[llvm] r342943 - [DebugInfo] Do not generate address info for removed debug labels.

[Hsiangkai Wang via llvm-commits]

It seems that -split-dwarf-file could not work correctly in macOS. So,
I added -mtriple=x86_64-unknown-linux-gnu to the test case to avoid
the problem in macOS.
On Wed, Sep 26, 2018 at 1:32 AM Justin Bogner <mail at justinbogner.com> wrote:
>
> The test that this adds is crashing on the macOS bots:
>
>   http://green.lab.llvm.org/green/job/clang-stage1-cmake-RA-incremental/53550/
>
> I've gone ahead and reverted the commit for now in r342993. Let me know
> if you need any help investigating this.
>
> Hsiangkai Wang via llvm-commits <llvm-commits at lists.llvm.org> writes:
> > Author: hsiangkai
> > Date: Mon Sep 24 23:09:50 2018
> > New Revision: 342943
> >
> > URL: http://llvm.org/viewvc/llvm-project?rev=342943&view=rev
> > Log:
> > [DebugInfo] Do not generate address info for removed debug labels.
> >
> > In some senario, LLVM will remove llvm.dbg.labels in IR. For example,
> > when the labels are in unreachable blocks, these labels will not
> > be generated in LLVM IR. In the case, these debug labels will have
> > address zero as their address. It is not legal address for debugger to
> > set breakpoints or query sources. So, the patch inhibits the address info
> > (DW_AT_low_pc) of removed labels.
> >
> > Differential Revision: https://reviews.llvm.org/D51908
> >
> > Added:
> >     llvm/trunk/test/DebugInfo/Generic/debug-label-unreached.ll
> > Modified:
> >     llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
> >
> > Modified: llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp
> > URL:
> > http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp?rev=342943&r1=342942&r2=342943&view=diff
> > ==============================================================================
> >
> > --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp (original)
> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp Mon Sep 24 23:09:50 2018
> > @@ -865,10 +865,9 @@ void DwarfCompileUnit::finishEntityDefin
> >        llvm_unreachable("DbgEntity must be DbgVariable or DbgLabel.");
> >    }
> >
> > -  if (Label) {
> > -    const MCSymbol *Sym = Label->getSymbol();
> > -    addLabelAddress(*Die, dwarf::DW_AT_low_pc, Sym);
> > -  }
> > +  if (Label)
> > +    if (const auto *Sym = Label->getSymbol())
> > +      addLabelAddress(*Die, dwarf::DW_AT_low_pc, Sym);
> >  }
> >
> >  DbgEntity *DwarfCompileUnit::getExistingAbstractEntity(const DINode *Node) {
> >
> > Added: llvm/trunk/test/DebugInfo/Generic/debug-label-unreached.ll
> > URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/DebugInfo/Generic/debug-label-unreached.ll?rev=342943&view=auto
> > ==============================================================================
> > --- llvm/trunk/test/DebugInfo/Generic/debug-label-unreached.ll (added)
> > +++ llvm/trunk/test/DebugInfo/Generic/debug-label-unreached.ll Mon Sep 24 23:09:50 2018
> > @@ -0,0 +1,39 @@
> > +; Test unreachable llvm.dbg.label
> > +;
> > +; RUN: llc -filetype=obj -split-dwarf-file debug.dwo -o - %s | llvm-dwarfdump -v - | FileCheck %s
> > +;
> > +; CHECK: .debug_info.dwo contents:
> > +; CHECK: DW_TAG_label
> > +; CHECK-NEXT: DW_AT_name {{.*}}"done"
> > +; CHECK-NOT: {{DW_TAG|NULL}}
> > +; CHECK: DW_AT_low_pc
> > +; CHECK: DW_TAG_label
> > +; CHECK-NEXT: DW_AT_name {{.*}}"removed"
> > +; CHECK-NOT: DW_AT_low_pc
> > +source_filename = "debug-label-unreached.c"
> > +
> > +define dso_local i32 @foo(i32 %a, i32 %b) !dbg !8 {
> > +entry:
> > +  %sum = add nsw i32 %a, %b, !dbg !12
> > +  call void @llvm.dbg.label(metadata !11), !dbg !12
> > +  ret i32 %sum, !dbg !13
> > +}
> > +
> > +declare void @llvm.dbg.label(metadata)
> > +
> > +!llvm.dbg.cu = !{!0}
> > +!llvm.module.flags = !{!4}
> > +
> > +!0 = distinct !DICompileUnit(language: DW_LANG_C99, file: !1, isOptimized: true, emissionKind: FullDebug, enums: !2)
> > +!1 = !DIFile(filename: "debug-label-unreached.c", directory: "./")
> > +!2 = !{}
> > +!4 = !{i32 2, !"Debug Info Version", i32 3}
> > +!5 = !DISubroutineType(types: !6)
> > +!6 = !{!7}
> > +!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
> > +!8 = distinct !DISubprogram(name: "foo", scope: !1, file: !1, line: 8, type: !5, isLocal: false, isDefinition: true, scopeLine: 9, flags: DIFlagPrototyped, isOptimized: true, unit: !0, retainedNodes: !9)
> > +!9 = !{!10, !11}
> > +!10 = !DILabel(scope: !8, name: "removed", file: !1, line: 11)
> > +!11 = !DILabel(scope: !8, name: "done", file: !1, line: 13)
> > +!12 = !DILocation(line: 13, column: 1, scope: !8)
> > +!13 = !DILocation(line: 14, column: 5, scope: !8)
> >
> >
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