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IsolatedStoreElimination.cpp
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/*******************************************************************************
* Copyright (c) 2000, 2019 IBM Corp. and others
*
* This program and the accompanying materials are made available under
* the terms of the Eclipse Public License 2.0 which accompanies this
* distribution and is available at http://eclipse.org/legal/epl-2.0
* or the Apache License, Version 2.0 which accompanies this distribution
* and is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License, v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception [1] and GNU General Public
* License, version 2 with the OpenJDK Assembly Exception [2].
*
* [1] https://www.gnu.org/software/classpath/license.html
* [2] http://openjdk.java.net/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0 WITH Classpath-exception-2.0 OR LicenseRef-GPL-2.0 WITH Assembly-exception
*******************************************************************************/
#include "optimizer/IsolatedStoreElimination.hpp"
#include <stdint.h>
#include <stdio.h>
#include "codegen/CodeGenerator.hpp"
#include "codegen/FrontEnd.hpp"
#include "compile/Compilation.hpp"
#include "compile/SymbolReferenceTable.hpp"
#include "control/Options.hpp"
#include "control/Options_inlines.hpp"
#include "cs2/bitvectr.h"
#include "env/IO.hpp"
#include "env/StackMemoryRegion.hpp"
#include "env/TRMemory.hpp"
#include "il/Block.hpp"
#include "il/DataTypes.hpp"
#include "il/ILOpCodes.hpp"
#include "il/ILOps.hpp"
#include "il/Node.hpp"
#include "il/Node_inlines.hpp"
#include "il/Symbol.hpp"
#include "il/SymbolReference.hpp"
#include "il/TreeTop.hpp"
#include "il/TreeTop_inlines.hpp"
#include "il/symbol/RegisterMappedSymbol.hpp"
#include "il/symbol/ResolvedMethodSymbol.hpp"
#include "infra/Array.hpp"
#include "infra/Assert.hpp"
#include "infra/BitVector.hpp"
#include "infra/Cfg.hpp"
#include "infra/List.hpp"
#include "infra/CfgEdge.hpp"
#include "infra/CfgNode.hpp"
#include "optimizer/Optimization.hpp"
#include "optimizer/Optimization_inlines.hpp"
#include "optimizer/Optimizations.hpp"
#include "optimizer/Optimizer.hpp"
#include "optimizer/Structure.hpp"
#include "optimizer/TransformUtil.hpp"
#include "optimizer/UseDefInfo.hpp"
#include "optimizer/VPConstraint.hpp"
#include "ras/Debug.hpp"
TR_IsolatedStoreElimination::TR_IsolatedStoreElimination(TR::OptimizationManager *manager)
: TR::Optimization(manager),
_mustUseUseDefInfo(false),
_deferUseDefInfoInvalidation(false),
_currentTree(NULL),
_usedSymbols(NULL),
_storeNodes(NULL),
_defParentOfUse(NULL),
_defStatus(NULL),
_groupsOfStoreNodes(NULL),
_trivialDefs(NULL)
{
}
struct UnsafeSubexpressionRemoval // PR69613
{
TR_IsolatedStoreElimination *_ise;
TR_BitVector _visitedNodes;
TR_BitVector _unsafeNodes; // Nodes whose mere evaluation is not safe
TR::Compilation *comp(){ return _ise->comp(); }
bool trace(){ return _ise->trace(); }
bool isVisited(TR::Node *node) { return _visitedNodes.isSet(node->getGlobalIndex()); }
bool isUnsafe(TR::Node *node)
{
TR_ASSERT(isVisited(node), "Cannot call isUnsafe on n%dn before anchorSafeChildrenOfUnsafeNodes", node->getGlobalIndex());
return _unsafeNodes.isSet(node->getGlobalIndex());
}
UnsafeSubexpressionRemoval(TR_IsolatedStoreElimination *ise):
_ise(ise),
_visitedNodes(ise->comp()->getNodeCount(), comp()->trMemory(), stackAlloc),
_unsafeNodes (ise->comp()->getNodeCount(), comp()->trMemory(), stackAlloc)
{}
void recordDeadUse(TR::Node *node)
{
_visitedNodes.set(node->getGlobalIndex());
_unsafeNodes .set(node->getGlobalIndex());
}
void anchorSafeChildrenOfUnsafeNodes(TR::Node *node, TR::TreeTop *anchorPoint)
{
if (isVisited(node))
return;
else
_visitedNodes.set(node->getGlobalIndex());
//
// Design note: we don't decrement refcounts in here. Conceptually,
// anchoring and decrementing are independent of each other. More
// pragmatically, you end up at with a well-defined state when this
// function finishes: if the top-level node is unsafe, the caller must
// unhook it and call recursivelyDecReferenceCount, which will do the
// right thing. Otherwise, no decrementing is necessary anyway.
