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      1 //===------ MemoryBuiltins.cpp - Identify calls to memory builtins --------===//
      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 family of functions identifies calls to builtin functions that allocate
     11 // or free memory.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #include "llvm/Analysis/MemoryBuiltins.h"
     16 #include "llvm/ADT/STLExtras.h"
     17 #include "llvm/ADT/Statistic.h"
     18 #include "llvm/Analysis/TargetLibraryInfo.h"
     19 #include "llvm/Analysis/ValueTracking.h"
     20 #include "llvm/IR/DataLayout.h"
     21 #include "llvm/IR/GlobalVariable.h"
     22 #include "llvm/IR/Instructions.h"
     23 #include "llvm/IR/Intrinsics.h"
     24 #include "llvm/IR/Metadata.h"
     25 #include "llvm/IR/Module.h"
     26 #include "llvm/Support/Debug.h"
     27 #include "llvm/Support/MathExtras.h"
     28 #include "llvm/Support/raw_ostream.h"
     29 #include "llvm/Transforms/Utils/Local.h"
     30 using namespace llvm;
     31 
     32 #define DEBUG_TYPE "memory-builtins"
     33 
     34 enum AllocType : uint8_t {
     35   OpNewLike          = 1<<0, // allocates; never returns null
     36   MallocLike         = 1<<1 | OpNewLike, // allocates; may return null
     37   CallocLike         = 1<<2, // allocates + bzero
     38   ReallocLike        = 1<<3, // reallocates
     39   StrDupLike         = 1<<4,
     40   AllocLike          = MallocLike | CallocLike | StrDupLike,
     41   AnyAlloc           = AllocLike | ReallocLike
     42 };
     43 
     44 struct AllocFnsTy {
     45   LibFunc::Func Func;
     46   AllocType AllocTy;
     47   unsigned char NumParams;
     48   // First and Second size parameters (or -1 if unused)
     49   signed char FstParam, SndParam;
     50 };
     51 
     52 // FIXME: certain users need more information. E.g., SimplifyLibCalls needs to
     53 // know which functions are nounwind, noalias, nocapture parameters, etc.
     54 static const AllocFnsTy AllocationFnData[] = {
     55   {LibFunc::malloc,              MallocLike,  1, 0,  -1},
     56   {LibFunc::valloc,              MallocLike,  1, 0,  -1},
     57   {LibFunc::Znwj,                OpNewLike,   1, 0,  -1}, // new(unsigned int)
     58   {LibFunc::ZnwjRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new(unsigned int, nothrow)
     59   {LibFunc::Znwm,                OpNewLike,   1, 0,  -1}, // new(unsigned long)
     60   {LibFunc::ZnwmRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new(unsigned long, nothrow)
     61   {LibFunc::Znaj,                OpNewLike,   1, 0,  -1}, // new[](unsigned int)
     62   {LibFunc::ZnajRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new[](unsigned int, nothrow)
     63   {LibFunc::Znam,                OpNewLike,   1, 0,  -1}, // new[](unsigned long)
     64   {LibFunc::ZnamRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new[](unsigned long, nothrow)
     65   {LibFunc::msvc_new_int,         OpNewLike,   1, 0,  -1}, // new(unsigned int)
     66   {LibFunc::msvc_new_int_nothrow, MallocLike,  2, 0,  -1}, // new(unsigned int, nothrow)
     67   {LibFunc::msvc_new_longlong,         OpNewLike,   1, 0,  -1}, // new(unsigned long long)
     68   {LibFunc::msvc_new_longlong_nothrow, MallocLike,  2, 0,  -1}, // new(unsigned long long, nothrow)
     69   {LibFunc::msvc_new_array_int,         OpNewLike,   1, 0,  -1}, // new[](unsigned int)
     70   {LibFunc::msvc_new_array_int_nothrow, MallocLike,  2, 0,  -1}, // new[](unsigned int, nothrow)
     71   {LibFunc::msvc_new_array_longlong,         OpNewLike,   1, 0,  -1}, // new[](unsigned long long)
     72   {LibFunc::msvc_new_array_longlong_nothrow, MallocLike,  2, 0,  -1}, // new[](unsigned long long, nothrow)
     73   {LibFunc::calloc,              CallocLike,  2, 0,   1},
     74   {LibFunc::realloc,             ReallocLike, 2, 1,  -1},
     75   {LibFunc::reallocf,            ReallocLike, 2, 1,  -1},
     76   {LibFunc::strdup,              StrDupLike,  1, -1, -1},
     77   {LibFunc::strndup,             StrDupLike,  2, 1,  -1}
     78   // TODO: Handle "int posix_memalign(void **, size_t, size_t)"
     79 };
     80 
     81 
     82 static Function *getCalledFunction(const Value *V, bool LookThroughBitCast) {
     83   if (LookThroughBitCast)
     84     V = V->stripPointerCasts();
     85 
     86   CallSite CS(const_cast<Value*>(V));
     87   if (!CS.getInstruction())
     88     return nullptr;
     89 
     90   if (CS.isNoBuiltin())
     91     return nullptr;
     92 
     93   Function *Callee = CS.getCalledFunction();
     94   if (!Callee || !Callee->isDeclaration())
     95     return nullptr;
     96   return Callee;
     97 }
     98 
     99 /// \brief Returns the allocation data for the given value if it is a call to a
    100 /// known allocation function, and NULL otherwise.
