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/Debug.h"
27 #include "llvm/Support/ManagedStatic.h"
28 #include "llvm/Support/raw_ostream.h"
29 #include "llvm/System/Mutex.h"
30 #include "llvm/ADT/StringExtras.h"
31 #include <algorithm>
32 #include <cstring>
33 using namespace llvm;
34 
35 // GetLibSupportInfoOutputFile - Return a file stream to print our output on.
36 namespace llvm { extern raw_ostream *GetLibSupportInfoOutputFile(); }
37 
38 /// -stats - Command line option to cause transformations to emit stats about
39 /// what they did.
40 ///
41 static cl::opt<bool>
42 Enabled("stats", cl::desc("Enable statistics output from program"));
43 
44 
45 namespace {
46 /// StatisticInfo - This class is used in a ManagedStatic so that it is created
47 /// on demand (when the first statistic is bumped) and destroyed only when
48 /// llvm_shutdown is called.  We print statistics from the destructor.
49 class StatisticInfo {
50   std::vector<const Statistic*> Stats;
51 public:
52   ~StatisticInfo();
53 
54   void addStatistic(const Statistic *S) {
55     Stats.push_back(S);
56   }
57 };
58 }
59 
60 static ManagedStatic<StatisticInfo> StatInfo;
61 static ManagedStatic<sys::SmartMutex<true> > StatLock;
62 
63 /// RegisterStatistic - The first time a statistic is bumped, this method is
64 /// called.
65 void Statistic::RegisterStatistic() {
66   // If stats are enabled, inform StatInfo that this statistic should be
67   // printed.
68   sys::SmartScopedLock<true> Writer(*StatLock);
69   if (!Initialized) {
70     if (Enabled)
71       StatInfo->addStatistic(this);
72 
73     sys::MemoryFence();
74     // Remember we have been registered.
75     Initialized = true;
76   }
77 }
78 
79 namespace {
80 
81 struct NameCompare {
82   bool operator()(const Statistic *LHS, const Statistic *RHS) const {
83     int Cmp = std::strcmp(LHS->getName(), RHS->getName());
84     if (Cmp != 0) return Cmp < 0;
85 
86     // Secondary key is the description.
87     return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
88   }
89 };
90 
91 }
92 
93 // Print information when destroyed, iff command line option is specified.
94 StatisticInfo::~StatisticInfo() {
95   // Statistics not enabled?
96   if (Stats.empty()) return;
97 
98   // Get the stream to write to.
99   raw_ostream &OutStream = *GetLibSupportInfoOutputFile();
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.size(); i != e; ++i) {
104     MaxValLen = std::max(MaxValLen,
105                          (unsigned)utostr(Stats[i]->getValue()).size());
106     MaxNameLen = std::max(MaxNameLen,
107                           (unsigned)std::strlen(Stats[i]->getName()));
108   }
109 
110   // Sort the fields by name.
111   std::stable_sort(Stats.begin(), Stats.end(), NameCompare());
112 
113   // Print out the statistics header...
114   OutStream << "===" << std::string(73, '-') << "===\n"
115             << "                          ... Statistics Collected ...\n"
116             << "===" << std::string(73, '-') << "===\n\n";
117 
118   // Print all of the statistics.
119   for (size_t i = 0, e = Stats.size(); i != e; ++i) {
120     std::string CountStr = utostr(Stats[i]->getValue());
121     OutStream << std::string(MaxValLen-CountStr.size(), ' ')
122               << CountStr << " " << Stats[i]->getName()
123               << std::string(MaxNameLen-std::strlen(Stats[i]->getName()), ' ')
124               << " - " << Stats[i]->getDesc() << "\n";
125 
126   }
127 
128   OutStream << '\n';  // Flush the output stream...
129   OutStream.flush();
130 
131   if (&OutStream != &outs() && &OutStream != &errs() && &OutStream != &dbgs())
132     delete &OutStream;   // Close the file.
133 }
134