C++ Use::getUser方法代码示例

// Replace direct callers of Old with New.
void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
  Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
  for (auto UI = Old->use_begin(), UE = Old->use_end(); UI != UE;) {
    Use *U = &*UI;
    ++UI;
    CallSite CS(U->getUser());
    if (CS && CS.isCallee(U)) {
      remove(CS.getInstruction()->getParent()->getParent());
      U->set(BitcastNew);
    }
  }
}

bool DominatorTree::dominates(const Instruction *Def,
                              const Use &U) const {
  Instruction *UserInst = cast<Instruction>(U.getUser());
  const BasicBlock *DefBB = Def->getParent();

  // Determine the block in which the use happens. PHI nodes use
  // their operands on edges; simulate this by thinking of the use
  // happening at the end of the predecessor block.
  const BasicBlock *UseBB;
  if (PHINode *PN = dyn_cast<PHINode>(UserInst))
    UseBB = PN->getIncomingBlock(U);
  else
    UseBB = UserInst->getParent();

  // Any unreachable use is dominated, even if Def == User.
  if (!isReachableFromEntry(UseBB))
    return true;

  // Unreachable definitions don't dominate anything.
  if (!isReachableFromEntry(DefBB))
    return false;

  // Invoke instructions define their return values on the edges
  // to their normal successors, so we have to handle them specially.
  // Among other things, this means they don't dominate anything in
  // their own block, except possibly a phi, so we don't need to
  // walk the block in any case.
  if (const InvokeInst *II = dyn_cast<InvokeInst>(Def)) {
    BasicBlock *NormalDest = II->getNormalDest();
    BasicBlockEdge E(DefBB, NormalDest);
    return dominates(E, U);
  }

  // If the def and use are in different blocks, do a simple CFG dominator
  // tree query.
  if (DefBB != UseBB)
    return dominates(DefBB, UseBB);

  // Ok, def and use are in the same block. If the def is an invoke, it
  // doesn't dominate anything in the block. If it's a PHI, it dominates
  // everything in the block.
  if (isa<PHINode>(UserInst))
    return true;

  // Otherwise, just loop through the basic block until we find Def or User.
  BasicBlock::const_iterator I = DefBB->begin();
  for (; &*I != Def && &*I != UserInst; ++I)
    /*empty*/;

  return &*I != UserInst;
}

bool DominatorTree::isReachableFromEntry(const Use &U) const {
  Instruction *I = dyn_cast<Instruction>(U.getUser());

  // ConstantExprs aren't really reachable from the entry block, but they
  // don't need to be treated like unreachable code either.
  if (!I) return true;

  // PHI nodes use their operands on their incoming edges.
  if (PHINode *PN = dyn_cast<PHINode>(I))
    return isReachableFromEntry(PN->getIncomingBlock(U));

  // Everything else uses their operands in their own block.
  return isReachableFromEntry(I->getParent());
}

void SSAUpdater::RewriteUse(Use &U) {
  Instruction *User = cast<Instruction>(U.getUser());

  Value *V;
  if (PHINode *UserPN = dyn_cast<PHINode>(User))
    V = GetValueAtEndOfBlock(UserPN->getIncomingBlock(U));
  else
    V = GetValueInMiddleOfBlock(User->getParent());

  // Notify that users of the existing value that it is being replaced.
  Value *OldVal = U.get();
  if (OldVal != V && OldVal->hasValueHandle())
    ValueHandleBase::ValueIsRAUWd(OldVal, V);

  U.set(V);
}

bool DominatorTree::dominates(const BasicBlockEdge &BBE, const Use &U) const {
  Instruction *UserInst = cast<Instruction>(U.getUser());
  // A PHI in the end of the edge is dominated by it.
  PHINode *PN = dyn_cast<PHINode>(UserInst);
  if (PN && PN->getParent() == BBE.getEnd() &&
      PN->getIncomingBlock(U) == BBE.getStart())
    return true;

  // Otherwise use the edge-dominates-block query, which
  // handles the crazy critical edge cases properly.
  const BasicBlock *UseBB;
  if (PN)
    UseBB = PN->getIncomingBlock(U);
  else
    UseBB = UserInst->getParent();
  return dominates(BBE, UseBB);
}

