1//===- llvm/Analysis/AliasSetTracker.h - Build Alias Sets -------*- 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 file defines two classes: AliasSetTracker and AliasSet. These interface 11// are used to classify a collection of pointer references into a maximal number 12// of disjoint sets. Each AliasSet object constructed by the AliasSetTracker 13// object refers to memory disjoint from the other sets. 14// 15//===----------------------------------------------------------------------===// 16 17#ifndef LLVM_ANALYSIS_ALIASSETTRACKER_H 18#define LLVM_ANALYSIS_ALIASSETTRACKER_H 19 20#include "llvm/ADT/DenseMap.h" 21#include "llvm/ADT/ilist.h" 22#include "llvm/ADT/ilist_node.h" 23#include "llvm/IR/ValueHandle.h" 24#include <vector> 25 26namespace llvm { 27 28class AliasAnalysis; 29class LoadInst; 30class StoreInst; 31class VAArgInst; 32class AliasSetTracker; 33class AliasSet; 34 35class AliasSet : public ilist_node<AliasSet> { 36 friend class AliasSetTracker; 37 38 class PointerRec { 39 Value *Val; // The pointer this record corresponds to. 40 PointerRec **PrevInList, *NextInList; 41 AliasSet *AS; 42 uint64_t Size; 43 const MDNode *TBAAInfo; 44 public: 45 PointerRec(Value *V) 46 : Val(V), PrevInList(nullptr), NextInList(nullptr), AS(nullptr), Size(0), 47 TBAAInfo(DenseMapInfo<const MDNode *>::getEmptyKey()) {} 48 49 Value *getValue() const { return Val; } 50 51 PointerRec *getNext() const { return NextInList; } 52 bool hasAliasSet() const { return AS != nullptr; } 53 54 PointerRec** setPrevInList(PointerRec **PIL) { 55 PrevInList = PIL; 56 return &NextInList; 57 } 58 59 void updateSizeAndTBAAInfo(uint64_t NewSize, const MDNode *NewTBAAInfo) { 60 if (NewSize > Size) Size = NewSize; 61 62 if (TBAAInfo == DenseMapInfo<const MDNode *>::getEmptyKey()) 63 // We don't have a TBAAInfo yet. Set it to NewTBAAInfo. 64 TBAAInfo = NewTBAAInfo; 65 else if (TBAAInfo != NewTBAAInfo) 66 // NewTBAAInfo conflicts with TBAAInfo. 67 TBAAInfo = DenseMapInfo<const MDNode *>::getTombstoneKey(); 68 } 69 70 uint64_t getSize() const { return Size; } 71 72 /// getTBAAInfo - Return the TBAAInfo, or null if there is no 73 /// information or conflicting information. 74 const MDNode *getTBAAInfo() const { 75 // If we have missing or conflicting TBAAInfo, return null. 76 if (TBAAInfo == DenseMapInfo<const MDNode *>::getEmptyKey() || 77 TBAAInfo == DenseMapInfo<const MDNode *>::getTombstoneKey()) 78 return nullptr; 79 return TBAAInfo; 80 } 81 82 AliasSet *getAliasSet(AliasSetTracker &AST) { 83 assert(AS && "No AliasSet yet!"); 84 if (AS->Forward) { 85 AliasSet *OldAS = AS; 86 AS = OldAS->getForwardedTarget(AST); 87 AS->addRef(); 88 OldAS->dropRef(AST); 89 } 90 return AS; 91 } 92 93 void setAliasSet(AliasSet *as) { 94 assert(!AS && "Already have an alias set!"); 95 AS = as; 96 } 97 98 void eraseFromList() { 99 if (NextInList) NextInList->PrevInList = PrevInList; 100 *PrevInList = NextInList; 101 if (AS->PtrListEnd == &NextInList) { 102 AS->PtrListEnd = PrevInList; 103 assert(*AS->PtrListEnd == nullptr && "List not terminated right!"); 104 } 105 delete this; 106 } 107 }; 108 109 PointerRec *PtrList, **PtrListEnd; // Doubly linked list of nodes. 110 AliasSet *Forward; // Forwarding pointer. 111 112 // All instructions without a specific address in this alias set. 113 std::vector<AssertingVH<Instruction> > UnknownInsts; 114 115 // RefCount - Number of nodes pointing to this AliasSet plus the number of 116 // AliasSets forwarding to it. 117 unsigned RefCount : 28; 118 119 /// AccessType - Keep track of whether this alias set merely refers to the 120 /// locations of memory, whether it modifies the memory, or whether it does 121 /// both. The lattice goes from "NoModRef" to either Refs or Mods, then to 122 /// ModRef as necessary. 