Revert "blockfreq: Rewrite BlockFrequencyInfoImpl"

This reverts commits r206548, r206549 and r206549.

There are some unit tests failing that aren't failing locally [1], so
reverting until I have time to investigate.

[1]: http://bb.pgr.jp/builders/ninja-x64-msvc-RA-centos6/builds/1816

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@206556 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 283 insertions, 1606 deletions

diff --git a/include/llvm/Analysis/BlockFrequencyInfoImpl.h b/include/llvm/Analysis/BlockFrequencyInfoImpl.h
index 66d27b7e4a..f891afdf55 100644
--- a/include/llvm/Analysis/BlockFrequencyInfoImpl.h
+++ b/include/llvm/Analysis/BlockFrequencyInfoImpl.h
@@ -7,7 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// Shared implementation of BlockFrequency for IR and Machine Instructions.
+// Shared implementation of BlockFrequencyInfo for IR and Machine Instructions.
 //
 //===----------------------------------------------------------------------===//
 
@@ -16,6 +16,8 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/PostOrderIterator.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/MachineFunction.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/Support/BlockFrequency.h"
 #include "llvm/Support/BranchProbability.h"
@@ -24,1699 +26,374 @@
 #include <string>
 #include <vector>
 
-//===----------------------------------------------------------------------===//
-//
-// PositiveFloat definition.
-//
-// TODO: Make this private to BlockFrequencyInfoImpl or delete.
-//
-//===----------------------------------------------------------------------===//
 namespace llvm {
 
-class PositiveFloatBase {
-public:
-  static const int MaxExponent = 16383;
-  static const int MinExponent = -16382;
-  static const int DefaultPrecision = 10;
-
-  static void dump(uint64_t D, int16_t E, int Width);
-  static raw_ostream &print(raw_ostream &OS, uint64_t D, int16_t E, int Width,
-                            unsigned Precision);
-  static std::string toString(uint64_t D, int16_t E, int Width,
-                              unsigned Precision);
-  static int countLeadingZeros32(uint32_t N) { return countLeadingZeros(N); }
-  static int countLeadingZeros64(uint64_t N) { return countLeadingZeros(N); }
-  static uint64_t getHalf(uint64_t N) { return (N >> 1) + (N & 1); }
-
-  static std::pair<uint64_t, bool> splitSigned(int64_t N) {
-    if (N >= 0)
-      return std::make_pair(N, false);
-    if (N == INT64_MIN)
-      return std::make_pair(uint64_t(N) + 1, true);
-    return std::make_pair(-N, true);
-  }
-  static int64_t joinSigned(uint64_t U, bool IsNeg) {
-    if (U > INT64_MAX)
-      return IsNeg ? INT64_MIN : INT64_MAX;
-    return IsNeg ? -int16_t(U) : U;
-  }
 
-  static int32_t extractLg(const std::pair<int32_t, int> &Lg) {
-    return Lg.first;
-  }
-  static int32_t extractLgFloor(const std::pair<int32_t, int> &Lg) {
-    return Lg.first - (Lg.second > 0);
-  }
-  static int32_t extractLgCeiling(const std::pair<int32_t, int> &Lg) {
-    return Lg.first + (Lg.second < 0);
-  }
-  static uint64_t getDiff(int16_t L, int16_t R) {
-    assert(L <= R && "arguments in wrong order");
-    return (uint64_t)R - (uint64_t)L;
-  }
-
-  static std::pair<uint64_t, int16_t> divide64(uint64_t L, uint64_t R);
-  static std::pair<uint64_t, int16_t> multiply64(uint64_t L, uint64_t R);
-
-  static int compare(uint64_t L, uint64_t R, int Shift) {
-    assert(Shift >= 0);
-    assert(Shift < 64);
-
-    uint64_t L_adjusted = L >> Shift;
-    if (L_adjusted < R)
-      return -1;
-    if (L_adjusted > R)
-      return 1;
+class BranchProbabilityInfo;
+class BlockFrequencyInfo;
+class MachineBranchProbabilityInfo;
+class MachineBlockFrequencyInfo;
 
-    return L > L_adjusted << Shift ? 1 : 0;
-  }
+namespace bfi_detail {
+template <class BlockT> struct TypeMap {};
+template <> struct TypeMap<BasicBlock> {
+  typedef BasicBlock BlockT;
+  typedef Function FunctionT;
+  typedef BranchProbabilityInfo BranchProbabilityInfoT;
 };
-
-/// \brief Simple representation of a positive floating point.
-///
-/// PositiveFloat is a positive floating point number.  It uses simple
-/// saturation arithmetic, and every operation is well-defined for every value.
-///
-/// The number is split into a signed exponent and unsigned digits.  The number
-/// represented is \c getDigits()*2^getExponent().  In this way, the digits are
-/// much like the mantissa in the x87 long double, but there is no canonical
-/// form, so the same number can be represented by many bit representations
-/// (it's always in "denormal" mode).
-///
-/// PositiveFloat is templated on the underlying integer type for digits, which
-/// is expected to be one of uint64_t, uint32_t, uint16_t or uint8_t.
-///
-/// Unlike builtin floating point types, PositiveFloat is portable.
-///
-/// Unlike APFloat, PositiveFloat does not model architecture floating point
-/// behaviour (this should make it a little faster), and implements most
-/// operators (this makes it usable).
-///
-/// PositiveFloat is totally ordered.  However, there is no canonical form, so
-/// there are multiple representations of most scalars.  E.g.:
-///
-///     PositiveFloat(8u, 0) == PositiveFloat(4u, 1)
-///     PositiveFloat(4u, 1) == PositiveFloat(2u, 2)
-///     PositiveFloat(2u, 2) == PositiveFloat(1u, 3)
-///
-/// PositiveFloat implements most arithmetic operations.  Precision is kept
-/// where possible.  Uses simple saturation arithmetic, so that operations
-/// saturate to 0.0 or getLargest() rather than under or overflowing.  It has
-/// some extra arithmetic for unit inversion.  0.0/0.0 is defined to be 0.0.
-/// Any other division by 0.0 is defined to be getLargest().
-///
-/// As a convenience for modifying the exponent, left and right shifting are
-/// both implemented, and both interpret negative shifts as positive shifts in
-/// the opposite direction.
-///
-/// Future work might extract most of the implementation into a base class
-/// (e.g., \c Float) that has an \c IsSigned template parameter.  The initial
-/// use case for this only needed positive semantics, but it wouldn't take much
-/// work to extend.
-///
-/// Exponents are limited to the range accepted by x87 long double.  This makes
-/// it trivial to add functionality to convert to APFloat (this is already
-/// relied on for the implementation of printing).
-template <class DigitsT> class PositiveFloat : PositiveFloatBase {
-public:
-  static_assert(!std::numeric_limits<DigitsT>::is_signed,
-                "only unsigned floats supported");
-
-  typedef DigitsT DigitsType;
-
-private:
-  typedef std::numeric_limits<DigitsType> DigitsLimits;
-
-  static const int Width = sizeof(DigitsType) * 8;
-  static_assert(Width <= 64, "invalid integer width for digits");
-
-private:
-  DigitsType Digits;
-  int16_t Exponent;
-
-public:
-  PositiveFloat() : Digits(0), Exponent(0) {}
-
-  PositiveFloat(DigitsType Digits, int16_t Exponent)
-      : Digits(Digits), Exponent(Exponent) {}
-
-private:
-  PositiveFloat(const std::pair<uint64_t, int16_t> &X)
-      : Digits(X.first), Exponent(X.second) {}
-
-public:
-  static PositiveFloat getZero() { return PositiveFloat(0, 0); }
-  static PositiveFloat getOne() { return PositiveFloat(1, 0); }
-  static PositiveFloat getLargest() {
-    return PositiveFloat(DigitsLimits::max(), MaxExponent);
-  }
-  static PositiveFloat getFloat(uint64_t N) { return adjustToWidth(N, 0); }
-  static PositiveFloat getInverseFloat(uint64_t N) {
-    return getFloat(N).invert();
-  }
-  static PositiveFloat getFraction(DigitsType N, DigitsType D) {
-    return getQuotient(N, D);
-  }
-
-  int16_t getExponent() const { return Exponent; }
-  DigitsType getDigits() const { return Digits; }
-
-  template <class IntT> IntT toInt() const;
-
-  bool isZero() const { return !Digits; }
-  bool isLargest() const { return *this == getLargest(); }
-  bool isOne() const {
-    if (Exponent > 0 || Exponent <= -Width)
-      return false;
-    return Digits == DigitsType(1) << -Exponent;
-  }
-
-  /// \brief The log base 2, rounded.
-  ///
-  /// Get the lg of the scalar.  lg 0 is defined to be INT32_MIN.
-  int32_t lg() const { return extractLg(lgImpl()); }
-
-  /// \brief The log base 2, rounded towards INT32_MIN.
-  ///
-  /// Get the lg floor.  lg 0 is defined to be INT32_MIN.
-  int32_t lgFloor() const { return extractLgFloor(lgImpl()); }
-
-  /// \brief The log base 2, rounded towards INT32_MAX.
-  ///
-  /// Get the lg ceiling.  lg 0 is defined to be INT32_MIN.
-  int32_t lgCeiling() const { return extractLgCeiling(lgImpl()); }
-
-  bool operator==(const PositiveFloat &X) const { return compare(X) == 0; }
-  bool operator<(const PositiveFloat &X) const { return compare(X) < 0; }
-  bool operator!=(const PositiveFloat &X) const { return compare(X) != 0; }
-  bool operator>(const PositiveFloat &X) const { return compare(X) > 0; }
-  bool operator<=(const PositiveFloat &X) const { return compare(X) <= 0; }
-  bool operator>=(const PositiveFloat &X) const { return compare(X) >= 0; }
-
-  bool operator!() const { return isZero(); }
-
-  /// \brief Convert to a decimal representation in a string.
-  ///
-  /// Convert to a string.  Uses scientific notation for very large/small
-  /// numbers.  Scientific notation is used roughly for numbers outside of the
-  /// range 2^-64 through 2^64.
-  ///
-  /// \c Precision indicates the number of decimal digits of precision to use;
-  /// 0 requests the maximum available.
-  ///
-  /// As a special case to make debugging easier, if the number is small enough
-  /// to convert without scientific notation and has more than \c Precision
-  /// digits before the decimal place, it's printed accurately to the first
-  /// digit past zero.  E.g., assuming 10 digits of precision:
-  ///
-  ///     98765432198.7654... => 98765432198.8
-  ///      8765432198.7654... =>  8765432198.8
-  ///       765432198.7654... =>   765432198.8
-  ///        65432198.7654... =>    65432198.77
-  ///         5432198.7654... =>     5432198.765
-  std::string toString(unsigned Precision = DefaultPrecision) {
-    return PositiveFloatBase::toString(Digits, Exponent, Width, Precision);
-  }
-
-  /// \brief Print a decimal representation.
-  ///
-  /// Print a string.  See toString for documentation.
-  raw_ostream &print(raw_ostream &OS,
-                     unsigned Precision = DefaultPrecision) const {
-    return PositiveFloatBase::print(OS, Digits, Exponent, Width, Precision);
-  }
-  void dump() const { return PositiveFloatBase::dump(Digits, Exponent, Width); }
-
-  PositiveFloat &operator+=(const PositiveFloat &X);
-  PositiveFloat &operator-=(const PositiveFloat &X);
-  PositiveFloat &operator*=(const PositiveFloat &X);
-  PositiveFloat &operator/=(const PositiveFloat &X);
-  PositiveFloat &operator<<=(int16_t Shift) { return shiftLeft(Shift); }
-  PositiveFloat &operator>>=(int16_t Shift) { return shiftRight(Shift); }
-
-private:
-  PositiveFloat &shiftLeft(int32_t Shift);
-  PositiveFloat &shiftRight(int32_t Shift);
-  PositiveFloat normalizeExponents(PositiveFloat X);
-
-public:
-  /// \brief Scale a large number accurately.
-  ///
-  /// Scale N (multiply it by this).  Uses full precision multiplication, even
-  /// if Width is smaller than 64, so information is not lost.
-  uint64_t scale(uint64_t N) const;
-  uint64_t scaleByInverse(uint64_t N) const {
-    // TODO: implement directly, rather than relying on inverse.  Inverse is
-    // expensive.
-    return inverse().scale(N);
-  }
-  int64_t scale(int64_t N) const {
-    std::pair<uint64_t, bool> Unsigned = splitSigned(N);
-    return joinSigned(scale(Unsigned.first), Unsigned.second);
-  }
-  int64_t scaleByInverse(int64_t N) const {
-    std::pair<uint64_t, bool> Unsigned = splitSigned(N);
-    return joinSigned(scaleByInverse(Unsigned.first), Unsigned.second);
-  }
-
-  int compare(const PositiveFloat &X) const;
-  int compareTo(uint64_t N) const {
-    PositiveFloat Float = getFloat(N);
-    int Compare = compare(Float);
-    if (Width == 64 || Compare != 0)
-      return Compare;
-
-    // Check for precision loss.  We know *this == RoundTrip.
-    uint64_t RoundTrip = Float.template toInt<uint64_t>();
-    return N == RoundTrip ? 0 : RoundTrip < N ? -1 : 1;
-  }
-  int compareTo(int64_t N) const { return N < 0 ? 1 : compareTo(uint64_t(N)); }
-
-  PositiveFloat &invert() { return *this = PositiveFloat::getFloat(1) / *this; }
-  PositiveFloat inverse() const { return PositiveFloat(*this).invert(); }
-
-private:
-  static PositiveFloat getProduct(DigitsType L, DigitsType R);
-  static PositiveFloat getQuotient(DigitsType Dividend, DigitsType Divisor);
-
-  std::pair<int32_t, int> lgImpl() const;
-  static int countLeadingZerosWidth(DigitsType Digits) {
-    if (Width == 64)
-      return countLeadingZeros64(Digits);
-    if (Width == 32)
-      return countLeadingZeros32(Digits);
-    return countLeadingZeros32(Digits) + Width - 32;
-  }
-
-  static PositiveFloat adjustToWidth(uint64_t N, int S) {
-    assert(S >= MinExponent);
-    assert(S <= MaxExponent);
-    if (Width == 64 || N <= DigitsLimits::max())
-      return PositiveFloat(N, S);
-
-    // Shift right.
-    int Shift = 64 - Width - countLeadingZeros64(N);
-    DigitsType Shifted = N >> Shift;
-
-    // Round.
-    assert(S + Shift <= MaxExponent);
-    return getRounded(PositiveFloat(Shifted, S + Shift),
-                      N & UINT64_C(1) << (Shift - 1));
-  }
-
-  static PositiveFloat getRounded(PositiveFloat P, bool Round) {
-    if (!Round)
-      return P;
-    if (P.Digits == DigitsLimits::max())
-      // Careful of overflow in the exponent.
-      return PositiveFloat(1, P.Exponent) <<= Width;
-    return PositiveFloat(P.Digits + 1, P.Exponent);
-  }
+template <> struct TypeMap<MachineBasicBlock> {
+  typedef MachineBasicBlock BlockT;
+  typedef MachineFunction FunctionT;
+  typedef MachineBranchProbabilityInfo BranchProbabilityInfoT;
 };
-
-template <class DigitsT>
-PositiveFloat<DigitsT> operator+(const PositiveFloat<DigitsT> &L,
-                                 const PositiveFloat<DigitsT> &R) {
-  return PositiveFloat<DigitsT>(L) += R;
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> operator-(const PositiveFloat<DigitsT> &L,
-                                 const PositiveFloat<DigitsT> &R) {
-  return PositiveFloat<DigitsT>(L) -= R;
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> operator*(const PositiveFloat<DigitsT> &L,
-                                 const PositiveFloat<DigitsT> &R) {
-  return PositiveFloat<DigitsT>(L) *= R;
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> operator/(const PositiveFloat<DigitsT> &L,
-                                 const PositiveFloat<DigitsT> &R) {
-  return PositiveFloat<DigitsT>(L) /= R;
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> operator<<(const PositiveFloat<DigitsT> &F,
-                                  int16_t Shift) {
-  return PositiveFloat<DigitsT>(F) <<= Shift;
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> operator>>(const PositiveFloat<DigitsT> &F,
-                                  int16_t Shift) {
-  return PositiveFloat<DigitsT>(F) >>= Shift;
 }
 
