1//===------ MemoryBuiltins.cpp - Identify calls to memory builtins --------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This family of functions identifies calls to builtin functions that allocate
11// or free memory.
12//
13//===----------------------------------------------------------------------===//
14
15#include "llvm/Analysis/MemoryBuiltins.h"
16#include "llvm/ADT/STLExtras.h"
17#include "llvm/ADT/Statistic.h"
18#include "llvm/Analysis/TargetLibraryInfo.h"
19#include "llvm/Analysis/ValueTracking.h"
20#include "llvm/IR/DataLayout.h"
21#include "llvm/IR/GlobalVariable.h"
22#include "llvm/IR/Instructions.h"
23#include "llvm/IR/Intrinsics.h"
24#include "llvm/IR/Metadata.h"
25#include "llvm/IR/Module.h"
26#include "llvm/Support/Debug.h"
27#include "llvm/Support/MathExtras.h"
28#include "llvm/Support/raw_ostream.h"
29#include "llvm/Transforms/Utils/Local.h"
30using namespace llvm;
31
32#define DEBUG_TYPE "memory-builtins"
33
34enum AllocType {
35  OpNewLike          = 1<<0, // allocates; never returns null
36  MallocLike         = 1<<1 | OpNewLike, // allocates; may return null
37  CallocLike         = 1<<2, // allocates + bzero
38  ReallocLike        = 1<<3, // reallocates
39  StrDupLike         = 1<<4,
40  AllocLike          = MallocLike | CallocLike | StrDupLike,
41  AnyAlloc           = AllocLike | ReallocLike
42};
43
44struct AllocFnsTy {
45  LibFunc::Func Func;
46  AllocType AllocTy;
47  unsigned char NumParams;
48  // First and Second size parameters (or -1 if unused)
49  signed char FstParam, SndParam;
50};
51
52// FIXME: certain users need more information. E.g., SimplifyLibCalls needs to
53// know which functions are nounwind, noalias, nocapture parameters, etc.
54static const AllocFnsTy AllocationFnData[] = {
55  {LibFunc::malloc,              MallocLike,  1, 0,  -1},
56  {LibFunc::valloc,              MallocLike,  1, 0,  -1},
57  {LibFunc::Znwj,                OpNewLike,   1, 0,  -1}, // new(unsigned int)
58  {LibFunc::ZnwjRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new(unsigned int, nothrow)
59  {LibFunc::Znwm,                OpNewLike,   1, 0,  -1}, // new(unsigned long)
60  {LibFunc::ZnwmRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new(unsigned long, nothrow)
61  {LibFunc::Znaj,                OpNewLike,   1, 0,  -1}, // new[](unsigned int)
62  {LibFunc::ZnajRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new[](unsigned int, nothrow)
63  {LibFunc::Znam,                OpNewLike,   1, 0,  -1}, // new[](unsigned long)
64  {LibFunc::ZnamRKSt9nothrow_t,  MallocLike,  2, 0,  -1}, // new[](unsigned long, nothrow)
65  {LibFunc::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  // TODO: Handle "int posix_memalign(void **, size_t, size_t)"
71};
72
73
74static Function *getCalledFunction(const Value *V, bool LookThroughBitCast) {
75  if (LookThroughBitCast)
76    V = V->stripPointerCasts();
77
78  CallSite CS(const_cast<Value*>(V));
79  if (!CS.getInstruction())
80    return nullptr;
81
82  if (CS.isNoBuiltin())
83    return nullptr;
84
85  Function *Callee = CS.getCalledFunction();
86  if (!Callee || !Callee->isDeclaration())
87    return nullptr;
88  return Callee;
89}
90
91/// \brief Returns the allocation data for the given value if it is a call to a
92/// known allocation function, and NULL otherwise.
93static const AllocFnsTy *getAllocationData(const Value *V, AllocType AllocTy,
94                                           const TargetLibraryInfo *TLI,
95                                           bool LookThroughBitCast = false) {
96  // Skip intrinsics
97  if (isa<IntrinsicInst>(V))
98    return nullptr;
99
100  Function *Callee = getCalledFunction(V, LookThroughBitCast);
101  if (!Callee)
102    return nullptr;
103
104  // Make sure that the function is available.
