[Attributor] Use IRPosition consistently

[jdoerfert]

Summary

The next attempt to clean up the Attributor interface before we grow it
further.

Before, we used a combination of two values (associated + anchor) and an
argument number (or -1) to determine a location. This was very fragile.
The new system uses exclusively IR positions and we restrict the
generation of IR positions to special constructor methods that verify
internal constraints we have. This will catch misuse early.

The auto-conversion, e.g., in getAAFor, is now performed through the
SubsumingPositionIterator. This iterator takes an IR position and allows
to visit all IR positions that "subsume" the given one, e.g., function
attributes "subsume" argument attributes of that function. For a
detailed breakdown see the class comment of SubsumingPositionIterator.

This patch also introduces the IRPosition::getAttrs() to extract IR
attributes at a certain position. The method knows how to look up in
different positions that are equivalent, e.g., the argument position for
call site arguments. We also introduce three new positions kinds such
that we have all IR positions where attributes can be placed and one for
"floating" values.

[sstefan1]

Generally looks good to me. Some initial comments inlined. Since it is a big patch I'd also wait for Hideto to read it. (Maybe I'll reread it as well.)

llvm/include/llvm/Transforms/IPO/Attributor.h

158

I don't see the need for it.

255

You mean if llvm_unreachable makes sense? To me it does. If I'm not wrong this also covers CallSites and I don't see anything else that should be covered.

286

Maybe put these 2 in default with unreachable?

[uenoku]

LGTM

llvm/include/llvm/Transforms/IPO/Attributor.h

158

What are the advantages to record the scope?

[jdoerfert]

More IRPosition uses in interfaces, cleanup, adjustment to follow up patches

[uenoku]

llvm/include/llvm/Transforms/IPO/Attributor.h

213

What does this TODO mean?

[jdoerfert]

Add missing documentation

llvm/include/llvm/Transforms/IPO/Attributor.h

158

We could then tie constants to functions, but again, I was also not sure why/if we want that.

213

It is a reminder to myself to describe the method ;). Done.

255

Yes, unreachable or nullptr was the question. And again, it is about constants (globals, constant integers, ...). It turns out, this is useful in the future so I use nullptr here.

286

I would prefer to make it explicit.

[sstefan1]

LGTM.

llvm/include/llvm/Transforms/IPO/Attributor.h

158

Ok, so we keep that for now (as it can't do no harm) and see how things go?

llvm/include/llvm/Transforms/IPO/Attributor.h

enum class ChangeStatus {
   CHANGED,
   UNCHANGED,
 };
 
 ChangeStatus operator|(ChangeStatus l, ChangeStatus r);
 ChangeStatus operator&(ChangeStatus l, ChangeStatus r);
 ///}
 
+/// Helper to describe and deal with positions in the LLVM-IR.
+///
+/// A position in the IR is described by an anchor value and an "offset" that
+/// could be the argument number, for call sites and arguments, or an indicator
+/// of the "position kind". The kinds, specified in the Kind enum below, include
+/// the locations in the attribute list, i.a., function scope and return value,
+/// as well as a distinction between call sites and functions. Finally, there
+/// are floating values that do not have a corresponding attribute list
+/// position.
+struct IRPosition {
+  virtual ~IRPosition() {}
+
+  /// The positions we distinguish in the IR.
+  ///
+  /// The values are chosen such that the KindOrArgNo member has a value >= 1
+  /// if it is an argument or call site argument while a value < 1 indicates the
+  /// respective kind of that value.
+  enum Kind : int {
+    IRP_INVALID = -6, ///< An invalid position.
+    IRP_FLOAT = -5, ///< A position that is not associated with a spot suitable
+                    ///< for attributes. This could be any value or instruction.
+    IRP_RETURNED = -4, ///< An attribute for the function return value.
+    IRP_CALL_SITE_RETURNED = -3, ///< An attribute for a call site return value.
+    IRP_FUNCTION = -2,           ///< An attribute for a function (scope).
+    IRP_CALL_SITE = -1, ///< An attribute for a call site (function scope).
+    IRP_ARGUMENT = 0,   ///< An attribute for a function argument.
+    IRP_CALL_SITE_ARGUMENT = 1, ///< An attribute for a call site argument.
+  };
+
+  /// Default constructor available to create invalid positions implicitly. All
+  /// other positions need to be created explicitly through the appropriate
+  /// static member function.
+  IRPosition() : AnchorVal(nullptr), KindOrArgNo(IRP_INVALID) { verify(); }
+
+  /// Create a position describing the value of \p V in \p AnchorScope.
+  static const IRPosition value(const Value &V, const Function &AnchorScope) {
+    // TODO: Determine if we need the scope at all.
+    if (auto *Arg = dyn_cast<Argument>(&V))
+      return IRPosition::argument(*Arg);
+    if (auto *CB = dyn_cast<CallBase>(&V))
+      return IRPosition::callsite_returned(*CB);
+    return IRPosition(const_cast<Value &>(V), IRP_FLOAT);
+  }
+
+  /// Create a position describing the value of \p I in its function.
+  static const IRPosition value(const Instruction &I) {
+    return IRPosition::value(I, *I.getFunction());
+  }
+
+  /// Create a position describing the function scope of \p F.
+  static const IRPosition function(const Function &F) {
+    return IRPosition(const_cast<Function &>(F), IRP_FUNCTION);
+  }
+
+  /// Create a position describing the returned value of \p F.
+  static const IRPosition returned(const Function &F) {
+    return IRPosition(const_cast<Function &>(F), IRP_RETURNED);
+  }
+
+  /// Create a position describing the argument \p Arg.
+  static const IRPosition argument(const Argument &Arg) {
+    return IRPosition(const_cast<Argument &>(Arg), Kind(Arg.getArgNo()));
+  }
+
+  /// Create a position describing the function scope of \p CB.
+  static const IRPosition callsite_function(const CallBase &CB) {
+    return IRPosition(const_cast<CallBase &>(CB), IRP_CALL_SITE);
+  }
+
+  /// Create a position describing the returned value of \p CB.
+  static const IRPosition callsite_returned(const CallBase &CB) {
+    return IRPosition(const_cast<CallBase &>(CB), IRP_CALL_SITE_RETURNED);
+  }
+
+  /// Create a position describing the argument of \p CB at position \p ArgNo.
+  static const IRPosition callsite_argument(const CallBase &CB,
+                                            unsigned ArgNo) {
+    return IRPosition(const_cast<CallBase &>(CB), Kind(ArgNo));
+  }
+
+  /// Create a position describing the function scope of \p ICS.
+  static const IRPosition callsite_function(ImmutableCallSite ICS) {
+    return IRPosition::callsite_function(cast<CallBase>(*ICS.getInstruction()));
+  }
+
+  /// Create a position describing the returned value of \p ICS.
+  static const IRPosition callsite_returned(ImmutableCallSite ICS) {
+    return IRPosition::callsite_returned(cast<CallBase>(*ICS.getInstruction()));
+  }
+
+  /// Create a position describing the argument of \p ICS at position \p ArgNo.
+  static const IRPosition callsite_argument(ImmutableCallSite ICS,
+                                            unsigned ArgNo) {
+    return IRPosition::callsite_argument(cast<CallBase>(*ICS.getInstruction()),
+                                         ArgNo);
+  }
+
+  bool operator==(const IRPosition &RHS) const {
+    return (AnchorVal == RHS.AnchorVal) && (KindOrArgNo == RHS.KindOrArgNo);
+  }
+  bool operator!=(const IRPosition &RHS) const { return !(*this == RHS); }
+
+  /// Return the value this abstract attribute is anchored with.
+  ///
+  /// The anchor value might not be the associated value if the latter is not
+  /// sufficient to determine where arguments will be manifested. This is, so
+  /// far, only the case for call site arguments as the value is not sufficient
+  /// to pinpoint them. Instead, we can use the call site as an anchor.
+  ///
+  ///{
+  Value &getAnchorValue() {
+    assert(KindOrArgNo != IRP_INVALID &&
+           "Invalid position does not have an anchor value!");
+    return *AnchorVal;
+  }
+  const Value &getAnchorValue() const {
+    return const_cast<IRPosition *>(this)->getAnchorValue();
+  }
+  ///}
+
+  /// Return the Function surrounding the anchor value.
+  ///
+  ///{
+  Function &getAnchorScope() {
+    assert(KindOrArgNo != IRP_INVALID &&
+           "Invalid position does not have an anchor scope!");
+    Value &V = getAnchorValue();
+    if (isa<Function>(V))
+      return cast<Function>(V);
+    if (isa<Argument>(V))
+      return *cast<Argument>(V).getParent();
+    if (isa<Instruction>(V))
+      return *cast<Instruction>(V).getFunction();
+    // TODO: Figure out if this makes sense.
+    llvm_unreachable("Could not determine scope!");
+  }
+  const Function &getAnchorScope() const {
+    return const_cast<IRPosition *>(this)->getAnchorScope();
+  }
+  ///}
+
+  /// Return the value this abstract attribute is associated with.
+  ///
+  ///{
+  Value &getAssociatedValue() {
+    assert(KindOrArgNo != IRP_INVALID &&
+           "Invalid position does not have an associated value!");
+    if (getArgNo() < 0 || isa<Argument>(AnchorVal))
+      return *AnchorVal;
+    assert(isa<CallBase>(AnchorVal) && "Expected a call base!");
+    return *cast<CallBase>(AnchorVal)->getArgOperand(getArgNo());
+  }
+  const Value &getAssociatedValue() const {
+    return const_cast<IRPosition *>(this)->getAssociatedValue();
+  }
+  ///}
+
+  /// Return the argument number of the associated value if it is an argument or
+  /// call site argument, otherwise a negative value.
+  int getArgNo() const { return KindOrArgNo; }
+
+  /// Return the index in the attribute list for this position.
+  unsigned getAttrIdx() const {
+    switch (getPositionKind()) {
+    case IRPosition::IRP_INVALID:
+    case IRPosition::IRP_FLOAT:
+      break;
+    case IRPosition::IRP_FUNCTION:
+    case IRPosition::IRP_CALL_SITE:
+      return AttributeList::FunctionIndex;
+    case IRPosition::IRP_RETURNED:
+    case IRPosition::IRP_CALL_SITE_RETURNED:
+      return AttributeList::ReturnIndex;
+    case IRPosition::IRP_ARGUMENT:
+    case IRPosition::IRP_CALL_SITE_ARGUMENT:
+      return KindOrArgNo + AttributeList::FirstArgIndex;
+    }
+    llvm_unreachable(
+        "There is no attribute index for a floating or invalid position!");
+  }
+
+  /// Return the associated position kind.
+  Kind getPositionKind() const {
+    if (getArgNo() >= 0) {
+      assert(((isa<Argument>(getAnchorValue()) &&
+               isa<Argument>(getAssociatedValue())) ||
+              isa<CallBase>(getAnchorValue())) &&
+             "Expected argument or call base due to argument number!");
+      if (isa<CallBase>(getAnchorValue()))
+        return IRP_CALL_SITE_ARGUMENT;
+      return IRP_ARGUMENT;
+    }
+
+    assert(KindOrArgNo < 0 &&
+           "Expected (call site) arguments to never reach this point!");
+    assert(!isa<Argument>(getAnchorValue()) &&
+           "Expected arguments to have an associated argument position!");
+    return Kind(KindOrArgNo);
+  }
+
+  /// TODO: Figure out if the attribute related helper functions should live
+  ///       here or somewhere else.
+
+  /// Return true if any kind in \p AKs existing in the IR at a position that
+  /// will affect this one. See also getAttrs(...).
+  bool hasAttr(ArrayRef<Attribute::AttrKind> AKs) const;
+
+  /// Return the attributes of any kind in \p AKs existing in the IR at a
+  /// position that will affect this one. While each position can only have a
+  /// single attribute of any kind in \p AKs, there are "subsuming" positions
+  /// that could have an attribute as well. This method returns all attributes
+  /// found in \p Attrs.
+  void getAttrs(ArrayRef<Attribute::AttrKind> AKs,
+                SmallVectorImpl<Attribute> &Attrs) const;
+
+  /// Return the attribute of kind \p AK existing in the IR at this position.
+  Attribute getAttr(Attribute::AttrKind AK) const {
+    if (getPositionKind() == IRP_INVALID || getPositionKind() == IRP_FLOAT)
+      return Attribute();
+
+    AttributeList AttrList;
+    if (ImmutableCallSite ICS = ImmutableCallSite(&getAnchorValue()))
+      AttrList = ICS.getAttributes();
+    else
+      AttrList = getAnchorScope().getAttributes();
+
+    if (AttrList.hasAttribute(getAttrIdx(), AK))
+      return AttrList.getAttribute(getAttrIdx(), AK);
+    return Attribute();
+  }
+
+  /// Return the data layout associated with the anchor scope.
+  const DataLayout &getDataLayout() const {
+    return getAnchorScope().getParent()->getDataLayout();
+  }
+
+  /// Special DenseMap key values.
+  ///
+  ///{
+  static const IRPosition EmptyKey;
+  static const IRPosition TombstoneKey;
+  ///}
+
+private:
+  /// Private constructor for special values only!
+  explicit IRPosition(int KindOrArgNo)
+      : AnchorVal(0), KindOrArgNo(KindOrArgNo) {}
+
+  /// IRPosition anchored at \p AnchorVal with kind/argument numbet \p PK.
+  explicit IRPosition(Value &AnchorVal, Kind PK)
+      : AnchorVal(&AnchorVal), KindOrArgNo(PK) {
+    verify();
+  }
+
+  /// Verify internal invariants.
+  void verify();
+
+  /// The value this position is anchored at.
+  Value *AnchorVal;
+
+  /// The argument number, if non-negative, or the position "kind".
+  int KindOrArgNo;
+};
+
+/// Helper that allows IRPosition as a key in a DenseMap.
+template <> struct DenseMapInfo<IRPosition> {
+  static inline IRPosition getEmptyKey() { return IRPosition::EmptyKey; }
+  static inline IRPosition getTombstoneKey() {
+    return IRPosition::TombstoneKey;
+  }
+  static unsigned getHashValue(const IRPosition &IRP) {
+    return (DenseMapInfo<Value *>::getHashValue(&IRP.getAnchorValue()) << 4) ^
+           (unsigned(IRP.getArgNo()));
+  }
+  static bool isEqual(const IRPosition &LHS, const IRPosition &RHS) {
+    return LHS == RHS;
+  }
+};
+
+/// A visitor class for IR positions.
+///
+/// Given a position P, the SubsumingPositionIterator allows to visit "subsuming
+/// positions" wrt. attributes/information. Thus, if a piece of information
+/// holds for a subsuming position, it also holds for the position P.
+///
+/// The subsuming positions always include the initial position and then,
+/// depending on the position kind, additionally the following ones:
+/// - for IRP_RETURNED:
+///   - the function (IRP_FUNCTION)
+/// - for IRP_ARGUMENT:
+///   - the function (IRP_FUNCTION)
+/// - for IRP_CALL_SITE:
+///   - the callee (IRP_FUNCTION), if known
+/// - for IRP_CALL_SITE_RETURNED:
+///   - the callee (IRP_RETURNED), if known
+///   - the call site (IRP_FUNCTION)
+///   - the callee (IRP_FUNCTION), if known
+/// - for IRP_CALL_SITE_ARGUMENT:
+///   - the argument of the callee (IRP_ARGUMENT), if known
+///   - the callee (IRP_FUNCTION), if known
+///   - the position the call site argument is associated with if it is not
+///     anchored to the call site, e.g., if it is an arugment then the argument
+///     (IRP_ARGUMENT)
+class SubsumingPositionIterator {
+  SmallVector<IRPosition, 4> IRPositions;
+  using iterator = decltype(IRPositions)::iterator;
+public:
+  SubsumingPositionIterator(const IRPosition &IRP);
+  iterator begin() { return IRPositions.begin(); }
+  iterator end() { return IRPositions.end(); }
+};
+
 /// The fixpoint analysis framework that orchestrates the attribute deduction.
 ///
 /// The Attributor provides a general abstract analysis framework (guided
 /// fixpoint iteration) as well as helper functions for the deduction of
 /// (LLVM-IR) attributes. However, also other code properties can be deduced,
 /// propagated, and ultimately manifested through the Attributor framework. This
 /// is particularly useful if these properties interact with attributes and a
 /// co-scheduled deduction allows to improve the solution. Even if not, thus if
struct Attributor {
   /// Run the analyses until a fixpoint is reached or enforced (timeout).
   ///
   /// The attributes registered with this Attributor can be used after as long
   /// as the Attributor is not destroyed (it owns the attributes now).
   ///
   /// \Returns CHANGED if the IR was changed, otherwise UNCHANGED.
   ChangeStatus run(InformationCache &InfoCache);
 
