akhuang created this revision.
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This attribute should match the behavior of MSVC's [[msvc::no_unique_address]]
attribute.
Bug: https://github.com/llvm/llvm-project/issues/49358
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D157762
Files:
clang/include/clang/Basic/Attr.td
clang/include/clang/Basic/AttrDocs.td
clang/lib/AST/Decl.cpp
clang/lib/AST/RecordLayoutBuilder.cpp
clang/lib/CodeGen/ABIInfoImpl.cpp
clang/lib/CodeGen/CGExprAgg.cpp
clang/lib/CodeGen/CGExprConstant.cpp
clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
clang/lib/Parse/ParseDeclCXX.cpp
clang/test/Layout/ms-no-unique-address.cpp
Index: clang/test/Layout/ms-no-unique-address.cpp
===================================================================
--- /dev/null
+++ clang/test/Layout/ms-no-unique-address.cpp
@@ -0,0 +1,254 @@
+// RUN: %clang_cc1 -std=c++2a -fsyntax-only -triple x86_64-pc-win32 -fdump-record-layouts %s | FileCheck %s
+
+namespace Empty {
+ struct A {};
+ 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 {};
+ struct D {
+ [[msvc::no_unique_address]] A a;
+ [[msvc::no_unique_address]] C c;
+ char d;
+ };
+ static_assert(sizeof(D) == 1);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::D
+ // CHECK-NEXT: 0 | struct Empty::A a (empty)
+ // CHECK-NEXT: 0 | struct Empty::C c (empty)
+ // CHECK-NEXT: 0 | char d
+ // CHECK-NEXT: | [sizeof=1, align=1,
+ // CHECK-NEXT: | nvsize=1, nvalign=1]
+
+ 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 OversizedEmpty : A {
+ ~OversizedEmpty();
+ [[msvc::no_unique_address]] A a;
+ };
+ static_assert(sizeof(OversizedEmpty) == 2);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct Empty::OversizedEmpty
+ // CHECK-NEXT: 0 | struct Empty::A (base) (empty)
+ // CHECK-NEXT: 1 | struct Empty::A a (empty)
+ // CHECK-NEXT: | [sizeof=2, align=1,
+ // CHECK-NEXT: | nvsize=2, nvalign=1]
+
+ struct HasOversizedEmpty {
+ [[msvc::no_unique_address]] OversizedEmpty m;
+ };
+ static_assert(sizeof(HasOversizedEmpty) == 2);
+
+ // 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: 1 | struct Empty::A a (empty)
+ // CHECK-NEXT: | [sizeof=2, align=1,
+ // CHECK-NEXT: | nvsize=2, 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 {
+ // Cannot reuse tail padding of a PDO type.
+ 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 NVSizeGreaterThanDSize {
+ // 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 alignas(8) A { ~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 NVSizeGreaterThanDSize::B
+ // CHECK-NEXT: 0 | struct NVSizeGreaterThanDSize::A (base) (empty)
+ // CHECK-NEXT: 0 | char c
+ // CHECK-NEXT: | [sizeof=8, align=8,
+ // CHECK-NEXT: | nvsize=8, nvalign=8]
+
+ struct V { int n; };
+
+ // V is at offset 16, not offset 12, because B's tail padding is strangely not
+ // usable for virtual bases.
+ struct C : B, virtual V {};
+ static_assert(sizeof(C) == 24);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct NVSizeGreaterThanDSize::C
+ // CHECK-NEXT: 0 | struct NVSizeGreaterThanDSize::B (base)
+ // CHECK-NEXT: 0 | struct NVSizeGreaterThanDSize::A (base) (empty)
+ // CHECK-NEXT: 0 | char c
+ // CHECK-NEXT: 8 | (C vbtable pointer)
+ // CHECK-NEXT: 16 | struct NVSizeGreaterThanDSize::V (virtual base)
+ // CHECK-NEXT: 16 | int n
+ // CHECK-NEXT: | [sizeof=24, align=8,
+ // CHECK-NEXT: | nvsize=16, nvalign=8]
+
+ struct D : virtual V {
+ [[msvc::no_unique_address]] B b;
+ };
+ static_assert(sizeof(D) == 24);
+
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct NVSizeGreaterThanDSize::D
+ // CHECK-NEXT: 0 | (D vbtable pointer)
+ // CHECK-NEXT: 8 | struct NVSizeGreaterThanDSize::B b
+ // CHECK-NEXT: 8 | struct NVSizeGreaterThanDSize::A (base) (empty)
+ // CHECK-NEXT: 8 | char c
+ // CHECK-NEXT: 16 | struct NVSizeGreaterThanDSize::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 E : virtual A {
+ [[msvc::no_unique_address]] A a;
+ // Here, we arrange for X to hang over the end of the nvsize of E. This
+ // should force the A vbase to be laid out at offset 24, not 16.