105  StringRef FnName = Callee->getName();
106  LibFunc::Func TLIFn;
107  if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
108    return nullptr;
109
110  unsigned i = 0;
111  bool found = false;
112  for ( ; i < array_lengthof(AllocationFnData); ++i) {
113    if (AllocationFnData[i].Func == TLIFn) {
114      found = true;
115      break;
116    }
117  }
118  if (!found)
119    return nullptr;
120
121  const AllocFnsTy *FnData = &AllocationFnData[i];
122  if ((FnData->AllocTy & AllocTy) != FnData->AllocTy)
123    return nullptr;
124
125  // Check function prototype.
126  int FstParam = FnData->FstParam;
127  int SndParam = FnData->SndParam;
128  FunctionType *FTy = Callee->getFunctionType();
129
130  if (FTy->getReturnType() == Type::getInt8PtrTy(FTy->getContext()) &&
131      FTy->getNumParams() == FnData->NumParams &&
132      (FstParam < 0 ||
133       (FTy->getParamType(FstParam)->isIntegerTy(32) ||
134        FTy->getParamType(FstParam)->isIntegerTy(64))) &&
135      (SndParam < 0 ||
136       FTy->getParamType(SndParam)->isIntegerTy(32) ||
137       FTy->getParamType(SndParam)->isIntegerTy(64)))
138    return FnData;
139  return nullptr;
140}
141
142static bool hasNoAliasAttr(const Value *V, bool LookThroughBitCast) {
143  ImmutableCallSite CS(LookThroughBitCast ? V->stripPointerCasts() : V);
144  return CS && CS.hasFnAttr(Attribute::NoAlias);
145}
146
147
148/// \brief Tests if a value is a call or invoke to a library function that
149/// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
150/// like).
151bool llvm::isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
152                          bool LookThroughBitCast) {
153  return getAllocationData(V, AnyAlloc, TLI, LookThroughBitCast);
154}
155
156/// \brief Tests if a value is a call or invoke to a function that returns a
157/// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
158bool llvm::isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
159                       bool LookThroughBitCast) {
160  // it's safe to consider realloc as noalias since accessing the original
161  // pointer is undefined behavior
162  return isAllocationFn(V, TLI, LookThroughBitCast) ||
163         hasNoAliasAttr(V, LookThroughBitCast);
164}
165
166/// \brief Tests if a value is a call or invoke to a library function that
167/// allocates uninitialized memory (such as malloc).
168bool llvm::isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
169                          bool LookThroughBitCast) {
170  return getAllocationData(V, MallocLike, TLI, LookThroughBitCast);
171}
172
173/// \brief Tests if a value is a call or invoke to a library function that
174/// allocates zero-filled memory (such as calloc).
175bool llvm::isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
176                          bool LookThroughBitCast) {
177  return getAllocationData(V, CallocLike, TLI, LookThroughBitCast);
178}
179
180/// \brief Tests if a value is a call or invoke to a library function that
181/// allocates memory (either malloc, calloc, or strdup like).
182bool llvm::isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
183                         bool LookThroughBitCast) {
184  return getAllocationData(V, AllocLike, TLI, LookThroughBitCast);
185}
186
187/// \brief Tests if a value is a call or invoke to a library function that
188/// reallocates memory (such as realloc).
189bool llvm::isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
190                           bool LookThroughBitCast) {
191  return getAllocationData(V, ReallocLike, TLI, LookThroughBitCast);
192}
193
194/// \brief Tests if a value is a call or invoke to a library function that
195/// allocates memory and never returns null (such as operator new).
196bool llvm::isOperatorNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
197                               bool LookThroughBitCast) {
198  return getAllocationData(V, OpNewLike, TLI, LookThroughBitCast);
199}
200
201/// extractMallocCall - Returns the corresponding CallInst if the instruction
202/// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
203/// ignore InvokeInst here.
204const CallInst *llvm::extractMallocCall(const Value *I,
205                                        const TargetLibraryInfo *TLI) {
206  return isMallocLikeFn(I, TLI) ? dyn_cast<CallInst>(I) : nullptr;
207}
208
209static Value *computeArraySize(const CallInst *CI, const DataLayout &DL,
210                               const TargetLibraryInfo *TLI,
211                               bool LookThroughSExt = false) {
212  if (!CI)
213    return nullptr;
214
215  // The size of the malloc's result type must be known to determine array size.
