AliasSetTracker.h revision 9055ccdb6b33607e32ac83a8e9289fba44d1989a 
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/Support/CallSite.h"
21#include "llvm/Support/ValueHandle.h"
22#include "llvm/ADT/DenseMap.h"
23#include "llvm/ADT/ilist.h"
24#include "llvm/ADT/ilist_node.h"
25#include <vector>
26
27namespace llvm {
28
29class AliasAnalysis;
30class LoadInst;
31class StoreInst;
32class VAArgInst;
33class AliasSetTracker;
34class AliasSet;
35
36class AliasSet : public ilist_node<AliasSet> {
37  friend class AliasSetTracker;
38
39  class PointerRec {
40    Value *Val;  // The pointer this record corresponds to.
41    PointerRec **PrevInList, *NextInList;
42    AliasSet *AS;
43    uint64_t Size;
44    const MDNode *TBAAInfo;
45  public:
46    PointerRec(Value *V)
47      : Val(V), PrevInList(0), NextInList(0), AS(0), Size(0),
48        TBAAInfo(DenseMapInfo<const MDNode *>::getEmptyKey()) {}
49
50    Value *getValue() const { return Val; }
51
52    PointerRec *getNext() const { return NextInList; }
53    bool hasAliasSet() const { return AS != 0; }
54
55    PointerRec** setPrevInList(PointerRec **PIL) {
56      PrevInList = PIL;
57      return &NextInList;
58    }
59
60    void updateSizeAndTBAAInfo(uint64_t NewSize, const MDNode *NewTBAAInfo) {
61      if (NewSize > Size) Size = NewSize;
62
63      if (TBAAInfo == DenseMapInfo<const MDNode *>::getEmptyKey())
64        // We don't have a TBAAInfo yet. Set it to NewTBAAInfo.
65        TBAAInfo = NewTBAAInfo;
66      else if (TBAAInfo != NewTBAAInfo)
67        // NewTBAAInfo conflicts with TBAAInfo.
68        TBAAInfo = DenseMapInfo<const MDNode *>::getTombstoneKey();
69    }
70
71    uint64_t getSize() const { return Size; }
72
73    /// getTBAAInfo - Return the TBAAInfo, or null if there is no
74    /// information or conflicting information.
75    const MDNode *getTBAAInfo() const {
76      // If we have missing or conflicting TBAAInfo, return null.
77      if (TBAAInfo == DenseMapInfo<const MDNode *>::getEmptyKey() ||
78          TBAAInfo == DenseMapInfo<const MDNode *>::getTombstoneKey())
79        return 0;
80      return TBAAInfo;
81    }
82
83    AliasSet *getAliasSet(AliasSetTracker &AST) {
84      assert(AS && "No AliasSet yet!");
85      if (AS->Forward) {
86        AliasSet *OldAS = AS;
87        AS = OldAS->getForwardedTarget(AST);
88        AS->addRef();
89        OldAS->dropRef(AST);
90      }
91      return AS;
92    }
93
94    void setAliasSet(AliasSet *as) {
95      assert(AS == 0 && "Already have an alias set!");
96      AS = as;
97    }
98
99    void eraseFromList() {
100      if (NextInList) NextInList->PrevInList = PrevInList;
101      *PrevInList = NextInList;
102      if (AS->PtrListEnd == &NextInList) {
103        AS->PtrListEnd = PrevInList;
104        assert(*AS->PtrListEnd == 0 && "List not terminated right!");
105      }
106      delete this;
107    }
108  };
109
110  PointerRec *PtrList, **PtrListEnd;  // Doubly linked list of nodes.
111  AliasSet *Forward;             // Forwarding pointer.
112  AliasSet *Next, *Prev;         // Doubly linked list of AliasSets.
113
114  // All calls & invokes in this alias set.
115  std::vector<AssertingVH<Instruction> > CallSites;
116
117  // RefCount - Number of nodes pointing to this AliasSet plus the number of
118  // AliasSets forwarding to it.
119  unsigned RefCount : 28;
120
121  /// AccessType - Keep track of whether this alias set merely refers to the
122  /// locations of memory, whether it modifies the memory, or whether it does
123  /// both.  The lattice goes from "NoModRef" to either Refs or Mods, then to
124  /// ModRef as necessary.
125  ///
126  enum AccessType {
127    NoModRef = 0, Refs = 1,         // Ref = bit 1
128    Mods     = 2, ModRef = 3        // Mod = bit 2
129  };
130  unsigned AccessTy : 2;
131
132  /// AliasType - Keep track the relationships between the pointers in the set.
133  /// Lattice goes from MustAlias to MayAlias.
134  ///
135  enum AliasType {
136    MustAlias = 0, MayAlias = 1
137  };
138  unsigned AliasTy : 1;
139
140  // Volatile - True if this alias set contains volatile loads or stores.
