bloomberg · tambry · Apr 2, 2024 · Apr 8, 2024
diff --git a/P2996.md b/P2996.md
diff --git a/README.md b/README.md
@@ -1,3 +1,10 @@
+# Clang/P2996: An LLVM fork
+
+Welcome to Clang/P2996, a fork of the [`llvm/llvm-project`](
+https://github.com/llvm/llvm-project) implementing experimental support for ISO
+C++ proposal [P2996](https://wg21.link/p2996) in `clang`. Please see [P2996.md](
+P2996.md) for more about this project.
+
 # The LLVM Compiler Infrastructure
 
 [![OpenSSF Scorecard](https://api.securityscorecards.dev/projects/github.com/llvm/llvm-project/badge)](https://securityscorecards.dev/viewer/?uri=github.com/llvm/llvm-project)

diff --git a/clang/include/clang-c/Index.h b/clang/include/clang-c/Index.h
@@ -3109,6 +3109,7 @@ enum CXTemplateArgumentKind {
   CXTemplateArgumentKind_Declaration,
   CXTemplateArgumentKind_NullPtr,
   CXTemplateArgumentKind_Integral,
+  CXTemplateArgumentKind_Reflection,
   CXTemplateArgumentKind_Template,
   CXTemplateArgumentKind_TemplateExpansion,
   CXTemplateArgumentKind_Expression,

diff --git a/clang/include/clang/AST/APValue.h b/clang/include/clang/AST/APValue.h
@@ -1,5 +1,7 @@
 //===--- APValue.h - Union class for APFloat/APSInt/Complex -----*- C++ -*-===//
 //
+// Copyright 2024 Bloomberg Finance L.P.
+//
 // 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
@@ -13,6 +15,7 @@
 #ifndef LLVM_CLANG_AST_APVALUE_H
 #define LLVM_CLANG_AST_APVALUE_H
 
+#include "clang/AST/Reflection.h"
 #include "clang/Basic/LLVM.h"
 #include "llvm/ADT/APFixedPoint.h"
 #include "llvm/ADT/APFloat.h"
@@ -35,6 +38,7 @@ template <typename T> class BasicReaderBase;
   class DiagnosticBuilder;
   class Expr;
   class FieldDecl;
+  class NamespaceDecl;
   struct PrintingPolicy;
   class Type;
   class ValueDecl;
@@ -118,7 +122,7 @@ template<> struct PointerLikeTypeTraits<clang::DynamicAllocLValue> {
 namespace clang {
 /// APValue - This class implements a discriminated union of [uninitialized]
 /// [APSInt] [APFloat], [Complex APSInt] [Complex APFloat], [Expr + Offset],
-/// [Vector: N * APValue], [Array: N * APValue]
+/// [Vector: N * APValue], [Array: N * APValue], [ReflectionValue]
 class APValue {
   typedef llvm::APFixedPoint APFixedPoint;
   typedef llvm::APSInt APSInt;
@@ -140,7 +144,8 @@ class APValue {
     Struct,
     Union,
     MemberPointer,
-    AddrLabelDiff
+    AddrLabelDiff,
+    Reflection
   };
 
   class LValueBase {
@@ -308,7 +313,8 @@ class APValue {
   // We ensure elsewhere that Data is big enough for LV and MemberPointerData.
   typedef llvm::AlignedCharArrayUnion<void *, APSInt, APFloat, ComplexAPSInt,
                                       ComplexAPFloat, Vec, Arr, StructData,
-                                      UnionData, AddrLabelDiffData> DataType;
+                                      UnionData, AddrLabelDiffData,
+                                      ReflectionValue> DataType;
   static const size_t DataSize = sizeof(DataType);
 
