Ejemplo n.º 1
0
/// 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);
}
// 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.
  CallSite CS = CallSite::get(PtrVal);
  if (CS.getInstruction()) {
    Function *F = CS.getCalledFunction();
    if (!F || !AA.doesNotAccessMemory(F)) {
      if (AliasSet *AS = findAliasSetForCallSite(CS))
        AS->removeCallSite(CS);
    }
  }

  // First, look up the PointerRec for this pointer.
  hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(PtrVal);
  if (I == PointerMap.end()) return;  // Noop

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

  // Unlink from the list of values...
  PtrValEnt.second.removeFromList();
  // Stop using the alias set
  AS->dropRef(*this);
  PointerMap.erase(I);
}
Ejemplo n.º 3
0
// 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(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);
}
Ejemplo n.º 4
0
/// 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!!");

  bool WasMustAlias = (Alias == SetMustAlias);
  // Update the alias and access types of this set...
  Access |= AS.Access;
  Alias  |= AS.Alias;

  if (Alias == SetMustAlias) {
    // 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(MemoryLocation(L->getValue(), L->getSize(), L->getAAInfo()),
                 MemoryLocation(R->getValue(), R->getSize(), R->getAAInfo())) !=
        MustAlias)
      Alias = SetMayAlias;
  }

  if (Alias == SetMayAlias) {
    if (WasMustAlias)
      AST.TotalMayAliasSetSize += size();
    if (AS.Alias == SetMustAlias)
      AST.TotalMayAliasSetSize += AS.size();
  }

  bool ASHadUnknownInsts = !AS.UnknownInsts.empty();
  if (UnknownInsts.empty()) {            // Merge call sites...
    if (ASHadUnknownInsts) {
      std::swap(UnknownInsts, AS.UnknownInsts);
      addRef();
    }
  } else if (ASHadUnknownInsts) {
    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) {
    SetSize += AS.size();
    AS.SetSize = 0;
    *PtrListEnd = AS.PtrList;
    AS.PtrList->setPrevInList(PtrListEnd);
    PtrListEnd = AS.PtrListEnd;

    AS.PtrList = nullptr;
    AS.PtrListEnd = &AS.PtrList;
    assert(*AS.PtrListEnd == nullptr && "End of list is not null?");
  }
  if (ASHadUnknownInsts)
    AS.dropRef(AST);
}
Ejemplo n.º 5
0
// 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.
  CallSite CS = CallSite::get(PtrVal);
  if (CS.getInstruction())
    if (!AA.doesNotAccessMemory(CS))
      if (AliasSet *AS = findAliasSetForCallSite(CS))
        AS->removeCallSite(CS);

  // First, look up the PointerRec for this pointer.
  PointerMapType::iterator I = PointerMap.find(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);
}
/// remove - Remove the specified (potentially non-empty) alias set from the
/// tracker.
void AliasSetTracker::remove(AliasSet &AS) {
  // Drop all call sites.
  AS.CallSites.clear();
  
  // Clear the alias set.
  unsigned NumRefs = 0;
  while (!AS.empty()) {
    AliasSet::HashNodePair *P = AS.PtrList;
    
    // Unlink from the list of values.
    P->second.removeFromList();
    
    // Remember how many references need to be dropped.
    ++NumRefs;

    // Finally, remove the entry.
    Value *Remove = P->first;   // Take a copy because it is invalid to pass
    PointerMap.erase(Remove);   // a reference to the data being erased.
  }
  
  // Stop using the alias set, removing it.
  AS.RefCount -= NumRefs;
  if (AS.RefCount == 0)
    AS.removeFromTracker(*this);
}
Ejemplo n.º 7
0
/// mergeAliasSetsForPointer - Given a pointer, merge all alias sets that may
/// alias the pointer. Return the unified set, or nullptr if no set that aliases
/// the pointer was found. MustAliasAll is updated to true/false if the pointer
/// is found to MustAlias all the sets it merged.
AliasSet *AliasSetTracker::mergeAliasSetsForPointer(const Value *Ptr,
                                                    LocationSize Size,
                                                    const AAMDNodes &AAInfo,
                                                    bool &MustAliasAll) {
  AliasSet *FoundSet = nullptr;
  AliasResult AllAR = MustAlias;
  for (iterator I = begin(), E = end(); I != E;) {
    iterator Cur = I++;
    if (Cur->Forward)
      continue;

    AliasResult AR = Cur->aliasesPointer(Ptr, Size, AAInfo, AA);
    if (AR == NoAlias)
      continue;

    AllAR =
        AliasResult(AllAR & AR); // Possible downgrade to May/Partial, even No

    if (!FoundSet) {
      // If this is the first alias set ptr can go into, remember it.
      FoundSet = &*Cur;
    } else {
      // Otherwise, we must merge the sets.
      FoundSet->mergeSetIn(*Cur, *this);
    }
  }

