C++ Block::getLastRealTreeTop方法代码示例

int32_t TR_AsyncCheckInsertion::insertReturnAsyncChecks(TR::Optimization *opt, const char *counterPrefix)
   {
   TR::Compilation * const comp = opt->comp();
   if (opt->trace())
      traceMsg(comp, "Inserting return asyncchecks (%s)\n", counterPrefix);

   int numAsyncChecksInserted = 0;
   for (TR::TreeTop *treeTop = comp->getStartTree();
        treeTop;
        /* nothing */ )
      {
      TR::Block *block = treeTop->getNode()->getBlock();
      if (block->getLastRealTreeTop()->getNode()->getOpCode().isReturn()
          && performTransformation(comp,
               "%sInserting return asynccheck (%s) in block_%d\n",
               opt->optDetailString(),
               counterPrefix,
               block->getNumber()))
         {
         insertAsyncCheck(block, comp, counterPrefix);
         numAsyncChecksInserted++;
         }

      treeTop = block->getExit()->getNextRealTreeTop();
      }
   return numAsyncChecksInserted;
   }

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);
   }

// 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);
   }

// 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.........

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
//.........这里部分代码省略.........

int32_t TR::DeadTreesElimination::process(TR::TreeTop *startTree, TR::TreeTop *endTree)
   {
   TR::StackMemoryRegion stackRegion(*comp()->trMemory());
   LongestPathMap longestPaths(std::less<TR::Node*>(), stackRegion);

   typedef TR::typed_allocator<CRAnchor, TR::Region&> CRAnchorAlloc;
   typedef TR::forward_list<CRAnchor, CRAnchorAlloc> CRAnchorList;
   CRAnchorList anchors(stackRegion);

   vcount_t visitCount = comp()->incOrResetVisitCount();
   TR::TreeTop *treeTop;
   for (treeTop = startTree; (treeTop != endTree); treeTop = treeTop->getNextTreeTop())
      treeTop->getNode()->initializeFutureUseCounts(visitCount);

   TR::Block *block = NULL;
   bool delayedRegStoresBeforeThisPass = _delayedRegStores;

   // Update visitCount as they are used in this optimization and need to be
   visitCount = comp()->incOrResetVisitCount();
   for (TR::TreeTopIterator iter(startTree, comp()); iter != endTree; ++iter)
      {
      TR::Node *node = iter.currentTree()->getNode();

      if (node->getOpCodeValue() == TR::BBStart)
         {
         block = node->getBlock();
         if (!block->isExtensionOfPreviousBlock())
            longestPaths.clear();
         }

      int vcountLimit = MAX_VCOUNT - 3;
      if (comp()->getVisitCount() > vcountLimit)
         {
         dumpOptDetails(comp(),
            "%sVisit count %d exceeds limit %d; stopping\n",
            optDetailString(), comp()->getVisitCount(), vcountLimit);
         return 0;
         }

      // correct at all intermediate stages
      //
      if ((node->getOpCodeValue() != TR::treetop) &&
          (!node->getOpCode().isAnchor() || (node->getFirstChild()->getReferenceCount() != 1)) &&
          (!node->getOpCode().isStoreReg() || (node->getFirstChild()->getReferenceCount() != 1)) &&
          (delayedRegStoresBeforeThisPass ||
           (iter.currentTree() == block->getLastRealTreeTop()) ||
           !node->getOpCode().isStoreReg() ||
           (node->getVisitCount() == visitCount)))
         {
         if (node->getOpCode().isAnchor() && node->getFirstChild()->getOpCode().isLoadIndirect())
            anchors.push_front(CRAnchor(iter.currentTree(), block));

         TR::TransformUtil::recursivelySetNodeVisitCount(node, visitCount);
         continue;
         }

      if (node->getOpCode().isStoreReg())
         _delayedRegStores = true;

      TR::Node *child = node->getFirstChild();
      if (child->getOpCodeValue() == TR::PassThrough)
         {
         TR::Node *newChild = child->getFirstChild();
         node->setAndIncChild(0, newChild);
         newChild->incFutureUseCount();
         if (child->getReferenceCount() <= 1)
            optimizer()->prepareForNodeRemoval(child);
         child->recursivelyDecReferenceCount();
         recursivelyDecFutureUseCount(child);
         child = newChild;
         }

      bool treeTopCanBeEliminated = false;

      // If the treetop child has been seen before then it must be anchored
      // somewhere above already; so we don't need the treetop to be anchoring
      // this node (as the computation is already done at the first reference to
      // the node).
      //

      if (visitCount == child->getVisitCount())
         {
         treeTopCanBeEliminated = true;
         }
      else
         {
         TR::ILOpCode &childOpCode = child->getOpCode();
         TR::ILOpCodes opCodeValue = childOpCode.getOpCodeValue();
         bool seenConditionalBranch = false;

         bool callWithNoSideEffects = child->getOpCode().isCall() &&
              child->getSymbolReference()->getSymbol()->isResolvedMethod() &&
              child->getSymbolReference()->getSymbol()->castToResolvedMethodSymbol()->isSideEffectFree();

         if (callWithNoSideEffects)
            {
            treeTopCanBeEliminated = true;
            }
         else if (!((childOpCode.isCall() && !callWithNoSideEffects) ||
               childOpCode.isStore() ||
//.........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.........