C++ DSNodeHandle::isNull方法代码示例

//
// Method: getDSNodeHandle()
//
// Description:
//  This method looks up the DSNodeHandle for a given LLVM value.  The context
//  of the value is the specified function, although if it is a global value,
//  the DSNodeHandle may exist within the global DSGraph.
//
// Return value:
//  A DSNodeHandle for the value is returned.  This DSNodeHandle could either
//  be in the function's DSGraph or from the GlobalsGraph.  Note that the
//  DSNodeHandle may represent a NULL DSNode.
//
DSNodeHandle
CompleteChecks::getDSNodeHandle (const Value * V, const Function * F) {
  //
  // Get access to the points-to results.
  //
  EQTDDataStructures & dsaPass = getAnalysis<EQTDDataStructures>();

  //
  // Ensure that the function has a DSGraph
  //
  assert (dsaPass.hasDSGraph(*F) && "No DSGraph for function!\n");

  //
  // Lookup the DSNode for the value in the function's DSGraph.
  //
  DSGraph * TDG = dsaPass.getDSGraph(*F);
  DSNodeHandle DSH = TDG->getNodeForValue(V);

  //
  // If the value wasn't found in the function's DSGraph, then maybe we can
  // find the value in the globals graph.
  //
  if ((DSH.isNull()) && (isa<GlobalValue>(V))) {
    //
    // Try looking up this DSNode value in the globals graph.  Note that
    // globals are put into equivalence classes; we may need to first find the
    // equivalence class to which our global belongs, find the global that
    // represents all globals in that equivalence class, and then look up the
    // DSNode Handle for *that* global.
    //
    DSGraph * GlobalsGraph = TDG->getGlobalsGraph ();
    DSH = GlobalsGraph->getNodeForValue(V);
    if (DSH.isNull()) {
      //
      // DSA does not currently handle global aliases.
      //
      if (!isa<GlobalAlias>(V)) {
        //
        // We have to dig into the globalEC of the DSGraph to find the DSNode.
        //
        const GlobalValue * GV = dyn_cast<GlobalValue>(V);
        const GlobalValue * Leader;
        Leader = GlobalsGraph->getGlobalECs().getLeaderValue(GV);
        DSH = GlobalsGraph->getNodeForValue(Leader);
      }
    }
  }

  return DSH;
}

void GraphBuilder::visitLoadInst(LoadInst &LI) {
  //
  // Create a DSNode for the pointer dereferenced by the load.  If the DSNode
  // is NULL, do nothing more (this can occur if the load is loading from a
  // NULL pointer constant (bugpoint can generate such code).
  //
  DSNodeHandle Ptr = getValueDest(LI.getPointerOperand());
  if (Ptr.isNull()) return; // Load from null

  // Make that the node is read from...
  Ptr.getNode()->setReadMarker();

  // Ensure a typerecord exists...
  Ptr.getNode()->growSizeForType(LI.getType(), Ptr.getOffset());

  if (isa<PointerType>(LI.getType()))
    setDestTo(LI, getLink(Ptr));

  // check that it is the inserted value
  if(TypeInferenceOptimize)
    if(LI.hasOneUse())
      if(StoreInst *SI = dyn_cast<StoreInst>(*(LI.use_begin())))
        if(SI->getOperand(0) == &LI) {
        ++NumIgnoredInst;
        return;
      }
  Ptr.getNode()->mergeTypeInfo(LI.getType(), Ptr.getOffset());
}

void DSMonitor::witness(DSNodeHandle N, std::vector<Value*> VS, std::string M) {
  if (N.isNull() || N.getNode()->isCollapsedNode())
    return;

  watch(N,VS,M);
  check();
}

// Method: getDSNodeHandle()
//
// Description:
//  This method looks up the DSNodeHandle for a given LLVM value.  The context
//  of the value is the specified function, although if it is a global value,
//  the DSNodeHandle may exist within the global DSGraph.
//
// Return value:
//  A DSNodeHandle for the value is returned.  This DSNodeHandle could either
//  be in the function's DSGraph or from the GlobalsGraph.  Note that the
//  DSNodeHandle may represent a NULL DSNode.
//
template<class dsa> DSNodeHandle
TypeSafety<dsa>::getDSNodeHandle (const Value * V, const Function * F) {
  //
  // Ensure that the function has a DSGraph
  //
  assert (dsaPass->hasDSGraph(*F) && "No DSGraph for function!\n");

