C++ ConstantInt::getRawValue方法代码示例

bool LoopUnroll::visitLoop(Loop *L) {
  bool Changed = false;

  // Recurse through all subloops before we process this loop.  Copy the loop
  // list so that the child can update the loop tree if it needs to delete the
  // loop.
  std::vector<Loop*> SubLoops(L->begin(), L->end());
  for (unsigned i = 0, e = SubLoops.size(); i != e; ++i)
    Changed |= visitLoop(SubLoops[i]);

  // We only handle single basic block loops right now.
  if (L->getBlocks().size() != 1)
    return Changed;

  BasicBlock *BB = L->getHeader();
  BranchInst *BI = dyn_cast<BranchInst>(BB->getTerminator());
  if (BI == 0) return Changed;  // Must end in a conditional branch

  ConstantInt *TripCountC = dyn_cast_or_null<ConstantInt>(L->getTripCount());
  if (!TripCountC) return Changed;  // Must have constant trip count!

  unsigned TripCount = TripCountC->getRawValue();
  if (TripCount != TripCountC->getRawValue() || TripCount == 0)
    return Changed; // More than 2^32 iterations???

  unsigned LoopSize = ApproximateLoopSize(L);
  DEBUG(std::cerr << "Loop Unroll: F[" << BB->getParent()->getName()
        << "] Loop %" << BB->getName() << " Loop Size = " << LoopSize
        << " Trip Count = " << TripCount << " - ");
  uint64_t Size = (uint64_t)LoopSize*(uint64_t)TripCount;
  if (Size > UnrollThreshold) {
    DEBUG(std::cerr << "TOO LARGE: " << Size << ">" << UnrollThreshold << "\n");
    return Changed;
  }
  DEBUG(std::cerr << "UNROLLING!\n");
  
  BasicBlock *LoopExit = BI->getSuccessor(L->contains(BI->getSuccessor(0)));

  // Create a new basic block to temporarily hold all of the cloned code.
  BasicBlock *NewBlock = new BasicBlock();

  // For the first iteration of the loop, we should use the precloned values for
  // PHI nodes.  Insert associations now.
  std::map<const Value*, Value*> LastValueMap;
  std::vector<PHINode*> OrigPHINode;
  for (BasicBlock::iterator I = BB->begin();
       PHINode *PN = dyn_cast<PHINode>(I); ++I) {
    OrigPHINode.push_back(PN);
    if (Instruction *I =dyn_cast<Instruction>(PN->getIncomingValueForBlock(BB)))
      if (I->getParent() == BB)
        LastValueMap[I] = I;
  }

  // Remove the exit branch from the loop
  BB->getInstList().erase(BI);

  assert(TripCount != 0 && "Trip count of 0 is impossible!");
  for (unsigned It = 1; It != TripCount; ++It) {
    char SuffixBuffer[100];
    sprintf(SuffixBuffer, ".%d", It);
    std::map<const Value*, Value*> ValueMap;
    BasicBlock *New = CloneBasicBlock(BB, ValueMap, SuffixBuffer);

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

    for (BasicBlock::iterator I = New->begin(), E = New->end(); I != E; ++I)
      RemapInstruction(I, ValueMap);

    // Now that all of the instructions are remapped, splice them into the end
    // of the NewBlock.
    NewBlock->getInstList().splice(NewBlock->end(), New->getInstList());
    delete New;

    // LastValue map now contains values from this iteration.
    std::swap(LastValueMap, ValueMap);
  }

  // If there was more than one iteration, replace any uses of values computed
  // in the loop with values computed during the last iteration of the loop.
  if (TripCount != 1) {
    std::set<User*> Users;
    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
      Users.insert(I->use_begin(), I->use_end());

    // We don't want to reprocess entries with PHI nodes in them.  For this
    // reason, we look at each operand of each user exactly once, performing the
    // stubstitution exactly once.
    for (std::set<User*>::iterator UI = Users.begin(), E = Users.end(); UI != E;
         ++UI) {
      Instruction *I = cast<Instruction>(*UI);
//.........这里部分代码省略.........