/**
 * Add to sets coveredNodes and coveredArcs the cfg arcs that are now
 * covered given the new region containing the translations in
 * selectedVec.
 */
static void markCovered(const TransCFG& cfg, const RegionDescPtr region,
                        const TransIDVec& selectedVec, const TransIDSet heads,
                        TransIDSet& coveredNodes,
                        TransCFG::ArcPtrSet& coveredArcs) {
  assert(selectedVec.size() > 0);
  TransID newHead = selectedVec[0];
  assert(!region->empty());
  assert(newHead == getTransId(region->entry()->id()));

  // Mark all region's nodes as covered.
  coveredNodes.insert(selectedVec.begin(), selectedVec.end());

  // Mark all incoming arcs into newHead from covered nodes as covered.
  for (auto arc : cfg.inArcs(newHead)) {
    TransID src = arc->src();
    if (coveredNodes.count(src)) {
      coveredArcs.insert(arc);
    }
  }

  // Mark all CFG arcs within the region as covered.
  region->forEachArc([&](RegionDesc::BlockId src, RegionDesc::BlockId dst) {
    if (!hasTransId(src) || !hasTransId(dst)) return;
    TransID srcTid = getTransId(src);
    TransID dstTid = getTransId(dst);
    assert(cfg.hasArc(srcTid, dstTid));
    bool foundArc = false;
    for (auto arc : cfg.outArcs(srcTid)) {
      if (arc->dst() == dstTid) {
        coveredArcs.insert(arc);
        foundArc = true;
      }
    }
    always_assert(foundArc);
  });

  // Mark all outgoing arcs from the region to a head node as covered.
  for (auto node : selectedVec) {
    for (auto arc : cfg.outArcs(node)) {
      if (heads.count(arc->dst())) {
        coveredArcs.insert(arc);
      }
    }
  }
}

/**
 * Add to sets coveredNodes and coveredArcs the cfg arcs that are now
 * covered given the new region containing the translations in
 * selectedVec.
 */
static void markCovered(const TransCFG& cfg, const TransIDVec selectedVec,
                        const TransIDSet heads, TransIDSet& coveredNodes,
                        TransCFG::ArcPtrSet& coveredArcs) {
  assert(selectedVec.size() > 0);
  TransID newHead = selectedVec[0];

  // Mark all region's nodes as covered.
  coveredNodes.insert(selectedVec.begin(), selectedVec.end());

  // Mark all incoming arcs into newHead from covered nodes as covered.
  for (auto arc : cfg.inArcs(newHead)) {
    TransID src = arc->src();
    if (coveredNodes.count(src)) {
      coveredArcs.insert(arc);
    }
  }

  // Mark all arcs between consecutive region nodes as covered.
  for (size_t i = 0; i < selectedVec.size() - 1; i++) {
    TransID node = selectedVec[i];
    TransID next = selectedVec[i + 1];
    bool foundArc = false;
    for (auto arc : cfg.outArcs(node)) {
      if (arc->dst() == next) {
        coveredArcs.insert(arc);
        foundArc = true;
      }
    }
    always_assert(foundArc);
  }

  // Mark all outgoing arcs from the region to a head node as covered.
  for (auto node : selectedVec) {
    for (auto arc : cfg.outArcs(node)) {
      if (heads.count(arc->dst())) {
        coveredArcs.insert(arc);
      }
    }
  }
}

/**
 * Returns the sum of the weights of the arcs going from srcs to dst.
 */
static int64_t interRegionWeight(const TransIDVec& srcs,
                                 TransID           dst,
                                 const TransCFG&   cfg) {
  int64_t totalWeight = 0;
  for (auto src : srcs) {
    for (auto arc : cfg.outArcs(src)) {
      if (arc->dst() == dst) {
        totalWeight += arc->weight();
      }
    }
  }
  return totalWeight;
}

/**
 * Sorts the regions vector in a linear order to be used for
 * translation.  The goal is to obtain an order that improves locality
 * when the function is executed.  Each region is translated separately.
 */
static void sortRegions(RegionVec&                  regions,
                        const Func*                 func,
                        const TransCFG&             cfg,
                        const ProfData*             profData,
                        const TransIDToRegionMap&   headToRegion,
                        const RegionToTransIDsMap&  regionToTransIds) {
  RegionVec sorted;
  RegionSet selected;

  if (regions.empty()) return;

