[llvm] r188297 - Output DW_AT_stmt_list dwarf debug info as DW_FORM_sec_offset instead of DW_FORM_data4 as it is a section offset (fixes the coff/dwarf debug info statement locations)

Eric Christopher echristo at gmail.com
Tue Sep 3 01:49:12 PDT 2013 

>
> Do you happen to have a proposal on what the best way is to either make
> sure DWARF3 debug info consumers can keep on parsing the LLVM debug info,
> or to properly encode in the debug info header that DWARF4 is produced,
> not DWARF3?
>

Pretty much exactly what I replied to with Carlo when he committed it.
Some support for conditionalizing dwarf versions was added a while
back, but it wasn't complete and the person that added it doesn't seem
to be working on that aspect any more. It's not the top of my list,
but I can easily specify that we're emitting dwarf 4 for now :)

-eric

> Thanks,
>
> Kristof
>
>> -----Original Message-----
>> From: llvm-commits-bounces at cs.uiuc.edu [mailto:llvm-commits-
>> bounces at cs.uiuc.edu] On Behalf Of Eric Christopher
>> Sent: 13 August 2013 19:00
>> To: Carlo Kok
>> Cc: llvm-commits at cs.uiuc.edu
>> Subject: Re: [llvm] r188297 - Output DW_AT_stmt_list dwarf debug info
>> as DW_FORM_sec_offset instead of DW_FORM_data4 as it is a section
>> offset (fixes the coff/dwarf debug info statement locations)
>>
>> As a note this may break the darwin gdb bot because of the newer form.
>> We can conditionalize it on the "support old gdb"/"we should have a
>> way to specify dwarf level" support.
>>
>> -eric
>>
>> On Tue, Aug 13, 2013 at 10:46 AM, Carlo Kok <ck at remobjects.com> wrote:
>> > Author: carlokok
>> > Date: Tue Aug 13 12:46:57 2013
>> > New Revision: 188297
>> >
>> > URL: http://llvm.org/viewvc/llvm-project?rev=188297&view=rev
>> > Log:
>> > Output DW_AT_stmt_list dwarf debug info as DW_FORM_sec_offset instead
>> of DW_FORM_data4 as it is a section offset (fixes the coff/dwarf debug
>> info statement locations)
>> >
>> > Added:
>> >     llvm/trunk/test/DebugInfo/X86/DW_AT_stmt_list_sec_offset.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=188297&r1=
>> 188296&r2=188297&view=diff
>> >
>> =======================================================================
>> =======
>> > --- llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp (original)
>> > +++ llvm/trunk/lib/CodeGen/AsmPrinter/DwarfDebug.cpp Tue Aug 13
>> 12:46:57 2013
>> > @@ -740,7 +740,7 @@ CompileUnit *DwarfDebug::constructCompil
>> >    // is not okay to use line_table_start here.
>> >    if (!useSplitDwarf()) {
>> >      if (Asm->MAI->doesDwarfUseRelocationsAcrossSections())
>> > -      NewCU->addLabel(Die, dwarf::DW_AT_stmt_list,
>> dwarf::DW_FORM_data4,
>> > +      NewCU->addLabel(Die, dwarf::DW_AT_stmt_list,
>> dwarf::DW_FORM_sec_offset,
>> >                        UseTheFirstCU ?
>> >                        Asm->GetTempSymbol("section_line") :
>> LineTableStartSym);
>> >      else if (UseTheFirstCU)
>> >
>> > Added: llvm/trunk/test/DebugInfo/X86/DW_AT_stmt_list_sec_offset.ll
