MemoryBuiltins.cpp revision 36b56886974eae4f9c5ebc96befd3e7bfe5de338
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/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/Target/TargetLibraryInfo.h" 30#include "llvm/Transforms/Utils/Local.h" 31using namespace llvm; 32 33enum AllocType { 34 OpNewLike = 1<<0, // allocates; never returns null 35 MallocLike = 1<<1 | OpNewLike, // allocates; may return null 36 CallocLike = 1<<2, // allocates + bzero 37 ReallocLike = 1<<3, // reallocates 38 StrDupLike = 1<<4, 39 AllocLike = MallocLike | CallocLike | StrDupLike, 40 AnyAlloc = AllocLike | ReallocLike 41}; 42 43struct AllocFnsTy { 44 LibFunc::Func Func; 45 AllocType AllocTy; 46 unsigned char NumParams; 47 // First and Second size parameters (or -1 if unused) 48 signed char FstParam, SndParam; 49}; 50 51// FIXME: certain users need more information. E.g., SimplifyLibCalls needs to 52// know which functions are nounwind, noalias, nocapture parameters, etc. 53static const AllocFnsTy AllocationFnData[] = { 54 {LibFunc::malloc, MallocLike, 1, 0, -1}, 55 {LibFunc::valloc, MallocLike, 1, 0, -1}, 56 {LibFunc::Znwj, OpNewLike, 1, 0, -1}, // new(unsigned int) 57 {LibFunc::ZnwjRKSt9nothrow_t, MallocLike, 2, 0, -1}, // new(unsigned int, nothrow) 58 {LibFunc::Znwm, OpNewLike, 1, 0, -1}, // new(unsigned long) 59 {LibFunc::ZnwmRKSt9nothrow_t, MallocLike, 2, 0, -1}, // new(unsigned long, nothrow) 60 {LibFunc::Znaj, OpNewLike, 1, 0, -1}, // new[](unsigned int) 61 {LibFunc::ZnajRKSt9nothrow_t, MallocLike, 2, 0, -1}, // new[](unsigned int, nothrow) 62 {LibFunc::Znam, OpNewLike, 1, 0, -1}, // new[](unsigned long) 63 {LibFunc::ZnamRKSt9nothrow_t, MallocLike, 2, 0, -1}, // new[](unsigned long, nothrow) 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 // TODO: Handle "int posix_memalign(void **, size_t, size_t)" 70}; 71 72 73static Function *getCalledFunction(const Value *V, bool LookThroughBitCast) { 74 if (LookThroughBitCast) 75 V = V->stripPointerCasts(); 76 77 CallSite CS(const_cast<Value*>(V)); 78 if (!CS.getInstruction()) 79 return 0; 80 81 if (CS.isNoBuiltin()) 82 return 0; 83 84 Function *Callee = CS.getCalledFunction(); 85 if (!Callee || !Callee->isDeclaration()) 86 return 0; 87 return Callee; 88} 89 90/// \brief Returns the allocation data for the given value if it is a call to a 91/// known allocation function, and NULL otherwise. 92static const AllocFnsTy *getAllocationData(const Value *V, AllocType AllocTy, 93 const TargetLibraryInfo *TLI, 94 bool LookThroughBitCast = false) { 95 // Skip intrinsics 96 if (isa<IntrinsicInst>(V)) 97 return 0; 98 99 Function *Callee = getCalledFunction(V, LookThroughBitCast); 100 if (!Callee) 101 return 0; 102 103 // Make sure that the function is available. 104 StringRef FnName = Callee->getName(); 105 LibFunc::Func TLIFn; 106 if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn)) 107 return 0; 108 109 unsigned i = 0; 110 bool found = false; 111 for ( ; i < array_lengthof(AllocationFnData); ++i) { 112 if (AllocationFnData[i].Func == TLIFn) { 113 found = true; 114 break; 115 } 116 } 117 if (!found) 118 return 0; 119 120 const AllocFnsTy *FnData = &AllocationFnData[i]; 121 if ((FnData->AllocTy & AllocTy) != FnData->AllocTy) 122 return 0; 123 124 // Check function prototype. 125 int FstParam = FnData->FstParam; 126 int SndParam = FnData->SndParam; 127 FunctionType *FTy = Callee->getFunctionType(); 128 129 if (FTy->getReturnType() == Type::getInt8PtrTy(FTy->getContext()) && 130 FTy->getNumParams() == FnData->NumParams && 131 (FstParam < 0 || 132 (FTy->getParamType(FstParam)->isIntegerTy(32) || 133 FTy->getParamType(FstParam)->isIntegerTy(64))) && 134 (SndParam < 0 || 135 FTy->getParamType(SndParam)->isIntegerTy(32) || 136 FTy->getParamType(SndParam)->isIntegerTy(64))) 137 return FnData; 138 return 0; 139} 140 141static bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) { 142 ImmutableCallSite CS(LookThroughBitCast ? V->stripPointerCasts() : V); 143 return CS && CS.hasFnAttr(Attribute::NoAlias); 144} 145 146 147/// \brief Tests if a value is a call or invoke to a library function that 148/// allocates or reallocates memory (either malloc, calloc, realloc, or strdup 149/// like). 