C++ SmallPtrSet::insert方法代码示例

static bool runImpl(CallGraphSCC &SCC, CallGraph &CG) {
  SmallPtrSet<CallGraphNode *, 8> SCCNodes;
  bool MadeChange = false;

  // Fill SCCNodes with the elements of the SCC.  Used for quickly
  // looking up whether a given CallGraphNode is in this SCC.
  for (CallGraphNode *I : SCC)
    SCCNodes.insert(I);

  // First pass, scan all of the functions in the SCC, simplifying them
  // according to what we know.
  for (CallGraphNode *I : SCC)
    if (Function *F = I->getFunction())
      MadeChange |= SimplifyFunction(F, CG);

  // Next, check to see if any callees might throw or if there are any external
  // functions in this SCC: if so, we cannot prune any functions in this SCC.
  // Definitions that are weak and not declared non-throwing might be 
  // overridden at linktime with something that throws, so assume that.
  // If this SCC includes the unwind instruction, we KNOW it throws, so
  // obviously the SCC might throw.
  //
  bool SCCMightUnwind = false, SCCMightReturn = false;
  for (CallGraphSCC::iterator I = SCC.begin(), E = SCC.end(); 
       (!SCCMightUnwind || !SCCMightReturn) && I != E; ++I) {
    Function *F = (*I)->getFunction();
    if (!F) {
      SCCMightUnwind = true;
      SCCMightReturn = true;
    } else if (!F->hasExactDefinition()) {
      SCCMightUnwind |= !F->doesNotThrow();
      SCCMightReturn |= !F->doesNotReturn();
    } else {
      bool CheckUnwind = !SCCMightUnwind && !F->doesNotThrow();
      bool CheckReturn = !SCCMightReturn && !F->doesNotReturn();
      // Determine if we should scan for InlineAsm in a naked function as it
      // is the only way to return without a ReturnInst.  Only do this for
      // no-inline functions as functions which may be inlined cannot
      // meaningfully return via assembly.
      bool CheckReturnViaAsm = CheckReturn &&
                               F->hasFnAttribute(Attribute::Naked) &&
                               F->hasFnAttribute(Attribute::NoInline);

      if (!CheckUnwind && !CheckReturn)
        continue;

      for (const BasicBlock &BB : *F) {
        const TerminatorInst *TI = BB.getTerminator();
        if (CheckUnwind && TI->mayThrow()) {
          SCCMightUnwind = true;
        } else if (CheckReturn && isa<ReturnInst>(TI)) {
          SCCMightReturn = true;
        }

        for (const Instruction &I : BB) {
          if ((!CheckUnwind || SCCMightUnwind) &&
              (!CheckReturnViaAsm || SCCMightReturn))
            break;

          // Check to see if this function performs an unwind or calls an
          // unwinding function.
          if (CheckUnwind && !SCCMightUnwind && I.mayThrow()) {
            bool InstMightUnwind = true;
            if (const auto *CI = dyn_cast<CallInst>(&I)) {
              if (Function *Callee = CI->getCalledFunction()) {
                CallGraphNode *CalleeNode = CG[Callee];
                // If the callee is outside our current SCC then we may throw
                // because it might.  If it is inside, do nothing.
                if (SCCNodes.count(CalleeNode) > 0)
                  InstMightUnwind = false;
              }
            }
            SCCMightUnwind |= InstMightUnwind;
          }
          if (CheckReturnViaAsm && !SCCMightReturn)
            if (auto ICS = ImmutableCallSite(&I))
              if (const auto *IA = dyn_cast<InlineAsm>(ICS.getCalledValue()))
                if (IA->hasSideEffects())
                  SCCMightReturn = true;
        }

        if (SCCMightUnwind && SCCMightReturn)
          break;
      }
    }
  }

  // If the SCC doesn't unwind or doesn't throw, note this fact.
  if (!SCCMightUnwind || !SCCMightReturn)
    for (CallGraphNode *I : SCC) {
      Function *F = I->getFunction();

      if (!SCCMightUnwind && !F->hasFnAttribute(Attribute::NoUnwind)) {
        F->addFnAttr(Attribute::NoUnwind);
        MadeChange = true;
      }

      if (!SCCMightReturn && !F->hasFnAttribute(Attribute::NoReturn)) {
        F->addFnAttr(Attribute::NoReturn);
        MadeChange = true;
//.........这里部分代码省略.........

/// processImplicitDefs - Process IMPLICIT_DEF instructions and make sure
/// there is one implicit_def for each use. Add isUndef marker to
/// implicit_def defs and their uses.
bool ProcessImplicitDefs::runOnMachineFunction(MachineFunction &fn) {

  DEBUG(dbgs() << "********** PROCESS IMPLICIT DEFS **********\n"
               << "********** Function: "
               << ((Value*)fn.getFunction())->getName() << '\n');

  bool Changed = false;

  TII = fn.getTarget().getInstrInfo();
  TRI = fn.getTarget().getRegisterInfo();
  MRI = &fn.getRegInfo();
  LV = &getAnalysis<LiveVariables>();

  SmallSet<unsigned, 8> ImpDefRegs;
  SmallVector<MachineInstr*, 8> ImpDefMIs;
  SmallVector<MachineInstr*, 4> RUses;
  SmallPtrSet<MachineBasicBlock*,16> Visited;
  SmallPtrSet<MachineInstr*, 8> ModInsts;

  MachineBasicBlock *Entry = fn.begin();
  for (df_ext_iterator<MachineBasicBlock*, SmallPtrSet<MachineBasicBlock*,16> >
         DFI = df_ext_begin(Entry, Visited), E = df_ext_end(Entry, Visited);
       DFI != E; ++DFI) {
    MachineBasicBlock *MBB = *DFI;
    for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end();
         I != E; ) {
      MachineInstr *MI = &*I;
      ++I;
      if (MI->isImplicitDef()) {
        ImpDefMIs.push_back(MI);
        // Is this a sub-register read-modify-write?
        if (MI->getOperand(0).readsReg())
          continue;
        unsigned Reg = MI->getOperand(0).getReg();
        ImpDefRegs.insert(Reg);
        if (TargetRegisterInfo::isPhysicalRegister(Reg)) {
          for (const unsigned *SS = TRI->getSubRegisters(Reg); *SS; ++SS)
            ImpDefRegs.insert(*SS);
        }
        continue;
      }

      // Eliminate %reg1032:sub<def> = COPY undef.
      if (MI->isCopy() && MI->getOperand(0).readsReg()) {
        MachineOperand &MO = MI->getOperand(1);
        if (MO.isUndef() || ImpDefRegs.count(MO.getReg())) {
          if (MO.isKill()) {
            LiveVariables::VarInfo& vi = LV->getVarInfo(MO.getReg());
            vi.removeKill(MI);
          }
          unsigned Reg = MI->getOperand(0).getReg();
          MI->eraseFromParent();
          Changed = true;

