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LoopReplicator.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/LoopReplicator.hpp"
#include <stdio.h> // for fflush, printf, stdout
#include <string.h> // for NULL, memset
#include "codegen/FrontEnd.hpp" // for feGetEnv
#include "compile/Compilation.hpp" // for Compilation
#include "compile/SymbolReferenceTable.hpp" // for SymbolReferenceTable
#include "env/TRMemory.hpp" // for TR_Link::operator new, TR_Memory, etc
#include "il/Block.hpp" // for Block, toBlock, TR_BlockCloner
#include "il/ILOpCodes.hpp" // for ILOpCodes::Goto, etc
#include "il/ILOps.hpp" // for ILOpCode
#include "il/Node.hpp" // for Node
#include "il/Node_inlines.hpp" // for Node::getChild, etc
#include "il/TreeTop.hpp" // for TreeTop
#include "il/TreeTop_inlines.hpp" // for TreeTop::getNode, TreeTop::join, etc
#include "infra/Assert.hpp" // for TR_ASSERT
#include "infra/BitVector.hpp" // for TR_BitVector
#include "infra/Cfg.hpp" // for CFG, MAX_COLD_BLOCK_COUNT
#include "infra/Stack.hpp" // for TR_Stack
#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_RegionStructure, etc
#include "ras/Debug.hpp" // for TR_DebugBase
#define OPT_DETAILS "O^O LOOP REPLICATOR: "
#define MIN_BLOCKS_IN_TRACE 5
#define INITIAL_BLOCK_WEIGHT -999
#define COLOR_BLACK 0
#define COLOR_WHITE 1
#define COLOR_GRAY -1
TR_LoopReplicator::TR_LoopReplicator(TR::OptimizationManager *manager)
: TR_LoopTransformer(manager),
_blocksCloned(trMemory())
{
_nodeCount = 0;
_nodesInCFG = 0;
_switchTree = NULL;
_maxNestingDepth = 0;
}
int32_t TR_LoopReplicator::perform()
{
// mainline entry
static char *disableLR = feGetEnv("TR_NoLoopReplicate");
if (disableLR)
return 0;
if (!comp()->mayHaveLoops() ||
optimizer()->optsThatCanCreateLoopsDisabled())
return 0;
if (comp()->isProfilingCompilation())
return 0;
_cfg = comp()->getFlowGraph();
_rootStructure = _cfg->getStructure();
_haveProfilingInfo = true;
static char *testLR = feGetEnv("TR_LRTest");
if (!_haveProfilingInfo)
{
dumpOptDetails(comp(), "Need profiling information in order to replicate...\n");
if (trace())
traceMsg(comp(), "method is %s \n", comp()->signature());
if (!testLR)
return 0;
}
_nodesInCFG = _cfg->getNextNodeNumber();
TR_Structure *root = _rootStructure;
// From this point on, stack memory allocations will die when the function returns
TR::StackMemoryRegion stackMemoryRegion(*trMemory());
_blocksInCFG = (TR::Block **) trMemory()->allocateStackMemory(_nodesInCFG * sizeof(TR::Block *));
memset(_blocksInCFG, 0, _nodesInCFG * sizeof(TR::Block *));
_blockWeights = (int32_t *) trMemory()->allocateStackMemory(_nodesInCFG * sizeof(int32_t));
memset(_blockWeights, 0, _nodesInCFG * sizeof(int32_t));
_seenBlocks = (int32_t *) trMemory()->allocateStackMemory(_nodesInCFG * sizeof(int32_t));
memset(_seenBlocks, 0, _nodesInCFG * sizeof(int32_t));
//
_blocksVisited = new (trStackMemory()) TR_BitVector(_nodesInCFG, trMemory(), stackAlloc);
for (TR::CFGNode *n = _cfg->getFirstNode(); n; n = n->getNext())
{
if (toBlock(n) && (n->getNumber() >= 0))
_blocksInCFG[n->getNumber()] = toBlock(n);
_blockWeights[n->getNumber()] = INITIAL_BLOCK_WEIGHT;
_seenBlocks[n->getNumber()] = COLOR_WHITE;
}
// initialize the bitvectors
_blocksVisited->empty();
if (trace() && getDebug())
{
traceMsg(comp(), "structure before replication :\n");
getDebug()->print(comp()->getOutFile(), _rootStructure, 6);
}
// collect info about potential
// loops for replication
perform(root);
// now modify trees & CFG
dumpOptDetails(comp(), "analysis complete...attempting to replicate\n");
modifyLoops();
return 0;
}
int32_t TR_LoopReplicator::perform(TR_Structure *str)
{
TR_RegionStructure *region;
