AliasSetTracker.cpp revision 7e4286eb7c0e3c391e2cdae3535eff4b412105df
1//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===//
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 implements the AliasSetTracker and AliasSet classes.
11//
12//===----------------------------------------------------------------------===//
13
14#include "llvm/Analysis/AliasSetTracker.h"
15#include "llvm/Analysis/AliasAnalysis.h"
16#include "llvm/Instructions.h"
17#include "llvm/IntrinsicInst.h"
18#include "llvm/Pass.h"
19#include "llvm/Type.h"
20#include "llvm/Target/TargetData.h"
21#include "llvm/Assembly/Writer.h"
22#include "llvm/Support/Compiler.h"
23#include "llvm/Support/InstIterator.h"
24#include "llvm/Support/Streams.h"
25using namespace llvm;
26
27/// mergeSetIn - Merge the specified alias set into this alias set.
28///
29void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
30  assert(!AS.Forward && "Alias set is already forwarding!");
31  assert(!Forward && "This set is a forwarding set!!");
32
33  // Update the alias and access types of this set...
34  AccessTy |= AS.AccessTy;
35  AliasTy  |= AS.AliasTy;
36
37  if (AliasTy == MustAlias) {
38    // Check that these two merged sets really are must aliases.  Since both
39    // used to be must-alias sets, we can just check any pointer from each set
40    // for aliasing.
41    AliasAnalysis &AA = AST.getAliasAnalysis();
42    HashNodePair *L = getSomePointer();
43    HashNodePair *R = AS.getSomePointer();
44
45    // If the pointers are not a must-alias pair, this set becomes a may alias.
46    if (AA.alias(L->first, L->second.getSize(), R->first, R->second.getSize())
47        != AliasAnalysis::MustAlias)
48      AliasTy = MayAlias;
49  }
50
51  if (CallSites.empty()) {            // Merge call sites...
52    if (!AS.CallSites.empty())
53      std::swap(CallSites, AS.CallSites);
54  } else if (!AS.CallSites.empty()) {
55    CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end());
56    AS.CallSites.clear();
57  }
58
59  AS.Forward = this;  // Forward across AS now...
60  addRef();           // AS is now pointing to us...
61
62  // Merge the list of constituent pointers...
63  if (AS.PtrList) {
64    *PtrListEnd = AS.PtrList;
65    AS.PtrList->second.setPrevInList(PtrListEnd);
66    PtrListEnd = AS.PtrListEnd;
67
68    AS.PtrList = 0;
69    AS.PtrListEnd = &AS.PtrList;
70    assert(*AS.PtrListEnd == 0 && "End of list is not null?");
71  }
72}
73
74void AliasSetTracker::removeAliasSet(AliasSet *AS) {
75  if (AliasSet *Fwd = AS->Forward) {
76    Fwd->dropRef(*this);
77    AS->Forward = 0;
78  }
79  AliasSets.erase(AS);
80}
81
82void AliasSet::removeFromTracker(AliasSetTracker &AST) {
83  assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
84  AST.removeAliasSet(this);
85}
86
87void AliasSet::addPointer(AliasSetTracker &AST, HashNodePair &Entry,
88                          unsigned Size, bool KnownMustAlias) {
89  assert(!Entry.second.hasAliasSet() && "Entry already in set!");
90
91  // Check to see if we have to downgrade to _may_ alias.
92  if (isMustAlias() && !KnownMustAlias)
93    if (HashNodePair *P = getSomePointer()) {
94      AliasAnalysis &AA = AST.getAliasAnalysis();
95      AliasAnalysis::AliasResult Result =
96        AA.alias(P->first, P->second.getSize(), Entry.first, Size);
97      if (Result == AliasAnalysis::MayAlias)
98        AliasTy = MayAlias;
99      else                  // First entry of must alias must have maximum size!
100        P->second.updateSize(Size);
101      assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
102    }
103
104  Entry.second.setAliasSet(this);
105  Entry.second.updateSize(Size);
106
107  // Add it to the end of the list...
108  assert(*PtrListEnd == 0 && "End of list is not null?");
109  *PtrListEnd = &Entry;
110  PtrListEnd = Entry.second.setPrevInList(PtrListEnd);
111  assert(*PtrListEnd == 0 && "End of list is not null?");
112  addRef();               // Entry points to alias set...
