lib/Transforms/Instrumentation/ProfilingUtils.cpp

   1 //===- ProfilingUtils.cpp - Helper functions shared by profilers ----------===//
   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 file implements a few helper functions which are used by profile
  11 // instrumentation code to instrument the code.  This allows the profiler pass
  12 // to worry about *what* to insert, and these functions take care of *how* to do
  13 // it.
  14 //
  15 //===----------------------------------------------------------------------===//
  16
  17 #include "ProfilingUtils.h"
  18 #include "llvm/Constants.h"
  19 #include "llvm/DerivedTypes.h"
  20 #include "llvm/Instructions.h"
  21 #include "llvm/LLVMContext.h"
  22 #include "llvm/Module.h"
  23
  24 void llvm::InsertProfilingInitCall(Function *MainFn, const char *FnName,
  25                                    GlobalValue *Array,
  26                                    PointerType *arrayType) {
  27   LLVMContext &Context = MainFn->getContext();
  28   const Type *ArgVTy =
  29     PointerType::getUnqual(Type::getInt8PtrTy(Context));
  30   const PointerType *UIntPtr = arrayType ? arrayType :
  31     Type::getInt32PtrTy(Context);
  32   Module &M = *MainFn->getParent();
  33   Constant *InitFn = M.getOrInsertFunction(FnName, Type::getInt32Ty(Context),
  34                                            Type::getInt32Ty(Context),
  35                                            ArgVTy, UIntPtr,
  36                                            Type::getInt32Ty(Context),
  37                                            (Type *)0);
  38
  39   // This could force argc and argv into programs that wouldn't otherwise have
  40   // them, but instead we just pass null values in.
  41   std::vector<Value*> Args(4);
  42   Args[0] = Constant::getNullValue(Type::getInt32Ty(Context));
  43   Args[1] = Constant::getNullValue(ArgVTy);
  44
  45   // Skip over any allocas in the entry block.
  46   BasicBlock *Entry = MainFn->begin();
  47   BasicBlock::iterator InsertPos = Entry->begin();
  48   while (isa<AllocaInst>(InsertPos)) ++InsertPos;
  49
  50   std::vector<Constant*> GEPIndices(2,
  51                              Constant::getNullValue(Type::getInt32Ty(Context)));
  52   unsigned NumElements = 0;
  53   if (Array) {
  54     Args[2] = ConstantExpr::getGetElementPtr(Array, &GEPIndices[0],
  55                                              GEPIndices.size());
  56     NumElements =
  57       cast<ArrayType>(Array->getType()->getElementType())->getNumElements();
  58   } else {
  59     // If this profiling instrumentation doesn't have a constant array, just
  60     // pass null.
  61     Args[2] = ConstantPointerNull::get(UIntPtr);
  62   }
  63   Args[3] = ConstantInt::get(Type::getInt32Ty(Context), NumElements);
  64
  65   CallInst *InitCall = CallInst::Create(InitFn, Args.begin(), Args.end(),
  66                                         "newargc", InsertPos);
  67
  68   // If argc or argv are not available in main, just pass null values in.
  69   Function::arg_iterator AI;
  70   switch (MainFn->arg_size()) {
  71   default:
  72   case 2:
  73     AI = MainFn->arg_begin(); ++AI;
  74     if (AI->getType() != ArgVTy) {
  75       Instruction::CastOps opcode = CastInst::getCastOpcode(AI, false, ArgVTy,
  76                                                             false);
  77       InitCall->setArgOperand(1,
  78           CastInst::Create(opcode, AI, ArgVTy, "argv.cast", InitCall));
  79     } else {
  80       InitCall->setArgOperand(1, AI);
  81     }
  82     /* FALL THROUGH */
  83
  84   case 1:
  85     AI = MainFn->arg_begin();
  86     // If the program looked at argc, have it look at the return value of the
  87     // init call instead.
