C++ DomTreeNode::end方法代码示例

/*update the dominator tree when a new block is created*/
void updateDT(BasicBlock *oldB, BasicBlock *newB, DominatorTree *DT) {
  errs() << "\n -----------------------" << oldB->getName()
         << "\n  dominated by  \n"
         << newB->getName() << "\n";

  DomTreeNode *OldNode = DT->getNode(oldB);
  if (OldNode) {
    std::vector<DomTreeNode *> Children;
    for (DomTreeNode::iterator I = OldNode->begin(), E = OldNode->end(); I != E;
         ++I)
      Children.push_back(*I);

    DomTreeNode *inDT = DT->getNode(newB);
    DomTreeNode *NewNode;

    if (inDT == 0)
      NewNode = DT->addNewBlock(newB, oldB);
    else
      NewNode = DT->getNode(newB);

    for (std::vector<DomTreeNode *>::iterator I = Children.begin(),
                                              E = Children.end();
         I != E; ++I)
      DT->changeImmediateDominator(*I, NewNode);
  }
}

/// SinkInstruction - Determine whether it is safe to sink the specified machine
/// instruction out of its current block into a successor.
bool Sinking::SinkInstruction(Instruction *Inst,
                              SmallPtrSetImpl<Instruction *> &Stores) {

  // Don't sink static alloca instructions.  CodeGen assumes allocas outside the
  // entry block are dynamically sized stack objects.
  if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
    if (AI->isStaticAlloca())
      return false;

  // Check if it's safe to move the instruction.
  if (!isSafeToMove(Inst, AA, Stores))
    return false;

  // FIXME: This should include support for sinking instructions within the
  // block they are currently in to shorten the live ranges.  We often get
  // instructions sunk into the top of a large block, but it would be better to
  // also sink them down before their first use in the block.  This xform has to
  // be careful not to *increase* register pressure though, e.g. sinking
  // "x = y + z" down if it kills y and z would increase the live ranges of y
  // and z and only shrink the live range of x.

  // SuccToSinkTo - This is the successor to sink this instruction to, once we
  // decide.
  BasicBlock *SuccToSinkTo = nullptr;

  // Instructions can only be sunk if all their uses are in blocks
  // dominated by one of the successors.
  // Look at all the postdominators and see if we can sink it in one.
  DomTreeNode *DTN = DT->getNode(Inst->getParent());
  for (DomTreeNode::iterator I = DTN->begin(), E = DTN->end();
      I != E && SuccToSinkTo == nullptr; ++I) {
    BasicBlock *Candidate = (*I)->getBlock();
    if ((*I)->getIDom()->getBlock() == Inst->getParent() &&
        IsAcceptableTarget(Inst, Candidate))
      SuccToSinkTo = Candidate;
  }

  // If no suitable postdominator was found, look at all the successors and
  // decide which one we should sink to, if any.
  for (succ_iterator I = succ_begin(Inst->getParent()),
      E = succ_end(Inst->getParent()); I != E && !SuccToSinkTo; ++I) {
    if (IsAcceptableTarget(Inst, *I))
      SuccToSinkTo = *I;
  }

  // If we couldn't find a block to sink to, ignore this instruction.
  if (!SuccToSinkTo)
    return false;

  DEBUG(dbgs() << "Sink" << *Inst << " (";
        Inst->getParent()->printAsOperand(dbgs(), false);
        dbgs() << " -> ";
        SuccToSinkTo->printAsOperand(dbgs(), false);
        dbgs() << ")\n");

  // Move the instruction.
  Inst->moveBefore(SuccToSinkTo->getFirstInsertionPt());
  return true;
}

