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1 //===- llvm/Analysis/MemoryBuiltins.h- Calls to memory builtins -*- C++ -*-===//
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 #ifndef LLVM_ANALYSIS_MEMORYBUILTINS_H
16 #define LLVM_ANALYSIS_MEMORYBUILTINS_H
17 
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include "llvm/Analysis/TargetFolder.h"
21 #include "llvm/IR/IRBuilder.h"
22 #include "llvm/IR/InstVisitor.h"
23 #include "llvm/IR/Operator.h"
24 #include "llvm/IR/ValueHandle.h"
25 #include "llvm/Support/DataTypes.h"
26 
27 namespace llvm {
28 class CallInst;
29 class PointerType;
30 class DataLayout;
31 class TargetLibraryInfo;
32 class Type;
33 class Value;
34 
35 enum class ObjSizeMode {
36   Exact = 0,
37   Min = 1,
38   Max = 2
39 };
40 
41 /// \brief Tests if a value is a call or invoke to a library function that
42 /// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
43 /// like).
44 bool isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
45                     bool LookThroughBitCast = false);
46 
47 /// \brief Tests if a value is a call or invoke to a function that returns a
48 /// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
49 bool isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
50                  bool LookThroughBitCast = false);
51 
52 /// \brief Tests if a value is a call or invoke to a library function that
53 /// allocates uninitialized memory (such as malloc).
54 bool isMallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
55                     bool LookThroughBitCast = false);
56 
57 /// \brief Tests if a value is a call or invoke to a library function that
58 /// allocates zero-filled memory (such as calloc).
59 bool isCallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
60                     bool LookThroughBitCast = false);
61 
62 /// \brief Tests if a value is a call or invoke to a library function that
63 /// allocates memory (either malloc, calloc, or strdup like).
64 bool isAllocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
65                    bool LookThroughBitCast = false);
66 
67 //===----------------------------------------------------------------------===//
68 //  malloc Call Utility Functions.
69 //
70 
71 /// extractMallocCall - Returns the corresponding CallInst if the instruction
72 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
73 /// ignore InvokeInst here.
74 const CallInst *extractMallocCall(const Value *I, const TargetLibraryInfo *TLI);
extractMallocCall(Value * I,const TargetLibraryInfo * TLI)75 static inline CallInst *extractMallocCall(Value *I,
76                                           const TargetLibraryInfo *TLI) {
77   return const_cast<CallInst*>(extractMallocCall((const Value*)I, TLI));
78 }
79 
80 /// getMallocType - Returns the PointerType resulting from the malloc call.
81 /// The PointerType depends on the number of bitcast uses of the malloc call:
82 ///   0: PointerType is the malloc calls' return type.
83 ///   1: PointerType is the bitcast's result type.
84 ///  >1: Unique PointerType cannot be determined, return NULL.
85 PointerType *getMallocType(const CallInst *CI, const TargetLibraryInfo *TLI);
86 
87 /// getMallocAllocatedType - Returns the Type allocated by malloc call.
88 /// The Type depends on the number of bitcast uses of the malloc call:
89 ///   0: PointerType is the malloc calls' return type.
90 ///   1: PointerType is the bitcast's result type.
91 ///  >1: Unique PointerType cannot be determined, return NULL.
92 Type *getMallocAllocatedType(const CallInst *CI, const TargetLibraryInfo *TLI);
93 
94 /// getMallocArraySize - Returns the array size of a malloc call.  If the
95 /// argument passed to malloc is a multiple of the size of the malloced type,
96 /// then return that multiple.  For non-array mallocs, the multiple is
97 /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
98 /// determined.
99 Value *getMallocArraySize(CallInst *CI, const DataLayout &DL,
100                           const TargetLibraryInfo *TLI,
101                           bool LookThroughSExt = false);
102 
103 //===----------------------------------------------------------------------===//
104 //  calloc Call Utility Functions.
105 //
106 
107 /// extractCallocCall - Returns the corresponding CallInst if the instruction
108 /// is a calloc call.
