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VirtualGuardCoalescer.cpp
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VirtualGuardCoalescer.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/VirtualGuardCoalescer.hpp"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "env/StackMemoryRegion.hpp"
#include "env/FrontEnd.hpp"
#include "compile/Compilation.hpp"
#include "compile/VirtualGuard.hpp"
#include "cs2/sparsrbit.h"
#include "env/jittypes.h"
#include "il/AliasSetInterface.hpp"
#include "il/Block.hpp"
#include "il/DataTypes.hpp"
#include "il/ILOps.hpp"
#include "il/ILOpCodes.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 "infra/Assert.hpp"
#include "infra/Cfg.hpp"
#include "infra/CfgEdge.hpp"
#include "infra/CfgNode.hpp"
#include "optimizer/Optimization_inlines.hpp"
#include "optimizer/Optimizations.hpp"
#include "optimizer/Optimizer.hpp"
#include "optimizer/Structure.hpp"
#include "optimizer/TransformUtil.hpp"
#include "optimizer/ValueNumberInfo.hpp"
#include "optimizer/LocalOpts.hpp"
#ifdef J9_PROJECT_SPECIFIC
#include "runtime/J9Profiler.hpp"
#include "runtime/J9ValueProfiler.hpp"
#endif
#define OPT_DETAILS "O^O VIRTUAL GUARD COALESCER: "
// A simple extension to TR_List, meant to make a List seem
// like a stack. The only thing missing in List was a
// good top() method.
//
template <class T> class ListStack : public List<T>
{
public:
ListStack(TR_Memory * m) : List<T>(m) { }
void push(T *t) { List<T>::add(t); }
T *pop() { return List<T>::popHead(); }
T *top() { return List<T>::_pHead ? List<T>::_pHead->getData() : NULL;}
};
TR_VirtualGuardTailSplitter::TR_VirtualGuardTailSplitter(TR::OptimizationManager *manager)
: TR::Optimization(manager)
{
_cfg = comp()->getFlowGraph();
}
int32_t TR_VirtualGuardTailSplitter::perform()
{
TR::StackMemoryRegion stackMemoryRegion(*trMemory());
_splitDone = false;
// Initialize any necessary data structures
//
initializeDataStructures();
int32_t numBlocks = _cfg->getNextNodeNumber();
int32_t nodeCount = comp()->getNodeCount();
_visitCount = comp()->incVisitCount();
// Attempt to split tails occurring in a linear control flow
//
splitLinear(toBlock(_cfg->getStart()), toBlock(_cfg->getEnd()));
if (trace())
{
comp()->dumpMethodTrees("Trees after splitLinear");
}
return 0;
}
void TR_VirtualGuardTailSplitter::initializeDataStructures()
{
vcount_t visitCount = comp()->incVisitCount();
List <VGInfo> allGuards(trMemory());
List <TR::Block> dfsList(trMemory());
ListStack<VGInfo> vgStack(trMemory());
uint32_t numGuards = 0;
// This CFG walk is very similar to a depth first search. We proceed
// in a DFS manner unless we encounter a virtual guard.
//
// Once we are inside a virtual guard, we make sure that we have visited
// all the nodes between the branch point and merge point of the guard
// before we visit the merge point.
//
// A major assumption is that the branch point dominates a the contents of the
// virtual guard, and the merge point post-dominates the contents. This is
// not true when there are exception edges in the contents. To solve this problem
// we refuse to recognize a guarded call with exception successors as a valid
// virtual guarded call.
