C++ PHINode::addIncoming方法代码示例

//.........这里部分代码省略.........
    // exit value and an equality or less than comparison.
    if (InitValue >= ExitValue ||
        NewPred == CmpInst::ICMP_SGT || NewPred == CmpInst::ICMP_SGE)
      return;
    
    uint32_t Range = uint32_t(ExitValue-InitValue);
    if (NewPred == CmpInst::ICMP_SLE) {
      // Normalize SLE -> SLT, check for infinite loop.
      if (++Range == 0) return;  // Range overflows.
    }
    
    unsigned Leftover = Range % uint32_t(IncValue);
    
    // If this is an equality comparison, we require that the strided value
    // exactly land on the exit value, otherwise the IV condition will wrap
    // around and do things the fp IV wouldn't.
    if ((NewPred == CmpInst::ICMP_EQ || NewPred == CmpInst::ICMP_NE) &&
        Leftover != 0)
      return;
    
    // If the stride would wrap around the i32 before exiting, we can't
    // transform the IV.
    if (Leftover != 0 && int32_t(ExitValue+IncValue) < ExitValue)
      return;
    
  } else {
    // If we have a negative stride, we require the init to be greater than the
    // exit value and an equality or greater than comparison.
    if (InitValue >= ExitValue ||
        NewPred == CmpInst::ICMP_SLT || NewPred == CmpInst::ICMP_SLE)
      return;
    
    uint32_t Range = uint32_t(InitValue-ExitValue);
    if (NewPred == CmpInst::ICMP_SGE) {
      // Normalize SGE -> SGT, check for infinite loop.
      if (++Range == 0) return;  // Range overflows.
    }
    
    unsigned Leftover = Range % uint32_t(-IncValue);
    
    // If this is an equality comparison, we require that the strided value
    // exactly land on the exit value, otherwise the IV condition will wrap
    // around and do things the fp IV wouldn't.
    if ((NewPred == CmpInst::ICMP_EQ || NewPred == CmpInst::ICMP_NE) &&
        Leftover != 0)
      return;
    
    // If the stride would wrap around the i32 before exiting, we can't
    // transform the IV.
    if (Leftover != 0 && int32_t(ExitValue+IncValue) > ExitValue)
      return;
  }
  
  const IntegerType *Int32Ty = Type::getInt32Ty(PN->getContext());

  // Insert new integer induction variable.
  PHINode *NewPHI = PHINode::Create(Int32Ty, PN->getName()+".int", PN);
  NewPHI->addIncoming(ConstantInt::get(Int32Ty, InitValue),
                      PN->getIncomingBlock(IncomingEdge));

  Value *NewAdd =
    BinaryOperator::CreateAdd(NewPHI, ConstantInt::get(Int32Ty, IncValue),
                              Incr->getName()+".int", Incr);
  NewPHI->addIncoming(NewAdd, PN->getIncomingBlock(BackEdge));

  ICmpInst *NewCompare = new ICmpInst(TheBr, NewPred, NewAdd,
                                      ConstantInt::get(Int32Ty, ExitValue),
                                      Compare->getName());

  // In the following deletions, PN may become dead and may be deleted.
  // Use a WeakVH to observe whether this happens.
  WeakVH WeakPH = PN;

  // Delete the old floating point exit comparison.  The branch starts using the
  // new comparison.
  NewCompare->takeName(Compare);
  Compare->replaceAllUsesWith(NewCompare);
  RecursivelyDeleteTriviallyDeadInstructions(Compare);

  // Delete the old floating point increment.
  Incr->replaceAllUsesWith(UndefValue::get(Incr->getType()));
  RecursivelyDeleteTriviallyDeadInstructions(Incr);

  // If the FP induction variable still has uses, this is because something else
  // in the loop uses its value.  In order to canonicalize the induction
  // variable, we chose to eliminate the IV and rewrite it in terms of an
  // int->fp cast.
  //
  // We give preference to sitofp over uitofp because it is faster on most
  // platforms.
  if (WeakPH) {
    Value *Conv = new SIToFPInst(NewPHI, PN->getType(), "indvar.conv",
                                 PN->getParent()->getFirstNonPHI());
    PN->replaceAllUsesWith(Conv);
    RecursivelyDeleteTriviallyDeadInstructions(PN);
  }

  // Add a new IVUsers entry for the newly-created integer PHI.
  IU->AddUsersIfInteresting(NewPHI);
}

// UnifyAllExitNodes - Unify all exit nodes of the CFG by creating a new
// BasicBlock, and converting all returns to unconditional branches to this
// new basic block.  The singular exit node is returned.
//
// If there are no return stmts in the Function, a null pointer is returned.
//
bool UnifyFunctionExitNodes::runOnFunction(Function &F) {
  // Loop over all of the blocks in a function, tracking all of the blocks that
  // return.
  //
  std::vector<BasicBlock*> ReturningBlocks;
  std::vector<BasicBlock*> UnreachableBlocks;
  for(Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
    if (isa<ReturnInst>(I->getTerminator()))
      ReturningBlocks.push_back(I);
    else if (isa<UnreachableInst>(I->getTerminator()))
      UnreachableBlocks.push_back(I);

  // Then unreachable blocks.
  if (UnreachableBlocks.empty()) {
    UnreachableBlock = nullptr;
  } else if (UnreachableBlocks.size() == 1) {
    UnreachableBlock = UnreachableBlocks.front();
  } else {
    UnreachableBlock = BasicBlock::Create(F.getContext(),
                                          "UnifiedUnreachableBlock", &F);
    new UnreachableInst(F.getContext(), UnreachableBlock);

    for (std::vector<BasicBlock*>::iterator I = UnreachableBlocks.begin(),
           E = UnreachableBlocks.end(); I != E; ++I) {
      BasicBlock *BB = *I;
      BB->getInstList().pop_back();  // Remove the unreachable inst.
      BranchInst::Create(UnreachableBlock, BB);
    }
  }

  // Now handle return blocks.
  if (ReturningBlocks.empty()) {
    ReturnBlock = nullptr;
    return false;                          // No blocks return
  } else if (ReturningBlocks.size() == 1) {
    ReturnBlock = ReturningBlocks.front(); // Already has a single return block
    return false;
  }

  // Otherwise, we need to insert a new basic block into the function, add a PHI
  // nodes (if the function returns values), and convert all of the return
  // instructions into unconditional branches.
  //
  BasicBlock *NewRetBlock = BasicBlock::Create(F.getContext(),
                                               "UnifiedReturnBlock", &F);

  PHINode *PN = nullptr;
  if (F.getReturnType()->isVoidTy()) {
    ReturnInst::Create(F.getContext(), nullptr, NewRetBlock);
  } else {
    // If the function doesn't return void... add a PHI node to the block...
    PN = PHINode::Create(F.getReturnType(), ReturningBlocks.size(),
                         "UnifiedRetVal");
    NewRetBlock->getInstList().push_back(PN);
    ReturnInst::Create(F.getContext(), PN, NewRetBlock);
  }

  // Loop over all of the blocks, replacing the return instruction with an
  // unconditional branch.
  //
  for (std::vector<BasicBlock*>::iterator I = ReturningBlocks.begin(),
         E = ReturningBlocks.end(); I != E; ++I) {
    BasicBlock *BB = *I;

    // Add an incoming element to the PHI node for every return instruction that
    // is merging into this new block...
    if (PN)
      PN->addIncoming(BB->getTerminator()->getOperand(0), BB);

    BB->getInstList().pop_back();  // Remove the return insn
    BranchInst::Create(NewRetBlock, BB);
  }
  ReturnBlock = NewRetBlock;
  return true;
}

//.........这里部分代码省略.........

