AliasSetTracker.h revision fb8096dee5df60f156e770b9f96f8417e9dbd4c9 
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    unsigned Size;
44    const MDNode *TBAAInfo;
45  public:
46    PointerRec(Value *V)
47      : Val(V), PrevInList(0), NextInList(0), AS(0), Size(0), TBAAInfo(0) {}
48
49    Value *getValue() const { return Val; }
50
51    PointerRec *getNext() const { return NextInList; }
52    bool hasAliasSet() const { return AS != 0; }
53
54    PointerRec** setPrevInList(PointerRec **PIL) {
55      PrevInList = PIL;
56      return &NextInList;
57    }
58
59    void updateSizeAndTBAAInfo(unsigned NewSize, const MDNode *NewTBAAInfo) {
60      if (NewSize > Size) Size = NewSize;
61
62      if (!TBAAInfo)
63        TBAAInfo = NewTBAAInfo;
64      else if (TBAAInfo != NewTBAAInfo)
65        TBAAInfo = reinterpret_cast<const MDNode *>(-1);
66    }
67
68    unsigned getSize() const { return Size; }
69
70    /// getRawTBAAInfo - Return the raw TBAAInfo member. In addition to
71    /// being null or a pointer to an MDNode, this could be -1, meaning
72    /// there was conflicting information.
73    const MDNode *getRawTBAAInfo() const {
74      return TBAAInfo;
75    }
76
77    /// getTBAAInfo - Return the TBAAInfo, or null if there is no
78    /// information or conflicting information.
79    const MDNode *getTBAAInfo() const {
80      // If we have conflicting TBAAInfo, return null.
81      if (TBAAInfo == reinterpret_cast<const MDNode *>(-1))
82        return 0;
83      return TBAAInfo;
84    }
85
86    AliasSet *getAliasSet(AliasSetTracker &AST) {
87      assert(AS && "No AliasSet yet!");
88      if (AS->Forward) {
89        AliasSet *OldAS = AS;
90        AS = OldAS->getForwardedTarget(AST);
91        AS->addRef();
92        OldAS->dropRef(AST);
93      }
94      return AS;
95    }
96
97    void setAliasSet(AliasSet *as) {
98      assert(AS == 0 && "Already have an alias set!");
99      AS = as;
100    }
101
102    void eraseFromList() {
103      if (NextInList) NextInList->PrevInList = PrevInList;
104      *PrevInList = NextInList;
105      if (AS->PtrListEnd == &NextInList) {
106        AS->PtrListEnd = PrevInList;
107        assert(*AS->PtrListEnd == 0 && "List not terminated right!");
108      }
109      delete this;
110    }
111  };
112
113  PointerRec *PtrList, **PtrListEnd;  // Doubly linked list of nodes.
114  AliasSet *Forward;             // Forwarding pointer.
115  AliasSet *Next, *Prev;         // Doubly linked list of AliasSets.
116
117  // All calls & invokes in this alias set.
118  std::vector<AssertingVH<Instruction> > CallSites;
119
120  // RefCount - Number of nodes pointing to this AliasSet plus the number of
121  // AliasSets forwarding to it.
122  unsigned RefCount : 28;
123
124  /// AccessType - Keep track of whether this alias set merely refers to the
125  /// locations of memory, whether it modifies the memory, or whether it does
126  /// both.  The lattice goes from "NoModRef" to either Refs or Mods, then to
127  /// ModRef as necessary.
128  ///
129  enum AccessType {
130    NoModRef = 0, Refs = 1,         // Ref = bit 1
131    Mods     = 2, ModRef = 3        // Mod = bit 2
132  };
133  unsigned AccessTy : 2;
134
135  /// AliasType - Keep track the relationships between the pointers in the set.
136  /// Lattice goes from MustAlias to MayAlias.
137  ///
138  enum AliasType {
139    MustAlias = 0, MayAlias = 1
140  };
141  unsigned AliasTy : 1;
142
143  // Volatile - True if this alias set contains volatile loads or stores.
