[IR] Refactor GlobalIFunc to inherit from GlobalObject, Remove GlobalIndirectSymbol

[ibookstein]

Summary

As discussed in:

• https://reviews.llvm.org/D94166
• https://lists.llvm.org/pipermail/llvm-dev/2020-September/145031.html

The GlobalIndirectSymbol class lost most of its meaning in
https://reviews.llvm.org/D109792, which disambiguated getBaseObject
(now getAliaseeObject) between GlobalIFunc and everything else.
In addition, as long as GlobalIFunc is not a GlobalObject and
getAliaseeObject returns GlobalObjects, a GlobalAlias whose aliasee
is a GlobalIFunc cannot currently be modeled properly. Creating
aliases for GlobalIFuncs does happen in the wild (e.g. glibc). In addition,
calling getAliaseeObject on a GlobalIFunc will currently return nullptr,
which is undesirable because it should return the object itself for
non-aliases.

This patch refactors the GlobalIFunc class to inherit directly from
GlobalObject, and removes GlobalIndirectSymbol (while inlining the
relevant parts into GlobalAlias and GlobalIFunc). This allows for
calling getAliaseeObject() on a GlobalIFunc to return the GlobalIFunc
itself, making getAliaseeObject() more consistent and enabling
alias-to-ifunc to be properly modeled in the IR.

I exercised some judgement in the API clients of GlobalIndirectSymbol:
some were 'monomorphized' for GlobalAlias and GlobalIFunc, and
some remained shared (with the type adapted to become GlobalValue).

[ibookstein]

Fixed the clang-tidy errors in GlobalIFunc.h.

[dexonsmith]

Just came across this; still thinking about it.

A couple of thoughts, assuming the direction gains consensus:

• It seems like many of the changes in the patch to use GlobalAlias and/or GlobalIFunc directly instead of GlobalIndirectSymbol could be committed separately / ahead of the change to the IR class hierarchy. (Maybe not worth splitting out until direction has consensus, but would be great to do at that point, to isolate the change as much as possible.)

• Would there be a benefit in leaving behind a GlobalIndirectSymbol utility, modeling a union between GlobalAlias and GlobalIFunc? (I seem to remember a CallSite utility before CallInst and InvokeInst shared the common base class CallBase... but I'm not sure if it'd be similarly useful here.)

llvm/unittests/IR/ConstantsTest.cpp

388–389

It's not obvious how this change is related to the patch... did it slip in accidentally?

[ibookstein]

Regarding leaving GlobalIndirectSymbol as a utility class, it seems to me that its utility is in direct proportion to the number of places I ended up converting to use GlobalValue rather than monomorphizing (to the degree that you agree with my tactical decisions in these places, of course :) ).
The major ones were the BitcodeReader, LLParser, IRLinker, SplitModule, ValueMapper.

Regarding the direction gaining consensus in general, I'm wondering myself whether the benefits of this direction outweigh the costs, I mainly wanted a working patch so that the discussion will no longer be theoretical.
Who would we want to weigh in / involve? I think the opinion of someone who understands the reasoning and design behind the GlobalValue <-> GlobalObject <-> GlobalAlias split will be valuable.
Git names @respindola as the author of that split.

Regarding the build error, looks like clang-format disapproves of the indentation in the LLVM_FOR_EACH_VALUE_SUBCLASS macro (I tried preserving its correlation with the class hierarchy).

llvm/unittests/IR/ConstantsTest.cpp

388–389

It's not accidental, but it could definitely be committed separately. It's a bugfix for a type mismatch error that was exposed by the change to the IR class hierarchy, since only afterwards does the code-path of GlobalAlias::create pass through the type check assertion in GlobalAlias::setAliasee:

void GlobalAlias::setAliasee(Constant *Aliasee) {
  assert((!Aliasee || Aliasee->getType() == getType()) &&
         "Alias and aliasee types should match!");
  ...
}

Before the change, the GlobalAlias::create code-path sets the aliasee via the GlobalIndirectSymbol::GlobalIndirectSymbol constructor, which unceremoniously sets Op<0>() = Symbol; without performing the type check (which it can't, because for GlobalIFunc that check would be incorrect).

[ibookstein]

Rebased past merge of https://reviews.llvm.org/D109792
Removed getRootObject

[ibookstein]

Rebased past merge of getBaseObject->getAliaseeObject rename.

[MaskRay]

The current behavior of GlobalValue::getBaseObject is inconsistent. For example, calling getBaseObject on a GlobalAlias whose Aliasee

This description needs update after renaming of getBaseObject.

llvm/docs/LangRef.rst

910

Drop the change?

An ifunc definition can be interposed/preempted.

[ibookstein]

llvm/docs/LangRef.rst

910

The change only documents the existing situation, though, as far as I can tell.
There are tests which check/specify a [PreemptionSpecifier]; If I remember correctly, if you'd drop the PrintDSOLocation/maybeSetDSOLocal you'd get test failures.
I searched for "dso_local ifunc" and got some hits from the tests.

[ibookstein]

Tiny clang-format fix on getGVPartitioningRoot.

[MaskRay]

Thanks. This makes sense. In the inheritance hierachy, GlobalIndirectSymbol does nothing useful now and can just be removed.

I'll wait a few days and commit on your behalf.

llvm/docs/LangRef.rst

910

If that's the case. The documentation change can be pushed separately to reflect the fact that it is unrelated to this change.

Pushed f66b1b2717e84edef8a9e132638de6d866d01eab

llvm/lib/AsmParser/LLParser.cpp

1067

Is this unneeded now?

llvm/lib/Transforms/IPO/LowerTypeTests.cpp

373

drop braces according to https://llvm.org/docs/CodingStandards.html#don-t-use-braces-on-simple-single-statement-bodies-of-if-else-loop-statements

[ibookstein]

llvm/lib/AsmParser/LLParser.cpp

1067

Note that GV is now a borrowed reference from either GA or GI, which are both std::unique_ptr-s. Their ownership is transferred into the Module in the release() calls in the 5 lines immediately above.

llvm/unittests/IR/ConstantsTest.cpp

388–389

@MaskRay this can also be pushed separately if you'd like

[ibookstein]

Fixed brace style comment.

[MaskRay]

This needs a rebase now.

[MaskRay]

clang-format

rebase

[MaskRay]

@ibookstein clang/lib/CodeGen/CodeGenModule.cpp has a use which hasn't been updated. ninja check-clang to run tests.

[ibookstein]

Right, only had llvm enabled so missed that. Looks like it requires a bit of untangling there, will take a deeper look tomorrow.

[ibookstein]

Ugh. should clang accept situations where the resolver of an ifunc is also an ifunc? The semantics are confusing, but neither compiler diagnoses anything:

itay ~/tmp/gis> cat attr-ifunc.c
int qux() { return 44; }
int (*foo_resolver())() { return qux; }
int foo() __attribute__((ifunc("foo_resolver")));

int (*(*bar_resolver_resolver())())() { return foo_resolver; }
int (*bar_resolver())() __attribute__((ifunc("bar_resolver_resolver")));
int bar() __attribute__((ifunc("bar_resolver")));

int main() { return foo() + bar(); }
itay ~/tmp/gis> gcc attr-ifunc.c -o attr-ifunc -g ; ./attr-ifunc
itay ~/tmp/gis [SIGTTIN]> clang-14 attr-ifunc.c -o attr-ifunc -g ; ./attr-ifunc
itay ~/tmp/gis [108]>

[ibookstein]

I'm not completely satisfied with the clang fix, but it passes the existing tests. It preserves the existing behavior of getAliasedGlobal, which drills through ifuncs even in alias-to-ifunc and ifunc-to-ifunc (?!) situations.
I think that following the addition of getResolverFunction, it makes sense for clang and llvm bitcode verifier to diagnose and reject situations where the resolver is not a function or an alias to one, and amend the tests in clang/test/Sema/attr-ifunc.c accordingly.

llvm/docs/LangRef.rst

 IFuncs have a name and a resolver that is a function called by dynamic linker
 that returns address of another function associated with the name.
 
 IFunc may have an optional :ref:`linkage type <linkage>` and an optional
 :ref:`visibility style <visibility>`.
 
 Syntax::
 
-    @<Name> = [Linkage] [Visibility] ifunc <IFuncTy>, <ResolverTy>* @<Resolver>
+    @<Name> = [Linkage] [PreemptionSpecifier] [Visibility] ifunc <IFuncTy>, <ResolverTy>* @<Resolver>
 
 
 .. _langref_comdats:
 
 Comdats
 -------
 
 Comdat IR provides access to object file COMDAT/section group functionality

llvm/include/llvm-c/Core.h

  * available by looking at the Doxygen source code. Instead, look at the
  * source definition of LLVM_FOR_EACH_VALUE_SUBCLASS and note the list
  * of value names given. These value names also correspond to classes in
  * the llvm::Value hierarchy.
  *
  * @{
  */
 
 #define LLVM_FOR_EACH_VALUE_SUBCLASS(macro) \
   macro(Argument)                           \
   macro(BasicBlock)                         \
   macro(InlineAsm)                          \
   macro(User)                               \
     macro(Constant)                         \
       macro(BlockAddress)                   \
       macro(ConstantAggregateZero)          \
       macro(ConstantArray)                  \
       macro(ConstantDataSequential)         \
         macro(ConstantDataArray)            \
         macro(ConstantDataVector)           \
       macro(ConstantExpr)                   \
       macro(ConstantFP)                     \
       macro(ConstantInt)                    \
       macro(ConstantPointerNull)            \
       macro(ConstantStruct)                 \
       macro(ConstantTokenNone)              \
       macro(ConstantVector)                 \
       macro(GlobalValue)                    \
         macro(GlobalAlias)                  \
-        macro(GlobalIFunc)                  \
         macro(GlobalObject)                 \
           macro(Function)                   \
           macro(GlobalVariable)             \
+          macro(GlobalIFunc)                \
       macro(UndefValue)                     \
       macro(PoisonValue)                    \
     macro(Instruction)                      \
       macro(UnaryOperator)                  \
       macro(BinaryOperator)                 \
       macro(CallInst)                       \
         macro(IntrinsicInst)                \
           macro(DbgInfoIntrinsic)           \

llvm/include/llvm/AsmParser/LLParser.h

private:
     bool parseGlobalType(bool &IsConstant);
     bool parseUnnamedGlobal();
     bool parseNamedGlobal();
     bool parseGlobal(const std::string &Name, LocTy NameLoc, unsigned Linkage,
                      bool HasLinkage, unsigned Visibility,
                      unsigned DLLStorageClass, bool DSOLocal,
                      GlobalVariable::ThreadLocalMode TLM,
                      GlobalVariable::UnnamedAddr UnnamedAddr);
-    bool parseIndirectSymbol(const std::string &Name, LocTy NameLoc,
-                             unsigned L, unsigned Visibility,
-                             unsigned DLLStorageClass, bool DSOLocal,
-                             GlobalVariable::ThreadLocalMode TLM,
-                             GlobalVariable::UnnamedAddr UnnamedAddr);
+    bool parseAliasOrIFunc(const std::string &Name, LocTy NameLoc, unsigned L,
+                           unsigned Visibility, unsigned DLLStorageClass,
+                           bool DSOLocal, GlobalVariable::ThreadLocalMode TLM,
     bool parseComdat();
     bool parseStandaloneMetadata();
     bool parseNamedMetadata();
     bool parseMDString(MDString *&Result);
     bool parseMDNodeID(MDNode *&Result);
     bool parseUnnamedAttrGrp();
     bool parseFnAttributeValuePairs(AttrBuilder &B,
                                     std::vector<unsigned> &FwdRefAttrGrps,

llvm/include/llvm/CodeGen/AsmPrinter.h

 class Constant;
 class ConstantArray;
 class DataLayout;
 class DIE;
 class DIEAbbrev;
 class DwarfDebug;
 class GCMetadataPrinter;
 class GCStrategy;
-class GlobalIndirectSymbol;
 class GlobalObject;
 class GlobalValue;
 class GlobalVariable;
 class MachineBasicBlock;
 class MachineConstantPoolValue;
 class MachineDominatorTree;
 class MachineFunction;
 class MachineInstr;
void emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
                           const MachineBasicBlock *MBB, unsigned uid) const;
   void emitLLVMUsedList(const ConstantArray *InitList);
   /// Emit llvm.ident metadata in an '.ident' directive.
   void emitModuleIdents(Module &M);
   /// Emit bytes for llvm.commandline metadata.
   void emitModuleCommandLines(Module &M);
 