  // First, pick the region starting at the lowest bytecode offset.
  // This will normally correspond to the main function entry (for
  // normal, regular bytecode), but it may not be for irregular
  // functions written in hhas (like array_map and array_filter).  If
  // there multiple regions starting at the lowest bytecode offset,
  // pick the one with the largest profile weight.
  RegionDescPtr entryRegion = nullptr;
  int64_t    maxEntryWeight = -1;
  Offset     lowestOffset   = kInvalidOffset;
  for (const auto& pair : regionToTransIds) {
    auto  r    = pair.first;
    auto& tids = pair.second;
    TransID firstTid = tids[0];
    Offset firstOffset = profData->transSrcKey(firstTid).offset();
    int64_t weight = cfg.weight(firstTid);
    if (lowestOffset == kInvalidOffset || firstOffset < lowestOffset ||
        (firstOffset == lowestOffset && weight > maxEntryWeight)) {
      entryRegion    = r;
      maxEntryWeight = weight;
      lowestOffset   = firstOffset;
    }
  }

  assert(entryRegion);
  sorted.push_back(entryRegion);
  selected.insert(entryRegion);

  RegionDescPtr region = entryRegion;
  // Select the remaining regions, iteratively picking the most likely
  // region to execute next.
  for (auto i = 1; i < regions.size(); i++) {
    int64_t      maxWeight = -1;
    int64_t  maxHeadWeight = -1;
    RegionDescPtr bestNext = nullptr;
    auto    regionTransIds = getRegionTransIDVec(regionToTransIds, region);
    for (auto next : regions) {
      if (selected.count(next)) continue;
      auto nextTransIds = getRegionTransIDVec(regionToTransIds, next);
      int64_t weight = interRegionWeight(regionTransIds, nextTransIds[0], cfg);
      int64_t headWeight = cfg.weight(nextTransIds[0]);
      if ((weight >  maxWeight) ||
          (weight == maxWeight && headWeight > maxHeadWeight)) {
        maxWeight     = weight;
        maxHeadWeight = headWeight;
        bestNext      = next;
      }
    }
    assert(bestNext);
    sorted.push_back(bestNext);
    selected.insert(bestNext);
    region = bestNext;
  }

  assert(sorted.size() == regions.size());
  regions = sorted;

  if (debug && Trace::moduleEnabled(HPHP::Trace::pgo, 5)) {
    for (size_t i = 0; i < regions.size(); i++) {
      auto r = regions[i];
      auto tids = getRegionTransIDVec(regionToTransIds, r);
      std::string transIds = folly::join(", ", tids);
      FTRACE(6, "sortRegions: region[{}]: {}\n", i, transIds);
    }
  }
}

RegionDescPtr selectHotTrace(TransID triggerId,
                             const ProfData* profData,
                             TransCFG& cfg,
                             TransIDSet& selectedSet,
                             TransIDVec* selectedVec) {
  auto region = std::make_shared<RegionDesc>();
  TransID tid    = triggerId;
  TransID prevId = kInvalidTransID;
  selectedSet.clear();
  if (selectedVec) selectedVec->clear();

  PostConditions accumPostConds;
  // Maps BlockIds to the set of BC offsets for its successor blocks.
  // Used to prevent multiple successors with the same SrcKey for now.
  // This can go away once task #4157613 is done.
  hphp_hash_map<RegionDesc::BlockId, SrcKeySet> succSKSet;

  // Maps from BlockIds to accumulated post conditions for that block.
  // Used to determine if we can add branch-over edges by checking the
  // pre-conditions of the successor block.
  hphp_hash_map<RegionDesc::BlockId, PostConditions> blockPostConds;

  while (!selectedSet.count(tid)) {

    RegionDescPtr blockRegion = profData->transRegion(tid);
    if (blockRegion == nullptr) break;

    // If the debugger is attached, only allow single-block regions.
    if (prevId != kInvalidTransID && isDebuggerAttachedProcess()) {
      FTRACE(2, "selectHotTrace: breaking region at Translation {} "
             "because of debugger is attached\n", tid);
      break;
    }

