From 3ca17443ef4af21bdb1f3b4fbcfff672cbc6176c Mon Sep 17 00:00:00 2001 From: eddyz87 Date: Tue, 18 Jun 2024 10:23:25 +0300 Subject: [DebugInfo][BPF] Add 'annotations' field for DIBasicType & DISubroutineType (#91422) Extend `DIBasicType` and `DISubroutineType` with additional field `annotations`, e.g. as below: ``` !5 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed, annotations: !6) !6 = !{!7} !7 = !{!"btf:type_tag", !"tag1"} ``` The field would be used by BPF backend to generate DWARF attributes corresponding to `btf_type_tag` type attributes, e.g.: ``` 0x00000029: DW_TAG_base_type DW_AT_name ("int") DW_AT_encoding (DW_ATE_signed) DW_AT_byte_size (0x04) 0x0000002d: DW_TAG_LLVM_annotation DW_AT_name ("btf:type_tag") DW_AT_const_value ("tag1") ``` Such DWARF entries would be used to generate BTF definitions by tools like [pahole](https://github.com/acmel/dwarves). Note: similar fields with similar purposes are already present in DIDerivedType and DICompositeType. Currently "btf_type_tag" attributes are represented in debug information as 'annotations' fields in DIDerivedType with DW_TAG_pointer_type tag. The annotation on a pointer corresponds to pointee having the attributes in the final BTF. The discussion in [thread](https://lore.kernel.org/bpf/87r0w9jjoq.fsf@oracle.com/) came to conclusion, that such annotations should apply to the annotated type itself. Hence the necessity to extend `DIBasicType` & `DISubroutineType` types with 'annotations' field to represent cases like below: ``` int __attribute__((btf_type_tag("foo"))) bar; ``` This was previously tracked as differential revision: https://reviews.llvm.org/D143966 --- llvm/lib/Bitcode/Writer/BitcodeWriter.cpp | 2 ++ 1 file changed, 2 insertions(+) (limited to 'llvm/lib/Bitcode/Writer/BitcodeWriter.cpp') diff --git a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp index b08d5c50e5ae..f3e87310310e 100644 --- a/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp +++ b/llvm/lib/Bitcode/Writer/BitcodeWriter.cpp @@ -1816,6 +1816,7 @@ void ModuleBitcodeWriter::writeDIBasicType(const DIBasicType *N, Record.push_back(N->getAlignInBits()); Record.push_back(N->getEncoding()); Record.push_back(N->getFlags()); + Record.push_back(VE.getMetadataOrNullID(N->getRawAnnotations())); Stream.EmitRecord(bitc::METADATA_BASIC_TYPE, Record, Abbrev); Record.clear(); @@ -1911,6 +1912,7 @@ void ModuleBitcodeWriter::writeDISubroutineType( Record.push_back(N->getFlags()); Record.push_back(VE.getMetadataOrNullID(N->getTypeArray().get())); Record.push_back(N->getCC()); + Record.push_back(VE.getMetadataOrNullID(N->getRawAnnotations())); Stream.EmitRecord(bitc::METADATA_SUBROUTINE_TYPE, Record, Abbrev); Record.clear(); -- cgit v1.2.3