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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