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RedundantAsyncCheckRemoval.cpp
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/*******************************************************************************
*
* (c) Copyright IBM Corp. 2000, 2016
*
* This program and the accompanying materials are made available
* under the terms of the Eclipse Public License v1.0 and
* Apache License v2.0 which accompanies this distribution.
*
* The Eclipse Public License is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* The Apache License v2.0 is available at
* http://www.opensource.org/licenses/apache2.0.php
*
* Contributors:
* Multiple authors (IBM Corp.) - initial implementation and documentation
*******************************************************************************/
#include "optimizer/RedundantAsyncCheckRemoval.hpp"
#include <algorithm> // for std::max, etc
#include <limits.h> // for INT_MAX
#include <stdlib.h> // for atoi
#include <string.h> // for strncmp, memset, NULL
#include "codegen/CodeGenerator.hpp" // for CodeGenerator
#include "codegen/FrontEnd.hpp" // for TR_FrontEnd, feGetEnv
#include "codegen/RecognizedMethods.hpp"
#include "compile/Compilation.hpp" // for Compilation
#include "compile/ResolvedMethod.hpp" // for TR_ResolvedMethod
#include "compile/SymbolReferenceTable.hpp" // for SymbolReferenceTable
#include "control/Options.hpp"
#include "control/Options_inlines.hpp"
#include "control/Recompilation.hpp" // for TR_Recompilation
#include "env/StackMemoryRegion.hpp"
#include "env/jittypes.h" // for TR_ByteCodeInfo, etc
#include "il/Block.hpp" // for Block, toBlock
#include "il/DataTypes.hpp" // for getMaxSigned, etc
#include "il/ILOps.hpp" // for ILOpCode, TR::ILOpCode
#include "il/Node.hpp" // for Node, vcount_t
#include "il/Node_inlines.hpp" // for Node::getFirstChild, etc
#include "il/Symbol.hpp" // for Symbol
#include "il/SymbolReference.hpp" // for SymbolReference
#include "il/TreeTop.hpp" // for TreeTop
#include "il/TreeTop_inlines.hpp" // for TreeTop::getNode, etc
#include "il/symbol/MethodSymbol.hpp" // for MethodSymbol
#include "infra/Assert.hpp" // for TR_ASSERT
#include "infra/BitVector.hpp" // for TR_BitVector
#include "infra/TRCfgEdge.hpp" // for CFGEdge
#include "infra/TRCfgNode.hpp" // for CFGNode
#include "optimizer/Optimization_inlines.hpp"
#include "optimizer/Optimizer.hpp" // for Optimizer
#include "optimizer/Structure.hpp" // for TR_StructureSubGraphNode, etc
#include "optimizer/TransformUtil.hpp" // for TransformUtil
#include "optimizer/VPConstraint.hpp" // for TR::VPConstraint
#include "optimizer/AsyncCheckInsertion.hpp"
#define OPT_DETAILS "O^O REDUNDANT ASYNC CHECK REMOVAL: "
#define SHORT_RUNNING_LOOP 1
#define SHORT_RUNNING_LOOP_BOUND 20000
#define NUMBER_OF_NODES_IN_LARGE_METHOD 2000
#define NUMBER_OF_NODES_IN_LARGE_WARM_ACYCLIC_METHOD 200
// The following macro(s) works on StructureSubGraphNodes
#define GET_ASYNC_INFO(x) ((AsyncInfo*)(((x)->getStructure())->getAnalysisInfo()))
// Find a loop that this regoin is contained in
//
static TR_RegionStructure *getOuterLoop(TR_RegionStructure *region)
{
if (region->getParent() == 0)
return 0;
TR_RegionStructure *parent = region->getParent()->asRegion();
if (parent->isNaturalLoop())
return parent;
return getOuterLoop(parent);
}
static TR_RegionStructure *getOuterImproperRegion(TR_Structure *region)
{
if (region->getParent() == 0)
return 0;
TR_RegionStructure *parent = region->getParent()->asRegion();
if (parent->containsInternalCycles())
return parent;
return getOuterImproperRegion(parent);
}
static inline int32_t ceiling(int32_t numer, int32_t denom)
{
return (numer % denom == 0) ?
numer / denom :
numer / denom + 1;
}
TR_RedundantAsyncCheckRemoval::TR_RedundantAsyncCheckRemoval(TR::OptimizationManager *manager)
: TR::Optimization(manager), _ancestors(trMemory())
{}
bool TR_RedundantAsyncCheckRemoval::shouldPerform()
{
// Don't run when profiling
//
if (comp()->isProfilingCompilation() || comp()->generateArraylets())
return false;
if (comp()->getOption(TR_EnableOSR)) // cannot move async checks around arbitrarily if OSR is possible
return false;
return true;
}
int32_t TR_RedundantAsyncCheckRemoval::perform()
{
TR::StackMemoryRegion stackMemoryRegion(*trMemory());
if (trace())
comp()->dumpMethodTrees("Before analysis:");
_asyncCheckInCurrentLoop = false;
_numAsyncChecksInserted = 0;
_foundShortRunningLoops = false;
_cfg = comp()->getFlowGraph();
// If this is a large acyclic method - add a yield point at each return from this method
// so that sampling will realize that we are actually in this method.