if (!(region = str->asRegion()))
return 0;
// replicate in post-order
TR_RegionStructure::Cursor sgnIt(*region);
for (TR_StructureSubGraphNode *n = sgnIt.getCurrent(); n; n = sgnIt.getNext())
perform(n->getStructure());
if (!region->isNaturalLoop())
{
dumpOptDetails(comp(), "region (%d) is not a natural loop\n", region->getNumber());
return 0;
}
// ignore loops known to be cold
TR::Block *entryBlock = region->getEntryBlock();
if (entryBlock->isCold())
{
dumpOptDetails(comp(), "region (%d) is a cold loop\n", region->getNumber());
return 0;
}
_blockMapper = (TR::Block **) trMemory()->allocateStackMemory(_nodesInCFG * sizeof(TR::Block *));
memset(_blockMapper, 0, _nodesInCFG * sizeof(TR::Block *));
// analyze 2 kinds of loops
// (a) do-while loops
// contain a block that has 2 edges - one edge exits the region and another edge is the
// loop back-edge
// region
// (b) while loops
// entry block (of the region) has an edge that exits the region. One of the predecessor
// edges of the entry is the loop back-edge
//
// there are 2 places where the controlling condition can be found
// (1) first treetop - (while loops)
// (2) originator of back-edge - (do-while loops)
if (trace())
traceMsg(comp(), "analyzing loop (%d)\n", region->getNumber());
// case 1
TR_StructureSubGraphNode *entryNode = region->getEntry();
TR_BlockStructure *entry = entryNode->getStructure()->asBlock();
if (entry)
{
for (auto edge = entryNode->getSuccessors().begin(); edge != entryNode->getSuccessors().end(); ++edge)
{
if (region->isExitEdge(*edge))
{
if (isWellFormedLoop(region, entry))
{
if (trace())
traceMsg(comp(), "found while loop\n");
_loopType = whileDo;
return replicateLoop(region, entryNode);
}
}
}
}
// case 2
TR_StructureSubGraphNode *branchNode = NULL;
TR_RegionStructure::Cursor snIt(*region);
for (TR_StructureSubGraphNode *sgNode = snIt.getCurrent();
sgNode && (branchNode == NULL);
sgNode = snIt.getNext())
{
bool hasBackEdge = false;
bool hasExitEdge = false;
for (auto edge = sgNode->getSuccessors().begin(); edge != sgNode->getSuccessors().end(); ++edge)
{
TR_StructureSubGraphNode *dest = toStructureSubGraphNode((*edge)->getTo());
if (region->isExitEdge(*edge))
hasExitEdge = true;
if (dest == region->getEntry())
hasBackEdge = true;
if (hasBackEdge && hasExitEdge)
{
if (isWellFormedLoop(region, sgNode->getStructure()))
branchNode = sgNode;
}
}
}
if (branchNode)
{
if (trace())
traceMsg(comp(), "found do-while loop\n");
_loopType = doWhile;
return replicateLoop(region, branchNode);
}
dumpOptDetails(comp(), "loop (%d) does not conform to required form & will not be replicated\n",
region->getNumber());
return false;
}
bool TR_LoopReplicator::isWellFormedLoop(TR_RegionStructure *region, TR_Structure *condBlock)
{
// FIXME:very simple checks for now
//
vcount_t visitCount = comp()->incVisitCount();
// (1)
// condition has to be in a block
if (!condBlock->asBlock())
return false;
// (2)
// iterate blocks and check for catch blocks; since they shouldnt be cloned
TR_ScratchList<TR::Block> blocksInLoop(trMemory());
region->getBlocks(&blocksInLoop);
ListIterator<TR::Block> bilIt(&blocksInLoop);
TR::Block *b = NULL;
int32_t numBlocks = 0;
for (b = bilIt.getCurrent(); b; b = bilIt.getNext(), numBlocks++)
{
if (b->hasExceptionPredecessors()) // catch
{
if (trace())
traceMsg(comp(), "block (%d) has exception predecessors - currently not supported\n", b->getNumber());
return false;
}
if (b->hasExceptionSuccessors()) // try
{
if (trace())
traceMsg(comp(), "block (%d) has exception successors\n", b->getNumber());
}
}
// (3)
// check if number of nodes in loop exceeds threshold
// FIXME: decide on a threshold; disabled for now
bilIt.reset();
