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<Statistic*> 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<Statistic *>::const_iterator;
  70
  71   StatisticInfo();
  72   ~StatisticInfo();
  73
  74   void addStatistic(Statistic *S) {
  75     Stats.push_back(S);
  76   }
  77
  78   const_iterator begin() const { return Stats.begin(); }
  79   const_iterator end() const { return Stats.end(); }
  80   iterator_range<const_iterator> statistics() const {
  81     return {begin(), end()};
  82   }
  83
  84   void reset();
  85 };
  86 } // end anonymous namespace
  87
  88 static ManagedStatic<StatisticInfo> StatInfo;
  89 static ManagedStatic<sys::SmartMutex<true> > StatLock;
  90
  91 /// RegisterStatistic - The first time a statistic is bumped, this method is
  92 /// called.
  93 void Statistic::RegisterStatistic() {
  94   // If stats are enabled, inform StatInfo that this statistic should be
  95   // printed.
  96   // llvm_shutdown calls destructors while holding the ManagedStatic mutex.
  97   // These destructors end up calling PrintStatistics, which takes StatLock.
  98   // Since dereferencing StatInfo and StatLock can require taking the
  99   // ManagedStatic mutex, doing so with StatLock held would lead to a lock
 100   // order inversion. To avoid that, we dereference the ManagedStatics first,
 101   // and only take StatLock afterwards.
 102   if (!Initialized.load(std::memory_order_relaxed)) {
 103     sys::SmartMutex<true> &Lock = *StatLock;
 104     StatisticInfo &SI = *StatInfo;
 105     sys::SmartScopedLock<true> Writer(Lock);
 106     // Check Initialized again after acquiring the lock.
 107     if (Initialized.load(std::memory_order_relaxed))
 108       return;
 109     if (Stats || Enabled)
 110       SI.addStatistic(this);
 111
 112     // Remember we have been registered.
 113     Initialized.store(true, std::memory_order_release);
 114   }
 115 }
 116
 117 StatisticInfo::StatisticInfo() {
 118   // Ensure timergroup lists are created first so they are destructed after us.
 119   TimerGroup::ConstructTimerLists();
 120 }
 121
 122 // Print information when destroyed, iff command line option is specified.
 123 StatisticInfo::~StatisticInfo() {
 124   if (::Stats || PrintOnExit)
 125     llvm::PrintStatistics();
 126 }
 127
 128 void llvm::EnableStatistics(bool PrintOnExit) {
 129   Enabled = true;
 130   ::PrintOnExit = PrintOnExit;
 131 }
 132
 133 bool llvm::AreStatisticsEnabled() {
 134   return Enabled || Stats;
 135 }
 136
 137 void StatisticInfo::sort() {
 138   std::stable_sort(Stats.begin(), Stats.end(),
 139                    [](const Statistic *LHS, const Statistic *RHS) {
 140     if (int Cmp = std::strcmp(LHS->getDebugType(), RHS->getDebugType()))
 141       return Cmp < 0;
 142
 143     if (int Cmp = std::strcmp(LHS->getName(), RHS->getName()))
 144       return Cmp < 0;
 145
 146     return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
 147   });
 148 }
 149
 150 void StatisticInfo::reset() {
 151   sys::SmartScopedLock<true> Writer(*StatLock);
 152
 153   // Tell each statistic that it isn't registered so it has to register
 154   // again. We're holding the lock so it won't be able to do so until we're
 155   // finished. Once we've forced it to re-register (after we return), then zero
 156   // the value.
 157   for (auto *Stat : Stats) {
 158     // Value updates to a statistic that complete before this statement in the
 159     // iteration for that statistic will be lost as intended.
 160     Stat->Initialized = false;
 161     Stat->Value = 0;
 162   }
 163
 164   // Clear the registration list and release the lock once we're done. Any
 165   // pending updates from other threads will safely take effect after we return.
 166   // That might not be what the user wants if they're measuring a compilation
 167   // but it's their responsibility to prevent concurrent compilations to make
 168   // a single compilation measurable.