      // Don't forward functions which are external in the test module too.
      if (TestFn && !TestFn->isDeclaration()) {
        // 1. Add a string constant with its name to the global file
        Constant *InitArray = ConstantArray::get(F->getContext(), F->getName());
        GlobalVariable *funcName =
          new GlobalVariable(*Safe, InitArray->getType(), true /*isConstant*/,
                             GlobalValue::InternalLinkage, InitArray,
                             F->getName() + "_name");

        // 2. Use `GetElementPtr *funcName, 0, 0' to convert the string to an
        // sbyte* so it matches the signature of the resolver function.

        // GetElementPtr *funcName, ulong 0, ulong 0
        std::vector<Constant*> GEPargs(2,
                     Constant::getNullValue(Type::getInt32Ty(F->getContext())));
        Value *GEP =
                ConstantExpr::getGetElementPtr(funcName, &GEPargs[0], 2);
        std::vector<Value*> ResolverArgs;
        ResolverArgs.push_back(GEP);

        // Rewrite uses of F in global initializers, etc. to uses of a wrapper
        // function that dynamically resolves the calls to F via our JIT API
        if (!F->use_empty()) {
          // Create a new global to hold the cached function pointer.
          Constant *NullPtr = ConstantPointerNull::get(F->getType());
          GlobalVariable *Cache =
            new GlobalVariable(*F->getParent(), F->getType(), 
                               false, GlobalValue::InternalLinkage,
                               NullPtr,F->getName()+".fpcache");

          // Construct a new stub function that will re-route calls to F
          const FunctionType *FuncTy = F->getFunctionType();
          Function *FuncWrapper = Function::Create(FuncTy,
                                                   GlobalValue::InternalLinkage,
                                                   F->getName() + "_wrapper",
                                                   F->getParent());
          BasicBlock *EntryBB  = BasicBlock::Create(F->getContext(),
                                                    "entry", FuncWrapper);
          BasicBlock *DoCallBB = BasicBlock::Create(F->getContext(),
                                                    "usecache", FuncWrapper);
          BasicBlock *LookupBB = BasicBlock::Create(F->getContext(),
                                                    "lookupfp", FuncWrapper);

          // Check to see if we already looked up the value.
          Value *CachedVal = new LoadInst(Cache, "fpcache", EntryBB);
          Value *IsNull = new ICmpInst(*EntryBB, ICmpInst::ICMP_EQ, CachedVal,
                                       NullPtr, "isNull");
          BranchInst::Create(LookupBB, DoCallBB, IsNull, EntryBB);

          // Resolve the call to function F via the JIT API:
          //
          // call resolver(GetElementPtr...)
          CallInst *Resolver =
            CallInst::Create(resolverFunc, ResolverArgs.begin(),
                             ResolverArgs.end(), "resolver", LookupBB);

          // Cast the result from the resolver to correctly-typed function.
          CastInst *CastedResolver =
            new BitCastInst(Resolver,
                            PointerType::getUnqual(F->getFunctionType()),
                            "resolverCast", LookupBB);

          // Save the value in our cache.
          new StoreInst(CastedResolver, Cache, LookupBB);
          BranchInst::Create(DoCallBB, LookupBB);

          PHINode *FuncPtr = PHINode::Create(NullPtr->getType(),
                                             "fp", DoCallBB);
          FuncPtr->addIncoming(CastedResolver, LookupBB);
          FuncPtr->addIncoming(CachedVal, EntryBB);

          // Save the argument list.
          std::vector<Value*> Args;
          for (Function::arg_iterator i = FuncWrapper->arg_begin(),
                 e = FuncWrapper->arg_end(); i != e; ++i)
            Args.push_back(i);

          // Pass on the arguments to the real function, return its result
          if (F->getReturnType() == Type::getVoidTy(F->getContext())) {
            CallInst::Create(FuncPtr, Args.begin(), Args.end(), "", DoCallBB);
            ReturnInst::Create(F->getContext(), DoCallBB);
          } else {
            CallInst *Call = CallInst::Create(FuncPtr, Args.begin(), Args.end(),
                                              "retval", DoCallBB);
            ReturnInst::Create(F->getContext(),Call, DoCallBB);
          }

          // Use the wrapper function instead of the old function
          F->replaceAllUsesWith(FuncWrapper);
        }
      }
    }
  }

  if (verifyModule(*Test) || verifyModule(*Safe)) {
    errs() << "Bugpoint has a bug, which corrupted a module!!\n";
    abort();
  }
}

Value *SSAUpdater::GetValueInMiddleOfBlock(BasicBlock *BB) {
  // If there is no definition of the renamed variable in this block, just use
  // GetValueAtEndOfBlock to do our work.
  if (!HasValueForBlock(BB))
    return GetValueAtEndOfBlock(BB);

  // Otherwise, we have the hard case.  Get the live-in values for each
  // predecessor.
  SmallVector<std::pair<BasicBlock*, Value*>, 8> PredValues;
  Value *SingularValue = nullptr;

  // We can get our predecessor info by walking the pred_iterator list, but it
  // is relatively slow.  If we already have PHI nodes in this block, walk one
  // of them to get the predecessor list instead.
  if (PHINode *SomePhi = dyn_cast<PHINode>(BB->begin())) {
    for (unsigned i = 0, e = SomePhi->getNumIncomingValues(); i != e; ++i) {
      BasicBlock *PredBB = SomePhi->getIncomingBlock(i);
      Value *PredVal = GetValueAtEndOfBlock(PredBB);
      PredValues.push_back(std::make_pair(PredBB, PredVal));

      // Compute SingularValue.
      if (i == 0)
        SingularValue = PredVal;
      else if (PredVal != SingularValue)
        SingularValue = nullptr;
    }
  } else {
    bool isFirstPred = true;
    for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI) {
      BasicBlock *PredBB = *PI;
      Value *PredVal = GetValueAtEndOfBlock(PredBB);
      PredValues.push_back(std::make_pair(PredBB, PredVal));

      // Compute SingularValue.
      if (isFirstPred) {
        SingularValue = PredVal;
        isFirstPred = false;
      } else if (PredVal != SingularValue)
        SingularValue = nullptr;
    }
  }

  // If there are no predecessors, just return undef.
  if (PredValues.empty())
    return UndefValue::get(ProtoType);

