YQ Connector: support managed ClickHouse

Со стороны dqrun можно обратиться к инстансу коннектора, который работает на streaming стенде, и извлечь данные из облачного CH.

1 files changed, 881 insertions, 0 deletions

diff --git a/contrib/libs/llvm16/lib/Analysis/BlockFrequencyInfoImpl.cpp b/contrib/libs/llvm16/lib/Analysis/BlockFrequencyInfoImpl.cpp
new file mode 100644
index 0000000000..0945c5688f
--- /dev/null
+++ b/contrib/libs/llvm16/lib/Analysis/BlockFrequencyInfoImpl.cpp
@@ -0,0 +1,881 @@
+//===- BlockFrequencyImplInfo.cpp - Block Frequency Info Implementation ---===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Loops should be simplified before this analysis.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
+#include "llvm/ADT/APInt.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SCCIterator.h"
+#include "llvm/Config/llvm-config.h"
+#include "llvm/IR/Function.h"
+#include "llvm/Support/BlockFrequency.h"
+#include "llvm/Support/BranchProbability.h"
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/ScaledNumber.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <iterator>
+#include <list>
+#include <numeric>
+#include <optional>
+#include <utility>
+#include <vector>
+
+using namespace llvm;
+using namespace llvm::bfi_detail;
+
+#define DEBUG_TYPE "block-freq"
+
+namespace llvm {
+cl::opt<bool> CheckBFIUnknownBlockQueries(
+    "check-bfi-unknown-block-queries",
+    cl::init(false), cl::Hidden,
+    cl::desc("Check if block frequency is queried for an unknown block "
+             "for debugging missed BFI updates"));
+
+cl::opt<bool> UseIterativeBFIInference(
+    "use-iterative-bfi-inference", cl::Hidden,
+    cl::desc("Apply an iterative post-processing to infer correct BFI counts"));
+
+cl::opt<unsigned> IterativeBFIMaxIterationsPerBlock(
+    "iterative-bfi-max-iterations-per-block", cl::init(1000), cl::Hidden,
+    cl::desc("Iterative inference: maximum number of update iterations "
+             "per block"));
+
+cl::opt<double> IterativeBFIPrecision(
+    "iterative-bfi-precision", cl::init(1e-12), cl::Hidden,
+    cl::desc("Iterative inference: delta convergence precision; smaller values "
+             "typically lead to better results at the cost of worsen runtime"));
+}
+
+ScaledNumber<uint64_t> BlockMass::toScaled() const {
+  if (isFull())
+    return ScaledNumber<uint64_t>(1, 0);
+  return ScaledNumber<uint64_t>(getMass() + 1, -64);
+}
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+LLVM_DUMP_METHOD void BlockMass::dump() const { print(dbgs()); }
+#endif
+
+static char getHexDigit(int N) {
+  assert(N < 16);
+  if (N < 10)
+    return '0' + N;
+  return 'a' + N - 10;
+}
+
+raw_ostream &BlockMass::print(raw_ostream &OS) const {
+  for (int Digits = 0; Digits < 16; ++Digits)
+    OS << getHexDigit(Mass >> (60 - Digits * 4) & 0xf);
+  return OS;
+}
+
+namespace {
+
+using BlockNode = BlockFrequencyInfoImplBase::BlockNode;
+using Distribution = BlockFrequencyInfoImplBase::Distribution;
+using WeightList = BlockFrequencyInfoImplBase::Distribution::WeightList;
+using Scaled64 = BlockFrequencyInfoImplBase::Scaled64;
+using LoopData = BlockFrequencyInfoImplBase::LoopData;
+using Weight = BlockFrequencyInfoImplBase::Weight;
+using FrequencyData = BlockFrequencyInfoImplBase::FrequencyData;
+
+/// Dithering mass distributer.
+///
+/// This class splits up a single mass into portions by weight, dithering to
+/// spread out error.  No mass is lost.  The dithering precision depends on the
+/// precision of the product of \a BlockMass and \a BranchProbability.
+///
+/// The distribution algorithm follows.
+///
+///  1. Initialize by saving the sum of the weights in \a RemWeight and the
+///     mass to distribute in \a RemMass.
+///
+///  2. For each portion:
+///
+///      1. Construct a branch probability, P, as the portion's weight divided
+///         by the current value of \a RemWeight.
+///      2. Calculate the portion's mass as \a RemMass times P.
+///      3. Update \a RemWeight and \a RemMass at each portion by subtracting
+///         the current portion's weight and mass.
