src/llvm/lib/Analysis/MemoryBuiltins.cpp

   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 #define DEBUG_TYPE "memory-builtins"
  16 #include "llvm/ADT/Statistic.h"
  17 #include "llvm/ADT/STLExtras.h"
  18 #include "llvm/Analysis/MemoryBuiltins.h"
  19 #include "llvm/GlobalVariable.h"
  20 #include "llvm/Instructions.h"
  21 #include "llvm/Intrinsics.h"
  22 #include "llvm/Metadata.h"
  23 #include "llvm/Module.h"
  24 #include "llvm/Analysis/ValueTracking.h"
  25 #include "llvm/Support/Debug.h"
  26 #include "llvm/Support/MathExtras.h"
  27 #include "llvm/Support/raw_ostream.h"
  28 #include "llvm/Target/TargetData.h"
  29 #include "llvm/Target/TargetLibraryInfo.h"
  30 #include "llvm/Transforms/Utils/Local.h"
  31 using namespace llvm;
  32
  33 enum AllocType {
  34   MallocLike         = 1<<0, // allocates
  35   CallocLike         = 1<<1, // allocates + bzero
  36   ReallocLike        = 1<<2, // reallocates
  37   StrDupLike         = 1<<3,
  38   AllocLike          = MallocLike | CallocLike | StrDupLike,
  39   AnyAlloc           = MallocLike | CallocLike | ReallocLike | StrDupLike
  40 };
  41
  42 struct AllocFnsTy {
  43   LibFunc::Func Func;
  44   AllocType AllocTy;
  45   unsigned char NumParams;
  46   // First and Second size parameters (or -1 if unused)
  47   signed char FstParam, SndParam;
  48 };
  49
  50 // FIXME: certain users need more information. E.g., SimplifyLibCalls needs to
  51 // know which functions are nounwind, noalias, nocapture parameters, etc.
  52 static const AllocFnsTy AllocationFnData[] = {
  53   {LibFunc::malloc,              MallocLike,  1, 0,  -1},
  54   {LibFunc::valloc,              MallocLike,  1, 0,  -1},
  55   {LibFunc::Znwj,                MallocLike,  1, 0,  -1}, // new(unsigned int)
  56   {LibFunc::ZnwjRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new(unsigned int, nothrow)
  57   {LibFunc::Znwm,                MallocLike,  1, 0,  -1}, // new(unsigned long)
  58   {LibFunc::ZnwmRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new(unsigned long, nothrow)
  59   {LibFunc::Znaj,                MallocLike,  1, 0,  -1}, // new[](unsigned int)
  60   {LibFunc::ZnajRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new[](unsigned int, nothrow)
  61   {LibFunc::Znam,                MallocLike,  1, 0,  -1}, // new[](unsigned long)
  62   {LibFunc::ZnamRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new[](unsigned long, nothrow)
  63   {LibFunc::posix_memalign,      MallocLike,  3, 2,  -1},
  64   {LibFunc::calloc,              CallocLike,  2, 0,   1},
  65   {LibFunc::realloc,             ReallocLike, 2, 1,  -1},
  66   {LibFunc::reallocf,            ReallocLike, 2, 1,  -1},
  67   {LibFunc::strdup,              StrDupLike,  1, -1, -1},
  68   {LibFunc::strndup,             StrDupLike,  2, 1,  -1}
  69 };
  70
  71
  72 static Function *getCalledFunction(const Value *V, bool LookThroughBitCast) {
  73   if (LookThroughBitCast)
  74     V = V->stripPointerCasts();
  75
  76   CallSite CS(const_cast<Value*>(V));
  77   if (!CS.getInstruction())
  78     return 0;
  79
  80   Function *Callee = CS.getCalledFunction();
  81   if (!Callee || !Callee->isDeclaration())
  82     return 0;
  83   return Callee;
  84 }
  85
  86 /// \brief Returns the allocation data for the given value if it is a call to a
  87 /// known allocation function, and NULL otherwise.
  88 static const AllocFnsTy *getAllocationData(const Value *V, AllocType AllocTy,
  89                                            const TargetLibraryInfo *TLI,
  90                                            bool LookThroughBitCast = false) {
  91   Function *Callee = getCalledFunction(V, LookThroughBitCast);
  92   if (!Callee)
  93     return 0;
  94
  95   // Make sure that the function is available.
