LLVM  8.0.0svn
DebugCounter.h
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1 //===- llvm/Support/DebugCounter.h - Debug counter support ------*- 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 /// \file
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
12 /// thing happening.
13 ///
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.
29 ////
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
32 /// counter, like so:
33 ///
34 /// if (!DebugCounter::shouldExecute(RenameCounter)
35 /// <continue or return or whatever not executing looks like>
36 ///
37 /// Now I can, from the command line, make it rename or not rename certain uses
38 /// by setting the skip and count.
39 /// So for example
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 //===----------------------------------------------------------------------===//
43 
44 #ifndef LLVM_SUPPORT_DEBUGCOUNTER_H
45 #define LLVM_SUPPORT_DEBUGCOUNTER_H
46 
47 #include "llvm/ADT/DenseMap.h"
48 #include "llvm/ADT/UniqueVector.h"
50 #include "llvm/Support/Debug.h"
52 #include <string>
53 
54 namespace llvm {
55 
56 class DebugCounter {
57 public:
58  ~DebugCounter();
59 
60  /// Returns a reference to the singleton instance.
61  static DebugCounter &instance();
62 
63  // Used by the command line option parser to push a new value it parsed.
64  void push_back(const std::string &);
65 
66  // Register a counter with the specified name.
67  //
68  // FIXME: Currently, counter registration is required to happen before command
69  // line option parsing. The main reason to register counters is to produce a
70  // nice list of them on the command line, but i'm not sure this is worth it.
71  static unsigned registerCounter(StringRef Name, StringRef Desc) {
72  return instance().addCounter(Name, Desc);
73  }
74  inline static bool shouldExecute(unsigned CounterName) {
75  if (!isCountingEnabled())
76  return true;
77 
78  auto &Us = instance();
79  auto Result = Us.Counters.find(CounterName);
80  if (Result != Us.Counters.end()) {
81  auto &CounterInfo = Result->second;
82  ++CounterInfo.Count;
83 
84  // We only execute while the Skip is not smaller than Count,
85  // and the StopAfter + Skip is larger than Count.
86  // Negative counters always execute.
87  if (CounterInfo.Skip < 0)
88  return true;
89  if (CounterInfo.Skip >= CounterInfo.Count)
90  return false;
91  if (CounterInfo.StopAfter < 0)
92  return true;
93  return CounterInfo.StopAfter + CounterInfo.Skip >= CounterInfo.Count;
94  }
95  // Didn't find the counter, should we warn?
96  return true;
97  }
98 
99  // Return true if a given counter had values set (either programatically or on
100  // the command line). This will return true even if those values are
101  // currently in a state where the counter will always execute.
102  static bool isCounterSet(unsigned ID) {
103  return instance().Counters[ID].IsSet;
104  }
105 
106  // Return the Count for a counter. This only works for set counters.
107  static int64_t getCounterValue(unsigned ID) {
108  auto &Us = instance();
109  auto Result = Us.Counters.find(ID);
110  assert(Result != Us.Counters.end() && "Asking about a non-set counter");
111  return Result->second.Count;
112  }
113 
114  // Set a registered counter to a given Count value.
115  static void setCounterValue(unsigned ID, int64_t Count) {
116  auto &Us = instance();
117  Us.Counters[ID].Count = Count;
118  }
119 
120  // Dump or print the current counter set into llvm::dbgs().
121  LLVM_DUMP_METHOD void dump() const;
122 
123  void print(raw_ostream &OS) const;
124 
125  // Get the counter ID for a given named counter, or return 0 if none is found.
126  unsigned getCounterId(const std::string &Name) const {
127  return RegisteredCounters.idFor(Name);
128  }
129 
130  // Return the number of registered counters.
131  unsigned int getNumCounters() const { return RegisteredCounters.size(); }
132 
133  // Return the name and description of the counter with the given ID.