-  /// Lookup an abstract attribute of type \p AAType anchored at value \p V and
-  /// argument number \p ArgNo. If no attribute is found and \p V is a call base
-  /// instruction, the called function is tried as a value next. Thus, the
-  /// returned abstract attribute might be anchored at the callee of \p V.
+  /// Lookup an abstract attribute of type \p AAType at position \p IRP. While
+  /// no abstract attribute is found equivalent positions are checked, see
+  /// SubsumingPositionIterator. Thus, the returned abstract attribute
+  /// might be anchored at a different position, e.g., the callee if \p IRP is a
+  /// call base.
   ///
   /// This method is the only (supported) way an abstract attribute can retrieve
   /// information from another abstract attribute. As an example, take an
   /// abstract attribute that determines the memory access behavior for a
   /// argument (readnone, readonly, ...). It should use `getAAFor` to get the
   /// most optimistic information for other abstract attributes in-flight, e.g.
   /// the one reasoning about the "captured" state for the argument or the one
   /// reasoning on the memory access behavior of the function as a whole.
   template <typename AAType>
-  const AAType *getAAFor(const AbstractAttribute &QueryingAA, const Value &V,
-                         int ArgNo = -1) {
+  const AAType *getAAFor(const AbstractAttribute &QueryingAA,
+                         const IRPosition &IRP) {
     static_assert(std::is_base_of<AbstractAttribute, AAType>::value,
                   "Cannot query an attribute with a type not derived from "
                   "'AbstractAttribute'!");
 
-    // Determine the argument number automatically for llvm::Arguments if none
-    // is set. Do not override a given one as it could be a use of the argument
-    // in a call site.
-    if (ArgNo == -1)
-      if (auto *Arg = dyn_cast<Argument>(&V))
-        ArgNo = Arg->getArgNo();
-
-    // If a function was given together with an argument number, perform the
-    // lookup for the actual argument instead. Don't do it for variadic
-    // arguments.
-    if (ArgNo >= 0 && isa<Function>(&V) &&
-        cast<Function>(&V)->arg_size() > (size_t)ArgNo)
-      return getAAFor<AAType>(
-          QueryingAA, *(cast<Function>(&V)->arg_begin() + ArgNo), ArgNo);
-
+    // Let's try an equivalent position if available, see
+    // SubsumingPositionIterator for more information.
+    for (const IRPosition &EquivIRP : SubsumingPositionIterator(IRP)) {
       // Lookup the abstract attribute of type AAType. If found, return it after
       // registering a dependence of QueryingAA on the one returned attribute.
-    const auto &KindToAbstractAttributeMap = AAMap.lookup({&V, ArgNo});
+      const auto &KindToAbstractAttributeMap =
+          AAMap.lookup(const_cast<IRPosition &>(EquivIRP));
       if (AAType *AA = static_cast<AAType *>(
               KindToAbstractAttributeMap.lookup(&AAType::ID))) {
-      // Do not return an attribute with an invalid state. This minimizes checks
-      // at the calls sites and allows the fallback below to kick in.
+        // Do not return an attribute with an invalid state. This minimizes
+        // checks at the calls sites and allows the fallback below to kick in.
         if (AA->getState().isValidState()) {
           QueryMap[AA].insert(const_cast<AbstractAttribute *>(&QueryingAA));
           return AA;
         }
       }
-
-    // If no abstract attribute was found and we look for a call site argument,
-    // defer to the actual argument instead.
-    ImmutableCallSite ICS(&V);
-    if (ICS && ICS.getCalledValue())
-      return getAAFor<AAType>(QueryingAA, *ICS.getCalledValue(), ArgNo);
+    }
 
     // No matching attribute found
     return nullptr;
   }
 
   /// Introduce a new abstract attribute into the fixpoint analysis.
   ///
   /// Note that ownership of the attribute is given to the Attributor. It will
   /// invoke delete for the Attributor on destruction of the Attributor.
   ///
-  /// Attributes are identified by
-  ///  (1) their anchored value (see AA.getAnchoredValue()),
-  ///  (2) their argument number (\p ArgNo, or Argument::getArgNo()), and
-  ///  (3) the address of their static member (see AAType::ID).
-  template <typename AAType> AAType &registerAA(AAType &AA, int ArgNo = -1) {
+  /// Attributes are identified by their IR position (AAType::getIRPosition())
+  /// and the address of their static member (see AAType::ID).
+  template <typename AAType> AAType &registerAA(AAType &AA) {
     static_assert(std::is_base_of<AbstractAttribute, AAType>::value,
                   "Cannot register an attribute with a type not derived from "
                   "'AbstractAttribute'!");
-
-    // Determine the anchor value and the argument number which are used to
-    // lookup the attribute together with AAType::ID. If passed an argument,
-    // use its argument number but do not override a given one as it could be a
-    // use of the argument at a call site.
-    Value &AnchorVal = AA.getIRPosition().getAnchorValue();
-    if (ArgNo == -1)
-      if (auto *Arg = dyn_cast<Argument>(&AnchorVal))
-        ArgNo = Arg->getArgNo();
-
     // Put the attribute in the lookup map structure and the container we use to
     // keep track of all attributes.
-    AAMap[{&AnchorVal, ArgNo}][&AAType::ID] = &AA;
+    IRPosition &IRP = AA.getIRPosition();
+    AAMap[IRP][&AAType::ID] = &AA;
     AllAbstractAttributes.push_back(&AA);
     return AA;
   }
 
   /// Determine opportunities to derive 'default' attributes in \p F and create
   /// abstract attribute objects for them.
   ///
   /// \param F The function that is checked for attribute opportunities.

 
 private:
   /// The set of all abstract attributes.
   ///{
   using AAVector = SmallVector<AbstractAttribute *, 64>;
   AAVector AllAbstractAttributes;
   ///}
 
-  /// A nested map to lookup abstract attributes based on the anchored value and
-  /// an argument positions (or -1) on the outer level, and the addresses of the
-  /// static member (AAType::ID) on the inner level.
+  /// A nested map to lookup abstract attributes based on the argument position
+  /// on the outer level, and the addresses of the static member (AAType::ID) on
+  /// the inner level.
   ///{
   using KindToAbstractAttributeMap =
       DenseMap<const char *, AbstractAttribute *>;
-  DenseMap<std::pair<const Value *, int>, KindToAbstractAttributeMap> AAMap;
+  DenseMap<IRPosition, KindToAbstractAttributeMap> AAMap;
   ///}
 
   /// A map from abstract attributes to the ones that queried them through calls
   /// to the getAAFor<...>(...) method.
   ///{
   using QueryMapTy =
       DenseMap<AbstractAttribute *, SetVector<AbstractAttribute *>>;
   QueryMapTy QueryMap;
private:
   base_t Assumed;
 };
 
 /// Simple wrapper for a single bit (boolean) state.
 struct BooleanState : public IntegerState {
   BooleanState() : IntegerState(1){};
 };
 
-/// Struct to encode the position in the LLVM-IR with regards to the associated
-/// value but also the attribute lists.
-struct IRPosition {
-
-  /// The positions attributes can be manifested in.
-  enum Kind {
-    IRP_FUNCTION = AttributeList::FunctionIndex, ///< An attribute for a
-                                                 ///< function as a whole.
-    IRP_RETURNED = AttributeList::ReturnIndex,   ///< An attribute for the
-                                                 ///< function return value.
-    IRP_ARGUMENT,           ///< An attribute for a function argument.
-    IRP_CALL_SITE_ARGUMENT, ///< An attribute for a call site argument.
-  };
-
-  /// Create an IRPosition for an argument.
-  explicit IRPosition(Argument &Arg) : IRPosition(&Arg, Arg, Arg.getArgNo()) {}
-
-  /// Create an IRPosition for a function return or function body position.
-  ///
-  /// \param Fn The value this abstract attributes is anchored at and
-  ///            associated with.
-  /// \param PK  The kind of attribute position, can not be a (call site)
-  ///            argument.
-  explicit IRPosition(Function &Fn, Kind PK)
-      : AssociatedVal(&Fn), AnchorVal(Fn), AttributeIdx(PK) {
-    assert((PK == IRP_RETURNED || PK == IRP_FUNCTION) &&
-           "Expected non-argument position!");
-  }
-
-  /// An abstract attribute associated with \p AssociatedVal and anchored at
-  /// \p AnchorVal.
-  ///
-  /// \param AssociatedVal The value this abstract attribute is associated with.
-  /// \param AnchorVal The value this abstract attributes is anchored at.
-  /// \param ArgumentNo The index in the attribute list, encodes also the
-  ///                     argument number if this is one.
-  explicit IRPosition(Value *AssociatedVal, Value &AnchorVal,
-                      unsigned ArgumentNo)
-      : AssociatedVal(AssociatedVal), AnchorVal(AnchorVal),
-        AttributeIdx(ArgumentNo + AttributeList::FirstArgIndex) {
-    assert(((isa<CallBase>(&AnchorVal) &&
-             cast<CallBase>(&AnchorVal)->arg_size() > ArgumentNo) ||
-            (isa<Argument>(AnchorVal) &&
-             cast<Argument>(AnchorVal).getArgNo() == ArgumentNo)) &&
-           "Expected a valid argument index!");
-  }
-
-#define IRPositionConstructorForward(NAME, BASE)                               \
-  explicit NAME(Argument &Arg) : BASE(Arg) {}                                  \
-  explicit NAME(Function &Fn, IRPosition::Kind PK) : BASE(Fn, PK) {}           \
-  NAME(Value *AssociatedVal, Value &AnchorVal, unsigned ArgumentNo)            \
-      : BASE(AssociatedVal, AnchorVal, ArgumentNo) {}
-
-  IRPosition(const IRPosition &AAP)
-      : IRPosition(AAP.AssociatedVal, AAP.AnchorVal, AAP.AttributeIdx) {}
-
-  /// Virtual destructor.
-  virtual ~IRPosition() {}
-
-  /// Return the value this abstract attribute is anchored with.
-  ///
-  /// The anchored value might not be the associated value if the latter is not
-  /// sufficient to determine where arguments will be manifested. This is mostly
-  /// the case for call site arguments as the value is not sufficient to
-  /// pinpoint them. Instead, we can use the call site as an anchor.
-  ///
-  ///{
-  Value &getAnchorValue() { return AnchorVal; }
-  const Value &getAnchorValue() const { return AnchorVal; }
-  ///}
-
-  /// Return the llvm::Function surrounding the anchored value.
-  ///
-  ///{
-  Function &getAnchorScope() {
-    Value &V = getAnchorValue();
-    if (isa<Function>(V))
-      return cast<Function>(V);
-    if (isa<Argument>(V))
-      return *cast<Argument>(V).getParent();
-    if (isa<Instruction>(V))
-      return *cast<Instruction>(V).getFunction();
-    llvm_unreachable("No scope for anchored value found!");
-  }
-  const Function &getAnchorScope() const {
-    return const_cast<IRPosition *>(this)->getAnchorScope();
-  }
-  ///}
-
-  /// Return the value this abstract attribute is associated with.
-  ///
-  /// The abstract state usually represents this value.
-  ///
-  ///{
-  Value *getAssociatedValue() { return AssociatedVal; }
-  const Value *getAssociatedValue() const { return AssociatedVal; }
-  ///}
-
-  /// Return the argument number of the associated value if it is an argument or
-  /// call site argument, otherwise a negative value.
-  int getArgNo() const { return AttributeIdx - AttributeList::FirstArgIndex; }
-
-  /// Return the position this abstract state is manifested in.
-  Kind getPositionKind() const {
-    if (getArgNo() >= 0) {
-      if (isa<CallBase>(getAnchorValue()))
-        return IRP_CALL_SITE_ARGUMENT;
-      assert((isa<Argument>(getAnchorValue()) ||
-              isa_and_nonnull<Argument>(getAssociatedValue()) ||
-              (!getAssociatedValue() && isa<Function>(getAnchorValue()))) &&
-             "Expected argument or call base due to argument number!");
-      return IRP_ARGUMENT;
-    }
-    return (Kind)AttributeIdx;
-  }
-
-  /// Return the index in the attribute list for this position.
-  int getAttrIdx() const { return AttributeIdx; }
-
-  /// Change the associated value.
-  void setAssociatedValue(Value *V) { AssociatedVal = V; }
-
-  /// Change the associated attribue list position.
-  void setAttributeIdx(int AttrIdx) { AttributeIdx = AttrIdx; }
-
-protected:
-  /// The value this abstract attribute is associated with.
-  Value *AssociatedVal;
-
-  /// The value this abstract attribute is anchored at.
-  Value &AnchorVal;
-
-  /// The index in the attribute list.
-  int AttributeIdx;
-};
-
 /// Helper struct necessary as the modular build fails if the virtual method
 /// IRAttribute::manifest is defined in the Attributor.cpp.
 struct IRAttributeManifest {
   static ChangeStatus manifestAttrs(Attributor &A, IRPosition &IRP,
                                     const ArrayRef<Attribute> &DeducedAttrs);
 };
 