-template <class DigitsT>
-raw_ostream &operator<<(raw_ostream &OS, const PositiveFloat<DigitsT> &X) {
-  return X.print(OS, 10);
-}
+/// BlockFrequencyInfoImpl implements block frequency algorithm for IR and
+/// Machine Instructions. Algorithm starts with value ENTRY_FREQ
+/// for the entry block and then propagates frequencies using branch weights
+/// from (Machine)BranchProbabilityInfo. LoopInfo is not required because
+/// algorithm can find "backedges" by itself.
+template <class BT>
+class BlockFrequencyInfoImpl {
+  typedef typename bfi_detail::TypeMap<BT>::BlockT BlockT;
+  typedef typename bfi_detail::TypeMap<BT>::FunctionT FunctionT;
+  typedef typename bfi_detail::TypeMap<BT>::BranchProbabilityInfoT
+  BranchProbabilityInfoT;
 
-template <class DigitsT>
-bool operator<(const PositiveFloat<DigitsT> &L, uint64_t R) {
-  return L.compareTo(R) < 0;
-}
-template <class DigitsT>
-bool operator>(const PositiveFloat<DigitsT> &L, uint64_t R) {
-  return L.compareTo(R) > 0;
-}
-template <class DigitsT>
-bool operator==(const PositiveFloat<DigitsT> &L, uint64_t R) {
-  return L.compareTo(R) == 0;
-}
-template <class DigitsT>
-bool operator!=(const PositiveFloat<DigitsT> &L, uint64_t R) {
-  return L.compareTo(R) != 0;
-}
-template <class DigitsT>
-bool operator<=(const PositiveFloat<DigitsT> &L, uint64_t R) {
-  return L.compareTo(R) <= 0;
-}
-template <class DigitsT>
-bool operator>=(const PositiveFloat<DigitsT> &L, uint64_t R) {
-  return L.compareTo(R) >= 0;
-}
+  DenseMap<const BlockT *, BlockFrequency> Freqs;
 
-template <class DigitsT>
-bool operator<(const PositiveFloat<DigitsT> &L, int64_t R) {
-  return L.compareTo(R) < 0;
-}
-template <class DigitsT>
-bool operator>(const PositiveFloat<DigitsT> &L, int64_t R) {
-  return L.compareTo(R) > 0;
-}
-template <class DigitsT>
-bool operator==(const PositiveFloat<DigitsT> &L, int64_t R) {
-  return L.compareTo(R) == 0;
-}
-template <class DigitsT>
-bool operator!=(const PositiveFloat<DigitsT> &L, int64_t R) {
-  return L.compareTo(R) != 0;
-}
-template <class DigitsT>
-bool operator<=(const PositiveFloat<DigitsT> &L, int64_t R) {
-  return L.compareTo(R) <= 0;
-}
-template <class DigitsT>
-bool operator>=(const PositiveFloat<DigitsT> &L, int64_t R) {
-  return L.compareTo(R) >= 0;
-}
+  BranchProbabilityInfoT *BPI;
 
-template <class DigitsT>
-bool operator<(const PositiveFloat<DigitsT> &L, uint32_t R) {
-  return L.compareTo(uint64_t(R)) < 0;
-}
-template <class DigitsT>
-bool operator>(const PositiveFloat<DigitsT> &L, uint32_t R) {
-  return L.compareTo(uint64_t(R)) > 0;
-}
-template <class DigitsT>
-bool operator==(const PositiveFloat<DigitsT> &L, uint32_t R) {
-  return L.compareTo(uint64_t(R)) == 0;
-}
-template <class DigitsT>
-bool operator!=(const PositiveFloat<DigitsT> &L, uint32_t R) {
-  return L.compareTo(uint64_t(R)) != 0;
-}
-template <class DigitsT>
-bool operator<=(const PositiveFloat<DigitsT> &L, uint32_t R) {
-  return L.compareTo(uint64_t(R)) <= 0;
-}
-template <class DigitsT>
-bool operator>=(const PositiveFloat<DigitsT> &L, uint32_t R) {
-  return L.compareTo(uint64_t(R)) >= 0;
-}
+  FunctionT *Fn;
 
