Author: Erich Keane Date: 2026-07-21T05:56:47-07:00 New Revision: 42972f5e5d950b6644a926f402dc54ea3ff06ec3
URL: https://github.com/llvm/llvm-project/commit/42972f5e5d950b6644a926f402dc54ea3ff06ec3 DIFF: https://github.com/llvm/llvm-project/commit/42972f5e5d950b6644a926f402dc54ea3ff06ec3.diff LOG: [CIR] Introduce data_member_offset attribute (#208777) Some fields, like no_unique_address marked ones, aren't present in the CIR struct type. This attribute represents an offset into a struct instead, since get_member isn't possible without a member. I also considered representing these types in the struct, but it ends up causing a lot of awful looking structs, and forces the LLVMIR to contain empty fields for each of these, but not in lexical order, which is particularly awful looking. I considered making this part of data-member, but it seems like not a particularly good idea, since this isn't really getting a 'member' in the traditional sense. Added: Modified: clang/include/clang/CIR/Dialect/IR/CIRAttrs.td clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp clang/lib/CIR/CodeGen/CIRGenModule.cpp clang/lib/CIR/CodeGen/CIRGenModule.h clang/lib/CIR/Dialect/IR/CIRDialect.cpp clang/lib/CIR/Dialect/Transforms/CXXABILowering.cpp clang/lib/CIR/Dialect/Transforms/TargetLowering/CIRCXXABI.h clang/lib/CIR/Dialect/Transforms/TargetLowering/LowerItaniumCXXABI.cpp clang/test/CIR/CodeGen/pointer-to-empty-data-member.cpp Removed: ################################################################################ diff --git a/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td b/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td index bf91a1831eeff..529e6e32c865e 100644 --- a/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td +++ b/clang/include/clang/CIR/Dialect/IR/CIRAttrs.td @@ -598,6 +598,45 @@ def CIR_DataMemberAttr : CIR_ValueLikeAttr<"DataMember", "data_member"> { }]; } +//===----------------------------------------------------------------------===// +// DataMemberOffsetAttr +//===----------------------------------------------------------------------===// + +def CIR_DataMemberOffsetAttr + : CIR_ValueLikeAttr<"DataMemberOffset", "data_member_offset"> { + let summary = "Constant pointer-to-data-member given by a byte offset"; + let parameters = (ins AttributeSelfTypeParameter< + "", "cir::DataMemberType">:$type, + "uint64_t":$offset); + let description = [{ + Like `#cir.data_member`, this is a literal attribute representing a constant + (non-null) pointer-to-data-member value. It is used for members that are + not laid out in the CIR record and therefore have no field-index path -- in + particular `[[no_unique_address]]` empty fields. The concrete byte offset + of the member within the class is stored directly. + + Example: + ``` + // Empty S::*p = &S::e (e is a no_unique_address empty field at byte 1) + #cir.data_member_offset<1> : !cir.data_member<!rec_Empty in !rec_S> + ``` + }]; + + let builders = [ + AttrBuilderWithInferredContext<(ins "cir::DataMemberType":$type, + "uint64_t":$offset), [{ + return $_get(type.getContext(), type, offset); + }]>, + ]; + + // This attribute gets lowered during CXXABILowering. + let hasAttrToValueLowering = 0; + + let assemblyFormat = [{ + `<` $offset `>` + }]; +} + //===----------------------------------------------------------------------===// // MethodAttr //===----------------------------------------------------------------------===// diff --git a/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp b/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp index 5e8ed1e3b78b9..3fcf577776663 100644 --- a/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp +++ b/clang/lib/CIR/CodeGen/CIRGenExprConstant.cpp @@ -1469,11 +1469,17 @@ mlir::Attribute ConstantEmitter::tryEmitPrivate(const APValue &value, const auto *fieldDecl = cast<FieldDecl>(memberDecl); const auto *mpt = destType->castAs<MemberPointerType>(); const auto *destClass = mpt->getMostRecentCXXRecordDecl(); - if (fieldDecl->hasAttr<NoUniqueAddressAttr>()) { - assert(!cir::MissingFeatures::noUniqueAddressLayout()); - cgm.errorNYI("ConstExprEmitter::tryEmitPrivate: no_unique_address field"); - return {}; + + // Empty [[no_unique_address]] fields have no CIR field index; represent the + // pointer-to-data-member by its concrete byte offset. + if (cgm.isEmptyFieldForMemberPointer(fieldDecl)) { + const ASTContext &astContext = cgm.getASTContext(); + CharUnits offset = + astContext.getMemberPointerPathAdjustment(value) + + astContext.toCharUnitsFromBits(astContext.getFieldOffset(fieldDecl)); + return cir::DataMemberOffsetAttr::get(cirTy, offset.getQuantity()); } + std::optional<llvm::SmallVector<int32_t>> path = cgm.buildMemberPath(destClass, fieldDecl); if (!path) diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.cpp b/clang/lib/CIR/CodeGen/CIRGenModule.cpp index 0d5caa6c424df..7079bb54f44e9 100644 --- a/clang/lib/CIR/CodeGen/CIRGenModule.cpp +++ b/clang/lib/CIR/CodeGen/CIRGenModule.cpp @@ -2307,11 +2307,19 @@ mlir::Value CIRGenModule::emitMemberPointerConstant(const UnaryOperator *e) { const auto *mpt = e->getType()->castAs<MemberPointerType>(); const auto *destClass = mpt->getMostRecentCXXRecordDecl(); - if (fieldDecl->hasAttr<NoUniqueAddressAttr>()) { - assert(!cir::MissingFeatures::noUniqueAddressLayout()); - errorNYI(e->getExprLoc(), - "emitMemberPointerConstant: no_unique_address field"); - return {}; + // Empty [[no_unique_address]] fields have no CIR field index; represent the + // pointer-to-data-member by its concrete byte offset within the class. + if (isEmptyFieldForMemberPointer(fieldDecl)) { + // This function should ONLY be accessed in reference to itself, I don't see + // any cases/couldn't find any cases where anything else could get here, and + // classic-codegen does the same. + assert(fieldDecl->getParent() == destClass && + "scalar member pointer should be relative to the declaring class"); + uint64_t offset = + astContext.toCharUnitsFromBits(astContext.getFieldOffset(fieldDecl)) + .getQuantity(); + return cir::ConstantOp::create(builder, loc, + cir::DataMemberOffsetAttr::get(ty, offset)); } std::optional<llvm::SmallVector<int32_t>> path = @@ -2325,8 +2333,6 @@ mlir::Value CIRGenModule::emitMemberPointerConstant(const UnaryOperator *e) { std::optional<llvm::SmallVector<int32_t>> CIRGenModule::buildMemberPath(const CXXRecordDecl *destClass, const FieldDecl *field) { - assert(!field->hasAttr<NoUniqueAddressAttr>()); - llvm::SmallVector<int32_t> path; if (!findFieldMemberPath(destClass, field, path)) return std::nullopt; @@ -2396,6 +2402,11 @@ bool CIRGenModule::findFieldMemberPath(const CXXRecordDecl *currentClass, return false; } +bool CIRGenModule::isEmptyFieldForMemberPointer(const FieldDecl *field) { + return isEmptyFieldForLayout(astContext, field) && + field->isPotentiallyOverlapping(); +} + void CIRGenModule::emitDeclContext(const DeclContext *dc) { for (Decl *decl : dc->decls()) { // Unlike other DeclContexts, the contents of an ObjCImplDecl at TU scope diff --git a/clang/lib/CIR/CodeGen/CIRGenModule.h b/clang/lib/CIR/CodeGen/CIRGenModule.h index e47498dbc1588..f5ac70a33aef5 100644 --- a/clang/lib/CIR/CodeGen/CIRGenModule.h +++ b/clang/lib/CIR/CodeGen/CIRGenModule.h @@ -726,6 +726,13 @@ class CIRGenModule : public CIRGenTypeCache { std::optional<llvm::SmallVector<int32_t>> buildMemberPath(const CXXRecordDecl *destClass, const FieldDecl *field); + /// Returns true if \p field is an empty field that isn't laid out in the CIR + /// record (e.g. a [[no_unique_address]] empty member). Such fields have no + /// CIR field index, so a pointer-to-data-member to them is represented by an + /// explicit byte offset (#cir.data_member_offset) rather than a field-index + /// path. + bool isEmptyFieldForMemberPointer(const FieldDecl *field); + llvm::StringRef getMangledName(clang::GlobalDecl gd); // This function is to support the OpenACC 'bind' clause, which names an // alternate name for the function to be called by. This function mangles diff --git a/clang/lib/CIR/Dialect/IR/CIRDialect.cpp b/clang/lib/CIR/Dialect/IR/CIRDialect.cpp index 281956a5e40a5..590b206f8258d 100644 --- a/clang/lib/CIR/Dialect/IR/CIRDialect.cpp +++ b/clang/lib/CIR/Dialect/IR/CIRDialect.cpp @@ -578,7 +578,8 @@ static LogicalResult checkConstantTypes(mlir::Operation *op, mlir::Type opType, return success(); } - if (isa<cir::DataMemberAttr, cir::MethodAttr>(attrType)) { + if (isa<cir::DataMemberAttr, cir::DataMemberOffsetAttr, cir::MethodAttr>( + attrType)) { // More detailed type verifications are already done in // DataMemberAttr::verify or MethodAttr::verify. Don't need to repeat here. return success(); diff --git a/clang/lib/CIR/Dialect/Transforms/CXXABILowering.cpp b/clang/lib/CIR/Dialect/Transforms/CXXABILowering.cpp index 704ebbeb1ecd9..50a51d9618118 100644 --- a/clang/lib/CIR/Dialect/Transforms/CXXABILowering.cpp +++ b/clang/lib/CIR/Dialect/Transforms/CXXABILowering.cpp @@ -67,7 +67,8 @@ bool isCXXABIAttributeLegal(const mlir::TypeConverter &tc, return true; // Data Member and method are ALWAYS illegal. - if (isa<cir::DataMemberAttr, cir::MethodAttr>(attr)) + if (isa<cir::DataMemberAttr, cir::DataMemberOffsetAttr, cir::MethodAttr>( + attr)) return false; return llvm::TypeSwitch<mlir::Attribute, bool>(attr) @@ -394,6 +395,12 @@ static mlir::TypedAttr lowerInitialValue(const LowerModule *lowerModule, mlir::Type ty, mlir::Attribute initVal) { if (mlir::isa<cir::DataMemberType>(ty)) { + // Members without a CIR field index (e.g. no_unique_address empty fields) + // are represented by an explicit byte offset instead of a field path. + if (auto offsetVal = + mlir::dyn_cast_if_present<cir::DataMemberOffsetAttr>(initVal)) + return lowerModule->getCXXABI().lowerDataMemberOffsetConstant(offsetVal, + layout, tc); auto dataMemberVal = mlir::cast_if_present<cir::DataMemberAttr>(initVal); return lowerModule->getCXXABI().lowerDataMemberConstant(dataMemberVal, layout, tc); diff --git a/clang/lib/CIR/Dialect/Transforms/TargetLowering/CIRCXXABI.h b/clang/lib/CIR/Dialect/Transforms/TargetLowering/CIRCXXABI.h index 55607e24ce836..5c5d6421aea71 100644 --- a/clang/lib/CIR/Dialect/Transforms/TargetLowering/CIRCXXABI.h +++ b/clang/lib/CIR/Dialect/Transforms/TargetLowering/CIRCXXABI.h @@ -57,6 +57,13 @@ class CIRCXXABI { const mlir::DataLayout &layout, const mlir::TypeConverter &typeConverter) const = 0; + /// Lower the given by-offset data member pointer constant (used for members + /// with no CIR field index, e.g. no_unique_address empty fields) to a + /// constant of the ABI type. + virtual mlir::TypedAttr lowerDataMemberOffsetConstant( + cir::DataMemberOffsetAttr attr, const mlir::DataLayout &layout, + const mlir::TypeConverter &typeConverter) const = 0; + /// Lower the given member function pointer constant to a constant of the ABI /// type. The returned constant is represented as an attribute as well. virtual mlir::TypedAttr diff --git a/clang/lib/CIR/Dialect/Transforms/TargetLowering/LowerItaniumCXXABI.cpp