144  bool Volatile : 1;
145
146  void addRef() { ++RefCount; }
147  void dropRef(AliasSetTracker &AST) {
148    assert(RefCount >= 1 && "Invalid reference count detected!");
149    if (--RefCount == 0)
150      removeFromTracker(AST);
151  }
152
153  CallSite getCallSite(unsigned i) const {
154    assert(i < CallSites.size());
155    return CallSite(CallSites[i]);
156  }
157
158public:
159  /// Accessors...
160  bool isRef() const { return AccessTy & Refs; }
161  bool isMod() const { return AccessTy & Mods; }
162  bool isMustAlias() const { return AliasTy == MustAlias; }
163  bool isMayAlias()  const { return AliasTy == MayAlias; }
164
165  // isVolatile - Return true if this alias set contains volatile loads or
166  // stores.
167  bool isVolatile() const { return Volatile; }
168
169  /// isForwardingAliasSet - Return true if this alias set should be ignored as
170  /// part of the AliasSetTracker object.
171  bool isForwardingAliasSet() const { return Forward; }
172
173  /// mergeSetIn - Merge the specified alias set into this alias set...
174  ///
175  void mergeSetIn(AliasSet &AS, AliasSetTracker &AST);
176
177  // Alias Set iteration - Allow access to all of the pointer which are part of
178  // this alias set...
179  class iterator;
180  iterator begin() const { return iterator(PtrList); }
181  iterator end()   const { return iterator(); }
182  bool empty() const { return PtrList == 0; }
183
184  void print(raw_ostream &OS) const;
185  void dump() const;
186
187  /// Define an iterator for alias sets... this is just a forward iterator.
188  class iterator : public std::iterator<std::forward_iterator_tag,
189                                        PointerRec, ptrdiff_t> {
190    PointerRec *CurNode;
191  public:
192    explicit iterator(PointerRec *CN = 0) : CurNode(CN) {}
193
194    bool operator==(const iterator& x) const {
195      return CurNode == x.CurNode;
196    }
197    bool operator!=(const iterator& x) const { return !operator==(x); }
198
199    const iterator &operator=(const iterator &I) {
200      CurNode = I.CurNode;
201      return *this;
202    }
203
204    value_type &operator*() const {
205      assert(CurNode && "Dereferencing AliasSet.end()!");
206      return *CurNode;
207    }
208    value_type *operator->() const { return &operator*(); }
209
210    Value *getPointer() const { return CurNode->getValue(); }
211    unsigned getSize() const { return CurNode->getSize(); }
212    const MDNode *getRawTBAAInfo() const { return CurNode->getRawTBAAInfo(); }
213    const MDNode *getTBAAInfo() const { return CurNode->getTBAAInfo(); }
214
215    iterator& operator++() {                // Preincrement
216      assert(CurNode && "Advancing past AliasSet.end()!");
217      CurNode = CurNode->getNext();
218      return *this;
219    }
220    iterator operator++(int) { // Postincrement
221      iterator tmp = *this; ++*this; return tmp;
222    }
223  };
224
225private:
226  // Can only be created by AliasSetTracker. Also, ilist creates one
227  // to serve as a sentinel.
228  friend struct ilist_sentinel_traits<AliasSet>;
229  AliasSet() : PtrList(0), PtrListEnd(&PtrList), Forward(0), RefCount(0),
230               AccessTy(NoModRef), AliasTy(MustAlias), Volatile(false) {
231  }
232
233  AliasSet(const AliasSet &AS);        // do not implement
234  void operator=(const AliasSet &AS);  // do not implement
235
236  PointerRec *getSomePointer() const {
237    return PtrList;
238  }
239
240  /// getForwardedTarget - Return the real alias set this represents.  If this
241  /// has been merged with another set and is forwarding, return the ultimate
242  /// destination set.  This also implements the union-find collapsing as well.