    101 static const AllocFnsTy *getAllocationData(const Value *V, AllocType AllocTy,
    102                                            const TargetLibraryInfo *TLI,
    103                                            bool LookThroughBitCast = false) {
    104   // Skip intrinsics
    105   if (isa<IntrinsicInst>(V))
    106     return nullptr;
    107 
    108   Function *Callee = getCalledFunction(V, LookThroughBitCast);
    109   if (!Callee)
    110     return nullptr;
    111 
    112   // Make sure that the function is available.
    113   StringRef FnName = Callee->getName();
    114   LibFunc::Func TLIFn;
    115   if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
    116     return nullptr;
    117 
    118   const AllocFnsTy *FnData =
    119       std::find_if(std::begin(AllocationFnData), std::end(AllocationFnData),
    120                    [TLIFn](const AllocFnsTy &Fn) { return Fn.Func == TLIFn; });
    121 
    122   if (FnData == std::end(AllocationFnData))
    123     return nullptr;
    124 
    125   if ((FnData->AllocTy & AllocTy) != FnData->AllocTy)
    126     return nullptr;
    127 
    128   // Check function prototype.
    129   int FstParam = FnData->FstParam;
    130   int SndParam = FnData->SndParam;
    131   FunctionType *FTy = Callee->getFunctionType();
    132 
    133   if (FTy->getReturnType() == Type::getInt8PtrTy(FTy->getContext()) &&
    134       FTy->getNumParams() == FnData->NumParams &&
    135       (FstParam < 0 ||
    136        (FTy->getParamType(FstParam)->isIntegerTy(32) ||
    137         FTy->getParamType(FstParam)->isIntegerTy(64))) &&
    138       (SndParam < 0 ||
    139        FTy->getParamType(SndParam)->isIntegerTy(32) ||
    140        FTy->getParamType(SndParam)->isIntegerTy(64)))
    141     return FnData;
    142   return nullptr;
    143 }
    144 
    145 static bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) {
    146   ImmutableCallSite CS(LookThroughBitCast ? V->stripPointerCasts() : V);
    147   return CS && CS.hasFnAttr(Attribute::NoAlias);
    148 }
    149 
    150 
    151 /// \brief Tests if a value is a call or invoke to a library function that
    152 /// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
    153 /// like).
    154 bool llvm::isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
    155                           bool LookThroughBitCast) {
    156   return getAllocationData(V, AnyAlloc, TLI, LookThroughBitCast);
    157 }
    158 
    159 /// \brief Tests if a value is a call or invoke to a function that returns a
    160 /// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
    161 bool llvm::isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
    162                        bool LookThroughBitCast) {
    163   // it's safe to consider realloc as noalias since accessing the original
    164   // pointer is undefined behavior
    165   return isAllocationFn(V, TLI, LookThroughBitCast) ||
    166          hasNoAliasAttr(V, LookThroughBitCast);
    167 }
    168 
    169 /// \brief Tests if a value is a call or invoke to a library function that
    170 /// allocates uninitialized memory (such as malloc).
