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/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 // CreateInfoOutputFile - Return a file stream to print our output on.
  36 namespace llvm { extern raw_ostream *CreateInfoOutputFile(); }
  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   friend void llvm::PrintStatistics();
  52   friend void llvm::PrintStatistics(raw_ostream &OS);
  53 public:
  54   ~StatisticInfo();
  55
  56   void addStatistic(const Statistic *S) {
  57     Stats.push_back(S);
  58   }
  59 };
  60 }
  61
  62 static ManagedStatic<StatisticInfo> StatInfo;
  63 static ManagedStatic<sys::SmartMutex<true> > StatLock;
  64
  65 /// RegisterStatistic - The first time a statistic is bumped, this method is
  66 /// called.
  67 void Statistic::RegisterStatistic() {
  68   // If stats are enabled, inform StatInfo that this statistic should be
  69   // printed.
  70   sys::SmartScopedLock<true> Writer(*StatLock);
  71   if (!Initialized) {
  72     if (Enabled)
  73       StatInfo->addStatistic(this);
  74
  75     sys::MemoryFence();
  76     // Remember we have been registered.
  77     Initialized = true;
  78   }
  79 }
  80
  81 namespace {
  82
  83 struct NameCompare {
  84   bool operator()(const Statistic *LHS, const Statistic *RHS) const {
  85     int Cmp = std::strcmp(LHS->getName(), RHS->getName());
  86     if (Cmp != 0) return Cmp < 0;
  87
  88     // Secondary key is the description.
  89     return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
  90   }
  91 };
  92
  93 }
  94
  95 // Print information when destroyed, iff command line option is specified.
  96 StatisticInfo::~StatisticInfo() {
  97   llvm::PrintStatistics();
  98 }
  99
 100 void llvm::EnableStatistics() {
 101   Enabled.setValue(true);
 102 }
 103
 104 void llvm::PrintStatistics(raw_ostream &OS) {
 105   StatisticInfo &Stats = *StatInfo;
 106
 107   // Figure out how long the biggest Value and Name fields are.
 108   unsigned MaxNameLen = 0, MaxValLen = 0;
 109   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
 110     MaxValLen = std::max(MaxValLen,
 111                          (unsigned)utostr(Stats.Stats[i]->getValue()).size());
 112     MaxNameLen = std::max(MaxNameLen,
 113                           (unsigned)std::strlen(Stats.Stats[i]->getName()));
 114   }
 115
 116   // Sort the fields by name.
 117   std::stable_sort(Stats.Stats.begin(), Stats.Stats.end(), NameCompare());
 118
 119   // Print out the statistics header...
 120   OS << "===" << std::string(73, '-') << "===\n"
 121      << "                          ... Statistics Collected ...\n"
 122      << "===" << std::string(73, '-') << "===\n\n";
 123
 124   // Print all of the statistics.
 125   for (size_t i = 0, e = Stats.Stats.size(); i != e; ++i) {
 126     std::string CountStr = utostr(Stats.Stats[i]->getValue());
 127     OS << std::string(MaxValLen-CountStr.size(), ' ')
 128        << CountStr << " " << Stats.Stats[i]->getName()
 129        << std::string(MaxNameLen-std::strlen(Stats.Stats[i]->getName()), ' ')
 130        << " - " << Stats.Stats[i]->getDesc() << "\n";
 131   }
 132
 133   OS << '\n';  // Flush the output stream.
 134   OS.flush();
 135
 136 }
 137
 138 void llvm::PrintStatistics() {
 139   StatisticInfo &Stats = *StatInfo;
 140
 141   // Statistics not enabled?
 142   if (Stats.Stats.empty()) return;
 143
 144   // Get the stream to write to.
 145   raw_ostream &OutStream = *CreateInfoOutputFile();
 146   PrintStatistics(OutStream);
 147   delete &OutStream;   // Close the file.
 148 }