[llvm] r304111 - DebugInfo: Omit an empty CU when a subprogram was moved into its use

[David Blaikie via llvm-commits]

Please provide repro steps

On Sun, May 28, 2017 at 10:18 PM Mehdi AMINI <joker.eph at gmail.com> wrote:

> GreenDragon is broken. Reverted in r304125.
>
> --
> Mehdi
>
> 2017-05-28 15:51 GMT-07:00 David Blaikie via llvm-commits <
> llvm-commits at lists.llvm.org>:
>
>> Author: dblaikie
>> Date: Sun May 28 17:51:37 2017
>> New Revision: 304111
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=304111&view=rev
>> Log:
>> DebugInfo: Omit an empty CU when a subprogram was moved into its use
>>
>> When the only use of a CU is for a subprogram that's only emitted into
>> the using CU (to avoid cross-CU references in DWO files), avoid creating
>> that CU at all.
>>
>> Added:
>>     llvm/trunk/test/DebugInfo/split-dwarf-omit-empty.ll
>> Modified:
>>     llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>>
>> Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp?rev=304111&r1=304110&r2=304111&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
>> +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Sun May 28 17:51:37
>> 2017
>> @@ -374,14 +374,18 @@ void DwarfDebug::constructAbstractSubpro
>>
>>    // Find the subprogram's DwarfCompileUnit in the SPMap in case the
>> subprogram
>>    // was inlined from another compile unit.
>> -  auto &CU = getOrCreateDwarfCompileUnit(SP->getUnit());
>> -  if (auto *SkelCU = CU.getSkeleton()) {
>> -    (shareAcrossDWOCUs() ? CU : SrcCU)
>> -        .constructAbstractSubprogramScopeDIE(Scope);
>> -    if (CU.getCUNode()->getSplitDebugInlining())
>> -      SkelCU->constructAbstractSubprogramScopeDIE(Scope);
>> -  } else {
>> -    CU.constructAbstractSubprogramScopeDIE(Scope);
>> +  if (useSplitDwarf() && !shareAcrossDWOCUs() &&
>> !SP->getUnit()->getSplitDebugInlining())
>> +    // Avoid building the original CU if it won't be used
>> +    SrcCU.constructAbstractSubprogramScopeDIE(Scope);
>> +  else {
>> +    auto &CU = getOrCreateDwarfCompileUnit(SP->getUnit());
>> +    if (auto *SkelCU = CU.getSkeleton()) {
>> +      (shareAcrossDWOCUs() ? CU : SrcCU)
>> +          .constructAbstractSubprogramScopeDIE(Scope);
>> +      if (CU.getCUNode()->getSplitDebugInlining())
>> +        SkelCU->constructAbstractSubprogramScopeDIE(Scope);
>> +    } else
>> +      CU.constructAbstractSubprogramScopeDIE(Scope);
>>    }
>>  }
>>
>>
>> Added: llvm/trunk/test/DebugInfo/split-dwarf-omit-empty.ll
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/split-dwarf-omit-empty.ll?rev=304111&view=auto
>>
>> ==============================================================================
>> --- llvm/trunk/test/DebugInfo/split-dwarf-omit-empty.ll (added)
>> +++ llvm/trunk/test/DebugInfo/split-dwarf-omit-empty.ll Sun May 28
>> 17:51:37 2017
>> @@ -0,0 +1,52 @@
>> +; RUN: %llc_dwarf -split-dwarf-file=foo.dwo  %s -filetype=obj -o - |
>> llvm-dwarfdump -debug-dump=info - | FileCheck %s
>> +
>> +; Created from:
>> +; a.cpp:
>> +;   void f1();
>> +;   inline __attribute__((always_inline)) __attribute__((used)) void
>> f2() { f1(); }
>> +; b.cpp:
>> +;   void f2();
>> +;   void f3() {
>> +;     f2();
>> +;   }
>> +; $ clang++ -fno-split-dwarf-inlining {a,b}.cpp -emit-llvm -S -g
>> +; $ llvm-link {a,b}.ll -S -o ab.ll
>> +; Then strip out the @llvm.used global, so no out of line definition of
>> 'f2'
>> +; will be emitted. This emulates something more like the
>> available_externally
>> +; import performed by ThinLTO.
>> +
>> +; CHECK: Compile Unit
>> +; CHECK-NOT: Compile Unit
>> +
>> +declare void @_Z2f1v()
>> +
>> +; Function Attrs: noinline norecurse uwtable
>> +define i32 @main() !dbg !9 {
>> +entry:
>> +  call void @_Z2f1v(), !dbg !13
>> +  ret i32 0, !dbg !18
>> +}
>> +
>> +!llvm.dbg.cu = !{!0, !3}
>> +!llvm.ident = !{!5, !5}
>> +!llvm.module.flags = !{!6, !7, !8}
>> +
>> +!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1,
>> producer: "clang version 5.0.0 (trunk 304054) (llvm/trunk 304080)",
>> isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2,
>> splitDebugInlining: false)
>> +!1 = !DIFile(filename: "a.cpp", directory:
>> "/usr/local/google/home/blaikie/dev/scratch")
>> +!2 = !{}
>> +!3 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !4,
>> producer: "clang version 5.0.0 (trunk 304054) (llvm/trunk 304080)",
>> isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2,
>> splitDebugInlining: false)
>> +!4 = !DIFile(filename: "b.cpp", directory:
>> "/usr/local/google/home/blaikie/dev/scratch")
>> +!5 = !{!"clang version 5.0.0 (trunk 304054) (llvm/trunk 304080)"}
>> +!6 = !{i32 2, !"Dwarf Version", i32 4}
>> +!7 = !{i32 2, !"Debug Info Version", i32 3}
>> +!8 = !{i32 1, !"wchar_size", i32 4}
>> +!9 = distinct !DISubprogram(name: "main", scope: !4, file: !4, line: 2,
>> type: !10, isLocal: false, isDefinition: true, scopeLine: 2, flags:
>> DIFlagPrototyped, isOptimized: false, unit: !3, variables: !2)
>> +!10 = !DISubroutineType(types: !11)
>> +!11 = !{!12}
>> +!12 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
>> +!13 = !DILocation(line: 2, column: 73, scope: !14, inlinedAt: !17)
>> +!14 = distinct !DISubprogram(name: "f2", linkageName: "_Z2f2v", scope:
>> !1, file: !1, line: 2, type: !15, isLocal: false, isDefinition: true,
>> scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0,
>> variables: !2)
>> +!15 = !DISubroutineType(types: !16)
>> +!16 = !{null}
>> +!17 = distinct !DILocation(line: 3, column: 3, scope: !9)
>> +!18 = !DILocation(line: 4, column: 1, scope: !9)
>>
>>
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