   DataType Data;
@@ -363,6 +369,10 @@ class APValue {
       : Kind(None) {
     MakeAddrLabelDiff(); setAddrLabelDiff(LHSExpr, RHSExpr);
   }
+  APValue(ReflectionValue::ReflectionKind ReflKind, const void *ReflEntity)
+      : Kind(None) {
+    MakeReflection(ReflKind, ReflEntity);
+  }
   static APValue IndeterminateValue() {
     APValue Result;
     Result.Kind = Indeterminate;
@@ -410,6 +420,7 @@ class APValue {
   bool isUnion() const { return Kind == Union; }
   bool isMemberPointer() const { return Kind == MemberPointer; }
   bool isAddrLabelDiff() const { return Kind == AddrLabelDiff; }
+  bool isReflection() const { return Kind == Reflection; }
 
   void dump() const;
   void dump(raw_ostream &OS, const ASTContext &Context) const;
@@ -585,6 +596,21 @@ class APValue {
     return ((const AddrLabelDiffData *)(const char *)&Data)->RHSExpr;
   }
 
+  ReflectionValue &getReflection() {
+    assert(isReflection() && "Invalid accessor");
+    return *(ReflectionValue *)(char *)&Data;
+  }
+  const ReflectionValue &getReflection() const {
+    return const_cast<APValue*>(this)->getReflection();
+  }
+  QualType getReflectedType() const;
+  ConstantExpr *getReflectedConstValueExpr() const;
+  ValueDecl *getReflectedDecl() const;
+  const TemplateName getReflectedTemplate() const;
+  Decl *getReflectedNamespace() const;
+  CXXBaseSpecifier *getReflectedBaseSpecifier() const;
+  TagDataMemberSpec *getReflectedDataMemberSpec() const;
+
   void setInt(APSInt I) {
     assert(isInt() && "Invalid accessor");
     *(APSInt *)(char *)&Data = std::move(I);
@@ -679,6 +705,14 @@ class APValue {
     new ((void *)(char *)&Data) AddrLabelDiffData();
     Kind = AddrLabelDiff;
   }
+  void MakeReflection(ReflectionValue::ReflectionKind ReflKind,
+                      const void *ReflEntity) {
+    assert(isAbsent() && "Bad state change");
+
+    new ((void *)(char *)Data.buffer) ReflectionValue(
+            ReflKind, const_cast<void *>(ReflEntity));
+    Kind = Reflection;
+  }
 
 private:
   /// The following functions are used as part of initialization, during

diff --git a/clang/include/clang/AST/ASTContext.h b/clang/include/clang/AST/ASTContext.h
@@ -1,5 +1,7 @@
 //===- ASTContext.h - Context to hold long-lived AST nodes ------*- C++ -*-===//
 //
+// Copyright 2024 Bloomberg Finance L.P.
+//
 // 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
@@ -235,6 +237,8 @@ class ASTContext : public RefCountedBase<ASTContext> {
                                      ASTContext&>
     DependentTemplateSpecializationTypes;
   llvm::FoldingSet<PackExpansionType> PackExpansionTypes;
+  mutable llvm::FoldingSet<DependentReflectionSpliceType>
+    DependentReflectionSpliceTypes;
   mutable llvm::FoldingSet<ObjCObjectTypeImpl> ObjCObjectTypes;
   mutable llvm::FoldingSet<ObjCObjectPointerType> ObjCObjectPointerTypes;
   mutable llvm::FoldingSet<DependentUnaryTransformType>
@@ -1116,6 +1120,7 @@ class ASTContext : public RefCountedBase<ASTContext> {
   CanQualType BFloat16Ty;
   CanQualType Float16Ty; // C11 extension ISO/IEC TS 18661-3
   CanQualType VoidPtrTy, NullPtrTy;
+  CanQualType MetaInfoTy;
   CanQualType DependentTy, OverloadTy, BoundMemberTy, UnknownAnyTy;
   CanQualType BuiltinFnTy;
   CanQualType PseudoObjectTy, ARCUnbridgedCastTy;
@@ -1692,6 +1697,8 @@ class ASTContext : public RefCountedBase<ASTContext> {
                                 std::optional<unsigned> NumExpansions,
                                 bool ExpectPackInType = true);
 
