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LoopCanonicalizer.cpp
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/*******************************************************************************
* Copyright IBM Corp. and others 2000
*
* 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 https://www.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] https://openjdk.org/legal/assembly-exception.html
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0 OR GPL-2.0-only WITH OpenJDK-assembly-exception-1.0
*******************************************************************************/
#include "optimizer/LoopCanonicalizer.hpp"
#include <limits.h>
#include <stdint.h>
#include <stdlib.h>
#include "codegen/CodeGenerator.hpp"
#include "env/FrontEnd.hpp"
#include "compile/Compilation.hpp"
#include "compile/SymbolReferenceTable.hpp"
#include "control/Options.hpp"
#include "control/Options_inlines.hpp"
#include "cs2/bitvectr.h"
#include "cs2/sparsrbit.h"
#include "env/StackMemoryRegion.hpp"
#include "env/TRMemory.hpp"
#include "il/AliasSetInterface.hpp"
#include "il/Block.hpp"
#include "il/DataTypes.hpp"
#include "il/ILOpCodes.hpp"
#include "il/ILOps.hpp"
#include "il/LabelSymbol.hpp"
#include "il/Node.hpp"
#include "il/Node_inlines.hpp"
#include "il/ResolvedMethodSymbol.hpp"
#include "il/Symbol.hpp"
#include "il/SymbolReference.hpp"
#include "il/TreeTop.hpp"
#include "il/TreeTop_inlines.hpp"
#include "infra/Assert.hpp"
#include "infra/BitVector.hpp"
#include "infra/Cfg.hpp"
#include "infra/ILWalk.hpp"
#include "infra/List.hpp"
#include "infra/CfgEdge.hpp"
#include "infra/CfgNode.hpp"
#include "infra/Checklist.hpp"
#include "optimizer/InductionVariable.hpp"
#include "optimizer/Optimization_inlines.hpp"
#include "optimizer/Optimizations.hpp"
#include "optimizer/Optimizer.hpp"
#include "optimizer/Structure.hpp"
#include "optimizer/UseDefInfo.hpp"
#include "optimizer/VPConstraint.hpp"
#include "ras/Debug.hpp"
namespace TR { class RegisterMappedSymbol; }
#define OPT_DETAILS "O^O LOOP TRANSFORMATION: "
/**
* Canonicalize While structures and convert them into If guarded
* Do While structures. We also add some empty blocks to split critical
* edges in the CFG for helping PRE (which is really the main optimization
* that benefits from canonicalization of loops). Note that the general
* critical edge splitter runs before structural analysis (so that it can
* avoid the problems associated with complex structure repair and because it
* does not really need structure for anything). There are some new CFG edges,
* structures, and trees (actually cloned) that are created in this pass, and
* for the part of the CFG that has changed now (the original While) we split
* critical edges in a specific manner.
*/
TR_LoopCanonicalizer::TR_LoopCanonicalizer(TR::OptimizationManager *manager)
: TR_LoopTransformer(manager)
{}
int32_t TR_LoopCanonicalizer::perform()
{
if (!comp()->mayHaveLoops())
return 0;
if (comp()->hasLargeNumberOfLoops())
{
return 0;
}
_loopTestBlock = NULL;
_storeTrees = NULL;
_currTree = NULL;
_insertionTreeTop = NULL;
_loopTestTree = NULL;
_asyncCheckTree = NULL;
_cannotBeEliminated = NULL;
_neverRead = NULL;
_neverWritten = NULL;
_writtenExactlyOnce.Clear();
_readExactlyOnce.Clear();
_allKilledSymRefs.Clear();
_allSymRefs.Clear();
_numberOfIterations = NULL;
_constNode = NULL;
_loadUsedInLoopIncrement = NULL;
_startOfHeader = NULL;
_cfg = NULL;
_rootStructure = NULL;
_hasPredictableExits = NULL;
_invariantBlocks.deleteAll();
_blocksToBeCleansed.deleteAll();
_analysisStack.clear();
_whileIndex = 0;
_visitCount = 0;
_topDfNum = 0;
_counter = 0;
_loopDrivingInductionVar = 0;
_nextExpression = 0;
_startExpressionForThisInductionVariable = 0;
_numberOfTreesInLoop = 0;
_isAddition = false;
_requiresAdditionalCheckForIncrement = false;
_doingVersioning = false;
{
TR::StackMemoryRegion stackMemoryRegion(*trMemory());
optimizer()->changeContinueLoopsToNestedLoops();
TR_ScratchList<TR::CFGNode> newEmptyBlocks(trMemory());
TR_ScratchList<TR::CFGNode> newEmptyExceptionBlocks(trMemory());
_cfg = comp()->getFlowGraph();
_rootStructure = _cfg->getStructure();
if (trace())
{
traceMsg(comp(), "Starting LoopCanonicalizer\n");
traceMsg(comp(), "\nCFG before loop canonicalization:\n");
getDebug()->print(comp()->getOutFile(), _cfg);
}
// printTrees();
// Recursive call through the structure tree that would
// collect all the While Structures (if any) in the method.