//
if (comp()->getMethodHotness() <= warm ||
!comp()->mayHaveLoops())
{
static const char *p;
static uint32_t numNodesInLargeMethod = (p = feGetEnv("TR_LargeMethodNodes")) ? atoi(p) : NUMBER_OF_NODES_IN_LARGE_METHOD;
if (!p && 0)
{
if (comp()->getMethodHotness() <= warm &&
!comp()->mayHaveLoops())
numNodesInLargeMethod = NUMBER_OF_NODES_IN_LARGE_WARM_ACYCLIC_METHOD;
}
if ((uint32_t) comp()->getNodeCount() > numNodesInLargeMethod ||
comp()->getLoopWasVersionedWrtAsyncChecks())
_numAsyncChecksInserted += TR_AsyncCheckInsertion::insertReturnAsyncChecks(comp());
return 1;
}
initialize(_cfg->getStructure());
comp()->incVisitCount();
int32_t count = perform(_cfg->getStructure());
// If all the loops are short running in the method, and we have
// resulted in the removal of all async checks - then sampling might
// be effected. Insert async checks on method exits.
//
if (comp()->getLoopWasVersionedWrtAsyncChecks() ||
(_numAsyncChecksInserted == 0 && _foundShortRunningLoops &&
comp()->getRecompilationInfo() &&
#ifdef J9_PROJECT_SPECIFIC
comp()->getRecompilationInfo()->useSampling() &&
#endif
comp()->getRecompilationInfo()->shouldBeCompiledAgain()))
{
_numAsyncChecksInserted += TR_AsyncCheckInsertion::insertReturnAsyncChecks(comp());
}
if (trace())
comp()->dumpMethodTrees("After analysis:");
return count;
}
int32_t TR_RedundantAsyncCheckRemoval::perform(TR_Structure *str, bool insideImproperRegion)
{
TR_RegionStructure *region = str->asRegion();
if (region == 0)
return processBlockStructure(str->asBlock());
bool origAsyncCheckFlag = _asyncCheckInCurrentLoop;
if (region->containsInternalCycles())
{
int32_t retValue = processImproperRegion(region);
if (origAsyncCheckFlag)
_asyncCheckInCurrentLoop = true;
return retValue;
}
bool asyncCheckFlag = false;
if (region->isNaturalLoop())
_asyncCheckInCurrentLoop = false;
TR_RegionStructure::Cursor it(*region);
TR_StructureSubGraphNode *node;
for (node = it.getFirst(); node != 0; node = it.getNext())
{
perform(node->getStructure());
if (_asyncCheckInCurrentLoop)
asyncCheckFlag = true;
if (trace())
traceMsg(comp(), "sub node %d flag %d\n", node->getNumber(), asyncCheckFlag);
if (region->isNaturalLoop())
_asyncCheckInCurrentLoop = false;
}
if (region->isNaturalLoop())
{
if (trace())
traceMsg(comp(), "region %d flag %d\n", region->getNumber(), asyncCheckFlag);
_asyncCheckInCurrentLoop = asyncCheckFlag;
int32_t retValue = processNaturalLoop(region, insideImproperRegion);
if (asyncCheckFlag || origAsyncCheckFlag)
_asyncCheckInCurrentLoop = true;
else
_asyncCheckInCurrentLoop = false;
return retValue;
}
_asyncCheckInCurrentLoop = asyncCheckFlag;
int32_t retValue = processAcyclicRegion(region);
if (asyncCheckFlag || origAsyncCheckFlag)
_asyncCheckInCurrentLoop = true;
else
_asyncCheckInCurrentLoop = false;
return retValue;
}
// Initializes the AsyncInfo analysis objects for each of the structures,
// ignoring any improper regoins
//
void TR_RedundantAsyncCheckRemoval::initialize(TR_Structure *str)
{
AsyncInfo *info = new (trStackMemory()) AsyncInfo(trMemory());
info->setVisitMarker(0);
str->setAnalysisInfo(info);
TR_RegionStructure *region = str->asRegion();
if (region == 0)
return;
TR_RegionStructure::Cursor it(*region);
for (TR_StructureSubGraphNode *node = it.getFirst(); node; node = it.getNext())
initialize(node->getStructure());
}
int32_t TR_RedundantAsyncCheckRemoval::processBlockStructure(TR_BlockStructure *b)
{
// We remove all explicit async checks from the block. All calls other than INL
// calls cause a yield point as well. We must ignore unresolved calls as well
// because they might resolve to INL calls.
