RE: [PATCH v4 0/9] Support Intel APX EGPR

["Cui, Lili" <lili.cui@intel.com>]

> On 20.12.2023 12:50, Cui, Lili wrote:
> >>>>>> On 19.12.2023 13:12, Cui, Lili wrote:
> >>>>>>> *** BLURB HERE ***
> >>>>>>> Future optimizations to be made.
> >>>>>>> 1. The current implementation of vexvvvvv needs to be optimized.
> >>>>>>> 2. The handling of double VEX/EVEX templates in check_register()
> >>>>>>> needs to
> >>>>>> be optimized.
> >>>>>>
> >>>>>> I hope this is just stale here, and the dependency on templates
> >>>>>> was now removed again from check_register().
> >>>>>
> >>>>> In fact, I didn't remove it in V4, I didn't find a better place to
> >>>>> deal with it. I
> >>>> don't know if you agree with this implementation below.
> >>>>
> >>>> I'm afraid I don't, both because it still isn't clear to me what's
> >>>> wrong with my alternative proposal, and also for the formal reason of ...
> >>>>
> >>>
> >>> For the alternative proposal, do you mean adding a new variable to
> >>> avoid
> >> introducing new loops over all operands? How about this ? or do you
> >> want to add other variable and handle it in check_register?
> >>
> >> No, the alternative proposal continues to be to introduce a new
> >> enumerator to record in i.vec_encoding (vex_encoding_egpr is what
> >> iirc I had suggested before, despite the naming anomaly). What you
> >> outline below would, however, still be better than adding another loop (as
> you had it earlier), imo.
> >>
> >
> > I guessed you want to add a new type like vex_encoding_egpr, but I don't
> know how to do it differently with before, when the instruction support
> legacy, vex and evex encodings, if we put the vex and eves templates in front
> of the legacy templates (in i386-opc.tbl), we'll assign the vex_encoding_egpr
> for the legacy input, and it will have the same problem as before. And we also
> need to handle it in check_register(). Maybe you hinted at some other way of
> handling it, but I didn't get it.
> >
> >
> >      if (current_templates.start->opcode_modifier.vex
> >         && current_templates.start->opcode_modifier.evex)
> >       i.vec_encoding = vex_encoding_egpr;
> 
> Since setting of the new encoding type has to happen in check_register(),
> using current_templates (as said several times before) is not an option.
> 
> Anyway, in the interest of forward progress, feel free to go with ...
> 
> >>> --- a/gas/config/tc-i386.c
> >>> +++ b/gas/config/tc-i386.c
> >>> @@ -464,6 +464,9 @@ struct _i386_insn
> >>>      /* Have NOTRACK prefix.  */
> >>>      const char *notrack_prefix;
> >>>
> >>> +    /* Has Egpr.  */
> >>> +    bool has_egpr;
> >>> +
> >>>      /* Error message.  */
> >>>      enum i386_error error;
> >>>    };
> >>
> >> As a general remark, when you add new fields to a struct, please try
> >> to find a slot that ideally is using existing padding _and_ is next
> >> to related fields, or at least one of the two.
> >>
> >
> > Moved to
> >
> > --- a/gas/config/tc-i386.c
> > +++ b/gas/config/tc-i386.c
> > @@ -438,6 +438,9 @@ struct _i386_insn
> >      /* Prefer the REX2 prefix in encoding.  */
> >      bool rex2_encoding;
> >
> > +    /* Has Egpr.  */
> > +    bool has_egpr;
> 
> ... this approach then, and subsequently I'll see if I can re-arrange things (and
> if I'm bothered enough to do so). The comment is pretty unhelpful as is, how
> about "Need to use an eGPR capable encoding (REX2 or EVEX)" or some such?
> 

Great, thanks!

--- a/gas/config/tc-i386.c
+++ b/gas/config/tc-i386.c
@@ -438,6 +438,9 @@ struct _i386_insn
     /* Prefer the REX2 prefix in encoding.  */
     bool rex2_encoding;

+    /* Need to use an Egpr capable encoding (REX2 or EVEX).  */
+    bool has_egpr;
+

Lili.