Exemplo n.º 1
0
void TR_Latestness::analyzeTreeTopsInBlockStructure(TR_BlockStructure *blockStructure)
   {
   TR::Block *block = blockStructure->getBlock();
   TR::TreeTop *currentTree = block->getExit();
   TR::TreeTop *entryTree = block->getEntry();
   /////copyFromInto(_regularInfo, _outSetInfo[blockStructure->getNumber()]);
   bool notSeenTreeWithChecks = true;
   _containsExceptionTreeTop = false;

   while (!(currentTree == entryTree))
      {
      if (notSeenTreeWithChecks)
         {
         bool currentTreeHasChecks = treeHasChecks(currentTree);
         if (currentTreeHasChecks)
            {
            notSeenTreeWithChecks = false;
            _containsExceptionTreeTop = true;
            /////compose(_regularInfo, _exceptionInfo);
            /////compose(_outSetInfo[blockStructure->getNumber()], _exceptionInfo);
            }
         }
      else
         break;

      if (!(currentTree == entryTree))
         currentTree = currentTree->getPrevTreeTop();
      }

   }
Exemplo n.º 2
0
static void moveBlockAfterDest(TR::CFG *cfg, TR::Block *toMove, TR::Block *dest)
   {
   TR::Compilation *comp = TR::comp();
   // Step1 splice out toMove
   TR::Block *toMovePrev = toMove->getPrevBlock();
   TR::Block *toMoveSucc = toMove->getNextBlock();

   toMovePrev->getExit()->join(toMoveSucc->getEntry());

   // Step 2 splice toMove in after dest
   TR::Block *destNext = dest->getNextBlock();
   dest->getExit()->join(toMove->getEntry());
   toMove->getExit()->join(destNext->getEntry());

   cfg->addEdge(toMove, destNext);
   cfg->addEdge(dest, toMove);
   cfg->removeEdge(dest, destNext);

   cfg->addEdge(toMovePrev, toMoveSucc);
   cfg->removeEdge(toMovePrev, toMove);
   cfg->removeEdge(toMove, toMoveSucc);
   }
Exemplo n.º 3
0
void
TR_ExpressionsSimplification::invalidateCandidates()
   {
   _visitCount = comp()->incVisitCount();

   if (trace())
      {
      traceMsg(comp(), "Checking which candidates may be invalidated\n");

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

   TR_ScratchList<TR::Block> blocksInLoop(trMemory());
   _currentRegion->getBlocks(&blocksInLoop);
   ListIterator<TR::Block> blocks(&blocksInLoop);

   for (TR::Block *currentBlock = blocks.getFirst(); currentBlock; currentBlock  = blocks.getNext())
      {
      TR::TreeTop *tt = currentBlock->getEntry();
      TR::TreeTop *exitTreeTop = currentBlock->getExit();
      while (tt != exitTreeTop)
         {
         TR::Node *currentNode = tt->getNode();

         if (trace())
            traceMsg(comp(), "Looking at treeTop [%p]\n", currentNode);

         removeCandidate(currentNode, tt);

         tt = tt->getNextTreeTop();
         }
      }
   removeUnsupportedCandidates();
   }
Exemplo n.º 4
0
int32_t TR_CatchBlockRemover::perform()
   {
   TR::CFG *cfg = comp()->getFlowGraph();
   if (cfg == NULL)
      {
      if (trace())
         traceMsg(comp(), "Can't do Catch Block Removal, no CFG\n");
      return 0;
      }

   if (trace())
      traceMsg(comp(), "Starting Catch Block Removal\n");

   bool thereMayBeRemovableCatchBlocks = false;

   {
   TR::StackMemoryRegion stackMemoryRegion(*trMemory());

   TR::Block *block;
   ListIterator<TR::CFGEdge> edgeIterator;

   // Go through all blocks that have exception successors and see if any of them
   // are not reached. Mark each of these edges with a visit count so they can
   // be identified later.
   //
   vcount_t visitCount = comp()->incOrResetVisitCount();