  // Otherwise, if all the merged values are the same, just use it.
  if (SingularValue)
    return SingularValue;

  // Otherwise, we do need a PHI: check to see if we already have one available
  // in this block that produces the right value.
  if (isa<PHINode>(BB->begin())) {
    SmallDenseMap<BasicBlock*, Value*, 8> ValueMapping(PredValues.begin(),
                                                       PredValues.end());
    PHINode *SomePHI;
    for (BasicBlock::iterator It = BB->begin();
         (SomePHI = dyn_cast<PHINode>(It)); ++It) {
      if (IsEquivalentPHI(SomePHI, ValueMapping))
        return SomePHI;
    }
  }

  // Ok, we have no way out, insert a new one now.
  PHINode *InsertedPHI = PHINode::Create(ProtoType, PredValues.size(),
                                         ProtoName, &BB->front());

  // Fill in all the predecessors of the PHI.
  for (unsigned i = 0, e = PredValues.size(); i != e; ++i)
    InsertedPHI->addIncoming(PredValues[i].second, PredValues[i].first);

  // See if the PHI node can be merged to a single value.  This can happen in
  // loop cases when we get a PHI of itself and one other value.
  if (Value *V =
          SimplifyInstruction(InsertedPHI, BB->getModule()->getDataLayout())) {
    InsertedPHI->eraseFromParent();
    return V;
  }

  // Set the DebugLoc of the inserted PHI, if available.
  DebugLoc DL;
  if (const Instruction *I = BB->getFirstNonPHI())
      DL = I->getDebugLoc();
  InsertedPHI->setDebugLoc(DL);

  // If the client wants to know about all new instructions, tell it.
  if (InsertedPHIs) InsertedPHIs->push_back(InsertedPHI);

  DEBUG(dbgs() << "  Inserted PHI: " << *InsertedPHI << "\n");
  return InsertedPHI;
}

/// Create a clone of the blocks in a loop and connect them together.
/// If UnrollProlog is true, 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.
///
static void CloneLoopBlocks(Loop *L, Value *NewIter, const bool UnrollProlog,
                            BasicBlock *InsertTop, BasicBlock *InsertBot,
                            std::vector<BasicBlock *> &NewBlocks,
                            LoopBlocksDFS &LoopBlocks, ValueToValueMapTy &VMap,
                            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();
    Loop *NewLoop = 0;
    Loop *ParentLoop = L->getParentLoop();
    if (!UnrollProlog) {
        NewLoop = new Loop();
        if (ParentLoop)
            ParentLoop->addChildLoop(NewLoop);
        else
            LI->addTopLevelLoop(NewLoop);
    }

    // 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, ".prol", F);
        NewBlocks.push_back(NewBB);

        if (NewLoop)
            NewLoop->addBasicBlockToLoop(NewBB, *LI);
        else if (ParentLoop)
            ParentLoop->addBasicBlockToLoop(NewBB, *LI);

        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 (Latch == *BB) {
            // For the last block, if UnrollProlog is true, 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 (UnrollProlog) {
                Builder.CreateBr(InsertBot);
            } else {
                PHINode *NewIdx = PHINode::Create(NewIter->getType(), 2, "prol.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 (UnrollProlog) {
            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]);
            idx = NewPHI->getBasicBlockIndex(Latch);
            Value *InVal = NewPHI->getIncomingValue(idx);
            NewPHI->setIncomingBlock(idx, NewLatch);
            if (VMap[InVal])
                NewPHI->setIncomingValue(idx, VMap[InVal]);
        }
    }
    if (NewLoop) {
        // Add unroll disable metadata to disable future unrolling for this loop.
        SmallVector<Metadata *, 4> MDs;
        // Reserve first location for self reference to the LoopID metadata node.
        MDs.push_back(nullptr);
        MDNode *LoopID = NewLoop->getLoopID();
        if (LoopID) {
            // First remove any existing loop unrolling metadata.
            for (unsigned i = 1, ie = LoopID->getNumOperands(); i < ie; ++i) {
                bool IsUnrollMetadata = false;
                MDNode *MD = dyn_cast<MDNode>(LoopID->getOperand(i));
                if (MD) {
                    const MDString *S = dyn_cast<MDString>(MD->getOperand(0));
//.........这里部分代码省略.........

/// EliminateMostlyEmptyBlock - Eliminate a basic block that have only phi's and
/// an unconditional branch in it.
void CodeGenPrepare::EliminateMostlyEmptyBlock(BasicBlock *BB) {
  BranchInst *BI = cast<BranchInst>(BB->getTerminator());
  BasicBlock *DestBB = BI->getSuccessor(0);

  DEBUG(dbgs() << "MERGING MOSTLY EMPTY BLOCKS - BEFORE:\n" << *BB << *DestBB);

  // If the destination block has a single pred, then this is a trivial edge,
  // just collapse it.
  if (BasicBlock *SinglePred = DestBB->getSinglePredecessor()) {
    if (SinglePred != DestBB) {
      // Remember if SinglePred was the entry block of the function.  If so, we
      // will need to move BB back to the entry position.
      bool isEntry = SinglePred == &SinglePred->getParent()->getEntryBlock();
      MergeBasicBlockIntoOnlyPred(DestBB, this);

      if (isEntry && BB != &BB->getParent()->getEntryBlock())
        BB->moveBefore(&BB->getParent()->getEntryBlock());
      
      DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
      return;
    }
  }

  // Otherwise, we have multiple predecessors of BB.  Update the PHIs in DestBB
  // to handle the new incoming edges it is about to have.
  PHINode *PN;
  for (BasicBlock::iterator BBI = DestBB->begin();
       (PN = dyn_cast<PHINode>(BBI)); ++BBI) {
    // Remove the incoming value for BB, and remember it.
    Value *InVal = PN->removeIncomingValue(BB, false);

    // Two options: either the InVal is a phi node defined in BB or it is some
    // value that dominates BB.
    PHINode *InValPhi = dyn_cast<PHINode>(InVal);
    if (InValPhi && InValPhi->getParent() == BB) {
      // Add all of the input values of the input PHI as inputs of this phi.
      for (unsigned i = 0, e = InValPhi->getNumIncomingValues(); i != e; ++i)
        PN->addIncoming(InValPhi->getIncomingValue(i),
                        InValPhi->getIncomingBlock(i));
    } else {
      // Otherwise, add one instance of the dominating value for each edge that
      // we will be adding.
      if (PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
        for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
          PN->addIncoming(InVal, BBPN->getIncomingBlock(i));
      } else {
        for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
          PN->addIncoming(InVal, *PI);
      }
    }
  }

  // The PHIs are now updated, change everything that refers to BB to use
  // DestBB and remove BB.
  BB->replaceAllUsesWith(DestBB);
  if (PFI) {
    PFI->replaceAllUses(BB, DestBB);
    PFI->removeEdge(ProfileInfo::getEdge(BB, DestBB));
  }
  BB->eraseFromParent();
  ++NumElim;

