LLVM  16.0.0git
Statistic.cpp
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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"
29 #include "llvm/Support/Compiler.h"
30 #include "llvm/Support/Debug.h"
31 #include "llvm/Support/Format.h"
33 #include "llvm/Support/Mutex.h"
34 #include "llvm/Support/Timer.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 
50  static cl::opt<bool, true> registerEnableStats{
51  "stats",
52  cl::desc(
53  "Enable statistics output from program (available with Asserts)"),
55  static cl::opt<bool, true> registerStatsAsJson{
56  "stats-json", cl::desc("Display statistics as json data"),
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 
95 
96 /// RegisterStatistic - The first time a statistic is bumped, this method is
97 /// called.
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)) {
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.
126 }
127 
128 // Print information when destroyed, iff command line option is specified.
129 StatisticInfo::~StatisticInfo() {
130  if (EnableStats || PrintOnExit)
132 }
133 
134 void llvm::EnableStatistics(bool DoPrintOnExit) {
135  Enabled = true;
136  PrintOnExit = DoPrintOnExit;
137 }
138 
140 
141 void StatisticInfo::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() {
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 
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 
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.
224 
225  OS << "\n}\n";
226  OS.flush();
227 }
228 
230 #if LLVM_ENABLE_STATS
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() {
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 
267  StatInfo->reset();
268 }
llvm
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Definition: Statistic.cpp:139
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Definition: Statistic.cpp:98
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Definition: ManagedStatic.h:83
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Definition: Statistic.cpp:203
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Definition: Statistic.cpp:44
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