134  std::pair<std::string, std::string> getCounterInfo(unsigned ID) const {
135  return std::make_pair(RegisteredCounters[ID], Counters.lookup(ID).Desc);
136  }
137 
138  // Iterate through the registered counters
141  return RegisteredCounters.begin();
142  }
143  CounterVector::const_iterator end() const { return RegisteredCounters.end(); }
144 
145  // Force-enables counting all DebugCounters.
146  //
147  // Since DebugCounters are incompatible with threading (not only do they not
148  // make sense, but we'll also see data races), this should only be used in
149  // contexts where we're certain we won't spawn threads.
150  static void enableAllCounters() { instance().Enabled = true; }
151 
152 private:
153  static bool isCountingEnabled() {
154 // Compile to nothing when debugging is off
155 #ifdef NDEBUG
156  return false;
157 #else
158  return instance().Enabled;
159 #endif
160  }
161 
162  unsigned addCounter(const std::string &Name, const std::string &Desc) {
163  unsigned Result = RegisteredCounters.insert(Name);
164  Counters[Result] = {};
165  Counters[Result].Desc = Desc;
166  return Result;
167  }
168  // Struct to store counter info.
169  struct CounterInfo {
170  int64_t Count = 0;
171  int64_t Skip = 0;
172  int64_t StopAfter = -1;
173  bool IsSet = false;
174  std::string Desc;
175  };
177  CounterVector RegisteredCounters;
178 
179  // Whether we should do DebugCounting at all. DebugCounters aren't
180  // thread-safe, so this should always be false in multithreaded scenarios.
181  bool Enabled = false;
182 };
183 
184 #define DEBUG_COUNTER(VARNAME, COUNTERNAME, DESC) \
185  static const unsigned VARNAME = \
186  DebugCounter::registerCounter(COUNTERNAME, DESC)
187 
188 } // namespace llvm
189 #endif
LLVM_DUMP_METHOD void dump() const
This class represents lattice values for constants.
Definition: AllocatorList.h:24
static void enableAllCounters()
Definition: DebugCounter.h:150
UniqueVector< std::string > CounterVector
Definition: DebugCounter.h:139
static DebugCounter & instance()
Returns a reference to the singleton instance.
static unsigned registerCounter(StringRef Name, StringRef Desc)
Definition: DebugCounter.h:71
std::pair< std::string, std::string > getCounterInfo(unsigned ID) const
Definition: DebugCounter.h:134
amdgpu Simplify well known AMD library false Value Value const Twine & Name
#define LLVM_DUMP_METHOD
Definition: Compiler.h:74
unsigned idFor(const T &Entry) const
idFor - return the ID for an existing entry.
Definition: UniqueVector.h:58
CounterVector::const_iterator end() const
Definition: DebugCounter.h:143
static bool isCounterSet(unsigned ID)
Definition: DebugCounter.h:102
unsigned int getNumCounters() const
Definition: DebugCounter.h:131
typename VectorType::const_iterator const_iterator
Definition: UniqueVector.h:29
static void setCounterValue(unsigned ID, int64_t Count)
Definition: DebugCounter.h:115
static int64_t getCounterValue(unsigned ID)
Definition: DebugCounter.h:107
iterator begin()
Return an iterator to the start of the vector.
Definition: UniqueVector.h:76
static bool shouldExecute(unsigned CounterName)
Definition: DebugCounter.h:74
size_t size() const
size - Returns the number of entries in the vector.
Definition: UniqueVector.h:88
iterator end()
Return an iterator to the end of the vector.
Definition: UniqueVector.h:82
void print(raw_ostream &OS) const
CounterVector::const_iterator begin() const
Definition: DebugCounter.h:140
unsigned getCounterId(const std::string &Name) const
Definition: DebugCounter.h:126
void push_back(const std::string &)
unsigned insert(const T &Entry)
insert - Append entry to the vector if it doesn&#39;t already exist.
Definition: UniqueVector.h:41
ValueT lookup(const_arg_type_t< KeyT > Val) const
lookup - Return the entry for the specified key, or a default constructed value if no such entry exis...
Definition: DenseMap.h:211
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
This class implements an extremely fast bulk output stream that can only output to a stream...
Definition: raw_ostream.h:46
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49