lib/Support/Statistic.cpp

   1 //===-- Statistic.cpp - Easy way to expose stats information --------------===//
   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 implements the 'Statistic' class, which is designed to be an easy
  10 // way to expose various success metrics from passes.  These statistics are
  11 // printed at the end of a run, when the -stats command line option is enabled
  12 // 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 NumInstEliminated("GCSE", "Number of instructions killed");
  18 //
  19 // Later, in the code: ++NumInstEliminated;
  20 //
  21 //===----------------------------------------------------------------------===//
  22
  23 #include "llvm/ADT/Statistic.h"
  24 #include "llvm/ADT/StringExtras.h"
  25 #include "llvm/Support/CommandLine.h"
  26 #include "llvm/Support/Compiler.h"
  27 #include "llvm/Support/Debug.h"
  28 #include "llvm/Support/Format.h"
  29 #include "llvm/Support/ManagedStatic.h"
  30 #include "llvm/Support/Mutex.h"
  31 #include "llvm/Support/Timer.h"
  32 #include "llvm/Support/YAMLTraits.h"
  33 #include "llvm/Support/raw_ostream.h"
  34 #include <algorithm>
  35 #include <cstring>
  36 using namespace llvm;
  37
  38 /// -stats - Command line option to cause transformations to emit stats about
  39 /// what they did.
  40 ///
  41 static cl::opt<bool> Stats(
  42     "stats",
  43     cl::desc("Enable statistics output from program (available with Asserts)"),
  44     cl::Hidden);
  45
  46 static cl::opt<bool> StatsAsJSON("stats-json",
  47                                  cl::desc("Display statistics as json data"),
  48                                  cl::Hidden);
  49
  50 static bool Enabled;
  51 static bool PrintOnExit;
  52
  53 namespace {
  54 /// This class is used in a ManagedStatic so that it is created on demand (when
  55 /// the first statistic is bumped) and destroyed only when llvm_shutdown is
  56 /// called. We print statistics from the destructor.
  57 /// This class is also used to look up statistic values from applications that
  58 /// use LLVM.
  59 class StatisticInfo {
  60   std::vector<TrackingStatistic *> Stats;
  61
  62   friend void llvm::PrintStatistics();
  63   friend void llvm::PrintStatistics(raw_ostream &OS);
  64   friend void llvm::PrintStatisticsJSON(raw_ostream &OS);
  65
  66   /// Sort statistics by debugtype,name,description.
  67   void sort();
  68 public:
  69   using const_iterator = std::vector<TrackingStatistic *>::const_iterator;
  70
  71   StatisticInfo();
  72   ~StatisticInfo();
  73
  74   void addStatistic(TrackingStatistic *S) { Stats.push_back(S); }
  75
  76   const_iterator begin() const { return Stats.begin(); }
  77   const_iterator end() const { return Stats.end(); }
  78   iterator_range<const_iterator> statistics() const {
  79     return {begin(), end()};
  80   }
  81
  82   void reset();
  83 };
  84 } // end anonymous namespace
  85
  86 static ManagedStatic<StatisticInfo> StatInfo;
  87 static ManagedStatic<sys::SmartMutex<true> > StatLock;
  88
  89 /// RegisterStatistic - The first time a statistic is bumped, this method is
  90 /// called.
  91 void TrackingStatistic::RegisterStatistic() {
  92   // If stats are enabled, inform StatInfo that this statistic should be
  93   // printed.
  94   // llvm_shutdown calls destructors while holding the ManagedStatic mutex.
  95   // These destructors end up calling PrintStatistics, which takes StatLock.
  96   // Since dereferencing StatInfo and StatLock can require taking the
  97   // ManagedStatic mutex, doing so with StatLock held would lead to a lock
  98   // order inversion. To avoid that, we dereference the ManagedStatics first,
  99   // and only take StatLock afterwards.
 100   if (!Initialized.load(std::memory_order_relaxed)) {
 101     sys::SmartMutex<true> &Lock = *StatLock;
 102     StatisticInfo &SI = *StatInfo;
 103     sys::SmartScopedLock<true> Writer(Lock);
 104     // Check Initialized again after acquiring the lock.
 105     if (Initialized.load(std::memory_order_relaxed))
 106       return;
 107     if (Stats || Enabled)
 108       SI.addStatistic(this);
 109
 110     // Remember we have been registered.
 111     Initialized.store(true, std::memory_order_release);
 112   }
 113 }
 114
 115 StatisticInfo::StatisticInfo() {
 116   // Ensure timergroup lists are created first so they are destructed after us.
 117   TimerGroup::ConstructTimerLists();
 118 }
 119
 120 // Print information when destroyed, iff command line option is specified.
