Author: Steven Wan Date: 2021-08-05T18:18:58-04:00 New Revision: a91916500d67155ca17bfdf3294541f871f90a45
URL: https://github.com/llvm/llvm-project/commit/a91916500d67155ca17bfdf3294541f871f90a45 DIFF: https://github.com/llvm/llvm-project/commit/a91916500d67155ca17bfdf3294541f871f90a45.diff LOG: [AIX] "aligned" attribute should not decrease type alignment returned by __alignof__ `__alignof__(x)` always returns `ABIAlign` if the "x" is marked `__attribute__((aligned()))`. However, the "aligned" attribute should 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. Reviewed By: sfertile Differential Revision: https://reviews.llvm.org/D107598 Added: clang/test/Layout/aix-alignof-align-and-pack-attr.cpp Modified: clang/lib/AST/ASTContext.cpp Removed: ################################################################################ diff --git a/clang/lib/AST/ASTContext.cpp b/clang/lib/AST/ASTContext.cpp index 4ff2aa5307bbe..4c9dc42c5b5dd 100644 --- a/clang/lib/AST/ASTContext.cpp +++ b/clang/lib/AST/ASTContext.cpp @@ -2478,11 +2478,16 @@ unsigned ASTContext::getPreferredTypeAlign(const Type *T) const { return ABIAlign; if (const auto *RT = T->getAs<RecordType>()) { - if (TI.AlignIsRequired || RT->getDecl()->isInvalidDecl()) + const RecordDecl *RD = RT->getDecl(); + + // When used as part of a typedef, or together with a 'packed' attribute, + // the 'aligned' attribute can be used to decrease alignment. + if ((TI.AlignIsRequired && T->getAs<TypedefType>() != nullptr) || + RD->isInvalidDecl()) return ABIAlign; unsigned PreferredAlign = static_cast<unsigned>( - toBits(getASTRecordLayout(RT->getDecl()).PreferredAlignment)); + toBits(getASTRecordLayout(RD).PreferredAlignment)); assert(PreferredAlign >= ABIAlign && "PreferredAlign should be at least as large as ABIAlign."); return PreferredAlign; diff --git a/clang/test/Layout/aix-alignof-align-and-pack-attr.cpp b/clang/test/Layout/aix-alignof-align-and-pack-attr.cpp new file mode 100644 index 0000000000000..51f3c5a2adc11 --- /dev/null +++ b/clang/test/Layout/aix-alignof-align-and-pack-attr.cpp @@ -0,0 +1,29 @@ +// 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 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits