C++ Block::getPredecessors方法代码示例

void
TR_ForwardReachabilityWithoutExceptionEdges::propagateInputs(blocknum_t blockNum, int32_t depth, blocknum_t *stack, blocknum_t *depth_map, TR_BitVector *closure)
   {
   TR::Block *block = getBlock(blockNum);
   for (auto edge = block->getPredecessors().begin(); edge != block->getPredecessors().end(); ++edge)
      {
      TR::Block *inputBlock = toBlock((*edge)->getFrom());
      propagateOneInput(inputBlock->getNumber(), blockNum, depth, stack, depth_map, closure);
      }
   }

/**
 * Search for direct loads in the taken side of a guard
 *
 * @param firstBlock The guard's branch destination
 * @param coldPathLoads BitVector of symbol reference numbers for any direct loads seen until the merge back to mainline
 */
static void collectColdPathLoads(TR::Block* firstBlock, TR_BitVector &coldPathLoads)
   {
   TR_Stack<TR::Block*> blocksToCheck(TR::comp()->trMemory(), 8, false, stackAlloc);
   blocksToCheck.push(firstBlock);
   TR::NodeChecklist checklist(TR::comp());

   coldPathLoads.empty();
   while (!blocksToCheck.isEmpty())
      {
      TR::Block *block = blocksToCheck.pop();

      for (TR::TreeTop *tt = block->getFirstRealTreeTop(); tt->getNode()->getOpCodeValue() != TR::BBEnd; tt = tt->getNextTreeTop())
         collectDirectLoads(tt->getNode(), coldPathLoads, checklist);

      // Search for any successors that have not merged with the mainline
      for (auto itr = block->getSuccessors().begin(), end = block->getSuccessors().end(); itr != end; ++itr)
         {
         TR::Block *dest = (*itr)->getTo()->asBlock();
         if (dest != TR::comp()->getFlowGraph()->getEnd() && dest->getPredecessors().size() == 1)
            blocksToCheck.push(dest);
         }
      }
   }

//.........这里部分代码省略.........
         //
         // The following code is to setup the various insert points based on the following diagrams
         // of basic blocks:
         //
         // start:               setup:                          end result after moving runtime guard'
         //                       |       |                        +-------+ <-- privargIns
         //                       |       | <-- privargIns             |
         //                       +-------+ <-- runtimeIns         +-------+
         //   |       |               |                            | Guard'|
         //   |       |               V                            +-------+ <-- runtimeIns
         //   +-------+           +-------+                            |
         //   | Guard |           | Guard |                            V
         //   +-------+           +-------+ <-- HCRIns             +-------+
         //       |        ===>       |                    ===>    | Guard |
         //       V                   V                            +-------+ <-- HCRIns
         //   +-------+           +-------+                            |
         //   |       |           |       |                            V
         //   |       |           |       |                        +-------+
         //
         // Note we always split the block - this may create an empty block but preserves the incoming
         // control flow we leave the rest to block extension to fix later

         block = block->split(block->getLastRealTreeTop(), cfg, true, false);
         TR::Block *privargIns = block->getPrevBlock();
         TR::Block *runtimeIns = block->getPrevBlock();
         TR::Block *HCRIns = block;

         // New outer guard so cold paths must be evaluated
         evaluatedColdPathLoads = false;

         // scan for candidate guards to merge with guard1 identified above
         for (TR::Block *nextBlock = block->getNextBlock(); nextBlock; nextBlock = nextBlock->getNextBlock())
            {
            if (!(nextBlock->getPredecessors().size() == 1) ||
                !nextBlock->hasPredecessor(block))
               {
               break;
               }

            TR::TreeTop *guard2Tree = NULL;
            if (isMergeableGuard(nextBlock->getFirstRealTreeTop()->getNode()))
               {
               guard2Tree = nextBlock->getFirstRealTreeTop();
               }
            else if (isMergeableGuard(nextBlock->getLastRealTreeTop()->getNode()))
               {
               guard2Tree = nextBlock->getLastRealTreeTop();
               }
            else
               break;

            TR::Node *guard2 = guard2Tree->getNode();
            TR::Block *guard2Block = nextBlock;

            // It is not possible to shift an OSR guard unless the destination is already an OSR point
            // as the necessary OSR state will not be available
            if (guard2->isOSRGuard() && !guard1->isOSRGuard())
               break;

            TR::Block *insertPoint = isStopTheWorldGuard(guard2) ? HCRIns : runtimeIns;
            if (!safeToMoveGuard(insertPoint, guard2Tree, guard1->getBranchDestination(), privArgSymRefs))
               break;

            // now we figure out if we can redirect guard2 to guard1's cold block
            // ie can we do the head merge
            TR::Block *cold2 = guard2->getBranchDestination()->getEnclosingBlock();

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);
//.........这里部分代码省略.........