[IR] Add additional addParamAttr/removeParamAttr to AttributeList API

[dneilson]

Summary

This is a NFC.

Fairly straightforward patch to fill in some of the holes in the attributes API with respect to accessing parameter/argument attributes. The patch aims to step further towards encapsulating the idx+FirstArgIndex pattern to access these attributes to within the AttributeList.

[dneilson]

clang-formatting patch

[rnk]

Thanks for working on this!

include/llvm/IR/Attributes.h

394

I'd like to remove this overload now that it is dead within LLVM. You may need to replace it with one that takes a single Index.

lib/IR/Attributes.cpp

1023

If we can delete this version, we don't need the comment.

[javed.absar]

Thanks a lot for this. Some small comments -

include/llvm/IR/Attributes.h

418

1. "returns a new set" => "returns a new list".

2. Nitpick - it would be nice to make all such sentences same, some places we seem to start with "Returns a .. because.." other places as "Because.... returns..."

591

Should this comment be "exists at the arg number"?

[dneilson]

include/llvm/IR/Attributes.h

394

This overload appears to be used in both InstCombineCalls.cpp and CorrelatedValuePropagation.cpp (see the two changed files at the end of this patch). If I remove these overloads, then I have to rewrite those bits of code to call addAttribute() directly, instead of push_back-ing the index into a list. Seems like a reasonable change to me. Do you concur?

418

Thanks. I agree with the nitpick; I'll try to make the comments in AttributeList more uniform.

591

Probably, yeah. I'm fairly new to LLVM's codebase. Are args typically referred to by "argument number" or "argument index" ?

[rnk]

include/llvm/IR/Attributes.h

394

I'm suggesting that you keep addParamAttributes(LLVMContext&, ArrayRef<unsigned>, Attribute A) but delete addAttribute(LLVMContext&, ArrayRef<unsigned>, Attribute A). Does that make sense?

Every call to addAttribute effectively leaks an AttributeListImpl. This code is attempting to carefully avoid making extra AttributeListImpl memory allocations, and I would like to keep that carefulness, even if not all passes are doing it. Especially because we can infer nonnull about so many call sites. The other attribute inference stuff doesn't fire nearly as often.

[dneilson]

include/llvm/IR/Attributes.h

394

Ah, yes. That makes far more sense. It also gets rid of the code clone. So, it's win-win.

[dneilson]

Addressing comments:

• Removed the addAttribute(Ctx, Indices, Attribute) method from AttributeList, and replaces with one that operates on a single Index instead of a list.
• Cleaned up the wording on all of the add/remove attribute comments referring to return values being immutable

[rnk]

include/llvm/IR/Attributes.h

418

Try to keep the triple-slash doxygen comments.

include/llvm/IR/Function.h

367

I think saying "AttributeList ArgNo" is misleading. There is no special AttributeList argument numbering scheme, just the obvious LLVM function prototype argument number.

[dneilson]

rnk comments + rebase

[dneilson]

ping -- To the reviewers: is this good-to-go as-is? If so, can someone please approve and push upstream (I do not have commit access).

include/llvm/IR/Attributes.h

public:
   static AttributeList get(LLVMContext &C, ArrayRef<AttributeList> Attrs);
   static AttributeList get(LLVMContext &C, unsigned Index,
                            ArrayRef<Attribute::AttrKind> Kinds);
   static AttributeList get(LLVMContext &C, unsigned Index,
                            ArrayRef<StringRef> Kind);
   static AttributeList get(LLVMContext &C, unsigned Index,
                            const AttrBuilder &B);
 
-  /// Add an argument attribute to the list. Returns a new list because
-  /// attribute lists are immutable.
-  AttributeList addParamAttribute(LLVMContext &C, unsigned ArgNo,
-                                  Attribute::AttrKind Kind) const {
-    return addAttribute(C, ArgNo + FirstArgIndex, Kind);
-  }
-
   /// \brief Add an attribute to the attribute set at the given index. Because
   /// attribute sets are immutable, this returns a new set.
   AttributeList addAttribute(LLVMContext &C, unsigned Index,
                              Attribute::AttrKind Kind) const;
 
   /// \brief Add an attribute to the attribute set at the given index. Because
   /// attribute sets are immutable, this returns a new set.
   AttributeList addAttribute(LLVMContext &C, unsigned Index, StringRef Kind,
                              StringRef Value = StringRef()) const;
 
   /// Add an attribute to the attribute set at the given indices. Because
   /// attribute sets are immutable, this returns a new set.
   AttributeList addAttribute(LLVMContext &C, ArrayRef<unsigned> Indices,
                              Attribute A) const;
 
   /// \brief Add attributes to the attribute set at the given index. Because
   /// attribute sets are immutable, this returns a new set.
   AttributeList addAttributes(LLVMContext &C, unsigned Index,
                               const AttrBuilder &B) const;
 
