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())
{
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();
if (guard1->getInlinedSiteIndex() == guard2->getInlinedSiteIndex())
{
if (trace())
traceMsg(comp(), " Guard1 [%p] is guarding the same call as Guard2 [%p] - proceeding with guard merging\n", guard1, guard2);
}
else if (guard2->getInlinedSiteIndex() > -1 &&
guard1->getInlinedSiteIndex() == TR::comp()->getInlinedCallSite(guard2->getInlinedSiteIndex())._byteCodeInfo.getCallerIndex())
{
if (trace())
traceMsg(comp(), " Guard1 [%p] is the caller of Guard2 [%p] - proceeding with guard merging\n", guard1, guard2);
}
else if ((cold1->getSuccessors().size() == 1) &&
cold1->hasSuccessor(cold2))
{
if (trace())
traceMsg(comp(), " Guard1 cold destination block_%d has guard2 cold destination block_%d as its only successor - proceeding with guard merging\n", cold1->getNumber(), cold2->getNumber());
}
else
{
if (trace())
traceMsg(comp(), " Cold1 block_%d and cold2 block_%d of guard2 [%p] in unknown relationship - abandon the merge attempt\n", cold1->getNumber(), cold2->getNumber(), guard2);
break;
}
// Runtime guards will shift their privargs, so it is necessary to check such a move is safe
// This is possible if a privarg temp was recycled for the inner call site, with a prior use as an
// argument for the outer call site. As the privargs for the inner call site must be evaluated before
// both guards, this would result in the recycled temp holding the incorrect value if the guard is ever
// taken.
if (!isStopTheWorldGuard(guard2))
{
if (!evaluatedColdPathLoads)
{
collectColdPathLoads(cold1, coldPathLoads);
evaluatedColdPathLoads = true;
}
if (coldPathLoads.intersects(privArgSymRefs))
{
if (trace())
traceMsg(comp(), " Recycled temp live in cold1 block_%d and used as privarg before guard2 [%p] - stop guard merging", cold1->getNumber(), guard2);
break;
}
}
if (!performTransformation(comp(), "%sRedirecting %s guard [%p] in block_%d to parent guard cold block_%d\n", OPT_DETAILS, isStopTheWorldGuard(guard2) ? "stop the world" : "runtime", guard2, guard2Block->getNumber(), cold1->getNumber()))
continue;
if (guard2->getBranchDestination() != guard1->getBranchDestination())
guard2Block->changeBranchDestination(guard1->getBranchDestination(), cfg);
if (guard2Tree != guard2Block->getFirstRealTreeTop())
{
cfg->setStructure(NULL);
// We should leave code ahead of an HCR guard in place because:
// 1, it might have side effect to runtime guards after it, moving it up might cause us to falsely merge
// the subsequent runtime guards
// 2, it might contain live monitor, moving it up above a guard can affect the monitor's live range
if (!isStopTheWorldGuard(guard2))
{
// the block created above guard2 contains only privarg treetops or monitor stores if
// guard2 is a runtime-patchable guard and is safe to merge. We need to move the priv
// args up to the runtime insert point and leave the monitor stores in place
// It's safe to do so because there is no data dependency between the monitor store and
// the priv arg store, because the priv arg store does not load the value from the temp
// holding the monitored object
// Split priv arg stores from monitor stores
// Monitor store is generated for the caller of the method guard2 protects, so should appear before
// priv arg stores for the method guard2 protects
TR::Block *privargBlock = guard2Block;
guard2Block = splitRuntimeGuardBlock(comp(), guard2Block, cfg);
if (privargBlock != guard2Block)
{
if (trace())
traceMsg(comp(), " Moving privarg block_%d after block_%d\n", privargBlock->getNumber(), privargIns->getNumber());
moveBlockAfterDest(cfg, privargBlock, privargIns);
if (HCRIns == privargIns)
HCRIns = privargBlock;
if (runtimeIns == privargIns)
runtimeIns = privargBlock;
privargIns = privargBlock;
// refresh the insertPoint since it could be stale after the above updates
insertPoint = runtimeIns;
}
}
guard2Block = guard2Block->split(guard2Tree, cfg, true, false);
if (trace())
traceMsg(comp(), " Created new block_%d to hold guard [%p] from block_%d\n", guard2Block->getNumber(), guard2, guard2Block->getNumber());
}
if (insertPoint != guard2Block->getPrevBlock())
{
TR::DebugCounter::incStaticDebugCounter(comp(), TR::DebugCounter::debugCounterName(comp(), "headMerger/%s_%s/(%s)", isStopTheWorldGuard(guard1) ? "stop the world" : "runtime", isStopTheWorldGuard(guard2) ? "stop the world" : "runtime", comp()->signature()));
cfg->setStructure(NULL);
block = nextBlock = guard2Block->getPrevBlock();
if (trace())
