lib/Analysis/AliasSetTracker.cpp - platform/external/llvm - Git at Google

 //===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements the AliasSetTracker and AliasSet classes.
 //
 //===----------------------------------------------------------------------===//

 #include "llvm/Analysis/AliasSetTracker.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Assembly/Writer.h"
 #include "llvm/DataLayout.h"
 #include "llvm/Instructions.h"
 #include "llvm/IntrinsicInst.h"
 #include "llvm/LLVMContext.h"
 #include "llvm/Pass.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/InstIterator.h"
 #include "llvm/Support/raw_ostream.h"
 #include "llvm/Type.h"
 using namespace llvm;

 /// mergeSetIn - Merge the specified alias set into this alias set.
 ///
 void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
   assert(!AS.Forward && "Alias set is already forwarding!");
   assert(!Forward && "This set is a forwarding set!!");

   // Update the alias and access types of this set...
   AccessTy |= AS.AccessTy;
   AliasTy  |= AS.AliasTy;
   Volatile |= AS.Volatile;

   if (AliasTy == MustAlias) {
     // Check that these two merged sets really are must aliases.  Since both
     // used to be must-alias sets, we can just check any pointer from each set
     // for aliasing.
     AliasAnalysis &AA = AST.getAliasAnalysis();
     PointerRec *L = getSomePointer();
     PointerRec *R = AS.getSomePointer();

     // If the pointers are not a must-alias pair, this set becomes a may alias.
     if (AA.alias(AliasAnalysis::Location(L->getValue(),
                                          L->getSize(),
                                          L->getTBAAInfo()),
                  AliasAnalysis::Location(R->getValue(),
                                          R->getSize(),
                                          R->getTBAAInfo()))
         != AliasAnalysis::MustAlias)
       AliasTy = MayAlias;
   }

   if (UnknownInsts.empty()) {            // Merge call sites...
     if (!AS.UnknownInsts.empty())
       std::swap(UnknownInsts, AS.UnknownInsts);
   } else if (!AS.UnknownInsts.empty()) {
     UnknownInsts.insert(UnknownInsts.end(), AS.UnknownInsts.begin(), AS.UnknownInsts.end());
     AS.UnknownInsts.clear();
   }

   AS.Forward = this;  // Forward across AS now...
   addRef();           // AS is now pointing to us...

   // Merge the list of constituent pointers...
   if (AS.PtrList) {
     *PtrListEnd = AS.PtrList;
     AS.PtrList->setPrevInList(PtrListEnd);
     PtrListEnd = AS.PtrListEnd;

     AS.PtrList = 0;
     AS.PtrListEnd = &AS.PtrList;
     assert(*AS.PtrListEnd == 0 && "End of list is not null?");
   }
 }

 void AliasSetTracker::removeAliasSet(AliasSet *AS) {
   if (AliasSet *Fwd = AS->Forward) {
     Fwd->dropRef(*this);
     AS->Forward = 0;
   }
   AliasSets.erase(AS);
 }

 void AliasSet::removeFromTracker(AliasSetTracker &AST) {
   assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
   AST.removeAliasSet(this);
 }

 void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
                           uint64_t Size, const MDNode *TBAAInfo,
                           bool KnownMustAlias) {
   assert(!Entry.hasAliasSet() && "Entry already in set!");

   // Check to see if we have to downgrade to _may_ alias.
   if (isMustAlias() && !KnownMustAlias)
     if (PointerRec *P = getSomePointer()) {
       AliasAnalysis &AA = AST.getAliasAnalysis();
       AliasAnalysis::AliasResult Result =
         AA.alias(AliasAnalysis::Location(P->getValue(), P->getSize(),
                                          P->getTBAAInfo()),
                  AliasAnalysis::Location(Entry.getValue(), Size, TBAAInfo));
       if (Result != AliasAnalysis::MustAlias)
         AliasTy = MayAlias;
       else                  // First entry of must alias must have maximum size!
         P->updateSizeAndTBAAInfo(Size, TBAAInfo);
       assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
     }

   Entry.setAliasSet(this);
   Entry.updateSizeAndTBAAInfo(Size, TBAAInfo);

   // Add it to the end of the list...
   assert(*PtrListEnd == 0 && "End of list is not null?");
   *PtrListEnd = &Entry;
   PtrListEnd = Entry.setPrevInList(PtrListEnd);
   assert(*PtrListEnd == 0 && "End of list is not null?");
   addRef();               // Entry points to alias set.
 }

 void AliasSet::addUnknownInst(Instruction *I, AliasAnalysis &AA) {
   UnknownInsts.push_back(I);

   if (!I->mayWriteToMemory()) {
     AliasTy = MayAlias;
     AccessTy |= Refs;
     return;
   }

   // FIXME: This should use mod/ref information to make this not suck so bad
   AliasTy = MayAlias;
   AccessTy = ModRef;
 }

 /// aliasesPointer - Return true if the specified pointer "may" (or must)
 /// alias one of the members in the set.
 ///
 bool AliasSet::aliasesPointer(const Value *Ptr, uint64_t Size,
                               const MDNode *TBAAInfo,
                               AliasAnalysis &AA) const {
   if (AliasTy == MustAlias) {
     assert(UnknownInsts.empty() && "Illegal must alias set!");

     // If this is a set of MustAliases, only check to see if the pointer aliases
     // SOME value in the set.
     PointerRec *SomePtr = getSomePointer();
     assert(SomePtr && "Empty must-alias set??");
     return AA.alias(AliasAnalysis::Location(SomePtr->getValue(),
                                             SomePtr->getSize(),
                                             SomePtr->getTBAAInfo()),
                     AliasAnalysis::Location(Ptr, Size, TBAAInfo));
   }

   // If this is a may-alias set, we have to check all of the pointers in the set
   // to be sure it doesn't alias the set...
   for (iterator I = begin(), E = end(); I != E; ++I)
     if (AA.alias(AliasAnalysis::Location(Ptr, Size, TBAAInfo),
                  AliasAnalysis::Location(I.getPointer(), I.getSize(),
                                          I.getTBAAInfo())))
       return true;

