1 //===-------- BlockFrequency.h - Block Frequency 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 // This file implements Block Frequency class.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #ifndef LLVM_SUPPORT_BLOCKFREQUENCY_H
15 #define LLVM_SUPPORT_BLOCKFREQUENCY_H
16 
17 #include "llvm/Support/DataTypes.h"
18 
19 namespace llvm {
20 
21 class raw_ostream;
22 class BranchProbability;
23 
24 // This class represents Block Frequency as a 64-bit value.
25 class BlockFrequency {
26 
27   uint64_t Frequency;
28   static const int64_t ENTRY_FREQ = 1 << 14;
29 
30   /// \brief Scale the given BlockFrequency by N/D. Return the remainder from
31   /// the division by D. Upon overflow, the routine will saturate and
32   /// additionally will return the remainder set to D.
33   uint32_t scale(uint32_t N, uint32_t D);
34 
35 public:
36   BlockFrequency(uint64_t Freq = 0) : Frequency(Freq) { }
37 
38   /// \brief Returns the frequency of the entry block of the function.
39   static uint64_t getEntryFrequency() { return ENTRY_FREQ; }
40 
41   /// \brief Returns the maximum possible frequency, the saturation value.
42   static uint64_t getMaxFrequency() { return -1ULL; }
43 
44   /// \brief Returns the frequency as a fixpoint number scaled by the entry
45   /// frequency.
46   uint64_t getFrequency() const { return Frequency; }
47 
48   /// \brief Multiplies with a branch probability. The computation will never
49   /// overflow.
50   BlockFrequency &operator*=(const BranchProbability &Prob);
51   const BlockFrequency operator*(const BranchProbability &Prob) const;
52 
53   /// \brief Divide by a non-zero branch probability using saturating
54   /// arithmetic.
55   BlockFrequency &operator/=(const BranchProbability &Prob);
56   BlockFrequency operator/(const BranchProbability &Prob) const;
57 
58   /// \brief Adds another block frequency using saturating arithmetic.
59   BlockFrequency &operator+=(const BlockFrequency &Freq);
60   const BlockFrequency operator+(const BlockFrequency &Freq) const;
61 
62   /// \brief Scale the given BlockFrequency by N/D. Return the remainder from
63   /// the division by D. Upon overflow, the routine will saturate.
64   uint32_t scale(const BranchProbability &Prob);
65 
66   bool operator<(const BlockFrequency &RHS) const {
67     return Frequency < RHS.Frequency;
68   }
69 
70   bool operator<=(const BlockFrequency &RHS) const {
71     return Frequency <= RHS.Frequency;
72   }
73 
74   bool operator>(const BlockFrequency &RHS) const {
75     return Frequency > RHS.Frequency;
76   }
77 
78   bool operator>=(const BlockFrequency &RHS) const {
79     return Frequency >= RHS.Frequency;
80   }
81 
82   void print(raw_ostream &OS) const;
83 };
84 
85 raw_ostream &operator<<(raw_ostream &OS, const BlockFrequency &Freq);
86 
87 }
88 
89 #endif
90