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. 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. 46 uint64_t div96bit(uint64_t W[2], uint32_t D) { 47 uint64_t y = W[0]; 48 uint64_t x = W[1]; 49 50 for (int i = 1; i <= 64; ++i) { 51 uint32_t t = (int)x >> 31; 52 x = (x << 1) | (y >> 63); 53 y = y << 1; 54 if ((x | t) >= D) { 55 x -= D; 56 ++y; 57 } 58 } 59 60 return y; 61 } 62 63 } 64 65 66 BlockFrequency &BlockFrequency::operator*=(const BranchProbability &Prob) { 67 uint32_t n = Prob.getNumerator(); 68 uint32_t d = Prob.getDenominator(); 69 70 assert(n <= d && "Probability must be less or equal to 1."); 71 72 // If we can overflow use 96-bit operations. 73 if (n > 0 && Frequency > UINT64_MAX / n) { 74 // 96-bit value represented as W[1]:W[0]. 75 uint64_t W[2]; 76 77 // Probability is less or equal to 1 which means that results must fit 78 // 64-bit. 79 mult96bit(Frequency, n, W); 80 Frequency = div96bit(W, d); 81 return *this; 82 } 83 84 Frequency *= n; 85 Frequency /= d; 86 return *this; 87 } 88 89 const BlockFrequency 90 BlockFrequency::operator*(const BranchProbability &Prob) const { 91 BlockFrequency Freq(Frequency); 92 Freq *= Prob; 93 return Freq; 94 } 95 96 BlockFrequency &BlockFrequency::operator+=(const BlockFrequency &Freq) { 97 uint64_t Before = Freq.Frequency; 98 Frequency += Freq.Frequency; 99 100 // If overflow, set frequency to the maximum value. 101 if (Frequency < Before) 102 Frequency = UINT64_MAX; 103 104 return *this; 105 } 106 107 const BlockFrequency 108 BlockFrequency::operator+(const BlockFrequency &Prob) const { 109 BlockFrequency Freq(Frequency); 110 Freq += Prob; 111 return Freq; 112 } 113 114 void BlockFrequency::print(raw_ostream &OS) const { 115 OS << Frequency; 116 } 117 118 namespace llvm { 119 120 raw_ostream &operator<<(raw_ostream &OS, const BlockFrequency &Freq) { 121 Freq.print(OS); 122 return OS; 123 } 124 125 } 126