>> > URL: http://llvm.org/viewvc/llvm-
>> project/llvm/trunk/test/DebugInfo/X86/DW_AT_stmt_list_sec_offset.ll?rev
>> =188297&view=auto
>> >
>> =======================================================================
>> =======
>> > --- llvm/trunk/test/DebugInfo/X86/DW_AT_stmt_list_sec_offset.ll
>> (added)
>> > +++ llvm/trunk/test/DebugInfo/X86/DW_AT_stmt_list_sec_offset.ll Tue
>> Aug 13 12:46:57 2013
>> > @@ -0,0 +1,40 @@
>> > +; RUN: llc -mtriple=i686-w64-mingw32 -o %t -filetype=obj %s
>> > +; RUN: llvm-dwarfdump -debug-dump=all %t | FileCheck %s
>> > +
>> > +; CHECK:        DW_AT_stmt_list [DW_FORM_sec_offset]
>> > +;
>> > +; generated from:
>> > +; clang -g -S -emit-llvm test.c -o test.ll
>> > +; int main()
>> > +; {
>> > +;      return 0;
>> > +; }
>> > +
>> > +; ModuleID = 'test.c'
>> > +target datalayout = "e-p:32:32:32-i1:8:8-i8:8:8-i16:16:16-i32:32:32-
>> i64:64:64-f32:32:32-f64:64:64-f80:128:128-v64:64:64-v128:128:128-
>> a0:0:64-f80:32:32-n8:16:32-S32"
>> > +target triple = "i686-pc-win32"
>> > +
>> > +; Function Attrs: nounwind
>> > +define i32 @main() #0 {
>> > +entry:
>> > +  %retval = alloca i32, align 4
>> > +  store i32 0, i32* %retval
>> > +  ret i32 0, !dbg !10
>> > +}
>> > +
>> > +attributes #0 = { nounwind "less-precise-fpmad"="false" "no-frame-
>> pointer-elim"="true" "no-frame-pointer-elim-non-leaf"="true" "no-infs-
>> fp-math"="false" "no-nans-fp-math"="false" "stack-protector-buffer-
>> size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
>> > +
>> > +!llvm.dbg.cu = !{!0}
>> > +!llvm.module.flags = !{!9}
>> > +
>> > +!0 = metadata !{i32 786449, metadata !1, i32 12, metadata !"clang
>> version 3.4 ", i1 false, metadata !"", i32 0, metadata !2, metadata !2,
>> metadata !3, metadata !2, metadata !2, metadata !""} ; [
>> DW_TAG_compile_unit ] [C:\Projects/test.c] [DW_LANG_C99]
>> > +!1 = metadata !{metadata !"test.c", metadata !"C:\5CProjects"}
>> > +!2 = metadata !{i32 0}
>> > +!3 = metadata !{metadata !4}
>> > +!4 = metadata !{i32 786478, metadata !1, metadata !5, metadata
>> !"main", metadata !"main", metadata !"", i32 1, metadata !6, i1 false,
>> i1 true, i32 0, i32 0, null, i32 0, i1 false, i32 ()* @main, null,
>> null, metadata !2, i32 2} ; [ DW_TAG_subprogram ] [line 1] [def] [scope
>> 2] [main]
>> > +!5 = metadata !{i32 786473, metadata !1}          ; [
>> DW_TAG_file_type ] [C:\Projects/test.c]
>> > +!6 = metadata !{i32 786453, i32 0, i32 0, metadata !"", i32 0, i64
>> 0, i64 0, i64 0, i32 0, null, metadata !7, i32 0, i32 0} ; [
>> DW_TAG_subroutine_type ] [line 0, size 0, align 0, offset 0] [from ]
>> > +!7 = metadata !{metadata !8}
>> > +!8 = metadata !{i32 786468, null, null, metadata !"int", i32 0, i64
>> 32, i64 32, i64 0, i32 0, i32 5} ; [ DW_TAG_base_type ] [int] [line 0,
>> size 32, align 32, offset 0, enc DW_ATE_signed]
>> > +!9 = metadata !{i32 2, metadata !"Dwarf Version", i32 3}
>> > +!10 = metadata !{i32 3, i32 0, metadata !4, null}
>> >
>> >
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