Rename accessor, add more tests for MS zero size conventions

Author: amykhuang

clang/include/clang/Basic/Attr.td

@@ -1801,7 +1801,7 @@ def ArmMveStrictPolymorphism : TypeAttr, TargetSpecificAttr<TargetARM> {
 def NoUniqueAddress : InheritableAttr {
   let Spellings = [CXX11<"", "no_unique_address", 201803>,
                    CXX11<"msvc", "no_unique_address", 201803>];
-  let Accessors = [Accessor<"isDefault", [CXX11<"", "no_unique_address", 201803>]>,
+  let Accessors = [Accessor<"isStandard", [CXX11<"", "no_unique_address", 201803>]>,
                    Accessor<"isMSVC", [CXX11<"msvc", "no_unique_address", 201803>]>];
   let Subjects = SubjectList<[NonBitField], ErrorDiag>;
   let Documentation = [NoUniqueAddressDocs];

clang/lib/AST/Decl.cpp

@@ -4510,7 +4510,8 @@ bool FieldDecl::isZeroSize(const ASTContext &Ctx) const {
   if (!Ctx.getTargetInfo().getCXXABI().isMicrosoft())
     return true;
 
-  // MS ABI: nonzero if class type with class type fields
+  // MS ABI: has nonzero size if it is a class type with class type fields,
+  // whether or not they have nonzero size
   return !llvm::any_of(CXXRD->fields(), [](const FieldDecl *Field) {
     return Field->getType()->getAs<RecordType>();
   });

clang/lib/AST/RecordLayoutBuilder.cpp

@@ -2599,10 +2599,6 @@ struct MicrosoftRecordLayoutBuilder {
       const CXXRecordDecl *RD) const;
   const ASTContext &Context;
   EmptySubobjectMap *EmptySubobjects;
-  llvm::SpecificBumpPtrAllocator<BaseSubobjectInfo> BaseSubobjectInfoAllocator;
-  typedef llvm::DenseMap<const CXXRecordDecl *, BaseSubobjectInfo *>
-      BaseSubobjectInfoMapTy;
-  BaseSubobjectInfoMapTy VirtualBaseInfo;
 
   /// The size of the record being laid out.
   CharUnits Size;
@@ -2873,12 +2869,12 @@ MicrosoftRecordLayoutBuilder::layoutNonVirtualBases(const CXXRecordDecl *RD) {
   bool CheckLeadingLayout = !PrimaryBase;
   // Iterate through the bases and lay out the non-virtual ones.
   for (const CXXBaseSpecifier &Base : RD->bases()) {
-    const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
-    const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
-
     if (Base.isVirtual())
       continue;
 
+    const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
+    const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
+
     // Only lay out bases without extendable VFPtrs on the second pass.
     if (BaseLayout.hasExtendableVFPtr()) {
       VBPtrOffset = Bases[BaseDecl] + BaseLayout.getNonVirtualSize();
@@ -3146,7 +3142,6 @@ void MicrosoftRecordLayoutBuilder::injectVFPtr(const CXXRecordDecl *RD) {
 void MicrosoftRecordLayoutBuilder::layoutVirtualBases(const CXXRecordDecl *RD) {
   if (!HasVBPtr)
     return;
-
   // Vtordisps are always 4 bytes (even in 64-bit mode)
   CharUnits VtorDispSize = CharUnits::fromQuantity(4);
   CharUnits VtorDispAlignment = VtorDispSize;

clang/lib/Sema/SemaDeclAttr.cpp

@@ -8374,7 +8374,7 @@ static void handleNoMergeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
 static void handleNoUniqueAddressAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
   NoUniqueAddressAttr TmpAttr(S.Context, AL);
   if (S.getLangOpts().MSVCCompat) {
-    if (TmpAttr.isDefault()) {
+    if (TmpAttr.isStandard()) {
       S.Diag(AL.getLoc(), diag::warn_attribute_ignored) << AL;
       return;
     }

clang/test/Layout/ms-no-unique-address.cpp

@@ -336,3 +336,46 @@ namespace VBases {
   // CHECK-NEXT:      | [sizeof=16, align=8,
   // CHECK-NEXT:      |  nvsize=16, nvalign=8]
 }
+
+namespace ZeroSize {
+  struct empty {};
+
+  union empty_union {};
+
+  struct empty_union_container {
+    [[msvc::no_unique_address]] empty_union x;
+  };
+
+  union union_of_empty {
+    [[msvc::no_unique_address]] empty x;
+  };
+
+  struct struct_of_empty {
+    [[msvc::no_unique_address]] empty x;
+  };
+
+  struct union_of_empty_container {
+    [[msvc::no_unique_address]] union_of_empty x;
+  };
+  static_assert(sizeof(union_of_empty_container) == 1);
+  // CHECK:*** Dumping AST Record Layout
+  // CHECK:         0 | struct ZeroSize::union_of_empty_container
+  // CHECK-NOT: (empty)
+  // CHECK:         0 |   union ZeroSize::union_of_empty x (empty)
+  // CHECK:         0 |     struct ZeroSize::empty x (empty)
+  // CHECK:           | [sizeof=1, align=1,
+  // CHECK:           |  nvsize=1, nvalign=1] 
+
+  struct struct_of_empty_container {
+    [[msvc::no_unique_address]] struct_of_empty x;
+  }; 
+  static_assert(sizeof(struct_of_empty_container) == 1);
+  // CHECK:*** Dumping AST Record Layout
+  // CHECK:         0 | struct ZeroSize::struct_of_empty_container
+  // CHECK-NOT: (empty)
+  // CHECK:         0 |   struct ZeroSize::struct_of_empty x (empty)
+  // CHECK:         0 |     struct ZeroSize::empty x (empty)
+  // CHECK:           | [sizeof=1, align=1,
+  // CHECK:           |  nvsize=1, nvalign=1] 
+
+}