+ [[msvc::no_unique_address]] X x;
+ };
+ static_assert(sizeof(E) == 24);
+
+ // FIXME this doesn't match what MSVC does
+ // In MSVC member a is at offset 16, x is at 24,
+ // and x.a is at 40, and the total size is 48
+ //
+ // CHECK:*** Dumping AST Record Layout
+ // CHECK: 0 | struct NVSizeGreaterThanDSize::E
+ // CHECK-NEXT: 0 | (E vbtable pointer)
+ // CHECK-NEXT: 8 | struct NVSizeGreaterThanDSize::A a (empty)
+ // CHECK-NEXT: 8 | struct NVSizeGreaterThanDSize::X x
+ // CHECK-NEXT: 8 | (X vbtable pointer)
+ // CHECK-NEXT: 16 | struct NVSizeGreaterThanDSize::A a (empty)
+ // CHECK-NEXT: 24 | struct NVSizeGreaterThanDSize::A (virtual base) (empty)
+ // CHECK-NEXT: 24 | struct NVSizeGreaterThanDSize::A (virtual base) (empty)
+ // CHECK-NEXT: | [sizeof=24, align=8,
+ // CHECK-NEXT: | nvsize=24, nvalign=8]
+}
Index: clang/lib/Parse/ParseDeclCXX.cpp
===================================================================
--- clang/lib/Parse/ParseDeclCXX.cpp
+++ clang/lib/Parse/ParseDeclCXX.cpp
@@ -4365,6 +4365,7 @@
case ParsedAttr::AT_FallThrough:
case ParsedAttr::AT_CXX11NoReturn:
case ParsedAttr::AT_NoUniqueAddress:
+ case ParsedAttr::AT_NoUniqueAddressMSVC:
case ParsedAttr::AT_Likely:
case ParsedAttr::AT_Unlikely:
return true;
Index: clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
===================================================================
--- clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
+++ clang/lib/CodeGen/CGRecordLayoutBuilder.cpp
@@ -756,7 +756,9 @@
Prior->Data = getByteArrayType(bitsToCharUnits(llvm::alignTo(
cast<llvm::IntegerType>(Prior->Data)->getIntegerBitWidth(), 8)));
else {
- assert(Prior->FD->hasAttr<NoUniqueAddressAttr>() &&
+ Prior->FD->dump();
+ assert((Prior->FD->hasAttr<NoUniqueAddressAttr>() ||
+ Prior->FD->hasAttr<NoUniqueAddressMSVCAttr>()) &&
"should not have reused this field's tail padding");
Prior->Data = getByteArrayType(
Context.getTypeInfoDataSizeInChars(Prior->FD->getType()).Width);
Index: clang/lib/CodeGen/CGExprConstant.cpp
===================================================================
--- clang/lib/CodeGen/CGExprConstant.cpp
+++ clang/lib/CodeGen/CGExprConstant.cpp
@@ -756,7 +756,8 @@
return false;
// After emitting a non-empty field with [[no_unique_address]], we may
// need to overwrite its tail padding.
- if (Field->hasAttr<NoUniqueAddressAttr>())
+ if (Field->hasAttr<NoUniqueAddressAttr>() ||
+ Field->hasAttr<NoUniqueAddressMSVCAttr>())
AllowOverwrite = true;
} else {
// Otherwise we have a bitfield.