+  /// Add an argument attribute to the list. Returns a new list because
+  /// attribute lists are immutable.
+  AttributeList addParamAttribute(LLVMContext &C, unsigned ArgNo,
+                                  Attribute::AttrKind Kind) const {
+    return addAttribute(C, ArgNo + FirstArgIndex, Kind);
+  }
+
+  /// Add an argument attribute to the list. Returns a new list because
+  /// attribute lists are immutable.
+  AttributeList addParamAttribute(LLVMContext &C, unsigned ArgNo,
+                                  StringRef Kind,
+                                  StringRef Value = StringRef()) const {
+    return addAttribute(C, ArgNo + FirstArgIndex, Kind, Value);
+  }
+
+  /// Add an attribute to the attribute set at the given arg indices. Because
+  /// attribute sets are immutable, this returns a new set.
+  AttributeList addParamAttribute(LLVMContext &C, ArrayRef<unsigned> ArgNos,
+                                  Attribute A) const;
+
+  /// Add an argument attribute to the list. Returns a new list because
+  /// attribute lists are immutable.
+  AttributeList addParamAttributes(LLVMContext &C, unsigned ArgNo,
+                                   const AttrBuilder &B) const {
+    return addAttributes(C, ArgNo + FirstArgIndex, B);
+  }
+
   /// \brief Remove the specified attribute at the specified index from this
   /// attribute list. Because attribute lists are immutable, this returns the
   /// new list.
   AttributeList removeAttribute(LLVMContext &C, unsigned Index,
                                 Attribute::AttrKind Kind) const;
 
   /// \brief Remove the specified attribute at the specified index from this
   /// attribute list. Because attribute lists are immutable, this returns the
   /// new list.
   AttributeList removeAttribute(LLVMContext &C, unsigned Index,
                                 StringRef Kind) const;
 
   /// \brief Remove the specified attributes at the specified index from this
   /// attribute list. Because attribute lists are immutable, this returns the
   /// new list.
   AttributeList removeAttributes(LLVMContext &C, unsigned Index,
                                  const AttrBuilder &AttrsToRemove) const;
 
   /// \brief Remove all attributes at the specified index from this
   /// attribute list. Because attribute lists are immutable, this returns the
   /// new list.
   AttributeList removeAttributes(LLVMContext &C, unsigned Index) const;
 
-  /// \brief Add the dereferenceable attribute to the attribute set at the given
+  /// \brief Remove the specified attribute at the specified arg index from this
+  /// attribute list. Because attribute lists are immutable, this returns the
+  /// new list.
+  AttributeList removeParamAttribute(LLVMContext &C, unsigned ArgNo,
+                                     Attribute::AttrKind Kind) const {
+    return removeAttribute(C, ArgNo + FirstArgIndex, Kind);
+  }
+
+  /// \brief Remove the specified attribute at the specified arg index from this
+  /// attribute list. Because attribute lists are immutable, this returns the
+  /// new list.
+  AttributeList removeParamAttribute(LLVMContext &C, unsigned ArgNo,
+                                     StringRef Kind) const {
+    return removeAttribute(C, ArgNo + FirstArgIndex, Kind);
+  }
+
+  /// \brief Remove the specified attribute at the specified arg index from this
+  /// attribute list. Because attribute lists are immutable, this returns the
+  /// new list.
+  AttributeList removeParamAttributes(LLVMContext &C, unsigned ArgNo,
+                                      const AttrBuilder &AttrsToRemove) const {
+    return removeAttributes(C, ArgNo + FirstArgIndex, AttrsToRemove);
+  }
+
+  /// \brief Remove all attributes at the specified arg index from this
+  /// attribute list. Because attribute lists are immutable, this returns the
+  /// new list.
+  AttributeList removeParamAttributes(LLVMContext &C, unsigned ArgNo) const {
+    return removeAttributes(C, ArgNo + FirstArgIndex);
+  }
+
+  /// \Brief Add the dereferenceable attribute to the attribute set at the given
   /// index. Because attribute sets are immutable, this returns a new set.
   AttributeList addDereferenceableAttr(LLVMContext &C, unsigned Index,
                                        uint64_t Bytes) const;
 
+  /// \Brief Add the dereferenceable attribute to the attribute set at the given
+  /// arg index. Because attribute sets are immutable, this returns a new set.
+  AttributeList addDereferenceableParamAttr(LLVMContext &C, unsigned ArgNo,
+                                            uint64_t Bytes) const {
+    return addDereferenceableAttr(C, ArgNo + FirstArgIndex, Bytes);
+  }
+
   /// \brief Add the dereferenceable_or_null attribute to the attribute set at
   /// the given index. Because attribute sets are immutable, this returns a new
   /// set.
   AttributeList addDereferenceableOrNullAttr(LLVMContext &C, unsigned Index,
                                              uint64_t Bytes) const;
 
+  /// \brief Add the dereferenceable_or_null attribute to the attribute set at
+  /// the given arg index. Because attribute sets are immutable, this returns a
+  /// new set.
+  AttributeList addDereferenceableOrNullParamAttr(LLVMContext &C,
+                                                  unsigned ArgNo,
+                                                  uint64_t Bytes) const {
+    return addDereferenceableOrNullAttr(C, ArgNo + FirstArgIndex, Bytes);
+  }
+
   /// Add the allocsize attribute to the attribute set at the given index.
   /// Because attribute sets are immutable, this returns a new set.
   AttributeList addAllocSizeAttr(LLVMContext &C, unsigned Index,
                                  unsigned ElemSizeArg,
                                  const Optional<unsigned> &NumElemsArg);
 
