[IR] Make AttributeSetNode public, avoid temporary AttributeList copies

[rnk]

Summary

AttributeList::get(Fn|Ret|Param)Attributes no longer creates a temporary
AttributeList just to hide the AttributeSetNode type.

I've also added a factory method to create AttributeLists from a
parallel array of AttributeSetNodes. This greatly simplified the
construction of AttributeLists during IPO transforms, in my opinion.
Previously we would test if a particular index had attributes, and
conditionally add a temporary attribute list to a vector. Now the
attribute set vector is parallel to the argument vector already that
these passes already construct.

My long term vision is to wrap AttributeSetNode* inside an AttributeSet
type that holds the enum attributes, but that will come in a follow up
change.

I haven't done any performance measurements for this change because
profiling hasn't shown that any of the affected code is hot.

[rnk]

• Fix bug in addAttribute implementation

[rnk]

• rebase

[pete]

Sorry for forgetting to review this.

LGTM with just these comments (but only comments so feel free to commit).

My only worry is that I view AttributeSetNode as an internal detail of the Attribute implementation. I think this is an incremental patch which eventually gets us to a cleaner set of APIs, so I'm fine with it for now, but I think the eventual goal shouldn't have AttributeSetNode be visible any more.

Note, when i looked at this a while ago, i created something I called AttributeRef which I guess was effectively the same as what you have here. But it still suffered from similar issues in terms of leaking implementation details. Its also possible that moving Attributes to the parameters just fixes most of this anyway.

[rnk]

In D31198#722892, @pete wrote:

Sorry for forgetting to review this.

NP, I got distracted by PDB stuff for a bit anyway.

LGTM with just these comments (but only comments so feel free to commit).

My only worry is that I view AttributeSetNode as an internal detail of the Attribute implementation. I think this is an incremental patch which eventually gets us to a cleaner set of APIs, so I'm fine with it for now, but I think the eventual goal shouldn't have AttributeSetNode be visible any more.

Note, when i looked at this a while ago, i created something I called AttributeRef which I guess was effectively the same as what you have here. But it still suffered from similar issues in terms of leaking implementation details. Its also possible that moving Attributes to the parameters just fixes most of this anyway.

I agree. I plan to wrap it back up in a new type called AttributeSet that will hold the enum attributes locally, so we can do much faster hasAttr tests.

llvm/include/llvm/IR/AttributeSetNode.h

-//===-- AttributeSetNode.h - AttributeList Internal Node ---------*- C++
-//-*-===//
+//===-- AttributeSetNode.h - AttributeList Internal Node --------*- C++ -*-===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
-/// \brief This file defines the node class used internally by AttributeList.
+/// \brief This file defines the class that represents a group of attributes
+/// that apply to one element: function, return type, or parameter.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_IR_ATTRIBUTESETNODE_H
 #define LLVM_IR_ATTRIBUTESETNODE_H
 
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/FoldingSet.h"

 
 public:
   // AttributesSetNode is uniqued, these should not be available.
   AttributeSetNode(const AttributeSetNode &) = delete;
   AttributeSetNode &operator=(const AttributeSetNode &) = delete;
 
   void operator delete(void *p) { ::operator delete(p); }
 
+  static AttributeSetNode *get(LLVMContext &C, const AttrBuilder &B);
+
   static AttributeSetNode *get(LLVMContext &C, ArrayRef<Attribute> Attrs);
 
   static AttributeSetNode *get(AttributeList AS, unsigned Index) {
     return AS.getAttributes(Index);
   }
 
   /// \brief Return the number of attributes this AttributeList contains.
   unsigned getNumAttributes() const { return NumAttrs; }

llvm/include/llvm/IR/Attributes.h

private:
   friend class AttributeSetNode;
 
   template <typename Ty> friend struct DenseMapInfo;
 
   /// \brief The attributes that we are managing. This can be null to represent
   /// the empty attributes list.
   AttributeListImpl *pImpl = nullptr;
 
-  /// \brief The attributes for the specified index are returned.
-  AttributeSetNode *getAttributes(unsigned Index) const;
-
+public:
   /// \brief Create an AttributeList with the specified parameters in it.
   static AttributeList get(LLVMContext &C,
                            ArrayRef<std::pair<unsigned, Attribute>> Attrs);
   static AttributeList
   get(LLVMContext &C, ArrayRef<std::pair<unsigned, AttributeSetNode *>> Attrs);
 
+  /// \brief Create an AttributeList from a vector of AttributeSetNodes. The
+  /// index of each set is implied by its position in the array \p Attrs:
+  ///   0      : Return attributes
+  /// 1 to n-1 : Argument attributes
+  ///   n      : Function attributes
+  /// Any element that has no entries should be left null.
+  static AttributeList get(LLVMContext &C, ArrayRef<AttributeSetNode *> Attrs);
+
   static AttributeList
   getImpl(LLVMContext &C,
           ArrayRef<std::pair<unsigned, AttributeSetNode *>> Attrs);
 
+private:
   explicit AttributeList(AttributeListImpl *LI) : pImpl(LI) {}
 
 public:
   AttributeList() = default;
 
   //===--------------------------------------------------------------------===//
   // AttributeList Construction and Mutation
   //===--------------------------------------------------------------------===//
public:
   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,
                               AttributeList Attrs) const;
 
+  AttributeList addAttributes(LLVMContext &C, unsigned Index,
+                              AttributeSetNode *AS) const;
+
+  AttributeList addAttributes(LLVMContext &C, unsigned Index,
+                              const AttrBuilder &B) 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,
                                 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,
                                  AttributeList Attrs) 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 &Attrs) 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
   /// 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_or_null attribute to the attribute set at
   /// the given index. Because attribute sets are immutable, this returns a new
   /// set.
public:
   //===--------------------------------------------------------------------===//
   // AttributeList Accessors
   //===--------------------------------------------------------------------===//
 
   /// \brief Retrieve the LLVM context.
   LLVMContext &getContext() const;
 
   /// \brief The attributes for the specified index are returned.
-  AttributeList getParamAttributes(unsigned Index) const;
+  AttributeSetNode *getAttributes(unsigned Index) const;
+
+  /// \brief The attributes for the specified index are returned.
+  AttributeSetNode *getParamAttributes(unsigned Index) const;
 
   /// \brief The attributes for the ret value are returned.
-  AttributeList getRetAttributes() const;
+  AttributeSetNode *getRetAttributes() const;
 
   /// \brief The function attributes are returned.
-  AttributeList getFnAttributes() const;
+  AttributeSetNode *getFnAttributes() const;
 
   /// \brief Return true if the attribute exists at the given index.
   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.
class AttrBuilder {
   uint64_t AllocSizeArgs = 0;
 
 public:
   AttrBuilder() = default;
   AttrBuilder(const Attribute &A) {
     addAttribute(A);
   }
   AttrBuilder(AttributeList AS, unsigned Idx);
+  AttrBuilder(AttributeSetNode *AS);
 
   void clear();
 
   /// \brief Add an attribute to the builder.
   AttrBuilder &addAttribute(Attribute::AttrKind Val);
 
   /// \brief Add the Attribute object to the builder.
   AttrBuilder &addAttribute(Attribute A);
 
   /// \brief Add the target-dependent attribute to the builder.
   AttrBuilder &addAttribute(StringRef A, StringRef V = StringRef());
 
   /// \brief Remove an attribute from the builder.
   AttrBuilder &removeAttribute(Attribute::AttrKind Val);
 
   /// \brief Remove the attributes from the builder.
-  AttrBuilder &removeAttributes(AttributeList A, uint64_t Index);
+  AttrBuilder &removeAttributes(AttributeList A, uint64_t WithoutIndex);
 
   /// \brief Remove the target-dependent attribute to the builder.
   AttrBuilder &removeAttribute(StringRef A);
 
   /// \brief Add the attributes from the builder.
   AttrBuilder &merge(const AttrBuilder &B);
 
   /// \brief Remove the attributes from the builder.

llvm/lib/AsmParser/LLParser.h

bool ParseTypeAndBasicBlock(BasicBlock *&BB, PerFunctionState &PFS) {
       LocTy Loc;
       return ParseTypeAndBasicBlock(BB, Loc, PFS);
     }
 
 
     struct ParamInfo {
       LocTy Loc;
       Value *V;
-      AttributeList Attrs;
-      ParamInfo(LocTy loc, Value *v, AttributeList attrs)
+      AttributeSetNode *Attrs;
+      ParamInfo(LocTy loc, Value *v, AttributeSetNode *attrs)
           : Loc(loc), V(v), Attrs(attrs) {}
     };
     bool ParseParameterList(SmallVectorImpl<ParamInfo> &ArgList,
                             PerFunctionState &PFS,
                             bool IsMustTailCall = false,
                             bool InVarArgsFunc = false);
 
     bool

 #define HANDLE_SPECIALIZED_MDNODE_LEAF(CLASS)                                  \
   bool Parse##CLASS(MDNode *&Result, bool IsDistinct);
 #include "llvm/IR/Metadata.def"
 
     // Function Parsing.
     struct ArgInfo {
       LocTy Loc;
       Type *Ty;
-      AttributeList Attrs;
+      AttributeSetNode *Attrs;
       std::string Name;
-      ArgInfo(LocTy L, Type *ty, AttributeList Attr, const std::string &N)
+      ArgInfo(LocTy L, Type *ty, AttributeSetNode *Attr, const std::string &N)
           : Loc(L), Ty(ty), Attrs(Attr), Name(N) {}
     };
     bool ParseArgumentList(SmallVectorImpl<ArgInfo> &ArgList, bool &isVarArg);
     bool ParseFunctionHeader(Function *&Fn, bool isDefine);
     bool ParseFunctionBody(Function &Fn);
     bool ParseBasicBlock(PerFunctionState &PFS);
 
     enum TailCallType { TCT_None, TCT_Tail, TCT_MustTail };

llvm/lib/AsmParser/LLParser.cpp

 #include "LLParser.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/AsmParser/SlotMapping.h"
 #include "llvm/IR/Argument.h"
+#include "llvm/IR/AttributeSetNode.h"
 #include "llvm/IR/AutoUpgrade.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/Comdat.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
for (const auto &RAG : ForwardRefAttrGroups) {
     const std::vector<unsigned> &Attrs = RAG.second;
     AttrBuilder B;
 
     for (const auto &Attr : Attrs)
       B.merge(NumberedAttrBuilders[Attr]);
 
     if (Function *Fn = dyn_cast<Function>(V)) {
       AttributeList AS = Fn->getAttributes();
-      AttrBuilder FnAttrs(AS.getFnAttributes(), AttributeList::FunctionIndex);
-      AS = AS.removeAttributes(Context, AttributeList::FunctionIndex,
-                               AS.getFnAttributes());
+      AttrBuilder FnAttrs(AS.getFnAttributes());
+      AS = AS.removeAttributes(Context, AttributeList::FunctionIndex);
 
       FnAttrs.merge(B);
 
       // If the alignment was parsed as an attribute, move to the alignment
       // field.
       if (FnAttrs.hasAlignmentAttr()) {
         Fn->setAlignment(FnAttrs.getAlignment());
         FnAttrs.removeAttribute(Attribute::Alignment);
       }
 