@@ -857,7 +858,8 @@
return false;
// After emitting a non-empty field with [[no_unique_address]], we may
// need to overwrite its tail padding.
- if (Field->hasAttr<NoUniqueAddressAttr>())
+ if (Field->hasAttr<NoUniqueAddressAttr>() ||
+ Field->hasAttr<NoUniqueAddressMSVCAttr>())
AllowOverwrite = true;
} else {
// Otherwise we have a bitfield.
Index: clang/lib/CodeGen/CGExprAgg.cpp
===================================================================
--- clang/lib/CodeGen/CGExprAgg.cpp
+++ clang/lib/CodeGen/CGExprAgg.cpp
@@ -2061,7 +2061,9 @@
AggValueSlot::Overlap_t
CodeGenFunction::getOverlapForFieldInit(const FieldDecl *FD) {
- if (!FD->hasAttr<NoUniqueAddressAttr>() || !FD->getType()->isRecordType())
+ if (!(FD->hasAttr<NoUniqueAddressAttr>() ||
+ FD->hasAttr<NoUniqueAddressMSVCAttr>()) ||
+ !FD->getType()->isRecordType())
return AggValueSlot::DoesNotOverlap;
// If the field lies entirely within the enclosing class's nvsize, its tail
Index: clang/lib/CodeGen/ABIInfoImpl.cpp
===================================================================
--- clang/lib/CodeGen/ABIInfoImpl.cpp
+++ clang/lib/CodeGen/ABIInfoImpl.cpp
@@ -280,7 +280,9 @@
// not arrays of records, so we must also check whether we stripped off an
// array type above.
if (isa<CXXRecordDecl>(RT->getDecl()) &&
- (WasArray || (!AsIfNoUniqueAddr && !FD->hasAttr<NoUniqueAddressAttr>())))
+ (WasArray ||
+ (!AsIfNoUniqueAddr && !(FD->hasAttr<NoUniqueAddressAttr>() ||
+ FD->hasAttr<NoUniqueAddressMSVCAttr>()))))
return false;
return isEmptyRecord(Context, FT, AllowArrays, AsIfNoUniqueAddr);
Index: clang/lib/AST/RecordLayoutBuilder.cpp
===================================================================
--- clang/lib/AST/RecordLayoutBuilder.cpp
+++ clang/lib/AST/RecordLayoutBuilder.cpp
@@ -474,7 +474,9 @@
// We are able to place the member variable at this offset.
// Make sure to update the empty field subobject map.
- UpdateEmptyFieldSubobjects(FD, Offset, FD->hasAttr<NoUniqueAddressAttr>());
+ bool PlacingOverlappingField = FD->hasAttr<NoUniqueAddressAttr>() ||
+ FD->hasAttr<NoUniqueAddressMSVCAttr>();
+ UpdateEmptyFieldSubobjects(FD, Offset, PlacingOverlappingField);
return true;
}
@@ -2545,7 +2547,10 @@
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;
@@ -2562,7 +2567,11 @@
void layoutNonVirtualBase(const CXXRecordDecl *RD,
const CXXRecordDecl *BaseDecl,
const ASTRecordLayout &BaseLayout,
- const ASTRecordLayout *&PreviousBaseLayout);
+ const ASTRecordLayout *&PreviousBaseLayout,
+ BaseSubobjectInfo *Base);
+ BaseSubobjectInfo *computeBaseSubobjectInfo(const CXXRecordDecl *RD,
+ bool IsVirtual,
+ BaseSubobjectInfo *Derived);
void injectVFPtr(const CXXRecordDecl *RD);
void injectVBPtr(const CXXRecordDecl *RD);
/// Lays out the fields of the record. Also rounds size up to
@@ -2595,6 +2604,12 @@
llvm::SmallPtrSetImpl<const CXXRecordDecl *> &HasVtorDispSet,
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;
/// The non-virtual size of the record layout.
