1//===- BranchProbability.h - Branch Probability Wrapper ---------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// Definition of BranchProbability shared by IR and Machine Instructions.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_SUPPORT_BRANCHPROBABILITY_H
15#define LLVM_SUPPORT_BRANCHPROBABILITY_H
16
17#include "llvm/Support/DataTypes.h"
18#include <cassert>
19
20namespace llvm {
21
22class raw_ostream;
23
24// This class represents Branch Probability as a non-negative fraction.
25class BranchProbability {
26  // Numerator
27  uint32_t N;
28
29  // Denominator
30  uint32_t D;
31
32public:
33  BranchProbability(uint32_t n, uint32_t d) : N(n), D(d) {
34    assert(d > 0 && "Denomiator cannot be 0!");
35    assert(n <= d && "Probability cannot be bigger than 1!");
36  }
37
38  static BranchProbability getZero() { return BranchProbability(0, 1); }
39  static BranchProbability getOne() { return BranchProbability(1, 1); }
40
41  uint32_t getNumerator() const { return N; }
42  uint32_t getDenominator() const { return D; }
43
44  // Return (1 - Probability).
45  BranchProbability getCompl() const {
46    return BranchProbability(D - N, D);
47  }
48
49  raw_ostream &print(raw_ostream &OS) const;
50
51  void dump() const;
52
53  /// \brief Scale a large integer.
54  ///
55  /// Scales \c Num.  Guarantees full precision.  Returns the floor of the
56  /// result.
57  ///
58  /// \return \c Num times \c this.
59  uint64_t scale(uint64_t Num) const;
60
61  /// \brief Scale a large integer by the inverse.
62  ///
63  /// Scales \c Num by the inverse of \c this.  Guarantees full precision.
64  /// Returns the floor of the result.
65  ///
66  /// \return \c Num divided by \c this.
67  uint64_t scaleByInverse(uint64_t Num) const;
68
69  bool operator==(BranchProbability RHS) const {
70    return (uint64_t)N * RHS.D == (uint64_t)D * RHS.N;
71  }
72  bool operator!=(BranchProbability RHS) const {
73    return !(*this == RHS);
74  }
75  bool operator<(BranchProbability RHS) const {
76    return (uint64_t)N * RHS.D < (uint64_t)D * RHS.N;
77  }
78  bool operator>(BranchProbability RHS) const { return RHS < *this; }
79  bool operator<=(BranchProbability RHS) const { return !(RHS < *this); }
80  bool operator>=(BranchProbability RHS) const { return !(*this < RHS); }
81};
82
83inline raw_ostream &operator<<(raw_ostream &OS, const BranchProbability &Prob) {
84  return Prob.print(OS);
85}
86
87}
88
89#endif
90