// Note that only while loops with a single block as its
// header will be detected here.
//
TR_ScratchList<TR_Structure> whileLoops(trMemory());
ListAppender<TR_Structure> whileLoopsInnerFirst(&whileLoops);
TR_ScratchList<TR_Structure> doWhileLoops(trMemory());
ListAppender<TR_Structure> doWhileLoopsInnerFirst(&doWhileLoops);
_nodesInCycle = new (trStackMemory()) TR_BitVector(_cfg->getNextNodeNumber(), trMemory(), stackAlloc);
//comp()->incVisitCount();
detectWhileLoops(whileLoopsInnerFirst, whileLoops, doWhileLoopsInnerFirst, doWhileLoops, _rootStructure, true);
if (whileLoops.isEmpty() && doWhileLoops.isEmpty())
{
return false;
}
if (trace())
traceMsg(comp(), "Number of WhileLoops = %d\n", whileLoops.getSize());
// _startOfHeader originally points to the last tree in the method;
// this variable is used as a placeholder to keep track of where
// trees can be moved (sometimes required for efficiency purposes
// to minimize gotos in the critical 'hot' path between the loop body
// and the new duplicate header that drives the new Do While loop.
//
_startOfHeader = comp()->getMethodSymbol()->getLastTreeTop();
_whileIndex = 0;
_counter = 0;
ListIterator<TR_Structure> whileLoopsIt(&whileLoops);
TR_Structure *nextWhileLoop;
for (nextWhileLoop = whileLoopsIt.getFirst(); nextWhileLoop != NULL; nextWhileLoop = whileLoopsIt.getNext())
{
// Can be used for debugging; to stop a particular loop from being
// and see if the problem persists or not.
//
// if (_counter == 1)
// break;
// else
// _counter++;
TR_RegionStructure *naturalLoop = nextWhileLoop->asRegion();
TR_ASSERT(naturalLoop && naturalLoop->isNaturalLoop(),"Loop canonicalizer, expecting natural loop");
if (naturalLoop->getEntryBlock()->isCold())
continue;
canonicalizeNaturalLoop(naturalLoop);
}
///comp()->dumpMethodTrees("Trees now\n");
if (trace())
traceMsg(comp(), "Number of cleansed blocks : %d\n", _blocksToBeCleansed.getSize());
//
// Move the trees around in this method so that the blocks that are currently
// violating the CFG constraints (only 1 branch in a block) are cleansed
//
ListIterator<TR::Block> cleansedBlocksIt(&_blocksToBeCleansed);
TR::Block *nextCleansedBlock = NULL;
for (nextCleansedBlock = cleansedBlocksIt.getCurrent(); nextCleansedBlock; nextCleansedBlock = cleansedBlocksIt.getNext())
{
cleanseTrees(nextCleansedBlock);
}
// Move the trees around in this method so that the invariant blocks
// fall through into the loop where possible
//
ListIterator<TR::Block> invariantBlocksIt(&_invariantBlocks);
TR::Block *nextInvariantBlock = NULL;
for (nextInvariantBlock = invariantBlocksIt.getCurrent(); nextInvariantBlock; nextInvariantBlock = invariantBlocksIt.getNext())
{
makeInvariantBlockFallThroughIfPossible(nextInvariantBlock);
}
if (trace())
traceMsg(comp(), "Number of DoWhileLoops = %d\n", doWhileLoops.getSize());
ListIterator<TR_Structure> doWhileLoopsIt(&doWhileLoops);
TR_Structure *nextDoWhileLoop;
for (nextDoWhileLoop = doWhileLoopsIt.getFirst(); nextDoWhileLoop != NULL; nextDoWhileLoop = doWhileLoopsIt.getNext())
{
// Can be used for debugging; to stop a particular loop from being
// and see if the problem persists or not.
//
// if (_counter == 1)
// break;
// else
// _counter++;
TR_RegionStructure *naturalLoop = nextDoWhileLoop->asRegion();
TR_ASSERT(naturalLoop && naturalLoop->isNaturalLoop(),"Loop canonicalizer, expecting natural loop");
if (naturalLoop->getEntryBlock()->isCold())
continue;
canonicalizeDoWhileLoop(naturalLoop);
}
/*
for (nextWhileLoop = whileLoopsIt.getFirst(); nextWhileLoop != NULL; nextWhileLoop = whileLoopsIt.getNext())
{
TR_RegionStructure *naturalLoop = nextWhileLoop->asRegion();
TR_ASSERT(naturalLoop && naturalLoop->isNaturalLoop(),"Loop canonicalizer, expecting natural loop");
if (naturalLoop->getEntryBlock()->isCold())
continue;
eliminateRedundantInductionVariablesFromLoop(naturalLoop);
}
for (nextDoWhileLoop = doWhileLoopsIt.getFirst(); nextDoWhileLoop != NULL; nextDoWhileLoop = doWhileLoopsIt.getNext())
{
TR_RegionStructure *naturalLoop = nextDoWhileLoop->asRegion();
TR_ASSERT(naturalLoop && naturalLoop->isNaturalLoop(),"Loop canonicalizer, expecting natural loop");
if (naturalLoop->getEntryBlock()->isCold())
continue;
eliminateRedundantInductionVariablesFromLoop(naturalLoop);
}
*/
// Use/def info and value number info are now bad.
