private static boolean canInsertContinue(
BlockNode pred,
List<BlockNode> predecessors,
BlockNode loopEnd,
Set<BlockNode> loopExitNodes) {
if (!pred.contains(AFlag.SYNTHETIC) || BlockUtils.checkLastInsnType(pred, InsnType.CONTINUE)) {
return false;
}
List<BlockNode> preds = pred.getPredecessors();
if (preds.isEmpty()) {
return false;
}
BlockNode codePred = preds.get(0);
if (codePred.contains(AFlag.SKIP)) {
return false;
}
if (loopEnd.isDominator(codePred) || loopExitNodes.contains(codePred)) {
return false;
}
if (isDominatedOnBlocks(codePred, predecessors)) {
return false;
}
boolean gotoExit = false;
for (BlockNode exit : loopExitNodes) {
if (BlockUtils.isPathExists(codePred, exit)) {
gotoExit = true;
break;
}
}
return gotoExit;
}
private boolean insertBreak(RegionStack stack, BlockNode loopExit, Edge exitEdge) {
BlockNode exit = exitEdge.getTarget();
BlockNode insertBlock = null;
boolean confirm = false;
// process special cases
if (loopExit == exit) {
// try/catch at loop end
BlockNode source = exitEdge.getSource();
if (source.contains(AType.CATCH_BLOCK) && source.getSuccessors().size() == 2) {
BlockNode other = BlockUtils.selectOther(loopExit, source.getSuccessors());
if (other != null) {
other = BlockUtils.skipSyntheticSuccessor(other);
if (other.contains(AType.EXC_HANDLER)) {
insertBlock = source;
confirm = true;
}
}
}
}
if (!confirm) {
while (exit != null) {
if (insertBlock != null && isPathExists(loopExit, exit)) {
// found cross
if (canInsertBreak(insertBlock)) {
confirm = true;
break;
}
return false;
}
insertBlock = exit;
List<BlockNode> cs = exit.getCleanSuccessors();
exit = cs.size() == 1 ? cs.get(0) : null;
}
}
if (!confirm) {
return false;
}
InsnNode breakInsn = new InsnNode(InsnType.BREAK, 0);
insertBlock.getInstructions().add(breakInsn);
stack.addExit(exit);
// add label to 'break' if needed
addBreakLabel(exitEdge, exit, breakInsn);
return true;
}
private boolean canInsertBreak(BlockNode exit) {
if (exit.contains(AFlag.RETURN) || BlockUtils.checkLastInsnType(exit, InsnType.BREAK)) {
return false;
}
List<BlockNode> simplePath = BlockUtils.buildSimplePath(exit);
if (!simplePath.isEmpty()) {
BlockNode lastBlock = simplePath.get(simplePath.size() - 1);
if (lastBlock.contains(AFlag.RETURN) || lastBlock.getSuccessors().isEmpty()) {
return false;
}
}
// check if there no outer switch (TODO: very expensive check)
Set<BlockNode> paths = BlockUtils.getAllPathsBlocks(mth.getEnterBlock(), exit);
for (BlockNode block : paths) {
if (BlockUtils.checkLastInsnType(block, InsnType.SWITCH)) {
return false;
}
}
return true;
}
/** Recursively traverse all blocks from 'block' until block from 'exits' */
private BlockNode traverse(IRegion r, BlockNode block, RegionStack stack) {
BlockNode next = null;
boolean processed = false;
List<LoopInfo> loops = block.getAll(AType.LOOP);
int loopCount = loops.size();
if (loopCount != 0 && block.contains(AFlag.LOOP_START)) {
if (loopCount == 1) {
next = processLoop(r, loops.get(0), stack);
processed = true;
} else {
for (LoopInfo loop : loops) {
if (loop.getStart() == block) {
next = processLoop(r, loop, stack);
processed = true;
break;
}
}
}
}
