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 
36 /// \brief Tests if a value is a call or invoke to a library function that
37 /// allocates or reallocates memory (either malloc, calloc, realloc, or strdup
38 /// like).
39 bool isAllocationFn(const Value *V, const TargetLibraryInfo *TLI,
40                     bool LookThroughBitCast = false);
41 
42 /// \brief Tests if a value is a call or invoke to a function that returns a
43 /// NoAlias pointer (including malloc/calloc/realloc/strdup-like functions).
44 bool isNoAliasFn(const Value *V, const TargetLibraryInfo *TLI,
45                  bool LookThroughBitCast = false);
46 
47 /// \brief Tests if a value is a call or invoke to a library function that
48 /// allocates uninitialized memory (such as malloc).
49 bool isMallocLikeFn(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 zero-filled memory (such as calloc).
54 bool isCallocLikeFn(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 memory (either malloc, calloc, or strdup like).
59 bool isAllocLikeFn(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 /// reallocates memory (such as realloc).
64 bool isReallocLikeFn(const Value *V, const TargetLibraryInfo *TLI,
65                      bool LookThroughBitCast = false);
66 
67 /// \brief Tests if a value is a call or invoke to a library function that
68 /// allocates memory and never returns null (such as operator new).
69 bool isOperatorNewLikeFn(const Value *V, const TargetLibraryInfo *TLI,
70                          bool LookThroughBitCast = false);
71 
72 //===----------------------------------------------------------------------===//
73 //  malloc Call Utility Functions.
74 //
75 
76 /// extractMallocCall - Returns the corresponding CallInst if the instruction
77 /// is a malloc call.  Since CallInst::CreateMalloc() only creates calls, we
78 /// ignore InvokeInst here.
79 const CallInst *extractMallocCall(const Value *I, const TargetLibraryInfo *TLI);
extractMallocCall(Value * I,const TargetLibraryInfo * TLI)80 static inline CallInst *extractMallocCall(Value *I,
81                                           const TargetLibraryInfo *TLI) {
82   return const_cast<CallInst*>(extractMallocCall((const Value*)I, TLI));
83 }
84 
85 /// getMallocType - Returns the PointerType resulting from the malloc call.
86 /// The PointerType depends on the number of bitcast uses of the malloc call:
87 ///   0: PointerType is the malloc calls' return type.
88 ///   1: PointerType is the bitcast's result type.
89 ///  >1: Unique PointerType cannot be determined, return NULL.
90 PointerType *getMallocType(const CallInst *CI, const TargetLibraryInfo *TLI);
91 
92 /// getMallocAllocatedType - Returns the Type allocated by malloc call.
93 /// The Type depends on the number of bitcast uses of the malloc call:
94 ///   0: PointerType is the malloc calls' return type.
95 ///   1: PointerType is the bitcast's result type.
96 ///  >1: Unique PointerType cannot be determined, return NULL.
97 Type *getMallocAllocatedType(const CallInst *CI, const TargetLibraryInfo *TLI);
98 
99 /// getMallocArraySize - Returns the array size of a malloc call.  If the
100 /// argument passed to malloc is a multiple of the size of the malloced type,
101 /// then return that multiple.  For non-array mallocs, the multiple is
102 /// constant 1.  Otherwise, return NULL for mallocs whose array size cannot be
103 /// determined.
104 Value *getMallocArraySize(CallInst *CI, const DataLayout &DL,
105                           const TargetLibraryInfo *TLI,
106                           bool LookThroughSExt = false);
107 
108 //===----------------------------------------------------------------------===//
109 //  calloc Call Utility Functions.
110 //
111 
112 /// extractCallocCall - Returns the corresponding CallInst if the instruction
113 /// is a calloc call.
114 const CallInst *extractCallocCall(const Value *I, const TargetLibraryInfo *TLI);
extractCallocCall(Value * I,const TargetLibraryInfo * TLI)115 static inline CallInst *extractCallocCall(Value *I,
116                                           const TargetLibraryInfo *TLI) {
117   return const_cast<CallInst*>(extractCallocCall((const Value*)I, TLI));
118 }
119 
120 
121 //===----------------------------------------------------------------------===//
122 //  free Call Utility Functions.
123 //
124 
125 /// isFreeCall - Returns non-null if the value is a call to the builtin free()
126 const CallInst *isFreeCall(const Value *I, const TargetLibraryInfo *TLI);
127 
isFreeCall(Value * I,const TargetLibraryInfo * TLI)128 static inline CallInst *isFreeCall(Value *I, const TargetLibraryInfo *TLI) {
129   return const_cast<CallInst*>(isFreeCall((const Value*)I, TLI));
130 }
131 
132 
133 //===----------------------------------------------------------------------===//
134 //  Utility functions to compute size of objects.
135 //
136 
137 /// \brief Compute the size of the object pointed by Ptr. Returns true and the
138 /// object size in Size if successful, and false otherwise. In this context, by
139 /// object we mean the region of memory starting at Ptr to the end of the
140 /// underlying object pointed to by Ptr.
141 /// If RoundToAlign is true, then Size is rounded up to the aligment of allocas,
142 /// byval arguments, and global variables.
143 bool getObjectSize(const Value *Ptr, uint64_t &Size, const DataLayout &DL,
144                    const TargetLibraryInfo *TLI, bool RoundToAlign = false);
145 
146 typedef std::pair<APInt, APInt> SizeOffsetType;
147 
148 /// \brief Evaluate the size and offset of an object pointed to by a Value*
149 /// statically. Fails if size or offset are not known at compile time.
150 class ObjectSizeOffsetVisitor
151   : public InstVisitor<ObjectSizeOffsetVisitor, SizeOffsetType> {
152 
153   const DataLayout &DL;
154   const TargetLibraryInfo *TLI;
155   bool RoundToAlign;
156   unsigned IntTyBits;
157   APInt Zero;
158   SmallPtrSet<Instruction *, 8> SeenInsts;
159 
160   APInt align(APInt Size, uint64_t Align);
161 
unknown()162   SizeOffsetType unknown() {
163     return std::make_pair(APInt(), APInt());
164   }
165 
166 public:
167   ObjectSizeOffsetVisitor(const DataLayout &DL, const TargetLibraryInfo *TLI,
168                           LLVMContext &Context, bool RoundToAlign = false);
169 
170   SizeOffsetType compute(Value *V);
171 
knownSize(SizeOffsetType & SizeOffset)172   bool knownSize(SizeOffsetType &SizeOffset) {
173     return SizeOffset.first.getBitWidth() > 1;
174   }
175 
knownOffset(SizeOffsetType & SizeOffset)176   bool knownOffset(SizeOffsetType &SizeOffset) {
177     return SizeOffset.second.getBitWidth() > 1;
178   }
179 
bothKnown(SizeOffsetType & SizeOffset)180   bool bothKnown(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<true, 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