   GCMetadataPrinter *GetOrCreateGCPrinter(GCStrategy &S);
-  /// Emit GlobalAlias or GlobalIFunc.
-  void emitGlobalIndirectSymbol(Module &M, const GlobalIndirectSymbol &GIS);
+  void emitGlobalAlias(Module &M, const GlobalAlias &GA);
+  void emitGlobalIFunc(Module &M, const GlobalIFunc &GI);
 
   /// This method decides whether the specified basic block requires a label.
   bool shouldEmitLabelForBasicBlock(const MachineBasicBlock &MBB) const;
 };
 
 } // end namespace llvm
 
 #endif // LLVM_CODEGEN_ASMPRINTER_H

llvm/include/llvm/IR/GlobalAlias.h

 // represents a single function or variable alias in the IR.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_IR_GLOBALALIAS_H
 #define LLVM_IR_GLOBALALIAS_H
 
 #include "llvm/ADT/ilist_node.h"
-#include "llvm/IR/GlobalIndirectSymbol.h"
+#include "llvm/IR/GlobalValue.h"
+#include "llvm/IR/OperandTraits.h"
 #include "llvm/IR/Value.h"
 
 namespace llvm {
 
 class Twine;
 class Module;
 template <typename ValueSubClass> class SymbolTableListTraits;
 
-class GlobalAlias : public GlobalIndirectSymbol,
-                    public ilist_node<GlobalAlias> {
+class GlobalAlias : public GlobalValue, public ilist_node<GlobalAlias> {
   friend class SymbolTableListTraits<GlobalAlias>;
 
   GlobalAlias(Type *Ty, unsigned AddressSpace, LinkageTypes Linkage,
               const Twine &Name, Constant *Aliasee, Module *Parent);
 
 public:
   GlobalAlias(const GlobalAlias &) = delete;
   GlobalAlias &operator=(const GlobalAlias &) = delete;
public:
 
   // Type, Parent and AddressSpace taken from the Aliasee.
   static GlobalAlias *create(LinkageTypes Linkage, const Twine &Name,
                              GlobalValue *Aliasee);
 
   // Linkage, Type, Parent and AddressSpace taken from the Aliasee.
   static GlobalAlias *create(const Twine &Name, GlobalValue *Aliasee);
 
+  // allocate space for exactly one operand
+  void *operator new(size_t S) { return User::operator new(S, 1); }
+  void operator delete(void *Ptr) { User::operator delete(Ptr); }
+
+  /// Provide fast operand accessors
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Constant);
+
+  void copyAttributesFrom(const GlobalAlias *Src) {
+    GlobalValue::copyAttributesFrom(Src);
+  }
+
   /// removeFromParent - This method unlinks 'this' from the containing module,
   /// but does not delete it.
   ///
   void removeFromParent();
 
   /// eraseFromParent - This method unlinks 'this' from the containing module
   /// and deletes it.
   ///
   void eraseFromParent();
 
   /// These methods retrieve and set alias target.
   void setAliasee(Constant *Aliasee);
   const Constant *getAliasee() const {
-    return getIndirectSymbol();
-  }
-  Constant *getAliasee() {
-    return getIndirectSymbol();
+    return static_cast<Constant *>(Op<0>().get());
   }
+  Constant *getAliasee() { return static_cast<Constant *>(Op<0>().get()); }
 
   const GlobalObject *getAliaseeObject() const;
   GlobalObject *getAliaseeObject() {
     return const_cast<GlobalObject *>(
         static_cast<const GlobalAlias *>(this)->getAliaseeObject());
   }
 
   static bool isValidLinkage(LinkageTypes L) {
     return isExternalLinkage(L) || isLocalLinkage(L) ||
       isWeakLinkage(L) || isLinkOnceLinkage(L);
   }
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Value *V) {
     return V->getValueID() == Value::GlobalAliasVal;
   }
 };
 
+template <>
+struct OperandTraits<GlobalAlias>
+    : public FixedNumOperandTraits<GlobalAlias, 1> {};
+
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalAlias, Constant)
+
 } // end namespace llvm
 
 #endif // LLVM_IR_GLOBALALIAS_H

llvm/include/llvm/IR/GlobalIFunc.h

 /// be resolved at runtime by calling a resolver function.
 ///
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_IR_GLOBALIFUNC_H
 #define LLVM_IR_GLOBALIFUNC_H
 
 #include "llvm/ADT/ilist_node.h"
-#include "llvm/IR/GlobalIndirectSymbol.h"
+#include "llvm/IR/Constant.h"
+#include "llvm/IR/GlobalObject.h"
+#include "llvm/IR/OperandTraits.h"
 #include "llvm/IR/Value.h"
 
 namespace llvm {
 
 class Twine;
 class Module;
 
 // Traits class for using GlobalIFunc in symbol table in Module.
 template <typename ValueSubClass> class SymbolTableListTraits;
 
-class GlobalIFunc final : public GlobalIndirectSymbol,
-                          public ilist_node<GlobalIFunc> {
+class GlobalIFunc final : public GlobalObject, public ilist_node<GlobalIFunc> {
   friend class SymbolTableListTraits<GlobalIFunc>;
 
   GlobalIFunc(Type *Ty, unsigned AddressSpace, LinkageTypes Linkage,
               const Twine &Name, Constant *Resolver, Module *Parent);
 
 public:
   GlobalIFunc(const GlobalIFunc &) = delete;
   GlobalIFunc &operator=(const GlobalIFunc &) = delete;
 
   /// If a parent module is specified, the ifunc is automatically inserted into
   /// the end of the specified module's ifunc list.
   static GlobalIFunc *create(Type *Ty, unsigned AddressSpace,
                              LinkageTypes Linkage, const Twine &Name,
                              Constant *Resolver, Module *Parent);
 
+  // allocate space for exactly one operand
+  void *operator new(size_t S) { return User::operator new(S, 1); }
+  void operator delete(void *Ptr) { User::operator delete(Ptr); }
+
+  /// Provide fast operand accessors
+  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Constant);
+
+  void copyAttributesFrom(const GlobalIFunc *Src) {
+    GlobalObject::copyAttributesFrom(Src);
+  }
+
   /// This method unlinks 'this' from the containing module, but does not
   /// delete it.
   void removeFromParent();
 
   /// This method unlinks 'this' from the containing module and deletes it.
   void eraseFromParent();
 
   /// These methods retrieve and set ifunc resolver function.
-  void setResolver(Constant *Resolver) {
-    setIndirectSymbol(Resolver);
+  void setResolver(Constant *Resolver) { Op<0>().set(Resolver); }
+  const Constant *getResolver() const {
+    return static_cast<Constant *>(Op<0>().get());
   }
-  const Constant *getResolver() const { return getIndirectSymbol(); }
-  Constant *getResolver() { return getIndirectSymbol(); }
+  Constant *getResolver() { return static_cast<Constant *>(Op<0>().get()); }
 
   // Return the resolver function after peeling off potential ConstantExpr
   // indirection.
   const Function *getResolverFunction() const;
   Function *getResolverFunction() {
     return const_cast<Function *>(
         static_cast<const GlobalIFunc *>(this)->getResolverFunction());
   }
 
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Value *V) {
     return V->getValueID() == Value::GlobalIFuncVal;
   }
 };
 
+template <>
+struct OperandTraits<GlobalIFunc>
+    : public FixedNumOperandTraits<GlobalIFunc, 1> {};
+
+DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalIFunc, Constant)
+
 } // end namespace llvm
 
 #endif // LLVM_IR_GLOBALIFUNC_H

llvm/include/llvm/IR/GlobalIndirectSymbol.h

-//===- llvm/GlobalIndirectSymbol.h - GlobalIndirectSymbol class -*- C++ -*-===//
-//
-// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
-// See https://llvm.org/LICENSE.txt for license information.
-// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
-//
-//===----------------------------------------------------------------------===//
-//
-// This file contains the declaration of the GlobalIndirectSymbol class, which
-// is a base class for GlobalAlias and GlobalIFunc. It contains all common code
-// for aliases and ifuncs.
-//
-//===----------------------------------------------------------------------===//
-
-#ifndef LLVM_IR_GLOBALINDIRECTSYMBOL_H
-#define LLVM_IR_GLOBALINDIRECTSYMBOL_H
-
-#include "llvm/IR/GlobalObject.h"
-#include "llvm/IR/GlobalValue.h"
-#include "llvm/IR/OperandTraits.h"
-#include "llvm/IR/User.h"
-#include "llvm/IR/Value.h"
-#include "llvm/Support/Casting.h"
-#include <cstddef>
-
-namespace llvm {
-
-class GlobalIndirectSymbol : public GlobalValue {
-protected:
-  GlobalIndirectSymbol(Type *Ty, ValueTy VTy, unsigned AddressSpace,
-      LinkageTypes Linkage, const Twine &Name, Constant *Symbol);
-
-public:
-  GlobalIndirectSymbol(const GlobalIndirectSymbol &) = delete;
-  GlobalIndirectSymbol &operator=(const GlobalIndirectSymbol &) = delete;
-
-  // allocate space for exactly one operand
-  void *operator new(size_t S) { return User::operator new(S, 1); }
-  void operator delete(void *Ptr) { User::operator delete(Ptr); }
-
-  /// Provide fast operand accessors
-  DECLARE_TRANSPARENT_OPERAND_ACCESSORS(Constant);
-
-  void copyAttributesFrom(const GlobalValue *Src) {
-    GlobalValue::copyAttributesFrom(Src);
-  }
-
-  /// These methods set and retrieve indirect symbol.
-  void setIndirectSymbol(Constant *Symbol) {
-    setOperand(0, Symbol);
-  }
-  const Constant *getIndirectSymbol() const {
-    return getOperand(0);
-  }
-  Constant *getIndirectSymbol() {
-    return const_cast<Constant *>(
-          static_cast<const GlobalIndirectSymbol *>(this)->getIndirectSymbol());
-  }
-
-  const GlobalObject *getAliaseeObject() const;
-  GlobalObject *getAliaseeObject() {
-    return const_cast<GlobalObject *>(
-        static_cast<const GlobalIndirectSymbol *>(this)->getAliaseeObject());
-  }
-
-  // Methods for support type inquiry through isa, cast, and dyn_cast:
-  static bool classof(const Value *V) {
-    return V->getValueID() == Value::GlobalAliasVal ||
-           V->getValueID() == Value::GlobalIFuncVal;
-  }
-};
-
-template <>
-struct OperandTraits<GlobalIndirectSymbol> :
-  public FixedNumOperandTraits<GlobalIndirectSymbol, 1> {
-};
-
-DEFINE_TRANSPARENT_OPERAND_ACCESSORS(GlobalIndirectSymbol, Constant)
-
-} // end namespace llvm
-
-#endif // LLVM_IR_GLOBALINDIRECTSYMBOL_H

llvm/include/llvm/IR/GlobalObject.h

 
 protected:
   void copyAttributesFrom(const GlobalObject *Src);
 
 public:
   // Methods for support type inquiry through isa, cast, and dyn_cast:
   static bool classof(const Value *V) {
     return V->getValueID() == Value::FunctionVal ||
-           V->getValueID() == Value::GlobalVariableVal;
+           V->getValueID() == Value::GlobalVariableVal ||
+           V->getValueID() == Value::GlobalIFuncVal;
   }
 
 private:
   void setGlobalObjectFlag(unsigned Bit, bool Val) {
     unsigned Mask = 1 << Bit;
     setGlobalValueSubClassData((~Mask & getGlobalValueSubClassData()) |
                                (Val ? Mask : 0u));
   }
 