  //
  // Lookup the DSNode for the value in the function's DSGraph.
  //
  const DSGraph * TDG = dsaPass->getDSGraph(*F);

  DSNodeHandle DSH;
  if(TDG->hasNodeForValue(V))
    DSH = TDG->getNodeForValue(V);

  //
  // If the value wasn't found in the function's DSGraph, then maybe we can
  // find the value in the globals graph.
  //
  if ((DSH.isNull()) && (isa<GlobalValue>(V))) {
    //
    // Try looking up this DSNode value in the globals graph.  Note that
    // globals are put into equivalence classes; we may need to first find the
    // equivalence class to which our global belongs, find the global that
    // represents all globals in that equivalence class, and then look up the
    // DSNode Handle for *that* global.
    //
    DSH = getDSNodeHandle(cast<GlobalValue>(V));
  }
  return DSH;
}

// Method: getDSNodeHandle()
//
// Description:
//  This method looks up the DSNodeHandle for a given LLVM globalvalue. 
//  The value is looked up in the globals graph
//
// Return value:
//  A DSNodeHandle for the value is returned.  This DSNodeHandle is from 
//  the GlobalsGraph.  Note that the DSNodeHandle may represent a NULL DSNode.
//
template<class dsa> DSNodeHandle
TypeSafety<dsa>::getDSNodeHandle(const GlobalValue *V) {
  DSNodeHandle DSH;
  const DSGraph * GlobalsGraph = dsaPass->getGlobalsGraph ();
  if(GlobalsGraph->hasNodeForValue(V)) {
    DSH = GlobalsGraph->getNodeForValue(V);
  }
  //
  // Try looking up this DSNode value in the globals graph.  Note that
  // globals are put into equivalence classes; we may need to first find the
  // equivalence class to which our global belongs, find the global that
  // represents all globals in that equivalence class, and then look up the
  // DSNode Handle for *that* global.
  //
  if (DSH.isNull()) {
    //
    // DSA does not currently handle global aliases.
    //
    if (!isa<GlobalAlias>(V)) {
      //
      // We have to dig into the globalEC of the DSGraph to find the DSNode.
      //
      const GlobalValue * GV = dyn_cast<GlobalValue>(V);
      const GlobalValue * Leader;
      Leader = GlobalsGraph->getGlobalECs().getLeaderValue(GV);
      DSH = GlobalsGraph->getNodeForValue(Leader);
    }
  }
  return DSH;
}

void GraphBuilder::visitVAArgInst(VAArgInst &I) {
  Module *M = FB->getParent();
  Triple TargetTriple(M->getTargetTriple());
  Triple::ArchType Arch = TargetTriple.getArch();
  switch(Arch) {
  case Triple::x86_64: {
    // On x86_64, we have va_list as a struct {i32, i32, i8*, i8* }
    // The first i8* is where arguments generally go, but the second i8* can
    // be used also to pass arguments by register.
    // We model this by having both the i8*'s point to an array of pointers
    // to the arguments.
    DSNodeHandle Ptr = G.getVANodeFor(*FB);
    DSNodeHandle Dest = getValueDest(&I);
    if (Ptr.isNull()) return;

    // Make that the node is read and written
    Ptr.getNode()->setReadMarker()->setModifiedMarker();

    // Not updating type info, as it is already a collapsed node

    if (isa<PointerType>(I.getType()))
      Dest.mergeWith(Ptr);
    return; 
  }

  default: {
    assert(0 && "What frontend generates this?");
    DSNodeHandle Ptr = getValueDest(I.getOperand(0));

    //FIXME: also updates the argument
    if (Ptr.isNull()) return;

