[clang] 4a55d42 - Implement [[msvc::no_unique_address]] (#65675)
via cfe-commits
cfe-commits at lists.llvm.org
Fri Sep 22 13:28:41 PDT 2023
Author: Amy Huang
Date: 2023-09-22T13:28:38-07:00
New Revision: 4a55d426967b9c70f5dea7b3a389e11393a4f4c4
URL: https://github.com/llvm/llvm-project/commit/4a55d426967b9c70f5dea7b3a389e11393a4f4c4
DIFF: https://github.com/llvm/llvm-project/commit/4a55d426967b9c70f5dea7b3a389e11393a4f4c4.diff
LOG: Implement [[msvc::no_unique_address]] (#65675)
This implements the [[msvc::no_unique_address]] attribute.
There is not ABI compatibility in this patch because the attribute is
relatively new and there's still some uncertainty in the MSVC version.
Bug: https://github.com/llvm/llvm-project/issues/49358
Also see https://reviews.llvm.org/D157762.
Added:
clang/test/Layout/ms-no-unique-address.cpp
clang/test/SemaCXX/cxx2a-ms-no-unique-address.cpp
Modified:
clang/include/clang/Basic/Attr.td
clang/include/clang/Basic/AttrDocs.td
clang/lib/AST/Decl.cpp
clang/lib/AST/RecordLayoutBuilder.cpp
clang/lib/Parse/ParseDeclCXX.cpp
clang/lib/Sema/SemaDeclAttr.cpp
clang/test/Preprocessor/has_attribute.cpp
Removed:
################################################################################
diff --git a/clang/include/clang/Basic/Attr.td b/clang/include/clang/Basic/Attr.td
index 21a3b5226623cf2..bb8d204f33dc531 100644
--- a/clang/include/clang/Basic/Attr.td
+++ b/clang/include/clang/Basic/Attr.td
@@ -1798,11 +1798,24 @@ def ArmMveStrictPolymorphism : TypeAttr, TargetSpecificAttr<TargetARM> {
let Documentation = [ArmMveStrictPolymorphismDocs];
}
-def NoUniqueAddress : InheritableAttr, TargetSpecificAttr<TargetItaniumCXXABI> {
- let Spellings = [CXX11<"", "no_unique_address", 201803>];
+def NoUniqueAddress : InheritableAttr {
let Subjects = SubjectList<[NonBitField], ErrorDiag>;
+ // No spellings because instances of this attribute are created by
+ // MSNoUniqueAddress and ItaniumNoUniqueAddress
+ let Spellings = [];
+ let Documentation = [NoUniqueAddressDocs];
+}
+
+def MSNoUniqueAddress : InheritableAttr, TargetSpecificAttr<TargetMicrosoftCXXABI> {
+ let Subjects = SubjectList<[NonBitField], ErrorDiag>;
+ let Spellings = [CXX11<"msvc", "no_unique_address", 201803>];
+ let Documentation = [NoUniqueAddressDocs];
+}
+
+def ItaniumNoUniqueAddress : InheritableAttr, TargetSpecificAttr<TargetItaniumCXXABI> {
+ let Subjects = SubjectList<[NonBitField], ErrorDiag>;
+ let Spellings = [CXX11<"", "no_unique_address", 201803>];
let Documentation = [NoUniqueAddressDocs];
- let SimpleHandler = 1;
}
def ReturnsTwice : InheritableAttr {
diff --git a/clang/include/clang/Basic/AttrDocs.td b/clang/include/clang/Basic/AttrDocs.td
index b13baa46754cfd4..18428d26b5dc8f2 100644
--- a/clang/include/clang/Basic/AttrDocs.td
+++ b/clang/include/clang/Basic/AttrDocs.td
@@ -1405,6 +1405,10 @@ Example usage:
``[[no_unique_address]]`` is a standard C++20 attribute. Clang supports its use
in C++11 onwards.
+
+On MSVC targets, ``[[no_unique_address]]`` is ignored; use
+``[[msvc::no_unique_address]]`` instead. Currently there is no guarantee of ABI
+compatibility or stability.
}];
}
diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 08ae2087cfe70eb..07aee0d87c835a8 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -4507,9 +4507,14 @@ bool FieldDecl::isZeroSize(const ASTContext &Ctx) const {
// Otherwise, [...] the circumstances under which the object has zero size
// are implementation-defined.
