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 /// \brief 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" 49 #include "llvm/Support/CommandLine.h" 50 #include "llvm/Support/Debug.h" 51 #include "llvm/Support/raw_ostream.h" 52 #include <string> 53 54 namespace llvm { 55 56 class DebugCounter { 57 public: 58 /// \brief Returns a reference to the singleton instance. 59 static DebugCounter &instance(); 60 61 // Used by the command line option parser to push a new value it parsed. 62 void push_back(const std::string &); 63 64 // Register a counter with the specified name. 65 // 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); 71 } 72 inline static bool shouldExecute(unsigned CounterName) { 73 // Compile to nothing when debugging is off 74 #ifdef NDEBUG 75 return true; 76 #else 77 auto &Us = instance(); 78 auto Result = Us.Counters.find(CounterName); 79 if (Result != Us.Counters.end()) { 80 auto &CounterPair = Result->second; 81 // We only execute while the skip (first) is zero and the count (second) 82 // is non-zero. 83 // Negative counters always execute. 84 if (CounterPair.first < 0) 85 return true; 86 if (CounterPair.first != 0) { 87 --CounterPair.first; 88 return false; 89 } 90 if (CounterPair.second < 0) 91 return true; 92 if (CounterPair.second != 0) { 93 --CounterPair.second; 94 return true; 95 } 96 return false; 97 } 98 // Didn't find the counter, should we warn? 99 return true; 100 #endif // NDEBUG 101 } 102 103 // Return true if a given counter had values set (either programatically or on 104 // the command line). This will return true even if those values are 105 // currently in a state where the counter will always execute. 106 static bool isCounterSet(unsigned ID) { 107 return instance().Counters.count(ID); 108 } 109 110 // Return the skip and count for a counter. This only works for set counters. 111 static std::pair<int, int> getCounterValue(unsigned ID) { 112 auto &Us = instance(); 113 auto Result = Us.Counters.find(ID); 114 assert(Result != Us.Counters.end() && "Asking about a non-set counter"); 115 return Result->second; 116 } 117 118 // Set a registered counter to a given value. 119 static void setCounterValue(unsigned ID, const std::pair<int, int> &Val) { 120 auto &Us = instance(); 121 Us.Counters[ID] = Val; 122 } 123 124 // Dump or print the current counter set into llvm::dbgs(). 125 LLVM_DUMP_METHOD void dump() const; 126 127 void print(raw_ostream &OS) const; 128 129 // Get the counter ID for a given named counter, or return 0 if none is found. 130 unsigned getCounterId(const std::string &Name) const { 131 return RegisteredCounters.idFor(Name); 132 } 133 134 // Return the number of registered counters. 135 unsigned int getNumCounters() const { return RegisteredCounters.size(); } 136 137 // Return the name and description of the counter with the given ID. 138 std::pair<std::string, std::string> getCounterInfo(unsigned ID) const { 139 return std::make_pair(RegisteredCounters[ID], CounterDesc.lookup(ID)); 140 } 141 142 // Iterate through the registered counters 143 typedef UniqueVector<std::string> CounterVector; 144 CounterVector::const_iterator begin() const { 145 return RegisteredCounters.begin(); 146 } 147 CounterVector::const_iterator end() const { return RegisteredCounters.end(); } 148 149 private: 150 unsigned addCounter(const std::string &Name, const std::string &Desc) { 151 unsigned Result = RegisteredCounters.insert(Name); 152 CounterDesc[Result] = Desc; 153 return Result; 154 } 155 DenseMap<unsigned, std::pair<long, long>> Counters; 156 DenseMap<unsigned, std::string> CounterDesc; 157 CounterVector RegisteredCounters; 158 }; 159 160 #define DEBUG_COUNTER(VARNAME, COUNTERNAME, DESC) \ 161 static const unsigned VARNAME = \ 162 DebugCounter::registerCounter(COUNTERNAME, DESC) 163 164 } // namespace llvm 165 #endif 166