include/llvm/ADT/Statistic.h

   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 PrintOnExit = 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