-template <class DigitsT>
-bool operator<(const PositiveFloat<DigitsT> &L, int32_t R) {
-  return L.compareTo(int64_t(R)) < 0;
-}
-template <class DigitsT>
-bool operator>(const PositiveFloat<DigitsT> &L, int32_t R) {
-  return L.compareTo(int64_t(R)) > 0;
-}
-template <class DigitsT>
-bool operator==(const PositiveFloat<DigitsT> &L, int32_t R) {
-  return L.compareTo(int64_t(R)) == 0;
-}
-template <class DigitsT>
-bool operator!=(const PositiveFloat<DigitsT> &L, int32_t R) {
-  return L.compareTo(int64_t(R)) != 0;
-}
-template <class DigitsT>
-bool operator<=(const PositiveFloat<DigitsT> &L, int32_t R) {
-  return L.compareTo(int64_t(R)) <= 0;
-}
-template <class DigitsT>
-bool operator>=(const PositiveFloat<DigitsT> &L, int32_t R) {
-  return L.compareTo(int64_t(R)) >= 0;
-}
+  typedef GraphTraits< Inverse<BlockT *> > GT;
 
-template <class DigitsT>
-bool operator<(uint64_t L, const PositiveFloat<DigitsT> &R) {
-  return R > L;
-}
-template <class DigitsT>
-bool operator>(uint64_t L, const PositiveFloat<DigitsT> &R) {
-  return R < L;
-}
-template <class DigitsT>
-bool operator==(uint64_t L, const PositiveFloat<DigitsT> &R) {
-  return R == L;
-}
-template <class DigitsT>
-bool operator<=(uint64_t L, const PositiveFloat<DigitsT> &R) {
-  return R >= L;
-}
-template <class DigitsT>
-bool operator>=(uint64_t L, const PositiveFloat<DigitsT> &R) {
-  return R <= L;
-}
-template <class DigitsT>
-bool operator!=(uint64_t L, const PositiveFloat<DigitsT> &R) {
-  return R != L;
-}
-template <class DigitsT>
-bool operator<(int64_t L, const PositiveFloat<DigitsT> &R) {
-  return R > L;
-}
-template <class DigitsT>
-bool operator>(int64_t L, const PositiveFloat<DigitsT> &R) {
-  return R < L;
-}
-template <class DigitsT>
-bool operator==(int64_t L, const PositiveFloat<DigitsT> &R) {
-  return R == L;
-}
-template <class DigitsT>
-bool operator<=(int64_t L, const PositiveFloat<DigitsT> &R) {
-  return R >= L;
-}
-template <class DigitsT>
-bool operator>=(int64_t L, const PositiveFloat<DigitsT> &R) {
-  return R <= L;
-}
-template <class DigitsT>
-bool operator!=(int64_t L, const PositiveFloat<DigitsT> &R) {
-  return R != L;
-}
-template <class DigitsT>
-bool operator<(uint32_t L, const PositiveFloat<DigitsT> &R) {
-  return R > L;
-}
-template <class DigitsT>
-bool operator>(uint32_t L, const PositiveFloat<DigitsT> &R) {
-  return R < L;
-}
-template <class DigitsT>
-bool operator==(uint32_t L, const PositiveFloat<DigitsT> &R) {
-  return R == L;
-}
-template <class DigitsT>
-bool operator<=(uint32_t L, const PositiveFloat<DigitsT> &R) {
-  return R >= L;
-}
-template <class DigitsT>
-bool operator>=(uint32_t L, const PositiveFloat<DigitsT> &R) {
-  return R <= L;
-}
-template <class DigitsT>
-bool operator!=(uint32_t L, const PositiveFloat<DigitsT> &R) {
-  return R != L;
-}
-template <class DigitsT>
-bool operator<(int32_t L, const PositiveFloat<DigitsT> &R) {
-  return R > L;
-}
-template <class DigitsT>
-bool operator>(int32_t L, const PositiveFloat<DigitsT> &R) {
-  return R < L;
-}
-template <class DigitsT>
-bool operator==(int32_t L, const PositiveFloat<DigitsT> &R) {
-  return R == L;
-}
-template <class DigitsT>
-bool operator<=(int32_t L, const PositiveFloat<DigitsT> &R) {
-  return R >= L;
-}
-template <class DigitsT>
-bool operator>=(int32_t L, const PositiveFloat<DigitsT> &R) {
-  return R <= L;
-}
-template <class DigitsT>
-bool operator!=(int32_t L, const PositiveFloat<DigitsT> &R) {
-  return R != L;
-}
+  static const uint64_t EntryFreq = 1 << 14;
 
-template <class DigitsT>
-uint64_t PositiveFloat<DigitsT>::scale(uint64_t N) const {
-  if (Width == 64 || N <= DigitsLimits::max())
-    return (getFloat(N) * *this).template toInt<uint64_t>();
-  std::pair<int32_t, int> Lg = lgImpl();
-  if (extractLgFloor(Lg) >= 64)
-    return UINT64_MAX;
-  if (extractLgCeiling(Lg) <= -64)
-    return 0;
-
-  uint64_t Result = 0;
-  for (int Bit = 0; Bit < 64; Bit += Width) {
-    PositiveFloat Digit = getFloat(N & DigitsLimits::max() << Bit);
-    Digit *= *this;
-
-    uint64_t Sum = Result + (Digit.toInt<uint64_t>() >> Bit);
-    if (Sum < Result)
-      return UINT64_MAX;
-    Result = Sum;
+  std::string getBlockName(BasicBlock *BB) const {
+    return BB->getName().str();
   }
-  return Result;
-}
 
-template <class DigitsT>
-PositiveFloat<DigitsT> PositiveFloat<DigitsT>::getProduct(DigitsType L,
-                                                          DigitsType R) {
-  // Check for zero.
-  if (!L || !R)
-    return getZero();
+  std::string getBlockName(MachineBasicBlock *MBB) const {
+    std::string str;
+    raw_string_ostream ss(str);
+    ss << "BB#" << MBB->getNumber();
 
-  // Check for numbers that we can compute with 64-bit math.
-  if (Width <= 32)
-    return adjustToWidth(uint64_t(L) * uint64_t(R), 0);
-
-  // Do the full thing.
-  return PositiveFloat(multiply64(L, R));
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> PositiveFloat<DigitsT>::getQuotient(DigitsType Dividend,
-                                                           DigitsType Divisor) {
-  // Check for zero.
-  if (!Dividend)
-    return getZero();
-  if (!Divisor)
-    return getLargest();
-
-  if (Width == 64)
-    return PositiveFloat(divide64(Dividend, Divisor));
-
-  // We can compute this with 64-bit math.
-  int Shift = countLeadingZeros64(Dividend);
-  uint64_t Shifted = uint64_t(Dividend) << Shift;
-  uint64_t Quotient = Shifted / Divisor;
-
-  // If Quotient needs to be shifted, then adjustToWidth will round.
-  if (Quotient > DigitsLimits::max())
-    return adjustToWidth(Quotient, -Shift);
-
-  // Round based on the value of the next bit.
-  return getRounded(PositiveFloat(Quotient, -Shift),
-                    Shifted % Divisor >= getHalf(Divisor));
-}
-
-template <class DigitsT>
-template <class IntT>
-IntT PositiveFloat<DigitsT>::toInt() const {
-  typedef std::numeric_limits<IntT> Limits;
-  if (*this < 1)
-    return 0;
-  if (*this >= Limits::max())
-    return Limits::max();
+    if (const BasicBlock *BB = MBB->getBasicBlock())
+      ss << " derived from LLVM BB " << BB->getName();
 
-  IntT N = Digits;
-  if (Exponent > 0) {
-    assert(size_t(Exponent) < sizeof(IntT) * 8);
-    return N << Exponent;
+    return ss.str();
   }
-  if (Exponent < 0) {
-    assert(size_t(-Exponent) < sizeof(IntT) * 8);
-    return N >> -Exponent;
-  }
-  return N;
-}
-
-template <class DigitsT>
-std::pair<int32_t, int> PositiveFloat<DigitsT>::lgImpl() const {
-  if (isZero())
-    return std::make_pair(INT32_MIN, 0);
-
-  // Get the floor of the lg of Digits.
-  int32_t LocalFloor = Width - countLeadingZerosWidth(Digits) - 1;
-
-  // Get the floor of the lg of this.
-  int32_t Floor = Exponent + LocalFloor;
-  if (Digits == UINT64_C(1) << LocalFloor)
-    return std::make_pair(Floor, 0);
 
-  // Round based on the next digit.
-  bool Round = Digits & UINT64_C(1) << (LocalFloor - 1);
-  return std::make_pair(Floor + Round, Round ? 1 : -1);
-}
-
-template <class DigitsT>
-PositiveFloat<DigitsT>
-PositiveFloat<DigitsT>::normalizeExponents(PositiveFloat X) {
-  if (isZero() || X.isZero())
-    return X;
-
-  if (Exponent > X.Exponent) {
-    // Reverse the arguments.
-    *this = X.normalizeExponents(*this);
-    return X;
+  void setBlockFreq(BlockT *BB, BlockFrequency Freq) {
+    Freqs[BB] = Freq;
+    DEBUG(dbgs() << "Frequency(" << getBlockName(BB) << ") = ";
+          printBlockFreq(dbgs(), Freq) << "\n");
   }
 
-  if (Exponent == X.Exponent)
-    return X;
-
-  int ExponentDiff = getDiff(Exponent, X.Exponent);
-  if (ExponentDiff >= 2 * Width) {
-    *this = getZero();
-    return X;
+  /// getEdgeFreq - Return edge frequency based on SRC frequency and Src -> Dst
+  /// edge probability.
+  BlockFrequency getEdgeFreq(BlockT *Src, BlockT *Dst) const {
+    BranchProbability Prob = BPI->getEdgeProbability(Src, Dst);
+    return getBlockFreq(Src) * Prob;
   }
 
-  // Use up any leading zeros on X, and then shift this.
-  int ShiftX = std::min(countLeadingZerosWidth(X.Digits), ExponentDiff);
-  int ShiftThis = ExponentDiff - ShiftX;
-
-  if (ShiftThis >= Width) {
-    *this = getZero();
-    return X;
+  /// incBlockFreq - Increase BB block frequency by FREQ.
+  ///
+  void incBlockFreq(BlockT *BB, BlockFrequency Freq) {
+    Freqs[BB] += Freq;
+    DEBUG(dbgs() << "Frequency(" << getBlockName(BB) << ") += ";
+          printBlockFreq(dbgs(), Freq) << " --> ";
+          printBlockFreq(dbgs(), Freqs[BB]) << "\n");
   }
 
