llvm/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
  25 #include "DebugOptions.h"
  26
  27 #include "llvm/ADT/StringExtras.h"
  28 #include "llvm/Support/CommandLine.h"
  29 #include "llvm/Support/Compiler.h"
  30 #include "llvm/Support/Debug.h"
  31 #include "llvm/Support/Format.h"
  32 #include "llvm/Support/ManagedStatic.h"
  33 #include "llvm/Support/Mutex.h"
  34 #include "llvm/Support/Timer.h"
  35 #include "llvm/Support/YAMLTraits.h"
  36 #include "llvm/Support/raw_ostream.h"
  37 #include <algorithm>
  38 #include <cstring>
  39 using namespace llvm;
  40
  41 /// -stats - Command line option to cause transformations to emit stats about
  42 /// what they did.
  43 ///
  44 static bool EnableStats;
  45 static bool StatsAsJSON;
  46 static bool Enabled;
  47 static bool PrintOnExit;
  48
  49 void llvm::initStatisticOptions() {
  50   static cl::opt<bool, true> registerEnableStats{
  51       "stats",
  52       cl::desc(
  53           "Enable statistics output from program (available with Asserts)"),
  54       cl::location(EnableStats), cl::Hidden};
  55   static cl::opt<bool, true> registerStatsAsJson{
  56       "stats-json", cl::desc("Display statistics as json data"),
  57       cl::location(StatsAsJSON), cl::Hidden};
  58 }
  59
  60 namespace {
  61 /// This class is used in a ManagedStatic so that it is created on demand (when
  62 /// the first statistic is bumped) and destroyed only when llvm_shutdown is
  63 /// called. We print statistics from the destructor.
  64 /// This class is also used to look up statistic values from applications that
  65 /// use LLVM.
  66 class StatisticInfo {
  67   std::vector<TrackingStatistic *> Stats;
  68
  69   friend void llvm::PrintStatistics();
  70   friend void llvm::PrintStatistics(raw_ostream &OS);
  71   friend void llvm::PrintStatisticsJSON(raw_ostream &OS);
  72
  73   /// Sort statistics by debugtype,name,description.
  74   void sort();
  75 public:
  76   using const_iterator = std::vector<TrackingStatistic *>::const_iterator;
  77
  78   StatisticInfo();
  79   ~StatisticInfo();
  80
  81   void addStatistic(TrackingStatistic *S) { Stats.push_back(S); }
  82
  83   const_iterator begin() const { return Stats.begin(); }
  84   const_iterator end() const { return Stats.end(); }
  85   iterator_range<const_iterator> statistics() const {
  86     return {begin(), end()};
  87   }
  88
  89   void reset();
  90 };
  91 } // end anonymous namespace
  92
  93 static ManagedStatic<StatisticInfo> StatInfo;
  94 static ManagedStatic<sys::SmartMutex<true> > StatLock;
  95
  96 /// RegisterStatistic - The first time a statistic is bumped, this method is
  97 /// called.
  98 void TrackingStatistic::RegisterStatistic() {
  99   // If stats are enabled, inform StatInfo that this statistic should be
 100   // printed.
 101   // llvm_shutdown calls destructors while holding the ManagedStatic mutex.
 102   // These destructors end up calling PrintStatistics, which takes StatLock.
 103   // Since dereferencing StatInfo and StatLock can require taking the
 104   // ManagedStatic mutex, doing so with StatLock held would lead to a lock
 105   // order inversion. To avoid that, we dereference the ManagedStatics first,
 106   // and only take StatLock afterwards.
 107   if (!Initialized.load(std::memory_order_relaxed)) {
 108     sys::SmartMutex<true> &Lock = *StatLock;
 109     StatisticInfo &SI = *StatInfo;
 110     sys::SmartScopedLock<true> Writer(Lock);
 111     // Check Initialized again after acquiring the lock.
 112     if (Initialized.load(std::memory_order_relaxed))
 113       return;
 114     if (EnableStats || Enabled)
 115       SI.addStatistic(this);
 116
 117     // Remember we have been registered.
 118     Initialized.store(true, std::memory_order_release);
 119   }
 120 }
 121
 122 StatisticInfo::StatisticInfo() {
 123   // Ensure timergroup lists are created first so they are destructed after us.
 124   TimerGroup::ConstructTimerLists();
 125 }
 126
 127 // Print information when destroyed, iff command line option is specified.
 128 StatisticInfo::~StatisticInfo() {
 129   if (EnableStats || PrintOnExit)
 130     llvm::PrintStatistics();
 131 }
 132
 133 void llvm::EnableStatistics(bool DoPrintOnExit) {
 134   Enabled = true;
 135   PrintOnExit = DoPrintOnExit;
 136 }
 137
 138 bool llvm::AreStatisticsEnabled() { return Enabled || EnableStats; }
 139
 140 void StatisticInfo::sort() {
 141   llvm::stable_sort(
 142       Stats, [](const TrackingStatistic *LHS, const TrackingStatistic *RHS) {
 143         if (int Cmp = std::strcmp(LHS->getDebugType(), RHS->getDebugType()))
 144           return Cmp < 0;
 145
 146         if (int Cmp = std::strcmp(LHS->getName(), RHS->getName()))
 147           return Cmp < 0;
 148
 149         return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
 150       });
 151 }
 152
 153 void StatisticInfo::reset() {
 154   sys::SmartScopedLock<true> Writer(*StatLock);
 155
 156   // Tell each statistic that it isn't registered so it has to register
 157   // again. We're holding the lock so it won't be able to do so until we're
 158   // finished. Once we've forced it to re-register (after we return), then zero
 159   // the value.
