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 // Doubly linked list of nodes.
119 PointerRec *PtrList, **PtrListEnd;
120 // Forwarding pointer.
123 /// All instructions without a specific address in this alias set.
124 std::vector<AssertingVH<Instruction> > UnknownInsts;
126 /// Number of nodes pointing to this AliasSet plus the number of AliasSets
127 /// forwarding to it.
128 unsigned RefCount : 27;
130 // Signifies that this set should be considered to alias any pointer.
131 // Use when the tracker holding this set is saturated.
132 unsigned AliasAny : 1;
134 /// The kinds of access this alias set models.
136 /// We keep track of whether this alias set merely refers to the locations of
137 /// memory (and not any particular access), whether it modifies or references
138 /// the memory, or whether it does both. The lattice goes from "NoAccess" to
139 /// either RefAccess or ModAccess, then to ModRefAccess as necessary.
144 ModRefAccess = RefAccess | ModAccess
148 /// The kind of alias relationship between pointers of the set.
150 /// These represent conservatively correct alias results between any members
151 /// of the set. We represent these independently of the values of alias
152 /// results in order to pack it into a single bit. Lattice goes from
153 /// MustAlias to MayAlias.
155 SetMustAlias = 0, SetMayAlias = 1
159 /// True if this alias set contains volatile loads or stores.
160 unsigned Volatile : 1;
164 void addRef() { ++RefCount; }
166 void dropRef(AliasSetTracker &AST) {
167 assert(RefCount >= 1 && "Invalid reference count detected!");
169 removeFromTracker(AST);
172 Instruction *getUnknownInst(unsigned i) const {
173 assert(i < UnknownInsts.size());
174 return UnknownInsts[i];
179 bool isRef() const { return Access & RefAccess; }
180 bool isMod() const { return Access & ModAccess; }
181 bool isMustAlias() const { return Alias == SetMustAlias; }
182 bool isMayAlias() const { return Alias == SetMayAlias; }
184 /// Return true if this alias set contains volatile loads or stores.
185 bool isVolatile() const { return Volatile; }
187 /// Return true if this alias set should be ignored as part of the
188 /// AliasSetTracker object.
189 bool isForwardingAliasSet() const { return Forward; }
191 /// Merge the specified alias set into this alias set.
192 void mergeSetIn(AliasSet &AS, AliasSetTracker &AST);
194 // Alias Set iteration - Allow access to all of the pointers which are part of
197 iterator begin() const { return iterator(PtrList); }
198 iterator end() const { return iterator(); }
199 bool empty() const { return PtrList == nullptr; }
201 // Unfortunately, ilist::size() is linear, so we have to add code to keep
202 // track of the list's exact size.
203 unsigned size() { return SetSize; }
205 void print(raw_ostream &OS) const;
208 /// Define an iterator for alias sets... this is just a forward iterator.
209 class iterator : public std::iterator<std::forward_iterator_tag,
210 PointerRec, ptrdiff_t> {
214 explicit iterator(PointerRec *CN = nullptr) : CurNode(CN) {}
216 bool operator==(const iterator& x) const {
217 return CurNode == x.CurNode;
219 bool operator!=(const iterator& x) const { return !operator==(x); }
221 value_type &operator*() const {
222 assert(CurNode && "Dereferencing AliasSet.end()!");
225 value_type *operator->() const { return &operator*(); }
227 Value *getPointer() const { return CurNode->getValue(); }
228 uint64_t getSize() const { return CurNode->getSize(); }
229 AAMDNodes getAAInfo() const { return CurNode->getAAInfo(); }
231 iterator& operator++() { // Preincrement
232 assert(CurNode && "Advancing past AliasSet.end()!");
233 CurNode = CurNode->getNext();
236 iterator operator++(int) { // Postincrement
237 iterator tmp = *this; ++*this; return tmp;
242 // Can only be created by AliasSetTracker.
244 : PtrList(nullptr), PtrListEnd(&PtrList), Forward(nullptr), RefCount(0),
245 AliasAny(false), Access(NoAccess), Alias(SetMustAlias),
246 Volatile(false), SetSize(0) {}
248 AliasSet(const AliasSet &AS) = delete;
249 void operator=(const AliasSet &AS) = delete;
251 PointerRec *getSomePointer() const {
255 /// Return the real alias set this represents. If this has been merged with
256 /// another set and is forwarding, return the ultimate destination set. This
257 /// also implements the union-find collapsing as well.
258 AliasSet *getForwardedTarget(AliasSetTracker &AST) {
259 if (!Forward) return this;
261 AliasSet *Dest = Forward->getForwardedTarget(AST);
262 if (Dest != Forward) {
264 Forward->dropRef(AST);
270 void removeFromTracker(AliasSetTracker &AST);
272 void addPointer(AliasSetTracker &AST, PointerRec &Entry, uint64_t Size,
273 const AAMDNodes &AAInfo,
274 bool KnownMustAlias = false);
275 void addUnknownInst(Instruction *I, AliasAnalysis &AA);
276 void removeUnknownInst(AliasSetTracker &AST, Instruction *I) {
277 bool WasEmpty = UnknownInsts.empty();
278 for (size_t i = 0, e = UnknownInsts.size(); i != e; ++i)
279 if (UnknownInsts[i] == I) {
280 UnknownInsts[i] = UnknownInsts.back();
281 UnknownInsts.pop_back();
282 --i; --e; // Revisit the moved entry.
284 if (!WasEmpty && UnknownInsts.empty())
287 void setVolatile() { Volatile = true; }
290 /// Return true if the specified pointer "may" (or must) alias one of the
291 /// members in the set.