-  X.Digits <<= ShiftX;
-  X.Exponent -= ShiftX;
-  Digits >>= ShiftThis;
-  Exponent += ShiftThis;
-  return X;
-}
+  // All blocks in postorder.
+  std::vector<BlockT *> POT;
 
-template <class DigitsT>
-PositiveFloat<DigitsT> &PositiveFloat<DigitsT>::
-operator+=(const PositiveFloat &X) {
-  if (isLargest() || X.isZero())
-    return *this;
-  if (isZero() || X.isLargest())
-    return *this = X;
-
-  // Normalize exponents.
-  PositiveFloat Scaled = normalizeExponents(X);
-
-  // Check for zero again.
-  if (isZero())
-    return *this = Scaled;
-  if (Scaled.isZero())
-    return *this;
-
-  // Compute sum.
-  DigitsType Sum = Digits + Scaled.Digits;
-  bool DidOverflow = Sum < Digits || Sum < Scaled.Digits;
-  Digits = Sum;
-  if (!DidOverflow)
-    return *this;
-
-  if (Exponent == MaxExponent)
-    return *this = getLargest();
-
-  ++Exponent;
-  Digits = Digits >> 1 | UINT64_C(1) << (Width - 1);
-
-  return *this;
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> &PositiveFloat<DigitsT>::
-operator-=(const PositiveFloat &X) {
-  if (X.isZero())
-    return *this;
-  if (*this <= X)
-    return *this = getZero();
-
-  // Normalize exponents.
-  PositiveFloat Scaled = normalizeExponents(X);
-  assert(Digits >= Scaled.Digits);
-
-  // Compute difference.
-  if (!Scaled.isZero()) {
-    Digits -= Scaled.Digits;
-    return *this;
-  }
+  // Map Block -> Position in reverse-postorder list.
+  DenseMap<BlockT *, unsigned> RPO;
 
-  // Check if X just barely lost its last bit.  E.g., for 32-bit:
-  //
-  //   1*2^32 - 1*2^0 == 0xffffffff != 1*2^32
-  if (*this == PositiveFloat(1, X.lgFloor() + Width)) {
-    Digits = DigitsType(0) - 1;
-    --Exponent;
-  }
-  return *this;
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> &PositiveFloat<DigitsT>::
-operator*=(const PositiveFloat &X) {
-  if (isZero())
-    return *this;
-  if (X.isZero())
-    return *this = X;
-
-  // Save the exponents.
-  int32_t Exponents = int32_t(Exponent) + int32_t(X.Exponent);
-
-  // Get the raw product.
-  *this = getProduct(Digits, X.Digits);
-
-  // Combine with exponents.
-  return *this <<= Exponents;
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> &PositiveFloat<DigitsT>::
-operator/=(const PositiveFloat &X) {
-  if (isZero())
-    return *this;
-  if (X.isZero())
-    return *this = getLargest();
-
-  // Save the exponents.
-  int32_t Exponents = int32_t(Exponent) + -int32_t(X.Exponent);
-
-  // Get the raw quotient.
-  *this = getQuotient(Digits, X.Digits);
-
-  // Combine with exponents.
-  return *this <<= Exponents;
-}
-template <class DigitsT>
-PositiveFloat<DigitsT> &PositiveFloat<DigitsT>::shiftLeft(int32_t Shift) {
-  if (Shift < 0)
-    return shiftRight(-Shift);
-  if (!Shift || isZero())
-    return *this;
-
-  // Shift as much as we can in the exponent.
-  int16_t ExponentShift = std::min(Shift, MaxExponent - Exponent);
-  Exponent += ExponentShift;
-  if (ExponentShift == Shift)
-    return *this;
-
-  // Check this late, since it's rare.
-  if (isLargest())
-    return *this;
-
-  // Shift as far as possible.
-  int32_t RawShift = std::min(Shift, countLeadingZerosWidth(Digits));
-  if (RawShift + ExponentShift < Shift)
-    // Saturate.
-    return *this = getLargest();
-
-  Digits <<= Shift;
-  return *this;
-}
+  // For each loop header, record the per-iteration probability of exiting the
+  // loop. This is the reciprocal of the expected number of loop iterations.
+  typedef DenseMap<BlockT*, BranchProbability> LoopExitProbMap;
+  LoopExitProbMap LoopExitProb;
 
-template <class DigitsT>
-PositiveFloat<DigitsT> &PositiveFloat<DigitsT>::shiftRight(int32_t Shift) {
-  if (Shift < 0)
-    return shiftLeft(-Shift);
-  if (!Shift || isZero())
-    return *this;
-
-  // Shift as much as we can in the exponent.
-  int16_t ExponentShift = std::min(Shift, Exponent - MinExponent);
-  Exponent -= ExponentShift;
-  if (ExponentShift == Shift)
-    return *this;
-
-  // Shift as far as possible.
-  int32_t RawShift = Shift - ExponentShift;
-  if (RawShift >= Width)
-    // Saturate.
-    return *this = getZero();
-
-  // May result in zero.
-  Digits >>= Shift;
-  return *this;
-}
+  // (reverse-)postorder traversal iterators.
+  typedef typename std::vector<BlockT *>::iterator pot_iterator;
+  typedef typename std::vector<BlockT *>::reverse_iterator rpot_iterator;
 
-template <class DigitsT>
-int PositiveFloat<DigitsT>::compare(const PositiveFloat &X) const {
-  // Check for zero.
-  if (isZero())
-    return X.isZero() ? 0 : -1;
-  if (X.isZero())
-    return 1;
-
-  // Check for the scale.  Use lgFloor to be sure that the exponent difference
-  // is always lower than 64.
-  int32_t lgL = lgFloor(), lgR = X.lgFloor();
-  if (lgL != lgR)
-    return lgL < lgR ? -1 : 1;
-
-  // Compare digits.
-  if (Exponent < X.Exponent)
-    return PositiveFloatBase::compare(Digits, X.Digits, X.Exponent - Exponent);
-
-  return -PositiveFloatBase::compare(X.Digits, Digits, Exponent - X.Exponent);
-}
+  pot_iterator pot_begin() { return POT.begin(); }
+  pot_iterator pot_end() { return POT.end(); }
 
-template <class T> struct isPodLike<PositiveFloat<T>> {
-  static const bool value = true;
-};
-}
-
-//===----------------------------------------------------------------------===//
-//
-// BlockMass definition.
-//
-// TODO: Make this private to BlockFrequencyInfoImpl or delete.
-//
-//===----------------------------------------------------------------------===//
-namespace llvm {
+  rpot_iterator rpot_begin() { return POT.rbegin(); }
+  rpot_iterator rpot_end() { return POT.rend(); }
 
-/// \brief Mass of a block.
-///
-/// This class implements a sort of fixed-point fraction always between 0.0 and
-/// 1.0.  getMass() == UINT64_MAX indicates a value of 1.0.
-///
-/// Masses can be added and subtracted.  Simple saturation arithmetic is used,
-/// so arithmetic operations never overflow or underflow.
-///
-/// Masses can be multiplied.  Multiplication treats full mass as 1.0 and uses
-/// an inexpensive floating-point algorithm that's off-by-one (almost, but not
-/// quite, maximum precision).
-///
-/// Masses can be scaled by \a BranchProbability at maximum precision.
-class BlockMass {
-  uint64_t Mass;
+  rpot_iterator rpot_at(BlockT *BB) {
+    rpot_iterator I = rpot_begin();
+    unsigned idx = RPO.lookup(BB);
+    assert(idx);
+    std::advance(I, idx - 1);
 
-public:
-  BlockMass() : Mass(0) {}
-  explicit BlockMass(uint64_t Mass) : Mass(Mass) {}
-
-  static BlockMass getEmpty() { return BlockMass(); }
-  static BlockMass getFull() { return BlockMass(UINT64_MAX); }
-
-  uint64_t getMass() const { return Mass; }
-
-  bool isFull() const { return Mass == UINT64_MAX; }
-  bool isEmpty() const { return !Mass; }
-
-  bool operator!() const { return isEmpty(); }
-
-  /// \brief Add another mass.
-  ///
-  /// Adds another mass, saturating at \a isFull() rather than overflowing.
-  BlockMass &operator+=(const BlockMass &X) {
-    uint64_t Sum = Mass + X.Mass;
-    Mass = Sum < Mass ? UINT64_MAX : Sum;
-    return *this;
+    assert(*I == BB);
+    return I;
   }
 
-  /// \brief Subtract another mass.
+  /// isBackedge - Return if edge Src -> Dst is a reachable backedge.
   ///
-  /// Subtracts another mass, saturating at \a isEmpty() rather than
-  /// undeflowing.
-  BlockMass &operator-=(const BlockMass &X) {
-    uint64_t Diff = Mass - X.Mass;
-    Mass = Diff > Mass ? 0 : Diff;
-    return *this;
+  bool isBackedge(BlockT *Src, BlockT *Dst) const {
+    unsigned a = RPO.lookup(Src);
+    if (!a)
+      return false;
+    unsigned b = RPO.lookup(Dst);
+    assert(b && "Destination block should be reachable");
+    return a >= b;
   }
 