//
optimizer()->setUseDefInfo(NULL);
optimizer()->setValueNumberInfo(NULL);
//requestOpt(loopVersioner);
requestOpt(OMR::loopVersionerGroup);
if (trace())
{
traceMsg(comp(), "\nCFG after loop canonicalization:\n");
getDebug()->print(comp()->getOutFile(), _cfg);
traceMsg(comp(), "Ending LoopCanonicalizer\n");
}
} // scope of the stack memory region
//if (trace())
{
if (trace())
comp()->dumpMethodTrees("Trees after canonicalization\n");
}
return 1; // actual cost
}
void TR_LoopTransformer::detectWhileLoopsInSubnodesInOrder(ListAppender<TR_Structure> &whileLoopsInnerFirst, List<TR_Structure> &whileLoops, ListAppender<TR_Structure> &doWhileLoopsInnerFirst, List<TR_Structure> &doWhileLoops, TR_Structure *root, TR_StructureSubGraphNode *rootNode, TR_RegionStructure *region, vcount_t visitCount, TR_BitVector *pendingList, bool innerFirst)
{
if (trace())
traceMsg(comp(), "Begin looking for canonicalizable loops in node %p numbered %d\n", root, root->getNumber());
bool alreadyVisitedNode = false;
//if (rootNode->getVisitCount() == visitCount)
if (_nodesInCycle->get(rootNode->getNumber()))
alreadyVisitedNode = true;
//rootNode->setVisitCount(visitCount);
_nodesInCycle->set(rootNode->getNumber());
for (auto pred = rootNode->getPredecessors().begin(); pred != rootNode->getPredecessors().end(); ++pred)
{
TR_StructureSubGraphNode *predNode = (TR_StructureSubGraphNode *) (*pred)->getFrom();
TR_Structure *predStructure = predNode->getStructure();
if (pendingList->get(predStructure->getNumber()) && (!alreadyVisitedNode))
{
detectWhileLoopsInSubnodesInOrder(whileLoopsInnerFirst, whileLoops, doWhileLoopsInnerFirst, doWhileLoops, predStructure, predNode, region, visitCount, pendingList, innerFirst);
return;
}
}
for (auto pred = rootNode->getExceptionPredecessors().begin(); pred != rootNode->getExceptionPredecessors().end(); ++pred)
{
TR_StructureSubGraphNode *predNode = (TR_StructureSubGraphNode *) (*pred)->getFrom();
TR_Structure *predStructure = predNode->getStructure();
if (pendingList->get(predStructure->getNumber()) && (!alreadyVisitedNode))
{
detectWhileLoopsInSubnodesInOrder(whileLoopsInnerFirst, whileLoops, doWhileLoopsInnerFirst, doWhileLoops, predStructure, predNode, region, visitCount, pendingList, innerFirst);
return;
}
}
_nodesInCycle->empty();
detectWhileLoops(whileLoopsInnerFirst, whileLoops, doWhileLoopsInnerFirst, doWhileLoops, root, innerFirst);
pendingList->reset(root->getNumber());
for (auto succ = rootNode->getSuccessors().begin(); succ != rootNode->getSuccessors().end(); ++succ)
{
TR_StructureSubGraphNode *succNode = (TR_StructureSubGraphNode *) (*succ)->getTo();
TR_Structure *succStructure = succNode->getStructure();
bool isExitEdge = false;
ListIterator<TR::CFGEdge> ei(®ion->getExitEdges());
TR::CFGEdge *edge;
for (edge = ei.getCurrent(); edge != NULL; edge = ei.getNext())
{
if (edge == *succ)
{
isExitEdge = true;
break;
}
}
if ((!isExitEdge) && pendingList->get(succStructure->getNumber()))
{
//comp()->incVisitCount();
_nodesInCycle->empty();
detectWhileLoopsInSubnodesInOrder(whileLoopsInnerFirst, whileLoops, doWhileLoopsInnerFirst, doWhileLoops, succStructure, succNode, region, visitCount, pendingList, innerFirst);
}
}
for (auto succ = rootNode->getExceptionSuccessors().begin(); succ != rootNode->getExceptionSuccessors().end(); ++succ)
{
TR_StructureSubGraphNode *succNode = (TR_StructureSubGraphNode *) (*succ)->getTo();
TR_Structure *succStructure = succNode->getStructure();
bool isExitEdge = false;
ListIterator<TR::CFGEdge> ei(®ion->getExitEdges());
TR::CFGEdge *edge;
for (edge = ei.getCurrent(); edge != NULL; edge = ei.getNext())
{
if (edge == *succ)
{
isExitEdge = true;
break;
}
}
if ((!isExitEdge) && pendingList->get(succStructure->getNumber()))
{
//comp()->incVisitCount();
_nodesInCycle->empty();
detectWhileLoopsInSubnodesInOrder(whileLoopsInnerFirst, whileLoops, doWhileLoopsInnerFirst, doWhileLoops, succStructure, succNode, region, visitCount, pendingList, innerFirst);
}
}
}