//
dfsList.add(toBlock(_cfg->getStart()));
while (!dfsList.isEmpty())
{
TR::Block *block = dfsList.popHead();
VGInfo *top = vgStack.top();
if (top && block == top->getMergeBlock())
{
// make sure all predecessors of the merge point have
// been visited
//
bool notDone = false;
TR_PredecessorIterator it(block);
for (TR::CFGEdge *edge = it.getFirst();
edge && !notDone;
edge = it.getNext())
{
if (edge->getFrom()->getVisitCount() != visitCount)
notDone = true;
}
if (notDone)
continue;
vgStack.pop();
// repush itself (to get to the else part below)
dfsList.add(block);
continue;
}
else // (this is the else the above comment is talking abt. )
{
if (block->getVisitCount() == visitCount)
continue;
block->setVisitCount(visitCount);
VGInfo *info = recognizeVirtualGuard(block, top);
if (info)
{
allGuards.add(info);
vgStack.push (info);
++numGuards;
}
}
TR_SuccessorIterator it(block);
for (TR::CFGEdge *edge = it.getFirst(); edge; edge = it.getNext())
{
TR::Block *to = toBlock(edge->getTo());
if (!to->isOSRInduceBlock() && !to->isOSRCatchBlock() && !to->isOSRCodeBlock())
dfsList.add(toBlock(edge->getTo()));
}
}
if (trace())
traceMsg(comp(), "Disjoint set forest:\n");
// Put the information into the virtual guard table
//
_numGuards = numGuards;
_table = (VGInfo **) trMemory()->allocateStackMemory(numGuards * sizeof(VGInfo *));
ListIterator<VGInfo> it(&allGuards);
uint32_t i = 0;
for (VGInfo *info = it.getFirst(); info; info = it.getNext())
{
putGuard(i++, info);
if (trace())
traceMsg(comp(), "%d -> %d\n", info->getNumber(), info->getParent()->getNumber());
}
}
// Given any block, return if is a virtual guard
//
TR_VirtualGuardTailSplitter::VGInfo *TR_VirtualGuardTailSplitter::getVirtualGuardInfo(TR::Block *block)
{
if (!block->getExit()) return 0;
else if (block->getLastRealTreeTop()->getNode()->isTheVirtualGuardForAGuardedInlinedCall())
return getGuard(block);
return 0;
}
void TR_VirtualGuardTailSplitter::splitLinear(TR::Block *start, TR::Block *end)
{
List<TR::Block> stack(trMemory());
List<VGInfo> deferred(trMemory());
stack.add(start);
while (!stack.isEmpty())
{
TR::Block *block = stack.popHead();
if (block->getVisitCount() == _visitCount)
continue;
block->setVisitCount(_visitCount);
VGInfo *info = getVirtualGuardInfo(block);
if (info)
{
if (!info->isLeaf())
deferred.add(info);
block = lookAheadAndSplit(info, &stack);
// If the return block is a guard, repush it and continue
info = getVirtualGuardInfo(block);
if (info)
{
stack.add(block);
continue;
}
if (block->getVisitCount() == _visitCount)
continue;
block->setVisitCount(_visitCount);
}
if (block != toBlock(_cfg->getEnd()))
{
TR_SuccessorIterator it(block);
for (TR::CFGEdge *edge = it.getFirst(); edge; edge = it.getNext())
{
stack.add(toBlock(edge->getTo()));
}
}
}
ListIterator<VGInfo> it(&deferred);
for (VGInfo *info = it.getCurrent(); info; info = it.getNext())
splitLinear(info->getFirstInlinedBlock(), info->getMergeBlock());
}
// This analysis recognizes and merges virtual guards that exisit
// on a linear control flow path. For example:
//
// | The restriction is that 'start' and 'end' of the
// / \ merge must form a proper interval (start dominates everything,
// \ / end post-dominates everything). This is enforced by ensuring
// | that all the nodes between the virtual guards have only one
// / \ successor and only one predecessor (except merge nodes, which
// \ / necessarily have two predecessors)
// |
//
// This method walks the cfg in concert with coalesceLinear. Returns the
// node with which coalesceLinear should proceed its walk. coalesceLinear
// walks the cfg until it hits a virtual guards, at which point, it asks
// lookAheadAndMerge to attempt to discover and merge virtual guards
// from this guard onwards. lookAheadAndMerge analyzes the control flow
// after the guard. The blocks that it encounters should be skipped by the
// callee. It returns the last block that it encounteres, and the calle
// proceeds the dfs walk from there onwards. (apologies for the non-intuitive
// control flow)
//
TR::Block *TR_VirtualGuardTailSplitter::lookAheadAndSplit(VGInfo *guard, List<TR::Block> *stack)
{
VGInfo *lastInfo = 0;
List<VGInfo> deferred(trMemory());
TR::Block *cursor = guard->getMergeBlock();
bool isMergeBlock = true;
while (cursor->getExit() != NULL)
{
//if (!cursor->getExceptionSuccessors().empty())
// break;
if (isMergeBlock)
{
if (!(cursor->getPredecessors().size() == 2))
break;
}
else
if (!(cursor->getPredecessors().size() == 1))
break;
VGInfo *info = getVirtualGuardInfo(cursor);
if (info && !info->stillExists())
break;
if (info)
{
// We should have a look at the inlined portion of the code to
// see if there was any opportunity to optimize there. But don't
// do that now, add to the deferred list.