-  /// \brief Scale by another mass.
-  ///
-  /// The current implementation is a little imprecise, but it's relatively
-  /// fast, never overflows, and maintains the property that 1.0*1.0==1.0
-  /// (where isFull represents the number 1.0).  It's an approximation of
-  /// 128-bit multiply that gets right-shifted by 64-bits.
-  ///
-  /// For a given digit size, multiplying two-digit numbers looks like:
-  ///
-  ///                  U1 .    L1
-  ///                * U2 .    L2
-  ///                ============
-  ///           0 .       . L1*L2
-  ///     +     0 . U1*L2 .     0 // (shift left once by a digit-size)
-  ///     +     0 . U2*L1 .     0 // (shift left once by a digit-size)
-  ///     + U1*L2 .     0 .     0 // (shift left twice by a digit-size)
-  ///
-  /// BlockMass has 64-bit numbers.  Split each into two 32-bit digits, stored
-  /// 64-bit.  Add 1 to the lower digits, to model isFull as 1.0; this won't
-  /// overflow, since we have 64-bit storage for each digit.
-  ///
-  /// To do this accurately, (a) multiply into two 64-bit digits, incrementing
-  /// the upper digit on overflows of the lower digit (carry), (b) subtract 1
-  /// from the lower digit, decrementing the upper digit on underflow (carry),
-  /// and (c) truncate the lower digit.  For the 1.0*1.0 case, the upper digit
-  /// will be 0 at the end of step (a), and then will underflow back to isFull
-  /// (1.0) in step (b).
-  ///
-  /// Instead, the implementation does something a little faster with a small
-  /// loss of accuracy: ignore the lower 64-bit digit entirely.  The loss of
-  /// accuracy is small, since the sum of the unmodelled carries is 0 or 1
-  /// (i.e., step (a) will overflow at most once, and step (b) will underflow
-  /// only if step (a) overflows).
-  ///
-  /// This is the formula we're calculating:
-  ///
-  ///     U1.L1 * U2.L2 == U1 * U2 + (U1 * (L2+1))>>32 + (U2 * (L1+1))>>32
-  ///
-  /// As a demonstration of 1.0*1.0, consider two 4-bit numbers that are both
-  /// full (1111).
-  ///
-  ///     U1.L1 * U2.L2 == U1 * U2 + (U1 * (L2+1))>>2 + (U2 * (L1+1))>>2
-  ///     11.11 * 11.11 == 11 * 11 + (11 * (11+1))/4 + (11 * (11+1))/4
-  ///                   == 1001 + (11 * 100)/4 + (11 * 100)/4
-  ///                   == 1001 + 1100/4 + 1100/4
-  ///                   == 1001 + 0011 + 0011
-  ///                   == 1111
-  BlockMass &operator*=(const BlockMass &X) {
-    uint64_t U1 = Mass >> 32, L1 = Mass & UINT32_MAX, U2 = X.Mass >> 32,
-             L2 = X.Mass & UINT32_MAX;
-    Mass = U1 * U2 + (U1 * (L2 + 1) >> 32) + ((L1 + 1) * U2 >> 32);
-    return *this;
-  }
+  /// getSingleBlockPred - return single BB block predecessor or NULL if
+  /// BB has none or more predecessors.
+  BlockT *getSingleBlockPred(BlockT *BB) {
+    typename GT::ChildIteratorType
+      PI = GraphTraits< Inverse<BlockT *> >::child_begin(BB),
+      PE = GraphTraits< Inverse<BlockT *> >::child_end(BB);
 
-  /// \brief Multiply by a branch probability.
-  ///
-  /// Multiply by P.  Guarantees full precision.
-  ///
-  /// This could be naively implemented by multiplying by the numerator and
-  /// dividing by the denominator, but in what order?  Multiplying first can
-  /// overflow, while dividing first will lose precision (potentially, changing
-  /// a non-zero mass to zero).
-  ///
-  /// The implementation mixes the two methods.  Since \a BranchProbability
-  /// uses 32-bits and \a BlockMass 64-bits, shift the mass as far to the left
-  /// as there is room, then divide by the denominator to get a quotient.
-  /// Multiplying by the numerator and right shifting gives a first
-  /// approximation.
-  ///
-  /// Calculate the error in this first approximation by calculating the
-  /// opposite mass (multiply by the opposite numerator and shift) and
-  /// subtracting both from teh original mass.
-  ///
-  /// Add to the first approximation the correct fraction of this error value.
-  /// This time, multiply first and then divide, since there is no danger of
-  /// overflow.
-  ///
-  /// \pre P represents a fraction between 0.0 and 1.0.
-  BlockMass &operator*=(const BranchProbability &P);
-
-  bool operator==(const BlockMass &X) const { return Mass == X.Mass; }
-  bool operator<(const BlockMass &X) const { return Mass < X.Mass; }
-  bool operator!=(const BlockMass &X) const { return !(*this == X); }
-  bool operator>(const BlockMass &X) const { return X < *this; }
-  bool operator<=(const BlockMass &X) const { return !(*this > X); }
-  bool operator>=(const BlockMass &X) const { return !(*this < X); }
+    if (PI == PE)
+      return nullptr;
 
-  /// \brief Convert to floating point.
-  ///
-  /// Convert to a float.  \a isFull() gives 1.0, while \a isEmpty() gives
-  /// slightly above 0.0.
-  PositiveFloat<uint64_t> toFloat() const;
-
-  void dump() const;
-  raw_ostream &print(raw_ostream &OS) const;
-};
-
-inline BlockMass operator+(const BlockMass &L, const BlockMass &R) {
-  return BlockMass(L) += R;
-}
-inline BlockMass operator-(const BlockMass &L, const BlockMass &R) {
-  return BlockMass(L) -= R;
-}
-inline BlockMass operator*(const BlockMass &L, const BlockMass &R) {
-  return BlockMass(L) *= R;
-}
-inline BlockMass operator*(const BlockMass &L, const BranchProbability &R) {
-  return BlockMass(L) *= R;
-}
-inline BlockMass operator*(const BranchProbability &L, const BlockMass &R) {
-  return BlockMass(R) *= L;
-}
+    BlockT *Pred = *PI;
 
-inline raw_ostream &operator<<(raw_ostream &OS, const BlockMass &X) {
-  return X.print(OS);
-}
+    ++PI;
+    if (PI != PE)
+      return nullptr;
 
-template <> struct isPodLike<BlockMass> {
-  static const bool value = true;
-};
-}
+    return Pred;
+  }
 
-//===----------------------------------------------------------------------===//
-//
-// BlockFrequencyInfoImpl definition.
-//
-//===----------------------------------------------------------------------===//
-namespace llvm {
+  void doBlock(BlockT *BB, BlockT *LoopHead,
+               SmallPtrSet<BlockT *, 8> &BlocksInLoop) {
 
-class BasicBlock;
-class BranchProbabilityInfo;
-class Function;
-class Loop;
-class LoopInfo;
-class MachineBasicBlock;
-class MachineBranchProbabilityInfo;
-class MachineFunction;
-class MachineLoop;
-class MachineLoopInfo;
-
-/// \brief Base class for BlockFrequencyInfoImpl
-///
-/// BlockFrequencyInfoImplBase has supporting data structures and some
-/// algorithms for BlockFrequencyInfoImplBase.  Only algorithms that depend on
-/// the block type (or that call such algorithms) are skipped here.
-///
-/// Nevertheless, the majority of the overall algorithm documention lives with
-/// BlockFrequencyInfoImpl.  See there for details.
-class BlockFrequencyInfoImplBase {
-public:
-  typedef PositiveFloat<uint64_t> Float;
+    DEBUG(dbgs() << "doBlock(" << getBlockName(BB) << ")\n");
+    setBlockFreq(BB, 0);
 
-  /// \brief Representative of a block.
-  ///
-  /// This is a simple wrapper around an index into the reverse-post-order
-  /// traversal of the blocks.
-  ///
-  /// Unlike a block pointer, its order has meaning (location in the
-  /// topological sort) and it's class is the same regardless of block type.
-  struct BlockNode {
-    typedef uint32_t IndexType;
-    IndexType Index;
-
-    bool operator==(const BlockNode &X) const { return Index == X.Index; }
-    bool operator!=(const BlockNode &X) const { return Index != X.Index; }
-    bool operator<=(const BlockNode &X) const { return Index <= X.Index; }
-    bool operator>=(const BlockNode &X) const { return Index >= X.Index; }
-    bool operator<(const BlockNode &X) const { return Index < X.Index; }
-    bool operator>(const BlockNode &X) const { return Index > X.Index; }
-
-    BlockNode() : Index(UINT32_MAX) {}
-    BlockNode(IndexType Index) : Index(Index) {}
-
-    bool isValid() const { return Index <= getMaxIndex(); }
-    static size_t getMaxIndex() { return UINT32_MAX - 1; }
-  };
-
-  /// \brief Stats about a block itself.
-  struct FrequencyData {
-    Float Floating;
-    uint64_t Integer;
-  };
-
-  /// \brief Index of loop information.
-  struct WorkingData {
-    BlockNode ContainingLoop; ///< The block whose loop this block is inside.
-    uint32_t LoopIndex;       ///< Index into PackagedLoops.
-    bool IsPackaged;          ///< Has ContainingLoop been packaged up?
-    bool IsAPackage;          ///< Has this block's loop been packaged up?
-    BlockMass Mass;           ///< Mass distribution from the entry block.
-
-    WorkingData()
-        : LoopIndex(UINT32_MAX), IsPackaged(false), IsAPackage(false) {}
-
-    bool hasLoopHeader() const { return ContainingLoop.isValid(); }
-    bool isLoopHeader() const { return LoopIndex != UINT32_MAX; }
-  };
-
-  /// \brief Unscaled probability weight.
-  ///
-  /// Probability weight for an edge in the graph (including the
-  /// successor/target node).
-  ///
-  /// All edges in the original function are 32-bit.  However, exit edges from
-  /// loop packages are taken from 64-bit exit masses, so we need 64-bits of
-  /// space in general.
-  ///
-  /// In addition to the raw weight amount, Weight stores the type of the edge
-  /// in the current context (i.e., the context of the loop being processed).
-  /// Is this a local edge within the loop, an exit from the loop, or a
-  /// backedge to the loop header?
-  struct Weight {
-    enum DistType { Local, Exit, Backedge };
-    DistType Type;
-    BlockNode TargetNode;
-    uint64_t Amount;
-    Weight() : Type(Local), Amount(0) {}
-  };
-
-  /// \brief Distribution of unscaled probability weight.
-  ///
-  /// Distribution of unscaled probability weight to a set of successors.
-  ///
-  /// This class collates the successor edge weights for later processing.
-  ///
-  /// \a DidOverflow indicates whether \a Total did overflow while adding to
-  /// the distribution.  It should never overflow twice.  There's no flag for
-  /// whether \a ForwardTotal overflows, since when \a Total exceeds 32-bits
-  /// they both get re-computed during \a normalize().
-  struct Distribution {
-    typedef SmallVector<Weight, 4> WeightList;
-    WeightList Weights;    ///< Individual successor weights.
-    uint64_t Total;        ///< Sum of all weights.
-    bool DidOverflow;      ///< Whether \a Total did overflow.
-    uint32_t ForwardTotal; ///< Total excluding backedges.
-
-    Distribution() : Total(0), DidOverflow(false), ForwardTotal(0) {}
-    void addLocal(const BlockNode &Node, uint64_t Amount) {
-      add(Node, Amount, Weight::Local);
+    if (BB == LoopHead) {
+      setBlockFreq(BB, EntryFreq);
+      return;
     }
-    void addExit(const BlockNode &Node, uint64_t Amount) {
-      add(Node, Amount, Weight::Exit);
+
+    if (BlockT *Pred = getSingleBlockPred(BB)) {
+      if (BlocksInLoop.count(Pred))
+        setBlockFreq(BB, getEdgeFreq(Pred, BB));
+      // TODO: else? irreducible, ignore it for now.
+      return;
     }
-    void addBackedge(const BlockNode &Node, uint64_t Amount) {
-      add(Node, Amount, Weight::Backedge);
+
+    bool isInLoop = false;
+    bool isLoopHead = false;
+
+    for (typename GT::ChildIteratorType
+         PI = GraphTraits< Inverse<BlockT *> >::child_begin(BB),
+         PE = GraphTraits< Inverse<BlockT *> >::child_end(BB);
+         PI != PE; ++PI) {
+      BlockT *Pred = *PI;
+
+      if (isBackedge(Pred, BB)) {
+        isLoopHead = true;
+      } else if (BlocksInLoop.count(Pred)) {
+        incBlockFreq(BB, getEdgeFreq(Pred, BB));
+        isInLoop = true;
+      }
+      // TODO: else? irreducible.
     }
 
