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#else
40#define LLVM_ENABLE_STATS 0
41#endif
42
43namespace llvm {
44
45class raw_ostream;
46class raw_fd_ostream;
47class StringRef;
48
49class TrackingStatistic {
50public:
51 const char *const DebugType;
52 const char *const Name;
53 const char *const Desc;
54
55 std::atomic<unsigned> Value;
56 std::atomic<bool> Initialized;
57
58 constexpr TrackingStatistic(const char *DebugType, const char *Name,
59 const char *Desc)
60 : DebugType(DebugType), Name(Name), Desc(Desc), Value(0),
61 Initialized(false) {}
62
63 const char *getDebugType() const { return DebugType; }
64 const char *getName() const { return Name; }
65 const char *getDesc() const { return Desc; }
66
67 unsigned getValue() const { return Value.load(std::memory_order_relaxed); }
68
69 // Allow use of this class as the value itself.
70 operator unsigned() const { return getValue(); }
71
72 const TrackingStatistic &operator=(unsigned Val) {
73 Value.store(Val, std::memory_order_relaxed);
74 return init();
75 }
76
77 const TrackingStatistic &operator++() {
78 Value.fetch_add(1, std::memory_order_relaxed);
79 return init();
80 }
81
82 unsigned operator++(int) {
83 init();
84 return Value.fetch_add(1, std::memory_order_relaxed);
85 }
86
87 const TrackingStatistic &operator--() {
88 Value.fetch_sub(1, std::memory_order_relaxed);
89 return init();
90 }
91
92 unsigned operator--(int) {
93 init();
94 return Value.fetch_sub(1, std::memory_order_relaxed);
95 }
96
97 const TrackingStatistic &operator+=(unsigned V) {
98 if (V == 0)
99 return *this;
100 Value.fetch_add(V, std::memory_order_relaxed);
101 return init();
102 }
103
104 const TrackingStatistic &operator-=(unsigned V) {
105 if (V == 0)
106 return *this;
107 Value.fetch_sub(V, std::memory_order_relaxed);
108 return init();
109 }
110
111 void updateMax(unsigned V) {
112 unsigned PrevMax = Value.load(std::memory_order_relaxed);
113 // Keep trying to update max until we succeed or another thread produces
114 // a bigger max than us.
115 while (V > PrevMax && !Value.compare_exchange_weak(
116 PrevMax, V, std::memory_order_relaxed)) {
117 }
118 init();
119 }
120
121protected:
122 TrackingStatistic &init() {
123 if (!Initialized.load(std::memory_order_acquire))
124 RegisterStatistic();
125 return *this;
126 }
127
128 void RegisterStatistic();
129};
130
131class NoopStatistic {
132public:
133 NoopStatistic(const char * /*DebugType*/, const char * /*Name*/,
134 const char * /*Desc*/) {}
135
136 unsigned getValue() const { return 0; }
137
138 // Allow use of this class as the value itself.
139 operator unsigned() const { return 0; }
140
141 const NoopStatistic &operator=(unsigned Val) { return *this; }
142
143 const NoopStatistic &operator++() { return *this; }
144
145 unsigned operator++(int) { return 0; }
146
147 const NoopStatistic &operator--() { return *this; }
148
149 unsigned operator--(int) { return 0; }
150
151 const NoopStatistic &operator+=(const unsigned &V) { return *this; }
152
153 const NoopStatistic &operator-=(const unsigned &V) { return *this; }
154
155 void updateMax(unsigned V) {}
156};
157
158#if LLVM_ENABLE_STATS
159using Statistic = TrackingStatistic;
160#else
161using Statistic = NoopStatistic;
162#endif
163
164// STATISTIC - A macro to make definition of statistics really simple. This
165// automatically passes the DEBUG_TYPE of the file into the statistic.
166#define STATISTIC(VARNAME, DESC) \
167 static llvm::Statistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC}
168
169// ALWAYS_ENABLED_STATISTIC - A macro to define a statistic like STATISTIC but
170// it is enabled even if LLVM_ENABLE_STATS is off.
171#define ALWAYS_ENABLED_STATISTIC(VARNAME, DESC) \
172 static llvm::TrackingStatistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC}
173
174/// Enable the collection and printing of statistics.
175void EnableStatistics(bool DoPrintOnExit = true);
176
177/// Check if statistics are enabled.
178bool AreStatisticsEnabled();
179
180/// Return a file stream to print our output on.
181std::unique_ptr<raw_fd_ostream> CreateInfoOutputFile();
182
183/// Print statistics to the file returned by CreateInfoOutputFile().
184void PrintStatistics();
185
186/// Print statistics to the given output stream.
187void PrintStatistics(raw_ostream &OS);
188
189/// Print statistics in JSON format. This does include all global timers (\see
190/// Timer, TimerGroup). Note that the timers are cleared after printing and will
191/// not be printed in human readable form or in a second call of
192/// PrintStatisticsJSON().
193void PrintStatisticsJSON(raw_ostream &OS);
194
195/// Get the statistics. This can be used to look up the value of
196/// statistics without needing to parse JSON.
197///
198/// This function does not prevent statistics being updated by other threads
199/// during it's execution. It will return the value at the point that it is
200/// read. However, it will prevent new statistics from registering until it
201/// completes.
202const std::vector<std::pair<StringRef, unsigned>> GetStatistics();
203
204/// Reset the statistics. This can be used to zero and de-register the
205/// statistics in order to measure a compilation.
206///
207/// When this function begins to call destructors prior to returning, all
208/// statistics will be zero and unregistered. However, that might not remain the
209/// case by the time this function finishes returning. Whether update from other
210/// threads are lost or merely deferred until during the function return is
211/// timing sensitive.
212///
213/// Callers who intend to use this to measure statistics for a single
214/// compilation should ensure that no compilations are in progress at the point
215/// this function is called and that only one compilation executes until calling
216/// GetStatistics().
217void ResetStatistics();
218
219} // end namespace llvm
220
221#endif // LLVM_ADT_STATISTIC_H
222