[Lldb-commits] [lldb] [clang-tools-extra] [clang] [c++20] P1907R1: Support for generalized non-type template arguments of scalar type. (PR #78041)

via lldb-commits lldb-commits at lists.llvm.org
Sat Jan 13 07:00:32 PST 2024


llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang

@llvm/pr-subscribers-lldb

Author: Andrey Ali Khan Bolshakov (bolshakov-a)

<details>
<summary>Changes</summary>

Previously committed as 9e08e51a20d0d2b1c5724bb17e969d036fced4cd, and reverted because a dependency commit was reverted, then committed again as 4b574008aef5a7235c1f894ab065fe300d26e786 and reverted again because "dependency commit" 5a391d38ac6c561ba908334d427f26124ed9132e was reverted. But it doesn't seem that 5a391d38ac6c was a real dependency for this.

This commit incorporates 4b574008aef5a7235c1f894ab065fe300d26e786 and 18e093faf726d15f210ab4917142beec51848258 by Richard Smith (@<!-- -->zygoloid), with some minor fixes, most notably:

- `UncommonValue` renamed to `StructuralValue`

- `VK_PRValue` instead of `VK_RValue` as default kind in lvalue and member pointer handling branch in `BuildExpressionFromNonTypeTemplateArgumentValue`;

- handling of `StructuralValue` in `IsTypeDeclaredInsideVisitor`;

- filling in `SugaredConverted` along with `CanonicalConverted` parameter in `Sema::CheckTemplateArgument`;

- minor cleanup in `TemplateInstantiator::transformNonTypeTemplateParmRef`;

- `TemplateArgument` constructors refactored;

- `ODRHash` calculation for `UncommonValue`;

- USR generation for `UncommonValue`;

- more correct MS compatibility mangling algorithm (tested on MSVC ver. 19.35; toolset ver. 143);

- IR emitting fixed on using a subobject as a template argument when the corresponding template parameter is used in an lvalue context;

- `noundef` attribute and opaque pointers in `template-arguments` test;

- analysis for C++17 mode is turned off for templates in `warn-bool-conversion` test; in C++17 and C++20 mode, array reference used as a template argument of pointer type produces template argument of UncommonValue type, and `BuildExpressionFromNonTypeTemplateArgumentValue` makes `OpaqueValueExpr` for it, and `DiagnoseAlwaysNonNullPointer` cannot see through it; despite of "These cases should not warn" comment, I'm not sure about correct behavior; I'd expect a suggestion to replace `if` by `if constexpr`;

- `temp.arg.nontype/p1.cpp` and `dr18xx.cpp` tests fixed.