    // Make that the node is read and written
    Ptr.getNode()->setReadMarker()->setModifiedMarker();

    // Ensure a type record exists.
    DSNode *PtrN = Ptr.getNode();
    PtrN->mergeTypeInfo(I.getType(), Ptr.getOffset());

    if (isa<PointerType>(I.getType()))
      setDestTo(I, getLink(Ptr));
  }
  }
}

void
PoolRegisterElimination::removeTypeSafeRegistrations (const char * name) {
  //
  // Scan through all uses of the registration function and see if it can be
  // safely removed.  If so, schedule it for removal.
  //
  std::vector<CallInst*> toBeRemoved;
  Function * F = intrinsic->getIntrinsic(name).F;

  //
  // Look for and record all registrations that can be deleted.
  //
  for (Value::use_iterator UI=F->use_begin(), UE=F->use_end();
       UI != UE;
       ++UI) {
    //
    // Get the pointer to the registered object.
    //
    CallInst * CI = cast<CallInst>(*UI);
    Value * Ptr = intrinsic->getValuePointer(CI);
    // Lookup the DSNode for the value in the function's DSGraph.
    //
    DSGraph * TDG = dsaPass->getDSGraph(*(CI->getParent()->getParent()));
    DSNodeHandle DSH = TDG->getNodeForValue(Ptr);
    assert ((!(DSH.isNull())) && "No DSNode for Value!\n");

    //
    // If the DSNode is type-safe and is never used as an array, then there
    // will never be a need to look it up in a splay tree, so remove its
    // registration.
    //
    DSNode * N = DSH.getNode();
    if(!N->isArrayNode() && 
       TS->isTypeSafe(Ptr, F)){
      toBeRemoved.push_back(CI);
    }
  }

  //
  // Update the statistics.
  //
  if (toBeRemoved.size()) {
    RemovedRegistration += toBeRemoved.size();
    TypeSafeRegistrations += toBeRemoved.size();
  }

  //
  // Remove the unnecesary registrations.
  //
  std::vector<CallInst*>::iterator it, end;
  for (it = toBeRemoved.begin(), end = toBeRemoved.end(); it != end; ++it) {
    (*it)->eraseFromParent();
  }
}

void GraphBuilder::visitAtomicCmpXchgInst(AtomicCmpXchgInst &I) {
  if (isa<PointerType>(I.getType())) {
    visitInstruction (I);
    return;
  }

  //
  // Create a DSNode for the dereferenced pointer .  If the DSNode is NULL, do
  // nothing more (this can occur if the pointer is a NULL constant; bugpoint
  // can generate such code).
  //
  DSNodeHandle Ptr = getValueDest(I.getPointerOperand());
  if (Ptr.isNull()) return;

  //
  // Make that the memory object is read and written.
  //
  Ptr.getNode()->setReadMarker();
  Ptr.getNode()->setModifiedMarker();

  //
  // If the result of the compare-and-swap is a pointer, then we need to do
  // a few things:
  //  o Merge the compare and swap values (which are pointers) with the result
  //  o Merge the DSNode of the pointer *within* the memory object with the
  //    DSNode of the compare, swap, and result DSNode.
  //
  if (isa<PointerType>(I.getType())) {
    //
    // Get the DSNodeHandle of the memory object returned from the load.  Make
    // it the DSNodeHandle of the instruction's result.
    //
    DSNodeHandle FieldPtr = getLink (Ptr);
    setDestTo(I, getLink(Ptr));

    //
    // Merge the result, compare, and swap values of the instruction.
    //
    FieldPtr.mergeWith (getValueDest (I.getCompareOperand()));
    FieldPtr.mergeWith (getValueDest (I.getNewValOperand()));
  }

  //
  // Modify the DSNode so that it has the loaded/written type at the
  // appropriate offset.
  //
  Ptr.getNode()->growSizeForType(I.getType(), Ptr.getOffset());
  Ptr.getNode()->mergeTypeInfo(I.getType(), Ptr.getOffset());
  return;
}