//
// 20020816: Return Paths as implicit yield points:
// Base Case: If the return is in "main", it is safe to omit the yield
// point on returning paths.
// Induction Step: Assume that the caller has correct yield points in it (it is safe).
// If you are returning to the caller, you need not do a yield, since you know
// that the caller will do it.
//
// By Induction, on the call depth, omitting yield points on paths that return is safe.
//
TR::Block *block = b->getBlock();
TR::TreeTop *treeTop;
TR::TreeTop *prev;
bool hasAYieldPoint = false;
bool hadAYieldPoint = false;
AsyncInfo *info = (AsyncInfo *)b->getAnalysisInfo();
TR::TreeTop *firstBlockEntry = block->startOfExtendedBlock()->getEntry();
TR::Block *curBlock = block;
TR::TreeTop *stopTree = NULL;
for (treeTop = firstBlockEntry; treeTop != block->getExit(); treeTop = treeTop->getNextTreeTop())
{
TR::Node *node = treeTop->getNode();
if (node->getOpCodeValue() == TR::BBStart)
{
stopTree = NULL;
curBlock = node->getBlock();
TR_RegionStructure *outerImproperRegion = getOuterImproperRegion(curBlock->getStructureOf());
TR_Structure * outerLoop = curBlock->getStructureOf()->getContainingLoop();
if ((node->getVisitCount() == comp()->getVisitCount()) ||
(outerImproperRegion && (!outerLoop || outerLoop->contains(outerImproperRegion))) ||
(curBlock->getStructureOf()->getContainingLoop() != b->getContainingLoop()))
{
stopTree = node->getBlock()->getExit()->getPrevTreeTop();
//continue;
}
node->setVisitCount(comp()->getVisitCount());
}
if (info->canHaveAYieldPoint() &&
containsImplicitInternalPointer(node))
{
// Mark all extendees as 'mustNotHaveAYieldPoint'
//
// Sometimes CSE creates implicit internal pointers in portions of code
// where there were no gc-points before. We cannot add a async check is such
// regions of code - since it will invalidate that optimization. Instead
// we recognize portions of extended basic blocks as "grey-areas" where its
// going to be dangerous to put a new async check.
//
markExtendees(curBlock, false);
}
if (!stopTree)
{
switch (node->getOpCodeValue())
{
case TR::asynccheck:
// Remove the async check
//
_asyncCheckInCurrentLoop = true;
if (trace())
traceMsg(comp(), "removing async check from block_%d\n", b->getNumber());
if (performTransformation(comp(), "%sremoving async check from block_%d\n", OPT_DETAILS, b->getNumber()))
{
prev = treeTop->getPrevTreeTop();
optimizer()->prepareForTreeRemoval(treeTop);
TR::TransformUtil::removeTree(comp(), treeTop);
treeTop = prev;
}
hadAYieldPoint = true;
break;
case TR::treetop:
case TR::NULLCHK:
case TR::ResolveCHK:
case TR::ResolveAndNULLCHK:
if (node->getFirstChild()->getOpCode().isCall() && !node->getFirstChild()->getSymbolReference()->isUnresolved())
{
if (callDoesAnImplicitAsyncCheck(node->getFirstChild()))
hasAYieldPoint = true;
}
break;
default:
if (node->getOpCode().isReturn())
hasAYieldPoint = true;
break;
}
}
}
// If we cannot have a yield point here because of a implicit internal pointer
// seen earlier in the extended basic block, then the internal pointer must go
// dead before the end of the block, since by definition, it cannot be live
// across a gc point. Any extendees of this block can have a asynccheck
// put into them
//
////if ((hasAYieldPoint || hadAYieldPoint) && !info->canHaveAYieldPoint())
//// markExtendees(block, true);
if (hasAYieldPoint)
info->setHardYieldPoint();
return 0;
}
bool TR_RedundantAsyncCheckRemoval::callDoesAnImplicitAsyncCheck(TR::Node *callNode)
{
TR::SymbolReference *symRef = callNode->getSymbolReference();
TR::MethodSymbol *symbol = callNode->getSymbol()->castToMethodSymbol();
TR::SymbolReferenceTable *symRefTab = comp()->getSymRefTab();
if (symbol->isVMInternalNative() || symbol->isJITInternalNative())
return false;
// This covers jitProfileValue, singlePrecisionSQRT and currentTimeMaxPrecision
if (symbol->isHelper())
return false;
#ifdef J9_PROJECT_SPECIFIC
if ((symbol->getRecognizedMethod()==TR::java_lang_Math_sqrt) ||
(symbol->getRecognizedMethod()==TR::java_lang_StrictMath_sqrt) ||
(symbol->getRecognizedMethod()==TR::java_lang_Math_max_I) ||
(symbol->getRecognizedMethod()==TR::java_lang_Math_min_I) ||
(symbol->getRecognizedMethod()==TR::java_lang_Math_max_L) ||
(symbol->getRecognizedMethod()==TR::java_lang_Math_min_L) ||
(symbol->getRecognizedMethod()==TR::java_lang_Math_abs_L) ||
(symbol->getRecognizedMethod()==TR::java_lang_Math_abs_D) ||
(symbol->getRecognizedMethod()==TR::java_lang_Math_abs_F) ||
(symbol->getRecognizedMethod()==TR::java_lang_Math_abs_I) ||
(symbol->getRecognizedMethod()==TR::java_lang_System_hiresClockImpl) ||
(symbol->getRecognizedMethod()==TR::java_lang_Integer_numberOfLeadingZeros) ||
(symbol->getRecognizedMethod()==TR::java_lang_Long_numberOfLeadingZeros) ||
(symbol->getRecognizedMethod()==TR::java_lang_Integer_numberOfTrailingZeros) ||
(symbol->getRecognizedMethod()==TR::java_lang_Long_numberOfTrailingZeros) ||
(symbol->getRecognizedMethod()==TR::java_lang_Integer_highestOneBit) ||
(symbol->getRecognizedMethod()==TR::java_lang_Long_reverseBytes) ||
(symbol->getRecognizedMethod()==TR::java_lang_Short_reverseBytes) ||
(symbol->getRecognizedMethod()==TR::java_lang_Integer_reverseBytes) ||
(symbol->getRecognizedMethod()==TR::java_lang_Long_highestOneBit) ||
(symbol->getRecognizedMethod()==TR::java_lang_Integer_rotateLeft) ||
(symbol->getRecognizedMethod()==TR::java_lang_Long_rotateLeft) ||
(symbol->getRecognizedMethod()==TR::java_lang_Integer_rotateRight) ||
(symbol->getRecognizedMethod()==TR::java_lang_Long_rotateRight) ||
(symbol->getRecognizedMethod()==TR::sun_misc_Unsafe_compareAndSwapInt_jlObjectJII_Z) ||
(symbol->getRecognizedMethod()==TR::sun_misc_Unsafe_compareAndSwapLong_jlObjectJJJ_Z) ||
(symbol->getRecognizedMethod()==TR::sun_misc_Unsafe_compareAndSwapObject_jlObjectJjlObjectjlObject_Z)
)
return false;
if ((symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPPerformHysteresis) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPUseDFP) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPHWAvailable) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPIntConstructor) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPLongConstructor) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPLongExpConstructor) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPAdd) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPSubtract) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPMultiply) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPDivide) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPScaledAdd) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPScaledSubtract) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPScaledMultiply) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPScaledDivide) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPRound) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPSetScale) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPCompareTo) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPSignificance) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPExponent) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPBCDDigits) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPUnscaledValue) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPConvertPackedToDFP) ||
(symbol->getRecognizedMethod()==TR::java_math_BigDecimal_DFPConvertDFPToPacked)
)
return false;
if ((symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_JITIntrinsicsEnabled) ||
(symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_DFPFacilityAvailable) ||
(symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_DFPUseDFP) ||
(symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_DFPConvertPackedToDFP) ||
(symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_DFPConvertDFPToPacked) ||
(symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_createZeroBigDecimal) ||
(symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_getlaside) ||
(symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_setlaside) ||
(symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_getflags) ||
(symbol->getRecognizedMethod()==TR::com_ibm_dataaccess_DecimalData_setflags))
return false;
if (symbol->getRecognizedMethod()==TR::java_lang_String_StrHWAvailable)
return false;
#endif
return true;
}
int32_t TR_RedundantAsyncCheckRemoval::processAcyclicRegion(TR_RegionStructure *region)
{
// We do not need to look inside an acyclic region, if it is
// not inside a loop.
