[DebugInfo] Fix emitting DWARF64 DWO compilation units and string offset tables (9/19).

[ikudrin]

Summary

These two fixes are better to go together because llvm-dwarfdump is unable to dump a table when another one is malformed.

[dblaikie]

llvm/test/DebugInfo/X86/debug-info-dwo-dwarf64.ll

8

Perhaps the abbr_offset should be printed with more digits to reflect the longer encoding size? (I think that's been the general approach elsewhere in the dump output format, yes?)

[jhenderson]

llvm/test/DebugInfo/X86/debug-info-dwo-dwarf64.ll

8

Optional more concise alternative to the existing regex, making use of FileCheck's new precision for numeric variables (strictly speaking, this pattern would allow a 17-digit number with no leading 0s, but that might be beyond what's needed). Not sure if you'd prefer it or not - happy either way.

[ikudrin]

llvm/test/DebugInfo/X86/debug-info-dwo-dwarf64.ll

8

As I don't care about the exact length that much, and as the abbr_offset was reported as 4-digit before my changes, and as abbreviation tables are not expected to be longer in DWARF64 compared to DWARF32, I did not change the format of that field. For me, the most reliable part is the format reported directly, and also the fact that the parser can correctly read all the expected information.

8

Maybe it is better to simplify this CHECK line even more? We do not care about the exact value of the length anyway.

[jhenderson]

llvm/test/DebugInfo/X86/debug-info-dwo-dwarf64.ll

8

Works for me too, if we've got some coverage showing the dumping code correctly formats the length field for a compile unit using 64-bit DWARF?

[ikudrin]

llvm/test/DebugInfo/X86/debug-info-dwo-dwarf64.ll

8

You mean, like llvm/test/tools/llvm-dwarfdump/X86/debug_info_min_dwarf64.s?

[jhenderson]

LGTM, with your suggested changes to the length check.

llvm/test/DebugInfo/X86/debug-info-dwo-dwarf64.ll

8

That should suffice, yes :-)

[ikudrin]

• Relaxed checking in the test. The line is a bit longer than I suggested because the test has to validate emitting the abbr_offset field.

llvm/lib/CodeGen/AsmPrinter/DwarfStringPool.cpp

if (OffsetSection) {
     // we can emit them in order.
     Entries.resize(NumIndexedStrings);
     for (const auto &Entry : Pool) {
       if (Entry.getValue().isIndexed())
         Entries[Entry.getValue().Index] = &Entry;
     }
 
     Asm.OutStreamer->SwitchSection(OffsetSection);
-    unsigned size = 4; // FIXME: DWARF64 is 8.
+    unsigned size = Asm.getDwarfOffsetByteSize();
     for (const auto &Entry : Entries)
       if (UseRelativeOffsets)
         Asm.emitDwarfStringOffset(Entry->getValue());
       else
         Asm.OutStreamer->emitIntValue(Entry->getValue().Offset, size);
   }
 }

llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp

void DwarfUnit::emitCommonHeader(bool UseOffsets, dwarf::UnitType UT) {
   }
 
   // We share one abbreviations table across all units so it's always at the
   // start of the section. Use a relocatable offset where needed to ensure
   // linking doesn't invalidate that offset.
   Asm->OutStreamer->AddComment("Offset Into Abbrev. Section");
   const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
   if (UseOffsets)
-    Asm->emitInt32(0);
+    Asm->emitDwarfLengthOrOffset(0);
   else
     Asm->emitDwarfSymbolReference(
         TLOF.getDwarfAbbrevSection()->getBeginSymbol(), false);
 
   if (Version <= 4) {
     Asm->OutStreamer->AddComment("Address Size (in bytes)");
     Asm->emitInt8(Asm->MAI->getCodePointerSize());
   }