   // Check the unknown instructions...
   if (!UnknownInsts.empty()) {
     for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i)
       if (AA.getModRefInfo(UnknownInsts[i],
                            AliasAnalysis::Location(Ptr, Size, TBAAInfo)) !=
             AliasAnalysis::NoModRef)
         return true;
   }

   return false;
 }

 bool AliasSet::aliasesUnknownInst(Instruction *Inst, AliasAnalysis &AA) const {
   if (!Inst->mayReadOrWriteMemory())
     return false;

   for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
     CallSite C1 = getUnknownInst(i), C2 = Inst;
     if (!C1 || !C2 ||
         AA.getModRefInfo(C1, C2) != AliasAnalysis::NoModRef ||
         AA.getModRefInfo(C2, C1) != AliasAnalysis::NoModRef)
       return true;
   }

   for (iterator I = begin(), E = end(); I != E; ++I)
     if (AA.getModRefInfo(Inst, AliasAnalysis::Location(I.getPointer(),
                                                        I.getSize(),
                                                        I.getTBAAInfo())) !=
            AliasAnalysis::NoModRef)
       return true;

   return false;
 }

 void AliasSetTracker::clear() {
   // Delete all the PointerRec entries.
   for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end();
        I != E; ++I)
     I->second->eraseFromList();

   PointerMap.clear();

   // The alias sets should all be clear now.
   AliasSets.clear();
 }


 /// findAliasSetForPointer - Given a pointer, find the one alias set to put the
 /// instruction referring to the pointer into.  If there are multiple alias sets
 /// that may alias the pointer, merge them together and return the unified set.
 ///
 AliasSet *AliasSetTracker::findAliasSetForPointer(const Value *Ptr,
                                                   uint64_t Size,
                                                   const MDNode *TBAAInfo) {
   AliasSet *FoundSet = 0;
   for (iterator I = begin(), E = end(); I != E; ++I) {
     if (I->Forward || !I->aliasesPointer(Ptr, Size, TBAAInfo, AA)) continue;

     if (FoundSet == 0) {  // If this is the first alias set ptr can go into.
       FoundSet = I;       // Remember it.
     } else {              // Otherwise, we must merge the sets.
       FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
     }
   }

   return FoundSet;
 }

 /// containsPointer - Return true if the specified location is represented by
 /// this alias set, false otherwise.  This does not modify the AST object or
 /// alias sets.
 bool AliasSetTracker::containsPointer(Value *Ptr, uint64_t Size,
                                       const MDNode *TBAAInfo) const {
   for (const_iterator I = begin(), E = end(); I != E; ++I)
     if (!I->Forward && I->aliasesPointer(Ptr, Size, TBAAInfo, AA))
       return true;
   return false;
 }


 AliasSet *AliasSetTracker::findAliasSetForUnknownInst(Instruction *Inst) {
   AliasSet *FoundSet = 0;
   for (iterator I = begin(), E = end(); I != E; ++I) {
     if (I->Forward || !I->aliasesUnknownInst(Inst, AA))
       continue;

     if (FoundSet == 0)        // If this is the first alias set ptr can go into.
       FoundSet = I;           // Remember it.
     else if (!I->Forward)     // Otherwise, we must merge the sets.
       FoundSet->mergeSetIn(*I, *this);     // Merge in contents.
   }
   return FoundSet;
 }


 /// getAliasSetForPointer - Return the alias set that the specified pointer
 /// lives in.
 AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, uint64_t Size,
                                                  const MDNode *TBAAInfo,
                                                  bool *New) {
   AliasSet::PointerRec &Entry = getEntryFor(Pointer);

   // Check to see if the pointer is already known.
   if (Entry.hasAliasSet()) {
     Entry.updateSizeAndTBAAInfo(Size, TBAAInfo);
     // Return the set!
     return *Entry.getAliasSet(*this)->getForwardedTarget(*this);
   }

   if (AliasSet *AS = findAliasSetForPointer(Pointer, Size, TBAAInfo)) {
     // Add it to the alias set it aliases.
     AS->addPointer(*this, Entry, Size, TBAAInfo);
     return *AS;
   }

   if (New) *New = true;
   // Otherwise create a new alias set to hold the loaded pointer.
   AliasSets.push_back(new AliasSet());
   AliasSets.back().addPointer(*this, Entry, Size, TBAAInfo);
   return AliasSets.back();
 }

 bool AliasSetTracker::add(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo) {
   bool NewPtr;
   addPointer(Ptr, Size, TBAAInfo, AliasSet::NoModRef, NewPtr);
   return NewPtr;
 }


 bool AliasSetTracker::add(LoadInst *LI) {
   if (LI->getOrdering() > Monotonic) return addUnknown(LI);
   AliasSet::AccessType ATy = AliasSet::Refs;
   if (!LI->isUnordered()) ATy = AliasSet::ModRef;
   bool NewPtr;
   AliasSet &AS = addPointer(LI->getOperand(0),
                             AA.getTypeStoreSize(LI->getType()),
                             LI->getMetadata(LLVMContext::MD_tbaa),
                             ATy, NewPtr);
   if (LI->isVolatile()) AS.setVolatile();
   return NewPtr;
 }

 bool AliasSetTracker::add(StoreInst *SI) {
   if (SI->getOrdering() > Monotonic) return addUnknown(SI);
   AliasSet::AccessType ATy = AliasSet::Mods;
   if (!SI->isUnordered()) ATy = AliasSet::ModRef;
   bool NewPtr;
   Value *Val = SI->getOperand(0);
   AliasSet &AS = addPointer(SI->getOperand(1),
                             AA.getTypeStoreSize(Val->getType()),
                             SI->getMetadata(LLVMContext::MD_tbaa),
                             ATy, NewPtr);
   if (SI->isVolatile()) AS.setVolatile();
   return NewPtr;
 }

 bool AliasSetTracker::add(VAArgInst *VAAI) {
   bool NewPtr;
   addPointer(VAAI->getOperand(0), AliasAnalysis::UnknownSize,
              VAAI->getMetadata(LLVMContext::MD_tbaa),
              AliasSet::ModRef, NewPtr);
   return NewPtr;
 }


 bool AliasSetTracker::addUnknown(Instruction *Inst) {
   if (isa<DbgInfoIntrinsic>(Inst))
     return true; // Ignore DbgInfo Intrinsics.
   if (!Inst->mayReadOrWriteMemory())
     return true; // doesn't alias anything