---

Patch is 101.36 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/78041.diff


47 Files Affected:

- (modified) clang-tools-extra/clangd/DumpAST.cpp (+1) 
- (modified) clang-tools-extra/clangd/FindTarget.cpp (+1) 
- (modified) clang/docs/ReleaseNotes.rst (+2) 
- (modified) clang/include/clang/AST/ODRHash.h (+3) 
- (modified) clang/include/clang/AST/PropertiesBase.td (+14) 
- (modified) clang/include/clang/AST/RecursiveASTVisitor.h (+2) 
- (modified) clang/include/clang/AST/TemplateArgumentVisitor.h (+2) 
- (modified) clang/include/clang/AST/TemplateBase.h (+55-31) 
- (modified) clang/include/clang/Basic/DiagnosticSemaKinds.td (-5) 
- (modified) clang/include/clang/Sema/Sema.h (+2-2) 
- (modified) clang/lib/AST/ASTContext.cpp (+5) 
- (modified) clang/lib/AST/ASTImporter.cpp (+13) 
- (modified) clang/lib/AST/ASTStructuralEquivalence.cpp (+4) 
- (modified) clang/lib/AST/Decl.cpp (+4) 
- (modified) clang/lib/AST/ItaniumMangle.cpp (+37-2) 
- (modified) clang/lib/AST/MicrosoftMangle.cpp (+62-16) 
- (modified) clang/lib/AST/ODRHash.cpp (+72) 
- (modified) clang/lib/AST/StmtProfile.cpp (+6) 
- (modified) clang/lib/AST/TemplateBase.cpp (+110-3) 
- (modified) clang/lib/AST/TypeLoc.cpp (+1) 
- (modified) clang/lib/CodeGen/CGDebugInfo.cpp (+10) 
- (modified) clang/lib/CodeGen/CGExpr.cpp (+12-3) 
- (modified) clang/lib/Index/USRGeneration.cpp (+10) 
- (modified) clang/lib/Sema/SemaLookup.cpp (+1) 
- (modified) clang/lib/Sema/SemaOverload.cpp (+9-1) 
- (modified) clang/lib/Sema/SemaTemplate.cpp (+130-88) 
- (modified) clang/lib/Sema/SemaTemplateDeduction.cpp (+46-18) 
- (modified) clang/lib/Sema/SemaTemplateInstantiate.cpp (+6-8) 
- (modified) clang/lib/Sema/SemaTemplateVariadic.cpp (+2) 
- (modified) clang/lib/Sema/TreeTransform.h (+10-2) 
- (modified) clang/lib/Serialization/ASTReader.cpp (+1) 
- (modified) clang/lib/Serialization/ASTWriter.cpp (+1) 
- (modified) clang/test/CXX/drs/dr18xx.cpp (+2-2) 
- (modified) clang/test/CXX/temp/temp.arg/temp.arg.nontype/p1.cpp (+3-1) 
- (modified) clang/test/CodeGenCXX/mangle-ms-templates.cpp (+48) 
- (modified) clang/test/CodeGenCXX/mangle-template.cpp (+39-1) 
- (added) clang/test/CodeGenCXX/template-arguments.cpp (+113) 
- (added) clang/test/Index/USR/structural-value-tpl-arg.cpp (+23) 
- (modified) clang/test/Modules/odr_hash.cpp (+190-3) 
- (modified) clang/test/SemaCXX/warn-bool-conversion.cpp (+2) 
- (modified) clang/test/SemaTemplate/temp_arg_nontype_cxx1z.cpp (+19-21) 
- (modified) clang/test/SemaTemplate/temp_arg_nontype_cxx20.cpp (+22-18) 
- (modified) clang/tools/libclang/CIndex.cpp (+5) 
- (modified) clang/tools/libclang/CXCursor.cpp (+3) 
- (modified) clang/www/cxx_status.html (+13-5) 
- (modified) lldb/include/lldb/lldb-enumerations.h (+1) 
- (modified) lldb/source/Plugins/TypeSystem/Clang/TypeSystemClang.cpp (+3) 


``````````diff
diff --git a/clang-tools-extra/clangd/DumpAST.cpp b/clang-tools-extra/clangd/DumpAST.cpp
index b0cec65c39fa31..9a525efb938e8d 100644
--- a/clang-tools-extra/clangd/DumpAST.cpp
+++ b/clang-tools-extra/clangd/DumpAST.cpp
@@ -143,6 +143,7 @@ class DumpVisitor : public RecursiveASTVisitor<DumpVisitor> {
       TEMPLATE_ARGUMENT_KIND(Declaration);
       TEMPLATE_ARGUMENT_KIND(Template);
       TEMPLATE_ARGUMENT_KIND(TemplateExpansion);
+      TEMPLATE_ARGUMENT_KIND(StructuralValue);
 #undef TEMPLATE_ARGUMENT_KIND
     }
     llvm_unreachable("Unhandled ArgKind enum");
diff --git a/clang-tools-extra/clangd/FindTarget.cpp b/clang-tools-extra/clangd/FindTarget.cpp
index 839cf6332fe8b0..a4a261030d399b 100644
--- a/clang-tools-extra/clangd/FindTarget.cpp
+++ b/clang-tools-extra/clangd/FindTarget.cpp
@@ -1032,6 +1032,7 @@ class ExplicitReferenceCollector
     case TemplateArgument::Pack:
     case TemplateArgument::Type:
     case TemplateArgument::Expression:
+    case TemplateArgument::StructuralValue:
