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      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   Type *ArgVTy =
     29     PointerType::getUnqual(Type::getInt8PtrTy(Context));
     30   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);
     55     NumElements =
     56       cast<ArrayType>(Array->getType()->getElementType())->getNumElements();
     57   } else {
     58     // If this profiling instrumentation doesn't have a constant array, just
     59     // pass null.
     60     Args[2] = ConstantPointerNull::get(UIntPtr);
     61   }
     62   Args[3] = ConstantInt::get(Type::getInt32Ty(Context), NumElements);
     63 
     64   CallInst *InitCall = CallInst::Create(InitFn, Args, "newargc", InsertPos);
     65 
     66   // If argc or argv are not available in main, just pass null values in.
     67   Function::arg_iterator AI;
     68   switch (MainFn->arg_size()) {
     69   default:
     70   case 2:
     71     AI = MainFn->arg_begin(); ++AI;
     72     if (AI->getType() != ArgVTy) {
     73       Instruction::CastOps opcode = CastInst::getCastOpcode(AI, false, ArgVTy,
     74                                                             false);
     75       InitCall->setArgOperand(1,
     76           CastInst::Create(opcode, AI, ArgVTy, "argv.cast", InitCall));
     77     } else {
     78       InitCall->setArgOperand(1, AI);
     79     }
     80     /* FALL THROUGH */
     81 
     82   case 1:
     83     AI = MainFn->arg_begin();
     84     // If the program looked at argc, have it look at the return value of the
     85     // init call instead.
     86     if (!AI->getType()->isIntegerTy(32)) {
     87       Instruction::CastOps opcode;
     88       if (!AI->use_empty()) {
     89         opcode = CastInst::getCastOpcode(InitCall, true, AI->getType(), true);
     90         AI->replaceAllUsesWith(
     91           CastInst::Create(opcode, InitCall, AI->getType(), "", InsertPos));
     92       }
     93       opcode = CastInst::getCastOpcode(AI, true,
     94                                        Type::getInt32Ty(Context), true);
     95       InitCall->setArgOperand(0,
     96           CastInst::Create(opcode, AI, Type::getInt32Ty(Context),
     97                            "argc.cast", InitCall));
     98     } else {
     99       AI->replaceAllUsesWith(InitCall);
    100       InitCall->setArgOperand(0, AI);
    101     }
    102 
    103   case 0: break;
    104   }
    105 }
    106 
    107 void llvm::IncrementCounterInBlock(BasicBlock *BB, unsigned CounterNum,
    108                                    GlobalValue *CounterArray, bool beginning) {
    109   // Insert the increment after any alloca or PHI instructions...
    110   BasicBlock::iterator InsertPos = beginning ? BB->getFirstInsertionPt() :
    111                                    BB->getTerminator();
    112   while (isa<AllocaInst>(InsertPos))
    113     ++InsertPos;
    114 
    115   LLVMContext &Context = BB->getContext();
    116 
    117   // Create the getelementptr constant expression
    118   std::vector<Constant*> Indices(2);
    119   Indices[0] = Constant::getNullValue(Type::getInt32Ty(Context));
    120   Indices[1] = ConstantInt::get(Type::getInt32Ty(Context), CounterNum);
    121   Constant *ElementPtr =
    122     ConstantExpr::getGetElementPtr(CounterArray, Indices);
    123 
    124   // Load, increment and store the value back.
    125   Value *OldVal = new LoadInst(ElementPtr, "OldFuncCounter", InsertPos);
    126   Value *NewVal = BinaryOperator::Create(Instruction::Add, OldVal,
    127                                  ConstantInt::get(Type::getInt32Ty(Context), 1),
    128                                          "NewFuncCounter", InsertPos);
    129   new StoreInst(NewVal, ElementPtr, InsertPos);
    130 }
    131 
    132 void llvm::InsertProfilingShutdownCall(Function *Callee, Module *Mod) {
    133   // llvm.global_dtors is an array of type { i32, void ()* }. Prepare those
    134   // types.
    135   Type *GlobalDtorElems[2] = {
    136     Type::getInt32Ty(Mod->getContext()),
    137     FunctionType::get(Type::getVoidTy(Mod->getContext()), false)->getPointerTo()
    138   };
    139   StructType *GlobalDtorElemTy =
    140       StructType::get(Mod->getContext(), GlobalDtorElems, false);
    141 
    142   // Construct the new element we'll be adding.
    143   Constant *Elem[2] = {
    144     ConstantInt::get(Type::getInt32Ty(Mod->getContext()), 65535),
    145     ConstantExpr::getBitCast(Callee, GlobalDtorElems[1])
    146   };
    147 
    148   // If llvm.global_dtors exists, make a copy of the things in its list and
    149   // delete it, to replace it with one that has a larger array type.
    150   std::vector<Constant *> dtors;
    151   if (GlobalVariable *GlobalDtors = Mod->getNamedGlobal("llvm.global_dtors")) {
    152     if (ConstantArray *InitList =
    153         dyn_cast<ConstantArray>(GlobalDtors->getInitializer())) {
    154       for (unsigned i = 0, e = InitList->getType()->getNumElements();
    155            i != e; ++i)
    156         dtors.push_back(cast<Constant>(InitList->getOperand(i)));
    157     }
    158     GlobalDtors->eraseFromParent();
    159   }
    160 
    161   // Build up llvm.global_dtors with our new item in it.
    162   GlobalVariable *GlobalDtors = new GlobalVariable(
    163       *Mod, ArrayType::get(GlobalDtorElemTy, 1), false,
    164       GlobalValue::AppendingLinkage, NULL, "llvm.global_dtors");
    165 
    166   dtors.push_back(ConstantStruct::get(GlobalDtorElemTy, Elem));
    167   GlobalDtors->setInitializer(ConstantArray::get(
    168       cast<ArrayType>(GlobalDtors->getType()->getElementType()), dtors));
    169 }
    170