- // FIXME: This might be Itanium ABI specific; we don't yet know what the MS
- // ABI will do.
- return true;
+ if (!Ctx.getTargetInfo().getCXXABI().isMicrosoft())
+ return true;
+
+ // 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>();
+ });
}
bool FieldDecl::isPotentiallyOverlapping() const {
diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp
index 8afd88ae7be27b3..f1f2275da44dcad 100644
--- a/clang/lib/AST/RecordLayoutBuilder.cpp
+++ b/clang/lib/AST/RecordLayoutBuilder.cpp
@@ -2545,7 +2545,10 @@ struct MicrosoftRecordLayoutBuilder {
CharUnits Alignment;
};
typedef llvm::DenseMap<const CXXRecordDecl *, CharUnits> BaseOffsetsMapTy;
- MicrosoftRecordLayoutBuilder(const ASTContext &Context) : Context(Context) {}
+ MicrosoftRecordLayoutBuilder(const ASTContext &Context,
+ EmptySubobjectMap *EmptySubobjects)
+ : Context(Context), EmptySubobjects(EmptySubobjects) {}
+
private:
MicrosoftRecordLayoutBuilder(const MicrosoftRecordLayoutBuilder &) = delete;
void operator=(const MicrosoftRecordLayoutBuilder &) = delete;
@@ -2595,6 +2598,8 @@ struct MicrosoftRecordLayoutBuilder {
llvm::SmallPtrSetImpl<const CXXRecordDecl *> &HasVtorDispSet,
const CXXRecordDecl *RD) const;
const ASTContext &Context;
+ EmptySubobjectMap *EmptySubobjects;
+
/// The size of the record being laid out.
CharUnits Size;
/// The non-virtual size of the record layout.
@@ -2908,8 +2913,7 @@ static bool recordUsesEBO(const RecordDecl *RD) {
}
void MicrosoftRecordLayoutBuilder::layoutNonVirtualBase(
- const CXXRecordDecl *RD,
- const CXXRecordDecl *BaseDecl,
+ const CXXRecordDecl *RD, const CXXRecordDecl *BaseDecl,
const ASTRecordLayout &BaseLayout,
const ASTRecordLayout *&PreviousBaseLayout) {
// Insert padding between two bases if the left first one is zero sized or
@@ -2942,6 +2946,7 @@ void MicrosoftRecordLayoutBuilder::layoutNonVirtualBase(
}
Bases.insert(std::make_pair(BaseDecl, BaseOffset));
Size += BaseLayout.getNonVirtualSize();
+ DataSize = Size;
PreviousBaseLayout = &BaseLayout;
}
@@ -2959,15 +2964,43 @@ void MicrosoftRecordLayoutBuilder::layoutField(const FieldDecl *FD) {
LastFieldIsNonZeroWidthBitfield = false;
ElementInfo Info = getAdjustedElementInfo(FD);
Alignment = std::max(Alignment, Info.Alignment);
- CharUnits FieldOffset;
- if (UseExternalLayout)
+
+ const CXXRecordDecl *FieldClass = FD->getType()->getAsCXXRecordDecl();
+ bool IsOverlappingEmptyField = FD->isPotentiallyOverlapping() &&
+ FieldClass->isEmpty() &&
+ FieldClass->fields().empty();
+ CharUnits FieldOffset = CharUnits::Zero();
+
+ if (UseExternalLayout) {
FieldOffset =
Context.toCharUnitsFromBits(External.getExternalFieldOffset(FD));
- else if (IsUnion)
+ } else if (IsUnion) {
FieldOffset = CharUnits::Zero();
- else
+ } else if (EmptySubobjects) {
+ if (!IsOverlappingEmptyField)
+ FieldOffset = DataSize.alignTo(Info.Alignment);
+
+ while (!EmptySubobjects->CanPlaceFieldAtOffset(FD, FieldOffset)) {
+ const CXXRecordDecl *ParentClass = cast<CXXRecordDecl>(FD->getParent());
+ bool HasBases = ParentClass && (!ParentClass->bases().empty() ||
+ !ParentClass->vbases().empty());
+ if (FieldOffset == CharUnits::Zero() && DataSize != CharUnits::Zero() &&
+ HasBases) {
+ // MSVC appears to only do this when there are base classes;
+ // otherwise it overlaps no_unique_address fields in non-zero offsets.