+  /// Add the allocsize attribute to the attribute set at the given arg index.
+  /// Because attribute sets are immutable, this returns a new set.
+  AttributeList addAllocSizeParamAttr(LLVMContext &C, unsigned ArgNo,
+                                      unsigned ElemSizeArg,
+                                      const Optional<unsigned> &NumElemsArg) {
+    return addAllocSizeAttr(C, ArgNo + FirstArgIndex, ElemSizeArg, NumElemsArg);
+  }
+
   //===--------------------------------------------------------------------===//
   // AttributeList Accessors
   //===--------------------------------------------------------------------===//
 
   /// \brief Retrieve the LLVM context.
   LLVMContext &getContext() const;
 
   /// \brief The attributes for the specified index are returned.
public:
   bool hasAttribute(unsigned Index, Attribute::AttrKind Kind) const;
 
   /// \brief Return true if the attribute exists at the given index.
   bool hasAttribute(unsigned Index, StringRef Kind) const;
 
   /// \brief Return true if attribute exists at the given index.
   bool hasAttributes(unsigned Index) const;
 
+  /// \brief Return true if the attribute exists for the given argument
+  bool hasParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) const {
+    return hasAttribute(ArgNo + FirstArgIndex, Kind);
+  }
+
+  /// \brief Return true if the attribute exists for the given argument
+  bool hasParamAttr(unsigned ArgNo, StringRef Kind) const {
+    return hasAttribute(ArgNo + FirstArgIndex, Kind);
+  }
+
+  /// \brief Return true if attributes exists for the given argument
+  bool hasParamAttrs(unsigned ArgNo) const {
+    return hasAttributes(ArgNo + FirstArgIndex);
+  }
+
   /// \brief Equivalent to hasAttribute(AttributeList::FunctionIndex, Kind) but
   /// may be faster.
   bool hasFnAttribute(Attribute::AttrKind Kind) const;
 
   /// \brief Equivalent to hasAttribute(AttributeList::FunctionIndex, Kind) but
   /// may be faster.
   bool hasFnAttribute(StringRef Kind) const;
 
   /// \brief Equivalent to hasAttribute(ArgNo + FirstArgIndex, Kind).
   bool hasParamAttribute(unsigned ArgNo, Attribute::AttrKind Kind) const;
 
   /// \brief Return true if the specified attribute is set for at least one
   /// parameter or for the return value. If Index is not nullptr, the index
   /// of a parameter with the specified attribute is provided.
   bool hasAttrSomewhere(Attribute::AttrKind Kind,
                         unsigned *Index = nullptr) const;
 
   /// \brief Return the attribute object that exists at the given index.
   Attribute getAttribute(unsigned Index, Attribute::AttrKind Kind) const;
 
   /// \brief Return the attribute object that exists at the given index.
   Attribute getAttribute(unsigned Index, StringRef Kind) const;
 
+  /// \brief Return the attribute object that exists at the arg index.
+  Attribute getParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) const {
+    return getAttribute(ArgNo + FirstArgIndex, Kind);
+  }
+
+  /// \brief Return the attribute object that exists at the given index.
+  Attribute getParamAttr(unsigned ArgNo, StringRef Kind) const {
+    return getAttribute(ArgNo + FirstArgIndex, Kind);
+  }
+
   /// \brief Return the alignment of the return value.
   unsigned getRetAlignment() const;
 
   /// \brief Return the alignment for the specified function parameter.
   unsigned getParamAlignment(unsigned ArgNo) const;
 
   /// \brief Get the stack alignment.
   unsigned getStackAlignment(unsigned Index) const;
 
   /// \brief Get the number of dereferenceable bytes (or zero if unknown).
   uint64_t getDereferenceableBytes(unsigned Index) const;
 
+  /// \brief Get the number of dereferenceable bytes (or zero if unknown) of an
+  /// arg.
+  uint64_t getParamDereferenceableBytes(unsigned ArgNo) const {
+    return getDereferenceableBytes(ArgNo + FirstArgIndex);
+  }
+
   /// \brief Get the number of dereferenceable_or_null bytes (or zero if
   /// unknown).
   uint64_t getDereferenceableOrNullBytes(unsigned Index) const;
 
+  /// \brief Get the number of dereferenceable_or_null bytes (or zero if
+  /// unknown) of an arg.
+  uint64_t getParamDereferenceableOrNullBytes(unsigned ArgNo) const {
+    return getDereferenceableOrNullBytes(ArgNo + FirstArgIndex);
+  }
+
   /// Get the allocsize argument numbers (or pair(0, 0) if unknown).
   std::pair<unsigned, Optional<unsigned>>
   getAllocSizeArgs(unsigned Index) const;
 
   /// \brief Return the attributes at the index as a string.
   std::string getAsString(unsigned Index, bool InAttrGrp = false) const;
 
+  /// \brief Return the attributes at the arg index as a string.
+  std::string getParamAsString(unsigned ArgNo, bool InAttrGrp = false) const {
+    return getAsString(ArgNo + FirstArgIndex, InAttrGrp);
+  }
+
   using iterator = ArrayRef<Attribute>::iterator;
 
   iterator begin(unsigned Slot) const;
   iterator end(unsigned Slot) const;
 