 /// Helper to tie a abstract state implementation to an abstract attribute.
 template <typename StateTy, typename Base>
 struct StateWrapper : public StateTy, public Base {
   /// Provide static access to the type of the state.
   using StateType = StateTy;
 
   /// See AbstractAttribute::getState(...).
   StateType &getState() override { return *this; }
 
   /// See AbstractAttribute::getState(...).
   const AbstractState &getState() const override { return *this; }
 };
 
 /// Helper class that provides common functionality to manifest IR attributes.
 template <Attribute::AttrKind AK, typename Base>
-struct IRAttribute : public IRPosition,
-                     public Base {
+struct IRAttribute : public IRPosition, public Base {
+  IRAttribute(const IRPosition &IRP) : IRPosition(IRP) {}
   ~IRAttribute() {}
 
-  /// Constructors for the IRPosition.
-  ///
-  ///{
-  IRPositionConstructorForward(IRAttribute, IRPosition);
-  ///}
-
   /// See AbstractAttribute::manifest(...).
   ChangeStatus manifest(Attributor &A) {
     SmallVector<Attribute, 4> DeducedAttrs;
     getDeducedAttributes(getAnchorScope().getContext(), DeducedAttrs);
     return IRAttributeManifest::manifestAttrs(A, getIRPosition(), DeducedAttrs);
   }
 
   /// Return the kind that identifies the abstract attribute implementation.

 
 /// ----------------------------------------------------------------------------
 ///                       Abstract Attribute Classes
 /// ----------------------------------------------------------------------------
 
 /// An abstract attribute for the returned values of a function.
 struct AAReturnedValues
     : public IRAttribute<Attribute::Returned, AbstractAttribute> {
-  IRPositionConstructorForward(AAReturnedValues, IRAttribute);
+  AAReturnedValues(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Check \p Pred on all returned values.
   ///
   /// This method will evaluate \p Pred on returned values and return
   /// true if (1) all returned values are known, and (2) \p Pred returned true
   /// for all returned values.
   ///
   /// Note: Unlike the Attributor::checkForAllReturnedValuesAndReturnInsts
   /// method, this one will not filter dead return instructions.
   virtual bool checkForAllReturnedValuesAndReturnInsts(
       const function_ref<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
           &Pred) const = 0;
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 struct AANoUnwind
     : public IRAttribute<Attribute::NoUnwind,
                          StateWrapper<BooleanState, AbstractAttribute>> {
-  IRPositionConstructorForward(AANoUnwind, IRAttribute);
+  AANoUnwind(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Returns true if nounwind is assumed.
   bool isAssumedNoUnwind() const { return getAssumed(); }
 
   /// Returns true if nounwind is known.
   bool isKnownNoUnwind() const { return getKnown(); }
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 struct AANoSync
     : public IRAttribute<Attribute::NoSync,
                          StateWrapper<BooleanState, AbstractAttribute>> {
-  IRPositionConstructorForward(AANoSync, IRAttribute);
+  AANoSync(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Returns true if "nosync" is assumed.
   bool isAssumedNoSync() const { return getAssumed(); }
 
   /// Returns true if "nosync" is known.
   bool isKnownNoSync() const { return getKnown(); }
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 /// An abstract interface for all nonnull attributes.
 struct AANonNull
     : public IRAttribute<Attribute::NonNull,
                          StateWrapper<BooleanState, AbstractAttribute>> {
-  IRPositionConstructorForward(AANonNull, IRAttribute);
+  AANonNull(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Return true if we assume that the underlying value is nonnull.
   bool isAssumedNonNull() const { return getAssumed(); }
 
   /// Return true if we know that underlying value is nonnull.
   bool isKnownNonNull() const { return getKnown(); }
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 /// An abstract attribute for norecurse.
 struct AANoRecurse
     : public IRAttribute<Attribute::NoRecurse,
                          StateWrapper<BooleanState, AbstractAttribute>> {
-  IRPositionConstructorForward(AANoRecurse, IRAttribute);
+  AANoRecurse(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Return true if "norecurse" is assumed.
   bool isAssumedNoRecurse() const { return getAssumed(); }
 
   /// Return true if "norecurse" is known.
   bool isKnownNoRecurse() const { return getKnown(); }
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 /// An abstract attribute for willreturn.
 struct AAWillReturn
     : public IRAttribute<Attribute::WillReturn,
                          StateWrapper<BooleanState, AbstractAttribute>> {
-  IRPositionConstructorForward(AAWillReturn, IRAttribute);
+  AAWillReturn(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Return true if "willreturn" is assumed.
   bool isAssumedWillReturn() const { return getAssumed(); }
 
   /// Return true if "willreturn" is known.
   bool isKnownWillReturn() const { return getKnown(); }
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 /// An abstract interface for all noalias attributes.
 struct AANoAlias
     : public IRAttribute<Attribute::NoAlias,
                          StateWrapper<BooleanState, AbstractAttribute>> {
-  IRPositionConstructorForward(AANoAlias, IRAttribute);
+  AANoAlias(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Return true if we assume that the underlying value is alias.
   bool isAssumedNoAlias() const { return getAssumed(); }
 
   /// Return true if we know that underlying value is noalias.
   bool isKnownNoAlias() const { return getKnown(); }
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 /// An AbstractAttribute for nofree.
 struct AANoFree
     : public IRAttribute<Attribute::NoFree,
                          StateWrapper<BooleanState, AbstractAttribute>> {
-  IRPositionConstructorForward(AANoFree, IRAttribute);
+  AANoFree(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Return true if "nofree" is assumed.
   bool isAssumedNoFree() const { return getAssumed(); }
 
   /// Return true if "nofree" is known.
   bool isKnownNoFree() const { return getKnown(); }
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 /// An AbstractAttribute for noreturn.
 struct AANoReturn
     : public IRAttribute<Attribute::NoReturn,
                          StateWrapper<BooleanState, AbstractAttribute>> {
-  IRPositionConstructorForward(AANoReturn, IRAttribute);
+  AANoReturn(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Return true if the underlying object is assumed to never return.
   bool isAssumedNoReturn() const { return getAssumed(); }
 
   /// Return true if the underlying object is known to never return.
   bool isKnownNoReturn() const { return getKnown(); }
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 /// An abstract interface for liveness abstract attribute.
 struct AAIsDead : public StateWrapper<BooleanState, AbstractAttribute>,
                   public IRPosition {
-  IRPositionConstructorForward(AAIsDead, IRPosition);
+  AAIsDead(const IRPosition &IRP) : IRPosition(IRP) {}
 
   /// Returns true if \p BB is assumed dead.
   virtual bool isAssumedDead(const BasicBlock *BB) const = 0;
 
   /// Returns true if \p BB is known dead.
   virtual bool isKnownDead(const BasicBlock *BB) const = 0;
 
   /// Returns true if \p I is assumed dead.
struct AAIsDead : public StateWrapper<BooleanState, AbstractAttribute>,
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 /// An abstract interface for all dereferenceable attribute.
 struct AADereferenceable
     : public IRAttribute<Attribute::Dereferenceable, AbstractAttribute> {
-  IRPositionConstructorForward(AADereferenceable, IRAttribute);
+  AADereferenceable(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Return true if we assume that the underlying value is nonnull.
   virtual bool isAssumedNonNull() const = 0;
 
   /// Return true if we know that underlying value is nonnull.
   virtual bool isKnownNonNull() const = 0;
 
   /// Return true if we assume that underlying value is
struct AADereferenceable
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 /// An abstract interface for all align attributes.
 struct AAAlign
     : public IRAttribute<Attribute::Alignment,
                          StateWrapper<IntegerState, AbstractAttribute>> {
-  IRPositionConstructorForward(AAAlign, IRAttribute);
+  AAAlign(const IRPosition &IRP) : IRAttribute(IRP) {}
 
   /// Return assumed alignment.
   unsigned getAssumedAlign() const { return getAssumed(); }
 
   /// Return known alignemnt.
   unsigned getKnownAlign() const { return getKnown(); }
 
   /// Unique ID (due to the unique address)
   static const char ID;
 };
 
 } // end namespace llvm
 
 #endif // LLVM_TRANSFORMS_IPO_FUNCTIONATTRS_H

llvm/lib/Transforms/IPO/Attributor.cpp

LLVM_DEBUG(dbgs() << "[Attributor] Update " << HasChanged << " " << *this
                     << "\n");
 
   return HasChanged;
 }
 
 ChangeStatus
 IRAttributeManifest::manifestAttrs(Attributor &A, IRPosition &IRP,
                                    const ArrayRef<Attribute> &DeducedAttrs) {
-  assert(IRP.getAssociatedValue() &&
-         "Attempted to manifest an attribute without associated value!");
-
   ChangeStatus HasChanged = ChangeStatus::UNCHANGED;
 
   Function &ScopeFn = IRP.getAnchorScope();
   LLVMContext &Ctx = ScopeFn.getContext();
   IRPosition::Kind PK = IRP.getPositionKind();
 
   // In the following some generic code that will manifest attributes in
   // DeducedAttrs if they improve the current IR. Due to the different
   // annotation positions we use the underlying AttributeList interface.
 
   AttributeList Attrs;
   switch (PK) {
+  case IRPosition::IRP_INVALID:
+  case IRPosition::IRP_FLOAT:
+    llvm_unreachable("Cannot manifest at a floating or invalid position!");
   case IRPosition::IRP_ARGUMENT:
   case IRPosition::IRP_FUNCTION:
   case IRPosition::IRP_RETURNED:
     Attrs = ScopeFn.getAttributes();
     break;
+  case IRPosition::IRP_CALL_SITE:
+  case IRPosition::IRP_CALL_SITE_RETURNED:
   case IRPosition::IRP_CALL_SITE_ARGUMENT:
     Attrs = ImmutableCallSite(&IRP.getAnchorValue()).getAttributes();
     break;
   }
 
   for (const Attribute &Attr : DeducedAttrs) {
     if (!addIfNotExistent(Ctx, Attr, Attrs, IRP.getAttrIdx()))
       continue;
 