  96   StringRef FnName = Callee->getName();
  97   LibFunc::Func TLIFn;
  98   if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
  99     return 0;
 100
 101   unsigned i = 0;
 102   bool found = false;
 103   for ( ; i < array_lengthof(AllocationFnData); ++i) {
 104     if (AllocationFnData[i].Func == TLIFn) {
 105       found = true;
 106       break;
 107     }
 108   }
 109   if (!found)
 110     return 0;
 111
 112   const AllocFnsTy *FnData = &AllocationFnData[i];
 113   if ((FnData->AllocTy & AllocTy) == 0)
 114     return 0;
 115
 116   // Check function prototype.
 117   int FstParam = FnData->FstParam;
 118   int SndParam = FnData->SndParam;
 119   FunctionType *FTy = Callee->getFunctionType();
 120
 121   if (FTy->getReturnType() == Type::getInt8PtrTy(FTy->getContext()) &&
 122       FTy->getNumParams() == FnData->NumParams &&
 123       (FstParam < 0 ||
 124        (FTy->getParamType(FstParam)->isIntegerTy(32) ||
 125         FTy->getParamType(FstParam)->isIntegerTy(64))) &&
 126       (SndParam < 0 ||
 127        FTy->getParamType(SndParam)->isIntegerTy(32) ||
 128        FTy->getParamType(SndParam)->isIntegerTy(64)))
 129     return FnData;
 130   return 0;
 131 }
 132
 133 static bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) {
 134   ImmutableCallSite CS(LookThroughBitCast ? V->stripPointerCasts() : V);
 135   return CS && CS.hasFnAttr(Attribute::NoAlias);
 136 }
 137
 138
 139 /// \brief Tests if a value is a call or invoke to a library function that
 140 /// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
 141 /// like).
 142 bool llvm::isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
 143                           bool LookThroughBitCast) {
 144   return getAllocationData(V, AnyAlloc, TLI, LookThroughBitCast);
 145 }
 146
 147 /// \brief Tests if a value is a call or invoke to a function that returns a
 148 /// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
 149 bool llvm::isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
 150                        bool LookThroughBitCast) {
 151   // it's safe to consider realloc as noalias since accessing the original
 152   // pointer is undefined behavior
 153   return isAllocationFn(V, TLI, LookThroughBitCast) ||
 154          hasNoAliasAttr(V, LookThroughBitCast);
 155 }
 156
 157 /// \brief Tests if a value is a call or invoke to a library function that
 158 /// allocates uninitialized memory (such as malloc).
 159 bool llvm::isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 160                           bool LookThroughBitCast) {
 161   return getAllocationData(V, MallocLike, TLI, LookThroughBitCast);
 162 }
 163
 164 /// \brief Tests if a value is a call or invoke to a library function that
 165 /// allocates zero-filled memory (such as calloc).
 166 bool llvm::isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 167                           bool LookThroughBitCast) {
 168   return getAllocationData(V, CallocLike, TLI, LookThroughBitCast);
 169 }
 170
 171 /// \brief Tests if a value is a call or invoke to a library function that
 172 /// allocates memory (either malloc, calloc, or strdup like).
 173 bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 174                          bool LookThroughBitCast) {
 175   return getAllocationData(V, AllocLike, TLI, LookThroughBitCast);
 176 }
 177
 178 /// \brief Tests if a value is a call or invoke to a library function that
 179 /// reallocates memory (such as realloc).
 180 bool llvm::isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
 181                            bool LookThroughBitCast) {
 182   return getAllocationData(V, ReallocLike, TLI, LookThroughBitCast);
 183 }
 184
 185 /// extractMallocCall - Returns the corresponding CallInst if the instruction
 186 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
 187 /// ignore InvokeInst here.
 188 const CallInst *llvm::extractMallocCall(const Value *I,
 189                                         const TargetLibraryInfo *TLI) {
 190   return isMallocLikeFn(I, TLI) ? dyn_cast<CallInst>(I) : 0;
 191 }
 192
 193 static Value *computeArraySize(const CallInst *CI, const TargetData *TD,
 194                                const TargetLibraryInfo *TLI,
 195                                bool LookThroughSExt = false) {
 196   if (!CI)
 197     return NULL;
 198
 199   // The size of the malloc's result type must be known to determine array size.