216  Type *T = getMallocAllocatedType(CI, TLI);
217  if (!T || !T->isSized())
218    return nullptr;
219
220  unsigned ElementSize = DL.getTypeAllocSize(T);
221  if (StructType *ST = dyn_cast<StructType>(T))
222    ElementSize = DL.getStructLayout(ST)->getSizeInBytes();
223
224  // If malloc call's arg can be determined to be a multiple of ElementSize,
225  // return the multiple.  Otherwise, return NULL.
226  Value *MallocArg = CI->getArgOperand(0);
227  Value *Multiple = nullptr;
228  if (ComputeMultiple(MallocArg, ElementSize, Multiple,
229                      LookThroughSExt))
230    return Multiple;
231
232  return nullptr;
233}
234
235/// getMallocType - Returns the PointerType resulting from the malloc call.
236/// The PointerType depends on the number of bitcast uses of the malloc call:
237///   0: PointerType is the calls' return type.
238///   1: PointerType is the bitcast's result type.
239///  >1: Unique PointerType cannot be determined, return NULL.
240PointerType *llvm::getMallocType(const CallInst *CI,
241                                 const TargetLibraryInfo *TLI) {
242  assert(isMallocLikeFn(CI, TLI) && "getMallocType and not malloc call");
243
244  PointerType *MallocType = nullptr;
245  unsigned NumOfBitCastUses = 0;
246
247  // Determine if CallInst has a bitcast use.
248  for (Value::const_user_iterator UI = CI->user_begin(), E = CI->user_end();
249       UI != E;)
250    if (const BitCastInst *BCI = dyn_cast<BitCastInst>(*UI++)) {
251      MallocType = cast<PointerType>(BCI->getDestTy());
252      NumOfBitCastUses++;
253    }
254
255  // Malloc call has 1 bitcast use, so type is the bitcast's destination type.
256  if (NumOfBitCastUses == 1)
257    return MallocType;
258
259  // Malloc call was not bitcast, so type is the malloc function's return type.
260  if (NumOfBitCastUses == 0)
261    return cast<PointerType>(CI->getType());
262
263  // Type could not be determined.
264  return nullptr;
265}
266
267/// getMallocAllocatedType - Returns the Type allocated by malloc call.
268/// The Type depends on the number of bitcast uses of the malloc call:
269///   0: PointerType is the malloc calls' return type.
270///   1: PointerType is the bitcast's result type.
271///  >1: Unique PointerType cannot be determined, return NULL.
272Type *llvm::getMallocAllocatedType(const CallInst *CI,
273                                   const TargetLibraryInfo *TLI) {
274  PointerType *PT = getMallocType(CI, TLI);
275  return PT ? PT->getElementType() : nullptr;
276}
277
278/// getMallocArraySize - Returns the array size of a malloc call.  If the
279/// argument passed to malloc is a multiple of the size of the malloced type,
280/// then return that multiple.  For non-array mallocs, the multiple is
281/// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
282/// determined.
283Value *llvm::getMallocArraySize(CallInst *CI, const DataLayout &DL,
284                                const TargetLibraryInfo *TLI,
285                                bool LookThroughSExt) {
286  assert(isMallocLikeFn(CI, TLI) && "getMallocArraySize and not malloc call");
287  return computeArraySize(CI, DL, TLI, LookThroughSExt);
288}
289
290
291/// extractCallocCall - Returns the corresponding CallInst if the instruction
292/// is a calloc call.