//
// TODO
//
template<class dsa> bool
TypeSafety<dsa>::isFieldDisjoint (const GlobalValue * V, unsigned offset) {
  //
  // Get the DSNode for the specified value.
  //
  DSNodeHandle DH = getDSNodeHandle (V);
  DSNode *node = DH.getNode();
  //unsigned offset = DH.getOffset();
  DEBUG(errs() << " check fields overlap at: " << offset << "\n");

  //
  // If there is no DSNode, claim that it is not type safe.
  //
  if (DH.isNull()) {
    return false;
  }
  //
  // If the DSNode is completely folded, then we know for sure that it is not
  // type-safe.
  //
  if (node->isNodeCompletelyFolded())
    return false;

  //
  // If the memory object represented by this DSNode can be manipulated by
  // external code or DSA has otherwise not finished analyzing all operations
  // on it, declare it type-unsafe.
  //
  if (node->isExternalNode() || node->isIncompleteNode())
    return false;

  //
  // If the pointer to the memory object came from some source not understood
  // by DSA or somehow came from/escapes to the realm of integers, declare it
  // type-unsafe.
  //
  if (node->isUnknownNode() || node->isIntToPtrNode() || node->isPtrToIntNode()) {
    return false;
  }

  return !((NodeInfo[node])[offset]); 
}

void DSMonitor::watch(DSNodeHandle N, std::vector<Value*> VS, std::string M) {
  if (N.isNull() || N.getNode()->isCollapsedNode()) {
    unwatch();
    return;
  }

  this->N = N;
  this->VS = VS;
  this->message = M;
  DSGraph *G = N.getNode()->getParentGraph();
  caption = getCaption(N.getNode(), G);

  if (!VS.empty()) {
    Instruction *I = getInstruction(VS[0]);
    if (I && I->getMetadata("dbg")) {
      const DebugLoc DL = I->getDebugLoc();
      auto *scope = cast<DIScope>(DL.getScope());
      location = scope->getFilename().str() + ":"
        + std::to_string(DL.getLine()) + ":"
        + std::to_string(DL.getCol());
    }
  }
}

 void initialize(const Module *M, const DataStructures *DS) {
   parseValue(M);
   assert(V && "Failed to parse value?");
   if (isa<GlobalValue>(V)) {
     DSGraph *G = DS->getGlobalsGraph();
     assert(G->hasNodeForValue(V) && "Node not in specified graph!");
     NH = G->getNodeForValue(V);
   } else {
     assert(F && "No function?");
     DSGraph *G = DS->getDSGraph(*F);
     assert(G->hasNodeForValue(V) && "Node not in specified graph!");
     NH = G->getNodeForValue(V);
   }
   // Handle offsets, if any
   // For each offset in the offsets vector, follow the link at that offset
   for (OffsetVectorTy::const_iterator I = offsets.begin(), E = offsets.end();
       I != E; ++I ) {
     assert(!NH.isNull() && "Null NodeHandle?");
     assert(NH.hasLink(*I) && "Handle doesn't have link?");
     // Follow the offset
     NH = NH.getLink(*I);
   }
 }

void GraphBuilder::visitStoreInst(StoreInst &SI) {
  Type *StoredTy = SI.getOperand(0)->getType();
  DSNodeHandle Dest = getValueDest(SI.getOperand(1));
  if (Dest.isNull()) return;

  // Mark that the node is written to...
  Dest.getNode()->setModifiedMarker();

  // Ensure a type-record exists...
  Dest.getNode()->growSizeForType(StoredTy, Dest.getOffset());

  // Avoid adding edges from null, or processing non-"pointer" stores
  if (isa<PointerType>(StoredTy))
    Dest.addEdgeTo(getValueDest(SI.getOperand(0)));

  if(TypeInferenceOptimize)
    if(SI.getOperand(0)->hasOneUse())
      if(isa<LoadInst>(SI.getOperand(0))){
        ++NumIgnoredInst;
        return;
      }
  Dest.getNode()->mergeTypeInfo(StoredTy, Dest.getOffset());
}

void GraphBuilder::visitAtomicRMWInst(AtomicRMWInst &I) {
  //
  // Create a DSNode for the dereferenced pointer .  If the DSNode is NULL, do
  // nothing more (this can occur if the pointer is a NULL constant; bugpoint
  // can generate such code).
  //
  DSNodeHandle Ptr = getValueDest(I.getPointerOperand());
  if (Ptr.isNull()) return;