    171 bool llvm::isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
    172                           bool LookThroughBitCast) {
    173   return getAllocationData(V, MallocLike, TLI, LookThroughBitCast);
    174 }
    175 
    176 /// \brief Tests if a value is a call or invoke to a library function that
    177 /// allocates zero-filled memory (such as calloc).
    178 bool llvm::isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
    179                           bool LookThroughBitCast) {
    180   return getAllocationData(V, CallocLike, TLI, LookThroughBitCast);
    181 }
    182 
    183 /// \brief Tests if a value is a call or invoke to a library function that
    184 /// allocates memory (either malloc, calloc, or strdup like).
    185 bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
    186                          bool LookThroughBitCast) {
    187   return getAllocationData(V, AllocLike, TLI, LookThroughBitCast);
    188 }
    189 
    190 /// \brief Tests if a value is a call or invoke to a library function that
    191 /// reallocates memory (such as realloc).
    192 bool llvm::isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
    193                            bool LookThroughBitCast) {
    194   return getAllocationData(V, ReallocLike, TLI, LookThroughBitCast);
    195 }
    196 
    197 /// \brief Tests if a value is a call or invoke to a library function that
    198 /// allocates memory and never returns null (such as operator new).
    199 bool llvm::isOperatorNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
    200                                bool LookThroughBitCast) {
    201   return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast);
    202 }
    203 
    204 /// extractMallocCall - Returns the corresponding CallInst if the instruction
    205 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
    206 /// ignore InvokeInst here.
    207 const CallInst *llvm::extractMallocCall(const Value *I,
    208                                         const TargetLibraryInfo *TLI) {
    209   return isMallocLikeFn(I, TLI) ? dyn_cast<CallInst>(I) : nullptr;
    210 }
    211 
    212 static Value *computeArraySize(const CallInst *CI, const DataLayout &DL,
    213                                const TargetLibraryInfo *TLI,
    214                                bool LookThroughSExt = false) {
    215   if (!CI)
    216     return nullptr;
    217 
    218   // The size of the malloc's result type must be known to determine array size.
    219   Type *T = getMallocAllocatedType(CI, TLI);
    220   if (!T || !T->isSized())
    221     return nullptr;
    222 
    223   unsigned ElementSize = DL.getTypeAllocSize(T);
    224   if (StructType *ST = dyn_cast<StructType>(T))
    225     ElementSize = DL.getStructLayout(ST)->getSizeInBytes();
    226 
    227   // If malloc call's arg can be determined to be a multiple of ElementSize,
    228   // return the multiple.  Otherwise, return NULL.
    229   Value *MallocArg = CI->getArgOperand(0);
    230   Value *Multiple = nullptr;
    231   if (ComputeMultiple(MallocArg, ElementSize, Multiple,
    232                       LookThroughSExt))
    233     return Multiple;
    234 
    235   return nullptr;
    236 }
    237 
    238 /// getMallocType - Returns the PointerType resulting from the malloc call.
    239 /// The PointerType depends on the number of bitcast uses of the malloc call:
    240 ///   0: PointerType is the calls' return type.
    241 ///   1: PointerType is the bitcast's result type.
    242 ///  >1: Unique PointerType cannot be determined, return NULL.
    243 PointerType *llvm::getMallocType(const CallInst *CI,
    244                                  const TargetLibraryInfo *TLI) {
    245   assert(isMallocLikeFn(CI, TLI) && "getMallocType and not malloc call");
    246 
    247   PointerType *MallocType = nullptr;
    248   unsigned NumOfBitCastUses = 0;
    249 
    250   // Determine if CallInst has a bitcast use.
    251   for (Value::const_user_iterator UI = CI->user_begin(), E = CI->user_end();
    252        UI != E;)
    253     if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) {
    254       MallocType = cast<PointerType>(BCI->getDestTy());
    255       NumOfBitCastUses++;
    256     }
    257 
    258   // Malloc call has 1 bitcast use, so type is the bitcast's destination type.
    259   if (NumOfBitCastUses == 1)
    260     return MallocType;
    261 
    262   // Malloc call was not bitcast, so type is the malloc function's return type.