     HasChanged = ChangeStatus::CHANGED;
   }
 
   if (HasChanged == ChangeStatus::UNCHANGED)
     return HasChanged;
 
   switch (PK) {
   case IRPosition::IRP_ARGUMENT:
   case IRPosition::IRP_FUNCTION:
   case IRPosition::IRP_RETURNED:
     ScopeFn.setAttributes(Attrs);
     break;
+  case IRPosition::IRP_CALL_SITE:
+  case IRPosition::IRP_CALL_SITE_RETURNED:
   case IRPosition::IRP_CALL_SITE_ARGUMENT:
     CallSite(&IRP.getAnchorValue()).setAttributes(Attrs);
+  case IRPosition::IRP_FLOAT:
+  case IRPosition::IRP_INVALID:
+    break;
   }
 
   return HasChanged;
 }
 
+const IRPosition IRPosition::EmptyKey(255);
+const IRPosition IRPosition::TombstoneKey(256);
+
+SubsumingPositionIterator::SubsumingPositionIterator(const IRPosition &IRP) {
+  IRPositions.emplace_back(IRP);
+
+  ImmutableCallSite ICS(&IRP.getAnchorValue());
+  switch (IRP.getPositionKind()) {
+  case IRPosition::IRP_INVALID:
+  case IRPosition::IRP_FLOAT:
+  case IRPosition::IRP_FUNCTION:
+    return;
+  case IRPosition::IRP_ARGUMENT:
+  case IRPosition::IRP_RETURNED:
+    IRPositions.emplace_back(IRPosition::function(IRP.getAnchorScope()));
+    return;
+  case IRPosition::IRP_CALL_SITE:
+    assert(ICS && "Expected call site!");
+    // TODO: We need to look at the operand bundles similar to the redirection
+    //       in CallBase.
+    if (!ICS.hasOperandBundles())
+      if (const Function *Callee = ICS.getCalledFunction())
+        IRPositions.emplace_back(IRPosition::function(*Callee));
+    return;
+  case IRPosition::IRP_CALL_SITE_RETURNED:
+    assert(ICS && "Expected call site!");
+    // TODO: We need to look at the operand bundles similar to the redirection
+    //       in CallBase.
+    if (!ICS.hasOperandBundles()) {
+      if (const Function *Callee = ICS.getCalledFunction()) {
+        IRPositions.emplace_back(IRPosition::returned(*Callee));
+        IRPositions.emplace_back(IRPosition::function(*Callee));
+      }
+    }
+    IRPositions.emplace_back(
+        IRPosition::callsite_function(cast<CallBase>(*ICS.getInstruction())));
+    return;
+  case IRPosition::IRP_CALL_SITE_ARGUMENT: {
+    int ArgNo = IRP.getArgNo();
+    assert(ICS && ArgNo >= 0 && "Expected call site!");
+    // TODO: We need to look at the operand bundles similar to the redirection
+    //       in CallBase.
+    if (!ICS.hasOperandBundles()) {
+      const Function *Callee = ICS.getCalledFunction();
+      if (Callee && Callee->arg_size() > unsigned(ArgNo))
+        IRPositions.emplace_back(IRPosition::argument(*Callee->getArg(ArgNo)));
+      if (Callee)
+        IRPositions.emplace_back(IRPosition::function(*Callee));
+    }
+    IRPositions.emplace_back(
+        IRPosition::value(IRP.getAssociatedValue(), IRP.getAnchorScope()));
+    return;
+  }
+  }
+}
+
+bool IRPosition::hasAttr(ArrayRef<Attribute::AttrKind> AKs) const {
+  for (const IRPosition &EquivIRP : SubsumingPositionIterator(*this))
+    for (Attribute::AttrKind AK : AKs)
+      if (EquivIRP.getAttr(AK).getKindAsEnum() == AK)
+        return true;
+  return false;
+}
+
+void IRPosition::getAttrs(ArrayRef<Attribute::AttrKind> AKs,
+                          SmallVectorImpl<Attribute> &Attrs) const {
+  for (const IRPosition &EquivIRP : SubsumingPositionIterator(*this))
+    for (Attribute::AttrKind AK : AKs) {
+      const Attribute &Attr = EquivIRP.getAttr(AK);
+      if (Attr.getKindAsEnum() == AK)
+        Attrs.push_back(Attr);
+    }
+}
+
+void IRPosition::verify() {
+  switch (KindOrArgNo) {
+  default:
+    assert(KindOrArgNo >= 0 && "Expected argument or call site argument!");
+    assert((isa<CallBase>(AnchorVal) || isa<Argument>(AnchorVal)) &&
+           "Expected call base or argument for positive attribute index!");
+    if (auto *Arg = dyn_cast<Argument>(AnchorVal)) {
+      assert(Arg->getArgNo() == unsigned(getArgNo()) &&
+             "Argument number mismatch!");
+      assert(Arg == &getAssociatedValue() && "Associated value mismatch!");
+    } else {
+      auto &CB = cast<CallBase>(*AnchorVal);
+      assert(CB.arg_size() > unsigned(getArgNo()) &&
+             "Call site argument number mismatch!");
+      assert(CB.getArgOperand(getArgNo()) == &getAssociatedValue() &&
+             "Associated value mismatch!");
+    }
+    break;
+  case IRP_INVALID:
+    assert(!AnchorVal && "Expected no value for an invalid position!");
+    break;
+  case IRP_FLOAT:
+    assert((!isa<CallBase>(&getAssociatedValue()) &&
+            !isa<Argument>(&getAssociatedValue())) &&
+           "Expected specialized kind for call base and argument values!");
+    break;
+  case IRP_RETURNED:
+    assert(isa<Function>(AnchorVal) &&
+           "Expected function for a 'returned' position!");
+    assert(AnchorVal == &getAssociatedValue() && "Associated value mismatch!");
+    break;
+  case IRP_CALL_SITE_RETURNED:
+    assert((isa<CallBase>(AnchorVal)) &&
+           "Expected call base for 'call site returned' position!");
+    assert(AnchorVal == &getAssociatedValue() && "Associated value mismatch!");
+    break;
+  case IRP_CALL_SITE:
+    assert((isa<CallBase>(AnchorVal)) &&
+           "Expected call base for 'call site function' position!");
+    assert(AnchorVal == &getAssociatedValue() && "Associated value mismatch!");
+    break;
+  case IRP_FUNCTION:
+    assert(isa<Function>(AnchorVal) &&
+           "Expected function for a 'function' position!");
+    assert(AnchorVal == &getAssociatedValue() && "Associated value mismatch!");
+    break;
+  }
+}
+
 /// -----------------------NoUnwind Function Attribute--------------------------
 
 struct AANoUnwindImpl : AANoUnwind {
-  IRPositionConstructorForward(AANoUnwindImpl, AANoUnwind);
+  AANoUnwindImpl(const IRPosition &IRP) : AANoUnwind(IRP) {}
 
   const std::string getAsStr() const override {
     return getAssumed() ? "nounwind" : "may-unwind";
   }
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 };
 
 struct AANoUnwindFunction final : public AANoUnwindImpl {
-  AANoUnwindFunction(Function &F) : AANoUnwindImpl(F, IRP_FUNCTION) {}
+  AANoUnwindFunction(const IRPosition &IRP) : AANoUnwindImpl(IRP) {}
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_FN_ATTR(nounwind)
   }
 };
 
 ChangeStatus AANoUnwindImpl::updateImpl(Attributor &A,
                                         InformationCache &InfoCache) {
   Function &F = getAnchorScope();
 
   // The map from instruction opcodes to those instructions in the function.
   auto Opcodes = {
       (unsigned)Instruction::Invoke,      (unsigned)Instruction::CallBr,
       (unsigned)Instruction::Call,        (unsigned)Instruction::CleanupRet,
       (unsigned)Instruction::CatchSwitch, (unsigned)Instruction::Resume};
 
   auto CheckForNoUnwind = [&](Instruction &I) {
     if (!I.mayThrow())
       return true;
 
-    auto *NoUnwindAA = A.getAAFor<AANoUnwind>(*this, I);
+    auto *NoUnwindAA = A.getAAFor<AANoUnwind>(*this, IRPosition::value(I));
     return NoUnwindAA && NoUnwindAA->isAssumedNoUnwind();
   };
 
   if (!A.checkForAllInstructions(F, CheckForNoUnwind, *this, InfoCache,
                                  Opcodes))
     return indicatePessimisticFixpoint();
 
   return ChangeStatus::UNCHANGED;
void collectValuesRecursively(
     // If we did abort the above traversal we haven't see all the values.
     // Consequently, we cannot know if the information we would derive is
     // accurate so we give up early.
     if (!Success)
       indicatePessimisticFixpoint();
   }
 
 public:
-  IRPositionConstructorForward(AAReturnedValuesImpl, AAReturnedValues);
+  AAReturnedValuesImpl(const IRPosition &IRP) : AAReturnedValues(IRP) {}
 
   /// See AbstractAttribute::initialize(...).
   void initialize(Attributor &A, InformationCache &InfoCache) override {
     // Reset the state.
-    setAssociatedValue(nullptr);
     IsFixed = false;
     IsValidState = true;
     HasOverdefinedReturnedCalls = false;
     ReturnedValues.clear();
 
     Function &F = getAnchorScope();
 
     // The map from instruction opcodes to those instructions in the function.
public:
 
   ChangeStatus indicatePessimisticFixpoint() override {
     IsFixed = true;
     IsValidState = false;
     return ChangeStatus::CHANGED;
   }
 };
 
-struct AAReturnedValuesFunction final : public AAReturnedValuesImpl {
-  AAReturnedValuesFunction(Function &F)
-      : AAReturnedValuesImpl(F, IRP_FUNCTION) {}
+struct AAReturnedValuesReturned final : public AAReturnedValuesImpl {
+  AAReturnedValuesReturned(const IRPosition &IRP) : AAReturnedValuesImpl(IRP) {}
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_ARG_ATTR(returned)
   }
 };
 
 ChangeStatus AAReturnedValuesImpl::manifest(Attributor &A) {
if (!UniqueRV.hasValue() || !UniqueRV.getValue())
     return Changed;
 
   // Bookkeeping.
   STATS_DECL_AND_TRACK(UniqueReturnValue, FunctionReturn,
                        "Number of function with unique return");
 
   // If the assumed unique return value is an argument, annotate it.
   if (auto *UniqueRVArg = dyn_cast<Argument>(UniqueRV.getValue())) {
-    setAssociatedValue(UniqueRVArg);
-    setAttributeIdx(UniqueRVArg->getArgNo() + AttributeList::FirstArgIndex);
+    getIRPosition() = IRPosition::argument(*UniqueRVArg);
     Changed = IRAttribute::manifest(A) | Changed;
   }
 
   return Changed;
 }
 
 const std::string AAReturnedValuesImpl::getAsStr() const {
   return (isAtFixpoint() ? "returns(#" : "may-return(#") +
ChangeStatus AAReturnedValuesImpl::updateImpl(Attributor &A,
 
   // Check if any of the returned values is a call site we can refine.
   decltype(ReturnedValues) AddRVs;
   bool HasCallSite = false;
 
   // Keep track of any change to trigger updates on dependent attributes.
   ChangeStatus Changed = ChangeStatus::UNCHANGED;
 
-  auto *LivenessAA = A.getAAFor<AAIsDead>(*this, getAnchorScope());
+  auto *LivenessAA = A.getAAFor<AAIsDead>(*this, getIRPosition());
 
   // Look at all returned call sites.
   for (auto &It : ReturnedValues) {
     SmallPtrSet<ReturnInst *, 2> &ReturnInsts = It.second;
     Value *RV = It.first;
 
     LLVM_DEBUG(dbgs() << "[AAReturnedValues] Potentially returned value " << *RV
                       << "\n");
for (auto &It : ReturnedValues) {
     if (LivenessAA &&
         !LivenessAA->isLiveInstSet(ReturnInsts.begin(), ReturnInsts.end())) {
       LLVM_DEBUG(dbgs() << "[AAReturnedValues] all returns are assumed dead, "
                            "skip it for now\n");
       continue;
     }
 
     // Try to find a assumed unique return value for the called function.
-    auto *RetCSAA = A.getAAFor<AAReturnedValuesImpl>(*this, *RV);
+    auto *RetCSAA = A.getAAFor<AAReturnedValuesImpl>(
+        *this, IRPosition::callsite_returned(RetCS));
     if (!RetCSAA) {
       if (!HasOverdefinedReturnedCalls)
         Changed = ChangeStatus::CHANGED;
       HasOverdefinedReturnedCalls = true;
       LLVM_DEBUG(dbgs() << "[AAReturnedValues] Returned call site (" << *RV
                         << ") with " << (RetCSAA ? "invalid" : "no")
                         << " associated state\n");
       continue;
     }
 
     // Try to find a assumed unique return value for the called function.
     Optional<Value *> AssumedUniqueRV = RetCSAA->getAssumedUniqueReturnValue(A);
 
     // If no assumed unique return value was found due to the lack of
     // candidates, we may need to resolve more calls (through more update
-    // iterations) or the called function will not return. Either way, we simply
-    // stick with the call sites as return values. Because there were not
-    // multiple possibilities, we do not treat it as overdefined.
+    // iterations) or the called function will not return. Either way, we
+    // simply stick with the call sites as return values. Because there were
+    // not multiple possibilities, we do not treat it as overdefined.
     if (!AssumedUniqueRV.hasValue())
       continue;
 
     // If multiple, non-refinable values were found, there cannot be a unique
     // return value for the called function. The returned call is overdefined!
     if (!AssumedUniqueRV.getValue()) {
       if (!HasOverdefinedReturnedCalls)
         Changed = ChangeStatus::CHANGED;
LLVM_DEBUG({
              << " unique return value: " << *AssumedUniqueRV << "\n";
     });
 
     // The assumed unique return value.
     Value *AssumedRetVal = AssumedUniqueRV.getValue();
 
     // If the assumed unique return value is an argument, lookup the matching
     // call site operand and recursively collect new returned values.
-    // If it is not an argument, it is just put into the set of returned values
-    // as we would have already looked through casts, phis, and similar values.
+    // If it is not an argument, it is just put into the set of returned
+    // values as we would have already looked through casts, phis, and similar
+    // values.
     if (Argument *AssumedRetArg = dyn_cast<Argument>(AssumedRetVal))
       collectValuesRecursively(A,
                                RetCS.getArgOperand(AssumedRetArg->getArgNo()),
                                ReturnInsts, AddRVs);
     else
       AddRVs[AssumedRetVal].insert(ReturnInsts.begin(), ReturnInsts.end());
   }
 
ChangeStatus AAReturnedValuesImpl::updateImpl(Attributor &A,
   }
 
   return Changed;
 }
 
 /// ------------------------ NoSync Function Attribute -------------------------
 
 struct AANoSyncImpl : AANoSync {
-  IRPositionConstructorForward(AANoSyncImpl, AANoSync);
+  AANoSyncImpl(const IRPosition &IRP) : AANoSync(IRP) {}
 
   const std::string getAsStr() const override {
     return getAssumed() ? "nosync" : "may-sync";
   }
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// Helper function used to determine whether an instruction is non-relaxed
   /// atomic. In other words, if an atomic instruction does not have unordered
   /// or monotonic ordering
   static bool isNonRelaxedAtomic(Instruction *I);
 
   /// Helper function used to determine whether an instruction is volatile.
   static bool isVolatile(Instruction *I);
 
   /// Helper function uset to check if intrinsic is volatile (memcpy, memmove,
   /// memset).
   static bool isNoSyncIntrinsic(Instruction *I);
 };
 
 struct AANoSyncFunction final : public AANoSyncImpl {
-  AANoSyncFunction(Function &F) : AANoSyncImpl(F, IRP_FUNCTION) {}
+  AANoSyncFunction(const IRPosition &IRP) : AANoSyncImpl(IRP) {}
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override { STATS_DECL_AND_TRACK_FN_ATTR(nosync) }
 };
 
 bool AANoSyncImpl::isNonRelaxedAtomic(Instruction *I) {
   if (!I->isAtomic())
     return false;

 ChangeStatus AANoSyncImpl::updateImpl(Attributor &A,
                                       InformationCache &InfoCache) {
   Function &F = getAnchorScope();
 
   auto CheckRWInstForNoSync = [&](Instruction &I) {
     /// We are looking for volatile instructions or Non-Relaxed atomics.
     /// FIXME: We should ipmrove the handling of intrinsics.
 