   TR::CFGNode *cfgNode;
   for (cfgNode = cfg->getFirstNode(); cfgNode; cfgNode = cfgNode->getNext())
      {
      if (cfgNode->getExceptionSuccessors().empty())
         continue;

      block = toBlock(cfgNode);
      uint32_t reachedExceptions = 0;
      TR::TreeTop *treeTop;
      for (treeTop = block->getEntry(); treeTop != block->getExit(); treeTop = treeTop->getNextTreeTop())
         {
         reachedExceptions |= treeTop->getNode()->exceptionsRaised();

         if (treeTop->getNode()->getOpCodeValue() == TR::monexitfence) // for live monitor metadata
            reachedExceptions |= TR::Block::CanCatchMonitorExit;
         }

      if (reachedExceptions & TR::Block::CanCatchUserThrows)
         continue;

      for (auto edge = block->getExceptionSuccessors().begin(); edge != block->getExceptionSuccessors().end();)
         {
         TR::CFGEdge * current = *(edge++);
         TR::Block *catchBlock = toBlock(current->getTo());
         if (catchBlock->isOSRCodeBlock() || catchBlock->isOSRCatchBlock()) continue;
         if (!reachedExceptions &&
             performTransformation(comp(), "%sRemove redundant exception edge from block_%d at [%p] to catch block_%d at [%p]\n", optDetailString(), block->getNumber(), block, catchBlock->getNumber(), catchBlock))
            {
            cfg->removeEdge(block, catchBlock);
            thereMayBeRemovableCatchBlocks = true;
            }
         else
            {
            if (!catchBlock->canCatchExceptions(reachedExceptions))
               {
               current->setVisitCount(visitCount);
               thereMayBeRemovableCatchBlocks = true;
               }
            }
         }
      }

   bool edgesRemoved = false;

   // Now look to see if there are any catch blocks for which all exception
   // predecessors have the visit count set. If so, the block is unreachable and
   // can be removed.
   // If only some of the exception predecessors are marked, these edges are
   // left in place to identify the try/catch structure properly.
   //
   while (thereMayBeRemovableCatchBlocks)
      {
      thereMayBeRemovableCatchBlocks = false;
      for (cfgNode = cfg->getFirstNode(); cfgNode; cfgNode = cfgNode->getNext())
         {
         if (cfgNode->getExceptionPredecessors().empty())
            continue;
         auto edgeIt = cfgNode->getExceptionPredecessors().begin();
         for (; edgeIt != cfgNode->getExceptionPredecessors().end(); ++edgeIt)
            {
            if ((*edgeIt)->getVisitCount() != visitCount)
               break;
            }

         if (edgeIt == cfgNode->getExceptionPredecessors().end() && performTransformation(comp(), "%sRemove redundant catch block_%d at [%p]\n", optDetailString(), cfgNode->getNumber(), cfgNode))
            {
            while (!cfgNode->getExceptionPredecessors().empty())
               {
               cfg->removeEdge(cfgNode->getExceptionPredecessors().front());
               }
            edgesRemoved = true;
            thereMayBeRemovableCatchBlocks = true;
            }
         }
      }


   // Any transformations invalidate use/def and value number information
   //
   if (edgesRemoved)
      {
      optimizer()->setUseDefInfo(NULL);
      optimizer()->setValueNumberInfo(NULL);
      requestOpt(OMR::treeSimplification, true);
      }

   } // scope of the stack memory region

   if (trace())
      traceMsg(comp(), "\nEnding Catch Block Removal\n");

   return 1; // actual cost
   }
Exemplo n.º 5
0
// This function splits a single succeesor block following an guard and is used to
// do the following transform
//    block - cold1         block - cold1
//      \     /        =>     |       |
//     nextBlock           nextBlock nextBlock' (called tailSplitBlock below)
//         |                  \      /
//        ...                   ...
void TR_VirtualGuardHeadMerger::tailSplitBlock(TR::Block * block, TR::Block * cold1)
   {
   TR::CFG *cfg = comp()->getFlowGraph();
   cfg->setStructure(NULL);
   TR_BlockCloner cloner(cfg);
   TR::Block *tailSplitBlock = cloner.cloneBlocks(block->getNextBlock(), block->getNextBlock());
   tailSplitBlock->setFrequency(cold1->getFrequency());
   if (cold1->isCold())
      tailSplitBlock->setIsCold();

   // physically put the block after cold1 since we want cold1 to fall through
   tailSplitBlock->getExit()->join(cold1->getExit()->getNextTreeTop());
   cold1->getExit()->join(tailSplitBlock->getEntry());

   // remove cold1's goto
   TR::TransformUtil::removeTree(comp(), cold1->getExit()->getPrevRealTreeTop());