   AliasSet *AS = findAliasSetForUnknownInst(Inst);
   if (AS) {
     AS->addUnknownInst(Inst, AA);
     return false;
   }
   AliasSets.push_back(new AliasSet());
   AS = &AliasSets.back();
   AS->addUnknownInst(Inst, AA);
   return true;
 }

 bool AliasSetTracker::add(Instruction *I) {
   // Dispatch to one of the other add methods.
   if (LoadInst *LI = dyn_cast<LoadInst>(I))
     return add(LI);
   if (StoreInst *SI = dyn_cast<StoreInst>(I))
     return add(SI);
   if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
     return add(VAAI);
   return addUnknown(I);
 }

 void AliasSetTracker::add(BasicBlock &BB) {
   for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
     add(I);
 }

 void AliasSetTracker::add(const AliasSetTracker &AST) {
   assert(&AA == &AST.AA &&
          "Merging AliasSetTracker objects with different Alias Analyses!");

   // Loop over all of the alias sets in AST, adding the pointers contained
   // therein into the current alias sets.  This can cause alias sets to be
   // merged together in the current AST.
   for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) {
     if (I->Forward) continue;   // Ignore forwarding alias sets

     AliasSet &AS = const_cast<AliasSet&>(*I);

     // If there are any call sites in the alias set, add them to this AST.
     for (unsigned i = 0, e = AS.UnknownInsts.size(); i != e; ++i)
       add(AS.UnknownInsts[i]);

     // Loop over all of the pointers in this alias set.
     bool X;
     for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
       AliasSet &NewAS = addPointer(ASI.getPointer(), ASI.getSize(),
                                    ASI.getTBAAInfo(),
                                    (AliasSet::AccessType)AS.AccessTy, X);
       if (AS.isVolatile()) NewAS.setVolatile();
     }
   }
 }

 /// remove - Remove the specified (potentially non-empty) alias set from the
 /// tracker.
 void AliasSetTracker::remove(AliasSet &AS) {
   // Drop all call sites.
   AS.UnknownInsts.clear();

   // Clear the alias set.
   unsigned NumRefs = 0;
   while (!AS.empty()) {
     AliasSet::PointerRec *P = AS.PtrList;

     Value *ValToRemove = P->getValue();

     // Unlink and delete entry from the list of values.
     P->eraseFromList();

     // Remember how many references need to be dropped.
     ++NumRefs;

     // Finally, remove the entry.
     PointerMap.erase(ValToRemove);
   }

   // Stop using the alias set, removing it.
   AS.RefCount -= NumRefs;
   if (AS.RefCount == 0)
     AS.removeFromTracker(*this);
 }

 bool
 AliasSetTracker::remove(Value *Ptr, uint64_t Size, const MDNode *TBAAInfo) {
   AliasSet *AS = findAliasSetForPointer(Ptr, Size, TBAAInfo);
   if (!AS) return false;
   remove(*AS);
   return true;
 }

 bool AliasSetTracker::remove(LoadInst *LI) {
   uint64_t Size = AA.getTypeStoreSize(LI->getType());
   const MDNode *TBAAInfo = LI->getMetadata(LLVMContext::MD_tbaa);
   AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size, TBAAInfo);
   if (!AS) return false;
   remove(*AS);
   return true;
 }

 bool AliasSetTracker::remove(StoreInst *SI) {
   uint64_t Size = AA.getTypeStoreSize(SI->getOperand(0)->getType());
   const MDNode *TBAAInfo = SI->getMetadata(LLVMContext::MD_tbaa);
   AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size, TBAAInfo);
   if (!AS) return false;
   remove(*AS);
   return true;
 }

 bool AliasSetTracker::remove(VAArgInst *VAAI) {
   AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0),
                                         AliasAnalysis::UnknownSize,
                                         VAAI->getMetadata(LLVMContext::MD_tbaa));
   if (!AS) return false;
   remove(*AS);
   return true;
 }

 bool AliasSetTracker::removeUnknown(Instruction *I) {
   if (!I->mayReadOrWriteMemory())
     return false; // doesn't alias anything

   AliasSet *AS = findAliasSetForUnknownInst(I);
   if (!AS) return false;
   remove(*AS);
   return true;
 }

 bool AliasSetTracker::remove(Instruction *I) {
   // Dispatch to one of the other remove methods...
   if (LoadInst *LI = dyn_cast<LoadInst>(I))
     return remove(LI);
   if (StoreInst *SI = dyn_cast<StoreInst>(I))
     return remove(SI);
   if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
     return remove(VAAI);
   return removeUnknown(I);
 }


 // deleteValue method - This method is used to remove a pointer value from the
 // AliasSetTracker entirely.  It should be used when an instruction is deleted
 // from the program to update the AST.  If you don't use this, you would have
 // dangling pointers to deleted instructions.
 //
 void AliasSetTracker::deleteValue(Value *PtrVal) {
   // Notify the alias analysis implementation that this value is gone.
   AA.deleteValue(PtrVal);

   // If this is a call instruction, remove the callsite from the appropriate
   // AliasSet (if present).
   if (Instruction *Inst = dyn_cast<Instruction>(PtrVal)) {
     if (Inst->mayReadOrWriteMemory()) {
       // Scan all the alias sets to see if this call site is contained.
       for (iterator I = begin(), E = end(); I != E; ++I) {
         if (I->Forward) continue;

         I->removeUnknownInst(Inst);
       }
     }
   }

   // First, look up the PointerRec for this pointer.
   PointerMapType::iterator I = PointerMap.find_as(PtrVal);
   if (I == PointerMap.end()) return;  // Noop