  MustAliasAll = (AllAR == MustAlias);
  return FoundSet;
}
Ejemplo n.º 8
0
void AliasSetTracker::addUnknown(Instruction *Inst) {
  if (isa<DbgInfoIntrinsic>(Inst))
    return; // Ignore DbgInfo Intrinsics.

  if (auto *II = dyn_cast<IntrinsicInst>(Inst)) {
    // These intrinsics will show up as affecting memory, but they are just
    // markers.
    switch (II->getIntrinsicID()) {
    default:
      break;
      // FIXME: Add lifetime/invariant intrinsics (See: PR30807).
    case Intrinsic::assume:
    case Intrinsic::sideeffect:
      return;
    }
  }
  if (!Inst->mayReadOrWriteMemory())
    return; // doesn't alias anything

  AliasSet *AS = findAliasSetForUnknownInst(Inst);
  if (AS) {
    AS->addUnknownInst(Inst, AA);
    return;
  }
  AliasSets.push_back(new AliasSet());
  AS = &AliasSets.back();
  AS->addUnknownInst(Inst, AA);
}
Ejemplo n.º 9
0
AliasSet *AliasSetTracker::findAliasSetForUnknownInst(Instruction *Inst) {
  AliasSet *FoundSet = nullptr;
  for (iterator I = begin(), E = end(); I != E;) {
    iterator Cur = I++;
    if (Cur->Forward || !Cur->aliasesUnknownInst(Inst, AA))
      continue;
    if (!FoundSet)            // If this is the first alias set ptr can go into.
      FoundSet = &*Cur;       // Remember it.
    else   // Otherwise, we must merge the sets.
      FoundSet->mergeSetIn(*Cur, *this);     // Merge in contents.
  }
  return FoundSet;
}
Ejemplo n.º 10
0
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;
}
AliasSet *AliasSetTracker::findAliasSetForCallSite(CallSite CS) {
  AliasSet *FoundSet = 0;
  for (iterator I = begin(), E = end(); I != E; ++I)
    if (!I->Forward && I->aliasesCallSite(CS, AA)) {
      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;
}
/// 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,
                                                  unsigned Size) {
  AliasSet *FoundSet = 0;
  for (iterator I = begin(), E = end(); I != E; ++I)
    if (!I->Forward && I->aliasesPointer(Ptr, Size, AA)) {
      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;
}
Ejemplo n.º 13
0
/// 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;
}
// 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.
  hash_map<Value*, AliasSet::PointerRec>::iterator I = PointerMap.find(From);
  if (I == PointerMap.end() || !I->second.hasAliasSet())
    return;  // Noop

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

  // Add it to the alias set it aliases...
  AliasSet *AS = I->second.getAliasSet(*this);
  AS->addPointer(*this, Entry, I->second.getSize(), true);
}
bool AliasSetTracker::add(CallSite CS) {
  if (Function *F = CS.getCalledFunction())
    if (AA.doesNotAccessMemory(F))
      return true; // doesn't alias anything

  AliasSet *AS = findAliasSetForCallSite(CS);
  if (!AS) {
    AliasSets.push_back(new AliasSet());
    AS = &AliasSets.back();
    AS->addCallSite(CS, AA);
    return true;
  } else {
    AS->addCallSite(CS, AA);
    return false;
  }
}
Ejemplo n.º 16
0
bool AliasSetTracker::add(CallSite CS) {
  if (isa<DbgInfoIntrinsic>(CS.getInstruction())) 
    return true; // Ignore DbgInfo Intrinsics.
  if (AA.doesNotAccessMemory(CS))
    return true; // doesn't alias anything

  AliasSet *AS = findAliasSetForCallSite(CS);
  if (AS) {
    AS->addCallSite(CS, AA);
    return false;
  }
  AliasSets.push_back(new AliasSet());
  AS = &AliasSets.back();
  AS->addCallSite(CS, AA);
  return true;
}
Ejemplo n.º 17
0
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;
}
Ejemplo n.º 18
0
/// mergeAliasSetsForPointer - Given a pointer, merge all alias sets that may
/// alias the pointer. Return the unified set, or nullptr if no set that aliases
/// the pointer was found.
AliasSet *AliasSetTracker::mergeAliasSetsForPointer(const Value *Ptr,
                                                    LocationSize Size,
                                                    const AAMDNodes &AAInfo) {
  AliasSet *FoundSet = nullptr;
  for (iterator I = begin(), E = end(); I != E;) {
    iterator Cur = I++;
    if (Cur->Forward || !Cur->aliasesPointer(Ptr, Size, AAInfo, AA)) continue;

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

  return FoundSet;
}
Ejemplo n.º 19
0
// 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) {
  // 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!

