturn = newReturnBlock;
  newReturnBlock = newReturnBlock->splitBasicBlock(
                                              newReturnBlock->getFirstNonPHI());
  BasicBlock::iterator I = preReturn->begin();
  BasicBlock::iterator Ins = newReturnBlock->begin();
  while (I != preReturn->end()) {
    PHINode* OldPhi = dyn_cast<PHINode>(I);
    if (!OldPhi) break;
    
    PHINode* retPhi = PHINode::Create(OldPhi->getType(), 2, "", Ins);
    OldPhi->replaceAllUsesWith(retPhi);
    Ins = newReturnBlock->getFirstNonPHI();
    
    retPhi->addIncoming(I, preReturn);
    retPhi->addIncoming(OldPhi->getIncomingValueForBlock(newEntryBlock),
                        newEntryBlock);
    OldPhi->removeIncomingValue(newEntryBlock);
    
    ++I;
  }
  newEntryBlock->getTerminator()->replaceUsesOfWith(preReturn, newReturnBlock);
  
  // Gather up the blocks that we're going to extract.
  std::vector<BasicBlock*> toExtract;
  toExtract.push_back(newNonReturnBlock);
  for (Function::iterator FI = duplicateFunction->begin(),
       FE = duplicateFunction->end(); FI != FE; ++FI)
    if (&*FI != newEntryBlock && &*FI != newReturnBlock &&
        &*FI != newNonReturnBlock)
      toExtract.push_back(FI);
      
  // The CodeExtractor needs a dominator tree.
  DominatorTree DT;
  DT.runOnFunction(*duplicateFunction);
  
  // Extract the body of the if.
  Function* extractedFunction
    = CodeExtractor(toExtract, &DT).extractCodeRegion();
  
  InlineFunctionInfo IFI;
  
  // Inline the top-level if test into all callers.
  std::vector<User*> Users(duplicateFunction->use_begin(), 
                           duplicateFunction->use_end());
  for (std::vector<User*>::iterator UI = Users.begin(), UE = Users.end();
       UI != UE; ++UI)
    if (CallInst *CI = dyn_cast<CallInst>(*UI))
      InlineFunction(CI, IFI);
    else if (InvokeInst *II = dyn_cast<InvokeInst>(*UI))
      InlineFunction(II, IFI);
  
  // Ditch the duplicate, since we're done with it, and rewrite all remaining
  // users (function pointers, etc.) back to the original function.
  duplicateFunction->replaceAllUsesWith(F);
  duplicateFunction->eraseFromParent();
  
  ++NumPartialInlined;
  
  return extractedFunction;
}

/// removePredecessor - This method is used to notify a BasicBlock that the
/// specified Predecessor of the block is no longer able to reach it.  This is
/// actually not used to update the Predecessor list, but is actually used to
/// update the PHI nodes that reside in the block.  Note that this should be
/// called while the predecessor still refers to this block.
///
void BasicBlock::removePredecessor(BasicBlock *Pred,
                                   bool DontDeleteUselessPHIs) {
  assert((hasNUsesOrMore(16)||// Reduce cost of this assertion for complex CFGs.
          find(pred_begin(this), pred_end(this), Pred) != pred_end(this)) &&
         "removePredecessor: BB is not a predecessor!");

  if (InstList.empty()) return;
  PHINode *APN = dyn_cast<PHINode>(&front());
  if (!APN) return;   // Quick exit.

  // If there are exactly two predecessors, then we want to nuke the PHI nodes
  // altogether.  However, we cannot do this, if this in this case:
  //
  //  Loop:
  //    %x = phi [X, Loop]
  //    %x2 = add %x, 1         ;; This would become %x2 = add %x2, 1
  //    br Loop                 ;; %x2 does not dominate all uses
  //
  // This is because the PHI node input is actually taken from the predecessor
  // basic block.  The only case this can happen is with a self loop, so we
  // check for this case explicitly now.
  //
  unsigned max_idx = APN->getNumIncomingValues();
  assert(max_idx != 0 && "PHI Node in block with 0 predecessors!?!?!");
  if (max_idx == 2) {
    BasicBlock *Other = APN->getIncomingBlock(APN->getIncomingBlock(0) == Pred);

