/**
* Constructs and inserts a new empty GOTO block {@code Z} between this block ({@code A}) and a
* current successor block ({@code B}). The new block will replace B as A's successor and A as B's
* predecessor. A and B will no longer be directly connected. If B is listed as a successor
* multiple times, all references are replaced.
*
* @param other current successor (B)
* @return {@code non-null;} an appropriately-constructed instance
*/
public SsaBasicBlock insertNewSuccessor(SsaBasicBlock other) {
SsaBasicBlock newSucc = parent.makeNewGotoBlock();
if (!successors.get(other.index)) {
throw new RuntimeException(
"Block " + other.getRopLabelString() + " not successor of " + getRopLabelString());
}
// Update the new block.
newSucc.predecessors.set(this.index);
newSucc.successors.set(other.index);
newSucc.successorList.add(other.index);
newSucc.primarySuccessor = other.index;
// Update us.
for (int i = successorList.size() - 1; i >= 0; i--) {
if (successorList.get(i) == other.index) {
successorList.set(i, newSucc.index);
}
}
if (primarySuccessor == other.index) {
primarySuccessor = newSucc.index;
}
successors.clear(other.index);
successors.set(newSucc.index);
// Update "other".
other.predecessors.set(newSucc.index);
other.predecessors.set(index, successors.get(other.index));
return newSucc;
}
/**
* Inserts a new empty GOTO block as a predecessor to this block. All previous predecessors will
* be predecessors to the new block.
*
* @return {@code non-null;} an appropriately-constructed instance
*/
public SsaBasicBlock insertNewPredecessor() {
SsaBasicBlock newPred = parent.makeNewGotoBlock();
// Update the new block.
newPred.predecessors = predecessors;
newPred.successors.set(index);
newPred.successorList.add(index);
newPred.primarySuccessor = index;
// Update us.
predecessors = new BitSet(parent.getBlocks().size());
predecessors.set(newPred.index);
// Update our (soon-to-be) old predecessors.
for (int i = newPred.predecessors.nextSetBit(0);
i >= 0;
i = newPred.predecessors.nextSetBit(i + 1)) {
SsaBasicBlock predBlock = parent.getBlocks().get(i);
predBlock.replaceSuccessor(index, newPred.index);
}
return newPred;
}
/**
* Creates a new SSA basic block from a ROP form basic block.
*
* @param rmeth original method
* @param basicBlockIndex index this block will have
* @param parent method of this block predecessor set will be updated
* @return new instance
*/
public static SsaBasicBlock newFromRop(
RopMethod rmeth, int basicBlockIndex, final SsaMethod parent) {
BasicBlockList ropBlocks = rmeth.getBlocks();
BasicBlock bb = ropBlocks.get(basicBlockIndex);
SsaBasicBlock result = new SsaBasicBlock(basicBlockIndex, bb.getLabel(), parent);
InsnList ropInsns = bb.getInsns();
result.insns.ensureCapacity(ropInsns.size());
for (int i = 0, sz = ropInsns.size(); i < sz; i++) {
result.insns.add(new NormalSsaInsn(ropInsns.get(i), result));
}
result.predecessors =
SsaMethod.bitSetFromLabelList(ropBlocks, rmeth.labelToPredecessors(bb.getLabel()));
result.successors = SsaMethod.bitSetFromLabelList(ropBlocks, bb.getSuccessors());
result.successorList = SsaMethod.indexListFromLabelList(ropBlocks, bb.getSuccessors());
if (result.successorList.size() != 0) {
int primarySuccessor = bb.getPrimarySuccessor();
result.primarySuccessor =
(primarySuccessor < 0) ? -1 : ropBlocks.indexOfLabel(primarySuccessor);
}
return result;
}
/** Applies the optimization. */
private void run() {
int regSz = ssaMeth.getRegCount();
ArrayList<TypedConstant> constantList = getConstsSortedByCountUse();
int toCollect = Math.min(constantList.size(), MAX_COLLECTED_CONSTANTS);
SsaBasicBlock start = ssaMeth.getEntryBlock();
// Constant to new register containing the constant
HashMap<TypedConstant, RegisterSpec> newRegs =
new HashMap<TypedConstant, RegisterSpec>(toCollect);
for (int i = 0; i < toCollect; i++) {
TypedConstant cst = constantList.get(i);
RegisterSpec result = RegisterSpec.make(ssaMeth.makeNewSsaReg(), cst);
Rop constRop = Rops.opConst(cst);
if (constRop.getBranchingness() == Rop.BRANCH_NONE) {
start.addInsnToHead(
new PlainCstInsn(
Rops.opConst(cst), SourcePosition.NO_INFO, result, RegisterSpecList.EMPTY, cst));
} else {
// We need two new basic blocks along with the new insn
SsaBasicBlock entryBlock = ssaMeth.getEntryBlock();
SsaBasicBlock successorBlock = entryBlock.getPrimarySuccessor();
// Insert a block containing the const insn.
SsaBasicBlock constBlock = entryBlock.insertNewSuccessor(successorBlock);
constBlock.replaceLastInsn(
new ThrowingCstInsn(
constRop, SourcePosition.NO_INFO, RegisterSpecList.EMPTY, StdTypeList.EMPTY, cst));
// Insert a block containing the move-result-pseudo insn.
