lib/Transforms/Instrumentation/BlockProfiling.cpp

   1 //===- BlockProfiling.cpp - Insert counters for block profiling -----------===//
   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 //
  10 // This pass instruments the specified program with counters for basic block or
  11 // function profiling.  This is the most basic form of profiling, which can tell
  12 // which blocks are hot, but cannot reliably detect hot paths through the CFG.
  13 // Block profiling counts the number of times each basic block executes, and
  14 // function profiling counts the number of times each function is called.
  15 //
  16 // Note that this implementation is very naive.  Control equivalent regions of
  17 // the CFG should not require duplicate counters, but we do put duplicate
  18 // counters in.
  19 //
  20 //===----------------------------------------------------------------------===//
  21
  22 #include "llvm/DerivedTypes.h"
  23 #include "llvm/Module.h"
  24 #include "llvm/Pass.h"
  25 #include "llvm/Support/raw_ostream.h"
  26 #include "llvm/Transforms/Instrumentation.h"
  27 #include "RSProfiling.h"
  28 #include "ProfilingUtils.h"
  29 using namespace llvm;
  30
  31 namespace {
  32   class FunctionProfiler : public RSProfilers_std {
  33   public:
  34     static char ID;
  35     bool runOnModule(Module &M);
  36   };
  37 }
  38
  39 char FunctionProfiler::ID = 0;
  40
  41 static RegisterPass<FunctionProfiler>
  42 X("insert-function-profiling",
  43   "Insert instrumentation for function profiling");
  44 static RegisterAnalysisGroup<RSProfilers> XG(X);
  45
  46 ModulePass *llvm::createFunctionProfilerPass() {
  47   return new FunctionProfiler();
  48 }
  49
  50 bool FunctionProfiler::runOnModule(Module &M) {
  51   Function *Main = M.getFunction("main");
  52   if (Main == 0) {
  53     errs() << "WARNING: cannot insert function profiling into a module"
  54            << " with no main function!\n";
  55     return false;  // No main, no instrumentation!
  56   }
  57
  58   unsigned NumFunctions = 0;
  59   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  60     if (!I->isDeclaration())
  61       ++NumFunctions;
  62
  63   const Type *ATy = ArrayType::get(Type::getInt32Ty(M.getContext()),
  64                                    NumFunctions);
  65   GlobalVariable *Counters =
  66     new GlobalVariable(M, ATy, false, GlobalValue::InternalLinkage,
  67                        Constant::getNullValue(ATy), "FuncProfCounters");
  68
  69   // Instrument all of the functions...
  70   unsigned i = 0;
  71   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  72     if (!I->isDeclaration())
  73       // Insert counter at the start of the function
  74       IncrementCounterInBlock(&I->getEntryBlock(), i++, Counters);
  75
  76   // Add the initialization call to main.
  77   InsertProfilingInitCall(Main, "llvm_start_func_profiling", Counters);
  78   return true;
  79 }
  80
  81
  82 namespace {
  83   class BlockProfiler : public RSProfilers_std {
  84     bool runOnModule(Module &M);
  85   public:
  86     static char ID;
  87   };
  88 }
  89
  90 char BlockProfiler::ID = 0;
  91 static RegisterPass<BlockProfiler>
  92 Y("insert-block-profiling", "Insert instrumentation for block profiling");
  93 static RegisterAnalysisGroup<RSProfilers> YG(Y);
  94
  95 ModulePass *llvm::createBlockProfilerPass() { return new BlockProfiler(); }
  96
  97 bool BlockProfiler::runOnModule(Module &M) {
  98   Function *Main = M.getFunction("main");
  99   if (Main == 0) {
 100     errs() << "WARNING: cannot insert block profiling into a module"
 101            << " with no main function!\n";
 102     return false;  // No main, no instrumentation!
 103   }
 104
 105   unsigned NumBlocks = 0;
 106   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
 107     if (!I->isDeclaration())
 108       NumBlocks += I->size();
 109
 110   const Type *ATy = ArrayType::get(Type::getInt32Ty(M.getContext()), NumBlocks);
 111   GlobalVariable *Counters =
 112     new GlobalVariable(M, ATy, false, GlobalValue::InternalLinkage,
 113                        Constant::getNullValue(ATy), "BlockProfCounters");
 114
 115   // Instrument all of the blocks...
 116   unsigned i = 0;
 117   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
 118     if (I->isDeclaration()) continue;
 119     for (Function::iterator BB = I->begin(), E = I->end(); BB != E; ++BB)
 120       // Insert counter at the start of the block
 121       IncrementCounterInBlock(BB, i++, Counters);
 122   }
 123
 124   // Add the initialization call to main.
 125   InsertProfilingInitCall(Main, "llvm_start_block_profiling", Counters);
 126   return true;
 127 }
 128