          // A REG_SEQUENCE may have been expanded into partial definitions.
          // If this was the last one, mark Reg as implicitly defined.
          if (TargetRegisterInfo::isVirtualRegister(Reg) && MRI->def_empty(Reg))
            ImpDefRegs.insert(Reg);
          continue;
        }
      }

      bool ChangedToImpDef = false;
      for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
        MachineOperand& MO = MI->getOperand(i);
        if (!MO.isReg() || !MO.readsReg())
          continue;
        unsigned Reg = MO.getReg();
        if (!Reg)
          continue;
        if (!ImpDefRegs.count(Reg))
          continue;
        // Use is a copy, just turn it into an implicit_def.
        if (CanTurnIntoImplicitDef(MI, Reg, i, ImpDefRegs)) {
          bool isKill = MO.isKill();
          MI->setDesc(TII->get(TargetOpcode::IMPLICIT_DEF));
          for (int j = MI->getNumOperands() - 1, ee = 0; j > ee; --j)
            MI->RemoveOperand(j);
          if (isKill) {
            ImpDefRegs.erase(Reg);
            LiveVariables::VarInfo& vi = LV->getVarInfo(Reg);
            vi.removeKill(MI);
          }
          ChangedToImpDef = true;
          Changed = true;
          break;
        }

        Changed = true;
        MO.setIsUndef();
        // This is a partial register redef of an implicit def.
        // Make sure the whole register is defined by the instruction.
        if (MO.isDef()) {
          MI->addRegisterDefined(Reg);
          continue;
        }
        if (MO.isKill() || MI->isRegTiedToDefOperand(i)) {
//.........这里部分代码省略.........

/// InlineCallIfPossible - If it is possible to inline the specified call site,
/// do so and update the CallGraph for this operation.
///
/// This function also does some basic book-keeping to update the IR.  The
/// InlinedArrayAllocas map keeps track of any allocas that are already
/// available from other  functions inlined into the caller.  If we are able to
/// inline this call site we attempt to reuse already available allocas or add
/// any new allocas to the set if not possible.
static bool InlineCallIfPossible(CallSite CS, InlineFunctionInfo &IFI,
                                 InlinedArrayAllocasTy &InlinedArrayAllocas,
                                 int InlineHistory, bool InsertLifetime) {
  Function *Callee = CS.getCalledFunction();
  Function *Caller = CS.getCaller();

  // Try to inline the function.  Get the list of static allocas that were
  // inlined.
  if (!InlineFunction(CS, IFI, InsertLifetime))
    return false;

  // If the inlined function had a higher stack protection level than the
  // calling function, then bump up the caller's stack protection level.
  if (Callee->hasFnAttr(Attribute::StackProtectReq))
    Caller->addFnAttr(Attribute::StackProtectReq);
  else if (Callee->hasFnAttr(Attribute::StackProtect) &&
           !Caller->hasFnAttr(Attribute::StackProtectReq))
    Caller->addFnAttr(Attribute::StackProtect);

  // Look at all of the allocas that we inlined through this call site.  If we
  // have already inlined other allocas through other calls into this function,
  // then we know that they have disjoint lifetimes and that we can merge them.
  //
  // There are many heuristics possible for merging these allocas, and the
  // different options have different tradeoffs.  One thing that we *really*
  // don't want to hurt is SRoA: once inlining happens, often allocas are no
  // longer address taken and so they can be promoted.
  //
  // Our "solution" for that is to only merge allocas whose outermost type is an
  // array type.  These are usually not promoted because someone is using a
  // variable index into them.  These are also often the most important ones to
  // merge.
  //
  // A better solution would be to have real memory lifetime markers in the IR
  // and not have the inliner do any merging of allocas at all.  This would
  // allow the backend to do proper stack slot coloring of all allocas that
  // *actually make it to the backend*, which is really what we want.
  //
  // Because we don't have this information, we do this simple and useful hack.
  //
  SmallPtrSet<AllocaInst*, 16> UsedAllocas;
  
  // When processing our SCC, check to see if CS was inlined from some other
  // call site.  For example, if we're processing "A" in this code:
  //   A() { B() }
  //   B() { x = alloca ... C() }
  //   C() { y = alloca ... }
  // Assume that C was not inlined into B initially, and so we're processing A
  // and decide to inline B into A.  Doing this makes an alloca available for
  // reuse and makes a callsite (C) available for inlining.  When we process
  // the C call site we don't want to do any alloca merging between X and Y
  // because their scopes are not disjoint.  We could make this smarter by
  // keeping track of the inline history for each alloca in the
  // InlinedArrayAllocas but this isn't likely to be a significant win.
  if (InlineHistory != -1)  // Only do merging for top-level call sites in SCC.
    return true;
  
  // Loop over all the allocas we have so far and see if they can be merged with
  // a previously inlined alloca.  If not, remember that we had it.
  for (unsigned AllocaNo = 0, e = IFI.StaticAllocas.size();
       AllocaNo != e; ++AllocaNo) {
    AllocaInst *AI = IFI.StaticAllocas[AllocaNo];
    
    // Don't bother trying to merge array allocations (they will usually be
    // canonicalized to be an allocation *of* an array), or allocations whose
    // type is not itself an array (because we're afraid of pessimizing SRoA).
    ArrayType *ATy = dyn_cast<ArrayType>(AI->getAllocatedType());
    if (ATy == 0 || AI->isArrayAllocation())
      continue;
    
    // Get the list of all available allocas for this array type.
    std::vector<AllocaInst*> &AllocasForType = InlinedArrayAllocas[ATy];
    
    // Loop over the allocas in AllocasForType to see if we can reuse one.  Note
    // that we have to be careful not to reuse the same "available" alloca for
    // multiple different allocas that we just inlined, we use the 'UsedAllocas'
    // set to keep track of which "available" allocas are being used by this
    // function.  Also, AllocasForType can be empty of course!
    bool MergedAwayAlloca = false;
    for (unsigned i = 0, e = AllocasForType.size(); i != e; ++i) {
      AllocaInst *AvailableAlloca = AllocasForType[i];
      
      // The available alloca has to be in the right function, not in some other
      // function in this SCC.
      if (AvailableAlloca->getParent() != AI->getParent())
        continue;
      
      // If the inlined function already uses this alloca then we can't reuse
      // it.
      if (!UsedAllocas.insert(AvailableAlloca))
        continue;
      
//.........这里部分代码省略.........

/// OptimizeMemoryInst - Load and Store Instructions often have
/// addressing modes that can do significant amounts of computation.  As such,
/// instruction selection will try to get the load or store to do as much
/// computation as possible for the program.  The problem is that isel can only
/// see within a single block.  As such, we sink as much legal addressing mode
/// stuff into the block as possible.
///
/// This method is used to optimize both load/store and inline asms with memory
/// operands.
bool CodeGenPrepare::OptimizeMemoryInst(Instruction *MemoryInst, Value *Addr,
                                        Type *AccessTy) {
  Value *Repl = Addr;
  
  // Try to collapse single-value PHI nodes.  This is necessary to undo 
  // unprofitable PRE transformations.
  SmallVector<Value*, 8> worklist;
  SmallPtrSet<Value*, 16> Visited;
  worklist.push_back(Addr);
  
  // Use a worklist to iteratively look through PHI nodes, and ensure that
  // the addressing mode obtained from the non-PHI roots of the graph
  // are equivalent.
  Value *Consensus = 0;
  unsigned NumUsesConsensus = 0;
  bool IsNumUsesConsensusValid = false;
  SmallVector<Instruction*, 16> AddrModeInsts;
  ExtAddrMode AddrMode;
  while (!worklist.empty()) {
    Value *V = worklist.back();
    worklist.pop_back();
    
