C++ IRInstruction::getParent方法代码示例

void initInstructions(Trace* trace, IRInstruction::List& wl) {
  IRInstruction::List instructions = trace->getInstructionList();
  IRInstruction::Iterator it;
  bool unreachable = false;
  TRACE(5, "DCE:vvvvvvvvvvvvvvvvvvvv\n");
  for (it = instructions.begin(); it != instructions.end(); it++) {
    IRInstruction* inst = *it;
    ASSERT(inst->getParent() == trace);
    Simplifier::copyProp(inst);
    // if this is a load that does not generate a guard, then get rid
    // of its label so that its not an essential control-flow
    // instruction
    if (isUnguardedLoad(inst)) {
      // LdStack and LdLoc instructions that produce generic types
      // and LdStack instruction that produce Cell types will not
      // generate guards, so remove the label from this instruction so
      // that its no longer an essential control-flow instruction
      inst->setLabel(NULL);
    }
    Opcode opc = inst->getOpcode();
    // decref of anything that isn't ref counted is a nop
    if ((opc == DecRef || opc == DecRefNZ) && !isRefCounted(inst->getSrc(0))) {
      inst->setId(DEAD);
      continue;
    }
    if (!unreachable && inst->isControlFlowInstruction()) {
      // mark the destination label so that the destination trace
      // is marked reachable
      inst->getLabel()->setId(LIVE);
    }
    if (!unreachable && isEssential(inst)) {
      inst->setId(LIVE);
      wl.push_back(inst);
    } else {
      if (moduleEnabled(HPHP::Trace::hhir, 5)) {
        std::ostringstream ss1;
        inst->printSrcs(ss1);
        TRACE(5, "DCE: %s\n", ss1.str().c_str());
        std::ostringstream ss2;
        inst->print(ss2);
        TRACE(5, "DCE: %s\n", ss2.str().c_str());
      }
      inst->setId(DEAD);
    }
    if (inst->getOpcode() == Jmp_) {
      unreachable = true;
    }
  }
  TRACE(5, "DCE:^^^^^^^^^^^^^^^^^^^^\n");
}

void eliminateDeadCode(Trace* trace, IRFactory* irFactory) {
  IRInstruction::List wl; // worklist of live instructions
  Trace::List& exitTraces = trace->getExitTraces();
  // first mark all exit traces as unreachable by setting the id on
  // their labels to 0
  for (Trace::Iterator it = exitTraces.begin();
       it != exitTraces.end();
       it++) {
    Trace* trace = *it;
    trace->getLabel()->setId(DEAD);
  }

  // mark the essential instructions and add them to the initial
  // work list; also mark the exit traces that are reachable by
  // any control flow instruction in the main trace.
  initInstructions(trace, wl);
  for (Trace::Iterator it = exitTraces.begin();
       it != exitTraces.end();
       it++) {
    // only process those exit traces that are reachable from
    // the main trace
    Trace* trace = *it;
    if (trace->getLabel()->getId() != DEAD) {
      initInstructions(trace, wl);
    }
  }

  // process the worklist
  while (!wl.empty()) {
    IRInstruction* inst = wl.front();
    wl.pop_front();
    for (uint32 i = 0; i < inst->getNumSrcs(); i++) {
      SSATmp* src = inst->getSrc(i);
      if (src->getInstruction()->isDefConst()) {
        continue;
      }
      IRInstruction* srcInst = src->getInstruction();
      if (srcInst->getId() == DEAD) {
        srcInst->setId(LIVE);
        wl.push_back(srcInst);
      }
      // <inst> consumes <srcInst> which is an IncRef,
      // so we mark <srcInst> as REFCOUNT_CONSUMED.
      if (inst->consumesReference(i) && srcInst->getOpcode() == IncRef) {
        if (inst->getParent()->isMain() || !srcInst->getParent()->isMain()) {
          // <srcInst> is consumed from its own trace.
          srcInst->setId(REFCOUNT_CONSUMED);
        } else {
          // <srcInst> is consumed off trace.
          if (srcInst->getId() != REFCOUNT_CONSUMED) {
            // mark <srcInst> as REFCOUNT_CONSUMED_OFF_TRACE unless it is
            // also consumed from its own trace.
            srcInst->setId(REFCOUNT_CONSUMED_OFF_TRACE);
          }
        }
      }
    }
  }

  // Optimize IncRefs and DecRefs.
  optimizeRefCount(trace);
  for (Trace::Iterator it = exitTraces.begin(); it != exitTraces.end(); ++it) {
    optimizeRefCount(*it);
  }

  if (RuntimeOption::EvalHHIREnableSinking) {
    // Sink IncRefs consumed off trace.
    IRInstruction::List toSink;
    sinkIncRefs(trace, irFactory, toSink);
  }

  // now remove instructions whose id == DEAD
  removeDeadInstructions(trace);
  for (Trace::Iterator it = exitTraces.begin(); it != exitTraces.end(); it++) {
    removeDeadInstructions(*it);
  }

  // If main trace ends with an unconditional jump, copy the target of
  // the jump to the end of the trace
  IRInstruction::List& instList = trace->getInstructionList();
  IRInstruction::Iterator lastInst = instList.end();
  lastInst--; // go back to the last instruction
  IRInstruction* jmpInst = *lastInst;
  if (jmpInst->getOpcode() == Jmp_) {
    Trace* targetTrace = jmpInst->getLabel()->getTrace();
    IRInstruction::List& targetInstList = targetTrace->getInstructionList();
    IRInstruction::Iterator instIter = targetInstList.begin();
    instIter++; // skip over label
    // update the parent trace of the moved instructions
    for (IRInstruction::Iterator it = instIter;
         it != targetInstList.end();
         ++it) {
      (*it)->setParent(trace);
    }
    instList.splice(lastInst, targetInstList, instIter, targetInstList.end());
    // delete the jump instruction
    instList.erase(lastInst);
  }

  // If main trace ends with a conditional jump with no side-effects on exit,
//.........这里部分代码省略.........