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/Streams.h"
  28 #include "llvm/System/Mutex.h"
  29 #include "llvm/ADT/StringExtras.h"
  30 #include <algorithm>
  31 #include <ostream>
  32 #include <cstring>
  33 using namespace llvm;
  34
  35 // GetLibSupportInfoOutputFile - Return a file stream to print our output on.
  36 namespace llvm { extern std::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::Mutex> 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::ScopedLock 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   std::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 << std::endl;  // Flush the output stream...
 129
 130   if (&OutStream != cerr.stream() && &OutStream != cout.stream())
 131     delete &OutStream;   // Close the file.
 132 }