[DebugInfo] Fix emitting DWARF64 .debug_macro[.dwo] sections (17/19).

[ikudrin]

Summary

The patch fixes emitting flags and the debug_line_offset field in the header, as well as the reference to the macro string for a pre-standard GNU .debug_macro extension.

[dstenb]

LGTM!

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

 /// Emit the header of a DWARF 5 macro section, or the GNU extension for
 /// DWARF 4.
 static void emitMacroHeader(AsmPrinter *Asm, const DwarfDebug &DD,
                             const DwarfCompileUnit &CU, uint16_t DwarfVersion) {
   enum HeaderFlagMask {
 #define HANDLE_MACRO_FLAG(ID, NAME) MACRO_FLAG_##NAME = ID,
 #include "llvm/BinaryFormat/Dwarf.def"
   };
-  uint8_t Flags = 0;
   Asm->OutStreamer->AddComment("Macro information version");
   Asm->emitInt16(DwarfVersion >= 5 ? DwarfVersion : 4);
-  // We are setting Offset and line offset flags unconditionally here,
-  // since we're only supporting DWARF32 and line offset should be mostly
-  // present.
-  // FIXME: Add support for DWARF64.
-  Flags |= MACRO_FLAG_DEBUG_LINE_OFFSET;
+  // We emit the line offset flag unconditionally here, since line offset should
+  // be mostly present.
+  if (Asm->isDwarf64()) {
+    Asm->OutStreamer->AddComment("Flags: 64 bit, debug_line_offset present");
+    Asm->emitInt8(MACRO_FLAG_OFFSET_SIZE | MACRO_FLAG_DEBUG_LINE_OFFSET);
+  } else {
     Asm->OutStreamer->AddComment("Flags: 32 bit, debug_line_offset present");
-  Asm->emitInt8(Flags);
+    Asm->emitInt8(MACRO_FLAG_DEBUG_LINE_OFFSET);
+  }
   Asm->OutStreamer->AddComment("debug_line_offset");
   if (DD.useSplitDwarf())
-    Asm->OutStreamer->emitIntValue(0, /*Size=*/4);
+    Asm->emitDwarfLengthOrOffset(0);
   else
-    Asm->OutStreamer->emitSymbolValue(CU.getLineTableStartSym(), /*Size=*/4);
+    Asm->emitDwarfSymbolReference(CU.getLineTableStartSym());
 }
 
 void DwarfDebug::handleMacroNodes(DIMacroNodeArray Nodes, DwarfCompileUnit &U) {
   for (auto *MN : Nodes) {
     if (auto *M = dyn_cast<DIMacro>(MN))
       emitMacro(*M);
     else if (auto *F = dyn_cast<DIMacroFile>(MN))
       emitMacroFile(*F, U);
if (getDwarfVersion() >= 5) {
       unsigned Type = M.getMacinfoType() == dwarf::DW_MACINFO_define
                           ? dwarf::DW_MACRO_GNU_define_indirect
                           : dwarf::DW_MACRO_GNU_undef_indirect;
       Asm->OutStreamer->AddComment(dwarf::GnuMacroString(Type));
       Asm->emitULEB128(Type);
       Asm->OutStreamer->AddComment("Line Number");
       Asm->emitULEB128(M.getLine());
       Asm->OutStreamer->AddComment("Macro String");
-      // FIXME: Add support for DWARF64.
-      Asm->OutStreamer->emitSymbolValue(
-          InfoHolder.getStringPool().getEntry(*Asm, Str).getSymbol(),
-          /*Size=*/4);
+      Asm->emitDwarfSymbolReference(
+          InfoHolder.getStringPool().getEntry(*Asm, Str).getSymbol());
     }
   } else {
     Asm->OutStreamer->AddComment(dwarf::MacinfoString(M.getMacinfoType()));
     Asm->emitULEB128(M.getMacinfoType());
     Asm->OutStreamer->AddComment("Line Number");
     Asm->emitULEB128(M.getLine());
     Asm->OutStreamer->AddComment("Macro String");
     Asm->OutStreamer->emitBytes(Str);

llvm/test/DebugInfo/X86/debug-macro-dwarf64.ll

+; This checks that .debug_macro[.dwo] can be generated in the DWARF64 format.
+
+; RUN: llc -mtriple=x86_64 -dwarf-version=4 -dwarf64 -use-gnu-debug-macro -filetype=obj %s -o %t
+; RUN: llvm-dwarfdump -debug-macro %t | FileCheck %s --check-prefix=DWARF4
+
+; RUN: llc -mtriple=x86_64 -dwarf-version=5 -dwarf64 -filetype=obj %s -o %t
+; RUN: llvm-dwarfdump -debug-macro %t | FileCheck %s --check-prefix=DWARF5
+
+; RUN: llc -mtriple=x86_64 -dwarf-version=5 -dwarf64 -split-dwarf-file=foo.dwo -filetype=obj %s -o %t
+; RUN: llvm-dwarfdump -debug-macro %t | FileCheck %s --check-prefixes=DWARF5,DWO
+
+; DWARF4:      .debug_macro contents:
+; DWARF4-NEXT: 0x00000000:
+; DWARF4-NEXT: macro header: version = 0x0004, flags = 0x03, format = DWARF64, debug_line_offset = 0x0000000000000000
+; DWARF4-NEXT: DW_MACRO_GNU_start_file - lineno: 0 filenum: 1
+; DWARF4-NEXT:  DW_MACRO_GNU_define_indirect - lineno: 1 macro: FOO 1
+; DWARF4-NEXT:  DW_MACRO_GNU_undef_indirect - lineno: 2 macro: BAR
+; DWARF4-NEXT: DW_MACRO_GNU_end_file
+
+; DWARF5:      .debug_macro contents:
+; DWO:         .debug_macro.dwo contents:
+; DWARF5-NEXT: 0x00000000:
+; DWARF5-NEXT: macro header: version = 0x0005, flags = 0x03, format = DWARF64, debug_line_offset = 0x0000000000000000
+; DWARF5-NEXT: DW_MACRO_start_file - lineno: 0 filenum: 0
+; DWARF5-NEXT:  DW_MACRO_define_strx - lineno: 1 macro: FOO 1
+; DWARF5-NEXT:  DW_MACRO_undef_strx - lineno: 2 macro: BAR
+; DWARF5-NEXT: DW_MACRO_end_file
+
+; IR generated and reduced from:
+; $ cat foo.c
+; #define FOO 1
+; #undef BAR
+; $ clang -g -S -emit-llvm -fdebug-macro foo.c -o foo.ll
+
+target triple = "x86_64-unknown-linux-gnu"
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!348, !349, !350}
+!llvm.ident = !{!351}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, producer: "clang version 12.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, macros: !3, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "foo.c", directory: "/tmp")
+!2 = !{}
+!3 = !{!4}
+!4 = !DIMacroFile(file: !1, nodes: !5)
+!5 = !{!6, !7}
+!6 = !DIMacro(type: DW_MACINFO_define, line: 1, name: "FOO", value: "1")
+!7 = !DIMacro(type: DW_MACINFO_undef, line: 2, name: "BAR")
+!348 = !{i32 7, !"Dwarf Version", i32 4}
+!349 = !{i32 2, !"Debug Info Version", i32 3}
+!350 = !{i32 1, !"wchar_size", i32 4}
+!351 = !{!"clang version 12.0.0"}