  88     if (!AI->getType()->isIntegerTy(32)) {
  89       Instruction::CastOps opcode;
  90       if (!AI->use_empty()) {
  91         opcode = CastInst::getCastOpcode(InitCall, true, AI->getType(), true);
  92         AI->replaceAllUsesWith(
  93           CastInst::Create(opcode, InitCall, AI->getType(), "", InsertPos));
  94       }
  95       opcode = CastInst::getCastOpcode(AI, true,
  96                                        Type::getInt32Ty(Context), true);
  97       InitCall->setArgOperand(0,
  98           CastInst::Create(opcode, AI, Type::getInt32Ty(Context),
  99                            "argc.cast", InitCall));
 100     } else {
 101       AI->replaceAllUsesWith(InitCall);
 102       InitCall->setArgOperand(0, AI);
 103     }
 104
 105   case 0: break;
 106   }
 107 }
 108
 109 void llvm::IncrementCounterInBlock(BasicBlock *BB, unsigned CounterNum,
 110                                    GlobalValue *CounterArray, bool beginning) {
 111   // Insert the increment after any alloca or PHI instructions...
 112   BasicBlock::iterator InsertPos = beginning ? BB->getFirstNonPHI() :
 113                                    BB->getTerminator();
 114   while (isa<AllocaInst>(InsertPos))
 115     ++InsertPos;
 116
 117   LLVMContext &Context = BB->getContext();
 118
 119   // Create the getelementptr constant expression
 120   std::vector<Constant*> Indices(2);
 121   Indices[0] = Constant::getNullValue(Type::getInt32Ty(Context));
 122   Indices[1] = ConstantInt::get(Type::getInt32Ty(Context), CounterNum);
 123   Constant *ElementPtr =
 124     ConstantExpr::getGetElementPtr(CounterArray, &Indices[0], Indices.size());
 125
 126   // Load, increment and store the value back.
 127   Value *OldVal = new LoadInst(ElementPtr, "OldFuncCounter", InsertPos);
 128   Value *NewVal = BinaryOperator::Create(Instruction::Add, OldVal,
 129                                  ConstantInt::get(Type::getInt32Ty(Context), 1),
 130                                          "NewFuncCounter", InsertPos);
 131   new StoreInst(NewVal, ElementPtr, InsertPos);
 132 }
 133
 134 void llvm::InsertProfilingShutdownCall(Function *Callee, Module *Mod) {
 135   // llvm.global_dtors is an array of type { i32, void ()* }. Prepare those
 136   // types.
 137   const Type *GlobalDtorElems[2] = {
 138     Type::getInt32Ty(Mod->getContext()),
 139     FunctionType::get(Type::getVoidTy(Mod->getContext()), false)->getPointerTo()
 140   };
 141   const StructType *GlobalDtorElemTy =
 142       StructType::get(Mod->getContext(), GlobalDtorElems, false);
 143
 144   // Construct the new element we'll be adding.
 145   Constant *Elem[2] = {
 146     ConstantInt::get(Type::getInt32Ty(Mod->getContext()), 65535),
 147     ConstantExpr::getBitCast(Callee, GlobalDtorElems[1])
 148   };
 149
 150   // If llvm.global_dtors exists, make a copy of the things in its list and
 151   // delete it, to replace it with one that has a larger array type.
 152   std::vector<Constant *> dtors;
 153   if (GlobalVariable *GlobalDtors = Mod->getNamedGlobal("llvm.global_dtors")) {
 154     if (ConstantArray *InitList =
 155         dyn_cast<ConstantArray>(GlobalDtors->getInitializer())) {
 156       for (unsigned i = 0, e = InitList->getType()->getNumElements();
 157            i != e; ++i)
 158         dtors.push_back(cast<Constant>(InitList->getOperand(i)));
 159     }
 160     GlobalDtors->eraseFromParent();
 161   }
 162
 163   // Build up llvm.global_dtors with our new item in it.
 164   GlobalVariable *GlobalDtors = new GlobalVariable(
 165       *Mod, ArrayType::get(GlobalDtorElemTy, 1), false,
 166       GlobalValue::AppendingLinkage, NULL, "llvm.global_dtors");
 167
 168   dtors.push_back(ConstantStruct::get(GlobalDtorElemTy, Elem));
 169   GlobalDtors->setInitializer(ConstantArray::get(
 170       cast<ArrayType>(GlobalDtors->getType()->getElementType()), dtors));
 171 }