for (b = bilIt.getCurrent(); b; b = bilIt.getNext())
{
TR::TreeTop *entryTT = b->getEntry();
TR::TreeTop *exitTT = b->getExit();
for (TR::TreeTop *tt = entryTT->getNextRealTreeTop();
tt != exitTT; tt = tt->getNextRealTreeTop())
{
_nodeCount += countChildren(tt->getNode(), visitCount);
}
}
int32_t currentNestingDepth = 0;
int32_t currentMaxNestingDepth = 0;
_maxNestingDepth = region->getMaxNestingDepth(¤tNestingDepth, ¤tMaxNestingDepth);
if (trace())
{
// loopproperties
traceMsg(comp(), "for loop (%d): \n", region->getNumber());
traceMsg(comp(), " number of nodes: %d\n", _nodeCount);
traceMsg(comp(), " number of blocks: %d\n", numBlocks);
traceMsg(comp(), " max nesting depth: %d\n", _maxNestingDepth);
}
if (_maxNestingDepth > MAX_REPLICATION_NESTING_DEPTH)
{
traceMsg(comp(), "for loop (%d), max nest depth thresholds exceeded\n", region->getNumber());
return false;
}
//growth factor, 33% of the loop
//
if ((numBlocks*MAX_REPLICATION_GROWTH_FACTOR) > MAX_REPLICATION_GROWTH_SIZE)
{
traceMsg(comp(), "for loop (%d), loop too big, thresholds exceeded\n", region->getNumber());
return false;
}
#if 0
if (_nodeCount > MAX_NODE_THRESHOLD_FOR_REPLICATION)
{
if (trace())
traceMsg(comp(), "no replication, node count exceeds threshold for loop (%d)\n",
region->getNumber());
return false;
}
#endif
return true;
}
// restructure loop by replication
int32_t TR_LoopReplicator::replicateLoop(TR_RegionStructure *region,
TR_StructureSubGraphNode *branchNode)
{
TR::Block *cBlock = branchNode->getStructure()->asBlock()->getBlock();
TR::TreeTop *lastTT = cBlock->getLastRealTreeTop();
if (!lastTT->getNode()->getOpCode().isBranch())
{
if (trace())
traceMsg(comp(), "no branch condition found in loop (%d)\n", region->getNumber());
return false;
}
dumpOptDetails(comp(), "picking trace in loop (%d)...\n", region->getNumber());
LoopInfo *lInfo = new (trStackMemory()) (LoopInfo);
lInfo->_regionNumber = region->getNumber();
lInfo->_replicated = false;
lInfo->_region = region;
_loopInfo.add(lInfo);
_curLoopInfo = lInfo;
// reset bitvector
//_blocksVisited->empty();
static char *pEnv = feGetEnv("TR_NewLRTracer");
if (pEnv)
{
///printf("computing weights for loop %d in method %s\n", region->getNumber(), comp()->signature());fflush(stdout);
calculateBlockWeights(region);
///printf("finished computing weights for loop %d in method %s\n", region->getNumber(), comp()->signature());fflush(stdout);
if (trace())
{
traceMsg(comp(), "propagated frequencies: \n");
for(int32_t i = 0; i < _nodesInCFG; i++)
traceMsg(comp(), "%d : %d\n", i, _blockWeights[i]);
}
}
static char *testLR = feGetEnv("TR_LRTest");
if (!testLR)
{
lInfo->_seedFreq = getSeedFreq(region);
// gathers the blocks in the common path
if (!heuristics(lInfo))
{
dumpOptDetails(comp(), "failed...unable to select trace inside the loop\n");
return false;
}
}
else
{
if (!heuristics(lInfo, true)) // testing mode
{
dumpOptDetails(comp(), "failed...unable to select trace inside the loop\n");
return false;
}
}
if (trace())
traceMsg(comp(), "gathered information for loop (%d)\n", lInfo->_regionNumber);
return true;
}
/////////////////////////////
// helper routines
//
//
int32_t TR_LoopReplicator::countChildren(TR::Node *node, vcount_t visitCount)
{
// counts children not yet visited
//
if (!node)
return 0;
if (node->getVisitCount() == visitCount)
return 0;
node->setVisitCount(visitCount);
int32_t nodeCount = 1;
for (int32_t i = node->getNumChildren()-1; i >= 0; i--)
{
nodeCount += countChildren(node->getChild(i), visitCount);
}
return nodeCount;
}
static void collectNonColdLoops(TR::Compilation *c, TR_RegionStructure *region, List<TR_RegionStructure> &innerLoops);
// Find non-cold loops strictly nested within region.