/// Compute the dominator tree levels for DT.
static void computeDomTreeLevels(DominanceInfo *DT,
                                 DomTreeLevelMap &DomTreeLevels) {
  // TODO: This should happen once per function.
  SmallVector<DomTreeNode *, 32> Worklist;
  DomTreeNode *Root = DT->getRootNode();
  DomTreeLevels[Root] = 0;
  Worklist.push_back(Root);
  while (!Worklist.empty()) {
    DomTreeNode *Node = Worklist.pop_back_val();
    unsigned ChildLevel = DomTreeLevels[Node] + 1;
    for (auto CI = Node->begin(), CE = Node->end(); CI != CE; ++CI) {
      DomTreeLevels[*CI] = ChildLevel;
      Worklist.push_back(*CI);
    }
  }
}

void CodeExtractor::splitReturnBlocks() {
  for (BasicBlock *Block : Blocks)
    if (ReturnInst *RI = dyn_cast<ReturnInst>(Block->getTerminator())) {
      BasicBlock *New =
          Block->splitBasicBlock(RI->getIterator(), Block->getName() + ".ret");
      if (DT) {
        // Old dominates New. New node dominates all other nodes dominated
        // by Old.
        DomTreeNode *OldNode = DT->getNode(Block);
        SmallVector<DomTreeNode *, 8> Children(OldNode->begin(),
                                               OldNode->end());

        DomTreeNode *NewNode = DT->addNewBlock(New, Block);

        for (DomTreeNode *I : Children)
          DT->changeImmediateDominator(I, NewNode);
      }
    }
}

void RegionExtractor::splitReturnBlocks() {
  for (SetVector<BasicBlock *>::iterator I = Blocks.begin(), E = Blocks.end();
       I != E; ++I)
    if (ReturnInst *RI = dyn_cast<ReturnInst>((*I)->getTerminator())) {
      BasicBlock *New = (*I)->splitBasicBlock(RI, (*I)->getName()+".ret");
      if (DT) {
        // Old dominates New. New node dominates all other nodes dominated
        // by Old.
        DomTreeNode *OldNode = DT->getNode(*I);
        SmallVector<DomTreeNode*, 8> Children;
        for (DomTreeNode::iterator DI = OldNode->begin(), DE = OldNode->end();
             DI != DE; ++DI)
          Children.push_back(*DI);

        DomTreeNode *NewNode = DT->addNewBlock(New, *I);
#if LLVM_VERSION_MINOR == 5
        for (SmallVectorImpl<DomTreeNode *>::iterator I = Children.begin(),
#else
        for (SmallVector<DomTreeNode *, 8>::iterator I = Children.begin(),
#endif
               E = Children.end(); I != E; ++I)
          DT->changeImmediateDominator(*I, NewNode);
      }
    }

void StackAllocationPromoter::promoteAllocationToPhi() {
  DEBUG(llvm::dbgs() << "*** Placing Phis for : " << *ASI);

  // A list of blocks that will require new Phi values.
  BlockSet PhiBlocks;

  // The "piggy-bank" data-structure that we use for processing the dom-tree
  // bottom-up.
  NodePriorityQueue PQ;

  // Collect all of the stores into the AllocStack. We know that at this point
  // we have at most one store per block.
  for (auto UI = ASI->use_begin(), E = ASI->use_end(); UI != E; ++UI) {
    SILInstruction *II = UI->getUser();
    // We need to place Phis for this block.
    if (isa<StoreInst>(II)) {
      // If the block is in the dom tree (dominated by the entry block).
      if (DomTreeNode *Node = DT->getNode(II->getParent()))
        PQ.push(std::make_pair(Node, DomTreeLevels[Node]));
    }
  }

  DEBUG(llvm::dbgs() << "*** Found: " << PQ.size() << " Defs\n");

  // A list of nodes for which we already calculated the dominator frontier.
  llvm::SmallPtrSet<DomTreeNode *, 32> Visited;

  SmallVector<DomTreeNode *, 32> Worklist;

  // Scan all of the definitions in the function bottom-up using the priority
  // queue.
  while (!PQ.empty()) {
    DomTreeNodePair RootPair = PQ.top();
    PQ.pop();
    DomTreeNode *Root = RootPair.first;
    unsigned RootLevel = RootPair.second;

    // Walk all dom tree children of Root, inspecting their successors. Only
    // J-edges, whose target level is at most Root's level are added to the
    // dominance frontier.
    Worklist.clear();
    Worklist.push_back(Root);

    while (!Worklist.empty()) {
      DomTreeNode *Node = Worklist.pop_back_val();
      SILBasicBlock *BB = Node->getBlock();