    // Break if block is not the first and requires reffiness checks.
    // Task #2589970: fix translateRegion to support mid-region reffiness checks
    if (prevId != kInvalidTransID) {
      auto nRefDeps = blockRegion->blocks[0]->reffinessPreds().size();
      if (nRefDeps > 0) {
        FTRACE(2, "selectHotTrace: breaking region because of refDeps ({}) at "
               "Translation {}\n", nRefDeps, tid);
        break;
      }
    }

    // Break if block is not the first and it corresponds to the main
    // function body entry.  This is to prevent creating multiple
    // large regions containing the function body (starting at various
    // DV funclets).
    if (prevId != kInvalidTransID) {
      const Func* func = profData->transFunc(tid);
      Offset  bcOffset = profData->transStartBcOff(tid);
      if (func->base() == bcOffset) {
        FTRACE(2, "selectHotTrace: breaking region because reached the main "
               "function body entry at Translation {} (BC offset {})\n",
               tid, bcOffset);
        break;
      }
    }

    if (prevId != kInvalidTransID) {
      auto sk = profData->transSrcKey(tid);
      if (profData->optimized(sk)) {
        FTRACE(2, "selectHotTrace: breaking region because next sk already "
               "optimized, for Translation {}\n", tid);
        break;
      }
    }

    // Break trace if translation tid cannot follow the execution of
    // the entire translation prevId.  This can only happen if the
    // execution of prevId takes a side exit that leads to the
    // execution of tid.
    if (prevId != kInvalidTransID) {
      Op* lastInstr = profData->transLastInstr(prevId);
      const Unit* unit = profData->transFunc(prevId)->unit();
      OffsetSet succOffs = findSuccOffsets(lastInstr, unit);
      if (!succOffs.count(profData->transSrcKey(tid).offset())) {
        if (HPHP::Trace::moduleEnabled(HPHP::Trace::pgo, 2)) {
          FTRACE(2, "selectHotTrace: WARNING: Breaking region @: {}\n",
                 show(*region));
          FTRACE(2, "selectHotTrace: next translation selected: tid = {}\n{}\n",
                 tid, show(*blockRegion));
          FTRACE(2, "\nsuccOffs = {}\n", folly::join(", ", succOffs));
        }
        break;
      }
    }
    if (region->blocks.size() > 0) {
      auto& newBlock   = blockRegion->blocks.front();
      auto newBlockId  = newBlock->id();
      auto predBlockId = region->blocks.back().get()->id();
      if (!RuntimeOption::EvalHHIRBytecodeControlFlow) {
        region->addArc(predBlockId, newBlockId);
      } else {
      // With bytecode control-flow, we add all forward arcs in the TransCFG
      // that are induced by the blocks in the region, as a simple way
      // to expose control-flow for now.
      // This can go away once Task #4075822 is done.
        auto newBlockSrcKey = blockRegion->blocks.front().get()->start();
//.........这里部分代码省略.........

RegionDescPtr selectHotTrace(TransID triggerId,
                             const ProfData* profData,
                             TransCFG& cfg,
                             TransIDSet& selectedSet,
                             TransIDVec* selectedVec) {
  auto region = std::make_shared<RegionDesc>();
  TransID tid    = triggerId;
  TransID prevId = kInvalidTransID;
  selectedSet.clear();
  if (selectedVec) selectedVec->clear();

  PostConditions accumPostConds;

  // Maps from BlockIds to accumulated post conditions for that block.
  // Used to determine if we can add branch-over edges by checking the
  // pre-conditions of the successor block.
  hphp_hash_map<RegionDesc::BlockId, PostConditions> blockPostConds;

  uint32_t numBCInstrs = 0;

  while (!selectedSet.count(tid)) {

    RegionDescPtr blockRegion = profData->transRegion(tid);
    if (blockRegion == nullptr) break;

    // Break if region would be larger than the specified limit.
    auto newInstrSize = numBCInstrs + blockRegion->instrSize();
    if (newInstrSize > RuntimeOption::EvalJitMaxRegionInstrs) {
      FTRACE(2, "selectHotTrace: breaking region at Translation {} because "
             "size ({}) would exceed of maximum translation limit\n",
             tid, newInstrSize);
      break;
    }

