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//===-- llvm/ADT/Statistic.h - Easy way to expose stats ---------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

///

/// \file

/// This file defines the 'Statistic' class, which is designed to be an easy way

/// to expose various metrics from passes.  These statistics are printed at the

/// end of a run (from llvm_shutdown), when the -stats command line option is

/// passed 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 NumInstsKilled("gcse", "Number of instructions killed");

///

/// Later, in the code: ++NumInstsKilled;

///

/// NOTE: Statistics *must* be declared as global variables.

///

//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_STATISTIC_H

#define LLVM_ADT_STATISTIC_H

#include "llvm/Config/llvm-config.h"

#include "llvm/Support/Compiler.h"

#include <atomic>

#include <memory>

#include <vector>

// Determine whether statistics should be enabled. We must do it here rather

// than in CMake because multi-config generators cannot determine this at

// configure time.

#if !defined(NDEBUG) || LLVM_FORCE_ENABLE_STATS

#define LLVM_ENABLE_STATS 1

#else

#define LLVM_ENABLE_STATS 0

#endif

namespace llvm {

class raw_ostream;

class raw_fd_ostream;

class StringRef;

class TrackingStatistic {

public:

  const char *const DebugType;

  const char *const Name;

  const char *const Desc;

  std::atomic<uint64_t> Value;

  std::atomic<bool> Initialized;

  constexpr TrackingStatistic(const char *DebugType, const char *Name,

                              const char *Desc)

      : DebugType(DebugType), Name(Name), Desc(Desc), Value(0),

        Initialized(false) {}

  const char *getDebugType() const { return DebugType; }

  const char *getName() const { return Name; }

  const char *getDesc() const { return Desc; }

  uint64_t getValue() const { return Value.load(std::memory_order_relaxed); }

  // Allow use of this class as the value itself.

  operator uint64_t() const { return getValue(); }

  const TrackingStatistic &operator=(uint64_t Val) {

    Value.store(Val, std::memory_order_relaxed);

    return init();

  }

  const TrackingStatistic &operator++() {

    Value.fetch_add(1, std::memory_order_relaxed);

    return init();

  }

  uint64_t operator++(int) {

    init();

    return Value.fetch_add(1, std::memory_order_relaxed);

  }

  const TrackingStatistic &operator--() {

    Value.fetch_sub(1, std::memory_order_relaxed);

    return init();

  }

  uint64_t operator--(int) {

    init();

    return Value.fetch_sub(1, std::memory_order_relaxed);

  }

  const TrackingStatistic &operator+=(uint64_t V) {

    if (V == 0)

      return *this;

    Value.fetch_add(V, std::memory_order_relaxed);

    return init();

  }

  const TrackingStatistic &operator-=(uint64_t V) {

    if (V == 0)

      return *this;

    Value.fetch_sub(V, std::memory_order_relaxed);

    return init();

  }

  void updateMax(uint64_t V) {

    uint64_t PrevMax = Value.load(std::memory_order_relaxed);

    // Keep trying to update max until we succeed or another thread produces

    // a bigger max than us.

    while (V > PrevMax && !Value.compare_exchange_weak(

                              PrevMax, V, std::memory_order_relaxed)) {

    }

    init();

  }

protected:

  TrackingStatistic &init() {

    if (!Initialized.load(std::memory_order_acquire))

      RegisterStatistic();

    return *this;

  }

  void RegisterStatistic();

};

class NoopStatistic {

public:

  NoopStatistic(const char * /*DebugType*/, const char * /*Name*/,

                const char * /*Desc*/) {}

  uint64_t getValue() const { return 0; }

  // Allow use of this class as the value itself.

  operator uint64_t() const { return 0; }

  const NoopStatistic &operator=(uint64_t Val) { return *this; }

  const NoopStatistic &operator++() { return *this; }

  uint64_t operator++(int) { return 0; }

  const NoopStatistic &operator--() { return *this; }

  uint64_t operator--(int) { return 0; }

  const NoopStatistic &operator+=(const uint64_t &V) { return *this; }

  const NoopStatistic &operator-=(const uint64_t &V) { return *this; }

  void updateMax(uint64_t V) {}

};

#if LLVM_ENABLE_STATS

using Statistic = TrackingStatistic;

#else

using Statistic = NoopStatistic;

#endif

// STATISTIC - A macro to make definition of statistics really simple.  This

// automatically passes the DEBUG_TYPE of the file into the statistic.

#define STATISTIC(VARNAME, DESC)                                               \

  static llvm::Statistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC}

// ALWAYS_ENABLED_STATISTIC - A macro to define a statistic like STATISTIC but

// it is enabled even if LLVM_ENABLE_STATS is off.

#define ALWAYS_ENABLED_STATISTIC(VARNAME, DESC)                                \

  static llvm::TrackingStatistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC}

/// Enable the collection and printing of statistics.

void EnableStatistics(bool DoPrintOnExit = true);

/// Check if statistics are enabled.

bool AreStatisticsEnabled();

/// Return a file stream to print our output on.

std::unique_ptr<raw_fd_ostream> CreateInfoOutputFile();

/// Print statistics to the file returned by CreateInfoOutputFile().

void PrintStatistics();

/// Print statistics to the given output stream.

void PrintStatistics(raw_ostream &OS);

/// Print statistics in JSON format. This does include all global timers (\see

/// Timer, TimerGroup). Note that the timers are cleared after printing and will

/// not be printed in human readable form or in a second call of

/// PrintStatisticsJSON().

void PrintStatisticsJSON(raw_ostream &OS);

/// Get the statistics. This can be used to look up the value of

/// statistics without needing to parse JSON.

///

/// This function does not prevent statistics being updated by other threads

/// during it's execution. It will return the value at the point that it is

/// read. However, it will prevent new statistics from registering until it

/// completes.

std::vector<std::pair<StringRef, uint64_t>> GetStatistics();

/// Reset the statistics. This can be used to zero and de-register the

/// statistics in order to measure a compilation.

///

/// When this function begins to call destructors prior to returning, all

/// statistics will be zero and unregistered. However, that might not remain the

/// case by the time this function finishes returning. Whether update from other

/// threads are lost or merely deferred until during the function return is

/// timing sensitive.

///

/// Callers who intend to use this to measure statistics for a single

/// compilation should ensure that no compilations are in progress at the point

/// this function is called and that only one compilation executes until calling

/// GetStatistics().

void ResetStatistics();

} // end namespace llvm

#endif // LLVM_ADT_STATISTIC_H