-    /// \brief Normalize the distribution.
-    ///
-    /// Combines multiple edges to the same \a Weight::TargetNode and scales
-    /// down so that \a Total fits into 32-bits.
-    ///
-    /// This is linear in the size of \a Weights.  For the vast majority of
-    /// cases, adjacent edge weights are combined by sorting WeightList and
-    /// combining adjacent weights.  However, for very large edge lists an
-    /// auxiliary hash table is used.
-    void normalize();
-
-  private:
-    void add(const BlockNode &Node, uint64_t Amount, Weight::DistType Type);
-  };
-
-  /// \brief Data for a packaged loop.
-  ///
-  /// Contains the data necessary to represent represent a loop as a node once
-  /// it's packaged.
-  ///
-  /// PackagedLoopData inherits from BlockData to give the node the necessary
-  /// stats.  Further, it has a list of successors, list of members, and stores
-  /// the backedge mass assigned to this loop.
-  struct PackagedLoopData {
-    typedef SmallVector<std::pair<BlockNode, BlockMass>, 4> ExitMap;
-    typedef SmallVector<BlockNode, 4> MemberList;
-    BlockNode Header;       ///< Header.
-    ExitMap Exits;          ///< Successor edges (and weights).
-    MemberList Members;     ///< Members of the loop.
-    BlockMass BackedgeMass; ///< Mass returned to loop header.
-    BlockMass Mass;
-    Float Scale;
-
-    PackagedLoopData(const BlockNode &Header) : Header(Header) {}
-  };
-
-  /// \brief Data about each block.  This is used downstream.
-  std::vector<FrequencyData> Freqs;
-
-  /// \brief Loop data: see initializeLoops().
-  std::vector<WorkingData> Working;
-
-  /// \brief Indexed information about packaged loops.
-  std::vector<PackagedLoopData> PackagedLoops;
-
-  /// \brief Create the initial loop packages.
-  ///
-  /// Initializes PackagedLoops using the data in Working about backedges
-  /// and containing loops.  Called by initializeLoops().
-  ///
-  /// \post WorkingData::LoopIndex has been initialized for every loop header
-  /// and PackagedLoopData::Members has been initialized.
+    if (!isInLoop)
+      return;
 
-  /// \brief Add all edges out of a packaged loop to the distribution.
-  ///
-  /// Adds all edges from LocalLoopHead to Dist.  Calls addToDist() to add each
-  /// successor edge.
-  void addLoopSuccessorsToDist(const BlockNode &LoopHead,
-                               const BlockNode &LocalLoopHead,
-                               Distribution &Dist);
+    if (!isLoopHead)
+      return;
 
-  /// \brief Add an edge to the distribution.
-  ///
-  /// Adds an edge to Succ to Dist.  If \c LoopHead.isValid(), then whether the
-  /// edge is forward/exit/backedge is in the context of LoopHead.  Otherwise,
-  /// every edge should be a forward edge (since all the loops are packaged
-  /// up).
-  void addToDist(Distribution &Dist, const BlockNode &LoopHead,
-                 const BlockNode &Pred, const BlockNode &Succ, uint64_t Weight);
-
-  PackagedLoopData &getLoopPackage(const BlockNode &Head) {
-    assert(Head.Index < Working.size());
-    size_t Index = Working[Head.Index].LoopIndex;
-    assert(Index < PackagedLoops.size());
-    return PackagedLoops[Index];
+    // This block is a loop header, so boost its frequency by the expected
+    // number of loop iterations. The loop blocks will be revisited so they all
+    // get this boost.
+    typename LoopExitProbMap::const_iterator I = LoopExitProb.find(BB);
+    assert(I != LoopExitProb.end() && "Loop header missing from table");
+    Freqs[BB] /= I->second;
+    DEBUG(dbgs() << "Loop header scaled to ";
+          printBlockFreq(dbgs(), Freqs[BB]) << ".\n");
   }
 
-  /// \brief Distribute mass according to a distribution.
-  ///
-  /// Distributes the mass in Source according to Dist.  If LoopHead.isValid(),
-  /// backedges and exits are stored in its entry in PackagedLoops.
-  ///
-  /// Mass is distributed in parallel from two copies of the source mass.
-  ///
-  /// The first mass (forward) represents the distribution of mass through the
-  /// local DAG.  This distribution should lose mass at loop exits and ignore
-  /// backedges.
-  ///
-  /// The second mass (general) represents the behavior of the loop in the
-  /// global context.  In a given distribution from the head, how much mass
-  /// exits, and to where?  How much mass returns to the loop head?
-  ///
-  /// The forward mass should be split up between local successors and exits,
-  /// but only actually distributed to the local successors.  The general mass
-  /// should be split up between all three types of successors, but distributed
-  /// only to exits and backedges.
-  void distributeMass(const BlockNode &Source, const BlockNode &LoopHead,
-                      Distribution &Dist);
-
-  /// \brief Compute the loop scale for a loop.
-  void computeLoopScale(const BlockNode &LoopHead);
-
-  /// \brief Package up a loop.
-  void packageLoop(const BlockNode &LoopHead);
-
-  /// \brief Finalize frequency metrics.
-  ///
-  /// Unwraps loop packages, calculates final frequencies, and cleans up
-  /// no-longer-needed data structures.
-  void finalizeMetrics();
+  /// doLoop - Propagate block frequency down through the loop.
+  void doLoop(BlockT *Head, BlockT *Tail) {
+    DEBUG(dbgs() << "doLoop(" << getBlockName(Head) << ", "
+                 << getBlockName(Tail) << ")\n");
 
-  /// \brief Clear all memory.
-  void clear();
+    SmallPtrSet<BlockT *, 8> BlocksInLoop;
 
-  virtual std::string getBlockName(const BlockNode &Node) const;
+    for (rpot_iterator I = rpot_at(Head), E = rpot_at(Tail); ; ++I) {
+      BlockT *BB = *I;
+      doBlock(BB, Head, BlocksInLoop);
 
-  virtual raw_ostream &print(raw_ostream &OS) const { return OS; }
-  void dump() const { print(dbgs()); }
-
-  Float getFloatingBlockFreq(const BlockNode &Node) const;
-
-  BlockFrequency getBlockFreq(const BlockNode &Node) const;
+      BlocksInLoop.insert(BB);
+      if (I == E)
+        break;
+    }
 
-  raw_ostream &printBlockFreq(raw_ostream &OS, const BlockNode &Node) const;
-  raw_ostream &printBlockFreq(raw_ostream &OS,
-                              const BlockFrequency &Freq) const;
+    // Compute loop's cyclic probability using backedges probabilities.
+    BlockFrequency BackFreq;
+    for (typename GT::ChildIteratorType
+         PI = GraphTraits< Inverse<BlockT *> >::child_begin(Head),
+         PE = GraphTraits< Inverse<BlockT *> >::child_end(Head);
+         PI != PE; ++PI) {
+      BlockT *Pred = *PI;
+      assert(Pred);
+      if (isBackedge(Pred, Head))
+        BackFreq += getEdgeFreq(Pred, Head);
+    }
 
-  uint64_t getEntryFreq() const {
-    assert(!Freqs.empty());
-    return Freqs[0].Integer;
+    // The cyclic probability is freq(BackEdges) / freq(Head), where freq(Head)
+    // only counts edges entering the loop, not the loop backedges.
+    // The probability of leaving the loop on each iteration is:
+    //
+    //   ExitProb = 1 - CyclicProb
+    //
+    // The Expected number of loop iterations is:
+    //
+    //   Iterations = 1 / ExitProb
+    //
+    uint64_t D = std::max(getBlockFreq(Head).getFrequency(), UINT64_C(1));
+    uint64_t N = std::max(BackFreq.getFrequency(), UINT64_C(1));
+    if (N < D)
+      N = D - N;
+    else
+      // We'd expect N < D, but rounding and saturation means that can't be
+      // guaranteed.
+      N = 1;
+
+    // Now ExitProb = N / D, make sure it fits in an i32/i32 fraction.
+    assert(N <= D);
+    if (D > UINT32_MAX) {
+      unsigned Shift = 32 - countLeadingZeros(D);
+      D >>= Shift;
+      N >>= Shift;
+      if (N == 0)
+        N = 1;
+    }
+    BranchProbability LEP = BranchProbability(N, D);
+    LoopExitProb.insert(std::make_pair(Head, LEP));
+    DEBUG(dbgs() << "LoopExitProb[" << getBlockName(Head) << "] = " << LEP
+          << " from 1 - ";
+          printBlockFreq(dbgs(), BackFreq) << " / ";
+          printBlockFreq(dbgs(), getBlockFreq(Head)) << ".\n");
   }
-  /// \brief Virtual destructor.
-  ///
-  /// Need a virtual destructor to mask the compiler warning about
-  /// getBlockName().
-  virtual ~BlockFrequencyInfoImplBase() {}
-};
 
-namespace bfi_detail {
-template <class BlockT> struct TypeMap {};
-template <> struct TypeMap<BasicBlock> {
-  typedef BasicBlock BlockT;
-  typedef Function FunctionT;
-  typedef BranchProbabilityInfo BranchProbabilityInfoT;
-  typedef Loop LoopT;
-  typedef LoopInfo LoopInfoT;
-};
-template <> struct TypeMap<MachineBasicBlock> {
-  typedef MachineBasicBlock BlockT;
-  typedef MachineFunction FunctionT;
-  typedef MachineBranchProbabilityInfo BranchProbabilityInfoT;
-  typedef MachineLoop LoopT;
-  typedef MachineLoopInfo LoopInfoT;
-};
-
-/// \brief Get the name of a MachineBasicBlock.
-///
-/// Get the name of a MachineBasicBlock.  It's templated so that including from
-/// CodeGen is unnecessary (that would be a layering issue).
-///
-/// This is used mainly for debug output.  The name is similar to
-/// MachineBasicBlock::getFullName(), but skips the name of the function.
-template <class BlockT> std::string getBlockName(const BlockT *BB) {
-  assert(BB && "Unexpected nullptr");
-  if (BB->getBasicBlock())
-    return BB->getName().str();
-  return (Twine("BB") + Twine(BB->getNumber())).str();
-}
-/// \brief Get the name of a BasicBlock.
-template <> inline std::string getBlockName(const BasicBlock *BB) {
-  assert(BB && "Unexpected nullptr");
-  return BB->getName().str();
-}
-}
-
-/// \brief Shared implementation for block frequency analysis.
-///
-/// This is a shared implementation of BlockFrequencyInfo and
-/// MachineBlockFrequencyInfo, and calculates the relative frequencies of
-/// blocks.
-///
-/// This algorithm leverages BlockMass and PositiveFloat to maintain precision,
-/// separates mass distribution from loop scaling, and dithers to eliminate
-/// probability mass loss.
-///
-/// The implementation is split between BlockFrequencyInfoImpl, which knows the
-/// type of graph being modelled (BasicBlock vs. MachineBasicBlock), and
-/// BlockFrequencyInfoImplBase, which doesn't.  The base class uses \a
-/// BlockNode, a wrapper around a uint32_t.  BlockNode is numbered from 0 in
-/// reverse-post order.  This gives two advantages:  it's easy to compare the
-/// relative ordering of two nodes, and maps keyed on BlockT can be represented
-/// by vectors.
-///
-/// This algorithm is O(V+E), unless there is irreducible control flow, in
-/// which case it's O(V*E) in the worst case.
-///
-/// These are the main stages:
-///
-///  0. Reverse post-order traversal (\a initializeRPOT()).
-///
-///     Run a single post-order traversal and save it (in reverse) in RPOT.
-///     All other stages make use of this ordering.  Save a lookup from BlockT
-///     to BlockNode (the index into RPOT) in Nodes.
-///
-///  1. Loop indexing (\a initializeLoops()).
-///
-///     Translate LoopInfo/MachineLoopInfo into a form suitable for the rest of
-///     the algorithm.  In particular, store the immediate members of each loop
-///     in reverse post-order.
-///
-///  2. Calculate mass and scale in loops (\a computeMassInLoops()).
-///
-///     For each loop (bottom-up), distribute mass through the DAG resulting
-///     from ignoring backedges and treating sub-loops as a single pseudo-node.
-///     Track the backedge mass distributed to the loop header, and use it to
-///     calculate the loop scale (number of loop iterations).
-///
-///     Visiting loops bottom-up is a post-order traversal of loop headers.
-///     For each loop, immediate members that represent sub-loops will already
-///     have been visited and packaged into a pseudo-node.
-///
-///     Distributing mass in a loop is a reverse-post-order traversal through
-///     the loop.  Start by assigning full mass to the Loop header.  For each
-///     node in the loop:
-///
-///         - Fetch and categorize the weight distribution for its successors.
-///           If this is a packaged-subloop, the weight distribution is stored
-///           in \a PackagedLoopData::Exits.  Otherwise, fetch it from
-///           BranchProbabilityInfo.
-///
-///         - Each successor is categorized as \a Weight::Local, a normal
-///           forward edge within the current loop, \a Weight::Backedge, a
-///           backedge to the loop header, or \a Weight::Exit, any successor
-///           outside the loop.  The weight, the successor, and its category
-///           are stored in \a Distribution.  There can be multiple edges to
-///           each successor.
-///
-///         - Normalize the distribution:  scale weights down so that their sum
-///           is 32-bits, and coalesce multiple edges to the same node.
-///
-///         - Distribute the mass accordingly, dithering to minimize mass loss,
-///           as described in \a distributeMass().  Mass is distributed in
-///           parallel in two ways: forward, and general.  Local successors
-///           take their mass from the forward mass, while exit and backedge
-///           successors take their mass from the general mass.  Additionally,
-///           exit edges use up (ignored) mass from the forward mass, and local
-///           edges use up (ignored) mass from the general distribution.
-///
-///     Finally, calculate the loop scale from the accumulated backedge mass.
-///
-///  3. Distribute mass in the function (\a computeMassInFunction()).
-///
-///     Finally, distribute mass through the DAG resulting from packaging all
-///     loops in the function.  This uses the same algorithm as distributing
-///     mass in a loop, except that there are no exit or backedge edges.
-///
-///  4. Loop unpackaging and cleanup (\a finalizeMetrics()).
-///
-///     Initialize the frequency to a floating point representation of its
-///     mass.
-///
-///     Visit loops top-down (reverse post-order), scaling the loop header's
-///     frequency by its psuedo-node's mass and loop scale.  Keep track of the
-///     minimum and maximum final frequencies.
-///
-///     Using the min and max frequencies as a guide, translate floating point
-///     frequencies to an appropriate range in uint64_t.
-///
-/// It has some known flaws.
-///
-///   - Irreducible control flow isn't modelled correctly.  In particular,
-///     LoopInfo and MachineLoopInfo ignore irreducible backedges.  The main
-///     result is that irreducible SCCs will under-scaled.  No mass is lost,
-///     but the computed branch weights for the loop pseudo-node will be
-///     incorrect.
-///
-///     Modelling irreducible control flow exactly involves setting up and
-///     solving a group of infinite geometric series.  Such precision is
-///     unlikely to be worthwhile, since most of our algorithms give up on
-///     irreducible control flow anyway.
-///
-///     Nevertheless, we might find that we need to get closer.  If
-///     LoopInfo/MachineLoopInfo flags loops with irreducible control flow
-///     (and/or the function as a whole), we can find the SCCs, compute an
-///     approximate exit frequency for the SCC as a whole, and scale up
-///     accordingly.
-///
-///   - Loop scale is limited to 4096 per loop (2^12) to avoid exhausting
-///     BlockFrequency's 64-bit integer precision.
-template <class BT> class BlockFrequencyInfoImpl : BlockFrequencyInfoImplBase {
-  typedef typename bfi_detail::TypeMap<BT>::BlockT BlockT;
-  typedef typename bfi_detail::TypeMap<BT>::FunctionT FunctionT;
-  typedef typename bfi_detail::TypeMap<BT>::BranchProbabilityInfoT
-  BranchProbabilityInfoT;
-  typedef typename bfi_detail::TypeMap<BT>::LoopT LoopT;
-  typedef typename bfi_detail::TypeMap<BT>::LoopInfoT LoopInfoT;
+  friend class BlockFrequencyInfo;
+  friend class MachineBlockFrequencyInfo;
 
-  typedef GraphTraits<const BlockT *> Successor;
-  typedef GraphTraits<Inverse<const BlockT *>> Predecessor;
+  BlockFrequencyInfoImpl() { }
 
-  const BranchProbabilityInfoT *BPI;
-  const LoopInfoT *LI;
-  const FunctionT *F;
+  void doFunction(FunctionT *fn, BranchProbabilityInfoT *bpi) {
+    Fn = fn;
+    BPI = bpi;
 
-  // All blocks in reverse postorder.
-  std::vector<const BlockT *> RPOT;
-  DenseMap<const BlockT *, BlockNode> Nodes;
+    // Clear everything.
+    RPO.clear();
+    POT.clear();
+    LoopExitProb.clear();
+    Freqs.clear();
 
-  typedef typename std::vector<const BlockT *>::const_iterator rpot_iterator;
+    BlockT *EntryBlock = fn->begin();
 
-  rpot_iterator rpot_begin() const { return RPOT.begin(); }
-  rpot_iterator rpot_end() const { return RPOT.end(); }
+    std::copy(po_begin(EntryBlock), po_end(EntryBlock), std::back_inserter(POT));
 
-  size_t getIndex(const rpot_iterator &I) const { return I - rpot_begin(); }
+    unsigned RPOidx = 0;
+    for (rpot_iterator I = rpot_begin(), E = rpot_end(); I != E; ++I) {
+      BlockT *BB = *I;
+      RPO[BB] = ++RPOidx;
+      DEBUG(dbgs() << "RPO[" << getBlockName(BB) << "] = " << RPO[BB] << "\n");
+    }
 
-  BlockNode getNode(const rpot_iterator &I) const {
-    return BlockNode(getIndex(I));
-  }
-  BlockNode getNode(const BlockT *BB) const { return Nodes.lookup(BB); }
+    // Travel over all blocks in postorder.
+    for (pot_iterator I = pot_begin(), E = pot_end(); I != E; ++I) {
+      BlockT *BB = *I;
+      BlockT *LastTail = nullptr;
+      DEBUG(dbgs() << "POT: " << getBlockName(BB) << "\n");
 
-  const BlockT *getBlock(const BlockNode &Node) const {
-    return RPOT[Node.Index];
-  }
+      for (typename GT::ChildIteratorType
+           PI = GraphTraits< Inverse<BlockT *> >::child_begin(BB),
+           PE = GraphTraits< Inverse<BlockT *> >::child_end(BB);
+           PI != PE; ++PI) {
 
-  void initializeRPOT();
-  void initializeLoops();
-  void runOnFunction(const FunctionT *F);
+        BlockT *Pred = *PI;
+        if (isBackedge(Pred, BB) && (!LastTail || RPO[Pred] > RPO[LastTail]))
+          LastTail = Pred;
+      }
 
-  void propagateMassToSuccessors(const BlockNode &LoopHead,
-                                 const BlockNode &Node);
-  void computeMassInLoops();
-  void computeMassInLoop(const BlockNode &LoopHead);
-  void computeMassInFunction();
+      if (LastTail)
+        doLoop(BB, LastTail);
+    }
 
-  std::string getBlockName(const BlockNode &Node) const override {
-    return bfi_detail::getBlockName(getBlock(Node));
+    // At the end assume the whole function as a loop, and travel over it once
+    // again.
+    doLoop(*(rpot_begin()), *(pot_begin()));
   }
 
 public:
-  const FunctionT *getFunction() const { return F; }
 
-  void doFunction(const FunctionT *F, const BranchProbabilityInfoT *BPI,
-                  const LoopInfoT *LI);
-  BlockFrequencyInfoImpl() : BPI(0), LI(0), F(0) {}
+  uint64_t getEntryFreq() { return EntryFreq; }
 