+ FieldOffset = DataSize.alignTo(Info.Alignment);
+ } else {
+ FieldOffset += Info.Alignment;
+ }
+ }
+ } else {
FieldOffset = Size.alignTo(Info.Alignment);
+ }
placeFieldAtOffset(FieldOffset);
+
+ if (!IsOverlappingEmptyField)
+ DataSize = std::max(DataSize, FieldOffset + Info.Size);
+
Size = std::max(Size, FieldOffset + Info.Size);
}
@@ -3013,6 +3046,7 @@ void MicrosoftRecordLayoutBuilder::layoutBitField(const FieldDecl *FD) {
Alignment = std::max(Alignment, Info.Alignment);
RemainingBitsInField = Context.toBits(Info.Size) - Width;
}
+ DataSize = Size;
}
void
@@ -3038,6 +3072,7 @@ MicrosoftRecordLayoutBuilder::layoutZeroWidthBitField(const FieldDecl *FD) {
Size = FieldOffset;
Alignment = std::max(Alignment, Info.Alignment);
}
+ DataSize = Size;
}
void MicrosoftRecordLayoutBuilder::injectVBPtr(const CXXRecordDecl *RD) {
@@ -3304,8 +3339,9 @@ ASTContext::getASTRecordLayout(const RecordDecl *D) const {
const ASTRecordLayout *NewEntry = nullptr;
if (isMsLayout(*this)) {
- MicrosoftRecordLayoutBuilder Builder(*this);
if (const auto *RD = dyn_cast<CXXRecordDecl>(D)) {
+ EmptySubobjectMap EmptySubobjects(*this, RD);
+ MicrosoftRecordLayoutBuilder Builder(*this, &EmptySubobjects);
Builder.cxxLayout(RD);
NewEntry = new (*this) ASTRecordLayout(
*this, Builder.Size, Builder.Alignment, Builder.Alignment,
@@ -3317,6 +3353,7 @@ ASTContext::getASTRecordLayout(const RecordDecl *D) const {
Builder.EndsWithZeroSizedObject, Builder.LeadsWithZeroSizedBase,
Builder.Bases, Builder.VBases);
} else {
+ MicrosoftRecordLayoutBuilder Builder(*this, /*EmptySubobjects=*/nullptr);
Builder.layout(D);
NewEntry = new (*this) ASTRecordLayout(
*this, Builder.Size, Builder.Alignment, Builder.Alignment,
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 5a6b5efbf6c1223..cc93fe7d5461967 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -4374,7 +4374,8 @@ static bool IsBuiltInOrStandardCXX11Attribute(IdentifierInfo *AttrName,
case ParsedAttr::AT_Deprecated:
case ParsedAttr::AT_FallThrough:
case ParsedAttr::AT_CXX11NoReturn:
- case ParsedAttr::AT_NoUniqueAddress:
+ case ParsedAttr::AT_MSNoUniqueAddress:
+ case ParsedAttr::AT_ItaniumNoUniqueAddress:
case ParsedAttr::AT_Likely:
case ParsedAttr::AT_Unlikely:
return true;
diff --git a/clang/lib/Sema/SemaDeclAttr.cpp b/clang/lib/Sema/SemaDeclAttr.cpp
index 090a54eedaa07d0..f3839b2c59e0dcf 100644
--- a/clang/lib/Sema/SemaDeclAttr.cpp
+++ b/clang/lib/Sema/SemaDeclAttr.cpp
@@ -8372,6 +8372,10 @@ static void handleNoMergeAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
D->addAttr(NoMergeAttr::Create(S.Context, AL));
}
+static void handleNoUniqueAddressAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
+ D->addAttr(NoUniqueAddressAttr::Create(S.Context, AL));
+}
+
static void handleSYCLKernelAttr(Sema &S, Decl *D, const ParsedAttr &AL) {
// The 'sycl_kernel' attribute applies only to function templates.