//
// A rule of thumb to remember is that this function will do nothing if
// the node is safe. If you call this, then find !isUnsafe(node), then
// the trees did not change.
//
// Propagate unsafeness from children, unless we've already done it
//
for (int32_t i = 0; i < node->getNumChildren(); ++i)
{
TR::Node *child = node->getChild(i);
anchorSafeChildrenOfUnsafeNodes(child, anchorPoint);
if (isUnsafe(child))
{
_unsafeNodes.set(node->getGlobalIndex());
if (trace())
{
TR::Node *child = node->getChild(i);
traceMsg(comp(), " (Marked %s n%dn unsafe due to dead child #%d %s n%dn)\n",
node->getOpCode().getName(), node->getGlobalIndex(), i,
child->getOpCode().getName(), child->getGlobalIndex());
}
}
}
// If node is safe, all its descendant nodes must be safe. Nothing to do.
//
// If node is unsafe, anchor all its safe children. Its unsafe children,
// at this point, must already have taken care of their own safe
// subexpressions recursively.
//
// Note that this could anchor some nodes multiple times, for complex
// subexpressions with commoning. We could make some feeble attempts to
// prevent that, but let's just leave it to deadTreesElimination.
//
if (isUnsafe(node))
{
for (int32_t i = 0; i < node->getNumChildren(); ++i)
{
TR::Node *child = node->getChild(i);
bool didIt = anchorIfSafe(child, anchorPoint);
if (didIt && trace())
{
traceMsg(comp(), " - Anchored child #%d %s n%d of %s n%d\n",
i,
child->getOpCode().getName(), child->getGlobalIndex(),
node->getOpCode().getName(), node->getGlobalIndex());
}
}
}
}
bool anchorIfSafe(TR::Node *node, TR::TreeTop *anchorPoint)
{
if (!isVisited(node))
anchorSafeChildrenOfUnsafeNodes(node, anchorPoint);
if (isUnsafe(node))
{
return false;
}
else
{
anchorPoint->insertBefore(TR::TreeTop::create(comp(), TR::Node::create(TR::treetop, 1, node)));
return true;
}
}
};
int32_t TR_IsolatedStoreElimination::perform()
{
TR::StackMemoryRegion stackMemoryRegion(*trMemory());
_storeNodes = new(trStackMemory()) TR_Array<TR::Node *>(trMemory(), 64, true, stackAlloc);
// If there is use/def information available, use it to find isolated stores.
// Otherwise we must munge through the trees.
//
TR_UseDefInfo *useDefInfo = optimizer()->getUseDefInfo();
int32_t cost = 0;
_mustUseUseDefInfo = false;
// The use of _mustUseUseDefInfo is temporary until all opts maintain proper
// changes to use/def info
//
if (useDefInfo)
{
if (trace())
traceMsg(comp(), "Starting Global Store Elimination (using use/def info)\n");
cost = performWithUseDefInfo();
}
else
{
if (trace())
traceMsg(comp(), "Starting Global Store Elimination (without using use/def info)\n");
cost = performWithoutUseDefInfo();
}
// Now remove the isolated stores.
//
bool eliminatedStore = false;
#ifdef J9_PROJECT_SPECIFIC
bool eliminatedBCDStore = false;
#endif
if (useDefInfo)
{
// Scan for unsafe nodes, which are loads that are uses of dead stores,
// or (recusrively) any node with at least one unsafe child.
// Even evaluating an unsafe node could cause incorrect behaviour; for
// example, if the unsafe node dereferences a load of a dead pointer
// whose store got deleted, then that dereference could crash at runtime.
