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>
39using namespace llvm;
40
41/// -stats - Command line option to cause transformations to emit stats about
42/// what they did.
43///
44static bool EnableStats;
45static bool StatsAsJSON;
46static bool Enabled;
47static bool PrintOnExit;
48
49void 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
60namespace {
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.
66class 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();
75public:
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
93static ManagedStatic<StatisticInfo> StatInfo;
94static ManagedStatic<sys::SmartMutex<true> > StatLock;
95
96/// RegisterStatistic - The first time a statistic is bumped, this method is
97/// called.
98void 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
122StatisticInfo::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.
129StatisticInfo::~StatisticInfo() {
130  if (EnableStats || PrintOnExit)
131    llvm::PrintStatistics();
132}
133
134void llvm::EnableStatistics(bool DoPrintOnExit) {
135  Enabled = true;
136  PrintOnExit = DoPrintOnExit;
137}
138
139bool llvm::AreStatisticsEnabled() { return Enabled || EnableStats; }
140
141void 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
154void 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
176void 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
203void 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
229void 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
257std::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
266void llvm::ResetStatistics() {
267  StatInfo->reset();
268}
269