1 //===- llvm/Analysis/AliasSetTracker.h - Build Alias Sets -------*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines two classes: AliasSetTracker and AliasSet. These interfaces
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.
15 //===----------------------------------------------------------------------===//
17 #ifndef LLVM_ANALYSIS_ALIASSETTRACKER_H
18 #define LLVM_ANALYSIS_ALIASSETTRACKER_H
20 #include "llvm/ADT/DenseMap.h"
21 #include "llvm/ADT/ilist.h"
22 #include "llvm/ADT/ilist_node.h"
23 #include "llvm/Analysis/AliasAnalysis.h"
24 #include "llvm/IR/Metadata.h"
25 #include "llvm/IR/ValueHandle.h"
34 class AliasSetTracker;
37 class AliasSet : public ilist_node<AliasSet> {
38 friend class AliasSetTracker;
41 Value *Val; // The pointer this record corresponds to.
42 PointerRec **PrevInList, *NextInList;
49 : Val(V), PrevInList(nullptr), NextInList(nullptr), AS(nullptr), Size(0),
50 AAInfo(DenseMapInfo<AAMDNodes>::getEmptyKey()) {}
52 Value *getValue() const { return Val; }
54 PointerRec *getNext() const { return NextInList; }
55 bool hasAliasSet() const { return AS != nullptr; }
57 PointerRec** setPrevInList(PointerRec **PIL) {
62 bool updateSizeAndAAInfo(uint64_t NewSize, const AAMDNodes &NewAAInfo) {
63 bool SizeChanged = false;
69 if (AAInfo == DenseMapInfo<AAMDNodes>::getEmptyKey())
70 // We don't have a AAInfo yet. Set it to NewAAInfo.
72 else if (AAInfo != NewAAInfo)
73 // NewAAInfo conflicts with AAInfo.
74 AAInfo = DenseMapInfo<AAMDNodes>::getTombstoneKey();
79 uint64_t getSize() const { return Size; }
81 /// Return the AAInfo, or null if there is no information or conflicting
83 AAMDNodes getAAInfo() const {
84 // If we have missing or conflicting AAInfo, return null.
85 if (AAInfo == DenseMapInfo<AAMDNodes>::getEmptyKey() ||
86 AAInfo == DenseMapInfo<AAMDNodes>::getTombstoneKey())
91 AliasSet *getAliasSet(AliasSetTracker &AST) {
92 assert(AS && "No AliasSet yet!");
95 AS = OldAS->getForwardedTarget(AST);
102 void setAliasSet(AliasSet *as) {
103 assert(!AS && "Already have an alias set!");
107 void eraseFromList() {
108 if (NextInList) NextInList->PrevInList = PrevInList;
109 *PrevInList = NextInList;
110 if (AS->PtrListEnd == &NextInList) {
111 AS->PtrListEnd = PrevInList;
112 assert(*AS->PtrListEnd == nullptr && "List not terminated right!");
118 PointerRec *PtrList, **PtrListEnd; // Doubly linked list of nodes.
119 AliasSet *Forward; // Forwarding pointer.
121 /// All instructions without a specific address in this alias set.
122 std::vector<AssertingVH<Instruction> > UnknownInsts;
124 /// Number of nodes pointing to this AliasSet plus the number of AliasSets
125 /// forwarding to it.
126 unsigned RefCount : 28;
128 /// The kinds of access this alias set models.
130 /// We keep track of whether this alias set merely refers to the locations of
131 /// memory (and not any particular access), whether it modifies or references
132 /// the memory, or whether it does both. The lattice goes from "NoAccess" to
133 /// either RefAccess or ModAccess, then to ModRefAccess as necessary.
138 ModRefAccess = RefAccess | ModAccess
142 /// The kind of alias relationship between pointers of the set.
144 /// These represent conservatively correct alias results between any members
145 /// of the set. We represent these independently of the values of alias
146 /// results in order to pack it into a single bit. Lattice goes from
147 /// MustAlias to MayAlias.
149 SetMustAlias = 0, SetMayAlias = 1
153 /// True if this alias set contains volatile loads or stores.
154 unsigned Volatile : 1;
156 void addRef() { ++RefCount; }
157 void dropRef(AliasSetTracker &AST) {
158 assert(RefCount >= 1 && "Invalid reference count detected!");
160 removeFromTracker(AST);
163 Instruction *getUnknownInst(unsigned i) const {
164 assert(i < UnknownInsts.size());
165 return UnknownInsts[i];
170 bool isRef() const { return Access & RefAccess; }
171 bool isMod() const { return Access & ModAccess; }
172 bool isMustAlias() const { return Alias == SetMustAlias; }
173 bool isMayAlias() const { return Alias == SetMayAlias; }
175 /// Return true if this alias set contains volatile loads or stores.