    // Disable PHI elimination!
    if (this == Other) max_idx = 3;
  }

  // <= Two predecessors BEFORE I remove one?
  if (max_idx <= 2 && !DontDeleteUselessPHIs) {
    // Yup, loop through and nuke the PHI nodes
    while (PHINode *PN = dyn_cast<PHINode>(&front())) {
      // Remove the predecessor first.
      PN->removeIncomingValue(Pred, !DontDeleteUselessPHIs);

      // If the PHI _HAD_ two uses, replace PHI node with its now *single* value
      if (max_idx == 2) {
        if (PN->getIncomingValue(0) != PN)
          PN->replaceAllUsesWith(PN->getIncomingValue(0));
        else
          // We are left with an infinite loop with no entries: kill the PHI.
          PN->replaceAllUsesWith(UndefValue::get(PN->getType()));
        getInstList().pop_front();    // Remove the PHI node
      }

      // If the PHI node already only had one entry, it got deleted by
      // removeIncomingValue.
    }
  } else {
    // Okay, now we know that we need to remove predecessor #pred_idx from all
    // PHI nodes.  Iterate over each PHI node fixing them up
    PHINode *PN;
    for (iterator II = begin(); (PN = dyn_cast<PHINode>(II)); ) {
      ++II;
      PN->removeIncomingValue(Pred, false);
      // If all incoming values to the Phi are the same, we can replace the Phi
      // with that value.
      Value* PNV = 0;
      if (!DontDeleteUselessPHIs && (PNV = PN->hasConstantValue()))
        if (PNV != PN) {
          PN->replaceAllUsesWith(PNV);
          PN->eraseFromParent();
        }
    }
  }
}

//.........这里部分代码省略.........
        // Also, clear out the new latch's back edge so that it doesn't look
        // like a new loop, so that it's amenable to being merged with adjacent
        // blocks later on.
        TerminatorInst *Term = New->getTerminator();
        assert(L->contains(Term->getSuccessor(!ContinueOnTrue)));
        assert(Term->getSuccessor(ContinueOnTrue) == LoopExit);
        Term->setSuccessor(!ContinueOnTrue, NULL);
      }

      NewBlocks.push_back(New);
    }
    
    // Remap all instructions in the most recent iteration
    for (unsigned i = 0; i < NewBlocks.size(); ++i)
      for (BasicBlock::iterator I = NewBlocks[i]->begin(),
           E = NewBlocks[i]->end(); I != E; ++I)
        RemapInstruction(I, LastValueMap);
  }
  
  // The latch block exits the loop.  If there are any PHI nodes in the
  // successor blocks, update them to use the appropriate values computed as the
  // last iteration of the loop.
  if (Count != 1) {
    SmallPtrSet<PHINode*, 8> Users;
    for (Value::use_iterator UI = LatchBlock->use_begin(),
         UE = LatchBlock->use_end(); UI != UE; ++UI)
      if (PHINode *phi = dyn_cast<PHINode>(*UI))
        Users.insert(phi);
    
    BasicBlock *LastIterationBB = cast<BasicBlock>(LastValueMap[LatchBlock]);
    for (SmallPtrSet<PHINode*,8>::iterator SI = Users.begin(), SE = Users.end();
         SI != SE; ++SI) {
      PHINode *PN = *SI;
      Value *InVal = PN->removeIncomingValue(LatchBlock, false);
      // If this value was defined in the loop, take the value defined by the
      // last iteration of the loop.
      if (Instruction *InValI = dyn_cast<Instruction>(InVal)) {
        if (L->contains(InValI->getParent()))
          InVal = LastValueMap[InVal];
      }
      PN->addIncoming(InVal, LastIterationBB);
    }
  }

  // Now, if we're doing complete unrolling, loop over the PHI nodes in the
  // original block, setting them to their incoming values.
  if (CompletelyUnroll) {
    BasicBlock *Preheader = L->getLoopPreheader();
    for (unsigned i = 0, e = OrigPHINode.size(); i != e; ++i) {
      PHINode *PN = OrigPHINode[i];
      PN->replaceAllUsesWith(PN->getIncomingValueForBlock(Preheader));
      Header->getInstList().erase(PN);
    }
  }

  // Now that all the basic blocks for the unrolled iterations are in place,
  // set up the branches to connect them.
  for (unsigned i = 0, e = Latches.size(); i != e; ++i) {
    // The original branch was replicated in each unrolled iteration.
    BranchInst *Term = cast<BranchInst>(Latches[i]->getTerminator());