static void collectNonColdInnerLoops(TR::Compilation *c, TR_RegionStructure *region, List<TR_RegionStructure> &innerLoops)
{
TR_RegionStructure::Cursor it(*region);
for (TR_StructureSubGraphNode *node = it.getFirst();
node;
node = it.getNext())
{
if (node->getStructure()->asRegion())
collectNonColdLoops(c, node->getStructure()->asRegion(), innerLoops);
}
}
// Find non-cold loops within region, possibly including region itself.
static void collectNonColdLoops(TR::Compilation *c, TR_RegionStructure *region, List<TR_RegionStructure> &loops)
{
if (region->getEntryBlock()->isCold())
return;
List<TR_RegionStructure> innerLoops(c->trMemory());
collectNonColdInnerLoops(c, region, innerLoops);
if (region->isNaturalLoop() && innerLoops.isEmpty())
loops.add(region);
else
loops.add(innerLoops);
}
bool TR_LoopReplicator::checkInnerLoopFrequencies(TR_RegionStructure *region, LoopInfo *lInfo)
{
// dont bother with small traces
//
int32_t count = 0;
for (BlockEntry *be = (lInfo->_nodesCommon).getFirst(); be; be = be->getNext())
count++;
if (count < MIN_BLOCKS_IN_TRACE)
return true;
if (comp()->getFlowGraph()->getMaxFrequency() <= 0)
{
if (trace())
traceMsg(comp(), "no frequency info\n");
return true; // maybe this should actually be false...
}
if (trace())
traceMsg(comp(), "inspecting non-cold inner loops\n");
List<TR_RegionStructure> innerLoops(trMemory());
collectNonColdInnerLoops(comp(), region, innerLoops);
if (innerLoops.isEmpty())
{
if (trace())
traceMsg(comp(), "failed to find non-cold inner loops; will attempt to replicate\n");
return true;
}
logTrace(lInfo);
TR_ScratchList<TR::Block> hotInnerLoopHeaders(trMemory());
int32_t outerLoopFrequency = region->getEntryBlock()->getFrequency();
ListIterator<TR_RegionStructure> it(&innerLoops);
for (TR_RegionStructure *loop = it.getFirst(); loop; loop = it.getNext())
{
if (trace())
traceMsg(comp(), "\tlooking at inner loop %d\n", loop->getNumber());
TR::Block * const innerLoopHeader = loop->getEntryBlock();
int32_t entryBlockFrequency = innerLoopHeader->getFrequency();
float outerLoopRelativeFrequency = entryBlockFrequency / (float)outerLoopFrequency;
bool isInnerLoopHot = (outerLoopRelativeFrequency > 1.3f); // FIXME: const
if (trace())
traceMsg(comp(), "\t outerloop relative frequency = %.3g\n", outerLoopRelativeFrequency);
if (!isInnerLoopHot && outerLoopFrequency == 6)
{
isInnerLoopHot = true;
if (trace())
traceMsg(comp(), "\t considered hot because outer loop has frequency 6\n");
}
if (isInnerLoopHot)
{
if (trace())
traceMsg(comp(), "\t this is a hot inner loop\n");
hotInnerLoopHeaders.add(innerLoopHeader);
if (!searchList(innerLoopHeader, common, lInfo))
{
traceMsg(comp(), "not going to replicate loop because hot inner loop %d is not on the trace\n", loop->getNumber());
return false;
}
}
}
return shouldReplicateWithHotInnerLoops(region, lInfo, &hotInnerLoopHeaders);
}
bool TR_LoopReplicator::shouldReplicateWithHotInnerLoops(
TR_RegionStructure *region,
LoopInfo *lInfo,
TR_ScratchList<TR::Block> *hotInnerLoopHeaders)
{
if (comp()->getOption(TR_DisableLoopReplicatorColdSideEntryCheck))
return true;
// If there are no hot inner loops, then replicate away.
if (hotInnerLoopHeaders->isEmpty())
return true;
// When there are hot inner loops, we only want to replicate when we'll
// remove confounding paths leading into those inner loops. Right now we're
// only hoping to eliminate cold paths. Otherwise, we don't really expect
// any benefit from replicating an outer loop.