   StringRef getSectionImpl() const;
 };
 
 } // end namespace llvm
 
 #endif // LLVM_IR_GLOBALOBJECT_H

llvm/include/llvm/IR/Value.h

 class BasicBlock;
 class Constant;
 class ConstantData;
 class ConstantAggregate;
 class DataLayout;
 class Function;
 class GlobalAlias;
 class GlobalIFunc;
-class GlobalIndirectSymbol;
 class GlobalObject;
 class GlobalValue;
 class GlobalVariable;
 class InlineAsm;
 class Instruction;
 class LLVMContext;
 class MDNode;
 class Module;

 };
 
 template <> struct isa_impl<GlobalIFunc, Value> {
   static inline bool doit(const Value &Val) {
     return Val.getValueID() == Value::GlobalIFuncVal;
   }
 };
 
-template <> struct isa_impl<GlobalIndirectSymbol, Value> {
-  static inline bool doit(const Value &Val) {
-    return isa<GlobalAlias>(Val) || isa<GlobalIFunc>(Val);
-  }
-};
-
 template <> struct isa_impl<GlobalValue, Value> {
   static inline bool doit(const Value &Val) {
-    return isa<GlobalObject>(Val) || isa<GlobalIndirectSymbol>(Val);
+    return isa<GlobalObject>(Val) || isa<GlobalAlias>(Val);
   }
 };
 
 template <> struct isa_impl<GlobalObject, Value> {
   static inline bool doit(const Value &Val) {
-    return isa<GlobalVariable>(Val) || isa<Function>(Val);
+    return isa<GlobalVariable>(Val) || isa<Function>(Val) ||
+           isa<GlobalIFunc>(Val);
   }
 };
 
 // Create wrappers for C Binding types (see CBindingWrapping.h).
 DEFINE_ISA_CONVERSION_FUNCTIONS(Value, LLVMValueRef)
 
 // Specialized opaque value conversions.
 inline Value **unwrap(LLVMValueRef *Vals) {

llvm/include/llvm/Transforms/Utils/ValueMapper.h

 #include "llvm/ADT/ArrayRef.h"
 #include "llvm/IR/ValueHandle.h"
 #include "llvm/IR/ValueMap.h"
 
 namespace llvm {
 
 class Constant;
 class Function;
-class GlobalIndirectSymbol;
 class GlobalVariable;
 class Instruction;
 class MDNode;
 class Metadata;
 class Type;
 class Value;
 
 using ValueToValueMapTy = ValueMap<const Value *, WeakTrackingVH>;

 /// - \a remapFunction().
 ///
 /// The \a ValueMaterializer can be used as a callback, but cannot invoke any
 /// of these top-level functions recursively.  Instead, callbacks should use
 /// one of the following to schedule work lazily in the \a ValueMapper
 /// instance:
 /// - \a scheduleMapGlobalInitializer()
 /// - \a scheduleMapAppendingVariable()
-/// - \a scheduleMapGlobalIndirectSymbol()
+/// - \a scheduleMapGlobalAlias()
+/// - \a scheduleMapGlobalIFunc()
 /// - \a scheduleRemapFunction()
 ///
 /// Sometimes a callback needs a different mapping context.  Such a context can
 /// be registered using \a registerAlternateMappingContext(), which takes an
 /// alternate \a ValueToValueMapTy and \a ValueMaterializer and returns a ID to
 /// pass into the schedule*() functions.
 ///
 /// TODO: lib/Linker really doesn't need the \a ValueHandle in the \a
public:
   void remapFunction(Function &F);
 
   void scheduleMapGlobalInitializer(GlobalVariable &GV, Constant &Init,
                                     unsigned MappingContextID = 0);
   void scheduleMapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
                                     bool IsOldCtorDtor,
                                     ArrayRef<Constant *> NewMembers,
                                     unsigned MappingContextID = 0);
-  void scheduleMapGlobalIndirectSymbol(GlobalIndirectSymbol &GIS,
-                                       Constant &Target,
-                                       unsigned MappingContextID = 0);
+  void scheduleMapGlobalAlias(GlobalAlias &GA, Constant &Aliasee,
+                              unsigned MappingContextID = 0);
+  void scheduleMapGlobalIFunc(GlobalIFunc &GI, Constant &Resolver,
   void scheduleRemapFunction(Function &F, unsigned MappingContextID = 0);
 };
 
 /// Look up or compute a value in the value map.
 ///
 /// Return a mapped value for a function-local value (Argument, Instruction,
 /// BasicBlock), or compute and memoize a value for a Constant.
 ///

llvm/lib/AsmParser/LLParser.cpp

bool LLParser::parseUnnamedGlobal() {
   bool DSOLocal;
   GlobalVariable::ThreadLocalMode TLM;
   GlobalVariable::UnnamedAddr UnnamedAddr;
   if (parseOptionalLinkage(Linkage, HasLinkage, Visibility, DLLStorageClass,
                            DSOLocal) ||
       parseOptionalThreadLocal(TLM) || parseOptionalUnnamedAddr(UnnamedAddr))
     return true;
 
-  if (Lex.getKind() != lltok::kw_alias && Lex.getKind() != lltok::kw_ifunc)
+  switch (Lex.getKind()) {
+  default:
     return parseGlobal(Name, NameLoc, Linkage, HasLinkage, Visibility,
                        DLLStorageClass, DSOLocal, TLM, UnnamedAddr);
-
-  return parseIndirectSymbol(Name, NameLoc, Linkage, Visibility,
+  case lltok::kw_alias:
+  case lltok::kw_ifunc:
+    return parseAliasOrIFunc(Name, NameLoc, Linkage, Visibility,
                              DLLStorageClass, DSOLocal, TLM, UnnamedAddr);
   }
+}
 
 /// parseNamedGlobal:
 ///   GlobalVar '=' OptionalVisibility (ALIAS | IFUNC) ...
 ///   GlobalVar '=' OptionalLinkage OptionalPreemptionSpecifier
 ///                 OptionalVisibility OptionalDLLStorageClass
 ///                                                     ...   -> global variable
 bool LLParser::parseNamedGlobal() {
   assert(Lex.getKind() == lltok::GlobalVar);
   LocTy NameLoc = Lex.getLoc();
   std::string Name = Lex.getStrVal();
   Lex.Lex();
 
   bool HasLinkage;
   unsigned Linkage, Visibility, DLLStorageClass;
   bool DSOLocal;
   GlobalVariable::ThreadLocalMode TLM;
   GlobalVariable::UnnamedAddr UnnamedAddr;
   if (parseToken(lltok::equal, "expected '=' in global variable") ||
       parseOptionalLinkage(Linkage, HasLinkage, Visibility, DLLStorageClass,
                            DSOLocal) ||
       parseOptionalThreadLocal(TLM) || parseOptionalUnnamedAddr(UnnamedAddr))
     return true;
 
-  if (Lex.getKind() != lltok::kw_alias && Lex.getKind() != lltok::kw_ifunc)
+  switch (Lex.getKind()) {
+  default:
     return parseGlobal(Name, NameLoc, Linkage, HasLinkage, Visibility,
                        DLLStorageClass, DSOLocal, TLM, UnnamedAddr);
-
-  return parseIndirectSymbol(Name, NameLoc, Linkage, Visibility,
+  case lltok::kw_alias:
+  case lltok::kw_ifunc:
+    return parseAliasOrIFunc(Name, NameLoc, Linkage, Visibility,
                              DLLStorageClass, DSOLocal, TLM, UnnamedAddr);
   }
+}
 
 bool LLParser::parseComdat() {
   assert(Lex.getKind() == lltok::ComdatVar);
   std::string Name = Lex.getStrVal();
   LocTy NameLoc = Lex.getLoc();
   Lex.Lex();
 
   if (parseToken(lltok::equal, "expected '=' here"))

 static std::string typeComparisonErrorMessage(StringRef Message, Type *Ty1,
                                               Type *Ty2) {
   std::string ErrString;
   raw_string_ostream ErrOS(ErrString);
   ErrOS << Message << " (" << *Ty1 << " vs " << *Ty2 << ")";
   return ErrOS.str();
 }
 
-/// parseIndirectSymbol:
+/// parseAliasOrIFunc:
 ///   ::= GlobalVar '=' OptionalLinkage OptionalPreemptionSpecifier
 ///                     OptionalVisibility OptionalDLLStorageClass
 ///                     OptionalThreadLocal OptionalUnnamedAddr
-///                     'alias|ifunc' IndirectSymbol IndirectSymbolAttr*
+///                     'alias|ifunc' AliaseeOrResolver SymbolAttrs*
 ///
-/// IndirectSymbol
+/// AliaseeOrResolver
 ///   ::= TypeAndValue
 ///
-/// IndirectSymbolAttr
+/// SymbolAttrs
 ///   ::= ',' 'partition' StringConstant
 ///
 /// Everything through OptionalUnnamedAddr has already been parsed.
 ///
-bool LLParser::parseIndirectSymbol(const std::string &Name, LocTy NameLoc,
-                                   unsigned L, unsigned Visibility,
-                                   unsigned DLLStorageClass, bool DSOLocal,
-                                   GlobalVariable::ThreadLocalMode TLM,
-                                   GlobalVariable::UnnamedAddr UnnamedAddr) {
+bool LLParser::parseAliasOrIFunc(const std::string &Name, LocTy NameLoc,
   bool IsAlias;
   if (Lex.getKind() == lltok::kw_alias)
     IsAlias = true;
   else if (Lex.getKind() == lltok::kw_ifunc)
     IsAlias = false;
   else
     llvm_unreachable("Not an alias or ifunc!");
   Lex.Lex();
bool LLParser::parseAliasOrIFunc(const std::string &Name, LocTy NameLoc,
   } else {
     auto I = ForwardRefValIDs.find(NumberedVals.size());
     if (I != ForwardRefValIDs.end()) {
       GVal = I->second.first;
       ForwardRefValIDs.erase(I);
     }
   }
 
-  // Okay, create the alias but do not insert it into the module yet.
-  std::unique_ptr<GlobalIndirectSymbol> GA;
-  if (IsAlias)
+  // Okay, create the alias/ifunc but do not insert it into the module yet.
+  std::unique_ptr<GlobalAlias> GA;
+  std::unique_ptr<GlobalIFunc> GI;
+  GlobalValue *GV;
+  if (IsAlias) {
     GA.reset(GlobalAlias::create(Ty, AddrSpace,
                                  (GlobalValue::LinkageTypes)Linkage, Name,
                                  Aliasee, /*Parent*/ nullptr));
-  else
-    GA.reset(GlobalIFunc::create(Ty, AddrSpace,
+    GV = GA.get();
+  } else {
+    GI.reset(GlobalIFunc::create(Ty, AddrSpace,
                                  (GlobalValue::LinkageTypes)Linkage, Name,
                                  Aliasee, /*Parent*/ nullptr));
-  GA->setThreadLocalMode(TLM);
-  GA->setVisibility((GlobalValue::VisibilityTypes)Visibility);
-  GA->setDLLStorageClass((GlobalValue::DLLStorageClassTypes)DLLStorageClass);
-  GA->setUnnamedAddr(UnnamedAddr);
-  maybeSetDSOLocal(DSOLocal, *GA);
+    GV = GI.get();
+  }
+  GV->setThreadLocalMode(TLM);
+  GV->setVisibility((GlobalValue::VisibilityTypes)Visibility);
+  GV->setDLLStorageClass((GlobalValue::DLLStorageClassTypes)DLLStorageClass);
+  GV->setUnnamedAddr(UnnamedAddr);
+  maybeSetDSOLocal(DSOLocal, *GV);
 