   // copy the exception edges
   for (auto e = block->getNextBlock()->getExceptionSuccessors().begin(); e != block->getNextBlock()->getExceptionSuccessors().end(); ++e)
      cfg->addExceptionEdge(tailSplitBlock, (*e)->getTo());

   cfg->addEdge(cold1, tailSplitBlock);
   // lastly fix up the exit of tailSplitBlock
   TR::Node *tailSplitEnd = tailSplitBlock->getExit()->getPrevRealTreeTop()->getNode();
   if (tailSplitEnd->getOpCode().isGoto())
      {
      tailSplitEnd->setBranchDestination(block->getNextBlock()->getLastRealTreeTop()->getNode()->getBranchDestination());
      cfg->addEdge(tailSplitBlock, block->getNextBlock()->getSuccessors().front()->getTo());
      }
   else if (tailSplitEnd->getOpCode().isBranch())
      {
      TR::Block *gotoBlock = TR::Block::createEmptyBlock(tailSplitEnd, comp(), cold1->getFrequency());
      if (cold1->isCold())
          gotoBlock->setIsCold(true);
      gotoBlock->getExit()->join(tailSplitBlock->getExit()->getNextTreeTop());
      tailSplitBlock->getExit()->join(gotoBlock->getEntry());
      cfg->addNode(gotoBlock);

      gotoBlock->append(TR::TreeTop::create(comp(), TR::Node::create(tailSplitEnd, TR::Goto, 0, block->getNextBlock()->getExit()->getNextTreeTop())));
      cfg->addEdge(tailSplitBlock, gotoBlock);
      cfg->addEdge(tailSplitBlock, tailSplitBlock->getLastRealTreeTop()->getNode()->getBranchDestination()->getEnclosingBlock());
      cfg->addEdge(gotoBlock, block->getNextBlock()->getNextBlock());
      }
   else if (
            !tailSplitEnd->getOpCode().isReturn() &&
            !tailSplitEnd->getOpCode().isJumpWithMultipleTargets() &&
             tailSplitEnd->getOpCodeValue() != TR::athrow &&
            !(tailSplitEnd->getNumChildren() >= 1 && tailSplitEnd->getFirstChild()->getOpCodeValue() == TR::athrow)
           )
      {
      tailSplitBlock->append(TR::TreeTop::create(comp(), TR::Node::create(tailSplitEnd, TR::Goto, 0, block->getNextBlock()->getExit()->getNextTreeTop())));
      cfg->addEdge(tailSplitBlock, block->getNextBlock()->getNextBlock());
      }
   else
      {
      for (auto e = block->getNextBlock()->getSuccessors().begin(); e != block->getNextBlock()->getSuccessors().end(); ++e)
         cfg->addEdge(tailSplitBlock, (*e)->getTo());
      }
   cfg->removeEdge(cold1, block->getNextBlock());

   optimizer()->setUseDefInfo(NULL);
   optimizer()->setValueNumberInfo(NULL);
   }
Exemplo n.º 6
0
TR_ExpressionsSimplification::LoopInfo*
TR_ExpressionsSimplification::findLoopInfo(TR_RegionStructure* region)
   {
   ListIterator<TR::CFGEdge> exitEdges(&region->getExitEdges());

   if (region->getExitEdges().getSize() != 1)
      {
      if (trace())
         traceMsg(comp(), "Region with more than 1 exit edges can't be handled\n");
      return 0;
      }

   TR_StructureSubGraphNode* exitNode = toStructureSubGraphNode(exitEdges.getFirst()->getFrom());

   if (!exitNode->getStructure()->asBlock())
      {
      if (trace())
         traceMsg(comp(), "The exit block can't be found\n");
      return 0;
      }

   TR::Block *exitBlock = exitNode->getStructure()->asBlock()->getBlock();
   TR::Node *lastTreeInExitBlock = exitBlock->getLastRealTreeTop()->getNode();

   if (trace())
      {
      traceMsg(comp(), "The exit block is %d\n", exitBlock->getNumber());
      traceMsg(comp(), "The branch node is %p\n", lastTreeInExitBlock);
      }


   if (!lastTreeInExitBlock->getOpCode().isBranch())
      {
      if (trace())
         traceMsg(comp(), "The branch node couldn't be found\n");
      return 0;
      }

   if (lastTreeInExitBlock->getNumChildren() < 2)
      {
      if (trace())
         traceMsg(comp(), "The branch node has less than 2 children\n");
      return 0;
      }

   TR::Node *firstChildOfLastTree = lastTreeInExitBlock->getFirstChild();
   TR::Node *secondChildOfLastTree = lastTreeInExitBlock->getSecondChild();

   if (!firstChildOfLastTree->getOpCode().hasSymbolReference())
      {
      if (trace())
         traceMsg(comp(), "The branch node's first child node %p - its opcode does not have a symbol reference\n", firstChildOfLastTree);
      return 0;
      }

