[ObjWriter] Enable DWARF debug information emitting for Mach-O

llvm/tools/objwriter/debugInfo/dwarf/dwarfAbbrev.cpp

@@ -38,6 +38,10 @@ void Dump(MCObjectStreamer *Streamer, uint16_t DwarfVersion, unsigned TargetPoin
         dwarf::DW_TAG_compile_unit, dwarf::DW_CHILDREN_yes,
         dwarf::DW_AT_producer, dwarf::DW_FORM_string,
         dwarf::DW_AT_language, dwarf::DW_FORM_data2,
+        dwarf::DW_AT_name, dwarf::DW_FORM_string,
+        dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string,
+        dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr,
+        dwarf::DW_AT_high_pc, DW_FORM_size,
         dwarf::DW_AT_stmt_list, (DwarfVersion >= 4 ? dwarf::DW_FORM_sec_offset : dwarf::DW_FORM_data4),
         0, 0,
 
@@ -125,6 +129,17 @@ void Dump(MCObjectStreamer *Streamer, uint16_t DwarfVersion, unsigned TargetPoin
         dwarf::DW_AT_declaration, dwarf::DW_FORM_flag_present,
         0, 0,
 
+    SubprogramStaticNoChildrenSpec,
+        dwarf::DW_TAG_subprogram, dwarf::DW_CHILDREN_no,
+        dwarf::DW_AT_name, dwarf::DW_FORM_strp,
+        dwarf::DW_AT_linkage_name, dwarf::DW_FORM_strp,
+        dwarf::DW_AT_decl_file, dwarf::DW_FORM_data1,
+        dwarf::DW_AT_decl_line, dwarf::DW_FORM_data1,
+        dwarf::DW_AT_type, dwarf::DW_FORM_ref4,
+        dwarf::DW_AT_external, dwarf::DW_FORM_flag_present,
+        dwarf::DW_AT_declaration, dwarf::DW_FORM_flag_present,
+        0, 0,
+
     Variable,
         dwarf::DW_TAG_variable, dwarf::DW_CHILDREN_no,
         dwarf::DW_AT_name, dwarf::DW_FORM_strp,

llvm/tools/objwriter/debugInfo/dwarf/dwarfAbbrev.h

@@ -30,6 +30,7 @@ enum DwarfAbbrev : uint16_t
   SubprogramStatic,
   SubprogramSpec,
   SubprogramStaticSpec,
+  SubprogramStaticNoChildrenSpec,
   Variable,
   VariableLoc,
   VariableStatic,

llvm/tools/objwriter/debugInfo/dwarf/dwarfGen.cpp

@@ -816,7 +816,7 @@ void SubprogramInfo::DumpTypeInfo(MCObjectStreamer *Streamer, UserDefinedDwarfTy
   EmitInfoOffset(Streamer, MethodTypeInfo, 4);
 
   // DW_AT_low_pc
-  MCSymbol *Sym = context.getOrCreateSymbol(Twine(Name));
+  MCSymbol *Sym = context.lookupSymbol(Twine(Name));
   const MCExpr *SymExpr = MCSymbolRefExpr::create(Sym, MCSymbolRefExpr::VK_None, context);
   Streamer->emitValue(SymExpr, TargetPointerSize);
 
@@ -907,6 +907,7 @@ void DwarfGen::SetTypeBuilder(UserDefinedDwarfTypesBuilder *TypeBuilder) {
 
 void DwarfGen::EmitCompileUnit() {
   MCContext &context = Streamer->getContext();
+  unsigned TargetPointerSize = context.getAsmInfo()->getCodePointerSize();
 
   MCSymbol *LineSectionSymbol = nullptr;
   MCSymbol *AbbrevSectionSymbol = nullptr;
@@ -966,6 +967,31 @@ void DwarfGen::EmitCompileUnit() {
   Streamer->emitIntValue(dwarf::DW_LANG_C_plus_plus, 2);
 #endif
 
+  // We need to generate DW_AT_name and DW_AT_compdir to get Apple's ld64 to correctly
+  // generate debug map in final executable. If we don't generate it then the linker
+  // will skip over the object file.
+  // Ref: https://github.com/apple-oss-distributions/ld64/blob/dbf8f7feb5579761f1623b004bd468bdea7c6225/src/ld/OutputFile.cpp#L7166
+
+  // DW_AT_name
+  Streamer->emitBytes(StringRef("IL.c"));
+  Streamer->emitIntValue(0, 1);
+
+  // DW_AT_compdir
+  Streamer->emitBytes(StringRef("/tmp"));
+  Streamer->emitIntValue(0, 1);
+
+  // There need to be global DW_AT_low_pc/DW_AT_high_pc symbols to indicate the base and
+  // size of the range covered by the symbols. Currently we use a shortcut where we emit
+  // a range starting at the beginning of file and ending at the start of the debug section
+  // which is located at the end of the object file.
+
+  // DW_AT_low_pc
+  Streamer->emitIntValue(0, TargetPointerSize);
+
+  // DW_AT_high_pc
+  const MCExpr *SymExpr = MCSymbolRefExpr::create(debugSection->getBeginSymbol(), MCSymbolRefExpr::VK_None, context);
+  Streamer->emitValue(SymExpr, TargetPointerSize);
+
   // DW_AT_stmt_list
   if (LineSectionSymbol == nullptr) {
     Streamer->emitIntValue(0, 4);

