| //===- llvm/Support/DebugCounter.h - Debug counter support ------*- C++ -*-===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| /// \file |
| /// \brief This file provides an implementation of debug counters. Debug |
| /// counters are a tool that let you narrow down a miscompilation to a specific |
| /// thing happening. |
| /// |
| /// To give a use case: Imagine you have a file, very large, and you |
| /// are trying to understand the minimal transformation that breaks it. Bugpoint |
| /// and bisection is often helpful here in narrowing it down to a specific pass, |
| /// but it's still a very large file, and a very complicated pass to try to |
| /// debug. That is where debug counting steps in. You can instrument the pass |
| /// with a debug counter before it does a certain thing, and depending on the |
| /// counts, it will either execute that thing or not. The debug counter itself |
| /// consists of a skip and a count. Skip is the number of times shouldExecute |
| /// needs to be called before it returns true. Count is the number of times to |
| /// return true once Skip is 0. So a skip=47, count=2 ,would skip the first 47 |
| /// executions by returning false from shouldExecute, then execute twice, and |
| /// then return false again. |
| /// Note that a counter set to a negative number will always execute. |
| /// For a concrete example, during predicateinfo creation, the renaming pass |
| /// replaces each use with a renamed use. |
| //// |
| /// If I use DEBUG_COUNTER to create a counter called "predicateinfo", and |
| /// variable name RenameCounter, and then instrument this renaming with a debug |
| /// counter, like so: |
| /// |
| /// if (!DebugCounter::shouldExecute(RenameCounter) |
| /// <continue or return or whatever not executing looks like> |
| /// |
| /// Now I can, from the command line, make it rename or not rename certain uses |
| /// by setting the skip and count. |
| /// So for example |
| /// bin/opt -debug-counter=predicateinfo-skip=47,predicateinfo-count=1 |
| /// will skip renaming the first 47 uses, then rename one, then skip the rest. |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_SUPPORT_DEBUGCOUNTER_H |
| #define LLVM_SUPPORT_DEBUGCOUNTER_H |
| |
| #include "llvm/ADT/DenseMap.h" |
| #include "llvm/ADT/UniqueVector.h" |
| #include "llvm/Support/CommandLine.h" |
| #include "llvm/Support/Debug.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include <string> |
| |
| namespace llvm { |
| |
| class DebugCounter { |
| public: |
| /// \brief Returns a reference to the singleton instance. |
| static DebugCounter &instance(); |
| |
| // Used by the command line option parser to push a new value it parsed. |
| void push_back(const std::string &); |
| |
| // Register a counter with the specified name. |
| // |
| // FIXME: Currently, counter registration is required to happen before command |
| // line option parsing. The main reason to register counters is to produce a |
| // nice list of them on the command line, but i'm not sure this is worth it. |
| static unsigned registerCounter(StringRef Name, StringRef Desc) { |
| return instance().addCounter(Name, Desc); |
| } |
| inline static bool shouldExecute(unsigned CounterName) { |
| // Compile to nothing when debugging is off |
| #ifdef NDEBUG |
| return true; |
| #else |
| auto &Us = instance(); |
| auto Result = Us.Counters.find(CounterName); |
| if (Result != Us.Counters.end()) { |
| auto &CounterPair = Result->second; |
| // We only execute while the skip (first) is zero and the count (second) |
| // is non-zero. |
| // Negative counters always execute. |
| if (CounterPair.first < 0) |
| return true; |
| if (CounterPair.first != 0) { |
| --CounterPair.first; |
| return false; |
| } |
| if (CounterPair.second < 0) |
| return true; |
| if (CounterPair.second != 0) { |
| --CounterPair.second; |
| return true; |
| } |
| return false; |
| } |
| // Didn't find the counter, should we warn? |
| return true; |
| #endif // NDEBUG |
| } |
| |
| // Return true if a given counter had values set (either programatically or on |
| // the command line). This will return true even if those values are |
| // currently in a state where the counter will always execute. |
| static bool isCounterSet(unsigned ID) { |
| return instance().Counters.count(ID); |
| } |
| |
| // Return the skip and count for a counter. This only works for set counters. |
| static std::pair<int, int> getCounterValue(unsigned ID) { |
| auto &Us = instance(); |
| auto Result = Us.Counters.find(ID); |
| assert(Result != Us.Counters.end() && "Asking about a non-set counter"); |
| return Result->second; |
| } |
| |
| // Set a registered counter to a given value. |
| static void setCounterValue(unsigned ID, const std::pair<int, int> &Val) { |
| auto &Us = instance(); |
| Us.Counters[ID] = Val; |
| } |
| |
| // Dump or print the current counter set into llvm::dbgs(). |
| LLVM_DUMP_METHOD void dump() const; |
| |
| void print(raw_ostream &OS) const; |
| |
| // Get the counter ID for a given named counter, or return 0 if none is found. |
| unsigned getCounterId(const std::string &Name) const { |
| return RegisteredCounters.idFor(Name); |
| } |
| |
| // Return the number of registered counters. |
| unsigned int getNumCounters() const { return RegisteredCounters.size(); } |
| |
| // Return the name and description of the counter with the given ID. |
| std::pair<std::string, std::string> getCounterInfo(unsigned ID) const { |
| return std::make_pair(RegisteredCounters[ID], CounterDesc.lookup(ID)); |
| } |
| |
| // Iterate through the registered counters |
| typedef UniqueVector<std::string> CounterVector; |
| CounterVector::const_iterator begin() const { |
| return RegisteredCounters.begin(); |
| } |
| CounterVector::const_iterator end() const { return RegisteredCounters.end(); } |
| |
| private: |
| unsigned addCounter(const std::string &Name, const std::string &Desc) { |
| unsigned Result = RegisteredCounters.insert(Name); |
| CounterDesc[Result] = Desc; |
| return Result; |
| } |
| DenseMap<unsigned, std::pair<long, long>> Counters; |
| DenseMap<unsigned, std::string> CounterDesc; |
| CounterVector RegisteredCounters; |
| }; |
| |
| #define DEBUG_COUNTER(VARNAME, COUNTERNAME, DESC) \ |
| static const unsigned VARNAME = \ |
| DebugCounter::registerCounter(COUNTERNAME, DESC) |
| |
| } // namespace llvm |
| #endif |