xref: /freebsd/contrib/llvm-project/llvm/lib/Support/Statistic.cpp (revision f976241773df2260e6170317080761d1c5814fe5)
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 #include "llvm/ADT/StringExtras.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Support/Compiler.h"
27 #include "llvm/Support/Debug.h"
28 #include "llvm/Support/Format.h"
29 #include "llvm/Support/ManagedStatic.h"
30 #include "llvm/Support/Mutex.h"
31 #include "llvm/Support/Timer.h"
32 #include "llvm/Support/YAMLTraits.h"
33 #include "llvm/Support/raw_ostream.h"
34 #include <algorithm>
35 #include <cstring>
36 using namespace llvm;
37 
38 /// -stats - Command line option to cause transformations to emit stats about
39 /// what they did.
40 ///
41 static cl::opt<bool> Stats(
42     "stats",
43     cl::desc("Enable statistics output from program (available with Asserts)"),
44     cl::Hidden);
45 
46 static cl::opt<bool> StatsAsJSON("stats-json",
47                                  cl::desc("Display statistics as json data"),
48                                  cl::Hidden);
49 
50 static bool Enabled;
51 static bool PrintOnExit;
52 
53 namespace {
54 /// This class is used in a ManagedStatic so that it is created on demand (when
55 /// the first statistic is bumped) and destroyed only when llvm_shutdown is
56 /// called. We print statistics from the destructor.
57 /// This class is also used to look up statistic values from applications that
58 /// use LLVM.
59 class StatisticInfo {
60   std::vector<Statistic*> Stats;
61 
62   friend void llvm::PrintStatistics();
63   friend void llvm::PrintStatistics(raw_ostream &OS);
64   friend void llvm::PrintStatisticsJSON(raw_ostream &OS);
65 
66   /// Sort statistics by debugtype,name,description.
67   void sort();
68 public:
69   using const_iterator = std::vector<Statistic *>::const_iterator;
70 
71   StatisticInfo();
72   ~StatisticInfo();
73 
74   void addStatistic(Statistic *S) {
75     Stats.push_back(S);
76   }
77 
78   const_iterator begin() const { return Stats.begin(); }
79   const_iterator end() const { return Stats.end(); }
80   iterator_range<const_iterator> statistics() const {
81     return {begin(), end()};
82   }
83 
84   void reset();
85 };
86 } // end anonymous namespace
87 
88 static ManagedStatic<StatisticInfo> StatInfo;
89 static ManagedStatic<sys::SmartMutex<true> > StatLock;
90 
91 /// RegisterStatistic - The first time a statistic is bumped, this method is
92 /// called.
93 void Statistic::RegisterStatistic() {
94   // If stats are enabled, inform StatInfo that this statistic should be
95   // printed.
96   // llvm_shutdown calls destructors while holding the ManagedStatic mutex.
97   // These destructors end up calling PrintStatistics, which takes StatLock.
98   // Since dereferencing StatInfo and StatLock can require taking the
99   // ManagedStatic mutex, doing so with StatLock held would lead to a lock
100   // order inversion. To avoid that, we dereference the ManagedStatics first,
101   // and only take StatLock afterwards.
102   if (!Initialized.load(std::memory_order_relaxed)) {
103     sys::SmartMutex<true> &Lock = *StatLock;
104     StatisticInfo &SI = *StatInfo;
105     sys::SmartScopedLock<true> Writer(Lock);
106     // Check Initialized again after acquiring the lock.
107     if (Initialized.load(std::memory_order_relaxed))
108       return;
109     if (Stats || Enabled)
110       SI.addStatistic(this);
111 
112     // Remember we have been registered.
113     Initialized.store(true, std::memory_order_release);
114   }
115 }
116 
117 StatisticInfo::StatisticInfo() {
118   // Ensure timergroup lists are created first so they are destructed after us.
119   TimerGroup::ConstructTimerLists();
120 }
121 
122 // Print information when destroyed, iff command line option is specified.
123 StatisticInfo::~StatisticInfo() {
124   if (::Stats || PrintOnExit)
125     llvm::PrintStatistics();
126 }
127 
128 void llvm::EnableStatistics(bool PrintOnExit) {
129   Enabled = true;
130   ::PrintOnExit = PrintOnExit;
131 }
132 
133 bool llvm::AreStatisticsEnabled() {
134   return Enabled || Stats;
135 }
136 
137 void StatisticInfo::sort() {
138   llvm::stable_sort(Stats, [](const Statistic *LHS, const Statistic *RHS) {
139     if (int Cmp = std::strcmp(LHS->getDebugType(), RHS->getDebugType()))
140       return Cmp < 0;
141 
142     if (int Cmp = std::strcmp(LHS->getName(), RHS->getName()))
143       return Cmp < 0;
144 
145     return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
146   });
147 }
148 
149 void StatisticInfo::reset() {
150   sys::SmartScopedLock<true> Writer(*StatLock);
151 
152   // Tell each statistic that it isn't registered so it has to register
153   // again. We're holding the lock so it won't be able to do so until we're
154   // finished. Once we've forced it to re-register (after we return), then zero
155   // the value.