 200   Type *T = getMallocAllocatedType(CI, TLI);
 201   if (!T || !T->isSized() || !TD)
 202     return NULL;
 203
 204   unsigned ElementSize = TD->getTypeAllocSize(T);
 205   if (StructType *ST = dyn_cast<StructType>(T))
 206     ElementSize = TD->getStructLayout(ST)->getSizeInBytes();
 207
 208   // If malloc call's arg can be determined to be a multiple of ElementSize,
 209   // return the multiple.  Otherwise, return NULL.
 210   Value *MallocArg = CI->getArgOperand(0);
 211   Value *Multiple = NULL;
 212   if (ComputeMultiple(MallocArg, ElementSize, Multiple,
 213                       LookThroughSExt))
 214     return Multiple;
 215
 216   return NULL;
 217 }
 218
 219 /// isArrayMalloc - Returns the corresponding CallInst if the instruction
 220 /// is a call to malloc whose array size can be determined and the array size
 221 /// is not constant 1.  Otherwise, return NULL.
 222 const CallInst *llvm::isArrayMalloc(const Value *I,
 223                                     const TargetData *TD,
 224                                     const TargetLibraryInfo *TLI) {
 225   const CallInst *CI = extractMallocCall(I, TLI);
 226   Value *ArraySize = computeArraySize(CI, TD, TLI);
 227
 228   if (ArraySize &&
 229       ArraySize != ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
 230     return CI;
 231
 232   // CI is a non-array malloc or we can't figure out that it is an array malloc.
 233   return NULL;
 234 }
 235
 236 /// getMallocType - Returns the PointerType resulting from the malloc call.
 237 /// The PointerType depends on the number of bitcast uses of the malloc call:
 238 ///   0: PointerType is the calls' return type.
 239 ///   1: PointerType is the bitcast's result type.
 240 ///  >1: Unique PointerType cannot be determined, return NULL.
 241 PointerType *llvm::getMallocType(const CallInst *CI,
 242                                  const TargetLibraryInfo *TLI) {
 243   assert(isMallocLikeFn(CI, TLI) && "getMallocType and not malloc call");
 244
 245   PointerType *MallocType = NULL;
 246   unsigned NumOfBitCastUses = 0;
 247
 248   // Determine if CallInst has a bitcast use.
 249   for (Value::const_use_iterator UI = CI->use_begin(), E = CI->use_end();
 250        UI != E; )
 251     if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) {
 252       MallocType = cast<PointerType>(BCI->getDestTy());
 253       NumOfBitCastUses++;
 254     }
 255
 256   // Malloc call has 1 bitcast use, so type is the bitcast's destination type.
 257   if (NumOfBitCastUses == 1)
 258     return MallocType;
 259
 260   // Malloc call was not bitcast, so type is the malloc function's return type.
 261   if (NumOfBitCastUses == 0)
 262     return cast<PointerType>(CI->getType());
 263
 264   // Type could not be determined.
 265   return NULL;
 266 }
 267
 268 /// getMallocAllocatedType - Returns the Type allocated by malloc call.
 269 /// The Type depends on the number of bitcast uses of the malloc call:
 270 ///   0: PointerType is the malloc calls' return type.
 271 ///   1: PointerType is the bitcast's result type.
 272 ///  >1: Unique PointerType cannot be determined, return NULL.
 273 Type *llvm::getMallocAllocatedType(const CallInst *CI,
 274                                    const TargetLibraryInfo *TLI) {
 275   PointerType *PT = getMallocType(CI, TLI);
 276   return PT ? PT->getElementType() : NULL;
 277 }
 278
 279 /// getMallocArraySize - Returns the array size of a malloc call.  If the
 280 /// argument passed to malloc is a multiple of the size of the malloced type,
 281 /// then return that multiple.  For non-array mallocs, the multiple is
 282 /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
 283 /// determined.
 284 Value *llvm::getMallocArraySize(CallInst *CI, const TargetData *TD,
 285                                 const TargetLibraryInfo *TLI,
 286                                 bool LookThroughSExt) {
 287   assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call");
 288   return computeArraySize(CI, TD, TLI, LookThroughSExt);
 289 }
 290
 291
 292 /// extractCallocCall - Returns the corresponding CallInst if the instruction
 293 /// is a calloc call.
