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.
73 AAMDNodes Intersection(AAInfo.intersect(NewAAInfo));
75 // NewAAInfo conflicts with AAInfo.
76 AAInfo = DenseMapInfo<AAMDNodes>::getTombstoneKey();
79 AAInfo = Intersection;
84 uint64_t getSize() const { return Size; }
86 /// Return the AAInfo, or null if there is no information or conflicting
88 AAMDNodes getAAInfo() const {
89 // If we have missing or conflicting AAInfo, return null.
90 if (AAInfo == DenseMapInfo<AAMDNodes>::getEmptyKey() ||
91 AAInfo == DenseMapInfo<AAMDNodes>::getTombstoneKey())
96 AliasSet *getAliasSet(AliasSetTracker &AST) {
97 assert(AS && "No AliasSet yet!");
100 AS = OldAS->getForwardedTarget(AST);
107 void setAliasSet(AliasSet *as) {
108 assert(!AS && "Already have an alias set!");
112 void eraseFromList() {
113 if (NextInList) NextInList->PrevInList = PrevInList;
114 *PrevInList = NextInList;
115 if (AS->PtrListEnd == &NextInList) {
116 AS->PtrListEnd = PrevInList;
117 assert(*AS->PtrListEnd == nullptr && "List not terminated right!");
123 // Doubly linked list of nodes.
124 PointerRec *PtrList, **PtrListEnd;
125 // Forwarding pointer.
128 /// All instructions without a specific address in this alias set.
129 /// In rare cases this vector can have a null'ed out WeakVH
130 /// instances (can happen if some other loop pass deletes an
131 /// instruction in this list).
132 std::vector<WeakVH> UnknownInsts;
134 /// Number of nodes pointing to this AliasSet plus the number of AliasSets
135 /// forwarding to it.
136 unsigned RefCount : 27;
138 // Signifies that this set should be considered to alias any pointer.
139 // Use when the tracker holding this set is saturated.
140 unsigned AliasAny : 1;
142 /// The kinds of access this alias set models.
144 /// We keep track of whether this alias set merely refers to the locations of
145 /// memory (and not any particular access), whether it modifies or references
146 /// the memory, or whether it does both. The lattice goes from "NoAccess" to
147 /// either RefAccess or ModAccess, then to ModRefAccess as necessary.
152 ModRefAccess = RefAccess | ModAccess
156 /// The kind of alias relationship between pointers of the set.
158 /// These represent conservatively correct alias results between any members
159 /// of the set. We represent these independently of the values of alias
160 /// results in order to pack it into a single bit. Lattice goes from
161 /// MustAlias to MayAlias.
163 SetMustAlias = 0, SetMayAlias = 1
167 /// True if this alias set contains volatile loads or stores.
168 unsigned Volatile : 1;
172 void addRef() { ++RefCount; }
174 void dropRef(AliasSetTracker &AST) {
175 assert(RefCount >= 1 && "Invalid reference count detected!");
177 removeFromTracker(AST);
180 Instruction *getUnknownInst(unsigned i) const {
181 assert(i < UnknownInsts.size());
182 return cast_or_null<Instruction>(UnknownInsts[i]);
187 bool isRef() const { return Access & RefAccess; }
188 bool isMod() const { return Access & ModAccess; }
189 bool isMustAlias() const { return Alias == SetMustAlias; }
190 bool isMayAlias() const { return Alias == SetMayAlias; }
192 /// Return true if this alias set contains volatile loads or stores.
193 bool isVolatile() const { return Volatile; }
195 /// Return true if this alias set should be ignored as part of the
196 /// AliasSetTracker object.
197 bool isForwardingAliasSet() const { return Forward; }
199 /// Merge the specified alias set into this alias set.
200 void mergeSetIn(AliasSet &AS, AliasSetTracker &AST);
202 // Alias Set iteration - Allow access to all of the pointers which are part of
205 iterator begin() const { return iterator(PtrList); }
206 iterator end() const { return iterator(); }
207 bool empty() const { return PtrList == nullptr; }
209 // Unfortunately, ilist::size() is linear, so we have to add code to keep
210 // track of the list's exact size.
211 unsigned size() { return SetSize; }
213 void print(raw_ostream &OS) const;
216 /// Define an iterator for alias sets... this is just a forward iterator.