109 const CallInst *extractCallocCall(const Value *I, const TargetLibraryInfo *TLI);
extractCallocCall(Value * I,const TargetLibraryInfo * TLI)110 static inline CallInst *extractCallocCall(Value *I,
111                                           const TargetLibraryInfo *TLI) {
112   return const_cast<CallInst*>(extractCallocCall((const Value*)I, TLI));
113 }
114 
115 
116 //===----------------------------------------------------------------------===//
117 //  free Call Utility Functions.
118 //
119 
120 /// isFreeCall - Returns non-null if the value is a call to the builtin free()
121 const CallInst *isFreeCall(const Value *I, const TargetLibraryInfo *TLI);
122 
isFreeCall(Value * I,const TargetLibraryInfo * TLI)123 static inline CallInst *isFreeCall(Value *I, const TargetLibraryInfo *TLI) {
124   return const_cast<CallInst*>(isFreeCall((const Value*)I, TLI));
125 }
126 
127 
128 //===----------------------------------------------------------------------===//
129 //  Utility functions to compute size of objects.
130 //
131 
132 /// \brief Compute the size of the object pointed by Ptr. Returns true and the
133 /// object size in Size if successful, and false otherwise. In this context, by
134 /// object we mean the region of memory starting at Ptr to the end of the
135 /// underlying object pointed to by Ptr.
136 /// If RoundToAlign is true, then Size is rounded up to the aligment of allocas,
137 /// byval arguments, and global variables.
138 /// If Mode is Min or Max the size will be evaluated even if it depends on
139 /// a condition and corresponding value will be returned (min or max).
140 bool getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
141                    const TargetLibraryInfo *TLI, bool RoundToAlign = false,
142                    ObjSizeMode Mode = ObjSizeMode::Exact);
143 
144 typedef std::pair<APInt, APInt> SizeOffsetType;
145 
146 /// \brief Evaluate the size and offset of an object pointed to by a Value*
147 /// statically. Fails if size or offset are not known at compile time.
148 class ObjectSizeOffsetVisitor
149   : public InstVisitor<ObjectSizeOffsetVisitor, SizeOffsetType> {
150 
151   const DataLayout &DL;
152   const TargetLibraryInfo *TLI;
153   bool RoundToAlign;
154   ObjSizeMode Mode;
155   unsigned IntTyBits;
156   APInt Zero;
157   SmallPtrSet<Instruction *, 8> SeenInsts;
158 
159   APInt align(APInt Size, uint64_t Align);
160 
unknown()161   SizeOffsetType unknown() {
162     return std::make_pair(APInt(), APInt());
163   }
164 
165 public:
166   ObjectSizeOffsetVisitor(const DataLayout &DL, const TargetLibraryInfo *TLI,
167                           LLVMContext &Context, bool RoundToAlign = false,
168                           ObjSizeMode Mode = ObjSizeMode::Exact);
169 
170   SizeOffsetType compute(Value *V);
171 
knownSize(const SizeOffsetType & SizeOffset)172   static bool knownSize(const SizeOffsetType &SizeOffset) {
173     return SizeOffset.first.getBitWidth() > 1;
174   }
175 
knownOffset(const SizeOffsetType & SizeOffset)176   static bool knownOffset(const SizeOffsetType &SizeOffset) {
177     return SizeOffset.second.getBitWidth() > 1;
178   }
179 
bothKnown(const SizeOffsetType & SizeOffset)180   static bool bothKnown(const SizeOffsetType &SizeOffset) {
181     return knownSize(SizeOffset) && knownOffset(SizeOffset);
182   }
183 
184   // These are "private", except they can't actually be made private. Only
185   // compute() should be used by external users.