 294 const CallInst *llvm::extractCallocCall(const Value *I,
 295                                         const TargetLibraryInfo *TLI) {
 296   return isCallocLikeFn(I, TLI) ? cast<CallInst>(I) : 0;
 297 }
 298
 299
 300 /// isFreeCall - Returns non-null if the value is a call to the builtin free()
 301 const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) {
 302   const CallInst *CI = dyn_cast<CallInst>(I);
 303   if (!CI)
 304     return 0;
 305   Function *Callee = CI->getCalledFunction();
 306   if (Callee == 0 || !Callee->isDeclaration())
 307     return 0;
 308
 309   StringRef FnName = Callee->getName();
 310   LibFunc::Func TLIFn;
 311   if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
 312     return 0;
 313
 314   if (TLIFn != LibFunc::free &&
 315       TLIFn != LibFunc::ZdlPv && // operator delete(void*)
 316       TLIFn != LibFunc::ZdaPv)   // operator delete[](void*)
 317     return 0;
 318
 319   // Check free prototype.
 320   // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
 321   // attribute will exist.
 322   FunctionType *FTy = Callee->getFunctionType();
 323   if (!FTy->getReturnType()->isVoidTy())
 324     return 0;
 325   if (FTy->getNumParams() != 1)
 326     return 0;
 327   if (FTy->getParamType(0) != Type::getInt8PtrTy(Callee->getContext()))
 328     return 0;
 329
 330   return CI;
 331 }
 332
 333
 334
 335 //===----------------------------------------------------------------------===//
 336 //  Utility functions to compute size of objects.
 337 //
 338
 339
 340 /// \brief Compute the size of the object pointed by Ptr. Returns true and the
 341 /// object size in Size if successful, and false otherwise.
 342 /// If RoundToAlign is true, then Size is rounded up to the aligment of allocas,
 343 /// byval arguments, and global variables.
 344 bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const TargetData *TD,
 345                          const TargetLibraryInfo *TLI, bool RoundToAlign) {
 346   if (!TD)
 347     return false;
 348
 349   ObjectSizeOffsetVisitor Visitor(TD, TLI, Ptr->getContext(), RoundToAlign);
 350   SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
 351   if (!Visitor.bothKnown(Data))
 352     return false;
 353
 354   APInt ObjSize = Data.first, Offset = Data.second;
 355   // check for overflow
 356   if (Offset.slt(0) || ObjSize.ult(Offset))
 357     Size = 0;
 358   else
 359     Size = (ObjSize - Offset).getZExtValue();
 360   return true;
 361 }
 362
 363
 364 STATISTIC(ObjectVisitorArgument,
 365           "Number of arguments with unsolved size and offset");
 366 STATISTIC(ObjectVisitorLoad,
 367           "Number of load instructions with unsolved size and offset");
 368
 369
 370 APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Align) {
 371   if (RoundToAlign && Align)
 372     return APInt(IntTyBits, RoundUpToAlignment(Size.getZExtValue(), Align));
 373   return Size;
 374 }
 375
 376 ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const TargetData *TD,
 377                                                  const TargetLibraryInfo *TLI,
 378                                                  LLVMContext &Context,
 379                                                  bool RoundToAlign)
 380 : TD(TD), TLI(TLI), RoundToAlign(RoundToAlign) {
 381   IntegerType *IntTy = TD->getIntPtrType(Context);
 382   IntTyBits = IntTy->getBitWidth();
 383   Zero = APInt::getNullValue(IntTyBits);
 384 }
 385
 386 SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
 387   V = V->stripPointerCasts();
 388   if (Instruction *I = dyn_cast<Instruction>(V)) {
 389     // If we have already seen this instruction, bail out. Cycles can happen in
 390     // unreachable code after constant propagation.
