This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Re: [PATCH v2 3/9] Introduce can_vector_compare_p function


On Fri, Aug 23, 2019 at 12:43 PM Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> Ilya Leoshkevich <iii@linux.ibm.com> writes:
> > @@ -3819,6 +3820,82 @@ can_compare_p (enum rtx_code code, machine_mode mode,
> >    return 0;
> >  }
> >
> > +/* can_vector_compare_p presents fake rtx binary operations to the the back-end
> > +   in order to determine its capabilities.  In order to avoid creating fake
> > +   operations on each call, values from previous calls are cached in a global
> > +   cached_binops hash_table.  It contains rtxes, which can be looked up using
> > +   binop_keys.  */
> > +
> > +struct binop_key {
> > +  enum rtx_code code;        /* Operation code.  */
> > +  machine_mode value_mode;   /* Result mode.     */
> > +  machine_mode cmp_op_mode;  /* Operand mode.    */
> > +};
> > +
> > +struct binop_hasher : pointer_hash_mark<rtx>, ggc_cache_remove<rtx> {
> > +  typedef rtx value_type;
> > +  typedef binop_key compare_type;
> > +
> > +  static hashval_t
> > +  hash (enum rtx_code code, machine_mode value_mode, machine_mode cmp_op_mode)
> > +  {
> > +    inchash::hash hstate (0);
> > +    hstate.add_int (code);
> > +    hstate.add_int (value_mode);
> > +    hstate.add_int (cmp_op_mode);
> > +    return hstate.end ();
> > +  }
> > +
> > +  static hashval_t
> > +  hash (const rtx &ref)
> > +  {
> > +    return hash (GET_CODE (ref), GET_MODE (ref), GET_MODE (XEXP (ref, 0)));
> > +  }
> > +
> > +  static bool
> > +  equal (const rtx &ref1, const binop_key &ref2)
> > +  {
> > +    return (GET_CODE (ref1) == ref2.code)
> > +        && (GET_MODE (ref1) == ref2.value_mode)
> > +        && (GET_MODE (XEXP (ref1, 0)) == ref2.cmp_op_mode);
> > +  }
> > +};
> > +
> > +static GTY ((cache)) hash_table<binop_hasher> *cached_binops;
> > +
> > +static rtx
> > +get_cached_binop (enum rtx_code code, machine_mode value_mode,
> > +               machine_mode cmp_op_mode)
> > +{
> > +  if (!cached_binops)
> > +    cached_binops = hash_table<binop_hasher>::create_ggc (1024);
> > +  binop_key key = { code, value_mode, cmp_op_mode };
> > +  hashval_t hash = binop_hasher::hash (code, value_mode, cmp_op_mode);
> > +  rtx *slot = cached_binops->find_slot_with_hash (key, hash, INSERT);
> > +  if (!*slot)
> > +    *slot = gen_rtx_fmt_ee (code, value_mode, gen_reg_rtx (cmp_op_mode),
> > +                         gen_reg_rtx (cmp_op_mode));
> > +  return *slot;
> > +}
>
> Sorry, I didn't mean anything this complicated.  I just meant that
> we should have a single cached rtx that we can change via PUT_CODE and
> PUT_MODE_RAW for each new query, rather than allocating a new rtx each
> time.
>
> Something like:
>
> static GTY ((cache)) rtx cached_binop;
>
> rtx
> get_cached_binop (machine_mode mode, rtx_code code, machine_mode op_mode)
> {
>   if (cached_binop)
>     {
>       PUT_CODE (cached_binop, code);
>       PUT_MODE_RAW (cached_binop, mode);
>       PUT_MODE_RAW (XEXP (cached_binop, 0), op_mode);
>       PUT_MODE_RAW (XEXP (cached_binop, 1), op_mode);
>     }
>   else
>     {
>       rtx reg1 = gen_raw_REG (op_mode, LAST_VIRTUAL_REGISTER + 1);
>       rtx reg2 = gen_raw_REG (op_mode, LAST_VIRTUAL_REGISTER + 2);
>       cached_binop = gen_rtx_fmt_ee (code, mode, reg1, reg2);
>     }
>   return cached_binop;
> }

Hmm, maybe we need  auto_rtx (code) that constructs such
RTX on the stack instead of wasting a GC root (and causing
issues for future threading of GCC ;)).

Richard.

>
> Thanks,
> Richard


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]