-  using BlockFrequencyInfoImplBase::getEntryFreq;
+  /// getBlockFreq - Return block frequency. Return 0 if we don't have it.
   BlockFrequency getBlockFreq(const BlockT *BB) const {
-    return BlockFrequencyInfoImplBase::getBlockFreq(getNode(BB));
-  }
-  Float getFloatingBlockFreq(const BlockT *BB) const {
-    return BlockFrequencyInfoImplBase::getFloatingBlockFreq(getNode(BB));
-  }
-
-  /// \brief Print the frequencies for the current function.
-  ///
-  /// Prints the frequencies for the blocks in the current function.
-  ///
-  /// Blocks are printed in the natural iteration order of the function, rather
-  /// than reverse post-order.  This provides two advantages:  writing -analyze
-  /// tests is easier (since blocks come out in source order), and even
-  /// unreachable blocks are printed.
-  raw_ostream &print(raw_ostream &OS) const override;
-  using BlockFrequencyInfoImplBase::dump;
-
-  using BlockFrequencyInfoImplBase::printBlockFreq;
-  raw_ostream &printBlockFreq(raw_ostream &OS, const BlockT *BB) const {
-    return BlockFrequencyInfoImplBase::printBlockFreq(OS, getNode(BB));
-  }
-};
-
-template <class BT>
-void BlockFrequencyInfoImpl<BT>::doFunction(const FunctionT *F,
-                                            const BranchProbabilityInfoT *BPI,
-                                            const LoopInfoT *LI) {
-  // Save the parameters.
-  this->BPI = BPI;
-  this->LI = LI;
-  this->F = F;
-
-  // Clean up left-over data structures.
-  BlockFrequencyInfoImplBase::clear();
-  RPOT.clear();
-  Nodes.clear();
-
-  // Initialize.
-  DEBUG(dbgs() << "\nblock-frequency: " << F->getName() << "\n================="
-               << std::string(F->getName().size(), '=') << "\n");
-  initializeRPOT();
-  initializeLoops();
-
-  // Visit loops in post-order to find thelocal mass distribution, and then do
-  // the full function.
-  computeMassInLoops();
-  computeMassInFunction();
-  finalizeMetrics();
-}
-
-template <class BT> void BlockFrequencyInfoImpl<BT>::initializeRPOT() {
-  const BlockT *Entry = F->begin();
-  RPOT.reserve(F->size());
-  std::copy(po_begin(Entry), po_end(Entry), std::back_inserter(RPOT));
-  std::reverse(RPOT.begin(), RPOT.end());
-
-  assert(RPOT.size() - 1 <= BlockNode::getMaxIndex() &&
-         "More nodes in function than Block Frequency Info supports");
-
-  DEBUG(dbgs() << "reverse-post-order-traversal\n");
-  for (rpot_iterator I = rpot_begin(), E = rpot_end(); I != E; ++I) {
-    BlockNode Node = getNode(I);
-    DEBUG(dbgs() << " - " << getIndex(I) << ": " << getBlockName(Node) << "\n");
-    Nodes[*I] = Node;
+    typename DenseMap<const BlockT *, BlockFrequency>::const_iterator
+      I = Freqs.find(BB);
+    if (I != Freqs.end())
+      return I->second;
+    return 0;
   }
 
-  Working.resize(RPOT.size());
-  Freqs.resize(RPOT.size());
-}
-
-template <class BT> void BlockFrequencyInfoImpl<BT>::initializeLoops() {
-  DEBUG(dbgs() << "loop-detection\n");
-  if (LI->empty())
-    return;
-
-  // Visit loops top down and assign them an index.
-  std::deque<const LoopT *> Q;
-  Q.insert(Q.end(), LI->begin(), LI->end());
-  while (!Q.empty()) {
-    const LoopT *Loop = Q.front();
-    Q.pop_front();
-    Q.insert(Q.end(), Loop->begin(), Loop->end());
-
-    // Save the order this loop was visited.
-    BlockNode Header = getNode(Loop->getHeader());
-    assert(Header.isValid());
-
-    Working[Header.Index].LoopIndex = PackagedLoops.size();
-    PackagedLoops.emplace_back(Header);
-    DEBUG(dbgs() << " - loop = " << getBlockName(Header) << "\n");
+  void print(raw_ostream &OS) const {
+    OS << "\n\n---- Block Freqs ----\n";
+    for (typename FunctionT::iterator I = Fn->begin(), E = Fn->end(); I != E;) {
+      BlockT *BB = I++;
+      OS << " " << getBlockName(BB) << " = ";
+      printBlockFreq(OS, getBlockFreq(BB)) << "\n";
+
+      for (typename GraphTraits<BlockT *>::ChildIteratorType
+           SI = GraphTraits<BlockT *>::child_begin(BB),
+           SE = GraphTraits<BlockT *>::child_end(BB); SI != SE; ++SI) {
+        BlockT *Succ = *SI;
+        OS << "  " << getBlockName(BB) << " -> " << getBlockName(Succ)
+           << " = "; printBlockFreq(OS, getEdgeFreq(BB, Succ)) << "\n";
+      }
+    }
   }
 
-  // Visit nodes in reverse post-order and add them to their deepest containing
-  // loop.
-  for (size_t Index = 0; Index < RPOT.size(); ++Index) {
-    const LoopT *Loop = LI->getLoopFor(RPOT[Index]);
-    if (!Loop)
-      continue;
-
-    // If this is a loop header, find its parent loop (if any).
-    if (Working[Index].isLoopHeader())
-      if (!(Loop = Loop->getParentLoop()))
-        continue;
-
-    // Add this node to its containing loop's member list.
-    BlockNode Header = getNode(Loop->getHeader());
-    assert(Header.isValid());
-    const auto &HeaderData = Working[Header.Index];
-    assert(HeaderData.isLoopHeader());
-
-    Working[Index].ContainingLoop = Header;
-    PackagedLoops[HeaderData.LoopIndex].Members.push_back(Index);
-    DEBUG(dbgs() << " - loop = " << getBlockName(Header)
-                 << ": member = " << getBlockName(Index) << "\n");
+  void dump() const {
+    print(dbgs());
   }
-}
-
-template <class BT> void BlockFrequencyInfoImpl<BT>::computeMassInLoops() {
-  // Visit loops with the deepest first, and the top-level loops last.
-  for (auto L = PackagedLoops.rbegin(), LE = PackagedLoops.rend(); L != LE; ++L)
-    computeMassInLoop(L->Header);
-}
-
-template <class BT>
-void BlockFrequencyInfoImpl<BT>::computeMassInLoop(const BlockNode &LoopHead) {
-  // Compute mass in loop.
-  DEBUG(dbgs() << "compute-mass-in-loop: " << getBlockName(LoopHead) << "\n");
-
-  Working[LoopHead.Index].Mass = BlockMass::getFull();
-  propagateMassToSuccessors(LoopHead, LoopHead);
-
-  for (const BlockNode &M : getLoopPackage(LoopHead).Members)
-    propagateMassToSuccessors(LoopHead, M);
-
-  computeLoopScale(LoopHead);
-  packageLoop(LoopHead);
-}
 
-template <class BT> void BlockFrequencyInfoImpl<BT>::computeMassInFunction() {
-  // Compute mass in function.
-  DEBUG(dbgs() << "compute-mass-in-function\n");
-  Working[0].Mass = BlockMass::getFull();
-  for (rpot_iterator I = rpot_begin(), IE = rpot_end(); I != IE; ++I) {
-    // Check for nodes that have been packaged.
-    BlockNode Node = getNode(I);
-    if (Working[Node.Index].hasLoopHeader())
-      continue;
-
-    propagateMassToSuccessors(BlockNode(), Node);
+  // Utility method that looks up the block frequency associated with BB and
+  // prints it to OS.
+  raw_ostream &printBlockFreq(raw_ostream &OS,
+                              const BlockT *BB) {
+    return printBlockFreq(OS, getBlockFreq(BB));
   }
-}
 
-template <class BT>
-void
-BlockFrequencyInfoImpl<BT>::propagateMassToSuccessors(const BlockNode &LoopHead,
-                                                      const BlockNode &Node) {
-  DEBUG(dbgs() << " - node: " << getBlockName(Node) << "\n");
-  // Calculate probability for successors.
-  Distribution Dist;
-  if (Node != LoopHead && Working[Node.Index].isLoopHeader())
-    addLoopSuccessorsToDist(LoopHead, Node, Dist);
-  else {
-    const BlockT *BB = getBlock(Node);
-    for (auto SI = Successor::child_begin(BB), SE = Successor::child_end(BB);
-         SI != SE; ++SI)
-      // Do not dereference SI, or getEdgeWeight() is linear in the number of
-      // successors.
-      addToDist(Dist, LoopHead, Node, getNode(*SI), BPI->getEdgeWeight(BB, SI));
+  raw_ostream &printBlockFreq(raw_ostream &OS,
+                              const BlockFrequency &Freq) const {
+    // Convert fixed-point number to decimal.
+    uint64_t Frequency = Freq.getFrequency();
+    OS << Frequency / EntryFreq << ".";
+    uint64_t Rem = Frequency % EntryFreq;
+    uint64_t Eps = 1;
+    do {
+      Rem *= 10;
+      Eps *= 10;
+      OS << Rem / EntryFreq;
+      Rem = Rem % EntryFreq;
+    } while (Rem >= Eps/2);
+    return OS;
   }
 
-  // Distribute mass to successors, saving exit and backedge data in the
-  // loop header.
-  distributeMass(Node, LoopHead, Dist);
-}
+};
 
-template <class BT>
-raw_ostream &BlockFrequencyInfoImpl<BT>::print(raw_ostream &OS) const {
-  if (!F)
-    return OS;
-  OS << "block-frequency-info: " << F->getName() << "\n";
-  for (const BlockT &BB : *F)
-    OS << " - " << bfi_detail::getBlockName(&BB)
-       << ": float = " << getFloatingBlockFreq(&BB)
-       << ", int = " << getBlockFreq(&BB).getFrequency() << "\n";
-
-  // Add an extra newline for readability.
-  OS << "\n";
-  return OS;
-}
 }
 
 #endif