C++ Node::getSecondChild方法代码示例

int32_t
TR::RegDepCopyRemoval::perform()
   {
   if (!cg()->supportsPassThroughCopyToNewVirtualRegister())
      return 0;

   discardAllNodeChoices();
   TR::TreeTop *tt;
   for (tt = comp()->getStartTree(); tt != NULL; tt = tt->getNextTreeTop())
      {
      TR::Node *node = tt->getNode();
      switch (node->getOpCodeValue())
         {
         case TR::BBStart:
            if (!node->getBlock()->isExtensionOfPreviousBlock())
               {
               if (trace())
                  traceMsg(comp(), "clearing remembered node choices at start of extended block at block_%d\n", node->getBlock()->getNumber());
               discardAllNodeChoices();
               }
            if (node->getNumChildren() > 0)
               processRegDeps(node->getFirstChild(), tt);
            break;
         case TR::BBEnd:
            if (node->getNumChildren() > 0)
               processRegDeps(node->getFirstChild(), tt);
            break;
         default:
            if (node->getOpCode().isSwitch())
               {
               TR::Node *defaultDest = node->getSecondChild();
               if (defaultDest->getNumChildren() > 0)
                  processRegDeps(defaultDest->getFirstChild(), tt);
               }
            else if (node->getOpCode().isBranch())
               {
               int nChildren = node->getNumChildren();
               // only the last child may be GlRegDeps
               for (int i = 0; i < nChildren - 1; i++)
                  TR_ASSERT(node->getChild(i)->getOpCodeValue() != TR::GlRegDeps, "GlRegDeps for branch is not the last child\n");
               if (nChildren > 0)
                  {
                  TR::Node *lastChild = node->getChild(nChildren - 1);
                  if (lastChild->getOpCodeValue() == TR::GlRegDeps)
                     processRegDeps(lastChild, tt);
                  }
               }
            break;
         }
      }
   return 1; // a bit arbitrary...
   }

TR::TreeTop *searchForStringAppend(TR::ValuePropagation *vp,const char *sig, TR::TreeTop *tt, TR::TreeTop *exitTree,
                                    TR::ILOpCodes opCode, TR::Node *newBuffer, vcount_t visitCount, TR::Node **string)
   {
   int len = 0;
   bool isGlobal = false;
   for (;tt != exitTree; tt = tt->getNextRealTreeTop())
      {
      TR::Node *node = tt->getNode();

      if (node->getNumChildren() == 1 &&
          node->getFirstChild()->getOpCodeValue() == opCode)
         {
         if (checkMethodSignature(vp,node->getFirstChild()->getSymbolReference(), sig))
            {
            TR::Node *call = node->getFirstChild();
            if (call->getFirstChild() == newBuffer)
               {
               if (vp->getConstraint(call->getSecondChild(),isGlobal))
                  {
                  if (vp->getConstraint(call->getSecondChild(),isGlobal)->getClassType())
                     {
                     const char *sigAppend = vp->getConstraint(call->getSecondChild(),isGlobal)->getClassType()->getClassSignature(len);
                     if (call->getSecondChild()->getOpCodeValue() ==  TR::aload && (!strncmp(sigAppend,"Ljava/lang/String;",18)))
                        {
                        *string = call->getSecondChild();
                        }
                     }
                  }
               }
            return tt;
            }
         else
            return tt;
         }

      //if (countNodeOccurrencesInSubTree(node, newBuffer, visitCount) > 0) return tt;
      }
   return tt;
   }

TR::Node *
OMR::TransformUtil::scalarizeArrayCopy(
      TR::Compilation *comp,
      TR::Node *node,
      TR::TreeTop *tt,
      bool useElementType,
      bool &didTransformArrayCopyNode,
      TR::SymbolReference *sourceRef,
      TR::SymbolReference *targetRef,
      bool castToIntegral)
   {
   TR::CodeGenerator *cg = comp->cg();

   didTransformArrayCopyNode = false;

   if ((comp->getOptLevel() == noOpt) ||
       !comp->getOption(TR_ScalarizeSSOps) ||
       node->getOpCodeValue() != TR::arraycopy ||
       node->getNumChildren() != 3 ||
       comp->requiresSpineChecks() ||
       !node->getChild(2)->getOpCode().isLoadConst() ||
       cg->getOptimizationPhaseIsComplete())
      return node;