  // getEntryFor above may invalidate iterator \c I, so reinitialize it.
  I = PointerMap.find_as(From);
  // Add it to the alias set it aliases...
  AliasSet *AS = I->second->getAliasSet(*this);
  AS->addPointer(*this, Entry, I->second->getSize(), I->second->getAAInfo(),
                 true, true);
}
Ejemplo n.º 20
0
 AliasSetIterator(AliasSet set)
   : flags(set.flags()), pos(0)
 {
     while (flags && (flags & 1) == 0) {
         flags >>= 1;
         pos++;
     }
 }
Ejemplo n.º 21
0
// 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(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(From);
  AliasSet *AS = I->second->getAliasSet(*this);
  AS->addPointer(*this, Entry, I->second->getSize(), true);
}
Ejemplo n.º 22
0
// 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) {
  // 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();

  if (AS->Alias == AliasSet::SetMayAlias) {
    AS->SetSize--;
    TotalMayAliasSetSize--;
  }

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

  PointerMap.erase(I);
}
Ejemplo n.º 23
0
/// 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 (CallSites.empty()) {            // Merge call sites...
    if (!AS.CallSites.empty())
      std::swap(CallSites, AS.CallSites);
  } else if (!AS.CallSites.empty()) {
    CallSites.insert(CallSites.end(), AS.CallSites.begin(), AS.CallSites.end());
    AS.CallSites.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?");
  }
}
Ejemplo n.º 24
0
AliasSet &AliasSetTracker::mergeAllAliasSets() {
  assert(!AliasAnyAS && (TotalMayAliasSetSize > SaturationThreshold) &&
         "Full merge should happen once, when the saturation threshold is "
         "reached");

  // Collect all alias sets, so that we can drop references with impunity
  // without worrying about iterator invalidation.
  std::vector<AliasSet *> ASVector;
  ASVector.reserve(SaturationThreshold);
  for (iterator I = begin(), E = end(); I != E; I++)
    ASVector.push_back(&*I);

  // Copy all instructions and pointers into a new set, and forward all other
  // sets to it.
  AliasSets.push_back(new AliasSet());
  AliasAnyAS = &AliasSets.back();
  AliasAnyAS->Alias = AliasSet::SetMayAlias;
  AliasAnyAS->Access = AliasSet::ModRefAccess;
  AliasAnyAS->AliasAny = true;

  for (auto Cur : ASVector) {
    // If Cur was already forwarding, just forward to the new AS instead.
    AliasSet *FwdTo = Cur->Forward;
    if (FwdTo) {
      Cur->Forward = AliasAnyAS;
      AliasAnyAS->addRef();
      FwdTo->dropRef(*this);
      continue;
    }

    // Otherwise, perform the actual merge.
    AliasAnyAS->mergeSetIn(*Cur, *this);
  }

  return *AliasAnyAS;
}
Ejemplo n.º 25
0
DeadMemOpElimination::instr_iterator
DeadMemOpElimination::handleMemOp(instr_iterator I, DefMapTy &Defs,
                                  AliasSetTracker &AST) {
  MachineInstr *MI = I;

  MachineMemOperand *MO = *MI->memoperands_begin();
  // AliasAnalysis cannot handle offset right now, so we pretend to write a
  // a big enough size to the location pointed by the base pointer.
  uint64_t Size = MO->getSize() + MO->getOffset();
  AliasSet *ASet = &AST.getAliasSetForPointer(const_cast<Value*>(MO->getValue()),
                                              Size, 0);

  MachineInstr *&LastMI = Defs[ASet];

  bool canHandleLastStore = LastMI && ASet->isMustAlias()
                            && LastMI->getOpcode() != VTM::VOpInternalCall
                            // FIXME: We may need to remember the last
                            // definition for all predicates.
                            && isPredIdentical(LastMI, MI);

  if (canHandleLastStore) {
    MachineMemOperand *LastMO = *LastMI->memoperands_begin();
    // We can only handle last store if and only if their memory operand have
    // the must-alias address and the same size.
    canHandleLastStore = LastMO->getSize() == MO->getSize()
                         && !LastMO->isVolatile()
                         && MachineMemOperandAlias(MO, LastMO, AA, SE)
                            == AliasAnalysis::MustAlias;
  }

  // FIXME: These elimination is only valid if we are in single-thread mode!
  if (VInstrInfo::mayStore(MI)) {
    if (canHandleLastStore) {
      // Dead store find, remove it.
      LastMI->eraseFromParent();
      ++DeadStoreEliminated;
    }

    // Update the definition.
    LastMI = MI;
    return I;
  }

  // Now MI is a load.
  if (!canHandleLastStore) return I;