      // For all successors of the node:
      for (auto &Succ : BB->getSuccessors()) {
        DomTreeNode *SuccNode = DT->getNode(Succ);

        // Skip D-edges (edges that are dom-tree edges).
        if (SuccNode->getIDom() == Node)
          continue;

        // Ignore J-edges that point to nodes that are not smaller or equal
        // to the root level.
        unsigned SuccLevel = DomTreeLevels[SuccNode];
        if (SuccLevel > RootLevel)
          continue;

        // Ignore visited nodes.
        if (!Visited.insert(SuccNode).second)
          continue;

        // If the new PHInode is not dominated by the allocation then it's dead.
        if (!DT->dominates(ASI->getParent(), SuccNode->getBlock()))
            continue;

        // If the new PHInode is properly dominated by the deallocation then it
        // is obviously a dead PHInode, so we don't need to insert it.
        if (DSI && DT->properlyDominates(DSI->getParent(),
                                         SuccNode->getBlock()))
          continue;

        // The successor node is a new PHINode. If this is a new PHI node
        // then it may require additional definitions, so add it to the PQ.
        if (PhiBlocks.insert(Succ).second)
          PQ.push(std::make_pair(SuccNode, SuccLevel));
      }

      // Add the children in the dom-tree to the worklist.
      for (auto CI = Node->begin(), CE = Node->end(); CI != CE; ++CI)
        if (!Visited.count(*CI))
          Worklist.push_back(*CI);
    }
  }

  DEBUG(llvm::dbgs() << "*** Found: " << PhiBlocks.size() << " new PHIs\n");
  NumPhiPlaced += PhiBlocks.size();

  // At this point we calculated the locations of all of the new Phi values.
  // Next, add the Phi values and promote all of the loads and stores into the
  // new locations.

  // Replace the dummy values with new block arguments.
  addBlockArguments(PhiBlocks);

  // Hook up the Phi nodes, loads, and debug_value_addr with incoming values.
  fixBranchesAndUses(PhiBlocks);
//.........这里部分代码省略.........

/// At this point, we're committed to promoting the alloca using IDF's, and the
/// standard SSA construction algorithm.  Determine which blocks need phi nodes
/// and see if we can optimize out some work by avoiding insertion of dead phi
/// nodes.
void PromoteMem2Reg::DetermineInsertionPoint(AllocaInst *AI, unsigned AllocaNum,
                                             AllocaInfo &Info) {
  // Unique the set of defining blocks for efficient lookup.
  SmallPtrSet<BasicBlock *, 32> DefBlocks;
  DefBlocks.insert(Info.DefiningBlocks.begin(), Info.DefiningBlocks.end());

  // Determine which blocks the value is live in.  These are blocks which lead
  // to uses.
  SmallPtrSet<BasicBlock *, 32> LiveInBlocks;
  ComputeLiveInBlocks(AI, Info, DefBlocks, LiveInBlocks);

  // Use a priority queue keyed on dominator tree level so that inserted nodes
  // are handled from the bottom of the dominator tree upwards.
  typedef std::priority_queue<DomTreeNodePair,
                              SmallVector<DomTreeNodePair, 32>,
                              DomTreeNodeCompare> IDFPriorityQueue;
  IDFPriorityQueue PQ;

  for (SmallPtrSet<BasicBlock *, 32>::const_iterator I = DefBlocks.begin(),
                                                     E = DefBlocks.end();
       I != E; ++I) {
    if (DomTreeNode *Node = DT.getNode(*I))
      PQ.push(std::make_pair(Node, DomLevels[Node]));
  }

  SmallVector<std::pair<unsigned, BasicBlock *>, 32> DFBlocks;
  SmallPtrSet<DomTreeNode *, 32> Visited;
  SmallVector<DomTreeNode *, 32> Worklist;
  while (!PQ.empty()) {
    DomTreeNodePair RootPair = PQ.top();
    PQ.pop();
    DomTreeNode *Root = RootPair.first;
    unsigned RootLevel = RootPair.second;

    // Walk all dominator tree children of Root, inspecting their CFG edges with
    // targets elsewhere on the dominator tree. Only targets whose level is at
    // most Root's level are added to the iterated dominance frontier of the
    // definition set.