    263   if (NumOfBitCastUses == 0)
    264     return cast<PointerType>(CI->getType());
    265 
    266   // Type could not be determined.
    267   return nullptr;
    268 }
    269 
    270 /// getMallocAllocatedType - Returns the Type allocated by malloc call.
    271 /// The Type depends on the number of bitcast uses of the malloc call:
    272 ///   0: PointerType is the malloc calls' return type.
    273 ///   1: PointerType is the bitcast's result type.
    274 ///  >1: Unique PointerType cannot be determined, return NULL.
    275 Type *llvm::getMallocAllocatedType(const CallInst *CI,
    276                                    const TargetLibraryInfo *TLI) {
    277   PointerType *PT = getMallocType(CI, TLI);
    278   return PT ? PT->getElementType() : nullptr;
    279 }
    280 
    281 /// getMallocArraySize - Returns the array size of a malloc call.  If the
    282 /// argument passed to malloc is a multiple of the size of the malloced type,
    283 /// then return that multiple.  For non-array mallocs, the multiple is
    284 /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
    285 /// determined.
    286 Value *llvm::getMallocArraySize(CallInst *CI, const DataLayout &DL,
    287                                 const TargetLibraryInfo *TLI,
    288                                 bool LookThroughSExt) {
    289   assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call");
    290   return computeArraySize(CI, DL, TLI, LookThroughSExt);
    291 }
    292 
    293 
    294 /// extractCallocCall - Returns the corresponding CallInst if the instruction
    295 /// is a calloc call.
    296 const CallInst *llvm::extractCallocCall(const Value *I,
    297                                         const TargetLibraryInfo *TLI) {
    298   return isCallocLikeFn(I, TLI) ? cast<CallInst>(I) : nullptr;
    299 }
    300 
    301 
    302 /// isFreeCall - Returns non-null if the value is a call to the builtin free()
    303 const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) {
    304   const CallInst *CI = dyn_cast<CallInst>(I);
    305   if (!CI || isa<IntrinsicInst>(CI))
    306     return nullptr;
    307   Function *Callee = CI->getCalledFunction();
    308   if (Callee == nullptr)
    309     return nullptr;
    310 
    311   StringRef FnName = Callee->getName();
    312   LibFunc::Func TLIFn;
    313   if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
    314     return nullptr;
    315 
    316   unsigned ExpectedNumParams;
    317   if (TLIFn == LibFunc::free ||
    318       TLIFn == LibFunc::ZdlPv || // operator delete(void*)
    319       TLIFn == LibFunc::ZdaPv || // operator delete[](void*)
    320       TLIFn == LibFunc::msvc_delete_ptr32 || // operator delete(void*)
    321       TLIFn == LibFunc::msvc_delete_ptr64 || // operator delete(void*)
    322       TLIFn == LibFunc::msvc_delete_array_ptr32 || // operator delete[](void*)
    323       TLIFn == LibFunc::msvc_delete_array_ptr64)   // operator delete[](void*)
    324     ExpectedNumParams = 1;
    325   else if (TLIFn == LibFunc::ZdlPvj ||              // delete(void*, uint)
    326            TLIFn == LibFunc::ZdlPvm ||              // delete(void*, ulong)
    327            TLIFn == LibFunc::ZdlPvRKSt9nothrow_t || // delete(void*, nothrow)
    328            TLIFn == LibFunc::ZdaPvj ||              // delete[](void*, uint)
    329            TLIFn == LibFunc::ZdaPvm ||              // delete[](void*, ulong)
    330            TLIFn == LibFunc::ZdaPvRKSt9nothrow_t || // delete[](void*, nothrow)
    331            TLIFn == LibFunc::msvc_delete_ptr32_int ||      // delete(void*, uint)
    332            TLIFn == LibFunc::msvc_delete_ptr64_longlong || // delete(void*, ulonglong)
    333            TLIFn == LibFunc::msvc_delete_ptr32_nothrow || // delete(void*, nothrow)
    334            TLIFn == LibFunc::msvc_delete_ptr64_nothrow || // delete(void*, nothrow)
    335            TLIFn == LibFunc::msvc_delete_array_ptr32_int ||      // delete[](void*, uint)
    336            TLIFn == LibFunc::msvc_delete_array_ptr64_longlong || // delete[](void*, ulonglong)
    337            TLIFn == LibFunc::msvc_delete_array_ptr32_nothrow || // delete[](void*, nothrow)
    338            TLIFn == LibFunc::msvc_delete_array_ptr64_nothrow)   // delete[](void*, nothrow)
    339     ExpectedNumParams = 2;
    340   else
    341     return nullptr;
    342 
    343   // Check free prototype.