   // If we found one, remove the pointer from the alias set it is in.
   AliasSet::PointerRec *PtrValEnt = I->second;
   AliasSet *AS = PtrValEnt->getAliasSet(*this);

   // Unlink and delete from the list of values.
   PtrValEnt->eraseFromList();

   // Stop using the alias set.
   AS->dropRef(*this);

   PointerMap.erase(I);
 }

 // copyValue - This method should be used whenever a preexisting value in the
 // program is copied or cloned, introducing a new value.  Note that it is ok for
 // clients that use this method to introduce the same value multiple times: if
 // the tracker already knows about a value, it will ignore the request.
 //
 void AliasSetTracker::copyValue(Value *From, Value *To) {
   // Notify the alias analysis implementation that this value is copied.
   AA.copyValue(From, To);

   // First, look up the PointerRec for this pointer.
   PointerMapType::iterator I = PointerMap.find_as(From);
   if (I == PointerMap.end())
     return;  // Noop
   assert(I->second->hasAliasSet() && "Dead entry?");

   AliasSet::PointerRec &Entry = getEntryFor(To);
   if (Entry.hasAliasSet()) return;    // Already in the tracker!

   // Add it to the alias set it aliases...
   I = PointerMap.find_as(From);
   AliasSet *AS = I->second->getAliasSet(*this);
   AS->addPointer(*this, Entry, I->second->getSize(),
                  I->second->getTBAAInfo(),
                  true);
 }


 //===----------------------------------------------------------------------===//
 //               AliasSet/AliasSetTracker Printing Support
 //===----------------------------------------------------------------------===//

 void AliasSet::print(raw_ostream &OS) const {
   OS << "  AliasSet[" << (const void*)this << ", " << RefCount << "] ";
   OS << (AliasTy == MustAlias ? "must" : "may") << " alias, ";
   switch (AccessTy) {
   case NoModRef: OS << "No access "; break;
   case Refs    : OS << "Ref       "; break;
   case Mods    : OS << "Mod       "; break;
   case ModRef  : OS << "Mod/Ref   "; break;
   default: llvm_unreachable("Bad value for AccessTy!");
   }
   if (isVolatile()) OS << "[volatile] ";
   if (Forward)
     OS << " forwarding to " << (void*)Forward;


   if (!empty()) {
     OS << "Pointers: ";
     for (iterator I = begin(), E = end(); I != E; ++I) {
       if (I != begin()) OS << ", ";
       WriteAsOperand(OS << "(", I.getPointer());
       OS << ", " << I.getSize() << ")";
     }
   }
   if (!UnknownInsts.empty()) {
     OS << "\n    " << UnknownInsts.size() << " Unknown instructions: ";
     for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
       if (i) OS << ", ";
       WriteAsOperand(OS, UnknownInsts[i]);
     }
   }
   OS << "\n";
 }

 void AliasSetTracker::print(raw_ostream &OS) const {
   OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for "
      << PointerMap.size() << " pointer values.\n";
   for (const_iterator I = begin(), E = end(); I != E; ++I)
     I->print(OS);
   OS << "\n";
 }

 #if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
 void AliasSet::dump() const { print(dbgs()); }
 void AliasSetTracker::dump() const { print(dbgs()); }
 #endif

 //===----------------------------------------------------------------------===//
 //                     ASTCallbackVH Class Implementation
 //===----------------------------------------------------------------------===//

 void AliasSetTracker::ASTCallbackVH::deleted() {
   assert(AST && "ASTCallbackVH called with a null AliasSetTracker!");
   AST->deleteValue(getValPtr());
   // this now dangles!
 }

 void AliasSetTracker::ASTCallbackVH::allUsesReplacedWith(Value *V) {
   AST->copyValue(getValPtr(), V);
 }

 AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value *V, AliasSetTracker *ast)
   : CallbackVH(V), AST(ast) {}

 AliasSetTracker::ASTCallbackVH &
 AliasSetTracker::ASTCallbackVH::operator=(Value *V) {
   return *this = ASTCallbackVH(V, AST);
 }

 //===----------------------------------------------------------------------===//
 //                            AliasSetPrinter Pass
 //===----------------------------------------------------------------------===//

 namespace {
   class AliasSetPrinter : public FunctionPass {
     AliasSetTracker *Tracker;
   public:
     static char ID; // Pass identification, replacement for typeid
     AliasSetPrinter() : FunctionPass(ID) {
       initializeAliasSetPrinterPass(*PassRegistry::getPassRegistry());
     }

     virtual void getAnalysisUsage(AnalysisUsage &AU) const {
       AU.setPreservesAll();
       AU.addRequired<AliasAnalysis>();
     }

     virtual bool runOnFunction(Function &F) {
       Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>());

       for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
         Tracker->add(&*I);
       Tracker->print(errs());
       delete Tracker;
       return false;
     }
   };
 }

 char AliasSetPrinter::ID = 0;
 INITIALIZE_PASS_BEGIN(AliasSetPrinter, "print-alias-sets",
                 "Alias Set Printer", false, true)
 INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
 INITIALIZE_PASS_END(AliasSetPrinter, "print-alias-sets",
                 "Alias Set Printer", false, true)
	//===- AliasSetTracker.cpp - Alias Sets Tracker implementation-------------===//
	//
	// The LLVM Compiler Infrastructure
	//
	// This file is distributed under the University of Illinois Open Source
	// License. See LICENSE.TXT for details.
	//
	//===----------------------------------------------------------------------===//
	//
	// This file implements the AliasSetTracker and AliasSet classes.
	//
	//===----------------------------------------------------------------------===//

	#include "llvm/Analysis/AliasSetTracker.h"
	#include "llvm/Analysis/AliasAnalysis.h"
	#include "llvm/Assembly/Writer.h"
	#include "llvm/DataLayout.h"
	#include "llvm/Instructions.h"
	#include "llvm/IntrinsicInst.h"
	#include "llvm/LLVMContext.h"
	#include "llvm/Pass.h"
	#include "llvm/Support/Debug.h"
	#include "llvm/Support/ErrorHandling.h"
	#include "llvm/Support/InstIterator.h"
	#include "llvm/Support/raw_ostream.h"
	#include "llvm/Type.h"
	using namespace llvm;

