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
87namespace {
88
89struct NameCompare {
90  bool operator()(const Statistic *LHS, const Statistic *RHS) const {
91    int Cmp = std::strcmp(LHS->getName(), RHS->getName());
92    if (Cmp != 0) return Cmp < 0;
93
94    // Secondary key is the description.
95    return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
96  }
97};
98
99}
100
101// Print information when destroyed, iff command line option is specified.
102StatisticInfo::~StatisticInfo() {
103  llvm::PrintStatistics();
104}
105
106void llvm::EnableStatistics() {
107  Enabled.setValue(true);
108}
109
110bool llvm::AreStatisticsEnabled() {
111  return Enabled;
112}
113
114void llvm::PrintStatistics(raw_ostream &OS) {
115  StatisticInfo &Stats = *StatInfo;
116
117  // Figure out how long the biggest Value and Name fields are.
118  unsigned MaxNameLen = 0, MaxValLen = 0;
119  for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
120    MaxValLen = std::max(MaxValLen,
121                         (unsigned)utostr(Stats.Stats[i]->getValue()).size());
122    MaxNameLen = std::max(MaxNameLen,
123                          (unsigned)std::strlen(Stats.Stats[i]->getName()));
124  }
125
126  // Sort the fields by name.
127  std::stable_sort(Stats.Stats.begin(), Stats.Stats.end(), NameCompare());
128
129  // Print out the statistics header...
130  OS << "===" << std::string(73, '-') << "===\n"
131     << "                          ... Statistics Collected ...\n"
132     << "===" << std::string(73, '-') << "===\n\n";
133
134  // Print all of the statistics.
135  for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i)
136    OS << format("%*u %-*s - %s\n",
137                 MaxValLen, Stats.Stats[i]->getValue(),
138                 MaxNameLen, Stats.Stats[i]->getName(),
139                 Stats.Stats[i]->getDesc());
140
141  OS << '\n';  // Flush the output stream.
142  OS.flush();
143
144}
145
146void llvm::PrintStatistics() {
147#if !defined(NDEBUG) || defined(LLVM_ENABLE_STATS)
148  StatisticInfo &Stats = *StatInfo;
149
150  // Statistics not enabled?
151  if (Stats.Stats.empty()) return;
152
153  // Get the stream to write to.
154  raw_ostream &OutStream = *CreateInfoOutputFile();
155  PrintStatistics(OutStream);
156  delete &OutStream;   // Close the file.
157#else
158  // Check if the -stats option is set instead of checking
159  // !Stats.Stats.empty().  In release builds, Statistics operators
160  // do nothing, so stats are never Registered.
161  if (Enabled) {
162    // Get the stream to write to.
163    raw_ostream &OutStream = *CreateInfoOutputFile();
164    OutStream << "Statistics are disabled.  "
165            << "Build with asserts or with -DLLVM_ENABLE_STATS\n";
166    OutStream.flush();
167    delete &OutStream;   // Close the file.
168  }
169#endif
170}
171