Re: [Bpf] [PATCH 1/1] bpf, docs: Specify twos complement as format for signed integers

["Jose E. Marchesi" <jemarch@gnu.org>]

> On Mon, Jul 10, 2023 at 2:58 PM Will Hawkins <hawkinsw@obs.cr> wrote:
>>
>> In the documentation of the eBPF ISA it is unspecified how integers are
>> represented. Specify that twos complement is used.
>>
>> Signed-off-by: Will Hawkins <hawkinsw@obs.cr>
>> ---
>>  Documentation/bpf/instruction-set.rst | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/Documentation/bpf/instruction-set.rst b/Documentation/bpf/instruction-set.rst
>> index 751e657973f0..63dfcba5eb9a 100644
>> --- a/Documentation/bpf/instruction-set.rst
>> +++ b/Documentation/bpf/instruction-set.rst
>> @@ -173,6 +173,11 @@ BPF_ARSH  0xc0   sign extending dst >>= (src & mask)
>>  BPF_END   0xd0   byte swap operations (see `Byte swap instructions`_ below)
>>  ========  =====  ==========================================================
>>
>> +eBPF supports 32- and 64-bit signed and unsigned integers. It does
>> +not support floating-point data types. All signed integers are represented in
>> +twos-complement format where the sign bit is stored in the most-significant
>> +bit.
>
> Could you point to another ISA document (like x86, arm, ...) that
> talks about signed and unsigned integers?

AFAIK the only signedness encoding aspect that is always found in ISA
specifications and should be specified is how numerical immediates are
encoded in stored instructions.

But that has nothing to do with "data types".