[DebugInfo] Fix emitting pre-v5 name lookup tables in the DWARF64 format (12/19).

[ikudrin]

Summary

The transition is done by using methods of AsmPrinter which automatically emit values in compliance with the selected DWARF format.

[dblaikie]

Looks good, thanks! (with the test expanded a bit, as mentioned)

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

7–16

Expand this test to verify that the offsets parsed from debug_pub* match the offsets of the DIEs they are meant to refer to.

[ikudrin]

• Extended the test. Note that this change required rearranging the patches in the set so that this patch comes after the patches for DWARF units.

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.cpp

 
 void DwarfDebug::emitDebugPubSection(bool GnuStyle, StringRef Name,
                                      DwarfCompileUnit *TheU,
                                      const StringMap<const DIE *> &Globals) {
   if (auto *Skeleton = TheU->getSkeleton())
     TheU = Skeleton;
 
   // Emit the header.
-  Asm->OutStreamer->AddComment("Length of Public " + Name + " Info");
   MCSymbol *BeginLabel = Asm->createTempSymbol("pub" + Name + "_begin");
   MCSymbol *EndLabel = Asm->createTempSymbol("pub" + Name + "_end");
-  Asm->emitLabelDifference(EndLabel, BeginLabel, 4);
+  Asm->emitDwarfUnitLength(EndLabel, BeginLabel,
+                           "Length of Public " + Name + " Info");
 
   Asm->OutStreamer->emitLabel(BeginLabel);
 
   Asm->OutStreamer->AddComment("DWARF Version");
   Asm->emitInt16(dwarf::DW_PUBNAMES_VERSION);
 
   Asm->OutStreamer->AddComment("Offset of Compilation Unit Info");
   emitSectionReference(*TheU);
 
   Asm->OutStreamer->AddComment("Compilation Unit Length");
-  Asm->emitInt32(TheU->getLength());
+  Asm->emitDwarfLengthOrOffset(TheU->getLength());
 
   // Emit the pubnames for this compilation unit.
   for (const auto &GI : Globals) {
     const char *Name = GI.getKeyData();
     const DIE *Entity = GI.second;
 
     Asm->OutStreamer->AddComment("DIE offset");
-    Asm->emitInt32(Entity->getOffset());
+    Asm->emitDwarfLengthOrOffset(Entity->getOffset());
 
     if (GnuStyle) {
       dwarf::PubIndexEntryDescriptor Desc = computeIndexValue(TheU, Entity);
       Asm->OutStreamer->AddComment(
           Twine("Attributes: ") + dwarf::GDBIndexEntryKindString(Desc.Kind) +
           ", " + dwarf::GDBIndexEntryLinkageString(Desc.Linkage));
       Asm->emitInt8(Desc.toBits());
     }
 
     Asm->OutStreamer->AddComment("External Name");
     Asm->OutStreamer->emitBytes(StringRef(Name, GI.getKeyLength() + 1));
   }
 
   Asm->OutStreamer->AddComment("End Mark");
-  Asm->emitInt32(0);
+  Asm->emitDwarfLengthOrOffset(0);
   Asm->OutStreamer->emitLabel(EndLabel);
 }
 
 /// Emit null-terminated strings into a debug str section.
 void DwarfDebug::emitDebugStr() {
   MCSection *StringOffsetsSection = nullptr;
   if (useSegmentedStringOffsetsTable()) {
     emitStringOffsetsTableHeader();

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

+; This checks that .debug_pubnames and .debug_pubtypes can be generated in the DWARF64 format.
+
+; RUN: llc -mtriple=x86_64 -dwarf64 -filetype=obj %s -o %t
+; RUN: llvm-dwarfdump -debug-info -debug-pubnames -debug-pubtypes %t | FileCheck %s
+
+; CHECK:      .debug_info contents:
+; CHECK:      0x[[VAR:.+]]:    DW_TAG_variable
+; CHECK-NEXT:                    DW_AT_name ("foo")
+; CHECK:      0x[[STRUCT:.+]]: DW_TAG_structure_type
+; CHECK-NEXT:                    DW_AT_name ("Foo")
+; CHECK:      0x[[BASET:.+]]:  DW_TAG_base_type
+; CHECK-NEXT:                    DW_AT_name ("int")
+
+; CHECK:      .debug_pubnames contents:
+; CHECK-NEXT: length = 0x0000000000000026, format = DWARF64, version = 0x0002, unit_offset =
+; CHECK-NEXT: Offset     Name
+; CHECK-NEXT: 0x00000000[[VAR]] "foo"
+
+; CHECK:      .debug_pubtypes contents:
+; CHECK-NEXT: length = 0x0000000000000032, format = DWARF64, version = 0x0002, unit_offset =
+; CHECK-NEXT: Offset     Name
+; CHECK-NEXT: 0x00000000[[STRUCT]] "Foo"
+; CHECK-NEXT: 0x00000000[[BASET]] "int"
+
+; IR generated and reduced from:
+; $ cat foo.c
+; struct Foo { int bar; };
+; struct Foo foo;
+; $ clang -g -gpubnames -S -emit-llvm foo.c -o foo.ll
+
+target triple = "x86_64-unknown-linux-gnu"
+
+%struct.Foo = type { i32 }
+
+@foo = dso_local global %struct.Foo zeroinitializer, align 4, !dbg !0
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!10, !11, !12}
+!llvm.ident = !{!13}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "foo", scope: !2, file: !3, line: 2, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 12.0.0", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, splitDebugInlining: false)
+!3 = !DIFile(filename: "foo.c", directory: "/tmp")
+!4 = !{}
+!5 = !{!0}
+!6 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Foo", file: !3, line: 1, size: 32, elements: !7)
+!7 = !{!8}
+!8 = !DIDerivedType(tag: DW_TAG_member, name: "bar", scope: !6, file: !3, line: 1, baseType: !9, size: 32)
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !{i32 7, !"Dwarf Version", i32 4}
+!11 = !{i32 2, !"Debug Info Version", i32 3}
+!12 = !{i32 1, !"wchar_size", i32 4}
+!13 = !{!"clang version 12.0.0"}