	/// mergeSetIn - Merge the specified alias set into this alias set.
	///
	void AliasSet::mergeSetIn(AliasSet &AS, AliasSetTracker &AST) {
	assert(!AS.Forward && "Alias set is already forwarding!");
	assert(!Forward && "This set is a forwarding set!!");

	// Update the alias and access types of this set...
	AccessTy \|= AS.AccessTy;
	AliasTy \|= AS.AliasTy;
	Volatile \|= AS.Volatile;

	if (AliasTy == MustAlias) {
	// Check that these two merged sets really are must aliases. Since both
	// used to be must-alias sets, we can just check any pointer from each set
	// for aliasing.
	AliasAnalysis &AA = AST.getAliasAnalysis();
	PointerRec *L = getSomePointer();
	PointerRec *R = AS.getSomePointer();

	// If the pointers are not a must-alias pair, this set becomes a may alias.
	if (AA.alias(AliasAnalysis::Location(L->getValue(),
	L->getSize(),
	L->getTBAAInfo()),
	AliasAnalysis::Location(R->getValue(),
	R->getSize(),
	R->getTBAAInfo()))
	!= AliasAnalysis::MustAlias)
	AliasTy = MayAlias;
	}

	if (UnknownInsts.empty()) { // Merge call sites...
	if (!AS.UnknownInsts.empty())
	std::swap(UnknownInsts, AS.UnknownInsts);
	} else if (!AS.UnknownInsts.empty()) {
	UnknownInsts.insert(UnknownInsts.end(), AS.UnknownInsts.begin(), AS.UnknownInsts.end());
	AS.UnknownInsts.clear();
	}

	AS.Forward = this; // Forward across AS now...
	addRef(); // AS is now pointing to us...

	// Merge the list of constituent pointers...
	if (AS.PtrList) {
	*PtrListEnd = AS.PtrList;
	AS.PtrList->setPrevInList(PtrListEnd);
	PtrListEnd = AS.PtrListEnd;

	AS.PtrList = 0;
	AS.PtrListEnd = &AS.PtrList;
	assert(*AS.PtrListEnd == 0 && "End of list is not null?");
	}
	}

	void AliasSetTracker::removeAliasSet(AliasSet *AS) {
	if (AliasSet *Fwd = AS->Forward) {
	Fwd->dropRef(*this);
	AS->Forward = 0;
	}
	AliasSets.erase(AS);
	}

	void AliasSet::removeFromTracker(AliasSetTracker &AST) {
	assert(RefCount == 0 && "Cannot remove non-dead alias set from tracker!");
	AST.removeAliasSet(this);
	}

	void AliasSet::addPointer(AliasSetTracker &AST, PointerRec &Entry,
	uint64_t Size, const MDNode *TBAAInfo,
	bool KnownMustAlias) {
	assert(!Entry.hasAliasSet() && "Entry already in set!");

	// Check to see if we have to downgrade to _may_ alias.
	if (isMustAlias() && !KnownMustAlias)
	if (PointerRec *P = getSomePointer()) {
	AliasAnalysis &AA = AST.getAliasAnalysis();
	AliasAnalysis::AliasResult Result =
	AA.alias(AliasAnalysis::Location(P->getValue(), P->getSize(),
	P->getTBAAInfo()),
	AliasAnalysis::Location(Entry.getValue(), Size, TBAAInfo));
	if (Result != AliasAnalysis::MustAlias)
	AliasTy = MayAlias;
	else // First entry of must alias must have maximum size!
	P->updateSizeAndTBAAInfo(Size, TBAAInfo);
	assert(Result != AliasAnalysis::NoAlias && "Cannot be part of must set!");
	}

	Entry.setAliasSet(this);
	Entry.updateSizeAndTBAAInfo(Size, TBAAInfo);

	// Add it to the end of the list...
	assert(*PtrListEnd == 0 && "End of list is not null?");
	*PtrListEnd = &Entry;
	PtrListEnd = Entry.setPrevInList(PtrListEnd);
	assert(*PtrListEnd == 0 && "End of list is not null?");
	addRef(); // Entry points to alias set.
	}

	void AliasSet::addUnknownInst(Instruction *I, AliasAnalysis &AA) {
	UnknownInsts.push_back(I);

	if (!I->mayWriteToMemory()) {
	AliasTy = MayAlias;
	AccessTy \|= Refs;
	return;
	}

	// FIXME: This should use mod/ref information to make this not suck so bad
	AliasTy = MayAlias;
	AccessTy = ModRef;
	}

	/// aliasesPointer - Return true if the specified pointer "may" (or must)
	/// alias one of the members in the set.
	///
	bool AliasSet::aliasesPointer(const Value *Ptr, uint64_t Size,
	const MDNode *TBAAInfo,
	AliasAnalysis &AA) const {
	if (AliasTy == MustAlias) {
	assert(UnknownInsts.empty() && "Illegal must alias set!");

	// If this is a set of MustAliases, only check to see if the pointer aliases
	// SOME value in the set.
	PointerRec *SomePtr = getSomePointer();
	assert(SomePtr && "Empty must-alias set??");
	return AA.alias(AliasAnalysis::Location(SomePtr->getValue(),
	SomePtr->getSize(),
	SomePtr->getTBAAInfo()),
	AliasAnalysis::Location(Ptr, Size, TBAAInfo));
	}

	// If this is a may-alias set, we have to check all of the pointers in the set
	// to be sure it doesn't alias the set...
	for (iterator I = begin(), E = end(); I != E; ++I)
	if (AA.alias(AliasAnalysis::Location(Ptr, Size, TBAAInfo),
	AliasAnalysis::Location(I.getPointer(), I.getSize(),
	I.getTBAAInfo())))
	return true;

