Re: [PATCH 1/5] x86: use VPTERNLOG for further bitwise two-vector operations

[Hongtao Liu <crazylht@gmail.com>]

On Sun, Jun 25, 2023 at 3:13 PM Hongtao Liu <crazylht@gmail.com> wrote:
>
> On Sun, Jun 25, 2023 at 1:52 PM Jan Beulich <jbeulich@suse.com> wrote:
> >
> > On 25.06.2023 06:42, Hongtao Liu wrote:
> > > On Wed, Jun 21, 2023 at 2:26 PM Jan Beulich via Gcc-patches
> > > <gcc-patches@gcc.gnu.org> wrote:
> > >>
> > >> +(define_code_iterator andor [and ior])
> > >> +(define_code_attr nlogic [(and "nor") (ior "nand")])
> > >> +(define_code_attr ternlog_nlogic [(and "0x11") (ior "0x77")])
> > >> +
> > >> +(define_insn "*<nlogic><mode>3"
> > >> +  [(set (match_operand:VI 0 "register_operand" "=v,v")
> > >> +       (andor:VI
> > >> +         (not:VI (match_operand:VI 1 "bcst_vector_operand" "%v,v"))
> > >> +         (not:VI (match_operand:VI 2 "bcst_vector_operand" "vBr,m"))))]
> > > I'm thinking of doing it in simplify_rtx or gimple match.pd to transform
> > > (and (not op1))  (not op2)) -> (not: (ior: op1 op2))
> >
> > This wouldn't be a win (not + andn) -> (or + not), but what's
> > more important is ...
> >
> > > (ior (not op1) (not op2)) -> (not : (and op1 op2))
> > >
> > > Even w/o avx512f, the transformation should also benefit since it
> > > takes less logic operations 3 -> 2.(or 2 -> 2 for pandn).
> >
> > ... that these transformations (from the, as per the doc,
> > canonical representation of nand and nor) are already occurring
> I see, there're already such simplifications in the gimple phase, so
> the question: is there any need for and/ior:not not pattern?
> Can you provide a testcase to demonstrate that and/ior: not not
> pattern is needed?

typedef int v4si __attribute__((vector_size(16)));
v4si
foo1 (v4si a, v4si b)
{
    return ~a & ~b;
}

I only gimple have optimized it to

  <bb 2> [local count: 1073741824]:
  # DEBUG BEGIN_STMT
  _1 = a_2(D) | b_3(D);
  _4 = ~_1;
  return _4;


But rtl still try to match

(set (reg:V4SI 86)
    (and:V4SI (not:V4SI (reg:V4SI 88))
        (not:V4SI (reg:V4SI 89))))

Hmm.
> > in common code, _if_ no suitable insn can be found. That was at
> > least the conclusion I drew from looking around a lot, supported
> > by the code that's generated prior to this change.
> >
> > Jan
>
>
>
> --
> BR,
> Hongtao



-- 
BR,
Hongtao