-    ImmutableCallSite ICS(&I);
-    auto *NoSyncAA = A.getAAFor<AANoSyncImpl>(*this, I);
-
     if (isa<IntrinsicInst>(&I) && isNoSyncIntrinsic(&I))
       return true;
 
-    if (ICS && (!NoSyncAA || !NoSyncAA->isAssumedNoSync()) &&
-        !ICS.hasFnAttr(Attribute::NoSync))
-      return false;
+    if (ImmutableCallSite ICS = ImmutableCallSite(&I)) {
+      if (ICS.hasFnAttr(Attribute::NoSync))
+        return true;
 
-    if (ICS)
+      auto *NoSyncAA =
+          A.getAAFor<AANoSyncImpl>(*this, IRPosition::callsite_function(ICS));
+      if (NoSyncAA && NoSyncAA->isAssumedNoSync())
         return true;
+      return false;
+    }
 
     if (!isVolatile(&I) && !isNonRelaxedAtomic(&I))
       return true;
 
     return false;
   };
 
   auto CheckForNoSync = [&](Instruction &I) {
if (!A.checkForAllReadWriteInstructions(F, CheckRWInstForNoSync, *this,
     return indicatePessimisticFixpoint();
 
   return ChangeStatus::UNCHANGED;
 }
 
 /// ------------------------ No-Free Attributes ----------------------------
 
 struct AANoFreeImpl : public AANoFree {
-  IRPositionConstructorForward(AANoFreeImpl, AANoFree);
+  AANoFreeImpl(const IRPosition &IRP) : AANoFree(IRP) {}
 
   /// See AbstractAttribute::getAsStr().
   const std::string getAsStr() const override {
     return getAssumed() ? "nofree" : "may-free";
   }
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 };
 
 struct AANoFreeFunction final : public AANoFreeImpl {
-  AANoFreeFunction(Function &F) : AANoFreeImpl(F, IRP_FUNCTION) {}
+  AANoFreeFunction(const IRPosition &IRP) : AANoFreeImpl(IRP) {}
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override { STATS_DECL_AND_TRACK_FN_ATTR(nofree) }
 };
 
 ChangeStatus AANoFreeImpl::updateImpl(Attributor &A,
                                       InformationCache &InfoCache) {
   Function &F = getAnchorScope();
 
   auto CheckForNoFree = [&](Instruction &I) {
-    if (ImmutableCallSite(&I).hasFnAttr(Attribute::NoFree))
+    ImmutableCallSite ICS(&I);
+    if (ICS.hasFnAttr(Attribute::NoFree))
       return true;
 
-    auto *NoFreeAA = A.getAAFor<AANoFreeImpl>(*this, I);
+    auto *NoFreeAA =
+        A.getAAFor<AANoFreeImpl>(*this, IRPosition::callsite_function(ICS));
     return NoFreeAA && NoFreeAA->isAssumedNoFree();
   };
 
   if (!A.checkForAllCallLikeInstructions(F, CheckForNoFree, *this, InfoCache))
     return indicatePessimisticFixpoint();
   return ChangeStatus::UNCHANGED;
 }
 
 /// ------------------------ NonNull Argument Attribute ------------------------
 struct AANonNullImpl : AANonNull {
-  IRPositionConstructorForward(AANonNullImpl, AANonNull);
+  AANonNullImpl(const IRPosition &IRP) : AANonNull(IRP) {}
 
   /// See AbstractAttribute::getAsStr().
   const std::string getAsStr() const override {
     return getAssumed() ? "nonnull" : "may-null";
   }
 
+  /// See AbstractAttribute::initialize(...).
+  void initialize(Attributor &A, InformationCache &InfoCache) override {
+    if (hasAttr({Attribute::NonNull, Attribute::Dereferenceable}))
+      indicateOptimisticFixpoint();
+  }
+
   /// Generate a predicate that checks if a given value is assumed nonnull.
   /// The generated function returns true if a value satisfies any of
   /// following conditions.
   /// (i) A value is known nonZero(=nonnull).
   /// (ii) A value is associated with AANonNull and its isAssumedNonNull() is
   /// true.
   std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
   generatePredicate(Attributor &);
 };
 
 std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
 AANonNullImpl::generatePredicate(Attributor &A) {
   // FIXME: The `AAReturnedValues` should provide the predicate with the
   // `ReturnInst` vector as well such that we can use the control flow sensitive
   // version of `isKnownNonZero`. This should fix `test11` in
   // `test/Transforms/FunctionAttrs/nonnull.ll`
 
+  const Function &F = getAnchorScope();
   std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> Pred =
       [&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &RetInsts) -> bool {
-    Function &F = getAnchorScope();
-
-    if (isKnownNonZero(&RV, F.getParent()->getDataLayout()))
+    if (isKnownNonZero(&RV, getDataLayout()))
       return true;
 
-    auto *NonNullAA = A.getAAFor<AANonNull>(*this, RV);
-
-    ImmutableCallSite ICS(&RV);
-
-    if ((!NonNullAA || !NonNullAA->isAssumedNonNull()) &&
-        (!ICS || !ICS.hasRetAttr(Attribute::NonNull)))
-      return false;
-
+    if (ImmutableCallSite ICS = ImmutableCallSite(&RV))
+      if (ICS.hasRetAttr(Attribute::NonNull))
         return true;
+
+    auto *NonNullAA = A.getAAFor<AANonNull>(*this, IRPosition::value(RV, F));
+    return (NonNullAA && NonNullAA->isAssumedNonNull());
   };
 
   return Pred;
 }
 
 /// NonNull attribute for function return value.
 struct AANonNullReturned final : AANonNullImpl {
-  AANonNullReturned(Function &F) : AANonNullImpl(F, IRP_RETURNED) {}
-
-  /// See AbstractAttribute::initialize(...).
-  void initialize(Attributor &A, InformationCache &InfoCache) override {
-    Function &F = getAnchorScope();
-
-    // Already nonnull.
-    if (F.getAttributes().hasAttribute(AttributeList::ReturnIndex,
-                                       Attribute::NonNull) ||
-        F.getAttributes().hasAttribute(AttributeList::ReturnIndex,
-                                       Attribute::Dereferenceable))
-      indicateOptimisticFixpoint();
-  }
+  AANonNullReturned(const IRPosition &IRP) : AANonNullImpl(IRP) {}
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_FNRET_ATTR(nonnull)
   }
 };
 
 ChangeStatus AANonNullReturned::updateImpl(Attributor &A,
                                            InformationCache &InfoCache) {
   Function &F = getAnchorScope();
 
   std::function<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)> Pred =
       this->generatePredicate(A);
 
   if (!A.checkForAllReturnedValuesAndReturnInsts(F, Pred, *this))
     return indicatePessimisticFixpoint();
   return ChangeStatus::UNCHANGED;
 }
 
 /// NonNull attribute for function argument.
 struct AANonNullArgument final : AANonNullImpl {
-  AANonNullArgument(Argument &A) : AANonNullImpl(A) {}
-
-  /// See AbstractAttriubute::initialize(...).
-  void initialize(Attributor &A, InformationCache &InfoCache) override {
-    Argument *Arg = cast<Argument>(getAssociatedValue());
-    if (Arg->hasNonNullAttr())
-      indicateOptimisticFixpoint();
-  }
+  AANonNullArgument(const IRPosition &IRP) : AANonNullImpl(IRP) {}
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_ARG_ATTR(nonnull)
   }
 };
 
 /// NonNull attribute for a call site argument.
 struct AANonNullCallSiteArgument final : AANonNullImpl {
-  AANonNullCallSiteArgument(Instruction &I, unsigned ArgNo)
-      : AANonNullImpl(CallSite(&I).getArgOperand(ArgNo), I, ArgNo) {}
+  AANonNullCallSiteArgument(const IRPosition &IRP) : AANonNullImpl(IRP) {}
 
   /// See AbstractAttribute::initialize(...).
   void initialize(Attributor &A, InformationCache &InfoCache) override {
-    CallSite CS(&getAnchorValue());
-    if (CS.paramHasAttr(getArgNo(), getAttrKind()) ||
-        CS.paramHasAttr(getArgNo(), Attribute::Dereferenceable) ||
-        isKnownNonZero(getAssociatedValue(),
-                       getAnchorScope().getParent()->getDataLayout()))
+    AANonNullImpl::initialize(A, InfoCache);
+    if (!isKnownNonNull() &&
+        isKnownNonZero(&getAssociatedValue(), getDataLayout()))
       indicateOptimisticFixpoint();
   }
 
   /// See AbstractAttribute::updateImpl(Attributor &A).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_CSARG_ATTR(nonnull)
   }
 };
 
 ChangeStatus AANonNullArgument::updateImpl(Attributor &A,
                                            InformationCache &InfoCache) {
   Function &F = getAnchorScope();
   unsigned ArgNo = getArgNo();
 
   // Callback function
   std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) {
     assert(CS && "Sanity check: Call site was not initialized properly!");
 
-    auto *NonNullAA =
-        A.getAAFor<AANonNullImpl>(*this, *CS.getInstruction(), ArgNo);
+    IRPosition CSArgPos = IRPosition::callsite_argument(CS, ArgNo);
+    if (CSArgPos.hasAttr({Attribute::NonNull, Attribute::Dereferenceable}))
+      return true;
 
     // Check that NonNullAA is AANonNullCallSiteArgument.
-    if (NonNullAA) {
+    if (auto *NonNullAA = A.getAAFor<AANonNullImpl>(*this, CSArgPos)) {
       ImmutableCallSite ICS(&NonNullAA->getAnchorValue());
       if (ICS && CS.getInstruction() == ICS.getInstruction())
         return NonNullAA->isAssumedNonNull();
       return false;
     }
 
-    if (CS.paramHasAttr(ArgNo, Attribute::NonNull))
-      return true;
-
     Value *V = CS.getArgOperand(ArgNo);
-    if (isKnownNonZero(V, getAnchorScope().getParent()->getDataLayout()))
+    if (isKnownNonZero(V, getDataLayout()))
       return true;
 
     return false;
   };
   if (!A.checkForAllCallSites(F, CallSiteCheck, *this, true))
     return indicatePessimisticFixpoint();
   return ChangeStatus::UNCHANGED;
 }
 
 ChangeStatus
 AANonNullCallSiteArgument::updateImpl(Attributor &A,
                                       InformationCache &InfoCache) {
   // NOTE: Never look at the argument of the callee in this method.
   //       If we do this, "nonnull" is always deduced because of the assumption.
 