//
UnsafeSubexpressionRemoval usr(this);
for (uint32_t groupIndex = 0; groupIndex < _groupsOfStoreNodes->size(); groupIndex++)
{
TR_BitVector *groupOfStores = _groupsOfStoreNodes->element(groupIndex);
if (trace())
traceMsg(comp(), " Scanning store group %d for dead uses\n", groupIndex);
if (groupOfStores)
{
TR_BitVectorIterator storeIter(*groupOfStores);
while (storeIter.hasMoreElements())
{
int32_t defIndex = storeIter.getNextElement() + useDefInfo->getFirstDefIndex();
if (trace())
{
TR::Node *defNode = useDefInfo->getNode(defIndex);
traceMsg(comp(), " Scanning def %d %s n%dn for dead uses\n", defIndex, defNode->getOpCode().getName(), defNode->getGlobalIndex());
}
TR_UseDefInfo::BitVector useIndexes(comp()->allocator());
useDefInfo->getUsesFromDef(useIndexes, defIndex);
TR_UseDefInfo::BitVector::Cursor useCursor(useIndexes);
for (useCursor.SetToFirstOne(); useCursor.Valid(); useCursor.SetToNextOne())
{
int32_t useIndex = (int32_t)useCursor + useDefInfo->getFirstUseIndex();
TR::Node *useNode = useDefInfo->getNode(useIndex);
usr.recordDeadUse(useNode);
if (trace())
traceMsg(comp(), " Marked use %d %s n%dn dead\n", useIndex, useNode->getOpCode().getName(), useNode->getGlobalIndex());
}
}
}
}
// Now eliminate the dead stores
//
for (uint32_t groupIndex = 0; groupIndex < _groupsOfStoreNodes->size(); groupIndex++)
{
TR_BitVector *groupOfStores = _groupsOfStoreNodes->element(groupIndex);
if (groupOfStores && performTransformation(comp(), "%sGlobal Store Elimination eliminating group %d:\n", optDetailString(), groupIndex))
{
TR_BitVectorIterator bviUses(*groupOfStores);
while (bviUses.hasMoreElements())
{
int32_t index = bviUses.getNextElement() + useDefInfo->getFirstDefIndex();
TR::Node *node = useDefInfo->getNode(index);
TR::TreeTop *treeTop = useDefInfo->getTreeTop(index);
TR_ASSERT(node, "node should not be NULL at this point");
dumpOptDetails(comp(), "%sRemoving %s n%dn [" POINTER_PRINTF_FORMAT "] %s\n",
optDetailString(), node->getOpCode().getName(), node->getGlobalIndex(), node, node->getSymbolReference()->getSymbol()->isShadow() ? "(shadow)" : "");
#ifdef J9_PROJECT_SPECIFIC
if (node->getOpCode().isBCDStore())
eliminatedBCDStore = true;
#endif
_trivialDefs->reset(index); // It's not a trivial def if we're handling it as a group. If we try to do both, BOOM!
// Time to delete the store. This is more complex than it sounds.
//
// Generally, we want to replace the store with a treetop (ie. a
// no-op). However, this is complicated by several factors, in
// order of increasing subtlety and complexity:
//
// 1. Stores can have multiple children -- as many as three for
// an iwrtbar. If the store is turning into a nop, we must
// anchor all the other children.
// 2. Stores can appear under other nodes like CHKs and
// compressedRefs. Particularly for the CHKs, we must
// perform the appropriate checks despite eliminating the
// store, and so we must leave the store node in the
// appropriate shape so its parents will do the right thing.
// 3. Some expressions are unsafe to evaluate after stores are
// eliminated, and those expressions themselves must NOT be
// anchored.
//
// In these transformations, we adopt the convention that we
// retain the original store whenever possible, modifying it
// in-place, and we retain its first child if possible. These
// conventions are sometimes required, and so we just adopt them
// universally for the sake of consistency, efficiency, and
// readability in the jit logs.
// Anchor all children but the first
//
for (int32_t i = 1; i < node->getNumChildren(); i++)
{
TR::Node *child = node->getChild(i);
usr.anchorIfSafe(child, treeTop);
child->recursivelyDecReferenceCount();
}
node->setNumChildren(1);
//
// Note that the node at this point could be half-baked: an indirect
// store or write barrier with one child. This is an intermediate
// state, and further surgery is required for correctness.
// Eliminate the store
//
if (treeTop->getNode()->getOpCode().isSpineCheck() && treeTop->getNode()->getFirstChild() == node)
{
// SpineCHKs are special. We don't want to require all the
// opts and codegens to do the right thing with a PassThrough
// child. Hence, we'll turn the tree into a const, which is
// a state the opts and codegens must cope with anyway,
// because if this tree had been a load instead of a store,
// the optimizer could have legitimately turned it into a const.
//
TR::Node *child = node->getChild(0);
usr.anchorIfSafe(child, treeTop);
child->recursivelyDecReferenceCount();
TR::Node::recreate(node, comp()->il.opCodeForConst(node->getSymbolReference()->getSymbol()->getDataType()));
node->setFlags(0);
node->setNumChildren(0);
}
else
{
// Vandalize the first child if it's unsafe to evaluate
//
TR::Node *child = node->getFirstChild();
usr.anchorSafeChildrenOfUnsafeNodes(child, treeTop);
if (usr.isUnsafe(child))
{
// Must eradicate the dead expression. Can't leave it
// anchored because it's not safe to evaluate.