    // If the debugger is attached, only allow single-block regions.
    if (prevId != kInvalidTransID && isDebuggerAttachedProcess()) {
      FTRACE(2, "selectHotTrace: breaking region at Translation {} "
             "because of debugger is attached\n", tid);
      break;
    }

    // Break if block is not the first and it corresponds to the main
    // function body entry.  This is to prevent creating multiple
    // large regions containing the function body (starting at various
    // DV funclets).
    if (prevId != kInvalidTransID) {
      const Func* func = profData->transFunc(tid);
      Offset  bcOffset = profData->transStartBcOff(tid);
      if (func->base() == bcOffset) {
        FTRACE(2, "selectHotTrace: breaking region because reached the main "
               "function body entry at Translation {} (BC offset {})\n",
               tid, bcOffset);
        break;
      }
    }

    if (prevId != kInvalidTransID) {
      auto sk = profData->transSrcKey(tid);
      if (profData->optimized(sk)) {
        FTRACE(2, "selectHotTrace: breaking region because next sk already "
               "optimized, for Translation {}\n", tid);
        break;
      }
    }

    bool hasPredBlock = !region->empty();
    RegionDesc::BlockId predBlockId = (hasPredBlock ?
                                       region->blocks().back().get()->id() : 0);
    auto const& newFirstBlock = blockRegion->entry();
    auto newFirstBlockId = newFirstBlock->id();
    auto newLastBlockId  = blockRegion->blocks().back()->id();

    // Add blockRegion's blocks and arcs to region.
    region->append(*blockRegion);
    numBCInstrs += blockRegion->instrSize();

    if (hasPredBlock) {
      region->addArc(predBlockId, newFirstBlockId);
    }

    // When Eval.JitLoops is set, insert back-edges in the region if
    // they exist in the TransCFG.
    if (RuntimeOption::EvalJitLoops) {
      assertx(hasTransId(newFirstBlockId));
      auto newTransId = getTransId(newFirstBlockId);
      // Don't add the arc if the last opcode in the source block ends
      // the region.
      if (!breaksRegion(*profData->transLastInstr(newTransId))) {
        auto& blocks = region->blocks();
        for (auto iOther = 0; iOther < blocks.size(); iOther++) {
          auto other = blocks[iOther];
          auto otherFirstBlockId = other.get()->id();
          if (!hasTransId(otherFirstBlockId)) continue;
          auto otherTransId = getTransId(otherFirstBlockId);
          if (cfg.hasArc(newTransId, otherTransId)) {
            region->addArc(newLastBlockId, otherFirstBlockId);
          }
        }
      }
    }
//.........这里部分代码省略.........

/**
 * Sorts the regions vector in a linear order to be used for
 * translation.  The goal is to obtain an order that improves locality
 * when the function is executed.
 */
static void sortRegion(RegionVec&                  regions,
                       const Func*                 func,
                       const TransCFG&             cfg,
                       const ProfData*             profData,
                       const TransIDToRegionMap&   headToRegion,
                       const RegionToTransIDsMap&  regionToTransIds) {
  RegionVec sorted;
  RegionSet selected;

  // First, pick the region for the function body entry.  There may be
  // multiple translations of the function body, so pick the one with
  // largest profile weight.
  RegionDescPtr entryRegion = nullptr;
  int64_t    maxEntryWeight = -1;
  for (const auto& pair : regionToTransIds) {
    auto  r    = pair.first;
    auto& tids = pair.second;
    for (auto tid : tids) {
      if (profData->transSrcKey(tid).offset() == func->base()) {
        int64_t weight = cfg.weight(tid);
        if (weight > maxEntryWeight) {
          entryRegion    = r;
          maxEntryWeight = weight;
        }
      }
    }
  }

  assert(entryRegion);
  sorted.push_back(entryRegion);
  selected.insert(entryRegion);