123 /// 124 enum AccessType { 125 NoModRef = 0, Refs = 1, // Ref = bit 1 126 Mods = 2, ModRef = 3 // Mod = bit 2 127 }; 128 unsigned AccessTy : 2; 129 130 /// AliasType - Keep track the relationships between the pointers in the set. 131 /// Lattice goes from MustAlias to MayAlias. 132 /// 133 enum AliasType { 134 MustAlias = 0, MayAlias = 1 135 }; 136 unsigned AliasTy : 1; 137 138 // Volatile - True if this alias set contains volatile loads or stores. 139 bool Volatile : 1; 140 141 void addRef() { ++RefCount; } 142 void dropRef(AliasSetTracker &AST) { 143 assert(RefCount >= 1 && "Invalid reference count detected!"); 144 if (--RefCount == 0) 145 removeFromTracker(AST); 146 } 147 148 Instruction *getUnknownInst(unsigned i) const { 149 assert(i < UnknownInsts.size()); 150 return UnknownInsts[i]; 151 } 152 153public: 154 /// Accessors... 155 bool isRef() const { return AccessTy & Refs; } 156 bool isMod() const { return AccessTy & Mods; } 157 bool isMustAlias() const { return AliasTy == MustAlias; } 158 bool isMayAlias() const { return AliasTy == MayAlias; } 159 160 // isVolatile - Return true if this alias set contains volatile loads or 161 // stores. 162 bool isVolatile() const { return Volatile; } 163 164 /// isForwardingAliasSet - Return true if this alias set should be ignored as 165 /// part of the AliasSetTracker object. 166 bool isForwardingAliasSet() const { return Forward; } 167 168 /// mergeSetIn - Merge the specified alias set into this alias set... 169 /// 170 void mergeSetIn(AliasSet &AS, AliasSetTracker &AST); 171 172 // Alias Set iteration - Allow access to all of the pointer which are part of 173 // this alias set... 174 class iterator; 175 iterator begin() const { return iterator(PtrList); } 176 iterator end() const { return iterator(); } 177 bool empty() const { return PtrList == nullptr; } 178 179 void print(raw_ostream &OS) const; 180 void dump() const; 181 182 /// Define an iterator for alias sets... this is just a forward iterator. 183 class iterator : public std::iterator<std::forward_iterator_tag, 184 PointerRec, ptrdiff_t> { 185 PointerRec *CurNode; 186 public: 187 explicit iterator(PointerRec *CN = nullptr) : CurNode(CN) {} 188 189 bool operator==(const iterator& x) const { 190 return CurNode == x.CurNode; 191 } 192 bool operator!=(const iterator& x) const { return !operator==(x); } 193 194 const iterator &operator=(const iterator &I) { 195 CurNode = I.CurNode; 196 return *this; 197 } 198 199 value_type &operator*() const { 200 assert(CurNode && "Dereferencing AliasSet.end()!"); 201 return *CurNode; 202 } 203 value_type *operator->() const { return &operator*(); } 204 205 Value *getPointer() const { return CurNode->getValue(); } 206 uint64_t getSize() const { return CurNode->getSize(); } 207 const MDNode *getTBAAInfo() const { return CurNode->getTBAAInfo(); } 208 209 iterator& operator++() { // Preincrement 210 assert(CurNode && "Advancing past AliasSet.end()!"); 211 CurNode = CurNode->getNext(); 212 return *this; 213 } 214 iterator operator++(int) { // Postincrement 215 iterator tmp = *this; ++*this; return tmp; 216 } 217 }; 218 219private: 220 // Can only be created by AliasSetTracker. Also, ilist creates one 221 // to serve as a sentinel. 222 friend struct ilist_sentinel_traits<AliasSet>; 223 AliasSet() 224 : PtrList(nullptr), PtrListEnd(&PtrList), Forward(nullptr), RefCount(0), 225 AccessTy(NoModRef), AliasTy(MustAlias), Volatile(false) { 226 } 227 228 AliasSet(const AliasSet &AS) LLVM_DELETED_FUNCTION; 229 void operator=(const AliasSet &AS) LLVM_DELETED_FUNCTION; 230 231 PointerRec *getSomePointer() const { 232 return PtrList; 233 } 234 235 /// getForwardedTarget - Return the real alias set this represents. If this 236 /// has been merged with another set and is forwarding, return the ultimate 237 /// destination set. This also implements the union-find collapsing as well. 238 AliasSet *getForwardedTarget(AliasSetTracker &AST) { 239 if (!Forward) return this; 240 241 AliasSet *Dest = Forward->getForwardedTarget(AST); 242 if (Dest != Forward) { 243 Dest->addRef(); 244 Forward->dropRef(AST); 245 Forward = Dest; 246 } 247 return Dest; 248 } 249 250 void removeFromTracker(AliasSetTracker &AST); 251 252 void addPointer(AliasSetTracker &AST, PointerRec &Entry, uint64_t Size, 253 const MDNode *TBAAInfo, 254 bool KnownMustAlias = false); 255 void addUnknownInst(Instruction *I, AliasAnalysis &AA); 256 void removeUnknownInst(Instruction *I) { 257 for (size_t i = 0, e = UnknownInsts.size(); i != e; ++i) 258 if (UnknownInsts[i] == I) { 259 UnknownInsts[i] = UnknownInsts.back(); 260 UnknownInsts.pop_back(); 261 --i; --e; // Revisit the moved entry. 262 } 263 } 264 void setVolatile() { Volatile = true; } 265 266public: 267 /// aliasesPointer - Return true if the specified pointer "may" (or must) 268 /// alias one of the members in the set. 269 /// 270 bool aliasesPointer(const Value *Ptr, uint64_t Size, const MDNode *TBAAInfo, 271 AliasAnalysis &AA) const; 272 bool aliasesUnknownInst(Instruction *Inst, AliasAnalysis &AA) const; 273}; 274 275inline raw_ostream& operator<<(raw_ostream &OS, const AliasSet &AS) { 276 AS.print(OS); 277 return OS; 278} 279 280 281class AliasSetTracker { 282 /// CallbackVH - A CallbackVH to arrange for AliasSetTracker to be 283 /// notified whenever a Value is deleted. 284 class ASTCallbackVH : public CallbackVH { 285 AliasSetTracker *AST; 286 void deleted() override; 287 void allUsesReplacedWith(Value *) override; 288 public: 289 ASTCallbackVH(Value *V, AliasSetTracker *AST = nullptr); 290 ASTCallbackVH &operator=(Value *V); 291 }; 292 /// ASTCallbackVHDenseMapInfo - Traits to tell DenseMap that tell us how to 293 /// compare and hash the value handle. 294 struct ASTCallbackVHDenseMapInfo : public DenseMapInfo<Value *> {}; 295 296 AliasAnalysis &AA; 297 ilist<AliasSet> AliasSets; 298 299 typedef DenseMap<ASTCallbackVH, AliasSet::PointerRec*, 300 ASTCallbackVHDenseMapInfo> 301 PointerMapType; 302 303 // Map from pointers to their node 304 PointerMapType PointerMap; 305 306public: 307 /// AliasSetTracker ctor - Create an empty collection of AliasSets, and use 308 /// the specified alias analysis object to disambiguate load and store 309 /// addresses. 310 explicit AliasSetTracker(AliasAnalysis &aa) : AA(aa) {} 311 ~AliasSetTracker() { clear(); } 312 313 /// add methods - These methods are used to add different types of 314 /// instructions to the alias sets. Adding a new instruction can result in 315 /// one of three actions happening: 316 /// 317 /// 1. If the instruction doesn't alias any other sets, create a new set. 318 /// 2. If the instruction aliases exactly one set, add it to the set 319 /// 3. If the instruction aliases multiple sets, merge the sets, and add 320 /// the instruction to the result. 321 /// 322 /// These methods return true if inserting the instruction resulted in the 323 /// addition of a new alias set (i.e., the pointer did not alias anything). 324 /// 325 bool add(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo); // Add a location 326 bool add(LoadInst *LI); 327 bool add(StoreInst *SI); 328 bool add(VAArgInst *VAAI); 329 bool add(Instruction *I); // Dispatch to one of the other add methods... 330 void add(BasicBlock &BB); // Add all instructions in basic block 331 void add(const AliasSetTracker &AST); // Add alias relations from another AST 332 bool addUnknown(Instruction *I); 333 334 /// remove methods - These methods are used to remove all entries that might 335 /// be aliased by the specified instruction. These methods return true if any 336 /// alias sets were eliminated. 