//
child->recursivelyDecReferenceCount();
TR::Node *dummyChild = node->setAndIncChild(0, TR::Node::createConstDead(child, TR::Int32, 0xbad1 /* eyecatcher */));
if (trace())
traceMsg(comp(), " - replace unsafe child %s n%dn with dummy %s n%dn\n",
child->getOpCode().getName(), child->getGlobalIndex(),
dummyChild->getOpCode().getName(), dummyChild->getGlobalIndex());
}
// Set opcode to nop
//
if (node->getReferenceCount() >= 1)
TR::Node::recreate(node, TR::PassThrough);
else
TR::Node::recreate(node, TR::treetop);
}
node->setFlags(0);
eliminatedStore = true;
}
}
}
TR_BitVectorIterator bvi(*_trivialDefs);
while (bvi.hasMoreElements())
{
int32_t index = bvi.getNextElement();
int32_t useDefIndex = index + useDefInfo->getFirstDefIndex();
TR::Node *node = useDefInfo->getNode(useDefIndex);
if (node)
{
if (trace())
{
traceMsg(comp(), "removing trivial node %p %s n%dn udi=%d\n", node, node->getOpCode().getName(), node->getGlobalIndex(), useDefIndex);
traceMsg(comp(), "correcting UseDefInfo:\n");
}
TR_UseDefInfo::BitVector defsOfRhs(comp()->allocator());
TR_UseDefInfo::BitVector nodeUses(comp()->allocator());
if (useDefInfo->getUseDef(defsOfRhs, node->getFirstChild()->getUseDefIndex()) && useDefInfo->getUsesFromDef(nodeUses, useDefIndex))
{
TR_UseDefInfo::BitVector::Cursor cursor1(defsOfRhs);
for (cursor1.SetToFirstOne(); cursor1.Valid(); cursor1.SetToNextOne())
{
int32_t nextDef = cursor1;
TR_UseDefInfo::BitVector::Cursor cursor2(nodeUses);
for (cursor2.SetToFirstOne(); cursor2.Valid(); cursor2.SetToNextOne())
{
int32_t nextUse = (int32_t) cursor2 + useDefInfo->getFirstUseIndex();
useDefInfo->resetUseDef(nextUse, index);
useDefInfo->setUseDef(nextUse, nextDef);
if (trace())
traceMsg(comp(), " useDefIndex %d defines %d\n", nextDef, nextUse);
}
}
}
useDefInfo->clearNode(node->getUseDefIndex());
if (node->getReferenceCount() < 1)
{
node->setFlags(0);
TR::Node::recreate(node, TR::treetop);
}
else
TR::Node::recreate(node, TR::PassThrough);
node->setFlags(0);
eliminatedStore = true;
dumpOptDetails(comp(), "%p \n",node);
}
}
//if (debug("deadStructure"))
//{
//
// Simplifying assumption made to avoid complications
// arising out of commoning across extended basic blocks that
// are partly in the loop and aprtly out of the loop.
// In such cases, the uses may appear to be all concentrated inside
// the loop but may not be the case because of commoning.
//
bool blocksHaveBeenExtended = false;
TR::Block *block = comp()->getStartTree()->getNode()->getBlock();
for (; block; block = block->getNextBlock())
{
if (block->isExtensionOfPreviousBlock())
{
blocksHaveBeenExtended = true;
break;
}
}
if (!blocksHaveBeenExtended && comp()->mayHaveLoops())
performDeadStructureRemoval(optimizer()->getUseDefInfo());
//}
}
else if (!_mustUseUseDefInfo)
{
for (int32_t i = _storeNodes->size()-1; i >= 0; --i)
{
TR::Node *node = _storeNodes->element(i);
if (node && performTransformation(comp(), "%s Global Store Elimination eliminating : %p\n", optDetailString(), node))
{
if (useDefInfo)
useDefInfo->clearNode(node->getUseDefIndex());
if (node->getReferenceCount() < 1)
{
node->setFlags(0);
TR::Node::recreate(node, TR::treetop);
}
else
TR::Node::recreate(node, TR::PassThrough);
node->setFlags(0);
eliminatedStore = true;
}
}
}
if (eliminatedStore)
{
#ifdef J9_PROJECT_SPECIFIC
if (eliminatedBCDStore)
requestOpt(OMR::treeSimplification); // some of the more complex BCD simplifications work best when refCounts == 1
#endif
requestDeadTreesCleanup();
requestOpt(OMR::catchBlockRemoval);
}
if (_deferUseDefInfoInvalidation)
{
_deferUseDefInfoInvalidation = false;
// useDefInfo was invalidated (deferred) so invalidate it now and release its memory
optimizer()->setUseDefInfo(NULL);
useDefInfo = NULL;
}
if (trace())
traceMsg(comp(), "\nEnding Global Store Elimination\n");
return cost; // Actual cost
}
bool TR_IsolatedStoreElimination::canRemoveStoreNode(TR::Node *node)
{
if (_currentTree) comp()->setCurrentBlock(_currentTree->getEnclosingBlock());
// We need to check for the special case when the RHS is a method meta data
// type as we have observed that this could in fact be some VM dependent
// operation that we do not want to remove.