   /// operator==/!= - Provide equality predicates.
   bool operator==(const AttributeList &RHS) const { return pImpl == RHS.pImpl; }
   bool operator!=(const AttributeList &RHS) const { return pImpl != RHS.pImpl; }

include/llvm/IR/Function.h

void addFnAttr(StringRef Kind, StringRef Val = StringRef()) {
     addAttribute(AttributeList::FunctionIndex,
                  Attribute::get(getContext(), Kind, Val));
   }
 
   void addFnAttr(Attribute Attr) {
     addAttribute(AttributeList::FunctionIndex, Attr);
   }
 
-  void addParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) {
-    addAttribute(ArgNo + AttributeList::FirstArgIndex, Kind);
-  }
-
   /// @brief Remove function attributes from this function.
   void removeFnAttr(Attribute::AttrKind Kind) {
     removeAttribute(AttributeList::FunctionIndex, Kind);
   }
 
   /// @brief Remove function attribute from this function.
   void removeFnAttr(StringRef Kind) {
     setAttributes(getAttributes().removeAttribute(
         getContext(), AttributeList::FunctionIndex, Kind));
   }
 
-  void removeParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) {
-    removeAttribute(ArgNo + AttributeList::FirstArgIndex, Kind);
-  }
-
   /// \brief Set the entry count for this function.
   ///
   /// Entry count is the number of times this function was executed based on
   /// pgo data. \p Imports points to a set of GUIDs that needs to be imported
   /// by the function for sample PGO, to enable the same inlines as the
   /// profiled optimized binary.
   void setEntryCount(uint64_t Count,
                      const DenseSet<GlobalValue::GUID> *Imports = nullptr);
public:
   void addAttribute(unsigned i, Attribute::AttrKind Kind);
 
   /// @brief adds the attribute to the list of attributes.
   void addAttribute(unsigned i, Attribute Attr);
 
   /// @brief adds the attributes to the list of attributes.
   void addAttributes(unsigned i, const AttrBuilder &Attrs);
 
+  /// @brief adds the attribute to the list of attributes for the given arg.
+  void addParamAttr(unsigned ArgNo, Attribute::AttrKind Kind);
+
+  /// @brief adds the attribute to the list of attributes for the given arg.
+  void addParamAttr(unsigned ArgNo, Attribute Attr);
+
+  /// @brief adds the attributes to the list of attributes for the given arg.
+  void addParamAttrs(unsigned ArgNo, const AttrBuilder &Attrs);
+
   /// @brief removes the attribute from the list of attributes.
   void removeAttribute(unsigned i, Attribute::AttrKind Kind);
 
   /// @brief removes the attribute from the list of attributes.
   void removeAttribute(unsigned i, StringRef Kind);
 
   /// @brief removes the attributes from the list of attributes.
   void removeAttributes(unsigned i, const AttrBuilder &Attrs);
 
+  /// @brief removes the attribute from the list of attributes.
+  void removeParamAttr(unsigned ArgNo, Attribute::AttrKind Kind);
+
+  /// @brief removes the attribute from the list of attributes.
+  void removeParamAttr(unsigned ArgNo, StringRef Kind);
+
+  /// @brief removes the attribute from the list of attributes.
+  void removeParamAttrs(unsigned ArgNo, const AttrBuilder &Attrs);
+
   /// @brief check if an attributes is in the list of attributes.
   bool hasAttribute(unsigned i, Attribute::AttrKind Kind) const {
     return getAttributes().hasAttribute(i, Kind);
   }
 
   /// @brief check if an attributes is in the list of attributes.
   bool hasParamAttribute(unsigned ArgNo, Attribute::AttrKind Kind) const {
     return getAttributes().hasParamAttribute(ArgNo, Kind);
   }
 
   Attribute getAttribute(unsigned i, Attribute::AttrKind Kind) const {
     return AttributeSets.getAttribute(i, Kind);
   }
 
   Attribute getAttribute(unsigned i, StringRef Kind) const {
     return AttributeSets.getAttribute(i, Kind);
   }
 
   /// @brief adds the dereferenceable attribute to the list of attributes.
   void addDereferenceableAttr(unsigned i, uint64_t Bytes);
 
+  /// @brief adds the dereferenceable attribute to the list of attributes for
+  /// the given arg.
+  void addDereferenceableParamAttr(unsigned ArgNo, uint64_t Bytes);
+
   /// @brief adds the dereferenceable_or_null attribute to the list of
   /// attributes.
   void addDereferenceableOrNullAttr(unsigned i, uint64_t Bytes);
 
+  /// @brief adds the dereferenceable_or_null attribute to the list of
+  /// attributes for the given arg.
+  void addDereferenceableOrNullParamAttr(unsigned ArgNo, uint64_t Bytes);
+
   /// @brief Extract the alignment for a call or parameter (0=unknown).
   unsigned getParamAlignment(unsigned ArgNo) const {
     return AttributeSets.getParamAlignment(ArgNo);
   }
 
   /// @brief Extract the number of dereferenceable bytes for a call or
   /// parameter (0=unknown).
   /// @param i AttributeList index, referring to a return value or argument.
   uint64_t getDereferenceableBytes(unsigned i) const {
     return AttributeSets.getDereferenceableBytes(i);
   }
 
