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 /// In rare cases this vector can have a null'ed out WeakVH
125 /// instances (can happen if some other loop pass deletes an
126 /// instruction in this list).
127 std::vector<WeakVH> UnknownInsts;
129 /// Number of nodes pointing to this AliasSet plus the number of AliasSets
130 /// forwarding to it.
131 unsigned RefCount : 27;
133 // Signifies that this set should be considered to alias any pointer.
134 // Use when the tracker holding this set is saturated.
135 unsigned AliasAny : 1;
137 /// The kinds of access this alias set models.
139 /// We keep track of whether this alias set merely refers to the locations of
140 /// memory (and not any particular access), whether it modifies or references
141 /// the memory, or whether it does both. The lattice goes from "NoAccess" to
142 /// either RefAccess or ModAccess, then to ModRefAccess as necessary.
147 ModRefAccess = RefAccess | ModAccess
151 /// The kind of alias relationship between pointers of the set.
153 /// These represent conservatively correct alias results between any members
154 /// of the set. We represent these independently of the values of alias
155 /// results in order to pack it into a single bit. Lattice goes from
156 /// MustAlias to MayAlias.
158 SetMustAlias = 0, SetMayAlias = 1
162 /// True if this alias set contains volatile loads or stores.
163 unsigned Volatile : 1;
167 void addRef() { ++RefCount; }
169 void dropRef(AliasSetTracker &AST) {
170 assert(RefCount >= 1 && "Invalid reference count detected!");
172 removeFromTracker(AST);
175 Instruction *getUnknownInst(unsigned i) const {
176 assert(i < UnknownInsts.size());
177 return cast_or_null<Instruction>(UnknownInsts[i]);
182 bool isRef() const { return Access & RefAccess; }
183 bool isMod() const { return Access & ModAccess; }
184 bool isMustAlias() const { return Alias == SetMustAlias; }
185 bool isMayAlias() const { return Alias == SetMayAlias; }
187 /// Return true if this alias set contains volatile loads or stores.
188 bool isVolatile() const { return Volatile; }
190 /// Return true if this alias set should be ignored as part of the
191 /// AliasSetTracker object.
192 bool isForwardingAliasSet() const { return Forward; }
194 /// Merge the specified alias set into this alias set.
195 void mergeSetIn(AliasSet &AS, AliasSetTracker &AST);
197 // Alias Set iteration - Allow access to all of the pointers which are part of
200 iterator begin() const { return iterator(PtrList); }
201 iterator end() const { return iterator(); }
202 bool empty() const { return PtrList == nullptr; }
204 // Unfortunately, ilist::size() is linear, so we have to add code to keep
205 // track of the list's exact size.
206 unsigned size() { return SetSize; }
208 void print(raw_ostream &OS) const;
211 /// Define an iterator for alias sets... this is just a forward iterator.
212 class iterator : public std::iterator<std::forward_iterator_tag,
213 PointerRec, ptrdiff_t> {
217 explicit iterator(PointerRec *CN = nullptr) : CurNode(CN) {}
219 bool operator==(const iterator& x) const {
220 return CurNode == x.CurNode;
222 bool operator!=(const iterator& x) const { return !operator==(x); }
224 value_type &operator*() const {
225 assert(CurNode && "Dereferencing AliasSet.end()!");
228 value_type *operator->() const { return &operator*(); }
230 Value *getPointer() const { return CurNode->getValue(); }
231 uint64_t getSize() const { return CurNode->getSize(); }
232 AAMDNodes getAAInfo() const { return CurNode->getAAInfo(); }
234 iterator& operator++() { // Preincrement
235 assert(CurNode && "Advancing past AliasSet.end()!");
236 CurNode = CurNode->getNext();
239 iterator operator++(int) { // Postincrement
240 iterator tmp = *this; ++*this; return tmp;
245 // Can only be created by AliasSetTracker.
247 : PtrList(nullptr), PtrListEnd(&PtrList), Forward(nullptr), RefCount(0),
248 AliasAny(false), Access(NoAccess), Alias(SetMustAlias),
249 Volatile(false), SetSize(0) {}
251 AliasSet(const AliasSet &AS) = delete;
252 void operator=(const AliasSet &AS) = delete;
254 PointerRec *getSomePointer() const {
258 /// Return the real alias set this represents. If this has been merged with
259 /// another set and is forwarding, return the ultimate destination set. This
260 /// also implements the union-find collapsing as well.
261 AliasSet *getForwardedTarget(AliasSetTracker &AST) {
262 if (!Forward) return this;
264 AliasSet *Dest = Forward->getForwardedTarget(AST);
265 if (Dest != Forward) {
267 Forward->dropRef(AST);
273 void removeFromTracker(AliasSetTracker &AST);
275 void addPointer(AliasSetTracker &AST, PointerRec &Entry, uint64_t Size,
276 const AAMDNodes &AAInfo,
277 bool KnownMustAlias = false);
278 void addUnknownInst(Instruction *I, AliasAnalysis &AA);
279 void removeUnknownInst(AliasSetTracker &AST, Instruction *I) {
280 bool WasEmpty = UnknownInsts.empty();
281 for (size_t i = 0, e = UnknownInsts.size(); i != e; ++i)
282 if (UnknownInsts[i] == I) {
283 UnknownInsts[i] = UnknownInsts.back();
284 UnknownInsts.pop_back();
285 --i; --e; // Revisit the moved entry.
287 if (!WasEmpty && UnknownInsts.empty())
290 void setVolatile() { Volatile = true; }
293 /// Return true if the specified pointer "may" (or must) alias one of the
294 /// members in the set.