    Worklist.clear();
    Worklist.push_back(Root);

    while (!Worklist.empty()) {
      DomTreeNode *Node = Worklist.pop_back_val();
      BasicBlock *BB = Node->getBlock();

      for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE;
           ++SI) {
        DomTreeNode *SuccNode = DT.getNode(*SI);

        // Quickly skip all CFG edges that are also dominator tree edges instead
        // of catching them below.
        if (SuccNode->getIDom() == Node)
          continue;

        unsigned SuccLevel = DomLevels[SuccNode];
        if (SuccLevel > RootLevel)
          continue;

        if (!Visited.insert(SuccNode))
          continue;

        BasicBlock *SuccBB = SuccNode->getBlock();
        if (!LiveInBlocks.count(SuccBB))
          continue;

        DFBlocks.push_back(std::make_pair(BBNumbers[SuccBB], SuccBB));
        if (!DefBlocks.count(SuccBB))
          PQ.push(std::make_pair(SuccNode, SuccLevel));
      }

      for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end(); CI != CE;
           ++CI) {
        if (!Visited.count(*CI))
          Worklist.push_back(*CI);
      }
    }
  }

  if (DFBlocks.size() > 1)
    std::sort(DFBlocks.begin(), DFBlocks.end());

  unsigned CurrentVersion = 0;
  for (unsigned i = 0, e = DFBlocks.size(); i != e; ++i)
    QueuePhiNode(DFBlocks[i].second, AllocaNum, CurrentVersion);
}

void PromoteMem2Reg::run() {
  Function &F = *DT.getRoot()->getParent();

  if (AST)
    PointerAllocaValues.resize(Allocas.size());
  AllocaDbgDeclares.resize(Allocas.size());

  AllocaInfo Info;
  LargeBlockInfo LBI;

  for (unsigned AllocaNum = 0; AllocaNum != Allocas.size(); ++AllocaNum) {
    AllocaInst *AI = Allocas[AllocaNum];

    //assert(isAllocaPromotable(AI) && "Cannot promote non-promotable alloca!");
    assert(AI->getParent()->getParent() == &F &&
           "All allocas should be in the same function, which is same as DF!");

    removeLifetimeIntrinsicUsers(AI);

    if (AI->use_empty()) {
      // If there are no uses of the alloca, just delete it now.
      if (AST)
        AST->deleteValue(AI);
      AI->eraseFromParent();

      // Remove the alloca from the Allocas list, since it has been processed
      RemoveFromAllocasList(AllocaNum);
      ++NumDeadAlloca;
      continue;
    }

    // Calculate the set of read and write-locations for each alloca.  This is
    // analogous to finding the 'uses' and 'definitions' of each variable.
    bool Good = Info.analyzeAlloca(*AI);
    (void)Good;
    assert(Good && "Cannot promote non-promotable alloca!");

    // If there is only a single store to this value, replace any loads of
    // it that are directly dominated by the definition with the value stored.
    if (Info.DefiningBlocks.size() == 1) {
      if (rewriteSingleStoreAlloca(AI, Info, LBI, DT, AST)) {
        // The alloca has been processed, move on.
        RemoveFromAllocasList(AllocaNum);
        ++NumSingleStore;
        continue;
      }
    }

    // If the alloca is only read and written in one basic block, just perform a
    // linear sweep over the block to eliminate it.
    if (Info.OnlyUsedInOneBlock) {
      promoteSingleBlockAlloca(AI, Info, LBI, AST);

      // The alloca has been processed, move on.
      RemoveFromAllocasList(AllocaNum);
      continue;
    }

    // If we haven't computed dominator tree levels, do so now.
    if (DomLevels.empty()) {
      SmallVector<DomTreeNode *, 32> Worklist;

