MemoryBuiltins.cpp revision d44f9f2ff88cd03e3f944ecdd6373737d5acdb90
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::posix_memalign, MallocLike, 3, 2, -1}, 65 {LibFunc::calloc, CallocLike, 2, 0, 1}, 66 {LibFunc::realloc, ReallocLike, 2, 1, -1}, 67 {LibFunc::reallocf, ReallocLike, 2, 1, -1}, 68 {LibFunc::strdup, StrDupLike, 1, -1, -1}, 69 {LibFunc::strndup, StrDupLike, 2, 1, -1} 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 *TD, 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() || !TD) 217 return 0; 218 219 unsigned ElementSize = TD->getTypeAllocSize(T); 220 if (StructType *ST = dyn_cast<StructType>(T)) 221 ElementSize = TD->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 *TD, 239 const TargetLibraryInfo *TLI) { 240 const CallInst *CI = extractMallocCall(I, TLI); 241 Value *ArraySize = computeArraySize(CI, TD, 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_use_iterator UI = CI->use_begin(), E = CI->use_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 *TD, 300 const TargetLibraryInfo *TLI, 301 bool LookThroughSExt) { 302 assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call"); 303 return computeArraySize(CI, TD, 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 *TD, 366 const TargetLibraryInfo *TLI, bool RoundToAlign) { 367 if (!TD) 368 return false; 369 370 ObjectSizeOffsetVisitor Visitor(TD, 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 *TD, 398 const TargetLibraryInfo *TLI, 399 LLVMContext &Context, 400 bool RoundToAlign) 401: TD(TD), TLI(TLI), RoundToAlign(RoundToAlign) { 402 IntegerType *IntTy = TD->getIntPtrType(Context); 403 IntTyBits = IntTy->getBitWidth(); 404 Zero = APInt::getNullValue(IntTyBits); 405} 406 407SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) { 408 V = V->stripPointerCasts(); 409 if (Instruction *I = dyn_cast<Instruction>(V)) { 410 // If we have already seen this instruction, bail out. Cycles can happen in 411 // unreachable code after constant propagation. 412 if (!SeenInsts.insert(I)) 413 return unknown(); 414 415 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) 416 return visitGEPOperator(*GEP); 417 return visit(*I); 418 } 419 if (Argument *A = dyn_cast<Argument>(V)) 420 return visitArgument(*A); 421 if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V)) 422 return visitConstantPointerNull(*P); 423 if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) 424 return visitGlobalAlias(*GA); 425 if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 426 return visitGlobalVariable(*GV); 427 if (UndefValue *UV = dyn_cast<UndefValue>(V)) 428 return visitUndefValue(*UV); 429 if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) { 430 if (CE->getOpcode() == Instruction::IntToPtr) 431 return unknown(); // clueless 432 if (CE->getOpcode() == Instruction::GetElementPtr) 433 return visitGEPOperator(cast<GEPOperator>(*CE)); 434 } 435 436 DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V 437 << '\n'); 438 return unknown(); 439} 440 441SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) { 442 if (!I.getAllocatedType()->isSized()) 443 return unknown(); 444 445 APInt Size(IntTyBits, TD->getTypeAllocSize(I.getAllocatedType())); 446 if (!I.isArrayAllocation()) 447 return std::make_pair(align(Size, I.getAlignment()), Zero); 448 449 Value *ArraySize = I.getArraySize(); 450 if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) { 451 Size *= C->getValue().zextOrSelf(IntTyBits); 452 return std::make_pair(align(Size, I.getAlignment()), Zero); 453 } 454 return unknown(); 455} 456 457SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) { 458 // no interprocedural analysis is done at the moment 459 if (!A.hasByValAttr()) { 460 ++ObjectVisitorArgument; 461 return unknown(); 462 } 463 PointerType *PT = cast<PointerType>(A.getType()); 464 APInt Size(IntTyBits, TD->getTypeAllocSize(PT->getElementType())); 465 return std::make_pair(align(Size, A.getParamAlignment()), Zero); 466} 467 468SizeOffsetType ObjectSizeOffsetVisitor::visitCallSite(CallSite CS) { 469 const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc, 470 TLI); 471 if (!FnData) 472 return unknown(); 473 474 // handle strdup-like functions separately 475 if (FnData->AllocTy == StrDupLike) { 476 APInt Size(IntTyBits, GetStringLength(CS.getArgument(0))); 477 if (!Size) 478 return unknown(); 479 480 // strndup limits strlen 481 if (FnData->FstParam > 0) { 482 ConstantInt *Arg= dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam)); 483 if (!Arg) 484 return unknown(); 485 486 APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits); 487 if (Size.ugt(MaxSize)) 488 Size = MaxSize + 1; 489 } 490 return std::make_pair(Size, Zero); 491 } 492 493 ConstantInt *Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam)); 494 if (!Arg) 495 return unknown(); 496 497 APInt Size = Arg->getValue().zextOrSelf(IntTyBits); 498 // size determined by just 1 