if (!processed && block.getInstructions().size() == 1) {
InsnNode insn = block.getInstructions().get(0);
switch (insn.getType()) {
case IF:
next = processIf(r, block, (IfNode) insn, stack);
processed = true;
break;
case SWITCH:
next = processSwitch(r, block, (SwitchNode) insn, stack);
processed = true;
break;
case MONITOR_ENTER:
next = processMonitorEnter(r, block, insn, stack);
processed = true;
break;
default:
break;
}
}
if (!processed) {
r.getSubBlocks().add(block);
next = getNextBlock(block);
}
if (next != null && !stack.containsExit(block) && !stack.containsExit(next)) {
return next;
}
return null;
}
/** Select loop exit and construct LoopRegion */
private LoopRegion makeLoopRegion(IRegion curRegion, LoopInfo loop, List<BlockNode> exitBlocks) {
for (BlockNode block : exitBlocks) {
if (block.contains(AType.EXC_HANDLER)
|| block.getInstructions().size() != 1
|| block.getInstructions().get(0).getType() != InsnType.IF) {
continue;
}
List<LoopInfo> loops = block.getAll(AType.LOOP);
if (!loops.isEmpty() && loops.get(0) != loop) {
// skip nested loop condition
continue;
}
LoopRegion loopRegion = new LoopRegion(curRegion, loop, block, block == loop.getEnd());
boolean found;
if (block == loop.getStart()
|| block == loop.getEnd()
|| BlockUtils.isEmptySimplePath(loop.getStart(), block)) {
found = true;
} else if (block.getPredecessors().contains(loop.getStart())) {
loopRegion.setPreCondition(loop.getStart());
// if we can't merge pre-condition this is not correct header
found = loopRegion.checkPreCondition();
} else {
found = false;
}
if (found) {
List<LoopInfo> list = mth.getAllLoopsForBlock(block);
if (list.size() >= 2) {
// bad condition if successors going out of all loops
boolean allOuter = true;
for (BlockNode outerBlock : block.getCleanSuccessors()) {
List<LoopInfo> outLoopList = mth.getAllLoopsForBlock(outerBlock);
outLoopList.remove(loop);
if (!outLoopList.isEmpty()) {
// goes to outer loop
allOuter = false;
break;
}
}
if (allOuter) {
found = false;
}
}
}
if (found) {
return loopRegion;
}
}
// no exit found => endless loop
return null;
}
private BlockNode processIf(
IRegion currentRegion, BlockNode block, IfNode ifnode, RegionStack stack) {
if (block.contains(AFlag.SKIP)) {
// block already included in other 'if' region
return ifnode.getThenBlock();
}
IfInfo currentIf = makeIfInfo(block);
IfInfo mergedIf = mergeNestedIfNodes(currentIf);
if (mergedIf != null) {
currentIf = mergedIf;
} else {
// invert simple condition (compiler often do it)
currentIf = IfInfo.invert(currentIf);
}
IfInfo modifiedIf = IfMakerHelper.restructureIf(mth, block, currentIf);
if (modifiedIf != null) {
currentIf = modifiedIf;
} else {
if (currentIf.getMergedBlocks().size() <= 1) {
return null;
}
currentIf = makeIfInfo(block);
currentIf = IfMakerHelper.restructureIf(mth, block, currentIf);
if (currentIf == null) {
// all attempts failed
return null;
}
}
confirmMerge(currentIf);
IfRegion ifRegion = new IfRegion(currentRegion, block);
ifRegion.setCondition(currentIf.getCondition());
currentRegion.getSubBlocks().add(ifRegion);
stack.push(ifRegion);
stack.addExit(currentIf.getOutBlock());