+struct DitheringDistributer {
+  uint32_t RemWeight;
+  BlockMass RemMass;
+
+  DitheringDistributer(Distribution &Dist, const BlockMass &Mass);
+
+  BlockMass takeMass(uint32_t Weight);
+};
+
+} // end anonymous namespace
+
+DitheringDistributer::DitheringDistributer(Distribution &Dist,
+                                           const BlockMass &Mass) {
+  Dist.normalize();
+  RemWeight = Dist.Total;
+  RemMass = Mass;
+}
+
+BlockMass DitheringDistributer::takeMass(uint32_t Weight) {
+  assert(Weight && "invalid weight");
+  assert(Weight <= RemWeight);
+  BlockMass Mass = RemMass * BranchProbability(Weight, RemWeight);
+
+  // Decrement totals (dither).
+  RemWeight -= Weight;
+  RemMass -= Mass;
+  return Mass;
+}
+
+void Distribution::add(const BlockNode &Node, uint64_t Amount,
+                       Weight::DistType Type) {
+  assert(Amount && "invalid weight of 0");
+  uint64_t NewTotal = Total + Amount;
+
+  // Check for overflow.  It should be impossible to overflow twice.
+  bool IsOverflow = NewTotal < Total;
+  assert(!(DidOverflow && IsOverflow) && "unexpected repeated overflow");
+  DidOverflow |= IsOverflow;
+
+  // Update the total.
+  Total = NewTotal;
+
+  // Save the weight.
+  Weights.push_back(Weight(Type, Node, Amount));
+}
+
+static void combineWeight(Weight &W, const Weight &OtherW) {
+  assert(OtherW.TargetNode.isValid());
+  if (!W.Amount) {
+    W = OtherW;
+    return;
+  }
+  assert(W.Type == OtherW.Type);
+  assert(W.TargetNode == OtherW.TargetNode);
+  assert(OtherW.Amount && "Expected non-zero weight");
+  if (W.Amount > W.Amount + OtherW.Amount)
+    // Saturate on overflow.
+    W.Amount = UINT64_MAX;
+  else
+    W.Amount += OtherW.Amount;
+}
+
+static void combineWeightsBySorting(WeightList &Weights) {
+  // Sort so edges to the same node are adjacent.
+  llvm::sort(Weights, [](const Weight &L, const Weight &R) {
+    return L.TargetNode < R.TargetNode;
+  });
+
+  // Combine adjacent edges.
+  WeightList::iterator O = Weights.begin();
+  for (WeightList::const_iterator I = O, L = O, E = Weights.end(); I != E;
+       ++O, (I = L)) {
+    *O = *I;
+
+    // Find the adjacent weights to the same node.
+    for (++L; L != E && I->TargetNode == L->TargetNode; ++L)
+      combineWeight(*O, *L);
+  }
+
+  // Erase extra entries.
+  Weights.erase(O, Weights.end());
+}
+
+static void combineWeightsByHashing(WeightList &Weights) {
+  // Collect weights into a DenseMap.
+  using HashTable = DenseMap<BlockNode::IndexType, Weight>;
+
+  HashTable Combined(NextPowerOf2(2 * Weights.size()));
+  for (const Weight &W : Weights)
+    combineWeight(Combined[W.TargetNode.Index], W);
+
+  // Check whether anything changed.
+  if (Weights.size() == Combined.size())
+    return;
+
+  // Fill in the new weights.
+  Weights.clear();
+  Weights.reserve(Combined.size());
+  for (const auto &I : Combined)
+    Weights.push_back(I.second);
+}
+
+static void combineWeights(WeightList &Weights) {
+  // Use a hash table for many successors to keep this linear.
+  if (Weights.size() > 128) {
+    combineWeightsByHashing(Weights);
+    return;
+  }
+
+  combineWeightsBySorting(Weights);
+}
+
+static uint64_t shiftRightAndRound(uint64_t N, int Shift) {
+  assert(Shift >= 0);
+  assert(Shift < 64);
+  if (!Shift)
+    return N;
+  return (N >> Shift) + (UINT64_C(1) & N >> (Shift - 1));
+}
+
+void Distribution::normalize() {
+  // Early exit for termination nodes.
+  if (Weights.empty())
+    return;
+
+  // Only bother if there are multiple successors.
+  if (Weights.size() > 1)
+    combineWeights(Weights);
+
+  // Early exit when combined into a single successor.
+  if (Weights.size() == 1) {
+    Total = 1;
+    Weights.front().Amount = 1;
+    return;
+  }
+
+  // Determine how much to shift right so that the total fits into 32-bits.