  DEBUG(dbgs() << "AFTER:\n" << *DestBB << "\n\n\n");
}

bool WebAssemblyLowerEmscriptenEHSjLj::runSjLjOnFunction(Function &F) {
  Module &M = *F.getParent();
  LLVMContext &C = F.getContext();
  IRBuilder<> IRB(C);
  SmallVector<Instruction *, 64> ToErase;
  // Vector of %setjmpTable values
  std::vector<Instruction *> SetjmpTableInsts;
  // Vector of %setjmpTableSize values
  std::vector<Instruction *> SetjmpTableSizeInsts;

  // Setjmp preparation

  // This instruction effectively means %setjmpTableSize = 4.
  // We create this as an instruction intentionally, and we don't want to fold
  // this instruction to a constant 4, because this value will be used in
  // SSAUpdater.AddAvailableValue(...) later.
  BasicBlock &EntryBB = F.getEntryBlock();
  BinaryOperator *SetjmpTableSize = BinaryOperator::Create(
      Instruction::Add, IRB.getInt32(4), IRB.getInt32(0), "setjmpTableSize",
      &*EntryBB.getFirstInsertionPt());
  // setjmpTable = (int *) malloc(40);
  Instruction *SetjmpTable = CallInst::CreateMalloc(
      SetjmpTableSize, IRB.getInt32Ty(), IRB.getInt32Ty(), IRB.getInt32(40),
      nullptr, nullptr, "setjmpTable");
  // setjmpTable[0] = 0;
  IRB.SetInsertPoint(SetjmpTableSize);
  IRB.CreateStore(IRB.getInt32(0), SetjmpTable);
  SetjmpTableInsts.push_back(SetjmpTable);
  SetjmpTableSizeInsts.push_back(SetjmpTableSize);

  // Setjmp transformation
  std::vector<PHINode *> SetjmpRetPHIs;
  Function *SetjmpF = M.getFunction("setjmp");
  for (User *U : SetjmpF->users()) {
    auto *CI = dyn_cast<CallInst>(U);
    if (!CI)
      report_fatal_error("Does not support indirect calls to setjmp");

    BasicBlock *BB = CI->getParent();
    if (BB->getParent() != &F) // in other function
      continue;

    // The tail is everything right after the call, and will be reached once
    // when setjmp is called, and later when longjmp returns to the setjmp
    BasicBlock *Tail = SplitBlock(BB, CI->getNextNode());
    // Add a phi to the tail, which will be the output of setjmp, which
    // indicates if this is the first call or a longjmp back. The phi directly
    // uses the right value based on where we arrive from
    IRB.SetInsertPoint(Tail->getFirstNonPHI());
    PHINode *SetjmpRet = IRB.CreatePHI(IRB.getInt32Ty(), 2, "setjmp.ret");

    // setjmp initial call returns 0
    SetjmpRet->addIncoming(IRB.getInt32(0), BB);
    // The proper output is now this, not the setjmp call itself
    CI->replaceAllUsesWith(SetjmpRet);
    // longjmp returns to the setjmp will add themselves to this phi
    SetjmpRetPHIs.push_back(SetjmpRet);

    // Fix call target
    // Our index in the function is our place in the array + 1 to avoid index
    // 0, because index 0 means the longjmp is not ours to handle.
    IRB.SetInsertPoint(CI);
    Value *Args[] = {CI->getArgOperand(0), IRB.getInt32(SetjmpRetPHIs.size()),
                     SetjmpTable, SetjmpTableSize};
    Instruction *NewSetjmpTable =
        IRB.CreateCall(SaveSetjmpF, Args, "setjmpTable");
    Instruction *NewSetjmpTableSize =
        IRB.CreateLoad(TempRet0GV, "setjmpTableSize");
    SetjmpTableInsts.push_back(NewSetjmpTable);
    SetjmpTableSizeInsts.push_back(NewSetjmpTableSize);
    ToErase.push_back(CI);
  }

  // Update each call that can longjmp so it can return to a setjmp where
  // relevant.

  // Because we are creating new BBs while processing and don't want to make
  // all these newly created BBs candidates again for longjmp processing, we
  // first make the vector of candidate BBs.
  std::vector<BasicBlock *> BBs;
  for (BasicBlock &BB : F)
    BBs.push_back(&BB);

  // BBs.size() will change within the loop, so we query it every time
  for (unsigned i = 0; i < BBs.size(); i++) {
    BasicBlock *BB = BBs[i];
    for (Instruction &I : *BB) {
      assert(!isa<InvokeInst>(&I));
      auto *CI = dyn_cast<CallInst>(&I);
      if (!CI)
        continue;

      const Value *Callee = CI->getCalledValue();
      if (!canLongjmp(M, Callee))
        continue;

      Value *Threw = nullptr;
      BasicBlock *Tail;
      if (Callee->getName().startswith(InvokePrefix)) {
        // If invoke wrapper has already been generated for this call in
//.........这里部分代码省略.........

//.........这里部分代码省略.........
         "splitBasicBlock broken!");
  Br->setOperand(0, FirstNewBlock);


  // Now that the function is correct, make it a little bit nicer.  In
  // particular, move the basic blocks inserted from the end of the function
  // into the space made by splitting the source basic block.
  Caller->getBasicBlockList().splice(AfterCallBB, Caller->getBasicBlockList(),
                                     FirstNewBlock, Caller->end());

  // Handle all of the return instructions that we just cloned in, and eliminate
  // any users of the original call/invoke instruction.
  Type *RTy = CalledFunc->getReturnType();

  PHINode *PHI = 0;
  if (Returns.size() > 1) {
    // The PHI node should go at the front of the new basic block to merge all
    // possible incoming values.
    if (!TheCall->use_empty()) {
      PHI = PHINode::Create(RTy, Returns.size(), TheCall->getName(),
                            AfterCallBB->begin());
      // Anything that used the result of the function call should now use the
      // PHI node as their operand.
      TheCall->replaceAllUsesWith(PHI);
    }

    // Loop over all of the return instructions adding entries to the PHI node
    // as appropriate.
    if (PHI) {
      for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
        ReturnInst *RI = Returns[i];
        assert(RI->getReturnValue()->getType() == PHI->getType() &&
               "Ret value not consistent in function!");
        PHI->addIncoming(RI->getReturnValue(), RI->getParent());
      }
    }


    // Add a branch to the merge points and remove return instructions.
    for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
      ReturnInst *RI = Returns[i];
      BranchInst::Create(AfterCallBB, RI);
      RI->eraseFromParent();
    }
  } else if (!Returns.empty()) {
    // Otherwise, if there is exactly one return value, just replace anything
    // using the return value of the call with the computed value.
    if (!TheCall->use_empty()) {
      if (TheCall == Returns[0]->getReturnValue())
        TheCall->replaceAllUsesWith(UndefValue::get(TheCall->getType()));
      else
        TheCall->replaceAllUsesWith(Returns[0]->getReturnValue());
    }