ifRegion.setThenRegion(makeRegion(currentIf.getThenBlock(), stack));
BlockNode elseBlock = currentIf.getElseBlock();
if (elseBlock == null || stack.containsExit(elseBlock)) {
ifRegion.setElseRegion(null);
} else {
ifRegion.setElseRegion(makeRegion(elseBlock, stack));
}
stack.pop();
return currentIf.getOutBlock();
}
private static void fixLastTryCatchAssign(MethodNode mth) {
for (BlockNode block : mth.getBasicBlocks()) {
PhiListAttr phiList = block.get(AType.PHI_LIST);
if (phiList == null || !block.contains(AType.EXC_HANDLER)) {
continue;
}
for (PhiInsn phi : phiList.getList()) {
for (int i = 0; i < phi.getArgsCount(); i++) {
RegisterArg arg = phi.getArg(i);
InsnNode parentInsn = arg.getAssignInsn();
if (parentInsn != null
&& parentInsn.getResult() != null
&& parentInsn.contains(AFlag.TRY_LEAVE)) {
phi.removeArg(arg);
}
}
}
}
}
private BlockNode makeEndlessLoop(
IRegion curRegion, RegionStack stack, LoopInfo loop, BlockNode loopStart) {
LoopRegion loopRegion = new LoopRegion(curRegion, loop, null, false);
curRegion.getSubBlocks().add(loopRegion);
loopStart.remove(AType.LOOP);
stack.push(loopRegion);
BlockNode loopExit = null;
// insert 'break' for exits
List<Edge> exitEdges = loop.getExitEdges();
for (Edge exitEdge : exitEdges) {
BlockNode exit = exitEdge.getTarget();
if (insertBreak(stack, exit, exitEdge)) {
BlockNode nextBlock = getNextBlock(exit);
if (nextBlock != null) {
stack.addExit(nextBlock);
loopExit = nextBlock;
}
}
}
Region body = makeRegion(loopStart, stack);
BlockNode loopEnd = loop.getEnd();
if (!RegionUtils.isRegionContainsBlock(body, loopEnd)
&& !loopEnd.contains(AType.EXC_HANDLER)
&& !inExceptionHandlerBlocks(loopEnd)) {
body.getSubBlocks().add(loopEnd);
}
loopRegion.setBody(body);
if (loopExit == null) {
BlockNode next = getNextBlock(loopEnd);
loopExit = RegionUtils.isRegionContainsBlock(body, next) ? null : next;
}
stack.pop();
loopStart.addAttr(AType.LOOP, loop);
return loopExit;
}
private BlockNode processSwitch(
IRegion currentRegion, BlockNode block, SwitchNode insn, RegionStack stack) {
SwitchRegion sw = new SwitchRegion(currentRegion, block);
currentRegion.getSubBlocks().add(sw);
int len = insn.getTargets().length;
// sort by target
Map<Integer, List<Object>> casesMap = new LinkedHashMap<Integer, List<Object>>(len);
for (int i = 0; i < len; i++) {
Object key = insn.getKeys()[i];
int targ = insn.getTargets()[i];
List<Object> keys = casesMap.get(targ);
if (keys == null) {
keys = new ArrayList<Object>(2);
casesMap.put(targ, keys);
}
keys.add(key);
}
Map<BlockNode, List<Object>> blocksMap = new LinkedHashMap<BlockNode, List<Object>>(len);
for (Map.Entry<Integer, List<Object>> entry : casesMap.entrySet()) {
BlockNode c = getBlockByOffset(entry.getKey(), block.getSuccessors());
assert c != null;
blocksMap.put(c, entry.getValue());
}
BlockNode defCase = getBlockByOffset(insn.getDefaultCaseOffset(), block.getSuccessors());
if (defCase != null) {
blocksMap.remove(defCase);
}
LoopInfo loop = mth.getLoopForBlock(block);
Map<BlockNode, BlockNode> fallThroughCases = new LinkedHashMap<BlockNode, BlockNode>();
List<BlockNode> basicBlocks = mth.getBasicBlocks();
BitSet outs = new BitSet(basicBlocks.size());