  //
  // Make that the memory object is read and written.
  //
  Ptr.getNode()->setReadMarker();
  Ptr.getNode()->setModifiedMarker();

  //
  // Modify the DSNode so that it has the loaded/written type at the
  // appropriate offset.
  //
  Ptr.getNode()->growSizeForType(I.getType(), Ptr.getOffset());
  Ptr.getNode()->mergeTypeInfo(I.getType(), Ptr.getOffset());
  return;
}

void GraphBuilder::visitCallSite(CallSite CS) {
  //
  // Get the called value.  Strip off any casts which are lossless.
  //
  Value *Callee = CS.getCalledValue()->stripPointerCasts();

  // Special case handling of certain libc allocation functions here.
  if (Function *F = dyn_cast<Function>(Callee))
    if (F->isIntrinsic() && visitIntrinsic(CS, F))
      return;

  //Can't do much about inline asm (yet!)
  if (isa<InlineAsm> (Callee)) {
    ++NumAsmCall;
    DSNodeHandle RetVal;
    Instruction *I = CS.getInstruction();
    if (isa<PointerType > (I->getType()))
      RetVal = getValueDest(I);

    // Calculate the arguments vector...
    for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end(); I != E; ++I)
      if (isa<PointerType > ((*I)->getType()))
        RetVal.mergeWith(getValueDest(*I));
    if (!RetVal.isNull())
      RetVal.getNode()->foldNodeCompletely();
    return;
  }

  // Set up the return value...
  DSNodeHandle RetVal;
  Instruction *I = CS.getInstruction();
  if (isa<PointerType>(I->getType()))
    RetVal = getValueDest(I);

  DSNode *CalleeNode = 0;
  if (!isa<Function>(Callee)) {
    CalleeNode = getValueDest(Callee).getNode();
    if (CalleeNode == 0) {
      DEBUG(errs() << "WARNING: Program is calling through a null pointer?\n" << *I);
      return;  // Calling a null pointer?
    }
  }

  // NOTE: This code is identical to 'DSGraph::getDSCallSiteForCallSite',
  // the reason it's duplicated is because this calls getValueDest instead
  // of getNodeForValue to get the DSNodes for the arguments.  Since we're in
  // local it's possible that we need to create a DSNode for the argument, as
  // opposed to getNodeForValue which simply retrieves the existing node.


  //Get the FunctionType for the called function
  const FunctionType *CalleeFuncType = DSCallSite::FunctionTypeOfCallSite(CS);
  int NumFixedArgs = CalleeFuncType->getNumParams();

  // Sanity check--this really, really shouldn't happen
  if (!CalleeFuncType->isVarArg())
    assert(CS.arg_size() == static_cast<unsigned>(NumFixedArgs) &&
           "Too many arguments/incorrect function signature!");

  std::vector<DSNodeHandle> Args;
  Args.reserve(CS.arg_end()-CS.arg_begin());
  DSNodeHandle VarArgNH;

  // Calculate the arguments vector...
  // Add all fixed pointer arguments, then merge the rest together
  for (CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
       I != E; ++I)
    if (isa<PointerType>((*I)->getType())) {
      DSNodeHandle ArgNode = getValueDest(*I);
      if (I - CS.arg_begin() < NumFixedArgs) {
        Args.push_back(ArgNode);
      } else {
        VarArgNH.mergeWith(ArgNode);
      }
    }

  // Add a new function call entry...
  if (CalleeNode) {
    ++NumIndirectCall;
    G.getFunctionCalls().push_back(DSCallSite(CS, RetVal, VarArgNH, CalleeNode,
                                              Args));
  } else {
    ++NumDirectCall;
    G.getFunctionCalls().push_back(DSCallSite(CS, RetVal, VarArgNH,
                                              cast<Function>(Callee),
                                              Args));
  }