const auto *FD = cast<FunctionDecl>(D);
@@ -9277,6 +9281,12 @@ ProcessDeclAttribute(Sema &S, Scope *scope, Decl *D, const ParsedAttr &AL,
case ParsedAttr::AT_NoMerge:
handleNoMergeAttr(S, D, AL);
break;
+ case ParsedAttr::AT_MSNoUniqueAddress:
+ handleNoUniqueAddressAttr(S, D, AL);
+ break;
+ case ParsedAttr::AT_ItaniumNoUniqueAddress:
+ handleNoUniqueAddressAttr(S, D, AL);
+ break;
case ParsedAttr::AT_AvailableOnlyInDefaultEvalMethod:
handleAvailableOnlyInDefaultEvalMethod(S, D, AL);
diff --git a/clang/test/Layout/ms-no-unique-address.cpp b/clang/test/Layout/ms-no-unique-address.cpp
new file mode 100644
index 000000000000000..51cfd9a6ae3b77f
--- /dev/null
+++ b/clang/test/Layout/ms-no-unique-address.cpp
@@ -0,0 +1,381 @@
+// RUN: %clang_cc1 -std=c++2a -fsyntax-only -triple x86_64-windows-msvc -fms-compatibility -fdump-record-layouts %s | FileCheck %s
+
+namespace Empty {
+ struct A {};
+ struct A2 {};
+ struct A3 { [[msvc::no_unique_address]] A a; };
+ struct alignas(8) A4 {};
+
+ struct B {
+ [[msvc::no_unique_address]] A a;
+ char b;
+ };
+ static_assert(sizeof(B) == 1);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::B
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: 0 | char b
+ // CHECK-NEXT: | [sizeof=1, align=1,
+ // CHECK-NEXT: | nvsize=1, nvalign=1]
+
+ struct C {
+ [[msvc::no_unique_address]] A a;
+ [[msvc::no_unique_address]] A2 a2;
+ char c;
+ };
+ static_assert(sizeof(C) == 1);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::C
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: 0 | struct Empty::A2 a2 (empty)
+ // CHECK-NEXT: 0 | char c
+ // CHECK-NEXT: | [sizeof=1, align=1,
+ // CHECK-NEXT: | nvsize=1, nvalign=1]
+
+ struct D {
+ [[msvc::no_unique_address]] A3 a;
+ int i;
+ };
+ static_assert(sizeof(D) == 8);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::D
+ // CHECK-NEXT: 0 | struct Empty::A3 a (empty)
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: 4 | int i
+ // CHECK-NEXT: | [sizeof=8, align=4,
+ // CHECK-NEXT: | nvsize=8, nvalign=4]
+
+ struct E {
+ [[msvc::no_unique_address]] A a1;
+ [[msvc::no_unique_address]] A a2;
+ char e;
+ };
+ static_assert(sizeof(E) == 2);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::E
+ // CHECK-NEXT: 0 | struct Empty::A a1 (empty)
+ // CHECK-NEXT: 1 | struct Empty::A a2 (empty)
+ // CHECK-NEXT: 0 | char e
+ // CHECK-NEXT: | [sizeof=2, align=1,
+ // CHECK-NEXT: | nvsize=2, nvalign=1]
+
+ struct F {
+ ~F();
+ [[msvc::no_unique_address]] A a1;
+ [[msvc::no_unique_address]] A a2;
+ char f;
+ };
+ static_assert(sizeof(F) == 2);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::F
+ // CHECK-NEXT: 0 | struct Empty::A a1 (empty)
+ // CHECK-NEXT: 1 | struct Empty::A a2 (empty)
+ // CHECK-NEXT: 0 | char f
+ // CHECK-NEXT: | [sizeof=2, align=1,
+ // CHECK-NEXT: | nvsize=2, nvalign=1]
+
+ struct G { [[msvc::no_unique_address]] A a; ~G(); };
+ static_assert(sizeof(G) == 1);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::G
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: | [sizeof=1, align=1,
+ // CHECK-NEXT: | nvsize=1, nvalign=1]
+
+ struct H {
+ [[msvc::no_unique_address]] A a;
+ [[msvc::no_unique_address]] A b;
+ ~H();
+ };
+ static_assert(sizeof(H) == 2);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::H
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: 1 | struct Empty::A b (empty)
+ // CHECK-NEXT: | [sizeof=2, align=1,
+ // CHECK-NEXT: | nvsize=2, nvalign=1]
+
+ struct I {
+ [[msvc::no_unique_address]] A4 a;
+ [[msvc::no_unique_address]] A4 b;
+ };
+ static_assert(sizeof(I) == 16);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::I
+ // CHECK-NEXT: 0 | struct Empty::A4 a (empty)
+ // CHECK-NEXT: 8 | struct Empty::A4 b (empty)
+ // CHECK-NEXT: | [sizeof=16, align=8,
+ // CHECK-NEXT: | nvsize=16, nvalign=8]
+
+ struct J {
+ [[msvc::no_unique_address]] A4 a;
+ A4 b;
+ };
+ static_assert(sizeof(J) == 16);
+
+ // MSVC puts a and b at the same offset.