   int64_t byteLen = node->getChild(2)->get64bitIntegralValue();
   if (byteLen == 0)
      {
      if (tt)
         {
         // Anchor the first two children
         if (!node->getFirstChild()->safeToDoRecursiveDecrement())
            TR::TreeTop::create(comp, tt->getPrevTreeTop(),
                               TR::Node::create(TR::treetop, 1, node->getFirstChild()));
         if (!node->getSecondChild()->safeToDoRecursiveDecrement())
            TR::TreeTop::create(comp, tt->getPrevTreeTop(),
                               TR::Node::create(TR::treetop, 1, node->getSecondChild()));
         tt->getPrevTreeTop()->join(tt->getNextTreeTop());
         tt->getNode()->recursivelyDecReferenceCount();
         didTransformArrayCopyNode = true;
         }
      return node;
      }
   else if (byteLen < 0)
      {
      return node;
      }
   else if (byteLen > TR_MAX_OTYPE_SIZE)
      {
      return node;
      }
   TR::DataType dataType = TR::Aggregate;

   // Get the element datatype from the (hidden) 4th child
   TR::DataType elementType = node->getArrayCopyElementType();
   int32_t elementSize = TR::Symbol::convertTypeToSize(elementType);

   if (byteLen == elementSize)
      {
      dataType = elementType;
      }
   else if (!useElementType)
      {
      switch (byteLen)
         {
         case 1: dataType = TR::Int8; break;
         case 2: dataType = TR::Int16; break;
         case 4: dataType = TR::Int32; break;
         case 8: dataType = TR::Int64; break;
         }
      }
   else
      {
      return node;
      }

   // load/store double on 64-bit PPC requires offset to be word aligned
   // abort if this requirement is not met.
   // TODO: also need to check if the first two children are aload nodes
   bool cannot_use_load_store_long = false;
   if (TR::Compiler->target.cpu.isPower())
      if (dataType == TR::Int64 && TR::Compiler->target.is64Bit())
         {
         TR::Node * firstChild = node->getFirstChild();
         if (firstChild->getNumChildren() == 2)
            {
            TR::Node *offsetChild = firstChild->getSecondChild();
            TR_ASSERT(offsetChild->getOpCodeValue() != TR::iconst, "iconst shouldn't be used for 64-bit array indexing");
            if (offsetChild->getOpCodeValue() == TR::lconst)
               {
               if ((offsetChild->getLongInt() & 0x3) != 0)
                  cannot_use_load_store_long = true;
               }
            }
         TR::Node *secondChild = node->getSecondChild();
         if (secondChild->getNumChildren() == 2)
            {
            TR::Node *offsetChild = secondChild->getSecondChild();
            TR_ASSERT(offsetChild->getOpCodeValue() != TR::iconst, "iconst shouldn't be used for 64-bit array indexing");
            if (offsetChild->getOpCodeValue() == TR::lconst)
               {
//.........这里部分代码省略.........

bool
OMR::Simplifier::isBoundDefinitelyGELength(TR::Node *boundChild, TR::Node *lengthChild)
   {
   TR::ILOpCodes boundOp = boundChild->getOpCodeValue();
   if (boundOp == TR::iadd)
      {
      TR::Node *first  = boundChild->getFirstChild();
      TR::Node *second = boundChild->getSecondChild();
      if (first == lengthChild)
         {
         TR::ILOpCodes secondOp = second->getOpCodeValue();
         if (second->getOpCode().isArrayLength()                          ||
             secondOp == TR::bu2i                                          ||
             secondOp == TR::su2i                                          ||

             (secondOp == TR::iconst &&
              second->getInt() >= 0)                                      ||

             (secondOp == TR::iand                                     &&
              second->getSecondChild()->getOpCodeValue() == TR::iconst &&
              (second->getSecondChild()->getInt() & 80000000) == 0)       ||

             (secondOp == TR::iushr                                    &&
              second->getSecondChild()->getOpCodeValue() == TR::iconst &&
              (second->getSecondChild()->getInt() & 0x1f) > 0))
            {
            return true;
            }
         }
      else if (second == lengthChild)
         {
         TR::ILOpCodes firstOp = first->getOpCodeValue();
         if (first->getOpCode().isArrayLength()                          ||
             firstOp == TR::bu2i                                          ||
             firstOp == TR::su2i                                          ||