/// \p returns true if \p U is the pointer operand of a memory instruction with
/// a single pointer operand that can have its address space changed by simply
/// mutating the use to a new value.
static bool isSimplePointerUseValidToReplace(Use &U) {
  User *Inst = U.getUser();
  unsigned OpNo = U.getOperandNo();

  if (auto *LI = dyn_cast<LoadInst>(Inst))
    return OpNo == LoadInst::getPointerOperandIndex() && !LI->isVolatile();

  if (auto *SI = dyn_cast<StoreInst>(Inst))
    return OpNo == StoreInst::getPointerOperandIndex() && !SI->isVolatile();

  if (auto *RMW = dyn_cast<AtomicRMWInst>(Inst))
    return OpNo == AtomicRMWInst::getPointerOperandIndex() && !RMW->isVolatile();

  if (auto *CmpX = dyn_cast<AtomicCmpXchgInst>(Inst)) {
    return OpNo == AtomicCmpXchgInst::getPointerOperandIndex() &&
           !CmpX->isVolatile();
  }

  return false;
}

bool DominatorTree::dominates(const BasicBlockEdge &BBE, const Use &U) const {
  // Assert that we have a single edge. We could handle them by simply
  // returning false, but since isSingleEdge is linear on the number of
  // edges, the callers can normally handle them more efficiently.
  assert(BBE.isSingleEdge());

  Instruction *UserInst = cast<Instruction>(U.getUser());
  // A PHI in the end of the edge is dominated by it.
  PHINode *PN = dyn_cast<PHINode>(UserInst);
  if (PN && PN->getParent() == BBE.getEnd() &&
      PN->getIncomingBlock(U) == BBE.getStart())
    return true;

  // Otherwise use the edge-dominates-block query, which
  // handles the crazy critical edge cases properly.
  const BasicBlock *UseBB;
  if (PN)
    UseBB = PN->getIncomingBlock(U);
  else
    UseBB = UserInst->getParent();
  return dominates(BBE, UseBB);
}

/// Handle a rare case where the disintegrated nodes instructions
/// no longer dominate all their uses. Not sure if this is really nessasary
void StructurizeCFG::rebuildSSA() {
  SSAUpdater Updater;
  for (Region::block_iterator I = ParentRegion->block_begin(),
                              E = ParentRegion->block_end();
       I != E; ++I) {

    BasicBlock *BB = *I;
    for (BasicBlock::iterator II = BB->begin(), IE = BB->end();
         II != IE; ++II) {

      bool Initialized = false;
      for (Use *I = &II->use_begin().getUse(), *Next; I; I = Next) {

        Next = I->getNext();

        Instruction *User = cast<Instruction>(I->getUser());
        if (User->getParent() == BB) {
          continue;

        } else if (PHINode *UserPN = dyn_cast<PHINode>(User)) {
          if (UserPN->getIncomingBlock(*I) == BB)
            continue;
        }

        if (DT->dominates(II, User))
          continue;

        if (!Initialized) {
          Value *Undef = UndefValue::get(II->getType());
          Updater.Initialize(II->getType(), "");
          Updater.AddAvailableValue(&Func->getEntryBlock(), Undef);
          Updater.AddAvailableValue(BB, II);
          Initialized = true;
        }
        Updater.RewriteUseAfterInsertions(*I);
      }
    }
  }
}

/// Returns Attribute::None, Attribute::ReadOnly or Attribute::ReadNone.
static Attribute::AttrKind
determinePointerReadAttrs(Argument *A,
                          const SmallPtrSet<Argument *, 8> &SCCNodes) {

  SmallVector<Use *, 32> Worklist;
  SmallSet<Use *, 32> Visited;

  // inalloca arguments are always clobbered by the call.
  if (A->hasInAllocaAttr())
    return Attribute::None;

  bool IsRead = false;
  // We don't need to track IsWritten. If A is written to, return immediately.

  for (Use &U : A->uses()) {
    Visited.insert(&U);
    Worklist.push_back(&U);
  }

  while (!Worklist.empty()) {
    Use *U = Worklist.pop_back_val();
    Instruction *I = cast<Instruction>(U->getUser());

    switch (I->getOpcode()) {
    case Instruction::BitCast:
    case Instruction::GetElementPtr:
    case Instruction::PHI:
    case Instruction::Select:
    case Instruction::AddrSpaceCast:
      // The original value is not read/written via this if the new value isn't.
      for (Use &UU : I->uses())
        if (Visited.insert(&UU).second)
          Worklist.push_back(&UU);
      break;

    case Instruction::Call:
    case Instruction::Invoke: {
      bool Captures = true;

      if (I->getType()->isVoidTy())
        Captures = false;

      auto AddUsersToWorklistIfCapturing = [&] {
        if (Captures)
          for (Use &UU : I->uses())
            if (Visited.insert(&UU).second)
              Worklist.push_back(&UU);
      };

      CallSite CS(I);
      if (CS.doesNotAccessMemory()) {
        AddUsersToWorklistIfCapturing();
        continue;
      }

      Function *F = CS.getCalledFunction();
      if (!F) {
        if (CS.onlyReadsMemory()) {
          IsRead = true;
          AddUsersToWorklistIfCapturing();
          continue;
        }
        return Attribute::None;
      }

      // Note: the callee and the two successor blocks *follow* the argument
      // operands.  This means there is no need to adjust UseIndex to account
      // for these.

      unsigned UseIndex = std::distance(CS.arg_begin(), U);

      // U cannot be the callee operand use: since we're exploring the
      // transitive uses of an Argument, having such a use be a callee would
      // imply the CallSite is an indirect call or invoke; and we'd take the
      // early exit above.
      assert(UseIndex < CS.data_operands_size() &&
             "Data operand use expected!");

      bool IsOperandBundleUse = UseIndex >= CS.getNumArgOperands();

      if (UseIndex >= F->arg_size() && !IsOperandBundleUse) {
        assert(F->isVarArg() && "More params than args in non-varargs call");
        return Attribute::None;
      }

      Captures &= !CS.doesNotCapture(UseIndex);

      // Since the optimizer (by design) cannot see the data flow corresponding
      // to a operand bundle use, these cannot participate in the optimistic SCC
      // analysis.  Instead, we model the operand bundle uses as arguments in
      // call to a function external to the SCC.
      if (IsOperandBundleUse ||
          !SCCNodes.count(&*std::next(F->arg_begin(), UseIndex))) {

        // The accessors used on CallSite here do the right thing for calls and
        // invokes with operand bundles.

        if (!CS.onlyReadsMemory() && !CS.onlyReadsMemory(UseIndex))
          return Attribute::None;
//.........这里部分代码省略.........

void llvm::PointerMayBeCaptured(const Value *V, CaptureTracker *Tracker) {
  assert(V->getType()->isPointerTy() && "Capture is for pointers only!");
  SmallVector<Use*, Threshold> Worklist;
  SmallSet<Use*, Threshold> Visited;
  int Count = 0;

  for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
       UI != UE; ++UI) {
    // If there are lots of uses, conservatively say that the value
    // is captured to avoid taking too much compile time.
    if (Count++ >= Threshold)
      return Tracker->tooManyUses();

    Use *U = &UI.getUse();
    if (!Tracker->shouldExplore(U)) continue;
    Visited.insert(U);
    Worklist.push_back(U);
  }

  while (!Worklist.empty()) {
    Use *U = Worklist.pop_back_val();
    Instruction *I = cast<Instruction>(U->getUser());
    V = U->get();

    switch (I->getOpcode()) {
    case Instruction::Call:
    case Instruction::Invoke: {
      CallSite CS(I);
      // Not captured if the callee is readonly, doesn't return a copy through
      // its return value and doesn't unwind (a readonly function can leak bits
      // by throwing an exception or not depending on the input value).
      if (CS.onlyReadsMemory() && CS.doesNotThrow() && I->getType()->isVoidTy())
        break;