    // The branch destination.
    unsigned j = (i + 1) % e;
    BasicBlock *Dest = Headers[j];
    bool NeedConditional = true;

/// Create a clone of the blocks in a loop and connect them together.
/// If CreateRemainderLoop is false, loop structure will not be cloned,
/// otherwise a new loop will be created including all cloned blocks, and the
/// iterator of it switches to count NewIter down to 0.
/// The cloned blocks should be inserted between InsertTop and InsertBot.
/// If loop structure is cloned InsertTop should be new preheader, InsertBot
/// new loop exit.
/// Return the new cloned loop that is created when CreateRemainderLoop is true.
static Loop *
CloneLoopBlocks(Loop *L, Value *NewIter, const bool CreateRemainderLoop,
                const bool UseEpilogRemainder, const bool UnrollRemainder,
                BasicBlock *InsertTop,
                BasicBlock *InsertBot, BasicBlock *Preheader,
                std::vector<BasicBlock *> &NewBlocks, LoopBlocksDFS &LoopBlocks,
                ValueToValueMapTy &VMap, DominatorTree *DT, LoopInfo *LI) {
  StringRef suffix = UseEpilogRemainder ? "epil" : "prol";
  BasicBlock *Header = L->getHeader();
  BasicBlock *Latch = L->getLoopLatch();
  Function *F = Header->getParent();
  LoopBlocksDFS::RPOIterator BlockBegin = LoopBlocks.beginRPO();
  LoopBlocksDFS::RPOIterator BlockEnd = LoopBlocks.endRPO();
  Loop *ParentLoop = L->getParentLoop();
  NewLoopsMap NewLoops;
  NewLoops[ParentLoop] = ParentLoop;
  if (!CreateRemainderLoop)
    NewLoops[L] = ParentLoop;

  // 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, "." + suffix, F);
    NewBlocks.push_back(NewBB);

    // If we're unrolling the outermost loop, there's no remainder loop,
    // and this block isn't in a nested loop, then the new block is not
    // in any loop. Otherwise, add it to loopinfo.
    if (CreateRemainderLoop || LI->getLoopFor(*BB) != L || ParentLoop)
      addClonedBlockToLoopInfo(*BB, NewBB, LI, NewLoops);

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

    if (DT) {
      if (Header == *BB) {
        // The header is dominated by the preheader.
        DT->addNewBlock(NewBB, InsertTop);
      } else {
        // Copy information from original loop to unrolled loop.
        BasicBlock *IDomBB = DT->getNode(*BB)->getIDom()->getBlock();
        DT->addNewBlock(NewBB, cast<BasicBlock>(VMap[IDomBB]));
      }
    }

    if (Latch == *BB) {
      // For the last block, if CreateRemainderLoop is false, create a direct
      // jump to InsertBot. If not, create a loop back to cloned head.
      VMap.erase((*BB)->getTerminator());
      BasicBlock *FirstLoopBB = cast<BasicBlock>(VMap[Header]);
      BranchInst *LatchBR = cast<BranchInst>(NewBB->getTerminator());
      IRBuilder<> Builder(LatchBR);
      if (!CreateRemainderLoop) {
        Builder.CreateBr(InsertBot);
      } else {
        PHINode *NewIdx = PHINode::Create(NewIter->getType(), 2,
                                          suffix + ".iter",
                                          FirstLoopBB->getFirstNonPHI());
        Value *IdxSub =
            Builder.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
                              NewIdx->getName() + ".sub");
        Value *IdxCmp =
            Builder.CreateIsNotNull(IdxSub, NewIdx->getName() + ".cmp");
        Builder.CreateCondBr(IdxCmp, FirstLoopBB, InsertBot);
        NewIdx->addIncoming(NewIter, InsertTop);
        NewIdx->addIncoming(IdxSub, NewBB);
      }
      LatchBR->eraseFromParent();
    }
  }

  // Change the incoming values to the ones defined in the preheader or
  // cloned loop.
  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
    PHINode *NewPHI = cast<PHINode>(VMap[&*I]);
    if (!CreateRemainderLoop) {
      if (UseEpilogRemainder) {
        unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
        NewPHI->setIncomingBlock(idx, InsertTop);
        NewPHI->removeIncomingValue(Latch, false);
      } else {
        VMap[&*I] = NewPHI->getIncomingValueForBlock(Preheader);
        cast<BasicBlock>(VMap[Header])->getInstList().erase(NewPHI);
      }
    } else {
      unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
      NewPHI->setIncomingBlock(idx, InsertTop);
      BasicBlock *NewLatch = cast<BasicBlock>(VMap[Latch]);
//.........这里部分代码省略.........