	// Check the unknown instructions...
	if (!UnknownInsts.empty()) {
	for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i)
	if (AA.getModRefInfo(UnknownInsts[i],
	AliasAnalysis::Location(Ptr, Size, TBAAInfo)) !=
	AliasAnalysis::NoModRef)
	return true;
	}

	return false;
	}

	bool AliasSet::aliasesUnknownInst(Instruction *Inst, AliasAnalysis &AA) const {
	if (!Inst->mayReadOrWriteMemory())
	return false;

	for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
	CallSite C1 = getUnknownInst(i), C2 = Inst;
	if (!C1 \|\| !C2 \|\|
	AA.getModRefInfo(C1, C2) != AliasAnalysis::NoModRef \|\|
	AA.getModRefInfo(C2, C1) != AliasAnalysis::NoModRef)
	return true;
	}

	for (iterator I = begin(), E = end(); I != E; ++I)
	if (AA.getModRefInfo(Inst, AliasAnalysis::Location(I.getPointer(),
	I.getSize(),
	I.getTBAAInfo())) !=
	AliasAnalysis::NoModRef)
	return true;

	return false;
	}

	void AliasSetTracker::clear() {
	// Delete all the PointerRec entries.
	for (PointerMapType::iterator I = PointerMap.begin(), E = PointerMap.end();
	I != E; ++I)
	I->second->eraseFromList();

	PointerMap.clear();

	// The alias sets should all be clear now.
	AliasSets.clear();
	}


	/// findAliasSetForPointer - Given a pointer, find the one alias set to put the
	/// instruction referring to the pointer into. If there are multiple alias sets
	/// that may alias the pointer, merge them together and return the unified set.
	///
	AliasSet AliasSetTracker::findAliasSetForPointer(const Value Ptr,
	uint64_t Size,
	const MDNode *TBAAInfo) {
	AliasSet *FoundSet = 0;
	for (iterator I = begin(), E = end(); I != E; ++I) {
	if (I->Forward \|\| !I->aliasesPointer(Ptr, Size, TBAAInfo, AA)) continue;

	if (FoundSet == 0) { // If this is the first alias set ptr can go into.
	FoundSet = I; // Remember it.
	} else { // Otherwise, we must merge the sets.
	FoundSet->mergeSetIn(I, this); // Merge in contents.
	}
	}

	return FoundSet;
	}

	/// containsPointer - Return true if the specified location is represented by
	/// this alias set, false otherwise. This does not modify the AST object or
	/// alias sets.
	bool AliasSetTracker::containsPointer(Value *Ptr, uint64_t Size,
	const MDNode *TBAAInfo) const {
	for (const_iterator I = begin(), E = end(); I != E; ++I)
	if (!I->Forward && I->aliasesPointer(Ptr, Size, TBAAInfo, AA))
	return true;
	return false;
	}



	AliasSet AliasSetTracker::findAliasSetForUnknownInst(Instruction Inst) {
	AliasSet *FoundSet = 0;
	for (iterator I = begin(), E = end(); I != E; ++I) {
	if (I->Forward \|\| !I->aliasesUnknownInst(Inst, AA))
	continue;

	if (FoundSet == 0) // If this is the first alias set ptr can go into.
	FoundSet = I; // Remember it.
	else if (!I->Forward) // Otherwise, we must merge the sets.
	FoundSet->mergeSetIn(I, this); // Merge in contents.
	}
	return FoundSet;
	}




	/// getAliasSetForPointer - Return the alias set that the specified pointer
	/// lives in.
	AliasSet &AliasSetTracker::getAliasSetForPointer(Value *Pointer, uint64_t Size,
	const MDNode *TBAAInfo,
	bool *New) {
	AliasSet::PointerRec &Entry = getEntryFor(Pointer);

	// Check to see if the pointer is already known.
	if (Entry.hasAliasSet()) {
	Entry.updateSizeAndTBAAInfo(Size, TBAAInfo);
	// Return the set!
	return Entry.getAliasSet(this)->getForwardedTarget(*this);
	}

	if (AliasSet *AS = findAliasSetForPointer(Pointer, Size, TBAAInfo)) {
	// Add it to the alias set it aliases.
	AS->addPointer(*this, Entry, Size, TBAAInfo);
	return *AS;
	}

	if (New) *New = true;
	// Otherwise create a new alias set to hold the loaded pointer.
	AliasSets.push_back(new AliasSet());
	AliasSets.back().addPointer(*this, Entry, Size, TBAAInfo);
	return AliasSets.back();
	}

	bool AliasSetTracker::add(Value Ptr, uint64_t Size, const MDNode TBAAInfo) {
	bool NewPtr;
	addPointer(Ptr, Size, TBAAInfo, AliasSet::NoModRef, NewPtr);
	return NewPtr;
	}


	bool AliasSetTracker::add(LoadInst *LI) {
	if (LI->getOrdering() > Monotonic) return addUnknown(LI);
	AliasSet::AccessType ATy = AliasSet::Refs;
	if (!LI->isUnordered()) ATy = AliasSet::ModRef;
	bool NewPtr;
	AliasSet &AS = addPointer(LI->getOperand(0),
	AA.getTypeStoreSize(LI->getType()),
	LI->getMetadata(LLVMContext::MD_tbaa),
	ATy, NewPtr);
	if (LI->isVolatile()) AS.setVolatile();
	return NewPtr;
	}

	bool AliasSetTracker::add(StoreInst *SI) {
	if (SI->getOrdering() > Monotonic) return addUnknown(SI);
	AliasSet::AccessType ATy = AliasSet::Mods;
	if (!SI->isUnordered()) ATy = AliasSet::ModRef;
	bool NewPtr;
	Value *Val = SI->getOperand(0);
	AliasSet &AS = addPointer(SI->getOperand(1),
	AA.getTypeStoreSize(Val->getType()),
	SI->getMetadata(LLVMContext::MD_tbaa),
	ATy, NewPtr);
	if (SI->isVolatile()) AS.setVolatile();
	return NewPtr;
	}

	bool AliasSetTracker::add(VAArgInst *VAAI) {
	bool NewPtr;
	addPointer(VAAI->getOperand(0), AliasAnalysis::UnknownSize,
	VAAI->getMetadata(LLVMContext::MD_tbaa),
	AliasSet::ModRef, NewPtr);
	return NewPtr;
	}


	bool AliasSetTracker::addUnknown(Instruction *Inst) {
	if (isa<DbgInfoIntrinsic>(Inst))
	return true; // Ignore DbgInfo Intrinsics.
	if (!Inst->mayReadOrWriteMemory())
	return true; // doesn't alias anything