-  Value &V = *getAssociatedValue();
-
-  auto *NonNullAA = A.getAAFor<AANonNull>(*this, V);
+  Value &V = getAssociatedValue();
+  auto *NonNullAA =
+      A.getAAFor<AANonNull>(*this, IRPosition::value(V, getAnchorScope()));
 
   if (!NonNullAA || !NonNullAA->isAssumedNonNull())
     return indicatePessimisticFixpoint();
 
   return ChangeStatus::UNCHANGED;
 }
 
 /// ------------------------ Will-Return Attributes ----------------------------
 
 struct AAWillReturnImpl : public AAWillReturn {
-  IRPositionConstructorForward(AAWillReturnImpl, AAWillReturn);
+  AAWillReturnImpl(const IRPosition &IRP) : AAWillReturn(IRP) {}
 
   /// See AbstractAttribute::getAsStr()
   const std::string getAsStr() const override {
     return getAssumed() ? "willreturn" : "may-noreturn";
   }
 };
 
 struct AAWillReturnFunction final : AAWillReturnImpl {
-  AAWillReturnFunction(Function &F) : AAWillReturnImpl(F, IRP_FUNCTION) {}
+  AAWillReturnFunction(const IRPosition &IRP) : AAWillReturnImpl(IRP) {}
 
   /// See AbstractAttribute::initialize(...).
   void initialize(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
ChangeStatus AAWillReturnFunction::updateImpl(Attributor &A,
   const Function &F = getAnchorScope();
   // The map from instruction opcodes to those instructions in the function.
 
   auto CheckForWillReturn = [&](Instruction &I) {
     ImmutableCallSite ICS(&I);
     if (ICS.hasFnAttr(Attribute::WillReturn))
       return true;
 
-    auto *WillReturnAA = A.getAAFor<AAWillReturn>(*this, I);
+    IRPosition IPos = IRPosition::callsite_function(ICS);
+    auto *WillReturnAA = A.getAAFor<AAWillReturn>(*this, IPos);
     if (!WillReturnAA || !WillReturnAA->isAssumedWillReturn())
       return false;
 
     // FIXME: Prohibit any recursion for now.
     if (ICS.hasFnAttr(Attribute::NoRecurse))
       return true;
 
-    auto *NoRecurseAA = A.getAAFor<AANoRecurse>(*this, I);
+    auto *NoRecurseAA = A.getAAFor<AANoRecurse>(*this, IPos);
     return NoRecurseAA && NoRecurseAA->isAssumedNoRecurse();
   };
 
   if (!A.checkForAllCallLikeInstructions(F, CheckForWillReturn, *this,
                                          InfoCache))
     return indicatePessimisticFixpoint();
 
   return ChangeStatus::UNCHANGED;
 }
 
 /// ------------------------ NoAlias Argument Attribute ------------------------
 
 struct AANoAliasImpl : AANoAlias {
-  IRPositionConstructorForward(AANoAliasImpl, AANoAlias);
+  AANoAliasImpl(const IRPosition &IRP) : AANoAlias(IRP) {}
 
   const std::string getAsStr() const override {
     return getAssumed() ? "noalias" : "may-alias";
   }
 };
 
 /// NoAlias attribute for function return value.
 struct AANoAliasReturned final : AANoAliasImpl {
-  AANoAliasReturned(Function &F) : AANoAliasImpl(F, IRP_RETURNED) {}
+  AANoAliasReturned(const IRPosition &IRP) : AANoAliasImpl(IRP) {}
 
   /// See AbstractAttriubute::initialize(...).
   void initialize(Attributor &A, InformationCache &InfoCache) override {
     Function &F = getAnchorScope();
 
     // Already noalias.
     if (F.returnDoesNotAlias()) {
       indicateOptimisticFixpoint();
auto CheckReturnValue = [&](Value &RV) -> bool {
 
     /// For now, we can only deduce noalias if we have call sites.
     /// FIXME: add more support.
     ImmutableCallSite ICS(&RV);
     if (!ICS)
       return false;
 
     if (!ICS.returnDoesNotAlias()) {
-      auto *NoAliasAA = A.getAAFor<AANoAlias>(*this, RV);
+      auto *NoAliasAA =
+          A.getAAFor<AANoAlias>(*this, IRPosition::callsite_returned(ICS));
       if (!NoAliasAA || !NoAliasAA->isAssumedNoAlias())
         return false;
     }
 
     /// FIXME: We can improve capture check in two ways:
     /// 1. Use the AANoCapture facilities.
     /// 2. Use the location of return insts for escape queries.
     if (PointerMayBeCaptured(&RV, /* ReturnCaptures */ false,
                              /* StoreCaptures */ true))
       return false;
 
     return true;
   };
 
   if (!A.checkForAllReturnedValues(F, CheckReturnValue, *this))
     return indicatePessimisticFixpoint();
 
   return ChangeStatus::UNCHANGED;
 }
 
 /// -------------------AAIsDead Function Attribute-----------------------
 
 struct AAIsDeadImpl : public AAIsDead {
-  IRPositionConstructorForward(AAIsDeadImpl, AAIsDead);
+  AAIsDeadImpl(const IRPosition &IRP) : AAIsDead(IRP) {}
 
   void initialize(Attributor &A, InformationCache &InfoCache) override {
     const Function &F = getAnchorScope();
 
     ToBeExploredPaths.insert(&(F.getEntryBlock().front()));
     AssumedLiveBlocks.insert(&(F.getEntryBlock()));
     for (size_t i = 0; i < ToBeExploredPaths.size(); ++i)
       if (const Instruction *NextNoReturnI =
for (const Instruction *NRC : NoReturnCalls) {
         BasicBlock *NormalDestBB = II->getNormalDest();
         SplitPos = &NormalDestBB->front();
 
         /// Invoke is replaced with a call and unreachable is placed after it if
         /// the callee is nounwind and noreturn. Otherwise, we keep the invoke
         /// and only place an unreachable in the normal successor.
         if (Invoke2CallAllowed) {
           if (Function *Callee = II->getCalledFunction()) {
-            auto *AANoUnw = A.getAAFor<AANoUnwind>(*this, *Callee);
+            auto *AANoUnw =
+                A.getAAFor<AANoUnwind>(*this, IRPosition::function(*Callee));
             if (Callee->hasFnAttribute(Attribute::NoUnwind) ||
                 (AANoUnw && AANoUnw->isAssumedNoUnwind())) {
               LLVM_DEBUG(dbgs()
                          << "[AAIsDead] Replace invoke with call inst\n");
               // We do not need an invoke (II) but instead want a call followed
               // by an unreachable. However, we do not remove II as other
               // abstract attributes might have it cached as part of their
               // results. Given that we modify the CFG anyway, we simply keep II
struct AAIsDeadImpl : public AAIsDead {
   /// Collection of all assumed live BasicBlocks.
   DenseSet<const BasicBlock *> AssumedLiveBlocks;
 
   /// Collection of calls with noreturn attribute, assumed or knwon.
   SmallSetVector<const Instruction *, 4> NoReturnCalls;
 };
 
 struct AAIsDeadFunction final : public AAIsDeadImpl {
-  AAIsDeadFunction(Function &F) : AAIsDeadImpl(F, IRP_FUNCTION) {}
+  AAIsDeadFunction(const IRPosition &IRP) : AAIsDeadImpl(IRP) {}
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL(DeadBlocks, Function,
                "Number of basic blocks classified as dead");
     BUILD_STAT_NAME(DeadBlocks, Function) +=
         getAnchorScope().size() - AssumedLiveBlocks.size();
     STATS_DECL(PartiallyDeadBlocks, Function,
const Instruction *AAIsDeadImpl::findNextNoReturn(Attributor &A,
   //       Edges could be from an instruction to the next or from a terminator
   //       to the successor. For now, we need to special case the unwind block
   //       of InvokeInst below.
 
   while (I) {
     ImmutableCallSite ICS(I);
 
     if (ICS) {
+      const IRPosition &IPos = IRPosition::callsite_function(ICS);
       // Regarless of the no-return property of an invoke instruction we only
       // learn that the regular successor is not reachable through this
       // instruction but the unwind block might still be.
       if (auto *Invoke = dyn_cast<InvokeInst>(I)) {
         // Use nounwind to justify the unwind block is dead as well.
-        auto *AANoUnw = A.getAAFor<AANoUnwind>(*this, *Invoke);
+        auto *AANoUnw = A.getAAFor<AANoUnwind>(*this, IPos);
         if (!Invoke2CallAllowed ||
             (!AANoUnw || !AANoUnw->isAssumedNoUnwind())) {
           AssumedLiveBlocks.insert(Invoke->getUnwindDest());
           ToBeExploredPaths.insert(&Invoke->getUnwindDest()->front());
         }
       }
 
-      auto *NoReturnAA = A.getAAFor<AANoReturn>(*this, *I);
+      auto *NoReturnAA = A.getAAFor<AANoReturn>(*this, IPos);
       if (ICS.hasFnAttr(Attribute::NoReturn) ||
           (NoReturnAA && NoReturnAA->isAssumedNoReturn()))
         return I;
     }
 
     I = I->getNextNode();
   }
 
struct DerefState : AbstractState {
   /// Equality for DerefState.
   bool operator==(const DerefState &R) {
     return this->DerefBytesState == R.DerefBytesState &&
            this->NonNullGlobalState == R.NonNullGlobalState;
   }
 };
 
 struct AADereferenceableImpl : AADereferenceable, DerefState {
-  IRPositionConstructorForward(AADereferenceableImpl, AADereferenceable);
+  AADereferenceableImpl(const IRPosition &IRP) : AADereferenceable(IRP) {}
   using StateType = DerefState;
 
   /// See AbstractAttribute::getState()
   /// {
   StateType &getState() override { return *this; }
   const StateType &getState() const override { return *this; }
   /// }
 
void getDeducedAttributes(LLVMContext &Ctx,
     else
       Attrs.emplace_back(Attribute::getWithDereferenceableOrNullBytes(
           Ctx, getAssumedDereferenceableBytes()));
   }
   uint64_t computeAssumedDerefenceableBytes(Attributor &A, Value &V,
                                             bool &IsNonNull, bool &IsGlobal);
 
   void initialize(Attributor &A, InformationCache &InfoCache) override {
-    Function &F = getAnchorScope();
-    unsigned AttrIdx = getIRPosition().getAttrIdx();
-
-    for (Attribute::AttrKind AK :
-         {Attribute::Dereferenceable, Attribute::DereferenceableOrNull})
-      if (F.getAttributes().hasAttribute(AttrIdx, AK))
-        takeKnownDerefBytesMaximum(F.getAttribute(AttrIdx, AK).getValueAsInt());
+    SmallVector<Attribute, 4> Attrs;
+    getAttrs({Attribute::Dereferenceable, Attribute::DereferenceableOrNull},
+             Attrs);
+    for (const Attribute &Attr : Attrs)
+      takeKnownDerefBytesMaximum(Attr.getValueAsInt());
   }
 
   /// See AbstractAttribute::getAsStr().
   const std::string getAsStr() const override {
     if (!getAssumedDereferenceableBytes())
       return "unknown-dereferenceable";
     return std::string("dereferenceable") +
            (isAssumedNonNull() ? "" : "_or_null") +
            (isAssumedGlobal() ? "_globally" : "") + "<" +
            std::to_string(getKnownDereferenceableBytes()) + "-" +
            std::to_string(getAssumedDereferenceableBytes()) + ">";
   }
 };
 
 struct AADereferenceableReturned final : AADereferenceableImpl {
-  AADereferenceableReturned(Function &F)
-      : AADereferenceableImpl(F, IRP_RETURNED) {}
+  AADereferenceableReturned(const IRPosition &IRP)
+      : AADereferenceableImpl(IRP) {}
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_FNRET_ATTR(dereferenceable)
   }
 };
 
 // Helper function that returns dereferenceable bytes.
 static uint64_t calcDifferenceIfBaseIsNonNull(int64_t DerefBytes,
                                               int64_t Offset, bool IsNonNull) {
   if (!IsNonNull)
     return 0;
   return std::max((int64_t)0, DerefBytes - Offset);
 }
 
 uint64_t AADereferenceableImpl::computeAssumedDerefenceableBytes(
     Attributor &A, Value &V, bool &IsNonNull, bool &IsGlobal) {
   // TODO: Tracking the globally flag.
   IsGlobal = false;
 
   // First, we try to get information about V from Attributor.
-  if (auto *DerefAA = A.getAAFor<AADereferenceable>(*this, V)) {
+  if (auto *DerefAA = A.getAAFor<AADereferenceable>(
+          *this, IRPosition::value(V, getAnchorScope()))) {
     IsNonNull &= DerefAA->isAssumedNonNull();
     return DerefAA->getAssumedDereferenceableBytes();
   }
 
   // Otherwise, we try to compute assumed bytes from base pointer.
-  const DataLayout &DL = getAnchorScope().getParent()->getDataLayout();
+  const DataLayout &DL = getDataLayout();
   unsigned IdxWidth =
       DL.getIndexSizeInBits(V.getType()->getPointerAddressSpace());
   APInt Offset(IdxWidth, 0);
   Value *Base = V.stripAndAccumulateInBoundsConstantOffsets(DL, Offset);
 
-  if (auto *BaseDerefAA = A.getAAFor<AADereferenceable>(*this, *Base)) {
+  if (auto *BaseDerefAA = A.getAAFor<AADereferenceable>(
+          *this, IRPosition::value(*Base, getAnchorScope()))) {
     IsNonNull &= Offset != 0;
     return calcDifferenceIfBaseIsNonNull(
         BaseDerefAA->getAssumedDereferenceableBytes(), Offset.getSExtValue(),
         Offset != 0 || BaseDerefAA->isAssumedNonNull());
   }
 
   // Then, use IR information.
 