217 class iterator : public std::iterator<std::forward_iterator_tag,
218 PointerRec, ptrdiff_t> {
222 explicit iterator(PointerRec *CN = nullptr) : CurNode(CN) {}
224 bool operator==(const iterator& x) const {
225 return CurNode == x.CurNode;
227 bool operator!=(const iterator& x) const { return !operator==(x); }
229 value_type &operator*() const {
230 assert(CurNode && "Dereferencing AliasSet.end()!");
233 value_type *operator->() const { return &operator*(); }
235 Value *getPointer() const { return CurNode->getValue(); }
236 uint64_t getSize() const { return CurNode->getSize(); }
237 AAMDNodes getAAInfo() const { return CurNode->getAAInfo(); }
239 iterator& operator++() { // Preincrement
240 assert(CurNode && "Advancing past AliasSet.end()!");
241 CurNode = CurNode->getNext();
244 iterator operator++(int) { // Postincrement
245 iterator tmp = *this; ++*this; return tmp;
250 // Can only be created by AliasSetTracker.
252 : PtrList(nullptr), PtrListEnd(&PtrList), Forward(nullptr), RefCount(0),
253 AliasAny(false), Access(NoAccess), Alias(SetMustAlias),
254 Volatile(false), SetSize(0) {}
256 AliasSet(const AliasSet &AS) = delete;
257 void operator=(const AliasSet &AS) = delete;
259 PointerRec *getSomePointer() const {
263 /// Return the real alias set this represents. If this has been merged with
264 /// another set and is forwarding, return the ultimate destination set. This
265 /// also implements the union-find collapsing as well.
266 AliasSet *getForwardedTarget(AliasSetTracker &AST) {
267 if (!Forward) return this;
269 AliasSet *Dest = Forward->getForwardedTarget(AST);
270 if (Dest != Forward) {
272 Forward->dropRef(AST);
278 void removeFromTracker(AliasSetTracker &AST);
280 void addPointer(AliasSetTracker &AST, PointerRec &Entry, uint64_t Size,
281 const AAMDNodes &AAInfo,
282 bool KnownMustAlias = false);
283 void addUnknownInst(Instruction *I, AliasAnalysis &AA);
284 void removeUnknownInst(AliasSetTracker &AST, Instruction *I) {
285 bool WasEmpty = UnknownInsts.empty();
286 for (size_t i = 0, e = UnknownInsts.size(); i != e; ++i)
287 if (UnknownInsts[i] == I) {
288 UnknownInsts[i] = UnknownInsts.back();
289 UnknownInsts.pop_back();
290 --i; --e; // Revisit the moved entry.
292 if (!WasEmpty && UnknownInsts.empty())
295 void setVolatile() { Volatile = true; }
298 /// Return true if the specified pointer "may" (or must) alias one of the
299 /// members in the set.
300 bool aliasesPointer(const Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo,
301 AliasAnalysis &AA) const;
302 bool aliasesUnknownInst(const Instruction *Inst, AliasAnalysis &AA) const;
305 inline raw_ostream& operator<<(raw_ostream &OS, const AliasSet &AS) {
310 class AliasSetTracker {
311 /// A CallbackVH to arrange for AliasSetTracker to be notified whenever a
312 /// Value is deleted.
313 class ASTCallbackVH final : public CallbackVH {
314 AliasSetTracker *AST;
315 void deleted() override;
316 void allUsesReplacedWith(Value *) override;
319 ASTCallbackVH(Value *V, AliasSetTracker *AST = nullptr);
320 ASTCallbackVH &operator=(Value *V);
322 /// Traits to tell DenseMap that tell us how to compare and hash the value
324 struct ASTCallbackVHDenseMapInfo : public DenseMapInfo<Value *> {};
327 ilist<AliasSet> AliasSets;
329 typedef DenseMap<ASTCallbackVH, AliasSet::PointerRec*,
330 ASTCallbackVHDenseMapInfo>
333 // Map from pointers to their node
334 PointerMapType PointerMap;
337 /// Create an empty collection of AliasSets, and use the specified alias
338 /// analysis object to disambiguate load and store addresses.
339 explicit AliasSetTracker(AliasAnalysis &aa)
340 : AA(aa), TotalMayAliasSetSize(0), AliasAnyAS(nullptr) {}
341 ~AliasSetTracker() { clear(); }
343 /// These methods are used to add different types of instructions to the alias
344 /// sets. Adding a new instruction can result in one of three actions
347 /// 1. If the instruction doesn't alias any other sets, create a new set.