//
if (node->getSymbolReference()->getSymbol()->isVolatile())
return false;
if (node->dontEliminateStores())
return false;
TR_UseDefInfo *useDefInfo = optimizer()->getUseDefInfo();
return true;
}
void TR_IsolatedStoreElimination::removeRedundantSpills()
{
// Checking the following:
//
// iRegStore #123
// iload #123
// ...
//
// istore #123 <<< can be removed
// iRegLoad #123
//
TR_UseDefInfo *useDefInfo = optimizer()->getUseDefInfo();
for (TR::TreeTop *tt = comp()->getStartTree(); tt != 0; tt = tt->getNextTreeTop())
{
TR::Node *node = tt->getNode();
if (node->getOpCode().isStoreDirect() &&
node->getFirstChild()->getOpCode().isLoadReg() &&
node->getSymbolReference() == node->getFirstChild()->getRegLoadStoreSymbolReference())
{
uint16_t useIndex = node->getFirstChild()->getUseDefIndex();
if (!useIndex || !useDefInfo->isUseIndex(useIndex))
continue;
TR_UseDefInfo::BitVector defs(comp()->allocator());
if (useDefInfo->getUseDef(defs, useIndex))
{
bool redundantStore= true;
TR_UseDefInfo::BitVector::Cursor cursor(defs);
for (cursor.SetToFirstOne(); cursor.Valid(); cursor.SetToNextOne())
{
int32_t defIndex = cursor;
TR::Node *defNode;
if (defIndex >= useDefInfo->getFirstRealDefIndex() &&
(defNode = useDefInfo->getNode(defIndex)) &&
defNode->getOpCode().isStoreReg() &&
defNode->getFirstChild()->getOpCode().isLoadVarDirect() &&
defNode->getFirstChild()->getSymbolReference() == node->getSymbolReference())
{
// traceMsg(comp(), "Redundant store node=%p defNode=%p \n", node, defNode);
}
else
{
redundantStore = false;
}
}
if (redundantStore &&
performTransformation(comp(), "%s Removing redundant spill: (%p)\n", optDetailString(), node))
{
TR::Node::recreate(node, TR::treetop);
node->setFlags(0);
}
}
}
}
}
int32_t TR_IsolatedStoreElimination::performWithUseDefInfo()
{
removeRedundantSpills();
TR_UseDefInfo *info = optimizer()->getUseDefInfo();
int32_t i;
// Build up the set of all defs that are used by or'ing the usedef info for
// each use. The isolated stores are the ones that are left.
//
const int32_t bitVectorSize = info->getNumDefOnlyNodes();
_defParentOfUse = new(trStackMemory()) TR_Array<int32_t>(trMemory(), info->getNumUseNodes(), true, stackAlloc);
for (i = 0; i < info->getNumUseNodes();i++)
_defParentOfUse->add(-1);
//*******************************************************************************************
//FIXME: instead of having an array of int, use 4 bitvectors of states.
//One bitvetor will indicate if the node was visited or not.
//For those that were visited the corresponding bit in one of the bitvectors for ("ToBeRemoved" and "ShouldNotBeRemoved") should be set.
//The 4th bitvector is inTransit vector.
//So "NotToBeExamine should set the bits in "Visited" and also on "ShouldNotBeRemoved".