293const CallInst *llvm::extractCallocCall(const Value *I,
294                                        const TargetLibraryInfo *TLI) {
295  return isCallocLikeFn(I, TLI) ? cast<CallInst>(I) : nullptr;
296}
297
298
299/// isFreeCall - Returns non-null if the value is a call to the builtin free()
300const CallInst *llvm::isFreeCall(const Value *I, const TargetLibraryInfo *TLI) {
301  const CallInst *CI = dyn_cast<CallInst>(I);
302  if (!CI || isa<IntrinsicInst>(CI))
303    return nullptr;
304  Function *Callee = CI->getCalledFunction();
305  if (Callee == nullptr)
306    return nullptr;
307
308  StringRef FnName = Callee->getName();
309  LibFunc::Func TLIFn;
310  if (!TLI || !TLI->getLibFunc(FnName, TLIFn) || !TLI->has(TLIFn))
311    return nullptr;
312
313  unsigned ExpectedNumParams;
314  if (TLIFn == LibFunc::free ||
315      TLIFn == LibFunc::ZdlPv || // operator delete(void*)
316      TLIFn == LibFunc::ZdaPv)   // operator delete[](void*)
317    ExpectedNumParams = 1;
318  else if (TLIFn == LibFunc::ZdlPvj ||              // delete(void*, uint)
319           TLIFn == LibFunc::ZdlPvm ||              // delete(void*, ulong)
320           TLIFn == LibFunc::ZdlPvRKSt9nothrow_t || // delete(void*, nothrow)
321           TLIFn == LibFunc::ZdaPvj ||              // delete[](void*, uint)
322           TLIFn == LibFunc::ZdaPvm ||              // delete[](void*, ulong)
323           TLIFn == LibFunc::ZdaPvRKSt9nothrow_t)   // delete[](void*, nothrow)
324    ExpectedNumParams = 2;
325  else
326    return nullptr;
327
328  // Check free prototype.
329  // FIXME: workaround for PR5130, this will be obsolete when a nobuiltin
330  // attribute will exist.
331  FunctionType *FTy = Callee->getFunctionType();
332  if (!FTy->getReturnType()->isVoidTy())
333    return nullptr;
334  if (FTy->getNumParams() != ExpectedNumParams)
335    return nullptr;
336  if (FTy->getParamType(0) != Type::getInt8PtrTy(Callee->getContext()))
337    return nullptr;
338
339  return CI;
340}
341
342
343
344//===----------------------------------------------------------------------===//
345//  Utility functions to compute size of objects.
346//
347
348
349/// \brief Compute the size of the object pointed by Ptr. Returns true and the
350/// object size in Size if successful, and false otherwise.
351/// If RoundToAlign is true, then Size is rounded up to the aligment of allocas,
352/// byval arguments, and global variables.
353bool llvm::getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
354                         const TargetLibraryInfo *TLI, bool RoundToAlign) {
355  ObjectSizeOffsetVisitor Visitor(DL, TLI, Ptr->getContext(), RoundToAlign);
356  SizeOffsetType Data = Visitor.compute(const_cast<Value*>(Ptr));
357  if (!Visitor.bothKnown(Data))
358    return false;
359
360  APInt ObjSize = Data.first, Offset = Data.second;
361  // check for overflow
362  if (Offset.slt(0) || ObjSize.ult(Offset))
363    Size = 0;
364  else
365    Size = (ObjSize - Offset).getZExtValue();
366  return true;
367}
368
369
370STATISTIC(ObjectVisitorArgument,
371          "Number of arguments with unsolved size and offset");
372STATISTIC(ObjectVisitorLoad,
373          "Number of load instructions with unsolved size and offset");
374
375
376APInt ObjectSizeOffsetVisitor::align(APInt Size, uint64_t Align) {
377  if (RoundToAlign && Align)
378    return APInt(IntTyBits, RoundUpToAlignment(Size.getZExtValue(), Align));
379  return Size;
380}
381
382ObjectSizeOffsetVisitor::ObjectSizeOffsetVisitor(const DataLayout &DL,
383                                                 const TargetLibraryInfo *TLI,
384                                                 LLVMContext &Context,
385                                                 bool RoundToAlign)
386    : DL(DL), TLI(TLI), RoundToAlign(RoundToAlign) {
387  // Pointer size must be rechecked for each object visited since it could have
388  // a different address space.
389}
390
391SizeOffsetType ObjectSizeOffsetVisitor::compute(Value *V) {
392  IntTyBits = DL.getPointerTypeSizeInBits(V->getType());
393  Zero = APInt::getNullValue(IntTyBits);
394
395  V = V->stripPointerCasts();
396  if (Instruction *I = dyn_cast<Instruction>(V)) {
397    // If we have already seen this instruction, bail out. Cycles can happen in
398    // unreachable code after constant propagation.
