C++ Block::getNextBlock方法代码示例

void
TR::RegDepCopyRemoval::makeFreshCopy(TR_GlobalRegisterNumber reg)
   {
   RegDepInfo &dep = getRegDepInfo(reg);
   if (!performTransformation(comp(),
         "%schange %s in GlRegDeps n%un to an explicit copy of n%un\n",
         optDetailString(),
         registerName(reg),
         _regDeps->getGlobalIndex(),
         dep.value->getGlobalIndex()))
      return;

   // Split the block at fallthrough if necessary to avoid putting copies
   // between branches and BBEnd.
   TR::Node *curNode = _treetop->getNode();
   if (curNode->getOpCodeValue() == TR::BBEnd)
      {
      TR::Block *curBlock = curNode->getBlock();
      if (curBlock->getLastRealTreeTop() != curBlock->getLastNonControlFlowTreeTop())
         {
         TR::Block *fallthrough = curBlock->getNextBlock();
         fallthrough = curBlock->splitEdge(curBlock, fallthrough, comp());
         TR_ASSERT(curBlock->getNextBlock() == fallthrough, "bad block placement from splitEdge\n");
         fallthrough->setIsExtensionOfPreviousBlock();
         _treetop = fallthrough->getExit();
         TR::Node *newNode = _treetop->getNode();
         newNode->setChild(0, _regDeps);
         newNode->setNumChildren(1);
         curNode->setNumChildren(0);
         if (trace())
            traceMsg(comp(), "\tsplit fallthrough edge to insert copy, created block_%d\n", fallthrough->getNumber());
         }
      }

   // Make and insert the copy
   TR::Node *copyNode = NULL;
   if (dep.value->getOpCode().isLoadConst())
      {
      // No need to depend on the other register.
      // TODO heuristic for whether this is really better than a reg-reg move?
      generateRegcopyDebugCounter("const-remat");
      copyNode = TR::Node::create(dep.value->getOpCodeValue(), 0);
      copyNode->setConstValue(dep.value->getConstValue());
      }
   else
      {
      generateRegcopyDebugCounter("fresh-copy");
      copyNode = TR::Node::create(TR::PassThrough, 1, dep.value);
      copyNode->setCopyToNewVirtualRegister();
      }

   TR::Node *copyTreetopNode = TR::Node::create(TR::treetop, 1, copyNode);
   _treetop->insertBefore(TR::TreeTop::create(comp(), copyTreetopNode));
   if (trace())
      traceMsg(comp(), "\tcopy is n%un\n", copyNode->getGlobalIndex());

   updateSingleRegDep(reg, copyNode);
   }

static void resetBlockVisitFlags(TR::Compilation *comp)
   {
   for (TR::Block *block = comp->getStartBlock(); block != NULL; block = block->getNextBlock())
      {
      block->setHasBeenVisited(false);
      }
   }

void
TR_ReachabilityAnalysis::perform(TR_BitVector *result)
   {
   TR::CFG *cfg = comp()->getFlowGraph();
   int32_t numBlockIndexes = cfg->getNextNodeNumber();
   int32_t numBlocks       = cfg->getNumberOfNodes();

   _blocks = cfg->createArrayOfBlocks();

   blocknum_t *stack    = (blocknum_t*)comp()->trMemory()->allocateStackMemory(numBlockIndexes * sizeof(stack[0]));
   blocknum_t *depthMap = (blocknum_t*)comp()->trMemory()->allocateStackMemory(numBlockIndexes * sizeof(depthMap[0]));
   memset(depthMap, 0, numBlockIndexes * sizeof(depthMap[0]));

   bool trace = comp()->getOption(TR_TraceReachability);

   if (trace)
      traceMsg(comp(), "BEGIN REACHABILITY: %d blocks\n", numBlocks);

   for (TR::Block *block = comp()->getStartBlock(); block; block = block->getNextBlock())
      {
      blocknum_t blockNum = block->getNumber();
      if (trace)
         traceMsg(comp(), "Visit block_%d\n", blockNum);
      if (depthMap[blockNum] == 0)
         traverse(blockNum, 0, stack, depthMap, result);
      else
         traceMsg(comp(), "  depth is already %d; skip\n", depthMap[blockNum]);
      }

   if (comp()->getOption(TR_TraceReachability))
      {
      traceMsg(comp(), "END REACHABILITY.  Result:\n");
      result->print(comp(), comp()->getOutFile());
      traceMsg(comp(), "\n");
      }
   }