       break; // Handled by VisitType and VisitExpression.
     };
     return RecursiveASTVisitor::TraverseTemplateArgumentLoc(A);
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 3cbce1be159437..57c444fd95be1b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -180,6 +180,8 @@ C++ Language Changes
 
 C++20 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
+- Implemented `P1907R1 <https://wg21.link/P1907R1>` which extends allowed non-type template argument
+  kinds with e.g. floating point values and pointers and references to subobjects.
 
 C++23 Feature Support
 ^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/AST/ODRHash.h b/clang/include/clang/AST/ODRHash.h
index cedf644520fc32..a1caa6d39a87c3 100644
--- a/clang/include/clang/AST/ODRHash.h
+++ b/clang/include/clang/AST/ODRHash.h
@@ -25,6 +25,7 @@
 
 namespace clang {
 
+class APValue;
 class Decl;
 class IdentifierInfo;
 class NestedNameSpecifier;
@@ -101,6 +102,8 @@ class ODRHash {
   // Save booleans until the end to lower the size of data to process.
   void AddBoolean(bool value);
 
+  void AddStructuralValue(const APValue &);
+
   static bool isSubDeclToBeProcessed(const Decl *D, const DeclContext *Parent);
 
 private:
diff --git a/clang/include/clang/AST/PropertiesBase.td b/clang/include/clang/AST/PropertiesBase.td
index d86c4eba6a2251..0270c086d06b6a 100644
--- a/clang/include/clang/AST/PropertiesBase.td
+++ b/clang/include/clang/AST/PropertiesBase.td
@@ -808,6 +808,20 @@ let Class = PropertyTypeCase<TemplateArgument, "Integral"> in {
     return TemplateArgument(ctx, value, type, isDefaulted);
   }]>;
 }
+let Class = PropertyTypeCase<TemplateArgument, "StructuralValue"> in {
+  def : Property<"value", APValue> {
+    let Read = [{ node.getAsStructuralValue() }];
+  }
+  def : Property<"type", QualType> {
+    let Read = [{ node.getStructuralValueType() }];
+  }
+  def : Property<"isDefaulted", Bool> {
+    let Read = [{ node.getIsDefaulted() }];
+  }
+  def : Creator<[{
+    return TemplateArgument(ctx, type, value, isDefaulted);
+  }]>;
+}
 let Class = PropertyTypeCase<TemplateArgument, "Template"> in {
   def : Property<"name", TemplateName> {
     let Read = [{ node.getAsTemplateOrTemplatePattern() }];
diff --git a/clang/include/clang/AST/RecursiveASTVisitor.h b/clang/include/clang/AST/RecursiveASTVisitor.h
index 8f2714e142bbe3..2aee6a947141b6 100644
--- a/clang/include/clang/AST/RecursiveASTVisitor.h
+++ b/clang/include/clang/AST/RecursiveASTVisitor.h
@@ -850,6 +850,7 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgument(
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
   case TemplateArgument::NullPtr:
+  case TemplateArgument::StructuralValue:
     return true;
 
   case TemplateArgument::Type:
@@ -882,6 +883,7 @@ bool RecursiveASTVisitor<Derived>::TraverseTemplateArgumentLoc(
   case TemplateArgument::Declaration:
   case TemplateArgument::Integral:
   case TemplateArgument::NullPtr:
+  case TemplateArgument::StructuralValue:
     return true;
 
   case TemplateArgument::Type: {
diff --git a/clang/include/clang/AST/TemplateArgumentVisitor.h b/clang/include/clang/AST/TemplateArgumentVisitor.h
index 190aa97adf4551..cf0d3220158063 100644
--- a/clang/include/clang/AST/TemplateArgumentVisitor.h
+++ b/clang/include/clang/AST/TemplateArgumentVisitor.h
@@ -37,6 +37,7 @@ class Base {
       DISPATCH(Declaration);
       DISPATCH(NullPtr);
       DISPATCH(Integral);
+      DISPATCH(StructuralValue);
       DISPATCH(Template);
       DISPATCH(TemplateExpansion);
       DISPATCH(Expression);
@@ -59,6 +60,7 @@ class Base {
   VISIT_METHOD(Declaration);
   VISIT_METHOD(NullPtr);
   VISIT_METHOD(Integral);
+  VISIT_METHOD(StructuralValue);
   VISIT_METHOD(Template);
   VISIT_METHOD(TemplateExpansion);
   VISIT_METHOD(Expression);
diff --git a/clang/include/clang/AST/TemplateBase.h b/clang/include/clang/AST/TemplateBase.h