113}
114
115void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) {
116  CallSites.push_back(CS);
117
118  AliasAnalysis::ModRefBehavior Behavior = AA.getModRefBehavior(CS);
119  if (Behavior == AliasAnalysis::DoesNotAccessMemory)
120    return;
121  else if (Behavior == AliasAnalysis::OnlyReadsMemory) {
122    AliasTy = MayAlias;
123    AccessTy |= Refs;
124    return;
125  }
126
127  // FIXME: This should use mod/ref information to make this not suck so bad
128  AliasTy = MayAlias;
129  AccessTy = ModRef;
130}
131
132/// aliasesPointer - Return true if the specified pointer "may" (or must)
133/// alias one of the members in the set.
134///
135bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size,
136                              AliasAnalysis &AA) const {
137  if (AliasTy == MustAlias) {
138    assert(CallSites.empty() && "Illegal must alias set!");
139
140    // If this is a set of MustAliases, only check to see if the pointer aliases
141    // SOME value in the set...
142    HashNodePair *SomePtr = getSomePointer();
143    assert(SomePtr && "Empty must-alias set??");
144    return AA.alias(SomePtr->first, SomePtr->second.getSize(), Ptr, Size);
145  }
146
147  // If this is a may-alias set, we have to check all of the pointers in the set
148  // to be sure it doesn't alias the set...
149  for (iterator I = begin(), E = end(); I != E; ++I)
150    if (AA.alias(Ptr, Size, I.getPointer(), I.getSize()))
151      return true;
152
153  // Check the call sites list and invoke list...
154  if (!CallSites.empty()) {
155    if (AA.hasNoModRefInfoForCalls())
156      return true;
157
158    for (unsigned i = 0, e = CallSites.size(); i != e; ++i)
159      if (AA.getModRefInfo(CallSites[i], const_cast<Value*>(Ptr), Size)
160                   != AliasAnalysis::NoModRef)
161        return true;
162  }
163
164  return false;
165}
166
167bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const {
168  if (AA.doesNotAccessMemory(CS))
169    return false;
170
171  if (AA.hasNoModRefInfoForCalls())
172    return true;
173
174  for (unsigned i = 0, e = CallSites.size(); i != e; ++i)
175    if (AA.getModRefInfo(CallSites[i], CS) != AliasAnalysis::NoModRef ||
176        AA.getModRefInfo(CS, CallSites[i]) != AliasAnalysis::NoModRef)
177      return true;
178
179  for (iterator I = begin(), E = end(); I != E; ++I)
180    if (AA.getModRefInfo(CS, I.getPointer(), I.getSize()) !=
181           AliasAnalysis::NoModRef)
182      return true;
183
184  return false;
185}
186
187
188/// findAliasSetForPointer - Given a pointer, find the one alias set to put the
189/// instruction referring to the pointer into.  If there are multiple alias sets
190/// that may alias the pointer, merge them together and return the unified set.
191///
192AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
193                                                  unsigned Size) {
194  AliasSet *FoundSet = 0;
195  for (iterator I = begin(), E = end(); I != E; ++I)
196    if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) {
197      if (FoundSet == 0) {  // If this is the first alias set ptr can go into.
198        FoundSet = I;       // Remember it.
199      } else {              // Otherwise, we must merge the sets.
200        FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
201      }
202    }
203
204  return FoundSet;
205}
206
207/// containsPointer - Return true if the specified location is represented by
208/// this alias set, false otherwise.  This does not modify the AST object or
209/// alias sets.
210bool AliasSetTracker::containsPointer(Value *Ptr, unsigned Size) const {
211  for (const_iterator I = begin(), E = end(); I != E; ++I)
212    if (!I->Forward && I->aliasesPointer(Ptr, Size, AA))
213      return true;
214  return false;
215}
216
217
218
219AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) {
220  AliasSet *FoundSet = 0;
221  for (iterator I = begin(), E = end(); I != E; ++I)
222    if (!I->Forward && I->aliasesCallSite(CS, AA)) {
223      if (FoundSet == 0) {  // If this is the first alias set ptr can go into.
224        FoundSet = I;       // Remember it.
225      } else if (!I->Forward) {     // Otherwise, we must merge the sets.
226        FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
227      }
228    }
229
230  return FoundSet;
231}
232
233
234
235
236/// getAliasSetForPointer - Return the alias set that the specified pointer
237/// lives in...
238AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size,
239                                                 bool *New) {
240  AliasSet::HashNodePair &Entry = getEntryFor(Pointer);
241
242  // Check to see if the pointer is already known...
243  if (Entry.second.hasAliasSet()) {
244    Entry.second.updateSize(Size);
245    // Return the set!
246    return *Entry.second.getAliasSet(*this)->getForwardedTarget(*this);
247  } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) {
248    // Add it to the alias set it aliases...
249    AS->addPointer(*this, Entry, Size);
250    return *AS;
251  } else {
252    if (New) *New = true;
253    // Otherwise create a new alias set to hold the loaded pointer...
254    AliasSets.push_back(new AliasSet());
255    AliasSets.back().addPointer(*this, Entry, Size);
256    return AliasSets.back();
257  }
258}
259
260bool AliasSetTracker::add(Value *Ptr, unsigned Size) {
261  bool NewPtr;
262  addPointer(Ptr, Size, AliasSet::NoModRef, NewPtr);
263  return NewPtr;
264}
265
266
267bool AliasSetTracker::add(LoadInst *LI) {
268  bool NewPtr;
269  AliasSet &AS = addPointer(LI->getOperand(0),
270                            AA.getTargetData().getTypeStoreSize(LI->getType()),
271                            AliasSet::Refs, NewPtr);
272  if (LI->isVolatile()) AS.setVolatile();
273  return NewPtr;
274}
275
276bool AliasSetTracker::add(StoreInst *SI) {
277  bool NewPtr;
278  Value *Val = SI->getOperand(0);
279  AliasSet &AS = addPointer(SI->getOperand(1),
280                            AA.getTargetData().getTypeStoreSize(Val->getType()),
281                            AliasSet::Mods, NewPtr);
282  if (SI->isVolatile()) AS.setVolatile();
283  return NewPtr;
284}
285
286bool AliasSetTracker::add(FreeInst *FI) {
287  bool NewPtr;
288  addPointer(FI->getOperand(0), ~0, AliasSet::Mods, NewPtr);
289  return NewPtr;
290}
291
292bool AliasSetTracker::add(VAArgInst *VAAI) {
293  bool NewPtr;
294  addPointer(VAAI->getOperand(0), ~0, AliasSet::ModRef, NewPtr);
295  return NewPtr;
296}
297
298
299bool AliasSetTracker::add(CallSite CS) {
300  if (isa<DbgInfoIntrinsic>(CS.getInstruction()))
301    return true; // Ignore DbgInfo Intrinsics.
302  if (AA.doesNotAccessMemory(CS))
303    return true; // doesn't alias anything
304
305  AliasSet *AS = findAliasSetForCallSite(CS);
306  if (!AS) {
307    AliasSets.push_back(new AliasSet());
308    AS = &AliasSets.back();
309    AS->addCallSite(CS, AA);
310    return true;
311  } else {
312    AS->addCallSite(CS, AA);
313    return false;
314  }
315}
316
317bool AliasSetTracker::add(Instruction *I) {
318  // Dispatch to one of the other add methods...
319  if (LoadInst *LI = dyn_cast<LoadInst>(I))
320    return add(LI);
321  else if (StoreInst *SI = dyn_cast<StoreInst>(I))
322    return add(SI);
323  else if (CallInst *CI = dyn_cast<CallInst>(I))
324    return add(CI);
325  else if (InvokeInst *II = dyn_cast<InvokeInst>(I))
326    return add(II);
327  else if (FreeInst *FI = dyn_cast<FreeInst>(I))
328    return add(FI);
329  else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
330    return add(VAAI);
331  return true;
332}
333
334void AliasSetTracker::add(BasicBlock &BB) {
335  for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
336    add(I);
337}
338
339void AliasSetTracker::add(const AliasSetTracker &AST) {
340  assert(&AA == &AST.AA &&
341         "Merging AliasSetTracker objects with different Alias Analyses!");
342
343  // Loop over all of the alias sets in AST, adding the pointers contained
344  // therein into the current alias sets.  This can cause alias sets to be
345  // merged together in the current AST.
346  for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I)
347    if (!I->Forward) {   // Ignore forwarding alias sets
348      AliasSet &AS = const_cast<AliasSet&>(*I);
349
350      // If there are any call sites in the alias set, add them to this AST.