//
// Removal of cold paths is helpful because they often contain things we
// don't want to consider, such as calls, and they're often reached by
// failing guards. Splitting the tail in this case can help later analysis,
// e.g. VP may be able to fold guards within the hot inner loops.
//
// The following generates a conservative answer to whether we'll be able to
// remove any such cold paths, by requiring that the trace encounter a
// side-entry directly from a cold block before it hits either a hot inner
// loop or a branch within the trace.
//
// If it does, then we can definitely remove cold paths from consideration.
//
// Otherwise, we may miss some opportunities. For instance, the side-entry
// could occur only after a branch within the trace, or it may not come
// directly from a cold block. It's also possible that the eliminated cold
// path doesn't lead to every hot inner loop, but only most of them, for
// example. The heuristic can be extended to cover such cases later as
// necessary.
//
if (trace())
traceMsg(comp(), "Loop has hot inner loops. Looking for early cold side-entry.\n");
TR::Block * const outerLoopHeader = region->getEntryBlock();
TR::Block *tracePrefixCursor = outerLoopHeader;
for (;;)
{
// If this block has only one successor in the trace, move to that one.
// If it has multiple, stop searching.
TR::Block *tracePrefixNext = NULL;
for (auto e = tracePrefixCursor->getSuccessors().begin(); e != tracePrefixCursor->getSuccessors().end(); ++e)
{
TR::Block * const succ = toBlock((*e)->getTo());
if (succ == outerLoopHeader)
continue; // Don't follow back-edges.
if (!searchList(succ, common, lInfo))
continue; // Don't leave the trace.
if (tracePrefixNext != NULL)
{
// Stop due to branching paths within the trace.
if (trace())
traceMsg(comp(), "Hit a branch without finding a cold side-entry. Will not replicate.\n");
return false;
}
tracePrefixNext = succ;
}
if (tracePrefixNext == NULL)
{
// This is supposed to be impossible, since it means that we've
// iterated over the entire trace without encountering a hot inner
// loop header. But there has to be a hot inner loop header in the
// trace, since we have at least one hot inner loop, and we verified
// in checkInnerLoopFrequencies that each hot inner loop header is in
// the trace.
//
// To see why we must have iterated over the entire trace, consider
// that reaching this point means that we haven't returned due to
// finding a branch within the trace. For any block on the trace,
// there is a path to it from outerLoopHeader, and that path has to be
// a prefix of the sequence of blocks considered by this loop.
//
TR_ASSERT(false, "cold side-entry detection ran out of trace\n");
// In production, just safely return false for this case.
if (trace())
traceMsg(comp(), "Ran out of trace without finding a cold side-entry. Will not replicate.\n");
return false;
}
tracePrefixCursor = tracePrefixNext;
if (trace())
traceMsg(comp(), "Checking for cold side-entries targeting block_%d\n", tracePrefixCursor->getNumber());
// If this block is the target of a side-entry from a cold block, good!
// Note that edges into outerLoopHeader are not side-entries, but we're
// not looking at outerLoopHeader here.
TR_ASSERT(tracePrefixCursor != outerLoopHeader,
"cold side-entry detection returned to outerLoopHeader\n");
for (auto e = tracePrefixCursor->getPredecessors().begin(); e != tracePrefixCursor->getPredecessors().end(); ++e)
{
TR::Block * const pred = toBlock((*e)->getFrom());
if (pred->isCold() && !searchList(pred, common, lInfo))
{
if (trace())
traceMsg(comp(), "Found a cold side-entry into block_%d from block_%d. Will replicate.\n", tracePrefixCursor->getNumber(), pred->getNumber());
return true;
}
}
// Don't search past the header of a hot inner loop.
