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/Debug.h"
28#include "llvm/Support/Format.h"
29#include "llvm/Support/ManagedStatic.h"
30#include "llvm/Support/Mutex.h"
31#include "llvm/Support/raw_ostream.h"
32#include <algorithm>
33#include <cstring>
34using namespace llvm;
35
36// CreateInfoOutputFile - Return a file stream to print our output on.
37namespace llvm { extern raw_ostream *CreateInfoOutputFile(); }
38
39/// -stats - Command line option to cause transformations to emit stats about
40/// what they did.
41///
42static cl::opt<bool>
43Enabled(
44    "stats",
45    cl::desc("Enable statistics output from program (available with Asserts)"));
46
47
48namespace {
49/// StatisticInfo - This class is used in a ManagedStatic so that it is created
50/// on demand (when the first statistic is bumped) and destroyed only when
51/// llvm_shutdown is called.  We print statistics from the destructor.
52class StatisticInfo {
53  std::vector<const Statistic*> Stats;
54  friend void llvm::PrintStatistics();
55  friend void llvm::PrintStatistics(raw_ostream &OS);
56public:
57  ~StatisticInfo();
58
59  void addStatistic(const Statistic *S) {
60    Stats.push_back(S);
61  }
62};
63}
64
65static ManagedStatic<StatisticInfo> StatInfo;
66static ManagedStatic<sys::SmartMutex<true> > StatLock;
67
68/// RegisterStatistic - The first time a statistic is bumped, this method is
69/// called.
70void Statistic::RegisterStatistic() {
71  // If stats are enabled, inform StatInfo that this statistic should be
72  // printed.
73  sys::SmartScopedLock<true> Writer(*StatLock);
74  if (!Initialized) {
75    if (Enabled)
76      StatInfo->addStatistic(this);
77
78    TsanHappensBefore(this);
79    sys::MemoryFence();
80    // Remember we have been registered.
81    TsanIgnoreWritesBegin();
82    Initialized = true;
83    TsanIgnoreWritesEnd();
84  }
85}
86
87// Print information when destroyed, iff command line option is specified.
88StatisticInfo::~StatisticInfo() {
89  llvm::PrintStatistics();
90}
91
92void llvm::EnableStatistics() {
93  Enabled.setValue(true);
94}
95
96bool llvm::AreStatisticsEnabled() {
97  return Enabled;
98}
99
100void llvm::PrintStatistics(raw_ostream &OS) {
101  StatisticInfo &Stats = *StatInfo;
102
103  // Figure out how long the biggest Value and Name fields are.
104  unsigned MaxNameLen = 0, MaxValLen = 0;
105  for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
106    MaxValLen = std::max(MaxValLen,
107                         (unsigned)utostr(Stats.Stats[i]->getValue()).size());
108    MaxNameLen = std::max(MaxNameLen,
109                          (unsigned)std::strlen(Stats.Stats[i]->getName()));
110  }
111
112  // Sort the fields by name.
113  std::stable_sort(Stats.Stats.begin(), Stats.Stats.end(),
114                   [](const Statistic *LHS, const Statistic *RHS) {
115    if (int Cmp = std::strcmp(LHS->getName(), RHS->getName()))
116      return Cmp < 0;
117
118    // Secondary key is the description.
119    return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
120  });
121
122  // Print out the statistics header...
123  OS << "===" << std::string(73, '-') << "===\n"
124     << "                          ... Statistics Collected ...\n"
125     << "===" << std::string(73, '-') << "===\n\n";
126
127  // Print all of the statistics.
128  for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i)
129    OS << format("%*u %-*s - %s\n",
130                 MaxValLen, Stats.Stats[i]->getValue(),
131                 MaxNameLen, Stats.Stats[i]->getName(),
132                 Stats.Stats[i]->getDesc());
133
134  OS << '\n';  // Flush the output stream.
135  OS.flush();
136
137}
138
139void llvm::PrintStatistics() {
140#if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
141  StatisticInfo &Stats = *StatInfo;
142
143  // Statistics not enabled?
144  if (Stats.Stats.empty()) return;
145
146  // Get the stream to write to.
147  raw_ostream &OutStream = *CreateInfoOutputFile();
148  PrintStatistics(OutStream);
149  delete &OutStream;   // Close the file.
150#else
151  // Check if the -stats option is set instead of checking
152  // !Stats.Stats.empty().  In release builds, Statistics operators
153  // do nothing, so stats are never Registered.
154  if (Enabled) {
155    // Get the stream to write to.
156    raw_ostream &OutStream = *CreateInfoOutputFile();
157    OutStream << "Statistics are disabled.  "
158            << "Build with asserts or with -DLLVM_ENABLE_STATS\n";
159    OutStream.flush();
160    delete &OutStream;   // Close the file.
161  }
162#endif
163}
164