150bool llvm::isAllocationFn(const Value *V, const TargetLibraryInfo *TLI, 151 bool LookThroughBitCast) { 152 return getAllocationData(V, AnyAlloc, TLI, LookThroughBitCast); 153} 154 155/// \brief Tests if a value is a call or invoke to a function that returns a 156/// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions). 157bool llvm::isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI, 158 bool LookThroughBitCast) { 159 // it's safe to consider realloc as noalias since accessing the original 160 // pointer is undefined behavior 161 return isAllocationFn(V, TLI, LookThroughBitCast) || 162 hasNoAliasAttr(V, LookThroughBitCast); 163} 164 165/// \brief Tests if a value is a call or invoke to a library function that 166/// allocates uninitialized memory (such as malloc). 167bool llvm::isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI, 168 bool LookThroughBitCast) { 169 return getAllocationData(V, MallocLike, TLI, LookThroughBitCast); 170} 171 172/// \brief Tests if a value is a call or invoke to a library function that 173/// allocates zero-filled memory (such as calloc). 174bool llvm::isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI, 175 bool LookThroughBitCast) { 176 return getAllocationData(V, CallocLike, TLI, LookThroughBitCast); 177} 178 179/// \brief Tests if a value is a call or invoke to a library function that 180/// allocates memory (either malloc, calloc, or strdup like). 181bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI, 182 bool LookThroughBitCast) { 183 return getAllocationData(V, AllocLike, TLI, LookThroughBitCast); 184} 185 186/// \brief Tests if a value is a call or invoke to a library function that 187/// reallocates memory (such as realloc). 188bool llvm::isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI, 189 bool LookThroughBitCast) { 190 return getAllocationData(V, ReallocLike, TLI, LookThroughBitCast); 191} 192 193/// \brief Tests if a value is a call or invoke to a library function that 194/// allocates memory and never returns null (such as operator new). 195bool llvm::isOperatorNewLikeFn(const Value *V, const TargetLibraryInfo *TLI, 196 bool LookThroughBitCast) { 197 return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast); 198} 199 200/// extractMallocCall - Returns the corresponding CallInst if the instruction 201/// is a malloc call. Since CallInst::CreateMalloc() only creates calls, we 202/// ignore InvokeInst here. 203const CallInst *llvm::extractMallocCall(const Value *I, 204 const TargetLibraryInfo *TLI) { 205 return isMallocLikeFn(I, TLI) ? dyn_cast<CallInst>(I) : 0; 206} 207 208static Value *computeArraySize(const CallInst *CI, const DataLayout *DL, 209 const TargetLibraryInfo *TLI, 210 bool LookThroughSExt = false) { 211 if (!CI) 212 return 0; 213 214 // The size of the malloc's result type must be known to determine array size. 215 Type *T = getMallocAllocatedType(CI, TLI); 216 if (!T || !T->isSized() || !DL) 217 return 0; 218 219 unsigned ElementSize = DL->getTypeAllocSize(T); 220 if (StructType *ST = dyn_cast<StructType>(T)) 221 ElementSize = DL->getStructLayout(ST)->getSizeInBytes(); 222 223 // If malloc call's arg can be determined to be a multiple of ElementSize, 224 // return the multiple. Otherwise, return NULL. 225 Value *MallocArg = CI->getArgOperand(0); 226 Value *Multiple = 0; 227 if (ComputeMultiple(MallocArg, ElementSize, Multiple, 