void TR_LoopTransformer::detectWhileLoopsInSubnodesInOrder(ListAppender<TR_Structure> &whileLoopsInnerFirst, List<TR_Structure> &whileLoops, ListAppender<TR_Structure> &doWhileLoopsInnerFirst, List<TR_Structure> &doWhileLoops, TR_RegionStructure *region, vcount_t visitCount, TR_BitVector *pendingList, bool innerFirst)
{
while (!_analysisStack.isEmpty() &&
_analysisStack.top()->getStructure() != region)
{
TR_StructureSubGraphNode *rootNode = _analysisStack.top();
TR_Structure *root = rootNode->getStructure();
if (!pendingList->get(root->getNumber()))
{
_analysisStack.pop();
continue;
}
if (trace())
traceMsg(comp(), "Begin looking for canonicalizable loops in node %p numbered %d\n", root, root->getNumber());
if (!_nodesInCycle->get(rootNode->getNumber()))
{
_nodesInCycle->set(rootNode->getNumber());
bool stopAnalyzingThisNode = false;
TR_PredecessorIterator precedingEdges(rootNode);
for (auto precedingEdge = precedingEdges.getFirst(); precedingEdge; precedingEdge = precedingEdges.getNext())
{
TR_StructureSubGraphNode *predNode = (TR_StructureSubGraphNode *) precedingEdge->getFrom();
TR_Structure *predStructure = predNode->getStructure();
if (pendingList->get(predStructure->getNumber()))
{
_analysisStack.pop();
_analysisStack.push(predNode);
stopAnalyzingThisNode = true;
break;
}
}
if (stopAnalyzingThisNode)
continue;
}
_nodesInCycle->empty();
detectWhileLoops(whileLoopsInnerFirst, whileLoops, doWhileLoopsInnerFirst, doWhileLoops, root, innerFirst);
pendingList->reset(root->getNumber());
_analysisStack.pop();
TR_SuccessorIterator succeedingEdges(rootNode);
for (auto succeedingEdge = succeedingEdges.getFirst(); succeedingEdge; succeedingEdge = succeedingEdges.getNext())
{
TR_StructureSubGraphNode *succNode = (TR_StructureSubGraphNode *) succeedingEdge->getTo();
TR_Structure *succStructure = succNode->getStructure();
bool isExitEdge = false;
ListIterator<TR::CFGEdge> ei(®ion->getExitEdges());
TR::CFGEdge *edge;
for (edge = ei.getCurrent(); edge != NULL; edge = ei.getNext())
{
if (edge == succeedingEdge)
{
isExitEdge = true;
break;
}
}
if ((!isExitEdge) && pendingList->get(succStructure->getNumber()))
{
_nodesInCycle->empty();
_analysisStack.push(succNode);
}
}
}
}
void TR_LoopTransformer::createWhileLoopsList(TR_ScratchList<TR_Structure>* whileLoops)
{
TR_ScratchList<TR::CFGNode> newEmptyBlocks(trMemory());
TR_ScratchList<TR::CFGNode> newEmptyExceptionBlocks(trMemory());
// printTrees();
// Recursive call through the structure tree that would
// collect all the While Structures (if any) in the method.
// Note that only while loops with a single block as its
// header will be detected here.
//
ListAppender<TR_Structure> whileLoopsInnerFirst(whileLoops);
TR_ScratchList<TR_Structure> doWhileLoops(trMemory());
ListAppender<TR_Structure> doWhileLoopsInnerFirst(&doWhileLoops);
//comp()->incVisitCount();
_cfg = comp()->getFlowGraph();
_rootStructure = _cfg->getStructure();
_nodesInCycle = new (trStackMemory()) TR_BitVector(_cfg->getNextNodeNumber(), trMemory(), stackAlloc);
if (asLoopVersioner())
detectWhileLoops(whileLoopsInnerFirst, *whileLoops, doWhileLoopsInnerFirst, doWhileLoops, _rootStructure, false);
else
detectWhileLoops(whileLoopsInnerFirst, *whileLoops, doWhileLoopsInnerFirst, doWhileLoops, _rootStructure, true);
/*
ListIterator<TR_Structure> whileLoopsIt(whileLoops);
TR_Structure *nextWhileLoop;
for (nextWhileLoop = whileLoopsIt.getFirst(); nextWhileLoop != NULL; nextWhileLoop = whileLoopsIt.getNext())
{
dumpOptDetails(comp(), "Loop is %d\n", nextWhileLoop->getNumber());
}
ListIterator<TR_Structure> doWhileLoopsIt(&doWhileLoops);
TR_Structure *nextDoWhileLoop;
for (nextDoWhileLoop = doWhileLoopsIt.getFirst(); nextDoWhileLoop != NULL; nextDoWhileLoop = doWhileLoopsIt.getNext())
{
dumpOptDetails(comp(), "Do While Loop is %d\n", nextDoWhileLoop->getNumber());
}
*/
// _startOfHeader originally points to the last tree in the method;
// this variable is used as a placeholder to keep track of where
// trees can be moved (sometimes required for efficiency purposes
// to minimize gotos in the critical 'hot' path between the loop body
// and the new duplicate header that drives the new Do While loop.