       AS = AS.addAttributes(
           Context, AttributeList::FunctionIndex,
           AttributeList::get(Context, AttributeList::FunctionIndex, FnAttrs));
       Fn->setAttributes(AS);
     } else if (CallInst *CI = dyn_cast<CallInst>(V)) {
       AttributeList AS = CI->getAttributes();
-      AttrBuilder FnAttrs(AS.getFnAttributes(), AttributeList::FunctionIndex);
-      AS = AS.removeAttributes(Context, AttributeList::FunctionIndex,
-                               AS.getFnAttributes());
+      AttrBuilder FnAttrs(AS.getFnAttributes());
+      AS = AS.removeAttributes(Context, AttributeList::FunctionIndex);
       FnAttrs.merge(B);
       AS = AS.addAttributes(
           Context, AttributeList::FunctionIndex,
           AttributeList::get(Context, AttributeList::FunctionIndex, FnAttrs));
       CI->setAttributes(AS);
     } else if (InvokeInst *II = dyn_cast<InvokeInst>(V)) {
       AttributeList AS = II->getAttributes();
-      AttrBuilder FnAttrs(AS.getFnAttributes(), AttributeList::FunctionIndex);
-      AS = AS.removeAttributes(Context, AttributeList::FunctionIndex,
-                               AS.getFnAttributes());
+      AttrBuilder FnAttrs(AS.getFnAttributes());
+      AS = AS.removeAttributes(Context, AttributeList::FunctionIndex);
       FnAttrs.merge(B);
       AS = AS.addAttributes(
           Context, AttributeList::FunctionIndex,
           AttributeList::get(Context, AttributeList::FunctionIndex, FnAttrs));
       II->setAttributes(AS);
     } else {
       llvm_unreachable("invalid object with forward attribute group reference");
     }

 ///  Arg
 ///    ::= Type OptionalAttributes Value OptionalAttributes
 bool LLParser::ParseParameterList(SmallVectorImpl<ParamInfo> &ArgList,
                                   PerFunctionState &PFS, bool IsMustTailCall,
                                   bool InVarArgsFunc) {
   if (ParseToken(lltok::lparen, "expected '(' in call"))
     return true;
 
-  unsigned AttrIndex = 1;
   while (Lex.getKind() != lltok::rparen) {
     // If this isn't the first argument, we need a comma.
     if (!ArgList.empty() &&
         ParseToken(lltok::comma, "expected ',' in argument list"))
       return true;
 
     // Parse an ellipsis if this is a musttail call in a variadic function.
     if (Lex.getKind() == lltok::dotdotdot) {
if (ArgTy->isMetadataTy()) {
       if (ParseMetadataAsValue(V, PFS))
         return true;
     } else {
       // Otherwise, handle normal operands.
       if (ParseOptionalParamAttrs(ArgAttrs) || ParseValue(ArgTy, V, PFS))
         return true;
     }
     ArgList.push_back(ParamInfo(
-        ArgLoc, V, AttributeList::get(V->getContext(), AttrIndex++, ArgAttrs)));
+        ArgLoc, V, AttributeSetNode::get(V->getContext(), ArgAttrs)));
   }
 
   if (IsMustTailCall && InVarArgsFunc)
     return TokError("expected '...' at end of argument list for musttail call "
                     "in varargs function");
 
   Lex.Lex();  // Lex the ')'.
   return false;
if (Lex.getKind() == lltok::rparen) {
     if (Lex.getKind() == lltok::LocalVar) {
       Name = Lex.getStrVal();
       Lex.Lex();
     }
 
     if (!FunctionType::isValidArgumentType(ArgTy))
       return Error(TypeLoc, "invalid type for function argument");
 
-    unsigned AttrIndex = 1;
-    ArgList.emplace_back(TypeLoc, ArgTy, AttributeList::get(ArgTy->getContext(),
-                                                            AttrIndex++, Attrs),
+    ArgList.emplace_back(TypeLoc, ArgTy,
+                         AttributeSetNode::get(ArgTy->getContext(), Attrs),
                          std::move(Name));
 
     while (EatIfPresent(lltok::comma)) {
       // Handle ... at end of arg list.
       if (EatIfPresent(lltok::dotdotdot)) {
         isVarArg = true;
         break;
       }
while (EatIfPresent(lltok::comma)) {
         Lex.Lex();
       } else {
         Name = "";
       }
 
       if (!ArgTy->isFirstClassType())
         return Error(TypeLoc, "invalid type for function argument");
 
-      ArgList.emplace_back(
-          TypeLoc, ArgTy,
-          AttributeList::get(ArgTy->getContext(), AttrIndex++, Attrs),
+      ArgList.emplace_back(TypeLoc, ArgTy,
+                           AttributeSetNode::get(ArgTy->getContext(), Attrs),
                            std::move(Name));
     }
   }
 
   return ParseToken(lltok::rparen, "expected ')' at end of argument list");
 }
 
 /// ParseFunctionType
 ///  ::= Type ArgumentList OptionalAttrs
 bool LLParser::ParseFunctionType(Type *&Result) {
   assert(Lex.getKind() == lltok::lparen);
 
   if (!FunctionType::isValidReturnType(Result))
     return TokError("invalid function return type");
 
   SmallVector<ArgInfo, 8> ArgList;
   bool isVarArg;
   if (ParseArgumentList(ArgList, isVarArg))
     return true;
 
   // Reject names on the arguments lists.
   for (unsigned i = 0, e = ArgList.size(); i != e; ++i) {
     if (!ArgList[i].Name.empty())
       return Error(ArgList[i].Loc, "argument name invalid in function type");
-    if (ArgList[i].Attrs.hasAttributes(i + 1))
+    if (ArgList[i].Attrs)
       return Error(ArgList[i].Loc,
                    "argument attributes invalid in function type");
   }
 
   SmallVector<Type*, 16> ArgListTy;
   for (unsigned i = 0, e = ArgList.size(); i != e; ++i)
     ArgListTy.push_back(ArgList[i].Ty);
 
bool LLParser::ParseFunctionHeader(Function *&Fn, bool isDefine) {
   if (FuncAttrs.hasAlignmentAttr()) {
     Alignment = FuncAttrs.getAlignment();
     FuncAttrs.removeAttribute(Attribute::Alignment);
   }
 
   // Okay, if we got here, the function is syntactically valid.  Convert types
   // and do semantic checks.
   std::vector<Type*> ParamTypeList;
-  SmallVector<AttributeList, 8> Attrs;
+  SmallVector<AttributeSetNode *, 8> Attrs;
 
-  if (RetAttrs.hasAttributes())
-    Attrs.push_back(AttributeList::get(RetType->getContext(),
-                                       AttributeList::ReturnIndex, RetAttrs));
+  Attrs.push_back(AttributeSetNode::get(Context, RetAttrs));
 
   for (unsigned i = 0, e = ArgList.size(); i != e; ++i) {
     ParamTypeList.push_back(ArgList[i].Ty);
-    if (ArgList[i].Attrs.hasAttributes(i + 1)) {
-      AttrBuilder B(ArgList[i].Attrs, i + 1);
-      Attrs.push_back(AttributeList::get(RetType->getContext(), i + 1, B));
-    }
+    Attrs.push_back(ArgList[i].Attrs);
   }
 
-  if (FuncAttrs.hasAttributes())
-    Attrs.push_back(AttributeList::get(
-        RetType->getContext(), AttributeList::FunctionIndex, FuncAttrs));
+  Attrs.push_back(AttributeSetNode::get(Context, FuncAttrs));
 
   AttributeList PAL = AttributeList::get(Context, Attrs);
 
   if (PAL.hasAttribute(1, Attribute::StructRet) && !RetType->isVoidTy())
     return Error(RetTypeLoc, "functions with 'sret' argument must return void");
 
   FunctionType *FT =
     FunctionType::get(RetType, ParamTypeList, isVarArg);
bool LLParser::ParseInvoke(Instruction *&Inst, PerFunctionState &PFS) {
   CalleeID.FTy = Ty;
 
   // Look up the callee.
   Value *Callee;
   if (ConvertValIDToValue(PointerType::getUnqual(Ty), CalleeID, Callee, &PFS))
     return true;
 
   // Set up the Attribute for the function.
-  SmallVector<AttributeList, 8> Attrs;
-  if (RetAttrs.hasAttributes())
-    Attrs.push_back(AttributeList::get(RetType->getContext(),
-                                       AttributeList::ReturnIndex, RetAttrs));
+  SmallVector<AttributeSetNode *, 8> Attrs;
+  Attrs.push_back(AttributeSetNode::get(Context, RetAttrs));
 
   SmallVector<Value*, 8> Args;
 
   // Loop through FunctionType's arguments and ensure they are specified
   // correctly.  Also, gather any parameter attributes.
   FunctionType::param_iterator I = Ty->param_begin();
   FunctionType::param_iterator E = Ty->param_end();
   for (unsigned i = 0, e = ArgList.size(); i != e; ++i) {
     Type *ExpectedTy = nullptr;
     if (I != E) {
       ExpectedTy = *I++;
     } else if (!Ty->isVarArg()) {
       return Error(ArgList[i].Loc, "too many arguments specified");
     }
 
     if (ExpectedTy && ExpectedTy != ArgList[i].V->getType())
       return Error(ArgList[i].Loc, "argument is not of expected type '" +
                    getTypeString(ExpectedTy) + "'");
     Args.push_back(ArgList[i].V);
-    if (ArgList[i].Attrs.hasAttributes(i + 1)) {
-      AttrBuilder B(ArgList[i].Attrs, i + 1);
-      Attrs.push_back(AttributeList::get(RetType->getContext(), i + 1, B));
-    }
+    Attrs.push_back(ArgList[i].Attrs);
   }
 
   if (I != E)
     return Error(CallLoc, "not enough parameters specified for call");
 
-  if (FnAttrs.hasAttributes()) {
-    if (FnAttrs.hasAlignmentAttr())
-      return Error(CallLoc, "invoke instructions may not have an alignment");
 
-    Attrs.push_back(AttributeList::get(RetType->getContext(),
-                                       AttributeList::FunctionIndex, FnAttrs));
-  }
+  Attrs.push_back(AttributeSetNode::get(Context, FnAttrs));
 
   // Finish off the Attribute and check them
   AttributeList PAL = AttributeList::get(Context, Attrs);
 
   InvokeInst *II =
       InvokeInst::Create(Ty, Callee, NormalBB, UnwindBB, Args, BundleList);
   II->setCallingConv(CC);
   II->setAttributes(PAL);
bool LLParser::ParseCall(Instruction *&Inst, PerFunctionState &PFS,
   CalleeID.FTy = Ty;
 
   // Look up the callee.
   Value *Callee;
   if (ConvertValIDToValue(PointerType::getUnqual(Ty), CalleeID, Callee, &PFS))
     return true;
 