  RegionDescPtr region = entryRegion;
  // Select the remaining regions, iteratively picking the most likely
  // region to execute next.
  for (auto i = 1; i < regions.size(); i++) {
    int64_t      maxWeight = -1;
    int64_t  maxHeadWeight = -1;
    RegionDescPtr bestNext = nullptr;
    auto    regionTransIds = getRegionTransIDVec(regionToTransIds, region);
    for (auto next : regions) {
      if (setContains(selected, next)) continue;
      auto nextTransIds = getRegionTransIDVec(regionToTransIds, next);
      int64_t weight = interRegionWeight(regionTransIds, nextTransIds[0], cfg);
      int64_t headWeight = cfg.weight(nextTransIds[0]);
      if ((weight >  maxWeight) ||
          (weight == maxWeight && headWeight > maxHeadWeight)) {
        maxWeight     = weight;
        maxHeadWeight = headWeight;
        bestNext      = next;
      }
    }
    assert(bestNext);
    sorted.push_back(bestNext);
    selected.insert(bestNext);
    region = bestNext;
  }

  assert(sorted.size() == regions.size());
  regions = sorted;

  if (debug && Trace::moduleEnabled(HPHP::Trace::pgo, 5)) {
    for (size_t i = 0; i < regions.size(); i++) {
      auto r = regions[i];
      auto tids = getRegionTransIDVec(regionToTransIds, r);
      std::string transIds = folly::join(", ", tids);
      FTRACE(6, "sortRegion: region[{}]: {}\n", i, transIds);
    }
  }
}

RegionDescPtr selectHotTrace(TransID triggerId,
                             const ProfData* profData,
                             TransCFG& cfg,
                             TransIDSet& selectedSet,
                             TransIDVec* selectedVec) {
  auto region = std::make_shared<RegionDesc>();
  TransID tid    = triggerId;
  TransID prevId = InvalidID;
  selectedSet.clear();
  if (selectedVec) selectedVec->clear();

  PostConditions accumPostConds;

  while (!selectedSet.count(tid)) {

    RegionDescPtr blockRegion = profData->transRegion(tid);
    if (blockRegion == nullptr) break;

    // If the debugger is attached, only allow single-block regions.
    if (prevId != InvalidID && isDebuggerAttachedProcess()) {
      FTRACE(2, "selectHotTrace: breaking region at Translation {} "
             "because of debugger is attached\n", tid);
      break;
    }

    // Break if block is not the first and requires reffiness checks.
    // Task #2589970: fix translateRegion to support mid-region reffiness checks
    if (prevId != InvalidID) {
      auto nRefDeps = blockRegion->blocks[0]->reffinessPreds().size();
      if (nRefDeps > 0) {
        FTRACE(2, "selectHotTrace: breaking region because of refDeps ({}) at "
               "Translation {}\n", nRefDeps, tid);
        break;
      }
    }

    // Break if block is not the first and it corresponds to the main
    // function body entry.  This is to prevent creating multiple
    // large regions containing the function body (starting at various
    // DV funclets).
    if (prevId != InvalidID) {
      const Func* func = profData->transFunc(tid);
      Offset  bcOffset = profData->transStartBcOff(tid);
      if (func->base() == bcOffset) {
        FTRACE(2, "selectHotTrace: breaking region because reached the main "
               "function body entry at Translation {} (BC offset {})\n",
               tid, bcOffset);
        break;
      }
    }

    if (prevId != InvalidID) {
      auto sk = profData->transSrcKey(tid);
      if (profData->optimized(sk)) {
        FTRACE(2, "selectHotTrace: breaking region because next sk already "
               "optimized, for Translation {}\n", tid);
        break;
      }
    }

    // Break trace if translation tid cannot follow the execution of
    // the entire translation prevId.  This can only happen if the
    // execution of prevId takes a side exit that leads to the
    // execution of tid.
    if (prevId != InvalidID) {
      Op* lastInstr = profData->transLastInstr(prevId);
      const Unit* unit = profData->transFunc(prevId)->unit();
      OffsetSet succOffs = findSuccOffsets(lastInstr, unit);
      if (!succOffs.count(profData->transSrcKey(tid).offset())) {
        if (HPHP::Trace::moduleEnabled(HPHP::Trace::pgo, 2)) {
          FTRACE(2, "selectHotTrace: WARNING: Breaking region @: {}\n",
                 JIT::show(*region));
          FTRACE(2, "selectHotTrace: next translation selected: tid = {}\n{}\n",
                 tid, JIT::show(*blockRegion));
          FTRACE(2, "\nsuccOffs = {}\n", folly::join(", ", succOffs));
        }
        break;
      }
    }
    region->blocks.insert(region->blocks.end(), blockRegion->blocks.begin(),
                          blockRegion->blocks.end());
    selectedSet.insert(tid);
    if (selectedVec) selectedVec->push_back(tid);