    // Break use-def graph loops.
    if (!Visited.insert(V)) {
      Consensus = 0;
      break;
    }
    
    // For a PHI node, push all of its incoming values.
    if (PHINode *P = dyn_cast<PHINode>(V)) {
      for (unsigned i = 0, e = P->getNumIncomingValues(); i != e; ++i)
        worklist.push_back(P->getIncomingValue(i));
      continue;
    }
    
    // For non-PHIs, determine the addressing mode being computed.
    SmallVector<Instruction*, 16> NewAddrModeInsts;
    ExtAddrMode NewAddrMode =
      AddressingModeMatcher::Match(V, AccessTy, MemoryInst,
                                   NewAddrModeInsts, *TLI);

    // This check is broken into two cases with very similar code to avoid using
    // getNumUses() as much as possible. Some values have a lot of uses, so
    // calling getNumUses() unconditionally caused a significant compile-time
    // regression.
    if (!Consensus) {
      Consensus = V;
      AddrMode = NewAddrMode;
      AddrModeInsts = NewAddrModeInsts;
      continue;
    } else if (NewAddrMode == AddrMode) {
      if (!IsNumUsesConsensusValid) {
        NumUsesConsensus = Consensus->getNumUses();
        IsNumUsesConsensusValid = true;
      }

      // Ensure that the obtained addressing mode is equivalent to that obtained
      // for all other roots of the PHI traversal.  Also, when choosing one
      // such root as representative, select the one with the most uses in order
      // to keep the cost modeling heuristics in AddressingModeMatcher
      // applicable.
      unsigned NumUses = V->getNumUses();
      if (NumUses > NumUsesConsensus) {
        Consensus = V;
        NumUsesConsensus = NumUses;
        AddrModeInsts = NewAddrModeInsts;
      }
      continue;
    }
    
    Consensus = 0;
    break;
  }
  
  // If the addressing mode couldn't be determined, or if multiple different
  // ones were determined, bail out now.
  if (!Consensus) return false;
  
  // Check to see if any of the instructions supersumed by this addr mode are
  // non-local to I's BB.
  bool AnyNonLocal = false;
  for (unsigned i = 0, e = AddrModeInsts.size(); i != e; ++i) {
    if (IsNonLocalValue(AddrModeInsts[i], MemoryInst->getParent())) {
      AnyNonLocal = true;
      break;
    }
  }

  // If all the instructions matched are already in this BB, don't do anything.
  if (!AnyNonLocal) {
    DEBUG(dbgs() << "CGP: Found      local addrmode: " << AddrMode << "\n");
//.........这里部分代码省略.........

/// PromoteArguments - This method checks the specified function to see if there
/// are any promotable arguments and if it is safe to promote the function (for
/// example, all callers are direct).  If safe to promote some arguments, it
/// calls the DoPromotion method.
///
CallGraphNode *ArgPromotion::PromoteArguments(CallGraphNode *CGN) {
  Function *F = CGN->getFunction();

  // Make sure that it is local to this module.
  if (!F || !F->hasLocalLinkage()) return 0;

  // First check: see if there are any pointer arguments!  If not, quick exit.
  SmallVector<std::pair<Argument*, unsigned>, 16> PointerArgs;
  unsigned ArgNo = 0;
  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
       I != E; ++I, ++ArgNo)
    if (I->getType()->isPointerTy())
      PointerArgs.push_back(std::pair<Argument*, unsigned>(I, ArgNo));
  if (PointerArgs.empty()) return 0;

  // Second check: make sure that all callers are direct callers.  We can't
  // transform functions that have indirect callers.  Also see if the function
  // is self-recursive.
  bool isSelfRecursive = false;
  for (Value::use_iterator UI = F->use_begin(), E = F->use_end();
       UI != E; ++UI) {
    CallSite CS(*UI);
    // Must be a direct call.
    if (CS.getInstruction() == 0 || !CS.isCallee(UI)) return 0;
    
    if (CS.getInstruction()->getParent()->getParent() == F)
      isSelfRecursive = true;
  }
  
  // Check to see which arguments are promotable.  If an argument is promotable,
  // add it to ArgsToPromote.
  SmallPtrSet<Argument*, 8> ArgsToPromote;
  SmallPtrSet<Argument*, 8> ByValArgsToTransform;
  for (unsigned i = 0; i != PointerArgs.size(); ++i) {
    bool isByVal = F->paramHasAttr(PointerArgs[i].second+1, Attribute::ByVal);
    Argument *PtrArg = PointerArgs[i].first;
    Type *AgTy = cast<PointerType>(PtrArg->getType())->getElementType();

    // If this is a byval argument, and if the aggregate type is small, just
    // pass the elements, which is always safe.
    if (isByVal) {
      if (StructType *STy = dyn_cast<StructType>(AgTy)) {
        if (maxElements > 0 && STy->getNumElements() > maxElements) {
          DEBUG(dbgs() << "argpromotion disable promoting argument '"
                << PtrArg->getName() << "' because it would require adding more"
                << " than " << maxElements << " arguments to the function.\n");
          continue;
        }
        
        // If all the elements are single-value types, we can promote it.
        bool AllSimple = true;
        for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
          if (!STy->getElementType(i)->isSingleValueType()) {
            AllSimple = false;
            break;
          }
        }

        // Safe to transform, don't even bother trying to "promote" it.
        // Passing the elements as a scalar will allow scalarrepl to hack on
        // the new alloca we introduce.
        if (AllSimple) {
          ByValArgsToTransform.insert(PtrArg);
          continue;
        }
      }
    }

    // If the argument is a recursive type and we're in a recursive
    // function, we could end up infinitely peeling the function argument.
    if (isSelfRecursive) {
      if (StructType *STy = dyn_cast<StructType>(AgTy)) {
        bool RecursiveType = false;
        for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
          if (STy->getElementType(i) == PtrArg->getType()) {
            RecursiveType = true;
            break;
          }
        }
        if (RecursiveType)
          continue;
      }
    }
    
    // Otherwise, see if we can promote the pointer to its value.
    if (isSafeToPromoteArgument(PtrArg, isByVal))
      ArgsToPromote.insert(PtrArg);
  }

  // No promotable pointer arguments.
  if (ArgsToPromote.empty() && ByValArgsToTransform.empty()) 
    return 0;

  return DoPromotion(F, ArgsToPromote, ByValArgsToTransform);
}

/// ClusterNeighboringLoads - Force nearby loads together by "gluing" them.
/// This function finds loads of the same base and different offsets. If the
/// offsets are not far apart (target specific), it add MVT::Glue inputs and
/// outputs to ensure they are scheduled together and in order. This
/// optimization may benefit some targets by improving cache locality.
void ScheduleDAGSDNodes::ClusterNeighboringLoads(SDNode *Node) {
  SDNode *Chain = nullptr;
  unsigned NumOps = Node->getNumOperands();
  if (Node->getOperand(NumOps-1).getValueType() == MVT::Other)
    Chain = Node->getOperand(NumOps-1).getNode();
  if (!Chain)
    return;