292 bool aliasesPointer(const Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo,
293 AliasAnalysis &AA) const;
294 bool aliasesUnknownInst(const Instruction *Inst, AliasAnalysis &AA) const;
297 inline raw_ostream& operator<<(raw_ostream &OS, const AliasSet &AS) {
302 class AliasSetTracker {
303 /// A CallbackVH to arrange for AliasSetTracker to be notified whenever a
304 /// Value is deleted.
305 class ASTCallbackVH final : public CallbackVH {
306 AliasSetTracker *AST;
307 void deleted() override;
308 void allUsesReplacedWith(Value *) override;
311 ASTCallbackVH(Value *V, AliasSetTracker *AST = nullptr);
312 ASTCallbackVH &operator=(Value *V);
314 /// Traits to tell DenseMap that tell us how to compare and hash the value
316 struct ASTCallbackVHDenseMapInfo : public DenseMapInfo<Value *> {};
319 ilist<AliasSet> AliasSets;
321 typedef DenseMap<ASTCallbackVH, AliasSet::PointerRec*,
322 ASTCallbackVHDenseMapInfo>
325 // Map from pointers to their node
326 PointerMapType PointerMap;
329 /// Create an empty collection of AliasSets, and use the specified alias
330 /// analysis object to disambiguate load and store addresses.
331 explicit AliasSetTracker(AliasAnalysis &aa)
332 : AA(aa), TotalMayAliasSetSize(0), AliasAnyAS(nullptr) {}
333 ~AliasSetTracker() { clear(); }
335 /// These methods are used to add different types of instructions to the alias
336 /// sets. Adding a new instruction can result in one of three actions
339 /// 1. If the instruction doesn't alias any other sets, create a new set.
340 /// 2. If the instruction aliases exactly one set, add it to the set
341 /// 3. If the instruction aliases multiple sets, merge the sets, and add
342 /// the instruction to the result.
344 /// These methods return true if inserting the instruction resulted in the
345 /// addition of a new alias set (i.e., the pointer did not alias anything).
347 void add(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo); // Add a loc.
348 void add(LoadInst *LI);
349 void add(StoreInst *SI);
350 void add(VAArgInst *VAAI);
351 void add(MemSetInst *MSI);
352 void add(MemTransferInst *MTI);
353 void add(Instruction *I); // Dispatch to one of the other add methods...
354 void add(BasicBlock &BB); // Add all instructions in basic block
355 void add(const AliasSetTracker &AST); // Add alias relations from another AST
356 void addUnknown(Instruction *I);
360 /// Return the alias sets that are active.
361 const ilist<AliasSet> &getAliasSets() const { return AliasSets; }
363 /// Return the alias set that the specified pointer lives in. If the New
364 /// argument is non-null, this method sets the value to true if a new alias
365 /// set is created to contain the pointer (because the pointer didn't alias
367 AliasSet &getAliasSetForPointer(Value *P, uint64_t Size,
368 const AAMDNodes &AAInfo);
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 instruction "may" (or must) alias one of the
378 /// members in any of the sets.
379 bool containsUnknown(const Instruction *I) const;
381 /// Return the underlying alias analysis object used by this tracker.
382 AliasAnalysis &getAliasAnalysis() const { return AA; }
384 /// This method is used to remove a pointer value from the AliasSetTracker
385 /// entirely. It should be used when an instruction is deleted from the
386 /// program to update the AST. If you don't use this, you would have dangling
387 /// pointers to deleted instructions.
388 void deleteValue(Value *PtrVal);
390 /// This method should be used whenever a preexisting value in the program is
391 /// copied or cloned, introducing a new value. Note that it is ok for clients
392 /// that use this method to introduce the same value multiple times: if the
393 /// tracker already knows about a value, it will ignore the request.
394 void copyValue(Value *From, Value *To);
396 typedef ilist<AliasSet>::iterator iterator;
397 typedef ilist<AliasSet>::const_iterator const_iterator;
399 const_iterator begin() const { return AliasSets.begin(); }
400 const_iterator end() const { return AliasSets.end(); }
402 iterator begin() { return AliasSets.begin(); }
403 iterator end() { return AliasSets.end(); }
405 void print(raw_ostream &OS) const;
409 friend class AliasSet;
411 // The total number of pointers contained in all "may" alias sets.
412 unsigned TotalMayAliasSetSize;
414 // A non-null value signifies this AST is saturated. A saturated AST lumps
415 // all pointers into a single "May" set.
416 AliasSet *AliasAnyAS;
418 void removeAliasSet(AliasSet *AS);
420 /// Just like operator[] on the map, except that it creates an entry for the
421 /// pointer if it doesn't already exist.
422 AliasSet::PointerRec &getEntryFor(Value *V) {
423 AliasSet::PointerRec *&Entry = PointerMap[ASTCallbackVH(V, this)];
425 Entry = new AliasSet::PointerRec(V);
429 AliasSet &addPointer(Value *P, uint64_t Size, const AAMDNodes &AAInfo,
430 AliasSet::AccessLattice E);
431 AliasSet *mergeAliasSetsForPointer(const Value *Ptr, uint64_t Size,
432 const AAMDNodes &AAInfo);
434 /// Merge all alias sets into a single set that is considered to alias any
436 AliasSet &mergeAllAliasSets();
438 AliasSet *findAliasSetForUnknownInst(Instruction *Inst);
441 inline raw_ostream& operator<<(raw_ostream &OS, const AliasSetTracker &AST) {
446 } // End llvm namespace