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

[Mehdi AMINI via llvm-commits]

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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