141  bool Volatile : 1;
142
143  void addRef() { ++RefCount; }
144  void dropRef(AliasSetTracker &AST) {
145    assert(RefCount >= 1 && "Invalid reference count detected!");
146    if (--RefCount == 0)
147      removeFromTracker(AST);
148  }
149
150  CallSite getCallSite(unsigned i) const {
151    assert(i < CallSites.size());
152    return CallSite(CallSites[i]);
153  }
154
155public:
156  /// Accessors...
157  bool isRef() const { return AccessTy & Refs; }
158  bool isMod() const { return AccessTy & Mods; }
159  bool isMustAlias() const { return AliasTy == MustAlias; }
160  bool isMayAlias()  const { return AliasTy == MayAlias; }
161
162  // isVolatile - Return true if this alias set contains volatile loads or
163  // stores.
164  bool isVolatile() const { return Volatile; }
165
166  /// isForwardingAliasSet - Return true if this alias set should be ignored as
167  /// part of the AliasSetTracker object.
168  bool isForwardingAliasSet() const { return Forward; }
169
170  /// mergeSetIn - Merge the specified alias set into this alias set...
171  ///
172  void mergeSetIn(AliasSet &AS, AliasSetTracker &AST);
173
174  // Alias Set iteration - Allow access to all of the pointer which are part of
175  // this alias set...
176  class iterator;
177  iterator begin() const { return iterator(PtrList); }
178  iterator end()   const { return iterator(); }
179  bool empty() const { return PtrList == 0; }
180
181  void print(raw_ostream &OS) const;
182  void dump() const;
183
184  /// Define an iterator for alias sets... this is just a forward iterator.
185  class iterator : public std::iterator<std::forward_iterator_tag,
186                                        PointerRec, ptrdiff_t> {
187    PointerRec *CurNode;
188  public:
189    explicit iterator(PointerRec *CN = 0) : CurNode(CN) {}
190
191    bool operator==(const iterator& x) const {
192      return CurNode == x.CurNode;
193    }
194    bool operator!=(const iterator& x) const { return !operator==(x); }
195
196    const iterator &operator=(const iterator &I) {
197      CurNode = I.CurNode;
198      return *this;
199    }
200
201    value_type &operator*() const {
202      assert(CurNode && "Dereferencing AliasSet.end()!");
203      return *CurNode;
204    }
205    value_type *operator->() const { return &operator*(); }
206
207    Value *getPointer() const { return CurNode->getValue(); }
208    uint64_t getSize() const { return CurNode->getSize(); }
209    const MDNode *getTBAAInfo() const { return CurNode->getTBAAInfo(); }
210
211    iterator& operator++() {                // Preincrement
212      assert(CurNode && "Advancing past AliasSet.end()!");
213      CurNode = CurNode->getNext();
214      return *this;
215    }
216    iterator operator++(int) { // Postincrement
217      iterator tmp = *this; ++*this; return tmp;
218    }
219  };
220
221private:
222  // Can only be created by AliasSetTracker. Also, ilist creates one
223  // to serve as a sentinel.
224  friend struct ilist_sentinel_traits<AliasSet>;
225  AliasSet() : PtrList(0), PtrListEnd(&PtrList), Forward(0), RefCount(0),
226               AccessTy(NoModRef), AliasTy(MustAlias), Volatile(false) {
227  }
228
229  AliasSet(const AliasSet &AS);        // do not implement
230  void operator=(const AliasSet &AS);  // do not implement
231
232  PointerRec *getSomePointer() const {
233    return PtrList;
234  }
235
236  /// getForwardedTarget - Return the real alias set this represents.  If this
237  /// has been merged with another set and is forwarding, return the ultimate
238  /// destination set.  This also implements the union-find collapsing as well.
239  AliasSet *getForwardedTarget(AliasSetTracker &AST) {
240    if (!Forward) return this;
241
242    AliasSet *Dest = Forward->getForwardedTarget(AST);
243    if (Dest != Forward) {
244      Dest->addRef();
245      Forward->dropRef(AST);
246      Forward = Dest;
247    }
248    return Dest;
249  }
250
251  void removeFromTracker(AliasSetTracker &AST);
252
253  void addPointer(AliasSetTracker &AST, PointerRec &Entry, uint64_t Size,
254                  const MDNode *TBAAInfo,
255                  bool KnownMustAlias = false);
256  void addCallSite(CallSite CS, AliasAnalysis &AA);
257  void removeCallSite(CallSite CS) {
258    for (size_t i = 0, e = CallSites.size(); i != e; ++i)
259      if (CallSites[i] == CS.getInstruction()) {
260        CallSites[i] = CallSites.back();
261        CallSites.pop_back();
262        --i; --e;  // Revisit the moved entry.