      DomTreeNode *Root = DT.getRootNode();
      DomLevels[Root] = 0;
      Worklist.push_back(Root);

      while (!Worklist.empty()) {
        DomTreeNode *Node = Worklist.pop_back_val();
        unsigned ChildLevel = DomLevels[Node] + 1;
        for (DomTreeNode::iterator CI = Node->begin(), CE = Node->end();
             CI != CE; ++CI) {
          DomLevels[*CI] = ChildLevel;
          Worklist.push_back(*CI);
        }
      }
    }

    // If we haven't computed a numbering for the BB's in the function, do so
    // now.
    if (BBNumbers.empty()) {
      unsigned ID = 0;
      for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I)
        BBNumbers[I] = ID++;
    }

    // If we have an AST to keep updated, remember some pointer value that is
    // stored into the alloca.
    if (AST)
      PointerAllocaValues[AllocaNum] = Info.AllocaPointerVal;

    // Remember the dbg.declare intrinsic describing this alloca, if any.
    if (Info.DbgDeclare)
      AllocaDbgDeclares[AllocaNum] = Info.DbgDeclare;

    // Keep the reverse mapping of the 'Allocas' array for the rename pass.
    AllocaLookup[Allocas[AllocaNum]] = AllocaNum;

    // At this point, we're committed to promoting the alloca using IDF's, and
    // the standard SSA construction algorithm.  Determine which blocks need PHI
    // nodes and see if we can optimize out some work by avoiding insertion of
//.........这里部分代码省略.........

void DSWP::buildPDG(Loop *L) {
    //Initialize PDG
	for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
		BasicBlock *BB = *bi;
		for (BasicBlock::iterator ui = BB->begin(); ui != BB->end(); ui++) {
			Instruction *inst = &(*ui);

			//standardlize the name for all expr
			if (util.hasNewDef(inst)) {
				inst->setName(util.genId());
				dname[inst] = inst->getNameStr();
			} else {
				dname[inst] = util.genId();
			}

			pdg[inst] = new vector<Edge>();
			rev[inst] = new vector<Edge>();
		}
	}

	//LoopInfo &li = getAnalysis<LoopInfo>();

	/*
	 * Memory dependency analysis
	 */
	MemoryDependenceAnalysis &mda = getAnalysis<MemoryDependenceAnalysis>();

	for (Loop::block_iterator bi = L->getBlocks().begin(); bi != L->getBlocks().end(); bi++) {
		BasicBlock *BB = *bi;
		for (BasicBlock::iterator ii = BB->begin(); ii != BB->end(); ii++) {
			Instruction *inst = &(*ii);

			//data dependence = register dependence + memory dependence

			//begin register dependence
			for (Value::use_iterator ui = ii->use_begin(); ui != ii->use_end(); ui++) {
				if (Instruction *user = dyn_cast<Instruction>(*ui)) {
					addEdge(inst, user, REG);
				}
			}
			//finish register dependence

			//begin memory dependence
			MemDepResult mdr = mda.getDependency(inst);
			//TODO not sure clobbers mean!!

			if (mdr.isDef()) {
				Instruction *dep = mdr.getInst();

				if (isa<LoadInst>(inst)) {
					if (isa<StoreInst>(dep)) {
						addEdge(dep, inst, DTRUE);	//READ AFTER WRITE
					}
				}
				if (isa<StoreInst>(inst)) {
					if (isa<LoadInst>(dep)) {
						addEdge(dep, inst, DANTI);	//WRITE AFTER READ
					}
					if (isa<StoreInst>(dep)) {
						addEdge(dep, inst, DOUT);	//WRITE AFTER WRITE
					}
				}
				//READ AFTER READ IS INSERT AFTER PDG BUILD
			}
			//end memory dependence
		}//for ii
	}//for bi

	/*
	 * begin control dependence
	 */
	PostDominatorTree &pdt = getAnalysis<PostDominatorTree>();
	//cout << pdt.getRootNode()->getBlock()->getNameStr() << endl;

