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 Statistic {
  48 public:
  49   const char *DebugType;
  50   const char *Name;
  51   const char *Desc;
  52   std::atomic<unsigned> Value;
  53   std::atomic<bool> Initialized;
  54
  55   unsigned getValue() const { return Value.load(std::memory_order_relaxed); }
  56   const char *getDebugType() const { return DebugType; }
  57   const char *getName() const { return Name; }
  58   const char *getDesc() const { return Desc; }
  59
  60   /// construct - This should only be called for non-global statistics.
  61   void construct(const char *debugtype, const char *name, const char *desc) {
  62     DebugType = debugtype;
  63     Name = name;
  64     Desc = desc;
  65     Value = 0;
  66     Initialized = false;
  67   }
  68
  69   // Allow use of this class as the value itself.
  70   operator unsigned() const { return getValue(); }
  71
  72 #if LLVM_ENABLE_STATS
  73    const Statistic &operator=(unsigned Val) {
  74     Value.store(Val, std::memory_order_relaxed);
  75     return init();
  76   }
  77
  78   const Statistic &operator++() {
  79     Value.fetch_add(1, std::memory_order_relaxed);
  80     return init();
  81   }
  82
  83   unsigned operator++(int) {
  84     init();
  85     return Value.fetch_add(1, std::memory_order_relaxed);
  86   }
  87
  88   const Statistic &operator--() {
  89     Value.fetch_sub(1, std::memory_order_relaxed);
  90     return init();
  91   }
  92
  93   unsigned operator--(int) {
  94     init();
  95     return Value.fetch_sub(1, std::memory_order_relaxed);
  96   }
  97
  98   const Statistic &operator+=(unsigned V) {
  99     if (V == 0)
 100       return *this;
 101     Value.fetch_add(V, std::memory_order_relaxed);
 102     return init();
 103   }
 104
 105   const Statistic &operator-=(unsigned V) {
 106     if (V == 0)
 107       return *this;
 108     Value.fetch_sub(V, std::memory_order_relaxed);
 109     return init();
 110   }
 111
 112   void updateMax(unsigned V) {
 113     unsigned PrevMax = Value.load(std::memory_order_relaxed);
 114     // Keep trying to update max until we succeed or another thread produces
 115     // a bigger max than us.
 116     while (V > PrevMax && !Value.compare_exchange_weak(
 117                               PrevMax, V, std::memory_order_relaxed)) {
 118     }
 119     init();
 120   }
 121
 122 #else  // Statistics are disabled in release builds.
 123
 124   const Statistic &operator=(unsigned Val) {
 125     return *this;
 126   }
 127
 128   const Statistic &operator++() {
 129     return *this;
 130   }
 131
 132   unsigned operator++(int) {
 133     return 0;
 134   }
 135
 136   const Statistic &operator--() {
 137     return *this;
 138   }
 139
 140   unsigned operator--(int) {
 141     return 0;
 142   }
 143
 144   const Statistic &operator+=(const unsigned &V) {
 145     return *this;
 146   }
 147
 148   const Statistic &operator-=(const unsigned &V) {
 149     return *this;
 150   }
 151
 152   void updateMax(unsigned V) {}
 153
 154 #endif  // LLVM_ENABLE_STATS
 155
 156 protected:
 157   Statistic &init() {
 158     if (!Initialized.load(std::memory_order_acquire))
 159       RegisterStatistic();
 160     return *this;
 161   }
 162
 163   void RegisterStatistic();
 164 };
 165
 166 // STATISTIC - A macro to make definition of statistics really simple.  This
 167 // automatically passes the DEBUG_TYPE of the file into the statistic.
 168 #define STATISTIC(VARNAME, DESC)                                               \
 169   static llvm::Statistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC, {0}, {false}}
 170
 171 /// Enable the collection and printing of statistics.
 172 void EnableStatistics(bool PrintOnExit = true);
 173
 174 /// Check if statistics are enabled.
 175 bool AreStatisticsEnabled();
 176
 177 /// Return a file stream to print our output on.
 178 std::unique_ptr<raw_fd_ostream> CreateInfoOutputFile();
 179
 180 /// Print statistics to the file returned by CreateInfoOutputFile().
 181 void PrintStatistics();
 182
 183 /// Print statistics to the given output stream.
 184 void PrintStatistics(raw_ostream &OS);
 185
 186 /// Print statistics in JSON format. This does include all global timers (\see
 187 /// Timer, TimerGroup). Note that the timers are cleared after printing and will
 188 /// not be printed in human readable form or in a second call of
 189 /// PrintStatisticsJSON().
 190 void PrintStatisticsJSON(raw_ostream &OS);
 191
 192 /// Get the statistics. This can be used to look up the value of
 193 /// statistics without needing to parse JSON.
 194 ///
 195 /// This function does not prevent statistics being updated by other threads
 196 /// during it's execution. It will return the value at the point that it is
 197 /// read. However, it will prevent new statistics from registering until it
 198 /// completes.
 199 const std::vector<std::pair<StringRef, unsigned>> GetStatistics();
 200
 201 /// Reset the statistics. This can be used to zero and de-register the
 202 /// statistics in order to measure a compilation.
 203 ///
 204 /// When this function begins to call destructors prior to returning, all
 205 /// statistics will be zero and unregistered. However, that might not remain the
 206 /// case by the time this function finishes returning. Whether update from other
 207 /// threads are lost or merely deferred until during the function return is
 208 /// timing sensitive.
 209 ///
 210 /// Callers who intend to use this to measure statistics for a single
 211 /// compilation should ensure that no compilations are in progress at the point
 212 /// this function is called and that only one compilation executes until calling
 213 /// GetStatistics().
 214 void ResetStatistics();
 215
 216 } // end namespace llvm
 217
 218 #endif // LLVM_ADT_STATISTIC_H