399    if (!SeenInsts.insert(I).second)
400      return unknown();
401
402    if (GEPOperator *GEP = dyn_cast<GEPOperator>(V))
403      return visitGEPOperator(*GEP);
404    return visit(*I);
405  }
406  if (Argument *A = dyn_cast<Argument>(V))
407    return visitArgument(*A);
408  if (ConstantPointerNull *P = dyn_cast<ConstantPointerNull>(V))
409    return visitConstantPointerNull(*P);
410  if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V))
411    return visitGlobalAlias(*GA);
412  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V))
413    return visitGlobalVariable(*GV);
414  if (UndefValue *UV = dyn_cast<UndefValue>(V))
415    return visitUndefValue(*UV);
416  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) {
417    if (CE->getOpcode() == Instruction::IntToPtr)
418      return unknown(); // clueless
419    if (CE->getOpcode() == Instruction::GetElementPtr)
420      return visitGEPOperator(cast<GEPOperator>(*CE));
421  }
422
423  DEBUG(dbgs() << "ObjectSizeOffsetVisitor::compute() unhandled value: " << *V
424        << '\n');
425  return unknown();
426}
427
428SizeOffsetType ObjectSizeOffsetVisitor::visitAllocaInst(AllocaInst &I) {
429  if (!I.getAllocatedType()->isSized())
430    return unknown();
431
432  APInt Size(IntTyBits, DL.getTypeAllocSize(I.getAllocatedType()));
433  if (!I.isArrayAllocation())
434    return std::make_pair(align(Size, I.getAlignment()), Zero);
435
436  Value *ArraySize = I.getArraySize();
437  if (const ConstantInt *C = dyn_cast<ConstantInt>(ArraySize)) {
438    Size *= C->getValue().zextOrSelf(IntTyBits);
439    return std::make_pair(align(Size, I.getAlignment()), Zero);
440  }
441  return unknown();
442}
443
444SizeOffsetType ObjectSizeOffsetVisitor::visitArgument(Argument &A) {
445  // no interprocedural analysis is done at the moment
446  if (!A.hasByValOrInAllocaAttr()) {
447    ++ObjectVisitorArgument;
448    return unknown();
449  }
450  PointerType *PT = cast<PointerType>(A.getType());
451  APInt Size(IntTyBits, DL.getTypeAllocSize(PT->getElementType()));
452  return std::make_pair(align(Size, A.getParamAlignment()), Zero);
453}
454
455SizeOffsetType ObjectSizeOffsetVisitor::visitCallSite(CallSite CS) {
456  const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc,
457                                               TLI);
458  if (!FnData)
459    return unknown();
460
461  // handle strdup-like functions separately
462  if (FnData->AllocTy == StrDupLike) {
463    APInt Size(IntTyBits, GetStringLength(CS.getArgument(0)));
464    if (!Size)
465      return unknown();
466
467    // strndup limits strlen
468    if (FnData->FstParam > 0) {
469      ConstantInt *Arg= dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
470      if (!Arg)
471        return unknown();
472
473      APInt MaxSize = Arg->getValue().zextOrSelf(IntTyBits);
474      if (Size.ugt(MaxSize))
475        Size = MaxSize + 1;
476    }
477    return std::make_pair(Size, Zero);
478  }
479
480  ConstantInt *Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->FstParam));
481  if (!Arg)
482    return unknown();
483
484  APInt Size = Arg->getValue().zextOrSelf(IntTyBits);
485  // size determined by just 1 parameter
486  if (FnData->SndParam < 0)
487    return std::make_pair(Size, Zero);
488
489  Arg = dyn_cast<ConstantInt>(CS.getArgument(FnData->SndParam));
490  if (!Arg)
491    return unknown();
492
493  Size *= Arg->getValue().zextOrSelf(IntTyBits);
494  return std::make_pair(Size, Zero);
495
496  // TODO: handle more standard functions (+ wchar cousins):
497  // - strdup / strndup
498  // - strcpy / strncpy
499  // - strcat / strncat
500  // - memcpy / memmove
501  // - strcat / strncat
502  // - memset
503}
504
505SizeOffsetType
506ObjectSizeOffsetVisitor::visitConstantPointerNull(ConstantPointerNull&) {
507  return std::make_pair(Zero, Zero);
508}
509
510SizeOffsetType
511ObjectSizeOffsetVisitor::visitExtractElementInst(ExtractElementInst&) {
512  return unknown();
513}
514
515SizeOffsetType
516ObjectSizeOffsetVisitor::visitExtractValueInst(ExtractValueInst&) {
517  // Easy cases were already folded by previous passes.