      // Not captured if only passed via 'nocapture' arguments.  Note that
      // calling a function pointer does not in itself cause the pointer to
      // be captured.  This is a subtle point considering that (for example)
      // the callee might return its own address.  It is analogous to saying
      // that loading a value from a pointer does not cause the pointer to be
      // captured, even though the loaded value might be the pointer itself
      // (think of self-referential objects).
      CallSite::arg_iterator B = CS.arg_begin(), E = CS.arg_end();
      for (CallSite::arg_iterator A = B; A != E; ++A)
        if (A->get() == V && !CS.doesNotCapture(A - B))
          // The parameter is not marked 'nocapture' - captured.
          if (Tracker->captured(U))
            return;
      break;
    }
    case Instruction::Load:
      // Loading from a pointer does not cause it to be captured.
      break;
    case Instruction::VAArg:
      // "va-arg" from a pointer does not cause it to be captured.
      break;
    case Instruction::Store:
      if (V == I->getOperand(0))
        // Stored the pointer - conservatively assume it may be captured.
        if (Tracker->captured(U))
          return;
      // Storing to the pointee does not cause the pointer to be captured.
      break;
    case Instruction::BitCast:
    case Instruction::GetElementPtr:
    case Instruction::PHI:
    case Instruction::Select:
      // The original value is not captured via this if the new value isn't.
      for (Instruction::use_iterator UI = I->use_begin(), UE = I->use_end();
           UI != UE; ++UI) {
        Use *U = &UI.getUse();
        if (Visited.insert(U))
          if (Tracker->shouldExplore(U))
            Worklist.push_back(U);
      }
      break;
    case Instruction::ICmp:
      // Don't count comparisons of a no-alias return value against null as
      // captures. This allows us to ignore comparisons of malloc results
      // with null, for example.
      if (ConstantPointerNull *CPN =
          dyn_cast<ConstantPointerNull>(I->getOperand(1)))
        if (CPN->getType()->getAddressSpace() == 0)
          if (isNoAliasCall(V->stripPointerCastsSafe()))
            break;
      // Otherwise, be conservative. There are crazy ways to capture pointers
      // using comparisons.
      if (Tracker->captured(U))
        return;
      break;
    default:
      // Something else - be conservative and say it is captured.
      if (Tracker->captured(U))
        return;
      break;
    }
  }

  // All uses examined.
}

DDGraph::DDGraph(ResolveResult& RR,Value* root) 
{
   auto& r = get<0>(RR);
   auto& u = get<1>(RR);
   auto& c = get<2>(RR);
   for(auto I : r){
      this->insert(make_value(I,DDGNode::NORMAL));
   }
   for(auto I : u){
      this->insert(make_value(I,DDGNode::UNSOLVED));
   }
   for(auto& N : *this){
      auto found = c.find(N.first);
      DDGNode& node = N.second;
      if(node.flags() & DDGNode::UNSOLVED) continue;
      Use* implicity = (found == c.end())?nullptr:found->second;
      if(implicity){
         DDGValue& v = *this->find(implicity->getUser());
         DDGNode& to = v.second;
         node.impl().push_back(&v);
         ++v.second.ref_count;
         node.flags_ = DDGNode::IMPLICITY;
         if(auto CI = dyn_cast<CallInst>(implicity->getUser())){
            Instruction* NI = dyn_cast<Instruction>(N.first);
            if(NI && CI->getCalledFunction() != NI->getParent()->getParent()){
               Argument* arg = findCallInstArgument(implicity);
               if(!arg) continue;
               auto found = c.find(cast<Value>(arg));
               Use* link = (found==c.end())?nullptr:found->second;
               if(link){
                  node.load_tg_ = &*this->find(link->getUser());
                  //++node.load_tg_->second.ref_count; // shouldn't add ref count for load_tg
                  to.impl().push_back(node.load_inst());
                  to.flags_ = DDGNode::IMPLICITY;
               }
            }else{
               if(isa<AllocaInst>(implicity->get())){
                  auto found = c.find(implicity->get());
                  Use* link = (found==c.end())?nullptr:found->second;
                  if(link) node.load_tg_ = &*this->find(link->getUser());
               }else 
                  node.load_tg_ = &*this->find(implicity->get());
               to.impl().push_back(node.load_inst());
               to.flags_ = DDGNode::IMPLICITY;
            }
         }
      }
   }
   for(auto& N : *this){
      // for stability, make sure all implicity marked over before this.
      auto found = c.find(N.first);
      if(found != c.end()) continue;

