MemoryBuiltins.cpp revision 44365353a415d37daae9df53fbf6a91677ed90d3
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/Analysis/MemoryBuiltins.h" 17#include "llvm/ADT/STLExtras.h" 18#include "llvm/ADT/Statistic.h" 19#include "llvm/Analysis/ValueTracking.h" 20#include "llvm/DataLayout.h" 21#include "llvm/GlobalVariable.h" 22#include "llvm/Instructions.h" 23#include "llvm/Intrinsics.h" 24#include "llvm/Metadata.h" 25#include "llvm/Module.h" 26#include "llvm/Support/Debug.h" 27#include "llvm/Support/MathExtras.h" 28#include "llvm/Support/raw_ostream.h" 29#include "llvm/Target/TargetLibraryInfo.h" 30#include "llvm/Transforms/Utils/Local.h" 31using namespace llvm; 32 33enum 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 42struct 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. 52static 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 72static 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. 88static 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 133static 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). 142bool 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). 149bool 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). 159bool 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). 166bool 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). 173bool 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). 180bool 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. 188const CallInst *llvm::extractMallocCall(const Value *I, 189 const TargetLibraryInfo *TLI) { 190 return isMallocLikeFn(I, TLI) ? dyn_cast<CallInst>(I) : 0; 191} 192 193static Value *computeArraySize(const CallInst *CI, const DataLayout *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. 222const CallInst *llvm::isArrayMalloc(const Value *I, 223 const DataLayout *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. 241PointerType *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. 273Type *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. 284Value *llvm::getMallocArraySize(CallInst *CI, const DataLayout *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. 294const 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() 301const 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. 344bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout *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 364STATISTIC(ObjectVisitorArgument, 365 "Number of arguments with unsolved size and offset"); 366STATISTIC(ObjectVisitorLoad, 367 "Number of load instructions with unsolved size and offset"); 368 369 370APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Align) { 371 if (RoundToAlign && Align) 372 return APInt(IntTyBits, RoundUpToAlignment(Size.getZExtValue(), Align)); 373 return Size; 374} 375 376ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout *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 386SizeOffsetType 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 (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) 403 return visitGlobalAlias(*GA); 404 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 405 return visitGlobalVariable(*GV); 406 if (UndefValue *UV = dyn_cast<UndefValue>(V)) 407 return visitUndefValue(*UV); 408 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 409 if (CE->getOpcode() == Instruction::IntToPtr) 410 return unknown(); // clueless 411 if (CE->getOpcode() == Instruction::GetElementPtr) 412 return visitGEPOperator(cast<GEPOperator>(*CE)); 413 } 414 415 DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V 416 << '\n'); 417 return unknown(); 418} 419 420SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) { 421 if (!I.getAllocatedType()->isSized()) 422 return unknown(); 423 424 APInt Size(IntTyBits, TD->getTypeAllocSize(I.getAllocatedType())); 425 if (!I.isArrayAllocation()) 426 return std::make_pair(align(Size, I.getAlignment()), Zero); 427 428 Value *ArraySize = I.getArraySize(); 429 if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) { 430 Size *= C->getValue().zextOrSelf(IntTyBits); 431 return std::make_pair(align(Size, I.getAlignment()), Zero); 432 } 433 return unknown(); 434} 435 436SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) { 437 // no interprocedural analysis is done at the moment 438 if (!A.hasByValAttr()) { 439 ++ObjectVisitorArgument; 440 return unknown(); 441 } 442 PointerType *PT = cast<PointerType>(A.getType()); 443 APInt Size(IntTyBits, TD->getTypeAllocSize(PT->getElementType())); 444 return std::make_pair(align(Size, A.getParamAlignment()), Zero); 445} 446 447SizeOffsetType ObjectSizeOffsetVisitor::visitCallSite(CallSite CS) { 448 const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc, 449 TLI); 450 if (!FnData) 451 return unknown(); 452 453 // handle strdup-like functions separately 454 if (FnData->AllocTy == StrDupLike) { 455 APInt Size(IntTyBits, GetStringLength(CS.getArgument(0))); 456 if (!Size) 457 return unknown(); 458 459 // strndup limits strlen 460 if (FnData->FstParam > 0) { 461 ConstantInt *Arg= dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam)); 462 if (!Arg) 