518  return unknown();
519}
520
521SizeOffsetType ObjectSizeOffsetVisitor::visitGEPOperator(GEPOperator &GEP) {
522  SizeOffsetType PtrData = compute(GEP.getPointerOperand());
523  APInt Offset(IntTyBits, 0);
524  if (!bothKnown(PtrData) || !GEP.accumulateConstantOffset(DL, Offset))
525    return unknown();
526
527  return std::make_pair(PtrData.first, PtrData.second + Offset);
528}
529
530SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalAlias(GlobalAlias &GA) {
531  if (GA.mayBeOverridden())
532    return unknown();
533  return compute(GA.getAliasee());
534}
535
536SizeOffsetType ObjectSizeOffsetVisitor::visitGlobalVariable(GlobalVariable &GV){
537  if (!GV.hasDefinitiveInitializer())
538    return unknown();
539
540  APInt Size(IntTyBits, DL.getTypeAllocSize(GV.getType()->getElementType()));
541  return std::make_pair(align(Size, GV.getAlignment()), Zero);
542}
543
544SizeOffsetType ObjectSizeOffsetVisitor::visitIntToPtrInst(IntToPtrInst&) {
545  // clueless
546  return unknown();
547}
548
549SizeOffsetType ObjectSizeOffsetVisitor::visitLoadInst(LoadInst&) {
550  ++ObjectVisitorLoad;
551  return unknown();
552}
553
554SizeOffsetType ObjectSizeOffsetVisitor::visitPHINode(PHINode&) {
555  // too complex to analyze statically.
556  return unknown();
557}
558
559SizeOffsetType ObjectSizeOffsetVisitor::visitSelectInst(SelectInst &I) {
560  SizeOffsetType TrueSide  = compute(I.getTrueValue());
561  SizeOffsetType FalseSide = compute(I.getFalseValue());
562  if (bothKnown(TrueSide) && bothKnown(FalseSide) && TrueSide == FalseSide)
563    return TrueSide;
564  return unknown();
565}
566
567SizeOffsetType ObjectSizeOffsetVisitor::visitUndefValue(UndefValue&) {
568  return std::make_pair(Zero, Zero);
569}
570
571SizeOffsetType ObjectSizeOffsetVisitor::visitInstruction(Instruction &I) {
572  DEBUG(dbgs() << "ObjectSizeOffsetVisitor unknown instruction:" << I << '\n');
573  return unknown();
574}
575
576ObjectSizeOffsetEvaluator::ObjectSizeOffsetEvaluator(
577    const DataLayout &DL, const TargetLibraryInfo *TLI, LLVMContext &Context,
578    bool RoundToAlign)
579    : DL(DL), TLI(TLI), Context(Context), Builder(Context, TargetFolder(DL)),
580      RoundToAlign(RoundToAlign) {
581  // IntTy and Zero must be set for each compute() since the address space may
582  // be different for later objects.
583}
584
585SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute(Value *V) {
586  // XXX - Are vectors of pointers possible here?
587  IntTy = cast<IntegerType>(DL.getIntPtrType(V->getType()));
588  Zero = ConstantInt::get(IntTy, 0);
589
590  SizeOffsetEvalType Result = compute_(V);
591
592  if (!bothKnown(Result)) {
593    // erase everything that was computed in this iteration from the cache, so
594    // that no dangling references are left behind. We could be a bit smarter if
595    // we kept a dependency graph. It's probably not worth the complexity.