if (hotInnerLoopHeaders->find(tracePrefixCursor))
{
if (trace())
traceMsg(comp(), "Hit a hot inner loop without finding a cold side-entry. Will not replicate.\n");
return false;
}
}
}
bool TR_LoopReplicator::heuristics(LoopInfo *lInfo)
{
// pick a trace in the loop based on some heuristics [basic block frequencies]
// any algorithm can be implemented here; however it should probably have the side
// effect of populating lInfo->_nodesCommon for a given loop
//
TR_RegionStructure *region = lInfo->_region;
if (trace())
traceMsg(comp(), "analyzing region - %d (%p)\n", region->getNumber(), region);
TR::Block *seed = region->getEntryBlock();
BlockEntry *be = new (trStackMemory()) BlockEntry;
be->_block = seed;
(lInfo->_nodesCommon).append(be);
if (trace())
traceMsg(comp(), " adding loop header %d as seed\n", seed->getNumber());
_blocksVisited->set(seed->getNumber());
// select path of desirable successors
TR::Block *X = seed;
TR_Queue<TR::Block> blockq(trMemory());
blockq.enqueue(X);
do
{
X = blockq.dequeue();
if (trace())
traceMsg(comp(), "current candidate block : %d\n", X->getNumber());
X = nextCandidate(X, region, true);
if (!X || searchList(X, common, lInfo))
continue;
else
{
// add this block to the common path
BlockEntry *be = new (trStackMemory()) BlockEntry;
be->_block = X;
_blocksVisited->set(X->getNumber());
(lInfo->_nodesCommon).append(be);
}
blockq.enqueue(X);
} while (!blockq.isEmpty());
// select path of desirable predecessors
#if 0
X = seed;
blockq.enqueue(X);
do
{
X = blockq.dequeue();
if (trace())
dumpOptDetails(comp(), "candidate block - %d\n", X->getNumber());
X = nextCandidate(X, region, false);
if (!X || searchList(X, common, lInfo))
continue;
else
{
// add this block to the common path
BlockEntry *be = new (trStackMemory()) BlockEntry;
be->_block = X;
_blocksVisited->set(X->getNumber());
(lInfo->_nodesCommon).append(be);
}
blockq.enqueue(X);
} while (!blockq.isEmpty());
#endif
// select desirable successors of all blocks
_bStack = new (trStackMemory()) TR_Stack<TR::Block *>(trMemory(), 32, false, stackAlloc);
BlockEntry *bE = NULL;
for (bE = (lInfo->_nodesCommon).getFirst(); bE; bE = bE->getNext())
_bStack->push(bE->_block);
if (trace())
traceMsg(comp(), "attempting to extend trace...\n");
while(!_bStack->isEmpty())
{
X = _bStack->pop();
processBlock(X, region, lInfo);
}
bool checkSideEntrances = true;
if (_maxNestingDepth > 1)
{
checkSideEntrances = checkInnerLoopFrequencies(region, lInfo);
}
if (checkSideEntrances)
lInfo->_replicated = gatherBlocksToBeCloned(lInfo);
else
lInfo->_replicated = false;
logTrace(lInfo);
if (!lInfo->_replicated)
dumpOptDetails(comp(), "no side entrance found into trace; no replication will be performed\n");
return true;
}
void TR_LoopReplicator::logTrace(LoopInfo *lInfo)
{
if (!trace())
return;
traceMsg(comp(), "trace selected in loop :\n");
traceMsg(comp(), "{ ");
for (BlockEntry *be = (lInfo->_nodesCommon).getFirst(); be; be = be->getNext())
traceMsg(comp(), "%d -> ", (be->_block)->getNumber());
traceMsg(comp(), " }\n");
}
TR::Block * TR_LoopReplicator::nextCandidate(TR::Block *X, TR_RegionStructure *region, bool doSucc)
{
TR::CFGEdge *edge = NULL;
TR::Block *seed = region->getEntryBlock();
TR::Block *cand = NULL;
TR::Block *Y = bestSuccessor(region, X, &edge);
if (Y)
{
// could be skipping over inner loops
// in which case edge will be null
if (!edge)
{
if (trace())
traceMsg(comp(), " candidate is %d\n", Y->getNumber());
cand = Y;
}
else if (computeWeight(edge))
{
if (trace())
traceMsg(comp(), " candidate (%d) satisfied weight computation\n", Y->getNumber());
cand = Y;
}
}
return cand;
}
