lib/Transforms/IPO/RaiseAllocations.cpp

   1 //===- RaiseAllocations.cpp - Convert @malloc & @free calls to insts ------===//
   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 defines the RaiseAllocations pass which convert malloc and free
  11 // calls to malloc and free instructions.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #define DEBUG_TYPE "raiseallocs"
  16 #include "llvm/Transforms/IPO.h"
  17 #include "llvm/Constants.h"
  18 #include "llvm/DerivedTypes.h"
  19 #include "llvm/Module.h"
  20 #include "llvm/Instructions.h"
  21 #include "llvm/Pass.h"
  22 #include "llvm/Support/CallSite.h"
  23 #include "llvm/Support/Compiler.h"
  24 #include "llvm/ADT/Statistic.h"
  25 #include <algorithm>
  26 using namespace llvm;
  27
  28 STATISTIC(NumRaised, "Number of allocations raised");
  29
  30 namespace {
  31   // RaiseAllocations - Turn @malloc and @free calls into the appropriate
  32   // instruction.
  33   //
  34   class VISIBILITY_HIDDEN RaiseAllocations : public ModulePass {
  35     Function *MallocFunc;   // Functions in the module we are processing
  36     Function *FreeFunc;     // Initialized by doPassInitializationVirt
  37   public:
  38     static char ID; // Pass identification, replacement for typeid
  39     RaiseAllocations()
  40       : ModulePass(&ID), MallocFunc(0), FreeFunc(0) {}
  41
  42     // doPassInitialization - For the raise allocations pass, this finds a
  43     // declaration for malloc and free if they exist.
  44     //
  45     void doInitialization(Module &M);
  46
  47     // run - This method does the actual work of converting instructions over.
  48     //
  49     bool runOnModule(Module &M);
  50   };
  51 }  // end anonymous namespace
  52
  53 char RaiseAllocations::ID = 0;
  54 static RegisterPass<RaiseAllocations>
  55 X("raiseallocs", "Raise allocations from calls to instructions");
  56
  57 // createRaiseAllocationsPass - The interface to this file...
  58 ModulePass *llvm::createRaiseAllocationsPass() {
  59   return new RaiseAllocations();
  60 }
  61
  62
  63 // If the module has a symbol table, they might be referring to the malloc and
  64 // free functions.  If this is the case, grab the method pointers that the
  65 // module is using.
  66 //
  67 // Lookup @malloc and @free in the symbol table, for later use.  If they don't
  68 // exist, or are not external, we do not worry about converting calls to that
  69 // function into the appropriate instruction.
  70 //
  71 void RaiseAllocations::doInitialization(Module &M) {
  72
  73   // Get Malloc and free prototypes if they exist!
  74   MallocFunc = M.getFunction("malloc");
  75   if (MallocFunc) {
  76     const FunctionType* TyWeHave = MallocFunc->getFunctionType();
  77
  78     // Get the expected prototype for malloc
  79     const FunctionType *Malloc1Type =
  80       FunctionType::get(PointerType::getUnqual(Type::Int8Ty),
  81                       std::vector<const Type*>(1, Type::Int64Ty), false);
  82
  83     // Chck to see if we got the expected malloc
  84     if (TyWeHave != Malloc1Type) {
  85       // Check to see if the prototype is wrong, giving us sbyte*(uint) * malloc
  86       // This handles the common declaration of: 'void *malloc(unsigned);'
  87       const FunctionType *Malloc2Type =
  88         FunctionType::get(PointerType::getUnqual(Type::Int8Ty),
  89                           std::vector<const Type*>(1, Type::Int32Ty), false);
  90       if (TyWeHave != Malloc2Type) {
  91         // Check to see if the prototype is missing, giving us
  92         // sbyte*(...) * malloc
  93         // This handles the common declaration of: 'void *malloc();'
  94         const FunctionType *Malloc3Type =
  95           FunctionType::get(PointerType::getUnqual(Type::Int8Ty),
  96                             std::vector<const Type*>(), true);
  97         if (TyWeHave != Malloc3Type)
  98           // Give up
  99           MallocFunc = 0;
 100       }
 101     }
 102   }
 103
 104   FreeFunc = M.getFunction("free");
 105   if (FreeFunc) {
 106     const FunctionType* TyWeHave = FreeFunc->getFunctionType();
 107
 108     // Get the expected prototype for void free(i8*)
 109     const FunctionType *Free1Type = FunctionType::get(Type::VoidTy,
 110       std::vector<const Type*>(1, PointerType::getUnqual(Type::Int8Ty)), false);
 111
 112     if (TyWeHave != Free1Type) {
 113       // Check to see if the prototype was forgotten, giving us
 114       // void (...) * free
 115       // This handles the common forward declaration of: 'void free();'
 116       const FunctionType* Free2Type = FunctionType::get(Type::VoidTy,
 117         std::vector<const Type*>(),true);
 118
 119       if (TyWeHave != Free2Type) {
 120         // One last try, check to see if we can find free as
 121         // int (...)* free.  This handles the case where NOTHING was declared.
 122         const FunctionType* Free3Type = FunctionType::get(Type::Int32Ty,
 123           std::vector<const Type*>(),true);
 124
 125         if (TyWeHave != Free3Type) {
 126           // Give up.