+  //
+  // If we shift at all, shift by 1 extra.  Otherwise, the lower limit of 1
+  // for each weight can cause a 32-bit overflow.
+  int Shift = 0;
+  if (DidOverflow)
+    Shift = 33;
+  else if (Total > UINT32_MAX)
+    Shift = 33 - countLeadingZeros(Total);
+
+  // Early exit if nothing needs to be scaled.
+  if (!Shift) {
+    // If we didn't overflow then combineWeights() shouldn't have changed the
+    // sum of the weights, but let's double-check.
+    assert(Total == std::accumulate(Weights.begin(), Weights.end(), UINT64_C(0),
+                                    [](uint64_t Sum, const Weight &W) {
+                      return Sum + W.Amount;
+                    }) &&
+           "Expected total to be correct");
+    return;
+  }
+
+  // Recompute the total through accumulation (rather than shifting it) so that
+  // it's accurate after shifting and any changes combineWeights() made above.
+  Total = 0;
+
+  // Sum the weights to each node and shift right if necessary.
+  for (Weight &W : Weights) {
+    // Scale down below UINT32_MAX.  Since Shift is larger than necessary, we
+    // can round here without concern about overflow.
+    assert(W.TargetNode.isValid());
+    W.Amount = std::max(UINT64_C(1), shiftRightAndRound(W.Amount, Shift));
+    assert(W.Amount <= UINT32_MAX);
+
+    // Update the total.
+    Total += W.Amount;
+  }
+  assert(Total <= UINT32_MAX);
+}
+
+void BlockFrequencyInfoImplBase::clear() {
+  // Swap with a default-constructed std::vector, since std::vector<>::clear()
+  // does not actually clear heap storage.
+  std::vector<FrequencyData>().swap(Freqs);
+  IsIrrLoopHeader.clear();
+  std::vector<WorkingData>().swap(Working);
+  Loops.clear();
+}
+
+/// Clear all memory not needed downstream.
+///
+/// Releases all memory not used downstream.  In particular, saves Freqs.
+static void cleanup(BlockFrequencyInfoImplBase &BFI) {
+  std::vector<FrequencyData> SavedFreqs(std::move(BFI.Freqs));
+  SparseBitVector<> SavedIsIrrLoopHeader(std::move(BFI.IsIrrLoopHeader));
+  BFI.clear();
+  BFI.Freqs = std::move(SavedFreqs);
+  BFI.IsIrrLoopHeader = std::move(SavedIsIrrLoopHeader);
+}
+
+bool BlockFrequencyInfoImplBase::addToDist(Distribution &Dist,
+                                           const LoopData *OuterLoop,
+                                           const BlockNode &Pred,
+                                           const BlockNode &Succ,
+                                           uint64_t Weight) {
+  if (!Weight)
+    Weight = 1;
+
+  auto isLoopHeader = [&OuterLoop](const BlockNode &Node) {
+    return OuterLoop && OuterLoop->isHeader(Node);
+  };
+
+  BlockNode Resolved = Working[Succ.Index].getResolvedNode();
+
+#ifndef NDEBUG
+  auto debugSuccessor = [&](const char *Type) {
+    dbgs() << "  =>"
+           << " [" << Type << "] weight = " << Weight;
+    if (!isLoopHeader(Resolved))
+      dbgs() << ", succ = " << getBlockName(Succ);
+    if (Resolved != Succ)
+      dbgs() << ", resolved = " << getBlockName(Resolved);
+    dbgs() << "\n";
+  };
+  (void)debugSuccessor;
+#endif
+
+  if (isLoopHeader(Resolved)) {
+    LLVM_DEBUG(debugSuccessor("backedge"));
+    Dist.addBackedge(Resolved, Weight);
+    return true;
+  }
+
+  if (Working[Resolved.Index].getContainingLoop() != OuterLoop) {
+    LLVM_DEBUG(debugSuccessor("  exit  "));
+    Dist.addExit(Resolved, Weight);
+    return true;
+  }
+
+  if (Resolved < Pred) {
+    if (!isLoopHeader(Pred)) {
+      // If OuterLoop is an irreducible loop, we can't actually handle this.
+      assert((!OuterLoop || !OuterLoop->isIrreducible()) &&
+             "unhandled irreducible control flow");
+
+      // Irreducible backedge.  Abort.
+      LLVM_DEBUG(debugSuccessor("abort!!!"));
+      return false;
+    }
+
+    // If "Pred" is a loop header, then this isn't really a backedge; rather,
+    // OuterLoop must be irreducible.  These false backedges can come only from
+    // secondary loop headers.