   // Set up the Attribute for the function.
-  SmallVector<AttributeList, 8> Attrs;
-  if (RetAttrs.hasAttributes())
-    Attrs.push_back(AttributeList::get(RetType->getContext(),
-                                       AttributeList::ReturnIndex, RetAttrs));
+  SmallVector<AttributeSetNode *, 8> Attrs;
+  Attrs.push_back(AttributeSetNode::get(Context, RetAttrs));
 
   SmallVector<Value*, 8> Args;
 
   // Loop through FunctionType's arguments and ensure they are specified
   // correctly.  Also, gather any parameter attributes.
   FunctionType::param_iterator I = Ty->param_begin();
   FunctionType::param_iterator E = Ty->param_end();
   for (unsigned i = 0, e = ArgList.size(); i != e; ++i) {
     Type *ExpectedTy = nullptr;
     if (I != E) {
       ExpectedTy = *I++;
     } else if (!Ty->isVarArg()) {
       return Error(ArgList[i].Loc, "too many arguments specified");
     }
 
     if (ExpectedTy && ExpectedTy != ArgList[i].V->getType())
       return Error(ArgList[i].Loc, "argument is not of expected type '" +
                    getTypeString(ExpectedTy) + "'");
     Args.push_back(ArgList[i].V);
-    if (ArgList[i].Attrs.hasAttributes(i + 1)) {
-      AttrBuilder B(ArgList[i].Attrs, i + 1);
-      Attrs.push_back(AttributeList::get(RetType->getContext(), i + 1, B));
-    }
+    Attrs.push_back(ArgList[i].Attrs);
   }
 
   if (I != E)
     return Error(CallLoc, "not enough parameters specified for call");
 
-  if (FnAttrs.hasAttributes()) {
-    if (FnAttrs.hasAlignmentAttr())
-      return Error(CallLoc, "call instructions may not have an alignment");
 
-    Attrs.push_back(AttributeList::get(RetType->getContext(),
-                                       AttributeList::FunctionIndex, FnAttrs));
-  }
+  Attrs.push_back(AttributeSetNode::get(Context, FnAttrs));
 
   // Finish off the Attribute and check them
   AttributeList PAL = AttributeList::get(Context, Attrs);
 
   CallInst *CI = CallInst::Create(Ty, Callee, Args, BundleList);
   CI->setTailCallKind(TCK);
   CI->setCallingConv(CC);
   if (FMF.any())

llvm/lib/IR/AsmWriter.cpp

 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/IR/AssemblyAnnotationWriter.h"
+#include "llvm/IR/AttributeSetNode.h"
+#include "llvm/IR/Attributes.h"
 #include "llvm/IR/CFG.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/IRPrintingPasses.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/IntrinsicInst.h"
private:
   ValueMap fMap;
   unsigned fNext;
 
   /// mdnMap - Map for MDNodes.
   DenseMap<const MDNode*, unsigned> mdnMap;
   unsigned mdnNext;
 
   /// asMap - The slot map for attribute sets.
-  DenseMap<AttributeList, unsigned> asMap;
+  DenseMap<AttributeSetNode *, unsigned> asMap;
   unsigned asNext;
 public:
   /// Construct from a module.
   ///
   /// If \c ShouldInitializeAllMetadata, initializes all metadata in all
   /// functions, giving correct numbering for metadata referenced only from
   /// within a function (even if no functions have been initialized).
   explicit SlotTracker(const Module *M,
                        bool ShouldInitializeAllMetadata = false);
   /// Construct from a function, starting out in incorp state.
   ///
   /// If \c ShouldInitializeAllMetadata, initializes all metadata in all
   /// functions, giving correct numbering for metadata referenced only from
   /// within a function (even if no functions have been initialized).
   explicit SlotTracker(const Function *F,
                        bool ShouldInitializeAllMetadata = false);
 
   /// Return the slot number of the specified value in it's type
   /// plane.  If something is not in the SlotTracker, return -1.
   int getLocalSlot(const Value *V);
   int getGlobalSlot(const GlobalValue *V);
   int getMetadataSlot(const MDNode *N);
-  int getAttributeGroupSlot(AttributeList AS);
+  int getAttributeGroupSlot(AttributeSetNode *AS);
 
   /// If you'd like to deal with a function instead of just a module, use
   /// this method to get its data into the SlotTracker.
   void incorporateFunction(const Function *F) {
     TheFunction = F;
     FunctionProcessed = false;
   }
 
   const Function *getFunction() const { return TheFunction; }
 
   /// After calling incorporateFunction, use this method to remove the
   /// most recently incorporated function from the SlotTracker. This
   /// will reset the state of the machine back to just the module contents.
   void purgeFunction();
 
   /// MDNode map iterators.
   typedef DenseMap<const MDNode*, unsigned>::iterator mdn_iterator;
   mdn_iterator mdn_begin() { return mdnMap.begin(); }
   mdn_iterator mdn_end() { return mdnMap.end(); }
   unsigned mdn_size() const { return mdnMap.size(); }
   bool mdn_empty() const { return mdnMap.empty(); }
 
-  /// AttributeList map iterators.
-  typedef DenseMap<AttributeList, unsigned>::iterator as_iterator;
+  /// AttributeSetNode map iterators.
+  typedef DenseMap<AttributeSetNode *, unsigned>::iterator as_iterator;
   as_iterator as_begin()   { return asMap.begin(); }
   as_iterator as_end()     { return asMap.end(); }
   unsigned as_size() const { return asMap.size(); }
   bool as_empty() const    { return asMap.empty(); }
 
   /// This function does the actual initialization.
   inline void initialize();
 
   // Implementation Details
 private:
   /// CreateModuleSlot - Insert the specified GlobalValue* into the slot table.
   void CreateModuleSlot(const GlobalValue *V);
 
   /// CreateMetadataSlot - Insert the specified MDNode* into the slot table.
   void CreateMetadataSlot(const MDNode *N);
 
   /// CreateFunctionSlot - Insert the specified Value* into the slot table.
   void CreateFunctionSlot(const Value *V);
 
-  /// \brief Insert the specified AttributeList into the slot table.
-  void CreateAttributeSetSlot(AttributeList AS);
+  /// \brief Insert the specified AttributeSetNode into the slot table.
+  void CreateAttributeSetSlot(AttributeSetNode *AS);
 
   /// Add all of the module level global variables (and their initializers)
   /// and function declarations, but not the contents of those functions.
   void processModule();
 
   /// Add all of the functions arguments, basic blocks, and instructions.
   void processFunction();
 
if (!F.hasName())
       // Add all the unnamed functions to the table.
       CreateModuleSlot(&F);
 
     if (ShouldInitializeAllMetadata)
       processFunctionMetadata(F);
 
     // Add all the function attributes to the table.
     // FIXME: Add attributes of other objects?
-    AttributeList FnAttrs = F.getAttributes().getFnAttributes();
-    if (FnAttrs.hasAttributes(AttributeList::FunctionIndex))
+    AttributeSetNode *FnAttrs = F.getAttributes().getFnAttributes();
+    if (FnAttrs)
       CreateAttributeSetSlot(FnAttrs);
   }
 
   ST_DEBUG("end processModule!\n");
 }
 
 // Process the arguments, basic blocks, and instructions  of a function.
 void SlotTracker::processFunction() {
for (auto &BB : *TheFunction) {
     for (auto &I : BB) {
       if (!I.getType()->isVoidTy() && !I.hasName())
         CreateFunctionSlot(&I);
 
       // We allow direct calls to any llvm.foo function here, because the
       // target may not be linked into the optimizer.
       if (const CallInst *CI = dyn_cast<CallInst>(&I)) {
         // Add all the call attributes to the table.
-        AttributeList Attrs = CI->getAttributes().getFnAttributes();
-        if (Attrs.hasAttributes(AttributeList::FunctionIndex))
+        AttributeSetNode *Attrs = CI->getAttributes().getFnAttributes();
+        if (Attrs)
           CreateAttributeSetSlot(Attrs);
       } else if (const InvokeInst *II = dyn_cast<InvokeInst>(&I)) {
         // Add all the call attributes to the table.
-        AttributeList Attrs = II->getAttributes().getFnAttributes();
-        if (Attrs.hasAttributes(AttributeList::FunctionIndex))
+        AttributeSetNode *Attrs = II->getAttributes().getFnAttributes();
+        if (Attrs)
           CreateAttributeSetSlot(Attrs);
       }
     }
   }
 
   FunctionProcessed = true;
 
   ST_DEBUG("end processFunction!\n");
int SlotTracker::getLocalSlot(const Value *V) {
 
   // Check for uninitialized state and do lazy initialization.
   initialize();
 
   ValueMap::iterator FI = fMap.find(V);
   return FI == fMap.end() ? -1 : (int)FI->second;
 }
 
-int SlotTracker::getAttributeGroupSlot(AttributeList AS) {
+int SlotTracker::getAttributeGroupSlot(AttributeSetNode *AS) {
   // Check for uninitialized state and do lazy initialization.
   initialize();
 
-  // Find the AttributeList in the module map.
+  // Find the AttributeSetNode in the module map.
   as_iterator AI = asMap.find(AS);
   return AI == asMap.end() ? -1 : (int)AI->second;
 }
 
 /// CreateModuleSlot - Insert the specified GlobalValue* into the slot table.
 void SlotTracker::CreateModuleSlot(const GlobalValue *V) {
   assert(V && "Can't insert a null Value into SlotTracker!");
   assert(!V->getType()->isVoidTy() && "Doesn't need a slot!");
void SlotTracker::CreateMetadataSlot(const MDNode *N) {
   ++mdnNext;
 
   // Recursively add any MDNodes referenced by operands.
   for (unsigned i = 0, e = N->getNumOperands(); i != e; ++i)
     if (const MDNode *Op = dyn_cast_or_null<MDNode>(N->getOperand(i)))
       CreateMetadataSlot(Op);
 }
 
-void SlotTracker::CreateAttributeSetSlot(AttributeList AS) {
-  assert(AS.hasAttributes(AttributeList::FunctionIndex) &&
-         "Doesn't need a slot!");
+void SlotTracker::CreateAttributeSetSlot(AttributeSetNode *AS) {
+  assert(AS && "Doesn't need a slot!");
 
   as_iterator I = asMap.find(AS);
   if (I != asMap.end())
     return;
 
   unsigned DestSlot = asNext++;
   asMap[AS] = DestSlot;
 }
void AssemblyWriter::printFunction(const Function *F) {
 
   if (AnnotationWriter) AnnotationWriter->emitFunctionAnnot(F, Out);
 
   if (F->isMaterializable())
     Out << "; Materializable\n";
 
   const AttributeList &Attrs = F->getAttributes();
   if (Attrs.hasAttributes(AttributeList::FunctionIndex)) {
-    AttributeList AS = Attrs.getFnAttributes();
+    AttributeSetNode *AS = Attrs.getFnAttributes();
     std::string AttrStr;
 