//After finding the group set the right bits in "ToBeRemoved" or "ShouldNotBeRemoved and update Visited vector. Also, emtpy InTransit vector
//*******************************************************************************************
_defStatus = new(trStackMemory()) TR_Array<defStatus>(trMemory(), info->getNumDefOnlyNodes(), true, stackAlloc);
_defStatus->setSize(info->getNumDefOnlyNodes());
_trivialDefs = new (trStackMemory()) TR_BitVector(info->getNumDefOnlyNodes(), trMemory(), stackAlloc);
_groupsOfStoreNodes = new(trStackMemory()) TR_Array<TR_BitVector *>(trMemory(), 4, true, stackAlloc);
info->buildDefUseInfo();
for (i = info->getNumDefOnlyNodes()-1; i >= 0; --i)
{
int32_t useDefIndex = i + info->getFirstDefIndex();
TR::Node *node = info->getNode(useDefIndex);
if (node && node->getOpCode().isStore())
{
TR::Symbol *sym = node->getSymbolReference()->getSymbol();
if (sym->isAuto() || sym->isParm() ||
sym->isAutoField() || sym->isParmField() ||
sym->isStatic() // the ones that reach exit will have it as a use
)
{
//into array of the size of uses walking the defs
collectDefParentInfo(useDefIndex,node,info);
TR::Node *firstChild = node->getFirstChild();
if (firstChild->getOpCode().isLoadVarDirect() &&
firstChild->getReferenceCount() == 1 &&
(firstChild->getSymbolReference() == node->getSymbolReference()))
{
_trivialDefs->set(i);
if (trace())
traceMsg(comp(), "Found trivial node %p %s n%dn udi=%d\n", node, node->getOpCode().getName(), node->getGlobalIndex(), i);
}
}
else
_defStatus->element(i) = doNotExamine;
}
else
_defStatus->element(i) = doNotExamine;
}
TR_BitVector currentGroupOfStores(bitVectorSize, trMemory(), stackAlloc);
for (i = info->getNumDefOnlyNodes()-1; i >= 0; --i)
{
if (_defStatus->element(i) == notVisited)
{
currentGroupOfStores.empty();
bool foundGroupOfStores = false;
foundGroupOfStores = groupIsolatedStores(i,¤tGroupOfStores, optimizer()->getUseDefInfo());
TR_BitVectorIterator bvi(currentGroupOfStores);
while (bvi.hasMoreElements())
{
int32_t index = bvi.getNextElement();
//update status
if (foundGroupOfStores)
_defStatus->element(index) = toBeRemoved;
else
_defStatus->element(index) = notToBeRemoved;
}
if (foundGroupOfStores)
{
TR_BitVector *newGroupOfStoresToRemove = new (trStackMemory()) TR_BitVector(bitVectorSize, trMemory(), stackAlloc);
newGroupOfStoresToRemove->setAll(bitVectorSize);
*newGroupOfStoresToRemove &= currentGroupOfStores;
_groupsOfStoreNodes->add(newGroupOfStoresToRemove);
}
}
}
return 0; // actual cost
}
void TR_IsolatedStoreElimination::collectDefParentInfo(int32_t defIndex,TR::Node *node, TR_UseDefInfo *info)
{
if (node->getReferenceCount() > 1)
return;
int32_t childNum;
for (childNum=0;childNum<node->getNumChildren();childNum++)
{
TR::Node *child = node->getChild(childNum);
if ((child->getReferenceCount() == 1) &&
child->getOpCode().isLoadVar())
{
int32_t index = child->getUseDefIndex();
if (index > 0) //parm or auto
{
int32_t useIndex = index - info->getFirstUseIndex();
_defParentOfUse->element(useIndex) = defIndex;
if (trace())
traceMsg(comp(), "DefParent - use %d has parent %d\n",useIndex,defIndex);
}
}
collectDefParentInfo(defIndex,child,info);
}
return;
}
// recusive check for node's children
static void examChildrenForValueNode(TR::TreeTop *tt, TR::Node *parent, TR::Node *valueNode, vcount_t visitCount)
{
if (parent->getVisitCount() == visitCount)
return;
parent->setVisitCount(visitCount);
for (int32_t childCount = 0; childCount < parent->getNumChildren(); childCount++)
{
TR::Node *child = parent->getChild(childCount);
if (child == valueNode)
child->decFutureUseCount();
examChildrenForValueNode(tt, child, valueNode, visitCount);
}
}
bool TR_IsolatedStoreElimination::groupIsolatedStores(int32_t defIndex,TR_BitVector *currentGroupOfStores, TR_UseDefInfo *info)
{
