ProfilingUtils.cpp revision c5b206b6be61d0d933b98b6af5e22f42edd48ad1 
1//===- ProfilingUtils.cpp - Helper functions shared by profilers ----------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This files 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/Module.h"
22
23void llvm::InsertProfilingInitCall(Function *MainFn, const char *FnName,
24                                   GlobalValue *Array) {
25  const Type *ArgVTy = PointerType::get(PointerType::get(Type::Int8Ty));
26  const PointerType *UIntPtr = PointerType::get(Type::Int32Ty);
27  Module &M = *MainFn->getParent();
28  Function *InitFn = M.getOrInsertFunction(FnName, Type::Int32Ty, Type::Int32Ty,
29                                           ArgVTy, UIntPtr, Type::Int32Ty,
30                                           (Type *)0);
31
32  // This could force argc and argv into programs that wouldn't otherwise have
33  // them, but instead we just pass null values in.
34  std::vector<Value*> Args(4);
35  Args[0] = Constant::getNullValue(Type::Int32Ty);
36  Args[1] = Constant::getNullValue(ArgVTy);
37
38  // Skip over any allocas in the entry block.
39  BasicBlock *Entry = MainFn->begin();
40  BasicBlock::iterator InsertPos = Entry->begin();
41  while (isa<AllocaInst>(InsertPos)) ++InsertPos;
42
43  std::vector<Constant*> GEPIndices(2, Constant::getNullValue(Type::Int32Ty));
44  unsigned NumElements = 0;
45  if (Array) {
46    Args[2] = ConstantExpr::getGetElementPtr(Array, GEPIndices);
47    NumElements =
48      cast<ArrayType>(Array->getType()->getElementType())->getNumElements();
49  } else {
50    // If this profiling instrumentation doesn't have a constant array, just
51    // pass null.
52    Args[2] = ConstantPointerNull::get(UIntPtr);
53  }
54  Args[3] = ConstantInt::get(Type::Int32Ty, NumElements);
55
56  Instruction *InitCall = new CallInst(InitFn, Args, "newargc", InsertPos);
57
58  // If argc or argv are not available in main, just pass null values in.
59  Function::arg_iterator AI;
60  switch (MainFn->arg_size()) {
61  default:
62  case 2:
63    AI = MainFn->arg_begin(); ++AI;
64    if (AI->getType() != ArgVTy) {
65      Instruction::CastOps opcode = CastInst::getCastOpcode(AI, false, ArgVTy,
66                                                            false);
67      InitCall->setOperand(2,
68          CastInst::create(opcode, AI, ArgVTy, "argv.cast", InitCall));
69    } else {
70      InitCall->setOperand(2, AI);
71    }
72    /* FALL THROUGH */
73
74  case 1:
75    AI = MainFn->arg_begin();
76    // If the program looked at argc, have it look at the return value of the
77    // init call instead.
78    if (AI->getType() != Type::Int32Ty) {
79      Instruction::CastOps opcode;
80      if (!AI->use_empty()) {
81        opcode = CastInst::getCastOpcode(InitCall, true, AI->getType(), true);
82        AI->replaceAllUsesWith(
83          CastInst::create(opcode, InitCall, AI->getType(), "", InsertPos));
84      }
85      opcode = CastInst::getCastOpcode(AI, true, Type::Int32Ty, true);
86      InitCall->setOperand(1,
87          CastInst::create(opcode, AI, Type::Int32Ty, "argc.cast", InitCall));
88    } else {
89      AI->replaceAllUsesWith(InitCall);
90      InitCall->setOperand(1, AI);
91    }
92
93  case 0: break;
94  }
95}
96
97void llvm::IncrementCounterInBlock(BasicBlock *BB, unsigned CounterNum,
98                                   GlobalValue *CounterArray) {
99  // Insert the increment after any alloca or PHI instructions...
100  BasicBlock::iterator InsertPos = BB->begin();
101  while (isa<AllocaInst>(InsertPos) || isa<PHINode>(InsertPos))
102    ++InsertPos;
103
104  // Create the getelementptr constant expression
105  std::vector<Constant*> Indices(2);
106  Indices[0] = Constant::getNullValue(Type::Int32Ty);
107  Indices[1] = ConstantInt::get(Type::Int32Ty, CounterNum);
108  Constant *ElementPtr = ConstantExpr::getGetElementPtr(CounterArray, Indices);
109
110  // Load, increment and store the value back.
111  Value *OldVal = new LoadInst(ElementPtr, "OldFuncCounter", InsertPos);
112  Value *NewVal = BinaryOperator::create(Instruction::Add, OldVal,
113                                         ConstantInt::get(Type::Int32Ty, 1),
114                                         "NewFuncCounter", InsertPos);
115  new StoreInst(NewVal, ElementPtr, InsertPos);
116}
117