463 return unknown(); 464 465 APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits); 466 if (Size.ugt(MaxSize)) 467 Size = MaxSize + 1; 468 } 469 return std::make_pair(Size, Zero); 470 } 471 472 ConstantInt *Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam)); 473 if (!Arg) 474 return unknown(); 475 476 APInt Size = Arg->getValue().zextOrSelf(IntTyBits); 477 // size determined by just 1 parameter 478 if (FnData->SndParam < 0) 479 return std::make_pair(Size, Zero); 480 481 Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->SndParam)); 482 if (!Arg) 483 return unknown(); 484 485 Size *= Arg->getValue().zextOrSelf(IntTyBits); 486 return std::make_pair(Size, Zero); 487 488 // TODO: handle more standard functions (+ wchar cousins): 489 // - strdup / strndup 490 // - strcpy / strncpy 491 // - strcat / strncat 492 // - memcpy / memmove 493 // - strcat / strncat 494 // - memset 495} 496 497SizeOffsetType 498ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull&) { 499 return std::make_pair(Zero, Zero); 500} 501 502SizeOffsetType 503ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) { 504 return unknown(); 505} 506 507SizeOffsetType 508ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) { 509 // Easy cases were already folded by previous passes. 510 return unknown(); 511} 512 513SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) { 514 SizeOffsetType PtrData = compute(GEP.getPointerOperand()); 515 APInt Offset(IntTyBits, 0); 516 if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(*TD, Offset)) 517 return unknown(); 518 519 return std::make_pair(PtrData.first, PtrData.second + Offset); 520} 521 522SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) { 523 if (GA.mayBeOverridden()) 524 return unknown(); 525 return compute(GA.getAliasee()); 526} 527 528SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){ 529 if (!GV.hasDefinitiveInitializer()) 530 return unknown(); 531 532 APInt Size(IntTyBits, TD->getTypeAllocSize(GV.getType()->getElementType())); 533 return std::make_pair(align(Size, GV.getAlignment()), Zero); 534} 535 536SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) { 537 // clueless 538 return unknown(); 539} 540 541SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) { 542 ++ObjectVisitorLoad; 543 return unknown(); 544} 545 546SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) { 547 // too complex to analyze statically. 548 return unknown(); 549} 550 551SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) { 552 SizeOffsetType TrueSide = compute(I.getTrueValue()); 553 SizeOffsetType FalseSide = compute(I.getFalseValue()); 554 if (bothKnown(TrueSide) && bothKnown(FalseSide) && TrueSide == FalseSide) 555 return TrueSide; 556 return unknown(); 557} 558 559SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) { 560 return std::make_pair(Zero, Zero); 561} 562 563SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) { 564 DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I << '\n'); 565 return unknown(); 566} 567 568 569ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(const DataLayout *TD, 570 const TargetLibraryInfo *TLI, 571 LLVMContext &Context) 572: TD(TD), TLI(TLI), Context(Context), Builder(Context, TargetFolder(TD)) { 573 IntTy = TD->getIntPtrType(Context); 574 Zero = ConstantInt::get(IntTy, 0); 575} 576 577SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) { 578 SizeOffsetEvalType Result = compute_(V); 579 580 if (!bothKnown(Result)) { 581 // erase everything that was computed in this iteration from the cache, so 582 // that no dangling references are left behind. We could be a bit smarter if 583 // we kept a dependency graph. It's probably not worth the complexity. 584 for (PtrSetTy::iterator I=SeenVals.begin(), E=SeenVals.end(); I != E; ++I) { 585 CacheMapTy::iterator CacheIt = CacheMap.find(*I); 586 // non-computable results can be safely cached 587 if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second)) 588 CacheMap.erase(CacheIt); 589 } 590 } 591 592 SeenVals.clear(); 593 return Result; 594} 595 596SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) { 597 ObjectSizeOffsetVisitor Visitor(TD, TLI, Context); 598 SizeOffsetType Const = Visitor.compute(V); 599 if (Visitor.bothKnown(Const)) 600 return std::make_pair(ConstantInt::get(Context, Const.first), 601 ConstantInt::get(Context, Const.second)); 602 603 V = V->stripPointerCasts(); 604 605 // check cache 606 CacheMapTy::iterator CacheIt = CacheMap.find(V); 607 if (CacheIt != CacheMap.end()) 608 return CacheIt->second; 609 610 // always generate code immediately before the instruction being 611 // processed, so that the generated code dominates the same BBs 612 Instruction *PrevInsertPoint = Builder.GetInsertPoint(); 613 if (Instruction *I = dyn_cast<Instruction>(V)) 614 Builder.SetInsertPoint(I); 615 616 // record the pointers that were handled in this run, so that they can be 617 // cleaned later if something fails 618 SeenVals.insert(V); 619 620 // now compute the size and offset 621 SizeOffsetEvalType Result; 622 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { 623 Result = visitGEPOperator(*GEP); 624 } else if (Instruction *I = dyn_cast<Instruction>(V)) { 625 Result = visit(*I); 626 } else if (isa<Argument>(V) || 627 (isa<ConstantExpr>(V) && 628 cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) || 629 isa<GlobalAlias>(V) || 630 isa<GlobalVariable>(V)) { 631 // ignore values where we cannot do more than what ObjectSizeVisitor can 632 Result = unknown(); 633 } else { 634 DEBUG(dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: " 635 << *V << '\n'); 636 Result = unknown(); 637 } 638 639 if (PrevInsertPoint) 640 Builder.SetInsertPoint(PrevInsertPoint); 641 642 // Don't reuse CacheIt since it may be invalid at this point. 