    Op lastOp = *(profData->transLastInstr(tid));
    if (breaksRegion(lastOp)) {
      FTRACE(2, "selectHotTrace: breaking region because of last instruction "
             "in Translation {}: {}\n", tid, opcodeToName(lastOp));
      break;
    }

    auto outArcs = cfg.outArcs(tid);
    if (outArcs.size() == 0) {
      FTRACE(2, "selectHotTrace: breaking region because there's no successor "
             "for Translation {}\n", tid);
      break;
    }

    auto lastNewBlock = blockRegion->blocks.back();
    discardPoppedTypes(accumPostConds,
//.........这里部分代码省略.........

RegionDescPtr selectHotTrace(TransID triggerId,
                             const ProfData* profData,
                             TransCFG& cfg,
                             TransIDSet& selectedSet,
                             TransIDVec* selectedVec) {
  auto region = std::make_shared<RegionDesc>();
  TransID tid    = triggerId;
  TransID prevId = kInvalidTransID;
  selectedSet.clear();
  if (selectedVec) selectedVec->clear();

  PostConditions accumPostConds;
  // Maps BlockIds to the set of BC offsets for its successor blocks.
  // Used to prevent multiple successors with the same SrcKey for now.
  // This can go away once task #4157613 is done.
  hphp_hash_map<RegionDesc::BlockId, SrcKeySet> succSKSet;

  // Maps from BlockIds to accumulated post conditions for that block.
  // Used to determine if we can add branch-over edges by checking the
  // pre-conditions of the successor block.
  hphp_hash_map<RegionDesc::BlockId, PostConditions> blockPostConds;

  while (!selectedSet.count(tid)) {

    RegionDescPtr blockRegion = profData->transRegion(tid);
    if (blockRegion == nullptr) break;

    // If the debugger is attached, only allow single-block regions.
    if (prevId != kInvalidTransID && isDebuggerAttachedProcess()) {
      FTRACE(2, "selectHotTrace: breaking region at Translation {} "
             "because of debugger is attached\n", tid);
      break;
    }

    // Break if block is not the first and it corresponds to the main
    // function body entry.  This is to prevent creating multiple
    // large regions containing the function body (starting at various
    // DV funclets).
    if (prevId != kInvalidTransID) {
      const Func* func = profData->transFunc(tid);
      Offset  bcOffset = profData->transStartBcOff(tid);
      if (func->base() == bcOffset) {
        FTRACE(2, "selectHotTrace: breaking region because reached the main "
               "function body entry at Translation {} (BC offset {})\n",
               tid, bcOffset);
        break;
      }
    }

    if (prevId != kInvalidTransID) {
      auto sk = profData->transSrcKey(tid);
      if (profData->optimized(sk)) {
        FTRACE(2, "selectHotTrace: breaking region because next sk already "
               "optimized, for Translation {}\n", tid);
        break;
      }
    }

    bool hasPredBlock = !region->empty();
    RegionDesc::BlockId predBlockId = (hasPredBlock ?
                                       region->blocks().back().get()->id() : 0);
    auto const& newFirstBlock = blockRegion->entry();
    auto newFirstBlockId = newFirstBlock->id();
    auto newFirstBlockSk = newFirstBlock->start();
    auto newLastBlockId  = blockRegion->blocks().back()->id();

    // Make sure we don't end up with multiple successors for the same
    // SrcKey. Task #4157613 will allow the following check to go away.
    // This needs to be done before we insert blockRegion into region,
    // to avoid creating unreachable blocks.
    if (RuntimeOption::EvalHHIRBytecodeControlFlow && hasPredBlock &&
        succSKSet[predBlockId].count(newFirstBlockSk)) {
      break;
    }

    // Add blockRegion's blocks and arcs to region.
    region->append(*blockRegion);

    if (hasPredBlock) {
      if (RuntimeOption::EvalHHIRBytecodeControlFlow) {
        // This is checked above.
        assert(succSKSet[predBlockId].count(newFirstBlockSk) == 0);
        succSKSet[predBlockId].insert(newFirstBlockSk);
      }
      region->addArc(predBlockId, newFirstBlockId);
    }