  // Loading the value that just be stored, the load is not necessary.
  MachineOperand LoadedMO = MI->getOperand(0);
  MachineOperand StoredMO = LastMI->getOperand(2);

  // Simply replace the load by a copy.
  DebugLoc dl = MI->getDebugLoc();
  I = *BuildMI(*MI->getParent(), I, dl, VInstrInfo::getDesc(VTM::VOpMove))
        .addOperand(LoadedMO).addOperand(StoredMO).
        addOperand(*VInstrInfo::getPredOperand(MI)).
        addOperand(*VInstrInfo::getTraceOperand(MI));

  MI->eraseFromParent();
  ++DeadLoadEliminated;
  return I;
}
Ejemplo n.º 26
0
Archivo: LICM.cpp Proyecto: CPFL/guc
/// PromoteAliasSet - Try to promote memory values to scalars by sinking
/// stores out of the loop and moving loads to before the loop.  We do this by
/// looping over the stores in the loop, looking for stores to Must pointers
/// which are loop invariant.
///
void LICM::PromoteAliasSet(AliasSet &AS) {
  // We can promote this alias set if it has a store, if it is a "Must" alias
  // set, if the pointer is loop invariant, and if we are not eliminating any
  // volatile loads or stores.
  if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() ||
      AS.isVolatile() || !CurLoop->isLoopInvariant(AS.begin()->getValue()))
    return;
  
  assert(!AS.empty() &&
         "Must alias set should have at least one pointer element in it!");
  Value *SomePtr = AS.begin()->getValue();

  // It isn't safe to promote a load/store from the loop if the load/store is
  // conditional.  For example, turning:
  //
  //    for () { if (c) *P += 1; }
  //
  // into:
  //
  //    tmp = *P;  for () { if (c) tmp +=1; } *P = tmp;
  //
  // is not safe, because *P may only be valid to access if 'c' is true.
  // 
  // It is safe to promote P if all uses are direct load/stores and if at
  // least one is guaranteed to be executed.
  bool GuaranteedToExecute = false;
  
  SmallVector<Instruction*, 64> LoopUses;
  SmallPtrSet<Value*, 4> PointerMustAliases;

  // Check that all of the pointers in the alias set have the same type.  We
  // cannot (yet) promote a memory location that is loaded and stored in
  // different sizes.
  for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
    Value *ASIV = ASI->getValue();
    PointerMustAliases.insert(ASIV);
    
    // Check that all of the pointers in the alias set have the same type.  We
    // cannot (yet) promote a memory location that is loaded and stored in
    // different sizes.
    if (SomePtr->getType() != ASIV->getType())
      return;
    
    for (Value::use_iterator UI = ASIV->use_begin(), UE = ASIV->use_end();
         UI != UE; ++UI) {
      // Ignore instructions that are outside the loop.
      Instruction *Use = dyn_cast<Instruction>(*UI);
      if (!Use || !CurLoop->contains(Use))
        continue;
      
      // If there is an non-load/store instruction in the loop, we can't promote
      // it.
      if (isa<LoadInst>(Use))
        assert(!cast<LoadInst>(Use)->isVolatile() && "AST broken");
      else if (isa<StoreInst>(Use)) {
        assert(!cast<StoreInst>(Use)->isVolatile() && "AST broken");
        if (Use->getOperand(0) == ASIV) return;
      } else
        return; // Not a load or store.
      
      if (!GuaranteedToExecute)
        GuaranteedToExecute = isSafeToExecuteUnconditionally(*Use);
      
      LoopUses.push_back(Use);
    }
  }
  
  // If there isn't a guaranteed-to-execute instruction, we can't promote.
  if (!GuaranteedToExecute)
    return;
  
  // Otherwise, this is safe to promote, lets do it!
  DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n');  
  Changed = true;
  ++NumPromoted;

  // We use the SSAUpdater interface to insert phi nodes as required.
  SmallVector<PHINode*, 16> NewPHIs;
  SSAUpdater SSA(&NewPHIs);
  
  // It wants to know some value of the same type as what we'll be inserting.
  Value *SomeValue;
  if (isa<LoadInst>(LoopUses[0]))
    SomeValue = LoopUses[0];
  else
    SomeValue = cast<StoreInst>(LoopUses[0])->getOperand(0);
  SSA.Initialize(SomeValue->getType(), SomeValue->getName());

  // First step: bucket up uses of the pointers by the block they occur in.
  // This is important because we have to handle multiple defs/uses in a block
  // ourselves: SSAUpdater is purely for cross-block references.
  // FIXME: Want a TinyVector<Instruction*> since there is usually 0/1 element.
  DenseMap<BasicBlock*, std::vector<Instruction*> > UsesByBlock;
  for (unsigned i = 0, e = LoopUses.size(); i != e; ++i) {
    Instruction *User = LoopUses[i];
    UsesByBlock[User->getParent()].push_back(User);
  }
  