348 /// 2. If the instruction aliases exactly one set, add it to the set
349 /// 3. If the instruction aliases multiple sets, merge the sets, and add
350 /// the instruction to the result.
352 /// These methods return true if inserting the instruction resulted in the
353 /// addition of a new alias set (i.e., the pointer did not alias anything).
355 void add(Value *Ptr, uint64_t Size, const AAMDNodes &AAInfo); // Add a loc.
356 void add(LoadInst *LI);
357 void add(StoreInst *SI);
358 void add(VAArgInst *VAAI);
359 void add(MemSetInst *MSI);
360 void add(MemTransferInst *MTI);
361 void add(Instruction *I); // Dispatch to one of the other add methods...
362 void add(BasicBlock &BB); // Add all instructions in basic block
363 void add(const AliasSetTracker &AST); // Add alias relations from another AST
364 void addUnknown(Instruction *I);
368 /// Return the alias sets that are active.
369 const ilist<AliasSet> &getAliasSets() const { return AliasSets; }
371 /// Return the alias set that the specified pointer lives in. If the New
372 /// argument is non-null, this method sets the value to true if a new alias
373 /// set is created to contain the pointer (because the pointer didn't alias
375 AliasSet &getAliasSetForPointer(Value *P, uint64_t Size,
376 const AAMDNodes &AAInfo);
378 /// Return the alias set containing the location specified if one exists,
379 /// otherwise return null.
380 AliasSet *getAliasSetForPointerIfExists(const Value *P, uint64_t Size,
381 const AAMDNodes &AAInfo) {
382 return mergeAliasSetsForPointer(P, Size, AAInfo);
385 /// Return true if the specified instruction "may" (or must) alias one of the
386 /// members in any of the sets.
387 bool containsUnknown(const Instruction *I) const;
389 /// Return the underlying alias analysis object used by this tracker.
390 AliasAnalysis &getAliasAnalysis() const { return AA; }
392 /// This method is used to remove a pointer value from the AliasSetTracker
393 /// entirely. It should be used when an instruction is deleted from the
394 /// program to update the AST. If you don't use this, you would have dangling
395 /// pointers to deleted instructions.
396 void deleteValue(Value *PtrVal);
398 /// This method should be used whenever a preexisting value in the program is
399 /// copied or cloned, introducing a new value. Note that it is ok for clients
400 /// that use this method to introduce the same value multiple times: if the
401 /// tracker already knows about a value, it will ignore the request.
402 void copyValue(Value *From, Value *To);
404 typedef ilist<AliasSet>::iterator iterator;
405 typedef ilist<AliasSet>::const_iterator const_iterator;
407 const_iterator begin() const { return AliasSets.begin(); }
408 const_iterator end() const { return AliasSets.end(); }
410 iterator begin() { return AliasSets.begin(); }
411 iterator end() { return AliasSets.end(); }
413 void print(raw_ostream &OS) const;
417 friend class AliasSet;
419 // The total number of pointers contained in all "may" alias sets.
420 unsigned TotalMayAliasSetSize;
422 // A non-null value signifies this AST is saturated. A saturated AST lumps
423 // all pointers into a single "May" set.
424 AliasSet *AliasAnyAS;
426 void removeAliasSet(AliasSet *AS);
428 /// Just like operator[] on the map, except that it creates an entry for the
429 /// pointer if it doesn't already exist.
430 AliasSet::PointerRec &getEntryFor(Value *V) {
431 AliasSet::PointerRec *&Entry = PointerMap[ASTCallbackVH(V, this)];
433 Entry = new AliasSet::PointerRec(V);
437 AliasSet &addPointer(Value *P, uint64_t Size, const AAMDNodes &AAInfo,
438 AliasSet::AccessLattice E);
439 AliasSet *mergeAliasSetsForPointer(const Value *Ptr, uint64_t Size,
440 const AAMDNodes &AAInfo);
442 /// Merge all alias sets into a single set that is considered to alias any
444 AliasSet &mergeAllAliasSets();
446 AliasSet *findAliasSetForUnknownInst(Instruction *Inst);
449 inline raw_ostream& operator<<(raw_ostream &OS, const AliasSetTracker &AST) {
454 } // End llvm namespace