/// NormalizeLandingPads - Normalize and discover landing pads, noting them
/// in the LandingPads set.  A landing pad is normal if the only CFG edges
/// that end at it are unwind edges from invoke instructions. If we inlined
/// through an invoke we could have a normal branch from the previous
/// unwind block through to the landing pad for the original invoke.
/// Abnormal landing pads are fixed up by redirecting all unwind edges to
/// a new basic block which falls through to the original.
bool DwarfEHPrepare::NormalizeLandingPads() {
  bool Changed = false;

  for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
    TerminatorInst *TI = I->getTerminator();
    if (!isa<InvokeInst>(TI))
      continue;
    BasicBlock *LPad = TI->getSuccessor(1);
    // Skip landing pads that have already been normalized.
    if (LandingPads.count(LPad))
      continue;

    // Check that only invoke unwind edges end at the landing pad.
    bool OnlyUnwoundTo = true;
    for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad);
         PI != PE; ++PI) {
      TerminatorInst *PT = (*PI)->getTerminator();
      if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) {
        OnlyUnwoundTo = false;
        break;
      }
    }

    if (OnlyUnwoundTo) {
      // Only unwind edges lead to the landing pad.  Remember the landing pad.
      LandingPads.insert(LPad);
      continue;
    }

    // At least one normal edge ends at the landing pad.  Redirect the unwind
    // edges to a new basic block which falls through into this one.

    // Create the new basic block.
    BasicBlock *NewBB = BasicBlock::Create(F->getContext(),
                                           LPad->getName() + "_unwind_edge");

    // Insert it into the function right before the original landing pad.
    LPad->getParent()->getBasicBlockList().insert(LPad, NewBB);

    // Redirect unwind edges from the original landing pad to NewBB.
    for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) {
      TerminatorInst *PT = (*PI++)->getTerminator();
      if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad)
        // Unwind to the new block.
        PT->setSuccessor(1, NewBB);
    }

    // If there are any PHI nodes in LPad, we need to update them so that they
    // merge incoming values from NewBB instead.
    for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) {
      PHINode *PN = cast<PHINode>(II);
      pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB);

      // Check to see if all of the values coming in via unwind edges are the
      // same.  If so, we don't need to create a new PHI node.
      Value *InVal = PN->getIncomingValueForBlock(*PB);
      for (pred_iterator PI = PB; PI != PE; ++PI) {
        if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) {
          InVal = 0;
          break;
        }
      }

      if (InVal == 0) {
        // Different unwind edges have different values.  Create a new PHI node
        // in NewBB.
        PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind",
                                         NewBB);
        // Add an entry for each unwind edge, using the value from the old PHI.
        for (pred_iterator PI = PB; PI != PE; ++PI)
          NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI);

        // Now use this new PHI as the common incoming value for NewBB in PN.
        InVal = NewPN;
      }

      // Revector exactly one entry in the PHI node to come from NewBB
      // and delete all other entries that come from unwind edges.  If
      // there are both normal and unwind edges from the same predecessor,
      // this leaves an entry for the normal edge.
      for (pred_iterator PI = PB; PI != PE; ++PI)
        PN->removeIncomingValue(*PI);
      PN->addIncoming(InVal, NewBB);
    }

    // Add a fallthrough from NewBB to the original landing pad.
    BranchInst::Create(LPad, NewBB);

    // Now update DominatorTree and DominanceFrontier analysis information.
    if (DT)
      DT->splitBlock(NewBB);
    if (DF)
      DF->splitBlock(NewBB);
//.........这里部分代码省略.........