// analyze a block's successors to see if they can be included
void TR_LoopReplicator::processBlock(TR::Block *X, TR_RegionStructure *region, LoopInfo *lInfo)
{
TR::Block *seed = region->getEntryBlock();
for (auto e = X->getSuccessors().begin(); e != X->getSuccessors().end(); ++e)
{
TR::Block *dest = toBlock((*e)->getTo());
// a successor could either be
// 1. cold
// 2. header of inner loop
// 3. back-edge -> header
// 4. loop exit -> exit of the region
// 5. normal loop block
if (dest->isCold())
continue;
else if (isBackEdgeOrLoopExit(*e, region))
continue;
BlockEntry *bE = searchList(dest, common, lInfo);
if (bE && bE->_nonLoop)
continue;
else if (_blocksVisited->get(dest->getNumber()))
continue;
if (computeWeight(*e))
{
if (trace())
traceMsg(comp(), " candidate (%d) satisfied weight computation, extending trace\n", dest->getNumber());
// favorable block found, extend the trace
BlockEntry *bE = new (trStackMemory()) BlockEntry;
bE->_block = dest;
(lInfo->_nodesCommon).append(bE);
_blocksVisited->set(dest->getNumber());
_bStack->push(dest);
}
}
}
bool TR_LoopReplicator::isBackEdgeOrLoopExit(TR::CFGEdge *e, TR_RegionStructure *region, bool testSGraph)
{
// check if this is the loop back-edge or an exit-edge
//
TR_Structure *destStructure = NULL;
if (!testSGraph)
destStructure = toBlock(e->getTo())->getStructureOf();
else
destStructure = toStructureSubGraphNode(e->getTo())->getStructure();
bool notExitEdge = region->contains(destStructure, region->getParent());
if (!notExitEdge || destStructure == region->getEntry()->getStructure())
return true;
return false;
}
bool TR_LoopReplicator::computeWeight(TR::CFGEdge *edge)
{
TR::Block *X = toBlock(edge->getFrom());
TR::Block *Y = toBlock(edge->getTo());
int32_t Xfreq = getBlockFreq(X);
int32_t Yfreq = getBlockFreq(Y);
int32_t seedFreq = _curLoopInfo->_seedFreq;
//float w1 = ((float)(edge->getFrequency()))/(float)Xfreq;
// the criteria currently used is that the successor block
// should be at least T% of the current block and Ts% of
// the seed (seed in our case is the loop entry)
// w(x->y)/w(x) >= T && w(y)/w(s) >= Ts
// where T = block threshold
// Ts = seed threshold
// x,y = blocks and x->y is the edge from x to y
//
float w1 = ((float)Yfreq)/(float)Xfreq;
float w2 = ((float)Yfreq)/(float)seedFreq;
if (trace())
{
traceMsg(comp(), " weighing candidate : %d (Y) predeccessor : %d (X)\n", Y->getNumber(), X->getNumber());
traceMsg(comp(), " w(Y): %d w(X): %d w(seed): %d w(Y)/w(X): %.4f w(Y)/w(seed): %.4f\n", Yfreq, Xfreq,
seedFreq, w1, w2);
}
return (w1 >= BLOCK_THRESHOLD && w2 >= SEED_THRESHOLD) ? true : false;
}
// return the potential successor node in the CFG
TR::Block * TR_LoopReplicator::bestSuccessor(TR_RegionStructure *region, TR::Block *node, TR::CFGEdge **edge)
{
TR::Block *cand = NULL;
if (trace())
traceMsg(comp(), " analyzing region %d (%p)\n", region->getNumber(), region);
int16_t candFreq = -1;
for (auto e = node->getSuccessors().begin(); e != node->getSuccessors().end(); ++e)
{
TR::Block *dest = toBlock((*e)->getTo());
if (trace())
traceMsg(comp(), " analyzing successor block : %d\n", dest->getNumber());
TR_Structure *destStructure = dest->getStructureOf();
TR_Structure *parentStructure = destStructure->getParent();
if (trace())
traceMsg(comp(), " found parent %p is block a direct descendent? (%s)\n", destStructure->getParent(),
(region->contains(parentStructure, region->getParent()) ? "yes" : "no"));
//dumpOptDetails(comp(), "destStruct - %p\n", findNodeInHierarchy(region, destStructure->getNumber()));
// check for exit edges & loop backedges
bool notExitEdge = region->contains(destStructure, region->getParent());