  // Look for other loads of the same chain. Find loads that are loading from
  // the same base pointer and different offsets.
  SmallPtrSet<SDNode*, 16> Visited;
  SmallVector<int64_t, 4> Offsets;
  DenseMap<long long, SDNode*> O2SMap;  // Map from offset to SDNode.
  bool Cluster = false;
  SDNode *Base = Node;
  // This algorithm requires a reasonably low use count before finding a match
  // to avoid uselessly blowing up compile time in large blocks.
  unsigned UseCount = 0;
  for (SDNode::use_iterator I = Chain->use_begin(), E = Chain->use_end();
       I != E && UseCount < 100; ++I, ++UseCount) {
    SDNode *User = *I;
    if (User == Node || !Visited.insert(User))
      continue;
    int64_t Offset1, Offset2;
    if (!TII->areLoadsFromSameBasePtr(Base, User, Offset1, Offset2) ||
        Offset1 == Offset2)
      // FIXME: Should be ok if they addresses are identical. But earlier
      // optimizations really should have eliminated one of the loads.
      continue;
    if (O2SMap.insert(std::make_pair(Offset1, Base)).second)
      Offsets.push_back(Offset1);
    O2SMap.insert(std::make_pair(Offset2, User));
    Offsets.push_back(Offset2);
    if (Offset2 < Offset1)
      Base = User;
    Cluster = true;
    // Reset UseCount to allow more matches.
    UseCount = 0;
  }

  if (!Cluster)
    return;

  // Sort them in increasing order.
  std::sort(Offsets.begin(), Offsets.end());

  // Check if the loads are close enough.
  SmallVector<SDNode*, 4> Loads;
  unsigned NumLoads = 0;
  int64_t BaseOff = Offsets[0];
  SDNode *BaseLoad = O2SMap[BaseOff];
  Loads.push_back(BaseLoad);
  for (unsigned i = 1, e = Offsets.size(); i != e; ++i) {
    int64_t Offset = Offsets[i];
    SDNode *Load = O2SMap[Offset];
    if (!TII->shouldScheduleLoadsNear(BaseLoad, Load, BaseOff, Offset,NumLoads))
      break; // Stop right here. Ignore loads that are further away.
    Loads.push_back(Load);
    ++NumLoads;
  }

  if (NumLoads == 0)
    return;

  // Cluster loads by adding MVT::Glue outputs and inputs. This also
  // ensure they are scheduled in order of increasing addresses.
  SDNode *Lead = Loads[0];
  SDValue InGlue = SDValue(nullptr, 0);
  if (AddGlue(Lead, InGlue, true, DAG))
    InGlue = SDValue(Lead, Lead->getNumValues() - 1);
  for (unsigned I = 1, E = Loads.size(); I != E; ++I) {
    bool OutGlue = I < E - 1;
    SDNode *Load = Loads[I];

    // If AddGlue fails, we could leave an unsused glue value. This should not
    // cause any
    if (AddGlue(Load, InGlue, OutGlue, DAG)) {
      if (OutGlue)
        InGlue = SDValue(Load, Load->getNumValues() - 1);

      ++LoadsClustered;
    }
    else if (!OutGlue && InGlue.getNode())
      RemoveUnusedGlue(InGlue.getNode(), DAG);
  }
}

void ScheduleDAGSDNodes::BuildSchedUnits() {
  // During scheduling, the NodeId field of SDNode is used to map SDNodes
  // to their associated SUnits by holding SUnits table indices. A value
  // of -1 means the SDNode does not yet have an associated SUnit.
  unsigned NumNodes = 0;
  for (SelectionDAG::allnodes_iterator NI = DAG->allnodes_begin(),
       E = DAG->allnodes_end(); NI != E; ++NI) {
    NI->setNodeId(-1);
    ++NumNodes;
  }

  // Reserve entries in the vector for each of the SUnits we are creating.  This
  // ensure that reallocation of the vector won't happen, so SUnit*'s won't get
  // invalidated.
  // FIXME: Multiply by 2 because we may clone nodes during scheduling.
  // This is a temporary workaround.
  SUnits.reserve(NumNodes * 2);

  // Add all nodes in depth first order.
  SmallVector<SDNode*, 64> Worklist;
  SmallPtrSet<SDNode*, 64> Visited;
  Worklist.push_back(DAG->getRoot().getNode());
  Visited.insert(DAG->getRoot().getNode());

  SmallVector<SUnit*, 8> CallSUnits;
  while (!Worklist.empty()) {
    SDNode *NI = Worklist.pop_back_val();

    // Add all operands to the worklist unless they've already been added.
    for (unsigned i = 0, e = NI->getNumOperands(); i != e; ++i)
      if (Visited.insert(NI->getOperand(i).getNode()))
        Worklist.push_back(NI->getOperand(i).getNode());

    if (isPassiveNode(NI))  // Leaf node, e.g. a TargetImmediate.
      continue;

    // If this node has already been processed, stop now.
    if (NI->getNodeId() != -1) continue;

    SUnit *NodeSUnit = newSUnit(NI);

    // See if anything is glued to this node, if so, add them to glued
    // nodes.  Nodes can have at most one glue input and one glue output.  Glue
    // is required to be the last operand and result of a node.

    // Scan up to find glued preds.
    SDNode *N = NI;
    while (N->getNumOperands() &&
           N->getOperand(N->getNumOperands()-1).getValueType() == MVT::Glue) {
      N = N->getOperand(N->getNumOperands()-1).getNode();
      assert(N->getNodeId() == -1 && "Node already inserted!");
      N->setNodeId(NodeSUnit->NodeNum);
      if (N->isMachineOpcode() && TII->get(N->getMachineOpcode()).isCall())
        NodeSUnit->isCall = true;
    }

    // Scan down to find any glued succs.
    N = NI;
    while (N->getValueType(N->getNumValues()-1) == MVT::Glue) {
      SDValue GlueVal(N, N->getNumValues()-1);

      // There are either zero or one users of the Glue result.
      bool HasGlueUse = false;
      for (SDNode::use_iterator UI = N->use_begin(), E = N->use_end();
           UI != E; ++UI)
        if (GlueVal.isOperandOf(*UI)) {
          HasGlueUse = true;
          assert(N->getNodeId() == -1 && "Node already inserted!");
          N->setNodeId(NodeSUnit->NodeNum);
          N = *UI;
          if (N->isMachineOpcode() && TII->get(N->getMachineOpcode()).isCall())
            NodeSUnit->isCall = true;
          break;
        }
      if (!HasGlueUse) break;
    }

    if (NodeSUnit->isCall)
      CallSUnits.push_back(NodeSUnit);

    // Schedule zero-latency TokenFactor below any nodes that may increase the
    // schedule height. Otherwise, ancestors of the TokenFactor may appear to
    // have false stalls.
    if (NI->getOpcode() == ISD::TokenFactor)
      NodeSUnit->isScheduleLow = true;

    // If there are glue operands involved, N is now the bottom-most node
    // of the sequence of nodes that are glued together.
    // Update the SUnit.
    NodeSUnit->setNode(N);
    assert(N->getNodeId() == -1 && "Node already inserted!");
    N->setNodeId(NodeSUnit->NodeNum);

    // Compute NumRegDefsLeft. This must be done before AddSchedEdges.
    InitNumRegDefsLeft(NodeSUnit);

    // Assign the Latency field of NodeSUnit using target-provided information.
    computeLatency(NodeSUnit);
  }

//.........这里部分代码省略.........