@@ -2818,6 +2833,8 @@
// Iterate through the bases and lay out the non-virtual ones.
for (const CXXBaseSpecifier &Base : RD->bases()) {
const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
+ BaseSubobjectInfo *Info =
+ computeBaseSubobjectInfo(BaseDecl, Base.isVirtual(), nullptr);
HasPolymorphicBaseClass |= BaseDecl->isPolymorphic();
const ASTRecordLayout &BaseLayout = Context.getASTRecordLayout(BaseDecl);
// Mark and skip virtual bases.
@@ -2839,7 +2856,7 @@
LeadsWithZeroSizedBase = BaseLayout.leadsWithZeroSizedBase();
}
// Lay out the base.
- layoutNonVirtualBase(RD, BaseDecl, BaseLayout, PreviousBaseLayout);
+ layoutNonVirtualBase(RD, BaseDecl, BaseLayout, PreviousBaseLayout, Info);
}
// Figure out if we need a fresh VFPtr for this class.
if (RD->isPolymorphic()) {
@@ -2880,7 +2897,9 @@
LeadsWithZeroSizedBase = BaseLayout.leadsWithZeroSizedBase();
}
// Lay out the base.
- layoutNonVirtualBase(RD, BaseDecl, BaseLayout, PreviousBaseLayout);
+ BaseSubobjectInfo *Info =
+ computeBaseSubobjectInfo(BaseDecl, Base.isVirtual(), nullptr);
+ layoutNonVirtualBase(RD, BaseDecl, BaseLayout, PreviousBaseLayout, Info);
VBPtrOffset = Bases[BaseDecl] + BaseLayout.getNonVirtualSize();
}
// Set our VBPtroffset if we know it at this point.
@@ -2908,10 +2927,9 @@
}
void MicrosoftRecordLayoutBuilder::layoutNonVirtualBase(
- const CXXRecordDecl *RD,
- const CXXRecordDecl *BaseDecl,
+ const CXXRecordDecl *RD, const CXXRecordDecl *BaseDecl,
const ASTRecordLayout &BaseLayout,
- const ASTRecordLayout *&PreviousBaseLayout) {
+ const ASTRecordLayout *&PreviousBaseLayout, BaseSubobjectInfo *Base) {
// Insert padding between two bases if the left first one is zero sized or
// contains a zero sized subobject and the right is zero sized or one leads
// with a zero sized base.
@@ -2938,13 +2956,93 @@
} else {
// Otherwise, lay the base out at the end of the MDC.
BaseOffset = Size = Size.alignTo(Info.Alignment);
+ while (!EmptySubobjects->CanPlaceBaseAtOffset(Base, BaseOffset))
+ BaseOffset += Info.Alignment;
}
}
+
Bases.insert(std::make_pair(BaseDecl, BaseOffset));
Size += BaseLayout.getNonVirtualSize();
+ DataSize = Size;
PreviousBaseLayout = &BaseLayout;
}
+BaseSubobjectInfo *MicrosoftRecordLayoutBuilder::computeBaseSubobjectInfo(
+ const CXXRecordDecl *RD, bool IsVirtual, BaseSubobjectInfo *Derived) {
+ BaseSubobjectInfo *Info;
+
+ if (IsVirtual) {
+ // Check if we already have info about this virtual base.
+ BaseSubobjectInfo *&InfoSlot = VirtualBaseInfo[RD];
+ if (InfoSlot) {
+ assert(InfoSlot->Class == RD && "Wrong class for virtual base info!");
+ return InfoSlot;
+ }
+
+ // We don't, create it.
+ InfoSlot = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
+ Info = InfoSlot;
+ } else {
+ Info = new (BaseSubobjectInfoAllocator.Allocate()) BaseSubobjectInfo;
+ }
+
+ Info->Class = RD;
+ Info->IsVirtual = IsVirtual;
+ Info->Derived = nullptr;
+ Info->PrimaryVirtualBaseInfo = nullptr;
+
+ const CXXRecordDecl *PrimaryVirtualBase = nullptr;
+ BaseSubobjectInfo *PrimaryVirtualBaseInfo = nullptr;
+
+ // Check if this base has a primary virtual base.
+ if (RD->getNumVBases()) {
+ const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
+ if (Layout.isPrimaryBaseVirtual()) {
+ // This base does have a primary virtual base.