+    assert(OuterLoop && OuterLoop->isIrreducible() && !isLoopHeader(Resolved) &&
+           "unhandled irreducible control flow");
+  }
+
+  LLVM_DEBUG(debugSuccessor(" local  "));
+  Dist.addLocal(Resolved, Weight);
+  return true;
+}
+
+bool BlockFrequencyInfoImplBase::addLoopSuccessorsToDist(
+    const LoopData *OuterLoop, LoopData &Loop, Distribution &Dist) {
+  // Copy the exit map into Dist.
+  for (const auto &I : Loop.Exits)
+    if (!addToDist(Dist, OuterLoop, Loop.getHeader(), I.first,
+                   I.second.getMass()))
+      // Irreducible backedge.
+      return false;
+
+  return true;
+}
+
+/// Compute the loop scale for a loop.
+void BlockFrequencyInfoImplBase::computeLoopScale(LoopData &Loop) {
+  // Compute loop scale.
+  LLVM_DEBUG(dbgs() << "compute-loop-scale: " << getLoopName(Loop) << "\n");
+
+  // Infinite loops need special handling. If we give the back edge an infinite
+  // mass, they may saturate all the other scales in the function down to 1,
+  // making all the other region temperatures look exactly the same. Choose an
+  // arbitrary scale to avoid these issues.
+  //
+  // FIXME: An alternate way would be to select a symbolic scale which is later
+  // replaced to be the maximum of all computed scales plus 1. This would
+  // appropriately describe the loop as having a large scale, without skewing
+  // the final frequency computation.
+  const Scaled64 InfiniteLoopScale(1, 12);
+
+  // LoopScale == 1 / ExitMass
+  // ExitMass == HeadMass - BackedgeMass
+  BlockMass TotalBackedgeMass;
+  for (auto &Mass : Loop.BackedgeMass)
+    TotalBackedgeMass += Mass;
+  BlockMass ExitMass = BlockMass::getFull() - TotalBackedgeMass;
+
+  // Block scale stores the inverse of the scale. If this is an infinite loop,
+  // its exit mass will be zero. In this case, use an arbitrary scale for the
+  // loop scale.
+  Loop.Scale =
+      ExitMass.isEmpty() ? InfiniteLoopScale : ExitMass.toScaled().inverse();
+
+  LLVM_DEBUG(dbgs() << " - exit-mass = " << ExitMass << " ("
+                    << BlockMass::getFull() << " - " << TotalBackedgeMass
+                    << ")\n"
+                    << " - scale = " << Loop.Scale << "\n");
+}
+
+/// Package up a loop.
+void BlockFrequencyInfoImplBase::packageLoop(LoopData &Loop) {
+  LLVM_DEBUG(dbgs() << "packaging-loop: " << getLoopName(Loop) << "\n");
+
+  // Clear the subloop exits to prevent quadratic memory usage.
+  for (const BlockNode &M : Loop.Nodes) {
+    if (auto *Loop = Working[M.Index].getPackagedLoop())
+      Loop->Exits.clear();
+    LLVM_DEBUG(dbgs() << " - node: " << getBlockName(M.Index) << "\n");
+  }
+  Loop.IsPackaged = true;
+}
+
+#ifndef NDEBUG
+static void debugAssign(const BlockFrequencyInfoImplBase &BFI,
+                        const DitheringDistributer &D, const BlockNode &T,
+                        const BlockMass &M, const char *Desc) {
+  dbgs() << "  => assign " << M << " (" << D.RemMass << ")";
+  if (Desc)
+    dbgs() << " [" << Desc << "]";
+  if (T.isValid())
+    dbgs() << " to " << BFI.getBlockName(T);
+  dbgs() << "\n";
+}
+#endif
+
+void BlockFrequencyInfoImplBase::distributeMass(const BlockNode &Source,
+                                                LoopData *OuterLoop,
+                                                Distribution &Dist) {
+  BlockMass Mass = Working[Source.Index].getMass();
+  LLVM_DEBUG(dbgs() << "  => mass:  " << Mass << "\n");
+
+  // Distribute mass to successors as laid out in Dist.
+  DitheringDistributer D(Dist, Mass);
+
+  for (const Weight &W : Dist.Weights) {
+    // Check for a local edge (non-backedge and non-exit).
+    BlockMass Taken = D.takeMass(W.Amount);
+    if (W.Type == Weight::Local) {
+      Working[W.TargetNode.Index].getMass() += Taken;
+      LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, nullptr));
+      continue;
+    }
+
+    // Backedges and exits only make sense if we're processing a loop.