/// Deduce nocapture attributes for the SCC.
static bool addArgumentAttrs(const SCCNodeSet &SCCNodes) {
  bool Changed = false;

  ArgumentGraph AG;

  AttrBuilder B;
  B.addAttribute(Attribute::NoCapture);

  // Check each function in turn, determining which pointer arguments are not
  // captured.
  for (Function *F : SCCNodes) {
    // We can infer and propagate function attributes only when we know that the
    // definition we'll get at link time is *exactly* the definition we see now.
    // For more details, see GlobalValue::mayBeDerefined.
    if (!F->hasExactDefinition())
      continue;

    // Functions that are readonly (or readnone) and nounwind and don't return
    // a value can't capture arguments. Don't analyze them.
    if (F->onlyReadsMemory() && F->doesNotThrow() &&
        F->getReturnType()->isVoidTy()) {
      for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end(); A != E;
           ++A) {
        if (A->getType()->isPointerTy() && !A->hasNoCaptureAttr()) {
          A->addAttr(AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
          ++NumNoCapture;
          Changed = true;
        }
      }
      continue;
    }

    for (Function::arg_iterator A = F->arg_begin(), E = F->arg_end(); A != E;
         ++A) {
      if (!A->getType()->isPointerTy())
        continue;
      bool HasNonLocalUses = false;
      if (!A->hasNoCaptureAttr()) {
        ArgumentUsesTracker Tracker(SCCNodes);
        PointerMayBeCaptured(&*A, &Tracker);
        if (!Tracker.Captured) {
          if (Tracker.Uses.empty()) {
            // If it's trivially not captured, mark it nocapture now.
            A->addAttr(
                AttributeSet::get(F->getContext(), A->getArgNo() + 1, B));
            ++NumNoCapture;
            Changed = true;
          } else {
            // If it's not trivially captured and not trivially not captured,
            // then it must be calling into another function in our SCC. Save
            // its particulars for Argument-SCC analysis later.
            ArgumentGraphNode *Node = AG[&*A];
            for (SmallVectorImpl<Argument *>::iterator
                     UI = Tracker.Uses.begin(),
                     UE = Tracker.Uses.end();
                 UI != UE; ++UI) {
              Node->Uses.push_back(AG[*UI]);
              if (*UI != &*A)
                HasNonLocalUses = true;
            }
          }
        }
        // Otherwise, it's captured. Don't bother doing SCC analysis on it.
      }
      if (!HasNonLocalUses && !A->onlyReadsMemory()) {
        // Can we determine that it's readonly/readnone without doing an SCC?
        // Note that we don't allow any calls at all here, or else our result
        // will be dependent on the iteration order through the functions in the
        // SCC.
        SmallPtrSet<Argument *, 8> Self;
        Self.insert(&*A);
        Attribute::AttrKind R = determinePointerReadAttrs(&*A, Self);
        if (R != Attribute::None) {
          AttrBuilder B;
          B.addAttribute(R);
          A->addAttr(AttributeSet::get(A->getContext(), A->getArgNo() + 1, B));
          Changed = true;
          R == Attribute::ReadOnly ? ++NumReadOnlyArg : ++NumReadNoneArg;
        }
      }
    }
  }

  // The graph we've collected is partial because we stopped scanning for
  // argument uses once we solved the argument trivially. These partial nodes
  // show up as ArgumentGraphNode objects with an empty Uses list, and for
  // these nodes the final decision about whether they capture has already been
  // made.  If the definition doesn't have a 'nocapture' attribute by now, it
  // captures.

  for (scc_iterator<ArgumentGraph *> I = scc_begin(&AG); !I.isAtEnd(); ++I) {
    const std::vector<ArgumentGraphNode *> &ArgumentSCC = *I;
    if (ArgumentSCC.size() == 1) {
      if (!ArgumentSCC[0]->Definition)
        continue; // synthetic root node

      // eg. "void f(int* x) { if (...) f(x); }"
      if (ArgumentSCC[0]->Uses.size() == 1 &&
          ArgumentSCC[0]->Uses[0] == ArgumentSCC[0]) {
//.........这里部分代码省略.........

static bool markAliveBlocks(BasicBlock *BB,
                            SmallPtrSet<BasicBlock*, 128> &Reachable) {

  SmallVector<BasicBlock*, 128> Worklist;
  Worklist.push_back(BB);
  bool Changed = false;
  do {
    BB = Worklist.pop_back_val();

    if (!Reachable.insert(BB))
      continue;

    // Do a quick scan of the basic block, turning any obviously unreachable
    // instructions into LLVM unreachable insts.  The instruction combining pass
    // canonicalizes unreachable insts into stores to null or undef.
    for (BasicBlock::iterator BBI = BB->begin(), E = BB->end(); BBI != E;++BBI){
      if (CallInst *CI = dyn_cast<CallInst>(BBI)) {
        if (CI->doesNotReturn()) {
          // If we found a call to a no-return function, insert an unreachable
          // instruction after it.  Make sure there isn't *already* one there
          // though.
          ++BBI;
          if (!isa<UnreachableInst>(BBI)) {
            // Don't insert a call to llvm.trap right before the unreachable.
            changeToUnreachable(BBI, false);
            Changed = true;
          }
          break;
        }
      }

      // Store to undef and store to null are undefined and used to signal that
      // they should be changed to unreachable by passes that can't modify the
      // CFG.
      if (StoreInst *SI = dyn_cast<StoreInst>(BBI)) {
        // Don't touch volatile stores.
        if (SI->isVolatile()) continue;

        Value *Ptr = SI->getOperand(1);

        if (isa<UndefValue>(Ptr) ||
            (isa<ConstantPointerNull>(Ptr) &&
             SI->getPointerAddressSpace() == 0)) {
          changeToUnreachable(SI, true);
          Changed = true;
          break;
        }
      }
    }

    // Turn invokes that call 'nounwind' functions into ordinary calls.
    if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
      Value *Callee = II->getCalledValue();
      if (isa<ConstantPointerNull>(Callee) || isa<UndefValue>(Callee)) {
        changeToUnreachable(II, true);
        Changed = true;
      } else if (II->doesNotThrow()) {
        if (II->use_empty() && II->onlyReadsMemory()) {
          // jump to the normal destination branch.
          BranchInst::Create(II->getNormalDest(), II);
          II->getUnwindDest()->removePredecessor(II->getParent());
          II->eraseFromParent();
        } else
          changeToCall(II);
        Changed = true;
      }
    }

    Changed |= ConstantFoldTerminator(BB, true);
    for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI)
      Worklist.push_back(*SI);
  } while (!Worklist.empty());
  return Changed;
}

/// findValueImpl - Implementation helper for findValue.
Value *Lint::findValueImpl(Value *V, bool OffsetOk,
                           SmallPtrSet<Value *, 4> &Visited) const {
  // Detect self-referential values.
  if (!Visited.insert(V))
    return UndefValue::get(V->getType());