    344   // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
    345   // attribute will exist.
    346   FunctionType *FTy = Callee->getFunctionType();
    347   if (!FTy->getReturnType()->isVoidTy())
    348     return nullptr;
    349   if (FTy->getNumParams() != ExpectedNumParams)
    350     return nullptr;
    351   if (FTy->getParamType(0) != Type::getInt8PtrTy(Callee->getContext()))
    352     return nullptr;
    353 
    354   return CI;
    355 }
    356 
    357 
    358 
    359 //===----------------------------------------------------------------------===//
    360 //  Utility functions to compute size of objects.
    361 //
    362 
    363 
    364 /// \brief Compute the size of the object pointed by Ptr. Returns true and the
    365 /// object size in Size if successful, and false otherwise.
    366 /// If RoundToAlign is true, then Size is rounded up to the aligment of allocas,
    367 /// byval arguments, and global variables.
    368 bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
    369                          const TargetLibraryInfo *TLI, bool RoundToAlign) {
    370   ObjectSizeOffsetVisitor Visitor(DL, TLI, Ptr->getContext(), RoundToAlign);
    371   SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
    372   if (!Visitor.bothKnown(Data))
    373     return false;
    374 
    375   APInt ObjSize = Data.first, Offset = Data.second;
    376   // check for overflow
    377   if (Offset.slt(0) || ObjSize.ult(Offset))
    378     Size = 0;
    379   else
    380     Size = (ObjSize - Offset).getZExtValue();
    381   return true;
    382 }
    383 
    384 
    385 STATISTIC(ObjectVisitorArgument,
    386           "Number of arguments with unsolved size and offset");
    387 STATISTIC(ObjectVisitorLoad,
    388           "Number of load instructions with unsolved size and offset");
    389 
    390 
    391 APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Align) {
    392   if (RoundToAlign && Align)
    393     return APInt(IntTyBits, RoundUpToAlignment(Size.getZExtValue(), Align));
    394   return Size;
    395 }
    396 
    397 ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL,
    398                                                  const TargetLibraryInfo *TLI,
    399                                                  LLVMContext &Context,
    400                                                  bool RoundToAlign)
    401     : DL(DL), TLI(TLI), RoundToAlign(RoundToAlign) {
    402   // Pointer size must be rechecked for each object visited since it could have
    403   // a different address space.
    404 }
    405 
    406 SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
    407   IntTyBits = DL.getPointerTypeSizeInBits(V->getType());
    408   Zero = APInt::getNullValue(IntTyBits);
    409 
    410   V = V->stripPointerCasts();
    411   if (Instruction *I = dyn_cast<Instruction>(V)) {
    412     // If we have already seen this instruction, bail out. Cycles can happen in
    413     // unreachable code after constant propagation.
