From ef4795280878526b547d021405a1e99dee653bf1 Mon Sep 17 00:00:00 2001 From: Michael Buch Date: Thu, 30 Oct 2025 09:36:53 +0000 Subject: [PATCH 1/3] [lldb][DWARF] Support DW_AT_bit_size on type tags One (DWARF-spec compliant) exmample is: https://github.com/llvm/llvm-project/pull/164372, where we attach a `DW_AT_bit_size` to `_BitInt` types that can't be exactly described by a byte-size. This patch adds support for `DW_AT_bit_size` to `DWARFASTParserClang` when parsing type tags. Note, we don't use this bit-size yet, but will do so in follow-up patches. --- .../SymbolFile/DWARF/DWARFASTParserClang.cpp | 8 +- .../SymbolFile/DWARF/DWARFASTParserClang.h | 1 + .../DWARF/DWARFASTParserClangTests.cpp | 90 +++++++++++++++++++ 3 files changed, 97 insertions(+), 2 deletions(-) diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp index 82e9d867c3ac0..71dc3de4137d4 100644 --- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp +++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp @@ -450,6 +450,10 @@ ParsedDWARFTypeAttributes::ParsedDWARFTypeAttributes(const DWARFDIE &die) { byte_size = form_value.Unsigned(); break; + case DW_AT_bit_size: + data_bit_size = form_value.Unsigned(); + break; + case DW_AT_alignment: alignment = form_value.Unsigned(); break; @@ -810,13 +814,13 @@ DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc, // there... [[fallthrough]]; - case DW_TAG_base_type: + case DW_TAG_base_type: { resolve_state = Type::ResolveState::Full; clang_type = m_ast.GetBuiltinTypeForDWARFEncodingAndBitSize( attrs.name.GetStringRef(), attrs.encoding, attrs.byte_size.value_or(0) * 8); break; - + } case DW_TAG_pointer_type: encoding_data_type = Type::eEncodingIsPointerUID; break; diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h index da58f4c146226..f5f707129d67d 100644 --- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h +++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.h @@ -574,6 +574,7 @@ struct ParsedDWARFTypeAttributes { lldb_private::plugin::dwarf::DWARFFormValue type; lldb::LanguageType class_language = lldb::eLanguageTypeUnknown; std::optional byte_size; + std::optional data_bit_size; std::optional alignment; size_t calling_convention = llvm::dwarf::DW_CC_normal; uint32_t bit_stride = 0; diff --git a/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp b/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp index 0cae01de2902a..646426b5cb31f 100644 --- a/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp +++ b/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp @@ -1617,3 +1617,93 @@ TEST_F(DWARFASTParserClangTests, TestObjectPointer_IndexEncoding) { EXPECT_EQ(param_die, ast_parser.GetObjectParameter(sub2, context_die)); } } + +TEST_F(DWARFASTParserClangTests, TestTypeBitSize) { + // Tests that we correctly parse DW_AT_bit_size of a DW_AT_base_type. + + const char *yamldata = R"( +--- !ELF +FileHeader: + Class: ELFCLASS64 + Data: ELFDATA2LSB + Type: ET_EXEC + Machine: EM_AARCH64 +DWARF: + debug_str: + - _BitInt(2) + debug_abbrev: + - ID: 0 + Table: + - Code: 0x1 + Tag: DW_TAG_compile_unit + Children: DW_CHILDREN_yes + Attributes: + - Attribute: DW_AT_language + Form: DW_FORM_data2 + - Code: 0x2 + Tag: DW_TAG_base_type + Children: DW_CHILDREN_no + Attributes: + - Attribute: DW_AT_name + Form: DW_FORM_strp + - Attribute: DW_AT_encoding + Form: DW_FORM_data1 + - Attribute: DW_AT_byte_size + Form: DW_FORM_data1 + - Attribute: DW_AT_bit_size + Form: DW_FORM_data1 + + debug_info: + - Version: 5 + UnitType: DW_UT_compile + AddrSize: 8 + Entries: + +# DW_TAG_compile_unit +# DW_AT_language [DW_FORM_data2] (DW_LANG_C_plus_plus) + + - AbbrCode: 0x1 + Values: + - Value: 0x04 + +# DW_TAG_base_type +# DW_AT_name [DW_FORM_strp] ('_BitInt(2)') + + - AbbrCode: 0x2 + Values: + - Value: 0x0 + - Value: 0x3e + - Value: 0x01 + - Value: 0x02 +... +)"; + + YAMLModuleTester t(yamldata); + + DWARFUnit *unit = t.GetDwarfUnit(); + ASSERT_NE(unit, nullptr); + const DWARFDebugInfoEntry *cu_entry = unit->DIE().GetDIE(); + ASSERT_EQ(cu_entry->Tag(), DW_TAG_compile_unit); + ASSERT_EQ(unit->GetDWARFLanguageType(), DW_LANG_C_plus_plus); + DWARFDIE cu_die(unit, cu_entry); + + auto holder = std::make_unique("ast"); + auto &ast_ctx = *holder->GetAST(); + DWARFASTParserClangStub ast_parser(ast_ctx); + + auto type_die = cu_die.GetFirstChild(); + ASSERT_TRUE(type_die.IsValid()); + ASSERT_EQ(type_die.Tag(), DW_TAG_base_type); + + ParsedDWARFTypeAttributes attrs(type_die); + EXPECT_EQ(attrs.byte_size.value_or(0), 1U); + EXPECT_EQ(attrs.data_bit_size.value_or(0), 2U); + + SymbolContext sc; + auto type_sp = + ast_parser.ParseTypeFromDWARF(sc, type_die, /*type_is_new_ptr=*/nullptr); + ASSERT_NE(type_sp, nullptr); + + EXPECT_EQ(llvm::expectedToOptional(type_sp->GetByteSize(nullptr)).value_or(0), + 1U); +} From fb45b0e7a81d429322f32ff7eb7b49b6269b5b32 Mon Sep 17 00:00:00 2001 From: Michael Buch Date: Thu, 30 Oct 2025 09:39:50 +0000 Subject: [PATCH 2/3] fixup! remove redundant change --- lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp index 71dc3de4137d4..2565446a26059 100644 --- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp +++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp @@ -814,13 +814,13 @@ DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc, // there... [[fallthrough]]; - case DW_TAG_base_type: { + case DW_TAG_base_type: resolve_state = Type::ResolveState::Full; clang_type = m_ast.GetBuiltinTypeForDWARFEncodingAndBitSize( attrs.name.GetStringRef(), attrs.encoding, attrs.byte_size.value_or(0) * 8); break; - } + case DW_TAG_pointer_type: encoding_data_type = Type::eEncodingIsPointerUID; break; From c8ab7e792fea453119b8d479f171c91e73cc084b Mon Sep 17 00:00:00 2001 From: Michael Buch Date: Thu, 30 Oct 2025 09:49:20 +0000 Subject: [PATCH 3/3] fixup! fix encoding --- lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp b/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp index 646426b5cb31f..d73ac87718e10 100644 --- a/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp +++ b/lldb/unittests/SymbolFile/DWARF/DWARFASTParserClangTests.cpp @@ -1672,7 +1672,7 @@ TEST_F(DWARFASTParserClangTests, TestTypeBitSize) { - AbbrCode: 0x2 Values: - Value: 0x0 - - Value: 0x3e + - Value: 0x05 - Value: 0x01 - Value: 0x02 ...