//
_startOfHeader = comp()->getMethodSymbol()->getLastTreeTop();
_whileIndex = 0;
_counter = 0;
}
/**
* Detect while loops in the structure control tree
*/
void TR_LoopTransformer::detectWhileLoops(ListAppender<TR_Structure> &whileLoopsInnerFirst, List<TR_Structure> &whileLoops, ListAppender<TR_Structure> &doWhileLoopsInnerFirst, List<TR_Structure> &doWhileLoops, TR_Structure *root, bool innerFirst)
{
TR_RegionStructure *region = root->asRegion();
if (!region)
return;
// Detect while loops in the subnodes
//
TR_StructureSubGraphNode *node;
int32_t numSubNodes = 0;
int32_t numberOfNodes = comp()->getFlowGraph()->getNextNodeNumber();
TR_BitVector *pendingList = new (trStackMemory()) TR_BitVector(numberOfNodes, trMemory(), stackAlloc);
pendingList->setAll(numberOfNodes);
vcount_t visitCount = comp()->getVisitCount();
//if (debug("nonRecursiveBVA"))
{
_analysisStack.push(region->getEntry());
detectWhileLoopsInSubnodesInOrder(whileLoopsInnerFirst, whileLoops, doWhileLoopsInnerFirst, doWhileLoops, region, visitCount, pendingList, innerFirst);
}
/*
else
detectWhileLoopsInSubnodesInOrder(whileLoopsInnerFirst, whileLoops, doWhileLoopsInnerFirst, doWhileLoops, region->getEntry()->getStructure(), region->getEntry(), region, visitCount, pendingList, innerFirst);
*/
TR_RegionStructure::Cursor si(*region);
for (node = si.getCurrent(); node; node = si.getNext())
numSubNodes++;
if (!region->isNaturalLoop())
return;
/*
// The loop must not have exception successors
//
if (region->getEntry()->hasExceptionOutEdges())
return;
*/
// The header of the loop must be a block.
//
TR_StructureSubGraphNode *entryNode = region->getEntry();
TR_BlockStructure *loopHeader = entryNode->getStructure()->asBlock();
bool isDoWhileLoop = false;
bool isWhileLoop = false;
if (asLoopCanonicalizer())
{
// There must be more than one subnode in the loop
//
/////if (numSubNodes <= 1)
///// return;
/////
if ((loopHeader && loopHeader->getBlock()->getNextBlock() && loopHeader->getBlock()->getNextBlock()->isExtensionOfPreviousBlock()) ||
(loopHeader && loopHeader->getBlock()->getLastRealTreeTop()->getNode()->getOpCode().isJumpWithMultipleTargets()) ||
(loopHeader && loopHeader->getBlock()->getLastRealTreeTop()->getNode()->getOpCode().isCompBranchOnly()))
{
isDoWhileLoop = true;
}
if (!isDoWhileLoop && loopHeader && (numSubNodes > 1))
{
// There must be no exception edges into or out of the header block.
//
TR::Block *hdrBlock = loopHeader->getBlock();
if ((hdrBlock->hasExceptionPredecessors() == false) &&
(hdrBlock->hasExceptionSuccessors() == false))
{
// There must be two edges out of the header, one internal and one external.