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::J
+ // CHECK-NEXT: 0 | struct Empty::A4 a (empty)
+ // CHECK-NEXT: 8 | struct Empty::A4 b (empty)
+ // CHECK-NEXT: | [sizeof=16, align=8,
+ // CHECK-NEXT: | nvsize=16, nvalign=8]
+
+ struct K {
+ [[msvc::no_unique_address]] A4 a;
+ [[msvc::no_unique_address]] char c;
+ [[msvc::no_unique_address]] A4 b;
+ };
+ static_assert(sizeof(K) == 16);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::K
+ // CHECK-NEXT: 0 | struct Empty::A4 a (empty)
+ // CHECK-NEXT: 0 | char c
+ // CHECK-NEXT: 8 | struct Empty::A4 b (empty)
+ // CHECK-NEXT: | [sizeof=16, align=8,
+ // CHECK-NEXT: | nvsize=16, nvalign=8]
+
+ struct OversizedEmpty : A {
+ ~OversizedEmpty();
+ [[msvc::no_unique_address]] A a;
+ };
+ static_assert(sizeof(OversizedEmpty) == 1);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::OversizedEmpty
+ // CHECK-NEXT: 0 | struct Empty::A (base) (empty)
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: | [sizeof=1, align=1,
+ // CHECK-NEXT: | nvsize=1, nvalign=1]
+
+ struct HasOversizedEmpty {
+ [[msvc::no_unique_address]] OversizedEmpty m;
+ };
+ static_assert(sizeof(HasOversizedEmpty) == 1);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::HasOversizedEmpty
+ // CHECK-NEXT: 0 | struct Empty::OversizedEmpty m (empty)
+ // CHECK-NEXT: 0 | struct Empty::A (base) (empty)
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: | [sizeof=1, align=1,
+ // CHECK-NEXT: | nvsize=1, nvalign=1]
+
+ struct EmptyWithNonzeroDSize {
+ [[msvc::no_unique_address]] A a;
+ int x;
+ [[msvc::no_unique_address]] A b;
+ int y;
+ [[msvc::no_unique_address]] A c;
+ };
+ static_assert(sizeof(EmptyWithNonzeroDSize) == 8);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::EmptyWithNonzeroDSize
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: 0 | int x
+ // CHECK-NEXT: 1 | struct Empty::A b (empty)
+ // CHECK-NEXT: 4 | int y
+ // CHECK-NEXT: 2 | struct Empty::A c (empty)
+ // CHECK-NEXT: | [sizeof=8, align=4,
+ // CHECK-NEXT: | nvsize=8, nvalign=4]
+
+ struct EmptyWithNonzeroDSizeNonPOD {
+ ~EmptyWithNonzeroDSizeNonPOD();
+ [[msvc::no_unique_address]] A a;
+ int x;
+ [[msvc::no_unique_address]] A b;
+ int y;
+ [[msvc::no_unique_address]] A c;
+ };
+ static_assert(sizeof(EmptyWithNonzeroDSizeNonPOD) == 8);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::EmptyWithNonzeroDSizeNonPOD
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: 0 | int x
+ // CHECK-NEXT: 1 | struct Empty::A b (empty)
+ // CHECK-NEXT: 4 | int y
+ // CHECK-NEXT: 2 | struct Empty::A c (empty)
+ // CHECK-NEXT: | [sizeof=8, align=4,
+ // CHECK-NEXT: | nvsize=8, nvalign=4]
+}
+
+namespace POD {
+ struct A { int n; char c[3]; };
+ struct B { [[msvc::no_unique_address]] A a; char d; };
+ static_assert(sizeof(B) == 12);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct POD::B
+ // CHECK-NEXT: 0 | struct POD::A a
+ // CHECK-NEXT: 0 | int n
+ // CHECK-NEXT: 4 | char[3] c
+ // CHECK-NEXT: 8 | char d
+ // CHECK-NEXT: | [sizeof=12, align=4,
+ // CHECK-NEXT: | nvsize=12, nvalign=4]
+}
+
+namespace NonPOD {
+ struct A { int n; char c[3]; ~A(); };
+ struct B { [[msvc::no_unique_address]] A a; char d; };
+ static_assert(sizeof(B) == 12);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct NonPOD::B
+ // CHECK-NEXT: 0 | struct NonPOD::A a
+ // CHECK-NEXT: 0 | int n
+ // CHECK-NEXT: 4 | char[3] c
+ // CHECK-NEXT: 8 | char d
+ // CHECK-NEXT: | [sizeof=12, align=4,
+ // CHECK-NEXT: | nvsize=12, nvalign=4]
+}
+
+namespace VBases {
+ // The nvsize of an object includes the complete size of its empty subobjects
+ // (although it's unclear why). Ensure this corner case is handled properly.