index b7cd71f17c9442..fea2c8ccfee675 100644
--- a/clang/include/clang/AST/TemplateBase.h
+++ b/clang/include/clang/AST/TemplateBase.h
@@ -50,6 +50,7 @@ template <> struct PointerLikeTypeTraits<clang::Expr *> {
 
 namespace clang {
 
+class APValue;
 class ASTContext;
 class Expr;
 struct PrintingPolicy;
@@ -80,6 +81,13 @@ class TemplateArgument {
     /// that was provided for an integral non-type template parameter.
     Integral,
 
+    /// The template argument is a non-type template argument that can't be
+    /// represented by the special-case Declaration, NullPtr, or Integral
+    /// forms. These values are only ever produced by constant evaluation,
+    /// so cannot be dependent.
+    /// TODO: merge Declaration, NullPtr and Integral into this?
+    StructuralValue,
+
     /// The template argument is a template name that was provided for a
     /// template template parameter.
     Template,
@@ -130,6 +138,14 @@ class TemplateArgument {
     };
     void *Type;
   };
+  struct V {
+    LLVM_PREFERRED_TYPE(ArgKind)
+    unsigned Kind : 31;
+    LLVM_PREFERRED_TYPE(bool)
+    unsigned IsDefaulted : 1;
+    APValue *Value;
+    void *Type;
+  };
   struct A {
     LLVM_PREFERRED_TYPE(ArgKind)
     unsigned Kind : 31;
@@ -156,11 +172,19 @@ class TemplateArgument {
   union {
     struct DA DeclArg;
     struct I Integer;
+    struct V Value;
     struct A Args;
     struct TA TemplateArg;
     struct TV TypeOrValue;
   };
 
+  void initFromType(QualType T, bool IsNullPtr, bool IsDefaulted);
+  void initFromDeclaration(ValueDecl *D, QualType QT, bool IsDefaulted);
+  void initFromIntegral(const ASTContext &Ctx, const llvm::APSInt &Value,
+                        QualType Type, bool IsDefaulted);
+  void initFromStructural(const ASTContext &Ctx, QualType Type,
+                          const APValue &V, bool IsDefaulted);
+
 public:
   /// Construct an empty, invalid template argument.
   constexpr TemplateArgument() : TypeOrValue({Null, 0, /* IsDefaulted */ 0}) {}
@@ -168,25 +192,22 @@ class TemplateArgument {
   /// Construct a template type argument.
   TemplateArgument(QualType T, bool isNullPtr = false,
                    bool IsDefaulted = false) {
-    TypeOrValue.Kind = isNullPtr ? NullPtr : Type;
-    TypeOrValue.IsDefaulted = IsDefaulted;
-    TypeOrValue.V = reinterpret_cast<uintptr_t>(T.getAsOpaquePtr());
+    initFromType(T, isNullPtr, IsDefaulted);
   }
 
-  /// Construct a template argument that refers to a
-  /// declaration, which is either an external declaration or a
-  /// template declaration.
+  /// Construct a template argument that refers to a (non-dependent)
+  /// declaration.
   TemplateArgument(ValueDecl *D, QualType QT, bool IsDefaulted = false) {
-    assert(D && "Expected decl");
-    DeclArg.Kind = Declaration;
-    DeclArg.IsDefaulted = IsDefaulted;
-    DeclArg.QT = QT.getAsOpaquePtr();
-    DeclArg.D = D;
+    initFromDeclaration(D, QT, IsDefaulted);
   }
 
   /// Construct an integral constant template argument. The memory to
   /// store the value is allocated with Ctx.
-  TemplateArgument(ASTContext &Ctx, const llvm::APSInt &Value, QualType Type,
+  TemplateArgument(const ASTContext &Ctx, const llvm::APSInt &Value,
+                   QualType Type, bool IsDefaulted = false);
+
+  /// Construct a template argument from an arbitrary constant value.
+  TemplateArgument(const ASTContext &Ctx, QualType Type, const APValue &Value,
                    bool IsDefaulted = false);
 
   /// Construct an integral constant template argument with the same
@@ -297,7 +318,7 @@ class TemplateArgument {
   /// Retrieve the type for a type template argument.
   QualType getAsType() const {
     assert(getKind() == Type && "Unexpected kind");
-    return QualType::getFromOpaquePtr(reinterpret_cast<void*>(TypeOrValue.V));
+    return QualType::getFromOpaquePtr(reinterpret_cast<void *>(TypeOrValue.V));