//
if (!info->isLeaf())
deferred.add(info);
lastInfo = info;
isMergeBlock = true;
cursor = info->getMergeBlock();
continue;
}
TR::CFGEdgeList &succs = cursor->getSuccessors();
if (!(succs.size() == 1))
{
TR::Block *newCursor = NULL;
TR::TreeTop *lastTree = cursor->getLastRealTreeTop();
if ((succs.size() == 2) &&
!lastTree->getNode()->getOpCode().isSwitch())
{
TR::CFGEdge *succ1 = succs.front();
TR::CFGEdge *succ2 = *(++succs.begin());
TR::Block *succBlock1 = toBlock(succ1->getTo());
if (succBlock1 == cursor->getNextBlock())
{
//TR::Block *nextBlock = toBlock(succBlock1->getSuccessors().front()->getTo());
TR::Block *nextBlock = succBlock1;
VGInfo *info = getVirtualGuardInfo(nextBlock);
if (info && info->stillExists())
{
newCursor = nextBlock;
stack->add(toBlock(succ2->getTo()));
}
}
if (!newCursor)
{
TR::Block *succBlock2 = toBlock(succ2->getTo());
if (succBlock2 == cursor->getNextBlock())
{
//TR::Block *nextBlock = toBlock(succBlock2->getSuccessors().front()->getTo());
TR::Block *nextBlock = succBlock2;
VGInfo *info = getVirtualGuardInfo(nextBlock);
if (info && info->stillExists())
{
newCursor = nextBlock;
stack->add(succBlock1);
}
}
}
}
if (newCursor)
cursor = newCursor;
else
break;
}
else
cursor = toBlock(succs.front()->getTo());
isMergeBlock = false;
} // while(cursor->getExit() != NULL)
if (lastInfo)
transformLinear(guard->getBranchBlock(), lastInfo->getMergeBlock());
ListIterator<VGInfo> it(&deferred);
for (VGInfo *info = it.getCurrent(); info; info = it.getNext())
{
splitLinear(info->getFirstInlinedBlock(), info->getMergeBlock());
}
return cursor;
}
// Given a proper interval marked by first and last, split
// all guards that fall between first and last, cloning any
// common blocks in between
// ________
// _/\__/\__/\_ transforms into _/ \ \ \_
// \/ \/ \/ \__\__\__/
//
void TR_VirtualGuardTailSplitter::transformLinear(TR::Block *first, TR::Block *last)
{
VGInfo *firstInfo = getVirtualGuardInfo(first);
TR_ASSERT(firstInfo, "first should be a virtual guard");
TR::Block *call = firstInfo->getCallBlock(); // used as a cursor (a misnomer)
TR::Block *next = firstInfo->getMergeBlock(); // used as a cursor
while (next != last)
{
TR_BlockCloner cloner(_cfg, true);
TR::Block *clone = cloner.cloneBlocks(next, next);
if (_cfg->getStructure())
{
next->getStructureOf()->getParent()->asRegion()->
addSubNode(new (_cfg->structureRegion()) TR_StructureSubGraphNode
(new (_cfg->structureRegion()) TR_BlockStructure(comp(), clone->getNumber(), clone)));
}
if (trace())
{
traceMsg(comp(), "$$$ Processing guards: first %d, last %d\n", firstInfo->getNumber(), last->getNumber());
traceMsg(comp(), "=> Call node %d, next node %d\n", call->getNumber(), next->getNumber());
traceMsg(comp(), "=> clone block is %d\n\n", clone->getNumber());
}
_splitDone = true;
_cfg->addEdge(call, clone);
for (auto e = next->getExceptionSuccessors().begin(); e != next->getExceptionSuccessors().end(); ++e)
_cfg->addExceptionEdge(clone, (*e)->getTo());
TR::Block *callNext = call->getNextBlock();
call->getExit()->join(clone->getEntry());
if (callNext)
clone->getExit()->join(callNext->getEntry());
else
clone->getExit()->setNextTreeTop(NULL);
//if (call->getLastRealTreeTop()->getNode()->getOpCode().isBranch())
if (call->getLastRealTreeTop()->getNode()->getOpCodeValue() == TR::Goto)
TR::TransformUtil::removeTree(comp(), call->getLastRealTreeTop());
VGInfo *info = getVirtualGuardInfo(next);
if (info)
{