228 LookThroughSExt)) 229 return Multiple; 230 231 return 0; 232} 233 234/// isArrayMalloc - Returns the corresponding CallInst if the instruction 235/// is a call to malloc whose array size can be determined and the array size 236/// is not constant 1. Otherwise, return NULL. 237const CallInst *llvm::isArrayMalloc(const Value *I, 238 const DataLayout *DL, 239 const TargetLibraryInfo *TLI) { 240 const CallInst *CI = extractMallocCall(I, TLI); 241 Value *ArraySize = computeArraySize(CI, DL, TLI); 242 243 if (ConstantInt *ConstSize = dyn_cast_or_null<ConstantInt>(ArraySize)) 244 if (ConstSize->isOne()) 245 return CI; 246 247 // CI is a non-array malloc or we can't figure out that it is an array malloc. 248 return 0; 249} 250 251/// getMallocType - Returns the PointerType resulting from the malloc call. 252/// The PointerType depends on the number of bitcast uses of the malloc call: 253/// 0: PointerType is the calls' return type. 254/// 1: PointerType is the bitcast's result type. 255/// >1: Unique PointerType cannot be determined, return NULL. 256PointerType *llvm::getMallocType(const CallInst *CI, 257 const TargetLibraryInfo *TLI) { 258 assert(isMallocLikeFn(CI, TLI) && "getMallocType and not malloc call"); 259 260 PointerType *MallocType = 0; 261 unsigned NumOfBitCastUses = 0; 262 263 // Determine if CallInst has a bitcast use. 264 for (Value::const_user_iterator UI = CI->user_begin(), E = CI->user_end(); 265 UI != E;) 266 if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) { 267 MallocType = cast<PointerType>(BCI->getDestTy()); 268 NumOfBitCastUses++; 269 } 270 271 // Malloc call has 1 bitcast use, so type is the bitcast's destination type. 272 if (NumOfBitCastUses == 1) 273 return MallocType; 274 275 // Malloc call was not bitcast, so type is the malloc function's return type. 276 if (NumOfBitCastUses == 0) 277 return cast<PointerType>(CI->getType()); 278 279 // Type could not be determined. 280 return 0; 281} 282 283/// getMallocAllocatedType - Returns the Type allocated by malloc call. 284/// The Type depends on the number of bitcast uses of the malloc call: 285/// 0: PointerType is the malloc calls' return type. 286/// 1: PointerType is the bitcast's result type. 287/// >1: Unique PointerType cannot be determined, return NULL. 288Type *llvm::getMallocAllocatedType(const CallInst *CI, 289 const TargetLibraryInfo *TLI) { 290 PointerType *PT = getMallocType(CI, TLI); 291 return PT ? PT->getElementType() : 0; 292} 293 294/// getMallocArraySize - Returns the array size of a malloc call. If the 295/// argument passed to malloc is a multiple of the size of the malloced type, 296/// then return that multiple. For non-array mallocs, the multiple is 297/// constant 1. Otherwise, return NULL for mallocs whose array size cannot be 298/// determined. 299Value *llvm::getMallocArraySize(CallInst *CI, const DataLayout *DL, 300 const TargetLibraryInfo *TLI, 301 bool LookThroughSExt) { 302 assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call"); 303 return computeArraySize(CI, DL, TLI, LookThroughSExt); 304} 305 306 307/// extractCallocCall - Returns the corresponding CallInst if the instruction 308/// is a calloc call. 309const CallInst *llvm::extractCallocCall(const Value *I, 310 const TargetLibraryInfo *TLI) { 311 return isCallocLikeFn(I, TLI) ? cast<CallInst>(I) : 0; 312} 313 314 315/// isFreeCall - Returns non-null if the value is a call to the builtin free() 316const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) { 317 const CallInst *CI = dyn_cast<CallInst>(I); 318 if (!CI || isa<IntrinsicInst>(CI)) 319 return 0; 320 Function *Callee = CI->getCalledFunction(); 321 if (Callee == 0 || !Callee->isDeclaration()) 322 return 0; 323 324 StringRef FnName = Callee->getName(); 325 LibFunc::Func TLIFn; 326 if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn)) 327 return 0; 328 329 unsigned ExpectedNumParams; 330 if (TLIFn == LibFunc::free || 331 TLIFn == LibFunc::ZdlPv || // operator delete(void*) 332 TLIFn == LibFunc::ZdaPv) // operator delete[](void*) 333 ExpectedNumParams = 1; 334 else if (TLIFn == LibFunc::ZdlPvRKSt9nothrow_t || // delete(void*, nothrow) 335 TLIFn == LibFunc::ZdaPvRKSt9nothrow_t) // delete[](void*, nothrow) 336 ExpectedNumParams = 2; 337 else 338 return 0; 339 340 // Check free prototype. 