    // Update PHI nodes that use the ReturnBB to use the AfterCallBB.
    BasicBlock *ReturnBB = Returns[0]->getParent();
    ReturnBB->replaceAllUsesWith(AfterCallBB);

    // Splice the code from the return block into the block that it will return
    // to, which contains the code that was after the call.
    AfterCallBB->getInstList().splice(AfterCallBB->begin(),
                                      ReturnBB->getInstList());

    // Delete the return instruction now and empty ReturnBB now.
    Returns[0]->eraseFromParent();
    ReturnBB->eraseFromParent();

/// UnswitchNontrivialCondition - We determined that the loop is profitable
/// to unswitch when LIC equal Val.  Split it into loop versions and test the
/// condition outside of either loop.  Return the loops created as Out1/Out2.
void LoopUnswitch::UnswitchNontrivialCondition(Value *LIC, Constant *Val,
                                               Loop *L) {
  Function *F = loopHeader->getParent();
  DEBUG(dbgs() << "loop-unswitch: Unswitching loop %"
        << loopHeader->getName() << " [" << L->getBlocks().size()
        << " blocks] in Function " << F->getName()
        << " when '" << *Val << "' == " << *LIC << "\n");

  if (ScalarEvolution *SE = getAnalysisIfAvailable<ScalarEvolution>())
    SE->forgetLoop(L);

  LoopBlocks.clear();
  NewBlocks.clear();

  // First step, split the preheader and exit blocks, and add these blocks to
  // the LoopBlocks list.
  BasicBlock *NewPreheader = SplitEdge(loopPreheader, loopHeader, this);
  LoopBlocks.push_back(NewPreheader);

  // We want the loop to come after the preheader, but before the exit blocks.
  LoopBlocks.insert(LoopBlocks.end(), L->block_begin(), L->block_end());

  SmallVector<BasicBlock*, 8> ExitBlocks;
  L->getUniqueExitBlocks(ExitBlocks);

  // Split all of the edges from inside the loop to their exit blocks.  Update
  // the appropriate Phi nodes as we do so.
  SplitExitEdges(L, ExitBlocks);

  // The exit blocks may have been changed due to edge splitting, recompute.
  ExitBlocks.clear();
  L->getUniqueExitBlocks(ExitBlocks);

  // Add exit blocks to the loop blocks.
  LoopBlocks.insert(LoopBlocks.end(), ExitBlocks.begin(), ExitBlocks.end());

  // Next step, clone all of the basic blocks that make up the loop (including
  // the loop preheader and exit blocks), keeping track of the mapping between
  // the instructions and blocks.
  NewBlocks.reserve(LoopBlocks.size());
  ValueToValueMapTy VMap;
  for (unsigned i = 0, e = LoopBlocks.size(); i != e; ++i) {
    BasicBlock *NewBB = CloneBasicBlock(LoopBlocks[i], VMap, ".us", F);

    NewBlocks.push_back(NewBB);
    VMap[LoopBlocks[i]] = NewBB;  // Keep the BB mapping.
    LPM->cloneBasicBlockSimpleAnalysis(LoopBlocks[i], NewBB, L);
  }

  // Splice the newly inserted blocks into the function right before the
  // original preheader.
  F->getBasicBlockList().splice(NewPreheader, F->getBasicBlockList(),
                                NewBlocks[0], F->end());

  // Now we create the new Loop object for the versioned loop.
  Loop *NewLoop = CloneLoop(L, L->getParentLoop(), VMap, LI, LPM);

  // Recalculate unswitching quota, inherit simplified switches info for NewBB,
  // Probably clone more loop-unswitch related loop properties.
  BranchesInfo.cloneData(NewLoop, L, VMap);

  Loop *ParentLoop = L->getParentLoop();
  if (ParentLoop) {
    // Make sure to add the cloned preheader and exit blocks to the parent loop
    // as well.
    ParentLoop->addBasicBlockToLoop(NewBlocks[0], LI->getBase());
  }

  for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
    BasicBlock *NewExit = cast<BasicBlock>(VMap[ExitBlocks[i]]);
    // The new exit block should be in the same loop as the old one.
    if (Loop *ExitBBLoop = LI->getLoopFor(ExitBlocks[i]))
      ExitBBLoop->addBasicBlockToLoop(NewExit, LI->getBase());

    assert(NewExit->getTerminator()->getNumSuccessors() == 1 &&
           "Exit block should have been split to have one successor!");
    BasicBlock *ExitSucc = NewExit->getTerminator()->getSuccessor(0);

    // If the successor of the exit block had PHI nodes, add an entry for
    // NewExit.
    PHINode *PN;
    for (BasicBlock::iterator I = ExitSucc->begin(); isa<PHINode>(I); ++I) {
      PN = cast<PHINode>(I);
      Value *V = PN->getIncomingValueForBlock(ExitBlocks[i]);
      ValueToValueMapTy::iterator It = VMap.find(V);
      if (It != VMap.end()) V = It->second;
      PN->addIncoming(V, NewExit);
    }

    if (LandingPadInst *LPad = NewExit->getLandingPadInst()) {
      PN = PHINode::Create(LPad->getType(), 0, "",
                           ExitSucc->getFirstInsertionPt());

      for (pred_iterator I = pred_begin(ExitSucc), E = pred_end(ExitSucc);
           I != E; ++I) {
        BasicBlock *BB = *I;
        LandingPadInst *LPI = BB->getLandingPadInst();
//.........这里部分代码省略.........

bool TailCallElim::EliminateRecursiveTailCall(CallInst *CI, ReturnInst *Ret,
                                       BasicBlock *&OldEntry,
                                       bool &TailCallsAreMarkedTail,
                                       SmallVectorImpl<PHINode *> &ArgumentPHIs,
                                       bool CannotTailCallElimCallsMarkedTail) {
  // If we are introducing accumulator recursion to eliminate operations after
  // the call instruction that are both associative and commutative, the initial
  // value for the accumulator is placed in this variable.  If this value is set
  // then we actually perform accumulator recursion elimination instead of
  // simple tail recursion elimination.  If the operation is an LLVM instruction
  // (eg: "add") then it is recorded in AccumulatorRecursionInstr.  If not, then
  // we are handling the case when the return instruction returns a constant C
  // which is different to the constant returned by other return instructions
  // (which is recorded in AccumulatorRecursionEliminationInitVal).  This is a
  // special case of accumulator recursion, the operation being "return C".
  Value *AccumulatorRecursionEliminationInitVal = 0;
  Instruction *AccumulatorRecursionInstr = 0;

  // Ok, we found a potential tail call.  We can currently only transform the
  // tail call if all of the instructions between the call and the return are
  // movable to above the call itself, leaving the call next to the return.
  // Check that this is the case now.
  BasicBlock::iterator BBI = CI;
  for (++BBI; &*BBI != Ret; ++BBI) {
    if (CanMoveAboveCall(BBI, CI)) continue;