 }
 
 ChangeStatus
 AADereferenceableReturned::updateImpl(Attributor &A,
                                       InformationCache &InfoCache) {
   Function &F = getAnchorScope();
   auto BeforeState = static_cast<DerefState>(*this);
 
-  syncNonNull(A.getAAFor<AANonNull>(*this, F));
+  syncNonNull(A.getAAFor<AANonNull>(*this, getIRPosition()));
 
   bool IsNonNull = isAssumedNonNull();
   bool IsGlobal = isAssumedGlobal();
 
   auto CheckReturnValue = [&](Value &RV) -> bool {
     takeAssumedDerefBytesMinimum(
         computeAssumedDerefenceableBytes(A, RV, IsNonNull, IsGlobal));
     return isValidState();
   };
 
   if (A.checkForAllReturnedValues(F, CheckReturnValue, *this)) {
     updateAssumedNonNullGlobalState(IsNonNull, IsGlobal);
     return BeforeState == static_cast<DerefState>(*this)
                ? ChangeStatus::UNCHANGED
                : ChangeStatus::CHANGED;
   }
   return indicatePessimisticFixpoint();
 }
 
 struct AADereferenceableArgument final : AADereferenceableImpl {
-  AADereferenceableArgument(Argument &A) : AADereferenceableImpl(A) {}
+  AADereferenceableArgument(const IRPosition &IRP)
+      : AADereferenceableImpl(IRP) {}
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_ARG_ATTR(dereferenceable)
   }
 };
 
 ChangeStatus
 AADereferenceableArgument::updateImpl(Attributor &A,
                                       InformationCache &InfoCache) {
   Function &F = getAnchorScope();
   Argument &Arg = cast<Argument>(getAnchorValue());
 
   auto BeforeState = static_cast<DerefState>(*this);
 
   unsigned ArgNo = Arg.getArgNo();
 
-  syncNonNull(A.getAAFor<AANonNull>(*this, F, ArgNo));
+  syncNonNull(A.getAAFor<AANonNull>(*this, getIRPosition()));
 
   bool IsNonNull = isAssumedNonNull();
   bool IsGlobal = isAssumedGlobal();
 
   // Callback function
   std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) -> bool {
     assert(CS && "Sanity check: Call site was not initialized properly!");
 
     // Check that DereferenceableAA is AADereferenceableCallSiteArgument.
-    if (auto *DereferenceableAA =
-            A.getAAFor<AADereferenceable>(*this, *CS.getInstruction(), ArgNo)) {
+    if (auto *DereferenceableAA = A.getAAFor<AADereferenceable>(
+            *this, IRPosition::callsite_argument(CS, ArgNo))) {
       ImmutableCallSite ICS(
           &DereferenceableAA->getIRPosition().getAnchorValue());
       if (ICS && CS.getInstruction() == ICS.getInstruction()) {
         takeAssumedDerefBytesMinimum(
             DereferenceableAA->getAssumedDereferenceableBytes());
         IsNonNull &= DereferenceableAA->isAssumedNonNull();
         IsGlobal &= DereferenceableAA->isAssumedGlobal();
         return isValidState();
AADereferenceableArgument::updateImpl(Attributor &A,
   updateAssumedNonNullGlobalState(IsNonNull, IsGlobal);
 
   return BeforeState == static_cast<DerefState>(*this) ? ChangeStatus::UNCHANGED
                                                        : ChangeStatus::CHANGED;
 }
 
 /// Dereferenceable attribute for a call site argument.
 struct AADereferenceableCallSiteArgument final : AADereferenceableImpl {
-  AADereferenceableCallSiteArgument(Instruction &I, unsigned ArgNo)
-      : AADereferenceableImpl(CallSite(&I).getArgOperand(ArgNo), I, ArgNo) {}
-
-  /// See AbstractAttribute::initialize(...).
-  void initialize(Attributor &A, InformationCache &InfoCache) override {
-    CallSite CS(&getAnchorValue());
-    if (CS.paramHasAttr(getArgNo(), Attribute::Dereferenceable))
-      takeKnownDerefBytesMaximum(CS.getDereferenceableBytes(getArgNo()));
-
-    if (CS.paramHasAttr(getArgNo(), Attribute::DereferenceableOrNull))
-      takeKnownDerefBytesMaximum(CS.getDereferenceableOrNullBytes(getArgNo()));
-  }
+  AADereferenceableCallSiteArgument(const IRPosition &IRP)
+      : AADereferenceableImpl(IRP) {}
 
   /// See AbstractAttribute::updateImpl(Attributor &A).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_CSARG_ATTR(dereferenceable)
   }
 };
 
 ChangeStatus
 AADereferenceableCallSiteArgument::updateImpl(Attributor &A,
                                               InformationCache &InfoCache) {
   // NOTE: Never look at the argument of the callee in this method.
   //       If we do this, "dereferenceable" is always deduced because of the
   //       assumption.
 
-  Value &V = *getAssociatedValue();
+  Value &V = getAssociatedValue();
 
   auto BeforeState = static_cast<DerefState>(*this);
 
-  syncNonNull(A.getAAFor<AANonNull>(*this, getAnchorValue(), getArgNo()));
+  syncNonNull(A.getAAFor<AANonNull>(*this, getIRPosition()));
   bool IsNonNull = isAssumedNonNull();
   bool IsGlobal = isKnownGlobal();
 
   takeAssumedDerefBytesMinimum(
       computeAssumedDerefenceableBytes(A, V, IsNonNull, IsGlobal));
   updateAssumedNonNullGlobalState(IsNonNull, IsGlobal);
 
   return BeforeState == static_cast<DerefState>(*this) ? ChangeStatus::UNCHANGED
                                                        : ChangeStatus::CHANGED;
 }
 
 // ------------------------ Align Argument Attribute ------------------------
 
 struct AAAlignImpl : AAAlign {
-  IRPositionConstructorForward(AAAlignImpl, AAAlign);
+  AAAlignImpl(const IRPosition &IRP) : AAAlign(IRP) {}
 
   // Max alignemnt value allowed in IR
   static const unsigned MAX_ALIGN = 1U << 29;
 
   const std::string getAsStr() const override {
     return getAssumedAlign() ? ("align<" + std::to_string(getKnownAlign()) +
                                 "-" + std::to_string(getAssumedAlign()) + ">")
                              : "unknown-align";
   }
 
   /// See AbstractAttriubute::initialize(...).
   void initialize(Attributor &A, InformationCache &InfoCache) override {
     takeAssumedMinimum(MAX_ALIGN);
 
-    Function &F = getAnchorScope();
-
-    unsigned AttrIdx = getAttrIdx();
-    // Already the function has align attribute on return value or argument.
-    if (F.getAttributes().hasAttribute(AttrIdx, Attribute::Alignment))
-      addKnownBits(
-          F.getAttribute(AttrIdx, Attribute::Alignment).getAlignment());
+    SmallVector<Attribute, 4> Attrs;
+    getAttrs({Attribute::Alignment}, Attrs);
+    for (const Attribute &Attr : Attrs)
+      takeKnownMaximum(Attr.getValueAsInt());
   }
 
   /// See AbstractAttribute::getDeducedAttributes
   virtual void
   getDeducedAttributes(LLVMContext &Ctx,
                        SmallVectorImpl<Attribute> &Attrs) const override {
     Attrs.emplace_back(Attribute::getWithAlignment(Ctx, getAssumedAlign()));
   }
 };
 
 /// Align attribute for function return value.
 struct AAAlignReturned final : AAAlignImpl {
-  AAAlignReturned(Function &F) : AAAlignImpl(F, IRP_RETURNED) {}
+  AAAlignReturned(const IRPosition &IRP) : AAAlignImpl(IRP) {}
 
   /// See AbstractAttribute::updateImpl(...).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_FNRET_ATTR(aligned)
   }
 };
 
 ChangeStatus AAAlignReturned::updateImpl(Attributor &A,
                                          InformationCache &InfoCache) {
   Function &F = getAnchorScope();
 
   // Currently, align<n> is deduced if alignments in return values are assumed
   // as greater than n. We reach pessimistic fixpoint if any of the return value
   // wouldn't have align. If no assumed state was used for reasoning, an
   // optimistic fixpoint is reached earlier.
 
   base_t BeforeState = getAssumed();
   auto CheckReturnValue =
       [&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &RetInsts) -> bool {
-    auto *AlignAA = A.getAAFor<AAAlign>(*this, RV);
+    auto *AlignAA = A.getAAFor<AAAlign>(*this, IRPosition::value(RV, F));
 
     if (AlignAA)
       takeAssumedMinimum(AlignAA->getAssumedAlign());
     else
       // Use IR information.
-      takeAssumedMinimum(RV.getPointerAlignment(
-          getAnchorScope().getParent()->getDataLayout()));
+      takeAssumedMinimum(RV.getPointerAlignment(getDataLayout()));
 
     return isValidState();
   };
 
   if (!A.checkForAllReturnedValuesAndReturnInsts(F, CheckReturnValue, *this))
     return indicatePessimisticFixpoint();
 
   return (getAssumed() != BeforeState) ? ChangeStatus::CHANGED
                                        : ChangeStatus::UNCHANGED;
 }
 
 /// Align attribute for function argument.
 struct AAAlignArgument final : AAAlignImpl {
-  AAAlignArgument(Argument &A) : AAAlignImpl(A) {}
+  AAAlignArgument(const IRPosition &IRP) : AAAlignImpl(IRP) {}
 
   /// See AbstractAttribute::updateImpl(...).
   virtual ChangeStatus updateImpl(Attributor &A,
                                   InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override{STATS_DECL_AND_TRACK_ARG_ATTR(aligned)};
 };
 
 ChangeStatus AAAlignArgument::updateImpl(Attributor &A,
                                          InformationCache &InfoCache) {
 
   Function &F = getAnchorScope();
   Argument &Arg = cast<Argument>(getAnchorValue());
 
   unsigned ArgNo = Arg.getArgNo();
-  const DataLayout &DL = F.getParent()->getDataLayout();
+  const DataLayout &DL = getDataLayout();
 
   auto BeforeState = getAssumed();
 
   // Callback function
   std::function<bool(CallSite)> CallSiteCheck = [&](CallSite CS) {
     assert(CS && "Sanity check: Call site was not initialized properly!");
 
-    auto *AlignAA = A.getAAFor<AAAlign>(*this, *CS.getInstruction(), ArgNo);
+    auto *AlignAA =
+        A.getAAFor<AAAlign>(*this, IRPosition::callsite_argument(CS, ArgNo));
 
     // Check that AlignAA is AAAlignCallSiteArgument.
     if (AlignAA) {
       ImmutableCallSite ICS(&AlignAA->getIRPosition().getAnchorValue());
       if (ICS && CS.getInstruction() == ICS.getInstruction()) {
         takeAssumedMinimum(AlignAA->getAssumedAlign());
         return isValidState();
       }
     }
 
     Value *V = CS.getArgOperand(ArgNo);
     takeAssumedMinimum(V->getPointerAlignment(DL));
     return isValidState();
   };
 
   if (!A.checkForAllCallSites(F, CallSiteCheck, *this, true))
     indicatePessimisticFixpoint();
 
   return BeforeState == getAssumed() ? ChangeStatus::UNCHANGED
                                      : ChangeStatus ::CHANGED;
 }
 
 struct AAAlignCallSiteArgument final : AAAlignImpl {
-  AAAlignCallSiteArgument(Instruction &I, unsigned ArgNo)
-      : AAAlignImpl(CallSite(&I).getArgOperand(ArgNo), I, ArgNo) {}
+  AAAlignCallSiteArgument(const IRPosition &IRP) : AAAlignImpl(IRP) {}
 
   /// See AbstractAttribute::initialize(...).
   void initialize(Attributor &A, InformationCache &InfoCache) override {
-    CallSite CS(&getAnchorValue());
-    takeKnownMaximum(getAssociatedValue()->getPointerAlignment(
-        getAnchorScope().getParent()->getDataLayout()));
+    takeKnownMaximum(getAssociatedValue().getPointerAlignment(getDataLayout()));
   }
 
   /// See AbstractAttribute::updateImpl(Attributor &A).
   ChangeStatus updateImpl(Attributor &A, InformationCache &InfoCache) override;
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_CSARG_ATTR(aligned)
   }
 };
 
 ChangeStatus AAAlignCallSiteArgument::updateImpl(Attributor &A,
                                                  InformationCache &InfoCache) {
   // NOTE: Never look at the argument of the callee in this method.
   //       If we do this, "align" is always deduced because of the assumption.
 
   auto BeforeState = getAssumed();
 
-  Value &V = *getAssociatedValue();
-
-  auto *AlignAA = A.getAAFor<AAAlign>(*this, V);
+  Value &V = getAssociatedValue();
+  auto *AlignAA =
+      A.getAAFor<AAAlign>(*this, IRPosition::value(V, getAnchorScope()));
 
   if (AlignAA)
     takeAssumedMinimum(AlignAA->getAssumedAlign());
   else
     indicatePessimisticFixpoint();
 
   return BeforeState == getAssumed() ? ChangeStatus::UNCHANGED
                                      : ChangeStatus::CHANGED;
 }
 
 /// ------------------ Function No-Return Attribute ----------------------------
 struct AANoReturnImpl : public AANoReturn {
-  IRPositionConstructorForward(AANoReturnImpl, AANoReturn);
+  AANoReturnImpl(const IRPosition &IRP) : AANoReturn(IRP) {}
 
   /// See AbstractAttribute::getAsStr().
   const std::string getAsStr() const override {
     return getAssumed() ? "noreturn" : "may-return";
   }
 
   /// See AbstractAttribute::initialize(...).
   void initialize(Attributor &A, InformationCache &InfoCache) override {
-    Function &F = getAnchorScope();
-    if (F.hasFnAttribute(getAttrKind()))
+    if (hasAttr({getAttrKind()}))
       indicateOptimisticFixpoint();
   }
 
   /// See AbstractAttribute::updateImpl(Attributor &A).
   virtual ChangeStatus updateImpl(Attributor &A,
                                   InformationCache &InfoCache) override {
     const Function &F = getAnchorScope();
     auto CheckForNoReturn = [](Instruction &) { return false; };
     if (!A.checkForAllInstructions(F, CheckForNoReturn, *this, InfoCache,
                                    {(unsigned)Instruction::Ret}))
       return indicatePessimisticFixpoint();
     return ChangeStatus::UNCHANGED;
   }
 };
 
 struct AANoReturnFunction final : AANoReturnImpl {
-  AANoReturnFunction(Function &F) : AANoReturnImpl(F, IRP_FUNCTION) {}
+  AANoReturnFunction(const IRPosition &IRP) : AANoReturnImpl(IRP) {}
 
   /// See AbstractAttribute::trackStatistics()
   void trackStatistics() const override {
     STATS_DECL_AND_TRACK_FN_ATTR(noreturn)
   }
 };
 
 /// ----------------------------------------------------------------------------
LLVM_DEBUG(
         dbgs()
         << "Attributor: Function " << F.getName()
         << " has no internal linkage, hence not all call sites are known\n");
     return false;
   }
 
   for (const Use &U : F.uses()) {
     Instruction *I = cast<Instruction>(U.getUser());
-    Function *AnchorValue = I->getParent()->getParent();
+    Function *Caller = I->getFunction();
 
-    auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, *AnchorValue);
+    auto *LivenessAA =
+        getAAFor<AAIsDead>(QueryingAA, IRPosition::function(*Caller));
 