243  AliasSet *getForwardedTarget(AliasSetTracker &AST) {
244    if (!Forward) return this;
245
246    AliasSet *Dest = Forward->getForwardedTarget(AST);
247    if (Dest != Forward) {
248      Dest->addRef();
249      Forward->dropRef(AST);
250      Forward = Dest;
251    }
252    return Dest;
253  }
254
255  void removeFromTracker(AliasSetTracker &AST);
256
257  void addPointer(AliasSetTracker &AST, PointerRec &Entry, unsigned Size,
258                  const MDNode *TBAAInfo,
259                  bool KnownMustAlias = false);
260  void addCallSite(CallSite CS, AliasAnalysis &AA);
261  void removeCallSite(CallSite CS) {
262    for (size_t i = 0, e = CallSites.size(); i != e; ++i)
263      if (CallSites[i] == CS.getInstruction()) {
264        CallSites[i] = CallSites.back();
265        CallSites.pop_back();
266      }
267  }
268  void setVolatile() { Volatile = true; }
269
270  /// aliasesPointer - Return true if the specified pointer "may" (or must)
271  /// alias one of the members in the set.
272  ///
273  bool aliasesPointer(const Value *Ptr, unsigned Size, const MDNode *TBAAInfo,
274                      AliasAnalysis &AA) const;
275  bool aliasesCallSite(CallSite CS, AliasAnalysis &AA) const;
276};
277
278inline raw_ostream& operator<<(raw_ostream &OS, const AliasSet &AS) {
279  AS.print(OS);
280  return OS;
281}
282
283
284class AliasSetTracker {
285  /// CallbackVH - A CallbackVH to arrange for AliasSetTracker to be
286  /// notified whenever a Value is deleted.
287  class ASTCallbackVH : public CallbackVH {
288    AliasSetTracker *AST;
289    virtual void deleted();
290  public:
291    ASTCallbackVH(Value *V, AliasSetTracker *AST = 0);
292    ASTCallbackVH &operator=(Value *V);
293  };
294  /// ASTCallbackVHDenseMapInfo - Traits to tell DenseMap that tell us how to
295  /// compare and hash the value handle.
296  struct ASTCallbackVHDenseMapInfo : public DenseMapInfo<Value *> {};
297
298  AliasAnalysis &AA;
299  ilist<AliasSet> AliasSets;
300
301  typedef DenseMap<ASTCallbackVH, AliasSet::PointerRec*,
302                   ASTCallbackVHDenseMapInfo>
303    PointerMapType;
304
305  // Map from pointers to their node
306  PointerMapType PointerMap;
307
308public:
309  /// AliasSetTracker ctor - Create an empty collection of AliasSets, and use
310  /// the specified alias analysis object to disambiguate load and store
311  /// addresses.
312  explicit AliasSetTracker(AliasAnalysis &aa) : AA(aa) {}
313  ~AliasSetTracker() { clear(); }
314
315  /// add methods - These methods are used to add different types of
316  /// instructions to the alias sets.  Adding a new instruction can result in
317  /// one of three actions happening:
318  ///
319  ///   1. If the instruction doesn't alias any other sets, create a new set.
320  ///   2. If the instruction aliases exactly one set, add it to the set
321  ///   3. If the instruction aliases multiple sets, merge the sets, and add
322  ///      the instruction to the result.
323  ///
324  /// These methods return true if inserting the instruction resulted in the
325  /// addition of a new alias set (i.e., the pointer did not alias anything).
326  ///
327  bool add(Value *Ptr, unsigned Size, const MDNode *TBAAInfo); // Add a location
328  bool add(LoadInst *LI);
329  bool add(StoreInst *SI);
330  bool add(VAArgInst *VAAI);
331  bool add(CallSite CS);          // Call/Invoke instructions
332  bool add(CallInst *CI)   { return add(CallSite(CI)); }
333  bool add(InvokeInst *II) { return add(CallSite(II)); }
334  bool add(Instruction *I);       // Dispatch to one of the other add methods...
335  void add(BasicBlock &BB);       // Add all instructions in basic block
336  void add(const AliasSetTracker &AST); // Add alias relations from another AST
337
338  /// remove methods - These methods are used to remove all entries that might
339  /// be aliased by the specified instruction.  These methods return true if any
340  /// alias sets were eliminated.