-    unsigned Idx = 0;
-    for (unsigned E = AS.getNumSlots(); Idx != E; ++Idx)
-      if (AS.getSlotIndex(Idx) == AttributeList::FunctionIndex)
-        break;
-
-    for (AttributeList::iterator I = AS.begin(Idx), E = AS.end(Idx); I != E;
-         ++I) {
-      Attribute Attr = *I;
+    for (const Attribute &Attr : *AS) {
       if (!Attr.isStringAttribute()) {
         if (!AttrStr.empty()) AttrStr += ' ';
         AttrStr += Attr.getAsString();
       }
     }
 
     if (!AttrStr.empty())
       Out << "; Function Attrs: " << AttrStr << '\n';
void AssemblyWriter::writeAllMDNodes() {
   }
 }
 
 void AssemblyWriter::printMDNodeBody(const MDNode *Node) {
   WriteMDNodeBodyInternal(Out, Node, &TypePrinter, &Machine, TheModule);
 }
 
 void AssemblyWriter::writeAllAttributeGroups() {
-  std::vector<std::pair<AttributeList, unsigned>> asVec;
+  std::vector<std::pair<AttributeSetNode *, unsigned>> asVec;
   asVec.resize(Machine.as_size());
 
   for (SlotTracker::as_iterator I = Machine.as_begin(), E = Machine.as_end();
        I != E; ++I)
     asVec[I->second] = *I;
 
   for (const auto &I : asVec)
     Out << "attributes #" << I.second << " = { "
-        << I.first.getAsString(AttributeList::FunctionIndex, true) << " }\n";
+        << I.first->getAsString(true) << " }\n";
 }
 
 void AssemblyWriter::printUseListOrder(const UseListOrder &Order) {
   bool IsInFunction = Machine.getFunction();
   if (IsInFunction)
     Out << "  ";
 
   Out << "uselistorder";

llvm/lib/IR/AttributeImpl.h

 /// \brief This file defines various helper methods and classes used by
 /// LLVMContextImpl for creating and managing attributes.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_LIB_IR_ATTRIBUTEIMPL_H
 #define LLVM_LIB_IR_ATTRIBUTEIMPL_H
 
-#include "AttributeSetNode.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/IR/AttributeSetNode.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/Support/TrailingObjects.h"
 #include <algorithm>
 #include <cassert>
 #include <climits>
 #include <cstddef>
 #include <cstdint>
 #include <string>

llvm/lib/IR/Attributes.cpp

 //===- Attributes.cpp - Implement AttributesList --------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // \file
 // \brief This file implements the Attribute, AttributeImpl, AttrBuilder,
 // AttributeListImpl, and AttributeList classes.
 //
 //===----------------------------------------------------------------------===//
 
 #include "AttributeImpl.h"
-#include "AttributeSetNode.h"
 #include "LLVMContextImpl.h"
 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/FoldingSet.h"
 #include "llvm/ADT/Optional.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringExtras.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/Twine.h"
+#include "llvm/IR/AttributeSetNode.h"
 #include "llvm/IR/Attributes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Type.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MathExtras.h"
if (!PA) {
     PA = new (Mem) AttributeSetNode(SortedAttrs);
     pImpl->AttrsSetNodes.InsertNode(PA, InsertPoint);
   }
 
   // Return the AttributeSetNode that we found or created.
   return PA;
 }
 
+AttributeSetNode *AttributeSetNode::get(LLVMContext &C, const AttrBuilder &B) {
+  // Add target-independent attributes.
+  SmallVector<Attribute, 8> Attrs;
+  for (Attribute::AttrKind Kind = Attribute::None;
+       Kind != Attribute::EndAttrKinds; Kind = Attribute::AttrKind(Kind + 1)) {
+    if (!B.contains(Kind))
+      continue;
+
+    Attribute Attr;
+    switch (Kind) {
+    case Attribute::Alignment:
+      Attr = Attribute::getWithAlignment(C, B.getAlignment());
+      break;
+    case Attribute::StackAlignment:
+      Attr = Attribute::getWithStackAlignment(C, B.getStackAlignment());
+      break;
+    case Attribute::Dereferenceable:
+      Attr = Attribute::getWithDereferenceableBytes(
+          C, B.getDereferenceableBytes());
+      break;
+    case Attribute::DereferenceableOrNull:
+      Attr = Attribute::getWithDereferenceableOrNullBytes(
+          C, B.getDereferenceableOrNullBytes());
+      break;
+    case Attribute::AllocSize: {
+      auto A = B.getAllocSizeArgs();
+      Attr = Attribute::getWithAllocSizeArgs(C, A.first, A.second);
+      break;
+    }
+    default:
+      Attr = Attribute::get(C, Kind);
+    }
+    Attrs.push_back(Attr);
+  }
+
+  // Add target-dependent (string) attributes.
+  for (const auto &TDA : B.td_attrs())
+    Attrs.emplace_back(Attribute::get(C, TDA.first, TDA.second));
+
+  return get(C, Attrs);
+}
+
 bool AttributeSetNode::hasAttribute(StringRef Kind) const {
   for (Attribute I : *this)
     if (I.hasAttribute(Kind))
       return true;
   return false;
 }
 
 Attribute AttributeSetNode::getAttribute(Attribute::AttrKind Kind) const {

 #endif
 
 //===----------------------------------------------------------------------===//
 // AttributeList Construction and Mutation Methods
 //===----------------------------------------------------------------------===//
 
 AttributeList AttributeList::getImpl(
     LLVMContext &C, ArrayRef<std::pair<unsigned, AttributeSetNode *>> Attrs) {
+  assert(!Attrs.empty() && "creating pointless AttributeList");
+#ifndef NDEBUG
+  unsigned LastIndex = 0;
+  bool IsFirst = true;
+  for (const auto &AttrPair : Attrs) {
+    assert((IsFirst || LastIndex < AttrPair.first) &&
+           "unsorted or duplicate AttributeList indices");
+    assert(AttrPair.second && "pointless AttributeList slot");
+    LastIndex = AttrPair.first;
+    IsFirst = false;
+  }
+#endif
+
   LLVMContextImpl *pImpl = C.pImpl;
   FoldingSetNodeID ID;
   AttributeListImpl::Profile(ID, Attrs);
 
   void *InsertPoint;
   AttributeListImpl *PA =
       pImpl->AttrsLists.FindNodeOrInsertPos(ID, InsertPoint);
 
AttributeList::get(LLVMContext &C,
                    ArrayRef<std::pair<unsigned, AttributeSetNode *>> Attrs) {
   // If there are no attributes then return a null AttributesList pointer.
   if (Attrs.empty())
     return AttributeList();
 
   return getImpl(C, Attrs);
 }
 
-AttributeList AttributeList::get(LLVMContext &C, unsigned Index,
-                                 const AttrBuilder &B) {
-  if (!B.hasAttributes())
-    return AttributeList();
-
-  // Add target-independent attributes.
-  SmallVector<std::pair<unsigned, Attribute>, 8> Attrs;
-  for (Attribute::AttrKind Kind = Attribute::None;
-       Kind != Attribute::EndAttrKinds; Kind = Attribute::AttrKind(Kind + 1)) {
-    if (!B.contains(Kind))
-      continue;
-
-    Attribute Attr;
-    switch (Kind) {
-    case Attribute::Alignment:
-      Attr = Attribute::getWithAlignment(C, B.getAlignment());
-      break;
-    case Attribute::StackAlignment:
-      Attr = Attribute::getWithStackAlignment(C, B.getStackAlignment());
-      break;
-    case Attribute::Dereferenceable:
-      Attr = Attribute::getWithDereferenceableBytes(
-          C, B.getDereferenceableBytes());
-      break;
-    case Attribute::DereferenceableOrNull:
-      Attr = Attribute::getWithDereferenceableOrNullBytes(
-          C, B.getDereferenceableOrNullBytes());
-      break;
-    case Attribute::AllocSize: {
-      auto A = B.getAllocSizeArgs();
-      Attr = Attribute::getWithAllocSizeArgs(C, A.first, A.second);
-      break;
+AttributeList AttributeList::get(LLVMContext &C, ArrayRef<AttributeSetNode*> Attrs) {
+  assert(Attrs.size() >= 2 &&
+         "should always have function and return attr slots");
+  SmallVector<std::pair<unsigned, AttributeSetNode *>, 8> AttrPairs;
+  size_t Index = 0;
+  for (AttributeSetNode *AS : Attrs) {
+    if (AS) {
+      // If this is the last AttributeSetNode, it's for the function.
+      if (Index == Attrs.size() - 1)
+        Index = AttributeList::FunctionIndex;
+      AttrPairs.emplace_back(Index, AS);
     }
-    default:
-      Attr = Attribute::get(C, Kind);
-    }
-    Attrs.emplace_back(Index, Attr);
-  }
+    ++Index;
+  if (AttrPairs.empty())
+    return AttributeList();
+  return getImpl(C, AttrPairs);
 
-  // Add target-dependent (string) attributes.
-  for (const auto &TDA : B.td_attrs())
-    Attrs.emplace_back(Index, Attribute::get(C, TDA.first, TDA.second));
-
-  return get(C, Attrs);
+AttributeList AttributeList::get(LLVMContext &C, unsigned Index,
+                                 const AttrBuilder &B) {
+  if (!B.hasAttributes())
+    return AttributeList();
+  AttributeSetNode *ASN = AttributeSetNode::get(C, B);
+  std::pair<unsigned, AttributeSetNode *> Arr[1] = {{Index, ASN}};
+  return getImpl(C, Arr);
 }
 
 AttributeList AttributeList::get(LLVMContext &C, unsigned Index,
                                  ArrayRef<Attribute::AttrKind> Kinds) {
   SmallVector<std::pair<unsigned, Attribute>, 8> Attrs;
   for (Attribute::AttrKind K : Kinds)
     Attrs.emplace_back(Index, Attribute::get(C, K));
   return get(C, Attrs);
AttributeList AttributeList::addAttribute(LLVMContext &C, unsigned Index,
   AttrBuilder B;
   B.addAttribute(Kind, Value);
   return addAttributes(C, Index, AttributeList::get(C, Index, B));
 }
 
 AttributeList AttributeList::addAttribute(LLVMContext &C,
                                           ArrayRef<unsigned> Indices,
                                           Attribute A) const {
+  assert(std::is_sorted(Indices.begin(), Indices.end()));
+
   unsigned I = 0, E = pImpl ? pImpl->getNumSlots() : 0;
-  auto IdxI = Indices.begin(), IdxE = Indices.end();
-  SmallVector<AttributeList, 4> AttrSet;
+  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->getSlotNode(I));
 
-  while (I != E && IdxI != IdxE) {
-    if (getSlotIndex(I) < *IdxI)
-      AttrSet.emplace_back(getSlotAttributes(I++));
-    else if (getSlotIndex(I) > *IdxI)
-      AttrSet.emplace_back(AttributeList::get(C, std::make_pair(*IdxI++, A)));
-    else {
-      AttrBuilder B(getSlotAttributes(I), *IdxI);
-      B.addAttribute(A);
-      AttrSet.emplace_back(AttributeList::get(C, *IdxI, B));
+    // 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->getSlotNode(I)));
       ++I;
-      ++IdxI;
     }
+    B.addAttribute(A);
+    AttrVec.emplace_back(Index, AttributeSetNode::get(C, B));
   }
 