b/clang/lib/CIR/Dialect/Transforms/TargetLowering/LowerItaniumCXXABI.cpp index 5218d4979f353..6c276a83f18cf 100644 --- a/clang/lib/CIR/Dialect/Transforms/TargetLowering/LowerItaniumCXXABI.cpp +++ b/clang/lib/CIR/Dialect/Transforms/TargetLowering/LowerItaniumCXXABI.cpp @@ -55,6 +55,10 @@ class LowerItaniumCXXABI : public CIRCXXABI { cir::DataMemberAttr attr, const mlir::DataLayout &layout, const mlir::TypeConverter &typeConverter) const override; + mlir::TypedAttr lowerDataMemberOffsetConstant( + cir::DataMemberOffsetAttr attr, const mlir::DataLayout &layout, + const mlir::TypeConverter &typeConverter) const override; + mlir::TypedAttr lowerMethodConstant(cir::MethodAttr attr, const mlir::DataLayout &layout, const mlir::TypeConverter &typeConverter) const override; @@ -217,6 +221,17 @@ mlir::TypedAttr LowerItaniumCXXABI::lowerDataMemberConstant( return cir::IntAttr::get(abiTy, memberOffset); } +mlir::TypedAttr LowerItaniumCXXABI::lowerDataMemberOffsetConstant( + cir::DataMemberOffsetAttr attr, const mlir::DataLayout &layout, + const mlir::TypeConverter &typeConverter) const { + // Itanium C++ ABI 2.3: + // A pointer to data member is an offset from the base address of the class + // object containing it, represented as a ptr diff _t. + // The offset is already known (the member has no CIR field index). + mlir::Type abiTy = lowerDataMemberType(attr.getType(), typeConverter); + return cir::IntAttr::get(abiTy, static_cast<int64_t>(attr.getOffset())); +} + mlir::TypedAttr LowerItaniumCXXABI::lowerMethodConstant( cir::MethodAttr attr, const mlir::DataLayout &layout, const mlir::TypeConverter &typeConverter) const { diff --git a/clang/test/CIR/CodeGen/pointer-to-empty-data-member.cpp b/clang/test/CIR/CodeGen/pointer-to-empty-data-member.cpp index 5d368f27033f5..0b493dc306594 100644 --- a/clang/test/CIR/CodeGen/pointer-to-empty-data-member.cpp +++ b/clang/test/CIR/CodeGen/pointer-to-empty-data-member.cpp @@ -87,7 +87,6 @@ struct hasNUA { [[no_unique_address]] EmptyBase eb6; int i; }; -// FIXME(cir): We should represent eb1-6 somehow // CIR-DAG: !rec_hasNUA = !cir.struct<"hasNUA" padded {!s32i, !cir.array<!u8i x 4>}> // LLVM-DAG: %struct.hasNUA = type { i32, [4 x i8] } @@ -96,19 +95,50 @@ const hasNUA nua = {{},{},{},{},{},{}, 1}; // LLVMCIR-DAG: @_ZL3nua = internal constant %struct.hasNUA { i32 1, [4 x i8] zeroinitializer } // OGCG-DAG: @_ZL3nua = internal constant %struct.hasNUA { i32 1, [4 x i8] undef } -// FIXME(cir): These are still an NYI, and we should enable tests here once we -// figure out how to represent these in IR. -//EmptyBase hasNUA::* eb1 = &hasNUA::eb1; -//EmptyBase hasNUA::* eb2 = &hasNUA::eb2; -//EmptyBase hasNUA::* eb3 = &hasNUA::eb3; -//EmptyBase hasNUA::* eb4 = &hasNUA::eb4; -//EmptyBase hasNUA::* eb5 = &hasNUA::eb5; -//EmptyBase hasNUA::* eb6 = &hasNUA::eb6; +// A pointer-to-data-member for a no_unique_address empty field has no CIR +// field index (the field isn't laid out), so it is represented by its concrete +// byte offset via #cir.data_member_offset. +EmptyBase hasNUA::* eb1 = &hasNUA::eb1; +// CIR-BEFORE-DAG: cir.global external @eb1 = #cir.data_member_offset<0> : !cir.data_member<!rec_EmptyBase in !rec_hasNUA> +// CIR-AFTER-DAG: cir.global external @eb1 = #cir.int<0> : !s64i +// LLVM-DAG: @eb1 = global i64 0 +EmptyBase hasNUA::* eb2 = &hasNUA::eb2; +// CIR-BEFORE-DAG: cir.global external @eb2 = #cir.data_member_offset<1> : !cir.data_member<!rec_EmptyBase in !rec_hasNUA> +// CIR-AFTER-DAG: cir.global external @eb2 = #cir.int<1> : !s64i +// LLVM-DAG: @eb2 = global i64 1 +EmptyBase hasNUA::* eb3 = &hasNUA::eb3; +// CIR-BEFORE-DAG: cir.global external @eb3 = #cir.data_member_offset<2> : !cir.data_member<!rec_EmptyBase in !rec_hasNUA> +// CIR-AFTER-DAG: cir.global external @eb3 = #cir.int<2> : !s64i +// LLVM-DAG: @eb3 = global i64 2 +EmptyBase hasNUA::* eb4 = &hasNUA::eb4; +// CIR-BEFORE-DAG: cir.global external @eb4 = #cir.data_member_offset<3> : !cir.data_member<!rec_EmptyBase in !rec_hasNUA> +// CIR-AFTER-DAG: cir.global external @eb4 = #cir.int<3> : !s64i +// LLVM-DAG: @eb4 = global i64 3 +EmptyBase hasNUA::* eb5 = &hasNUA::eb5; +// CIR-BEFORE-DAG: cir.global external @eb5 = #cir.data_member_offset<4> : !cir.data_member<!rec_EmptyBase in !rec_hasNUA> +// CIR-AFTER-DAG: cir.global external @eb5 = #cir.int<4> : !s64i +// LLVM-DAG: @eb5 = global i64 4 +EmptyBase hasNUA::* eb6 = &hasNUA::eb6; +// CIR-BEFORE-DAG: cir.global external @eb6 = #cir.data_member_offset<5> : !cir.data_member<!rec_EmptyBase in !rec_hasNUA> +// CIR-AFTER-DAG: cir.global external @eb6 = #cir.int<5> : !s64i +// LLVM-DAG: @eb6 = global i64 5 int hasNUA::* nua_i = &hasNUA::i; // CIR-BEFORE-DAG: cir.global external @nua_i = #cir.data_member<[0]> : !cir.data_member<!s32i in !rec_hasNUA> // CIR-AFTER-DAG: cir.global external @nua_i = #cir.int<0> : !s64i // LLVM-DAG: @nua_i = global i64 0 +struct FirstField { int a; }; +struct HoldsNUA { int b; [[no_unique_address]] EmptyBase e; [[no_unique_address]] EmptyBase e2; }; +struct DerivesNUA : FirstField, HoldsNUA {}; +EmptyBase DerivesNUA::* nua_in_base = &DerivesNUA::e; +// CIR-BEFORE-DAG: cir.global external @nua_in_base = #cir.data_member_offset<4> : !cir.data_member<!rec_EmptyBase in !rec_DerivesNUA> +// CIR-AFTER-DAG: cir.global external @nua_in_base = #cir.int<4> : !s64i +// LLVM-DAG: @nua_in_base = global i64 4 +EmptyBase DerivesNUA::* nua_in_base2 = &DerivesNUA::e2; +// CIR-BEFORE-DAG: cir.global external @nua_in_base2 = #cir.data_member_offset<8> : !cir.data_member<!rec_EmptyBase in !rec_DerivesNUA> +// CIR-AFTER-DAG: cir.global external @nua_in_base2 = #cir.int<8> : !s64i +// LLVM-DAG: @nua_in_base2 = global i64 8 + union U1 { EmptyBase eb; }; @@ -205,9 +235,14 @@ int U6::* u6i = &U6::i; // CIR-AFTER-DAG: cir.global external @u6i = #cir.int<0> : !s64i // LLVM-DAG: @u6i = global i64 0 -// FIXME(cir): See above. -//EmptyBase U6::* u6eb = &U6::eb; -//EmptyBase U6::* u6eb2 = &U6::eb2; +EmptyBase U6::* u6eb = &U6::eb; +// CIR-BEFORE-DAG: cir.global external @u6eb = #cir.data_member_offset<0> : !cir.data_member<!rec_EmptyBase in !rec_U6> +// CIR-AFTER-DAG: cir.global external @u6eb = #cir.int<0> : !s64i +// LLVM-DAG: @u6eb = global i64 0 +EmptyBase U6::* u6eb2 = &U6::eb2; +// CIR-BEFORE-DAG: cir.global external @u6eb2 = #cir.data_member_offset<0> : !cir.data_member<!rec_EmptyBase in !rec_U6> +// CIR-AFTER-DAG: cir.global external @u6eb2 = #cir.int<0> : !s64i +// LLVM-DAG: @u6eb2 = global i64 0 union U7 { int i; @@ -222,9 +257,14 @@ int U7::* u7i = &U7::i; // CIR-AFTER-DAG: cir.global external @u7i = #cir.int<0> : !s64i // LLVM-DAG: @u7i = global i64 0 -// FIXME(cir): See above. -//EmptyBase U7::* u7eb = &U7::eb; -//EmptyBase U7::* u7eb2 = &U7::eb2; +EmptyBase U7::* u7eb = &U7::eb; +// CIR-BEFORE-DAG: cir.global external @u7eb = #cir.data_member_offset<0> : !cir.data_member<!rec_EmptyBase in !rec_U7> +// CIR-AFTER-DAG: cir.global external @u7eb = #cir.int<0> : !s64i +// LLVM-DAG: @u7eb = global i64 0 +EmptyBase U7::* u7eb2 = &U7::eb2; +// CIR-BEFORE-DAG: cir.global external @u7eb2 = #cir.data_member_offset<0> : !cir.data_member<!rec_EmptyBase in !rec_U7> +// CIR-AFTER-DAG: cir.global external @u7eb2 = #cir.int<0> : !s64i +// LLVM-DAG: @u7eb2 = global i64 0 void uses() { auto x = &HasEmpty::s; _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