    // If we can't move the instruction above the call, it might be because it
    // is an associative and commutative operation that could be transformed
    // using accumulator recursion elimination.  Check to see if this is the
    // case, and if so, remember the initial accumulator value for later.
    if ((AccumulatorRecursionEliminationInitVal =
                           CanTransformAccumulatorRecursion(BBI, CI))) {
      // Yes, this is accumulator recursion.  Remember which instruction
      // accumulates.
      AccumulatorRecursionInstr = BBI;
    } else {
      return false;   // Otherwise, we cannot eliminate the tail recursion!
    }
  }

  // We can only transform call/return pairs that either ignore the return value
  // of the call and return void, ignore the value of the call and return a
  // constant, return the value returned by the tail call, or that are being
  // accumulator recursion variable eliminated.
  if (Ret->getNumOperands() == 1 && Ret->getReturnValue() != CI &&
      !isa<UndefValue>(Ret->getReturnValue()) &&
      AccumulatorRecursionEliminationInitVal == 0 &&
      !getCommonReturnValue(0, CI)) {
    // One case remains that we are able to handle: the current return
    // instruction returns a constant, and all other return instructions
    // return a different constant.
    if (!isDynamicConstant(Ret->getReturnValue(), CI, Ret))
      return false; // Current return instruction does not return a constant.
    // Check that all other return instructions return a common constant.  If
    // so, record it in AccumulatorRecursionEliminationInitVal.
    AccumulatorRecursionEliminationInitVal = getCommonReturnValue(Ret, CI);
    if (!AccumulatorRecursionEliminationInitVal)
      return false;
  }

  BasicBlock *BB = Ret->getParent();
  Function *F = BB->getParent();

  // OK! We can transform this tail call.  If this is the first one found,
  // create the new entry block, allowing us to branch back to the old entry.
  if (OldEntry == 0) {
    OldEntry = &F->getEntryBlock();
    BasicBlock *NewEntry = BasicBlock::Create(F->getContext(), "", F, OldEntry);
    NewEntry->takeName(OldEntry);
    OldEntry->setName("tailrecurse");
    BranchInst::Create(OldEntry, NewEntry);

    // If this tail call is marked 'tail' and if there are any allocas in the
    // entry block, move them up to the new entry block.
    TailCallsAreMarkedTail = CI->isTailCall();
    if (TailCallsAreMarkedTail)
      // Move all fixed sized allocas from OldEntry to NewEntry.
      for (BasicBlock::iterator OEBI = OldEntry->begin(), E = OldEntry->end(),
             NEBI = NewEntry->begin(); OEBI != E; )
        if (AllocaInst *AI = dyn_cast<AllocaInst>(OEBI++))
          if (isa<ConstantInt>(AI->getArraySize()))
            AI->moveBefore(NEBI);

    // Now that we have created a new block, which jumps to the entry
    // block, insert a PHI node for each argument of the function.
    // For now, we initialize each PHI to only have the real arguments
    // which are passed in.
    Instruction *InsertPos = OldEntry->begin();
    for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
         I != E; ++I) {
      PHINode *PN = PHINode::Create(I->getType(), 2,
                                    I->getName() + ".tr", InsertPos);
      I->replaceAllUsesWith(PN); // Everyone use the PHI node now!
      PN->addIncoming(I, NewEntry);
      ArgumentPHIs.push_back(PN);
    }
  }

  // If this function has self recursive calls in the tail position where some
  // are marked tail and some are not, only transform one flavor or another.  We
//.........这里部分代码省略.........

//.........这里部分代码省略.........
  if (++PI != pred_end(DestBB))
    return false;

  // Bail out if all the relevant blocks aren't distinct (this can happen,
  // for example, if SI is in an infinite loop)
  if (StoreBB == DestBB || OtherBB == DestBB)
    return false;

  // Verify that the other block ends in a branch and is not otherwise empty.
  BasicBlock::iterator BBI(OtherBB->getTerminator());
  BranchInst *OtherBr = dyn_cast<BranchInst>(BBI);
  if (!OtherBr || BBI == OtherBB->begin())
    return false;

  // If the other block ends in an unconditional branch, check for the 'if then
  // else' case.  there is an instruction before the branch.
  StoreInst *OtherStore = nullptr;
  if (OtherBr->isUnconditional()) {
    --BBI;
    // Skip over debugging info.
    while (isa<DbgInfoIntrinsic>(BBI) ||
           (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) {
      if (BBI==OtherBB->begin())
        return false;
      --BBI;
    }
    // If this isn't a store, isn't a store to the same location, or is not the
    // right kind of store, bail out.
    OtherStore = dyn_cast<StoreInst>(BBI);
    if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1) ||
        !SI.isSameOperationAs(OtherStore))
      return false;
  } else {
    // Otherwise, the other block ended with a conditional branch. If one of the
    // destinations is StoreBB, then we have the if/then case.
    if (OtherBr->getSuccessor(0) != StoreBB &&
        OtherBr->getSuccessor(1) != StoreBB)
      return false;

    // Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an
    // if/then triangle.  See if there is a store to the same ptr as SI that
    // lives in OtherBB.
    for (;; --BBI) {
      // Check to see if we find the matching store.
      if ((OtherStore = dyn_cast<StoreInst>(BBI))) {
        if (OtherStore->getOperand(1) != SI.getOperand(1) ||
            !SI.isSameOperationAs(OtherStore))
          return false;
        break;
      }
      // If we find something that may be using or overwriting the stored
      // value, or if we run out of instructions, we can't do the xform.
      if (BBI->mayReadFromMemory() || BBI->mayWriteToMemory() ||
          BBI == OtherBB->begin())
        return false;
    }

    // In order to eliminate the store in OtherBr, we have to
    // make sure nothing reads or overwrites the stored value in
    // StoreBB.
    for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) {
      // FIXME: This should really be AA driven.
      if (I->mayReadFromMemory() || I->mayWriteToMemory())
        return false;
    }
  }

  // Insert a PHI node now if we need it.
  Value *MergedVal = OtherStore->getOperand(0);
  if (MergedVal != SI.getOperand(0)) {
    PHINode *PN = PHINode::Create(MergedVal->getType(), 2, "storemerge");
    PN->addIncoming(SI.getOperand(0), SI.getParent());
    PN->addIncoming(OtherStore->getOperand(0), OtherBB);
    MergedVal = InsertNewInstBefore(PN, DestBB->front());
  }

  // Advance to a place where it is safe to insert the new store and
  // insert it.
  BBI = DestBB->getFirstInsertionPt();
  StoreInst *NewSI = new StoreInst(MergedVal, SI.getOperand(1),
                                   SI.isVolatile(),
                                   SI.getAlignment(),
                                   SI.getOrdering(),
                                   SI.getSynchScope());
  InsertNewInstBefore(NewSI, *BBI);
  NewSI->setDebugLoc(OtherStore->getDebugLoc());

  // If the two stores had AA tags, merge them.
  AAMDNodes AATags;
  SI.getAAMetadata(AATags);
  if (AATags) {
    OtherStore->getAAMetadata(AATags, /* Merge = */ true);
    NewSI->setAAMetadata(AATags);
  }