-  while (I != E)
-    AttrSet.emplace_back(getSlotAttributes(I++));
-
-  while (IdxI != IdxE)
-    AttrSet.emplace_back(AttributeList::get(C, std::make_pair(*IdxI++, A)));
+  // Add remaining attributes.
+  for (; I < E; ++I)
+    AttrVec.emplace_back(getSlotIndex(I), pImpl->getSlotNode(I));
 
-  return get(C, AttrSet);
+  return get(C, AttrVec);
 }
 
 AttributeList AttributeList::addAttributes(LLVMContext &C, unsigned Index,
                                            AttributeList Attrs) const {
   if (!pImpl) return Attrs;
   if (!Attrs.pImpl) return *this;
 
+  return addAttributes(C, Index, Attrs.getAttributes(Index));
+}
+
+AttributeList AttributeList::addAttributes(LLVMContext &C, unsigned Index,
+                                           AttributeSetNode *AS) const {
+  if (!AS)
+    return *this;
+
 #ifndef NDEBUG
   // FIXME it is not obvious how this should work for alignment. For now, say
   // we can't change a known alignment.
   unsigned OldAlign = getParamAlignment(Index);
-  unsigned NewAlign = Attrs.getParamAlignment(Index);
+  unsigned NewAlign = AS->getAlignment();
   assert((!OldAlign || !NewAlign || OldAlign == NewAlign) &&
          "Attempt to change alignment!");
 #endif
 
-  // Add the attribute slots before the one we're trying to add.
-  SmallVector<AttributeList, 4> AttrSet;
+  SmallVector<std::pair<unsigned, AttributeSetNode *>, 4> AttrSet;
   uint64_t NumAttrs = pImpl->getNumSlots();
-  AttributeList AS;
-  uint64_t LastIndex = 0;
-  for (unsigned I = 0, E = NumAttrs; I != E; ++I) {
-    if (getSlotIndex(I) >= Index) {
-      if (getSlotIndex(I) == Index) AS = getSlotAttributes(LastIndex++);
-      break;
-    }
-    LastIndex = I + 1;
-    AttrSet.push_back(getSlotAttributes(I));
-  }
+  unsigned I;
 
-  // Now add the attribute into the correct slot. There may already be an
-  // AttributeList there.
-  AttrBuilder B(AS, Index);
-
-  for (unsigned I = 0, E = Attrs.pImpl->getNumSlots(); I != E; ++I)
-    if (Attrs.getSlotIndex(I) == Index) {
-      for (AttributeListImpl::iterator II = Attrs.pImpl->begin(I),
-                                       IE = Attrs.pImpl->end(I);
-           II != IE; ++II)
-        B.addAttribute(*II);
+  // Add all the attribute slots before the one we need to merge.
+  for (I = 0; I < NumAttrs; ++I) {
+    if (getSlotIndex(I) >= Index)
       break;
-    }
+    AttrSet.emplace_back(getSlotIndex(I), pImpl->getSlotNode(I));
 
-  AttrSet.push_back(AttributeList::get(C, Index, B));
+  if (I < NumAttrs && getSlotIndex(I) == Index) {
+    // We need to merge two AttributeSetNodes.
+    AttributeSetNode *Merged = AttributeSetNode::get(
+        C, AttrBuilder(pImpl->getSlotNode(I)).merge(AttrBuilder(AS)));
+    AttrSet.emplace_back(Index, Merged);
+    ++I;
+  } else {
+    // Otherwise, there were no attributes at this position in the original
+    // list. Add the set as is.
+    AttrSet.emplace_back(Index, AS);
+  }
 
-  // Add the remaining attribute slots.
-  for (unsigned I = LastIndex, E = NumAttrs; I < E; ++I)
-    AttrSet.push_back(getSlotAttributes(I));
+  // Add the remaining entries.
+  for (; I < NumAttrs; ++I)
+    AttrSet.emplace_back(getSlotIndex(I), pImpl->getSlotNode(I));
 
   return get(C, AttrSet);
 }
 
+AttributeList AttributeList::addAttributes(LLVMContext &C, unsigned Index,
+                                           const AttrBuilder &B) const {
+  return get(C, Index, AttributeSetNode::get(C, B));
+}
+
 AttributeList AttributeList::removeAttribute(LLVMContext &C, unsigned Index,
                                              Attribute::AttrKind Kind) const {
   if (!hasAttribute(Index, Kind)) return *this;
   return removeAttributes(C, Index, AttributeList::get(C, Index, Kind));
 }
 
 AttributeList AttributeList::removeAttribute(LLVMContext &C, unsigned Index,
                                              StringRef Kind) const {
AttributeList AttributeList::removeAttributes(LLVMContext &C, unsigned Index,
 
   // Add the remaining attribute slots.
   for (unsigned I = LastIndex, E = NumAttrs; I < E; ++I)
     AttrSet.push_back(getSlotAttributes(I));
 
   return get(C, AttrSet);
 }
 
+AttributeList AttributeList::removeAttributes(LLVMContext &C,
+                                              unsigned WithoutIndex) const {
+  if (!pImpl)
+    return AttributeList();
+
+  SmallVector<std::pair<unsigned, AttributeSetNode *>, 4> AttrSet;
+  for (unsigned I = 0, E = pImpl->getNumSlots(); I != E; ++I) {
+    unsigned Index = getSlotIndex(I);
+    if (Index != WithoutIndex)
+      AttrSet.push_back({Index, pImpl->getSlotNode(I)});
+  }
+  return get(C, AttrSet);
+}
+
 AttributeList AttributeList::addDereferenceableAttr(LLVMContext &C,
                                                     unsigned Index,
                                                     uint64_t Bytes) const {
   AttrBuilder B;
   B.addDereferenceableAttr(Bytes);
   return addAttributes(C, Index, AttributeList::get(C, Index, B));
 }
 

 }
 
 //===----------------------------------------------------------------------===//
 // AttributeList Accessor Methods
 //===----------------------------------------------------------------------===//
 
 LLVMContext &AttributeList::getContext() const { return pImpl->getContext(); }
 
-AttributeList AttributeList::getParamAttributes(unsigned Index) const {
-  return pImpl && hasAttributes(Index)
-             ? AttributeList::get(
-                   pImpl->getContext(),
-                   ArrayRef<std::pair<unsigned, AttributeSetNode *>>(
-                       std::make_pair(Index, getAttributes(Index))))
-             : AttributeList();
-}
-
-AttributeList AttributeList::getRetAttributes() const {
-  return pImpl && hasAttributes(ReturnIndex)
-             ? AttributeList::get(
-                   pImpl->getContext(),
-                   ArrayRef<std::pair<unsigned, AttributeSetNode *>>(
-                       std::make_pair(ReturnIndex, getAttributes(ReturnIndex))))
-             : AttributeList();
-}
-
-AttributeList AttributeList::getFnAttributes() const {
-  return pImpl && hasAttributes(FunctionIndex)
-             ? AttributeList::get(
-                   pImpl->getContext(),
-                   ArrayRef<std::pair<unsigned, AttributeSetNode *>>(
-                       std::make_pair(FunctionIndex,
-                                      getAttributes(FunctionIndex))))
-             : AttributeList();
+AttributeSetNode *AttributeList::getParamAttributes(unsigned Index) const {
+  return getAttributes(Index);
+}
+
+AttributeSetNode *AttributeList::getRetAttributes() const {
+  return getAttributes(ReturnIndex);
+}
+
+AttributeSetNode *AttributeList::getFnAttributes() const {
+  return getAttributes(FunctionIndex);
 }
 
 bool AttributeList::hasAttribute(unsigned Index,
                                  Attribute::AttrKind Kind) const {
   AttributeSetNode *ASN = getAttributes(Index);
   return ASN && ASN->hasAttribute(Kind);
 }
 
for (unsigned I = 0, E = pImpl->getNumSlots(); I != E; ++I) {
     for (AttributeListImpl::iterator II = pImpl->begin(I), IE = pImpl->end(I);
          II != IE; ++II)
       addAttribute(*II);
 
     break;
   }
 }
 
+AttrBuilder::AttrBuilder(AttributeSetNode *AS) {
+  if (AS) {
+    for (const Attribute &A : *AS)
+      addAttribute(A);
+  }
+}
+
 void AttrBuilder::clear() {
   Attrs.reset();
   TargetDepAttrs.clear();
   Alignment = StackAlignment = DerefBytes = DerefOrNullBytes = 0;
   AllocSizeArgs = 0;
 }
 
 AttrBuilder &AttrBuilder::addAttribute(Attribute::AttrKind Val) {

llvm/lib/IR/Core.cpp

 // for libLLVMCore.a, which implements the LLVM intermediate representation.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm-c/Core.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/IR/Attributes.h"
-#include "AttributeSetNode.h"
+#include "llvm/IR/AttributeSetNode.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/DiagnosticInfo.h"
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/IRBuilder.h"

llvm/lib/Transforms/IPO/ArgumentPromotion.cpp

 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AssumptionCache.h"
 #include "llvm/Analysis/BasicAliasAnalysis.h"
 #include "llvm/Analysis/CallGraph.h"
 #include "llvm/Analysis/CallGraphSCCPass.h"
 #include "llvm/Analysis/LazyCallGraph.h"
 #include "llvm/Analysis/Loads.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
+#include "llvm/IR/AttributeSetNode.h"
 #include "llvm/IR/CFG.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/LLVMContext.h"
doPromotion(Function *F, SmallPtrSetImpl<Argument *> &ArgsToPromote,
   // what the new GEP/Load instructions we are inserting look like.
   // We need to keep the original loads for each argument and the elements
   // of the argument that are accessed.
   std::map<std::pair<Argument *, IndicesVector>, LoadInst *> OriginalLoads;
 
   // Attribute - Keep track of the parameter attributes for the arguments
   // that we are *not* promoting. For the ones that we do promote, the parameter
   // attributes are lost
-  SmallVector<AttributeList, 8> AttributesVec;
+  SmallVector<AttributeSetNode *, 8> AttributesVec;
   const AttributeList &PAL = F->getAttributes();
 
   // Add any return attributes.
-  if (PAL.hasAttributes(AttributeList::ReturnIndex))
-    AttributesVec.push_back(
-        AttributeList::get(F->getContext(), PAL.getRetAttributes()));
+  AttributesVec.push_back(PAL.getRetAttributes());
 
   // First, determine the new argument list
   unsigned ArgIndex = 1;
   for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
        ++I, ++ArgIndex) {
     if (ByValArgsToTransform.count(&*I)) {
       // Simple byval argument? Just add all the struct element types.
       Type *AgTy = cast<PointerType>(I->getType())->getElementType();
       StructType *STy = cast<StructType>(AgTy);
       Params.insert(Params.end(), STy->element_begin(), STy->element_end());
+      AttributesVec.insert(AttributesVec.end(), STy->getNumElements(), nullptr);
       ++NumByValArgsPromoted;
     } else if (!ArgsToPromote.count(&*I)) {
       // Unchanged argument
       Params.push_back(I->getType());
-      AttributeList attrs = PAL.getParamAttributes(ArgIndex);
-      if (attrs.hasAttributes(ArgIndex)) {
-        AttrBuilder B(attrs, ArgIndex);
-        AttributesVec.push_back(
-            AttributeList::get(F->getContext(), Params.size(), B));
-      }
+      AttributesVec.push_back(PAL.getParamAttributes(ArgIndex));
     } else if (I->use_empty()) {
       // Dead argument (which are always marked as promotable)
       ++NumArgumentsDead;
     } else {
       // Okay, this is being promoted. This means that the only uses are loads
       // or GEPs which are only used by loads
 