             (firstOp == TR::iand                                     &&
              first->getSecondChild()->getOpCodeValue() == TR::iconst &&
              (first->getSecondChild()->getInt() & 80000000) == 0)       ||

             (firstOp == TR::iushr &&
              first->getSecondChild()->getOpCodeValue() == TR::iconst &&
              (first->getSecondChild()->getInt() & 0x1f) > 0))
            {
            return true;
            }
         }
      }
   else if (boundOp == TR::isub)
      {
      TR::Node *first  = boundChild->getFirstChild();
      TR::Node *second = boundChild->getSecondChild();
      if (first  == lengthChild)
         {
         TR::ILOpCodes secondOp = second->getOpCodeValue();
         if ((secondOp == TR::iconst &&
              second->getInt() < 0)                                      ||

             (secondOp == TR::ior                                      &&
              second->getSecondChild()->getOpCodeValue() == TR::iconst &&
              (second->getSecondChild()->getInt() & 0x80000000) != 0))
            {
            return true;
            }
         }
      }

   return false;
   }

TR::Node *
OMR::Simplifier::unaryCancelOutWithChild(TR::Node * node, TR::Node * firstChild, TR::TreeTop *anchorTree, TR::ILOpCodes opcode, bool anchorChildren)
   {
   if (!isLegalToUnaryCancel(node, firstChild, opcode))
      return NULL;

   if (firstChild->getOpCodeValue() == opcode &&
       (node->getType().isAggregate() || firstChild->getType().isAggregate()) &&
       (node->getSize() > firstChild->getSize() || node->getSize() != firstChild->getFirstChild()->getSize()))
      {
      // ensure a truncation side-effect of a conversion is not lost
      // o2a size=3
      //   a2o size=3 // conversion truncates in addition to type cast so cannot be removed
      //     loadaddr size=4
      // This restriction could be loosened to only disallow intermediate truncations (see BCD case above) but then would require a node
      // op that would just correct for size (e.g. addrSizeMod size=3 to replace the o2a/a2o pair)
      //
      // Do allow cases when all three sizes are the same and when the middle node widens but the top and bottom node have the same size, e.g.
      //
      // i2o size=3
      //   o2i size=4
      //     oload size=3
      //
      // Also allow the special case where the grandchild is not really truncated as the 'truncated' bytes are known to be zero
      // (i.e. there really isn't an intermediate truncation of 4->3 even though it appears that way from looking at the sizes alone)
      // o2i
      //   i2o size=3
      //     iushr
      //       x
      //       iconst 8
      bool disallow = true;
      TR::Node *grandChild = firstChild->getFirstChild();
      size_t nodeSize = node->getSize();
      if (node->getType().isIntegral() &&
          nodeSize == grandChild->getSize() &&
          nodeSize > firstChild->getSize())
         {
         size_t truncatedBits = (nodeSize - firstChild->getSize()) * 8;
         if (grandChild->getOpCode().isRightShift() && grandChild->getOpCode().isShiftLogical() &&
             grandChild->getSecondChild()->getOpCode().isLoadConst() &&
             (grandChild->getSecondChild()->get64bitIntegralValue() == truncatedBits))
            {
            disallow = false;
            if (trace())
               traceMsg(comp(),"do allow unaryCancel of node %s (%p) and firstChild %s (%p) as grandChild %s (%p) zeros the %d truncated bytes\n",
                       node->getOpCode().getName(),node,firstChild->getOpCode().getName(),firstChild,
                       grandChild->getOpCode().getName(),grandChild,truncatedBits/8);
            }
         }

      if (disallow)
         {
         if (trace())
            traceMsg(comp(),"disallow unaryCancel of node %s (%p) and firstChild %s (%p) due to unequal sizes (nodeSize %d, firstChildSize %d, firstChild->childSize %d)\n",
                    node->getOpCode().getName(),node,firstChild->getOpCode().getName(),firstChild,
                    node->getSize(),firstChild->getSize(),firstChild->getFirstChild()->getSize());
         return NULL;
         }
      }