  // Nuke the old stores.
  EraseInstFromFunction(SI);
  EraseInstFromFunction(*OtherStore);
  return true;
}

// If we have a PHI node with a vector type that has only 2 uses: feed
// itself and be an operand of extractelemnt at a constant location,
// try to replace the PHI of the vector type with a PHI of a scalar type
Instruction *InstCombiner::scalarizePHI(ExtractElementInst &EI, PHINode *PN) {
  // Verify that the PHI node has exactly 2 uses. Otherwise return NULL.
  if (!PN->hasNUses(2))
    return NULL;

  // If so, it's known at this point that one operand is PHI and the other is
  // an extractelement node. Find the PHI user that is not the extractelement
  // node.
  Value::use_iterator iu = PN->use_begin();
  Instruction *PHIUser = dyn_cast<Instruction>(*iu);
  if (PHIUser == cast<Instruction>(&EI))
    PHIUser = cast<Instruction>(*(++iu));

  // Verify that this PHI user has one use, which is the PHI itself,
  // and that it is a binary operation which is cheap to scalarize.
  // otherwise return NULL.
  if (!PHIUser->hasOneUse() || !(PHIUser->use_back() == PN) ||
    !(isa<BinaryOperator>(PHIUser)) ||
    !CheapToScalarize(PHIUser, true))
    return NULL;

  // Create a scalar PHI node that will replace the vector PHI node
  // just before the current PHI node.
  PHINode * scalarPHI = cast<PHINode>(
    InsertNewInstWith(PHINode::Create(EI.getType(),
    PN->getNumIncomingValues(), ""), *PN));
  // Scalarize each PHI operand.
  for (unsigned i=0; i < PN->getNumIncomingValues(); i++) {
    Value *PHIInVal = PN->getIncomingValue(i);
    BasicBlock *inBB = PN->getIncomingBlock(i);
    Value *Elt = EI.getIndexOperand();
    // If the operand is the PHI induction variable:
    if (PHIInVal == PHIUser) {
      // Scalarize the binary operation. Its first operand is the
      // scalar PHI and the second operand is extracted from the other
      // vector operand.
      BinaryOperator *B0 = cast<BinaryOperator>(PHIUser);
      unsigned opId = (B0->getOperand(0) == PN) ? 1: 0;
      Value *Op = Builder->CreateExtractElement(
        B0->getOperand(opId), Elt, B0->getOperand(opId)->getName()+".Elt");
      Value *newPHIUser = InsertNewInstWith(
        BinaryOperator::Create(B0->getOpcode(), scalarPHI,Op),
        *B0);
      scalarPHI->addIncoming(newPHIUser, inBB);
    } else {
      // Scalarize PHI input:
      Instruction *newEI =
        ExtractElementInst::Create(PHIInVal, Elt, "");
      // Insert the new instruction into the predecessor basic block.
      Instruction *pos = dyn_cast<Instruction>(PHIInVal);
      BasicBlock::iterator InsertPos;
      if (pos && !isa<PHINode>(pos)) {
        InsertPos = pos;
        ++InsertPos;
      } else {
        InsertPos = inBB->getFirstInsertionPt();
      }

      InsertNewInstWith(newEI, *InsertPos);

      scalarPHI->addIncoming(newEI, inBB);
    }
  }
  return ReplaceInstUsesWith(EI, scalarPHI);
}

/// InsertUniqueBackedgeBlock - This method is called when the specified loop
/// has more than one backedge in it.  If this occurs, revector all of these
/// backedges to target a new basic block and have that block branch to the loop
/// header.  This ensures that loops have exactly one backedge.
///
BasicBlock *
LoopSimplify::InsertUniqueBackedgeBlock(Loop *L, BasicBlock *Preheader) {
  assert(L->getNumBackEdges() > 1 && "Must have > 1 backedge!");

  // Get information about the loop
  BasicBlock *Header = L->getHeader();
  Function *F = Header->getParent();

  // Unique backedge insertion currently depends on having a preheader.
  if (!Preheader)
    return 0;

  // Figure out which basic blocks contain back-edges to the loop header.
  std::vector<BasicBlock*> BackedgeBlocks;
  for (pred_iterator I = pred_begin(Header), E = pred_end(Header); I != E; ++I){
    BasicBlock *P = *I;

    // Indirectbr edges cannot be split, so we must fail if we find one.
    if (isa<IndirectBrInst>(P->getTerminator()))
      return 0;

    if (P != Preheader) BackedgeBlocks.push_back(P);
  }

  // Create and insert the new backedge block...
  BasicBlock *BEBlock = BasicBlock::Create(Header->getContext(),
                                           Header->getName()+".backedge", F);
  BranchInst *BETerminator = BranchInst::Create(Header, BEBlock);

  DEBUG(dbgs() << "LoopSimplify: Inserting unique backedge block "
               << BEBlock->getName() << "\n");

  // Move the new backedge block to right after the last backedge block.
  Function::iterator InsertPos = BackedgeBlocks.back(); ++InsertPos;
  F->getBasicBlockList().splice(InsertPos, F->getBasicBlockList(), BEBlock);

  // Now that the block has been inserted into the function, create PHI nodes in
  // the backedge block which correspond to any PHI nodes in the header block.
  for (BasicBlock::iterator I = Header->begin(); isa<PHINode>(I); ++I) {
    PHINode *PN = cast<PHINode>(I);
    PHINode *NewPN = PHINode::Create(PN->getType(), BackedgeBlocks.size(),
                                     PN->getName()+".be", BETerminator);
    if (AA) AA->copyValue(PN, NewPN);

    // Loop over the PHI node, moving all entries except the one for the
    // preheader over to the new PHI node.
    unsigned PreheaderIdx = ~0U;
    bool HasUniqueIncomingValue = true;
    Value *UniqueValue = 0;
    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
      BasicBlock *IBB = PN->getIncomingBlock(i);
      Value *IV = PN->getIncomingValue(i);
      if (IBB == Preheader) {
        PreheaderIdx = i;
      } else {
        NewPN->addIncoming(IV, IBB);
        if (HasUniqueIncomingValue) {
          if (UniqueValue == 0)
            UniqueValue = IV;
          else if (UniqueValue != IV)
            HasUniqueIncomingValue = false;
        }
      }
    }

    // Delete all of the incoming values from the old PN except the preheader's
    assert(PreheaderIdx != ~0U && "PHI has no preheader entry??");
    if (PreheaderIdx != 0) {
      PN->setIncomingValue(0, PN->getIncomingValue(PreheaderIdx));
      PN->setIncomingBlock(0, PN->getIncomingBlock(PreheaderIdx));
    }
    // Nuke all entries except the zero'th.
    for (unsigned i = 0, e = PN->getNumIncomingValues()-1; i != e; ++i)
      PN->removeIncomingValue(e-i, false);

    // Finally, add the newly constructed PHI node as the entry for the BEBlock.
    PN->addIncoming(NewPN, BEBlock);

    // As an optimization, if all incoming values in the new PhiNode (which is a
    // subset of the incoming values of the old PHI node) have the same value,
    // eliminate the PHI Node.
    if (HasUniqueIncomingValue) {
      NewPN->replaceAllUsesWith(UniqueValue);
      if (AA) AA->deleteValue(NewPN);
      BEBlock->getInstList().erase(NewPN);
    }
  }

  // Now that all of the PHI nodes have been inserted and adjusted, modify the
  // backedge blocks to just to the BEBlock instead of the header.
  for (unsigned i = 0, e = BackedgeBlocks.size(); i != e; ++i) {
    TerminatorInst *TI = BackedgeBlocks[i]->getTerminator();
    for (unsigned Op = 0, e = TI->getNumSuccessors(); Op != e; ++Op)
      if (TI->getSuccessor(Op) == Header)
        TI->setSuccessor(Op, BEBlock);
//.........这里部分代码省略.........