   // At this point we've parsed everything except for the IndirectSymbolAttrs.
   // Now parse them if there are any.
   while (Lex.getKind() == lltok::comma) {
     Lex.Lex();
 
     if (Lex.getKind() == lltok::kw_partition) {
       Lex.Lex();
-      GA->setPartition(Lex.getStrVal());
+      GV->setPartition(Lex.getStrVal());
       if (parseToken(lltok::StringConstant, "expected partition string"))
         return true;
     } else {
       return tokError("unknown alias or ifunc property!");
     }
   }
 
   if (Name.empty())
-    NumberedVals.push_back(GA.get());
+    NumberedVals.push_back(GV);
 
   if (GVal) {
     // Verify that types agree.
-    if (GVal->getType() != GA->getType())
+    if (GVal->getType() != GV->getType())
       return error(
           ExplicitTypeLoc,
           "forward reference and definition of alias have different types");
 
     // If they agree, just RAUW the old value with the alias and remove the
     // forward ref info.
-    GVal->replaceAllUsesWith(GA.get());
+    GVal->replaceAllUsesWith(GV);
     GVal->eraseFromParent();
   }
 
   // Insert into the module, we know its name won't collide now.
   if (IsAlias)
-    M->getAliasList().push_back(cast<GlobalAlias>(GA.get()));
+    M->getAliasList().push_back(GA.release());
   else
-    M->getIFuncList().push_back(cast<GlobalIFunc>(GA.get()));
-  assert(GA->getName() == Name && "Should not be a name conflict!");
-
-  // The module owns this now
-  GA.release();
+    M->getIFuncList().push_back(GI.release());
+  assert(GV->getName() == Name && "Should not be a name conflict!");
 
   return false;
 }
 
 /// parseGlobal
 ///   ::= GlobalVar '=' OptionalLinkage OptionalPreemptionSpecifier
 ///       OptionalVisibility OptionalDLLStorageClass
 ///       OptionalThreadLocal OptionalUnnamedAddr OptionalAddrSpace

llvm/lib/Bitcode/Reader/BitcodeReader.cpp

 #include "llvm/IR/DebugInfo.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GVMaterializer.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalIFunc.h"
-#include "llvm/IR/GlobalIndirectSymbol.h"
 #include "llvm/IR/GlobalObject.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/InstIterator.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
class BitcodeReader : public BitcodeReaderBase, public GVMaterializer {
   std::vector<Type*> TypeList;
   DenseMap<Function *, FunctionType *> FunctionTypes;
   BitcodeReaderValueList ValueList;
   Optional<MetadataLoader> MDLoader;
   std::vector<Comdat *> ComdatList;
   SmallVector<Instruction *, 64> InstructionList;
 
   std::vector<std::pair<GlobalVariable *, unsigned>> GlobalInits;
-  std::vector<std::pair<GlobalIndirectSymbol *, unsigned>> IndirectSymbolInits;
+  std::vector<std::pair<GlobalValue *, unsigned>> IndirectSymbolInits;
 
   struct FunctionOperandInfo {
     Function *F;
     unsigned PersonalityFn;
     unsigned Prefix;
     unsigned Prologue;
   };
   std::vector<FunctionOperandInfo> FunctionOperands;
if (V != 1)
     return -(V >> 1);
   // There is no such thing as -0 with integers.  "-0" really means MININT.
   return 1ULL << 63;
 }
 
 /// Resolve all of the initializers for global values and aliases that we can.
 Error BitcodeReader::resolveGlobalAndIndirectSymbolInits() {
   std::vector<std::pair<GlobalVariable *, unsigned>> GlobalInitWorklist;
-  std::vector<std::pair<GlobalIndirectSymbol *, unsigned>>
-      IndirectSymbolInitWorklist;
+  std::vector<std::pair<GlobalValue *, unsigned>> IndirectSymbolInitWorklist;
   std::vector<FunctionOperandInfo> FunctionOperandWorklist;
 
   GlobalInitWorklist.swap(GlobalInits);
   IndirectSymbolInitWorklist.swap(IndirectSymbolInits);
   FunctionOperandWorklist.swap(FunctionOperands);
 
   while (!GlobalInitWorklist.empty()) {
     unsigned ValID = GlobalInitWorklist.back().second;
Error BitcodeReader::resolveGlobalAndIndirectSymbolInits() {
   while (!IndirectSymbolInitWorklist.empty()) {
     unsigned ValID = IndirectSymbolInitWorklist.back().second;
     if (ValID >= ValueList.size()) {
       IndirectSymbolInits.push_back(IndirectSymbolInitWorklist.back());
     } else {
       Constant *C = dyn_cast_or_null<Constant>(ValueList[ValID]);
       if (!C)
         return error("Expected a constant");
-      GlobalIndirectSymbol *GIS = IndirectSymbolInitWorklist.back().first;
-      if (isa<GlobalAlias>(GIS) && C->getType() != GIS->getType())
+      GlobalValue *GV = IndirectSymbolInitWorklist.back().first;
+      if (auto *GA = dyn_cast<GlobalAlias>(GV)) {
+        if (C->getType() != GV->getType())
           return error("Alias and aliasee types don't match");
-      GIS->setIndirectSymbol(C);
+        GA->setAliasee(C);
+      } else if (auto *GI = dyn_cast<GlobalIFunc>(GV)) {
+        GI->setResolver(C);
+      } else {
+        return error("Expected an alias or an ifunc");
+      }
     }
     IndirectSymbolInitWorklist.pop_back();
   }
 
   while (!FunctionOperandWorklist.empty()) {
     FunctionOperandInfo &Info = FunctionOperandWorklist.back();
     if (Info.PersonalityFn) {
       unsigned ValID = Info.PersonalityFn - 1;
Error BitcodeReader::globalCleanup() {
   for (auto &Pair : UpgradedVariables) {
     Pair.first->eraseFromParent();
     TheModule->getGlobalList().push_back(Pair.second);
   }
 
   // Force deallocation of memory for these vectors to favor the client that
   // want lazy deserialization.
   std::vector<std::pair<GlobalVariable *, unsigned>>().swap(GlobalInits);
-  std::vector<std::pair<GlobalIndirectSymbol *, unsigned>>().swap(
-      IndirectSymbolInits);
+  std::vector<std::pair<GlobalValue *, unsigned>>().swap(IndirectSymbolInits);
   return Error::success();
 }
 
 /// Support for lazy parsing of function bodies. This is required if we
 /// either have an old bitcode file without a VST forward declaration record,
 /// or if we have an anonymous function being materialized, since anonymous
 /// functions do not have a name and are therefore not in the VST.
 Error BitcodeReader::rememberAndSkipFunctionBodies() {
if (!NewRecord) {
     Ty = PTy->getElementType();
     AddrSpace = PTy->getAddressSpace();
   } else {
     AddrSpace = Record[OpNum++];
   }
 
   auto Val = Record[OpNum++];
   auto Linkage = Record[OpNum++];
-  GlobalIndirectSymbol *NewGA;
+  GlobalValue *NewGA;
   if (BitCode == bitc::MODULE_CODE_ALIAS ||
       BitCode == bitc::MODULE_CODE_ALIAS_OLD)
     NewGA = GlobalAlias::create(Ty, AddrSpace, getDecodedLinkage(Linkage), Name,
                                 TheModule);
   else
     NewGA = GlobalIFunc::create(Ty, AddrSpace, getDecodedLinkage(Linkage), Name,
                                 nullptr, TheModule);
 

llvm/lib/Bitcode/Reader/MetadataLoader.cpp

 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DebugLoc.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GVMaterializer.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalIFunc.h"
-#include "llvm/IR/GlobalIndirectSymbol.h"
 #include "llvm/IR/GlobalObject.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/IntrinsicInst.h"

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DataLayout.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GCStrategy.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalIFunc.h"
-#include "llvm/IR/GlobalIndirectSymbol.h"
 #include "llvm/IR/GlobalObject.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Mangler.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/Operator.h"
if (Cnt)
       FailedCandidates.push_back(GV);
   }
   GlobalGOTEquivs.clear();
 
   for (auto *GV : FailedCandidates)
     emitGlobalVariable(GV);
 }
 
-void AsmPrinter::emitGlobalIndirectSymbol(Module &M,
-                                          const GlobalIndirectSymbol& GIS) {
-  MCSymbol *Name = getSymbol(&GIS);
-  bool IsFunction = GIS.getValueType()->isFunctionTy();
+void AsmPrinter::emitGlobalAlias(Module &M, const GlobalAlias &GA) {
+  MCSymbol *Name = getSymbol(&GA);
+  bool IsFunction = GA.getValueType()->isFunctionTy();
   // Treat bitcasts of functions as functions also. This is important at least
   // on WebAssembly where object and function addresses can't alias each other.
   if (!IsFunction)
-    if (auto *CE = dyn_cast<ConstantExpr>(GIS.getIndirectSymbol()))
+    if (auto *CE = dyn_cast<ConstantExpr>(GA.getAliasee()))
       if (CE->getOpcode() == Instruction::BitCast)
         IsFunction =
           CE->getOperand(0)->getType()->getPointerElementType()->isFunctionTy();
 
   // AIX's assembly directive `.set` is not usable for aliasing purpose,
   // so AIX has to use the extra-label-at-definition strategy. At this
   // point, all the extra label is emitted, we just have to emit linkage for
   // those labels.
   if (TM.getTargetTriple().isOSBinFormatXCOFF()) {
-    assert(!isa<GlobalIFunc>(GIS) && "IFunc is not supported on AIX.");
     assert(MAI->hasVisibilityOnlyWithLinkage() &&
            "Visibility should be handled with emitLinkage() on AIX.");
-    emitLinkage(&GIS, Name);
+    emitLinkage(&GA, Name);
     // If it's a function, also emit linkage for aliases of function entry
     // point.
     if (IsFunction)
-      emitLinkage(&GIS,
-                  getObjFileLowering().getFunctionEntryPointSymbol(&GIS, TM));
+      emitLinkage(&GA,
+                  getObjFileLowering().getFunctionEntryPointSymbol(&GA, TM));
     return;
   }
 
-  if (GIS.hasExternalLinkage() || !MAI->getWeakRefDirective())
+  if (GA.hasExternalLinkage() || !MAI->getWeakRefDirective())
     OutStreamer->emitSymbolAttribute(Name, MCSA_Global);
-  else if (GIS.hasWeakLinkage() || GIS.hasLinkOnceLinkage())
+  else if (GA.hasWeakLinkage() || GA.hasLinkOnceLinkage())
     OutStreamer->emitSymbolAttribute(Name, MCSA_WeakReference);
   else
-    assert(GIS.hasLocalLinkage() && "Invalid alias or ifunc linkage");
+    assert(GA.hasLocalLinkage() && "Invalid alias linkage");
 
   // Set the symbol type to function if the alias has a function type.
   // This affects codegen when the aliasee is not a function.
   if (IsFunction)
-    OutStreamer->emitSymbolAttribute(Name, isa<GlobalIFunc>(GIS)
-                                               ? MCSA_ELF_TypeIndFunction
-                                               : MCSA_ELF_TypeFunction);
+    OutStreamer->emitSymbolAttribute(Name, MCSA_ELF_TypeFunction);
 
-  emitVisibility(Name, GIS.getVisibility());
+  emitVisibility(Name, GA.getVisibility());
 
-  const MCExpr *Expr = lowerConstant(GIS.getIndirectSymbol());
+  const MCExpr *Expr = lowerConstant(GA.getAliasee());
 
-  if (isa<GlobalAlias>(&GIS) && MAI->hasAltEntry() && isa<MCBinaryExpr>(Expr))
+  if (MAI->hasAltEntry() && isa<MCBinaryExpr>(Expr))
     OutStreamer->emitSymbolAttribute(Name, MCSA_AltEntry);
 