 121 StatisticInfo::~StatisticInfo() {
 122   if (::Stats || PrintOnExit)
 123     llvm::PrintStatistics();
 124 }
 125
 126 void llvm::EnableStatistics(bool PrintOnExit) {
 127   Enabled = true;
 128   ::PrintOnExit = PrintOnExit;
 129 }
 130
 131 bool llvm::AreStatisticsEnabled() {
 132   return Enabled || Stats;
 133 }
 134
 135 void StatisticInfo::sort() {
 136   llvm::stable_sort(
 137       Stats, [](const TrackingStatistic *LHS, const TrackingStatistic *RHS) {
 138         if (int Cmp = std::strcmp(LHS->getDebugType(), RHS->getDebugType()))
 139           return Cmp < 0;
 140
 141         if (int Cmp = std::strcmp(LHS->getName(), RHS->getName()))
 142           return Cmp < 0;
 143
 144         return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
 145       });
 146 }
 147
 148 void StatisticInfo::reset() {
 149   sys::SmartScopedLock<true> Writer(*StatLock);
 150
 151   // Tell each statistic that it isn't registered so it has to register
 152   // again. We're holding the lock so it won't be able to do so until we're
 153   // finished. Once we've forced it to re-register (after we return), then zero
 154   // the value.
 155   for (auto *Stat : Stats) {
 156     // Value updates to a statistic that complete before this statement in the
 157     // iteration for that statistic will be lost as intended.
 158     Stat->Initialized = false;
 159     Stat->Value = 0;
 160   }
 161
 162   // Clear the registration list and release the lock once we're done. Any
 163   // pending updates from other threads will safely take effect after we return.
 164   // That might not be what the user wants if they're measuring a compilation
 165   // but it's their responsibility to prevent concurrent compilations to make
 166   // a single compilation measurable.
 167   Stats.clear();
 168 }
 169
 170 void llvm::PrintStatistics(raw_ostream &OS) {
 171   StatisticInfo &Stats = *StatInfo;
 172
 173   // Figure out how long the biggest Value and Name fields are.
 174   unsigned MaxDebugTypeLen = 0, MaxValLen = 0;
 175   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
 176     MaxValLen = std::max(MaxValLen,
 177                          (unsigned)utostr(Stats.Stats[i]->getValue()).size());
 178     MaxDebugTypeLen = std::max(MaxDebugTypeLen,
 179                          (unsigned)std::strlen(Stats.Stats[i]->getDebugType()));
 180   }
 181
 182   Stats.sort();
 183
 184   // Print out the statistics header...
 185   OS << "===" << std::string(73, '-') << "===\n"
 186      << "                          ... Statistics Collected ...\n"
 187      << "===" << std::string(73, '-') << "===\n\n";
 188
 189   // Print all of the statistics.
 190   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i)
 191     OS << format("%*u %-*s - %s\n",
 192                  MaxValLen, Stats.Stats[i]->getValue(),
 193                  MaxDebugTypeLen, Stats.Stats[i]->getDebugType(),
 194                  Stats.Stats[i]->getDesc());
 195
 196   OS << '\n';  // Flush the output stream.
 197   OS.flush();
 198 }
 199
 200 void llvm::PrintStatisticsJSON(raw_ostream &OS) {
 201   sys::SmartScopedLock<true> Reader(*StatLock);
 202   StatisticInfo &Stats = *StatInfo;
 203
 204   Stats.sort();
 205
 206   // Print all of the statistics.
 207   OS << "{\n";
 208   const char *delim = "";
 209   for (const TrackingStatistic *Stat : Stats.Stats) {
 210     OS << delim;
 211     assert(yaml::needsQuotes(Stat->getDebugType()) == yaml::QuotingType::None &&
 212            "Statistic group/type name is simple.");
 213     assert(yaml::needsQuotes(Stat->getName()) == yaml::QuotingType::None &&
 214            "Statistic name is simple");
 215     OS << "\t\"" << Stat->getDebugType() << '.' << Stat->getName() << "\": "
 216        << Stat->getValue();
 217     delim = ",\n";
 218   }
 219   // Print timers.
 220   TimerGroup::printAllJSONValues(OS, delim);
 221
 222   OS << "\n}\n";
 223   OS.flush();
 224 }
 225
 226 void llvm::PrintStatistics() {
 227 #if LLVM_ENABLE_STATS
 228   sys::SmartScopedLock<true> Reader(*StatLock);
 229   StatisticInfo &Stats = *StatInfo;
 230
 231   // Statistics not enabled?
 232   if (Stats.Stats.empty()) return;
 233
 234   // Get the stream to write to.
 235   std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
 236   if (StatsAsJSON)
 237     PrintStatisticsJSON(*OutStream);
 238   else
 239     PrintStatistics(*OutStream);
 240
 241 #else
 242   // Check if the -stats option is set instead of checking
 243   // !Stats.Stats.empty().  In release builds, Statistics operators
 244   // do nothing, so stats are never Registered.
 245   if (Stats) {
 246     // Get the stream to write to.
 247     std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
 248     (*OutStream) << "Statistics are disabled.  "
 249                  << "Build with asserts or with -DLLVM_ENABLE_STATS\n";
 250   }
 251 #endif
 252 }
 253
 254 const std::vector<std::pair<StringRef, unsigned>> llvm::GetStatistics() {
 255   sys::SmartScopedLock<true> Reader(*StatLock);
 256   std::vector<std::pair<StringRef, unsigned>> ReturnStats;
 257
 258   for (const auto &Stat : StatInfo->statistics())
 259     ReturnStats.emplace_back(Stat->getName(), Stat->getValue());
 260   return ReturnStats;
 261 }
 262
 263 void llvm::ResetStatistics() {
 264   StatInfo->reset();
 265 }