Re: [PATCH 4/5]: Enhancements to "flags": i386 cleanup

[Doug Evans <dje@google.com>]

On Thu, Aug 11, 2016 at 11:10 AM, Pedro Alves <palves@redhat.com> wrote:
> On 08/09/2016 06:55 PM, Pedro Alves wrote:
>
>> Thanks!  All looks good to me.
>
> A thought has been running through my mind though.
>
> Is the "type" attribute used for anything in <flags> elements?
> Does changing the type of a flag bitfield have any user-visible
> effect at all?  I.e., does a 1-bit uint32_t bitfield flag
> print differently from a bool bitfield flag?

There may be some simplification possible, but note that bools do
print differently: if false we don't print the field at all.

[digression: I'm not sure it's possible today, but while I understand
the desire to avoid the extra verbosity if we always printed false
fields, there are times when I *do* want the field printed even if
false]

>
> Wondering if we could remove the bool-special case, because
> before 8151645076ce927e0ee866c598a19f192e68e103, we used to say,
> for <struct>:
>
>                             There are two forms of the @samp{<struct>}
>  element; a @samp{<struct>} element must either contain only bitfields
>  or contain no bitfields.  If the structure contains only bitfields,
>  its total size in bytes must be specified, each bitfield must have an
>  explicit start and end, and bitfields are automatically assigned an
>                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>  integer type.  The field's @var{start} should be less than or
>  ^^^^^^^^^^^^
>  equal to its @var{end}, and zero represents the least significant bit.
>
> And for flags, we used to say:
>
>  @cindex <flags>
>  If a register's value is a series of single-bit flags, define it with
>  a flags type.  The @samp{<flags>} element has an explicit @var{size}
>  and contains one or more @samp{<field>} elements.  Each field has a
>  @var{name}, a @var{start}, and an @var{end}.  Only single-bit flags
>  are supported.
>
> I think I may be very confused by this all, though.
>
> Thanks,
> Pedro Alves
>