//
if (getOuterLoop(region) == 0)
return 0;
_ancestors.deleteAll();
comp()->incVisitCount();
computeCoverageInfo(region->getEntry(), region->getEntry());
if (GET_ASYNC_INFO(region->getEntry())->getCoverage() != FullyCovered)
{
comp()->incVisitCount();
TR_RegionStructure::Cursor it(*region);
TR_StructureSubGraphNode *node;
for (node = it.getFirst(); node; node = it.getNext())
{
AsyncInfo *info = GET_ASYNC_INFO(node);
if (info->hasYieldPoint())
markAncestors(node, region->getEntry());
}
ListIterator<TR_StructureSubGraphNode> ait(&_ancestors);
if (!_ancestors.isEmpty())
{
for (node = ait.getFirst(); node; node = ait.getNext())
{
getNearestAncestors(node, node, region->getEntry());
}
while ((node = findSmallestAncestor()) != 0)
{
insertAsyncCheckOnSubTree(node, region->getEntry());
}
}
}
AsyncInfo *info = (AsyncInfo *)region->getAnalysisInfo();
AsyncInfo *entryInfo = GET_ASYNC_INFO(region->getEntry());
// At this point, an ac region can either be not covered or
// fully covered. It may /seem/ partially covered because of
// exit successors. For such cases:
//
if (entryInfo->getCoverage() == PartiallyCovered)
entryInfo->setCoverage(FullyCovered);
info->setCoverage(entryInfo->getCoverage());
return 0;
}
// Recursively propagates coverage information about nodes in a loop or acylic region
//
void TR_RedundantAsyncCheckRemoval::computeCoverageInfo(TR_StructureSubGraphNode *node, TR_StructureSubGraphNode *entry)
{
if (node->getVisitCount() == comp()->getVisitCount())
return;
node->setVisitCount(comp()->getVisitCount());
AsyncInfo *info = GET_ASYNC_INFO(node);
if (!info->hasYieldPoint())
{
// This node is not FullyCovered, if all it's successors are covered.
// If it is covered on some paths then it is PartirallyCovered
// If it is not covered on any path, then it is NotCovered.
//
bool coveredOnSomePaths = false;
bool notCoveredOnSomePaths = false;
bool hasRealSuccessors = false;
for (auto edge = node->getSuccessors().begin(); edge != node->getSuccessors().end(); ++edge)
{
TR_StructureSubGraphNode *succ = toStructureSubGraphNode((*edge)->getTo());
// If there is an exit edge from node, we are not covered on that path
//
if (!succ->getStructure())
notCoveredOnSomePaths = true;
else
{
hasRealSuccessors = true;
if (succ == entry)
notCoveredOnSomePaths = true;
else
{
computeCoverageInfo(succ, entry);
switch (GET_ASYNC_INFO(succ)->getCoverage())
{
case NotCovered:
notCoveredOnSomePaths = true;
break;
case PartiallyCovered:
coveredOnSomePaths = true;
notCoveredOnSomePaths = true;
break;
case FullyCovered:
coveredOnSomePaths = true;
break;
}
}
}
}
if (hasRealSuccessors)
{
if (coveredOnSomePaths && notCoveredOnSomePaths)
info->setCoverage(PartiallyCovered);
else if (coveredOnSomePaths && !notCoveredOnSomePaths)
info->setCoverage(FullyCovered);
else if (!coveredOnSomePaths && notCoveredOnSomePaths)
info->setCoverage(NotCovered);
else
info->setCoverage(NotCovered);
}
else
info->setCoverage(NotCovered);
}
if (trace())
traceMsg(comp(), "for node: %d coverage: %d\n", node->getNumber(), info->getCoverage());
}
bool TR_RedundantAsyncCheckRemoval::isMaxLoopIterationGuardedLoop(TR_RegionStructure *loop)
{
// FIXME: this is much easier if dominator trees are available
TR_RegionStructure *parent = loop->getParent()->asRegion();
TR_StructureSubGraphNode *node = parent->findSubNodeInRegion(loop->getNumber());
if (!(node->getPredecessors().size() == 1))
return false;
TR_StructureSubGraphNode *pred = node->getPredecessors().front()->getFrom()
->asStructureSubGraphNode();
// If parent is an improper region, give up
//
if (parent->containsInternalCycles())
return false;
// The following is a rather intricate structure walk, and requires some explanation
// we start at the node representing the loop in the parent region. What we want to do
// is to find a dominating if-block that contains the max-loop-iteration guard for this
// loop. Traditionally, the guard is not the parent region, but infact there are several
// other versioning guards intervening between the loop and the iter guard. Each of
// these guards forms its own acyclic region, nesting the inner guards.