/// Connect the unrolling prolog code to the original loop.
/// The unrolling prolog code contains code to execute the
/// 'extra' iterations if the run-time trip count modulo the
/// unroll count is non-zero.
///
/// This function performs the following:
/// - Create PHI nodes at prolog end block to combine values
///   that exit the prolog code and jump around the prolog.
/// - Add a PHI operand to a PHI node at the loop exit block
///   for values that exit the prolog and go around the loop.
/// - Branch around the original loop if the trip count is less
///   than the unroll factor.
///
static void ConnectProlog(Loop *L, Value *BECount, unsigned Count,
                          BasicBlock *PrologExit,
                          BasicBlock *OriginalLoopLatchExit,
                          BasicBlock *PreHeader, BasicBlock *NewPreHeader,
                          ValueToValueMapTy &VMap, DominatorTree *DT,
                          LoopInfo *LI, bool PreserveLCSSA) {
  BasicBlock *Latch = L->getLoopLatch();
  assert(Latch && "Loop must have a latch");
  BasicBlock *PrologLatch = cast<BasicBlock>(VMap[Latch]);

  // Create a PHI node for each outgoing value from the original loop
  // (which means it is an outgoing value from the prolog code too).
  // The new PHI node is inserted in the prolog end basic block.
  // The new PHI node value is added as an operand of a PHI node in either
  // the loop header or the loop exit block.
  for (BasicBlock *Succ : successors(Latch)) {
    for (Instruction &BBI : *Succ) {
      PHINode *PN = dyn_cast<PHINode>(&BBI);
      // Exit when we passed all PHI nodes.
      if (!PN)
        break;
      // Add a new PHI node to the prolog end block and add the
      // appropriate incoming values.
      PHINode *NewPN = PHINode::Create(PN->getType(), 2, PN->getName() + ".unr",
                                       PrologExit->getFirstNonPHI());
      // Adding a value to the new PHI node from the original loop preheader.
      // This is the value that skips all the prolog code.
      if (L->contains(PN)) {
        NewPN->addIncoming(PN->getIncomingValueForBlock(NewPreHeader),
                           PreHeader);
      } else {
        NewPN->addIncoming(UndefValue::get(PN->getType()), PreHeader);
      }

      Value *V = PN->getIncomingValueForBlock(Latch);
      if (Instruction *I = dyn_cast<Instruction>(V)) {
        if (L->contains(I)) {
          V = VMap.lookup(I);
        }
      }
      // Adding a value to the new PHI node from the last prolog block
      // that was created.
      NewPN->addIncoming(V, PrologLatch);

      // Update the existing PHI node operand with the value from the
      // new PHI node.  How this is done depends on if the existing
      // PHI node is in the original loop block, or the exit block.
      if (L->contains(PN)) {
        PN->setIncomingValue(PN->getBasicBlockIndex(NewPreHeader), NewPN);
      } else {
        PN->addIncoming(NewPN, PrologExit);
      }
    }
  }

  // Make sure that created prolog loop is in simplified form
  SmallVector<BasicBlock *, 4> PrologExitPreds;
  Loop *PrologLoop = LI->getLoopFor(PrologLatch);
  if (PrologLoop) {
    for (BasicBlock *PredBB : predecessors(PrologExit))
      if (PrologLoop->contains(PredBB))
        PrologExitPreds.push_back(PredBB);

    SplitBlockPredecessors(PrologExit, PrologExitPreds, ".unr-lcssa", DT, LI,
                           PreserveLCSSA);
  }

  // Create a branch around the original loop, which is taken if there are no
  // iterations remaining to be executed after running the prologue.
  Instruction *InsertPt = PrologExit->getTerminator();
  IRBuilder<> B(InsertPt);

  assert(Count != 0 && "nonsensical Count!");

  // If BECount <u (Count - 1) then (BECount + 1) % Count == (BECount + 1)
  // This means %xtraiter is (BECount + 1) and all of the iterations of this
  // loop were executed by the prologue.  Note that if BECount <u (Count - 1)
  // then (BECount + 1) cannot unsigned-overflow.
  Value *BrLoopExit =
      B.CreateICmpULT(BECount, ConstantInt::get(BECount->getType(), Count - 1));
  // Split the exit to maintain loop canonicalization guarantees
  SmallVector<BasicBlock *, 4> Preds(predecessors(OriginalLoopLatchExit));
  SplitBlockPredecessors(OriginalLoopLatchExit, Preds, ".unr-lcssa", DT, LI,
                         PreserveLCSSA);
  // Add the branch to the exit block (around the unrolled loop)
  B.CreateCondBr(BrLoopExit, OriginalLoopLatchExit, NewPreHeader);
  InsertPt->eraseFromParent();
//.........这里部分代码省略.........

//.........这里部分代码省略.........

      // Loop over all of the PHI nodes in the block, changing them to use the
      // incoming values from the previous block.
      if (*BB == Header)
        for (unsigned i = 0, e = OrigPHINode.size(); i != e; ++i) {
          PHINode *NewPHI = cast<PHINode>(VMap[OrigPHINode[i]]);
          Value *InVal = NewPHI->getIncomingValueForBlock(LatchBlock);
          if (Instruction *InValI = dyn_cast<Instruction>(InVal))
            if (It > 1 && L->contains(InValI))
              InVal = LastValueMap[InValI];
          VMap[OrigPHINode[i]] = InVal;
          New->getInstList().erase(NewPHI);
        }

      // Update our running map of newest clones
      LastValueMap[*BB] = New;
      for (ValueToValueMapTy::iterator VI = VMap.begin(), VE = VMap.end();
           VI != VE; ++VI)
        LastValueMap[VI->first] = VI->second;

      L->addBasicBlockToLoop(New, LI->getBase());

      // Add phi entries for newly created values to all exit blocks.
      for (succ_iterator SI = succ_begin(*BB), SE = succ_end(*BB);
           SI != SE; ++SI) {
        if (L->contains(*SI))
          continue;
        for (BasicBlock::iterator BBI = (*SI)->begin();
             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))