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/Support/CommandLine.h"
26 #include "llvm/Support/ManagedStatic.h"
27 #include "llvm/Support/raw_ostream.h"
28 #include "llvm/System/Mutex.h"
29 #include "llvm/ADT/StringExtras.h"
30 #include <algorithm>
31 #include <cstring>
32 using namespace llvm;
33 
34 // GetLibSupportInfoOutputFile - Return a file stream to print our output on.
35 namespace llvm { extern raw_ostream *GetLibSupportInfoOutputFile(); }
36 
37 /// -stats - Command line option to cause transformations to emit stats about
38 /// what they did.
39 ///
40 static cl::opt<bool>
41 Enabled("stats", cl::desc("Enable statistics output from program"));
42 
43 
44 namespace {
45 /// StatisticInfo - This class is used in a ManagedStatic so that it is created
46 /// on demand (when the first statistic is bumped) and destroyed only when
47 /// llvm_shutdown is called.  We print statistics from the destructor.
48 class StatisticInfo {
49   std::vector<const Statistic*> Stats;
50 public:
51   ~StatisticInfo();
52 
53   void addStatistic(const Statistic *S) {
54     Stats.push_back(S);
55   }
56 };
57 }
58 
59 static ManagedStatic<StatisticInfo> StatInfo;
60 static ManagedStatic<sys::SmartMutex<true> > StatLock;
61 
62 /// RegisterStatistic - The first time a statistic is bumped, this method is
63 /// called.
64 void Statistic::RegisterStatistic() {
65   // If stats are enabled, inform StatInfo that this statistic should be
66   // printed.
67   sys::SmartScopedLock<true> Writer(*StatLock);
68   if (!Initialized) {
69     if (Enabled)
70       StatInfo->addStatistic(this);
71 
72     sys::MemoryFence();
73     // Remember we have been registered.
74     Initialized = true;
75   }
76 }
77 
78 namespace {
79 
80 struct NameCompare {
81   bool operator()(const Statistic *LHS, const Statistic *RHS) const {
82     int Cmp = std::strcmp(LHS->getName(), RHS->getName());
83     if (Cmp != 0) return Cmp < 0;
84 
85     // Secondary key is the description.
86     return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
87   }
88 };
89 
90 }
91 
92 // Print information when destroyed, iff command line option is specified.
93 StatisticInfo::~StatisticInfo() {
94   // Statistics not enabled?
95   if (Stats.empty()) return;
96 
97   // Get the stream to write to.
98   raw_ostream &OutStream = *GetLibSupportInfoOutputFile();
99 
100   // Figure out how long the biggest Value and Name fields are.
101   unsigned MaxNameLen = 0, MaxValLen = 0;
102   for (size_t i = 0, e = Stats.size(); i != e; ++i) {
103     MaxValLen = std::max(MaxValLen,
104                          (unsigned)utostr(Stats[i]->getValue()).size());
105     MaxNameLen = std::max(MaxNameLen,
106                           (unsigned)std::strlen(Stats[i]->getName()));
107   }
108 
109   // Sort the fields by name.
110   std::stable_sort(Stats.begin(), Stats.end(), NameCompare());
111 
112   // Print out the statistics header...
113   OutStream << "===" << std::string(73, '-') << "===\n"
114             << "                          ... Statistics Collected ...\n"
115             << "===" << std::string(73, '-') << "===\n\n";
116 
117   // Print all of the statistics.
118   for (size_t i = 0, e = Stats.size(); i != e; ++i) {
119     std::string CountStr = utostr(Stats[i]->getValue());
120     OutStream << std::string(MaxValLen-CountStr.size(), ' ')
121               << CountStr << " " << Stats[i]->getName()
122               << std::string(MaxNameLen-std::strlen(Stats[i]->getName()), ' ')
123               << " - " << Stats[i]->getDesc() << "\n";
124 
125   }
126 
127   OutStream << '\n';  // Flush the output stream...
128   OutStream.flush();
129 
130   if (&OutStream != &outs() && &OutStream != &errs())
131     delete &OutStream;   // Close the file.
132 }
133