       // In this table, we will track which indices are loaded from the argument
if (ByValArgsToTransform.count(&*I)) {
       }
 
       // Add a parameter to the function for each element passed in.
       for (const auto &ArgIndex : ArgIndices) {
         // not allowed to dereference ->begin() if size() is 0
         Params.push_back(GetElementPtrInst::getIndexedType(
             cast<PointerType>(I->getType()->getScalarType())->getElementType(),
             ArgIndex.second));
+        AttributesVec.push_back(nullptr);
         assert(Params.back());
       }
 
       if (ArgIndices.size() == 1 && ArgIndices.begin()->second.empty())
         ++NumArgumentsPromoted;
       else
         ++NumAggregatesPromoted;
     }
   }
 
   // Add any function attributes.
-  if (PAL.hasAttributes(AttributeList::FunctionIndex))
-    AttributesVec.push_back(
-        AttributeList::get(FTy->getContext(), PAL.getFnAttributes()));
+  AttributesVec.push_back(PAL.getFnAttributes());
 
   Type *RetTy = FTy->getReturnType();
 
   // Construct the new function type using the new arguments.
   FunctionType *NFTy = FunctionType::get(RetTy, Params, FTy->isVarArg());
 
   // Create the new function body and insert it into the module.
   Function *NF = Function::Create(NFTy, F->getLinkage(), F->getName());
doPromotion(Function *F, SmallPtrSetImpl<Argument *> &ArgsToPromote,
   SmallVector<Value *, 16> Args;
   while (!F->use_empty()) {
     CallSite CS(F->user_back());
     assert(CS.getCalledFunction() == F);
     Instruction *Call = CS.getInstruction();
     const AttributeList &CallPAL = CS.getAttributes();
 
     // Add any return attributes.
-    if (CallPAL.hasAttributes(AttributeList::ReturnIndex))
-      AttributesVec.push_back(
-          AttributeList::get(F->getContext(), CallPAL.getRetAttributes()));
+    AttributesVec.push_back(CallPAL.getRetAttributes());
 
     // Loop over the operands, inserting GEP and loads in the caller as
     // appropriate.
     CallSite::arg_iterator AI = CS.arg_begin();
     ArgIndex = 1;
     for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
          ++I, ++AI, ++ArgIndex)
       if (!ArgsToPromote.count(&*I) && !ByValArgsToTransform.count(&*I)) {
         Args.push_back(*AI); // Unmodified argument
-
-        if (CallPAL.hasAttributes(ArgIndex)) {
-          AttrBuilder B(CallPAL, ArgIndex);
-          AttributesVec.push_back(
-              AttributeList::get(F->getContext(), Args.size(), B));
-        }
+        AttributesVec.push_back(CallPAL.getAttributes(ArgIndex));
       } else if (ByValArgsToTransform.count(&*I)) {
         // Emit a GEP and load for each element of the struct.
         Type *AgTy = cast<PointerType>(I->getType())->getElementType();
         StructType *STy = cast<StructType>(AgTy);
         Value *Idxs[2] = {
             ConstantInt::get(Type::getInt32Ty(F->getContext()), 0), nullptr};
         for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
           Idxs[1] = ConstantInt::get(Type::getInt32Ty(F->getContext()), i);
           Value *Idx = GetElementPtrInst::Create(
               STy, *AI, Idxs, (*AI)->getName() + "." + Twine(i), Call);
           // TODO: Tell AA about the new values?
           Args.push_back(new LoadInst(Idx, Idx->getName() + ".val", Call));
+          AttributesVec.push_back(nullptr);
         }
       } else if (!I->use_empty()) {
         // Non-dead argument: insert GEPs and loads as appropriate.
         ScalarizeTable &ArgIndices = ScalarizedElements[&*I];
         // Store the Value* version of the indices in here, but declare it now
         // for reuse.
         std::vector<Value *> Ops;
         for (const auto &ArgIndex : ArgIndices) {
for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end(); I != E;
           LoadInst *newLoad = new LoadInst(V, V->getName() + ".val", Call);
           newLoad->setAlignment(OrigLoad->getAlignment());
           // Transfer the AA info too.
           AAMDNodes AAInfo;
           OrigLoad->getAAMetadata(AAInfo);
           newLoad->setAAMetadata(AAInfo);
 
           Args.push_back(newLoad);
+          AttributesVec.push_back(nullptr);
         }
       }
 
     // Push any varargs arguments on the list.
     for (; AI != CS.arg_end(); ++AI, ++ArgIndex) {
       Args.push_back(*AI);
-      if (CallPAL.hasAttributes(ArgIndex)) {
-        AttrBuilder B(CallPAL, ArgIndex);
-        AttributesVec.push_back(
-            AttributeList::get(F->getContext(), Args.size(), B));
-      }
+      AttributesVec.push_back(CallPAL.getAttributes(ArgIndex));
     }
 
     // Add any function attributes.
-    if (CallPAL.hasAttributes(AttributeList::FunctionIndex))
-      AttributesVec.push_back(
-          AttributeList::get(Call->getContext(), CallPAL.getFnAttributes()));
+    AttributesVec.push_back(CallPAL.getFnAttributes());
 
     SmallVector<OperandBundleDef, 1> OpBundles;
     CS.getOperandBundlesAsDefs(OpBundles);
 
     Instruction *New;
     if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
       New = InvokeInst::Create(NF, II->getNormalDest(), II->getUnwindDest(),
                                Args, OpBundles, "", Call);

llvm/lib/Transforms/IPO/DeadArgumentElimination.cpp

 // interprocedural passes, which add possibly-dead arguments or return values.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Transforms/IPO/DeadArgumentElimination.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/StringExtras.h"
+#include "llvm/IR/AttributeSetNode.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/DIBuilder.h"
 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"
for (Value::user_iterator I = Fn.user_begin(), E = Fn.user_end(); I != E; ) {
 
     // Drop any attributes that were on the vararg arguments.
     AttributeList PAL = CS.getAttributes();
     if (!PAL.isEmpty() && PAL.getSlotIndex(PAL.getNumSlots() - 1) > NumArgs) {
       SmallVector<AttributeList, 8> AttributesVec;
       for (unsigned i = 0; PAL.getSlotIndex(i) <= NumArgs; ++i)
         AttributesVec.push_back(PAL.getSlotAttributes(i));
       if (PAL.hasAttributes(AttributeList::FunctionIndex))
-        AttributesVec.push_back(
-            AttributeList::get(Fn.getContext(), PAL.getFnAttributes()));
+        AttributesVec.push_back(AttributeList::get(Fn.getContext(),
+                                                   AttributeList::FunctionIndex,
+                                                   PAL.getFnAttributes()));
       PAL = AttributeList::get(Fn.getContext(), AttributesVec);
     }
 
     SmallVector<OperandBundleDef, 1> OpBundles;
     CS.getOperandBundlesAsDefs(OpBundles);
 
     Instruction *New;
     if (InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
bool DeadArgumentEliminationPass::RemoveDeadStuffFromFunction(Function *F) {
   // the old function, but has fewer arguments and a different return type.
   FunctionType *FTy = F->getFunctionType();
   std::vector<Type*> Params;
 
   // Keep track of if we have a live 'returned' argument
   bool HasLiveReturnedArg = false;
 
   // Set up to build a new list of parameter attributes.
-  SmallVector<AttributeList, 8> AttributesVec;
+  SmallVector<AttributeSetNode *, 8> AttributesVec;
   const AttributeList &PAL = F->getAttributes();
 
+  // Reserve an empty slot for the return value attributes, which we will
+  // compute last.
+  AttributesVec.push_back(nullptr);
+
   // Remember which arguments are still alive.
   SmallVector<bool, 10> ArgAlive(FTy->getNumParams(), false);
   // Construct the new parameter list from non-dead arguments. Also construct
   // a new set of parameter attributes to correspond. Skip the first parameter
   // attribute, since that belongs to the return value.
   unsigned i = 0;
   for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
        I != E; ++I, ++i) {
     RetOrArg Arg = CreateArg(F, i);
     if (LiveValues.erase(Arg)) {
       Params.push_back(I->getType());
       ArgAlive[i] = true;
-
-      // Get the original parameter attributes (skipping the first one, that is
-      // for the return value.
-      if (PAL.hasAttributes(i + 1)) {
-        AttrBuilder B(PAL, i + 1);
-        if (B.contains(Attribute::Returned))
-          HasLiveReturnedArg = true;
-        AttributesVec.push_back(
-            AttributeList::get(F->getContext(), Params.size(), B));
-      }
+      AttributesVec.push_back(PAL.getParamAttributes(i + 1));
+      HasLiveReturnedArg |= PAL.hasAttribute(i + 1, Attribute::Returned);
     } else {
       ++NumArgumentsEliminated;
       DEBUG(dbgs() << "DeadArgumentEliminationPass - Removing argument " << i
                    << " (" << I->getName() << ") from " << F->getName()
                    << "\n");
     }
   }
 
if (RetTy->isVoidTy() || HasLiveReturnedArg) {
     else if (RetTypes.size() == 0)
       // No return types? Make it void, but only if we didn't use to return {}.
       NRetTy = Type::getVoidTy(F->getContext());
   }
 
   assert(NRetTy && "No new return type found?");
 
   // The existing function return attributes.
-  AttributeList RAttrs = PAL.getRetAttributes();
+  AttrBuilder RAttrs(PAL.getRetAttributes());
 
   // Remove any incompatible attributes, but only if we removed all return
   // values. Otherwise, ensure that we don't have any conflicting attributes
   // here. Currently, this should not be possible, but special handling might be
   // required when new return value attributes are added.
   if (NRetTy->isVoidTy())
-    RAttrs = RAttrs.removeAttributes(NRetTy->getContext(),
-                                     AttributeList::ReturnIndex,
-                                     AttributeFuncs::typeIncompatible(NRetTy));
+    RAttrs.remove(AttributeFuncs::typeIncompatible(NRetTy));
   else
-    assert(!AttrBuilder(RAttrs, AttributeList::ReturnIndex)
-                .overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
+    assert(!RAttrs.overlaps(AttributeFuncs::typeIncompatible(NRetTy)) &&
            "Return attributes no longer compatible?");
 
-  if (RAttrs.hasAttributes(AttributeList::ReturnIndex))
-    AttributesVec.push_back(AttributeList::get(NRetTy->getContext(), RAttrs));
+  AttributesVec[0] = AttributeSetNode::get(F->getContext(), RAttrs);
 
-  if (PAL.hasAttributes(AttributeList::FunctionIndex))
-    AttributesVec.push_back(
-        AttributeList::get(F->getContext(), PAL.getFnAttributes()));
+  // Transfer the function attributes, if any.
+  AttributesVec.push_back(PAL.getFnAttributes());
 