176 bool isVolatile() const { return Volatile; }
178 /// Return true if this alias set should be ignored as part of the
179 /// AliasSetTracker object.
180 bool isForwardingAliasSet() const { return Forward; }
182 /// Merge the specified alias set into this alias set.
183 void mergeSetIn(AliasSet &AS, AliasSetTracker &AST);
185 // Alias Set iteration - Allow access to all of the pointers which are part of
188 iterator begin() const { return iterator(PtrList); }
189 iterator end() const { return iterator(); }
190 bool empty() const { return PtrList == nullptr; }
192 void print(raw_ostream &OS) const;
195 /// Define an iterator for alias sets... this is just a forward iterator.
196 class iterator : public std::iterator<std::forward_iterator_tag,
197 PointerRec, ptrdiff_t> {
201 explicit iterator(PointerRec *CN = nullptr) : CurNode(CN) {}
203 bool operator==(const iterator& x) const {
204 return CurNode == x.CurNode;
206 bool operator!=(const iterator& x) const { return !operator==(x); }
208 value_type &operator*() const {
209 assert(CurNode && "Dereferencing AliasSet.end()!");
212 value_type *operator->() const { return &operator*(); }
214 Value *getPointer() const { return CurNode->getValue(); }
215 uint64_t getSize() const { return CurNode->getSize(); }
216 AAMDNodes getAAInfo() const { return CurNode->getAAInfo(); }
218 iterator& operator++() { // Preincrement
219 assert(CurNode && "Advancing past AliasSet.end()!");
220 CurNode = CurNode->getNext();
223 iterator operator++(int) { // Postincrement
224 iterator tmp = *this; ++*this; return tmp;
229 // Can only be created by AliasSetTracker. Also, ilist creates one
230 // to serve as a sentinel.
231 friend struct ilist_sentinel_traits<AliasSet>;
233 : PtrList(nullptr), PtrListEnd(&PtrList), Forward(nullptr), RefCount(0),
234 Access(NoAccess), Alias(SetMustAlias), Volatile(false) {
237 AliasSet(const AliasSet &AS) = delete;
238 void operator=(const AliasSet &AS) = delete;
240 PointerRec *getSomePointer() const {
244 /// Return the real alias set this represents. If this has been merged with
245 /// another set and is forwarding, return the ultimate destination set. This
246 /// also implements the union-find collapsing as well.
247 AliasSet *getForwardedTarget(AliasSetTracker &AST) {
248 if (!Forward) return this;
250 AliasSet *Dest = Forward->getForwardedTarget(AST);
251 if (Dest != Forward) {
253 Forward->dropRef(AST);
259 void removeFromTracker(AliasSetTracker &AST);
261 void addPointer(AliasSetTracker &AST, PointerRec &Entry, uint64_t Size,
262 const AAMDNodes &AAInfo,
263 bool KnownMustAlias = false);
264 void addUnknownInst(Instruction *I, AliasAnalysis &AA);
265 void removeUnknownInst(AliasSetTracker &AST, Instruction *I) {
266 bool WasEmpty = UnknownInsts.empty();
267 for (size_t i = 0, e = UnknownInsts.size(); i != e; ++i)
268 if (UnknownInsts[i] == I) {
269 UnknownInsts[i] = UnknownInsts.back();
270 UnknownInsts.pop_back();
271 --i; --e; // Revisit the moved entry.
273 if (!WasEmpty && UnknownInsts.empty())
276 void setVolatile() { Volatile = true; }
279 /// Return true if the specified pointer "may" (or must) alias one of the
280 /// members in the set.
281 bool aliasesPointer(const Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo,
282 AliasAnalysis &AA) const;
283 bool aliasesUnknownInst(const Instruction *Inst, AliasAnalysis &AA) const;
286 inline raw_ostream& operator<<(raw_ostream &OS, const AliasSet &AS) {
291 class AliasSetTracker {
292 /// A CallbackVH to arrange for AliasSetTracker to be notified whenever a
293 /// Value is deleted.
294 class ASTCallbackVH final : public CallbackVH {
295 AliasSetTracker *AST;
296 void deleted() override;
297 void allUsesReplacedWith(Value *) override;
300 ASTCallbackVH(Value *V, AliasSetTracker *AST = nullptr);
301 ASTCallbackVH &operator=(Value *V);
303 /// Traits to tell DenseMap that tell us how to compare and hash the value
305 struct ASTCallbackVHDenseMapInfo : public DenseMapInfo<Value *> {};
308 ilist<AliasSet> AliasSets;
310 typedef DenseMap<ASTCallbackVH, AliasSet::PointerRec*,
311 ASTCallbackVHDenseMapInfo>
314 // Map from pointers to their node
315 PointerMapType PointerMap;
318 /// Create an empty collection of AliasSets, and use the specified alias
319 /// analysis object to disambiguate load and store addresses.