TR::Block *dest = info->getCallBlock();
_cfg->addEdge(clone, dest);
_cfg->removeEdge(call, next);
TR::TransformUtil::removeTree(comp(), clone->getLastRealTreeTop());
TR::Node *gotoNode = TR::Node::create(next->getLastRealTreeTop()->getNode(), TR::Goto);
TR::TreeTop *gotoTree = TR::TreeTop::create(comp(), gotoNode);
TR::TreeTop *lastTree = clone->getLastRealTreeTop();
gotoTree->join(lastTree->getNextTreeTop());
lastTree->join(gotoTree);
gotoNode->setBranchDestination(dest->getEntry());
info->markRemoved();
next = info->getMergeBlock();
call = dest;
}
else
{
TR::Block *dest = NULL;
TR::Block *otherDest = NULL;
TR::CFGEdgeList &succs = next->getSuccessors();
if (succs.size() == 1)
{
dest = toBlock(succs.front()->getTo());
}
else if (succs.size() == 2)
{
TR::CFGEdge *succ1 = succs.front();
TR::CFGEdge *succ2 = *(++succs.begin());
TR::Block *succBlock1 = toBlock(succ1->getTo());
TR::Block *succBlock2 = toBlock(succ2->getTo());
if (succBlock1 == next->getNextBlock())
{
TR::Block *nextBlock = succBlock1;
VGInfo *info = getVirtualGuardInfo(nextBlock);
if (info && info->stillExists())
{
dest = succBlock1;
otherDest = succBlock2;
}
}
if (!dest)
{
if (succBlock2 == next->getNextBlock())
{
TR::Block *nextBlock = succBlock2;
VGInfo *info = getVirtualGuardInfo(nextBlock);
if (info && info->stillExists())
{
dest = succBlock2;
otherDest = succBlock1;
}
}
}
}
TR_ASSERT(dest, "Should find a destination block in the sequence\n");
_cfg->addEdge(clone, dest);
if (otherDest)
_cfg->addEdge(clone, otherDest);
_cfg->removeEdge(call, next);
TR::TreeTop *lastTree = clone->getLastRealTreeTop();
if (lastTree->getNode()->getOpCode().isBranch())
{
if (lastTree->getNode()->getOpCodeValue() == TR::Goto)
lastTree->getNode()->setBranchDestination(dest->getEntry());
else
{
if (!otherDest)
{
// A special case: "if (blah) goto 3; else goto 3;"
// replace the if by a goto
//
TR::TransformUtil::removeTree(comp(), lastTree);
TR::Node *gotoNode = TR::Node::create(lastTree->getNode(), TR::Goto);
gotoNode->setBranchDestination(dest->getEntry());
clone->append(TR::TreeTop::create(comp(), gotoNode));
}
}
}
else if (lastTree->getNode()->getOpCode().isSwitch())
{
// A special case, all cases go the same place
// replace the switch by a goto
//
TR::TransformUtil::removeTree(comp(), lastTree);
TR::Node *gotoNode = TR::Node::create( lastTree->getNode(), TR::Goto);
gotoNode->setBranchDestination(dest->getEntry());
clone->append(TR::TreeTop::create(comp(), gotoNode));
}
else
{
TR::Node *gotoNode = TR::Node::create(next->getLastRealTreeTop()->getNode(), TR::Goto);
TR::TreeTop *gotoTree = TR::TreeTop::create(comp(), gotoNode);
gotoTree->join(lastTree->getNextTreeTop());
lastTree->join(gotoTree);
gotoNode->setBranchDestination(dest->getEntry());
}
call = clone;
next = dest;
}
}
}
TR_VirtualGuardTailSplitter::VGInfo *TR_VirtualGuardTailSplitter::recognizeVirtualGuard
(TR::Block *block, VGInfo *parent)
{
if (!block->getExit())
return 0;
TR::Node *guardNode = block->getLastRealTreeTop()->getNode();
if (!block->getLastRealTreeTop()->getNode()->isTheVirtualGuardForAGuardedInlinedCall())
return 0;
TR::CFGEdgeList &succ = block->getSuccessors();
if (!(succ.size() == 2))
{
block->getLastRealTreeTop()->getNode()->setLocalIndex(MALFORMED_GUARD);
return 0;
}
TR::Block *first, *second, *call=0, *inlined=0;
first = toBlock(succ.front()->getTo());
second = toBlock((*(++succ.begin()))->getTo());