// TR_ASSERT(defIndex < info->getNumDefOnlyNodes(),"DSE: not a real def");
defStatus status = _defStatus->element(defIndex);
if ( status == inTransit || status == toBeRemoved)
{
if (trace())
traceMsg(comp(), "groupIsolated - DEF %d is inTransit or toBeRemoved - \n",defIndex);
return true;
}
else if ( status == notToBeRemoved)
{
if (trace())
traceMsg(comp(), "groupIsolated - DEF %d is notToBeRemoved - \n",defIndex);
return false;
}
else if (status == notVisited)
{
_defStatus->element(defIndex) = inTransit;
currentGroupOfStores->set(defIndex);
if (trace())
traceMsg(comp(), "groupIsolated - DEF %d is now investigated - \n", defIndex);
}
TR::Node *node = info->getNode(defIndex + info->getFirstDefIndex());
TR_ASSERT(node, "assertion failure");
TR::TreeTop *tt = info->getTreeTop(defIndex + info->getFirstDefIndex());
if (tt)
{
comp()->setCurrentBlock(tt->getEnclosingBlock());
#ifdef J9_PROJECT_SPECIFIC
// checking for killing of InMemoryLoadStore
if (node->getValueChild()->getOpCode().isBCDLoadVar() &&
node->getValueChild()->getOpCode().hasSymbolReference() &&
comp()->cg()->IsInMemoryType(node->getValueChild()->getType()) &&
node->getValueChild()->getReferenceCount() > 1)
{
TR::Node *valueChild = node->getValueChild();
valueChild->setFutureUseCount(valueChild->getReferenceCount() - 1);
vcount_t visitCount = comp()->incVisitCount();
for (TR::TreeTop *ttTemp = tt->getNextTreeTop(); ttTemp && (valueChild->getFutureUseCount() > 0); ttTemp = ttTemp->getNextTreeTop())
{
TR::Node *defNode = ttTemp->getNode()->getOpCodeValue() == TR::treetop ? ttTemp->getNode()->getFirstChild() : ttTemp->getNode();
bool defNodeHasSymRef = defNode->getOpCode().hasSymbolReference() && defNode->getSymbolReference();
if (defNodeHasSymRef && defNode->getSymbolReference()->canKill(valueChild->getSymbolReference()))
{
if (trace())
traceMsg(comp(), "%s groupIsolated - DEF %d cannot be removed due to InMemoryLoadStoreMarking \n", optDetailString(), defIndex);
return false;
}
examChildrenForValueNode(ttTemp, defNode, valueChild, visitCount);
}
}
#endif
}
if (!canRemoveStoreNode(node))
{
if (trace())
traceMsg(comp(), "groupIsolated - DEF %d cannot be removed \n",defIndex);
return false;
}
//Test that all uses of the def are under other store nodes (i.e. set in the defParent array).
//If even one of the uses is not under store node, then it imposible to remove this def, and thus return.
TR_UseDefInfo::BitVector usesOfThisDef(comp()->allocator());
if (!info->getUsesFromDef(usesOfThisDef, defIndex+info->getFirstDefIndex()))
{
if (trace())
traceMsg(comp(), "groupIsolated - DEF %d has no uses - can be removed \n", defIndex);
return true;
}
else
{
if (trace())
{
(*comp()) << usesOfThisDef << "\n";
}
}
TR_UseDefInfo::BitVector::Cursor cursor(usesOfThisDef);
for (cursor.SetToFirstOne(); cursor.Valid(); cursor.SetToNextOne())
{
int32_t useIndex = cursor;
//if store has no uses, can be removed.
if (_defParentOfUse->element(useIndex)== -1)
{
if (trace())
traceMsg(comp(), "groupIsolated - Use %d has no def parent - \n",useIndex);
return false;
}
}
//recurse: for each use of the def, get its parent store and recurse.
for (cursor.SetToFirstOne(); cursor.Valid(); cursor.SetToNextOne())
{
int32_t useIndex = cursor;
int32_t defParentIndex = _defParentOfUse->element(useIndex);
if (trace())
traceMsg(comp(), "groupIsolated - recursing for Def %d (parent of %d) - \n",defParentIndex,useIndex);
if (!groupIsolatedStores(defParentIndex,currentGroupOfStores,info))
return false;
}
return true;
}
//------------------------------------------------------------------------
//------------------------------------------------------------------------
int32_t TR_IsolatedStoreElimination::performWithoutUseDefInfo()
{
dumpOptDetails(comp(), "Perform without use def info\n");
// Assign an index to each local and parameter symbol.