295 bool aliasesPointer(const Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo,
296 AliasAnalysis &AA) const;
297 bool aliasesUnknownInst(const Instruction *Inst, AliasAnalysis &AA) const;
300 inline raw_ostream& operator<<(raw_ostream &OS, const AliasSet &AS) {
305 class AliasSetTracker {
306 /// A CallbackVH to arrange for AliasSetTracker to be notified whenever a
307 /// Value is deleted.
308 class ASTCallbackVH final : public CallbackVH {
309 AliasSetTracker *AST;
310 void deleted() override;
311 void allUsesReplacedWith(Value *) override;
314 ASTCallbackVH(Value *V, AliasSetTracker *AST = nullptr);
315 ASTCallbackVH &operator=(Value *V);
317 /// Traits to tell DenseMap that tell us how to compare and hash the value
319 struct ASTCallbackVHDenseMapInfo : public DenseMapInfo<Value *> {};
322 ilist<AliasSet> AliasSets;
324 typedef DenseMap<ASTCallbackVH, AliasSet::PointerRec*,
325 ASTCallbackVHDenseMapInfo>
328 // Map from pointers to their node
329 PointerMapType PointerMap;
332 /// Create an empty collection of AliasSets, and use the specified alias
333 /// analysis object to disambiguate load and store addresses.
334 explicit AliasSetTracker(AliasAnalysis &aa)
335 : AA(aa), TotalMayAliasSetSize(0), AliasAnyAS(nullptr) {}
336 ~AliasSetTracker() { clear(); }
338 /// These methods are used to add different types of instructions to the alias
339 /// sets. Adding a new instruction can result in one of three actions
342 /// 1. If the instruction doesn't alias any other sets, create a new set.
343 /// 2. If the instruction aliases exactly one set, add it to the set
344 /// 3. If the instruction aliases multiple sets, merge the sets, and add
345 /// the instruction to the result.
347 /// These methods return true if inserting the instruction resulted in the
348 /// addition of a new alias set (i.e., the pointer did not alias anything).
350 void add(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo); // Add a loc.
351 void add(LoadInst *LI);
352 void add(StoreInst *SI);
353 void add(VAArgInst *VAAI);
354 void add(MemSetInst *MSI);
355 void add(MemTransferInst *MTI);
356 void add(Instruction *I); // Dispatch to one of the other add methods...
357 void add(BasicBlock &BB); // Add all instructions in basic block
358 void add(const AliasSetTracker &AST); // Add alias relations from another AST
359 void addUnknown(Instruction *I);
363 /// Return the alias sets that are active.
364 const ilist<AliasSet> &getAliasSets() const { return AliasSets; }
366 /// Return the alias set that the specified pointer lives in. If the New
367 /// argument is non-null, this method sets the value to true if a new alias
368 /// set is created to contain the pointer (because the pointer didn't alias
370 AliasSet &getAliasSetForPointer(Value *P, uint64_t Size,
371 const AAMDNodes &AAInfo);
373 /// Return the alias set containing the location specified if one exists,
374 /// otherwise return null.
375 AliasSet *getAliasSetForPointerIfExists(const Value *P, uint64_t Size,
376 const AAMDNodes &AAInfo) {
377 return mergeAliasSetsForPointer(P, Size, AAInfo);
380 /// Return true if the specified instruction "may" (or must) alias one of the
381 /// members in any of the sets.
382 bool containsUnknown(const Instruction *I) const;
384 /// Return the underlying alias analysis object used by this tracker.
385 AliasAnalysis &getAliasAnalysis() const { return AA; }
387 /// This method is used to remove a pointer value from the AliasSetTracker
388 /// entirely. It should be used when an instruction is deleted from the
389 /// program to update the AST. If you don't use this, you would have dangling
390 /// pointers to deleted instructions.
391 void deleteValue(Value *PtrVal);
393 /// This method should be used whenever a preexisting value in the program is
394 /// copied or cloned, introducing a new value. Note that it is ok for clients
395 /// that use this method to introduce the same value multiple times: if the
396 /// tracker already knows about a value, it will ignore the request.
397 void copyValue(Value *From, Value *To);
399 typedef ilist<AliasSet>::iterator iterator;
400 typedef ilist<AliasSet>::const_iterator const_iterator;
402 const_iterator begin() const { return AliasSets.begin(); }
403 const_iterator end() const { return AliasSets.end(); }
405 iterator begin() { return AliasSets.begin(); }
406 iterator end() { return AliasSets.end(); }
408 void print(raw_ostream &OS) const;
412 friend class AliasSet;
414 // The total number of pointers contained in all "may" alias sets.
415 unsigned TotalMayAliasSetSize;
417 // A non-null value signifies this AST is saturated. A saturated AST lumps
418 // all pointers into a single "May" set.
419 AliasSet *AliasAnyAS;
421 void removeAliasSet(AliasSet *AS);
423 /// Just like operator[] on the map, except that it creates an entry for the
424 /// pointer if it doesn't already exist.
425 AliasSet::PointerRec &getEntryFor(Value *V) {
426 AliasSet::PointerRec *&Entry = PointerMap[ASTCallbackVH(V, this)];
428 Entry = new AliasSet::PointerRec(V);
432 AliasSet &addPointer(Value *P, uint64_t Size, const AAMDNodes &AAInfo,
433 AliasSet::AccessLattice E);
434 AliasSet *mergeAliasSetsForPointer(const Value *Ptr, uint64_t Size,
435 const AAMDNodes &AAInfo);
437 /// Merge all alias sets into a single set that is considered to alias any
439 AliasSet &mergeAllAliasSets();
441 AliasSet *findAliasSetForUnknownInst(Instruction *Inst);
444 inline raw_ostream& operator<<(raw_ostream &OS, const AliasSetTracker &AST) {
449 } // End llvm namespace