1 //===- llvm/Support/DebugCounter.h - Debug counter support ------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 /// This file provides an implementation of debug counters. Debug
11 /// counters are a tool that let you narrow down a miscompilation to a specific
14 /// To give a use case: Imagine you have a file, very large, and you
15 /// are trying to understand the minimal transformation that breaks it. Bugpoint
16 /// and bisection is often helpful here in narrowing it down to a specific pass,
17 /// but it's still a very large file, and a very complicated pass to try to
18 /// debug. That is where debug counting steps in. You can instrument the pass
19 /// with a debug counter before it does a certain thing, and depending on the
20 /// counts, it will either execute that thing or not. The debug counter itself
21 /// consists of a skip and a count. Skip is the number of times shouldExecute
22 /// needs to be called before it returns true. Count is the number of times to
23 /// return true once Skip is 0. So a skip=47, count=2 ,would skip the first 47
24 /// executions by returning false from shouldExecute, then execute twice, and
25 /// then return false again.
26 /// Note that a counter set to a negative number will always execute.
27 /// For a concrete example, during predicateinfo creation, the renaming pass
28 /// replaces each use with a renamed use.
30 /// If I use DEBUG_COUNTER to create a counter called "predicateinfo", and
31 /// variable name RenameCounter, and then instrument this renaming with a debug
34 /// if (!DebugCounter::shouldExecute(RenameCounter)
35 /// <continue or return or whatever not executing looks like>
37 /// Now I can, from the command line, make it rename or not rename certain uses
38 /// by setting the skip and count.
40 /// bin/opt -debug-counter=predicateinfo-skip=47,predicateinfo-count=1
41 /// will skip renaming the first 47 uses, then rename one, then skip the rest.
42 //===----------------------------------------------------------------------===//
44 #ifndef LLVM_SUPPORT_DEBUGCOUNTER_H
45 #define LLVM_SUPPORT_DEBUGCOUNTER_H
47 #include "llvm/ADT/DenseMap.h"
48 #include "llvm/ADT/UniqueVector.h"
49 #include "llvm/Support/CommandLine.h"
50 #include "llvm/Support/Debug.h"
51 #include "llvm/Support/raw_ostream.h"
58 /// Returns a reference to the singleton instance.
59 static DebugCounter &instance();
61 // Used by the command line option parser to push a new value it parsed.
62 void push_back(const std::string &);
64 // Register a counter with the specified name.
66 // FIXME: Currently, counter registration is required to happen before command
67 // line option parsing. The main reason to register counters is to produce a
68 // nice list of them on the command line, but i'm not sure this is worth it.
69 static unsigned registerCounter(StringRef Name, StringRef Desc) {
70 return instance().addCounter(Name, Desc);
72 inline static bool shouldExecute(unsigned CounterName) {
73 if (!isCountingEnabled())
76 auto &Us = instance();
77 auto Result = Us.Counters.find(CounterName);
78 if (Result != Us.Counters.end()) {
79 auto &CounterInfo = Result->second;
82 // We only execute while the Skip is not smaller than Count,
83 // and the StopAfter + Skip is larger than Count.
84 // Negative counters always execute.
85 if (CounterInfo.Skip < 0)
87 if (CounterInfo.Skip >= CounterInfo.Count)
89 if (CounterInfo.StopAfter < 0)
91 return CounterInfo.StopAfter + CounterInfo.Skip >= CounterInfo.Count;
93 // Didn't find the counter, should we warn?
97 // Return true if a given counter had values set (either programatically or on
98 // the command line). This will return true even if those values are
99 // currently in a state where the counter will always execute.
100 static bool isCounterSet(unsigned ID) {
101 return instance().Counters[ID].IsSet;
104 // Return the Count for a counter. This only works for set counters.
105 static int64_t getCounterValue(unsigned ID) {
106 auto &Us = instance();
107 auto Result = Us.Counters.find(ID);
108 assert(Result != Us.Counters.end() && "Asking about a non-set counter");
109 return Result->second.Count;
112 // Set a registered counter to a given Count value.
113 static void setCounterValue(unsigned ID, int64_t Count) {
114 auto &Us = instance();
115 Us.Counters[ID].Count = Count;
118 // Dump or print the current counter set into llvm::dbgs().
119 LLVM_DUMP_METHOD void dump() const;
121 void print(raw_ostream &OS) const;
123 // Get the counter ID for a given named counter, or return 0 if none is found.
124 unsigned getCounterId(const std::string &Name) const {
125 return RegisteredCounters.idFor(Name);
128 // Return the number of registered counters.
129 unsigned int getNumCounters() const { return RegisteredCounters.size(); }
131 // Return the name and description of the counter with the given ID.
132 std::pair<std::string, std::string> getCounterInfo(unsigned ID) const {
133 return std::make_pair(RegisteredCounters[ID], Counters.lookup(ID).Desc);
136 // Iterate through the registered counters
137 typedef UniqueVector<std::string> CounterVector;
138 CounterVector::const_iterator begin() const {
139 return RegisteredCounters.begin();
141 CounterVector::const_iterator end() const { return RegisteredCounters.end(); }
143 // Force-enables counting all DebugCounters.
145 // Since DebugCounters are incompatible with threading (not only do they not
146 // make sense, but we'll also see data races), this should only be used in
147 // contexts where we're certain we won't spawn threads.
148 static void enableAllCounters() { instance().Enabled = true; }
151 static bool isCountingEnabled() {
152 // Compile to nothing when debugging is off
156 return instance().Enabled;
160 unsigned addCounter(const std::string &Name, const std::string &Desc) {
161 unsigned Result = RegisteredCounters.insert(Name);
162 Counters[Result] = {};
163 Counters[Result].Desc = Desc;
166 // Struct to store counter info.
170 int64_t StopAfter = -1;
174 DenseMap<unsigned, CounterInfo> Counters;
175 CounterVector RegisteredCounters;
177 // Whether we should do DebugCounting at all. DebugCounters aren't
178 // thread-safe, so this should always be false in multithreaded scenarios.
179 bool Enabled = false;
182 #define DEBUG_COUNTER(VARNAME, COUNTERNAME, DESC) \
183 static const unsigned VARNAME = \
184 DebugCounter::registerCounter(COUNTERNAME, DESC)