 391     if (!SeenInsts.insert(I))
 392       return unknown();
 393
 394     if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
 395       return visitGEPOperator(*GEP);
 396     return visit(*I);
 397   }
 398   if (Argument *A = dyn_cast<Argument>(V))
 399     return visitArgument(*A);
 400   if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
 401     return visitConstantPointerNull(*P);
 402   if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
 403     return visitGlobalVariable(*GV);
 404   if (UndefValue *UV = dyn_cast<UndefValue>(V))
 405     return visitUndefValue(*UV);
 406   if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
 407     if (CE->getOpcode() == Instruction::IntToPtr)
 408       return unknown(); // clueless
 409     if (CE->getOpcode() == Instruction::GetElementPtr)
 410       return visitGEPOperator(cast<GEPOperator>(*CE));
 411   }
 412
 413   DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
 414         << '\n');
 415   return unknown();
 416 }
 417
 418 SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
 419   if (!I.getAllocatedType()->isSized())
 420     return unknown();
 421
 422   APInt Size(IntTyBits, TD->getTypeAllocSize(I.getAllocatedType()));
 423   if (!I.isArrayAllocation())
 424     return std::make_pair(align(Size, I.getAlignment()), Zero);
 425
 426   Value *ArraySize = I.getArraySize();
 427   if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) {
 428     Size *= C->getValue().zextOrSelf(IntTyBits);
 429     return std::make_pair(align(Size, I.getAlignment()), Zero);
 430   }
 431   return unknown();
 432 }
 433
 434 SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
 435   // no interprocedural analysis is done at the moment
 436   if (!A.hasByValAttr()) {
 437     ++ObjectVisitorArgument;
 438     return unknown();
 439   }
 440   PointerType *PT = cast<PointerType>(A.getType());
 441   APInt Size(IntTyBits, TD->getTypeAllocSize(PT->getElementType()));
 442   return std::make_pair(align(Size, A.getParamAlignment()), Zero);
 443 }
 444
 445 SizeOffsetType ObjectSizeOffsetVisitor::visitCallSite(CallSite CS) {
 446   const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc,
 447                                                TLI);
 448   if (!FnData)
 449     return unknown();
 450
 451   // handle strdup-like functions separately
 452   if (FnData->AllocTy == StrDupLike) {
 453     APInt Size(IntTyBits, GetStringLength(CS.getArgument(0)));
 454     if (!Size)
 455       return unknown();
 456
 457     // strndup limits strlen
 458     if (FnData->FstParam > 0) {
 459       ConstantInt *Arg= dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
 460       if (!Arg)
 461         return unknown();
 462
 463       APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits);
 464       if (Size.ugt(MaxSize))
 465         Size = MaxSize + 1;
 466     }
 467     return std::make_pair(Size, Zero);
 468   }
 469
 470   ConstantInt *Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
 471   if (!Arg)
 472     return unknown();
 473
 474   APInt Size = Arg->getValue().zextOrSelf(IntTyBits);
 475   // size determined by just 1 parameter
 476   if (FnData->SndParam < 0)
 477     return std::make_pair(Size, Zero);
 478
 479   Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->SndParam));
 480   if (!Arg)
 481     return unknown();
 482
 483   Size *= Arg->getValue().zextOrSelf(IntTyBits);
 484   return std::make_pair(Size, Zero);
 485
 486   // TODO: handle more standard functions (+ wchar cousins):
 487   // - strdup / strndup
 488   // - strcpy / strncpy
 489   // - strcat / strncat
 490   // - memcpy / memmove
 491   // - strcat / strncat
 492   // - memset
 493 }
 494
 495 SizeOffsetType
 496 ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull&) {
 497   return std::make_pair(Zero, Zero);
 498 }
 499
 500 SizeOffsetType
 501 ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) {
 502   return unknown();
 503 }
 504
 505 SizeOffsetType
 506 ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) {
 507   // Easy cases were already folded by previous passes.
 508   return unknown();
 509 }
 510
 511 SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) {
 512   SizeOffsetType PtrData = compute(GEP.getPointerOperand());
 513   if (!bothKnown(PtrData) || !GEP.hasAllConstantIndices())
 514     return unknown();
 515
 516   SmallVector<Value*, 8> Ops(GEP.idx_begin(), GEP.idx_end());
 517   APInt Offset(IntTyBits,TD->getIndexedOffset(GEP.getPointerOperandType(),Ops));
 518   return std::make_pair(PtrData.first, PtrData.second + Offset);
 519 }
 520
 521 SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){
 522   if (!GV.hasDefinitiveInitializer())
 523     return unknown();
 524
 525   APInt Size(IntTyBits, TD->getTypeAllocSize(GV.getType()->getElementType()));
 526   return std::make_pair(align(Size, GV.getAlignment()), Zero);
 527 }
 528
 529 SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) {
 530   // clueless
 531   return unknown();
 532 }
 533
 534 SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
 535   ++ObjectVisitorLoad;
 536   return unknown();
 537 }
 538
 539 SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
 540   // too complex to analyze statically.