+ PrimaryVirtualBase = Layout.getPrimaryBase();
+ assert(PrimaryVirtualBase && "Didn't have a primary virtual base!");
+
+ // Now check if we have base subobject info about this primary base.
+ PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
+
+ if (PrimaryVirtualBaseInfo) {
+ if (PrimaryVirtualBaseInfo->Derived) {
+ // We did have info about this primary base, and it turns out that it
+ // has already been claimed as a primary virtual base for another
+ // base.
+ PrimaryVirtualBase = nullptr;
+ } else {
+ // We can claim this base as our primary base.
+ Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
+ PrimaryVirtualBaseInfo->Derived = Info;
+ }
+ }
+ }
+ }
+
+ // Now go through all direct bases.
+ for (const auto &I : RD->bases()) {
+ bool IsVirtual = I.isVirtual();
+
+ const CXXRecordDecl *BaseDecl = I.getType()->getAsCXXRecordDecl();
+
+ Info->Bases.push_back(computeBaseSubobjectInfo(BaseDecl, IsVirtual, Info));
+ }
+
+ if (PrimaryVirtualBase && !PrimaryVirtualBaseInfo) {
+ // Traversing the bases must have created the base info for our primary
+ // virtual base.
+ PrimaryVirtualBaseInfo = VirtualBaseInfo.lookup(PrimaryVirtualBase);
+ assert(PrimaryVirtualBaseInfo && "Did not create a primary virtual base!");
+
+ // Claim the primary virtual base as our primary virtual base.
+ Info->PrimaryVirtualBaseInfo = PrimaryVirtualBaseInfo;
+ PrimaryVirtualBaseInfo->Derived = Info;
+ }
+
+ return Info;
+}
+
void MicrosoftRecordLayoutBuilder::layoutFields(const RecordDecl *RD) {
LastFieldIsNonZeroWidthBitfield = false;
for (const FieldDecl *Field : RD->fields())
@@ -2956,19 +3054,40 @@
layoutBitField(FD);
return;
}
+
LastFieldIsNonZeroWidthBitfield = false;
ElementInfo Info = getAdjustedElementInfo(FD);
Alignment = std::max(Alignment, Info.Alignment);
- CharUnits FieldOffset;
- if (UseExternalLayout)
+
+ auto *FieldClass = FD->getType()->getAsCXXRecordDecl();
+ bool IsOverlappingEmptyField =
+ FD->isPotentiallyOverlapping() && FieldClass->isEmpty();
+ 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) {
+ while (!EmptySubobjects->CanPlaceFieldAtOffset(FD, FieldOffset))
+ FieldOffset += Info.Alignment;
+ } else {
+ FieldOffset = DataSize.alignTo(Info.Alignment);
+ }
+ } else {
FieldOffset = Size.alignTo(Info.Alignment);
+ }
+
placeFieldAtOffset(FieldOffset);
- Size = std::max(Size, FieldOffset + Info.Size);
+
+ if (!IsOverlappingEmptyField) {
+ DataSize = std::max(DataSize, FieldOffset + Info.Size);
+ Size = std::max(Size, FieldOffset + Info.Size);
+ } else {
+ Size = std::max(Size, FieldOffset + Info.Size);
+ }
}
void MicrosoftRecordLayoutBuilder::layoutBitField(const FieldDecl *FD) {
@@ -3003,13 +3122,13 @@
Alignment = std::max(Alignment, Info.Alignment);
} else if (IsUnion) {
placeFieldAtOffset(CharUnits::Zero());
- Size = std::max(Size, Info.Size);
+ DataSize = Size = std::max(Size, Info.Size);
// TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
} else {
// Allocate a new block of memory and place the bitfield in it.
CharUnits FieldOffset = Size.alignTo(Info.Alignment);
placeFieldAtOffset(FieldOffset);
- Size = FieldOffset + Info.Size;
+ DataSize = Size = FieldOffset + Info.Size;
Alignment = std::max(Alignment, Info.Alignment);
RemainingBitsInField = Context.toBits(Info.Size) - Width;
}
@@ -3029,13 +3148,13 @@
ElementInfo Info = getAdjustedElementInfo(FD);
if (IsUnion) {
placeFieldAtOffset(CharUnits::Zero());
- Size = std::max(Size, Info.Size);
+ DataSize = Size = std::max(Size, Info.Size);
// TODO: Add a Sema warning that MS ignores bitfield alignment in unions.
