Author: Fangrui Song Date: 2026-03-11T18:17:43-07:00 New Revision: da3efc79f0cc6d41a4c5627a3dc9fce6f5c701b4
URL: https://github.com/llvm/llvm-project/commit/da3efc79f0cc6d41a4c5627a3dc9fce6f5c701b4 DIFF: https://github.com/llvm/llvm-project/commit/da3efc79f0cc6d41a4c5627a3dc9fce6f5c701b4.diff LOG: Fix packed being ignored on ms_struct bitfields (#182792) For ms_struct structs on Itanium layout targets, the packed attribute is ignored on bit-fields (2014 commit 76e1818a2b1248579557de2927c135c322577c82), mismatching the GCC behavior. Remove the `!IsMsStruct` guard to fix it. Added: clang/test/CodeGen/ms_struct-packed.c Modified: clang/lib/AST/RecordLayoutBuilder.cpp clang/test/CodeGen/ms_struct-bitfield.c Removed: ################################################################################ diff --git a/clang/lib/AST/RecordLayoutBuilder.cpp b/clang/lib/AST/RecordLayoutBuilder.cpp index 0b1bf813efd10..f417588accd78 100644 --- a/clang/lib/AST/RecordLayoutBuilder.cpp +++ b/clang/lib/AST/RecordLayoutBuilder.cpp @@ -1676,7 +1676,7 @@ void ItaniumRecordLayoutBuilder::LayoutBitField(const FieldDecl *D) { unsigned UnpackedFieldAlign = FieldAlign; // Ignore the field alignment if the field is packed unless it has zero-size. - if (!IsMsStruct && FieldPacked && FieldSize != 0) + if (FieldPacked && FieldSize != 0) FieldAlign = 1; // But, if there's an 'aligned' attribute on the field, honor that. diff --git a/clang/test/CodeGen/ms_struct-bitfield.c b/clang/test/CodeGen/ms_struct-bitfield.c index 37b0245e57c45..4598b880dd975 100644 --- a/clang/test/CodeGen/ms_struct-bitfield.c +++ b/clang/test/CodeGen/ms_struct-bitfield.c @@ -172,5 +172,5 @@ struct { __attribute__((packed)) unsigned short c : 6; } ATTR t13; int s13 = sizeof(t13); -// CHECK: @s13 ={{.*}} global i32 4 -// CHECK-ARM: @s13 ={{.*}} global i32 4 +// CHECK: @s13 ={{.*}} global i32 3 +// CHECK-ARM: @s13 ={{.*}} global i32 3 diff --git a/clang/test/CodeGen/ms_struct-packed.c b/clang/test/CodeGen/ms_struct-packed.c new file mode 100644 index 0000000000000..0cbf61a759b81 --- /dev/null +++ b/clang/test/CodeGen/ms_struct-packed.c @@ -0,0 +1,18 @@ +// RUN: %clang_cc1 -emit-llvm-only -triple x86_64 %s + +/// Packed struct: diff erent storage unit types should pack without alignment +/// padding between storage units. +struct __attribute__((packed,ms_struct)) P1 { + short a : 8; + int b : 30; +}; + +static int p1[(sizeof(struct P1) == 6) ? 1 : -1]; + +// Packed struct with char and int fields. +struct [[gnu::ms_struct,gnu::packed]] P2 { + char a : 4; + int b : 20; +}; + +static int p2[(sizeof(struct P2) == 5) ? 1 : -1]; _______________________________________________ cfe-commits mailing list [email protected] https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