+  /// @brief Extract the number of dereferenceable bytes for a parameter.
+  /// @param ArgNo AttributeList ArgNo, referring to an argument.
+  uint64_t getParamDereferenceableBytes(unsigned ArgNo) const {
+    return AttributeSets.getParamDereferenceableBytes(ArgNo);
+  }
+
   /// @brief Extract the number of dereferenceable_or_null bytes for a call or
   /// parameter (0=unknown).
   /// @param i AttributeList index, referring to a return value or argument.
   uint64_t getDereferenceableOrNullBytes(unsigned i) const {
     return AttributeSets.getDereferenceableOrNullBytes(i);
   }
 
+  /// @brief Extract the number of dereferenceable_or_null bytes for a
+  /// parameter.
+  /// @param ArgNo AttributeList ArgNo, referring to an argument.
+  uint64_t getParamDereferenceableOrNullBytes(unsigned ArgNo) const {
+    return AttributeSets.getParamDereferenceableOrNullBytes(ArgNo);
+  }
+
   /// @brief Determine if the function does not access memory.
   bool doesNotAccessMemory() const {
     return hasFnAttribute(Attribute::ReadNone);
   }
   void setDoesNotAccessMemory() {
     addFnAttr(Attribute::ReadNone);
   }
 

include/llvm/IR/Instructions.h

public:
   void addAttribute(unsigned i, Attribute::AttrKind Kind);
 
   /// adds the attribute to the list of attributes.
   void addAttribute(unsigned i, Attribute Attr);
 
   /// Adds the attribute to the indicated argument
   void addParamAttr(unsigned ArgNo, Attribute::AttrKind Kind);
 
+  /// Adds the attribute to the indicated argument
+  void addParamAttr(unsigned ArgNo, Attribute Attr);
+
   /// removes the attribute from the list of attributes.
   void removeAttribute(unsigned i, Attribute::AttrKind Kind);
 
   /// removes the attribute from the list of attributes.
   void removeAttribute(unsigned i, StringRef Kind);
 
   /// Removes the attribute from the given argument
   void removeParamAttr(unsigned ArgNo, Attribute::AttrKind Kind);
 
+  /// Removes the attribute from the given argument
+  void removeParamAttr(unsigned ArgNo, StringRef Kind);
+
   /// adds the dereferenceable attribute to the list of attributes.
   void addDereferenceableAttr(unsigned i, uint64_t Bytes);
 
   /// adds the dereferenceable_or_null attribute to the list of
   /// attributes.
   void addDereferenceableOrNullAttr(unsigned i, uint64_t Bytes);
 
   /// Determine whether this call has the given attribute.
Attribute getAttribute(unsigned i, Attribute::AttrKind Kind) const {
     return getAttributes().getAttribute(i, Kind);
   }
 
   /// Get the attribute of a given kind at a position.
   Attribute getAttribute(unsigned i, StringRef Kind) const {
     return getAttributes().getAttribute(i, Kind);
   }
 
+  /// Get the attribute of a given kind from a given arg
+  Attribute getParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) const {
+    assert(ArgNo < getNumArgOperands() && "Out of bounds");
+    return getAttributes().getParamAttr(ArgNo, Kind);
+  }
+
+  /// Get the attribute of a given kind from a given arg
+  Attribute getParamAttr(unsigned ArgNo, StringRef Kind) const {
+    assert(ArgNo < getNumArgOperands() && "Out of bounds");
+    return getAttributes().getParamAttr(ArgNo, Kind);
+  }
+
   /// Return true if the data operand at index \p i has the attribute \p
   /// A.
   ///
   /// Data operands include call arguments and values used in operand bundles,
   /// but does not include the callee operand.  This routine dispatches to the
   /// underlying AttributeList or the OperandBundleUser as appropriate.
   ///
   /// The index \p i is interpreted as

lib/IR/Attributes.cpp

AttributeList AttributeList::addAttribute(LLVMContext &C, unsigned Index,
   AttrBuilder B;
   B.addAttribute(Kind, Value);
   return addAttributes(C, Index, B);
 }
 
 AttributeList AttributeList::addAttribute(LLVMContext &C,
                                           ArrayRef<unsigned> Indices,
                                           Attribute A) const {
+  // Note: Code-cloned to AttributeList::addParamAttr(C, ArgNos, A). Any edits
+  // here must be mirrored there.
   assert(std::is_sorted(Indices.begin(), Indices.end()));
 
   unsigned I = 0, E = pImpl ? pImpl->getNumSlots() : 0;
   SmallVector<IndexAttrPair, 4> AttrVec;
   for (unsigned Index : Indices) {
     // Add all attribute slots before the current index.
     for (; I < E && getSlotIndex(I) < Index; ++I)
       AttrVec.emplace_back(getSlotIndex(I), pImpl->getSlotAttributes(I));
#endif
 