  // Okay, now we can iterate over all the blocks in the loop with uses,
  // processing them.  Keep track of which loads are loading a live-in value.
  SmallVector<LoadInst*, 32> LiveInLoads;
  DenseMap<Value*, Value*> ReplacedLoads;
  
  for (unsigned LoopUse = 0, e = LoopUses.size(); LoopUse != e; ++LoopUse) {
    Instruction *User = LoopUses[LoopUse];
    std::vector<Instruction*> &BlockUses = UsesByBlock[User->getParent()];
    
    // If this block has already been processed, ignore this repeat use.
    if (BlockUses.empty()) continue;
    
    // Okay, this is the first use in the block.  If this block just has a
    // single user in it, we can rewrite it trivially.
    if (BlockUses.size() == 1) {
      // If it is a store, it is a trivial def of the value in the block.
      if (isa<StoreInst>(User)) {
        SSA.AddAvailableValue(User->getParent(),
                              cast<StoreInst>(User)->getOperand(0));
      } else {
        // Otherwise it is a load, queue it to rewrite as a live-in load.
        LiveInLoads.push_back(cast<LoadInst>(User));
      }
      BlockUses.clear();
      continue;
    }
    
    // Otherwise, check to see if this block is all loads.  If so, we can queue
    // them all as live in loads.
    bool HasStore = false;
    for (unsigned i = 0, e = BlockUses.size(); i != e; ++i) {
      if (isa<StoreInst>(BlockUses[i])) {
        HasStore = true;
        break;
      }
    }
    
    if (!HasStore) {
      for (unsigned i = 0, e = BlockUses.size(); i != e; ++i)
        LiveInLoads.push_back(cast<LoadInst>(BlockUses[i]));
      BlockUses.clear();
      continue;
    }

    // Otherwise, we have mixed loads and stores (or just a bunch of stores).
    // Since SSAUpdater is purely for cross-block values, we need to determine
    // the order of these instructions in the block.  If the first use in the
    // block is a load, then it uses the live in value.  The last store defines
    // the live out value.  We handle this by doing a linear scan of the block.
    BasicBlock *BB = User->getParent();
    Value *StoredValue = 0;
    for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
      if (LoadInst *L = dyn_cast<LoadInst>(II)) {
        // If this is a load from an unrelated pointer, ignore it.
        if (!PointerMustAliases.count(L->getOperand(0))) continue;

        // If we haven't seen a store yet, this is a live in use, otherwise
        // use the stored value.
        if (StoredValue) {
          L->replaceAllUsesWith(StoredValue);
          ReplacedLoads[L] = StoredValue;
        } else {
          LiveInLoads.push_back(L);
        }
        continue;
      }
      
      if (StoreInst *S = dyn_cast<StoreInst>(II)) {
        // If this is a store to an unrelated pointer, ignore it.
        if (!PointerMustAliases.count(S->getOperand(1))) continue;

        // Remember that this is the active value in the block.
        StoredValue = S->getOperand(0);
      }
    }
    
    // The last stored value that happened is the live-out for the block.
    assert(StoredValue && "Already checked that there is a store in block");
    SSA.AddAvailableValue(BB, StoredValue);
    BlockUses.clear();
  }
  
  // Now that all the intra-loop values are classified, set up the preheader.
  // It gets a load of the pointer we're promoting, and it is the live-out value
  // from the preheader.
  LoadInst *PreheaderLoad = new LoadInst(SomePtr,SomePtr->getName()+".promoted",
                                         Preheader->getTerminator());
  SSA.AddAvailableValue(Preheader, PreheaderLoad);

  // Now that the preheader is good to go, set up the exit blocks.  Each exit
  // block gets a store of the live-out values that feed them.  Since we've
  // already told the SSA updater about the defs in the loop and the preheader
  // definition, it is all set and we can start using it.
  SmallVector<BasicBlock*, 8> ExitBlocks;
  CurLoop->getUniqueExitBlocks(ExitBlocks);
  for (unsigned i = 0, e = ExitBlocks.size(); i != e; ++i) {
    BasicBlock *ExitBlock = ExitBlocks[i];
    Value *LiveInValue = SSA.GetValueInMiddleOfBlock(ExitBlock);
    Instruction *InsertPos = ExitBlock->getFirstNonPHI();
    new StoreInst(LiveInValue, SomePtr, InsertPos);
  }