   TR::SymbolReference *firstChildSymRef = firstChildOfLastTree->getSymbolReference();

   if (trace())
      traceMsg(comp(), "Symbol Reference: %p Symbol: %p\n", firstChildSymRef, firstChildSymRef->getSymbol());

   // Locate the induction variable that matches with the exit node symbol
   //
   TR_InductionVariable *indVar = region->findMatchingIV(firstChildSymRef);
   if (!indVar) return 0;

   if (!indVar->getIncr()->asIntConst())
      {
      if (trace())
         traceMsg(comp(), "Increment is not a constant\n");
      return 0;
      }

   int32_t increment = indVar->getIncr()->getLowInt();

   _visitCount = comp()->incVisitCount();
   bool indVarWrittenAndUsedUnexpectedly = false;
   if (firstChildOfLastTree->getReferenceCount() > 1)
      {
      TR::TreeTop *cursorTreeTopInExitBlock = exitBlock->getEntry();
      TR::TreeTop *exitTreeTopInExitBlock = exitBlock->getExit();

      bool loadSeen = false;
      while (cursorTreeTopInExitBlock != exitTreeTopInExitBlock)
         {
         TR::Node *cursorNode = cursorTreeTopInExitBlock->getNode();
         if (checkForLoad(cursorNode, firstChildOfLastTree))
            loadSeen = true;

         if (!cursorNode->getOpCode().isStore() &&
             (cursorNode->getNumChildren() > 0))
           cursorNode = cursorNode->getFirstChild();

         if (cursorNode->getOpCode().isStore() &&
             (cursorNode->getSymbolReference() == firstChildSymRef))
            {
            indVarWrittenAndUsedUnexpectedly = true;
            if ((cursorNode->getFirstChild() == firstChildOfLastTree) ||
                !loadSeen)
               indVarWrittenAndUsedUnexpectedly = false;
            else
               break;
            }

         cursorTreeTopInExitBlock = cursorTreeTopInExitBlock->getNextTreeTop();
         }
      }

   if (indVarWrittenAndUsedUnexpectedly)
      {
      return 0;
      }

   int32_t lowerBound;
   int32_t upperBound = 0;
   TR::Node *bound = 0;
   bool equals = false;

   switch(lastTreeInExitBlock->getOpCodeValue())
      {
      case TR::ificmplt:
      case TR::ificmpgt:
         equals = true;
      case TR::ificmple:
      case TR::ificmpge:
         if (!(indVar->getEntry() && indVar->getEntry()->asIntConst()))
            {
            if (trace())
               traceMsg(comp(), "Entry value is not a constant\n");
            return 0;
            }
         lowerBound = indVar->getEntry()->getLowInt();

         if (secondChildOfLastTree->getOpCode().isLoadConst())
            {
            upperBound = secondChildOfLastTree->getInt();
            }
         else if (secondChildOfLastTree->getOpCode().isLoadVar())
            {
            bound = secondChildOfLastTree;
            }
         else
            {
            if (trace())
               traceMsg(comp(), "Second child is not a const or a load\n");
            return 0;
            }
         return new (trStackMemory()) LoopInfo(bound, lowerBound, upperBound, increment, equals);


      default:
         if (trace())
            traceMsg(comp(), "The condition has not been implemeted\n");
         return 0;
      }

   return 0;
   }
Exemplo n.º 7
0
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;
         }
      }
   }
Exemplo n.º 8
0
void TR::DeadTreesElimination::prePerformOnBlocks()
   {
   _cannotBeEliminated = false;
   _delayedRegStores = false;

   _targetTrees.deleteAll();

   // Walk through all the blocks to remove trivial dead trees of the form
   // treetop
   //   => node
   // The problem with these trees is in the scenario where the earlier use
   // of 'node' is also dead.  However, our analysis won't find that because
   // the reference count is > 1.
   vcount_t visitCount = comp()->incOrResetVisitCount();
   for (TR::TreeTop *tt = comp()->getStartTree();
        tt != 0;
        tt = tt->getNextTreeTop())
      {
      bool removed = false;