llvm/test/DebugInfo/X86/debug-info-dwo-dwarf64.ll

+; This checks that .debug_info.dwo can be generated in the DWARF64 format.
+
+; RUN: llc -mtriple=x86_64 -dwarf-version=5 -dwarf64 -split-dwarf-file=foo.dwo -filetype=obj %s -o %t
+; RUN: llvm-dwarfdump -debug-info %t | FileCheck %s
+
+; CHECK:      .debug_info.dwo contents:
+; CHECK-NEXT: Compile Unit: {{.+}}, format = DWARF64, version = 0x0005, unit_type = DW_UT_split_compile, abbr_offset = 0x0000,
+
+; IR generated and reduced from:
+; $ cat foo.c
+; int foo;
+; $ clang -g -S -emit-llvm foo.c -o foo.ll
+
+target triple = "x86_64-unknown-linux-gnu"
+
+@foo = dso_local global i32 0, align 4, !dbg !0
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "foo", scope: !2, file: !3, line: 1, 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, nameTableKind: None)
+!3 = !DIFile(filename: "foo.c", directory: "/tmp")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 7, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!10 = !{!"clang version 12.0.0"}

llvm/test/DebugInfo/X86/debug-str-offsets-dwo-dwarf64.ll

+; This checks that .debug_str_offsets.dwo can be generated in the DWARF64 format.
+
+; RUN: llc -mtriple=x86_64 -dwarf-version=5 -dwarf64 -split-dwarf-file=foo.dwo -filetype=obj %s -o %t
+; RUN: llvm-dwarfdump -debug-info -debug-str -debug-str-offsets -v %t | \
+; RUN:   FileCheck %s
+
+; CHECK:      .debug_info.dwo contents:
+; CHECK-NEXT: Compile Unit: {{.*}}, format = DWARF64,
+; CHECK:      DW_TAG_compile_unit [1] *
+; CHECK:        DW_AT_producer [DW_FORM_strx1] (indexed (00000002) string = "clang version 12.0.0")
+; CHECK:        DW_AT_name [DW_FORM_strx1] (indexed (00000003) string = "foo.c")
+; CHECK:        DW_AT_dwo_name [DW_FORM_strx1] (indexed (00000004) string = "foo.dwo")
+; CHECK:      DW_TAG_variable [2]
+; CHECK:        DW_AT_name [DW_FORM_strx1] (indexed (00000000) string = "foo")
+; CHECK:      DW_TAG_base_type [3]
+; CHECK:        DW_AT_name [DW_FORM_strx1] (indexed (00000001) string = "int")
+
+; CHECK:      .debug_str.dwo contents:
+; CHECK-NEXT: 0x00000000: "foo"
+; CHECK-NEXT: 0x00000004: "int"
+; CHECK-NEXT: 0x00000008: "clang version 12.0.0"
+; CHECK-NEXT: 0x0000001d: "foo.c"
+; CHECK-NEXT: 0x00000023: "foo.dwo"
+
+; CHECK:      .debug_str_offsets.dwo contents:
+; CHECK-NEXT: 0x00000000: Contribution size = 44, Format = DWARF64, Version = 5
+; CHECK-NEXT: 0x00000010: 0000000000000000 "foo"
+; CHECK-NEXT: 0x00000018: 0000000000000004 "int"
+; CHECK-NEXT: 0x00000020: 0000000000000008 "clang version 12.0.0"
+; CHECK-NEXT: 0x00000028: 000000000000001d "foo.c"
+; CHECK-NEXT: 0x00000030: 0000000000000023 "foo.dwo"
+
+; IR generated and reduced from:
+; $ cat foo.c
+; int foo;
+; $ clang -g -S -emit-llvm foo.c -o foo.ll
+
+target triple = "x86_64-unknown-linux-gnu"
+
+@foo = dso_local global i32 0, align 4, !dbg !0
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!7, !8, !9}
+!llvm.ident = !{!10}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "foo", scope: !2, file: !3, line: 1, 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, nameTableKind: None)
+!3 = !DIFile(filename: "foo.c", directory: "/tmp")
+!4 = !{}
+!5 = !{!0}
+!6 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!7 = !{i32 7, !"Dwarf Version", i32 4}
+!8 = !{i32 2, !"Debug Info Version", i32 3}
+!9 = !{i32 1, !"wchar_size", i32 4}
+!10 = !{!"clang version 12.0.0"}