+  QualType getReflectionSpliceType(Expr *E, QualType UnderlyingType) const;
+
   QualType getObjCInterfaceType(const ObjCInterfaceDecl *Decl,
                                 ObjCInterfaceDecl *PrevDecl = nullptr) const;
 
@@ -2217,6 +2224,7 @@ class ASTContext : public RefCountedBase<ASTContext> {
                                         const IdentifierInfo *Name) const;
   TemplateName getDependentTemplateName(NestedNameSpecifier *NNS,
                                         OverloadedOperatorKind Operator) const;
+  TemplateName getDependentTemplateName(CXXIndeterminateSpliceExpr *S) const;
   TemplateName
   getSubstTemplateTemplateParm(TemplateName replacement, Decl *AssociatedDecl,
                                unsigned Index,

diff --git a/clang/include/clang/AST/AbstractBasicReader.h b/clang/include/clang/AST/AbstractBasicReader.h
@@ -177,6 +177,10 @@ class DataStreamBasicReader : public BasicReaderBase<Impl> {
     return llvm::APInt(bitWidth, numWords, &data[0]);
   }
 
+  ReflectionValue readReflectionValue() {
+    llvm_unreachable("unimplemented");
+  }
+
   llvm::FixedPointSemantics readFixedPointSemantics() {
     unsigned width = asImpl().readUInt32();
     unsigned scale = asImpl().readUInt32();
@@ -284,6 +288,13 @@ class DataStreamBasicReader : public BasicReaderBase<Impl> {
         cur = NestedNameSpecifier::SuperSpecifier(ctx,
                                             asImpl().readCXXRecordDeclRef());
         continue;
+
+      case NestedNameSpecifier::IndeterminateSplice:
+        cur = NestedNameSpecifier::IndeterminateSpliceSpecifier(
+                ctx,
+                reinterpret_cast<CXXIndeterminateSpliceExpr *>(
+                      asImpl().readExprRef()));
+        continue;
       }
       llvm_unreachable("bad nested name specifier kind");
     }

diff --git a/clang/include/clang/AST/AbstractBasicWriter.h b/clang/include/clang/AST/AbstractBasicWriter.h
@@ -263,6 +263,10 @@ class DataStreamBasicWriter : public BasicWriterBase<Impl> {
       case NestedNameSpecifier::Super:
         asImpl().writeDeclRef(NNS->getAsRecordDecl());
         continue;
+
+      case NestedNameSpecifier::IndeterminateSplice:
+        asImpl().writeExprRef(NNS->getAsSpliceExpr());
+        continue;
       }
       llvm_unreachable("bad nested name specifier kind");
     }

diff --git a/clang/include/clang/AST/BuiltinTypes.def b/clang/include/clang/AST/BuiltinTypes.def
@@ -1,5 +1,7 @@
 //===-- BuiltinTypes.def - Metadata about BuiltinTypes ----------*- C++ -*-===//
 //
+// Copyright 2024 Bloomberg Finance L.P.
+//
 // 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
@@ -226,6 +228,10 @@ FLOATING_TYPE(Ibm128, Ibm128Ty)
 // This is the type of C++0x 'nullptr'.
 BUILTIN_TYPE(NullPtr, NullPtrTy)
 
+// This is this type proposed for C++2c by P2996 for representing
+// internal compiler objects reflected by a value.
+BUILTIN_TYPE(MetaInfo, MetaInfoTy)
+
 // The primitive Objective C 'id' type.  The user-visible 'id'
 // type is a typedef of an ObjCObjectPointerType to an
 // ObjCObjectType with this as its base.  In fact, this only ever

diff --git a/clang/include/clang/AST/ComputeDependence.h b/clang/include/clang/AST/ComputeDependence.h
@@ -1,5 +1,7 @@
 //===--- ComputeDependence.h -------------------------------------- C++ -*-===//
 //
+// Copyright 2024 Bloomberg Finance L.P.
+//
 // 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
@@ -94,6 +96,13 @@ class DesignatedInitExpr;
 class ParenListExpr;
 class PseudoObjectExpr;
 class AtomicExpr;
+class CXXReflectExpr;
+class CXXMetafunctionExpr;
+class CXXIndeterminateSpliceExpr;
+class CXXExprSpliceExpr;
+class CXXDependentMemberSpliceExpr;
+class StackLocationExpr;
+class ValueOfLValueExpr;
 class OMPArraySectionExpr;
 class OMPArrayShapingExpr;
 class OMPIteratorExpr;
@@ -189,6 +198,14 @@ ExprDependence computeDependence(ParenListExpr *E);
 ExprDependence computeDependence(PseudoObjectExpr *E);
 ExprDependence computeDependence(AtomicExpr *E);
 
