Re: [PATCH] [DWARF] Fix hierarchy of debug information for offload kernels.

[Hafiz Abid Qadeer <abid_qadeer@mentor.com>]

On 27/07/2021 09:39, Richard Biener wrote:

> Yes, that's true - there could be a one-to-many relationship there.  But then I
> wonder in which case such lookup in the DIE tree would be the correct thing
> to do.  If I lookup a variable from the parent then the concrete
> instance of that
> should be found by unwinding unless it is a static variable in which case
> the lookup can be done in any of the concrete instances.
> 
> But then the original issue that the consumer skips the function if it doesn't
> have a PC range and thus skips over childs looks like an invalid optimization.
> 
> Btw, the situation you run into can be simulated by
> 
> int main(int argc, char **argv)
> {
>   void foo ()
>     {
>       __builtin_puts ("bar");
>     }
>   foo ();
>   return 0;
> }
> 
> and compiling with -g -flto -flto-partition=max which forces main and foo
> into different LTRANS units and get's us
> 
>  <1><114>: Abbrev Number: 2 (DW_TAG_subprogram)
>     <115>   DW_AT_abstract_origin: <0x155>
>  <2><119>: Abbrev Number: 3 (DW_TAG_subprogram)
>     <11a>   DW_AT_abstract_origin: <0x179>
>     <11e>   DW_AT_low_pc      : 0x400515
>     <126>   DW_AT_high_pc     : 0x19
>     <12e>   DW_AT_frame_base  : 1 byte block: 9c        (DW_OP_call_frame_cfa)
>     <130>   DW_AT_static_link : 4 byte block: 91 68 6 6         (DW_OP_fbreg: -2
> 
> gdb then fails to see 'foo' at all (cannot break on it) and the lookup of 'argc'
> inside it fails (setting a breakpoint also fails without -flto-partition=max,
> but I can print argc just fine).
> 
> I suggest you file a bug with gdb and see how that resolves.

I have filed https://sourceware.org/bugzilla/show_bug.cgi?id=28147 for this issue.

Thanks,
-- 
Hafiz Abid Qadeer
Mentor, a Siemens Business