     // Skip dead calls.
     if (LivenessAA && LivenessAA->isAssumedDead(I))
       continue;
 
     CallSite CS(U.getUser());
     if (!CS || !CS.isCallee(&U) || !CS.getCaller()->hasExactDefinition()) {
       if (!RequireAllCallSites)

 }
 
 bool Attributor::checkForAllReturnedValuesAndReturnInsts(
     const Function &F,
     const function_ref<bool(Value &, const SmallPtrSetImpl<ReturnInst *> &)>
         &Pred,
     const AbstractAttribute &QueryingAA) {
 
-  auto *AARetVal = getAAFor<AAReturnedValues>(QueryingAA, F);
+  auto *AARetVal =
+      getAAFor<AAReturnedValues>(QueryingAA, IRPosition::returned(F));
   if (!AARetVal)
     return false;
 
-  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
+  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, IRPosition::function(F));
   if (!LivenessAA)
     return AARetVal->checkForAllReturnedValuesAndReturnInsts(Pred);
 
   auto LivenessFilter = [&](Value &RV,
                             const SmallPtrSetImpl<ReturnInst *> &ReturnInsts) {
     SmallPtrSet<ReturnInst *, 4> FilteredReturnInsts;
     for (ReturnInst *RI : ReturnInsts)
       if (!LivenessAA->isAssumedDead(RI))
         FilteredReturnInsts.insert(RI);
     if (!FilteredReturnInsts.empty())
       return Pred(RV, FilteredReturnInsts);
     return true;
   };
 
   return AARetVal->checkForAllReturnedValuesAndReturnInsts(LivenessFilter);
 }
 
 bool Attributor::checkForAllReturnedValues(
     const Function &F, const function_ref<bool(Value &)> &Pred,
     const AbstractAttribute &QueryingAA) {
 
-  auto *AARetVal = getAAFor<AAReturnedValues>(QueryingAA, F);
+  auto *AARetVal =
+      getAAFor<AAReturnedValues>(QueryingAA, IRPosition::returned(F));
   if (!AARetVal)
     return false;
 
-  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
+  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, IRPosition::function(F));
   if (!LivenessAA)
     return AARetVal->checkForAllReturnedValuesAndReturnInsts(
         [&](Value &RV, const SmallPtrSetImpl<ReturnInst *> &) {
           return Pred(RV);
         });
 
   auto LivenessFilter = [&](Value &RV,
                             const SmallPtrSetImpl<ReturnInst *> &ReturnInsts) {
     if (LivenessAA->isLiveInstSet(ReturnInsts.begin(), ReturnInsts.end()))
       return Pred(RV);
     return true;
   };
 
   return AARetVal->checkForAllReturnedValuesAndReturnInsts(LivenessFilter);
 }
 
 bool Attributor::checkForAllInstructions(
     const Function &F, const llvm::function_ref<bool(Instruction &)> &Pred,
     const AbstractAttribute &QueryingAA, InformationCache &InfoCache,
     const ArrayRef<unsigned> &Opcodes) {
 
-  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
+  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, IRPosition::function(F));
 
   auto &OpcodeInstMap = InfoCache.getOpcodeInstMapForFunction(F);
   for (unsigned Opcode : Opcodes) {
     for (Instruction *I : OpcodeInstMap[Opcode]) {
       // Skip dead instructions.
       if (LivenessAA && LivenessAA->isAssumedDead(I))
         continue;
 
       if (!Pred(*I))
         return false;
     }
   }
 
   return true;
 }
 
 bool Attributor::checkForAllReadWriteInstructions(
     const Function &F, const llvm::function_ref<bool(Instruction &)> &Pred,
     AbstractAttribute &QueryingAA, InformationCache &InfoCache) {
 
-  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, F);
+  auto *LivenessAA = getAAFor<AAIsDead>(QueryingAA, IRPosition::function(F));
 
   for (Instruction *I : InfoCache.getReadOrWriteInstsForFunction(F)) {
     // Skip dead instructions.
     if (LivenessAA && LivenessAA->isAssumedDead(I))
       continue;
 
     if (!Pred(*I))
       return false;
ChangeStatus Attributor::run(InformationCache &InfoCache) {
 
   NumAttributesManifested += NumManifested;
   NumAttributesValidFixpoint += NumAtFixpoint;
 
   return ManifestChange;
 }
 
 /// Helper function that checks if an abstract attribute of type \p AAType
-/// should be created for \p V (with argument number \p ArgNo) and if so creates
-/// and registers it with the Attributor \p A.
+/// should be created for IR position \p IRP and if so creates and registers it
+/// with the Attributor \p A.
 ///
 /// This method will look at the provided whitelist. If one is given and the
 /// kind \p AAType::ID is not contained, no abstract attribute is created.
 ///
 /// \returns The created abstract argument, or nullptr if none was created.
-template <typename AAType, typename ValueType, typename... ArgsTy>
-static AAType *checkAndRegisterAA(const Function &F, Attributor &A,
-                                  DenseSet<const char *> *Whitelist,
-                                  ValueType &V, int ArgNo, ArgsTy... Args) {
+template <typename AAType>
+static AAType *checkAndRegisterAA(IRPosition &IRP, Attributor &A,
+                                  DenseSet<const char *> *Whitelist) {
   if (Whitelist && !Whitelist->count(&AAType::ID))
     return nullptr;
 
-  return &A.registerAA<AAType>(*new AAType(V, Args...), ArgNo);
+  return &A.registerAA<AAType>(*new AAType(IRP));
 }
 
 void Attributor::identifyDefaultAbstractAttributes(
     Function &F, InformationCache &InfoCache,
     DenseSet<const char *> *Whitelist) {
 
+  IRPosition FPos = IRPosition::function(F);
+
   // Check for dead BasicBlocks in every function.
   // We need dead instruction detection because we do not want to deal with
   // broken IR in which SSA rules do not apply.
-  checkAndRegisterAA<AAIsDeadFunction>(F, *this, /* Whitelist */ nullptr, F,
-                                       -1);
+  checkAndRegisterAA<AAIsDeadFunction>(FPos, *this, /* Whitelist */ nullptr);
 
   // Every function might be "will-return".
-  checkAndRegisterAA<AAWillReturnFunction>(F, *this, Whitelist, F, -1);
+  checkAndRegisterAA<AAWillReturnFunction>(FPos, *this, Whitelist);
 
   // Every function can be nounwind.
-  checkAndRegisterAA<AANoUnwindFunction>(F, *this, Whitelist, F, -1);
+  checkAndRegisterAA<AANoUnwindFunction>(FPos, *this, Whitelist);
 
   // Every function might be marked "nosync"
-  checkAndRegisterAA<AANoSyncFunction>(F, *this, Whitelist, F, -1);
+  checkAndRegisterAA<AANoSyncFunction>(FPos, *this, Whitelist);
 
   // Every function might be "no-free".
-  checkAndRegisterAA<AANoFreeFunction>(F, *this, Whitelist, F, -1);
+  checkAndRegisterAA<AANoFreeFunction>(FPos, *this, Whitelist);
 
   // Every function might be "no-return".
-  checkAndRegisterAA<AANoReturnFunction>(F, *this, Whitelist, F, -1);
+  checkAndRegisterAA<AANoReturnFunction>(FPos, *this, Whitelist);
 
   // Return attributes are only appropriate if the return type is non void.
   Type *ReturnType = F.getReturnType();
   if (!ReturnType->isVoidTy()) {
+    IRPosition RetPos = IRPosition::returned(F);
     // Argument attribute "returned" --- Create only one per function even
     // though it is an argument attribute.
-    checkAndRegisterAA<AAReturnedValuesFunction>(F, *this, Whitelist, F, -1);
+    checkAndRegisterAA<AAReturnedValuesReturned>(RetPos, *this, Whitelist);
 
     if (ReturnType->isPointerTy()) {
       // Every function with pointer return type might be marked align.
-      checkAndRegisterAA<AAAlignReturned>(F, *this, Whitelist, F, -1);
+      checkAndRegisterAA<AAAlignReturned>(RetPos, *this, Whitelist);
 
       // Every function with pointer return type might be marked nonnull.
-      checkAndRegisterAA<AANonNullReturned>(F, *this, Whitelist, F, -1);
+      checkAndRegisterAA<AANonNullReturned>(RetPos, *this, Whitelist);
 
       // Every function with pointer return type might be marked noalias.
-      checkAndRegisterAA<AANoAliasReturned>(F, *this, Whitelist, F, -1);
+      checkAndRegisterAA<AANoAliasReturned>(RetPos, *this, Whitelist);
 
       // Every function with pointer return type might be marked
       // dereferenceable.
-      checkAndRegisterAA<AADereferenceableReturned>(F, *this, Whitelist, F, -1);
+      checkAndRegisterAA<AADereferenceableReturned>(RetPos, *this, Whitelist);
     }
   }
 
   for (Argument &Arg : F.args()) {
     if (Arg.getType()->isPointerTy()) {
+      IRPosition ArgPos = IRPosition::argument(Arg);
       // Every argument with pointer type might be marked nonnull.
-      checkAndRegisterAA<AANonNullArgument>(F, *this, Whitelist, Arg,
-                                            Arg.getArgNo());
+      checkAndRegisterAA<AANonNullArgument>(ArgPos, *this, Whitelist);
 
       // Every argument with pointer type might be marked dereferenceable.
-      checkAndRegisterAA<AADereferenceableArgument>(F, *this, Whitelist, Arg,
-                                                    Arg.getArgNo());
+      checkAndRegisterAA<AADereferenceableArgument>(ArgPos, *this, Whitelist);
 
       // Every argument with pointer type might be marked align.
-      checkAndRegisterAA<AAAlignArgument>(F, *this, Whitelist, Arg,
-                                          Arg.getArgNo());
+      checkAndRegisterAA<AAAlignArgument>(ArgPos, *this, Whitelist);
     }
   }
 
   // Walk all instructions to find more attribute opportunities and also
   // interesting instructions that might be queried by abstract attributes
   // during their initialization or update.
   auto &ReadOrWriteInsts = InfoCache.FuncRWInstsMap[&F];
   auto &InstOpcodeMap = InfoCache.FuncInstOpcodeMap[&F];
for (Instruction &I : instructions(&F)) {
     if (I.mayReadOrWriteMemory())
       ReadOrWriteInsts.push_back(&I);
 
     CallSite CS(&I);
     if (CS && CS.getCalledFunction()) {
       for (int i = 0, e = CS.getCalledFunction()->arg_size(); i < e; i++) {
         if (!CS.getArgument(i)->getType()->isPointerTy())
           continue;
+        IRPosition CSArgPos = IRPosition::callsite_argument(CS, i);
 
         // Call site argument attribute "non-null".
-        checkAndRegisterAA<AANonNullCallSiteArgument>(F, *this, Whitelist, I, i,
-                                                      i);
+        checkAndRegisterAA<AANonNullCallSiteArgument>(CSArgPos, *this,
+                                                      Whitelist);
 
         // Call site argument attribute "dereferenceable".
-        checkAndRegisterAA<AADereferenceableCallSiteArgument>(
-            F, *this, Whitelist, I, i, i);
+        checkAndRegisterAA<AADereferenceableCallSiteArgument>(CSArgPos, *this,
+                                                              Whitelist);
 
         // Call site argument attribute "align".
-        checkAndRegisterAA<AAAlignCallSiteArgument>(F, *this, Whitelist, I, i,
-                                                    i);
+        checkAndRegisterAA<AAAlignCallSiteArgument>(CSArgPos, *this, Whitelist);
       }
     }
   }
 }
 
 /// Helpers to ease debugging through output streams and print calls.
 ///
 ///{
 raw_ostream &llvm::operator<<(raw_ostream &OS, ChangeStatus S) {
   return OS << (S == ChangeStatus::CHANGED ? "changed" : "unchanged");
 }
 
 raw_ostream &llvm::operator<<(raw_ostream &OS, IRPosition::Kind AP) {
   switch (AP) {
+  case IRPosition::IRP_INVALID:
+    return OS << "inv";
+  case IRPosition::IRP_FLOAT:
+    return OS << "flt";
+  case IRPosition::IRP_RETURNED:
+    return OS << "fn_ret";
+  case IRPosition::IRP_CALL_SITE_RETURNED:
+    return OS << "cs_ret";
+  case IRPosition::IRP_FUNCTION:
+    return OS << "fn";
+  case IRPosition::IRP_CALL_SITE:
+    return OS << "cs";
   case IRPosition::IRP_ARGUMENT:
     return OS << "arg";
   case IRPosition::IRP_CALL_SITE_ARGUMENT:
     return OS << "cs_arg";
-  case IRPosition::IRP_FUNCTION:
-    return OS << "fn";
-  case IRPosition::IRP_RETURNED:
-    return OS << "fn_ret";
   }
   llvm_unreachable("Unknown attribute position!");
 }
 
 raw_ostream &llvm::operator<<(raw_ostream &OS, const IRPosition &Pos) {
-  const Value *AV = Pos.getAssociatedValue();
-  return OS << "{" << Pos.getPositionKind() << ":"
-            << (AV ? AV->getName() : "n/a") << " ["
+  const Value &AV = Pos.getAssociatedValue();
+  return OS << "{" << Pos.getPositionKind() << ":" << AV.getName() << " ["
             << Pos.getAnchorValue().getName() << "@" << Pos.getArgNo() << "]}";
 }
 
 raw_ostream &llvm::operator<<(raw_ostream &OS, const AbstractState &S) {
   return OS << (!S.isValidState() ? "top" : (S.isAtFixpoint() ? "fix" : ""));
 }
 
 raw_ostream &llvm::operator<<(raw_ostream &OS, const AbstractAttribute &AA) {