   }
 
   /// Retrieve the declaration for a declaration non-type
@@ -315,7 +336,7 @@ class TemplateArgument {
   /// Retrieve the type for null non-type template argument.
   QualType getNullPtrType() const {
     assert(getKind() == NullPtr && "Unexpected kind");
-    return QualType::getFromOpaquePtr(reinterpret_cast<void*>(TypeOrValue.V));
+    return QualType::getFromOpaquePtr(reinterpret_cast<void *>(TypeOrValue.V));
   }
 
   /// Retrieve the template name for a template name argument.
@@ -371,6 +392,14 @@ class TemplateArgument {
   /// default template parameter.
   bool getIsDefaulted() const { return (bool)TypeOrValue.IsDefaulted; }
 
+  /// Get the value of a StructuralValue.
+  const APValue &getAsStructuralValue() const { return *Value.Value; }
+
+  /// Get the type of a StructuralValue.
+  QualType getStructuralValueType() const {
+    return QualType::getFromOpaquePtr(Value.Type);
+  }
+
   /// If this is a non-type template argument, get its type. Otherwise,
   /// returns a null QualType.
   QualType getNonTypeTemplateArgumentType() const;
@@ -516,6 +545,7 @@ class TemplateArgumentLoc {
     assert(Argument.getKind() == TemplateArgument::NullPtr ||
            Argument.getKind() == TemplateArgument::Integral ||
            Argument.getKind() == TemplateArgument::Declaration ||
+           Argument.getKind() == TemplateArgument::StructuralValue ||
            Argument.getKind() == TemplateArgument::Expression);
   }
 
@@ -541,13 +571,9 @@ class TemplateArgumentLoc {
   /// - Fetches the full source range of the argument.
   SourceRange getSourceRange() const LLVM_READONLY;
 
-  const TemplateArgument &getArgument() const {
-    return Argument;
-  }
+  const TemplateArgument &getArgument() const { return Argument; }
 
-  TemplateArgumentLocInfo getLocInfo() const {
-    return LocInfo;
-  }
+  TemplateArgumentLocInfo getLocInfo() const { return LocInfo; }
 
   TypeSourceInfo *getTypeSourceInfo() const {
     if (Argument.getKind() != TemplateArgument::Type)
@@ -575,6 +601,11 @@ class TemplateArgumentLoc {
     return LocInfo.getAsExpr();
   }
 
+  Expr *getSourceStructuralValueExpression() const {
+    assert(Argument.getKind() == TemplateArgument::StructuralValue);
+    return LocInfo.getAsExpr();
+  }
+
   NestedNameSpecifierLoc getTemplateQualifierLoc() const {
     if (Argument.getKind() != TemplateArgument::Template &&
         Argument.getKind() != TemplateArgument::TemplateExpansion)
@@ -606,8 +637,7 @@ class TemplateArgumentListInfo {
 public:
   TemplateArgumentListInfo() = default;
 
-  TemplateArgumentListInfo(SourceLocation LAngleLoc,
-                           SourceLocation RAngleLoc)
+  TemplateArgumentListInfo(SourceLocation LAngleLoc, SourceLocation RAngleLoc)
       : LAngleLoc(LAngleLoc), RAngleLoc(RAngleLoc) {}
 
   // This can leak if used in an AST node, use ASTTemplateArgumentListInfo
@@ -626,21 +656,15 @@ class TemplateArgumentListInfo {
     return Arguments.data();
   }
 
-  llvm::ArrayRef<TemplateArgumentLoc> arguments() const {
-    return Arguments;
-  }
+  llvm::ArrayRef<TemplateArgumentLoc> arguments() const { return Arguments; }
 
   const TemplateArgumentLoc &operator[](unsigned I) const {
     return Arguments[I];
   }
 
-  TemplateArgumentLoc &operator[](unsigned I) {
-    return Arguments[I];
-  }
+  TemplateArgumentLoc &operator[](unsigned I) { return Arguments[I]; }
 
-  void addArgument(const TemplateArgumentLoc &Loc) {
-    Arguments.push_back(Loc);
-  }
+  void addArgument(const TemplateArgumentLoc &Loc) { Arguments.push_back(Loc); }
 };
 
 /// Represents an explicit template argument list in C++, e.g.,
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index 1a79892e40030a..8c74d12e674624 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -5138,8 +5138,6 @@ def err_non_type_template_arg_subobject : Error<