596    for (PtrSetTy::iterator I=SeenVals.begin(), E=SeenVals.end(); I != E; ++I) {
597      CacheMapTy::iterator CacheIt = CacheMap.find(*I);
598      // non-computable results can be safely cached
599      if (CacheIt != CacheMap.end() && anyKnown(CacheIt->second))
600        CacheMap.erase(CacheIt);
601    }
602  }
603
604  SeenVals.clear();
605  return Result;
606}
607
608SizeOffsetEvalType ObjectSizeOffsetEvaluator::compute_(Value *V) {
609  ObjectSizeOffsetVisitor Visitor(DL, TLI, Context, RoundToAlign);
610  SizeOffsetType Const = Visitor.compute(V);
611  if (Visitor.bothKnown(Const))
612    return std::make_pair(ConstantInt::get(Context, Const.first),
613                          ConstantInt::get(Context, Const.second));
614
615  V = V->stripPointerCasts();
616
617  // check cache
618  CacheMapTy::iterator CacheIt = CacheMap.find(V);
619  if (CacheIt != CacheMap.end())
620    return CacheIt->second;
621
622  // always generate code immediately before the instruction being
623  // processed, so that the generated code dominates the same BBs
624  Instruction *PrevInsertPoint = Builder.GetInsertPoint();
625  if (Instruction *I = dyn_cast<Instruction>(V))
626    Builder.SetInsertPoint(I);
627
628  // now compute the size and offset
629  SizeOffsetEvalType Result;
630
631  // Record the pointers that were handled in this run, so that they can be
632  // cleaned later if something fails. We also use this set to break cycles that
633  // can occur in dead code.
634  if (!SeenVals.insert(V).second) {
635    Result = unknown();
636  } else if (GEPOperator *GEP = dyn_cast<GEPOperator>(V)) {
637    Result = visitGEPOperator(*GEP);
638  } else if (Instruction *I = dyn_cast<Instruction>(V)) {
639    Result = visit(*I);
640  } else if (isa<Argument>(V) ||
641             (isa<ConstantExpr>(V) &&
642              cast<ConstantExpr>(V)->getOpcode() == Instruction::IntToPtr) ||
643             isa<GlobalAlias>(V) ||
644             isa<GlobalVariable>(V)) {
645    // ignore values where we cannot do more than what ObjectSizeVisitor can
646    Result = unknown();
647  } else {
648    DEBUG(dbgs() << "ObjectSizeOffsetEvaluator::compute() unhandled value: "
649          << *V << '\n');
650    Result = unknown();
651  }
652
653  if (PrevInsertPoint)
654    Builder.SetInsertPoint(PrevInsertPoint);
655
656  // Don't reuse CacheIt since it may be invalid at this point.
657  CacheMap[V] = Result;
658  return Result;
659}
660
661SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitAllocaInst(AllocaInst &I) {
662  if (!I.getAllocatedType()->isSized())
663    return unknown();
664
665  // must be a VLA
666  assert(I.isArrayAllocation());
667  Value *ArraySize = I.getArraySize();
668  Value *Size = ConstantInt::get(ArraySize->getType(),
669                                 DL.getTypeAllocSize(I.getAllocatedType()));
670  Size = Builder.CreateMul(Size, ArraySize);
671  return std::make_pair(Size, Zero);
672}
673
674SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitCallSite(CallSite CS) {
675  const AllocFnsTy *FnData = getAllocationData(CS.getInstruction(), AnyAlloc,
676                                               TLI);
677  if (!FnData)
678    return unknown();
679
680  // handle strdup-like functions separately
681  if (FnData->AllocTy == StrDupLike) {
682    // TODO
683    return unknown();
684  }
685
686  Value *FirstArg = CS.getArgument(FnData->FstParam);
687  FirstArg = Builder.CreateZExt(FirstArg, IntTy);
688  if (FnData->SndParam < 0)
689    return std::make_pair(FirstArg, Zero);
690
691  Value *SecondArg = CS.getArgument(FnData->SndParam);
692  SecondArg = Builder.CreateZExt(SecondArg, IntTy);