TR::Node *node = getFirstCallNode(first); //->getFirstRealTreeTop()->getNode()->getFirstChild();
//TR::Node *node = first->getFirstRealTreeTop()->getNode()->getFirstChild();
if (node && node->isTheVirtualCallNodeForAGuardedInlinedCall())
{
call = first;
inlined = second;
}
else
{
node = getFirstCallNode(second); //->getFirstRealTreeTop()->getNode()->getFirstChild();
//node = second->getFirstRealTreeTop()->getNode()->getFirstChild();
if (node && node->isTheVirtualCallNodeForAGuardedInlinedCall())
{
call = second;
inlined = first;
}
}
#ifdef J9_PROJECT_SPECIFIC
if (call && guardNode->isProfiledGuard())
{
TR_AddressInfo *valueInfo = static_cast<TR_AddressInfo*>(TR_ValueProfileInfoManager::getProfiledValueInfo(node, comp(), AddressInfo));
float profiledGuardProbabilityThreshold = 0.98f;
static char *profiledGuardSplitProbabilityThresholdStr = feGetEnv("TR_ProfiledGuardSplitProbabilityThreshold");
if (profiledGuardSplitProbabilityThresholdStr)
{
profiledGuardProbabilityThreshold = ((float)atof(profiledGuardSplitProbabilityThresholdStr));
}
bool allowSplit = false;
if (valueInfo)
{
if (valueInfo->getTopProbability() >= profiledGuardProbabilityThreshold)
allowSplit = true;
}
if (!allowSplit)
{
guardNode->setLocalIndex(MALFORMED_GUARD);
return 0;
}
}
#endif
// the call-block must not have any exception edges. exception edges break the
// assumption that a virtual guard interval is a proper interval.
//
/////if (!call /* || !call->getExceptionSuccessors().empty() */)
if (!call || !(call->getSuccessors().size() == 1))
{
block->getLastRealTreeTop()->getNode()->setLocalIndex(MALFORMED_GUARD);
return 0;
}
TR_ASSERT((call->getSuccessors().size() == 1), "malformed virtual guard");
TR::Block * merge = toBlock(call->getSuccessors().front()->getTo());
//check if the merge block has back edges, if so exclude such guards from this opt to
//prevent dead zone in initializeDataStructures()
bool invalidMergeBlock = ( merge == _cfg->getEnd() || merge->getPredecessors().size() > 2);
if (invalidMergeBlock)
{
block->getLastRealTreeTop()->getNode()->setLocalIndex(MALFORMED_GUARD);
return 0;
}
return new (trStackMemory()) VGInfo(block, call, inlined, merge, parent);
}
bool TR_VirtualGuardTailSplitter::isKill(TR::Block *block)
{
if (!block->getEntry()) return false;
TR::TreeTop *tree = block->getFirstRealTreeTop();
TR::TreeTop *exit = block->getExit();
for (; tree != exit; tree = tree->getNextRealTreeTop())
{
if (isKill(tree->getNode()))
return true;
}
return false;
}
bool TR_VirtualGuardTailSplitter::isKill(TR::Node *node)
{
TR::ILOpCode &opcode = node->getOpCode();
if (opcode.isCall())
return true;
if (opcode.hasSymbolReference() &&
node->getSymbolReference()->isUnresolved())
return true;
for (int c = node->getNumChildren() - 1; c >= 0; --c)
{
if (isKill(node->getChild(c)))
return true;
}
return false;
}
void TR_VirtualGuardTailSplitter::putGuard(uint32_t index, VGInfo *info)
{
TR_ASSERT(index < _numGuards, "overflow");
TR::Block *branch = info->getBranchBlock();
TR::Node *node = branch->getLastRealTreeTop()->getNode();
node->setLocalIndex(index);
_table[index] = info;
}
void TR_VirtualGuardTailSplitter::VGInfo::markRemoved()
{
_parent->removeChild(this);
_branch = 0;
_valid = 0;
}
void TR_VirtualGuardTailSplitter::remergeGuard(TR_BlockCloner &cloner, VGInfo *info)
{
TR::Block *block = info->getBranchBlock();
dumpOptDetails(comp(), "%sperforming global split on guard block_%d\n", OPT_DETAILS, block->getNumber());
// ----- -----