341 // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin 342 // attribute will exist. 343 FunctionType *FTy = Callee->getFunctionType(); 344 if (!FTy->getReturnType()->isVoidTy()) 345 return 0; 346 if (FTy->getNumParams() != ExpectedNumParams) 347 return 0; 348 if (FTy->getParamType(0) != Type::getInt8PtrTy(Callee->getContext())) 349 return 0; 350 351 return CI; 352} 353 354 355 356//===----------------------------------------------------------------------===// 357// Utility functions to compute size of objects. 358// 359 360 361/// \brief Compute the size of the object pointed by Ptr. Returns true and the 362/// object size in Size if successful, and false otherwise. 363/// If RoundToAlign is true, then Size is rounded up to the aligment of allocas, 364/// byval arguments, and global variables. 365bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout *DL, 366 const TargetLibraryInfo *TLI, bool RoundToAlign) { 367 if (!DL) 368 return false; 369 370 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 385STATISTIC(ObjectVisitorArgument, 386 "Number of arguments with unsolved size and offset"); 387STATISTIC(ObjectVisitorLoad, 388 "Number of load instructions with unsolved size and offset"); 389 390 391APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Align) { 392 if (RoundToAlign && Align) 393 return APInt(IntTyBits, RoundUpToAlignment(Size.getZExtValue(), Align)); 394 return Size; 395} 396 397ObjectSizeOffsetVisitor::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 406SizeOffsetType 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)) 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 443SizeOffsetType 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 459SizeOffsetType 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 470SizeOffsetType 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 520SizeOffsetType 521ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull&) { 522 return std::make_pair(Zero, Zero); 523} 524 525SizeOffsetType 526ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) { 527 return unknown(); 528} 529 530SizeOffsetType 531ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) { 532 // Easy cases were already folded by previous passes. 533 return unknown(); 534} 535 536SizeOffsetType 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 545SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) { 546 if (GA.mayBeOverridden()) 547 return unknown(); 548 return compute(GA.getAliasee()); 549} 550 551SizeOffsetType 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 559SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) { 560 // clueless 561 return unknown(); 562} 563 564SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) { 565 ++ObjectVisitorLoad; 566 return unknown(); 567} 568 569SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) { 570 // too complex to analyze statically. 