    414     if (!SeenInsts.insert(I).second)
    415       return unknown();
    416 
    417     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
    418       return visitGEPOperator(*GEP);
    419     return visit(*I);
    420   }
    421   if (Argument *A = dyn_cast<Argument>(V))
    422     return visitArgument(*A);
    423   if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
    424     return visitConstantPointerNull(*P);
    425   if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
    426     return visitGlobalAlias(*GA);
    427   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
    428     return visitGlobalVariable(*GV);
    429   if (UndefValue *UV = dyn_cast<UndefValue>(V))
    430     return visitUndefValue(*UV);
    431   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
    432     if (CE->getOpcode() == Instruction::IntToPtr)
    433       return unknown(); // clueless
    434     if (CE->getOpcode() == Instruction::GetElementPtr)
    435       return visitGEPOperator(cast<GEPOperator>(*CE));
    436   }
    437 
    438   DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
    439         << '\n');
    440   return unknown();
    441 }
    442 
    443 SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
    444   if (!I.getAllocatedType()->isSized())
    445     return unknown();
    446 
    447   APInt Size(IntTyBits, DL.getTypeAllocSize(I.getAllocatedType()));
    448   if (!I.isArrayAllocation())
    449     return std::make_pair(align(Size, I.getAlignment()), Zero);
    450 
    451   Value *ArraySize = I.getArraySize();
    452   if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) {
    453     Size *= C->getValue().zextOrSelf(IntTyBits);
    454     return std::make_pair(align(Size, I.getAlignment()), Zero);
    455   }
    456   return unknown();
    457 }
    458 
    459 SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
    460   // no interprocedural analysis is done at the moment
    461   if (!A.hasByValOrInAllocaAttr()) {
    462     ++ObjectVisitorArgument;
    463     return unknown();
    464   }
    465   PointerType *PT = cast<PointerType>(A.getType());
    466   APInt Size(IntTyBits, DL.getTypeAllocSize(PT->getElementType()));
    467   return std::make_pair(align(Size, A.getParamAlignment()), Zero);
    468 }
    469 
    470 SizeOffsetType ObjectSizeOffsetVisitor::visitCallSite(CallSite CS) {
    471   const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc,
    472                                                TLI);
    473   if (!FnData)
    474     return unknown();
    475 
    476   // handle strdup-like functions separately
    477   if (FnData->AllocTy == StrDupLike) {
    478     APInt Size(IntTyBits, GetStringLength(CS.getArgument(0)));
    479     if (!Size)
    480       return unknown();
    481 
    482     // strndup limits strlen
    483     if (FnData->FstParam > 0) {
    484       ConstantInt *Arg= dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
    485       if (!Arg)
    486         return unknown();
    487 
    488       APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits);
    489       if (Size.ugt(MaxSize))
    490         Size = MaxSize + 1;
    491     }
    492     return std::make_pair(Size, Zero);
    493   }
    494 
    495   ConstantInt *Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
    496   if (!Arg)
    497     return unknown();
    498 
    499   APInt Size = Arg->getValue().zextOrSelf(IntTyBits);
    500   // size determined by just 1 parameter
    501   if (FnData->SndParam < 0)
    502     return std::make_pair(Size, Zero);
    503 
    504   Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->SndParam));
    505   if (!Arg)
    506     return unknown();
    507 
    508   Size *= Arg->getValue().zextOrSelf(IntTyBits);
    509   return std::make_pair(Size, Zero);
    510 
    511   // TODO: handle more standard functions (+ wchar cousins):
    512   // - strdup / strndup
    513   // - strcpy / strncpy
    514   // - strcat / strncat
    515   // - memcpy / memmove
    516   // - strcat / strncat
    517   // - memset
    518 }
    519 
    520 SizeOffsetType
    521 ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull&) {
    522   return std::make_pair(Zero, Zero);
    523 }
    524 
    525 SizeOffsetType
    526 ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) {
    527   return unknown();
    528 }
    529 
    530 SizeOffsetType
    531 ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) {
    532   // Easy cases were already folded by previous passes.
    533   return unknown();
    534 }
    535 
    536 SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) {
    537   SizeOffsetType PtrData = compute(GEP.getPointerOperand());
    538   APInt Offset(IntTyBits, 0);
    539   if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(DL, Offset))
    540     return unknown();
    541 
    542   return std::make_pair(PtrData.first, PtrData.second + Offset);
    543 }
    544 
    545 SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) {
    546   if (GA.mayBeOverridden())
    547     return unknown();
    548   return compute(GA.getAliasee());
    549 }
    550 
    551 SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){
    552   if (!GV.hasDefinitiveInitializer())
    553     return unknown();
    554 
    555   APInt Size(IntTyBits, DL.getTypeAllocSize(GV.getType()->getElementType()));
    556   return std::make_pair(align(Size, GV.getAlignment()), Zero);
    557 }
    558 
    559 SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) {
    560   // clueless
    561   return unknown();
    562 }
    563 
    564 SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
    565   ++ObjectVisitorLoad;
    566   return unknown();
    567 }
    568 
    569 SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
    570   // too complex to analyze statically.
