Update LLVM for 3.5 rebase (r209712).

Change-Id: I149556c940fb7dc92d075273c87ff584f400941f

1 files changed, 995 insertions, 0 deletions

diff --git a/lib/Analysis/BlockFrequencyInfoImpl.cpp b/lib/Analysis/BlockFrequencyInfoImpl.cpp
new file mode 100644
index 0000000..87d93a4
--- /dev/null
+++ b/lib/Analysis/BlockFrequencyInfoImpl.cpp
@@ -0,0 +1,995 @@
+//===- BlockFrequencyImplInfo.cpp - Block Frequency Info Implementation ---===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Loops should be simplified before this analysis.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/BlockFrequencyInfoImpl.h"
+#include "llvm/ADT/APFloat.h"
+#include "llvm/ADT/SCCIterator.h"
+#include "llvm/Support/raw_ostream.h"
+#include <deque>
+
+using namespace llvm;
+using namespace llvm::bfi_detail;
+
+#define DEBUG_TYPE "block-freq"
+
+//===----------------------------------------------------------------------===//
+//
+// UnsignedFloat implementation.
+//
+//===----------------------------------------------------------------------===//
+#ifndef _MSC_VER
+const int32_t UnsignedFloatBase::MaxExponent;
+const int32_t UnsignedFloatBase::MinExponent;
+#endif
+
+static void appendDigit(std::string &Str, unsigned D) {
+  assert(D < 10);
+  Str += '0' + D % 10;
+}
+
+static void appendNumber(std::string &Str, uint64_t N) {
+  while (N) {
+    appendDigit(Str, N % 10);
+    N /= 10;
+  }
+}
+
+static bool doesRoundUp(char Digit) {
+  switch (Digit) {
+  case '5':
+  case '6':
+  case '7':
+  case '8':
+  case '9':
+    return true;
+  default:
+    return false;
+  }
+}
+
+static std::string toStringAPFloat(uint64_t D, int E, unsigned Precision) {
+  assert(E >= UnsignedFloatBase::MinExponent);
+  assert(E <= UnsignedFloatBase::MaxExponent);
+
+  // Find a new E, but don't let it increase past MaxExponent.
+  int LeadingZeros = UnsignedFloatBase::countLeadingZeros64(D);
+  int NewE = std::min(UnsignedFloatBase::MaxExponent, E + 63 - LeadingZeros);
+  int Shift = 63 - (NewE - E);
+  assert(Shift <= LeadingZeros);
+  assert(Shift == LeadingZeros || NewE == UnsignedFloatBase::MaxExponent);
+  D <<= Shift;
+  E = NewE;
+
+  // Check for a denormal.
+  unsigned AdjustedE = E + 16383;
+  if (!(D >> 63)) {
+    assert(E == UnsignedFloatBase::MaxExponent);
+    AdjustedE = 0;
+  }
+
+  // Build the float and print it.
+  uint64_t RawBits[2] = {D, AdjustedE};
+  APFloat Float(APFloat::x87DoubleExtended, APInt(80, RawBits));
+  SmallVector<char, 24> Chars;
+  Float.toString(Chars, Precision, 0);
+  return std::string(Chars.begin(), Chars.end());
+}
+
+static std::string stripTrailingZeros(const std::string &Float) {
+  size_t NonZero = Float.find_last_not_of('0');
+  assert(NonZero != std::string::npos && "no . in floating point string");
+
+  if (Float[NonZero] == '.')
+    ++NonZero;
+
+  return Float.substr(0, NonZero + 1);
+}
+
+std::string UnsignedFloatBase::toString(uint64_t D, int16_t E, int Width,
+                                        unsigned Precision) {
+  if (!D)
+    return "0.0";
+
+  // Canonicalize exponent and digits.
+  uint64_t Above0 = 0;
+  uint64_t Below0 = 0;
+  uint64_t Extra = 0;
+  int ExtraShift = 0;
+  if (E == 0) {
+    Above0 = D;
+  } else if (E > 0) {
+    if (int Shift = std::min(int16_t(countLeadingZeros64(D)), E)) {
+      D <<= Shift;
+      E -= Shift;
+
+      if (!E)
+        Above0 = D;
+    }
+  } else if (E > -64) {
+    Above0 = D >> -E;
+    Below0 = D << (64 + E);
+  } else if (E > -120) {
+    Below0 = D >> (-E - 64);
+    Extra = D << (128 + E);
+    ExtraShift = -64 - E;
+  }
+
+  // Fall back on APFloat for very small and very large numbers.