//
TR::SymbolReferenceTable *symRefTab = comp()->getSymRefTab();
int32_t symRefCount = comp()->getSymRefCount();
int32_t i;
int32_t numSymbols = 1;
for (i = symRefTab->getIndexOfFirstSymRef(); i < symRefCount; i++)
{
TR::SymbolReference *symRef = symRefTab->getSymRef(i);
if (symRef)
{
TR::Symbol *sym = symRef->getSymbol();
if (sym)
{
if (sym->isParm() || sym->isAuto())
sym->setLocalIndex(numSymbols++);
else
sym->setLocalIndex(0);
}
}
}
_usedSymbols = new(trStackMemory()) TR_BitVector(numSymbols, trMemory(), stackAlloc);
// Go through the trees and
// 1) Mark each symbol referenced by a load as used
// 2) Remember all the stores to each symbol
//
vcount_t visitCount = comp()->incVisitCount();
bool seenMultiplyReferencedParent;
for (TR::TreeTop *treeTop = comp()->getStartTree(); treeTop; treeTop = treeTop->getNextTreeTop())
{
_currentTree = treeTop;
seenMultiplyReferencedParent = false;
examineNode(treeTop->getNode(), visitCount, seenMultiplyReferencedParent);
}
// Remove those stores that were not used when they were encountered in the
// tree walk but are now used.
//
for (i = _storeNodes->size()-1; i >= 0; --i)
{
TR::Node *node = _storeNodes->element(i);
if (node && _usedSymbols->get(node->getSymbolReference()->getSymbol()->getLocalIndex()))
_storeNodes->element(i) = NULL;
}
return 1; // actual cost
}
void TR_IsolatedStoreElimination::examineNode(TR::Node *node, vcount_t visitCount, bool seenMultiplyReferencedParent)
{
if (node->getVisitCount() == visitCount)
return;
node->setVisitCount(visitCount);
if (node->getReferenceCount() > 1)
seenMultiplyReferencedParent = true;
// Process the children
//
for (int32_t i = node->getNumChildren()-1; i >= 0; --i)
{
examineNode(node->getChild(i), visitCount, seenMultiplyReferencedParent);
}
// Now process this node. We are looking for stores or uses of a symbol to
// which we've assigned a non-zero local index (i.e. a local or a parm)
//
if (!node->getOpCode().hasSymbolReference())
return;
TR::SymbolReference *symRef = node->getSymbolReference();
if (symRef == NULL)
return;
TR::Symbol *sym = symRef->getSymbol();
if (!sym || !sym->getLocalIndex())
return;
// This is a reference to a symbol we're interested in.
//
if (node->getOpCode().isStore())
{
if (!_usedSymbols->get(sym->getLocalIndex()))
{
// Store to a local or parm that is (as yet) unused
//
if (canRemoveStoreNode(node))
_storeNodes->add(node);
}
}
else
{
if (seenMultiplyReferencedParent ||
(!(_currentTree->getNode()->getOpCode().isStore() &&
(_currentTree->getNode()->getSymbolReference()->getSymbol() == sym))))
{
// Use of a local or parm
//
_usedSymbols->set(sym->getLocalIndex());
}
//else
// printf("Ignoring load in same tree as store in %s\n", signature(comp()->getCurrentMethod()));
}
}
#define MAX_TOTAL_NODES 50000
#define MAX_CFG_SIZE 5000
void TR_IsolatedStoreElimination::performDeadStructureRemoval(TR_UseDefInfo *info)
{
TR::CFG * cfg = comp()->getFlowGraph();
if (info->getTotalNodes() > MAX_TOTAL_NODES || cfg->getNumberOfNodes() > MAX_CFG_SIZE)
return;
TR::StackMemoryRegion stackMemoryRegion(*trMemory());
vcount_t visitCount = comp()->incVisitCount();
TR_Structure *rootStructure = comp()->getFlowGraph()->getStructure();
bool propagateRemovalToParent = false;
TR_BitVector *nodesInStructure = new (trStackMemory()) TR_BitVector(0, trMemory(), stackAlloc, growable);
TR_BitVector *defsInStructure = new (trStackMemory()) TR_BitVector(0, trMemory(), stackAlloc, growable);
findStructuresAndNodesUsedIn(info, rootStructure, visitCount, nodesInStructure, defsInStructure, &propagateRemovalToParent);
}
bool
TR_IsolatedStoreElimination::findStructuresAndNodesUsedIn(TR_UseDefInfo *info, TR_Structure *structure, vcount_t visitCount, TR_BitVector *nodesInStructure, TR_BitVector *defsInStructure, bool *propagateRemovalToParent)
{
bool canRemoveStructure = true;
int32_t onlyExitEdge = -1;
if (trace())
{
if (structure->asRegion())
traceMsg(comp(), "Inspecting region structure %d\n", structure->getNumber());
else
traceMsg(comp(), "Inspecting block structure %d\n",structure->getNumber());
}
if (structure->asRegion())
{
TR_RegionStructure *regionStructure = structure->asRegion();
if (regionStructure->isNaturalLoop() &&
regionStructure->numSubNodes() == 1 &&
(regionStructure->getParent() &&
regionStructure->getParent()->asRegion()->isCanonicalizedLoop()))