1//===-- llvm/ADT/Statistic.h - Easy way to expose stats ---------*- C++ -*-===//
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 defines the 'Statistic' class, which is designed to be an easy way
11// to expose various metrics from passes. These statistics are printed at the
12// end of a run (from llvm_shutdown), when the -stats command line option is
13// passed 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 NumInstsKilled("gcse", "Number of instructions killed");
19//
20// Later, in the code: ++NumInstsKilled;
21//
22// NOTE: Statistics *must* be declared as global variables.
23//
24//===----------------------------------------------------------------------===//
25
26#ifndef LLVM_ADT_STATISTIC_H
27#define LLVM_ADT_STATISTIC_H
28
29#include "llvm/Config/llvm-config.h"
30#include "llvm/Support/Compiler.h"
31#include <atomic>
32#include <memory>
33#include <vector>
34
35// Determine whether statistics should be enabled. We must do it here rather
36// than in CMake because multi-config generators cannot determine this at
37// configure time.
38#if !defined(NDEBUG) || LLVM_FORCE_ENABLE_STATS
39#define LLVM_ENABLE_STATS 1
40#endif
41
42namespace llvm {
43
44class raw_ostream;
45class raw_fd_ostream;
46class StringRef;
47
48class Statistic {
49public:
50 const char *DebugType;
51 const char *Name;
52 const char *Desc;
53 std::atomic<unsigned> Value;
54 std::atomic<bool> Initialized;
55
56 unsigned getValue() const { return Value.load(std::memory_order_relaxed); }
57 const char *getDebugType() const { return DebugType; }
58 const char *getName() const { return Name; }
59 const char *getDesc() const { return Desc; }
60
61 /// construct - This should only be called for non-global statistics.
62 void construct(const char *debugtype, const char *name, const char *desc) {
63 DebugType = debugtype;
64 Name = name;
65 Desc = desc;
66 Value = 0;
67 Initialized = false;
68 }
69
70 // Allow use of this class as the value itself.
71 operator unsigned() const { return getValue(); }
72
73#if LLVM_ENABLE_STATS
74 const Statistic &operator=(unsigned Val) {
75 Value.store(Val, std::memory_order_relaxed);
76 return init();
77 }
78
79 const Statistic &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 Statistic &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 Statistic &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 Statistic &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
123#else // Statistics are disabled in release builds.
124
125 const Statistic &operator=(unsigned Val) {
126 return *this;
127 }
128
129 const Statistic &operator++() {
130 return *this;
131 }
132
133 unsigned operator++(int) {
134 return 0;
135 }
136
137 const Statistic &operator--() {
138 return *this;
139 }
140
141 unsigned operator--(int) {
142 return 0;
143 }
144
145 const Statistic &operator+=(const unsigned &V) {
146 return *this;
147 }
148
149 const Statistic &operator-=(const unsigned &V) {
150 return *this;
151 }
152
153 void updateMax(unsigned V) {}
154
155#endif // LLVM_ENABLE_STATS
156
157protected:
158 Statistic &init() {
159 if (!Initialized.load(std::memory_order_acquire))
160 RegisterStatistic();
161 return *this;
162 }
163
164 void RegisterStatistic();
165};
166
167// STATISTIC - A macro to make definition of statistics really simple. This
168// automatically passes the DEBUG_TYPE of the file into the statistic.
169#define STATISTIC(VARNAME, DESC) \
170 static llvm::Statistic VARNAME = {DEBUG_TYPE, #VARNAME, DESC, {0}, {false}}
171
172/// Enable the collection and printing of statistics.
173void EnableStatistics(bool PrintOnExit = true);
174
175/// Check if statistics are enabled.
176bool AreStatisticsEnabled();
177
178/// Return a file stream to print our output on.
179std::unique_ptr<raw_fd_ostream> CreateInfoOutputFile();
180
181/// Print statistics to the file returned by CreateInfoOutputFile().
182void PrintStatistics();
183
184/// Print statistics to the given output stream.
185void PrintStatistics(raw_ostream &OS);
186
187/// Print statistics in JSON format. This does include all global timers (\see
188/// Timer, TimerGroup). Note that the timers are cleared after printing and will
189/// not be printed in human readable form or in a second call of
190/// PrintStatisticsJSON().
191void PrintStatisticsJSON(raw_ostream &OS);
192
193/// Get the statistics. This can be used to look up the value of
194/// statistics without needing to parse JSON.
195///
196/// This function does not prevent statistics being updated by other threads
197/// during it's execution. It will return the value at the point that it is
198/// read. However, it will prevent new statistics from registering until it
199/// completes.
200const std::vector<std::pair<StringRef, unsigned>> GetStatistics();
201
202/// Reset the statistics. This can be used to zero and de-register the
203/// statistics in order to measure a compilation.
204///
205/// When this function begins to call destructors prior to returning, all
206/// statistics will be zero and unregistered. However, that might not remain the
207/// case by the time this function finishes returning. Whether update from other
208/// threads are lost or merely deferred until during the function return is
209/// timing sensitive.
210///
211/// Callers who intend to use this to measure statistics for a single
212/// compilation should ensure that no compilations are in progress at the point
213/// this function is called and that only one compilation executes until calling
214/// GetStatistics().
215void ResetStatistics();
216
217} // end namespace llvm
218
219#endif // LLVM_ADT_STATISTIC_H
220