156   for (auto *Stat : Stats) {
157     // Value updates to a statistic that complete before this statement in the
158     // iteration for that statistic will be lost as intended.
159     Stat->Initialized = false;
160     Stat->Value = 0;
161   }
162 
163   // Clear the registration list and release the lock once we're done. Any
164   // pending updates from other threads will safely take effect after we return.
165   // That might not be what the user wants if they're measuring a compilation
166   // but it's their responsibility to prevent concurrent compilations to make
167   // a single compilation measurable.
168   Stats.clear();
169 }
170 
171 void llvm::PrintStatistics(raw_ostream &OS) {
172   StatisticInfo &Stats = *StatInfo;
173 
174   // Figure out how long the biggest Value and Name fields are.
175   unsigned MaxDebugTypeLen = 0, MaxValLen = 0;
176   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
177     MaxValLen = std::max(MaxValLen,
178                          (unsigned)utostr(Stats.Stats[i]->getValue()).size());
179     MaxDebugTypeLen = std::max(MaxDebugTypeLen,
180                          (unsigned)std::strlen(Stats.Stats[i]->getDebugType()));
181   }
182 
183   Stats.sort();
184 
185   // Print out the statistics header...
186   OS << "===" << std::string(73, '-') << "===\n"
187      << "                          ... Statistics Collected ...\n"
188      << "===" << std::string(73, '-') << "===\n\n";
189 
190   // Print all of the statistics.
191   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i)
192     OS << format("%*u %-*s - %s\n",
193                  MaxValLen, Stats.Stats[i]->getValue(),
194                  MaxDebugTypeLen, Stats.Stats[i]->getDebugType(),
195                  Stats.Stats[i]->getDesc());
196 
197   OS << '\n';  // Flush the output stream.
198   OS.flush();
199 }
200 
201 void llvm::PrintStatisticsJSON(raw_ostream &OS) {
202   sys::SmartScopedLock<true> Reader(*StatLock);
203   StatisticInfo &Stats = *StatInfo;
204 
205   Stats.sort();
206 
207   // Print all of the statistics.
208   OS << "{\n";
209   const char *delim = "";
210   for (const Statistic *Stat : Stats.Stats) {
211     OS << delim;
212     assert(yaml::needsQuotes(Stat->getDebugType()) == yaml::QuotingType::None &&
213            "Statistic group/type name is simple.");
214     assert(yaml::needsQuotes(Stat->getName()) == yaml::QuotingType::None &&
215            "Statistic name is simple");
216     OS << "\t\"" << Stat->getDebugType() << '.' << Stat->getName() << "\": "
217        << Stat->getValue();
218     delim = ",\n";
219   }
220   // Print timers.
221   TimerGroup::printAllJSONValues(OS, delim);
222 
223   OS << "\n}\n";
224   OS.flush();
225 }
226 
227 void llvm::PrintStatistics() {
228 #if LLVM_ENABLE_STATS
229   sys::SmartScopedLock<true> Reader(*StatLock);
230   StatisticInfo &Stats = *StatInfo;
231 
232   // Statistics not enabled?
233   if (Stats.Stats.empty()) return;
234 
235   // Get the stream to write to.
236   std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
237   if (StatsAsJSON)
238     PrintStatisticsJSON(*OutStream);
239   else
240     PrintStatistics(*OutStream);
241 
242 #else
243   // Check if the -stats option is set instead of checking
244   // !Stats.Stats.empty().  In release builds, Statistics operators
245   // do nothing, so stats are never Registered.
246   if (Stats) {
247     // Get the stream to write to.
248     std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
249     (*OutStream) << "Statistics are disabled.  "
250                  << "Build with asserts or with -DLLVM_ENABLE_STATS\n";
251   }
252 #endif
253 }
254 
255 const std::vector<std::pair<StringRef, unsigned>> llvm::GetStatistics() {
256   sys::SmartScopedLock<true> Reader(*StatLock);
257   std::vector<std::pair<StringRef, unsigned>> ReturnStats;
258 
259   for (const auto &Stat : StatInfo->statistics())
260     ReturnStats.emplace_back(Stat->getName(), Stat->getValue());
261   return ReturnStats;
262 }
263 
264 void llvm::ResetStatistics() {
265   StatInfo->reset();
266 }
267