    // With bytecode control-flow, we add all forward arcs in the TransCFG
    // that are induced by the blocks in the region, as a simple way
    // to expose control-flow for now.
    // This can go away once Task #4075822 is done.
    if (RuntimeOption::EvalHHIRBytecodeControlFlow) {
      assert(hasTransId(newFirstBlockId));
      auto newTransId = getTransId(newFirstBlockId);
      auto& blocks = region->blocks();
      for (auto iOther = 0; iOther < blocks.size(); iOther++) {
        auto other = blocks[iOther];
        auto otherFirstBlockId = other.get()->id();
        if (!hasTransId(otherFirstBlockId)) continue;
        auto otherTransId = getTransId(otherFirstBlockId);
//.........这里部分代码省略.........

RegionDescPtr selectHotTrace(TransID triggerId,
                             const ProfData* profData,
                             TransCFG& cfg,
                             TransIDSet& selectedSet) {
  JIT::RegionDescPtr region = smart::make_unique<JIT::RegionDesc>();
  TransID tid    = triggerId;
  TransID prevId = InvalidID;
  selectedSet.clear();

  while (!setContains(selectedSet, tid)) {

    RegionDesc::BlockPtr block = profData->transBlock(tid);
    if (block == nullptr) break;

    // If the debugger is attached, only allow single-block regions.
    if (prevId != InvalidID && isDebuggerAttachedProcess()) {
      FTRACE(5, "selectHotRegion: breaking region at Translation {} "
             "because of debugger is attached\n", tid);
      break;
    }

    // Break if block is not the first and requires reffiness checks.
    // Task #2589970: fix translateRegion to support mid-region reffiness checks
    if (prevId != InvalidID) {
      auto nRefDeps = block->reffinessPreds().size();
      if (nRefDeps > 0) {
        FTRACE(5, "selectHotRegion: breaking region because of refDeps ({}) at "
               "Translation {}\n", nRefDeps, tid);
        break;
      }
    }

    // Break trace if translation tid cannot follow the execution of
    // the entire translation prevTd.  This can only happen if the
    // execution of prevId takes a side exit that leads to the
    // execution of tid.
    if (prevId != InvalidID) {
      Op* lastInstr = profData->transLastInstr(prevId);
      const Unit* unit = profData->transFunc(prevId)->unit();
      OffsetSet succOffs = findSuccOffsets(lastInstr, unit);
      if (!setContains(succOffs, profData->transSrcKey(tid).offset())) {
        if (HPHP::Trace::moduleEnabled(HPHP::Trace::pgo, 5)) {
          FTRACE(5, "selectHotTrace: WARNING: Breaking region @: {}\n",
                 JIT::show(*region));
          FTRACE(5, "selectHotTrace: next translation selected: tid = {}\n{}\n",
                 tid, JIT::show(*block));
          std::string succStr("succOffs = ");
          for (auto succ : succOffs) {
            succStr += lexical_cast<std::string>(succ);
          }
          FTRACE(5, "\n{}\n", succStr);
        }
        break;
      }
    }
    region->blocks.emplace_back(block);
    selectedSet.insert(tid);

    Op lastOp = *(profData->transLastInstr(tid));
    if (breaksRegion(lastOp)) {
      FTRACE(5, "selectHotTrace: breaking region because of last instruction "
             "in Translation {}: {}\n", tid, opcodeToName(lastOp));
      break;
    }

    auto outArcs = cfg.outArcs(tid);
    if (outArcs.size() == 0) {
      FTRACE(5, "selectHotTrace: breaking region because there's no successor "
             "for Translation {}\n", tid);
      break;
    }

    auto maxWeight = std::numeric_limits<int64_t>::min();
    TransCFG::Arc* maxArc = nullptr;
    for (auto arc : outArcs) {
      if (arc->weight() >= maxWeight) {
        maxWeight = arc->weight();
        maxArc = arc;
      }
    }
    assert(maxArc != nullptr);

    prevId = tid;
    tid = maxArc->dst();
  }

  return region;
}