+ExprDependence computeDependence(CXXReflectExpr *E, const ASTContext &C);
+ExprDependence computeDependence(CXXMetafunctionExpr *E);
+ExprDependence computeDependence(CXXIndeterminateSpliceExpr *E);
+ExprDependence computeDependence(CXXExprSpliceExpr *E);
+ExprDependence computeDependence(CXXDependentMemberSpliceExpr *E);
+ExprDependence computeDependence(StackLocationExpr *E);
+ExprDependence computeDependence(ValueOfLValueExpr *E);
+
 ExprDependence computeDependence(OMPArraySectionExpr *E);
 ExprDependence computeDependence(OMPArrayShapingExpr *E);
 ExprDependence computeDependence(OMPIteratorExpr *E);

diff --git a/clang/include/clang/AST/Decl.h b/clang/include/clang/AST/Decl.h
@@ -562,10 +562,12 @@ class NamespaceDecl : public NamedDecl, public DeclContext,
   llvm::PointerIntPair<NamespaceDecl *, 2, unsigned>
       AnonOrFirstNamespaceAndFlags;
 
-  NamespaceDecl(ASTContext &C, DeclContext *DC, bool Inline,
+protected:
+  NamespaceDecl(Kind K, ASTContext &C, DeclContext *DC, bool Inline,
                 SourceLocation StartLoc, SourceLocation IdLoc,
                 IdentifierInfo *Id, NamespaceDecl *PrevDecl, bool Nested);
 
+private:
   using redeclarable_base = Redeclarable<NamespaceDecl>;
 
   NamespaceDecl *getNextRedeclarationImpl() override;
@@ -689,7 +691,9 @@ class NamespaceDecl : public NamedDecl, public DeclContext,
 
   // Implement isa/cast/dyncast/etc.
   static bool classof(const Decl *D) { return classofKind(D->getKind()); }
-  static bool classofKind(Kind K) { return K == Namespace; }
+  static bool classofKind(Kind K) {
+    return K >= firstNamespace && K <= lastNamespace;
+  }
   static DeclContext *castToDeclContext(const NamespaceDecl *D) {
     return static_cast<DeclContext *>(const_cast<NamespaceDecl*>(D));
   }
@@ -4296,6 +4300,10 @@ class RecordDecl : public TagDecl {
 
   void setIsRandomized(bool V) { RecordDeclBits.IsRandomized = V; }
 
+  bool isMetaType() const { return RecordDeclBits.IsMetaType; }
+
+  void setIsMetaType(bool V) { RecordDeclBits.IsMetaType = V; }
+
   void reorderDecls(const SmallVectorImpl<Decl *> &Decls);
 
   /// Determines whether this declaration represents the

diff --git a/clang/include/clang/AST/DeclBase.h b/clang/include/clang/AST/DeclBase.h
@@ -1668,9 +1668,13 @@ class DeclContext {
     LLVM_PREFERRED_TYPE(bool)
     uint64_t IsRandomized : 1;
 
+    /// Indicates whether this struct is a meta type.
+    LLVM_PREFERRED_TYPE(bool)
+    uint64_t IsMetaType : 1;
+
     /// True if a valid hash is stored in ODRHash. This should shave off some
     /// extra storage and prevent CXXRecordDecl to store unused bits.
-    uint64_t ODRHash : 26;
+    uint64_t ODRHash : 25;
   };
 
   /// Number of inherited and non-inherited bits in RecordDeclBitfields.