   if (firstChild->getOpCodeValue() == opcode &&
       performTransformation(comp(), "%sRemoving node [" POINTER_PRINTF_FORMAT "] %s and its child [" POINTER_PRINTF_FORMAT "] %s\n",
             optDetailString(), node, node->getOpCode().getName(), firstChild, firstChild->getOpCode().getName()))
      {
      TR::Node *grandChild = firstChild->getFirstChild();
      grandChild->incReferenceCount();
      bool anchorChildrenNeeded = anchorChildren &&
         (node->getNumChildren() > 1 ||
          firstChild->getNumChildren() > 1 ||
          node->getOpCode().hasSymbolReference() ||
          firstChild->getOpCode().hasSymbolReference());
      prepareToStopUsingNode(node, anchorTree, anchorChildrenNeeded);
      node->recursivelyDecReferenceCount();
      node->setVisitCount(0);
      return grandChild;
      }

   return NULL;
   }

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.........

bool TR_ExpressionsSimplification::tranformSummationReductionCandidate(TR::TreeTop *treeTop, LoopInfo *loopInfo, bool *isPreheaderBlockInvalid)
   {
   TR::Node *node = treeTop->getNode();
   TR::Node *opNode = node->getFirstChild();
   TR::Node *expNode = NULL;
   int32_t expChildNumber = 0;
   bool removeOnly = false;
   bool replaceWithNewNode = false;

   if (opNode->getOpCodeValue() == TR::iadd || opNode->getOpCodeValue() == TR::isub)
      {
      if (opNode->getSecondChild()->getOpCode().hasSymbolReference() &&
            node->getSymbolReference() == opNode->getSecondChild()->getSymbolReference())
         {
         expChildNumber = 0;
         expNode = opNode->getFirstChild();
         }
      else
         {
         expChildNumber = 1;
         expNode = opNode->getSecondChild();
         }
      expNode = iaddisubSimplifier(expNode, loopInfo);
      replaceWithNewNode = true;
      }
   else if (opNode->getOpCodeValue() == TR::ixor || opNode->getOpCodeValue() == TR::ineg)
      {
      expNode = ixorinegSimplifier(opNode, loopInfo, &removeOnly);
      }

   if (expNode)
      {
      if (trace())
         comp()->getDebug()->print(comp()->getOutFile(), expNode, 0, true);

      TR::Block *entryBlock = _currentRegion->getEntryBlock();
      TR::Block *preheaderBlock = findPredecessorBlock(entryBlock);

      if (!preheaderBlock)
         {
         if (trace())
            traceMsg(comp(), "Fail to find a place to put the hoist code in\n");
         *isPreheaderBlockInvalid = true;
         return true;
         }

      if (loopInfo->getNumIterations() > 0 ||     // make sure that the loop is going to be executed at least once
            _currentRegion->isCanonicalizedLoop())  // or that the loop is canonicalized, in which case the preheader is
         {                                        // executed in its first iteration and is protected.
         if (performTransformation(comp(), "%sMove out loop-invariant node [%p] to block_%d\n", OPT_DETAILS, node, preheaderBlock->getNumber()))
            {
            if (!(removeOnly))
               {
               TR::Node *newNode = node->duplicateTree();
               if (replaceWithNewNode)
                  newNode->getFirstChild()->setAndIncChild(expChildNumber, expNode);
               transformNode(newNode, preheaderBlock);
               }
            TR::TransformUtil::removeTree(comp(), treeTop);
            }
         }
      }
      return (expNode != NULL);
   }

void TR_ExpressionsSimplification::setSummationReductionCandidates(TR::Node *node, TR::TreeTop *tt)
   {
   // Must be a store node
   //
   if (node->getOpCodeValue() != TR::istore
   /* || node->getOpCodeValue() != TR::astore */)
      {
      if (trace())
         traceMsg(comp(), "Node %p: The opcode is not istore so not a summation reduction candidate\n",node);
      return;
      }

   TR::Node *opNode = node->getFirstChild();

   if (opNode->getOpCodeValue() == TR::iadd ||
       opNode->getOpCodeValue() == TR::isub)
      {
      TR::Node *firstNode = opNode->getFirstChild();
      TR::Node *secondNode = opNode->getSecondChild();

      if (firstNode->getOpCode().hasSymbolReference() &&
            node->getSymbolReference() == firstNode->getSymbolReference() &&
            opNode->getReferenceCount() == 1 && firstNode->getReferenceCount() == 1)
         {
         // The second node must be loop invariant
         //
         if (!_currentRegion->isExprInvariant(secondNode))
            {
            if (trace())
               {
               traceMsg(comp(), "The node %p is not loop invariant\n",secondNode);