outs.or(block.getDomFrontier());
for (BlockNode s : block.getCleanSuccessors()) {
BitSet df = s.getDomFrontier();
// fall through case block
if (df.cardinality() > 1) {
if (df.cardinality() > 2) {
LOG.debug("Unexpected case pattern, block: {}, mth: {}", s, mth);
} else {
BlockNode first = basicBlocks.get(df.nextSetBit(0));
BlockNode second = basicBlocks.get(df.nextSetBit(first.getId() + 1));
if (second.getDomFrontier().get(first.getId())) {
fallThroughCases.put(s, second);
df = new BitSet(df.size());
df.set(first.getId());
} else if (first.getDomFrontier().get(second.getId())) {
fallThroughCases.put(s, first);
df = new BitSet(df.size());
df.set(second.getId());
}
}
}
outs.or(df);
}
outs.clear(block.getId());
if (loop != null) {
outs.clear(loop.getStart().getId());
}
stack.push(sw);
stack.addExits(BlockUtils.bitSetToBlocks(mth, outs));
// check cases order if fall through case exists
if (!fallThroughCases.isEmpty()) {
if (isBadCasesOrder(blocksMap, fallThroughCases)) {
LOG.debug("Fixing incorrect switch cases order, method: {}", mth);
blocksMap = reOrderSwitchCases(blocksMap, fallThroughCases);
if (isBadCasesOrder(blocksMap, fallThroughCases)) {
LOG.error("Can't fix incorrect switch cases order, method: {}", mth);
mth.add(AFlag.INCONSISTENT_CODE);
}
}
}
// filter 'out' block
if (outs.cardinality() > 1) {
// remove exception handlers
BlockUtils.cleanBitSet(mth, outs);
}
if (outs.cardinality() > 1) {
// filter loop start and successors of other blocks
for (int i = outs.nextSetBit(0); i >= 0; i = outs.nextSetBit(i + 1)) {
BlockNode b = basicBlocks.get(i);
outs.andNot(b.getDomFrontier());
if (b.contains(AFlag.LOOP_START)) {
outs.clear(b.getId());
} else {
for (BlockNode s : b.getCleanSuccessors()) {
outs.clear(s.getId());
}
}
}
}
if (loop != null && outs.cardinality() > 1) {
outs.clear(loop.getEnd().getId());
}
if (outs.cardinality() == 0) {
// one or several case blocks are empty,
// run expensive algorithm for find 'out' block
for (BlockNode maybeOut : block.getSuccessors()) {
boolean allReached = true;
for (BlockNode s : block.getSuccessors()) {
if (!isPathExists(s, maybeOut)) {
allReached = false;
break;
}
}
if (allReached) {
outs.set(maybeOut.getId());
break;
}
}
}
BlockNode out = null;
if (outs.cardinality() == 1) {
out = basicBlocks.get(outs.nextSetBit(0));
stack.addExit(out);
} else if (loop == null && outs.cardinality() > 1) {
LOG.warn("Can't detect out node for switch block: {} in {}", block, mth);
}
if (loop != null) {
// check if 'continue' must be inserted
BlockNode end = loop.getEnd();
if (out != end && out != null) {
insertContinueInSwitch(block, out, end);
}
}
if (!stack.containsExit(defCase)) {
sw.setDefaultCase(makeRegion(defCase, stack));
}
for (Entry<BlockNode, List<Object>> entry : blocksMap.entrySet()) {
BlockNode caseBlock = entry.getKey();
if (stack.containsExit(caseBlock)) {
// empty case block
sw.addCase(entry.getValue(), new Region(stack.peekRegion()));
} else {
BlockNode next = fallThroughCases.get(caseBlock);
stack.addExit(next);
Region caseRegion = makeRegion(caseBlock, stack);
stack.removeExit(next);
if (next != null) {
next.add(AFlag.FALL_THROUGH);