    571   return unknown();
    572 }
    573 
    574 SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
    575   SizeOffsetType TrueSide  = compute(I.getTrueValue());
    576   SizeOffsetType FalseSide = compute(I.getFalseValue());
    577   if (bothKnown(TrueSide) && bothKnown(FalseSide) && TrueSide == FalseSide)
    578     return TrueSide;
    579   return unknown();
    580 }
    581 
    582 SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) {
    583   return std::make_pair(Zero, Zero);
    584 }
    585 
    586 SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) {
    587   DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I << '\n');
    588   return unknown();
    589 }
    590 
    591 ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(
    592     const DataLayout &DL, const TargetLibraryInfo *TLI, LLVMContext &Context,
    593     bool RoundToAlign)
    594     : DL(DL), TLI(TLI), Context(Context), Builder(Context, TargetFolder(DL)),
    595       RoundToAlign(RoundToAlign) {
    596   // IntTy and Zero must be set for each compute() since the address space may
    597   // be different for later objects.
    598 }
    599 
    600 SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) {
    601   // XXX - Are vectors of pointers possible here?
    602   IntTy = cast<IntegerType>(DL.getIntPtrType(V->getType()));
    603   Zero = ConstantInt::get(IntTy, 0);
    604 
    605   SizeOffsetEvalType Result = compute_(V);
    606 
    607   if (!bothKnown(Result)) {
    608     // erase everything that was computed in this iteration from the cache, so
    609     // that no dangling references are left behind. We could be a bit smarter if
    610     // we kept a dependency graph. It's probably not worth the complexity.
    611     for (PtrSetTy::iterator I=SeenVals.begin(), E=SeenVals.end(); I != E; ++I) {
    612       CacheMapTy::iterator CacheIt = CacheMap.find(*I);
    613       // non-computable results can be safely cached
    614       if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second))
    615         CacheMap.erase(CacheIt);
    616     }
    617   }
    618 
    619   SeenVals.clear();
    620   return Result;
    621 }
    622 
    623 SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
    624   ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, RoundToAlign);
    625   SizeOffsetType Const = Visitor.compute(V);
    626   if (Visitor.bothKnown(Const))
    627     return std::make_pair(ConstantInt::get(Context, Const.first),
    628                           ConstantInt::get(Context, Const.second));
    629 
    630   V = V->stripPointerCasts();
    631 
    632   // check cache
    633   CacheMapTy::iterator CacheIt = CacheMap.find(V);
    634   if (CacheIt != CacheMap.end())
    635     return CacheIt->second;
    636 
    637   // always generate code immediately before the instruction being
    638   // processed, so that the generated code dominates the same BBs
    639   BuilderTy::InsertPointGuard Guard(Builder);
    640   if (Instruction *I = dyn_cast<Instruction>(V))
    641     Builder.SetInsertPoint(I);
    642 
    643   // now compute the size and offset
    644   SizeOffsetEvalType Result;
    645 
    646   // Record the pointers that were handled in this run, so that they can be
    647   // cleaned later if something fails. We also use this set to break cycles that
    648   // can occur in dead code.
    649   if (!SeenVals.insert(V).second) {
    650     Result = unknown();
    651   } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
    652     Result = visitGEPOperator(*GEP);
    653   } else if (Instruction *I = dyn_cast<Instruction>(V)) {
    654     Result = visit(*I);
    655   } else if (isa<Argument>(V) ||
    656              (isa<ConstantExpr>(V) &&
    657               cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) ||
    658              isa<GlobalAlias>(V) ||
    659              isa<GlobalVariable>(V)) {
    660     // ignore values where we cannot do more than what ObjectSizeVisitor can
    661     Result = unknown();
    662   } else {
    663     DEBUG(dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: "
    664           << *V << '\n');
    665     Result = unknown();
    666   }
    667 
    668   // Don't reuse CacheIt since it may be invalid at this point.