//.........这里部分代码省略.........
    exn = findExceptionInBlock(exnBlock);
  } while (!exn);

  // Look for a selector call for the exception we found.
  EHSelectorInst *selector = findSelectorForException(exn);
  if (!selector) return 0;

  // The easy case is when the landing pad still dominates the
  // exception call, in which case we can just move both calls back to
  // the landing pad.
  if (dominates) {
    selector->moveBefore(lpad->getFirstNonPHI());
    exn->moveBefore(selector);
    return selector;
  }

  // Otherwise, we have to split at the first non-dominating block.
  // The CFG looks basically like this:
  //    lpad:
  //      phis_0
  //      insnsAndBranches_1
  //      br label %nonDominated
  //    nonDominated:
  //      phis_2
  //      insns_3
  //      %exn = call i8* @llvm.eh.exception()
  //      insnsAndBranches_4
  //      %selector = call @llvm.eh.selector(i8* %exn, ...
  // We need to turn this into:
  //    lpad:
  //      phis_0
  //      %exn0 = call i8* @llvm.eh.exception()
  //      %selector0 = call @llvm.eh.selector(i8* %exn0, ...
  //      insnsAndBranches_1
  //      br label %split // from lastDominated
  //    nonDominated:
  //      phis_2 (without edge from lastDominated)
  //      %exn1 = call i8* @llvm.eh.exception()
  //      %selector1 = call i8* @llvm.eh.selector(i8* %exn1, ...
  //      br label %split
  //    split:
  //      phis_2 (edge from lastDominated, edge from split)
  //      %exn = phi ...
  //      %selector = phi ...
  //      insns_3
  //      insnsAndBranches_4

  assert(nonDominated);
  assert(lastDominated);

  // First, make clones of the intrinsics to go in lpad.
  EHExceptionInst *lpadExn = cast<EHExceptionInst>(exn->clone());
  EHSelectorInst *lpadSelector = cast<EHSelectorInst>(selector->clone());
  lpadSelector->setArgOperand(0, lpadExn);
  lpadSelector->insertBefore(lpad->getFirstNonPHI());
  lpadExn->insertBefore(lpadSelector);

  // Split the non-dominated block.
  BasicBlock *split =
    nonDominated->splitBasicBlock(nonDominated->getFirstNonPHI(),
                                  nonDominated->getName() + ".lpad-fix");

  // Redirect the last dominated branch there.
  cast<BranchInst>(lastDominated->back()).setSuccessor(0, split);

  // Move the existing intrinsics to the end of the old block.
  selector->moveBefore(&nonDominated->back());
  exn->moveBefore(selector);

  Instruction *splitIP = &split->front();

  // For all the phis in nonDominated, make a new phi in split to join
  // that phi with the edge from lastDominated.
  for (BasicBlock::iterator
         i = nonDominated->begin(), e = nonDominated->end(); i != e; ++i) {
    PHINode *phi = dyn_cast<PHINode>(i);
    if (!phi) break;

    PHINode *splitPhi = PHINode::Create(phi->getType(), 2, phi->getName(),
                                        splitIP);
    phi->replaceAllUsesWith(splitPhi);
    splitPhi->addIncoming(phi, nonDominated);
    splitPhi->addIncoming(phi->removeIncomingValue(lastDominated),
                          lastDominated);
  }

  // Make new phis for the exception and selector.
  PHINode *exnPhi = PHINode::Create(exn->getType(), 2, "", splitIP);
  exn->replaceAllUsesWith(exnPhi);
  selector->setArgOperand(0, exn); // except for this use
  exnPhi->addIncoming(exn, nonDominated);
  exnPhi->addIncoming(lpadExn, lastDominated);

  PHINode *selectorPhi = PHINode::Create(selector->getType(), 2, "", splitIP);
  selector->replaceAllUsesWith(selectorPhi);
  selectorPhi->addIncoming(selector, nonDominated);
  selectorPhi->addIncoming(lpadSelector, lastDominated);

  return lpadSelector;
}

//.........这里部分代码省略.........
             PHINode *phi = dyn_cast<PHINode>(BBI); ++BBI) {
          Value *Incoming = phi->getIncomingValueForBlock(*BB);
          ValueToValueMapTy::iterator It = LastValueMap.find(Incoming);
          if (It != LastValueMap.end())
            Incoming = It->second;
          phi->addIncoming(Incoming, New);
        }
      }
      // Keep track of new headers and latches as we create them, so that
      // we can insert the proper branches later.
      if (*BB == Header)
        Headers.push_back(New);
      if (*BB == LatchBlock)
        Latches.push_back(New);