 169   Stats.clear();
 170 }
 171
 172 void llvm::PrintStatistics(raw_ostream &OS) {
 173   StatisticInfo &Stats = *StatInfo;
 174
 175   // Figure out how long the biggest Value and Name fields are.
 176   unsigned MaxDebugTypeLen = 0, MaxValLen = 0;
 177   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
 178     MaxValLen = std::max(MaxValLen,
 179                          (unsigned)utostr(Stats.Stats[i]->getValue()).size());
 180     MaxDebugTypeLen = std::max(MaxDebugTypeLen,
 181                          (unsigned)std::strlen(Stats.Stats[i]->getDebugType()));
 182   }
 183
 184   Stats.sort();
 185
 186   // Print out the statistics header...
 187   OS << "===" << std::string(73, '-') << "===\n"
 188      << "                          ... Statistics Collected ...\n"
 189      << "===" << std::string(73, '-') << "===\n\n";
 190
 191   // Print all of the statistics.
 192   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i)
 193     OS << format("%*u %-*s - %s\n",
 194                  MaxValLen, Stats.Stats[i]->getValue(),
 195                  MaxDebugTypeLen, Stats.Stats[i]->getDebugType(),
 196                  Stats.Stats[i]->getDesc());
 197
 198   OS << '\n';  // Flush the output stream.
 199   OS.flush();
 200 }
 201
 202 void llvm::PrintStatisticsJSON(raw_ostream &OS) {
 203   sys::SmartScopedLock<true> Reader(*StatLock);
 204   StatisticInfo &Stats = *StatInfo;
 205
 206   Stats.sort();
 207
 208   // Print all of the statistics.
 209   OS << "{\n";
 210   const char *delim = "";
 211   for (const Statistic *Stat : Stats.Stats) {
 212     OS << delim;
 213     assert(yaml::needsQuotes(Stat->getDebugType()) == yaml::QuotingType::None &&
 214            "Statistic group/type name is simple.");
 215     assert(yaml::needsQuotes(Stat->getName()) == yaml::QuotingType::None &&
 216            "Statistic name is simple");
 217     OS << "\t\"" << Stat->getDebugType() << '.' << Stat->getName() << "\": "
 218        << Stat->getValue();
 219     delim = ",\n";
 220   }
 221   // Print timers.
 222   TimerGroup::printAllJSONValues(OS, delim);
 223
 224   OS << "\n}\n";
 225   OS.flush();
 226 }
 227
 228 void llvm::PrintStatistics() {
 229 #if LLVM_ENABLE_STATS
 230   sys::SmartScopedLock<true> Reader(*StatLock);
 231   StatisticInfo &Stats = *StatInfo;
 232
 233   // Statistics not enabled?
 234   if (Stats.Stats.empty()) return;
 235
 236   // Get the stream to write to.
 237   std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
 238   if (StatsAsJSON)
 239     PrintStatisticsJSON(*OutStream);
 240   else
 241     PrintStatistics(*OutStream);
 242
 243 #else
 244   // Check if the -stats option is set instead of checking
 245   // !Stats.Stats.empty().  In release builds, Statistics operators
 246   // do nothing, so stats are never Registered.
 247   if (Stats) {
 248     // Get the stream to write to.
 249     std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
 250     (*OutStream) << "Statistics are disabled.  "
 251                  << "Build with asserts or with -DLLVM_ENABLE_STATS\n";
 252   }
 253 #endif
 254 }
 255
 256 const std::vector<std::pair<StringRef, unsigned>> llvm::GetStatistics() {
 257   sys::SmartScopedLock<true> Reader(*StatLock);
 258   std::vector<std::pair<StringRef, unsigned>> ReturnStats;
 259
 260   for (const auto &Stat : StatInfo->statistics())
 261     ReturnStats.emplace_back(Stat->getName(), Stat->getValue());
 262   return ReturnStats;
 263 }
 264
 265 void llvm::ResetStatistics() {
 266   StatInfo->reset();
 267 }