  // Okay, now we rewrite all loads that use live-in values in the loop,
  // inserting PHI nodes as necessary.
  for (unsigned i = 0, e = LiveInLoads.size(); i != e; ++i) {
    LoadInst *ALoad = LiveInLoads[i];
    Value *NewVal = SSA.GetValueInMiddleOfBlock(ALoad->getParent());
    ALoad->replaceAllUsesWith(NewVal);
    CurAST->copyValue(ALoad, NewVal);
    ReplacedLoads[ALoad] = NewVal;
  }
  
  // If the preheader load is itself a pointer, we need to tell alias analysis
  // about the new pointer we created in the preheader block and about any PHI
  // nodes that just got inserted.
  if (PreheaderLoad->getType()->isPointerTy()) {
    // Copy any value stored to or loaded from a must-alias of the pointer.
    CurAST->copyValue(SomeValue, PreheaderLoad);
    
    for (unsigned i = 0, e = NewPHIs.size(); i != e; ++i)
      CurAST->copyValue(SomeValue, NewPHIs[i]);
  }
  
  // Now that everything is rewritten, delete the old instructions from the body
  // of the loop.  They should all be dead now.
  for (unsigned i = 0, e = LoopUses.size(); i != e; ++i) {
    Instruction *User = LoopUses[i];
    
    // If this is a load that still has uses, then the load must have been added
    // as a live value in the SSAUpdate data structure for a block (e.g. because
    // the loaded value was stored later).  In this case, we need to recursively
    // propagate the updates until we get to the real value.
    if (!User->use_empty()) {
      Value *NewVal = ReplacedLoads[User];
      assert(NewVal && "not a replaced load?");
      
      // Propagate down to the ultimate replacee.  The intermediately loads
      // could theoretically already have been deleted, so we don't want to
      // dereference the Value*'s.
      DenseMap<Value*, Value*>::iterator RLI = ReplacedLoads.find(NewVal);
      while (RLI != ReplacedLoads.end()) {
        NewVal = RLI->second;
        RLI = ReplacedLoads.find(NewVal);
      }
      
      User->replaceAllUsesWith(NewVal);
      CurAST->copyValue(User, NewVal);
    }
    
    CurAST->deleteValue(User);
    User->eraseFromParent();
  }
  
  // fwew, we're done!
}
Ejemplo n.º 27
0
Archivo: LICM.cpp Proyecto: nobled/llvm
/// PromoteAliasSet - Try to promote memory values to scalars by sinking
/// stores out of the loop and moving loads to before the loop.  We do this by
/// looping over the stores in the loop, looking for stores to Must pointers
/// which are loop invariant.
///
void LICM::PromoteAliasSet(AliasSet &AS) {
  // We can promote this alias set if it has a store, if it is a "Must" alias
  // set, if the pointer is loop invariant, and if we are not eliminating any
  // volatile loads or stores.
  if (AS.isForwardingAliasSet() || !AS.isMod() || !AS.isMustAlias() ||
      AS.isVolatile() || !CurLoop->isLoopInvariant(AS.begin()->getValue()))
    return;

  assert(!AS.empty() &&
         "Must alias set should have at least one pointer element in it!");
  Value *SomePtr = AS.begin()->getValue();

  // It isn't safe to promote a load/store from the loop if the load/store is
  // conditional.  For example, turning:
  //
  //    for () { if (c) *P += 1; }
  //
  // into:
  //
  //    tmp = *P;  for () { if (c) tmp +=1; } *P = tmp;
  //
  // is not safe, because *P may only be valid to access if 'c' is true.
  //
  // It is safe to promote P if all uses are direct load/stores and if at
  // least one is guaranteed to be executed.
  bool GuaranteedToExecute = false;

  SmallVector<Instruction*, 64> LoopUses;
  SmallPtrSet<Value*, 4> PointerMustAliases;

  // We start with an alignment of one and try to find instructions that allow
  // us to prove better alignment.
  unsigned Alignment = 1;

  // Check that all of the pointers in the alias set have the same type.  We
  // cannot (yet) promote a memory location that is loaded and stored in
  // different sizes.
  for (AliasSet::iterator ASI = AS.begin(), E = AS.end(); ASI != E; ++ASI) {
    Value *ASIV = ASI->getValue();
    PointerMustAliases.insert(ASIV);

    // Check that all of the pointers in the alias set have the same type.  We
    // cannot (yet) promote a memory location that is loaded and stored in
    // different sizes.
    if (SomePtr->getType() != ASIV->getType())
      return;

    for (Value::use_iterator UI = ASIV->use_begin(), UE = ASIV->use_end();
         UI != UE; ++UI) {
      // Ignore instructions that are outside the loop.
      Instruction *Use = dyn_cast<Instruction>(*UI);
      if (!Use || !CurLoop->contains(Use))
        continue;

      // If there is an non-load/store instruction in the loop, we can't promote
      // it.
      if (LoadInst *load = dyn_cast<LoadInst>(Use)) {
        assert(!load->isVolatile() && "AST broken");
        if (!load->isSimple())
          return;
      } else if (StoreInst *store = dyn_cast<StoreInst>(Use)) {
        // Stores *of* the pointer are not interesting, only stores *to* the
        // pointer.
        if (Use->getOperand(1) != ASIV)
          continue;
        assert(!store->isVolatile() && "AST broken");
        if (!store->isSimple())
          return;

        // Note that we only check GuaranteedToExecute inside the store case
        // so that we do not introduce stores where they did not exist before
        // (which would break the LLVM concurrency model).