  // TODO: Look through sext or zext cast, when the result is known to
  // be interpreted as signed or unsigned, respectively.
  // TODO: Look through eliminable cast pairs.
  // TODO: Look through calls with unique return values.
  // TODO: Look through vector insert/extract/shuffle.
  V = OffsetOk ? V->getUnderlyingObject() : V->stripPointerCasts();
  if (LoadInst *L = dyn_cast<LoadInst>(V)) {
    BasicBlock::iterator BBI = L;
    BasicBlock *BB = L->getParent();
    SmallPtrSet<BasicBlock *, 4> VisitedBlocks;
    for (;;) {
      if (!VisitedBlocks.insert(BB)) break;
      if (Value *U = FindAvailableLoadedValue(L->getPointerOperand(),
                                              BB, BBI, 6, AA))
        return findValueImpl(U, OffsetOk, Visited);
      if (BBI != BB->begin()) break;
      BB = BB->getUniquePredecessor();
      if (!BB) break;
      BBI = BB->end();
    }
  } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
    if (Value *W = PN->hasConstantValue())
      if (W != V)
        return findValueImpl(W, OffsetOk, Visited);
  } else if (CastInst *CI = dyn_cast<CastInst>(V)) {
    if (CI->isNoopCast(TD ? TD->getIntPtrType(V->getContext()) :
                            Type::getInt64Ty(V->getContext())))
      return findValueImpl(CI->getOperand(0), OffsetOk, Visited);
  } else if (ExtractValueInst *Ex = dyn_cast<ExtractValueInst>(V)) {
    if (Value *W = FindInsertedValue(Ex->getAggregateOperand(),
                                     Ex->idx_begin(),
                                     Ex->idx_end()))
      if (W != V)
        return findValueImpl(W, OffsetOk, Visited);
  } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
    // Same as above, but for ConstantExpr instead of Instruction.
    if (Instruction::isCast(CE->getOpcode())) {
      if (CastInst::isNoopCast(Instruction::CastOps(CE->getOpcode()),
                               CE->getOperand(0)->getType(),
                               CE->getType(),
                               TD ? TD->getIntPtrType(V->getContext()) :
                                    Type::getInt64Ty(V->getContext())))
        return findValueImpl(CE->getOperand(0), OffsetOk, Visited);
    } else if (CE->getOpcode() == Instruction::ExtractValue) {
      const SmallVector<unsigned, 4> &Indices = CE->getIndices();
      if (Value *W = FindInsertedValue(CE->getOperand(0),
                                       Indices.begin(),
                                       Indices.end()))
        if (W != V)
          return findValueImpl(W, OffsetOk, Visited);
    }
  }

  // As a last resort, try SimplifyInstruction or constant folding.
  if (Instruction *Inst = dyn_cast<Instruction>(V)) {
    if (Value *W = SimplifyInstruction(Inst, TD, DT))
      return findValueImpl(W, OffsetOk, Visited);
  } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
    if (Value *W = ConstantFoldConstantExpression(CE, TD))
      if (W != V)
        return findValueImpl(W, OffsetOk, Visited);
  }

  return V;
}

/// CanMergeBlocks - Return true if we can merge BB into DestBB if there is a
/// single uncond branch between them, and BB contains no other non-phi
/// instructions.
bool CodeGenPrepare::CanMergeBlocks(const BasicBlock *BB,
                                    const BasicBlock *DestBB) const {
  // We only want to eliminate blocks whose phi nodes are used by phi nodes in
  // the successor.  If there are more complex condition (e.g. preheaders),
  // don't mess around with them.
  BasicBlock::const_iterator BBI = BB->begin();
  while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
    for (Value::const_use_iterator UI = PN->use_begin(), E = PN->use_end();
         UI != E; ++UI) {
      const Instruction *User = cast<Instruction>(*UI);
      if (User->getParent() != DestBB || !isa<PHINode>(User))
        return false;
      // If User is inside DestBB block and it is a PHINode then check
      // incoming value. If incoming value is not from BB then this is
      // a complex condition (e.g. preheaders) we want to avoid here.
      if (User->getParent() == DestBB) {
        if (const PHINode *UPN = dyn_cast<PHINode>(User))
          for (unsigned I = 0, E = UPN->getNumIncomingValues(); I != E; ++I) {
            Instruction *Insn = dyn_cast<Instruction>(UPN->getIncomingValue(I));
            if (Insn && Insn->getParent() == BB &&
                Insn->getParent() != UPN->getIncomingBlock(I))
              return false;
          }
      }
    }
  }

  // If BB and DestBB contain any common predecessors, then the phi nodes in BB
  // and DestBB may have conflicting incoming values for the block.  If so, we
  // can't merge the block.
  const PHINode *DestBBPN = dyn_cast<PHINode>(DestBB->begin());
  if (!DestBBPN) return true;  // no conflict.

  // Collect the preds of BB.
  SmallPtrSet<const BasicBlock*, 16> BBPreds;
  if (const PHINode *BBPN = dyn_cast<PHINode>(BB->begin())) {
    // It is faster to get preds from a PHI than with pred_iterator.
    for (unsigned i = 0, e = BBPN->getNumIncomingValues(); i != e; ++i)
      BBPreds.insert(BBPN->getIncomingBlock(i));
  } else {
    BBPreds.insert(pred_begin(BB), pred_end(BB));
  }

  // Walk the preds of DestBB.
  for (unsigned i = 0, e = DestBBPN->getNumIncomingValues(); i != e; ++i) {
    BasicBlock *Pred = DestBBPN->getIncomingBlock(i);
    if (BBPreds.count(Pred)) {   // Common predecessor?
      BBI = DestBB->begin();
      while (const PHINode *PN = dyn_cast<PHINode>(BBI++)) {
        const Value *V1 = PN->getIncomingValueForBlock(Pred);
        const Value *V2 = PN->getIncomingValueForBlock(BB);

        // If V2 is a phi node in BB, look up what the mapped value will be.
        if (const PHINode *V2PN = dyn_cast<PHINode>(V2))
          if (V2PN->getParent() == BB)
            V2 = V2PN->getIncomingValueForBlock(Pred);

        // If there is a conflict, bail out.
        if (V1 != V2) return false;
      }
    }
  }

  return true;
}

bool ReduceCrashingBlocks::TestBlocks(std::vector<const BasicBlock*> &BBs) {
  // Clone the program to try hacking it apart...
  ValueToValueMapTy VMap;
  Module *M = CloneModule(BD.getProgram(), VMap).release();

  // Convert list to set for fast lookup...
  SmallPtrSet<BasicBlock*, 8> Blocks;
  for (unsigned i = 0, e = BBs.size(); i != e; ++i)
    Blocks.insert(cast<BasicBlock>(VMap[BBs[i]]));

  outs() << "Checking for crash with only these blocks:";
  unsigned NumPrint = Blocks.size();
  if (NumPrint > 10) NumPrint = 10;
  for (unsigned i = 0, e = NumPrint; i != e; ++i)
    outs() << " " << BBs[i]->getName();
  if (NumPrint < Blocks.size())
    outs() << "... <" << Blocks.size() << " total>";
  outs() << ": ";

  // Loop over and delete any hack up any blocks that are not listed...
  for (Module::iterator I = M->begin(), E = M->end(); I != E; ++I)
    for (Function::iterator BB = I->begin(), E = I->end(); BB != E; ++BB)
      if (!Blocks.count(&*BB) && BB->getTerminator()->getNumSuccessors()) {
        // Loop over all of the successors of this block, deleting any PHI nodes
        // that might include it.
        for (succ_iterator SI = succ_begin(&*BB), E = succ_end(&*BB); SI != E;
             ++SI)
          (*SI)->removePredecessor(&*BB);