	AliasSet *AS = findAliasSetForUnknownInst(Inst);
	if (AS) {
	AS->addUnknownInst(Inst, AA);
	return false;
	}
	AliasSets.push_back(new AliasSet());
	AS = &AliasSets.back();
	AS->addUnknownInst(Inst, AA);
	return true;
	}

	bool AliasSetTracker::add(Instruction *I) {
	// Dispatch to one of the other add methods.
	if (LoadInst *LI = dyn_cast<LoadInst>(I))
	return add(LI);
	if (StoreInst *SI = dyn_cast<StoreInst>(I))
	return add(SI);
	if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
	return add(VAAI);
	return addUnknown(I);
	}

	void AliasSetTracker::add(BasicBlock &BB) {
	for (BasicBlock::iterator I = BB.begin(), E = BB.end(); I != E; ++I)
	add(I);
	}

	void AliasSetTracker::add(const AliasSetTracker &AST) {
	assert(&AA == &AST.AA &&
	"Merging AliasSetTracker objects with different Alias Analyses!");

	// Loop over all of the alias sets in AST, adding the pointers contained
	// therein into the current alias sets. This can cause alias sets to be
	// merged together in the current AST.
	for (const_iterator I = AST.begin(), E = AST.end(); I != E; ++I) {
	if (I->Forward) continue; // Ignore forwarding alias sets

	AliasSet &AS = const_cast<AliasSet&>(*I);

	// If there are any call sites in the alias set, add them to this AST.
	for (unsigned i = 0, e = AS.UnknownInsts.size(); i != e; ++i)
	add(AS.UnknownInsts[i]);

	// Loop over all of the pointers in this alias set.
	bool X;
	for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
	AliasSet &NewAS = addPointer(ASI.getPointer(), ASI.getSize(),
	ASI.getTBAAInfo(),
	(AliasSet::AccessType)AS.AccessTy, X);
	if (AS.isVolatile()) NewAS.setVolatile();
	}
	}
	}

	/// remove - Remove the specified (potentially non-empty) alias set from the
	/// tracker.
	void AliasSetTracker::remove(AliasSet &AS) {
	// Drop all call sites.
	AS.UnknownInsts.clear();

	// Clear the alias set.
	unsigned NumRefs = 0;
	while (!AS.empty()) {
	AliasSet::PointerRec *P = AS.PtrList;

	Value *ValToRemove = P->getValue();

	// Unlink and delete entry from the list of values.
	P->eraseFromList();

	// Remember how many references need to be dropped.
	++NumRefs;

	// Finally, remove the entry.
	PointerMap.erase(ValToRemove);
	}

	// Stop using the alias set, removing it.
	AS.RefCount -= NumRefs;
	if (AS.RefCount == 0)
	AS.removeFromTracker(*this);
	}

	bool
	AliasSetTracker::remove(Value Ptr, uint64_t Size, const MDNode TBAAInfo) {
	AliasSet *AS = findAliasSetForPointer(Ptr, Size, TBAAInfo);
	if (!AS) return false;
	remove(*AS);
	return true;
	}

	bool AliasSetTracker::remove(LoadInst *LI) {
	uint64_t Size = AA.getTypeStoreSize(LI->getType());
	const MDNode *TBAAInfo = LI->getMetadata(LLVMContext::MD_tbaa);
	AliasSet *AS = findAliasSetForPointer(LI->getOperand(0), Size, TBAAInfo);
	if (!AS) return false;
	remove(*AS);
	return true;
	}

	bool AliasSetTracker::remove(StoreInst *SI) {
	uint64_t Size = AA.getTypeStoreSize(SI->getOperand(0)->getType());
	const MDNode *TBAAInfo = SI->getMetadata(LLVMContext::MD_tbaa);
	AliasSet *AS = findAliasSetForPointer(SI->getOperand(1), Size, TBAAInfo);
	if (!AS) return false;
	remove(*AS);
	return true;
	}

	bool AliasSetTracker::remove(VAArgInst *VAAI) {
	AliasSet *AS = findAliasSetForPointer(VAAI->getOperand(0),
	AliasAnalysis::UnknownSize,
	VAAI->getMetadata(LLVMContext::MD_tbaa));
	if (!AS) return false;
	remove(*AS);
	return true;
	}

	bool AliasSetTracker::removeUnknown(Instruction *I) {
	if (!I->mayReadOrWriteMemory())
	return false; // doesn't alias anything

	AliasSet *AS = findAliasSetForUnknownInst(I);
	if (!AS) return false;
	remove(*AS);
	return true;
	}

	bool AliasSetTracker::remove(Instruction *I) {
	// Dispatch to one of the other remove methods...
	if (LoadInst *LI = dyn_cast<LoadInst>(I))
	return remove(LI);
	if (StoreInst *SI = dyn_cast<StoreInst>(I))
	return remove(SI);
	if (VAArgInst *VAAI = dyn_cast<VAArgInst>(I))
	return remove(VAAI);
	return removeUnknown(I);
	}


	// deleteValue method - This method is used to remove a pointer value from the
	// AliasSetTracker entirely. It should be used when an instruction is deleted
	// from the program to update the AST. If you don't use this, you would have
	// dangling pointers to deleted instructions.
	//
	void AliasSetTracker::deleteValue(Value *PtrVal) {
	// Notify the alias analysis implementation that this value is gone.
	AA.deleteValue(PtrVal);