traceMsg(comp(), " Moving guard2 block block_%d after block_%d\n", guard2Block->getNumber(), insertPoint->getNumber());
moveBlockAfterDest(cfg, guard2Block, insertPoint);
if (HCRIns == insertPoint)
HCRIns = guard2Block;
if (runtimeIns == insertPoint)
runtimeIns = guard2Block;
}
else
{
block = guard2Block;
}
guard1 = guard2;
}
}
}
return 1;
}
TR_ExpressionsSimplification::LoopInfo*
TR_ExpressionsSimplification::findLoopInfo(TR_RegionStructure* region)
{
ListIterator<TR::CFGEdge> exitEdges(®ion->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;
}
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() ||
((opCodeValue == TR::New ||
opCodeValue == TR::anewarray ||
opCodeValue == TR::newarray) &&
child->getReferenceCount() > 1) ||
opCodeValue == TR::multianewarray ||
opCodeValue == TR::MergeNew ||
opCodeValue == TR::checkcast ||
opCodeValue == TR::Prefetch ||
opCodeValue == TR::iu2l ||
((childOpCode.isDiv() ||
childOpCode.isRem()) &&
child->getNumChildren() == 3)))
{
// Perform the rather complex check to see whether its safe
// to disconnect the child node from the treetop
//
bool safeToReplaceNode = false;
if (child->getReferenceCount() == 1)
{
safeToReplaceNode = true;
#ifdef J9_PROJECT_SPECIFIC
if (child->getOpCode().isPackedExponentiation())
{
// pdexp has a possible message side effect in truncating or no significant digits left cases
safeToReplaceNode = false;
}
#endif
if (opCodeValue == TR::loadaddr)
treeTopCanBeEliminated = true;
}
else if (!_cannotBeEliminated)
{
safeToReplaceNode = isSafeToReplaceNode(
child,
iter.currentTree(),
&seenConditionalBranch,
visitCount,
comp(),
&_targetTrees,
_cannotBeEliminated,
longestPaths);
}
if (safeToReplaceNode)
{
if (childOpCode.hasSymbolReference())
{
TR::SymbolReference *symRef = child->getSymbolReference();
if (symRef->getSymbol()->isAuto() || symRef->getSymbol()->isParm())
treeTopCanBeEliminated = true;
else
{
if (childOpCode.isLoad() ||
(opCodeValue == TR::loadaddr) ||
(opCodeValue == TR::instanceof) ||
(((opCodeValue == TR::New) ||
(opCodeValue == TR::anewarray ||
opCodeValue == TR::newarray)) &&
///child->getFirstChild()->isNonNegative()))
child->markedAllocationCanBeRemoved()))
// opCodeValue == TR::multianewarray ||
// opCodeValue == TR::MergeNew)
treeTopCanBeEliminated = true;
}
}
else
treeTopCanBeEliminated = true;
}
}
// Fix for the case when a float to non-float conversion node swings
// down past a branch on IA32; this would cause a FP value to be commoned
// across a branch where there was none originally; this causes pblms
// as a value is left on the stack.
//
if (treeTopCanBeEliminated &&
seenConditionalBranch)
{
if (!cg()->getSupportsJavaFloatSemantics())
{
if (child->getOpCode().isConversion() ||
child->getOpCode().isBooleanCompare())
{
if (child->getFirstChild()->getOpCode().isFloatingPoint() &&
!child->getOpCode().isFloatingPoint())
treeTopCanBeEliminated = false;
}
}
}
if (treeTopCanBeEliminated)
{
TR::NodeChecklist visited(comp());
bool containsFloatingPoint = false;
for (int32_t i = 0; i < child->getNumChildren(); ++i)
{
// Anchor nodes with reference count > 1
//
bool highGlobalIndex = false;
if (fixUpTree(child->getChild(i), iter.currentTree(), visited, highGlobalIndex, self(), visitCount))
containsFloatingPoint = true;
if (highGlobalIndex)
{
dumpOptDetails(comp(),
"%sGlobal index limit exceeded; stopping\n",
optDetailString());
return 0;
}
}
if (seenConditionalBranch &&
containsFloatingPoint)
{
if (!cg()->getSupportsJavaFloatSemantics())
treeTopCanBeEliminated = false;
}
}
}
// Update visitCount as they are used in this optimization and need to be
// correct at all intermediate stages
//
if (!treeTopCanBeEliminated)
TR::TransformUtil::recursivelySetNodeVisitCount(node, visitCount);
if (treeTopCanBeEliminated)
{
TR::TreeTop *prevTree = iter.currentTree()->getPrevTreeTop();
TR::TreeTop *nextTree = iter.currentTree()->getNextTreeTop();
if (!node->getOpCode().isStoreReg() || (node->getFirstChild()->getReferenceCount() == 1))
{
// Actually going to remove the treetop now
//
if (performTransformation(comp(), "%sRemove tree : [" POINTER_PRINTF_FORMAT "] ([" POINTER_PRINTF_FORMAT "] = %s)\n", optDetailString(), node, node->getFirstChild(), node->getFirstChild()->getOpCode().getName()))
{
prevTree->join(nextTree);
optimizer()->prepareForNodeRemoval(node);
///child->recursivelyDecReferenceCount();
node->recursivelyDecReferenceCount();
recursivelyDecFutureUseCount(child);
iter.jumpTo(prevTree);
if (child->getReferenceCount() == 1)
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
}
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;
}
}