   // Reconstruct the AttributesList based on the vector we constructed.
+  assert(AttributesVec.size() == Params.size() + 2);
   AttributeList NewPAL = AttributeList::get(F->getContext(), AttributesVec);
 
   // Create the new function type based on the recomputed parameters.
   FunctionType *NFTy = FunctionType::get(NRetTy, Params, FTy->isVarArg());
 
   // No change?
   if (NFTy == FTy)
     return false;
bool DeadArgumentEliminationPass::RemoveDeadStuffFromFunction(Function *F) {
   std::vector<Value*> Args;
   while (!F->use_empty()) {
     CallSite CS(F->user_back());
     Instruction *Call = CS.getInstruction();
 
     AttributesVec.clear();
     const AttributeList &CallPAL = CS.getAttributes();
 
-    // The call return attributes.
-    AttributeList RAttrs = CallPAL.getRetAttributes();
-
-    // Adjust in case the function was changed to return void.
-    RAttrs = RAttrs.removeAttributes(
-        NRetTy->getContext(), AttributeList::ReturnIndex,
-        AttributeFuncs::typeIncompatible(NF->getReturnType()));
-    if (RAttrs.hasAttributes(AttributeList::ReturnIndex))
-      AttributesVec.push_back(AttributeList::get(NF->getContext(), RAttrs));
+    // Adjust the call return attributes in case the function was changed to
+    // return void.
+    AttrBuilder RAttrs(CallPAL.getRetAttributes());
+    RAttrs.remove(AttributeFuncs::typeIncompatible(NRetTy));
+    AttributesVec.push_back(AttributeSetNode::get(F->getContext(), RAttrs));
 
     // Declare these outside of the loops, so we can reuse them for the second
     // loop, which loops the varargs.
     CallSite::arg_iterator I = CS.arg_begin();
     unsigned i = 0;
     // Loop over those operands, corresponding to the normal arguments to the
     // original function, and add those that are still alive.
     for (unsigned e = FTy->getNumParams(); i != e; ++I, ++i)
       if (ArgAlive[i]) {
         Args.push_back(*I);
         // Get original parameter attributes, but skip return attributes.
-        if (CallPAL.hasAttributes(i + 1)) {
-          AttrBuilder B(CallPAL, i + 1);
+        AttributeSetNode *Attrs = CallPAL.getParamAttributes(i + 1);
+        if (NRetTy != RetTy && Attrs &&
+            Attrs->hasAttribute(Attribute::Returned)) {
           // If the return type has changed, then get rid of 'returned' on the
           // call site. The alternative is to make all 'returned' attributes on
           // call sites keep the return value alive just like 'returned'
-          // attributes on function declaration but it's less clearly a win
-          // and this is not an expected case anyway
-          if (NRetTy != RetTy && B.contains(Attribute::Returned))
-            B.removeAttribute(Attribute::Returned);
-          AttributesVec.push_back(
-              AttributeList::get(F->getContext(), Args.size(), B));
+          // attributes on function declaration but it's less clearly a win and
+          // this is not an expected case anyway
+          AttributesVec.push_back(AttributeSetNode::get(
+              F->getContext(),
+              AttrBuilder(Attrs).removeAttribute(Attribute::Returned)));
+        } else {
+          // Otherwise, use the original attributes.
+          AttributesVec.push_back(Attrs);
         }
       }
 
     // Push any varargs arguments on the list. Don't forget their attributes.
     for (CallSite::arg_iterator E = CS.arg_end(); I != E; ++I, ++i) {
       Args.push_back(*I);
-      if (CallPAL.hasAttributes(i + 1)) {
-        AttrBuilder B(CallPAL, i + 1);
-        AttributesVec.push_back(
-            AttributeList::get(F->getContext(), Args.size(), B));
-      }
+      AttributesVec.push_back(CallPAL.getParamAttributes(i + 1));
     }
 
-    if (CallPAL.hasAttributes(AttributeList::FunctionIndex))
-      AttributesVec.push_back(
-          AttributeList::get(Call->getContext(), CallPAL.getFnAttributes()));
+    AttributesVec.push_back(CallPAL.getFnAttributes());
 
     // Reconstruct the AttributesList based on the vector we constructed.
     AttributeList NewCallPAL =
         AttributeList::get(F->getContext(), AttributesVec);
 
     SmallVector<OperandBundleDef, 1> OpBundles;
     CS.getOperandBundlesAsDefs(OpBundles);
 

llvm/lib/Transforms/IPO/MergeFunctions.cpp

if (CS && CS.isCallee(U)) {
       auto &Context = New->getContext();
       auto NewFuncAttrs = New->getAttributes();
       auto CallSiteAttrs = CS.getAttributes();
 
       CallSiteAttrs = CallSiteAttrs.addAttributes(
           Context, AttributeList::ReturnIndex, NewFuncAttrs.getRetAttributes());
 
       for (unsigned argIdx = 0; argIdx < CS.arg_size(); argIdx++) {
-        AttributeList Attrs = NewFuncAttrs.getParamAttributes(argIdx);
-        if (Attrs.getNumSlots())
+        if (AttributeSetNode *Attrs = NewFuncAttrs.getParamAttributes(argIdx))
           CallSiteAttrs = CallSiteAttrs.addAttributes(Context, argIdx, Attrs);
       }
 
       CS.setAttributes(CallSiteAttrs);
 
       remove(CS.getInstruction()->getParent()->getParent());
       U->set(BitcastNew);
     }

llvm/lib/Transforms/InstCombine/InstCombineCalls.cpp

 #include "llvm/ADT/None.h"
 #include "llvm/ADT/Statistic.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Analysis/MemoryBuiltins.h"
 #include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/AttributeSetNode.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/CallSite.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/InstrTypes.h"
bool InstCombiner::transformConstExprCastCall(CallSite CS) {
   CallSite::arg_iterator AI = CS.arg_begin();
   for (unsigned i = 0, e = NumCommonArgs; i != e; ++i, ++AI) {
     Type *ParamTy = FT->getParamType(i);
     Type *ActTy = (*AI)->getType();
 
     if (!CastInst::isBitOrNoopPointerCastable(ActTy, ParamTy, DL))
       return false;   // Cannot transform this parameter value.
 
-    if (AttrBuilder(CallerPAL.getParamAttributes(i + 1), i + 1).
+    if (AttrBuilder(CallerPAL.getParamAttributes(i + 1)).
           overlaps(AttributeFuncs::typeIncompatible(ParamTy)))
       return false;   // Attribute not compatible with transformed value.
 
     if (CS.isInAllocaArgument(i))
       return false;   // Cannot transform to and from inalloca.
 
     // If the parameter is passed as a byval argument, then we have to have a
     // sized type and the sized type has to have the same size as the old type.
-    if (ParamTy != ActTy &&
-        CallerPAL.getParamAttributes(i + 1).hasAttribute(i + 1,
-                                                         Attribute::ByVal)) {
+    if (ParamTy != ActTy && CallerPAL.hasAttribute(i + 1, Attribute::ByVal)) {
       PointerType *ParamPTy = dyn_cast<PointerType>(ParamTy);
       if (!ParamPTy || !ParamPTy->getElementType()->isSized())
         return false;
 
       Type *CurElTy = ActTy->getPointerElementType();
       if (DL.getTypeAllocSize(CurElTy) !=
           DL.getTypeAllocSize(ParamPTy->getElementType()))
         return false;
for (unsigned i = 0; i != NumCommonArgs; ++i, ++AI) {
 
     if ((*AI)->getType() == ParamTy) {
       Args.push_back(*AI);
     } else {
       Args.push_back(Builder->CreateBitOrPointerCast(*AI, ParamTy));
     }
 
     // Add any parameter attributes.
-    AttrBuilder PAttrs(CallerPAL.getParamAttributes(i + 1), i + 1);
+    AttrBuilder PAttrs(CallerPAL.getParamAttributes(i + 1));
     if (PAttrs.hasAttributes())
       attrVec.push_back(
           AttributeList::get(Caller->getContext(), i + 1, PAttrs));
   }
 
   // If the function takes more arguments than the call was taking, add them
   // now.
   for (unsigned i = NumCommonArgs; i != FT->getNumParams(); ++i)
if (FT->isVarArg()) {
           Instruction::CastOps opcode =
             CastInst::getCastOpcode(*AI, false, PTy, false);
           Args.push_back(Builder->CreateCast(opcode, *AI, PTy));
         } else {
           Args.push_back(*AI);
         }
 
         // Add any parameter attributes.
-        AttrBuilder PAttrs(CallerPAL.getParamAttributes(i + 1), i + 1);
+        AttrBuilder PAttrs(CallerPAL.getParamAttributes(i + 1));
         if (PAttrs.hasAttributes())
           attrVec.push_back(
               AttributeList::get(FT->getContext(), i + 1, PAttrs));
       }
     }
   }
 
-  AttributeList FnAttrs = CallerPAL.getFnAttributes();
+  AttributeSetNode *FnAttrs = CallerPAL.getFnAttributes();
   if (CallerPAL.hasAttributes(AttributeList::FunctionIndex))
-    attrVec.push_back(AttributeList::get(Callee->getContext(), FnAttrs));
+    attrVec.push_back(AttributeList::get(Callee->getContext(),
+                                         AttributeList::FunctionIndex,
+                                         AttrBuilder(FnAttrs)));
 
   if (NewRetTy->isVoidTy())
     Caller->setName("");   // Void type should not have a name.
 
   const AttributeList &NewCallerPAL =
       AttributeList::get(Callee->getContext(), attrVec);
 
   SmallVector<OperandBundleDef, 1> OpBundles;

 /// Turn a call to a function created by init_trampoline / adjust_trampoline
 /// intrinsic pair into a direct call to the underlying function.
 Instruction *
 InstCombiner::transformCallThroughTrampoline(CallSite CS,
                                              IntrinsicInst *Tramp) {
   Value *Callee = CS.getCalledValue();
   PointerType *PTy = cast<PointerType>(Callee->getType());
   FunctionType *FTy = cast<FunctionType>(PTy->getElementType());
-  const AttributeList &Attrs = CS.getAttributes();
+  AttributeList Attrs = CS.getAttributes();
 
   // If the call already has the 'nest' attribute somewhere then give up -
   // otherwise 'nest' would occur twice after splicing in the chain.
   if (Attrs.hasAttrSomewhere(Attribute::Nest))
     return nullptr;
 
   assert(Tramp &&
          "transformCallThroughTrampoline called with incorrect CallSite.");
 
   Function *NestF =cast<Function>(Tramp->getArgOperand(1)->stripPointerCasts());
   FunctionType *NestFTy = cast<FunctionType>(NestF->getValueType());
 
-  const AttributeList &NestAttrs = NestF->getAttributes();
+  AttributeList NestAttrs = NestF->getAttributes();
   if (!NestAttrs.isEmpty()) {
     unsigned NestIdx = 1;
     Type *NestTy = nullptr;
-    AttributeList NestAttr;
+    AttributeSetNode *NestAttr;
 
     // Look for a parameter marked with the 'nest' attribute.
     for (FunctionType::param_iterator I = NestFTy->param_begin(),
          E = NestFTy->param_end(); I != E; ++NestIdx, ++I)
       if (NestAttrs.hasAttribute(NestIdx, Attribute::Nest)) {
         // Record the parameter type and any other attributes.
         NestTy = *I;
         NestAttr = NestAttrs.getParamAttributes(NestIdx);
         break;
       }
 
     if (NestTy) {
       Instruction *Caller = CS.getInstruction();
       std::vector<Value*> NewArgs;
+      std::vector<AttributeSetNode *> NewAttrs;
       NewArgs.reserve(CS.arg_size() + 1);
-
-      SmallVector<AttributeList, 8> NewAttrs;
-      NewAttrs.reserve(Attrs.getNumSlots() + 1);
+      NewAttrs.reserve(CS.arg_size() + 2);
 
       // Insert the nest argument into the call argument list, which may
       // mean appending it.  Likewise for attributes.
 