// This opt tries to reduce merge backs from cold code that are the result of inliner
// gnerated nopable virtual guards
// It looks for one basic pattern
//
// guard1 -> cold1
// BBEND
// BBSTART
// guard2 -> cold2
// if guard1 is the guard for a method which calls the method guard2 protects or cold1 is
// a predecessor of cold2 (a situation commonly greated by virtual guard tail splitter) we
// can transform the guards as follows when guard1 and guard2 a
// guard1 -> cold1
// BBEND
// BBSTART
// guard2 -> cold1
// This is safe because there are no trees between the guards and calling the caller will
// result in the call to the callee if we need to patch guard2. cold2 and its mergebacks
// can then be eliminated
//
// In addition this opt will try to move guard2 up from the end of a block to the
// start of the block. We can do this if guard2 is an HCR guard and there is no GC point
// between BBSTART and guard2 since HCR is a stop-the-world event.
//
// Finally, there is a simple tail splitting step run before the analysis of a guard if we
// detect that the taken side of the guard merges back in the next block - this happens
// for some empty methods and is common for Object.<init> at the top of constructors.
int32_t TR_VirtualGuardHeadMerger::perform() {
   static char *disableVGHeadMergerTailSplitting = feGetEnv("TR_DisableVGHeadMergerTailSplitting");
   TR::CFG *cfg = comp()->getFlowGraph();

   // Cache the loads for the outer guard's cold path
   TR_BitVector coldPathLoads(comp()->trMemory()->currentStackRegion());
   TR_BitVector privArgSymRefs(comp()->trMemory()->currentStackRegion());
   bool evaluatedColdPathLoads = false;

   for (TR::Block *block = optimizer()->getMethodSymbol()->getFirstTreeTop()->getNode()->getBlock();
        block; block = block->getNextBlock())
      {
      TR::Node *guard1 = block->getLastRealTreeTop()->getNode();

      if (isMergeableGuard(guard1))
         {
         if (trace())
            traceMsg(comp(), "Found mergeable guard in block_%d\n", block->getNumber());
         TR::Block *cold1 = guard1->getBranchDestination()->getEnclosingBlock();

         // check for an immediate merge back from the cold block and
         // tail split one block if we can - we only handle splitting a block
         // ending in a fallthrough, a branch or a goto for now for simplicity
         if (!disableVGHeadMergerTailSplitting &&
             (cold1->getSuccessors().size() == 1) &&
             cold1->hasSuccessor(block->getNextBlock()) &&
             cold1->getLastRealTreeTop()->getNode()->getOpCode().isGoto())
            {
            // TODO handle moving code earlier in the block down below the guard
            // tail split
            if ((block->getNextBlock()->getSuccessors().size() == 1) ||
                ((block->getNextBlock()->getSuccessors().size() == 2) &&
                 block->getNextBlock()->getLastRealTreeTop()->getNode()->getOpCode().isBranch()) &&
                performTransformation(comp(), "%sCloning block_%d and placing clone after block_%d to reduce HCR guard nops\n", OPT_DETAILS, block->getNextBlock()->getNumber(), cold1->getNumber()))
               tailSplitBlock(block, cold1);
            }

         // guard motion is fairly complex but what we want to achieve around guard1 is a sequence
         // of relocated privarg blocks, followed by a sequence of runtime patchable guards going to
         // guard1's cold block, followed by a sequence of stop-the-world guards going to guard1's
         // cold block
         //
         // 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())
            {
//.........这里部分代码省略.........

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.........