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/Constants.h"
  23 #include "llvm/DerivedTypes.h"
  24 #include "llvm/Module.h"
  25 #include "llvm/Pass.h"
  26 #include "llvm/Support/Compiler.h"
  27 #include "llvm/Support/Streams.h"
  28 #include "llvm/Transforms/Instrumentation.h"
  29 #include "RSProfiling.h"
  30 #include "ProfilingUtils.h"
  31 using namespace llvm;
  32
  33 namespace {
  34   class VISIBILITY_HIDDEN FunctionProfiler : public RSProfilers_std {
  35   public:
  36     static char ID;
  37     bool runOnModule(Module &M);
  38   };
  39 }
  40
  41 char FunctionProfiler::ID = 0;
  42
  43 static RegisterPass<FunctionProfiler>
  44 X("insert-function-profiling",
  45   "Insert instrumentation for function profiling");
  46 static RegisterAnalysisGroup<RSProfilers> XG(X);
  47
  48 ModulePass *llvm::createFunctionProfilerPass() {
  49   return new FunctionProfiler();
  50 }
  51
  52 bool FunctionProfiler::runOnModule(Module &M) {
  53   Function *Main = M.getFunction("main");
  54   if (Main == 0) {
  55     cerr << "WARNING: cannot insert function profiling into a module"
  56          << " with no main function!\n";
  57     return false;  // No main, no instrumentation!
  58   }
  59
  60   unsigned NumFunctions = 0;
  61   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  62     if (!I->isDeclaration())
  63       ++NumFunctions;
  64
  65   const Type *ATy = ArrayType::get(Type::Int32Ty, NumFunctions);
  66   GlobalVariable *Counters =
  67     new GlobalVariable(ATy, false, GlobalValue::InternalLinkage,
  68                        Constant::getNullValue(ATy), "FuncProfCounters", &M);
  69
  70   // Instrument all of the functions...
  71   unsigned i = 0;
  72   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
  73     if (!I->isDeclaration())
  74       // Insert counter at the start of the function
  75       IncrementCounterInBlock(&I->getEntryBlock(), i++, Counters);
  76
  77   // Add the initialization call to main.
  78   InsertProfilingInitCall(Main, "llvm_start_func_profiling", Counters);
  79   return true;
  80 }
  81
  82
  83 namespace {
  84   class BlockProfiler : public RSProfilers_std {
  85     bool runOnModule(Module &M);
  86   public:
  87     static char ID;
  88   };
  89 }
  90
  91 char BlockProfiler::ID = 0;
  92 static RegisterPass<BlockProfiler>
  93 Y("insert-block-profiling", "Insert instrumentation for block profiling");
  94 static RegisterAnalysisGroup<RSProfilers> YG(Y);
  95
  96 ModulePass *llvm::createBlockProfilerPass() { return new BlockProfiler(); }
  97
  98 bool BlockProfiler::runOnModule(Module &M) {
  99   Function *Main = M.getFunction("main");
 100   if (Main == 0) {
 101     cerr << "WARNING: cannot insert block profiling into a module"
 102          << " with no main function!\n";
 103     return false;  // No main, no instrumentation!
 104   }
 105
 106   unsigned NumBlocks = 0;
 107   for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
 108     NumBlocks += I->size();
 109
 110   const Type *ATy = ArrayType::get(Type::Int32Ty, NumBlocks);
 111   GlobalVariable *Counters =
 112     new GlobalVariable(ATy, false, GlobalValue::InternalLinkage,
 113                        Constant::getNullValue(ATy), "BlockProfCounters", &M);
 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     for (Function::iterator BB = I->begin(), E = I->end(); BB != E; ++BB)
 119       // Insert counter at the start of the block
 120       IncrementCounterInBlock(BB, i++, Counters);
 121
 122   // Add the initialization call to main.
 123   InsertProfilingInitCall(Main, "llvm_start_block_profiling", Counters);
 124   return true;
 125 }
 126