Statistic.cpp

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//===-- Statistic.cpp - Easy way to expose stats information --------------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the 'Statistic' class, which is designed to be an easy
// way to expose various success metrics from passes.  These statistics are
// printed at the end of a run, when the -stats command line option is enabled
// on the command line.
//
// This is useful for reporting information like the number of instructions
// simplified, optimized or removed by various transformations, like this:
//
// static Statistic NumInstEliminated("GCSE", "Number of instructions killed");
//
// Later, in the code: ++NumInstEliminated;
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/Statistic.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ManagedStatic.h"
#include "llvm/Support/Streams.h"
#include "llvm/ADT/StringExtras.h"
#include <algorithm>
#include <ostream>
#include <cstring>
using namespace llvm;

// GetLibSupportInfoOutputFile - Return a file stream to print our output on.
namespace llvm { extern std::ostream *GetLibSupportInfoOutputFile(); }

/// -stats - Command line option to cause transformations to emit stats about
/// what they did.
///
static cl::opt<bool>
Enabled("stats", cl::desc("Enable statistics output from program"));


namespace {
/// StatisticInfo - This class is used in a ManagedStatic so that it is created
/// on demand (when the first statistic is bumped) and destroyed only when 
/// llvm_shutdown is called.  We print statistics from the destructor.
class StatisticInfo {
  std::vector<const Statistic*> Stats;
public:
  ~StatisticInfo();
  
  void addStatistic(const Statistic *S) {
    Stats.push_back(S);
  }
};
}

static ManagedStatic<StatisticInfo> StatInfo;


/// RegisterStatistic - The first time a statistic is bumped, this method is
/// called.
void Statistic::RegisterStatistic() {
  // If stats are enabled, inform StatInfo that this statistic should be
  // printed.
  if (Enabled)
    StatInfo->addStatistic(this);
  // Remember we have been registered.
  Initialized = true;
}

namespace {

struct NameCompare {
  bool operator()(const Statistic *LHS, const Statistic *RHS) const {
    int Cmp = std::strcmp(LHS->getName(), RHS->getName());
    if (Cmp != 0) return Cmp < 0;
    
    // Secondary key is the description.
    return std::strcmp(LHS->getDesc(), RHS->getDesc()) < 0;
  }
};

}

// Print information when destroyed, iff command line option is specified.
StatisticInfo::~StatisticInfo() {
  // Statistics not enabled?
  if (Stats.empty()) return;

  // Get the stream to write to.
  std::ostream &OutStream = *GetLibSupportInfoOutputFile();

  // Figure out how long the biggest Value and Name fields are.
  unsigned MaxNameLen = 0, MaxValLen = 0;
  for (size_t i = 0, e = Stats.size(); i != e; ++i) {
    MaxValLen = std::max(MaxValLen,
                         (unsigned)utostr(Stats[i]->getValue()).size());
    MaxNameLen = std::max(MaxNameLen,
                          (unsigned)std::strlen(Stats[i]->getName()));
  }
  
  // Sort the fields by name.
  std::stable_sort(Stats.begin(), Stats.end(), NameCompare());

  // Print out the statistics header...
  OutStream << "===" << std::string(73, '-') << "===\n"
            << "                          ... Statistics Collected ...\n"
            << "===" << std::string(73, '-') << "===\n\n";
  
  // Print all of the statistics.
  for (size_t i = 0, e = Stats.size(); i != e; ++i) {
    std::string CountStr = utostr(Stats[i]->getValue());
    OutStream << std::string(MaxValLen-CountStr.size(), ' ')
              << CountStr << " " << Stats[i]->getName()
              << std::string(MaxNameLen-std::strlen(Stats[i]->getName()), ' ')
              << " - " << Stats[i]->getDesc() << "\n";
    
  }
  
  OutStream << std::endl;  // Flush the output stream...
  
  if (&OutStream != cerr.stream() && &OutStream != cout.stream())
    delete &OutStream;   // Close the file.
}