   // Emit the directives as assignments aka .set:
   OutStreamer->emitAssignment(Name, Expr);
-  MCSymbol *LocalAlias = getSymbolPreferLocal(GIS);
+  MCSymbol *LocalAlias = getSymbolPreferLocal(GA);
   if (LocalAlias != Name)
     OutStreamer->emitAssignment(LocalAlias, Expr);
 
-  if (auto *GA = dyn_cast<GlobalAlias>(&GIS)) {
-    // If the aliasee does not correspond to a symbol in the output, i.e. the
-    // alias is not of an object or the aliased object is private, then set the
-    // size of the alias symbol from the type of the alias. We don't do this in
-    // other situations as the alias and aliasee having differing types but same
-    // size may be intentional.
-    const GlobalObject *Aliasee = GA->getAliaseeObject();
-    if (MAI->hasDotTypeDotSizeDirective() && GA->getValueType()->isSized() &&
-        (!Aliasee || Aliasee->hasPrivateLinkage())) {
-      const DataLayout &DL = M.getDataLayout();
-      uint64_t Size = DL.getTypeAllocSize(GA->getValueType());
-      OutStreamer->emitELFSize(Name, MCConstantExpr::create(Size, OutContext));
-    }
-  }
+  const GlobalObject *BaseObject = GA.getAliaseeObject();
+  if (MAI->hasDotTypeDotSizeDirective() && GA.getValueType()->isSized() &&
+      (!BaseObject || BaseObject->hasPrivateLinkage())) {
+    uint64_t Size = DL.getTypeAllocSize(GA.getValueType());
+
+void AsmPrinter::emitGlobalIFunc(Module &M, const GlobalIFunc &GI) {
+  assert(!TM.getTargetTriple().isOSBinFormatXCOFF() &&
+         "IFunc is not supported on AIX.");
+
+  MCSymbol *Name = getSymbol(&GI);
+
+  if (GI.hasExternalLinkage() || !MAI->getWeakRefDirective())
+    OutStreamer->emitSymbolAttribute(Name, MCSA_Global);
+  else if (GI.hasWeakLinkage() || GI.hasLinkOnceLinkage())
+    OutStreamer->emitSymbolAttribute(Name, MCSA_WeakReference);
+  else
+    assert(GI.hasLocalLinkage() && "Invalid ifunc linkage");
+
+  OutStreamer->emitSymbolAttribute(Name, MCSA_ELF_TypeIndFunction);
+  emitVisibility(Name, GI.getVisibility());
+
+  // Emit the directives as assignments aka .set:
+  const MCExpr *Expr = lowerConstant(GI.getResolver());
+  OutStreamer->emitAssignment(Name, Expr);
+  MCSymbol *LocalAlias = getSymbolPreferLocal(GI);
+  if (LocalAlias != Name)
+    OutStreamer->emitAssignment(LocalAlias, Expr);
 }
 
 void AsmPrinter::emitRemarksSection(remarks::RemarkStreamer &RS) {
   if (!RS.needsSection())
     return;
 
   remarks::RemarkSerializer &RemarkSerializer = RS.getSerializer();
 
bool AsmPrinter::doFinalization(Module &M) {
   for (const auto &Alias : M.aliases()) {
     for (const GlobalAlias *Cur = &Alias; Cur;
          Cur = dyn_cast<GlobalAlias>(Cur->getAliasee())) {
       if (!AliasVisited.insert(Cur).second)
         break;
       AliasStack.push_back(Cur);
     }
     for (const GlobalAlias *AncestorAlias : llvm::reverse(AliasStack))
-      emitGlobalIndirectSymbol(M, *AncestorAlias);
+      emitGlobalAlias(M, *AncestorAlias);
     AliasStack.clear();
   }
   for (const auto &IFunc : M.ifuncs())
-    emitGlobalIndirectSymbol(M, IFunc);
+    emitGlobalIFunc(M, IFunc);
 
   GCModuleInfo *MI = getAnalysisIfAvailable<GCModuleInfo>();
   assert(MI && "AsmPrinter didn't require GCModuleInfo?");
   for (GCModuleInfo::iterator I = MI->end(), E = MI->begin(); I != E; )
     if (GCMetadataPrinter *MP = GetOrCreateGCPrinter(**--I))
       MP->finishAssembly(M, *MI, *this);
 
   // Emit llvm.ident metadata in an '.ident' directive.

llvm/lib/IR/AsmWriter.cpp

 #include "llvm/IR/Comdat.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalIFunc.h"
-#include "llvm/IR/GlobalIndirectSymbol.h"
 #include "llvm/IR/GlobalObject.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/IRPrintingPasses.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/InstrTypes.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
public:
   void writeAllMDNodes();
   void writeMDNode(unsigned Slot, const MDNode *Node);
   void writeAttribute(const Attribute &Attr, bool InAttrGroup = false);
   void writeAttributeSet(const AttributeSet &AttrSet, bool InAttrGroup = false);
   void writeAllAttributeGroups();
 
   void printTypeIdentities();
   void printGlobal(const GlobalVariable *GV);
-  void printIndirectSymbol(const GlobalIndirectSymbol *GIS);
+  void printAlias(const GlobalAlias *GA);
+  void printIFunc(const GlobalIFunc *GI);
   void printComdat(const Comdat *C);
   void printFunction(const Function *F);
   void printArgument(const Argument *FA, AttributeSet Attrs);
   void printBasicBlock(const BasicBlock *BB);
   void printInstructionLine(const Instruction &I);
   void printInstruction(const Instruction &I);
 
   void printUseListOrder(const Value *V, const std::vector<unsigned> &Shuffle);
void AssemblyWriter::printModule(const Module *M) {
   if (!M->global_empty()) Out << '\n';
   for (const GlobalVariable &GV : M->globals()) {
     printGlobal(&GV); Out << '\n';
   }
 
   // Output all aliases.
   if (!M->alias_empty()) Out << "\n";
   for (const GlobalAlias &GA : M->aliases())
-    printIndirectSymbol(&GA);
+    printAlias(&GA);
 
   // Output all ifuncs.
   if (!M->ifunc_empty()) Out << "\n";
   for (const GlobalIFunc &GI : M->ifuncs())
-    printIndirectSymbol(&GI);
+    printIFunc(&GI);
 
   // Output all of the functions.
   for (const Function &F : *M) {
     Out << '\n';
     printFunction(&F);
   }
 
   // Output global use-lists.
void AssemblyWriter::printGlobal(const GlobalVariable *GV) {
 
   auto Attrs = GV->getAttributes();
   if (Attrs.hasAttributes())
     Out << " #" << Machine.getAttributeGroupSlot(Attrs);
 
   printInfoComment(*GV);
 }
 
-void AssemblyWriter::printIndirectSymbol(const GlobalIndirectSymbol *GIS) {
-  if (GIS->isMaterializable())
+void AssemblyWriter::printAlias(const GlobalAlias *GA) {
+  if (GA->isMaterializable())
     Out << "; Materializable\n";
 
-  AsmWriterContext WriterCtx(&TypePrinter, &Machine, GIS->getParent());
-  WriteAsOperandInternal(Out, GIS, WriterCtx);
+  AsmWriterContext WriterCtx(&TypePrinter, &Machine, GA->getParent());
+  WriteAsOperandInternal(Out, GA, WriterCtx);
   Out << " = ";
 
-  Out << getLinkageNameWithSpace(GIS->getLinkage());
-  PrintDSOLocation(*GIS, Out);
-  PrintVisibility(GIS->getVisibility(), Out);
-  PrintDLLStorageClass(GIS->getDLLStorageClass(), Out);
-  PrintThreadLocalModel(GIS->getThreadLocalMode(), Out);
-  StringRef UA = getUnnamedAddrEncoding(GIS->getUnnamedAddr());
+  Out << getLinkageNameWithSpace(GA->getLinkage());
+  PrintDSOLocation(*GA, Out);
+  PrintVisibility(GA->getVisibility(), Out);
+  PrintDLLStorageClass(GA->getDLLStorageClass(), Out);
+  PrintThreadLocalModel(GA->getThreadLocalMode(), Out);
+  StringRef UA = getUnnamedAddrEncoding(GA->getUnnamedAddr());
   if (!UA.empty())
       Out << UA << ' ';
 
-  if (isa<GlobalAlias>(GIS))
-    Out << "alias ";
-  else if (isa<GlobalIFunc>(GIS))
-    Out << "ifunc ";
-  else
-    llvm_unreachable("Not an alias or ifunc!");
-
-  TypePrinter.print(GIS->getValueType(), Out);
 
+  TypePrinter.print(GA->getValueType(), Out);
   Out << ", ";
 
-  const Constant *IS = GIS->getIndirectSymbol();
-
-  if (!IS) {
-    TypePrinter.print(GIS->getType(), Out);
+  if (const Constant *Aliasee = GA->getAliasee()) {
+    writeOperand(Aliasee, !isa<ConstantExpr>(Aliasee));
+  } else {
+    TypePrinter.print(GA->getType(), Out);
     Out << " <<NULL ALIASEE>>";
+  }
+
+  if (GA->hasPartition()) {
+    Out << ", partition \"";
+    printEscapedString(GA->getPartition(), Out);
+    Out << '"';
+  }
+
+  printInfoComment(*GA);
+  Out << '\n';
+}
+
+void AssemblyWriter::printIFunc(const GlobalIFunc *GI) {
+  if (GI->isMaterializable())
+    Out << "; Materializable\n";
+
+  AsmWriterContext WriterCtx(&TypePrinter, &Machine, GI->getParent());
+  WriteAsOperandInternal(Out, GI, WriterCtx);
+  Out << " = ";
+
+  Out << getLinkageNameWithSpace(GI->getLinkage());
+  PrintDSOLocation(*GI, Out);
+  PrintVisibility(GI->getVisibility(), Out);
+
+  Out << "ifunc ";
+
+  TypePrinter.print(GI->getValueType(), Out);
+  Out << ", ";
+
+  if (const Constant *Resolver = GI->getResolver()) {
+    writeOperand(Resolver, !isa<ConstantExpr>(Resolver));
   } else {
-    writeOperand(IS, !isa<ConstantExpr>(IS));
+    TypePrinter.print(GI->getType(), Out);
+    Out << " <<NULL RESOLVER>>";
   }
 
-  if (GIS->hasPartition()) {
+  if (GI->hasPartition()) {
     Out << ", partition \"";
-    printEscapedString(GIS->getPartition(), Out);
+    printEscapedString(GI->getPartition(), Out);
     Out << '"';
   }
 
-  printInfoComment(*GIS);
+  printInfoComment(*GI);
   Out << '\n';
 }
 
 void AssemblyWriter::printComdat(const Comdat *C) {
   C->print(Out);
 }
 
 void AssemblyWriter::printTypeIdentities() {
if (const Instruction *I = dyn_cast<Instruction>(this)) {
     AssemblyWriter W(OS, SlotTable, getModuleFromVal(BB), nullptr, IsForDebug);
     W.printBasicBlock(BB);
   } else if (const GlobalValue *GV = dyn_cast<GlobalValue>(this)) {
     AssemblyWriter W(OS, SlotTable, GV->getParent(), nullptr, IsForDebug);
     if (const GlobalVariable *V = dyn_cast<GlobalVariable>(GV))
       W.printGlobal(V);
     else if (const Function *F = dyn_cast<Function>(GV))
       W.printFunction(F);
+    else if (const GlobalAlias *A = dyn_cast<GlobalAlias>(GV))
+      W.printAlias(A);
+    else if (const GlobalIFunc *I = dyn_cast<GlobalIFunc>(GV))
+      W.printIFunc(I);
     else
-      W.printIndirectSymbol(cast<GlobalIndirectSymbol>(GV));
+      llvm_unreachable("Unknown GlobalValue to print out!");
   } else if (const MetadataAsValue *V = dyn_cast<MetadataAsValue>(this)) {
     V->getMetadata()->print(ROS, MST, getModuleFromVal(V));
   } else if (const Constant *C = dyn_cast<Constant>(this)) {
     TypePrinting TypePrinter;
     TypePrinter.print(C->getType(), OS);
     OS << ' ';
     AsmWriterContext WriterCtx(&TypePrinter, MST.getMachine());
     WriteConstantInternal(OS, C, WriterCtx);

llvm/lib/IR/Globals.cpp

bool GlobalValue::isDeclaration() const {
   if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(this))
     return GV->getNumOperands() == 0;
 
