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(L&: EnableStats), cl::Hidden};
55 static cl::opt<bool, true> registerStatsAsJson{
56 "stats-json", cl::desc("Display statistics as json data"),
57 cl::location(L&: 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(x: 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(m: 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(m: std::memory_order_relaxed))
113 return;
114 if (EnableStats || Enabled)
115 SI.addStatistic(S: this);
116
117 // Remember we have been registered.
118 Initialized.store(i: true, m: 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 Range&: Stats, C: [](const TrackingStatistic *LHS, const TrackingStatistic *RHS) {
144 if (int Cmp = std::strcmp(s1: LHS->getDebugType(), s2: RHS->getDebugType()))
145 return Cmp < 0;
146
147 if (int Cmp = std::strcmp(s1: LHS->getName(), s2: RHS->getName()))
148 return Cmp < 0;
149
150 return std::strcmp(s1: LHS->getDesc(), s2: 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(a: MaxValLen, b: (unsigned)utostr(X: Stat->getValue()).size());
183 MaxDebugTypeLen =
184 std::max(a: MaxDebugTypeLen, b: (unsigned)std::strlen(s: 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(Fmt: "%*" PRIu64 " %-*s - %s\n", Vals: MaxValLen, Vals: Stat->getValue(),
197 Vals: MaxDebugTypeLen, Vals: Stat->getDebugType(), Vals: 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(args: Stat->getName(), args: Stat->getValue());
263 return ReturnStats;
264}
265
266void llvm::ResetStatistics() {
267 StatInfo->reset();
268}
269