341  // Remove a location
342  bool remove(Value *Ptr, unsigned Size, const MDNode *TBAAInfo);
343  bool remove(LoadInst *LI);
344  bool remove(StoreInst *SI);
345  bool remove(VAArgInst *VAAI);
346  bool remove(CallSite CS);
347  bool remove(CallInst *CI)   { return remove(CallSite(CI)); }
348  bool remove(InvokeInst *II) { return remove(CallSite(II)); }
349  bool remove(Instruction *I);
350  void remove(AliasSet &AS);
351
352  void clear();
353
354  /// getAliasSets - Return the alias sets that are active.
355  ///
356  const ilist<AliasSet> &getAliasSets() const { return AliasSets; }
357
358  /// getAliasSetForPointer - Return the alias set that the specified pointer
359  /// lives in.  If the New argument is non-null, this method sets the value to
360  /// true if a new alias set is created to contain the pointer (because the
361  /// pointer didn't alias anything).
362  AliasSet &getAliasSetForPointer(Value *P, unsigned Size,
363                                  const MDNode *TBAAInfo,
364                                  bool *New = 0);
365
366  /// getAliasSetForPointerIfExists - Return the alias set containing the
367  /// location specified if one exists, otherwise return null.
368  AliasSet *getAliasSetForPointerIfExists(Value *P, unsigned Size,
369                                          const MDNode *TBAAInfo) {
370    return findAliasSetForPointer(P, Size, TBAAInfo);
371  }
372
373  /// containsPointer - Return true if the specified location is represented by
374  /// this alias set, false otherwise.  This does not modify the AST object or
375  /// alias sets.
376  bool containsPointer(Value *P, unsigned Size, const MDNode *TBAAInfo) const;
377
378  /// getAliasAnalysis - Return the underlying alias analysis object used by
379  /// this tracker.
380  AliasAnalysis &getAliasAnalysis() const { return AA; }
381
382  /// deleteValue method - This method is used to remove a pointer value from
383  /// the AliasSetTracker entirely.  It should be used when an instruction is
384  /// deleted from the program to update the AST.  If you don't use this, you
385  /// would have dangling pointers to deleted instructions.
386  ///
387  void deleteValue(Value *PtrVal);
388
389  /// copyValue - This method should be used whenever a preexisting value in the
390  /// program is copied or cloned, introducing a new value.  Note that it is ok
391  /// for clients that use this method to introduce the same value multiple
392  /// times: if the tracker already knows about a value, it will ignore the
393  /// request.
394  ///
395  void copyValue(Value *From, Value *To);
396
397
398  typedef ilist<AliasSet>::iterator iterator;
399  typedef ilist<AliasSet>::const_iterator const_iterator;
400
401  const_iterator begin() const { return AliasSets.begin(); }
402  const_iterator end()   const { return AliasSets.end(); }
403
404  iterator begin() { return AliasSets.begin(); }
405  iterator end()   { return AliasSets.end(); }
406
407  void print(raw_ostream &OS) const;
408  void dump() const;
409
410private:
411  friend class AliasSet;
412  void removeAliasSet(AliasSet *AS);
413
414  // getEntryFor - Just like operator[] on the map, except that it creates an
415  // entry for the pointer if it doesn't already exist.
416  AliasSet::PointerRec &getEntryFor(Value *V) {
417    AliasSet::PointerRec *&Entry = PointerMap[ASTCallbackVH(V, this)];
418    if (Entry == 0)
419      Entry = new AliasSet::PointerRec(V);
420    return *Entry;
421  }
422
423  AliasSet &addPointer(Value *P, unsigned Size, const MDNode *TBAAInfo,
424                       AliasSet::AccessType E,
425                       bool &NewSet) {
426    NewSet = false;
427    AliasSet &AS = getAliasSetForPointer(P, Size, TBAAInfo, &NewSet);
428    AS.AccessTy |= E;
429    return AS;
430  }
431  AliasSet *findAliasSetForPointer(const Value *Ptr, unsigned Size,
432                                   const MDNode *TBAAInfo);
433
434  AliasSet *findAliasSetForCallSite(CallSite CS);
435};
436
437inline raw_ostream& operator<<(raw_ostream &OS, const AliasSetTracker &AST) {
438  AST.print(OS);
439  return OS;
440}
441
442} // End llvm namespace
443
444#endif
445