lib/Support/Statistic.cpp

   1 //===-- Statistic.cpp - Easy way to expose stats information --------------===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file implements the 'Statistic' class, which is designed to be an easy
  11 // way to expose various success metrics from passes.  These statistics are
  12 // printed at the end of a run, when the -stats command line option is enabled
  13 // on the command line.
  14 //
  15 // This is useful for reporting information like the number of instructions
  16 // simplified, optimized or removed by various transformations, like this:
  17 //
  18 // static Statistic NumInstEliminated("GCSE", "Number of instructions killed");
  19 //
  20 // Later, in the code: ++NumInstEliminated;
  21 //
  22 //===----------------------------------------------------------------------===//
  23
  24 #include "llvm/ADT/Statistic.h"
  25 #include "llvm/ADT/StringExtras.h"
  26 #include "llvm/Support/CommandLine.h"
  27 #include "llvm/Support/Compiler.h"
  28 #include "llvm/Support/Debug.h"
  29 #include "llvm/Support/Format.h"
  30 #include "llvm/Support/ManagedStatic.h"
  31 #include "llvm/Support/Mutex.h"
  32 #include "llvm/Support/Timer.h"
  33 #include "llvm/Support/YAMLTraits.h"
  34 #include "llvm/Support/raw_ostream.h"
  35 #include <algorithm>
  36 #include <cstring>
  37 using namespace llvm;
  38
  39 /// -stats - Command line option to cause transformations to emit stats about
  40 /// what they did.
  41 ///
  42 static cl::opt<bool> Stats(
  43     "stats",
  44     cl::desc("Enable statistics output from program (available with Asserts)"),
  45     cl::Hidden);
  46
  47 static cl::opt<bool> StatsAsJSON("stats-json",
  48                                  cl::desc("Display statistics as json data"),
  49                                  cl::Hidden);
  50
  51 static bool Enabled;
  52 static bool PrintOnExit;
  53
  54 namespace {
  55 /// This class is used in a ManagedStatic so that it is created on demand (when
  56 /// the first statistic is bumped) and destroyed only when llvm_shutdown is
  57 /// called. We print statistics from the destructor.
  58 /// This class is also used to look up statistic values from applications that
  59 /// use LLVM.
  60 class StatisticInfo {
  61   std::vector<Statistic*> Stats;
  62
  63   friend void llvm::PrintStatistics();
  64   friend void llvm::PrintStatistics(raw_ostream &OS);
  65   friend void llvm::PrintStatisticsJSON(raw_ostream &OS);
  66
  67   /// Sort statistics by debugtype,name,description.
  68   void sort();
  69 public:
  70   using const_iterator = std::vector<Statistic *>::const_iterator;
  71
  72   StatisticInfo();
  73   ~StatisticInfo();
  74
  75   void addStatistic(Statistic *S) {
  76     Stats.push_back(S);
  77   }
  78
  79   const_iterator begin() const { return Stats.begin(); }
  80   const_iterator end() const { return Stats.end(); }
  81   iterator_range<const_iterator> statistics() const {
  82     return {begin(), end()};
  83   }
  84
  85   void reset();
  86 };
  87 } // end anonymous namespace
  88
  89 static ManagedStatic<StatisticInfo> StatInfo;
  90 static ManagedStatic<sys::SmartMutex<true> > StatLock;
  91
  92 /// RegisterStatistic - The first time a statistic is bumped, this method is
  93 /// called.
  94 void Statistic::RegisterStatistic() {
  95   // If stats are enabled, inform StatInfo that this statistic should be
  96   // printed.
  97   // llvm_shutdown calls destructors while holding the ManagedStatic mutex.
  98   // These destructors end up calling PrintStatistics, which takes StatLock.
  99   // Since dereferencing StatInfo and StatLock can require taking the
 100   // ManagedStatic mutex, doing so with StatLock held would lead to a lock
 101   // order inversion. To avoid that, we dereference the ManagedStatics first,
 102   // and only take StatLock afterwards.
