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 "llvm/Transforms/Instrumentation.h" 00027 #include "RSProfiling.h" 00028 #include "ProfilingUtils.h" 00029 #include <iostream> 00030 00031 using namespace llvm; 00032 00033 namespace { 00034 class FunctionProfiler : public RSProfilers_std { 00035 bool runOnModule(Module &M); 00036 }; 00037 00038 RegisterOpt<FunctionProfiler> X("insert-function-profiling", 00039 "Insert instrumentation for function profiling"); 00040 RegisterAnalysisGroup<RSProfilers, FunctionProfiler> XG; 00041 00042 } 00043 00044 ModulePass *llvm::createFunctionProfilerPass() { 00045 return new FunctionProfiler(); 00046 } 00047 00048 bool FunctionProfiler::runOnModule(Module &M) { 00049 Function *Main = M.getMainFunction(); 00050 if (Main == 0) { 00051 std::cerr << "WARNING: cannot insert function profiling into a module" 00052 << " with no main function!\n"; 00053 return false; // No main, no instrumentation! 00054 } 00055 00056 unsigned NumFunctions = 0; 00057 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 00058 if (!I->isExternal()) 00059 ++NumFunctions; 00060 00061 const Type *ATy = ArrayType::get(Type::UIntTy, NumFunctions); 00062 GlobalVariable *Counters = 00063 new GlobalVariable(ATy, false, GlobalValue::InternalLinkage, 00064 Constant::getNullValue(ATy), "FuncProfCounters", &M); 00065 00066 // Instrument all of the functions... 00067 unsigned i = 0; 00068 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 00069 if (!I->isExternal()) 00070 // Insert counter at the start of the function 00071 IncrementCounterInBlock(I->begin(), i++, Counters); 00072 00073 // Add the initialization call to main. 00074 InsertProfilingInitCall(Main, "llvm_start_func_profiling", Counters); 00075 return true; 00076 } 00077 00078 00079 namespace { 00080 class BlockProfiler : public RSProfilers_std { 00081 bool runOnModule(Module &M); 00082 }; 00083 00084 RegisterOpt<BlockProfiler> Y("insert-block-profiling", 00085 "Insert instrumentation for block profiling"); 00086 RegisterAnalysisGroup<RSProfilers, BlockProfiler> YG; 00087 } 00088 00089 ModulePass *llvm::createBlockProfilerPass() { return new BlockProfiler(); } 00090 00091 bool BlockProfiler::runOnModule(Module &M) { 00092 Function *Main = M.getMainFunction(); 00093 if (Main == 0) { 00094 std::cerr << "WARNING: cannot insert block profiling into a module" 00095 << " with no main function!\n"; 00096 return false; // No main, no instrumentation! 00097 } 00098 00099 unsigned NumBlocks = 0; 00100 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 00101 NumBlocks += I->size(); 00102 00103 const Type *ATy = ArrayType::get(Type::UIntTy, NumBlocks); 00104 GlobalVariable *Counters = 00105 new GlobalVariable(ATy, false, GlobalValue::InternalLinkage, 00106 Constant::getNullValue(ATy), "BlockProfCounters", &M); 00107 00108 // Instrument all of the blocks... 00109 unsigned i = 0; 00110 for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) 00111 for (Function::iterator BB = I->begin(), E = I->end(); BB != E; ++BB) 00112 // Insert counter at the start of the block 00113 IncrementCounterInBlock(BB, i++, Counters); 00114 00115 // Add the initialization call to main. 00116 InsertProfilingInitCall(Main, "llvm_start_block_profiling", Counters); 00117 return true; 00118 } 00119