C++ ListIterator::getFirst方法代码示例

void
TR_ExpressionsSimplification::removeUncertainBlocks(TR_RegionStructure* region, List<TR::Block> *candidateBlocksList)
   {
   // Examine the top region block first
   //
   TR::Block *entryBlock = _currentRegion->getEntryBlock();
   ListIterator<TR::Block> blocks;
   blocks.set(candidateBlocksList);

   if (trace())
      traceMsg(comp(), "Number of blocks %d, entry block number %d\n", candidateBlocksList->getSize(), entryBlock->getNumber());

   for (TR::Block *block = blocks.getFirst(); block; block = blocks.getNext())
      {
      TR::CFGNode *cfgNode = block;
      if (!(cfgNode->getExceptionSuccessors().empty()) || blockHasCalls(block, comp()))
         {
         if (trace())
            traceMsg(comp(), "An exception can be thrown from block_%d. Removing all the blocks, since we cannot know the number of iterations.\n", block->getNumber());
         candidateBlocksList->deleteAll();
         break;
         }
      }

   TR_PostDominators postDominators(comp());
   if (postDominators.isValid())
      {
	  postDominators.findControlDependents();
      for (TR::Block *block = blocks.getFirst(); block; block = blocks.getNext())
         {
         if (postDominators.dominates(block, entryBlock) == 0)
            {
            candidateBlocksList->remove(block);
            if (trace())
               traceMsg(comp(), "Block_%d is not guaranteed to be executed at least once. Removing it from the list.\n", block->getNumber());
            }
         }
      }
   else
      {
	  if (trace())
	     traceMsg(comp(), "There is no post dominators information. Removing all the blocks.\n");
	  for (TR::Block *block = blocks.getFirst(); block; block = blocks.getNext())
	     {
	     candidateBlocksList->remove(block);
	     if (trace())
	        traceMsg(comp(), "Block_%d is removed from the list\n", block->getNumber());
	     }
      }
   }

void TR_ExpressionsSimplification::simplifyInvariantLoopExpressions(ListIterator<TR::Block> &blocks)
   {
   // Need to locate the induction variable of the loop
   //
   LoopInfo *loopInfo = findLoopInfo(_currentRegion);

   if (trace())
      {
      if (!loopInfo)
         {
         traceMsg(comp(), "Accurate loop info is not found, cannot carry out summation reduction\n");
         }
      else
         {
         traceMsg(comp(), "Accurate loop info has been found, will try to carry out summation reduction\n");
         if (loopInfo->getBoundaryNode())
            {
            traceMsg(comp(), "Variable iterations from node %p has not been handled\n",loopInfo->getBoundaryNode());
            }
         else
            {
            traceMsg(comp(), "Natural Loop %p will run %d times\n", _currentRegion, loopInfo->getNumIterations());
            }
         }
      }

   // Initialize the list of candidates
   //
   _candidateTTs = new (trStackMemory()) TR_ScratchList<TR::TreeTop>(trMemory());

   for (TR::Block *currentBlock = blocks.getFirst(); currentBlock; currentBlock  = blocks.getNext())
      {
      if (trace())
         traceMsg(comp(), "Analyzing block #%d, which must be executed once per iteration\n", currentBlock->getNumber());


      // Scan through each node in the block
      //
      TR::TreeTop *tt = currentBlock->getEntry();
      TR::TreeTop *exitTreeTop = currentBlock->getExit();
      while (tt != exitTreeTop)
         {
         TR::Node *currentNode = tt->getNode();
         if (trace())
            traceMsg(comp(), "Analyzing tree top node %p\n", currentNode);

         if (loopInfo)
            {
            // requires loop info for the number of iterations
            setSummationReductionCandidates(currentNode, tt);
            }
         setStoreMotionCandidates(currentNode, tt);

         tt = tt->getNextTreeTop();
         }
      }

   // New code: without using any UDI
   // walk through the trees in the loop
   // to invalidate the candidates
   //
   if (!_supportedExpressions)
      {
      _supportedExpressions = new (trStackMemory()) TR_BitVector(comp()->getNodeCount(), trMemory(), stackAlloc, growable);
      }

   invalidateCandidates();

   ListIterator<TR::TreeTop> treeTops(_candidateTTs);
   for (TR::TreeTop *treeTop = treeTops.getFirst(); treeTop; treeTop = treeTops.getNext())
      {
      if (trace())
         traceMsg(comp(), "Candidate TreeTop: %p, Node:%p\n", treeTop, treeTop->getNode());

      bool usedCandidate = false;
      bool isPreheaderBlockInvalid = false;

      if (loopInfo)
         {
         usedCandidate = tranformSummationReductionCandidate(treeTop, loopInfo, &isPreheaderBlockInvalid);
         }

      if (isPreheaderBlockInvalid)
         {
         break;
         }

      if (!usedCandidate)
         {
         tranformStoreMotionCandidate(treeTop, &isPreheaderBlockInvalid);
         }
      if (isPreheaderBlockInvalid)
         {
         break;
         }
      }
   }