        TerminatorInst *BBTerm = BB->getTerminator();
        if (BBTerm->isEHPad())
          continue;
        if (!BBTerm->getType()->isVoidTy() && !BBTerm->getType()->isTokenTy())
          BBTerm->replaceAllUsesWith(Constant::getNullValue(BBTerm->getType()));

        // Replace the old terminator instruction.
        BB->getInstList().pop_back();
        new UnreachableInst(BB->getContext(), &*BB);
      }

  // The CFG Simplifier pass may delete one of the basic blocks we are
  // interested in.  If it does we need to take the block out of the list.  Make
  // a "persistent mapping" by turning basic blocks into <function, name> pairs.
  // This won't work well if blocks are unnamed, but that is just the risk we
  // have to take.
  std::vector<std::pair<std::string, std::string> > BlockInfo;

  for (BasicBlock *BB : Blocks)
    BlockInfo.emplace_back(BB->getParent()->getName(), BB->getName());

  // Now run the CFG simplify pass on the function...
  std::vector<std::string> Passes;
  Passes.push_back("simplifycfg");
  Passes.push_back("verify");
  std::unique_ptr<Module> New = BD.runPassesOn(M, Passes);
  delete M;
  if (!New) {
    errs() << "simplifycfg failed!\n";
    exit(1);
  }
  M = New.release();

  // Try running on the hacked up program...
  if (TestFn(BD, M)) {
    BD.setNewProgram(M);      // It crashed, keep the trimmed version...

    // Make sure to use basic block pointers that point into the now-current
    // module, and that they don't include any deleted blocks.
    BBs.clear();
    const ValueSymbolTable &GST = M->getValueSymbolTable();
    for (unsigned i = 0, e = BlockInfo.size(); i != e; ++i) {
      Function *F = cast<Function>(GST.lookup(BlockInfo[i].first));
      ValueSymbolTable &ST = F->getValueSymbolTable();
      Value* V = ST.lookup(BlockInfo[i].second);
      if (V && V->getType() == Type::getLabelTy(V->getContext()))
        BBs.push_back(cast<BasicBlock>(V));
    }
    return true;
  }
  delete M;  // It didn't crash, try something else.
  return false;
}

/// DupRetToEnableTailCallOpts - Look for opportunities to duplicate return
/// instructions to the predecessor to enable tail call optimizations. The
/// case it is currently looking for is:
/// bb0:
///   %tmp0 = tail call i32 @f0()
///   br label %return
/// bb1:
///   %tmp1 = tail call i32 @f1()
///   br label %return
/// bb2:
///   %tmp2 = tail call i32 @f2()
///   br label %return
/// return:
///   %retval = phi i32 [ %tmp0, %bb0 ], [ %tmp1, %bb1 ], [ %tmp2, %bb2 ]
///   ret i32 %retval
///
/// =>
///
/// bb0:
///   %tmp0 = tail call i32 @f0()
///   ret i32 %tmp0
/// bb1:
///   %tmp1 = tail call i32 @f1()
///   ret i32 %tmp1
/// bb2:
///   %tmp2 = tail call i32 @f2()
///   ret i32 %tmp2
///
bool CodeGenPrepare::DupRetToEnableTailCallOpts(ReturnInst *RI) {
  if (!TLI)
    return false;

  Value *V = RI->getReturnValue();
  PHINode *PN = V ? dyn_cast<PHINode>(V) : NULL;
  if (V && !PN)
    return false;

  BasicBlock *BB = RI->getParent();
  if (PN && PN->getParent() != BB)
    return false;

  // It's not safe to eliminate the sign / zero extension of the return value.
  // See llvm::isInTailCallPosition().
  const Function *F = BB->getParent();
  Attributes CallerRetAttr = F->getAttributes().getRetAttributes();
  if ((CallerRetAttr & Attribute::ZExt) || (CallerRetAttr & Attribute::SExt))
    return false;

  // Make sure there are no instructions between the PHI and return, or that the
  // return is the first instruction in the block.
  if (PN) {
    BasicBlock::iterator BI = BB->begin();
    do { ++BI; } while (isa<DbgInfoIntrinsic>(BI));
    if (&*BI != RI)
      return false;
  } else {
    BasicBlock::iterator BI = BB->begin();
    while (isa<DbgInfoIntrinsic>(BI)) ++BI;
    if (&*BI != RI)
      return false;
  }

  /// Only dup the ReturnInst if the CallInst is likely to be emitted as a tail
  /// call.
  SmallVector<CallInst*, 4> TailCalls;
  if (PN) {
    for (unsigned I = 0, E = PN->getNumIncomingValues(); I != E; ++I) {
      CallInst *CI = dyn_cast<CallInst>(PN->getIncomingValue(I));
      // Make sure the phi value is indeed produced by the tail call.
      if (CI && CI->hasOneUse() && CI->getParent() == PN->getIncomingBlock(I) &&
          TLI->mayBeEmittedAsTailCall(CI))
        TailCalls.push_back(CI);
    }
  } else {
    SmallPtrSet<BasicBlock*, 4> VisitedBBs;
    for (pred_iterator PI = pred_begin(BB), PE = pred_end(BB); PI != PE; ++PI) {
      if (!VisitedBBs.insert(*PI))
        continue;

      BasicBlock::InstListType &InstList = (*PI)->getInstList();
      BasicBlock::InstListType::reverse_iterator RI = InstList.rbegin();
      BasicBlock::InstListType::reverse_iterator RE = InstList.rend();
      do { ++RI; } while (RI != RE && isa<DbgInfoIntrinsic>(&*RI));
      if (RI == RE)
        continue;

      CallInst *CI = dyn_cast<CallInst>(&*RI);
      if (CI && CI->use_empty() && TLI->mayBeEmittedAsTailCall(CI))
        TailCalls.push_back(CI);
    }
  }

  bool Changed = false;
  for (unsigned i = 0, e = TailCalls.size(); i != e; ++i) {
    CallInst *CI = TailCalls[i];
    CallSite CS(CI);

    // Conservatively require the attributes of the call to match those of the
    // return. Ignore noalias because it doesn't affect the call sequence.
    Attributes CalleeRetAttr = CS.getAttributes().getRetAttributes();
//.........这里部分代码省略.........

void TypeChecker::configureInterfaceType(AbstractFunctionDecl *func) {
  Type funcTy;
  Type initFuncTy;

  auto *sig = func->getGenericSignature();

  if (auto fn = dyn_cast<FuncDecl>(func)) {
    funcTy = fn->getBodyResultTypeLoc().getType();
    
    if (!funcTy) {
      funcTy = TupleType::getEmpty(Context);
    } else {
      funcTy = getResultType(*this, fn, funcTy);
    }

  } else if (auto ctor = dyn_cast<ConstructorDecl>(func)) {
    auto *dc = ctor->getDeclContext();

    funcTy = dc->getSelfInterfaceType();