+    assert(OuterLoop && "backedge or exit outside of loop");
+
+    // Check for a backedge.
+    if (W.Type == Weight::Backedge) {
+      OuterLoop->BackedgeMass[OuterLoop->getHeaderIndex(W.TargetNode)] += Taken;
+      LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, "back"));
+      continue;
+    }
+
+    // This must be an exit.
+    assert(W.Type == Weight::Exit);
+    OuterLoop->Exits.push_back(std::make_pair(W.TargetNode, Taken));
+    LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, "exit"));
+  }
+}
+
+static void convertFloatingToInteger(BlockFrequencyInfoImplBase &BFI,
+                                     const Scaled64 &Min, const Scaled64 &Max) {
+  // Scale the Factor to a size that creates integers.  Ideally, integers would
+  // be scaled so that Max == UINT64_MAX so that they can be best
+  // differentiated.  However, in the presence of large frequency values, small
+  // frequencies are scaled down to 1, making it impossible to differentiate
+  // small, unequal numbers. When the spread between Min and Max frequencies
+  // fits well within MaxBits, we make the scale be at least 8.
+  const unsigned MaxBits = 64;
+  const unsigned SpreadBits = (Max / Min).lg();
+  Scaled64 ScalingFactor;
+  if (SpreadBits <= MaxBits - 3) {
+    // If the values are small enough, make the scaling factor at least 8 to
+    // allow distinguishing small values.
+    ScalingFactor = Min.inverse();
+    ScalingFactor <<= 3;
+  } else {
+    // If the values need more than MaxBits to be represented, saturate small
+    // frequency values down to 1 by using a scaling factor that benefits large
+    // frequency values.
+    ScalingFactor = Scaled64(1, MaxBits) / Max;
+  }
+
+  // Translate the floats to integers.
+  LLVM_DEBUG(dbgs() << "float-to-int: min = " << Min << ", max = " << Max
+                    << ", factor = " << ScalingFactor << "\n");
+  for (size_t Index = 0; Index < BFI.Freqs.size(); ++Index) {
+    Scaled64 Scaled = BFI.Freqs[Index].Scaled * ScalingFactor;
+    BFI.Freqs[Index].Integer = std::max(UINT64_C(1), Scaled.toInt<uint64_t>());
+    LLVM_DEBUG(dbgs() << " - " << BFI.getBlockName(Index) << ": float = "
+                      << BFI.Freqs[Index].Scaled << ", scaled = " << Scaled
+                      << ", int = " << BFI.Freqs[Index].Integer << "\n");
+  }
+}
+
+/// Unwrap a loop package.
+///
+/// Visits all the members of a loop, adjusting their BlockData according to
+/// the loop's pseudo-node.
+static void unwrapLoop(BlockFrequencyInfoImplBase &BFI, LoopData &Loop) {
+  LLVM_DEBUG(dbgs() << "unwrap-loop-package: " << BFI.getLoopName(Loop)
+                    << ": mass = " << Loop.Mass << ", scale = " << Loop.Scale
+                    << "\n");
+  Loop.Scale *= Loop.Mass.toScaled();
+  Loop.IsPackaged = false;
+  LLVM_DEBUG(dbgs() << "  => combined-scale = " << Loop.Scale << "\n");
+
+  // Propagate the head scale through the loop.  Since members are visited in
+  // RPO, the head scale will be updated by the loop scale first, and then the
+  // final head scale will be used for updated the rest of the members.
+  for (const BlockNode &N : Loop.Nodes) {
+    const auto &Working = BFI.Working[N.Index];
+    Scaled64 &F = Working.isAPackage() ? Working.getPackagedLoop()->Scale
+                                       : BFI.Freqs[N.Index].Scaled;
+    Scaled64 New = Loop.Scale * F;
+    LLVM_DEBUG(dbgs() << " - " << BFI.getBlockName(N) << ": " << F << " => "
+                      << New << "\n");
+    F = New;
+  }
+}
+
+void BlockFrequencyInfoImplBase::unwrapLoops() {
+  // Set initial frequencies from loop-local masses.
+  for (size_t Index = 0; Index < Working.size(); ++Index)
+    Freqs[Index].Scaled = Working[Index].Mass.toScaled();
+
+  for (LoopData &Loop : Loops)
+    unwrapLoop(*this, Loop);
+}
+
+void BlockFrequencyInfoImplBase::finalizeMetrics() {
+  // Unwrap loop packages in reverse post-order, tracking min and max
+  // frequencies.
