e731a2678c
Split DWARF doesn't handle LTO of any form (roughly there's an assumption that each dwo file will have one CU - it's not explicitly documented, nor explicitly handled, so the ecosystem isn't really well understood/tested/etc). This had previously been handled by implementing (& disabling by default) the `-split-dwarf-cross-cu-references` flag, which would disable use of ref_addr across two dwo CUs. This worked for a while, at least in LTO (it didn't address Split DWARF+Full LTO, but that's an unlikely combination, as the benefits of Split DWARF are more limited in a full LTO build) - because the only source of cross-CU references was inlined functions, so by making those non-cross-CU (by moving the referenced inlined function DWARF description into the referencing CU) the result was one CU per dwo. But recently the Function Specialization pass was added to the ThinLTO pipeline, which caused imported functions that may not be inlined to be emitted by a backend compile. This meant foreign CU entities (not just abstract origins/cross-CU referenced entities)/standalone foreign CUs could be emitted by a backend compile. The end result was, due to a bug* in binutils dwp (I think basically it saw two CUs in a single dwo and reprocessed the offsets in the shared debug_str_offsets.dwo section) this situation lead to corrupted strings. So to make this more robust, I've generalized the definition of the `-split-dwarf-cross-cu-references` flag (perhaps it should be renamed at this point, but it's /really/ niche, doubt anyone's using it - more or less there for experimentation when we get around to figuring out spec'ing LTO+Split DWARF) to mean "single CU in a dwo file" and added more general handling for this. There's certainly some weird corner cases that could come up in terms of "how do we choose which CU to put everything in" - for now it's "first come, first served" which is probably going to be OK for ThinLTO - the base module will have the first functions and first CU, imported fragments will come after that. For LTO the choice will be fairly arbitrary - but, again, essentially whichever module comes first. * Arguably a bug in binutils dwp, but since the feature isn't well specified, I'd rather avoid dabbling in this uncertain area and ensure LLVM doesn't produce especially novel DWARF (dwos with multiple CUs) regardless of whether binutils dwp would/should be fixed. I'm not confident debuggers could read such a dwo file well, etc.
76 lines
3.7 KiB
LLVM
76 lines
3.7 KiB
LLVM
; RUN: llc -mtriple=x86_64-unknown-linux-gnu -split-dwarf-file=foo.dwo -filetype=obj < %s \
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; RUN: | llvm-dwarfdump -v - | FileCheck %s
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; This triggers a situation where the order of entries in the .debug_str and
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; .debug_str_offsets sections does not match and makes sure that all entries are
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; still wired up correctly.
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; Produced with "clang -S -emit-llvm -gdwarf-5" from source "int X;", copied
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; three times and modified by hand. The modifications consisted of modifying the
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; compilation directory and the variable names to trigger the insertion of names
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; in different order.
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; CHECK: .debug_info contents:
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; CHECK: DW_TAG_compile_unit
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; CHECK: DW_AT_name [DW_FORM_strx1] (indexed (00000000) string = "X1")
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; CHECK: DW_AT_name [DW_FORM_strx1] (indexed (00000002) string = "X2")
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; CHECK: DW_AT_name [DW_FORM_strx1] (indexed (00000003) string = "X3")
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; CHECK: .debug_str contents:
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; CHECK: 0x[[X3:[0-9a-f]*]]: "X3"
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; CHECK: 0x[[X1:[0-9a-f]*]]: "X1"
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; CHECK: 0x[[X2:[0-9a-f]*]]: "X2"
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; CHECK: .debug_str_offsets contents:
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; CHECK: Format = DWARF32, Version = 5
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; CHECK: [[X3]] "X3"
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; CHECK: [[X1]] "X1"
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; CHECK: [[X2]] "X2"
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!llvm.dbg.cu = !{!10, !20, !30}
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!llvm.module.flags = !{!0, !1, !2}
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!llvm.ident = !{!3}
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!0 = !{i32 2, !"Dwarf Version", i32 5}
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!1 = !{i32 2, !"Debug Info Version", i32 3}
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!2 = !{i32 1, !"wchar_size", i32 4}
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!3 = !{!"clang version 7.0.0 (trunk 337353) (llvm/trunk 337361)"}
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@X1 = dso_local global i32 0, align 4, !dbg !11
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!10 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !13, producer: "clang version 7.0.0 (trunk 337353) (llvm/trunk 337361)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !14, globals: !15)
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!11 = !DIGlobalVariableExpression(var: !12, expr: !DIExpression())
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!12 = distinct !DIGlobalVariable(name: "X1", scope: !10, file: !16, line: 1, type: !17, isLocal: false, isDefinition: true)
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!13 = !DIFile(filename: "-", directory: "X3", checksumkind: CSK_MD5, checksum: "f2e6e10e303927a308f1645fbf6f710e")
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!14 = !{}
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!15 = !{!11}
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!16 = !DIFile(filename: "<stdin>", directory: "X3", checksumkind: CSK_MD5, checksum: "f2e6e10e303927a308f1645fbf6f710e")
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!17 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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@X2 = dso_local global i32 0, align 4, !dbg !21
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!20 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !23, producer: "clang version 7.0.0 (trunk 337353) (llvm/trunk 337361)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !24, globals: !25)
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!21 = !DIGlobalVariableExpression(var: !22, expr: !DIExpression())
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!22 = distinct !DIGlobalVariable(name: "X2", scope: !20, file: !26, line: 1, type: !27, isLocal: false, isDefinition: true)
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!23 = !DIFile(filename: "-", directory: "X2", checksumkind: CSK_MD5, checksum: "f2e6e10e303927a308f1645fbf6f710e")
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!24 = !{}
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!25 = !{!21}
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!26 = !DIFile(filename: "<stdin>", directory: "X2", checksumkind: CSK_MD5, checksum: "f2e6e10e303927a308f1645fbf6f710e")
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!27 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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@X3 = dso_local global i32 0, align 4, !dbg !31
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!30 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !33, producer: "clang version 7.0.0 (trunk 337353) (llvm/trunk 337361)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !34, globals: !35)
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!31 = !DIGlobalVariableExpression(var: !32, expr: !DIExpression())
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!32 = distinct !DIGlobalVariable(name: "X3", scope: !30, file: !36, line: 1, type: !37, isLocal: false, isDefinition: true)
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!33 = !DIFile(filename: "-", directory: "X1", checksumkind: CSK_MD5, checksum: "f2e6e10e303927a308f1645fbf6f710e")
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!34 = !{}
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!35 = !{!31}
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!36 = !DIFile(filename: "<stdin>", directory: "X1", checksumkind: CSK_MD5, checksum: "f2e6e10e303927a308f1645fbf6f710e")
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!37 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
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