1 //===-- llvm/ADT/Statistic.h - Easy way to expose stats ---------*- C++ -*-===// 2 // 3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 // See https://llvm.org/LICENSE.txt for license information. 5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 // 7 //===----------------------------------------------------------------------===// 8 // 9 // This file defines the 'Statistic' class, which is designed to be an easy way 10 // to expose various metrics from passes. These statistics are printed at the 11 // end of a run (from llvm_shutdown), when the -stats command line option is 12 // passed on the command line. 13 // 14 // This is useful for reporting information like the number of instructions 15 // simplified, optimized or removed by various transformations, like this: 16 // 17 // static Statistic NumInstsKilled("gcse", "Number of instructions killed"); 18 // 19 // Later, in the code: ++NumInstsKilled; 20 // 21 // NOTE: Statistics *must* be declared as global variables. 22 // 23 //===----------------------------------------------------------------------===// 24 25 #ifndef LLVM_ADT_STATISTIC_H 26 #define LLVM_ADT_STATISTIC_H 27 28 #include "llvm/Config/llvm-config.h" 29 #include "llvm/Support/Compiler.h" 30 #include <atomic> 31 #include <memory> 32 #include <vector> 33 34 // Determine whether statistics should be enabled. We must do it here rather 35 // than in CMake because multi-config generators cannot determine this at 36 // configure time. 37 #if !defined(NDEBUG) || LLVM_FORCE_ENABLE_STATS 38 #define LLVM_ENABLE_STATS 1 39 #endif 40 41 namespace llvm { 42 43 class raw_ostream; 44 class raw_fd_ostream; 45 class StringRef; 46 47 class StatisticBase { 48 public: 49 const char *DebugType; 50 const char *Name; 51 const char *Desc; 52 53 StatisticBase(const char *DebugType, const char *Name, const char *Desc) 54 : DebugType(DebugType), Name(Name), Desc(Desc) {} 55 56 const char *getDebugType() const { return DebugType; } 57 const char *getName() const { return Name; } 58 const char *getDesc() const { return Desc; } 59 }; 60 61 class TrackingStatistic : public StatisticBase { 62 public: 63 std::atomic<unsigned> Value; 64 std::atomic<bool> Initialized; 65 66 TrackingStatistic(const char *DebugType, const char *Name, const char *Desc) 67 : StatisticBase(DebugType, Name, Desc), Value(0), Initialized(false) {} 68 69 unsigned getValue() const { return Value.load(std::memory_order_relaxed); } 70 71 // Allow use of this class as the value itself. 72 operator unsigned() const { return getValue(); } 73 74 const TrackingStatistic &operator=(unsigned Val) { 75 Value.store(Val, std::memory_order_relaxed); 76 return init(); 77 } 78 79 const TrackingStatistic &operator++() { 80 Value.fetch_add(1, std::memory_order_relaxed); 81 return init(); 82 } 83 84 unsigned operator++(int) { 85 init(); 86 return Value.fetch_add(1, std::memory_order_relaxed); 87 } 88 89 const TrackingStatistic &operator--() { 90 Value.fetch_sub(1, std::memory_order_relaxed); 91 return init(); 92 } 93 94 unsigned operator--(int) { 95 init(); 96 return Value.fetch_sub(1, std::memory_order_relaxed); 97 } 98 99 const TrackingStatistic &operator+=(unsigned V) { 100 if (V == 0) 101 return *this; 102 Value.fetch_add(V, std::memory_order_relaxed); 103 return init(); 104 } 105 106 const TrackingStatistic &operator-=(unsigned V) { 107 if (V == 0) 108 return *this; 109 Value.fetch_sub(V, std::memory_order_relaxed); 110 return init(); 111 } 112 113 void updateMax(unsigned V) { 114 unsigned PrevMax = Value.load(std::memory_order_relaxed); 115 // Keep trying to update max until we succeed or another thread produces 116 // a bigger max than us. 117 while (V > PrevMax && !Value.compare_exchange_weak( 118 PrevMax, V, std::memory_order_relaxed)) { 119 } 120 init(); 121 } 122 123 protected: 124 TrackingStatistic &init() { 125 if (!Initialized.load(std::memory_order_acquire)) 126 RegisterStatistic(); 127 return *this; 128 } 129 130 void RegisterStatistic(); 131 }; 132 133 class NoopStatistic : public StatisticBase { 134 public: 135 using StatisticBase::StatisticBase; 136 137 unsigned getValue() const { return 0; } 138 139 // Allow use of this class as the value itself. 