+  if (!Above0 && !Below0)
+    return toStringAPFloat(D, E, Precision);
+
+  // Append the digits before the decimal.
+  std::string Str;
+  size_t DigitsOut = 0;
+  if (Above0) {
+    appendNumber(Str, Above0);
+    DigitsOut = Str.size();
+  } else
+    appendDigit(Str, 0);
+  std::reverse(Str.begin(), Str.end());
+
+  // Return early if there's nothing after the decimal.
+  if (!Below0)
+    return Str + ".0";
+
+  // Append the decimal and beyond.
+  Str += '.';
+  uint64_t Error = UINT64_C(1) << (64 - Width);
+
+  // We need to shift Below0 to the right to make space for calculating
+  // digits.  Save the precision we're losing in Extra.
+  Extra = (Below0 & 0xf) << 56 | (Extra >> 8);
+  Below0 >>= 4;
+  size_t SinceDot = 0;
+  size_t AfterDot = Str.size();
+  do {
+    if (ExtraShift) {
+      --ExtraShift;
+      Error *= 5;
+    } else
+      Error *= 10;
+
+    Below0 *= 10;
+    Extra *= 10;
+    Below0 += (Extra >> 60);
+    Extra = Extra & (UINT64_MAX >> 4);
+    appendDigit(Str, Below0 >> 60);
+    Below0 = Below0 & (UINT64_MAX >> 4);
+    if (DigitsOut || Str.back() != '0')
+      ++DigitsOut;
+    ++SinceDot;
+  } while (Error && (Below0 << 4 | Extra >> 60) >= Error / 2 &&
+           (!Precision || DigitsOut <= Precision || SinceDot < 2));
+
+  // Return early for maximum precision.
+  if (!Precision || DigitsOut <= Precision)
+    return stripTrailingZeros(Str);
+
+  // Find where to truncate.
+  size_t Truncate =
+      std::max(Str.size() - (DigitsOut - Precision), AfterDot + 1);
+
+  // Check if there's anything to truncate.
+  if (Truncate >= Str.size())
+    return stripTrailingZeros(Str);
+
+  bool Carry = doesRoundUp(Str[Truncate]);
+  if (!Carry)
+    return stripTrailingZeros(Str.substr(0, Truncate));
+
+  // Round with the first truncated digit.
+  for (std::string::reverse_iterator I(Str.begin() + Truncate), E = Str.rend();
+       I != E; ++I) {
+    if (*I == '.')
+      continue;
+    if (*I == '9') {
+      *I = '0';
+      continue;
+    }
+
+    ++*I;
+    Carry = false;
+    break;
+  }
+
+  // Add "1" in front if we still need to carry.
+  return stripTrailingZeros(std::string(Carry, '1') + Str.substr(0, Truncate));
+}
+
+raw_ostream &UnsignedFloatBase::print(raw_ostream &OS, uint64_t D, int16_t E,
+                                      int Width, unsigned Precision) {
+  return OS << toString(D, E, Width, Precision);
+}
+
+void UnsignedFloatBase::dump(uint64_t D, int16_t E, int Width) {
+  print(dbgs(), D, E, Width, 0) << "[" << Width << ":" << D << "*2^" << E
+                                << "]";
+}
+
+static std::pair<uint64_t, int16_t>
+getRoundedFloat(uint64_t N, bool ShouldRound, int64_t Shift) {
+  if (ShouldRound)
+    if (!++N)
+      // Rounding caused an overflow.
+      return std::make_pair(UINT64_C(1), Shift + 64);
+  return std::make_pair(N, Shift);
+}
+
+std::pair<uint64_t, int16_t> UnsignedFloatBase::divide64(uint64_t Dividend,
+                                                         uint64_t Divisor) {
+  // Input should be sanitized.
+  assert(Divisor);
+  assert(Dividend);
+
+  // Minimize size of divisor.
+  int16_t Shift = 0;
+  if (int Zeros = countTrailingZeros(Divisor)) {
+    Shift -= Zeros;
+    Divisor >>= Zeros;
+  }
+
+  // Check for powers of two.