//
if (entryNode->getSuccessors().size() == 2)
{
auto it = entryNode->getSuccessors().begin();
TR::CFGEdge* succ1 = *it;
++it;
TR::CFGEdge* succ2 = *it;
bool succ1Internal = region->contains(toStructureSubGraphNode(succ1->getTo())->getStructure(), region->getParent());
bool succ2Internal = region->contains(toStructureSubGraphNode(succ2->getTo())->getStructure(), region->getParent());
if (succ1Internal ^ succ2Internal)
{
TR::TreeTop *firstTree = hdrBlock->getFirstRealTreeTop();
static const bool skipTt = feGetEnv("TR_canonicalizerStopAtTreetop") == NULL;
static const bool skipCRAnchor = feGetEnv("TR_canonicalizerStopAtCompressedRefsAnchor") == NULL;
while ((firstTree &&
(firstTree->getNode()->getOpCodeValue() == TR::asynccheck ||
(skipTt && firstTree->getNode()->getOpCodeValue() == TR::treetop) ||
(skipCRAnchor && firstTree->getNode()->getOpCodeValue() == TR::compressedRefs) ||
firstTree->getNode()->getOpCode().isCheck())))
firstTree = firstTree->getNextTreeTop();
if (firstTree == hdrBlock->getLastRealTreeTop() ||
firstTree->getNextTreeTop() == hdrBlock->getLastRealTreeTop())
{
TR_ScratchList<TR::Block> exitBlocks(trMemory());
region->collectExitBlocks(&exitBlocks);
bool doNotConsiderAsWhile = false;
if (!exitBlocks.isSingleton())
{
TR::TreeTop *hdrBlockLoopTestTree = hdrBlock->getLastRealTreeTop();
bool foundInductionVariable =
findMatchingIVInRegion(hdrBlockLoopTestTree, region);
if (!foundInductionVariable)
{
ListIterator<TR::Block> blocksIt(&exitBlocks);
TR::Block *exitBlock;
for (exitBlock = blocksIt.getCurrent(); exitBlock; exitBlock = blocksIt.getNext())
{
if (exitBlock != hdrBlock)
{
if (exitBlock->getSuccessors().size() == 2)
{
auto it = exitBlock->getSuccessors().begin();
TR::CFGEdge* exitSucc1 = *it;
++it;
TR::CFGEdge* exitSucc2 = *it;
bool successor1Internal = region->contains(toBlock(exitSucc1->getTo())->getStructureOf(), region->getParent());
bool successor2Internal = region->contains(toBlock(exitSucc2->getTo())->getStructureOf(), region->getParent());
if (successor1Internal ^ successor2Internal)
{
TR::TreeTop *exitBlockLoopTestTree = exitBlock->getLastRealTreeTop();
if (exitBlockLoopTestTree->getNode()->getOpCode().isCompBranchOnly() ||
exitBlockLoopTestTree->getNode()->getOpCode().isJumpWithMultipleTargets()) continue;
foundInductionVariable =
findMatchingIVInRegion(exitBlockLoopTestTree, region);
}
}
}
if (foundInductionVariable)
{
doNotConsiderAsWhile = true;
break;
}
}
}
}
if (!doNotConsiderAsWhile)
isWhileLoop = true;
else
{
//printf("Found a fake while loop in %s\n", comp()->signature());
//fflush(stdout);
}
}
}
}
}
}
if (!isWhileLoop)
{
TR_StructureSubGraphNode *blockNode = entryNode;
while (!blockNode->getStructure()->asBlock())
blockNode = blockNode->getStructure()->asRegion()->getEntry();
/*
// There must be no exception edges into or out of the header block.
//
TR::Block *hdrBlock = blockNode->getStructure()->asBlock()->getBlock();
if (!(hdrBlock->getExceptionPredecessors().empty() &&
hdrBlock->getExceptionSuccessors().empty()))
return;
*/
isDoWhileLoop = true;
}
}
else if (asLoopVersioner())
{
if ((loopHeader && loopHeader->getBlock()->getLastRealTreeTop()->getNode()->getOpCode().isJumpWithMultipleTargets()) ||
(loopHeader && loopHeader->getBlock()->getLastRealTreeTop()->getNode()->getOpCode().isCompBranchOnly()))
return;
TR_RegionStructure *parentStructure = region->getParent()->asRegion();
if (parentStructure)
{
TR_RegionStructure::Cursor si(*parentStructure);
TR_StructureSubGraphNode *subNode;
for (subNode = si.getCurrent(); subNode != NULL; subNode = si.getNext())
{
TR_Structure *subStruct = subNode->getStructure();
if (subStruct == region)
{
/*
if (!(subNode->getExceptionPredecessors().empty() &&
subNode->getExceptionSuccessors().empty()))
return;
*/
if (subNode->getPredecessors().empty())
return;
TR_BlockStructure *pred = toStructureSubGraphNode(subNode->getPredecessors().front()->getFrom())->getStructure()->asBlock();
if (!pred ||
!pred->isLoopInvariantBlock())
return;
// This condition is required as we cannot create new catch blocks easily;
// a catch block normally has some specific info (handler info etc.) that are
// created by IL generator and if we try to create new catch blocks, then
// there was a crash when generating exception table entries.
//
TR_ScratchList<TR::Block> blocksInRegion(trMemory());
region->getBlocks(&blocksInRegion);
ListIterator<TR::Block> blocksIt(&blocksInRegion);
TR::Block *nextBlock;
for (nextBlock = blocksIt.getCurrent(); nextBlock; nextBlock=blocksIt.getNext())
if (!nextBlock->getExceptionPredecessors().empty())
return;
break;
}
}
}
//
//ListIterator<TR::CFGEdge> preds(&entryNode->getPredecessors());
//TR::CFGEdge *pred1 = preds.getCurrent();
//TR::CFGEdge *pred2 = preds.getNext();
//if (!pred1 || !pred2 || preds.getNext())
// return;
//bool pred1Internal = region->contains(toStructureSubGraphNode(pred1->getFrom())->getStructure(), region->getParent());
//bool pred2Internal = region->contains(toStructureSubGraphNode(pred2->getFrom())->getStructure(), region->getParent());
//if (!(pred1Internal ^ pred2Internal))
// return;
}
// This has satisfied all the criteria for a while loop that can be
// transformed.