351      for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i)
352        add(AS.CallSites[i]);
353
354      // Loop over all of the pointers in this alias set...
355      AliasSet::iterator I = AS.begin(), E = AS.end();
356      bool X;
357      for (; I != E; ++I) {
358        AliasSet &NewAS = addPointer(I.getPointer(), I.getSize(),
359                                     (AliasSet::AccessType)AS.AccessTy, X);
360        if (AS.isVolatile()) NewAS.setVolatile();
361      }
362    }
363}
364
365/// remove - Remove the specified (potentially non-empty) alias set from the
366/// tracker.
367void AliasSetTracker::remove(AliasSet &AS) {
368  // Drop all call sites.
369  AS.CallSites.clear();
370
371  // Clear the alias set.
372  unsigned NumRefs = 0;
373  while (!AS.empty()) {
374    AliasSet::HashNodePair *P = AS.PtrList;
375
376    // Unlink from the list of values.
377    P->second.removeFromList();
378
379    // Remember how many references need to be dropped.
380    ++NumRefs;
381
382    // Finally, remove the entry.
383    Value *Remove = P->first;   // Take a copy because it is invalid to pass
384    PointerMap.erase(Remove);   // a reference to the data being erased.
385  }
386
387  // Stop using the alias set, removing it.
388  AS.RefCount -= NumRefs;
389  if (AS.RefCount == 0)
390    AS.removeFromTracker(*this);
391}
392
393bool AliasSetTracker::remove(Value *Ptr, unsigned Size) {
394  AliasSet *AS = findAliasSetForPointer(Ptr, Size);
395  if (!AS) return false;
396  remove(*AS);
397  return true;
398}
399
400bool AliasSetTracker::remove(LoadInst *LI) {
401  unsigned Size = AA.getTargetData().getTypeStoreSize(LI->getType());
402  AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size);
403  if (!AS) return false;
404  remove(*AS);
405  return true;
406}
407
408bool AliasSetTracker::remove(StoreInst *SI) {
409  unsigned Size =
410    AA.getTargetData().getTypeStoreSize(SI->getOperand(0)->getType());
411  AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size);
412  if (!AS) return false;
413  remove(*AS);
414  return true;
415}
416
417bool AliasSetTracker::remove(FreeInst *FI) {
418  AliasSet *AS = findAliasSetForPointer(FI->getOperand(0), ~0);
419  if (!AS) return false;
420  remove(*AS);
421  return true;
422}
423
424bool AliasSetTracker::remove(VAArgInst *VAAI) {
425  AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0), ~0);
426  if (!AS) return false;
427  remove(*AS);
428  return true;
429}
430
431bool AliasSetTracker::remove(CallSite CS) {
432  if (AA.doesNotAccessMemory(CS))
433    return false; // doesn't alias anything
434
435  AliasSet *AS = findAliasSetForCallSite(CS);
436  if (!AS) return false;
437  remove(*AS);
438  return true;
439}
440
441bool AliasSetTracker::remove(Instruction *I) {
442  // Dispatch to one of the other remove methods...
443  if (LoadInst *LI = dyn_cast<LoadInst>(I))
444    return remove(LI);
445  else if (StoreInst *SI = dyn_cast<StoreInst>(I))
446    return remove(SI);
447  else if (CallInst *CI = dyn_cast<CallInst>(I))
448    return remove(CI);
449  else if (FreeInst *FI = dyn_cast<FreeInst>(I))
450    return remove(FI);
451  else if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
452    return remove(VAAI);
453  return true;
454}
455
456
457// deleteValue method - This method is used to remove a pointer value from the
458// AliasSetTracker entirely.  It should be used when an instruction is deleted
459// from the program to update the AST.  If you don't use this, you would have
460// dangling pointers to deleted instructions.
461//
462void AliasSetTracker::deleteValue(Value *PtrVal) {
463  // Notify the alias analysis implementation that this value is gone.
464  AA.deleteValue(PtrVal);
465
466  // If this is a call instruction, remove the callsite from the appropriate
467  // AliasSet.
468  CallSite CS = CallSite::get(PtrVal);
469  if (CS.getInstruction())
470    if (!AA.doesNotAccessMemory(CS))
471      if (AliasSet *AS = findAliasSetForCallSite(CS))
472        AS->removeCallSite(CS);
473
474  // First, look up the PointerRec for this pointer.