        // If the alignment of this instruction allows us to specify a more
        // restrictive (and performant) alignment and if we are sure this
        // instruction will be executed, update the alignment.
        // Larger is better, with the exception of 0 being the best alignment.
        unsigned InstAlignment = store->getAlignment();
        if ((InstAlignment > Alignment || InstAlignment == 0)
            && (Alignment != 0))
          if (isGuaranteedToExecute(*Use)) {
            GuaranteedToExecute = true;
            Alignment = InstAlignment;
          }

        if (!GuaranteedToExecute)
          GuaranteedToExecute = isGuaranteedToExecute(*Use);

      } else
        return; // Not a load or store.

      LoopUses.push_back(Use);
    }
  }

  // If there isn't a guaranteed-to-execute instruction, we can't promote.
  if (!GuaranteedToExecute)
    return;

  // Otherwise, this is safe to promote, lets do it!
  DEBUG(dbgs() << "LICM: Promoting value stored to in loop: " <<*SomePtr<<'\n');
  Changed = true;
  ++NumPromoted;

  // Grab a debug location for the inserted loads/stores; given that the
  // inserted loads/stores have little relation to the original loads/stores,
  // this code just arbitrarily picks a location from one, since any debug
  // location is better than none.
  DebugLoc DL = LoopUses[0]->getDebugLoc();

  SmallVector<BasicBlock*, 8> ExitBlocks;
  CurLoop->getUniqueExitBlocks(ExitBlocks);

  // We use the SSAUpdater interface to insert phi nodes as required.
  SmallVector<PHINode*, 16> NewPHIs;
  SSAUpdater SSA(&NewPHIs);
  LoopPromoter Promoter(SomePtr, LoopUses, SSA, PointerMustAliases, ExitBlocks,
                        *CurAST, DL, Alignment);

  // Set up the preheader to have a definition of the value.  It is the live-out
  // value from the preheader that uses in the loop will use.
  LoadInst *PreheaderLoad =
    new LoadInst(SomePtr, SomePtr->getName()+".promoted",
                 Preheader->getTerminator());
  PreheaderLoad->setAlignment(Alignment);
  PreheaderLoad->setDebugLoc(DL);
  SSA.AddAvailableValue(Preheader, PreheaderLoad);

  // Rewrite all the loads in the loop and remember all the definitions from
  // stores in the loop.
  Promoter.run(LoopUses);

  // If the SSAUpdater didn't use the load in the preheader, just zap it now.
  if (PreheaderLoad->use_empty())
    PreheaderLoad->eraseFromParent();
}
Ejemplo n.º 28
0
// This pass annotates every load instruction with the last store instruction
// on which it depends. The algorithm is optimistic in that it ignores explicit
// dependencies and only considers loads and stores.
//
// Loads inside loops only have an implicit dependency on a store before the
// loop header if no instruction inside the loop body aliases it. To calculate
// this efficiently, we maintain a list of maybe-invariant loads and the combined
// alias set for all stores inside the loop. When we see the loop's backedge, this
// information is used to mark every load we wrongly assumed to be loop invariant as
// having an implicit dependency on the last instruction of the loop header, so that
// it's never moved before the loop header.
//
// The algorithm depends on the invariant that both control instructions and effectful
// instructions (stores) are never hoisted.
bool
AliasAnalysis::analyze()
{
    Vector<MInstructionVector, AliasSet::NumCategories, JitAllocPolicy> stores(alloc());

    // Initialize to the first instruction.
    MInstruction* firstIns = *graph_.entryBlock()->begin();
    for (unsigned i = 0; i < AliasSet::NumCategories; i++) {
        MInstructionVector defs(alloc());
        if (!defs.append(firstIns))
            return false;
        if (!stores.append(Move(defs)))
            return false;
    }