//
if (isDoWhileLoop)
{
if (trace())
traceMsg(comp(), "Adding structure %d(%p) as a doWhile loop\n", region->getNumber(), region);
if (innerFirst)
doWhileLoopsInnerFirst.add(region);
else
doWhileLoops.add(region);
}
else
{
if (trace())
traceMsg(comp(), "Adding structure %d(%p) as a While loop\n", region->getNumber(), region);
if (innerFirst)
whileLoopsInnerFirst.add(region);
else
whileLoops.add(region);
}
}
bool TR_LoopTransformer::findMatchingIVInRegion(TR::TreeTop* loopTestTree, TR_RegionStructure* region)
{
TR::Node *firstChild = loopTestTree->getNode()->getFirstChild();
TR::SymbolReference *firstChildSymRef = NULL;
if (firstChild->getOpCode().hasSymbolReference())
firstChildSymRef = firstChild->getSymbolReference();
else
{
if ((firstChild->getOpCode().isAdd() || firstChild->getOpCode().isSub()) &&
(firstChild->getReferenceCount() > 1) &&
firstChild->getSecondChild()->getOpCode().isLoadConst())
{
firstChild = firstChild->getFirstChild();
}
if (firstChild &&
firstChild->getOpCode().hasSymbolReference())
firstChildSymRef = firstChild->getSymbolReference();
}
if (!firstChildSymRef)
return false;
if (region->findMatchingIV(firstChildSymRef))
return true;
TR_PrimaryInductionVariable *piv = region->getPrimaryInductionVariable();
if (piv && piv->getSymRef()->getSymbol() == firstChildSymRef->getSymbol())
return true;
ListIterator<TR_BasicInductionVariable> it(®ion->getBasicInductionVariables());
for (TR_BasicInductionVariable *biv = it.getFirst(); biv; biv = it.getNext())
if (biv->getSymRef()->getSymbol() == firstChildSymRef->getSymbol())
return true;
return false;
}
/**
* @verbatim
* The loop is changed from this: to this:
* | |
* | |
* --->| |
* | | |
* | ----- ----- ----- -----
* | | H |---->| E | | H |---->| S1 |------
* | ----- ----- ----- ----- |
* | | | |
* | | ----- |
* | ----- | S2 | |
* | | B | ----- |
* | ----- ---->| |
* | | | ----- |
* ---- | | B | |
* | ----- |
* | | V
* | ----- ----- -----
* | | H1 |---->| G |-->| E |
* | ----- ----- -----
* | |
* -----
* @endverbatim
* The new block H1 is a clone of the original header H
* The new blocks S1 and S2 are empty critical-edge-splitting blocks
* The new block G is optional, it may be necessary to contain an extra
* goto.
*/
void TR_LoopCanonicalizer::canonicalizeNaturalLoop(TR_RegionStructure *whileLoop)
{
rewritePostToPreIncrementTestInRegion(whileLoop);
if (!performTransformation(comp(), "%sCanonicalizing natural loop %d\n", OPT_DETAILS, whileLoop->getNumber()))
return;
if (trace())
comp()->dumpMethodTrees("Trees at this stage");
TR_StructureSubGraphNode *entryGraphNode = whileLoop->getEntry();
TR_ASSERT(entryGraphNode->getStructure()->asBlock(), "Loop canonicalizer, header is not a block");
// Find the basic blocks that represent the loop header and the
// first block in the loop body.
//
TR::Block *loopHeader = entryGraphNode->getStructure()->asBlock()->getBlock();
TR::Block *loopBody = NULL;
for (auto nextSucc = loopHeader->getSuccessors().begin(); nextSucc != loopHeader->getSuccessors().end(); ++nextSucc)
{
TR::Block *dest = toBlock((*nextSucc)->getTo());
if (whileLoop->contains(dest->getStructureOf(), whileLoop->getParent()))
{
loopBody = dest;
break;
}
}
TR_ScratchList<TR::Block> newBlocks(trMemory());
TR_ScratchList<TR::CFGEdge> removedEdges(trMemory());
TR::TreeTop *entryTree = loopHeader->getEntry();
TR::TreeTop *exitTree = loopHeader->getExit();
TR::Node *entryNode = entryTree->getNode();
TR::Block *fallThroughBlock;
if (!_blocksToBeCleansed.find(loopHeader))
fallThroughBlock = exitTree->getNextTreeTop()->getNode()->getBlock();
else
{
TR_ASSERT(loopHeader->getLastRealTreeTop()->getNode()->getOpCodeValue() == TR::Goto, "Unexpected opcode instead of TR::Goto\n");
fallThroughBlock = loopHeader->getLastRealTreeTop()->getNode()->getBranchDestination()->getNode()->getBlock();
}
// Create a new empty block to hold the cloned header H1.
