1//===-- Statistic.cpp - Easy way to expose stats information --------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This file implements the 'Statistic' class, which is designed to be an easy
11// way to expose various success metrics from passes.  These statistics are
12// printed at the end of a run, when the -stats command line option is enabled
13// on the command line.
14//
15// This is useful for reporting information like the number of instructions
16// simplified, optimized or removed by various transformations, like this:
17//
18// static Statistic NumInstEliminated("GCSE", "Number of instructions killed");
19//
20// Later, in the code: ++NumInstEliminated;
21//
22//===----------------------------------------------------------------------===//
23
24#include "llvm/ADT/Statistic.h"
25#include "llvm/ADT/StringExtras.h"
26#include "llvm/Support/CommandLine.h"
27#include "llvm/Support/Compiler.h"
28#include "llvm/Support/Debug.h"
29#include "llvm/Support/Format.h"
30#include "llvm/Support/ManagedStatic.h"
31#include "llvm/Support/Mutex.h"
32#include "llvm/Support/raw_ostream.h"
33#include <algorithm>
34#include <cstring>
35using namespace llvm;
36
37/// -stats - Command line option to cause transformations to emit stats about
38/// what they did.
39///
40static cl::opt<bool>
41Enabled(
42    "stats",
43    cl::desc("Enable statistics output from program (available with Asserts)"));
44
45
46namespace {
47/// StatisticInfo - This class is used in a ManagedStatic so that it is created
48/// on demand (when the first statistic is bumped) and destroyed only when
49/// llvm_shutdown is called.  We print statistics from the destructor.
50class StatisticInfo {
51  std::vector<const Statistic*> Stats;
52  friend void llvm::PrintStatistics();
53  friend void llvm::PrintStatistics(raw_ostream &OS);
54public:
55  ~StatisticInfo();
56
57  void addStatistic(const Statistic *S) {
58    Stats.push_back(S);
59  }
60};
61}
62
63static ManagedStatic<StatisticInfo> StatInfo;
64static ManagedStatic<sys::SmartMutex<true> > StatLock;
65
66/// RegisterStatistic - The first time a statistic is bumped, this method is
67/// called.
68void Statistic::RegisterStatistic() {
69  // If stats are enabled, inform StatInfo that this statistic should be
70  // printed.
71  sys::SmartScopedLock<true> Writer(*StatLock);
72  if (!Initialized) {
73    if (Enabled)
74      StatInfo->addStatistic(this);
75
76    TsanHappensBefore(this);
77    sys::MemoryFence();
78    // Remember we have been registered.
79    TsanIgnoreWritesBegin();
80    Initialized = true;
81    TsanIgnoreWritesEnd();
82  }
83}
84
85// Print information when destroyed, iff command line option is specified.
86StatisticInfo::~StatisticInfo() {
87  llvm::PrintStatistics();
88}
89
90void llvm::EnableStatistics() {
91  Enabled.setValue(true);
92}
93
94bool llvm::AreStatisticsEnabled() {
95  return Enabled;
96}
97
98void llvm::PrintStatistics(raw_ostream &OS) {
99  StatisticInfo &Stats = *StatInfo;
100
101  // Figure out how long the biggest Value and Name fields are.
102  unsigned MaxNameLen = 0, MaxValLen = 0;
103  for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
104    MaxValLen = std::max(MaxValLen,
105                         (unsigned)utostr(Stats.Stats[i]->getValue()).size());
106    MaxNameLen = std::max(MaxNameLen,
107                          (unsigned)std::strlen(Stats.Stats[i]->getName()));
108  }
109
110  // Sort the fields by name.
111  std::stable_sort(Stats.Stats.begin(), Stats.Stats.end(),
112                   [](const Statistic *LHS, const Statistic *RHS) {
113    if (int Cmp = std::strcmp(LHS->getName(), RHS->getName()))
114      return Cmp < 0;
115
116    // Secondary key is the description.
117    return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
118  });
119
120  // Print out the statistics header...
121  OS << "===" << std::string(73, '-') << "===\n"
122     << "                          ... Statistics Collected ...\n"
123     << "===" << std::string(73, '-') << "===\n\n";
124
125  // Print all of the statistics.
126  for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i)
127    OS << format("%*u %-*s - %s\n",
128                 MaxValLen, Stats.Stats[i]->getValue(),
129                 MaxNameLen, Stats.Stats[i]->getName(),
130                 Stats.Stats[i]->getDesc());
131
132  OS << '\n';  // Flush the output stream.
133  OS.flush();
134
135}
136
137void llvm::PrintStatistics() {
138#if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
139  StatisticInfo &Stats = *StatInfo;
140
141  // Statistics not enabled?
142  if (Stats.Stats.empty()) return;
143
144  // Get the stream to write to.
145  std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
146  PrintStatistics(*OutStream);
147
148#else
149  // Check if the -stats option is set instead of checking
150  // !Stats.Stats.empty().  In release builds, Statistics operators
151  // do nothing, so stats are never Registered.
152  if (Enabled) {
153    // Get the stream to write to.
154    std::unique_ptr<raw_ostream> OutStream = CreateInfoOutputFile();
155    (*OutStream) << "Statistics are disabled.  "
156                 << "Build with asserts or with -DLLVM_ENABLE_STATS\n";
157  }
158#endif
159}
160