               // This can be the arithmetic series case
               // only when the node is an induction variable
               if (secondNode->getNumChildren() == 1 && secondNode->getOpCode().hasSymbolReference())
                  {
                  TR_InductionVariable *indVar = _currentRegion->findMatchingIV(secondNode->getSymbolReference());
                  if (indVar)
                     {
                     //printf("Found Candidate of arithmetic series\n" );
                     }
                  }
               }
            return;
            }

         _candidateTTs->add(tt);
         }
      else if (secondNode->getOpCode().hasSymbolReference() &&
            node->getSymbolReference() == secondNode->getSymbolReference() &&
            opNode->getReferenceCount() == 1 && secondNode->getReferenceCount() == 1 &&
            _currentRegion->isExprInvariant(firstNode))
         {
         _candidateTTs->add(tt);
         }
      }
   else if (opNode->getOpCodeValue() == TR::ixor ||
            opNode->getOpCodeValue() == TR::ineg)
      {
      if (opNode->getFirstChild()->getOpCode().hasSymbolReference() &&
            node->getSymbolReference() == opNode->getFirstChild()->getSymbolReference() &&
            opNode->getReferenceCount() == 1 && opNode->getFirstChild()->getReferenceCount() == 1 &&
            (opNode->getOpCodeValue() == TR::ineg || _currentRegion->isExprInvariant(opNode->getSecondChild())))
         _candidateTTs->add(tt);
      else if (opNode->getOpCodeValue() == TR::ixor && opNode->getSecondChild()->getOpCode().hasSymbolReference() &&
            node->getSymbolReference() == opNode->getSecondChild()->getSymbolReference() &&
            opNode->getReferenceCount() == 1 && opNode->getSecondChild()->getReferenceCount() == 1 &&
            _currentRegion->isExprInvariant(opNode->getFirstChild()))
         _candidateTTs->add(tt);
      }
   }

//.........这里部分代码省略.........
         _nullCheckNodesAsArray = NULL;
      else
         {
         _nullCheckNodesAsArray = (TR::Node**)trMemory()->allocateStackMemory(_numNullChecks*sizeof(TR::Node*));
         memset(_nullCheckNodesAsArray, 0, _numNullChecks*sizeof(TR::Node*));
         }

      currentTree = comp()->getStartTree();
      int32_t symRefCount = comp()->getSymRefCount();
      _checkSymbolReferences = new (trStackMemory()) TR_BitVector(symRefCount, trMemory(), stackAlloc);

      _numNodes = 1;
      _numNullChecks = 0;

      // This loop counts all the nodes that are going to take part in PRE.
      // This is a computation intensive loop as we check if the node that
      // is syntactically equivalent to a given node has been seen before
      // and if so we use the local index of the original node (that
      // is syntactically equivalent to the given node). Could be improved
      // in complexity with value numbering at some stage.
      //
      _visitCount = comp()->incVisitCount();
      while (currentTree)
         {
         TR::Node *firstNodeInTree = currentTree->getNode();
         TR::ILOpCode *opCode = &firstNodeInTree->getOpCode();

         if (((firstNodeInTree->getOpCodeValue() == TR::treetop) ||
              (comp()->useAnchors() && firstNodeInTree->getOpCode().isAnchor())) &&
             (firstNodeInTree->getFirstChild()->getOpCode().isStore()))
            {
            firstNodeInTree->setLocalIndex(-1);
            if (comp()->useAnchors() && firstNodeInTree->getOpCode().isAnchor())
               firstNodeInTree->getSecondChild()->setLocalIndex(-1);

            firstNodeInTree = firstNodeInTree->getFirstChild();
            opCode = &firstNodeInTree->getOpCode();
            }

         // This call finds nodes with opcodes that are supported by PRE
         // in this subtree; this accounts for all opcodes other than stores/checks
         // which are handled later on below
         //
         bool firstNodeInTreeHasCallsInStoreLhs = false;
         countSupportedNodes(firstNodeInTree, NULL, firstNodeInTreeHasCallsInStoreLhs);

         if ((opCode->isStore() && !firstNodeInTree->getSymbolReference()->getSymbol()->isAutoOrParm()) ||
             opCode->isCheck())
            {
            int32_t oldExpressionOnRhs = hasOldExpressionOnRhs(firstNodeInTree);