+  auto Min = Scaled64::getLargest();
+  auto Max = Scaled64::getZero();
+  for (size_t Index = 0; Index < Working.size(); ++Index) {
+    // Update min/max scale.
+    Min = std::min(Min, Freqs[Index].Scaled);
+    Max = std::max(Max, Freqs[Index].Scaled);
+  }
+
+  // Convert to integers.
+  convertFloatingToInteger(*this, Min, Max);
+
+  // Clean up data structures.
+  cleanup(*this);
+
+  // Print out the final stats.
+  LLVM_DEBUG(dump());
+}
+
+BlockFrequency
+BlockFrequencyInfoImplBase::getBlockFreq(const BlockNode &Node) const {
+  if (!Node.isValid()) {
+#ifndef NDEBUG
+    if (CheckBFIUnknownBlockQueries) {
+      SmallString<256> Msg;
+      raw_svector_ostream OS(Msg);
+      OS << "*** Detected BFI query for unknown block " << getBlockName(Node);
+      report_fatal_error(OS.str());
+    }
+#endif
+    return 0;
+  }
+  return Freqs[Node.Index].Integer;
+}
+
+std::optional<uint64_t>
+BlockFrequencyInfoImplBase::getBlockProfileCount(const Function &F,
+                                                 const BlockNode &Node,
+                                                 bool AllowSynthetic) const {
+  return getProfileCountFromFreq(F, getBlockFreq(Node).getFrequency(),
+                                 AllowSynthetic);
+}
+
+std::optional<uint64_t>
+BlockFrequencyInfoImplBase::getProfileCountFromFreq(const Function &F,
+                                                    uint64_t Freq,
+                                                    bool AllowSynthetic) const {
+  auto EntryCount = F.getEntryCount(AllowSynthetic);
+  if (!EntryCount)
+    return std::nullopt;
+  // Use 128 bit APInt to do the arithmetic to avoid overflow.
+  APInt BlockCount(128, EntryCount->getCount());
+  APInt BlockFreq(128, Freq);
+  APInt EntryFreq(128, getEntryFreq());
+  BlockCount *= BlockFreq;
+  // Rounded division of BlockCount by EntryFreq. Since EntryFreq is unsigned
+  // lshr by 1 gives EntryFreq/2.
+  BlockCount = (BlockCount + EntryFreq.lshr(1)).udiv(EntryFreq);
+  return BlockCount.getLimitedValue();
+}
+
+bool
+BlockFrequencyInfoImplBase::isIrrLoopHeader(const BlockNode &Node) {
+  if (!Node.isValid())
+    return false;
+  return IsIrrLoopHeader.test(Node.Index);
+}
+
+Scaled64
+BlockFrequencyInfoImplBase::getFloatingBlockFreq(const BlockNode &Node) const {
+  if (!Node.isValid())
+    return Scaled64::getZero();
+  return Freqs[Node.Index].Scaled;
+}
+
+void BlockFrequencyInfoImplBase::setBlockFreq(const BlockNode &Node,
+                                              uint64_t Freq) {
+  assert(Node.isValid() && "Expected valid node");
+  assert(Node.Index < Freqs.size() && "Expected legal index");
+  Freqs[Node.Index].Integer = Freq;
+}
+
+std::string
+BlockFrequencyInfoImplBase::getBlockName(const BlockNode &Node) const {
+  return {};
+}
+
+std::string
+BlockFrequencyInfoImplBase::getLoopName(const LoopData &Loop) const {
+  return getBlockName(Loop.getHeader()) + (Loop.isIrreducible() ? "**" : "*");
+}
+
+raw_ostream &
+BlockFrequencyInfoImplBase::printBlockFreq(raw_ostream &OS,
+                                           const BlockNode &Node) const {
+  return OS << getFloatingBlockFreq(Node);
+}
+
+raw_ostream &
+BlockFrequencyInfoImplBase::printBlockFreq(raw_ostream &OS,
+                                           const BlockFrequency &Freq) const {
+  Scaled64 Block(Freq.getFrequency(), 0);
+  Scaled64 Entry(getEntryFreq(), 0);
+
+  return OS << Block / Entry;
+}
+
+void IrreducibleGraph::addNodesInLoop(const BFIBase::LoopData &OuterLoop) {
+  Start = OuterLoop.getHeader();
+  Nodes.reserve(OuterLoop.Nodes.size());
+  for (auto N : OuterLoop.Nodes)
+    addNode(N);
+  indexNodes();
+}
+
+void IrreducibleGraph::addNodesInFunction() {
