Re: GCC and binutils support for BPF V4 instructions

["Jose E. Marchesi" <jose.marchesi@oracle.com>]

> On Fri, Jul 28, 2023 at 9:41 AM Jose E. Marchesi
> <jose.marchesi@oracle.com> wrote:
>>
>>
>> Hello.
>>
>> Just a heads up regarding the new BPF V4 instructions and their support
>> in the GNU Toolchain.
>
> Awesome. Thanks for the update!
>
>> V4 sdiv/smod instructions
>>
>>   Binutils has been updated to use the V4 encoding of these
>>   instructions, which used to be part of the xbpf testing dialect used
>>   in GCC.  GCC generates these instructions for signed division when
>>   -mcpu=v4 or higher.
>
> With sdiv/smod implemented do you still have a need for xbpf flag?
> Anything still missing or you can start using -mcpu=v4 in gcc selftests
> and remove xbpf completely?

Just `call %r' (what the clang disassembler calls callx.)

>> So I think we are done with this.  Please let us know if these
>> instructions ever change.
>
> Fingers crossed, they will never change.
> How far are we from running bpf selftests with gcc?

We are getting there, but not quite yet.
See https://gcc.gnu.org/wiki/BPFBackEnd where we track our work.

(The CO-RE builtins entry is basically done, but we are still polishing
 the details before sending the patch to GCC upstream.)