   // Functions are definitions if they have a body.
   if (const Function *F = dyn_cast<Function>(this))
     return F->empty() && !F->isMaterializable();
 
   // Aliases and ifuncs are always definitions.
-  assert(isa<GlobalIndirectSymbol>(this));
+  assert(isa<GlobalAlias>(this) || isa<GlobalIFunc>(this));
   return false;
 }
 
 bool GlobalObject::canIncreaseAlignment() const {
   // Firstly, can only increase the alignment of a global if it
   // is a strong definition.
   if (!isStrongDefinitionForLinker())
     return false;
bool GlobalObject::canIncreaseAlignment() const {
   bool isELF =
       (!Parent || Triple(Parent->getTargetTriple()).isOSBinFormatELF());
   if (isELF && !isDSOLocal())
     return false;
 
   return true;
 }
 
-const GlobalObject *GlobalValue::getAliaseeObject() const {
-  if (auto *GO = dyn_cast<GlobalObject>(this))
+static const GlobalObject *
+findBaseObject(const Constant *C, DenseSet<const GlobalAlias *> &Aliases) {
+  if (auto *GO = dyn_cast<GlobalObject>(C))
     return GO;
-  if (auto *GA = dyn_cast<GlobalAlias>(this))
-    return GA->getAliaseeObject();
+  if (auto *GA = dyn_cast<GlobalAlias>(C))
+    if (Aliases.insert(GA).second)
+      return findBaseObject(GA->getOperand(0), Aliases);
+  if (auto *CE = dyn_cast<ConstantExpr>(C)) {
+    switch (CE->getOpcode()) {
+    case Instruction::Add: {
+      auto *LHS = findBaseObject(CE->getOperand(0), Aliases);
+      auto *RHS = findBaseObject(CE->getOperand(1), Aliases);
+      if (LHS && RHS)
+        return nullptr;
+      return LHS ? LHS : RHS;
+    }
+    case Instruction::Sub: {
+      if (findBaseObject(CE->getOperand(1), Aliases))
+        return nullptr;
+      return findBaseObject(CE->getOperand(0), Aliases);
+    }
+    case Instruction::IntToPtr:
+    case Instruction::PtrToInt:
+    case Instruction::BitCast:
+    case Instruction::GetElementPtr:
+      return findBaseObject(CE->getOperand(0), Aliases);
+    default:
+      break;
+    }
+  }
   return nullptr;
 }
 
+const GlobalObject *GlobalValue::getAliaseeObject() const {
+  DenseSet<const GlobalAlias *> Aliases;
+  return findBaseObject(this, Aliases);
+}
+
 bool GlobalValue::isAbsoluteSymbolRef() const {
   auto *GO = dyn_cast<GlobalObject>(this);
   if (!GO)
     return false;
 
   return GO->getMetadata(LLVMContext::MD_absolute_symbol);
 }
 

 }
 
 void GlobalVariable::dropAllReferences() {
   User::dropAllReferences();
   clearMetadata();
 }
 
 //===----------------------------------------------------------------------===//
-// GlobalIndirectSymbol Implementation
-//===----------------------------------------------------------------------===//
-
-GlobalIndirectSymbol::GlobalIndirectSymbol(Type *Ty, ValueTy VTy,
-    unsigned AddressSpace, LinkageTypes Linkage, const Twine &Name,
-    Constant *Symbol)
-    : GlobalValue(Ty, VTy, &Op<0>(), 1, Linkage, Name, AddressSpace) {
-    Op<0>() = Symbol;
-}
-
-static const GlobalObject *
-findBaseObject(const Constant *C, DenseSet<const GlobalAlias *> &Aliases) {
-  if (auto *GO = dyn_cast<GlobalObject>(C))
-    return GO;
-  if (auto *GA = dyn_cast<GlobalAlias>(C))
-    if (Aliases.insert(GA).second)
-      return findBaseObject(GA->getOperand(0), Aliases);
-  if (auto *CE = dyn_cast<ConstantExpr>(C)) {
-    switch (CE->getOpcode()) {
-    case Instruction::Add: {
-      auto *LHS = findBaseObject(CE->getOperand(0), Aliases);
-      auto *RHS = findBaseObject(CE->getOperand(1), Aliases);
-      if (LHS && RHS)
-        return nullptr;
-      return LHS ? LHS : RHS;
-    }
-    case Instruction::Sub: {
-      if (findBaseObject(CE->getOperand(1), Aliases))
-        return nullptr;
-      return findBaseObject(CE->getOperand(0), Aliases);
-    }
-    case Instruction::IntToPtr:
-    case Instruction::PtrToInt:
-    case Instruction::BitCast:
-    case Instruction::GetElementPtr:
-      return findBaseObject(CE->getOperand(0), Aliases);
-    default:
-      break;
-    }
-  }
-  return nullptr;
-}
-
-//===----------------------------------------------------------------------===//
 // GlobalAlias Implementation
 //===----------------------------------------------------------------------===//
 
 GlobalAlias::GlobalAlias(Type *Ty, unsigned AddressSpace, LinkageTypes Link,
                          const Twine &Name, Constant *Aliasee,
                          Module *ParentModule)
-    : GlobalIndirectSymbol(Ty, Value::GlobalAliasVal, AddressSpace, Link, Name,
-                           Aliasee) {
+    : GlobalValue(Ty, Value::GlobalAliasVal, &Op<0>(), 1, Link, Name,
+                  AddressSpace) {
+  setAliasee(Aliasee);
   if (ParentModule)
     ParentModule->getAliasList().push_back(this);
 }
 
 GlobalAlias *GlobalAlias::create(Type *Ty, unsigned AddressSpace,
                                  LinkageTypes Link, const Twine &Name,
                                  Constant *Aliasee, Module *ParentModule) {
   return new GlobalAlias(Ty, AddressSpace, Link, Name, Aliasee, ParentModule);

 
 void GlobalAlias::eraseFromParent() {
   getParent()->getAliasList().erase(getIterator());
 }
 
 void GlobalAlias::setAliasee(Constant *Aliasee) {
   assert((!Aliasee || Aliasee->getType() == getType()) &&
          "Alias and aliasee types should match!");
-  setIndirectSymbol(Aliasee);
+  Op<0>().set(Aliasee);
 }
 
 const GlobalObject *GlobalAlias::getAliaseeObject() const {
   DenseSet<const GlobalAlias *> Aliases;
   return findBaseObject(getOperand(0), Aliases);
 }
 
 //===----------------------------------------------------------------------===//
 // GlobalIFunc Implementation
 //===----------------------------------------------------------------------===//
 
 GlobalIFunc::GlobalIFunc(Type *Ty, unsigned AddressSpace, LinkageTypes Link,
                          const Twine &Name, Constant *Resolver,
                          Module *ParentModule)
-    : GlobalIndirectSymbol(Ty, Value::GlobalIFuncVal, AddressSpace, Link, Name,
-                           Resolver) {
+    : GlobalObject(Ty, Value::GlobalIFuncVal, &Op<0>(), 1, Link, Name,
+                   AddressSpace) {
+  setResolver(Resolver);
   if (ParentModule)
     ParentModule->getIFuncList().push_back(this);
 }
 
 GlobalIFunc *GlobalIFunc::create(Type *Ty, unsigned AddressSpace,
                                  LinkageTypes Link, const Twine &Name,
                                  Constant *Resolver, Module *ParentModule) {
   return new GlobalIFunc(Ty, AddressSpace, Link, Name, Resolver, ParentModule);
 }
 
 void GlobalIFunc::removeFromParent() {
   getParent()->getIFuncList().remove(getIterator());
 }
 
 void GlobalIFunc::eraseFromParent() {
   getParent()->getIFuncList().erase(getIterator());
 }
 
 const Function *GlobalIFunc::getResolverFunction() const {
   DenseSet<const GlobalAlias *> Aliases;
-  return cast<Function>(findBaseObject(getIndirectSymbol(), Aliases));
+  return cast<Function>(findBaseObject(getResolver(), Aliases));
 }

llvm/lib/Linker/IRMover.cpp

class IRLinker {
   bool shouldLink(GlobalValue *DGV, GlobalValue &SGV);
   Expected<Constant *> linkGlobalValueProto(GlobalValue *GV,
                                             bool ForIndirectSymbol);
 
   Error linkModuleFlagsMetadata();
 
   void linkGlobalVariable(GlobalVariable &Dst, GlobalVariable &Src);
   Error linkFunctionBody(Function &Dst, Function &Src);
-  void linkIndirectSymbolBody(GlobalIndirectSymbol &Dst,
-                              GlobalIndirectSymbol &Src);
+  void linkAliasAliasee(GlobalAlias &Dst, GlobalAlias &Src);
+  void linkIFuncResolver(GlobalIFunc &Dst, GlobalIFunc &Src);
   Error linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src);
 
   /// Replace all types in the source AttributeList with the
   /// corresponding destination type.
   AttributeList mapAttributeTypes(LLVMContext &C, AttributeList Attrs);
 
   /// Functions that take care of cloning a specific global value type
   /// into the destination module.
   GlobalVariable *copyGlobalVariableProto(const GlobalVariable *SGVar);
   Function *copyFunctionProto(const Function *SF);
-  GlobalValue *copyGlobalIndirectSymbolProto(const GlobalIndirectSymbol *SGIS);
+  GlobalValue *copyIndirectSymbolProto(const GlobalValue *SGV);
 
   /// Perform "replace all uses with" operations. These work items need to be
   /// performed as part of materialization, but we postpone them to happen after
   /// materialization is done. The materializer called by ValueMapper is not
   /// expected to delete constants, as ValueMapper is holding pointers to some
   /// of them, but constant destruction may be indirectly triggered by RAUW.
   /// Hence, the need to move this out of the materialization call chain.
   void flushRAUWWorklist();
Value *IRLinker::materialize(Value *V, bool ForIndirectSymbol) {
 
   // If we already created the body, just return.
   if (auto *F = dyn_cast<Function>(New)) {
     if (!F->isDeclaration())
       return New;
   } else if (auto *V = dyn_cast<GlobalVariable>(New)) {
     if (V->hasInitializer() || V->hasAppendingLinkage())
       return New;
-  } else {
-    auto *IS = cast<GlobalIndirectSymbol>(New);
-    if (IS->getIndirectSymbol())
+  } else if (auto *GA = dyn_cast<GlobalAlias>(New)) {
+    if (GA->getAliasee())
+      return New;
+  } else if (auto *GI = dyn_cast<GlobalIFunc>(New)) {
+    if (GI->getResolver())
       return New;
+  } else {
+    llvm_unreachable("Invalid GlobalValue type");
   }
 
   // If the global is being linked for an indirect symbol, it may have already
   // been scheduled to satisfy a regular symbol. Similarly, a global being linked
   // for a regular symbol may have already been scheduled for an indirect
   // symbol. Check for these cases by looking in the other value map and
   // confirming the same value has been scheduled.  If there is an entry in the
   // ValueMap but the value is different, it means that the value already had a
auto *F = Function::Create(TypeMap.get(SF->getFunctionType()),
                              SF->getAddressSpace(), SF->getName(), &DstM);
   F->copyAttributesFrom(SF);
   F->setAttributes(mapAttributeTypes(F->getContext(), F->getAttributes()));
   return F;
 }
 
