AliasSetTracker.cpp revision 63e9930498a0eefaa6cfcca72213ec527cc72198 
1//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file was developed by the LLVM research group and is distributed under
6// the University of Illinois Open Source 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/iMemory.h"
17#include "llvm/iOther.h"
18#include "llvm/iTerminators.h"
19#include "llvm/Pass.h"
20#include "llvm/Target/TargetData.h"
21#include "llvm/Assembly/Writer.h"
22#include "llvm/Support/InstIterator.h"
23#include <iostream>
24using namespace llvm;
25
26/// mergeSetIn - Merge the specified alias set into this alias set...
27///
28void AliasSet::mergeSetIn(AliasSet &AS) {
29  assert(!AS.Forward && "Alias set is already forwarding!");
30  assert(!Forward && "This set is a forwarding set!!");
31
32  // Update the alias and access types of this set...
33  AccessTy |= AS.AccessTy;
34  AliasTy  |= AS.AliasTy;
35
36  if (CallSites.empty()) {            // Merge call sites...
37    if (!AS.CallSites.empty())
38      std::swap(CallSites, AS.CallSites);
39  } else if (!AS.CallSites.empty()) {
40    CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end());
41    AS.CallSites.clear();
42  }
43
44  AS.Forward = this;  // Forward across AS now...
45  addRef();           // AS is now pointing to us...
46
47  // Merge the list of constituent pointers...
48  if (AS.PtrList) {
49    *PtrListEnd = AS.PtrList;
50    AS.PtrList->second.setPrevInList(PtrListEnd);
51    PtrListEnd = AS.PtrListEnd;
52
53    AS.PtrList = 0;
54    AS.PtrListEnd = &AS.PtrList;
55  }
56}
57
58void AliasSetTracker::removeAliasSet(AliasSet *AS) {
59  if (AliasSet *Fwd = AS->Forward) {
60    Fwd->dropRef(*this);
61    AS->Forward = 0;
62  }
63  AliasSets.erase(AS);
64}
65
66void AliasSet::removeFromTracker(AliasSetTracker &AST) {
67  assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
68  AST.removeAliasSet(this);
69}
70
71void AliasSet::addPointer(AliasSetTracker &AST, HashNodePair &Entry,
72                          unsigned Size) {
73  assert(!Entry.second.hasAliasSet() && "Entry already in set!");
74
75  AliasAnalysis &AA = AST.getAliasAnalysis();
76
77  if (isMustAlias())    // Check to see if we have to downgrade to _may_ alias
78    if (HashNodePair *P = getSomePointer()) {
79      AliasAnalysis::AliasResult Result =
80        AA.alias(P->first, P->second.getSize(), Entry.first, Size);
81      if (Result == AliasAnalysis::MayAlias)
82        AliasTy = MayAlias;
83      else                  // First entry of must alias must have maximum size!
84        P->second.updateSize(Size);
85      assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
86    }
87
88  Entry.second.setAliasSet(this);
89  Entry.second.updateSize(Size);
90
91  // Add it to the end of the list...
92  assert(*PtrListEnd == 0 && "End of list is not null?");
93  *PtrListEnd = &Entry;
94  PtrListEnd = Entry.second.setPrevInList(PtrListEnd);
95  addRef();               // Entry points to alias set...
96}
97
98void AliasSet::addCallSite(CallSite CS, AliasAnalysis &AA) {
99  CallSites.push_back(CS);
100
101  if (Function *F = CS.getCalledFunction()) {
102    if (AA.doesNotAccessMemory(F))
103      return;
104    else if (AA.onlyReadsMemory(F)) {
105      AliasTy = MayAlias;
106      AccessTy |= Refs;
107      return;
108    }
109  }
110
111  // FIXME: This should use mod/ref information to make this not suck so bad
112  AliasTy = MayAlias;
113  AccessTy = ModRef;
114}
115
116/// aliasesPointer - Return true if the specified pointer "may" (or must)
117/// alias one of the members in the set.
118///
119bool AliasSet::aliasesPointer(const Value *Ptr, unsigned Size,
120                              AliasAnalysis &AA) const {
121  if (AliasTy == MustAlias) {
122    assert(CallSites.empty() && "Illegal must alias set!");
123
124    // If this is a set of MustAliases, only check to see if the pointer aliases
125    // SOME value in the set...
126    HashNodePair *SomePtr = getSomePointer();
127    assert(SomePtr && "Empty must-alias set??");
128    return AA.alias(SomePtr->first, SomePtr->second.getSize(), Ptr, Size);
129  }
130
131  // If this is a may-alias set, we have to check all of the pointers in the set
132  // to be sure it doesn't alias the set...
