Re: [PATCH] Partially lift restriction from loc_list_from_tree_1

[Richard Biener]

On Mon, May 12, 2025 at 11:24 AM Eric Botcazou <botca...@adacore.com> wrote:
>
> Hi,
>
> the function accepts all handled_component_p expressions and decodes them by
> means of get_inner_reference as expected, but bails out on bitfields:
>
>      /* TODO: We can extract value of the small expression via shifting even
>            for nonzero bitpos.  */
>         if (list_ret == 0)
>           return 0;
>         if (!multiple_p (bitpos, BITS_PER_UNIT, &bytepos)
>             || !multiple_p (bitsize, BITS_PER_UNIT))
>           {
>             expansion_failed (loc, NULL_RTX,
>                               "bitfield access");
>             return 0;
>           }
>
> This lifts the second part of the restriction, which helps for obscure cases
> of packed discriminated record types in Ada, although this requires the latest
> GDB sources.
>
> Tested on x86-64/Linux, OK for the mainline?

OK.

Btw, can we try to add a "guality" for gnat.dg?  Or are you making sure to
add coverage to the gdb testsuite?

Thanks,
Richard.

>
> 2025-05-12  Eric Botcazou  <ebotca...@adacore.com>
>
>         * dwarf2out.cc (loc_list_from_tree_1) <COMPONENT_REF>: Do not bail
>         out when the size is not a multiple of a byte.
>         Deal with bit-fields whose size is not a multiple of a byte when
>         dereferencing an address.
>
> --
> Eric Botcazou