    // Type analysis may have inserted new instructions. Since this pass depends
    // on the instruction number ordering, all instructions are renumbered.
    uint32_t newId = 0;

    for (ReversePostorderIterator block(graph_.rpoBegin()); block != graph_.rpoEnd(); block++) {
        if (mir->shouldCancel("Alias Analysis (main loop)"))
            return false;

        if (block->isLoopHeader()) {
            JitSpew(JitSpew_Alias, "Processing loop header %d", block->id());
            loop_ = new(alloc()) LoopAliasInfo(alloc(), loop_, *block);
        }

        for (MPhiIterator def(block->phisBegin()), end(block->phisEnd()); def != end; ++def)
            def->setId(newId++);

        for (MInstructionIterator def(block->begin()), end(block->begin(block->lastIns()));
             def != end;
             ++def)
        {
            def->setId(newId++);

            AliasSet set = def->getAliasSet();
            if (set.isNone())
                continue;

            // For the purposes of alias analysis, all recoverable operations
            // are treated as effect free as the memory represented by these
            // operations cannot be aliased by others.
            if (def->canRecoverOnBailout())
                continue;

            if (set.isStore()) {
                for (AliasSetIterator iter(set); iter; iter++) {
                    if (!stores[*iter].append(*def))
                        return false;
                }

                if (JitSpewEnabled(JitSpew_Alias)) {
                    Fprinter& out = JitSpewPrinter();
                    out.printf("Processing store ");
                    def->printName(out);
                    out.printf(" (flags %x)\n", set.flags());
                }
            } else {
                // Find the most recent store on which this instruction depends.
                MInstruction* lastStore = firstIns;

                for (AliasSetIterator iter(set); iter; iter++) {
                    MInstructionVector& aliasedStores = stores[*iter];
                    for (int i = aliasedStores.length() - 1; i >= 0; i--) {
                        MInstruction* store = aliasedStores[i];
                        if (genericMightAlias(*def, store) != MDefinition::AliasType::NoAlias &&
                            def->mightAlias(store) != MDefinition::AliasType::NoAlias &&
                            BlockMightReach(store->block(), *block))
                        {
                            if (lastStore->id() < store->id())
                                lastStore = store;
                            break;
                        }
                    }
                }

                def->setDependency(lastStore);
                IonSpewDependency(*def, lastStore, "depends", "");

                // If the last store was before the current loop, we assume this load
                // is loop invariant. If a later instruction writes to the same location,
                // we will fix this at the end of the loop.
                if (loop_ && lastStore->id() < loop_->firstInstruction()->id()) {
                    if (!loop_->addInvariantLoad(*def))
                        return false;
                }
            }
        }

        // Renumber the last instruction, as the analysis depends on this and the order.
        block->lastIns()->setId(newId++);

        if (block->isLoopBackedge()) {
            MOZ_ASSERT(loop_->loopHeader() == block->loopHeaderOfBackedge());
            JitSpew(JitSpew_Alias, "Processing loop backedge %d (header %d)", block->id(),
                    loop_->loopHeader()->id());
            LoopAliasInfo* outerLoop = loop_->outer();
            MInstruction* firstLoopIns = *loop_->loopHeader()->begin();

            const MInstructionVector& invariant = loop_->invariantLoads();

            for (unsigned i = 0; i < invariant.length(); i++) {
                MInstruction* ins = invariant[i];
                AliasSet set = ins->getAliasSet();
                MOZ_ASSERT(set.isLoad());

                bool hasAlias = false;
                for (AliasSetIterator iter(set); iter; iter++) {
                    MInstructionVector& aliasedStores = stores[*iter];
                    for (int i = aliasedStores.length() - 1;; i--) {
                        MInstruction* store = aliasedStores[i];
                        if (store->id() < firstLoopIns->id())
                            break;
                        if (genericMightAlias(ins, store) != MDefinition::AliasType::NoAlias &&
                            ins->mightAlias(store) != MDefinition::AliasType::NoAlias)
                        {
                            hasAlias = true;
                            IonSpewDependency(ins, store, "aliases", "store in loop body");
                            break;
                        }
                    }
                    if (hasAlias)
                        break;
                }

                if (hasAlias) {
                    // This instruction depends on stores inside the loop body. Mark it as having a
                    // dependency on the last instruction of the loop header. The last instruction is a
                    // control instruction and these are never hoisted.
                    MControlInstruction* controlIns = loop_->loopHeader()->lastIns();
                    IonSpewDependency(ins, controlIns, "depends", "due to stores in loop body");
                    ins->setDependency(controlIns);
                } else {
                    IonSpewAliasInfo("Load", ins, "does not depend on any stores in this loop");

                    if (outerLoop && ins->dependency()->id() < outerLoop->firstInstruction()->id()) {
                        IonSpewAliasInfo("Load", ins, "may be invariant in outer loop");
                        if (!outerLoop->addInvariantLoad(ins))
                            return false;
                    }
                }
            }
            loop_ = loop_->outer();
        }
    }

    spewDependencyList();

    MOZ_ASSERT(loop_ == nullptr);
    return true;
}