Author: Steven Wan Date: 2021-08-29T21:33:05-04:00 New Revision: 71b170ccf36ee02e6a4c472bc1d3e89bbaf0e2b4
URL: https://github.com/llvm/llvm-project/commit/71b170ccf36ee02e6a4c472bc1d3e89bbaf0e2b4 DIFF: https://github.com/llvm/llvm-project/commit/71b170ccf36ee02e6a4c472bc1d3e89bbaf0e2b4.diff LOG: [AIX] "aligned" attribute does not decrease alignment The "aligned" attribute can only increase the alignment of a struct, or struct member, unless it's used together with the "packed" attribute, or used as a part of a typedef, in which case, the "aligned" attribute can both increase and decrease alignment. That said, we expect: 1. "aligned" attribute alone: does not interfere with the alignment upgrade instrumented by the AIX "power" alignment rule, 2. "aligned" attribute + typedef: overrides any computed alignment, 3. "aligned" attribute + "packed" attribute: overrides any computed alignment. The old implementation achieved 2 and 3, but didn't get 1 right, in that any field marked attribute "aligned" would not go through the alignment upgrade. Reviewed By: rjmccall Differential Revision: https://reviews.llvm.org/D107394 Added: clang/test/Layout/aix-type-align-and-pack-attr.cpp Modified: clang/lib/AST/RecordLayoutBuilder.cpp clang/test/Layout/aix-power-alignment-typedef.cpp Removed: clang/test/Layout/aix-alignof-align-and-pack-attr.cpp ################################################################################ diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp index 30e88da9ac4f5..5c86b06da835e 100644 --- a/clang/lib/AST/RecordLayoutBuilder.cpp +++ b/clang/lib/AST/RecordLayoutBuilder.cpp @@ -1968,6 +1968,19 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D, } } + // When used as part of a typedef, or together with a 'packed' attribute, the + // 'aligned' attribute can be used to decrease alignment. In that case, it + // overrides any computed alignment we have, and there is no need to upgrade + // the alignment. + auto alignedAttrCanDecreaseAIXAlignment = [AlignRequirement, FieldPacked] { + // Enum alignment sources can be safely ignored here, because this only + // helps decide whether we need the AIX alignment upgrade, which only + // applies to floating-point types. + return AlignRequirement == AlignRequirementKind::RequiredByTypedef || + (AlignRequirement == AlignRequirementKind::RequiredByRecord && + FieldPacked); + }; + // The AIX `power` alignment rules apply the natural alignment of the // "first member" if it is of a floating-point data type (or is an aggregate // whose recursively "first" member or element is such a type). The alignment @@ -1978,8 +1991,7 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D, // and zero-width bit-fields count as prior members; members of empty class // types marked `no_unique_address` are not considered to be prior members. CharUnits PreferredAlign = FieldAlign; - if (DefaultsToAIXPowerAlignment && - AlignRequirement == AlignRequirementKind::None && + if (DefaultsToAIXPowerAlignment && !alignedAttrCanDecreaseAIXAlignment() && (FoundFirstNonOverlappingEmptyFieldForAIX || IsNaturalAlign)) { auto performBuiltinTypeAlignmentUpgrade = [&](const BuiltinType *BTy) { if (BTy->getKind() == BuiltinType::Double || @@ -1990,12 +2002,13 @@ void ItaniumRecordLayoutBuilder::LayoutField(const FieldDecl *D, } }; - const Type *Ty = D->getType()->getBaseElementTypeUnsafe(); - if (const ComplexType *CTy = Ty->getAs<ComplexType>()) { - performBuiltinTypeAlignmentUpgrade(CTy->getElementType()->castAs<BuiltinType>()); - } else if (const BuiltinType *BTy = Ty->getAs<BuiltinType>()) { + const Type *BaseTy = D->getType()->getBaseElementTypeUnsafe(); + if (const ComplexType *CTy = BaseTy->getAs<ComplexType>()) { + performBuiltinTypeAlignmentUpgrade( + CTy->getElementType()->castAs<BuiltinType>()); + } else if (const BuiltinType *BTy = BaseTy->getAs<BuiltinType>()) { performBuiltinTypeAlignmentUpgrade(BTy); - } else if (const RecordType *RT = Ty->getAs<RecordType>()) { + } else if (const RecordType *RT = BaseTy->getAs<RecordType>()) { const RecordDecl *RD = RT->getDecl(); assert(RD && "Expected non-null RecordDecl."); const ASTRecordLayout &FieldRecord = Context.getASTRecordLayout(RD); diff --git a/clang/test/Layout/aix-alignof-align-and-pack-attr.cpp b/clang/test/Layout/aix-alignof-align-and-pack-attr.cpp deleted file mode 100644 index 51f3c5a2adc11..0000000000000 --- a/clang/test/Layout/aix-alignof-align-and-pack-attr.cpp +++ /dev/null @@ -1,29 +0,0 @@ -// RUN: %clang_cc1 -triple powerpc-ibm-aix-xcoff -S -emit-llvm -x c++ < %s | \ -// RUN: FileCheck %s - -// RUN: %clang_cc1 -triple powerpc64-ibm-aix-xcoff -S -emit-llvm -x c++ < %s | \ -// RUN: FileCheck %s - -namespace test1 { -struct __attribute__((__aligned__(2))) C { - double x; -} c; - -// CHECK: @{{.*}}test1{{.*}}c{{.*}} = global %"struct.test1::C" zeroinitializer, align 8 -} // namespace test1 - -namespace test2 { -struct __attribute__((__aligned__(2), packed)) C { - double x; -} c; - -// CHECK: @{{.*}}test2{{.*}}c{{.*}} = global %"struct.test2::C" zeroinitializer, align 2 -} // namespace test2 - -namespace test3 { -struct __attribute__((__aligned__(16))) C { - double x; -} c; - -// CHECK: @{{.*}}test3{{.*}}c{{.*}} = global %"struct.test3::C" zeroinitializer, align 16 -} // namespace test3 diff --git a/clang/test/Layout/aix-power-alignment-typedef.cpp b/clang/test/Layout/aix-power-alignment-typedef.cpp index fc973a1fdfd81..f6925c34b1712 100644 --- a/clang/test/Layout/aix-power-alignment-typedef.cpp +++ b/clang/test/Layout/aix-power-alignment-typedef.cpp @@ -37,3 +37,39 @@ int x = sizeof(U); // CHECK-NEXT: | nvsize=2, nvalign=2, preferrednvalign=2] } // namespace test2 + +namespace test3 { +typedef double DblArr[] __attribute__((__aligned__(2))); + +union U { + DblArr da; + char x; +}; + +int x = sizeof(U); + +// CHECK: 0 | union test3::U +// CHECK-NEXT: 0 | test3::DblArr da +// CHECK-NEXT: 0 | char x +// CHECK-NEXT: | [sizeof=2, dsize=2, align=2, preferredalign=2, +// CHECK-NEXT: | nvsize=2, nvalign=2, preferrednvalign=2] + +} // namespace test3 + +namespace test4 { +typedef double Dbl __attribute__((__aligned__(2))); + +union U { + Dbl DblArr[]; + char x; +}; + +int x = sizeof(U); + +// CHECK: 0 | union test4::U +// CHECK-NEXT: 0 | test4::Dbl [] DblArr +// CHECK-NEXT: 0 | char x +// CHECK-NEXT: | [sizeof=2, dsize=2, align=2, preferredalign=2, +// CHECK-NEXT: | nvsize=2, nvalign=2, preferrednvalign=2] + +} // namespace test4 diff --git a/clang/test/Layout/aix-type-align-and-pack-attr.cpp b/clang/test/Layout/aix-type-align-and-pack-attr.cpp new file mode 100644 index 0000000000000..d119511b141f2 --- /dev/null +++ b/clang/test/Layout/aix-type-align-and-pack-attr.cpp @@ -0,0 +1,59 @@ +// RUN: %clang_cc1 -triple powerpc-ibm-aix-xcoff -S -emit-llvm -x c++ < %s | \ +// RUN: FileCheck %s + +// RUN: %clang_cc1 -triple powerpc64-ibm-aix-xcoff -S -emit-llvm -x c++ < %s | \ +// RUN: FileCheck %s + +namespace test1 { +struct __attribute__((__aligned__(2))) S { + double d; +}; + +S s; + +// CHECK: @{{.*}}test1{{.*}}s{{.*}} = global %"struct.test1::S" zeroinitializer, align 8 +} // namespace test1 + +namespace test2 { +struct __attribute__((__aligned__(2), packed)) S { + double d; +}; + +S s; + +// CHECK: @{{.*}}test2{{.*}}s{{.*}} = global %"struct.test2::S" zeroinitializer, align 2 +} // namespace test2 + +namespace test3 { +struct __attribute__((__aligned__(16))) S { + double d; +}; + +S s; + +// CHECK: @{{.*}}test3{{.*}}s{{.*}} = global %"struct.test3::S" zeroinitializer, align 16 +} // namespace test3 + +namespace test4 { +struct __attribute__((aligned(2))) SS { + double d; +}; + +struct S { + struct SS ss; +} s; + +// CHECK: @{{.*}}test4{{.*}}s{{.*}} = global %"struct.test4::S" zeroinitializer, align 8 +} // namespace test4 + +namespace test5 { +struct __attribute__((aligned(2), packed)) SS { + double d; +}; + +struct S { + struct SS ss; +} s; + +// CHECK: @{{.*}}test5{{.*}}s{{.*}} = global %"struct.test5::S" zeroinitializer, align 2 +} // namespace test5 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
