// Sink IncRefs consumed off trace.
// When <trace> is an exit trace, <toSink> contains all live IncRefs in the
// main trace that are consumed off trace.
void sinkIncRefs(Trace* trace,
IRFactory* irFactory,
IRInstruction::List& toSink) {
IRInstruction::List& instList = trace->getInstructionList();
IRInstruction::Iterator it;
std::map<SSATmp*, SSATmp*> sunkTmps;
if (!trace->isMain()) {
// Sink REFCOUNT_CONSUMED_OFF_TRACE IncRefs before the first non-label
// instruction, and create a mapping between the original tmps to the sunk
// tmps so that we can later replace the original ones with the sunk ones.
for (IRInstruction::ReverseIterator j = toSink.rbegin();
j != toSink.rend();
++j) {
// prependInstruction inserts an instruction to the beginning. Therefore,
// we iterate through toSink in the reversed order.
IRInstruction* sunkInst = irFactory->incRef((*j)->getSrc(0));
sunkInst->setId(LIVE);
trace->prependInstruction(sunkInst);
ASSERT((*j)->getDst());
ASSERT(!sunkTmps.count((*j)->getDst()));
sunkTmps[(*j)->getDst()] = irFactory->getSSATmp(sunkInst);
}
}
// An exit trace may be entered from multiple exit points. We keep track of
// which exit traces we already pushed sunk IncRefs to, so that we won't push
// them multiple times.
std::set<Trace*> pushedTo;
for (it = instList.begin(); it != instList.end(); ++it) {
IRInstruction* inst = *it;
if (trace->isMain()) {
if (inst->getOpcode() == IncRef) {
// Must be REFCOUNT_CONSUMED or REFCOUNT_CONSUMED_OFF_TRACE;
// otherwise, it should be already removed in optimizeRefCount.
ASSERT(inst->getId() == REFCOUNT_CONSUMED ||
inst->getId() == REFCOUNT_CONSUMED_OFF_TRACE);
if (inst->getId() == REFCOUNT_CONSUMED_OFF_TRACE) {
inst->setOpcode(Mov);
// Mark them as dead so that they'll be removed later.
inst->setId(DEAD);
// Put all REFCOUNT_CONSUMED_OFF_TRACE IncRefs to the sinking list.
toSink.push_back(inst);
}
}
if (inst->getOpcode() == DecRefNZ) {
IRInstruction* srcInst = inst->getSrc(0)->getInstruction();
if (srcInst->getId() == DEAD) {
inst->setId(DEAD);
// This may take O(I) time where I is the number of IncRefs
// in the main trace.
toSink.remove(srcInst);
}
}
if (LabelInstruction* label = inst->getLabel()) {
Trace* exitTrace = label->getTrace();
if (!pushedTo.count(exitTrace)) {
pushedTo.insert(exitTrace);
sinkIncRefs(exitTrace, irFactory, toSink);
}
}
} else {
// Replace the original tmps with the sunk tmps.
for (uint32 i = 0; i < inst->getNumSrcs(); ++i) {
SSATmp* src = inst->getSrc(i);
if (SSATmp* sunkTmp = sunkTmps[src]) {
inst->setSrc(i, sunkTmp);
}
}
}
}
// Do copyProp at last, because we need to keep REFCOUNT_CONSUMED_OFF_TRACE
// Movs as the prototypes for sunk instructions.
for (it = instList.begin(); it != instList.end(); ++it) {
Simplifier::copyProp(*it);
}
}