571 return unknown(); 572} 573 574SizeOffsetType 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 582SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) { 583 return std::make_pair(Zero, Zero); 584} 585 586SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) { 587 DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I << '\n'); 588 return unknown(); 589} 590 591ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(const DataLayout *DL, 592 const TargetLibraryInfo *TLI, 593 LLVMContext &Context, 594 bool RoundToAlign) 595: DL(DL), TLI(TLI), Context(Context), Builder(Context, TargetFolder(DL)), 596 RoundToAlign(RoundToAlign) { 597 // IntTy and Zero must be set for each compute() since the address space may 598 // be different for later objects. 599} 600 601SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) { 602 // XXX - Are vectors of pointers possible here? 603 IntTy = cast<IntegerType>(DL->getIntPtrType(V->getType())); 604 Zero = ConstantInt::get(IntTy, 0); 605 606 SizeOffsetEvalType Result = compute_(V); 607 608 if (!bothKnown(Result)) { 609 // erase everything that was computed in this iteration from the cache, so 610 // that no dangling references are left behind. We could be a bit smarter if 611 // we kept a dependency graph. It's probably not worth the complexity. 612 for (PtrSetTy::iterator I=SeenVals.begin(), E=SeenVals.end(); I != E; ++I) { 613 CacheMapTy::iterator CacheIt = CacheMap.find(*I); 614 // non-computable results can be safely cached 615 if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second)) 616 CacheMap.erase(CacheIt); 617 } 618 } 619 620 SeenVals.clear(); 621 return Result; 622} 623 624SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) { 625 ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, RoundToAlign); 626 SizeOffsetType Const = Visitor.compute(V); 627 if (Visitor.bothKnown(Const)) 628 return std::make_pair(ConstantInt::get(Context, Const.first), 629 ConstantInt::get(Context, Const.second)); 630 631 V = V->stripPointerCasts(); 632 633 // check cache 634 CacheMapTy::iterator CacheIt = CacheMap.find(V); 635 if (CacheIt != CacheMap.end()) 636 return CacheIt->second; 637 638 // always generate code immediately before the instruction being 639 // processed, so that the generated code dominates the same BBs 640 Instruction *PrevInsertPoint = Builder.GetInsertPoint(); 641 if (Instruction *I = dyn_cast<Instruction>(V)) 642 Builder.SetInsertPoint(I); 643 644 // now compute the size and offset 645 SizeOffsetEvalType Result; 646 647 // Record the pointers that were handled in this run, so that they can be 648 // cleaned later if something fails. We also use this set to break cycles that 649 // can occur in dead code. 650 if (!SeenVals.insert(V)) { 651 Result = unknown(); 652 } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { 653 Result = visitGEPOperator(*GEP); 654 } else if (Instruction *I = dyn_cast<Instruction>(V)) { 655 Result = visit(*I); 656 } else if (isa<Argument>(V) || 657 (isa<ConstantExpr>(V) && 658 cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) || 659 isa<GlobalAlias>(V) || 660 isa<GlobalVariable>(V)) { 661 // ignore values where we cannot do more than what ObjectSizeVisitor can 662 Result = unknown(); 663 } else { 664 DEBUG(dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: " 665 << *V << '\n'); 666 Result = unknown(); 667 } 668 669 if (PrevInsertPoint) 670 Builder.SetInsertPoint(PrevInsertPoint); 671 672 // Don't reuse CacheIt since it may be invalid at this point. 673 CacheMap[V] = Result; 674 return Result; 675} 676 677SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) { 678 if (!I.getAllocatedType()->isSized()) 679 return unknown(); 680 681 // must be a VLA 682 assert(I.isArrayAllocation()); 683 Value *ArraySize = I.getArraySize(); 684 Value *Size = ConstantInt::get(ArraySize->getType(), 685 DL->getTypeAllocSize(I.getAllocatedType())); 686 Size = Builder.CreateMul(Size, ArraySize); 687 return std::make_pair(Size, Zero); 688} 689 690SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) { 691 const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc, 