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
initStatisticOptions()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
addStatistic(TrackingStatistic * S)81 void addStatistic(TrackingStatistic *S) { Stats.push_back(S); }
82
begin() const83 const_iterator begin() const { return Stats.begin(); }
end() const84 const_iterator end() const { return Stats.end(); }
statistics() const85 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.
RegisterStatistic()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
StatisticInfo()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.
~StatisticInfo()128 StatisticInfo::~StatisticInfo() {
129 if (EnableStats || PrintOnExit)
130 llvm::PrintStatistics();
131 }
132
EnableStatistics(bool DoPrintOnExit)133 void llvm::EnableStatistics(bool DoPrintOnExit) {
134 Enabled = true;
135 PrintOnExit = DoPrintOnExit;
136 }
137
AreStatisticsEnabled()138 bool llvm::AreStatisticsEnabled() { return Enabled || EnableStats; }
139
sort()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
reset()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
PrintStatistics(raw_ostream & OS)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 (TrackingStatistic *Stat : Stats.Stats) {
181 MaxValLen = std::max(MaxValLen, (unsigned)utostr(Stat->getValue()).size());
182 MaxDebugTypeLen =
183 std::max(MaxDebugTypeLen, (unsigned)std::strlen(Stat->getDebugType()));
184 }
185
186 Stats.sort();
187
188 // Print out the statistics header...
189 OS << "===" << std::string(73, '-') << "===\n"
190 << " ... Statistics Collected ...\n"
191 << "===" << std::string(73, '-') << "===\n\n";
192
193 // Print all of the statistics.
194 for (TrackingStatistic *Stat : Stats.Stats)
195 OS << format("%*" PRIu64 " %-*s - %s\n", MaxValLen, Stat->getValue(),
196 MaxDebugTypeLen, Stat->getDebugType(), Stat->getDesc());
197
198 OS << '\n'; // Flush the output stream.
199 OS.flush();
200 }
201
PrintStatisticsJSON(raw_ostream & OS)202 void llvm::PrintStatisticsJSON(raw_ostream &OS) {
203 sys::SmartScopedLock<true> Reader(*StatLock);
204 StatisticInfo &Stats = *StatInfo;
205
206 Stats.sort();
207
208 // Print all of the statistics.
209 OS << "{\n";
210 const char *delim = "";
211 for (const TrackingStatistic *Stat : Stats.Stats) {
212 OS << delim;
213 assert(yaml::needsQuotes(Stat->getDebugType()) == yaml::QuotingType::None &&
214 "Statistic group/type name is simple.");
215 assert(yaml::needsQuotes(Stat->getName()) == yaml::QuotingType::None &&
216 "Statistic name is simple");
217 OS << "\t\"" << Stat->getDebugType() << '.' << Stat->getName() << "\": "
218 << Stat->getValue();
219 delim = ",\n";
220 }
221 // Print timers.
222 TimerGroup::printAllJSONValues(OS, delim);
223
224 OS << "\n}\n";
225 OS.flush();
226 }
227
PrintStatistics()228 void llvm::PrintStatistics() {
229 #if LLVM_ENABLE_STATS
230 sys::SmartScopedLock<true> Reader(*StatLock);
231 StatisticInfo &Stats = *StatInfo;
232
233 // Statistics not enabled?
234 if (Stats.Stats.empty()) return;
235
236 // Get the stream to write to.
237 std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
238 if (StatsAsJSON)
239 PrintStatisticsJSON(*OutStream);
240 else
241 PrintStatistics(*OutStream);
242
243 #else
244 // Check if the -stats option is set instead of checking
245 // !Stats.Stats.empty(). In release builds, Statistics operators
246 // do nothing, so stats are never Registered.
247 if (EnableStats) {
248 // Get the stream to write to.
249 std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
250 (*OutStream) << "Statistics are disabled. "
251 << "Build with asserts or with -DLLVM_FORCE_ENABLE_STATS\n";
252 }
253 #endif
254 }
255
GetStatistics()256 const std::vector<std::pair<StringRef, uint64_t>> llvm::GetStatistics() {
257 sys::SmartScopedLock<true> Reader(*StatLock);
258 std::vector<std::pair<StringRef, uint64_t>> ReturnStats;
259
260 for (const auto &Stat : StatInfo->statistics())
261 ReturnStats.emplace_back(Stat->getName(), Stat->getValue());
262 return ReturnStats;
263 }
264
ResetStatistics()265 void llvm::ResetStatistics() {
266 StatInfo->reset();
267 }
268