 /// Set up prototypes for any indirect symbols that come over from the source
 /// module.
-GlobalValue *
-IRLinker::copyGlobalIndirectSymbolProto(const GlobalIndirectSymbol *SGIS) {
+GlobalValue *IRLinker::copyIndirectSymbolProto(const GlobalValue *SGV) {
   // If there is no linkage to be performed or we're linking from the source,
   // bring over SGA.
-  auto *Ty = TypeMap.get(SGIS->getValueType());
-  GlobalIndirectSymbol *GIS;
-  if (isa<GlobalAlias>(SGIS))
-    GIS = GlobalAlias::create(Ty, SGIS->getAddressSpace(),
-                              GlobalValue::ExternalLinkage, SGIS->getName(),
-                              &DstM);
-  else
-    GIS = GlobalIFunc::create(Ty, SGIS->getAddressSpace(),
-                              GlobalValue::ExternalLinkage, SGIS->getName(),
-                              nullptr, &DstM);
-  GIS->copyAttributesFrom(SGIS);
-  return GIS;
+  auto *Ty = TypeMap.get(SGV->getValueType());
+
+  if (auto *GA = dyn_cast<GlobalAlias>(SGV)) {
+    auto *DGA = GlobalAlias::create(Ty, SGV->getAddressSpace(),
+                                    GlobalValue::ExternalLinkage,
+                                    SGV->getName(), &DstM);
+    DGA->copyAttributesFrom(GA);
+    return DGA;
+  }
+
+  if (auto *GI = dyn_cast<GlobalIFunc>(SGV)) {
+    auto *DGI = GlobalIFunc::create(Ty, SGV->getAddressSpace(),
+                                    GlobalValue::ExternalLinkage,
+                                    SGV->getName(), nullptr, &DstM);
+    DGI->copyAttributesFrom(GI);
+    return DGI;
+  }
+
+  llvm_unreachable("Invalid source global value type");
 }
 
 GlobalValue *IRLinker::copyGlobalValueProto(const GlobalValue *SGV,
                                             bool ForDefinition) {
   GlobalValue *NewGV;
   if (auto *SGVar = dyn_cast<GlobalVariable>(SGV)) {
     NewGV = copyGlobalVariableProto(SGVar);
   } else if (auto *SF = dyn_cast<Function>(SGV)) {
     NewGV = copyFunctionProto(SF);
   } else {
     if (ForDefinition)
-      NewGV = copyGlobalIndirectSymbolProto(cast<GlobalIndirectSymbol>(SGV));
+      NewGV = copyIndirectSymbolProto(SGV);
     else if (SGV->getValueType()->isFunctionTy())
       NewGV =
           Function::Create(cast<FunctionType>(TypeMap.get(SGV->getValueType())),
                            GlobalValue::ExternalLinkage, SGV->getAddressSpace(),
                            SGV->getName(), &DstM);
     else
       NewGV =
           new GlobalVariable(DstM, TypeMap.get(SGV->getValueType()),
Error IRLinker::linkFunctionBody(Function &Dst, Function &Src) {
   Dst.stealArgumentListFrom(Src);
   Dst.getBasicBlockList().splice(Dst.end(), Src.getBasicBlockList());
 
   // Everything has been moved over.  Remap it.
   Mapper.scheduleRemapFunction(Dst);
   return Error::success();
 }
 
-void IRLinker::linkIndirectSymbolBody(GlobalIndirectSymbol &Dst,
-                                      GlobalIndirectSymbol &Src) {
-  Mapper.scheduleMapGlobalIndirectSymbol(Dst, *Src.getIndirectSymbol(),
-                                         IndirectSymbolMCID);
+void IRLinker::linkAliasAliasee(GlobalAlias &Dst, GlobalAlias &Src) {
+  Mapper.scheduleMapGlobalAlias(Dst, *Src.getAliasee(), IndirectSymbolMCID);
+}
+
+void IRLinker::linkIFuncResolver(GlobalIFunc &Dst, GlobalIFunc &Src) {
+  Mapper.scheduleMapGlobalIFunc(Dst, *Src.getResolver(), IndirectSymbolMCID);
 }
 
 Error IRLinker::linkGlobalValueBody(GlobalValue &Dst, GlobalValue &Src) {
   if (auto *F = dyn_cast<Function>(&Src))
     return linkFunctionBody(cast<Function>(Dst), *F);
   if (auto *GVar = dyn_cast<GlobalVariable>(&Src)) {
     linkGlobalVariable(cast<GlobalVariable>(Dst), *GVar);
     return Error::success();
   }
-  linkIndirectSymbolBody(cast<GlobalIndirectSymbol>(Dst), cast<GlobalIndirectSymbol>(Src));
+  if (auto *GA = dyn_cast<GlobalAlias>(&Src)) {
+    linkAliasAliasee(cast<GlobalAlias>(Dst), *GA);
+    return Error::success();
+  }
+  linkIFuncResolver(cast<GlobalIFunc>(Dst), cast<GlobalIFunc>(Src));
   return Error::success();
 }
 
 void IRLinker::flushRAUWWorklist() {
   for (const auto &Elem : RAUWWorklist) {
     GlobalValue *Old;
     Value *New;
     std::tie(Old, New) = Elem;

llvm/lib/Object/ModuleSymbolTable.cpp

uint32_t ModuleSymbolTable::getSymbolFlags(Symbol S) const {
   if (GV->isDeclarationForLinker())
     Res |= BasicSymbolRef::SF_Undefined;
   else if (GV->hasHiddenVisibility() && !GV->hasLocalLinkage())
     Res |= BasicSymbolRef::SF_Hidden;
   if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV)) {
     if (GVar->isConstant())
       Res |= BasicSymbolRef::SF_Const;
   }
-  if (isa_and_nonnull<Function>(GV->getAliaseeObject()) || isa<GlobalIFunc>(GV))
+  if (const GlobalObject *GO = GV->getAliaseeObject())
+    if (isa<Function>(GO) || isa<GlobalIFunc>(GO))
       Res |= BasicSymbolRef::SF_Executable;
   if (isa<GlobalAlias>(GV))
     Res |= BasicSymbolRef::SF_Indirect;
   if (GV->hasPrivateLinkage())
     Res |= BasicSymbolRef::SF_FormatSpecific;
   if (!GV->hasLocalLinkage())
     Res |= BasicSymbolRef::SF_Global;
   if (GV->hasCommonLinkage())
     Res |= BasicSymbolRef::SF_Common;

llvm/lib/Transforms/IPO/LowerTypeTests.cpp

 
 private:
   size_t NTargets;
 };
 
 struct ScopedSaveAliaseesAndUsed {
   Module &M;
   SmallVector<GlobalValue *, 4> Used, CompilerUsed;
-  std::vector<std::pair<GlobalIndirectSymbol *, Function *>> FunctionAliases;
+  std::vector<std::pair<GlobalAlias *, Function *>> FunctionAliases;
+  std::vector<std::pair<GlobalIFunc *, Function *>> ResolverIFuncs;
 
   ScopedSaveAliaseesAndUsed(Module &M) : M(M) {
     // The users of this class want to replace all function references except
     // for aliases and llvm.used/llvm.compiler.used with references to a jump
     // table. We avoid replacing aliases in order to avoid introducing a double
     // indirection (or an alias pointing to a declaration in ThinLTO mode), and
     // we avoid replacing llvm.used/llvm.compiler.used because these global
     // variables describe properties of the global, not the jump table (besides,
     // offseted references to the jump table in llvm.used are invalid).
     // Unfortunately, LLVM doesn't have a "RAUW except for these (possibly
     // indirect) users", so what we do is save the list of globals referenced by
     // llvm.used/llvm.compiler.used and aliases, erase the used lists, let RAUW
     // replace the aliasees and then set them back to their original values at
     // the end.
     if (GlobalVariable *GV = collectUsedGlobalVariables(M, Used, false))
       GV->eraseFromParent();
     if (GlobalVariable *GV = collectUsedGlobalVariables(M, CompilerUsed, true))
       GV->eraseFromParent();
 
-    for (auto &GIS : concat<GlobalIndirectSymbol>(M.aliases(), M.ifuncs())) {
+    for (auto &GA : M.aliases()) {
       // FIXME: This should look past all aliases not just interposable ones,
       // see discussion on D65118.
-      if (auto *F =
-              dyn_cast<Function>(GIS.getIndirectSymbol()->stripPointerCasts()))
-        FunctionAliases.push_back({&GIS, F});
+      if (auto *F = dyn_cast<Function>(GA.getAliasee()->stripPointerCasts()))
+        FunctionAliases.push_back({&GA, F});
+    }
+
+    for (auto &GI : M.ifuncs()) {
+      if (auto *F = dyn_cast<Function>(GI.getResolver()->stripPointerCasts()))
+        ResolverIFuncs.push_back({&GI, F});
     }
   }
 
   ~ScopedSaveAliaseesAndUsed() {
     appendToUsed(M, Used);
     appendToCompilerUsed(M, CompilerUsed);
 
     for (auto P : FunctionAliases)
-      P.first->setIndirectSymbol(
+      P.first->setAliasee(
           ConstantExpr::getBitCast(P.second, P.first->getType()));
+
+    for (auto P : ResolverIFuncs) {
+      // This does not preserve pointer casts that may have been stripped by the
+      // constructor, but the resolver's type is different from that of the
+      // ifunc anyway.
+      P.first->setResolver(P.second);
+    }
   }
 };
 
 class LowerTypeTestsModule {
   Module &M;
 
   ModuleSummaryIndex *ExportSummary;
   const ModuleSummaryIndex *ImportSummary;

llvm/lib/Transforms/Utils/SplitModule.cpp

 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/IR/Comdat.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/Function.h"
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalObject.h"
-#include "llvm/IR/GlobalIndirectSymbol.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Module.h"
 #include "llvm/IR/User.h"
 #include "llvm/IR/Value.h"
 #include "llvm/Support/Casting.h"
 #include "llvm/Support/Debug.h"

 
 static void addNonConstUser(ClusterMapType &GVtoClusterMap,
                             const GlobalValue *GV, const User *U) {
   assert((!isa<Constant>(U) || isa<GlobalValue>(U)) && "Bad user");
 
   if (const Instruction *I = dyn_cast<Instruction>(U)) {
     const GlobalValue *F = I->getParent()->getParent();
     GVtoClusterMap.unionSets(GV, F);
-  } else if (isa<GlobalIndirectSymbol>(U) || isa<Function>(U) ||
-             isa<GlobalVariable>(U)) {
-    GVtoClusterMap.unionSets(GV, cast<GlobalValue>(U));
+  } else if (const GlobalValue *GVU = dyn_cast<GlobalValue>(U)) {
+    GVtoClusterMap.unionSets(GV, GVU);
   } else {
     llvm_unreachable("Underimplemented use case");
   }
 }
 
 // Adds all GlobalValue users of V to the same cluster as GV.
 static void addAllGlobalValueUsers(ClusterMapType &GVtoClusterMap,
                                    const GlobalValue *GV, const Value *V) {
   for (auto *U : V->users()) {
     SmallVector<const User *, 4> Worklist;
     Worklist.push_back(U);
     while (!Worklist.empty()) {
       const User *UU = Worklist.pop_back_val();
       // For each constant that is not a GV (a pure const) recurse.
       if (isa<Constant>(UU) && !isa<GlobalValue>(UU)) {
         Worklist.append(UU->user_begin(), UU->user_end());
         continue;
       }
       addNonConstUser(GVtoClusterMap, GV, UU);
     }
   }
 }
 