133  for (iterator I = begin(), E = end(); I != E; ++I)
134    if (AA.alias(Ptr, Size, I.getPointer(), I.getSize()))
135      return true;
136
137  // Check the call sites list and invoke list...
138  if (!CallSites.empty()) {
139    if (AA.hasNoModRefInfoForCalls())
140      return true;
141
142    for (unsigned i = 0, e = CallSites.size(); i != e; ++i)
143      if (AA.getModRefInfo(CallSites[i], const_cast<Value*>(Ptr), Size)
144                   != AliasAnalysis::NoModRef)
145        return true;
146  }
147
148  return false;
149}
150
151bool AliasSet::aliasesCallSite(CallSite CS, AliasAnalysis &AA) const {
152  if (Function *F = CS.getCalledFunction())
153    if (AA.doesNotAccessMemory(F))
154      return false;
155
156  if (AA.hasNoModRefInfoForCalls())
157    return true;
158
159  for (unsigned i = 0, e = CallSites.size(); i != e; ++i)
160    if (AA.getModRefInfo(CallSites[i], CS) != AliasAnalysis::NoModRef ||
161        AA.getModRefInfo(CS, CallSites[i]) != AliasAnalysis::NoModRef)
162      return true;
163
164  for (iterator I = begin(), E = end(); I != E; ++I)
165    if (AA.getModRefInfo(CS, I.getPointer(), I.getSize()) !=
166           AliasAnalysis::NoModRef)
167      return true;
168
169  return false;
170}
171
172
173/// findAliasSetForPointer - Given a pointer, find the one alias set to put the
174/// instruction referring to the pointer into.  If there are multiple alias sets
175/// that may alias the pointer, merge them together and return the unified set.
176///
177AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
178                                                  unsigned Size) {
179  AliasSet *FoundSet = 0;
180  for (iterator I = begin(), E = end(); I != E; ++I)
181    if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) {
182      if (FoundSet == 0) {  // If this is the first alias set ptr can go into...
183        FoundSet = I;       // Remember it.
184      } else {              // Otherwise, we must merge the sets...
185        FoundSet->mergeSetIn(*I);     // Merge in contents...
186      }
187    }
188
189  return FoundSet;
190}
191
192AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) {
193  AliasSet *FoundSet = 0;
194  for (iterator I = begin(), E = end(); I != E; ++I)
195    if (!I->Forward && I->aliasesCallSite(CS, AA)) {
196      if (FoundSet == 0) {  // If this is the first alias set ptr can go into...
197        FoundSet = I;       // Remember it.
198      } else if (!I->Forward) {     // Otherwise, we must merge the sets...
199        FoundSet->mergeSetIn(*I);     // Merge in contents...
200      }
201    }
202
203  return FoundSet;
204}
205
206
207
208
209/// getAliasSetForPointer - Return the alias set that the specified pointer
210/// lives in...
211AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, unsigned Size,
212                                                 bool *New) {
213  AliasSet::HashNodePair &Entry = getEntryFor(Pointer);
214
215  // Check to see if the pointer is already known...
216  if (Entry.second.hasAliasSet()) {
217    Entry.second.updateSize(Size);
218    // Return the set!
219    return *Entry.second.getAliasSet(*this)->getForwardedTarget(*this);
220  } else if (AliasSet *AS = findAliasSetForPointer(Pointer, Size)) {
221    // Add it to the alias set it aliases...
222    AS->addPointer(*this, Entry, Size);
223    return *AS;
224  } else {
225    if (New) *New = true;
226    // Otherwise create a new alias set to hold the loaded pointer...