+  Start = 0;
+  for (uint32_t Index = 0; Index < BFI.Working.size(); ++Index)
+    if (!BFI.Working[Index].isPackaged())
+      addNode(Index);
+  indexNodes();
+}
+
+void IrreducibleGraph::indexNodes() {
+  for (auto &I : Nodes)
+    Lookup[I.Node.Index] = &I;
+}
+
+void IrreducibleGraph::addEdge(IrrNode &Irr, const BlockNode &Succ,
+                               const BFIBase::LoopData *OuterLoop) {
+  if (OuterLoop && OuterLoop->isHeader(Succ))
+    return;
+  auto L = Lookup.find(Succ.Index);
+  if (L == Lookup.end())
+    return;
+  IrrNode &SuccIrr = *L->second;
+  Irr.Edges.push_back(&SuccIrr);
+  SuccIrr.Edges.push_front(&Irr);
+  ++SuccIrr.NumIn;
+}
+
+namespace llvm {
+
+template <> struct GraphTraits<IrreducibleGraph> {
+  using GraphT = bfi_detail::IrreducibleGraph;
+  using NodeRef = const GraphT::IrrNode *;
+  using ChildIteratorType = GraphT::IrrNode::iterator;
+
+  static NodeRef getEntryNode(const GraphT &G) { return G.StartIrr; }
+  static ChildIteratorType child_begin(NodeRef N) { return N->succ_begin(); }
+  static ChildIteratorType child_end(NodeRef N) { return N->succ_end(); }
+};
+
+} // end namespace llvm
+
+/// Find extra irreducible headers.
+///
+/// Find entry blocks and other blocks with backedges, which exist when \c G
+/// contains irreducible sub-SCCs.
+static void findIrreducibleHeaders(
+    const BlockFrequencyInfoImplBase &BFI,
+    const IrreducibleGraph &G,
+    const std::vector<const IrreducibleGraph::IrrNode *> &SCC,
+    LoopData::NodeList &Headers, LoopData::NodeList &Others) {
+  // Map from nodes in the SCC to whether it's an entry block.
+  SmallDenseMap<const IrreducibleGraph::IrrNode *, bool, 8> InSCC;
+
+  // InSCC also acts the set of nodes in the graph.  Seed it.
+  for (const auto *I : SCC)
+    InSCC[I] = false;
+
+  for (auto I = InSCC.begin(), E = InSCC.end(); I != E; ++I) {
+    auto &Irr = *I->first;
+    for (const auto *P : make_range(Irr.pred_begin(), Irr.pred_end())) {
+      if (InSCC.count(P))
+        continue;
+
+      // This is an entry block.
+      I->second = true;
+      Headers.push_back(Irr.Node);
+      LLVM_DEBUG(dbgs() << "  => entry = " << BFI.getBlockName(Irr.Node)
+                        << "\n");
+      break;
+    }
+  }
+  assert(Headers.size() >= 2 &&
+         "Expected irreducible CFG; -loop-info is likely invalid");
+  if (Headers.size() == InSCC.size()) {
+    // Every block is a header.
+    llvm::sort(Headers);
+    return;
+  }
+
+  // Look for extra headers from irreducible sub-SCCs.
+  for (const auto &I : InSCC) {
+    // Entry blocks are already headers.
+    if (I.second)
+      continue;
+
+    auto &Irr = *I.first;
+    for (const auto *P : make_range(Irr.pred_begin(), Irr.pred_end())) {
+      // Skip forward edges.
+      if (P->Node < Irr.Node)
+        continue;
+
+      // Skip predecessors from entry blocks.  These can have inverted
+      // ordering.
+      if (InSCC.lookup(P))
+        continue;
+
+      // Store the extra header.
+      Headers.push_back(Irr.Node);
+      LLVM_DEBUG(dbgs() << "  => extra = " << BFI.getBlockName(Irr.Node)
+                        << "\n");
+      break;
+    }
+    if (Headers.back() == Irr.Node)
+      // Added this as a header.
+      continue;
+
+    // This is not a header.
+    Others.push_back(Irr.Node);
+    LLVM_DEBUG(dbgs() << "  => other = " << BFI.getBlockName(Irr.Node) << "\n");
+  }
+  llvm::sort(Headers);
+  llvm::sort(Others);
+}
+
+static void createIrreducibleLoop(
+    BlockFrequencyInfoImplBase &BFI, const IrreducibleGraph &G,
+    LoopData *OuterLoop, std::list<LoopData>::iterator Insert,
+    const std::vector<const IrreducibleGraph::IrrNode *> &SCC) {
+  // Translate the SCC into RPO.