}

void GraphBuilder::visitGetElementPtrInst(User &GEP) {
  //
  // Ensure that the indexed pointer has a DSNode.
  //
  DSNodeHandle Value = getValueDest(GEP.getOperand(0));
  if (Value.isNull())
    Value = createNode();

  //
  // There are a few quick and easy cases to handle.  If  the DSNode of the 
  // indexed pointer is already folded, then we know that the result of the 
  // GEP will have the same offset into the same DSNode 
  // as the indexed pointer.
  //

  if (!Value.isNull() &&
      Value.getNode()->isNodeCompletelyFolded()) {
    setDestTo(GEP, Value);
    return;
  }

  //
  // Okay, no easy way out.  Calculate the offset into the object being
  // indexed.
  //

  int Offset = 0;

  // FIXME: I am not sure if the code below is completely correct (especially
  //        if we start doing fancy analysis on non-constant array indices).
  //        What if the array is indexed using a larger index than its declared
  //        size?  Does the LLVM verifier catch such issues?
  //

  //
  // Determine the offset (in bytes) between the result of the GEP and the
  // GEP's pointer operand.
  //
  // Note: All of these subscripts are indexing INTO the elements we have...
  //
  // FIXME: We can do better for array indexing.  First, if the array index is
  //        constant, we can determine how much farther we're moving the
  //        pointer.  Second, we can try to use the results of other analysis
  //        passes (e.g., ScalarEvolution) to find min/max values to do less
  //        conservative type-folding.
  //
  for (gep_type_iterator I = gep_type_begin(GEP), E = gep_type_end(GEP);
       I != E; ++I)
    if (StructType *STy = dyn_cast<StructType>(*I)) {
      // indexing into a structure
      // next index must be a constant
      const ConstantInt* CUI = cast<ConstantInt>(I.getOperand());
      int FieldNo = CUI->getSExtValue();
      // increment the offset by the actual byte offset being accessed

      unsigned requiredSize = TD.getTypeAllocSize(STy) + Value.getOffset() + Offset;
      if(!Value.getNode()->isArrayNode() || Value.getNode()->getSize() <= 0){
        if (requiredSize > Value.getNode()->getSize())
          Value.getNode()->growSize(requiredSize);
      }
      Offset += (unsigned)TD.getStructLayout(STy)->getElementOffset(FieldNo);
      if(TypeInferenceOptimize) {
        if(ArrayType* AT = dyn_cast<ArrayType>(STy->getTypeAtIndex(FieldNo))) {
          Value.getNode()->mergeTypeInfo(AT, Value.getOffset() + Offset);
          if((++I) == E) {
            break;
          }
          // Check if we are still indexing into an array.
          // We only record the topmost array type of any nested array.
          // Keep skipping indexes till we reach a non-array type.
          // J is the type of the next index.
          // Uncomment the line below to get all the nested types.
          gep_type_iterator J = I;
          while(isa<ArrayType>(*(++J))) {
            //      Value.getNode()->mergeTypeInfo(AT1, Value.getOffset() + Offset);
            if((++I) == E) {
              break;
            }
            J = I;
          }
          if((I) == E) {
            break;
          }
        }
      }
    } else if(ArrayType *ATy = dyn_cast<ArrayType>(*I)) {
      // indexing into an array.
      Value.getNode()->setArrayMarker();
      Type *CurTy = ATy->getElementType();

      if(!isa<ArrayType>(CurTy) &&
         Value.getNode()->getSize() <= 0) {
        Value.getNode()->growSize(TD.getTypeAllocSize(CurTy));
      } else if(isa<ArrayType>(CurTy) && Value.getNode()->getSize() <= 0){
        Type *ETy = (cast<ArrayType>(CurTy))->getElementType();
        while(isa<ArrayType>(ETy)) {
          ETy = (cast<ArrayType>(ETy))->getElementType();
        }
        Value.getNode()->growSize(TD.getTypeAllocSize(ETy));
      }
//.........这里部分代码省略.........