227    AliasSets.push_back(new AliasSet());
228    AliasSets.back().addPointer(*this, Entry, Size);
229    return AliasSets.back();
230  }
231}
232
233bool AliasSetTracker::add(Value *Ptr, unsigned Size) {
234  bool NewPtr;
235  addPointer(Ptr, Size, AliasSet::NoModRef, NewPtr);
236  return NewPtr;
237}
238
239
240bool AliasSetTracker::add(LoadInst *LI) {
241  bool NewPtr;
242  AliasSet &AS = addPointer(LI->getOperand(0),
243                            AA.getTargetData().getTypeSize(LI->getType()),
244                            AliasSet::Refs, NewPtr);
245  if (LI->isVolatile()) AS.setVolatile();
246  return NewPtr;
247}
248
249bool AliasSetTracker::add(StoreInst *SI) {
250  bool NewPtr;
251  Value *Val = SI->getOperand(0);
252  AliasSet &AS = addPointer(SI->getOperand(1),
253                            AA.getTargetData().getTypeSize(Val->getType()),
254                            AliasSet::Mods, NewPtr);
255  if (SI->isVolatile()) AS.setVolatile();
256  return NewPtr;
257}
258
259bool AliasSetTracker::add(FreeInst *FI) {
260  bool NewPtr;
261  AliasSet &AS = addPointer(FI->getOperand(0), ~0,
262                            AliasSet::Mods, NewPtr);
263  return NewPtr;
264}
265
266
267bool AliasSetTracker::add(CallSite CS) {
268  bool NewPtr;
269  if (Function *F = CS.getCalledFunction())
270    if (AA.doesNotAccessMemory(F))
271      return true; // doesn't alias anything
272
273  AliasSet *AS = findAliasSetForCallSite(CS);
274  if (!AS) {
275    AliasSets.push_back(new AliasSet());
276    AS = &AliasSets.back();
277    AS->addCallSite(CS, AA);
278    return true;
279  } else {
280    AS->addCallSite(CS, AA);
281    return false;
282  }
283}
284
285bool AliasSetTracker::add(Instruction *I) {
286  // Dispatch to one of the other add methods...
287  if (LoadInst *LI = dyn_cast<LoadInst>(I))
288    return add(LI);
289  else if (StoreInst *SI = dyn_cast<StoreInst>(I))
290    return add(SI);
291  else if (CallInst *CI = dyn_cast<CallInst>(I))
292    return add(CI);
293  else if (InvokeInst *II = dyn_cast<InvokeInst>(I))
294    return add(II);
295  else if (FreeInst *FI = dyn_cast<FreeInst>(I))
296    return add(FI);
297  return true;
298}
299
300void AliasSetTracker::add(BasicBlock &BB) {
301  for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
302    add(I);
303}
304
305void AliasSetTracker::add(const AliasSetTracker &AST) {
306  assert(&AA == &AST.AA &&
307         "Merging AliasSetTracker objects with different Alias Analyses!");
308
309  // Loop over all of the alias sets in AST, adding the pointers contained
310  // therein into the current alias sets.  This can cause alias sets to be
311  // merged together in the current AST.
312  for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I)
313    if (!I->Forward) {   // Ignore forwarding alias sets
314      AliasSet &AS = const_cast<AliasSet&>(*I);
315
316      // If there are any call sites in the alias set, add them to this AST.
317      for (unsigned i = 0, e = AS.CallSites.size(); i != e; ++i)
318        add(AS.CallSites[i]);
319
320      // Loop over all of the pointers in this alias set...
321      AliasSet::iterator I = AS.begin(), E = AS.end();
322      bool X;
323      for (; I != E; ++I)
324        addPointer(I.getPointer(), I.getSize(),
325                   (AliasSet::AccessType)AS.AccessTy, X);
326    }
327}
328
329/// remove - Remove the specified (potentially non-empty) alias set from the
330/// tracker.
331void AliasSetTracker::remove(AliasSet &AS) {
332  bool SetDead;
333  do {
334    AliasSet::iterator I = AS.begin();
335    Value *Ptr = I.getPointer(); ++I;
336
337    // deleteValue will delete the set automatically when the last pointer
338    // reference is destroyed.  "Predict" when this will happen.
339    SetDead = I == AS.end();
340    deleteValue(Ptr);  // Delete all of the pointers from the set
341  } while (!SetDead);
342}
343
344bool AliasSetTracker::remove(Value *Ptr, unsigned Size) {
345  AliasSet *AS = findAliasSetForPointer(Ptr, Size);
346  if (!AS) return false;
347  remove(*AS);
348  return true;
349}
350
351bool AliasSetTracker::remove(LoadInst *LI) {
352  unsigned Size = AA.getTargetData().getTypeSize(LI->getType());
353  AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size);
354  if (!AS) return false;
355  remove(*AS);
356  return true;
357}
358
359bool AliasSetTracker::remove(StoreInst *SI) {
360  unsigned Size = AA.getTargetData().getTypeSize(SI->getOperand(0)->getType());
361  AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size);
362  if (!AS) return false;
363  remove(*AS);
364  return true;
365}
366
367bool AliasSetTracker::remove(FreeInst *FI) {
368  AliasSet *AS = findAliasSetForPointer(FI->getOperand(0), ~0);
369  if (!AS) return false;
370  remove(*AS);
371  return true;
372}
373
374bool AliasSetTracker::remove(CallSite CS) {
375  if (Function *F = CS.getCalledFunction())
376    if (AA.doesNotAccessMemory(F))
377      return false; // doesn't alias anything
378
379  AliasSet *AS = findAliasSetForCallSite(CS);
380  if (!AS) return false;
381  remove(*AS);
382  return true;
383}
384
385bool AliasSetTracker::remove(Instruction *I) {
386  // Dispatch to one of the other remove methods...