    669   CacheMap[V] = Result;
    670   return Result;
    671 }
    672 
    673 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) {
    674   if (!I.getAllocatedType()->isSized())
    675     return unknown();
    676 
    677   // must be a VLA
    678   assert(I.isArrayAllocation());
    679   Value *ArraySize = I.getArraySize();
    680   Value *Size = ConstantInt::get(ArraySize->getType(),
    681                                  DL.getTypeAllocSize(I.getAllocatedType()));
    682   Size = Builder.CreateMul(Size, ArraySize);
    683   return std::make_pair(Size, Zero);
    684 }
    685 
    686 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) {
    687   const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc,
    688                                                TLI);
    689   if (!FnData)
    690     return unknown();
    691 
    692   // handle strdup-like functions separately
    693   if (FnData->AllocTy == StrDupLike) {
    694     // TODO
    695     return unknown();
    696   }
    697 
    698   Value *FirstArg = CS.getArgument(FnData->FstParam);
    699   FirstArg = Builder.CreateZExt(FirstArg, IntTy);
    700   if (FnData->SndParam < 0)
    701     return std::make_pair(FirstArg, Zero);
    702 
    703   Value *SecondArg = CS.getArgument(FnData->SndParam);
    704   SecondArg = Builder.CreateZExt(SecondArg, IntTy);
    705   Value *Size = Builder.CreateMul(FirstArg, SecondArg);
    706   return std::make_pair(Size, Zero);
    707 
    708   // TODO: handle more standard functions (+ wchar cousins):
    709   // - strdup / strndup
    710   // - strcpy / strncpy
    711   // - strcat / strncat
    712   // - memcpy / memmove
    713   // - strcat / strncat
    714   // - memset
    715 }
    716 
    717 SizeOffsetEvalType
    718 ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) {
    719   return unknown();
    720 }
    721 
    722 SizeOffsetEvalType
    723 ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) {
    724   return unknown();
    725 }
    726 
    727 SizeOffsetEvalType
    728 ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) {
    729   SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand());
    730   if (!bothKnown(PtrData))
    731     return unknown();
    732 
    733   Value *Offset = EmitGEPOffset(&Builder, DL, &GEP, /*NoAssumptions=*/true);
    734   Offset = Builder.CreateAdd(PtrData.second, Offset);
    735   return std::make_pair(PtrData.first, Offset);
    736 }
    737 
    738 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) {
    739   // clueless
    740   return unknown();
    741 }
    742 
    743 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) {
    744   return unknown();
    745 }
    746 
    747 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) {
    748   // create 2 PHIs: one for size and another for offset
    749   PHINode *SizePHI   = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
    750   PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
    751 
    752   // insert right away in the cache to handle recursive PHIs
    753   CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI);
    754 
    755   // compute offset/size for each PHI incoming pointer
    756   for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) {
    757     Builder.SetInsertPoint(&*PHI.getIncomingBlock(i)->getFirstInsertionPt());
    758     SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i));
    759 
    760     if (!bothKnown(EdgeData)) {
    761       OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy));
    762       OffsetPHI->eraseFromParent();
    763       SizePHI->replaceAllUsesWith(UndefValue::get(IntTy));
    764       SizePHI->eraseFromParent();
    765       return unknown();
    766     }
    767     SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
    768     OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
    769   }
    770 
    771   Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp;
    772   if ((Tmp = SizePHI->hasConstantValue())) {
    773     Size = Tmp;
    774     SizePHI->replaceAllUsesWith(Size);
    775     SizePHI->eraseFromParent();
    776   }
    777   if ((Tmp = OffsetPHI->hasConstantValue())) {
    778     Offset = Tmp;
    779     OffsetPHI->replaceAllUsesWith(Offset);
    780     OffsetPHI->eraseFromParent();
    781   }
    782   return std::make_pair(Size, Offset);
    783 }
    784 
    785 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) {
    786   SizeOffsetEvalType TrueSide  = compute_(I.getTrueValue());
    787   SizeOffsetEvalType FalseSide = compute_(I.getFalseValue());
    788 
    789   if (!bothKnown(TrueSide) || !bothKnown(FalseSide))
    790     return unknown();
    791   if (TrueSide == FalseSide)
    792     return TrueSide;
    793 
    794   Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first,
    795                                      FalseSide.first);
    796   Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second,
    797                                        FalseSide.second);
    798   return std::make_pair(Size, Offset);
    799 }
    800 
    801 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) {
    802   DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I <<'\n');
    803   return unknown();
    804 }
    805