186   SizeOffsetType visitAllocaInst(AllocaInst &I);
187   SizeOffsetType visitArgument(Argument &A);
188   SizeOffsetType visitCallSite(CallSite CS);
189   SizeOffsetType visitConstantPointerNull(ConstantPointerNull&);
190   SizeOffsetType visitExtractElementInst(ExtractElementInst &I);
191   SizeOffsetType visitExtractValueInst(ExtractValueInst &I);
192   SizeOffsetType visitGEPOperator(GEPOperator &GEP);
193   SizeOffsetType visitGlobalAlias(GlobalAlias &GA);
194   SizeOffsetType visitGlobalVariable(GlobalVariable &GV);
195   SizeOffsetType visitIntToPtrInst(IntToPtrInst&);
196   SizeOffsetType visitLoadInst(LoadInst &I);
197   SizeOffsetType visitPHINode(PHINode&);
198   SizeOffsetType visitSelectInst(SelectInst &I);
199   SizeOffsetType visitUndefValue(UndefValue&);
200   SizeOffsetType visitInstruction(Instruction &I);
201 };
202 
203 typedef std::pair<Value*, Value*> SizeOffsetEvalType;
204 
205 
206 /// \brief Evaluate the size and offset of an object pointed to by a Value*.
207 /// May create code to compute the result at run-time.
208 class ObjectSizeOffsetEvaluator
209   : public InstVisitor<ObjectSizeOffsetEvaluator, SizeOffsetEvalType> {
210 
211   typedef IRBuilder<TargetFolder> BuilderTy;
212   typedef std::pair<WeakVH, WeakVH> WeakEvalType;
213   typedef DenseMap<const Value*, WeakEvalType> CacheMapTy;
214   typedef SmallPtrSet<const Value*, 8> PtrSetTy;
215 
216   const DataLayout &DL;
217   const TargetLibraryInfo *TLI;
218   LLVMContext &Context;
219   BuilderTy Builder;
220   IntegerType *IntTy;
221   Value *Zero;
222   CacheMapTy CacheMap;
223   PtrSetTy SeenVals;
224   bool RoundToAlign;
225 
unknown()226   SizeOffsetEvalType unknown() {
227     return std::make_pair(nullptr, nullptr);
228   }
229   SizeOffsetEvalType compute_(Value *V);
230 
231 public:
232   ObjectSizeOffsetEvaluator(const DataLayout &DL, const TargetLibraryInfo *TLI,
233                             LLVMContext &Context, bool RoundToAlign = false);
234   SizeOffsetEvalType compute(Value *V);
235 
knownSize(SizeOffsetEvalType SizeOffset)236   bool knownSize(SizeOffsetEvalType SizeOffset) {
237     return SizeOffset.first;
238   }
239 
knownOffset(SizeOffsetEvalType SizeOffset)240   bool knownOffset(SizeOffsetEvalType SizeOffset) {
241     return SizeOffset.second;
242   }
243 
anyKnown(SizeOffsetEvalType SizeOffset)244   bool anyKnown(SizeOffsetEvalType SizeOffset) {
245     return knownSize(SizeOffset) || knownOffset(SizeOffset);
246   }
247 
bothKnown(SizeOffsetEvalType SizeOffset)248   bool bothKnown(SizeOffsetEvalType SizeOffset) {
249     return knownSize(SizeOffset) && knownOffset(SizeOffset);
250   }
251 
252   // The individual instruction visitors should be treated as private.
253   SizeOffsetEvalType visitAllocaInst(AllocaInst &I);
254   SizeOffsetEvalType visitCallSite(CallSite CS);
255   SizeOffsetEvalType visitExtractElementInst(ExtractElementInst &I);
256   SizeOffsetEvalType visitExtractValueInst(ExtractValueInst &I);
257   SizeOffsetEvalType visitGEPOperator(GEPOperator &GEP);
258   SizeOffsetEvalType visitIntToPtrInst(IntToPtrInst&);
259   SizeOffsetEvalType visitLoadInst(LoadInst &I);
260   SizeOffsetEvalType visitPHINode(PHINode &PHI);
261   SizeOffsetEvalType visitSelectInst(SelectInst &I);
262   SizeOffsetEvalType visitInstruction(Instruction &I);
263 };
264 
265 } // End llvm namespace
266 
267 #endif
268