// It will be filled out with duplicate trees soon .
//
TR::Block *clonedHeader = TR::Block::createEmptyBlock(entryNode, comp(), loopHeader->getFrequency(), loopHeader);
bool needToSetFlag = false;
if (loopHeader->getStructureOf()->isEntryOfShortRunningLoop())
needToSetFlag = true;
newBlocks.add(clonedHeader);
TR::TreeTop *newEntryTree = clonedHeader->getEntry();
TR::TreeTop *newExitTree = clonedHeader->getExit();
TR::TreeTop *prevTree = entryTree->getPrevTreeTop();
// Since we will be explicitly doing structure repair later, remove the
// structure so that repair is not attempted as we modify the CFG.
//
_cfg->setStructure(NULL);
// Start fixing up the predecessors of the original loop
// header; i.e. make all of the back edges now point to the
// new duplicate header block; but maintain the incoming edges to the
// original header as the new If guarded structure must still be entered
// through the If guard (which is where the original loop header
// is present after canonicalization).
//
int32_t sumPredFreq = 0;
TR::Block *adjPred = NULL;
for (auto edge = loopHeader->getPredecessors().begin(); edge != loopHeader->getPredecessors().end(); ++edge)
{
TR::Block *pred = toBlock((*edge)->getFrom());
if ((*edge)->getCreatedByTailRecursionElimination())
needToSetFlag = true;
if (!whileLoop->contains(pred->getStructureOf(), whileLoop->getParent()))
{
sumPredFreq = sumPredFreq + (*edge)->getFrequency();
//
// This is NOT a back edge as the predecessor is not part of the loop.
// The operations here are to insert gotos at the end of this
// predecessor block as its not certain what the optimal
// positioning of the trees in the original header would be
// right now. Since this control flow path is guaranteed to be
// less 'hot' than the actual loop, we are trying to remove
// any constraints that might keep us from moving the trees
// in the original loop header; we might want to move trees
// in this original header in order to specifically take advantage
// of falling through in the 'hot' path between the loop body
// and the new duplicate header.
//
if (pred->getExit())
loopHeader->getEntry()->getNode()->copyByteCodeInfo(pred->getExit()->getNode());
//dumpOptDetails(comp(), "Block loopHeader %d gets info from pred %d\n", loopHeader->getNumber(), pred->getNumber());
if (!(pred == _cfg->getStart()))
{
TR::TreeTop *lastNonFenceTree = pred->getLastRealTreeTop();
if (_blocksToBeCleansed.find(pred))
lastNonFenceTree = lastNonFenceTree->getPrevRealTreeTop();
TR::Node * lastNonFenceNode = lastNonFenceTree->getNode();
if (lastNonFenceTree->getNode()->getOpCode().isBranch())
{
// If the predecessor had a branch but was still falling
// through rather than branching explicitly to the original
// header. Note that a switch always has explicit branches;
// so it cannot be falling through to the original header.
//
if (lastNonFenceTree->getNode()->getBranchDestination() != entryTree)
{
// We add a goto at the end of a block already having
// a branch; so we MUST fix this up by moving trees
// at the end. The reasoning here is that in general in
// a nested while loop we might have the headers
// falling through to each other and the body falling
// through to the innermost header. In such cases we
// want our canonicalized nested do whiles to also
// utilize maximum fall through like originally but
// with the new duplicate headers now. So two or more
// original header blocks (their trees) would need to be
// moved out of the 'hot' path first and then at the end,
// we patch up the trees properly and get rid of this
// goto we have inserted that breaks CFG constraints
// temporarily.
//
TR::TreeTop *gotoTreeTop = TR::TreeTop::create(comp(), TR::Node::create(entryNode, TR::Goto, 0, entryTree));
TR::TreeTop *treeTop = lastNonFenceTree->getNextTreeTop();
lastNonFenceTree->join(gotoTreeTop);
gotoTreeTop->join(treeTop);
_blocksToBeCleansed.add(pred);
}
}
else if (!lastNonFenceTree->getNode()->getOpCode().isJumpWithMultipleTargets() &&
!lastNonFenceTree->getNode()->getOpCode().isCompBranchOnly())
{
if (adjPred)
{
// If the predecessor used to fall through into the
// original header (no branch or switch)
//
TR::TreeTop *gotoTreeTop = TR::TreeTop::create(comp(), TR::Node::create(entryNode, TR::Goto, 0, entryTree));
TR::TreeTop *treeTop = lastNonFenceTree->getNextTreeTop();
lastNonFenceTree->join(gotoTreeTop);
gotoTreeTop->join(treeTop);
}
else
{
adjPred = pred;