      Instruction* Inst = dyn_cast<llvm::Instruction>(N.first);
      DDGNode& node = N.second;
      if(!Inst) continue;
      if(isa<CallInst>(Inst) && (N.second.flags_ & DDGNode::IMPLICITY))
         continue; // implicity callinst never can be direct solve
      for(auto O = Inst->op_begin(),E=Inst->op_end();O!=E;++O){
         auto Target = this->find(*O);
         if(Target != this->end()){
            DDGValue* v = &*Target;
            ++v->second.ref_count;
            node.impl().push_back(v);
         }
      }
   }
   this->root = &*this->find(root);
}

IOCode Aa::get_io_code(Use &u)
{
	return get_io_code(u.getUser());
}

void WinEHPrepare::replaceUseWithLoad(Value *V, Use &U, AllocaInst *&SpillSlot,
                                      DenseMap<BasicBlock *, Value *> &Loads,
                                      Function &F) {
  // Lazilly create the spill slot.
  if (!SpillSlot)
    SpillSlot = new AllocaInst(V->getType(), DL->getAllocaAddrSpace(), nullptr,
                               Twine(V->getName(), ".wineh.spillslot"),
                               &F.getEntryBlock().front());

  auto *UsingInst = cast<Instruction>(U.getUser());
  if (auto *UsingPHI = dyn_cast<PHINode>(UsingInst)) {
    // If this is a PHI node, we can't insert a load of the value before
    // the use.  Instead insert the load in the predecessor block
    // corresponding to the incoming value.
    //
    // Note that if there are multiple edges from a basic block to this
    // PHI node that we cannot have multiple loads.  The problem is that
    // the resulting PHI node will have multiple values (from each load)
    // coming in from the same block, which is illegal SSA form.
    // For this reason, we keep track of and reuse loads we insert.
    BasicBlock *IncomingBlock = UsingPHI->getIncomingBlock(U);
    if (auto *CatchRet =
            dyn_cast<CatchReturnInst>(IncomingBlock->getTerminator())) {
      // Putting a load above a catchret and use on the phi would still leave
      // a cross-funclet def/use.  We need to split the edge, change the
      // catchret to target the new block, and put the load there.
      BasicBlock *PHIBlock = UsingInst->getParent();
      BasicBlock *NewBlock = SplitEdge(IncomingBlock, PHIBlock);
      // SplitEdge gives us:
      //   IncomingBlock:
      //     ...
      //     br label %NewBlock
      //   NewBlock:
      //     catchret label %PHIBlock
      // But we need:
      //   IncomingBlock:
      //     ...
      //     catchret label %NewBlock
      //   NewBlock:
      //     br label %PHIBlock
      // So move the terminators to each others' blocks and swap their
      // successors.
      BranchInst *Goto = cast<BranchInst>(IncomingBlock->getTerminator());
      Goto->removeFromParent();
      CatchRet->removeFromParent();
      IncomingBlock->getInstList().push_back(CatchRet);
      NewBlock->getInstList().push_back(Goto);
      Goto->setSuccessor(0, PHIBlock);
      CatchRet->setSuccessor(NewBlock);
      // Update the color mapping for the newly split edge.
      // Grab a reference to the ColorVector to be inserted before getting the
      // reference to the vector we are copying because inserting the new
      // element in BlockColors might cause the map to be reallocated.
      ColorVector &ColorsForNewBlock = BlockColors[NewBlock];
      ColorVector &ColorsForPHIBlock = BlockColors[PHIBlock];
      ColorsForNewBlock = ColorsForPHIBlock;
      for (BasicBlock *FuncletPad : ColorsForPHIBlock)
        FuncletBlocks[FuncletPad].push_back(NewBlock);
      // Treat the new block as incoming for load insertion.
      IncomingBlock = NewBlock;
    }
    Value *&Load = Loads[IncomingBlock];
    // Insert the load into the predecessor block
    if (!Load)
      Load = new LoadInst(SpillSlot, Twine(V->getName(), ".wineh.reload"),
                          /*Volatile=*/false, IncomingBlock->getTerminator());

    U.set(Load);
  } else {
    // Reload right before the old use.
    auto *Load = new LoadInst(SpillSlot, Twine(V->getName(), ".wineh.reload"),
                              /*Volatile=*/false, UsingInst);
    U.set(Load);
  }
}