 160   for (auto *Stat : Stats) {
 161     // Value updates to a statistic that complete before this statement in the
 162     // iteration for that statistic will be lost as intended.
 163     Stat->Initialized = false;
 164     Stat->Value = 0;
 165   }
 166
 167   // Clear the registration list and release the lock once we're done. Any
 168   // pending updates from other threads will safely take effect after we return.
 169   // That might not be what the user wants if they're measuring a compilation
 170   // but it's their responsibility to prevent concurrent compilations to make
 171   // a single compilation measurable.
 172   Stats.clear();
 173 }
 174
 175 void llvm::PrintStatistics(raw_ostream &OS) {
 176   StatisticInfo &Stats = *StatInfo;
 177
 178   // Figure out how long the biggest Value and Name fields are.
 179   unsigned MaxDebugTypeLen = 0, MaxValLen = 0;
 180   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
 181     MaxValLen = std::max(MaxValLen,
 182                          (unsigned)utostr(Stats.Stats[i]->getValue()).size());
 183     MaxDebugTypeLen = std::max(MaxDebugTypeLen,
 184                          (unsigned)std::strlen(Stats.Stats[i]->getDebugType()));
 185   }
 186
 187   Stats.sort();
 188
 189   // Print out the statistics header...
 190   OS << "===" << std::string(73, '-') << "===\n"
 191      << "                          ... Statistics Collected ...\n"
 192      << "===" << std::string(73, '-') << "===\n\n";
 193
 194   // Print all of the statistics.
 195   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i)
 196     OS << format("%*u %-*s - %s\n",
 197                  MaxValLen, Stats.Stats[i]->getValue(),
 198                  MaxDebugTypeLen, Stats.Stats[i]->getDebugType(),
 199                  Stats.Stats[i]->getDesc());
 200
 201   OS << '\n';  // Flush the output stream.
 202   OS.flush();
 203 }
 204
 205 void llvm::PrintStatisticsJSON(raw_ostream &OS) {
 206   sys::SmartScopedLock<true> Reader(*StatLock);
 207   StatisticInfo &Stats = *StatInfo;
 208
 209   Stats.sort();
 210
 211   // Print all of the statistics.
 212   OS << "{\n";
 213   const char *delim = "";
 214   for (const TrackingStatistic *Stat : Stats.Stats) {
 215     OS << delim;
 216     assert(yaml::needsQuotes(Stat->getDebugType()) == yaml::QuotingType::None &&
 217            "Statistic group/type name is simple.");
 218     assert(yaml::needsQuotes(Stat->getName()) == yaml::QuotingType::None &&
 219            "Statistic name is simple");
 220     OS << "\t\"" << Stat->getDebugType() << '.' << Stat->getName() << "\": "
 221        << Stat->getValue();
 222     delim = ",\n";
 223   }
 224   // Print timers.
 225   TimerGroup::printAllJSONValues(OS, delim);
 226
 227   OS << "\n}\n";
 228   OS.flush();
 229 }
 230
 231 void llvm::PrintStatistics() {
 232 #if LLVM_ENABLE_STATS
 233   sys::SmartScopedLock<true> Reader(*StatLock);
 234   StatisticInfo &Stats = *StatInfo;
 235
 236   // Statistics not enabled?
 237   if (Stats.Stats.empty()) return;
 238
 239   // Get the stream to write to.
 240   std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
 241   if (StatsAsJSON)
 242     PrintStatisticsJSON(*OutStream);
 243   else
 244     PrintStatistics(*OutStream);
 245
 246 #else
 247   // Check if the -stats option is set instead of checking
 248   // !Stats.Stats.empty().  In release builds, Statistics operators
 249   // do nothing, so stats are never Registered.
 250   if (EnableStats) {
 251     // Get the stream to write to.
 252     std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
 253     (*OutStream) << "Statistics are disabled.  "
 254                  << "Build with asserts or with -DLLVM_FORCE_ENABLE_STATS\n";
 255   }
 256 #endif
 257 }
 258
 259 const std::vector<std::pair<StringRef, unsigned>> llvm::GetStatistics() {
 260   sys::SmartScopedLock<true> Reader(*StatLock);
 261   std::vector<std::pair<StringRef, unsigned>> ReturnStats;
 262
 263   for (const auto &Stat : StatInfo->statistics())
 264     ReturnStats.emplace_back(Stat->getName(), Stat->getValue());
 265   return ReturnStats;
 266 }
 267
 268 void llvm::ResetStatistics() {
 269   StatInfo->reset();
 270 }