//
// We start the search in the parent region, walking the predecessors of the loop region.
// By definition there must exist an acyclic path between the loop and the guard. Ignore
// backedges and just walk the preds. There cannot be a region structure en route
// since that would imply that there was some control flow not typical of guarded versioned
// loops. If we hit the entry of the parent region, we start the same process in the
// parent of the parent region, until we hit the start-node, which implies failure.
//
// Each node en route must have exactly one predecessor, otherwise we have control flow
// not typical of a versioned loop.
//
// The walk below uses a queue for traversal just to look like a canonical backwards
// reverse post order walk, however there is never more than one element in the queue.
// NOTE: there is no use of visit counts in this loop, a node can never be visited twice
// in the following walk
//
TR_Queue<TR_StructureSubGraphNode> q(trMemory());
q.enqueue(pred);
while (!q.isEmpty())
{
TR_StructureSubGraphNode *cursor = q.dequeue();
// cannot have a region between the guard and the actual loop
//
if (cursor->getStructure()->asRegion())
return false;
// Check the cursor block
//
TR::Block *block = cursor->getStructure()->asBlock()->getBlock();
if (block == _cfg->getStart()->asBlock())
return false;
TR::TreeTop *tt = block->getLastRealTreeTop();
if (tt->getNode()->isMaxLoopIterationGuard())
return true;
// if we have hit the entry of the parent, we need to start looking in the
// parent's parent
//
TR_RegionStructure *cursorParent = cursor->getStructure()->getParent()->asRegion();
if (cursor == cursorParent->getEntry())
{
// if the parent was a loop, we know already that the guard was not found
// (cannot be improper, otherwise we would never have enqueued it)
//
if (cursorParent->isNaturalLoop())
return false;
// if we hit the start of the cfg, we have failed
//
if (!cursorParent->getParent())
return false;
cursorParent = cursorParent->getParent()->asRegion();
// If the parent is improper, give up
//
if (cursorParent->containsInternalCycles())
return false;
cursor = cursorParent->findSubNodeInRegion(cursor->getNumber());
}
// Enqueue the predecessors of the cursor
// there must be one unique predecessor
//
if (!(cursor->getPredecessors().size() == 1))
return false;
TR_StructureSubGraphNode *pred = cursor->getPredecessors().front()->getFrom()
->asStructureSubGraphNode();
q.enqueue(pred);
}
return false;
}
bool
TR_RedundantAsyncCheckRemoval::containsImplicitInternalPointer(TR::Node *node)
{
if (node->getVisitCount() == comp()->getVisitCount())
return false;
node->setVisitCount(comp()->getVisitCount());
bool result = false;
if (node->getOpCode().isArrayRef() && node->getReferenceCount() > 1 &&
(!comp()->cg()->supportsInternalPointers() || !node->isInternalPointer() || !node->getPinningArrayPointer()))
{
result = true;
}
else
{
for (int32_t c = node->getNumChildren()-1; c >= 0; --c)
{
if (containsImplicitInternalPointer(node->getChild(c)))
{
result = true;
break;
}
}
}
if (trace())
traceMsg(comp(), " containsImplicitInternalPointer(%p) = %s\n", node, result?"true":"false");
return result;
}
void
TR_RedundantAsyncCheckRemoval::markExtendees(TR::Block *block, bool canHaveAYieldPoint)
{
for (TR::Block *cursor = block->getNextBlock();
cursor && cursor->isExtensionOfPreviousBlock();
cursor = cursor->getNextBlock())
{
TR_BlockStructure *s = cursor->getStructureOf();
AsyncInfo *ai = ((AsyncInfo*)s->getAnalysisInfo());
if (trace())
{
traceMsg(comp(), " block_%d canHaveAYieldPoint %s -> %s\n",
cursor->getNumber(),
ai->canHaveAYieldPoint()? "true":"false",
canHaveAYieldPoint? "true":"false");
}
ai->setCanHaveAYieldPoint(canHaveAYieldPoint);
}
}
#define FIND_LOOP_ITERATIONS(Type,Name,NAME) \
bool Killme_CantBeginMacroWith_HASH_HASH; \
Type incr = incrVal->getLow##Name(); \
Type in, out, iters, diff; \
if (incr == 0) continue; \