} else {
// Round up the current record size to the field's alignment boundary.
CharUnits FieldOffset = Size.alignTo(Info.Alignment);
placeFieldAtOffset(FieldOffset);
- Size = FieldOffset;
+ DataSize = Size = FieldOffset;
Alignment = std::max(Alignment, Info.Alignment);
}
}
@@ -3103,6 +3222,7 @@
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;
@@ -3136,7 +3256,7 @@
if ((PreviousBaseLayout && PreviousBaseLayout->endsWithZeroSizedObject() &&
BaseLayout.leadsWithZeroSizedBase() && !recordUsesEBO(RD)) ||
HasVtordisp) {
- Size = Size.alignTo(VtorDispAlignment) + VtorDispSize;
+ DataSize = Size = Size.alignTo(VtorDispAlignment) + VtorDispSize;
Alignment = std::max(VtorDispAlignment, Alignment);
}
// Insert the virtual base.
@@ -3304,8 +3424,9 @@
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 +3438,7 @@
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,
Index: clang/lib/AST/Decl.cpp
===================================================================
--- clang/lib/AST/Decl.cpp
+++ clang/lib/AST/Decl.cpp
@@ -4486,7 +4486,7 @@
// C++2a [intro.object]p7:
// An object has nonzero size if it
// -- is not a potentially-overlapping subobject, or
- if (!hasAttr<NoUniqueAddressAttr>())
+ if (!(hasAttr<NoUniqueAddressAttr>() || hasAttr<NoUniqueAddressMSVCAttr>()))
return false;
// -- is not of class type, or
@@ -4505,6 +4505,13 @@
if (!CXXRD->isEmpty())
return false;
+ if (Ctx.getTargetInfo().getCXXABI().isMicrosoft() && CXXRD->isUnion()) {
+ // Unions containing structs aren't zero sized?
+ for (const FieldDecl *Field : CXXRD->fields())
+ if (Field->getType()->getAsCXXRecordDecl())
+ return false;
+ }
+
// 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
@@ -4513,7 +4520,9 @@
}
bool FieldDecl::isPotentiallyOverlapping() const {
- return hasAttr<NoUniqueAddressAttr>() && getType()->getAsCXXRecordDecl();
+ return (hasAttr<NoUniqueAddressAttr>() ||
+ hasAttr<NoUniqueAddressMSVCAttr>()) &&
+ getType()->getAsCXXRecordDecl();
}
unsigned FieldDecl::getFieldIndex() const {
Index: clang/include/clang/Basic/AttrDocs.td
===================================================================
--- clang/include/clang/Basic/AttrDocs.td
+++ clang/include/clang/Basic/AttrDocs.td
@@ -1405,6 +1405,9 @@
``[[no_unique_address]]`` is a standard C++20 attribute. Clang supports its use
in C++11 onwards.
+
+ For Windows targets, ``[[no_unique_address]]`` is ignored, but there is a
+ similar attribute spelled ``[[msvc::no_unique_address]]``.
}];
}
Index: clang/include/clang/Basic/Attr.td
===================================================================
--- clang/include/clang/Basic/Attr.td
+++ clang/include/clang/Basic/Attr.td
@@ -1794,6 +1794,13 @@
let SimpleHandler = 1;
}
+def NoUniqueAddressMSVC : InheritableAttr, TargetSpecificAttr<TargetMicrosoftCXXABI> {
+ let Spellings = [CXX11<"msvc", "no_unique_address", 201803>];
+ let Subjects = SubjectList<[NonBitField], ErrorDiag>;
+ let Documentation = [NoUniqueAddressDocs];
+ let SimpleHandler = 1;
+}
+
def ReturnsTwice : InheritableAttr {
let Spellings = [GCC<"returns_twice">];
let Subjects = SubjectList<[Function]>;
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