   "non-type template argument refers to subobject '%0'">;
 def err_non_type_template_arg_addr_label_diff : Error<
   "template argument / label address difference / what did you expect?">;
-def err_non_type_template_arg_unsupported : Error<
-  "sorry, non-type template argument of type %0 is not yet supported">;
 def err_template_arg_not_convertible : Error<
   "non-type template argument of type %0 cannot be converted to a value "
   "of type %1">;
@@ -5191,9 +5189,6 @@ def err_template_arg_not_object_or_func : Error<
   "non-type template argument does not refer to an object or function">;
 def err_template_arg_not_pointer_to_member_form : Error<
   "non-type template argument is not a pointer to member constant">;
-def err_template_arg_member_ptr_base_derived_not_supported : Error<
-  "sorry, non-type template argument of pointer-to-member type %1 that refers "
-  "to member %q0 of a different class is not supported yet">;
 def err_template_arg_invalid : Error<
   "non-type template argument '%0' is invalid">;
 def ext_template_arg_extra_parens : ExtWarn<
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index cf2d4fbe6d3ba1..a3881709263daa 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -8569,8 +8569,8 @@ class Sema final {
                                           QualType ParamType,
                                           SourceLocation Loc);
   ExprResult
-  BuildExpressionFromIntegralTemplateArgument(const TemplateArgument &Arg,
-                                              SourceLocation Loc);
+  BuildExpressionFromNonTypeTemplateArgument(const TemplateArgument &Arg,
+                                             SourceLocation Loc);
 
   /// Enumeration describing how template parameter lists are compared
   /// for equality.
diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp
index d9cefcaa84d7e5..2df986c8541057 100644
--- a/clang/lib/AST/ASTContext.cpp
+++ b/clang/lib/AST/ASTContext.cpp
@@ -6753,6 +6753,11 @@ ASTContext::getCanonicalTemplateArgument(const TemplateArgument &Arg) const {
     case TemplateArgument::Integral:
       return TemplateArgument(Arg, getCanonicalType(Arg.getIntegralType()));
 
+    case TemplateArgument::StructuralValue:
+      return TemplateArgument(*this,
+                              getCanonicalType(Arg.getStructuralValueType()),
+                              Arg.getAsStructuralValue());
+
     case TemplateArgument::Type:
       return TemplateArgument(getCanonicalType(Arg.getAsType()),
                               /*isNullPtr*/ false, Arg.getIsDefaulted());
diff --git a/clang/lib/AST/ASTImporter.cpp b/clang/lib/AST/ASTImporter.cpp
index b762d6a4cd3800..8c279dd1eb048b 100644
--- a/clang/lib/AST/ASTImporter.cpp
+++ b/clang/lib/AST/ASTImporter.cpp
@@ -823,6 +823,17 @@ ASTNodeImporter::import(const TemplateArgument &From) {
                             From.getIsDefaulted());
   }
 
+  case TemplateArgument::StructuralValue: {
+    ExpectedType ToTypeOrErr = import(From.getStructuralValueType());
+    if (!ToTypeOrErr)
+      return ToTypeOrErr.takeError();
+    Expected<APValue> ToValueOrErr = import(From.getAsStructuralValue());
+    if (!ToValueOrErr)
+      return ToValueOrErr.takeError();
+    return TemplateArgument(Importer.getToContext(), *ToTypeOrErr,
+                            *ToValueOrErr);
+  }
+
   case TemplateArgument::Template: {
     Expected<TemplateName> ToTemplateOrErr = import(From.getAsTemplate());
     if (!ToTemplateOrErr)
@@ -3572,6 +3583,8 @@ class IsTypeDeclaredInsideVisitor
     case TemplateArgument::NullPtr:
       // FIXME: The type is not allowed to be in the function?
       return CheckType(Arg.getNullPtrType());
+    case TemplateArgument::StructuralValue:
+      return CheckType(Arg.getStructuralValueType());
     case TemplateArgument::Pack:
       for (const auto &PackArg : Arg.getPackAsArray())
