lib/Support/Statistic.cpp

   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::Mutex> 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::ScopedLock 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 }