if (entryVal && exitVal && entryVal->as##Name##Const() && exitVal->as##Name##Const()) \
{ \
in = entryVal->getLow##Name(); \
out = exitVal->getLow##Name(); \
} \
else if (entryVal && entryVal->as##Name##Const()) \
{ \
Type lo, hi; \
if (exitVal) \
{ \
lo = exitVal->getLow##Name(); \
hi = exitVal->getHigh##Name(); \
} \
else \
{ \
lo = TR::getMinSigned<NAME>(); \
hi = TR::getMaxSigned<NAME>(); \
} \
in = entryVal->getLow##Name(); \
if (incr > 0 && in < lo) \
out = lo; \
else if (incr < 0 && in > hi) \
out = hi; \
else \
continue; \
} \
else \
continue; \
diff = in-out; \
if (diff == TR::getMinSigned<NAME>()) \
continue; \
iters = (diff < 0) ? -diff/incr : diff/-incr;
int32_t TR_RedundantAsyncCheckRemoval::estimateLoopIterations(TR_RegionStructure *loop)
{
int32_t estimate = INT_MAX;
TR_InductionVariable *indVar;
for (indVar = loop->getFirstInductionVariable();
indVar != 0;
indVar = indVar->getNext())
{
TR::VPConstraint *entryVal = indVar->getEntry();
TR::VPConstraint *exitVal = indVar->getExit();
TR::VPConstraint *incrVal = indVar->getIncr();
if (incrVal->asLongConst() || (entryVal && entryVal->asLongConst()) || (exitVal && exitVal->asLongConst()))
{
FIND_LOOP_ITERATIONS(int64_t,Long,TR::Int64);
if (iters < estimate)
estimate = (int32_t) iters;
}
else
{
FIND_LOOP_ITERATIONS(int32_t,Int,TR::Int32);
if (iters < estimate)
estimate = iters;
}
}
if (isMaxLoopIterationGuardedLoop(loop))
{
return SHORT_RUNNING_LOOP;
}
if (loop->getFirstInductionVariable() == 0)
{
TR_LoopEstimator est(comp()->getFlowGraph(), loop, trace());
estimate = est.estimateLoopIterationsUpperBound();
}
return estimate;
}
int32_t TR_RedundantAsyncCheckRemoval::findShallowestCommonCaller(int32_t callSiteIndex1, int32_t callSiteIndex2)
{
while ((callSiteIndex1 != -1) && (callSiteIndex1 != -1) && (callSiteIndex1 != callSiteIndex2))
{
if (callSiteIndex1 > callSiteIndex2)
callSiteIndex1 = comp()->getInlinedCallSite(callSiteIndex1)._byteCodeInfo.getCallerIndex();
else
callSiteIndex2 = comp()->getInlinedCallSite(callSiteIndex2)._byteCodeInfo.getCallerIndex();
}
if ((callSiteIndex1 == callSiteIndex2))
return callSiteIndex1;
else
return -1;
}
bool TR_RedundantAsyncCheckRemoval::originatesFromShortRunningMethod(TR_RegionStructure* region)
{
// Loops originating from java/lang/String methods are assumed to be short running unless
// they contain loops that are inlined from methods outsides the above classes.
// The following is an algorithm to detect such loops. In the algorithm, we assume that if all branches of all basic blocks of a loop
// have the same owning method, then that loop originates from that method.
//First build a list of branches in all basic blocks of the loop (region)
TR_ScratchList<TR::Block> blocksInRegion(trMemory());
region->getBlocks(&blocksInRegion);
ListIterator<TR::Block> blocksIt(&blocksInRegion);
TR_ScratchList<TR::Node> branches(trMemory());
for (TR::Block * block = blocksIt.getCurrent(); block; block=blocksIt.getNext())
{
TR::TreeTop* lastTreeTop = block->getLastRealTreeTop();
if (lastTreeTop != block->getEntry() && lastTreeTop->getNode()->getOpCode().isBranch())
branches.add(lastTreeTop->getNode());
}
TR_ASSERT(!branches.isEmpty(), "there are no branches in this loop!\n");
if (branches.isEmpty())
return false;
ListIterator<TR::Node> branchNodeIt(&branches);
int32_t commonCaller = branchNodeIt.getFirst()->getByteCodeInfo().getCallerIndex();
for (TR::Node* branchNode = branchNodeIt.getNext(); branchNode; branchNode = branchNodeIt.getNext())
{
commonCaller = findShallowestCommonCaller(commonCaller,
branchNode->getByteCodeInfo().getCallerIndex());
}
while ((commonCaller != -1) && !comp()->isShortRunningMethod(commonCaller))
commonCaller = comp()->getInlinedCallSite(commonCaller)._byteCodeInfo.getCallerIndex();
if (commonCaller == -1)
return false;
//Check all the branches. Either their origin must be the
//same as the common ancestor, or they must be called by the
//same origin through short-running or loopless methods.
