[PATCH] D115325: [DWARF] Fix PR51087 Extraneous enum record in DWARF with type units

[David Blaikie via Phabricator via llvm-commits]

dblaikie added a comment.

Seems to have broken some ThinLTO+Split DWARF situation, as follows:

  target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
  target triple = "x86_64-grtev4-linux-gnu"
  
  !llvm.dbg.cu = !{!0}
  !llvm.module.flags = !{!18}
  
  !0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, emissionKind: FullDebug, enums: !2, nameTableKind: GNU)
  !1 = !DIFile(filename: "x.cc", directory: "/proc/self/cwd")
  !2 = !{!3}
  !3 = distinct !DICompositeType(tag: DW_TAG_enumeration_type, name: "E", baseType: !8, size: 64, flags: DIFlagEnumClass, elements: !9, identifier: "_Z1E")
  !8 = !DIBasicType(name: "unsigned long", size: 64, encoding: DW_ATE_unsigned)
  !9 = !{}
  !18 = !{i32 2, !"Debug Info Version", i32 3}

Built with:

  llc test.ll -split-dwarf-file=out.dwo -generate-type-units

This will produce an invalid `.debug_gnu_pubnames` with 0 offset values (`.long 0 # DIE offset`), or, if you apply this patch (this patch isn't perfectly clean for the codebase just yet - I need to cleanup one other mistake - but for the purpose of testing this patch it'll give a good signal as to where things have gone wrong), it'll assert:

  diff --git llvm/include/llvm/CodeGen/DIE.h llvm/include/llvm/CodeGen/DIE.h
  index 9e94c401bfae..60bd52ee4032 100644
  --- llvm/include/llvm/CodeGen/DIE.h
  +++ llvm/include/llvm/CodeGen/DIE.h
  @@ -774,7 +774,10 @@ public:
     unsigned getAbbrevNumber() const { return AbbrevNumber; }
     dwarf::Tag getTag() const { return Tag; }
     /// Get the compile/type unit relative offset of this DIE.
  -  unsigned getOffset() const { return Offset; }
  +  unsigned getOffset() const {
  +    assert(Offset && "Offset being queried before it's been computed.");
  +    return Offset;
  +  }
     unsigned getSize() const { return Size; }
     bool hasChildren() const { return ForceChildren || !Children.empty(); }
     void setForceChildren(bool B) { ForceChildren = B; }


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D115325/new/

https://reviews.llvm.org/D115325