475  hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(PtrVal);
476  if (I == PointerMap.end()) return;  // Noop
477
478  // If we found one, remove the pointer from the alias set it is in.
479  AliasSet::HashNodePair &PtrValEnt = *I;
480  AliasSet *AS = PtrValEnt.second.getAliasSet(*this);
481
482  // Unlink from the list of values...
483  PtrValEnt.second.removeFromList();
484  // Stop using the alias set
485  AS->dropRef(*this);
486  PointerMap.erase(I);
487}
488
489// copyValue - This method should be used whenever a preexisting value in the
490// program is copied or cloned, introducing a new value.  Note that it is ok for
491// clients that use this method to introduce the same value multiple times: if
492// the tracker already knows about a value, it will ignore the request.
493//
494void AliasSetTracker::copyValue(Value *From, Value *To) {
495  // Notify the alias analysis implementation that this value is copied.
496  AA.copyValue(From, To);
497
498  // First, look up the PointerRec for this pointer.
499  hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(From);
500  if (I == PointerMap.end() || !I->second.hasAliasSet())
501    return;  // Noop
502
503  AliasSet::HashNodePair &Entry = getEntryFor(To);
504  if (Entry.second.hasAliasSet()) return;    // Already in the tracker!
505
506  // Add it to the alias set it aliases...
507  AliasSet *AS = I->second.getAliasSet(*this);
508  AS->addPointer(*this, Entry, I->second.getSize(), true);
509}
510
511
512
513//===----------------------------------------------------------------------===//
514//               AliasSet/AliasSetTracker Printing Support
515//===----------------------------------------------------------------------===//
516
517void AliasSet::print(std::ostream &OS) const {
518  OS << "  AliasSet[" << (void*)this << "," << RefCount << "] ";
519  OS << (AliasTy == MustAlias ? "must" : "may") << " alias, ";
520  switch (AccessTy) {
521  case NoModRef: OS << "No access "; break;
522  case Refs    : OS << "Ref       "; break;
523  case Mods    : OS << "Mod       "; break;
524  case ModRef  : OS << "Mod/Ref   "; break;
525  default: assert(0 && "Bad value for AccessTy!");
526  }
527  if (isVolatile()) OS << "[volatile] ";
528  if (Forward)
529    OS << " forwarding to " << (void*)Forward;
530
531
532  if (!empty()) {
533    OS << "Pointers: ";
534    for (iterator I = begin(), E = end(); I != E; ++I) {
535      if (I != begin()) OS << ", ";
536      WriteAsOperand(OS << "(", I.getPointer());
537      OS << ", " << I.getSize() << ")";
538    }
539  }
540  if (!CallSites.empty()) {
541    OS << "\n    " << CallSites.size() << " Call Sites: ";
542    for (unsigned i = 0, e = CallSites.size(); i != e; ++i) {
543      if (i) OS << ", ";
544      WriteAsOperand(OS, CallSites[i].getCalledValue());
545    }
546  }
547  OS << "\n";
548}
549
550void AliasSetTracker::print(std::ostream &OS) const {
551  OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for "
552     << PointerMap.size() << " pointer values.\n";
553  for (const_iterator I = begin(), E = end(); I != E; ++I)
554    I->print(OS);
555  OS << "\n";
556}
557
558void AliasSet::dump() const { print (cerr); }
559void AliasSetTracker::dump() const { print(cerr); }
560
561//===----------------------------------------------------------------------===//
562//                            AliasSetPrinter Pass
563//===----------------------------------------------------------------------===//
564
565namespace {
566  class VISIBILITY_HIDDEN AliasSetPrinter : public FunctionPass {
567    AliasSetTracker *Tracker;
568  public:
569    static char ID; // Pass identification, replacement for typeid
570    AliasSetPrinter() : FunctionPass(&ID) {}
571
572    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
573      AU.setPreservesAll();
574      AU.addRequired<AliasAnalysis>();
575    }
576
577    virtual bool runOnFunction(Function &F) {
578      Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>());
579
580      for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
581        Tracker->add(&*I);
582      Tracker->print(cerr);
583      delete Tracker;
584      return false;
585    }
586  };
587}
588
589char AliasSetPrinter::ID = 0;
590static RegisterPass<AliasSetPrinter>
591X("print-alias-sets", "Alias Set Printer", false, true);
592