+static const GlobalObject *getGVPartitioningRoot(const GlobalValue *GV)
+{
+  const GlobalObject *GO = GV->getAliaseeObject();
+  if (const auto *GI = dyn_cast_or_null<GlobalIFunc>(GO))
+    GO = GI->getResolverFunction();
+  return GO;
+}
+
 // Find partitions for module in the way that no locals need to be
 // globalized.
 // Try to balance pack those partitions into N files since this roughly equals
 // thread balancing for the backend codegen step.
 static void findPartitions(Module &M, ClusterIDMapType &ClusterIDMap,
                            unsigned N) {
   // At this point module should have the proper mix of globals and locals.
   // As we attempt to partition this module, we must not change any
auto recordGVSet = [&GVtoClusterMap, &ComdatMembers](GlobalValue &GV) {
     if (const Comdat *C = GV.getComdat()) {
       auto &Member = ComdatMembers[C];
       if (Member)
         GVtoClusterMap.unionSets(Member, &GV);
       else
         Member = &GV;
     }
 
-    // For aliases we should not separate them from their aliasees regardless
-    // of linkage.
-    if (auto *GIS = dyn_cast<GlobalAlias>(&GV)) {
-      if (const GlobalObject *Aliasee = GIS->getAliaseeObject())
-        GVtoClusterMap.unionSets(&GV, Aliasee);
-    } else if (auto *GIS = dyn_cast<GlobalIFunc>(&GV)) {
-      GVtoClusterMap.unionSets(&GV, GIS->getResolverFunction());
-    }
+    // Aliases should not be separated from their aliasees and ifuncs should
+    // not be separated from their resolvers regardless of linkage.
+    if (const GlobalObject *Root = getGVPartitioningRoot(&GV))
+      if (&GV != Root)
+        GVtoClusterMap.unionSets(&GV, Root);
 
     if (const Function *F = dyn_cast<Function>(&GV)) {
       for (const BasicBlock &BB : *F) {
         BlockAddress *BA = BlockAddress::lookup(&BB);
         if (!BA || !BA->isConstantUsed())
           continue;
         addAllGlobalValueUsers(GVtoClusterMap, F, BA);
       }
static void externalize(GlobalValue *GV) {
   // Unnamed entities must be named consistently between modules. setName will
   // give a distinct name to each such entity.
   if (!GV->hasName())
     GV->setName("__llvmsplit_unnamed");
 }
 
 // Returns whether GV should be in partition (0-based) I of N.
 static bool isInPartition(const GlobalValue *GV, unsigned I, unsigned N) {
-  if (auto *GIS = dyn_cast<GlobalAlias>(GV)) {
-    if (const GlobalObject *Base = GIS->getAliaseeObject())
-      GV = Base;
-  } else if (auto *GIS = dyn_cast<GlobalIFunc>(GV)) {
-    GV = GIS->getResolverFunction();
-  }
+  if (const GlobalObject *Root = getGVPartitioningRoot(GV))
+    GV = Root;
 
   StringRef Name;
   if (const Comdat *C = GV->getComdat())
     Name = C->getName();
   else
     Name = GV->getName();
 
   // Partition by MD5 hash. We only need a few bits for evenness as the number

llvm/lib/Transforms/Utils/ValueMapper.cpp

 #include "llvm/ADT/SmallVector.h"
 #include "llvm/IR/Argument.h"
 #include "llvm/IR/BasicBlock.h"
 #include "llvm/IR/Constant.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/DerivedTypes.h"
 #include "llvm/IR/Function.h"
-#include "llvm/IR/GlobalIndirectSymbol.h"
+#include "llvm/IR/GlobalAlias.h"
+#include "llvm/IR/GlobalIFunc.h"
 #include "llvm/IR/GlobalObject.h"
 #include "llvm/IR/GlobalVariable.h"
 #include "llvm/IR/InlineAsm.h"
 #include "llvm/IR/Instruction.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/IR/Operator.h"
 #include "llvm/IR/Type.h"
DelayedBasicBlock(const BlockAddress &Old)
       : OldBB(Old.getBasicBlock()),
         TempBB(BasicBlock::Create(Old.getContext())) {}
 };
 
 struct WorklistEntry {
   enum EntryKind {
     MapGlobalInit,
     MapAppendingVar,
-    MapGlobalIndirectSymbol,
+    MapAliasOrIFunc,
     RemapFunction
   };
   struct GVInitTy {
     GlobalVariable *GV;
     Constant *Init;
   };
   struct AppendingGVTy {
     GlobalVariable *GV;
     Constant *InitPrefix;
   };
-  struct GlobalIndirectSymbolTy {
-    GlobalIndirectSymbol *GIS;
+  struct AliasOrIFuncTy {
+    GlobalValue *GV;
     Constant *Target;
   };
 
   unsigned Kind : 2;
   unsigned MCID : 29;
   unsigned AppendingGVIsOldCtorDtor : 1;
   unsigned AppendingGVNumNewMembers;
   union {
     GVInitTy GVInit;
     AppendingGVTy AppendingGV;
-    GlobalIndirectSymbolTy GlobalIndirectSymbol;
+    AliasOrIFuncTy AliasOrIFunc;
     Function *RemapF;
   } Data;
 };
 
 struct MappingContext {
   ValueToValueMapTy *VM;
   ValueMaterializer *Materializer = nullptr;
 
public:
   Metadata *mapMetadata(const Metadata *MD);
 
   void scheduleMapGlobalInitializer(GlobalVariable &GV, Constant &Init,
                                     unsigned MCID);
   void scheduleMapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
                                     bool IsOldCtorDtor,
                                     ArrayRef<Constant *> NewMembers,
                                     unsigned MCID);
-  void scheduleMapGlobalIndirectSymbol(GlobalIndirectSymbol &GIS, Constant &Target,
-                                       unsigned MCID);
+  void scheduleMapAliasOrIFunc(GlobalValue &GV, Constant &Target,
   void scheduleRemapFunction(Function &F, unsigned MCID);
 
   void flush();
 
 private:
   void mapAppendingVariable(GlobalVariable &GV, Constant *InitPrefix,
                             bool IsOldCtorDtor,
                             ArrayRef<Constant *> NewMembers);
case WorklistEntry::MapAppendingVar: {
       SmallVector<Constant *, 8> NewInits(
           drop_begin(AppendingInits, PrefixSize));
       AppendingInits.resize(PrefixSize);
       mapAppendingVariable(*E.Data.AppendingGV.GV,
                            E.Data.AppendingGV.InitPrefix,
                            E.AppendingGVIsOldCtorDtor, makeArrayRef(NewInits));
       break;
     }
-    case WorklistEntry::MapGlobalIndirectSymbol:
-      E.Data.GlobalIndirectSymbol.GIS->setIndirectSymbol(
-          mapConstant(E.Data.GlobalIndirectSymbol.Target));
+    case WorklistEntry::MapAliasOrIFunc: {
+      GlobalValue *GV = E.Data.AliasOrIFunc.GV;
+      Constant *Target = mapConstant(E.Data.AliasOrIFunc.Target);
+      if (auto *GA = dyn_cast<GlobalAlias>(GV))
+        GA->setAliasee(Target);
+      else if (auto *GI = dyn_cast<GlobalIFunc>(GV))
+        GI->setResolver(Target);
+      else
+        llvm_unreachable("Not alias or ifunc");
       break;
+    }
     case WorklistEntry::RemapFunction:
       remapFunction(*E.Data.RemapF);
       break;
     }
   }
   CurrentMCID = 0;
 
   // Finish logic for block addresses now that all global values have been
void Mapper::scheduleMapAppendingVariable(GlobalVariable &GV,
   WE.Data.AppendingGV.GV = &GV;
   WE.Data.AppendingGV.InitPrefix = InitPrefix;
   WE.AppendingGVIsOldCtorDtor = IsOldCtorDtor;
   WE.AppendingGVNumNewMembers = NewMembers.size();
   Worklist.push_back(WE);
   AppendingInits.append(NewMembers.begin(), NewMembers.end());
 }
 
-void Mapper::scheduleMapGlobalIndirectSymbol(GlobalIndirectSymbol &GIS,
-                                             Constant &Target, unsigned MCID) {
-  assert(AlreadyScheduled.insert(&GIS).second && "Should not reschedule");
+void Mapper::scheduleMapAliasOrIFunc(GlobalValue &GV, Constant &Target,
+                                     unsigned MCID) {
+  assert(AlreadyScheduled.insert(&GV).second && "Should not reschedule");
+  assert((isa<GlobalAlias>(GV) || isa<GlobalIFunc>(GV)) &&
+         "Should be alias or ifunc");
   assert(MCID < MCs.size() && "Invalid mapping context");
 
   WorklistEntry WE;
-  WE.Kind = WorklistEntry::MapGlobalIndirectSymbol;
+  WE.Kind = WorklistEntry::MapAliasOrIFunc;
   WE.MCID = MCID;
-  WE.Data.GlobalIndirectSymbol.GIS = &GIS;
-  WE.Data.GlobalIndirectSymbol.Target = &Target;
+  WE.Data.AliasOrIFunc.GV = &GV;
+  WE.Data.AliasOrIFunc.Target = &Target;
   Worklist.push_back(WE);
 }
 
 void Mapper::scheduleRemapFunction(Function &F, unsigned MCID) {
   assert(AlreadyScheduled.insert(&F).second && "Should not reschedule");
   assert(MCID < MCs.size() && "Invalid mapping context");
 
   WorklistEntry WE;
void ValueMapper::scheduleMapAppendingVariable(GlobalVariable &GV,
                                                Constant *InitPrefix,
                                                bool IsOldCtorDtor,
                                                ArrayRef<Constant *> NewMembers,
                                                unsigned MCID) {
   getAsMapper(pImpl)->scheduleMapAppendingVariable(
       GV, InitPrefix, IsOldCtorDtor, NewMembers, MCID);
 }
 
-void ValueMapper::scheduleMapGlobalIndirectSymbol(GlobalIndirectSymbol &GIS,
-                                                  Constant &Target,
-                                                  unsigned MCID) {
-  getAsMapper(pImpl)->scheduleMapGlobalIndirectSymbol(GIS, Target, MCID);
+void ValueMapper::scheduleMapGlobalAlias(GlobalAlias &GA, Constant &Aliasee,
+                                         unsigned MCID) {
+  getAsMapper(pImpl)->scheduleMapAliasOrIFunc(GA, Aliasee, MCID);
+}
+
+void ValueMapper::scheduleMapGlobalIFunc(GlobalIFunc &GI, Constant &Resolver,
+  getAsMapper(pImpl)->scheduleMapAliasOrIFunc(GI, Resolver, MCID);
 }
 
 void ValueMapper::scheduleRemapFunction(Function &F, unsigned MCID) {
   getAsMapper(pImpl)->scheduleRemapFunction(F, MCID);
 }

llvm/unittests/IR/ConstantsTest.cpp

auto *Placeholder = new GlobalVariable(
       *M, IntTy, false, GlobalValue::ExternalWeakLinkage, nullptr);
   auto *GEP = ConstantExpr::getGetElementPtr(IntTy, Placeholder, C1);
   ASSERT_EQ(GEP->getOperand(0), Placeholder);
 
   auto *Ref =
       new GlobalVariable(*M, PtrTy, false, GlobalValue::ExternalLinkage, GEP);
   ASSERT_EQ(GEP, Ref->getInitializer());
 
-  auto *Global = new GlobalVariable(*M, PtrTy, false,
+  auto *Global = new GlobalVariable(*M, IntTy, false,
                                     GlobalValue::ExternalLinkage, nullptr);
   auto *Alias = GlobalAlias::create(IntTy, 0, GlobalValue::ExternalLinkage,
                                     "alias", Global, M.get());
   Placeholder->replaceAllUsesWith(Alias);
   ASSERT_EQ(GEP, Ref->getInitializer());
   ASSERT_EQ(GEP->getOperand(0), Alias);
 }
 
 TEST(ConstantsTest, AliasCAPI) {