693  Value *Size = Builder.CreateMul(FirstArg, SecondArg);
694  return std::make_pair(Size, Zero);
695
696  // TODO: handle more standard functions (+ wchar cousins):
697  // - strdup / strndup
698  // - strcpy / strncpy
699  // - strcat / strncat
700  // - memcpy / memmove
701  // - strcat / strncat
702  // - memset
703}
704
705SizeOffsetEvalType
706ObjectSizeOffsetEvaluator::visitExtractElementInst(ExtractElementInst&) {
707  return unknown();
708}
709
710SizeOffsetEvalType
711ObjectSizeOffsetEvaluator::visitExtractValueInst(ExtractValueInst&) {
712  return unknown();
713}
714
715SizeOffsetEvalType
716ObjectSizeOffsetEvaluator::visitGEPOperator(GEPOperator &GEP) {
717  SizeOffsetEvalType PtrData = compute_(GEP.getPointerOperand());
718  if (!bothKnown(PtrData))
719    return unknown();
720
721  Value *Offset = EmitGEPOffset(&Builder, DL, &GEP, /*NoAssumptions=*/true);
722  Offset = Builder.CreateAdd(PtrData.second, Offset);
723  return std::make_pair(PtrData.first, Offset);
724}
725
726SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitIntToPtrInst(IntToPtrInst&) {
727  // clueless
728  return unknown();
729}
730
731SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitLoadInst(LoadInst&) {
732  return unknown();
733}
734
735SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitPHINode(PHINode &PHI) {
736  // create 2 PHIs: one for size and another for offset
737  PHINode *SizePHI   = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
738  PHINode *OffsetPHI = Builder.CreatePHI(IntTy, PHI.getNumIncomingValues());
739
740  // insert right away in the cache to handle recursive PHIs
741  CacheMap[&PHI] = std::make_pair(SizePHI, OffsetPHI);
742
743  // compute offset/size for each PHI incoming pointer
744  for (unsigned i = 0, e = PHI.getNumIncomingValues(); i != e; ++i) {
745    Builder.SetInsertPoint(PHI.getIncomingBlock(i)->getFirstInsertionPt());
746    SizeOffsetEvalType EdgeData = compute_(PHI.getIncomingValue(i));
747
748    if (!bothKnown(EdgeData)) {
749      OffsetPHI->replaceAllUsesWith(UndefValue::get(IntTy));
750      OffsetPHI->eraseFromParent();
751      SizePHI->replaceAllUsesWith(UndefValue::get(IntTy));
752      SizePHI->eraseFromParent();
753      return unknown();
754    }
755    SizePHI->addIncoming(EdgeData.first, PHI.getIncomingBlock(i));
756    OffsetPHI->addIncoming(EdgeData.second, PHI.getIncomingBlock(i));
757  }
758
759  Value *Size = SizePHI, *Offset = OffsetPHI, *Tmp;
760  if ((Tmp = SizePHI->hasConstantValue())) {
761    Size = Tmp;
762    SizePHI->replaceAllUsesWith(Size);
763    SizePHI->eraseFromParent();
764  }
765  if ((Tmp = OffsetPHI->hasConstantValue())) {
766    Offset = Tmp;
767    OffsetPHI->replaceAllUsesWith(Offset);
768    OffsetPHI->eraseFromParent();
769  }
770  return std::make_pair(Size, Offset);
771}
772
773SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitSelectInst(SelectInst &I) {
774  SizeOffsetEvalType TrueSide  = compute_(I.getTrueValue());
775  SizeOffsetEvalType FalseSide = compute_(I.getFalseValue());
776
777  if (!bothKnown(TrueSide) || !bothKnown(FalseSide))
778    return unknown();
779  if (TrueSide == FalseSide)
780    return TrueSide;
781
782  Value *Size = Builder.CreateSelect(I.getCondition(), TrueSide.first,
783                                     FalseSide.first);
784  Value *Offset = Builder.CreateSelect(I.getCondition(), TrueSide.second,
785                                       FalseSide.second);
786  return std::make_pair(Size, Offset);
787}
788
789SizeOffsetEvalType ObjectSizeOffsetEvaluator::visitInstruction(Instruction &I) {
790  DEBUG(dbgs() << "ObjectSizeOffsetEvaluator unknown instruction:" << I <<'\n');
791  return unknown();
792}
793