1 //====--------------- lib/Support/BlockFrequency.cpp -----------*- 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 #include "llvm/Support/BranchProbability.h"
15 #include "llvm/Support/BlockFrequency.h"
16 #include "llvm/Support/raw_ostream.h"
17 #include <cassert>
18
19 using namespace llvm;
20
21 namespace {
22
23 /// mult96bit - Multiply FREQ by N and store result in W array.
mult96bit(uint64_t freq,uint32_t N,uint64_t W[2])24 void mult96bit(uint64_t freq, uint32_t N, uint64_t W[2]) {
25 uint64_t u0 = freq & UINT32_MAX;
26 uint64_t u1 = freq >> 32;
27
28 // Represent 96-bit value as w[2]:w[1]:w[0];
29 uint32_t w[3] = { 0, 0, 0 };
30
31 uint64_t t = u0 * N;
32 uint64_t k = t >> 32;
33 w[0] = t;
34 t = u1 * N + k;
35 w[1] = t;
36 w[2] = t >> 32;
37
38 // W[1] - higher bits.
39 // W[0] - lower bits.
40 W[0] = w[0] + ((uint64_t) w[1] << 32);
41 W[1] = w[2];
42 }
43
44
45 /// div96bit - Divide 96-bit value stored in W array by D. Return 64-bit frequency.
div96bit(uint64_t W[2],uint32_t D)46 uint64_t div96bit(uint64_t W[2], uint32_t D) {
47 uint64_t y = W[0];
48 uint64_t x = W[1];
49 int i;
50
51 for (i = 1; i <= 64 && x; ++i) {
52 uint32_t t = (int)x >> 31;
53 x = (x << 1) | (y >> 63);
54 y = y << 1;
55 if ((x | t) >= D) {
56 x -= D;
57 ++y;
58 }
59 }
60
61 return y << (64 - i + 1);
62 }
63
64 }
65
66
operator *=(const BranchProbability & Prob)67 BlockFrequency &BlockFrequency::operator*=(const BranchProbability &Prob) {
68 uint32_t n = Prob.getNumerator();
69 uint32_t d = Prob.getDenominator();
70
71 assert(n <= d && "Probability must be less or equal to 1.");
72
73 // Calculate Frequency * n.
74 uint64_t mulLo = (Frequency & UINT32_MAX) * n;
75 uint64_t mulHi = (Frequency >> 32) * n;
76 uint64_t mulRes = (mulHi << 32) + mulLo;
77
78 // If there was overflow use 96-bit operations.
79 if (mulHi > UINT32_MAX || mulRes < mulLo) {
80 // 96-bit value represented as W[1]:W[0].
81 uint64_t W[2];
82
83 // Probability is less or equal to 1 which means that results must fit
84 // 64-bit.
85 mult96bit(Frequency, n, W);
86 Frequency = div96bit(W, d);
87 return *this;
88 }
89
90 Frequency = mulRes / d;
91 return *this;
92 }
93
94 const BlockFrequency
operator *(const BranchProbability & Prob) const95 BlockFrequency::operator*(const BranchProbability &Prob) const {
96 BlockFrequency Freq(Frequency);
97 Freq *= Prob;
98 return Freq;
99 }
100
operator +=(const BlockFrequency & Freq)101 BlockFrequency &BlockFrequency::operator+=(const BlockFrequency &Freq) {
102 uint64_t Before = Freq.Frequency;
103 Frequency += Freq.Frequency;
104
105 // If overflow, set frequency to the maximum value.
106 if (Frequency < Before)
107 Frequency = UINT64_MAX;
108
109 return *this;
110 }
111
112 const BlockFrequency
operator +(const BlockFrequency & Prob) const113 BlockFrequency::operator+(const BlockFrequency &Prob) const {
114 BlockFrequency Freq(Frequency);
115 Freq += Prob;
116 return Freq;
117 }
118
print(raw_ostream & OS) const119 void BlockFrequency::print(raw_ostream &OS) const {
120 OS << Frequency;
121 }
122
123 namespace llvm {
124
operator <<(raw_ostream & OS,const BlockFrequency & Freq)125 raw_ostream &operator<<(raw_ostream &OS, const BlockFrequency &Freq) {
126 Freq.print(OS);
127 return OS;
128 }
129
130 }
131