140 operator unsigned() const { return 0; } 141 142 const NoopStatistic &operator=(unsigned Val) { return *this; } 143 144 const NoopStatistic &operator++() { return *this; } 145 146 unsigned operator++(int) { return 0; } 147 148 const NoopStatistic &operator--() { return *this; } 149 150 unsigned operator--(int) { return 0; } 151 152 const NoopStatistic &operator+=(const unsigned &V) { return *this; } 153 154 const NoopStatistic &operator-=(const unsigned &V) { return *this; } 155 156 void updateMax(unsigned V) {} 157 }; 158 159 #if LLVM_ENABLE_STATS 160 using Statistic = TrackingStatistic; 161 #else 162 using Statistic = NoopStatistic; 163 #endif 164 165 // STATISTIC - A macro to make definition of statistics really simple. This 166 // automatically passes the DEBUG_TYPE of the file into the statistic. 167 #define STATISTIC(VARNAME, DESC) \ 168 static llvm::Statistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC} 169 170 // ALWAYS_ENABLED_STATISTIC - A macro to define a statistic like STATISTIC but 171 // it is enabled even if LLVM_ENABLE_STATS is off. 172 #define ALWAYS_ENABLED_STATISTIC(VARNAME, DESC) \ 173 static llvm::TrackingStatistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC} 174 175 /// Enable the collection and printing of statistics. 176 void EnableStatistics(bool DoPrintOnExit = true); 177 178 /// Check if statistics are enabled. 179 bool AreStatisticsEnabled(); 180 181 /// Return a file stream to print our output on. 182 std::unique_ptr<raw_fd_ostream> CreateInfoOutputFile(); 183 184 /// Print statistics to the file returned by CreateInfoOutputFile(). 185 void PrintStatistics(); 186 187 /// Print statistics to the given output stream. 188 void PrintStatistics(raw_ostream &OS); 189 190 /// Print statistics in JSON format. This does include all global timers (\see 191 /// Timer, TimerGroup). Note that the timers are cleared after printing and will 192 /// not be printed in human readable form or in a second call of 193 /// PrintStatisticsJSON(). 194 void PrintStatisticsJSON(raw_ostream &OS); 195 196 /// Get the statistics. This can be used to look up the value of 197 /// statistics without needing to parse JSON. 198 /// 199 /// This function does not prevent statistics being updated by other threads 200 /// during it's execution. It will return the value at the point that it is 201 /// read. However, it will prevent new statistics from registering until it 202 /// completes. 203 const std::vector<std::pair<StringRef, unsigned>> GetStatistics(); 204 205 /// Reset the statistics. This can be used to zero and de-register the 206 /// statistics in order to measure a compilation. 207 /// 208 /// When this function begins to call destructors prior to returning, all 209 /// statistics will be zero and unregistered. However, that might not remain the 210 /// case by the time this function finishes returning. Whether update from other 211 /// threads are lost or merely deferred until during the function return is 212 /// timing sensitive. 213 /// 214 /// Callers who intend to use this to measure statistics for a single 215 /// compilation should ensure that no compilations are in progress at the point 216 /// this function is called and that only one compilation executes until calling 217 /// GetStatistics(). 218 void ResetStatistics(); 219 220 } // end namespace llvm 221 222 #endif // LLVM_ADT_STATISTIC_H 223