    // Adjust result type for failability.
    if (ctor->getFailability() != OTK_None)
      funcTy = OptionalType::get(ctor->getFailability(), funcTy);

    initFuncTy = funcTy;
  } else {
    assert(isa<DestructorDecl>(func));
    funcTy = TupleType::getEmpty(Context);
  }

  auto paramLists = func->getParameterLists();
  SmallVector<ParameterList*, 4> storedParamLists;

  // FIXME: Destructors don't have the '()' pattern in their signature, so
  // paste it here.
  if (isa<DestructorDecl>(func)) {
    assert(paramLists.size() == 1 && "Only the self paramlist");
    storedParamLists.push_back(paramLists[0]);
    storedParamLists.push_back(ParameterList::createEmpty(Context));
    paramLists = storedParamLists;
  }

  bool hasSelf = func->getDeclContext()->isTypeContext();
  for (unsigned i = 0, e = paramLists.size(); i != e; ++i) {
    Type argTy;
    Type initArgTy;

    Type selfTy;
    if (i == e-1 && hasSelf) {
      selfTy = func->computeInterfaceSelfType(/*isInitializingCtor=*/false);
      // Substitute in our own 'self' parameter.

      argTy = selfTy;
      if (initFuncTy) {
        initArgTy = func->computeInterfaceSelfType(/*isInitializingCtor=*/true);
      }
    } else {
      argTy = paramLists[e - i - 1]->getInterfaceType(func->getDeclContext());

      if (initFuncTy)
        initArgTy = argTy;
    }

    // 'throws' only applies to the innermost function.
    AnyFunctionType::ExtInfo info;
    if (i == 0 && func->hasThrows())
      info = info.withThrows();

    assert(!argTy->hasArchetype());
    assert(!funcTy->hasArchetype());
    if (initFuncTy)
      assert(!initFuncTy->hasArchetype());

    if (sig && i == e-1) {
      funcTy = GenericFunctionType::get(sig, argTy, funcTy, info);
      if (initFuncTy)
        initFuncTy = GenericFunctionType::get(sig, initArgTy, initFuncTy, info);
    } else {
      funcTy = FunctionType::get(argTy, funcTy, info);
      if (initFuncTy)
        initFuncTy = FunctionType::get(initArgTy, initFuncTy, info);
    }
  }

  // Record the interface type.
  func->setInterfaceType(funcTy);
  if (initFuncTy)
    cast<ConstructorDecl>(func)->setInitializerInterfaceType(initFuncTy);

  if (func->getGenericParams()) {
    // Collect all generic params referenced in parameter types,
    // return type or requirements.
    SmallPtrSet<GenericTypeParamDecl *, 4> referencedGenericParams;

    auto visitorFn = [&referencedGenericParams](Type t) {
      if (auto *paramTy = t->getAs<GenericTypeParamType>())
        referencedGenericParams.insert(paramTy->getDecl());
    };

    funcTy->castTo<AnyFunctionType>()->getInput().visit(visitorFn);
//.........这里部分代码省略.........

/// runOnLoop - Remove dead loops, by which we mean loops that do not impact the
/// observable behavior of the program other than finite running time.  Note
/// we do ensure that this never remove a loop that might be infinite, as doing
/// so could change the halting/non-halting nature of a program.
/// NOTE: This entire process relies pretty heavily on LoopSimplify and LCSSA
/// in order to make various safety checks work.
bool LoopDeletion::runOnLoop(Loop *L, LPPassManager &LPM) {
  // We can only remove the loop if there is a preheader that we can
  // branch from after removing it.
  BasicBlock *preheader = L->getLoopPreheader();
  if (!preheader)
    return false;

  // If LoopSimplify form is not available, stay out of trouble.
  if (!L->hasDedicatedExits())
    return false;

  // We can't remove loops that contain subloops.  If the subloops were dead,
  // they would already have been removed in earlier executions of this pass.
  if (L->begin() != L->end())
    return false;

  SmallVector<BasicBlock*, 4> exitingBlocks;
  L->getExitingBlocks(exitingBlocks);

  SmallVector<BasicBlock*, 4> exitBlocks;
  L->getUniqueExitBlocks(exitBlocks);

  // We require that the loop only have a single exit block.  Otherwise, we'd
  // be in the situation of needing to be able to solve statically which exit
  // block will be branched to, or trying to preserve the branching logic in
  // a loop invariant manner.
  if (exitBlocks.size() != 1)
    return false;

  // Finally, we have to check that the loop really is dead.
  bool Changed = false;
  if (!isLoopDead(L, exitingBlocks, exitBlocks, Changed, preheader))
    return Changed;

  // Don't remove loops for which we can't solve the trip count.
  // They could be infinite, in which case we'd be changing program behavior.
  ScalarEvolution &SE = getAnalysis<ScalarEvolution>();
  const SCEV *S = SE.getMaxBackedgeTakenCount(L);
  if (isa<SCEVCouldNotCompute>(S))
    return Changed;

  // Now that we know the removal is safe, remove the loop by changing the
  // branch from the preheader to go to the single exit block.
  BasicBlock *exitBlock = exitBlocks[0];

  // Because we're deleting a large chunk of code at once, the sequence in which
  // we remove things is very important to avoid invalidation issues.  Don't
  // mess with this unless you have good reason and know what you're doing.

  // Tell ScalarEvolution that the loop is deleted. Do this before
  // deleting the loop so that ScalarEvolution can look at the loop
  // to determine what it needs to clean up.
  SE.forgetLoop(L);

  // Connect the preheader directly to the exit block.
  TerminatorInst *TI = preheader->getTerminator();
  TI->replaceUsesOfWith(L->getHeader(), exitBlock);

  // Rewrite phis in the exit block to get their inputs from
  // the preheader instead of the exiting block.
  BasicBlock *exitingBlock = exitingBlocks[0];
  BasicBlock::iterator BI = exitBlock->begin();
  while (PHINode *P = dyn_cast<PHINode>(BI)) {
    int j = P->getBasicBlockIndex(exitingBlock);
    assert(j >= 0 && "Can't find exiting block in exit block's phi node!");
    P->setIncomingBlock(j, preheader);
    for (unsigned i = 1; i < exitingBlocks.size(); ++i)
      P->removeIncomingValue(exitingBlocks[i]);
    ++BI;
  }

  // Update the dominator tree and remove the instructions and blocks that will
  // be deleted from the reference counting scheme.
  DominatorTree &DT = getAnalysis<DominatorTree>();
  SmallVector<DomTreeNode*, 8> ChildNodes;
  for (Loop::block_iterator LI = L->block_begin(), LE = L->block_end();
       LI != LE; ++LI) {
    // Move all of the block's children to be children of the preheader, which
    // allows us to remove the domtree entry for the block.
    ChildNodes.insert(ChildNodes.begin(), DT[*LI]->begin(), DT[*LI]->end());
    for (SmallVector<DomTreeNode*, 8>::iterator DI = ChildNodes.begin(),
         DE = ChildNodes.end(); DI != DE; ++DI) {
      DT.changeImmediateDominator(*DI, DT[preheader]);
    }

    ChildNodes.clear();
    DT.eraseNode(*LI);

    // Remove the block from the reference counting scheme, so that we can
    // delete it freely later.
    (*LI)->dropAllReferences();
  }

  // Erase the instructions and the blocks without having to worry
//.........这里部分代码省略.........