Add Type::isSingleCapabilityRecord() helper function

This is duplicated twice in RISCVABIInfo and I intend to reuse this in
the following commit.

clang/include/clang/AST/Type.h

@@ -2239,6 +2239,9 @@ class alignas(8) Type : public ExtQualsTypeCommonBase {
   /// pointers.
   bool isCHERICapabilityType(const ASTContext &Context,
                              bool IncludeIntCap = true) const;
+  /// Returns true if this is a struct/union type that contains exactly one
+  /// capability element.
+  bool isSingleCapabilityRecord(const ASTContext &Context) const;
   /// Returns true for __uintcap_t or __intcap_t (and enums/_Atomic with that
   /// underlying type)
   bool isIntCapType() const;

clang/lib/AST/Type.cpp

@@ -650,6 +650,18 @@ bool Type::isCHERICapabilityType(const ASTContext &Context,
   return false;
 }
 
+bool Type::isSingleCapabilityRecord(const ASTContext &Context) const {
+  if (auto *RT = getAs<RecordType>())
+    return Context.containsCapabilities(RT->getDecl()) &&
+           Context.getTypeSize(this) ==
+               Context.getTargetInfo().getCHERICapabilityWidth();
+  if (const AtomicType *AT = getAs<AtomicType>())
+    return AT->getValueType()->isSingleCapabilityRecord(Context);
+  if (const AttributedType *AT = getAs<AttributedType>())
+    return AT->getModifiedType()->isSingleCapabilityRecord(Context);
+  return false;
+}
+
 bool Type::isIntCapType() const {
   if (const BuiltinType *BT = dyn_cast<BuiltinType>(CanonicalType))
     return BT->getKind() == BuiltinType::IntCap ||

clang/lib/CodeGen/Targets/RISCV.cpp

@@ -345,11 +345,7 @@ ABIArgInfo RISCVABIInfo::classifyArgumentType(QualType Ty, bool IsFixed,
 
   uint64_t Size = getContext().getTypeSize(Ty);
 
-  bool IsSingleCapRecord = false;
-  if (auto *RT = Ty->getAs<RecordType>())
-    IsSingleCapRecord = Size == getTarget().getCHERICapabilityWidth() &&
-                        getContext().containsCapabilities(RT->getDecl());
-
+  bool IsSingleCapRecord = Ty->isSingleCapabilityRecord(getContext());
   bool IsCapability = Ty->isCHERICapabilityType(getContext()) ||
                       IsSingleCapRecord;
 
@@ -495,13 +491,7 @@ Address RISCVABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
 
   auto TInfo = getContext().getTypeInfoInChars(Ty);
 
-  bool IsSingleCapRecord = false;
-  CharUnits CapabilityWidth =
-    CharUnits::fromQuantity(getTarget().getCHERICapabilityWidth() / 8);
-  if (const auto *RT = Ty->getAs<RecordType>())
-    IsSingleCapRecord = TInfo.Width == CapabilityWidth &&
-                        getContext().containsCapabilities(RT->getDecl());
-
+  bool IsSingleCapRecord = Ty->isSingleCapabilityRecord(getContext());
   bool IsCapability = Ty->isCHERICapabilityType(getContext()) ||
                       IsSingleCapRecord;