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 that necessary timer global objects are created first so they are
 124   // destructed after us.
 125   TimerGroup::constructForStatistics();
 126 }
 127
 128 // Print information when destroyed, iff command line option is specified.
 129 StatisticInfo::~StatisticInfo() {
 130   if (EnableStats || PrintOnExit)
 131     llvm::PrintStatistics();
 132 }
 133
 134 void llvm::EnableStatistics(bool DoPrintOnExit) {
 135   Enabled = true;
 136   PrintOnExit = DoPrintOnExit;
 137 }
 138
 139 bool llvm::AreStatisticsEnabled() { return Enabled || EnableStats; }
 140
 141 void StatisticInfo::sort() {
 142   llvm::stable_sort(
 143       Stats, [](const TrackingStatistic *LHS, const TrackingStatistic *RHS) {
 144         if (int Cmp = std::strcmp(LHS->getDebugType(), RHS->getDebugType()))
 145           return Cmp < 0;
 146
 147         if (int Cmp = std::strcmp(LHS->getName(), RHS->getName()))
 148           return Cmp < 0;
 149
 150         return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
 151       });
 152 }
 153
 154 void StatisticInfo::reset() {
 155   sys::SmartScopedLock<true> Writer(*StatLock);
 156
 157   // Tell each statistic that it isn't registered so it has to register
 158   // again. We're holding the lock so it won't be able to do so until we're
 159   // finished. Once we've forced it to re-register (after we return), then zero
 160   // the value.
 161   for (auto *Stat : Stats) {
 162     // Value updates to a statistic that complete before this statement in the
 163     // iteration for that statistic will be lost as intended.
 164     Stat->Initialized = false;
 165     Stat->Value = 0;
 166   }
 167
 168   // Clear the registration list and release the lock once we're done. Any
 169   // pending updates from other threads will safely take effect after we return.
 170   // That might not be what the user wants if they're measuring a compilation
 171   // but it's their responsibility to prevent concurrent compilations to make
 172   // a single compilation measurable.
 173   Stats.clear();
 174 }
 175
 176 void llvm::PrintStatistics(raw_ostream &OS) {
 177   StatisticInfo &Stats = *StatInfo;
 178
 179   // Figure out how long the biggest Value and Name fields are.
 180   unsigned MaxDebugTypeLen = 0, MaxValLen = 0;
 181   for (TrackingStatistic *Stat : Stats.Stats) {
 182     MaxValLen = std::max(MaxValLen, (unsigned)utostr(Stat->getValue()).size());
 183     MaxDebugTypeLen =
 184         std::max(MaxDebugTypeLen, (unsigned)std::strlen(Stat->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 (TrackingStatistic *Stat : Stats.Stats)
 196     OS << format("%*" PRIu64 " %-*s - %s\n", MaxValLen, Stat->getValue(),
 197                  MaxDebugTypeLen, Stat->getDebugType(), Stat->getDesc());
 198
 199   OS << '\n';  // Flush the output stream.
 200   OS.flush();
 201 }
 202
 203 void llvm::PrintStatisticsJSON(raw_ostream &OS) {
 204   sys::SmartScopedLock<true> Reader(*StatLock);
 205   StatisticInfo &Stats = *StatInfo;
 206
 207   Stats.sort();
 208
 209   // Print all of the statistics.
 210   OS << "{\n";
 211   const char *delim = "";
 212   for (const TrackingStatistic *Stat : Stats.Stats) {
 213     OS << delim;
 214     assert(yaml::needsQuotes(Stat->getDebugType()) == yaml::QuotingType::None &&
 215            "Statistic group/type name is simple.");
 216     assert(yaml::needsQuotes(Stat->getName()) == yaml::QuotingType::None &&
 217            "Statistic name is simple");
 218     OS << "\t\"" << Stat->getDebugType() << '.' << Stat->getName() << "\": "
 219        << Stat->getValue();
 220     delim = ",\n";
 221   }
 222   // Print timers.
 223   TimerGroup::printAllJSONValues(OS, delim);
 224
 225   OS << "\n}\n";
 226   OS.flush();
 227 }
 228
 229 void llvm::PrintStatistics() {
 230 #if LLVM_ENABLE_STATS
 231   sys::SmartScopedLock<true> Reader(*StatLock);
 232   StatisticInfo &Stats = *StatInfo;
 233
 234   // Statistics not enabled?
 235   if (Stats.Stats.empty()) return;
 236
 237   // Get the stream to write to.
 238   std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
 239   if (StatsAsJSON)
 240     PrintStatisticsJSON(*OutStream);
 241   else
 242     PrintStatistics(*OutStream);
 243
 244 #else
 245   // Check if the -stats option is set instead of checking
 246   // !Stats.Stats.empty().  In release builds, Statistics operators
 247   // do nothing, so stats are never Registered.
 248   if (EnableStats) {
 249     // Get the stream to write to.
 250     std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
 251     (*OutStream) << "Statistics are disabled.  "
 252                  << "Build with asserts or with -DLLVM_FORCE_ENABLE_STATS\n";
 253   }
 254 #endif
 255 }
 256
 257 std::vector<std::pair<StringRef, uint64_t>> llvm::GetStatistics() {
 258   sys::SmartScopedLock<true> Reader(*StatLock);
 259   std::vector<std::pair<StringRef, uint64_t>> ReturnStats;
 260
 261   for (const auto &Stat : StatInfo->statistics())
 262     ReturnStats.emplace_back(Stat->getName(), Stat->getValue());
 263   return ReturnStats;
 264 }
 265
 266 void llvm::ResetStatistics() {
 267   StatInfo->reset();
 268 }