   // Add the remaining entries.
   for (; I < NumAttrs; ++I)
     AttrVec.emplace_back(getSlotIndex(I), pImpl->getSlotAttributes(I));
 
   return get(C, AttrVec);
 }
 
+AttributeList AttributeList::addParamAttribute(LLVMContext &C,
+                                               ArrayRef<unsigned> ArgNos,
+                                               Attribute A) const {
+  // Note: Code-clone of AttributeList::addAttribute(C, Indices, A). Any edits
+  // here must be mirrored there.
+  assert(std::is_sorted(ArgNos.begin(), ArgNos.end()));
+
+  unsigned I = 0, E = pImpl ? pImpl->getNumSlots() : 0;
+  SmallVector<IndexAttrPair, 4> AttrVec;
+  for (unsigned ArgNo : ArgNos) {
+    unsigned Index = ArgNo + FirstArgIndex;
+    // Add all attribute slots before the current index.
+    for (; I < E && getSlotIndex(I) < Index; ++I)
+      AttrVec.emplace_back(getSlotIndex(I), pImpl->getSlotAttributes(I));
+
+    // Add the attribute at this index. If we already have attributes at this
+    // index, merge them into a new set.
+    AttrBuilder B;
+    if (I < E && getSlotIndex(I) == Index) {
+      B.merge(AttrBuilder(pImpl->getSlotAttributes(I)));
+      ++I;
+    }
+    B.addAttribute(A);
+    AttrVec.emplace_back(Index, AttributeSet::get(C, B));
+  }
+
+  // Add remaining attributes.
+  for (; I < E; ++I)
+    AttrVec.emplace_back(getSlotIndex(I), pImpl->getSlotAttributes(I));
+
+  return get(C, AttrVec);
+}
+
 AttributeList AttributeList::removeAttribute(LLVMContext &C, unsigned Index,
                                              Attribute::AttrKind Kind) const {
   if (!hasAttribute(Index, Kind)) return *this;
   AttrBuilder B;
   B.addAttribute(Kind);
   return removeAttributes(C, Index, B);
 }
 

lib/IR/Function.cpp

 unsigned Argument::getParamAlignment() const {
   assert(getType()->isPointerTy() && "Only pointers have alignments");
   return getParent()->getParamAlignment(getArgNo());
 }
 
 uint64_t Argument::getDereferenceableBytes() const {
   assert(getType()->isPointerTy() &&
          "Only pointers have dereferenceable bytes");
-  return getParent()->getDereferenceableBytes(getArgNo() +
-                                              AttributeList::FirstArgIndex);
+  return getParent()->getParamDereferenceableBytes(getArgNo());
 }
 
 uint64_t Argument::getDereferenceableOrNullBytes() const {
   assert(getType()->isPointerTy() &&
          "Only pointers have dereferenceable bytes");
-  return getParent()->getDereferenceableOrNullBytes(
-      getArgNo() + AttributeList::FirstArgIndex);
+  return getParent()->getParamDereferenceableOrNullBytes(getArgNo());
 }
 
 bool Argument::hasNestAttr() const {
   if (!getType()->isPointerTy()) return false;
   return hasAttribute(Attribute::Nest);
 }
 
 bool Argument::hasNoAliasAttr() const {

 bool Argument::onlyReadsMemory() const {
   AttributeList Attrs = getParent()->getAttributes();
   return Attrs.hasParamAttribute(getArgNo(), Attribute::ReadOnly) ||
          Attrs.hasParamAttribute(getArgNo(), Attribute::ReadNone);
 }
 
 void Argument::addAttrs(AttrBuilder &B) {
   AttributeList AL = getParent()->getAttributes();
-  AL = AL.addAttributes(Parent->getContext(),
-                        getArgNo() + AttributeList::FirstArgIndex, B);
+  AL = AL.addParamAttributes(Parent->getContext(), getArgNo(), B);
   getParent()->setAttributes(AL);
 }
 
 void Argument::addAttr(Attribute::AttrKind Kind) {
-  getParent()->addAttribute(getArgNo() + AttributeList::FirstArgIndex, Kind);
+  getParent()->addParamAttr(getArgNo(), Kind);
 }
 
 void Argument::addAttr(Attribute Attr) {
-  getParent()->addAttribute(getArgNo() + AttributeList::FirstArgIndex, Attr);
+  getParent()->addParamAttr(getArgNo(), Attr);
 }
 
 void Argument::removeAttr(Attribute::AttrKind Kind) {
-  getParent()->removeAttribute(getArgNo() + AttributeList::FirstArgIndex, Kind);
+  getParent()->removeParamAttr(getArgNo(), Kind);
 }
 
 bool Argument::hasAttribute(Attribute::AttrKind Kind) const {
   return getParent()->hasParamAttribute(getArgNo(), Kind);
 }
 
 //===----------------------------------------------------------------------===//
 // Helper Methods in Function

 }
 
 void Function::addAttributes(unsigned i, const AttrBuilder &Attrs) {
   AttributeList PAL = getAttributes();
   PAL = PAL.addAttributes(getContext(), i, Attrs);
   setAttributes(PAL);
 }
 
+void Function::addParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) {
+  AttributeList PAL = getAttributes();
+  PAL = PAL.addParamAttribute(getContext(), ArgNo, Kind);
+  setAttributes(PAL);
+}
+
+void Function::addParamAttr(unsigned ArgNo, Attribute Attr) {
+  AttributeList PAL = getAttributes();
+  PAL = PAL.addParamAttribute(getContext(), ArgNo, Attr);
+  setAttributes(PAL);
+}
+
+void Function::addParamAttrs(unsigned ArgNo, const AttrBuilder &Attrs) {
+  AttributeList PAL = getAttributes();
+  PAL = PAL.addParamAttributes(getContext(), ArgNo, Attrs);
+  setAttributes(PAL);
+}
+
 void Function::removeAttribute(unsigned i, Attribute::AttrKind Kind) {
   AttributeList PAL = getAttributes();
   PAL = PAL.removeAttribute(getContext(), i, Kind);
   setAttributes(PAL);
 }
 
 void Function::removeAttribute(unsigned i, StringRef Kind) {
   AttributeList PAL = getAttributes();
   PAL = PAL.removeAttribute(getContext(), i, Kind);
   setAttributes(PAL);
 }
 
 void Function::removeAttributes(unsigned i, const AttrBuilder &Attrs) {
   AttributeList PAL = getAttributes();
   PAL = PAL.removeAttributes(getContext(), i, Attrs);
   setAttributes(PAL);
 }
 