// | G | | G'|
// ----- -----
// / \ / \
// / \ / \
// ----- ----- ----- -----
// | A | | B | | A'| | B'|
// ----- ----- ----- -----
// Is transformed to:
//
// ----- -----
// | G | | G'|
// ----- -----
// / \__________________\
// / \
// ----- ----- ----- -----
// | A | | B | | A'| | B'|
// ----- ----- ----- -----
// Block B and A' will be killed as a result,
// ----- -----
// | G | | G'|
// ----- -----
// |\__________________ |
// | \|
// ----- -----
// | A | | B'|
// ----- -----
TR::Block *blockA = info->getFirstInlinedBlock();
TR::Block *cloneA = cloner.getToBlock(blockA);
TR::Block *blockB = info->getCallBlock();
TR::Block *cloneB = cloner.getToBlock(blockB);
TR::Block *cloneG = cloner.getToBlock(block);
_cfg->addEdge(block, cloneB);
_cfg->removeEdge(block, blockB);
_cfg->removeEdge(cloneG, cloneA);
// convert the last treetop in G' into a goto
//
TR::TreeTop *ifTree = cloneG->getLastRealTreeTop();
ifTree->getNode()->removeAllChildren();
TR::Node::recreate(ifTree->getNode(), TR::Goto);
// Fix the if tree in G
//
block->getLastRealTreeTop()->getNode()->setBranchDestination(cloneB->getEntry());
#if 0
char fileName[20];
sprintf(fileName, "split%d.vcg", block->getNumber());
FILE *file = fopen(fileName, "w");
comp->getDebug()->printVCG(file, _cfg, fileName);
fclose(file);
#endif
if (trace())
traceMsg(comp(), "Split Guard Block %d->(%d,%d), %d->(%d,%d)\n",
block ->getNumber(), blockA->getNumber(), blockB->getNumber(),
cloneG->getNumber(), cloneA->getNumber(), cloneB->getNumber());
}
TR::Node *TR_VirtualGuardTailSplitter::getFirstCallNode(TR::Block *block)
{
TR::TreeTop *treeTop = block->getFirstRealTreeTop();
TR::TreeTop *exitTree = block->getExit();
while (treeTop != exitTree)
{
TR::Node *node = treeTop->getNode();
if (node->getOpCode().isCall())
return node;
else if (node->getNumChildren() > 0)
{
if (node->getFirstChild()->getOpCode().isCall())
return node->getFirstChild();
}
treeTop = treeTop->getNextTreeTop();
}
return NULL;
}
const char *
TR_VirtualGuardTailSplitter::optDetailString() const throw()
{
return "O^O VIRTUAL GUARD COALESCER: ";
}
TR_InnerPreexistence::TR_InnerPreexistence(TR::OptimizationManager *manager)
: TR::Optimization(manager)
{}
int32_t
TR_InnerPreexistence::perform()
{
// disable opt if virtual guard-noping is not enabled
if (!comp()->performVirtualGuardNOPing())
return 0;
TR::StackMemoryRegion stackMemoryRegion(*trMemory());
if (trace())
comp()->dumpMethodTrees("Trees before InnerPreexistence");
int32_t candidates = initialize();
if (candidates > 0)
{
transform();
}
return 1;
}
int32_t
TR_InnerPreexistence::initialize()
{
_numInlinedSites = comp()->getNumInlinedCallSites();
// array of guard blocks index by the inlined call site index of the guarded method
TR::Block **guardBlocks = (TR::Block **) trMemory()->allocateStackMemory(_numInlinedSites * sizeof(TR::Block *));
memset(guardBlocks, 0, _numInlinedSites * sizeof(TR::Block *));
int32_t numGuards = 0;
TR::TreeTop *treeTop, *exitTree;
for (treeTop = comp()->getStartTree(); treeTop; treeTop = exitTree->getNextTreeTop())
{
TR::Block *block = treeTop->getNode()->getBlock();
exitTree = block->getExit();
TR::Node *lastNode = block->getLastRealTreeTop()->getNode();
if (lastNode->isTheVirtualGuardForAGuardedInlinedCall())
{
TR_VirtualGuard *info = comp()->findVirtualGuardInfo(lastNode);
// Both the inner guard and the outer guard must be nop-able for inner preexistence