parameter 499 if (FnData->SndParam < 0) 500 return std::make_pair(Size, Zero); 501 502 Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->SndParam)); 503 if (!Arg) 504 return unknown(); 505 506 Size *= Arg->getValue().zextOrSelf(IntTyBits); 507 return std::make_pair(Size, Zero); 508 509 // TODO: handle more standard functions (+ wchar cousins): 510 // - strdup / strndup 511 // - strcpy / strncpy 512 // - strcat / strncat 513 // - memcpy / memmove 514 // - strcat / strncat 515 // - memset 516} 517 518SizeOffsetType 519ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull&) { 520 return std::make_pair(Zero, Zero); 521} 522 523SizeOffsetType 524ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) { 525 return unknown(); 526} 527 528SizeOffsetType 529ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) { 530 // Easy cases were already folded by previous passes. 531 return unknown(); 532} 533 534SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) { 535 SizeOffsetType PtrData = compute(GEP.getPointerOperand()); 536 APInt Offset(IntTyBits, 0); 537 if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(*TD, Offset)) 538 return unknown(); 539 540 return std::make_pair(PtrData.first, PtrData.second + Offset); 541} 542 543SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) { 544 if (GA.mayBeOverridden()) 545 return unknown(); 546 return compute(GA.getAliasee()); 547} 548 549SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){ 550 if (!GV.hasDefinitiveInitializer()) 551 return unknown(); 552 553 APInt Size(IntTyBits, TD->getTypeAllocSize(GV.getType()->getElementType())); 554 return std::make_pair(align(Size, GV.getAlignment()), Zero); 555} 556 557SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) { 558 // clueless 559 return unknown(); 560} 561 562SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) { 563 ++ObjectVisitorLoad; 564 return unknown(); 565} 566 567SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) { 568 // too complex to analyze statically. 569 return unknown(); 570} 571 572SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) { 573 SizeOffsetType TrueSide = compute(I.getTrueValue()); 574 SizeOffsetType FalseSide = compute(I.getFalseValue()); 575 if (bothKnown(TrueSide) && bothKnown(FalseSide) && TrueSide == FalseSide) 576 return TrueSide; 577 return unknown(); 578} 579 580SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) { 581 return std::make_pair(Zero, Zero); 582} 583 584SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) { 585 DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I << '\n'); 586 return unknown(); 587} 588 589 590ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(const DataLayout *TD, 591 const TargetLibraryInfo *TLI, 592 LLVMContext &Context) 593: TD(TD), TLI(TLI), Context(Context), Builder(Context, TargetFolder(TD)) { 594 IntTy = TD->getIntPtrType(Context); 595 Zero = ConstantInt::get(IntTy, 0); 596} 597 598SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) { 599 SizeOffsetEvalType Result = compute_(V); 600 601 if (!bothKnown(Result)) { 602 // erase everything that was computed in this iteration from the cache, so 603 // that no dangling references are left behind. We could be a bit smarter if 604 // we kept a dependency graph. It's probably not worth the complexity. 605 for (PtrSetTy::iterator I=SeenVals.begin(), E=SeenVals.end(); I != E; ++I) { 606 CacheMapTy::iterator CacheIt = CacheMap.find(*I); 607 // non-computable results can be safely cached 608 if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second)) 609 CacheMap.erase(CacheIt); 610 } 611 } 612 613 SeenVals.clear(); 614 return Result; 615} 616 617SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) { 618 ObjectSizeOffsetVisitor Visitor(TD, TLI, Context); 619 SizeOffsetType Const = Visitor.compute(V); 620 if (Visitor.bothKnown(Const)) 621 return std::make_pair(ConstantInt::get(Context, Const.first), 622 ConstantInt::get(Context, Const.second)); 623 624 V = V->stripPointerCasts(); 625 626 // check cache 627 CacheMapTy::iterator CacheIt = CacheMap.find(V); 628 if (CacheIt != CacheMap.end()) 629 return CacheIt->second; 630 631 // always generate code immediately before the instruction being 632 // processed, so that the generated code dominates the same BBs 633 Instruction *PrevInsertPoint = Builder.GetInsertPoint(); 634 if (Instruction *I = dyn_cast<Instruction>(V)) 635 Builder.SetInsertPoint(I); 636 637 // record the pointers that were handled in this run, so that they can be 638 // cleaned later if something fails 639 SeenVals.insert(V); 640 641 // now compute the size and offset 642 SizeOffsetEvalType Result; 643 if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) { 644 Result = visitGEPOperator(*GEP); 645 } else if (Instruction *I = dyn_cast<Instruction>(V)) { 646 Result = visit(*I); 647 } else if (isa<Argument>(V) || 648 (isa<ConstantExpr>(V) && 649 cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) || 650 isa<GlobalAlias>(V) || 651 isa<GlobalVariable>(V)) { 652 // ignore values where we cannot do more than what ObjectSizeVisitor can 653 Result = unknown(); 654 } else { 655 DEBUG(dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: " 656 << *V << '\n'); 657 Result = unknown(); 658 } 659 660 if (PrevInsertPoint) 661 Builder.SetInsertPoint(PrevInsertPoint); 662 663 // Don't reuse CacheIt since it may be invalid at this point. 