 541   return unknown();
 542 }
 543
 544 SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
 545   SizeOffsetType TrueSide  = compute(I.getTrueValue());
 546   SizeOffsetType FalseSide = compute(I.getFalseValue());
 547   if (bothKnown(TrueSide) && bothKnown(FalseSide) && TrueSide == FalseSide)
 548     return TrueSide;
 549   return unknown();
 550 }
 551
 552 SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) {
 553   return std::make_pair(Zero, Zero);
 554 }
 555
 556 SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) {
 557   DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I << '\n');
 558   return unknown();
 559 }
 560
 561
 562 ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(const TargetData *TD,
 563                                                    const TargetLibraryInfo *TLI,
 564                                                      LLVMContext &Context)
 565 : TD(TD), TLI(TLI), Context(Context), Builder(Context, TargetFolder(TD)) {
 566   IntTy = TD->getIntPtrType(Context);
 567   Zero = ConstantInt::get(IntTy, 0);
 568 }
 569
 570 SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) {
 571   SizeOffsetEvalType Result = compute_(V);
 572
 573   if (!bothKnown(Result)) {
 574     // erase everything that was computed in this iteration from the cache, so
 575     // that no dangling references are left behind. We could be a bit smarter if
 576     // we kept a dependency graph. It's probably not worth the complexity.
 577     for (PtrSetTy::iterator I=SeenVals.begin(), E=SeenVals.end(); I != E; ++I) {
 578       CacheMapTy::iterator CacheIt = CacheMap.find(*I);
 579       // non-computable results can be safely cached
 580       if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second))
 581         CacheMap.erase(CacheIt);
 582     }
 583   }
 584
 585   SeenVals.clear();
 586   return Result;
 587 }
 588
 589 SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
 590   ObjectSizeOffsetVisitor Visitor(TD, TLI, Context);
 591   SizeOffsetType Const = Visitor.compute(V);
 592   if (Visitor.bothKnown(Const))
 593     return std::make_pair(ConstantInt::get(Context, Const.first),
 594                           ConstantInt::get(Context, Const.second));
 595
 596   V = V->stripPointerCasts();
 597
 598   // check cache
 599   CacheMapTy::iterator CacheIt = CacheMap.find(V);
 600   if (CacheIt != CacheMap.end())
 601     return CacheIt->second;
 602
 603   // always generate code immediately before the instruction being
 604   // processed, so that the generated code dominates the same BBs
 605   Instruction *PrevInsertPoint = Builder.GetInsertPoint();
 606   if (Instruction *I = dyn_cast<Instruction>(V))
 607     Builder.SetInsertPoint(I);
 608
 609   // record the pointers that were handled in this run, so that they can be
 610   // cleaned later if something fails
 611   SeenVals.insert(V);
 612
 613   // now compute the size and offset
 614   SizeOffsetEvalType Result;
 615   if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
 616     Result = visitGEPOperator(*GEP);
 617   } else if (Instruction *I = dyn_cast<Instruction>(V)) {
 618     Result = visit(*I);
 619   } else if (isa<Argument>(V) ||
 620              (isa<ConstantExpr>(V) &&
 621               cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) ||
 622              isa<GlobalVariable>(V)) {
 623     // ignore values where we cannot do more than what ObjectSizeVisitor can
 624     Result = unknown();
 625   } else {
 626     DEBUG(dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: "
 627           << *V << '\n');
 628     Result = unknown();
 629   }
 630
 631   if (PrevInsertPoint)
 632     Builder.SetInsertPoint(PrevInsertPoint);
 633
 634   // Don't reuse CacheIt since it may be invalid at this point.