692 TLI); 693 if (!FnData) 694 return unknown(); 695 696 // handle strdup-like functions separately 697 if (FnData->AllocTy == StrDupLike) { 698 // TODO 699 return unknown(); 700 } 701 702 Value *FirstArg = CS.getArgument(FnData->FstParam); 703 FirstArg = Builder.CreateZExt(FirstArg, IntTy); 704 if (FnData->SndParam < 0) 705 return std::make_pair(FirstArg, Zero); 706 707 Value *SecondArg = CS.getArgument(FnData->SndParam); 708 SecondArg = Builder.CreateZExt(SecondArg, IntTy); 709 Value *Size = Builder.CreateMul(FirstArg, SecondArg); 710 return std::make_pair(Size, Zero); 711 712 // TODO: handle more standard functions (+ wchar cousins): 713 // - strdup / strndup 714 // - strcpy / strncpy 715 // - strcat / strncat 716 // - memcpy / memmove 717 // - strcat / strncat 718 // - memset 719} 720 721SizeOffsetEvalType 722ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) { 723 return unknown(); 724} 725 726SizeOffsetEvalType 727ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) { 728 return unknown(); 729} 730 731SizeOffsetEvalType 732ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) { 733 SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand()); 734 if (!bothKnown(PtrData)) 735 return unknown(); 736 737 Value *Offset = EmitGEPOffset(&Builder, *DL, &GEP, /*NoAssumptions=*/true); 738 Offset = Builder.CreateAdd(PtrData.second, Offset); 739 return std::make_pair(PtrData.first, Offset); 740} 741 742SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) { 743 // clueless 744 return unknown(); 745} 746 747SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) { 748 return unknown(); 749} 750 751SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) { 752 // create 2 PHIs: one for size and another for offset 753 PHINode *SizePHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues()); 754 PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues()); 755 756 // insert right away in the cache to handle recursive PHIs 757 CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI); 758 759 // compute offset/size for each PHI incoming pointer 760 for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) { 761 Builder.SetInsertPoint(PHI.getIncomingBlock(i)->getFirstInsertionPt()); 762 SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i)); 763 764 if (!bothKnown(EdgeData)) { 765 OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy)); 766 OffsetPHI->eraseFromParent(); 767 SizePHI->replaceAllUsesWith(UndefValue::get(IntTy)); 768 SizePHI->eraseFromParent(); 769 return unknown(); 770 } 771 SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i)); 772 OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i)); 773 } 774 775 Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp; 776 if ((Tmp = SizePHI->hasConstantValue())) { 777 Size = Tmp; 778 SizePHI->replaceAllUsesWith(Size); 779 SizePHI->eraseFromParent(); 780 } 781 if ((Tmp = OffsetPHI->hasConstantValue())) { 782 Offset = Tmp; 783 OffsetPHI->replaceAllUsesWith(Offset); 784 OffsetPHI->eraseFromParent(); 785 } 786 return std::make_pair(Size, Offset); 787} 788 789SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) { 790 SizeOffsetEvalType TrueSide = compute_(I.getTrueValue()); 791 SizeOffsetEvalType FalseSide = compute_(I.getFalseValue()); 792 793 if (!bothKnown(TrueSide) || !bothKnown(FalseSide)) 794 return unknown(); 795 if (TrueSide == FalseSide) 796 return TrueSide; 797 798 Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first, 799 FalseSide.first); 800 Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second, 801 FalseSide.second); 802 return std::make_pair(Size, Offset); 803} 804 805SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) { 806 DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I <<'\n'); 807 return unknown(); 808} 809