       // Add any result attributes.
-      if (Attrs.hasAttributes(AttributeList::ReturnIndex))
-        NewAttrs.push_back(
-            AttributeList::get(Caller->getContext(), Attrs.getRetAttributes()));
+      NewAttrs.push_back(Attrs.getRetAttributes());
 
       {
         unsigned Idx = 1;
         CallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
         do {
           if (Idx == NestIdx) {
             // Add the chain argument and attributes.
             Value *NestVal = Tramp->getArgOperand(2);
             if (NestVal->getType() != NestTy)
               NestVal = Builder->CreateBitCast(NestVal, NestTy, "nest");
             NewArgs.push_back(NestVal);
-            NewAttrs.push_back(
-                AttributeList::get(Caller->getContext(), NestAttr));
+            NewAttrs.push_back(NestAttr);
           }
 
           if (I == E)
             break;
 
           // Add the original argument and attributes.
           NewArgs.push_back(*I);
-          AttributeList Attr = Attrs.getParamAttributes(Idx);
-          if (Attr.hasAttributes(Idx)) {
-            AttrBuilder B(Attr, Idx);
-            NewAttrs.push_back(AttributeList::get(Caller->getContext(),
-                                                  Idx + (Idx >= NestIdx), B));
-          }
+          NewAttrs.push_back(Attrs.getParamAttributes(Idx));
 
           ++Idx;
           ++I;
         } while (true);
       }
 
       // Add any function attributes.
-      if (Attrs.hasAttributes(AttributeList::FunctionIndex))
-        NewAttrs.push_back(
-            AttributeList::get(FTy->getContext(), Attrs.getFnAttributes()));
+      NewAttrs.push_back(Attrs.getFnAttributes());
 
       // The trampoline may have been bitcast to a bogus type (FTy).
       // Handle this by synthesizing a new function type, equal to FTy
       // with the chain parameter inserted.
 
       std::vector<Type*> NewTypes;
       NewTypes.reserve(FTy->getNumParams()+1);
 
if (NestTy) {
       // Replace the trampoline call with a direct call.  Let the generic
       // code sort out any function type mismatches.
       FunctionType *NewFTy = FunctionType::get(FTy->getReturnType(), NewTypes,
                                                 FTy->isVarArg());
       Constant *NewCallee =
         NestF->getType() == PointerType::getUnqual(NewFTy) ?
         NestF : ConstantExpr::getBitCast(NestF,
                                          PointerType::getUnqual(NewFTy));
-      const AttributeList &NewPAL =
-          AttributeList::get(FTy->getContext(), NewAttrs);
+      AttributeList NewPAL = AttributeList::get(FTy->getContext(), NewAttrs);
 
       SmallVector<OperandBundleDef, 1> OpBundles;
       CS.getOperandBundlesAsDefs(OpBundles);
 
       Instruction *NewCaller;
       if (InvokeInst *II = dyn_cast<InvokeInst>(Caller)) {
         NewCaller = InvokeInst::Create(NewCallee,
                                        II->getNormalDest(), II->getUnwindDest(),

llvm/lib/Transforms/Scalar/RewriteStatepointsForGC.cpp

if (F->getIntrinsicID() == Intrinsic::experimental_deoptimize) {
           F->getParent()->getOrInsertFunction("__llvm_deoptimize", FTy);
 
       IsDeoptimize = true;
     }
   }
 
   // Create the statepoint given all the arguments
   Instruction *Token = nullptr;
-  AttributeList ReturnAttrs;
   if (CS.isCall()) {
     CallInst *ToReplace = cast<CallInst>(CS.getInstruction());
     CallInst *Call = Builder.CreateGCStatepointCall(
         StatepointID, NumPatchBytes, CallTarget, Flags, CallArgs,
         TransitionArgs, DeoptArgs, GCArgs, "safepoint_token");
 
     Call->setTailCallKind(ToReplace->getTailCallKind());
     Call->setCallingConv(ToReplace->getCallingConv());
 
     // Currently we will fail on parameter attributes and on certain
     // function attributes.
     AttributeList NewAttrs = legalizeCallAttributes(ToReplace->getAttributes());
     // In case if we can handle this set of attributes - set up function attrs
     // directly on statepoint and return attrs later for gc_result intrinsic.
-    Call->setAttributes(NewAttrs.getFnAttributes());
-    ReturnAttrs = NewAttrs.getRetAttributes();
+    Call->setAttributes(AttributeList::get(Call->getContext(),
+                                           AttributeList::FunctionIndex,
+                                           NewAttrs.getFnAttributes()));
 
     Token = Call;
 
     // Put the following gc_result and gc_relocate calls immediately after the
     // the old call (which we're about to delete)
     assert(ToReplace->getNextNode() && "Not a terminator, must have next!");
     Builder.SetInsertPoint(ToReplace->getNextNode());
     Builder.SetCurrentDebugLocation(ToReplace->getNextNode()->getDebugLoc());
if (CS.isCall()) {
 
     Invoke->setCallingConv(ToReplace->getCallingConv());
 
     // Currently we will fail on parameter attributes and on certain
     // function attributes.
     AttributeList NewAttrs = legalizeCallAttributes(ToReplace->getAttributes());
     // In case if we can handle this set of attributes - set up function attrs
     // directly on statepoint and return attrs later for gc_result intrinsic.
-    Invoke->setAttributes(NewAttrs.getFnAttributes());
-    ReturnAttrs = NewAttrs.getRetAttributes();
+    Invoke->setAttributes(AttributeList::get(Invoke->getContext(),
+                                             AttributeList::FunctionIndex,
+                                             NewAttrs.getFnAttributes()));
 
     Token = Invoke;
 
     // Generate gc relocates in exceptional path
     BasicBlock *UnwindBlock = ToReplace->getUnwindDest();
     assert(!isa<PHINode>(UnwindBlock->begin()) &&
            UnwindBlock->getUniquePredecessor() &&
            "can't safely insert in this block!");
if (IsDeoptimize) {
     Replacements.push_back(
         DeferredReplacement::createDeoptimizeReplacement(CS.getInstruction()));
   } else {
     Token->setName("statepoint_token");
     if (!CS.getType()->isVoidTy() && !CS.getInstruction()->use_empty()) {
       StringRef Name =
           CS.getInstruction()->hasName() ? CS.getInstruction()->getName() : "";
       CallInst *GCResult = Builder.CreateGCResult(Token, CS.getType(), Name);
-      GCResult->setAttributes(CS.getAttributes().getRetAttributes());
+      GCResult->setAttributes(
+          AttributeList::get(GCResult->getContext(), AttributeList::ReturnIndex,
+                             CS.getAttributes().getRetAttributes()));
 
       // We cannot RAUW or delete CS.getInstruction() because it could be in the
       // live set of some other safepoint, in which case that safepoint's
       // PartiallyConstructedSafepointRecord will hold a raw pointer to this
       // llvm::Instruction.  Instead, we defer the replacement and deletion to
       // after the live sets have been made explicit in the IR, and we no longer
       // have raw pointers to worry about.
       Replacements.emplace_back(

llvm/lib/Transforms/Utils/CloneFunction.cpp

#endif
 
   // Fix up the personality function that got copied over.
   if (OldFunc->hasPersonalityFn())
     NewFunc->setPersonalityFn(
         MapValue(OldFunc->getPersonalityFn(), VMap,
                  ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,
                  TypeMapper, Materializer));
 
+  SmallVector<std::pair<unsigned, AttributeSetNode*>, 4> AttrVec;
   AttributeList OldAttrs = OldFunc->getAttributes();
+
+  // Copy the return attributes.
+  if (auto *RetAttrs = OldAttrs.getRetAttributes())
+    AttrVec.emplace_back(AttributeList::ReturnIndex, RetAttrs);
+
   // Clone any argument attributes that are present in the VMap.
   for (const Argument &OldArg : OldFunc->args())
     if (Argument *NewArg = dyn_cast<Argument>(VMap[&OldArg])) {
-      AttributeList attrs = OldAttrs.getParamAttributes(OldArg.getArgNo() + 1);
-      if (attrs.getNumSlots() > 0)
-        NewArg->addAttr(attrs);
+      if (auto *ParmAttrs = OldAttrs.getParamAttributes(OldArg.getArgNo() + 1))
+        AttrVec.emplace_back(NewArg->getArgNo() + 1, ParmAttrs);
     }
 
-  NewFunc->setAttributes(
-      NewFunc->getAttributes()
-          .addAttributes(NewFunc->getContext(), AttributeList::ReturnIndex,
-                         OldAttrs.getRetAttributes())
-          .addAttributes(NewFunc->getContext(), AttributeList::FunctionIndex,
-                         OldAttrs.getFnAttributes()));
+  // Copy any function attributes.
+  if (auto *FnAttrs = OldAttrs.getFnAttributes())
+    AttrVec.emplace_back(AttributeList::FunctionIndex, FnAttrs);
+
+  NewFunc->setAttributes(AttributeList::get(NewFunc->getContext(), AttrVec));
 
   SmallVector<std::pair<unsigned, MDNode *>, 1> MDs;
   OldFunc->getAllMetadata(MDs);
   for (auto MD : MDs)
     NewFunc->addMetadata(
         MD.first,
         *MapMetadata(MD.second, VMap,
                      ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges,

llvm/lib/Transforms/Utils/CodeExtractor.cpp

if (oldFunction->hasUWTable())
     newFunction->setHasUWTable();
 
   // Inherit all of the target dependent attributes.
   //  (e.g. If the extracted region contains a call to an x86.sse
   //  instruction we need to make sure that the extracted region has the
   //  "target-features" attribute allowing it to be lowered.
   // FIXME: This should be changed to check to see if a specific
   //           attribute can not be inherited.
-  AttributeList OldFnAttrs = oldFunction->getAttributes().getFnAttributes();
-  AttrBuilder AB(OldFnAttrs, AttributeList::FunctionIndex);
+  AttrBuilder AB(oldFunction->getAttributes().getFnAttributes());
   for (const auto &Attr : AB.td_attrs())
     newFunction->addFnAttr(Attr.first, Attr.second);
 
   newFunction->getBasicBlockList().push_back(newRootNode);
 
   // Create an iterator to name all of the arguments we inserted.
   Function::arg_iterator AI = newFunction->arg_begin();