 635   CacheMap[V] = Result;
 636   return Result;
 637 }
 638
 639 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) {
 640   if (!I.getAllocatedType()->isSized())
 641     return unknown();
 642
 643   // must be a VLA
 644   assert(I.isArrayAllocation());
 645   Value *ArraySize = I.getArraySize();
 646   Value *Size = ConstantInt::get(ArraySize->getType(),
 647                                  TD->getTypeAllocSize(I.getAllocatedType()));
 648   Size = Builder.CreateMul(Size, ArraySize);
 649   return std::make_pair(Size, Zero);
 650 }
 651
 652 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) {
 653   const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc,
 654                                                TLI);
 655   if (!FnData)
 656     return unknown();
 657
 658   // handle strdup-like functions separately
 659   if (FnData->AllocTy == StrDupLike) {
 660     // TODO
 661     return unknown();
 662   }
 663
 664   Value *FirstArg = CS.getArgument(FnData->FstParam);
 665   FirstArg = Builder.CreateZExt(FirstArg, IntTy);
 666   if (FnData->SndParam < 0)
 667     return std::make_pair(FirstArg, Zero);
 668
 669   Value *SecondArg = CS.getArgument(FnData->SndParam);
 670   SecondArg = Builder.CreateZExt(SecondArg, IntTy);
 671   Value *Size = Builder.CreateMul(FirstArg, SecondArg);
 672   return std::make_pair(Size, Zero);
 673
 674   // TODO: handle more standard functions (+ wchar cousins):
 675   // - strdup / strndup
 676   // - strcpy / strncpy
 677   // - strcat / strncat
 678   // - memcpy / memmove
 679   // - strcat / strncat
 680   // - memset
 681 }
 682
 683 SizeOffsetEvalType
 684 ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) {
 685   return unknown();
 686 }
 687
 688 SizeOffsetEvalType
 689 ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) {
 690   return unknown();
 691 }
 692
 693 SizeOffsetEvalType
 694 ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) {
 695   SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand());
 696   if (!bothKnown(PtrData))
 697     return unknown();
 698
 699   Value *Offset = EmitGEPOffset(&Builder, *TD, &GEP, /*NoAssumptions=*/true);
 700   Offset = Builder.CreateAdd(PtrData.second, Offset);
 701   return std::make_pair(PtrData.first, Offset);
 702 }
 703
 704 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) {
 705   // clueless
 706   return unknown();
 707 }
 708
 709 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) {
 710   return unknown();
 711 }
 712
 713 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) {
 714   // create 2 PHIs: one for size and another for offset
 715   PHINode *SizePHI   = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
 716   PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
 717
 718   // insert right away in the cache to handle recursive PHIs
 719   CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI);
 720
 721   // compute offset/size for each PHI incoming pointer
 722   for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) {
 723     Builder.SetInsertPoint(PHI.getIncomingBlock(i)->getFirstInsertionPt());
 724     SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i));
 725
 726     if (!bothKnown(EdgeData)) {
 727       OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy));
 728       OffsetPHI->eraseFromParent();
 729       SizePHI->replaceAllUsesWith(UndefValue::get(IntTy));
 730       SizePHI->eraseFromParent();
 731       return unknown();
 732     }
 733     SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
 734     OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
 735   }
 736
 737   Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp;
 738   if ((Tmp = SizePHI->hasConstantValue())) {
 739     Size = Tmp;
 740     SizePHI->replaceAllUsesWith(Size);
 741     SizePHI->eraseFromParent();
 742   }
 743   if ((Tmp = OffsetPHI->hasConstantValue())) {
 744     Offset = Tmp;
 745     OffsetPHI->replaceAllUsesWith(Offset);
 746     OffsetPHI->eraseFromParent();
 747   }
 748   return std::make_pair(Size, Offset);
 749 }
 750
 751 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) {
 752   SizeOffsetEvalType TrueSide  = compute_(I.getTrueValue());
 753   SizeOffsetEvalType FalseSide = compute_(I.getFalseValue());
 754
 755   if (!bothKnown(TrueSide) || !bothKnown(FalseSide))
 756     return unknown();
 757   if (TrueSide == FalseSide)
 758     return TrueSide;
 759
 760   Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first,
 761                                      FalseSide.first);
 762   Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second,
 763                                        FalseSide.second);
 764   return std::make_pair(Size, Offset);
 765 }
 766
 767 SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) {
 768   DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I <<'\n');
 769   return unknown();
 770 }