+  if (Divisor == 1)
+    return std::make_pair(Dividend, Shift);
+
+  // Maximize size of dividend.
+  if (int Zeros = countLeadingZeros64(Dividend)) {
+    Shift -= Zeros;
+    Dividend <<= Zeros;
+  }
+
+  // Start with the result of a divide.
+  uint64_t Quotient = Dividend / Divisor;
+  Dividend %= Divisor;
+
+  // Continue building the quotient with long division.
+  //
+  // TODO: continue with largers digits.
+  while (!(Quotient >> 63) && Dividend) {
+    // Shift Dividend, and check for overflow.
+    bool IsOverflow = Dividend >> 63;
+    Dividend <<= 1;
+    --Shift;
+
+    // Divide.
+    bool DoesDivide = IsOverflow || Divisor <= Dividend;
+    Quotient = (Quotient << 1) | uint64_t(DoesDivide);
+    Dividend -= DoesDivide ? Divisor : 0;
+  }
+
+  // Round.
+  if (Dividend >= getHalf(Divisor))
+    if (!++Quotient)
+      // Rounding caused an overflow in Quotient.
+      return std::make_pair(UINT64_C(1), Shift + 64);
+
+  return getRoundedFloat(Quotient, Dividend >= getHalf(Divisor), Shift);
+}
+
+std::pair<uint64_t, int16_t> UnsignedFloatBase::multiply64(uint64_t L,
+                                                           uint64_t R) {
+  // Separate into two 32-bit digits (U.L).
+  uint64_t UL = L >> 32, LL = L & UINT32_MAX, UR = R >> 32, LR = R & UINT32_MAX;
+
+  // Compute cross products.
+  uint64_t P1 = UL * UR, P2 = UL * LR, P3 = LL * UR, P4 = LL * LR;
+
+  // Sum into two 64-bit digits.
+  uint64_t Upper = P1, Lower = P4;
+  auto addWithCarry = [&](uint64_t N) {
+    uint64_t NewLower = Lower + (N << 32);
+    Upper += (N >> 32) + (NewLower < Lower);
+    Lower = NewLower;
+  };
+  addWithCarry(P2);
+  addWithCarry(P3);
+
+  // Check whether the upper digit is empty.
+  if (!Upper)
+    return std::make_pair(Lower, 0);
+
+  // Shift as little as possible to maximize precision.
+  unsigned LeadingZeros = countLeadingZeros64(Upper);
+  int16_t Shift = 64 - LeadingZeros;
+  if (LeadingZeros)
+    Upper = Upper << LeadingZeros | Lower >> Shift;
+  bool ShouldRound = Shift && (Lower & UINT64_C(1) << (Shift - 1));
+  return getRoundedFloat(Upper, ShouldRound, Shift);
+}
+
+//===----------------------------------------------------------------------===//
+//
+// BlockMass implementation.
+//
+//===----------------------------------------------------------------------===//
+UnsignedFloat<uint64_t> BlockMass::toFloat() const {
+  if (isFull())
+    return UnsignedFloat<uint64_t>(1, 0);
+  return UnsignedFloat<uint64_t>(getMass() + 1, -64);
+}
+
+void BlockMass::dump() const { print(dbgs()); }
+
+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;
+}
+
+//===----------------------------------------------------------------------===//
+//
+// BlockFrequencyInfoImpl implementation.
+//
+//===----------------------------------------------------------------------===//
+namespace {
+
+typedef BlockFrequencyInfoImplBase::BlockNode BlockNode;
+typedef BlockFrequencyInfoImplBase::Distribution Distribution;
+typedef BlockFrequencyInfoImplBase::Distribution::WeightList WeightList;
+typedef BlockFrequencyInfoImplBase::Float Float;
+typedef BlockFrequencyInfoImplBase::LoopData LoopData;
+typedef BlockFrequencyInfoImplBase::Weight Weight;
+typedef BlockFrequencyInfoImplBase::FrequencyData FrequencyData;
+
+/// \brief 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);
+};
+}
+
+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.
+  Weight W;
+  W.TargetNode = Node;
+  W.Amount = Amount;
+  W.Type = Type;
+  Weights.push_back(W);
+}
+
+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(W.Amount < W.Amount + OtherW.Amount && "Unexpected overflow");
+  W.Amount += OtherW.Amount;
+}
+static void combineWeightsBySorting(WeightList &Weights) {
+  // Sort so edges to the same node are adjacent.
