1//===-- llvm/ADT/Statistic.h - Easy way to expose stats ---------*- C++ -*-===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file defines the 'Statistic' class, which is designed to be an easy way
10// to expose various metrics from passes. These statistics are printed at the
11// end of a run (from llvm_shutdown), when the -stats command line option is
12// passed on the command line.
13//
14// This is useful for reporting information like the number of instructions
15// simplified, optimized or removed by various transformations, like this:
16//
17// static Statistic NumInstsKilled("gcse", "Number of instructions killed");
18//
19// Later, in the code: ++NumInstsKilled;
20//
21// NOTE: Statistics *must* be declared as global variables.
22//
23//===----------------------------------------------------------------------===//
24
25#ifndef LLVM_ADT_STATISTIC_H
26#define LLVM_ADT_STATISTIC_H
27
28#include "llvm/Config/llvm-config.h"
29#include "llvm/Support/Compiler.h"
30#include <atomic>
31#include <memory>
32#include <vector>
33
34// Determine whether statistics should be enabled. We must do it here rather
35// than in CMake because multi-config generators cannot determine this at
36// configure time.
37#if !defined(NDEBUG) || LLVM_FORCE_ENABLE_STATS
38#define LLVM_ENABLE_STATS 1
39#endif
40
41namespace llvm {
42
43class raw_ostream;
44class raw_fd_ostream;
45class StringRef;
46
47class StatisticBase {
48public:
49 const char *DebugType;
50 const char *Name;
51 const char *Desc;
52
53 StatisticBase(const char *DebugType, const char *Name, const char *Desc)
54 : DebugType(DebugType), Name(Name), Desc(Desc) {}
55
56 const char *getDebugType() const { return DebugType; }
57 const char *getName() const { return Name; }
58 const char *getDesc() const { return Desc; }
59};
60
61class TrackingStatistic : public StatisticBase {
62public:
63 std::atomic<unsigned> Value;
64 std::atomic<bool> Initialized;
65
66 TrackingStatistic(const char *DebugType, const char *Name, const char *Desc)
67 : StatisticBase(DebugType, Name, Desc), Value(0), Initialized(false) {}
68
69 unsigned getValue() const { return Value.load(std::memory_order_relaxed); }
70
71 // Allow use of this class as the value itself.
72 operator unsigned() const { return getValue(); }
73
74 const TrackingStatistic &operator=(unsigned Val) {
75 Value.store(Val, std::memory_order_relaxed);
76 return init();
77 }
78
79 const TrackingStatistic &operator++() {
80 Value.fetch_add(1, std::memory_order_relaxed);
81 return init();
82 }
83
84 unsigned operator++(int) {
85 init();
86 return Value.fetch_add(1, std::memory_order_relaxed);
87 }
88
89 const TrackingStatistic &operator--() {
90 Value.fetch_sub(1, std::memory_order_relaxed);
91 return init();
92 }
93
94 unsigned operator--(int) {
95 init();
96 return Value.fetch_sub(1, std::memory_order_relaxed);
97 }
98
99 const TrackingStatistic &operator+=(unsigned V) {
100 if (V == 0)
101 return *this;
102 Value.fetch_add(V, std::memory_order_relaxed);
103 return init();
104 }
105
106 const TrackingStatistic &operator-=(unsigned V) {
107 if (V == 0)
108 return *this;
109 Value.fetch_sub(V, std::memory_order_relaxed);
110 return init();
111 }
112
113 void updateMax(unsigned V) {
114 unsigned PrevMax = Value.load(std::memory_order_relaxed);
115 // Keep trying to update max until we succeed or another thread produces
116 // a bigger max than us.
117 while (V > PrevMax && !Value.compare_exchange_weak(
118 PrevMax, V, std::memory_order_relaxed)) {
119 }
120 init();
121 }
122
123protected:
124 TrackingStatistic &init() {
125 if (!Initialized.load(std::memory_order_acquire))
126 RegisterStatistic();
127 return *this;
128 }
129
130 void RegisterStatistic();
131};
132
133class NoopStatistic : public StatisticBase {
134public:
135 using StatisticBase::StatisticBase;
136
137 unsigned getValue() const { return 0; }
138
139 // Allow use of this class as the value itself.
140 operator unsigned() const { return 0; }
141
142 const NoopStatistic &operator=(unsigned Val) { return *this; }
143
144 const NoopStatistic &operator++() { return *this; }
145
146 unsigned operator++(int) { return 0; }
147
148 const NoopStatistic &operator--() { return *this; }
149
150 unsigned operator--(int) { return 0; }
151
152 const NoopStatistic &operator+=(const unsigned &V) { return *this; }
153
154 const NoopStatistic &operator-=(const unsigned &V) { return *this; }
155
156 void updateMax(unsigned V) {}
157};
158
159#if LLVM_ENABLE_STATS
160using Statistic = TrackingStatistic;
161#else
162using Statistic = NoopStatistic;
163#endif
164
165// STATISTIC - A macro to make definition of statistics really simple. This
166// automatically passes the DEBUG_TYPE of the file into the statistic.
167#define STATISTIC(VARNAME, DESC) \
168 static llvm::Statistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC}
169
170// ALWAYS_ENABLED_STATISTIC - A macro to define a statistic like STATISTIC but
171// it is enabled even if LLVM_ENABLE_STATS is off.
172#define ALWAYS_ENABLED_STATISTIC(VARNAME, DESC) \
173 static llvm::TrackingStatistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC}
174
175/// Enable the collection and printing of statistics.
176void EnableStatistics(bool DoPrintOnExit = true);
177
178/// Check if statistics are enabled.
179bool AreStatisticsEnabled();
180
181/// Return a file stream to print our output on.
182std::unique_ptr<raw_fd_ostream> CreateInfoOutputFile();
183
184/// Print statistics to the file returned by CreateInfoOutputFile().
185void PrintStatistics();
186
187/// Print statistics to the given output stream.
188void PrintStatistics(raw_ostream &OS);
189
190/// Print statistics in JSON format. This does include all global timers (\see
191/// Timer, TimerGroup). Note that the timers are cleared after printing and will
192/// not be printed in human readable form or in a second call of
193/// PrintStatisticsJSON().
194void PrintStatisticsJSON(raw_ostream &OS);
195
196/// Get the statistics. This can be used to look up the value of
197/// statistics without needing to parse JSON.
198///
199/// This function does not prevent statistics being updated by other threads
200/// during it's execution. It will return the value at the point that it is
201/// read. However, it will prevent new statistics from registering until it
202/// completes.
203const std::vector<std::pair<StringRef, unsigned>> GetStatistics();
204
205/// Reset the statistics. This can be used to zero and de-register the
206/// statistics in order to measure a compilation.
207///
208/// When this function begins to call destructors prior to returning, all
209/// statistics will be zero and unregistered. However, that might not remain the
210/// case by the time this function finishes returning. Whether update from other
211/// threads are lost or merely deferred until during the function return is
212/// timing sensitive.
213///
214/// Callers who intend to use this to measure statistics for a single
215/// compilation should ensure that no compilations are in progress at the point
216/// this function is called and that only one compilation executes until calling
217/// GetStatistics().
218void ResetStatistics();
219
220} // end namespace llvm
221
222#endif // LLVM_ADT_STATISTIC_H
223