 103   if (!Initialized.load(std::memory_order_relaxed)) {
 104     sys::SmartMutex<true> &Lock = *StatLock;
 105     StatisticInfo &SI = *StatInfo;
 106     sys::SmartScopedLock<true> Writer(Lock);
 107     // Check Initialized again after acquiring the lock.
 108     if (Initialized.load(std::memory_order_relaxed))
 109       return;
 110     if (Stats || Enabled)
 111       SI.addStatistic(this);
 112
 113     // Remember we have been registered.
 114     Initialized.store(true, std::memory_order_release);
 115   }
 116 }
 117
 118 StatisticInfo::StatisticInfo() {
 119   // Ensure timergroup lists are created first so they are destructed after us.
 120   TimerGroup::ConstructTimerLists();
 121 }
 122
 123 // Print information when destroyed, iff command line option is specified.
 124 StatisticInfo::~StatisticInfo() {
 125   if (::Stats || PrintOnExit)
 126     llvm::PrintStatistics();
 127 }
 128
 129 void llvm::EnableStatistics(bool PrintOnExit) {
 130   Enabled = true;
 131   ::PrintOnExit = PrintOnExit;
 132 }
 133
 134 bool llvm::AreStatisticsEnabled() {
 135   return Enabled || Stats;
 136 }
 137
 138 void StatisticInfo::sort() {
 139   std::stable_sort(Stats.begin(), Stats.end(),
 140                    [](const Statistic *LHS, const Statistic *RHS) {
 141     if (int Cmp = std::strcmp(LHS->getDebugType(), RHS->getDebugType()))
 142       return Cmp < 0;
 143
 144     if (int Cmp = std::strcmp(LHS->getName(), RHS->getName()))
 145       return Cmp < 0;
 146
 147     return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
 148   });
 149 }
 150
 151 void StatisticInfo::reset() {
 152   sys::SmartScopedLock<true> Writer(*StatLock);
 153
 154   // Tell each statistic that it isn't registered so it has to register
 155   // again. We're holding the lock so it won't be able to do so until we're
 156   // finished. Once we've forced it to re-register (after we return), then zero
 157   // the value.
 158   for (auto *Stat : Stats) {
 159     // Value updates to a statistic that complete before this statement in the
 160     // iteration for that statistic will be lost as intended.
 161     Stat->Initialized = false;
 162     Stat->Value = 0;
 163   }
 164
 165   // Clear the registration list and release the lock once we're done. Any
 166   // pending updates from other threads will safely take effect after we return.
 167   // That might not be what the user wants if they're measuring a compilation
 168   // but it's their responsibility to prevent concurrent compilations to make
 169   // a single compilation measurable.
 170   Stats.clear();
 171 }
 172
 173 void llvm::PrintStatistics(raw_ostream &OS) {
 174   StatisticInfo &Stats = *StatInfo;
 175
 176   // Figure out how long the biggest Value and Name fields are.
 177   unsigned MaxDebugTypeLen = 0, MaxValLen = 0;
 178   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
 179     MaxValLen = std::max(MaxValLen,
 180                          (unsigned)utostr(Stats.Stats[i]->getValue()).size());
 181     MaxDebugTypeLen = std::max(MaxDebugTypeLen,
 182                          (unsigned)std::strlen(Stats.Stats[i]->getDebugType()));
 183   }
 184
 185   Stats.sort();
 186
 187   // Print out the statistics header...
 188   OS << "===" << std::string(73, '-') << "===\n"
 189      << "                          ... Statistics Collected ...\n"
 190      << "===" << std::string(73, '-') << "===\n\n";
 191
 192   // Print all of the statistics.
 193   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i)
 194     OS << format("%*u %-*s - %s\n",
 195                  MaxValLen, Stats.Stats[i]->getValue(),
 196                  MaxDebugTypeLen, Stats.Stats[i]->getDebugType(),
 197                  Stats.Stats[i]->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 Statistic *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 (Stats) {
 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_ENABLE_STATS\n";
 253   }
 254 #endif
 255 }
 256
 257 const std::vector<std::pair<StringRef, unsigned>> llvm::GetStatistics() {
 258   sys::SmartScopedLock<true> Reader(*StatLock);
 259   std::vector<std::pair<StringRef, unsigned>> 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 }