llvm/tools/objwriter/debugInfo/dwarf/dwarfTypeBuilder.cpp

@@ -601,8 +601,12 @@ void DwarfMemberFunctionIdTypeInfo::DumpStrings(MCObjectStreamer *Streamer) {
 void DwarfMemberFunctionIdTypeInfo::DumpTypeInfo(MCObjectStreamer *Streamer, UserDefinedDwarfTypesBuilder *TypeBuilder) {
   // Abbrev Number
   bool IsStatic = MemberFunctionTypeInfo->IsStatic();
+  bool HasParameters = MemberFunctionTypeInfo->GetArgTypes().size();
 
-  Streamer->emitULEB128IntValue(IsStatic ? DwarfAbbrev::SubprogramStaticSpec : DwarfAbbrev::SubprogramSpec);
+  Streamer->emitULEB128IntValue(
+      IsStatic ? (HasParameters ? DwarfAbbrev::SubprogramStaticSpec
+                                : DwarfAbbrev::SubprogramStaticNoChildrenSpec)
+               : DwarfAbbrev::SubprogramSpec);
 
   // DW_AT_name
   EmitSectionOffset(Streamer, StrSymbol, 4);
@@ -652,8 +656,10 @@ void DwarfMemberFunctionIdTypeInfo::DumpTypeInfo(MCObjectStreamer *Streamer, Use
     EmitInfoOffset(Streamer, ArgTypeInfo, 4);
   }
 
-  // Ternimate DIE
-  Streamer->emitIntValue(0, 1);
+  // Terminate DIE (skip for SubprogramStaticNoChildrenSpec which has no children)
+  if (!IsStatic || HasParameters) {
+    Streamer->emitIntValue(0, 1);
+  }
 }
 
 // DwarfTypesBuilder

llvm/tools/objwriter/objwriter.cpp

@@ -152,10 +152,8 @@ bool ObjectWriter::Init(llvm::StringRef ObjectFilePath, const char* tripleName)
   unsigned TargetPointerSize = Streamer->getContext().getAsmInfo()->getCodePointerSize();
   TypeBuilder->SetTargetPointerSize(TargetPointerSize);
 
-  if (ObjFileInfo->getObjectFileType() == ObjFileInfo->IsELF) {
-    DwarfGenerator.reset(new DwarfGen());
-    DwarfGenerator->SetTypeBuilder(static_cast<UserDefinedDwarfTypesBuilder*>(TypeBuilder.get()));
-  }
+  DwarfGenerator.reset(new DwarfGen());
+  DwarfGenerator->SetTypeBuilder(static_cast<UserDefinedDwarfTypesBuilder*>(TypeBuilder.get()));
 
   CFIsPerOffset.set_size(0);
 
@@ -256,6 +254,12 @@ MCSection *ObjectWriter::GetSpecificSection(const char *SectionName,
     if (attributes & CustomSectionAttributes_MachO_Init_Func_Pointers) {
       typeAndAttributes |= MachO::SectionType::S_MOD_INIT_FUNC_POINTERS;
     }
+    if (attributes & CustomSectionAttributes_Executable) {
+      // Needs to be set on sections with actual code. The linker uses
+      // it to determine code sections and emit information about function
+      // boundaries.
+      typeAndAttributes |= MachO::S_ATTR_PURE_INSTRUCTIONS;
+    }
     Section = OutContext->getMachOSection(
         (attributes & CustomSectionAttributes_Executable) ? "__TEXT" : "__DATA",
         SectionName, typeAndAttributes, Kind);
@@ -882,9 +886,8 @@ void ObjectWriter::EmitDebugFunctionInfo(const char *FunctionName,
       Streamer->emitSymbolAttribute(Sym, MCSA_ELF_TypeFunction);
       Streamer->emitELFSize(Sym,
                             MCConstantExpr::create(FunctionSize, *OutContext));
-      EmitDwarfFunctionInfo(FunctionName, FunctionSize, MethodTypeIndex);
     }
-    // TODO: Should test it for Macho.
+    EmitDwarfFunctionInfo(FunctionName, FunctionSize, MethodTypeIndex);
   }
 }
 
@@ -963,12 +966,10 @@ void ObjectWriter::EmitDebugModuleInfo() {
     Streamer->SwitchSection(Section);
     Streamer->emitCVFileChecksumsDirective();
     Streamer->emitCVStringTableDirective();
-  } else if (ObjFileInfo->getObjectFileType() == ObjFileInfo->IsELF) {
+  } else {
     DwarfGenerator->EmitAbbrev();
     DwarfGenerator->EmitAranges();
     DwarfGenerator->Finish();
-  } else {
-    OutContext->setGenDwarfForAssembly(true);
   }
 }