SsaBasicBlock resultBlock = constBlock.insertNewSuccessor(successorBlock);
PlainInsn insn =
new PlainInsn(
Rops.opMoveResultPseudo(result.getTypeBearer()),
SourcePosition.NO_INFO,
result,
RegisterSpecList.EMPTY);
resultBlock.addInsnToHead(insn);
}
newRegs.put(cst, result);
}
updateConstUses(newRegs, regSz);
}
/**
* Adds a move instruction to the end of this basic block, just before the last instruction. If
* the result of the final instruction is the source in question, then the move is placed at the
* beginning of the primary successor block. This is for unversioned registers.
*
* @param result move destination
* @param source move source
*/
public void addMoveToEnd(RegisterSpec result, RegisterSpec source) {
if (result.getReg() == source.getReg()) {
// Sometimes we end up with no-op moves. Ignore them here.
return;
}
/*
* The last Insn has to be a normal SSA insn: a phi can't branch or
* return or cause an exception, etc.
*/
NormalSsaInsn lastInsn;
lastInsn = (NormalSsaInsn) insns.get(insns.size() - 1);
if (lastInsn.getResult() != null || lastInsn.getSources().size() > 0) {
/*
* The final insn in this block has a source or result register, and
* the moves we may need to place and schedule may interfere. We
* need to insert this instruction at the beginning of the primary
* successor block instead. We know this is safe, because when we
* edge-split earlier, we ensured that each successor has only us as
* a predecessor.
*/
for (int i = successors.nextSetBit(0); i >= 0; i = successors.nextSetBit(i + 1)) {
SsaBasicBlock succ;
succ = parent.getBlocks().get(i);
succ.addMoveToBeginning(result, source);
}
} else {
/*
* We can safely add a move to the end of the block just before the
* last instruction, because the final insn does not assign to
* anything.
*/
RegisterSpecList sources = RegisterSpecList.make(source);
NormalSsaInsn toAdd =
new NormalSsaInsn(
new PlainInsn(Rops.opMove(result.getType()), SourcePosition.NO_INFO, result, sources),
this);
insns.add(insns.size() - 1, toAdd);
movesFromPhisAtEnd++;
}
}
/**
* Processes a single block.
*
* @param blockIndex {@code >= 0;} block index of the block to process
*/
private void processBlock(int blockIndex) {
RegisterSpecSet primaryState = resultInfo.mutableCopyOfStarts(blockIndex);
SsaBasicBlock block = blocks.get(blockIndex);
List<SsaInsn> insns = block.getInsns();
int insnSz = insns.size();
// The exit block has no insns and no successors
if (blockIndex == method.getExitBlockIndex()) {
return;
}
/*
* We may have to treat the last instruction specially: If it
* can (but doesn't always) throw, and the exception can be
* caught within the same method, then we need to use the
* state *before* executing it to be what is merged into
* exception targets.
*/
SsaInsn lastInsn = insns.get(insnSz - 1);
boolean hasExceptionHandlers = lastInsn.getOriginalRopInsn().getCatches().size() != 0;
boolean canThrowDuringLastInsn = hasExceptionHandlers && (lastInsn.getResult() != null);
int freezeSecondaryStateAt = insnSz - 1;
RegisterSpecSet secondaryState = primaryState;
/*
* Iterate over the instructions, adding information for each place
* that the active variable set changes.
*/
for (int i = 0; i < insnSz; i++) {
if (canThrowDuringLastInsn && (i == freezeSecondaryStateAt)) {
// Until this point, primaryState == secondaryState.
primaryState.setImmutable();
primaryState = primaryState.mutableCopy();
}
SsaInsn insn = insns.get(i);
RegisterSpec result;
result = insn.getLocalAssignment();
if (result == null) {
// We may be nuking an existing local
result = insn.getResult();
if (result != null && primaryState.get(result.getReg()) != null) {
primaryState.remove(primaryState.get(result.getReg()));
}
continue;
}
result = result.withSimpleType();
RegisterSpec already = primaryState.get(result);
/*
* The equals() check ensures we only add new info if
* the instruction causes a change to the set of
* active variables.
*/
if (!result.equals(already)) {
/*
* If this insn represents a local moving from one register
* to another, remove the association between the old register
* and the local.
*/
RegisterSpec previous = primaryState.localItemToSpec(result.getLocalItem());
if (previous != null && (previous.getReg() != result.getReg())) {
primaryState.remove(previous);
}
resultInfo.addAssignment(insn, result);
primaryState.put(result);
}
}
primaryState.setImmutable();
/*
* Merge this state into the start state for each successor,
* and update the work set where required (that is, in cases
* where the start state for a block changes).
*/
IntList successors = block.getSuccessorList();
int succSz = successors.size();
int primarySuccessor = block.getPrimarySuccessorIndex();
for (int i = 0; i < succSz; i++) {
int succ = successors.get(i);
RegisterSpecSet state = (succ == primarySuccessor) ? primaryState : secondaryState;
if (resultInfo.mergeStarts(succ, state)) {
workSet.set(succ);
}
}
}