664 CacheMap[V] = Result; 665 return Result; 666} 667 668SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) { 669 if (!I.getAllocatedType()->isSized()) 670 return unknown(); 671 672 // must be a VLA 673 assert(I.isArrayAllocation()); 674 Value *ArraySize = I.getArraySize(); 675 Value *Size = ConstantInt::get(ArraySize->getType(), 676 TD->getTypeAllocSize(I.getAllocatedType())); 677 Size = Builder.CreateMul(Size, ArraySize); 678 return std::make_pair(Size, Zero); 679} 680 681SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) { 682 const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc, 683 TLI); 684 if (!FnData) 685 return unknown(); 686 687 // handle strdup-like functions separately 688 if (FnData->AllocTy == StrDupLike) { 689 // TODO 690 return unknown(); 691 } 692 693 Value *FirstArg = CS.getArgument(FnData->FstParam); 694 FirstArg = Builder.CreateZExt(FirstArg, IntTy); 695 if (FnData->SndParam < 0) 696 return std::make_pair(FirstArg, Zero); 697 698 Value *SecondArg = CS.getArgument(FnData->SndParam); 699 SecondArg = Builder.CreateZExt(SecondArg, IntTy); 700 Value *Size = Builder.CreateMul(FirstArg, SecondArg); 701 return std::make_pair(Size, Zero); 702 703 // TODO: handle more standard functions (+ wchar cousins): 704 // - strdup / strndup 705 // - strcpy / strncpy 706 // - strcat / strncat 707 // - memcpy / memmove 708 // - strcat / strncat 709 // - memset 710} 711 712SizeOffsetEvalType 713ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) { 714 return unknown(); 715} 716 717SizeOffsetEvalType 718ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) { 719 return unknown(); 720} 721 722SizeOffsetEvalType 723ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) { 724 SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand()); 725 if (!bothKnown(PtrData)) 726 return unknown(); 727 728 Value *Offset = EmitGEPOffset(&Builder, *TD, &GEP, /*NoAssumptions=*/true); 729 Offset = Builder.CreateAdd(PtrData.second, Offset); 730 return std::make_pair(PtrData.first, Offset); 731} 732 733SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) { 734 // clueless 735 return unknown(); 736} 737 738SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) { 739 return unknown(); 740} 741 742SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) { 743 // create 2 PHIs: one for size and another for offset 744 PHINode *SizePHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues()); 745 PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues()); 746 747 // insert right away in the cache to handle recursive PHIs 748 CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI); 749 750 // compute offset/size for each PHI incoming pointer 751 for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) { 752 Builder.SetInsertPoint(PHI.getIncomingBlock(i)->getFirstInsertionPt()); 753 SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i)); 754 755 if (!bothKnown(EdgeData)) { 756 OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy)); 757 OffsetPHI->eraseFromParent(); 758 SizePHI->replaceAllUsesWith(UndefValue::get(IntTy)); 759 SizePHI->eraseFromParent(); 760 return unknown(); 761 } 762 SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i)); 763 OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i)); 764 } 765 766 Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp; 767 if ((Tmp = SizePHI->hasConstantValue())) { 768 Size = Tmp; 769 SizePHI->replaceAllUsesWith(Size); 770 SizePHI->eraseFromParent(); 771 } 772 if ((Tmp = OffsetPHI->hasConstantValue())) { 773 Offset = Tmp; 774 OffsetPHI->replaceAllUsesWith(Offset); 775 OffsetPHI->eraseFromParent(); 776 } 777 return std::make_pair(Size, Offset); 778} 779 780SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) { 781 SizeOffsetEvalType TrueSide = compute_(I.getTrueValue()); 782 SizeOffsetEvalType FalseSide = compute_(I.getFalseValue()); 783 784 if (!bothKnown(TrueSide) || !bothKnown(FalseSide)) 785 return unknown(); 786 if (TrueSide == FalseSide) 787 return TrueSide; 788 789 Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first, 790 FalseSide.first); 791 Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second, 792 FalseSide.second); 793 return std::make_pair(Size, Offset); 794} 795 796SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) { 797 DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I <<'\n'); 798 return unknown(); 799} 800