643 CacheMap[V] = Result; 644 return Result; 645} 646 647SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) { 648 if (!I.getAllocatedType()->isSized()) 649 return unknown(); 650 651 // must be a VLA 652 assert(I.isArrayAllocation()); 653 Value *ArraySize = I.getArraySize(); 654 Value *Size = ConstantInt::get(ArraySize->getType(), 655 TD->getTypeAllocSize(I.getAllocatedType())); 656 Size = Builder.CreateMul(Size, ArraySize); 657 return std::make_pair(Size, Zero); 658} 659 660SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) { 661 const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc, 662 TLI); 663 if (!FnData) 664 return unknown(); 665 666 // handle strdup-like functions separately 667 if (FnData->AllocTy == StrDupLike) { 668 // TODO 669 return unknown(); 670 } 671 672 Value *FirstArg = CS.getArgument(FnData->FstParam); 673 FirstArg = Builder.CreateZExt(FirstArg, IntTy); 674 if (FnData->SndParam < 0) 675 return std::make_pair(FirstArg, Zero); 676 677 Value *SecondArg = CS.getArgument(FnData->SndParam); 678 SecondArg = Builder.CreateZExt(SecondArg, IntTy); 679 Value *Size = Builder.CreateMul(FirstArg, SecondArg); 680 return std::make_pair(Size, Zero); 681 682 // TODO: handle more standard functions (+ wchar cousins): 683 // - strdup / strndup 684 // - strcpy / strncpy 685 // - strcat / strncat 686 // - memcpy / memmove 687 // - strcat / strncat 688 // - memset 689} 690 691SizeOffsetEvalType 692ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) { 693 return unknown(); 694} 695 696SizeOffsetEvalType 697ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) { 698 return unknown(); 699} 700 701SizeOffsetEvalType 702ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) { 703 SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand()); 704 if (!bothKnown(PtrData)) 705 return unknown(); 706 707 Value *Offset = EmitGEPOffset(&Builder, *TD, &GEP, /*NoAssumptions=*/true); 708 Offset = Builder.CreateAdd(PtrData.second, Offset); 709 return std::make_pair(PtrData.first, Offset); 710} 711 712SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) { 713 // clueless 714 return unknown(); 715} 716 717SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) { 718 return unknown(); 719} 720 721SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) { 722 // create 2 PHIs: one for size and another for offset 723 PHINode *SizePHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues()); 724 PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues()); 725 726 // insert right away in the cache to handle recursive PHIs 727 CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI); 728 729 // compute offset/size for each PHI incoming pointer 730 for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) { 731 Builder.SetInsertPoint(PHI.getIncomingBlock(i)->getFirstInsertionPt()); 732 SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i)); 733 734 if (!bothKnown(EdgeData)) { 735 OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy)); 736 OffsetPHI->eraseFromParent(); 737 SizePHI->replaceAllUsesWith(UndefValue::get(IntTy)); 738 SizePHI->eraseFromParent(); 739 return unknown(); 740 } 741 SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i)); 742 OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i)); 743 } 744 745 Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp; 746 if ((Tmp = SizePHI->hasConstantValue())) { 747 Size = Tmp; 748 SizePHI->replaceAllUsesWith(Size); 749 SizePHI->eraseFromParent(); 750 } 751 if ((Tmp = OffsetPHI->hasConstantValue())) { 752 Offset = Tmp; 753 OffsetPHI->replaceAllUsesWith(Offset); 754 OffsetPHI->eraseFromParent(); 755 } 756 return std::make_pair(Size, Offset); 757} 758 759SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) { 760 SizeOffsetEvalType TrueSide = compute_(I.getTrueValue()); 761 SizeOffsetEvalType FalseSide = compute_(I.getFalseValue()); 762 763 if (!bothKnown(TrueSide) || !bothKnown(FalseSide)) 764 return unknown(); 765 if (TrueSide == FalseSide) 766 return TrueSide; 767 768 Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first, 769 FalseSide.first); 770 Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second, 771 FalseSide.second); 772 return std::make_pair(Size, Offset); 773} 774 775SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) { 776 DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I <<'\n'); 777 return unknown(); 778} 779