LLVM  3.7.0
BranchProbability.h
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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 
20 namespace llvm {
21 
22 class raw_ostream;
23 
24 // This class represents Branch Probability as a non-negative fraction.
26  // Numerator
27  uint32_t N;
28 
29  // Denominator
30  uint32_t D;
31 
32 public:
33  BranchProbability(uint32_t n, uint32_t d) : N(n), D(d) {
34  assert(d > 0 && "Denominator 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).
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 
84  return Prob.print(OS);
85 }
86 
87 }
88 
89 #endif
uint32_t getNumerator() const
bool operator>(BranchProbability RHS) const
static BranchProbability getOne()
bool operator>=(BranchProbability RHS) const
bool operator==(BranchProbability RHS) const
BranchProbability(uint32_t n, uint32_t d)
uint64_t scaleByInverse(uint64_t Num) const
Scale a large integer by the inverse.
raw_ostream & print(raw_ostream &OS) const
bool operator!=(BranchProbability RHS) const
bool operator<=(BranchProbability RHS) const
bool operator<(BranchProbability RHS) const
uint64_t scale(uint64_t Num) const
Scale a large integer.
uint32_t getDenominator() const
raw_ostream & operator<<(raw_ostream &OS, const APInt &I)
Definition: APInt.h:1738
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:38
static BranchProbability getZero()
BranchProbability getCompl() const