for (TR::Node* branchNode = branchNodeIt.getFirst(); branchNode; branchNode = branchNodeIt.getNext())
{
int32_t callerIndex = branchNode->getByteCodeInfo().getCallerIndex();
bool callerMatch = false;
while (callerIndex != -1)
{
if (callerIndex == commonCaller)
{
callerMatch = true;
break;
}
TR_InlinedCallSite &ics = comp()->getInlinedCallSite(callerIndex);
if (!comp()->isShortRunningMethod(callerIndex) &&
comp()->fe()->hasBackwardBranches((TR_OpaqueMethodBlock*)ics._vmMethodInfo))
break;
//set callerIndex to its caller
callerIndex = comp()->getInlinedCallSite(callerIndex)._byteCodeInfo.getCallerIndex();
}
if (!callerMatch)
return false;
}
return true;
}
bool TR_RedundantAsyncCheckRemoval::hasEarlyExit(TR_RegionStructure *region)
{
ListIterator<TR::CFGEdge> eit2(®ion->getExitEdges());
for (TR::CFGEdge *edge2 = eit2.getCurrent(); edge2 != 0; edge2 = eit2.getNext())
{
TR_StructureSubGraphNode *pred2 = edge2->getFrom()->asStructureSubGraphNode();
bool earlyExit = true;
for (auto edge = region->getEntry()->getPredecessors().begin(); edge != region->getEntry()->getPredecessors().end();
++edge)
{
if (pred2 == (*edge)->getFrom())
{
if (trace())
{
traceMsg(comp(), "pred2 = %d\n", pred2 ? pred2->getNumber() : -1);
traceMsg(comp(), "edge->getFrom = %d\n", (*edge)->getFrom() ? (*edge)->getFrom()->getNumber() : -1);
}
earlyExit = false;
break;
}
}
if (earlyExit)
{
if (trace())
traceMsg(comp(), "found earlyExit in region %d \n", region->getNumber());
return true;
}
}
return false;
}
int32_t TR_RedundantAsyncCheckRemoval::processNaturalLoop(TR_RegionStructure *region, bool isInsideImproperRegion)
{
if (trace())
traceMsg(comp(), "==> Forward Processing natural loop %d\n", region->getNumber());
bool isShortRunning = false;
bool needsForwardAnalysis = true;
if (!isInsideImproperRegion)
{
// There is no need to put async checks in loops created by tail recursion
// elimination. The reasoning is that if the loop were long-running, we
// would have resulted in a stack overflow to begin with.
//
TR::Block *entryBlock = region->getEntryBlock();
for (auto edge = entryBlock->getPredecessors().begin(); (edge != entryBlock->getPredecessors().end())&& !isShortRunning; ++edge)
{
if ((*edge)->getCreatedByTailRecursionElimination())
{
isShortRunning = true;
if (trace())
traceMsg(comp(), "Loop %d was created by TailRecursionElim. Skipping\n", region->getNumber());
}
}
if ((comp()->getMethodHotness() == scorching) && originatesFromShortRunningMethod(region))
{
isShortRunning = true;
if (trace())
traceMsg(comp(), "Loop %d originates from a trusted method, and therefore, is tagged as short running. Skipping\n", region->getNumber());
}
// Async check did not exist in this loop at beginning of RACR
// This implies that loop versioning eliminated the asynccheck
// from the loop based on short running guard.
//
if (!_asyncCheckInCurrentLoop)
{
isShortRunning = true;
if (trace())
traceMsg(comp(), "Loop %d is a Short running loop. Skipping\n", region->getNumber());
}
// Spill Loops generated by the General Loop Unroller do not need any async checks
// either since they are guaranteed to be short running
//
if (entryBlock->getStructureOf()->isEntryOfShortRunningLoop())
{
isShortRunning = true;
if (trace())
traceMsg(comp(), "Loop %d is a Short running loop. Skipping\n", region->getNumber());
}
if (!isShortRunning && (estimateLoopIterations(region) < SHORT_RUNNING_LOOP_BOUND))
{
isShortRunning = true;
if (trace())
traceMsg(comp(), "Loop %d is short running. Skipping\n", region->getNumber());
}
}
bool cannotClaimFullCoverage = false;
if (!isShortRunning)
{
_ancestors.deleteAll();
// First of all, compute coverage information for all subnodes
//
comp()->incVisitCount();
computeCoverageInfo(region->getEntry(), region->getEntry());
// If the entry is Fully Covered, we do not need to perform the analysis
//
if (GET_ASYNC_INFO(region->getEntry())->getCoverage() == FullyCovered)
{
if (trace())