      TR::Node *node = tt->getNode();
      if (node->getOpCodeValue() == TR::treetop &&
          node->getFirstChild()->getVisitCount() == visitCount &&
          performTransformation(comp(), "%sRemove trivial dead tree: %p\n", optDetailString(), node))
         {
         TR::TransformUtil::removeTree(comp(), tt);
         removed = true;
         }
      else
         {
         if (node->getOpCode().isCheck() &&
             node->getFirstChild()->getOpCode().isCall() &&
             node->getFirstChild()->getReferenceCount() == 1 &&
             node->getFirstChild()->getSymbolReference()->getSymbol()->isResolvedMethod() &&
             node->getFirstChild()->getSymbolReference()->getSymbol()->castToResolvedMethodSymbol()->isSideEffectFree() &&
             performTransformation(comp(), "%sRemove dead check of side-effect free call: %p\n", optDetailString(), node))
            {
            TR::TransformUtil::removeTree(comp(), tt);
            removed = true;
            }
         }

      if (removed
          && tt->getNextTreeTop()->getNode()->getOpCodeValue() == TR::Goto
          && tt->getPrevTreeTop()->getNode()->getOpCodeValue() == TR::BBStart
          && !tt->getPrevTreeTop()->getNode()->getBlock()->isExtensionOfPreviousBlock())
         {
         requestOpt(OMR::redundantGotoElimination, tt->getEnclosingBlock());
         }

      if (node->getVisitCount() >= visitCount)
         continue;
      TR::TransformUtil::recursivelySetNodeVisitCount(tt->getNode(), visitCount);
      }

   // If the last use of an iRegLoad has been removed, then remove the node from
   // the BBStart and remove the corresponding dependency node from each of the block's
   // predecessors.
   //
   while (1)
      {
      bool glRegDepRemoved = false;
      for (TR::Block * b = comp()->getStartBlock(); b; b = b->getNextBlock())
         {
         TR::TreeTop * startTT = b->getEntry();
         TR::Node * startNode = startTT->getNode();
         if (startNode->getNumChildren() > 0 && !debug("disableEliminationOfGlRegDeps"))
            {
            TR::Node * glRegDeps = startNode->getFirstChild();
            TR_ASSERT(glRegDeps->getOpCodeValue() == TR::GlRegDeps, "expected TR::GlRegDeps");
            for (int32_t i = glRegDeps->getNumChildren() - 1; i >= 0; --i)
               {
               TR::Node * dep = glRegDeps->getChild(i);
               if (dep->getReferenceCount() == 1 &&
                   (!dep->getOpCode().isFloatingPoint() ||
                    cg()->getSupportsJavaFloatSemantics()) &&
                   performTransformation(comp(), "%sRemove GlRegDep : %p\n", optDetailString(), glRegDeps->getChild(i)))

                  {
                  glRegDeps->removeChild(i);
                  glRegDepRemoved = true;
                  TR_GlobalRegisterNumber registerNum = dep->getGlobalRegisterNumber();
                  for (auto e = b->getPredecessors().begin(); e != b->getPredecessors().end(); ++e)
                     {
                     TR::Block * pred = toBlock((*e)->getFrom());
                     if (pred == comp()->getFlowGraph()->getStart())
                        continue;

                     TR::Node * parent = pred->getLastRealTreeTop()->getNode();
                     if ( parent->getOpCode().isJumpWithMultipleTargets() && parent->getOpCode().hasBranchChildren())
                        {
                        for (int32_t j = parent->getCaseIndexUpperBound() - 1; j > 0; --j)
                           {
                           TR::Node * caseNode = parent->getChild(j);
                           TR_ASSERT(caseNode->getOpCode().isCase() || caseNode->getOpCodeValue() == TR::branch,
                                  "having problems navigating a switch");
                           if (caseNode->getBranchDestination() == startTT &&
                               caseNode->getNumChildren() > 0 &&
                               0) // can't do this now that all glRegDeps are hung off the default branch
                              removeGlRegDep(caseNode, registerNum, pred, this);
                           }
                        }
                     else if (!parent->getOpCode().isReturn() &&
                              parent->getOpCodeValue() != TR::igoto &&
                              !( parent->getOpCode().isJumpWithMultipleTargets() && parent->getOpCode().hasBranchChildren()) &&
                              !(parent->getOpCodeValue()==TR::treetop &&
                              parent->getFirstChild()->getOpCode().isCall() &&
                              parent->getFirstChild()->getOpCode().isIndirect()))

                        {
                        if (pred->getNextBlock() == b)
                           parent = pred->getExit()->getNode();
                        removeGlRegDep(parent, registerNum, pred, this);
                        }
                     }
                  }
               }

            if (glRegDeps->getNumChildren() == 0)
               startNode->removeChild(0);
            }
         }

      if (!glRegDepRemoved)
         break;
      }
   }