+void Function::removeParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) {
+  AttributeList PAL = getAttributes();
+  PAL = PAL.removeParamAttribute(getContext(), ArgNo, Kind);
+  setAttributes(PAL);
+}
+
+void Function::removeParamAttr(unsigned ArgNo, StringRef Kind) {
+  AttributeList PAL = getAttributes();
+  PAL = PAL.removeParamAttribute(getContext(), ArgNo, Kind);
+  setAttributes(PAL);
+}
+
+void Function::removeParamAttrs(unsigned ArgNo, const AttrBuilder &Attrs) {
+  AttributeList PAL = getAttributes();
+  PAL = PAL.removeParamAttributes(getContext(), ArgNo, Attrs);
+  setAttributes(PAL);
+}
+
 void Function::addDereferenceableAttr(unsigned i, uint64_t Bytes) {
   AttributeList PAL = getAttributes();
   PAL = PAL.addDereferenceableAttr(getContext(), i, Bytes);
   setAttributes(PAL);
 }
 
+void Function::addDereferenceableParamAttr(unsigned ArgNo, uint64_t Bytes) {
+  AttributeList PAL = getAttributes();
+  PAL = PAL.addDereferenceableParamAttr(getContext(), ArgNo, Bytes);
+  setAttributes(PAL);
+}
+
 void Function::addDereferenceableOrNullAttr(unsigned i, uint64_t Bytes) {
   AttributeList PAL = getAttributes();
   PAL = PAL.addDereferenceableOrNullAttr(getContext(), i, Bytes);
   setAttributes(PAL);
 }
 
+void Function::addDereferenceableOrNullParamAttr(unsigned ArgNo,
+                                                 uint64_t Bytes) {
+  AttributeList PAL = getAttributes();
+  PAL = PAL.addDereferenceableOrNullParamAttr(getContext(), ArgNo, Bytes);
+  setAttributes(PAL);
+}
+
 const std::string &Function::getGC() const {
   assert(hasGC() && "Function has no collector");
   return getContext().getGC(*this);
 }
 
 void Function::setGC(std::string Str) {
   setValueSubclassDataBit(14, !Str.empty());
   getContext().setGC(*this, std::move(Str));

lib/IR/Instructions.cpp

 
 void CallInst::addAttribute(unsigned i, Attribute Attr) {
   AttributeList PAL = getAttributes();
   PAL = PAL.addAttribute(getContext(), i, Attr);
   setAttributes(PAL);
 }
 
 void CallInst::addParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) {
-  addAttribute(ArgNo + AttributeList::FirstArgIndex, Kind);
+  assert(ArgNo < getNumArgOperands() && "Out of bounds");
+  AttributeList PAL = getAttributes();
+  PAL = PAL.addParamAttribute(getContext(), ArgNo, Kind);
+  setAttributes(PAL);
+}
+
+void CallInst::addParamAttr(unsigned ArgNo, Attribute Attr) {
+  assert(ArgNo < getNumArgOperands() && "Out of bounds");
+  AttributeList PAL = getAttributes();
+  PAL = PAL.addParamAttribute(getContext(), ArgNo, Attr);
+  setAttributes(PAL);
 }
 
 void CallInst::removeAttribute(unsigned i, Attribute::AttrKind Kind) {
   AttributeList PAL = getAttributes();
   PAL = PAL.removeAttribute(getContext(), i, Kind);
   setAttributes(PAL);
 }
 
 void CallInst::removeAttribute(unsigned i, StringRef Kind) {
   AttributeList PAL = getAttributes();
   PAL = PAL.removeAttribute(getContext(), i, Kind);
   setAttributes(PAL);
 }
 
 void CallInst::removeParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) {
-  removeAttribute(ArgNo + AttributeList::FirstArgIndex, Kind);
+  assert(ArgNo < getNumArgOperands() && "Out of bounds");
+  AttributeList PAL = getAttributes();
+  PAL = PAL.removeParamAttribute(getContext(), ArgNo, Kind);
+  setAttributes(PAL);
+}
+
+void CallInst::removeParamAttr(unsigned ArgNo, StringRef Kind) {
+  assert(ArgNo < getNumArgOperands() && "Out of bounds");
+  AttributeList PAL = getAttributes();
+  PAL = PAL.removeParamAttribute(getContext(), ArgNo, Kind);
+  setAttributes(PAL);
 }
 
 void CallInst::addDereferenceableAttr(unsigned i, uint64_t Bytes) {
   AttributeList PAL = getAttributes();
   PAL = PAL.addDereferenceableAttr(getContext(), i, Bytes);
   setAttributes(PAL);
 }
 