if (!notExitEdge || destStructure == region->getEntry()->getStructure())
{
if (trace())
traceMsg(comp(), " isRegionExit? (%s) successor structure %p\n", (!notExitEdge ? "yes" : "no"),
destStructure);
continue;
}
// ignore cold successors
if (dest->isCold())
continue;
int32_t destFreq = dest->getFrequency();
static char *pEnv = feGetEnv("TR_NewLRTracer");
if (pEnv)
destFreq = _blockWeights[dest->getNumber()];
if (destFreq > candFreq)
{
candFreq = destFreq;
cand = dest;
*edge = *e;
}
}
if (cand)
{
// skip over loops already examined
nextSuccessor(region, &cand, edge);
if (trace())
traceMsg(comp(), " next candidate chosen : %d (Y)\n", cand->getNumber());
}
return cand;
}
// if the current candidate is the start of an inner loop [which would have already been
// analyzed]; this routine skips the loop, picking the inner loop exit
void TR_LoopReplicator::nextSuccessor(TR_RegionStructure *region, TR::Block **cand, TR::CFGEdge **edge)
{
TR::CFGEdge *succEdge = NULL;
TR_Structure *candStructure = (*cand)->getStructureOf();
TR_RegionStructure *parentStructure = candStructure->getParent()->asRegion();
if ((parentStructure != region) &&
(parentStructure && parentStructure->isNaturalLoop()))
{
ListIterator<TR::CFGEdge> eIt(&parentStructure->getExitEdges());
if (trace())
traceMsg(comp(), " inner loop detected : %p , exit edges are :\n", parentStructure);
TR::CFGEdge *e = NULL;
for (e = eIt.getFirst(); e; e = eIt.getNext())
{
// an exit edge could be on either the header or
// the block containing the back edge. search the exit edges
// to see if there is an exit to a block in the outer
// loop [there could be edges to say blocks which throw exceptions
// or return & these blocks will be in the parentstructure of the
// outer loop which is an acyclic region]
TR_Structure *dest = (_blocksInCFG[e->getTo()->getNumber()])->getStructureOf();
TR_Structure *source = (_blocksInCFG[e->getFrom()->getNumber()])->getStructureOf();
if (trace())
traceMsg(comp(), " %d (%p) -> %d (%p)\n", e->getFrom()->getNumber(), source,
e->getTo()->getNumber(), dest);
if (region->contains(dest, region->getParent()))
{
if (trace())
traceMsg(comp(), " found edge to %p (%d)\n", dest, _blocksInCFG[e->getTo()->getNumber()]);
succEdge = e;
break;
}
}
if (!succEdge)
{
// FIXME: this branch should not be taken
TR_ASSERT(succEdge, "loopReplicator: no exit edge found for loop!\n");
*cand = NULL;
*edge = NULL;
return;
}
//if (succEdge)
{
int32_t num = succEdge->getTo()->getNumber();
if (trace())
traceMsg(comp(), " choosing candidate : %d (%p)\n", num, _blocksInCFG[num]);
LoopInfo *lInfo = findLoopInfo(region->getNumber());
TR_ASSERT(lInfo, "no loop info for loop?\n");
// add all the blocks in the inner loop to the current trace
TR_ScratchList<TR::Block> blocksInLoop(trMemory());
parentStructure->getBlocks(&blocksInLoop);
ListIterator<TR::Block> bIt(&blocksInLoop);
for (TR::Block *b = bIt.getFirst(); b; b = bIt.getNext())
{
if (!searchList(b, common, lInfo))
{
BlockEntry *bE = new (trStackMemory()) BlockEntry;
// poison the blocks
bE->_nonLoop = true;
bE->_block = b;
(lInfo->_nodesCommon).append(bE);
_blocksVisited->set(b->getNumber());
}
}
*cand = _blocksInCFG[num];
//*edge = succEdge;
*edge = NULL;
return;
}
}
}
// analyze the trace looking for side-entrances; if any are found, then the loop
// is replicated
bool TR_LoopReplicator::gatherBlocksToBeCloned(LoopInfo *lInfo)
{
TR_RegionStructure *region = lInfo->_region;
TR::Block *entry = region->getEntryBlock();
bool sideEntrance = false;
if (trace())
traceMsg(comp(), "checking for side-entrances :\n");
BlockEntry *be;
for (be = (lInfo->_nodesCommon).getFirst(); be; be = be->getNext())
{