+ struct Empty {};
+ struct alignas(8) A {}; // dsize 0, nvsize 0, size 8
+ struct B : A { char c; }; // dsize 1, nvsize 8, size 8
+ static_assert(sizeof(B) == 8);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct VBases::B
+ // CHECK-NEXT: 0 | struct VBases::A (base) (empty)
+ // CHECK-NEXT: 0 | char c
+ // CHECK-NEXT: | [sizeof=8, align=8,
+ // CHECK-NEXT: | nvsize=8, nvalign=8]
+
+ struct V { int n; };
+
+ struct C : B, virtual V {};
+ static_assert(sizeof(C) == 24);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct VBases::C
+ // CHECK-NEXT: 0 | struct VBases::B (base)
+ // CHECK-NEXT: 0 | struct VBases::A (base) (empty)
+ // CHECK-NEXT: 0 | char c
+ // CHECK-NEXT: 8 | (C vbtable pointer)
+ // CHECK-NEXT: 16 | struct VBases::V (virtual base)
+ // CHECK-NEXT: 16 | int n
+ // CHECK-NEXT: | [sizeof=24, align=8,
+ // CHECK-NEXT: | nvsize=16, nvalign=8]
+
+ struct D : virtual Empty {
+ [[msvc::no_unique_address]] Empty a;
+ };
+ static_assert(sizeof(D) == 16);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct VBases::D
+ // CHECK-NEXT: 0 | (D vbtable pointer)
+ // CHECK-NEXT: 8 | struct VBases::Empty a
+ // CHECK-NEXT: 16 | struct VBases::Empty (virtual base) (empty)
+ // CHECK-NEXT: | [sizeof=16, align=8,
+ // CHECK-NEXT: | nvsize=16, nvalign=8]
+
+ struct E : virtual V {
+ [[msvc::no_unique_address]] B b;
+ };
+ static_assert(sizeof(E) == 24);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct VBases::E
+ // CHECK-NEXT: 0 | (E vbtable pointer)
+ // CHECK-NEXT: 8 | struct VBases::B b
+ // CHECK-NEXT: 8 | struct VBases::A (base) (empty)
+ // CHECK-NEXT: 8 | char c
+ // CHECK-NEXT: 16 | struct VBases::V (virtual base)
+ // CHECK-NEXT: 16 | int n
+ // CHECK-NEXT: | [sizeof=24, align=8,
+ // CHECK-NEXT: | nvsize=16, nvalign=8]
+
+ struct X : virtual A { [[msvc::no_unique_address]] A a; };
+ struct F : virtual A {
+ [[msvc::no_unique_address]] A a;
+ [[msvc::no_unique_address]] X x;
+ };
+ static_assert(sizeof(F) == 24);
+
+ // MSVC places x after a and the total size is 48.
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct VBases::F
+ // CHECK-NEXT: 0 | (F vbtable pointer)
+ // CHECK-NEXT: 8 | struct VBases::A a (empty)
+ // CHECK-NEXT: 8 | struct VBases::X x
+ // CHECK-NEXT: 8 | (X vbtable pointer)
+ // CHECK-NEXT: 16 | struct VBases::A a (empty)
+ // CHECK-NEXT: 24 | struct VBases::A (virtual base) (empty)
+ // CHECK-NEXT: 24 | struct VBases::A (virtual base) (empty)
+ // CHECK-NEXT: | [sizeof=24, align=8,
+ // CHECK-NEXT: | nvsize=24, nvalign=8]
+
+ struct G : virtual Empty {
+ int i;
+ [[msvc::no_unique_address]] A a;
+ };
+ static_assert(sizeof(G) == 16);
+
+ // MSVC places a at offset 12.
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct VBases::G
+ // CHECK-NEXT: 0 | (G vbtable pointer)
+ // CHECK-NEXT: 8 | int i
+ // CHECK-NEXT: 8 | struct VBases::A a (empty)
+ // CHECK-NEXT: 16 | struct VBases::Empty (virtual base) (empty)
+ // 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]
+
+}
diff --git a/clang/test/Preprocessor/has_attribute.cpp b/clang/test/Preprocessor/has_attribute.cpp
index bf0f9b3bc4a8f08..3fb99eda699b3cf 100644
--- a/clang/test/Preprocessor/has_attribute.cpp
+++ b/clang/test/Preprocessor/has_attribute.cpp
@@ -43,6 +43,7 @@ CXX11(fallthrough)
CXX11(likely)
CXX11(maybe_unused)
CXX11(no_unique_address)
+CXX11(msvc::no_unique_address)
CXX11(nodiscard)
CXX11(noreturn)
CXX11(unlikely)
@@ -55,7 +56,9 @@ CXX11(unlikely)
// CHECK: likely: 201803L
// CHECK: maybe_unused: 201603L
// ITANIUM: no_unique_address: 201803L
-// WINDOWS: no_unique_address: 0
+// WINDOWS: no_unique_address: 0
+// ITANIUM: msvc::no_unique_address: 0
+// WINDOWS: msvc::no_unique_address: 201803L
// CHECK: nodiscard: 201907L
// CHECK: noreturn: 200809L
// CHECK: unlikely: 201803L
diff --git a/clang/test/SemaCXX/cxx2a-ms-no-unique-address.cpp b/clang/test/SemaCXX/cxx2a-ms-no-unique-address.cpp
new file mode 100644
index 000000000000000..42058559a087a53
--- /dev/null
+++ b/clang/test/SemaCXX/cxx2a-ms-no-unique-address.cpp
@@ -0,0 +1,19 @@
+// RUN: %clang_cc1 -std=c++2a %s -verify=unsupported -triple x86_64-linux-gnu
+// RUN: %clang_cc1 -std=c++2a %s -verify -triple x86_64-windows -fms-compatibility
+
+[[msvc::no_unique_address]] int a; // expected-error {{only applies to non-bit-field non-static data members}} unsupported-warning {{unknown}}
+[[msvc::no_unique_address]] void f(); // expected-error {{only applies to non-bit-field non-static data members}} unsupported-warning {{unknown}}
+struct [[msvc::no_unique_address]] S { // expected-error {{only applies to non-bit-field non-static data members}} unsupported-warning {{unknown}}
+ [[msvc::no_unique_address]] int a; // unsupported-warning {{unknown}}
+ [[msvc::no_unique_address]] void f(); // expected-error {{only applies to non-bit-field non-static data members}} unsupported-warning {{unknown}}
+ [[msvc::no_unique_address]] static int sa;// expected-error {{only applies to non-bit-field non-static data members}} unsupported-warning {{unknown}}
+ [[msvc::no_unique_address]] static void sf(); // expected-error {{only applies to non-bit-field non-static data members}} unsupported-warning {{unknown}}
+ [[msvc::no_unique_address]] int b : 3; // expected-error {{only applies to non-bit-field non-static data members}} unsupported-warning {{unknown}}
+
+ [[msvc::no_unique_address, msvc::no_unique_address]] int duplicated; // ok
+ // unsupported-warning at -1 2{{unknown}}
+ [[msvc::no_unique_address]] [[msvc::no_unique_address]] int duplicated2; // unsupported-warning 2{{unknown}}
+ [[msvc::no_unique_address()]] int arglist; // expected-error {{cannot have an argument list}} unsupported-warning {{unknown}}
+
+ int [[msvc::no_unique_address]] c; // expected-error {{cannot be applied to types}} unsupported-error {{cannot be applied to types}}
+};
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