C++ iterator::isUsedOutsideOfBlock方法代码示例

/// isSafeToClone - Return true if the loop body is safe to clone in practice.
/// Routines that reform the loop CFG and split edges often fail on indirectbr.
bool Loop::isSafeToClone() const {
  // Return false if any loop blocks contain indirectbrs, or there are any calls
  // to noduplicate functions.
  for (Loop::block_iterator I = block_begin(), E = block_end(); I != E; ++I) {
    if (isa<IndirectBrInst>((*I)->getTerminator()))
      return false;

    if (const InvokeInst *II = dyn_cast<InvokeInst>((*I)->getTerminator()))
      if (II->cannotDuplicate())
        return false;

    for (BasicBlock::iterator BI = (*I)->begin(), BE = (*I)->end(); BI != BE; ++BI) {
      if (const CallInst *CI = dyn_cast<CallInst>(BI)) {
        if (CI->cannotDuplicate())
          return false;
      }
      if (BI->getType()->isTokenTy() && BI->isUsedOutsideOfBlock(*I))
        return false;
    }
  }
  return true;
}

void fixStack(Function *f) {
  // Try to remove phi node and demote reg to stack
  std::vector<PHINode *> tmpPhi;
  std::vector<Instruction *> tmpReg;
  BasicBlock *bbEntry = f->begin();

  do {
    tmpPhi.clear();
    tmpReg.clear();

    for (Function::iterator i = f->begin(); i != f->end(); ++i) {

      for (BasicBlock::iterator j = i->begin(); j != i->end(); ++j) {

        if (isa<PHINode>(j)) {
          PHINode *phi = cast<PHINode>(j);
          tmpPhi.push_back(phi);
          continue;
        }
        if (!(isa<AllocaInst>(j) && j->getParent() == bbEntry) &&
            (valueEscapes(j) || j->isUsedOutsideOfBlock(i))) {
          tmpReg.push_back(j);
          continue;
        }
      }
    }
    for (unsigned int i = 0; i != tmpReg.size(); ++i) {
      DemoteRegToStack(*tmpReg.at(i), f->begin()->getTerminator());
    }

    for (unsigned int i = 0; i != tmpPhi.size(); ++i) {
      DemotePHIToStack(tmpPhi.at(i), f->begin()->getTerminator());
    }

  } while (tmpReg.size() != 0 || tmpPhi.size() != 0);
}

/// eliminateUnconditionalBranch - Clone the instructions from the destination
/// block into the source block, eliminating the specified unconditional branch.
/// If the destination block defines values used by successors of the dest
/// block, we may need to insert PHI nodes.
///
void TailDup::eliminateUnconditionalBranch(BranchInst *Branch) {
  BasicBlock *SourceBlock = Branch->getParent();
  BasicBlock *DestBlock = Branch->getSuccessor(0);
  assert(SourceBlock != DestBlock && "Our predicate is broken!");

  DEBUG(errs() << "TailDuplication[" << SourceBlock->getParent()->getName()
        << "]: Eliminating branch: " << *Branch);

  // See if we can avoid duplicating code by moving it up to a dominator of both
  // blocks.
  if (BasicBlock *DomBlock = FindObviousSharedDomOf(SourceBlock, DestBlock)) {
    DEBUG(errs() << "Found shared dominator: " << DomBlock->getName() << "\n");

    // If there are non-phi instructions in DestBlock that have no operands
    // defined in DestBlock, and if the instruction has no side effects, we can
    // move the instruction to DomBlock instead of duplicating it.
    BasicBlock::iterator BBI = DestBlock->getFirstNonPHI();
    while (!isa<TerminatorInst>(BBI)) {
      Instruction *I = BBI++;

      bool CanHoist = I->isSafeToSpeculativelyExecute() &&
                      !I->mayReadFromMemory();
      if (CanHoist) {
        for (unsigned op = 0, e = I->getNumOperands(); op != e; ++op)
          if (Instruction *OpI = dyn_cast<Instruction>(I->getOperand(op)))
            if (OpI->getParent() == DestBlock ||
                (isa<InvokeInst>(OpI) && OpI->getParent() == DomBlock)) {
              CanHoist = false;
              break;
            }
        if (CanHoist) {
          // Remove from DestBlock, move right before the term in DomBlock.
          DestBlock->getInstList().remove(I);
          DomBlock->getInstList().insert(DomBlock->getTerminator(), I);
          DEBUG(errs() << "Hoisted: " << *I);
        }
      }
    }
  }

  // Tail duplication can not update SSA properties correctly if the values
  // defined in the duplicated tail are used outside of the tail itself.  For
  // this reason, we spill all values that are used outside of the tail to the
  // stack.
  for (BasicBlock::iterator I = DestBlock->begin(); I != DestBlock->end(); ++I)
    if (I->isUsedOutsideOfBlock(DestBlock)) {
      // We found a use outside of the tail.  Create a new stack slot to
      // break this inter-block usage pattern.
      DemoteRegToStack(*I);
    }

  // We are going to have to map operands from the original block B to the new
  // copy of the block B'.  If there are PHI nodes in the DestBlock, these PHI
  // nodes also define part of this mapping.  Loop over these PHI nodes, adding
  // them to our mapping.
  //
  std::map<Value*, Value*> ValueMapping;

  BasicBlock::iterator BI = DestBlock->begin();
  bool HadPHINodes = isa<PHINode>(BI);
  for (; PHINode *PN = dyn_cast<PHINode>(BI); ++BI)
    ValueMapping[PN] = PN->getIncomingValueForBlock(SourceBlock);

  // Clone the non-phi instructions of the dest block into the source block,
  // keeping track of the mapping...
  //
  for (; BI != DestBlock->end(); ++BI) {
    Instruction *New = BI->clone();
    New->setName(BI->getName());
    SourceBlock->getInstList().push_back(New);
    ValueMapping[BI] = New;
  }

  // Now that we have built the mapping information and cloned all of the
  // instructions (giving us a new terminator, among other things), walk the new
  // instructions, rewriting references of old instructions to use new
  // instructions.
  //
  BI = Branch; ++BI;  // Get an iterator to the first new instruction
  for (; BI != SourceBlock->end(); ++BI)
    for (unsigned i = 0, e = BI->getNumOperands(); i != e; ++i) {
      std::map<Value*, Value*>::const_iterator I =
        ValueMapping.find(BI->getOperand(i));
      if (I != ValueMapping.end())
        BI->setOperand(i, I->second);
    }

  // Next we check to see if any of the successors of DestBlock had PHI nodes.
  // If so, we need to add entries to the PHI nodes for SourceBlock now.
  for (succ_iterator SI = succ_begin(DestBlock), SE = succ_end(DestBlock);
       SI != SE; ++SI) {
    BasicBlock *Succ = *SI;
    for (BasicBlock::iterator PNI = Succ->begin(); isa<PHINode>(PNI); ++PNI) {
      PHINode *PN = cast<PHINode>(PNI);
      // Ok, we have a PHI node.  Figure out what the incoming value was for the
//.........这里部分代码省略.........