// to work. Ie. both the guards must give rise to assumptions
//
if (info->isNopable())
{
int16_t methodIndex = lastNode->getInlinedSiteIndex();
guardBlocks[methodIndex] = block;
numGuards++;
}
}
}
if (numGuards == 0)
return 0;
_guardTable = (GuardInfo **) trMemory()->allocateStackMemory(_numInlinedSites * sizeof(GuardInfo *));
memset(_guardTable, 0, _numInlinedSites * sizeof(GuardInfo*));
_vnInfo = optimizer()->getValueNumberInfo();
int32_t numInnerGuards = 0;
for (int32_t i = 0; i < _numInlinedSites; ++i)
{
TR::Block *guard = guardBlocks[i];
if (!guard) continue;
int16_t cursor = i;
GuardInfo *outerGuard = 0;
do
{
TR_InlinedCallSite &ics = comp()->getInlinedCallSite(cursor);
int16_t caller = ics._byteCodeInfo.getCallerIndex();
if (caller == -1)
break;
outerGuard = _guardTable[caller];
cursor = caller;
}
while (cursor >= 0 && !outerGuard);
GuardInfo *info = new (trStackMemory()) GuardInfo(comp(), guard, outerGuard, _vnInfo, _numInlinedSites);
if (outerGuard)
numInnerGuards++;
_guardTable[i] = info;
}
return numInnerGuards;
}
TR_InnerPreexistence::GuardInfo::GuardInfo(TR::Compilation * comp, TR::Block *block, GuardInfo *parent, TR_ValueNumberInfo *vnInfo, uint32_t numInlinedSites)
: _block(block), _parent(parent), _hasBeenDevirtualized(false)
{
TR::Node *guardNode = block->getLastRealTreeTop()->getNode();
TR::Node * callNode = guardNode->getVirtualCallNodeForGuard();
TR_ASSERT_FATAL(callNode->getOpCode().isIndirect(), "Guarded calls must be indirect");
_argVNs = new (comp->trStackMemory()) TR_BitVector(20, comp->trMemory(), stackAlloc, growable);
_innerSubTree = new (comp->trStackMemory()) TR_BitVector(numInlinedSites, comp->trMemory(), stackAlloc, notGrowable);
int32_t firstArgIndex = callNode->getFirstArgumentIndex();
_thisVN = vnInfo->getValueNumber(callNode->getChild(firstArgIndex));
_argVNs->set(_thisVN);
for (int32_t i = callNode->getNumChildren() - 1; i > firstArgIndex; --i)
{
TR::Node *child = callNode->getChild(i);
if (child->getDataType() == TR::Address)
_argVNs->set(vnInfo->getValueNumber(child));
}
}
void
TR_InnerPreexistence::transform()
{
int32_t i;
for (i = _numInlinedSites - 1; i > 0; --i) // intentionally skipping i = 0 case
{
GuardInfo *info = _guardTable[i];
if (!info)
continue;
// Find out which ancestors we can reach from here
//
GuardInfo *ancestor = info->getParent();
while (ancestor)
{
if (ancestor->getArgVNs()->isSet(info->getThisVN()))
{
//info->setReachableAncestor(ancestor);
ancestor->setVisible(i);
}
ancestor = ancestor->getParent();
}
}
for (i = 0; i < _numInlinedSites; ++i)
{
GuardInfo *info = _guardTable[i];
if (!info)
continue;
GuardInfo *parent = info->getParent();
if (trace())
{
TR_BitVectorIterator bvi;
traceMsg(comp(), "Site %d (block_%d, parent-block_%d): thisVN: %d, argsVNs: {",
i, info->getBlock()->getNumber(),
parent ? parent->getBlock()->getNumber() : -1,
info->getThisVN());
bvi.setBitVector(*(info->getArgVNs()));
while (bvi.hasMoreElements())
{
uint32_t c = bvi.getNextElement();
traceMsg(comp(), "%d ", c);
}
traceMsg(comp(), "}\n\tReachable Subtree: {");
bvi.setBitVector(*(info->getVisibleGuards()));
while (bvi.hasMoreElements())
{
uint32_t c = bvi.getNextElement();
traceMsg(comp(), "%d ", c);
}
traceMsg(comp(), "}\n");
}
}
// FIXME: the following is a heuristic, probably we can do better
//
bool somethingDone = false;
for (i = 0; i < _numInlinedSites; ++i)
{
GuardInfo *info = _guardTable[i];
if (!info || info->getHasBeenDevirtualized())
continue;