+  LLVM_DEBUG(dbgs() << " - found-scc\n");
+
+  LoopData::NodeList Headers;
+  LoopData::NodeList Others;
+  findIrreducibleHeaders(BFI, G, SCC, Headers, Others);
+
+  auto Loop = BFI.Loops.emplace(Insert, OuterLoop, Headers.begin(),
+                                Headers.end(), Others.begin(), Others.end());
+
+  // Update loop hierarchy.
+  for (const auto &N : Loop->Nodes)
+    if (BFI.Working[N.Index].isLoopHeader())
+      BFI.Working[N.Index].Loop->Parent = &*Loop;
+    else
+      BFI.Working[N.Index].Loop = &*Loop;
+}
+
+iterator_range<std::list<LoopData>::iterator>
+BlockFrequencyInfoImplBase::analyzeIrreducible(
+    const IrreducibleGraph &G, LoopData *OuterLoop,
+    std::list<LoopData>::iterator Insert) {
+  assert((OuterLoop == nullptr) == (Insert == Loops.begin()));
+  auto Prev = OuterLoop ? std::prev(Insert) : Loops.end();
+
+  for (auto I = scc_begin(G); !I.isAtEnd(); ++I) {
+    if (I->size() < 2)
+      continue;
+
+    // Translate the SCC into RPO.
+    createIrreducibleLoop(*this, G, OuterLoop, Insert, *I);
+  }
+
+  if (OuterLoop)
+    return make_range(std::next(Prev), Insert);
+  return make_range(Loops.begin(), Insert);
+}
+
+void
+BlockFrequencyInfoImplBase::updateLoopWithIrreducible(LoopData &OuterLoop) {
+  OuterLoop.Exits.clear();
+  for (auto &Mass : OuterLoop.BackedgeMass)
+    Mass = BlockMass::getEmpty();
+  auto O = OuterLoop.Nodes.begin() + 1;
+  for (auto I = O, E = OuterLoop.Nodes.end(); I != E; ++I)
+    if (!Working[I->Index].isPackaged())
+      *O++ = *I;
+  OuterLoop.Nodes.erase(O, OuterLoop.Nodes.end());
+}
+
+void BlockFrequencyInfoImplBase::adjustLoopHeaderMass(LoopData &Loop) {
+  assert(Loop.isIrreducible() && "this only makes sense on irreducible loops");
+
+  // Since the loop has more than one header block, the mass flowing back into
+  // each header will be different. Adjust the mass in each header loop to
+  // reflect the masses flowing through back edges.
+  //
+  // To do this, we distribute the initial mass using the backedge masses
+  // as weights for the distribution.
+  BlockMass LoopMass = BlockMass::getFull();
+  Distribution Dist;
+
+  LLVM_DEBUG(dbgs() << "adjust-loop-header-mass:\n");
+  for (uint32_t H = 0; H < Loop.NumHeaders; ++H) {
+    auto &HeaderNode = Loop.Nodes[H];
+    auto &BackedgeMass = Loop.BackedgeMass[Loop.getHeaderIndex(HeaderNode)];
+    LLVM_DEBUG(dbgs() << " - Add back edge mass for node "
+                      << getBlockName(HeaderNode) << ": " << BackedgeMass
+                      << "\n");
+    if (BackedgeMass.getMass() > 0)
+      Dist.addLocal(HeaderNode, BackedgeMass.getMass());
+    else
+      LLVM_DEBUG(dbgs() << "   Nothing added. Back edge mass is zero\n");
+  }
+
+  DitheringDistributer D(Dist, LoopMass);
+
+  LLVM_DEBUG(dbgs() << " Distribute loop mass " << LoopMass
+                    << " to headers using above weights\n");
+  for (const Weight &W : Dist.Weights) {
+    BlockMass Taken = D.takeMass(W.Amount);
+    assert(W.Type == Weight::Local && "all weights should be local");
+    Working[W.TargetNode.Index].getMass() = Taken;
+    LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, nullptr));
+  }
+}
+
+void BlockFrequencyInfoImplBase::distributeIrrLoopHeaderMass(Distribution &Dist) {
+  BlockMass LoopMass = BlockMass::getFull();
+  DitheringDistributer D(Dist, LoopMass);
+  for (const Weight &W : Dist.Weights) {
+    BlockMass Taken = D.takeMass(W.Amount);
+    assert(W.Type == Weight::Local && "all weights should be local");
+    Working[W.TargetNode.Index].getMass() = Taken;
+    LLVM_DEBUG(debugAssign(*this, D, W.TargetNode, Taken, nullptr));
+  }
+}