387  if (LoadInst *LI = dyn_cast<LoadInst>(I))
388    return remove(LI);
389  else if (StoreInst *SI = dyn_cast<StoreInst>(I))
390    return remove(SI);
391  else if (CallInst *CI = dyn_cast<CallInst>(I))
392    return remove(CI);
393  else if (FreeInst *FI = dyn_cast<FreeInst>(I))
394    return remove(FI);
395  return true;
396}
397
398
399// deleteValue method - This method is used to remove a pointer value from the
400// AliasSetTracker entirely.  It should be used when an instruction is deleted
401// from the program to update the AST.  If you don't use this, you would have
402// dangling pointers to deleted instructions.
403//
404void AliasSetTracker::deleteValue(Value *PtrVal) {
405  // First, look up the PointerRec for this pointer...
406  hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(PtrVal);
407  if (I == PointerMap.end()) return;  // Noop
408
409  // If we found one, remove the pointer from the alias set it is in.
410  AliasSet::HashNodePair &PtrValEnt = *I;
411  AliasSet *AS = PtrValEnt.second.getAliasSet(*this);
412
413  // Unlink from the list of values...
414  PtrValEnt.second.removeFromList();
415  // Stop using the alias set
416  AS->dropRef(*this);
417  PointerMap.erase(I);
418}
419
420
421//===----------------------------------------------------------------------===//
422//               AliasSet/AliasSetTracker Printing Support
423//===----------------------------------------------------------------------===//
424
425void AliasSet::print(std::ostream &OS) const {
426  OS << "  AliasSet[" << (void*)this << "," << RefCount << "] ";
427  OS << (AliasTy == MustAlias ? "must" : "may ") << " alias, ";
428  switch (AccessTy) {
429  case NoModRef: OS << "No access "; break;
430  case Refs    : OS << "Ref       "; break;
431  case Mods    : OS << "Mod       "; break;
432  case ModRef  : OS << "Mod/Ref   "; break;
433  default: assert(0 && "Bad value for AccessTy!");
434  }
435  if (isVolatile()) OS << "[volatile] ";
436  if (Forward)
437    OS << " forwarding to " << (void*)Forward;
438
439
440  if (begin() != end()) {
441    OS << "Pointers: ";
442    for (iterator I = begin(), E = end(); I != E; ++I) {
443      if (I != begin()) OS << ", ";
444      WriteAsOperand(OS << "(", I.getPointer());
445      OS << ", " << I.getSize() << ")";
446    }
447  }
448  if (!CallSites.empty()) {
449    OS << "\n    " << CallSites.size() << " Call Sites: ";
450    for (unsigned i = 0, e = CallSites.size(); i != e; ++i) {
451      if (i) OS << ", ";
452      WriteAsOperand(OS, CallSites[i].getCalledValue());
453    }
454  }
455  OS << "\n";
456}
457
458void AliasSetTracker::print(std::ostream &OS) const {
459  OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for "
460     << PointerMap.size() << " pointer values.\n";
461  for (const_iterator I = begin(), E = end(); I != E; ++I)
462    I->print(OS);
463  OS << "\n";
464}
465
466void AliasSet::dump() const { print (std::cerr); }
467void AliasSetTracker::dump() const { print(std::cerr); }
468
469//===----------------------------------------------------------------------===//
470//                            AliasSetPrinter Pass
471//===----------------------------------------------------------------------===//
472
473namespace {
474  class AliasSetPrinter : public FunctionPass {
475    AliasSetTracker *Tracker;
476  public:
477    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
478      AU.setPreservesAll();
479      AU.addRequired<AliasAnalysis>();
480    }
481
482    virtual bool runOnFunction(Function &F) {
483      Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>());
484
485      for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
486        Tracker->add(&*I);
487      return false;
488    }
489
490    /// print - Convert to human readable form
491    virtual void print(std::ostream &OS) const {
492      Tracker->print(OS);
493    }
494
495    virtual void releaseMemory() {
496      delete Tracker;
497    }
498  };
499  RegisterPass<AliasSetPrinter> X("print-alias-sets", "Alias Set Printer",
500                                  PassInfo::Analysis | PassInfo::Optimization);
501}
502