> Am 23.08.2019 um 13:24 schrieb Richard Biener <richard.guent...@gmail.com>:
>
> On Fri, Aug 23, 2019 at 12:43 PM Richard Sandiford
> <richard.sandif...@arm.com> wrote:
>>
>> Ilya Leoshkevich <i...@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 ;)).
Do you mean something like this?
union {
char raw[rtx_code_size[code]];
rtx rtx;
} binop;
Does this exist already (git grep auto.*rtx / rtx.*auto doesn't show
anything useful), or should I implement this?