      NewBlocks.push_back(New);
    }

    // Remap all instructions in the most recent iteration
    for (unsigned i = 0; i < NewBlocks.size(); ++i)
      for (BasicBlock::iterator I = NewBlocks[i]->begin(),
           E = NewBlocks[i]->end(); I != E; ++I)
        ::RemapInstruction(I, LastValueMap);
  }

  // Loop over the PHI nodes in the original block, setting incoming values.
  for (unsigned i = 0, e = OrigPHINode.size(); i != e; ++i) {
    PHINode *PN = OrigPHINode[i];
    if (CompletelyUnroll) {
      PN->replaceAllUsesWith(PN->getIncomingValueForBlock(Preheader));
      Header->getInstList().erase(PN);
    }
    else if (Count > 1) {
      Value *InVal = PN->removeIncomingValue(LatchBlock, false);
      // If this value was defined in the loop, take the value defined by the
      // last iteration of the loop.
      if (Instruction *InValI = dyn_cast<Instruction>(InVal)) {
        if (L->contains(InValI))
          InVal = LastValueMap[InVal];
      }
      assert(Latches.back() == LastValueMap[LatchBlock] && "bad last latch");
      PN->addIncoming(InVal, Latches.back());
    }
  }

  // Now that all the basic blocks for the unrolled iterations are in place,
  // set up the branches to connect them.
  for (unsigned i = 0, e = Latches.size(); i != e; ++i) {
    // The original branch was replicated in each unrolled iteration.
    BranchInst *Term = cast<BranchInst>(Latches[i]->getTerminator());

    // The branch destination.
    unsigned j = (i + 1) % e;
    BasicBlock *Dest = Headers[j];
    bool NeedConditional = true;

    if (RuntimeTripCount && j != 0) {
      NeedConditional = false;
    }

    // For a complete unroll, make the last iteration end with a branch
    // to the exit block.
    if (CompletelyUnroll && j == 0) {
      Dest = LoopExit;
      NeedConditional = false;
    }

static bool convertFunction(Function *Func) {
  bool Changed = false;
  IntegerType *I32 = Type::getInt32Ty(Func->getContext());

  // Skip zero in case programs treat a null pointer as special.
  uint32_t NextNum = 1;
  DenseMap<BasicBlock *, ConstantInt *> LabelNums;
  BasicBlock *DefaultBB = NULL;

  // Replace each indirectbr with a switch.
  //
  // If there are multiple indirectbr instructions in the function,
  // this could be expensive.  While an indirectbr is usually
  // converted to O(1) machine instructions, the switch we generate
  // here will be O(n) in the number of target labels.
  //
  // However, Clang usually generates just a single indirectbr per
  // function anyway when compiling C computed gotos.
  //
  // We could try to generate one switch to handle all the indirectbr
  // instructions in the function, but that would be complicated to
  // implement given that variables that are live at one indirectbr
  // might not be live at others.
  for (llvm::Function::iterator BB = Func->begin(), E = Func->end();
       BB != E; ++BB) {
    if (IndirectBrInst *Br = dyn_cast<IndirectBrInst>(BB->getTerminator())) {
      Changed = true;

      if (!DefaultBB) {
        DefaultBB = BasicBlock::Create(Func->getContext(),
                                       "indirectbr_default", Func);
        new UnreachableInst(Func->getContext(), DefaultBB);
      }

      // An indirectbr can list the same target block multiple times.
      // Keep track of the basic blocks we've handled to avoid adding
      // the same case multiple times.
      DenseSet<BasicBlock *> BlocksSeen;

      Value *Cast = new PtrToIntInst(Br->getAddress(), I32,
                                     "indirectbr_cast", Br);
      unsigned Count = Br->getNumSuccessors();
      SwitchInst *Switch = SwitchInst::Create(Cast, DefaultBB, Count, Br);
      for (unsigned I = 0; I < Count; ++I) {
        BasicBlock *Dest = Br->getSuccessor(I);
        if (!BlocksSeen.insert(Dest).second) {
          // Remove duplicated entries from phi nodes.
          for (BasicBlock::iterator Inst = Dest->begin(); ; ++Inst) {
            PHINode *Phi = dyn_cast<PHINode>(Inst);
            if (!Phi)
              break;
            Phi->removeIncomingValue(Br->getParent());
          }
          continue;
        }
        ConstantInt *Val;
        if (LabelNums.count(Dest) == 0) {
          Val = ConstantInt::get(I32, NextNum++);
          LabelNums[Dest] = Val;