	/*
	 * alien code part 1
	 */
	LoopInfo *LI = &getAnalysis<LoopInfo>();
	std::set<BranchInst*> backedgeParents;
	for (Loop::block_iterator bi = L->getBlocks().begin(); bi
			!= L->getBlocks().end(); bi++) {
		BasicBlock *BB = *bi;
		for (BasicBlock::iterator ii = BB->begin(); ii != BB->end(); ii++) {
			Instruction *inst = ii;
			if (BranchInst *brInst = dyn_cast<BranchInst>(inst)) {
				// get the loop this instruction (and therefore basic block) belongs to
				Loop *instLoop = LI->getLoopFor(BB);
				bool branchesToHeader = false;
				for (int i = brInst->getNumSuccessors() - 1; i >= 0
						&& !branchesToHeader; i--) {
					// if the branch could exit, store it
					if (LI->getLoopFor(brInst->getSuccessor(i)) != instLoop) {
						branchesToHeader = true;
					}
				}
				if (branchesToHeader) {
					backedgeParents.insert(brInst);
				}
			}
		}
//.........这里部分代码省略.........

/// Renames all variables in the specified BasicBlock.
/// Only variables that need to be rename will be.
///
void SSI::rename(BasicBlock *BB) {
  SmallPtrSet<Instruction*, 8> defined;

  // Iterate through instructions and make appropriate renaming.
  // For SSI_PHI (b = PHI()), store b at value_stack as a new
  // definition of the variable it represents.
  // For SSI_SIG (b = PHI(a)), substitute a with the current
  // value of a, present in the value_stack.
  // Then store bin the value_stack as the new definition of a.
  // For all other instructions (b = OP(a, c, d, ...)), we need to substitute
  // all operands with its current value, present in value_stack.
  for (BasicBlock::iterator begin = BB->begin(), end = BB->end();
       begin != end; ++begin) {
    Instruction *I = begin;
    if (PHINode *PN = dyn_cast<PHINode>(I)) { // Treat PHI functions
      Instruction* position;

      // Treat SSI_PHI
      if ((position = getPositionPhi(PN))) {
        value_stack[position].push_back(PN);
        defined.insert(position);
      // Treat SSI_SIG
      } else if ((position = getPositionSigma(PN))) {
        substituteUse(I);
        value_stack[position].push_back(PN);
        defined.insert(position);
      }

      // Treat all other PHI functions
      else {
        substituteUse(I);
      }
    }

    // Treat all other functions
    else {
      substituteUse(I);
    }
  }

  // This loop iterates in all BasicBlocks that are successors of the current
  // BasicBlock. For each SSI_PHI instruction found, insert an operand.
  // This operand is the current operand in value_stack for the variable
  // in "position". And the BasicBlock this operand represents is the current
  // BasicBlock.
  for (succ_iterator SI = succ_begin(BB), SE = succ_end(BB); SI != SE; ++SI) {
    BasicBlock *BB_succ = *SI;

    for (BasicBlock::iterator begin = BB_succ->begin(),
         notPhi = BB_succ->getFirstNonPHI(); begin != *notPhi; ++begin) {
      Instruction *I = begin;
      PHINode *PN = dyn_cast<PHINode>(I);
      Instruction* position;
      if (PN && ((position = getPositionPhi(PN)))) {
        PN->addIncoming(value_stack[position].back(), BB);
      }
    }
  }

  // This loop calls rename on all children from this block. This time children
  // refers to a successor block in the dominance tree.
  DomTreeNode *DTN = DT_->getNode(BB);
  for (DomTreeNode::iterator begin = DTN->begin(), end = DTN->end();
       begin != end; ++begin) {
    DomTreeNodeBase<BasicBlock> *DTN_children = *begin;
    BasicBlock *BB_children = DTN_children->getBlock();
    rename(BB_children);
  }

  // Now we remove all inserted definitions of a variable from the top of
  // the stack leaving the previous one as the top.
  for (SmallPtrSet<Instruction*, 8>::iterator DI = defined.begin(),
       DE = defined.end(); DI != DE; ++DI)
    value_stack[*DI].pop_back();
}