+  std::sort(Weights.begin(), Weights.end(),
+            [](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());
+  return;
+}
+static void combineWeightsByHashing(WeightList &Weights) {
+  // Collect weights into a DenseMap.
+  typedef DenseMap<BlockNode::IndexType, Weight> HashTable;
+  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)
+    return;
+
+  // Recompute the total through accumulation (rather than shifting it) so that
+  // it's accurate after shifting.
+  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);
+  std::vector<WorkingData>().swap(Working);
+  Loops.clear();
+}
+
+/// \brief 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));
+  BFI.clear();
+  BFI.Freqs = std::move(SavedFreqs);
+}
+
+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)) {
+    DEBUG(debugSuccessor("backedge"));
+    Dist.addBackedge(OuterLoop->getHeader(), Weight);
+    return true;
+  }
+
+  if (Working[Resolved.Index].getContainingLoop() != OuterLoop) {
+    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.
+      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");
+  }
+
+  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;
+}
+
+/// \brief Get the maximum allowed loop scale.
+///
+/// Gives the maximum number of estimated iterations allowed for a loop.  Very
+/// large numbers cause problems downstream (even within 64-bits).
+static Float getMaxLoopScale() { return Float(1, 12); }
+
+/// \brief Compute the loop scale for a loop.
+void BlockFrequencyInfoImplBase::computeLoopScale(LoopData &Loop) {
+  // Compute loop scale.
+  DEBUG(dbgs() << "compute-loop-scale: " << getLoopName(Loop) << "\n");
+
+  // LoopScale == 1 / ExitMass
+  // ExitMass == HeadMass - BackedgeMass
+  BlockMass ExitMass = BlockMass::getFull() - Loop.BackedgeMass;
+
+  // Block scale stores the inverse of the scale.
+  Loop.Scale = ExitMass.toFloat().inverse();
+
+  DEBUG(dbgs() << " - exit-mass = " << ExitMass << " (" << BlockMass::getFull()
+               << " - " << Loop.BackedgeMass << ")\n"
+               << " - scale = " << Loop.Scale << "\n");
+
+  if (Loop.Scale > getMaxLoopScale()) {
+    Loop.Scale = getMaxLoopScale();
+    DEBUG(dbgs() << " - reduced-to-max-scale: " << getMaxLoopScale() << "\n");
+  }
+}
+
+/// \brief Package up a loop.
+void BlockFrequencyInfoImplBase::packageLoop(LoopData &Loop) {
+  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();
+    DEBUG(dbgs() << " - node: " << getBlockName(M.Index) << "\n");
+  }
+  Loop.IsPackaged = true;
+}
+
+void BlockFrequencyInfoImplBase::distributeMass(const BlockNode &Source,
+                                                LoopData *OuterLoop,
+                                                Distribution &Dist) {
+  BlockMass Mass = Working[Source.Index].getMass();
+  DEBUG(dbgs() << "  => mass:  " << Mass << "\n");
+
+  // Distribute mass to successors as laid out in Dist.
+  DitheringDistributer D(Dist, Mass);
+
+#ifndef NDEBUG
+  auto debugAssign = [&](const BlockNode &T, const BlockMass &M,
+                         const char *Desc) {
+    dbgs() << "  => assign " << M << " (" << D.RemMass << ")";
+    if (Desc)
+      dbgs() << " [" << Desc << "]";
+    if (T.isValid())
+      dbgs() << " to " << getBlockName(T);
+    dbgs() << "\n";
+  };
+  (void)debugAssign;
+#endif
+
+  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;
+      DEBUG(debugAssign(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 += Taken;
+      DEBUG(debugAssign(BlockNode(), Taken, "back"));
+      continue;
+    }
+
+    // This must be an exit.
+    assert(W.Type == Weight::Exit);
+    OuterLoop->Exits.push_back(std::make_pair(W.TargetNode, Taken));
+    DEBUG(debugAssign(W.TargetNode, Taken, "exit"));
+  }
+}
+
+static void convertFloatingToInteger(BlockFrequencyInfoImplBase &BFI,
+                                     const Float &Min, const Float &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, the register allocator currently deals poorly
+  // with large numbers.  Instead, push Min up a little from 1 to give some
+  // room to differentiate small, unequal numbers.
