LLVM API Documentation
00001 //===- BlockProfiling.cpp - Insert counters for block profiling -----------===// 00002 // 00003 // The LLVM Compiler Infrastructure 00004 // 00005 // This file was developed by the LLVM research group and is distributed under 00006 // the University of Illinois Open Source License. See LICENSE.TXT for details. 00007 // 00008 //===----------------------------------------------------------------------===// 00009 // 00010 // This pass instruments the specified program with counters for basic block or 00011 // function profiling. This is the most basic form of profiling, which can tell 00012 // which blocks are hot, but cannot reliably detect hot paths through the CFG. 00013 // Block profiling counts the number of times each basic block executes, and 00014 // function profiling counts the number of times each function is called. 00015 // 00016 // Note that this implementation is very naive. Control equivalent regions of 00017 // the CFG should not require duplicate counters, but we do put duplicate 00018 // counters in. 00019 // 00020 //===----------------------------------------------------------------------===// 00021 00022 #include "llvm/Constants.h" 00023 #include "llvm/DerivedTypes.h" 00024 #include "llvm/Module.h" 00025 #include "llvm/Pass.h" 00026 #include "ProfilingUtils.h" 00027 #include <iostream> 00028 00029 using namespace llvm; 00030 00031 namespace { 00032 class FunctionProfiler : public ModulePass { 00033 bool runOnModule(Module &M); 00034 }; 00035 00036 RegisterOpt<FunctionProfiler> X("insert-function-profiling", 00037 "Insert instrumentation for function profiling"); 00038 } 00039 00040 bool FunctionProfiler::runOnModule(Module &M) { 00041 Function *Main = M.getMainFunction(); 00042 if (Main == 0) { 00043 std::cerr << "WARNING: cannot insert function profiling into a module" 00044 << " with no main function!\n"; 00045 return false; // No main, no instrumentation! 00046 } 00047 00048 unsigned NumFunctions = 0; 00049 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 00050 if (!I->isExternal()) 00051 ++NumFunctions; 00052 00053 const Type *ATy = ArrayType::get(Type::UIntTy, NumFunctions); 00054 GlobalVariable *Counters = 00055 new GlobalVariable(ATy, false, GlobalValue::InternalLinkage, 00056 Constant::getNullValue(ATy), "FuncProfCounters", &M); 00057 00058 // Instrument all of the functions... 00059 unsigned i = 0; 00060 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 00061 if (!I->isExternal()) 00062 // Insert counter at the start of the function 00063 IncrementCounterInBlock(I->begin(), i++, Counters); 00064 00065 // Add the initialization call to main. 00066 InsertProfilingInitCall(Main, "llvm_start_func_profiling", Counters); 00067 return true; 00068 } 00069 00070 00071 namespace { 00072 class BlockProfiler : public ModulePass { 00073 bool runOnModule(Module &M); 00074 }; 00075 00076 RegisterOpt<BlockProfiler> Y("insert-block-profiling", 00077 "Insert instrumentation for block profiling"); 00078 } 00079 00080 bool BlockProfiler::runOnModule(Module &M) { 00081 Function *Main = M.getMainFunction(); 00082 if (Main == 0) { 00083 std::cerr << "WARNING: cannot insert block profiling into a module" 00084 << " with no main function!\n"; 00085 return false; // No main, no instrumentation! 00086 } 00087 00088 unsigned NumBlocks = 0; 00089 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 00090 NumBlocks += I->size(); 00091 00092 const Type *ATy = ArrayType::get(Type::UIntTy, NumBlocks); 00093 GlobalVariable *Counters = 00094 new GlobalVariable(ATy, false, GlobalValue::InternalLinkage, 00095 Constant::getNullValue(ATy), "BlockProfCounters", &M); 00096 00097 // Instrument all of the blocks... 00098 unsigned i = 0; 00099 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 00100 for (Function::iterator BB = I->begin(), E = I->end(); BB != E; ++BB) 00101 // Insert counter at the start of the block 00102 IncrementCounterInBlock(BB, i++, Counters); 00103 00104 // Add the initialization call to main. 00105 InsertProfilingInitCall(Main, "llvm_start_block_profiling", Counters); 00106 return true; 00107 } 00108