            //
            // Return value 0 denotes that the node contains some sub-expression
            // that cannot participate in PRE; e.g. a call or a new
            //
            // Return value -1 denotes that the node can participate in PRE
            // but did not match with any existing expression seen so far
            //
            // Any other return value (should be positive always) denotes that
            // the node can participate in PRE and has been matched with a seen
            // expression having local index == return value
            //
            if (oldExpressionOnRhs == -1)
               {
               if (trace())
                  {

//.........这里部分代码省略.........
                  requestOpt(OMR::treeSimplification, true, block);

               if (nextTree->getNode()->getOpCodeValue() == TR::Goto
                   && prevTree->getNode()->getOpCodeValue() == TR::BBStart
                   && !prevTree->getNode()->getBlock()->isExtensionOfPreviousBlock())
                  {
                  requestOpt(
                     OMR::redundantGotoElimination,
                     prevTree->getNode()->getBlock());
                  }
               }
            }
         else
            {
            if (performTransformation(comp(), "%sMove tree : [" POINTER_PRINTF_FORMAT "]([" POINTER_PRINTF_FORMAT "] = %s) to end of block\n", optDetailString(), node, node->getFirstChild(), node->getFirstChild()->getOpCode().getName()))
               {
               prevTree->join(nextTree);
               node->setVisitCount(visitCount);

               TR::TreeTop *lastTree = findLastTreetop(block, prevTree);
               TR::TreeTop *prevLastTree = lastTree->getPrevTreeTop();

               TR::TreeTop *cursorTreeTop = nextTree;
               while (cursorTreeTop != lastTree)
                  {
                  if (cursorTreeTop->getNode()->getOpCode().isStoreReg() &&
                      (cursorTreeTop->getNode()->getGlobalRegisterNumber() == iter.currentTree()->getNode()->getGlobalRegisterNumber()))
                     {
                     lastTree = cursorTreeTop;
                     prevLastTree = lastTree->getPrevTreeTop();
                     break;
                     }

                  cursorTreeTop = cursorTreeTop->getNextTreeTop();
                  }

               if (lastTree->getNode()->getOpCodeValue() == TR::BBStart)
                  {
                  prevLastTree = lastTree;
                  lastTree = block->getExit();
                  }

               TR::Node *lastNode = lastTree->getNode();
               TR::Node *prevLastNode = prevLastTree->getNode();

               if (lastNode->getOpCode().isIf() && !lastNode->getOpCode().isCompBranchOnly() &&
                   prevLastNode->getOpCode().isStoreReg() &&
                   ((prevLastNode->getFirstChild() == lastNode->getFirstChild()) ||
                    (prevLastNode->getFirstChild() == lastNode->getSecondChild())))
                  {
                  lastTree = prevLastTree;
                  prevLastTree = lastTree->getPrevTreeTop();
                  }

               prevLastTree->join(iter.currentTree());
               iter.currentTree()->join(lastTree);

               iter.jumpTo(prevTree);
               requestOpt(OMR::treeSimplification, true, block);
               }
            }
         }
      }

   for (auto it = anchors.begin(); it != anchors.end(); ++it)
      {
      TR::Node *anchor = it->tree->getNode();
      TR::Node *load = anchor->getChild(0);
      if (load->getReferenceCount() > 1)
         continue;

      // We can eliminate the indirect load immediately, but for the moment the
      // subtree providing the base object has to be anchored.

      TR::Node *heapBase = anchor->getChild(1);

      TR::Node::recreate(anchor, TR::treetop);
      anchor->setAndIncChild(0, load->getChild(0));
      anchor->setChild(1, NULL);
      anchor->setNumChildren(1);

      if (!heapBase->getOpCode().isLoadConst())
         {
         it->tree->insertAfter(
            TR::TreeTop::create(
               comp(),
               TR::Node::create(heapBase, TR::treetop, 1, heapBase)));
         }

      load->recursivelyDecReferenceCount();
      heapBase->recursivelyDecReferenceCount();

      // A later pass of dead trees can likely move (or even remove) the base
      // object expression.

      requestOpt(OMR::deadTreesElimination, true, it->block);
      }

   return 1; // actual cost
   }