caseRegion.add(AFlag.FALL_THROUGH);
}
sw.addCase(entry.getValue(), caseRegion);
// 'break' instruction will be inserted in RegionMakerVisitor.PostRegionVisitor
}
}
stack.pop();
return out;
}
private BlockNode processLoop(IRegion curRegion, LoopInfo loop, RegionStack stack) {
BlockNode loopStart = loop.getStart();
Set<BlockNode> exitBlocksSet = loop.getExitNodes();
// set exit blocks scan order priority
// this can help if loop have several exits (after using 'break' or 'return' in loop)
List<BlockNode> exitBlocks = new ArrayList<BlockNode>(exitBlocksSet.size());
BlockNode nextStart = getNextBlock(loopStart);
if (nextStart != null && exitBlocksSet.remove(nextStart)) {
exitBlocks.add(nextStart);
}
if (exitBlocksSet.remove(loopStart)) {
exitBlocks.add(loopStart);
}
if (exitBlocksSet.remove(loop.getEnd())) {
exitBlocks.add(loop.getEnd());
}
exitBlocks.addAll(exitBlocksSet);
LoopRegion loopRegion = makeLoopRegion(curRegion, loop, exitBlocks);
if (loopRegion == null) {
BlockNode exit = makeEndlessLoop(curRegion, stack, loop, loopStart);
insertContinue(loop);
return exit;
}
curRegion.getSubBlocks().add(loopRegion);
IRegion outerRegion = stack.peekRegion();
stack.push(loopRegion);
IfInfo condInfo = makeIfInfo(loopRegion.getHeader());
condInfo = searchNestedIf(condInfo);
confirmMerge(condInfo);
if (!loop.getLoopBlocks().contains(condInfo.getThenBlock())) {
// invert loop condition if 'then' points to exit
condInfo = IfInfo.invert(condInfo);
}
loopRegion.setCondition(condInfo.getCondition());
exitBlocks.removeAll(condInfo.getMergedBlocks());
if (!exitBlocks.isEmpty()) {
BlockNode loopExit = condInfo.getElseBlock();
if (loopExit != null) {
// add 'break' instruction before path cross between main loop exit and sub-exit
for (Edge exitEdge : loop.getExitEdges()) {
if (!exitBlocks.contains(exitEdge.getSource())) {
continue;
}
insertBreak(stack, loopExit, exitEdge);
}
}
}
BlockNode out;
if (loopRegion.isConditionAtEnd()) {
BlockNode thenBlock = condInfo.getThenBlock();
out = thenBlock == loopStart ? condInfo.getElseBlock() : thenBlock;
loopStart.remove(AType.LOOP);
loop.getEnd().add(AFlag.SKIP);
stack.addExit(loop.getEnd());
loopRegion.setBody(makeRegion(loopStart, stack));
loopStart.addAttr(AType.LOOP, loop);
loop.getEnd().remove(AFlag.SKIP);
} else {
out = condInfo.getElseBlock();
if (outerRegion != null
&& out.contains(AFlag.LOOP_START)
&& !out.getAll(AType.LOOP).contains(loop)
&& RegionUtils.isRegionContainsBlock(outerRegion, out)) {
// exit to already processed outer loop
out = null;
}
stack.addExit(out);
BlockNode loopBody = condInfo.getThenBlock();
Region body = makeRegion(loopBody, stack);
// add blocks from loop start to first condition block
BlockNode conditionBlock = condInfo.getIfBlock();
if (loopStart != conditionBlock) {
Set<BlockNode> blocks = BlockUtils.getAllPathsBlocks(loopStart, conditionBlock);
blocks.remove(conditionBlock);
for (BlockNode block : blocks) {
if (block.getInstructions().isEmpty()
&& !block.contains(AFlag.SKIP)
&& !RegionUtils.isRegionContainsBlock(body, block)) {
body.add(block);
}
}
}
loopRegion.setBody(body);
}
stack.pop();
insertContinue(loop);
return out;
}