 
 void InvokeInst::addAttribute(unsigned i, Attribute Attr) {
   AttributeList PAL = getAttributes();
   PAL = PAL.addAttribute(getContext(), i, Attr);
   setAttributes(PAL);
 }
 
 void InvokeInst::addParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) {
-  addAttribute(ArgNo + AttributeList::FirstArgIndex, Kind);
+  AttributeList PAL = getAttributes();
+  PAL = PAL.addParamAttribute(getContext(), ArgNo, Kind);
+  setAttributes(PAL);
 }
 
 void InvokeInst::removeAttribute(unsigned i, Attribute::AttrKind Kind) {
   AttributeList PAL = getAttributes();
   PAL = PAL.removeAttribute(getContext(), i, Kind);
   setAttributes(PAL);
 }
 
 void InvokeInst::removeAttribute(unsigned i, StringRef Kind) {
   AttributeList PAL = getAttributes();
   PAL = PAL.removeAttribute(getContext(), i, Kind);
   setAttributes(PAL);
 }
 
 void InvokeInst::removeParamAttr(unsigned ArgNo, Attribute::AttrKind Kind) {
-  removeAttribute(ArgNo + AttributeList::FirstArgIndex, Kind);
+  AttributeList PAL = getAttributes();
+  PAL = PAL.removeParamAttribute(getContext(), ArgNo, Kind);
+  setAttributes(PAL);
 }
 
 void InvokeInst::addDereferenceableAttr(unsigned i, uint64_t Bytes) {
   AttributeList PAL = getAttributes();
   PAL = PAL.addDereferenceableAttr(getContext(), i, Bytes);
   setAttributes(PAL);
 }
 

lib/Transforms/InstCombine/InstCombineCalls.cpp

Instruction *InstCombiner::visitCallSite(CallSite CS) {
   if (isAllocLikeFn(CS.getInstruction(), &TLI))
     return visitAllocSite(*CS.getInstruction());
 
   bool Changed = false;
 
   // Mark any parameters that are known to be non-null with the nonnull
   // attribute.  This is helpful for inlining calls to functions with null
   // checks on their arguments.
-  SmallVector<unsigned, 4> Indices;
+  SmallVector<unsigned, 4> ArgNos;
   unsigned ArgNo = 0;
 
   for (Value *V : CS.args()) {
     if (V->getType()->isPointerTy() &&
         !CS.paramHasAttr(ArgNo, Attribute::NonNull) &&
         isKnownNonNullAt(V, CS.getInstruction(), &DT))
-      Indices.push_back(ArgNo + AttributeList::FirstArgIndex);
+      ArgNos.push_back(ArgNo);
     ArgNo++;
   }
 
   assert(ArgNo == CS.arg_size() && "sanity check");
 
-  if (!Indices.empty()) {
+  if (!ArgNos.empty()) {
     AttributeList AS = CS.getAttributes();
     LLVMContext &Ctx = CS.getInstruction()->getContext();
-    AS = AS.addAttribute(Ctx, Indices,
+    AS = AS.addParamAttribute(Ctx, ArgNos,
                          Attribute::get(Ctx, Attribute::NonNull));
     CS.setAttributes(AS);
     Changed = true;
   }
 
   // If the callee is a pointer to a function, attempt to move any casts to the
   // arguments of the call/invoke.
   Value *Callee = CS.getCalledValue();

lib/Transforms/Scalar/CorrelatedValuePropagation.cpp

if (Changed)
     // by a branch then do so now.
     ConstantFoldTerminator(BB);
 
   return Changed;
 }
 
 /// Infer nonnull attributes for the arguments at the specified callsite.
 static bool processCallSite(CallSite CS, LazyValueInfo *LVI) {
-  SmallVector<unsigned, 4> Indices;
+  SmallVector<unsigned, 4> ArgNos;
   unsigned ArgNo = 0;
 
   for (Value *V : CS.args()) {
     PointerType *Type = dyn_cast<PointerType>(V->getType());
     // Try to mark pointer typed parameters as non-null.  We skip the
     // relatively expensive analysis for constants which are obviously either
     // null or non-null to start with.
     if (Type && !CS.paramHasAttr(ArgNo, Attribute::NonNull) &&
         !isa<Constant>(V) && 
         LVI->getPredicateAt(ICmpInst::ICMP_EQ, V,
                             ConstantPointerNull::get(Type),
                             CS.getInstruction()) == LazyValueInfo::False)
-      Indices.push_back(ArgNo + AttributeList::FirstArgIndex);
+      ArgNos.push_back(ArgNo);
     ArgNo++;
   }
 
   assert(ArgNo == CS.arg_size() && "sanity check");
 
-  if (Indices.empty())
+  if (ArgNos.empty())
     return false;
 
   AttributeList AS = CS.getAttributes();
   LLVMContext &Ctx = CS.getInstruction()->getContext();
-  AS = AS.addAttribute(Ctx, Indices, Attribute::get(Ctx, Attribute::NonNull));
+  AS = AS.addParamAttribute(Ctx, ArgNos,
+                            Attribute::get(Ctx, Attribute::NonNull));
   CS.setAttributes(AS);
 
   return true;
 }
 
 // Helper function to rewrite srem and sdiv. As a policy choice, we choose not
 // to waste compile time on anything where the operands are local defs.  While
 // LVI can sometimes reason about such cases, it's not its primary purpose.