263      }
264  }
265  void setVolatile() { Volatile = true; }
266
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 aliasesCallSite(CallSite CS, 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    virtual void deleted();
287    virtual void allUsesReplacedWith(Value *);
288  public:
289    ASTCallbackVH(Value *V, AliasSetTracker *AST = 0);
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(CallSite CS);          // Call/Invoke instructions
330  bool add(CallInst *CI)   { return add(CallSite(CI)); }
331  bool add(InvokeInst *II) { return add(CallSite(II)); }
332  bool add(Instruction *I);       // Dispatch to one of the other add methods...
333  void add(BasicBlock &BB);       // Add all instructions in basic block
334  void add(const AliasSetTracker &AST); // Add alias relations from another AST
335
336  /// remove methods - These methods are used to remove all entries that might
337  /// be aliased by the specified instruction.  These methods return true if any
338  /// alias sets were eliminated.
339  // Remove a location
340  bool remove(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo);
341  bool remove(LoadInst *LI);
342  bool remove(StoreInst *SI);
343  bool remove(VAArgInst *VAAI);
344  bool remove(CallSite CS);
345  bool remove(CallInst *CI)   { return remove(CallSite(CI)); }
346  bool remove(InvokeInst *II) { return remove(CallSite(II)); }
347  bool remove(Instruction *I);
348  void remove(AliasSet &AS);
349
350  void clear();
351
352  /// getAliasSets - Return the alias sets that are active.
353  ///
354  const ilist<AliasSet> &getAliasSets() const { return AliasSets; }
355
356  /// getAliasSetForPointer - Return the alias set that the specified pointer
357  /// lives in.  If the New argument is non-null, this method sets the value to
358  /// true if a new alias set is created to contain the pointer (because the
359  /// pointer didn't alias anything).
360  AliasSet &getAliasSetForPointer(Value *P, uint64_t Size,
361                                  const MDNode *TBAAInfo,
362                                  bool *New = 0);
363
364  /// getAliasSetForPointerIfExists - Return the alias set containing the
365  /// location specified if one exists, otherwise return null.
366  AliasSet *getAliasSetForPointerIfExists(Value *P, uint64_t Size,
367                                          const MDNode *TBAAInfo) {
368    return findAliasSetForPointer(P, Size, TBAAInfo);
369  }
370
371  /// containsPointer - Return true if the specified location is represented by
372  /// this alias set, false otherwise.  This does not modify the AST object or
373  /// alias sets.
374  bool containsPointer(Value *P, uint64_t Size, const MDNode *TBAAInfo) const;
375
376  /// getAliasAnalysis - Return the underlying alias analysis object used by
377  /// this tracker.
378  AliasAnalysis &getAliasAnalysis() const { return AA; }
379
380  /// deleteValue method - This method is used to remove a pointer value from
381  /// the AliasSetTracker entirely.  It should be used when an instruction is
382  /// deleted from the program to update the AST.  If you don't use this, you
383  /// would have dangling pointers to deleted instructions.
384  ///
385  void deleteValue(Value *PtrVal);
386
387  /// copyValue - This method should be used whenever a preexisting value in the
388  /// program is copied or cloned, introducing a new value.  Note that it is ok
389  /// for clients that use this method to introduce the same value multiple
390  /// times: if the tracker already knows about a value, it will ignore the
391  /// request.
392  ///
393  void copyValue(Value *From, Value *To);
394
395
396  typedef ilist<AliasSet>::iterator iterator;
397  typedef ilist<AliasSet>::const_iterator const_iterator;
398
399  const_iterator begin() const { return AliasSets.begin(); }
400  const_iterator end()   const { return AliasSets.end(); }
401
402  iterator begin() { return AliasSets.begin(); }
403  iterator end()   { return AliasSets.end(); }
404
405  void print(raw_ostream &OS) const;
406  void dump() const;
407
408private:
409  friend class AliasSet;
410  void removeAliasSet(AliasSet *AS);
411
412  // getEntryFor - Just like operator[] on the map, except that it creates an
413  // entry for the pointer if it doesn't already exist.
414  AliasSet::PointerRec &getEntryFor(Value *V) {
415    AliasSet::PointerRec *&Entry = PointerMap[ASTCallbackVH(V, this)];
416    if (Entry == 0)
417      Entry = new AliasSet::PointerRec(V);
418    return *Entry;
419  }
420
421  AliasSet &addPointer(Value *P, uint64_t Size, const MDNode *TBAAInfo,
422                       AliasSet::AccessType E,
423                       bool &NewSet) {
424    NewSet = false;
425    AliasSet &AS = getAliasSetForPointer(P, Size, TBAAInfo, &NewSet);
426    AS.AccessTy |= E;
427    return AS;
428  }
429  AliasSet *findAliasSetForPointer(const Value *Ptr, uint64_t Size,
430                                   const MDNode *TBAAInfo);
431
432  AliasSet *findAliasSetForCallSite(CallSite CS);
433};
434
435inline raw_ostream& operator<<(raw_ostream &OS, const AliasSetTracker &AST) {
436  AST.print(OS);
437  return OS;
438}
439
440} // End llvm namespace
441
442#endif
443