+  //
+  // TODO: fix issues downstream so that ScalingFactor can be Float(1,64)/Max.
+  Float ScalingFactor = Min.inverse();
+  if ((Max / Min).lg() < 60)
+    ScalingFactor <<= 3;
+
+  // Translate the floats to integers.
+  DEBUG(dbgs() << "float-to-int: min = " << Min << ", max = " << Max
+               << ", factor = " << ScalingFactor << "\n");
+  for (size_t Index = 0; Index < BFI.Freqs.size(); ++Index) {
+    Float Scaled = BFI.Freqs[Index].Floating * ScalingFactor;
+    BFI.Freqs[Index].Integer = std::max(UINT64_C(1), Scaled.toInt<uint64_t>());
+    DEBUG(dbgs() << " - " << BFI.getBlockName(Index) << ": float = "
+                 << BFI.Freqs[Index].Floating << ", scaled = " << Scaled
+                 << ", int = " << BFI.Freqs[Index].Integer << "\n");
+  }
+}
+
+/// \brief 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) {
+  DEBUG(dbgs() << "unwrap-loop-package: " << BFI.getLoopName(Loop)
+               << ": mass = " << Loop.Mass << ", scale = " << Loop.Scale
+               << "\n");
+  Loop.Scale *= Loop.Mass.toFloat();
+  Loop.IsPackaged = false;
+  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];
+    Float &F = Working.isAPackage() ? Working.getPackagedLoop()->Scale
+                                    : BFI.Freqs[N.Index].Floating;
+    Float New = Loop.Scale * F;
+    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].Floating = Working[Index].Mass.toFloat();
+
+  for (LoopData &Loop : Loops)
+    unwrapLoop(*this, Loop);
+}
+
+void BlockFrequencyInfoImplBase::finalizeMetrics() {
+  // Unwrap loop packages in reverse post-order, tracking min and max
+  // frequencies.
+  auto Min = Float::getLargest();
+  auto Max = Float::getZero();
+  for (size_t Index = 0; Index < Working.size(); ++Index) {
+    // Update min/max scale.
+    Min = std::min(Min, Freqs[Index].Floating);
+    Max = std::max(Max, Freqs[Index].Floating);
+  }
+
+  // Convert to integers.
+  convertFloatingToInteger(*this, Min, Max);
+
+  // Clean up data structures.
+  cleanup(*this);
+
+  // Print out the final stats.
+  DEBUG(dump());
+}
+
+BlockFrequency
+BlockFrequencyInfoImplBase::getBlockFreq(const BlockNode &Node) const {
+  if (!Node.isValid())
+    return 0;
+  return Freqs[Node.Index].Integer;
+}
+Float
+BlockFrequencyInfoImplBase::getFloatingBlockFreq(const BlockNode &Node) const {
+  if (!Node.isValid())
+    return Float::getZero();
+  return Freqs[Node.Index].Floating;
+}
+
+std::string
+BlockFrequencyInfoImplBase::getBlockName(const BlockNode &Node) const {
+  return std::string();
+}
+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 {
+  Float Block(Freq.getFrequency(), 0);
+  Float 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> {
+  typedef bfi_detail::IrreducibleGraph GraphT;
+
+  typedef const GraphT::IrrNode NodeType;
+  typedef GraphT::IrrNode::iterator ChildIteratorType;
+
+  static const NodeType *getEntryNode(const GraphT &G) {
+    return G.StartIrr;
+  }
+  static ChildIteratorType child_begin(NodeType *N) { return N->succ_begin(); }
+  static ChildIteratorType child_end(NodeType *N) { return N->succ_end(); }
+};
+}
+
+/// \brief 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);
+      DEBUG(dbgs() << "  => entry = " << BFI.getBlockName(Irr.Node) << "\n");
+      break;
+    }
+  }
+  assert(Headers.size() >= 2 && "Should be irreducible");
+  if (Headers.size() == InSCC.size()) {
+    // Every block is a header.
+    std::sort(Headers.begin(), Headers.end());
+    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);
+      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);
+    DEBUG(dbgs() << "  => other = " << BFI.getBlockName(Irr.Node) << "\n");
+  }
+  std::sort(Headers.begin(), Headers.end());
+  std::sort(Others.begin(), Others.end());
+}
+
+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.
+  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();
+  OuterLoop.BackedgeMass = 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());
+}