llvm dev - Feb 2017 - [DebugInfo] [DWARFv5] .debug_abbrev contents for different implicit_const values

Hello all, it looks like we have a bug here but I am not sure. Currently 
if we have two similar types with implicit_const attributes and 
different values we end up with only one abbrev in .debug_abbrev 
section. For example consider two structures: S1 with implicit_const 
attribute ATTR and value VAL1 and S2 with implicit_const ATTR and value 
VAL2. The .debug_abbrev section will contain only 1 related record:

[N] DW_TAG_structure_type       DW_CHILDREN_yes
         DW_AT_ATTR        DW_FORM_implicit_const  VAL1
         // ....

However it looks like we need to have two different abbreviations here:

[N] DW_TAG_structure_type       DW_CHILDREN_yes
         DW_AT_ATTR        DW_FORM_implicit_const  VAL1
         // ....

[M] DW_TAG_structure_type       DW_CHILDREN_yes
         DW_AT_ATTR        DW_FORM_implicit_const  VAL2
         // ....

What do you think? If it is a bug I will fix it (as I was the one who 
added support for DW_FORM_implicit_const).

-- 
Best Regards,
Victor

Sure enough sounds like a bug to me.

On Sat, Feb 25, 2017 at 7:42 AM Victor Leschuk via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hello all, it looks like we have a bug here but I am not sure. Currently
> if we have two similar types with implicit_const attributes and
> different values we end up with only one abbrev in .debug_abbrev
> section. For example consider two structures: S1 with implicit_const
> attribute ATTR and value VAL1 and S2 with implicit_const ATTR and value
> VAL2. The .debug_abbrev section will contain only 1 related record:
>
> [N] DW_TAG_structure_type       DW_CHILDREN_yes
>          DW_AT_ATTR        DW_FORM_implicit_const  VAL1
>          // ....
>
> However it looks like we need to have two different abbreviations here:
>
> [N] DW_TAG_structure_type       DW_CHILDREN_yes
>          DW_AT_ATTR        DW_FORM_implicit_const  VAL1
>          // ....
>
> [M] DW_TAG_structure_type       DW_CHILDREN_yes
>          DW_AT_ATTR        DW_FORM_implicit_const  VAL2
>          // ....
>
> What do you think? If it is a bug I will fix it (as I was the one who
> added support for DW_FORM_implicit_const).
>
> --
> Best Regards,
> Victor
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
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Thanks for confirmation. Will fix and post review to phab.


On 02/27/2017 09:15 PM, David Blaikie wrote:
> Sure enough sounds like a bug to me.
>
> On Sat, Feb 25, 2017 at 7:42 AM Victor Leschuk via llvm-dev 
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at
lists.llvm.org>> wrote:
>
>     Hello all, it looks like we have a bug here but I am not sure.
>     Currently
>     if we have two similar types with implicit_const attributes and
>     different values we end up with only one abbrev in .debug_abbrev
>     section. For example consider two structures: S1 with implicit_const
>     attribute ATTR and value VAL1 and S2 with implicit_const ATTR and
>     value
>     VAL2. The .debug_abbrev section will contain only 1 related record:
>
>     [N] DW_TAG_structure_type       DW_CHILDREN_yes
>              DW_AT_ATTR        DW_FORM_implicit_const  VAL1
>              // ....
>
>     However it looks like we need to have two different abbreviations
>     here:
>
>     [N] DW_TAG_structure_type       DW_CHILDREN_yes
>              DW_AT_ATTR        DW_FORM_implicit_const  VAL1
>              // ....
>
>     [M] DW_TAG_structure_type       DW_CHILDREN_yes
>              DW_AT_ATTR        DW_FORM_implicit_const  VAL2
>              // ....
>
>     What do you think? If it is a bug I will fix it (as I was the one who
>     added support for DW_FORM_implicit_const).
>
>     --
>     Best Regards,
>     Victor
>
>     _______________________________________________
>     LLVM Developers mailing list
>     llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org>
>     http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
-- 
Best Regards,
Victor

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