         if (checkTemplateArgument(PackArg))
diff --git a/clang/lib/AST/ASTStructuralEquivalence.cpp b/clang/lib/AST/ASTStructuralEquivalence.cpp
index a9e0d1698a9178..39a2f7ce61e135 100644
--- a/clang/lib/AST/ASTStructuralEquivalence.cpp
+++ b/clang/lib/AST/ASTStructuralEquivalence.cpp
@@ -628,6 +628,10 @@ static bool IsStructurallyEquivalent(StructuralEquivalenceContext &Context,
     return IsStructurallyEquivalent(Context, Arg1.getAsExpr(),
                                     Arg2.getAsExpr());
 
+  case TemplateArgument::StructuralValue:
+    // FIXME: Do we need to customize the comparison?
+    return Arg1.structurallyEquals(Arg2);
+
   case TemplateArgument::Pack:
     return IsStructurallyEquivalent(Context, Arg1.pack_elements(),
                                     Arg2.pack_elements());
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index e1440e5183a4e6..a2f50ae4ce8eeb 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -343,6 +343,10 @@ LinkageComputer::getLVForTemplateArgumentList(ArrayRef<TemplateArgument> Args,
       LV.merge(getTypeLinkageAndVisibility(Arg.getNullPtrType()));
       continue;
 
+    case TemplateArgument::StructuralValue:
+      LV.merge(getLVForValue(Arg.getAsStructuralValue(), computation));
+      continue;
+
     case TemplateArgument::Template:
     case TemplateArgument::TemplateExpansion:
       if (TemplateDecl *Template =
diff --git a/clang/lib/AST/ItaniumMangle.cpp b/clang/lib/AST/ItaniumMangle.cpp
index b1678479888eb7..d3ef822b371d5e 100644
--- a/clang/lib/AST/ItaniumMangle.cpp
+++ b/clang/lib/AST/ItaniumMangle.cpp
@@ -4833,9 +4833,26 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity,
     E = cast<CXXStdInitializerListExpr>(E)->getSubExpr();
     goto recurse;
 
-  case Expr::SubstNonTypeTemplateParmExprClass:
+  case Expr::SubstNonTypeTemplateParmExprClass: {
+    // Mangle a substituted parameter the same way we mangle the template
+    // argument.
+    auto *SNTTPE = cast<SubstNonTypeTemplateParmExpr>(E);
+    if (auto *CE = dyn_cast<ConstantExpr>(SNTTPE->getReplacement())) {
+      // Pull out the constant value and mangle it as a template argument.
+      QualType ParamType = SNTTPE->getParameterType(Context.getASTContext());
+      if (CE->hasAPValueResult())
+        mangleValueInTemplateArg(ParamType, CE->getResultAsAPValue(), false,
+                                 /*NeedExactType=*/true);
+      else
+        mangleValueInTemplateArg(ParamType, CE->getAPValueResult(), false,
+                                 /*NeedExactType=*/true);
+      break;
+    }
+    // The remaining cases all happen to be substituted with expressions that
+    // mangle the same as a corresponding template argument anyway.
     E = cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement();
     goto recurse;
+  }
 
   case Expr::UserDefinedLiteralClass:
     // We follow g++'s approach of mangling a UDL as a call to the literal
@@ -6064,6 +6081,11 @@ void CXXNameMangler::mangleTemplateArg(TemplateArgument A, bool NeedExactType) {
     mangleNullPointer(A.getNullPtrType());
     break;
   }
+  case TemplateArgument::StructuralValue:
+    mangleValueInTemplateArg(A.getStructuralValueType(),
+                             A.getAsStructuralValue(),
+                             /*TopLevel=*/true, NeedExactType);
+    break;
   case TemplateArgument::Pack: {
     //  <template-arg> ::= J <template-arg>* E
     Out << 'J';
@@ -6472,7 +6494,20 @@ void CXXNameMangler::mangleValueInTemplateArg(QualType T, const APValue &V,
       Out << "plcvPcad";
       Kind = Offset;
     } else {
-      if (!V.getLValuePath().empty() || V.isLValueOnePastTheEnd()) {
+      // Clang 11 and before mangled ...
[truncated]

``````````

</details>


https://github.com/llvm/llvm-project/pull/78041


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