[DWARFYAML][debug_abbrev] Make the abbreviation code optional.

[Higuoxing]

Summary

This patch helps make the Code optional in abbreviations table.

[grimar]

llvm/lib/ObjectYAML/DWARFEmitter.cpp

95

Looks unformatted.

It is also more common to write in the following way I think:

(uint64_t)*AbbrevDecl.Code

(i.e. no brackets around the AbbrevDecl.Code)

llvm/test/tools/yaml2obj/ELF/DWARF/debug-abbrev.yaml

278

Could you add a one more DW_TAG_subprogram with the same Code and one more DW_TAG_subprogram after it
somewhere here to demostrate the behavior in this case?

[Higuoxing]

Seems that build bots are not happy with this change. I'll update it later.

[jhenderson]

The premerge bot is complaining about several failing tests in ObjectYAML. You should probably investigate those.

Edit to add: oh I see you've spotted that already.

llvm/lib/ObjectYAML/DWARFEmitter.cpp

95

Something looks off in this formatting. Did you run clang-format and/or mean (uint64_t)(*AbbrevDecl.Code) perhaps?

[Higuoxing]

Address comments.

[jhenderson]

llvm/include/llvm/ObjectYAML/DWARFYAML.h

55

I would suggest you keep this as a Hex64 in this patch, and change it to a uint64_t in a separate patch, although I'm not entirely convinced either way whether it should be done at all. Perhaps @grimar has some thoughts?

[Higuoxing]

Address comment.

llvm/include/llvm/ObjectYAML/DWARFYAML.h

55

Sure, I will leave it as yaml::Hex64 in this patch. I think dumping abbreviation codes in a decimal format has better readability than dumping it in a hexadecimal format. But I'm convincible here :)

[grimar]

llvm/include/llvm/ObjectYAML/DWARFYAML.h

55

I'd change to uint64_t, but separatelly. I think that abbreviation codes in a decimal format would probably look better, because it is just an index?

[jhenderson]

LGTM.

[Higuoxing]

Rebase.

llvm/include/llvm/ObjectYAML/DWARFYAML.h

 
 struct AttributeAbbrev {
   llvm::dwarf::Attribute Attribute;
   llvm::dwarf::Form Form;
   llvm::yaml::Hex64 Value; // Some DWARF5 attributes have values
 };
 
 struct Abbrev {
-  llvm::yaml::Hex32 Code;
+  Optional<llvm::yaml::Hex64> Code;
   llvm::dwarf::Tag Tag;
   llvm::dwarf::Constants Children;
   std::vector<AttributeAbbrev> Attributes;
 };
 
 struct ARangeDescriptor {
   llvm::yaml::Hex64 Address;
   uint64_t Length;

llvm/lib/ObjectYAML/DWARFEmitter.cpp

for (auto Str : DI.DebugStrings) {
     OS.write(Str.data(), Str.size());
     OS.write('\0');
   }
 
   return Error::success();
 }
 
 Error DWARFYAML::emitDebugAbbrev(raw_ostream &OS, const DWARFYAML::Data &DI) {
+  uint64_t AbbrevCode = 0;
   for (auto AbbrevDecl : DI.AbbrevDecls) {
-    encodeULEB128(AbbrevDecl.Code, OS);
+    AbbrevCode =
+        AbbrevDecl.Code ? (uint64_t) * (AbbrevDecl.Code) : AbbrevCode + 1;
+    encodeULEB128(AbbrevCode, OS);
     encodeULEB128(AbbrevDecl.Tag, OS);
     OS.write(AbbrevDecl.Children);
     for (auto Attr : AbbrevDecl.Attributes) {
       encodeULEB128(Attr.Attribute, OS);
       encodeULEB128(Attr.Form, OS);
       if (Attr.Form == dwarf::DW_FORM_implicit_const)
         encodeSLEB128(Attr.Value, OS);
     }

llvm/lib/ObjectYAML/DWARFYAML.cpp

void MappingTraits<DWARFYAML::Data>::mapping(IO &IO, DWARFYAML::Data &DWARF) {
   IO.mapOptional("debug_gnu_pubtypes", DWARF.GNUPubTypes);
   IO.mapOptional("debug_info", DWARF.CompileUnits);
   IO.mapOptional("debug_line", DWARF.DebugLines);
   IO.setContext(&oldContext);
 }
 
 void MappingTraits<DWARFYAML::Abbrev>::mapping(IO &IO,
                                                DWARFYAML::Abbrev &Abbrev) {
-  IO.mapRequired("Code", Abbrev.Code);
+  IO.mapOptional("Code", Abbrev.Code);
   IO.mapRequired("Tag", Abbrev.Tag);
   IO.mapRequired("Children", Abbrev.Children);
   IO.mapRequired("Attributes", Abbrev.Attributes);
 }
 
 void MappingTraits<DWARFYAML::AttributeAbbrev>::mapping(
     IO &IO, DWARFYAML::AttributeAbbrev &AttAbbrev) {
   IO.mapRequired("Attribute", AttAbbrev.Attribute);

llvm/test/tools/yaml2obj/ELF/DWARF/debug-abbrev.yaml

Sections:
   - Name:         .sec        # Linked by .debug_abbrev.
     Type:         SHT_STRTAB
 DWARF:
   debug_abbrev:
     - Code:       1
       Tag:        DW_TAG_compile_unit
       Children:   DW_CHILDREN_no
       Attributes: []
+
+## h) Test that yaml2obj automatically generates abbreviation codes for us.
+
+# RUN: yaml2obj --docnum=8 %s -o %t8.o
+# RUN: llvm-readelf --hex-dump=.debug_abbrev %t8.o | FileCheck %s --check-prefix=CODE
+
+#      CODE: 0x00000000 01110000 00022e00 0000042e 00000005
+##                      |          |          |          |
+##                      |          |          |          +- abbreviation code (ULEB128) 0x05
+##                      |          |          +- abbreviation code (ULEB128) 0x04
+##                      |          +- abbreviation code (ULEB128) 0x02
+##                      +- abbreviation code (ULEB128) 0x01
+# CODE-NEXT: 0x00000010 2e000000 062e0000 00
+##                               |
+##                               +- abbreviation code (ULEB128) 0x06
+
+--- !ELF
+FileHeader:
+  Class:   ELFCLASS64
+  Data:    ELFDATA2LSB
+  Type:    ET_EXEC
+  Machine: EM_X86_64
+DWARF:
+  debug_abbrev:
+    - Tag:        DW_TAG_compile_unit
+      Children:   DW_CHILDREN_no
+      Attributes: []
+    - Tag:        DW_TAG_subprogram
+      Children:   DW_CHILDREN_no
+      Attributes: []
+    - Code: 4
+      Tag:        DW_TAG_subprogram
+      Children:   DW_CHILDREN_no
+      Attributes: []
+    - Tag:        DW_TAG_subprogram
+      Children:   DW_CHILDREN_no
+      Attributes: []
+    - Tag:        DW_TAG_subprogram
+      Children:   DW_CHILDREN_no
+      Attributes: []