          BlockAddress *BA = BlockAddress::get(Func, Dest);
          Value *ValAsPtr = ConstantExpr::getIntToPtr(Val, BA->getType());
          BA->replaceAllUsesWith(ValAsPtr);
          BA->destroyConstant();
        } else {
          Val = LabelNums[Dest];
        }
        Switch->addCase(Val, Br->getSuccessor(I));
      }
      Br->eraseFromParent();
    }
  }

  // If there are any blockaddresses that are never used by an
  // indirectbr, replace them with dummy values.
  SmallVector<Value *, 20> Users(Func->user_begin(), Func->user_end());
  for (auto U : Users) {
    if (BlockAddress *BA = dyn_cast<BlockAddress>(U)) {
      Changed = true;
      Value *DummyVal = ConstantExpr::getIntToPtr(ConstantInt::get(I32, ~0L),
                                                  BA->getType());
      BA->replaceAllUsesWith(DummyVal);
      BA->destroyConstant();
    }
  }
  return Changed;
}

/// Create a clone of the blocks in a loop and connect them together.
/// If CreateRemainderLoop is false, loop structure will not be cloned,
/// otherwise a new loop will be created including all cloned blocks, and the
/// iterator of it switches to count NewIter down to 0.
/// The cloned blocks should be inserted between InsertTop and InsertBot.
/// If loop structure is cloned InsertTop should be new preheader, InsertBot
/// new loop exit.
/// Return the new cloned loop that is created when CreateRemainderLoop is true.
static Loop *
CloneLoopBlocks(Loop *L, Value *NewIter, const bool CreateRemainderLoop,
                const bool UseEpilogRemainder, const bool UnrollRemainder,
                BasicBlock *InsertTop,
                BasicBlock *InsertBot, BasicBlock *Preheader,
                std::vector<BasicBlock *> &NewBlocks, LoopBlocksDFS &LoopBlocks,
                ValueToValueMapTy &VMap, DominatorTree *DT, LoopInfo *LI) {
  StringRef suffix = UseEpilogRemainder ? "epil" : "prol";
  BasicBlock *Header = L->getHeader();
  BasicBlock *Latch = L->getLoopLatch();
  Function *F = Header->getParent();
  LoopBlocksDFS::RPOIterator BlockBegin = LoopBlocks.beginRPO();
  LoopBlocksDFS::RPOIterator BlockEnd = LoopBlocks.endRPO();
  Loop *ParentLoop = L->getParentLoop();
  NewLoopsMap NewLoops;
  NewLoops[ParentLoop] = ParentLoop;
  if (!CreateRemainderLoop)
    NewLoops[L] = ParentLoop;

  // 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, "." + suffix, F);
    NewBlocks.push_back(NewBB);

    // If we're unrolling the outermost loop, there's no remainder loop,
    // and this block isn't in a nested loop, then the new block is not
    // in any loop. Otherwise, add it to loopinfo.
    if (CreateRemainderLoop || LI->getLoopFor(*BB) != L || ParentLoop)
      addClonedBlockToLoopInfo(*BB, NewBB, LI, NewLoops);

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

    if (DT) {
      if (Header == *BB) {
        // The header is dominated by the preheader.
        DT->addNewBlock(NewBB, InsertTop);
      } else {
        // Copy information from original loop to unrolled loop.
        BasicBlock *IDomBB = DT->getNode(*BB)->getIDom()->getBlock();
        DT->addNewBlock(NewBB, cast<BasicBlock>(VMap[IDomBB]));
      }
    }

    if (Latch == *BB) {
      // For the last block, if CreateRemainderLoop is false, create a direct
      // jump to InsertBot. If not, create a loop back to cloned head.
      VMap.erase((*BB)->getTerminator());
      BasicBlock *FirstLoopBB = cast<BasicBlock>(VMap[Header]);
      BranchInst *LatchBR = cast<BranchInst>(NewBB->getTerminator());
      IRBuilder<> Builder(LatchBR);
      if (!CreateRemainderLoop) {
        Builder.CreateBr(InsertBot);
      } else {
        PHINode *NewIdx = PHINode::Create(NewIter->getType(), 2,
                                          suffix + ".iter",
                                          FirstLoopBB->getFirstNonPHI());
        Value *IdxSub =
            Builder.CreateSub(NewIdx, ConstantInt::get(NewIdx->getType(), 1),
                              NewIdx->getName() + ".sub");
        Value *IdxCmp =
            Builder.CreateIsNotNull(IdxSub, NewIdx->getName() + ".cmp");
        Builder.CreateCondBr(IdxCmp, FirstLoopBB, InsertBot);
        NewIdx->addIncoming(NewIter, InsertTop);
        NewIdx->addIncoming(IdxSub, NewBB);
      }
      LatchBR->eraseFromParent();
    }
  }

  // Change the incoming values to the ones defined in the preheader or
  // cloned loop.
  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
    PHINode *NewPHI = cast<PHINode>(VMap[&*I]);
    if (!CreateRemainderLoop) {
      if (UseEpilogRemainder) {
        unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
        NewPHI->setIncomingBlock(idx, InsertTop);
        NewPHI->removeIncomingValue(Latch, false);
      } else {
        VMap[&*I] = NewPHI->getIncomingValueForBlock(Preheader);
        cast<BasicBlock>(VMap[Header])->getInstList().erase(NewPHI);
      }
    } else {
      unsigned idx = NewPHI->getBasicBlockIndex(Preheader);
      NewPHI->setIncomingBlock(idx, InsertTop);
      BasicBlock *NewLatch = cast<BasicBlock>(VMap[Latch]);
//.........这里部分代码省略.........

//.........这里部分代码省略.........
      //
      BasicBlock::iterator It = I;
    
      // Check to see if the second argument is an expression that can
      // be converted to the appropriate size... if so, allow it.
      //
      std::vector<Value*> Indices;
      const Type *ElTy = ConvertibleToGEP(NewVal->getType(), I->getOperand(1),
                                          Indices, TD, &It);
      assert(ElTy != 0 && "GEP Conversion Failure!");
      
      Res = new GetElementPtrInst(NewVal, Indices, Name);
    } else {
      // Convert a getelementptr ulong * %reg123, uint %N
      // to        getelementptr  long * %reg123, uint %N
      // ... where the type must simply stay the same size...
      //
      GetElementPtrInst *GEP = cast<GetElementPtrInst>(I);
      std::vector<Value*> Indices(GEP->idx_begin(), GEP->idx_end());
      Res = new GetElementPtrInst(NewVal, Indices, Name);
    }
#endif
    break;

  case Instruction::PHI: {
    PHINode *OldPN = cast<PHINode>(I);
    PHINode *NewPN = new PHINode(NewTy, Name);
    VMC.ExprMap[I] = NewPN;

    while (OldPN->getNumOperands()) {
      BasicBlock *BB = OldPN->getIncomingBlock(0);
      Value *OldVal = OldPN->getIncomingValue(0);
      ValueHandle OldValHandle(VMC, OldVal);
      OldPN->removeIncomingValue(BB, false);
      Value *V = ConvertExpressionToType(OldVal, NewTy, VMC, TD);
      NewPN->addIncoming(V, BB);
    }
    Res = NewPN;
    break;
  }

  case Instruction::Call: {
    Value *Meth = I->getOperand(0);
    std::vector<Value*> Params(I->op_begin()+1, I->op_end());

    if (Meth == OldVal) {   // Changing the function pointer?
      const PointerType *NewPTy = cast<PointerType>(NewVal->getType());
      const FunctionType *NewTy = cast<FunctionType>(NewPTy->getElementType());

      if (NewTy->getReturnType() == Type::VoidTy)
        Name = "";  // Make sure not to name a void call!

      // Get an iterator to the call instruction so that we can insert casts for
      // operands if need be.  Note that we do not require operands to be
      // convertible, we can insert casts if they are convertible but not
      // compatible.  The reason for this is that we prefer to have resolved
      // functions but casted arguments if possible.
      //
      BasicBlock::iterator It = I;

      // Convert over all of the call operands to their new types... but only
      // convert over the part that is not in the vararg section of the call.
      //
      for (unsigned i = 0; i != NewTy->getNumParams(); ++i)
        if (Params[i]->getType() != NewTy->getParamType(i)) {
          // Create a cast to convert it to the right type, we know that this