	// If this is a call instruction, remove the callsite from the appropriate
	// AliasSet (if present).
	if (Instruction *Inst = dyn_cast<Instruction>(PtrVal)) {
	if (Inst->mayReadOrWriteMemory()) {
	// Scan all the alias sets to see if this call site is contained.
	for (iterator I = begin(), E = end(); I != E; ++I) {
	if (I->Forward) continue;

	I->removeUnknownInst(Inst);
	}
	}
	}

	// First, look up the PointerRec for this pointer.
	PointerMapType::iterator I = PointerMap.find_as(PtrVal);
	if (I == PointerMap.end()) return; // Noop

	// If we found one, remove the pointer from the alias set it is in.
	AliasSet::PointerRec *PtrValEnt = I->second;
	AliasSet AS = PtrValEnt->getAliasSet(this);

	// Unlink and delete from the list of values.
	PtrValEnt->eraseFromList();

	// Stop using the alias set.
	AS->dropRef(*this);

	PointerMap.erase(I);
	}

	// copyValue - This method should be used whenever a preexisting value in the
	// program is copied or cloned, introducing a new value. Note that it is ok for
	// clients that use this method to introduce the same value multiple times: if
	// the tracker already knows about a value, it will ignore the request.
	//
	void AliasSetTracker::copyValue(Value From, Value To) {
	// Notify the alias analysis implementation that this value is copied.
	AA.copyValue(From, To);

	// First, look up the PointerRec for this pointer.
	PointerMapType::iterator I = PointerMap.find_as(From);
	if (I == PointerMap.end())
	return; // Noop
	assert(I->second->hasAliasSet() && "Dead entry?");

	AliasSet::PointerRec &Entry = getEntryFor(To);
	if (Entry.hasAliasSet()) return; // Already in the tracker!

	// Add it to the alias set it aliases...
	I = PointerMap.find_as(From);
	AliasSet AS = I->second->getAliasSet(this);
	AS->addPointer(*this, Entry, I->second->getSize(),
	I->second->getTBAAInfo(),
	true);
	}



	//===----------------------------------------------------------------------===//
	// AliasSet/AliasSetTracker Printing Support
	//===----------------------------------------------------------------------===//

	void AliasSet::print(raw_ostream &OS) const {
	OS << " AliasSet[" << (const void*)this << ", " << RefCount << "] ";
	OS << (AliasTy == MustAlias ? "must" : "may") << " alias, ";
	switch (AccessTy) {
	case NoModRef: OS << "No access "; break;
	case Refs : OS << "Ref "; break;
	case Mods : OS << "Mod "; break;
	case ModRef : OS << "Mod/Ref "; break;
	default: llvm_unreachable("Bad value for AccessTy!");
	}
	if (isVolatile()) OS << "[volatile] ";
	if (Forward)
	OS << " forwarding to " << (void*)Forward;


	if (!empty()) {
	OS << "Pointers: ";
	for (iterator I = begin(), E = end(); I != E; ++I) {
	if (I != begin()) OS << ", ";
	WriteAsOperand(OS << "(", I.getPointer());
	OS << ", " << I.getSize() << ")";
	}
	}
	if (!UnknownInsts.empty()) {
	OS << "\n " << UnknownInsts.size() << " Unknown instructions: ";
	for (unsigned i = 0, e = UnknownInsts.size(); i != e; ++i) {
	if (i) OS << ", ";
	WriteAsOperand(OS, UnknownInsts[i]);
	}
	}
	OS << "\n";
	}

	void AliasSetTracker::print(raw_ostream &OS) const {
	OS << "Alias Set Tracker: " << AliasSets.size() << " alias sets for "
	<< PointerMap.size() << " pointer values.\n";
	for (const_iterator I = begin(), E = end(); I != E; ++I)
	I->print(OS);
	OS << "\n";
	}

	#if !defined(NDEBUG) \|\| defined(LLVM_ENABLE_DUMP)
	void AliasSet::dump() const { print(dbgs()); }
	void AliasSetTracker::dump() const { print(dbgs()); }
	#endif

	//===----------------------------------------------------------------------===//
	// ASTCallbackVH Class Implementation
	//===----------------------------------------------------------------------===//

	void AliasSetTracker::ASTCallbackVH::deleted() {
	assert(AST && "ASTCallbackVH called with a null AliasSetTracker!");
	AST->deleteValue(getValPtr());
	// this now dangles!
	}

	void AliasSetTracker::ASTCallbackVH::allUsesReplacedWith(Value *V) {
	AST->copyValue(getValPtr(), V);
	}

	AliasSetTracker::ASTCallbackVH::ASTCallbackVH(Value V, AliasSetTracker ast)
	: CallbackVH(V), AST(ast) {}

	AliasSetTracker::ASTCallbackVH &
	AliasSetTracker::ASTCallbackVH::operator=(Value *V) {
	return *this = ASTCallbackVH(V, AST);
	}

	//===----------------------------------------------------------------------===//
	// AliasSetPrinter Pass
	//===----------------------------------------------------------------------===//

	namespace {
	class AliasSetPrinter : public FunctionPass {
	AliasSetTracker *Tracker;
	public:
	static char ID; // Pass identification, replacement for typeid
	AliasSetPrinter() : FunctionPass(ID) {
	initializeAliasSetPrinterPass(*PassRegistry::getPassRegistry());
	}

	virtual void getAnalysisUsage(AnalysisUsage &AU) const {
	AU.setPreservesAll();
	AU.addRequired<AliasAnalysis>();
	}

	virtual bool runOnFunction(Function &F) {
	Tracker = new AliasSetTracker(getAnalysis<AliasAnalysis>());

	for (inst_iterator I = inst_begin(F), E = inst_end(F); I != E; ++I)
	Tracker->add(&*I);
	Tracker->print(errs());
	delete Tracker;
	return false;
	}
	};
	}

	char AliasSetPrinter::ID = 0;
	INITIALIZE_PASS_BEGIN(AliasSetPrinter, "print-alias-sets",
	"Alias Set Printer", false, true)
	INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
	INITIALIZE_PASS_END(AliasSetPrinter, "print-alias-sets",
	"Alias Set Printer", false, true)