320 explicit AliasSetTracker(AliasAnalysis &aa) : AA(aa) {}
321 ~AliasSetTracker() { clear(); }
323 /// These methods are used to add different types of instructions to the alias
324 /// sets. Adding a new instruction can result in one of three actions
327 /// 1. If the instruction doesn't alias any other sets, create a new set.
328 /// 2. If the instruction aliases exactly one set, add it to the set
329 /// 3. If the instruction aliases multiple sets, merge the sets, and add
330 /// the instruction to the result.
332 /// These methods return true if inserting the instruction resulted in the
333 /// addition of a new alias set (i.e., the pointer did not alias anything).
335 bool add(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo); // Add a loc.
336 bool add(LoadInst *LI);
337 bool add(StoreInst *SI);
338 bool add(VAArgInst *VAAI);
339 bool add(MemSetInst *MSI);
340 bool add(Instruction *I); // Dispatch to one of the other add methods...
341 void add(BasicBlock &BB); // Add all instructions in basic block
342 void add(const AliasSetTracker &AST); // Add alias relations from another AST
343 bool addUnknown(Instruction *I);
345 /// These methods are used to remove all entries that might be aliased by the
346 /// specified instruction. These methods return true if any alias sets were
348 bool remove(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo);
349 bool remove(LoadInst *LI);
350 bool remove(StoreInst *SI);
351 bool remove(VAArgInst *VAAI);
352 bool remove(MemSetInst *MSI);
353 bool remove(Instruction *I);
354 void remove(AliasSet &AS);
355 bool removeUnknown(Instruction *I);
359 /// Return the alias sets that are active.
360 const ilist<AliasSet> &getAliasSets() const { return AliasSets; }
362 /// Return the alias set that the specified pointer lives in. If the New
363 /// argument is non-null, this method sets the value to true if a new alias
364 /// set is created to contain the pointer (because the pointer didn't alias
366 AliasSet &getAliasSetForPointer(Value *P, uint64_t Size,
367 const AAMDNodes &AAInfo,
368 bool *New = nullptr);
370 /// Return the alias set containing the location specified if one exists,
371 /// otherwise return null.
372 AliasSet *getAliasSetForPointerIfExists(const Value *P, uint64_t Size,
373 const AAMDNodes &AAInfo) {
374 return mergeAliasSetsForPointer(P, Size, AAInfo);
377 /// Return true if the specified location is represented by this alias set,
378 /// false otherwise. This does not modify the AST object or alias sets.
379 bool containsPointer(const Value *P, uint64_t Size,
380 const AAMDNodes &AAInfo) const;
382 /// Return true if the specified instruction "may" (or must) alias one of the
383 /// members in any of the sets.
384 bool containsUnknown(const Instruction *I) const;
386 /// Return the underlying alias analysis object used by this tracker.
387 AliasAnalysis &getAliasAnalysis() const { return AA; }
389 /// This method is used to remove a pointer value from the AliasSetTracker
390 /// entirely. It should be used when an instruction is deleted from the
391 /// program to update the AST. If you don't use this, you would have dangling
392 /// pointers to deleted instructions.
393 void deleteValue(Value *PtrVal);
395 /// This method should be used whenever a preexisting value in the program is
396 /// copied or cloned, introducing a new value. Note that it is ok for clients
397 /// that use this method to introduce the same value multiple times: if the
398 /// tracker already knows about a value, it will ignore the request.
399 void copyValue(Value *From, Value *To);
401 typedef ilist<AliasSet>::iterator iterator;
402 typedef ilist<AliasSet>::const_iterator const_iterator;
404 const_iterator begin() const { return AliasSets.begin(); }
405 const_iterator end() const { return AliasSets.end(); }
407 iterator begin() { return AliasSets.begin(); }
408 iterator end() { return AliasSets.end(); }
410 void print(raw_ostream &OS) const;
414 friend class AliasSet;
415 void removeAliasSet(AliasSet *AS);
417 /// Just like operator[] on the map, except that it creates an entry for the
418 /// pointer if it doesn't already exist.
419 AliasSet::PointerRec &getEntryFor(Value *V) {
420 AliasSet::PointerRec *&Entry = PointerMap[ASTCallbackVH(V, this)];
422 Entry = new AliasSet::PointerRec(V);
426 AliasSet &addPointer(Value *P, uint64_t Size, const AAMDNodes &AAInfo,
427 AliasSet::AccessLattice E,
430 AliasSet &AS = getAliasSetForPointer(P, Size, AAInfo, &NewSet);
434 AliasSet *mergeAliasSetsForPointer(const Value *Ptr, uint64_t Size,
435 const AAMDNodes &AAInfo);
437 AliasSet *findAliasSetForUnknownInst(Instruction *Inst);
440 inline raw_ostream& operator<<(raw_ostream &OS, const AliasSetTracker &AST) {
445 } // End llvm namespace