 127           FreeFunc = 0;
 128         }
 129       }
 130     }
 131   }
 132
 133   // Don't mess with locally defined versions of these functions...
 134   if (MallocFunc && !MallocFunc->isDeclaration()) MallocFunc = 0;
 135   if (FreeFunc && !FreeFunc->isDeclaration())     FreeFunc = 0;
 136 }
 137
 138 // run - Transform calls into instructions...
 139 //
 140 bool RaiseAllocations::runOnModule(Module &M) {
 141   // Find the malloc/free prototypes...
 142   doInitialization(M);
 143
 144   bool Changed = false;
 145
 146   // First, process all of the malloc calls...
 147   if (MallocFunc) {
 148     std::vector<User*> Users(MallocFunc->use_begin(), MallocFunc->use_end());
 149     std::vector<Value*> EqPointers;   // Values equal to MallocFunc
 150     while (!Users.empty()) {
 151       User *U = Users.back();
 152       Users.pop_back();
 153
 154       if (Instruction *I = dyn_cast<Instruction>(U)) {
 155         CallSite CS = CallSite::get(I);
 156         if (CS.getInstruction() && !CS.arg_empty() &&
 157             (CS.getCalledFunction() == MallocFunc ||
 158              std::find(EqPointers.begin(), EqPointers.end(),
 159                        CS.getCalledValue()) != EqPointers.end())) {
 160
 161           Value *Source = *CS.arg_begin();
 162
 163           // If no prototype was provided for malloc, we may need to cast the
 164           // source size.
 165           if (Source->getType() != Type::Int32Ty)
 166             Source =
 167               CastInst::CreateIntegerCast(Source, Type::Int32Ty, false/*ZExt*/,
 168                                           "MallocAmtCast", I);
 169
 170           MallocInst *MI = new MallocInst(Type::Int8Ty, Source, "", I);
 171           MI->takeName(I);
 172           I->replaceAllUsesWith(MI);
 173
 174           // If the old instruction was an invoke, add an unconditional branch
 175           // before the invoke, which will become the new terminator.
 176           if (InvokeInst *II = dyn_cast<InvokeInst>(I))
 177             BranchInst::Create(II->getNormalDest(), I);
 178
 179           // Delete the old call site
 180           I->eraseFromParent();
 181           Changed = true;
 182           ++NumRaised;
 183         }
 184       } else if (GlobalValue *GV = dyn_cast<GlobalValue>(U)) {
 185         Users.insert(Users.end(), GV->use_begin(), GV->use_end());
 186         EqPointers.push_back(GV);
 187       } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
 188         if (CE->isCast()) {
 189           Users.insert(Users.end(), CE->use_begin(), CE->use_end());
 190           EqPointers.push_back(CE);
 191         }
 192       }
 193     }
 194   }
 195
 196   // Next, process all free calls...
 197   if (FreeFunc) {
 198     std::vector<User*> Users(FreeFunc->use_begin(), FreeFunc->use_end());
 199     std::vector<Value*> EqPointers;   // Values equal to FreeFunc
 200
 201     while (!Users.empty()) {
 202       User *U = Users.back();
 203       Users.pop_back();
 204
 205       if (Instruction *I = dyn_cast<Instruction>(U)) {
 206         if (isa<InvokeInst>(I))
 207           continue;
 208         CallSite CS = CallSite::get(I);
 209         if (CS.getInstruction() && !CS.arg_empty() &&
 210             (CS.getCalledFunction() == FreeFunc ||
 211              std::find(EqPointers.begin(), EqPointers.end(),
 212                        CS.getCalledValue()) != EqPointers.end())) {
 213
 214           // If no prototype was provided for free, we may need to cast the
 215           // source pointer.  This should be really uncommon, but it's necessary
 216           // just in case we are dealing with weird code like this:
 217           //   free((long)ptr);
 218           //
 219           Value *Source = *CS.arg_begin();
 220           if (!isa<PointerType>(Source->getType()))
 221             Source = new IntToPtrInst(Source,
 222                                       PointerType::getUnqual(Type::Int8Ty),
 223                                       "FreePtrCast", I);
 224           new FreeInst(Source, I);
 225
 226           // If the old instruction was an invoke, add an unconditional branch
 227           // before the invoke, which will become the new terminator.
 228           if (InvokeInst *II = dyn_cast<InvokeInst>(I))
 229             BranchInst::Create(II->getNormalDest(), I);
 230
 231           // Delete the old call site
 232           if (I->getType() != Type::VoidTy)
 233             I->replaceAllUsesWith(UndefValue::get(I->getType()));
 234           I->eraseFromParent();
 235           Changed = true;
 236           ++NumRaised;
 237         }
 238       } else if (GlobalValue *GV = dyn_cast<GlobalValue>(U)) {
 239         Users.insert(Users.end(), GV->use_begin(), GV->use_end());
 240         EqPointers.push_back(GV);
 241       } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
 242         if (CE->isCast()) {
 243           Users.insert(Users.end(), CE->use_begin(), CE->use_end());
 244           EqPointers.push_back(CE);
 245         }
 246       }
 247     }
 248   }
 249
 250   return Changed;
 251 }