337 // Remove a location 338 bool remove(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo); 339 bool remove(LoadInst *LI); 340 bool remove(StoreInst *SI); 341 bool remove(VAArgInst *VAAI); 342 bool remove(Instruction *I); 343 void remove(AliasSet &AS); 344 bool removeUnknown(Instruction *I); 345 346 void clear(); 347 348 /// getAliasSets - Return the alias sets that are active. 349 /// 350 const ilist<AliasSet> &getAliasSets() const { return AliasSets; } 351 352 /// getAliasSetForPointer - Return the alias set that the specified pointer 353 /// lives in. If the New argument is non-null, this method sets the value to 354 /// true if a new alias set is created to contain the pointer (because the 355 /// pointer didn't alias anything). 356 AliasSet &getAliasSetForPointer(Value *P, uint64_t Size, 357 const MDNode *TBAAInfo, 358 bool *New = nullptr); 359 360 /// getAliasSetForPointerIfExists - Return the alias set containing the 361 /// location specified if one exists, otherwise return null. 362 AliasSet *getAliasSetForPointerIfExists(Value *P, uint64_t Size, 363 const MDNode *TBAAInfo) { 364 return findAliasSetForPointer(P, Size, TBAAInfo); 365 } 366 367 /// containsPointer - Return true if the specified location is represented by 368 /// this alias set, false otherwise. This does not modify the AST object or 369 /// alias sets. 370 bool containsPointer(Value *P, uint64_t Size, const MDNode *TBAAInfo) const; 371 372 /// getAliasAnalysis - Return the underlying alias analysis object used by 373 /// this tracker. 374 AliasAnalysis &getAliasAnalysis() const { return AA; } 375 376 /// deleteValue method - This method is used to remove a pointer value from 377 /// the AliasSetTracker entirely. It should be used when an instruction is 378 /// deleted from the program to update the AST. If you don't use this, you 379 /// would have dangling pointers to deleted instructions. 380 /// 381 void deleteValue(Value *PtrVal); 382 383 /// copyValue - This method should be used whenever a preexisting value in the 384 /// program is copied or cloned, introducing a new value. Note that it is ok 385 /// for clients that use this method to introduce the same value multiple 386 /// times: if the tracker already knows about a value, it will ignore the 387 /// request. 388 /// 389 void copyValue(Value *From, Value *To); 390 391 392 typedef ilist<AliasSet>::iterator iterator; 393 typedef ilist<AliasSet>::const_iterator const_iterator; 394 395 const_iterator begin() const { return AliasSets.begin(); } 396 const_iterator end() const { return AliasSets.end(); } 397 398 iterator begin() { return AliasSets.begin(); } 399 iterator end() { return AliasSets.end(); } 400 401 void print(raw_ostream &OS) const; 402 void dump() const; 403 404private: 405 friend class AliasSet; 406 void removeAliasSet(AliasSet *AS); 407 408 // getEntryFor - Just like operator[] on the map, except that it creates an 409 // entry for the pointer if it doesn't already exist. 410 AliasSet::PointerRec &getEntryFor(Value *V) { 411 AliasSet::PointerRec *&Entry = PointerMap[ASTCallbackVH(V, this)]; 412 if (!Entry) 413 Entry = new AliasSet::PointerRec(V); 414 return *Entry; 415 } 416 417 AliasSet &addPointer(Value *P, uint64_t Size, const MDNode *TBAAInfo, 418 AliasSet::AccessType E, 419 bool &NewSet) { 420 NewSet = false; 421 AliasSet &AS = getAliasSetForPointer(P, Size, TBAAInfo, &NewSet); 422 AS.AccessTy |= E; 423 return AS; 424 } 425 AliasSet *findAliasSetForPointer(const Value *Ptr, uint64_t Size, 426 const MDNode *TBAAInfo); 427 428 AliasSet *findAliasSetForUnknownInst(Instruction *Inst); 429}; 430 431inline raw_ostream& operator<<(raw_ostream &OS, const AliasSetTracker &AST) { 432 AST.print(OS); 433 return OS; 434} 435 436} // End llvm namespace 437 438#endif 439