Hi Hongtao,
在 2024/8/23 9:47, Hongtao Liu 写道:
> On Thu, Aug 22, 2024 at 4:06 PM HAO CHEN GUI <guih...@linux.ibm.com> wrote:
>>
>> Hi Hongtao,
>>
>> 在 2024/8/21 11:21, Hongtao Liu 写道:
>>> r15-3058-gbb42c551905024 support const0 operand for movv16qi, please
>>> rebase your patch and see if there's still the regressions.
>>
>> There's still regressions. The patch enables V16QI const0 store, but
>> it also enables V8QI const0 store. The vector mode is preferable than
>> scalar mode so that V8QI is used for 8-byte memory clear instead of
>> DI. It's sub-optimal.
> Could we check if mode_size is greater than HOST_BITS_PER_WIDE_INT?
Not sure if all targets prefer it. Richard & Jeff, what's your opinion?
IMHO, could we disable it from predicate or convert it to DI mode store
if V8QI const0 store is sub-optimal on i386?
>>
>> Another issue is it takes lots of subreg to generate an all-zero
>> V16QI register sometime. As PR92080 has been fixed, it can't reuse
>> existing all-zero V16QI register.
>>
>> (insn 16 15 17 (set (reg:V4SI 118)
>> (const_vector:V4SI [
>> (const_int 0 [0]) repeated x4
>> ])) "auto-init-7.c":25:12 -1
>> (nil))
>>
>> (insn 17 16 18 (set (reg:V8HI 117)
>> (subreg:V8HI (reg:V4SI 118) 0)) "auto-init-7.c":25:12 -1
>> (nil))
>>
>> (insn 18 17 19 (set (reg:V16QI 116)
>> (subreg:V16QI (reg:V8HI 117) 0)) "auto-init-7.c":25:12 -1
>> (nil))
>>
>> (insn 19 18 0 (set (mem/c:V16QI (plus:DI (reg:DI 114)
>> (const_int 12 [0xc])) [0 MEM <char[1:28]> [(void
>> *)&temp3]+12 S16 A32])
>> (reg:V16QI 116)) "auto-init-7.c":25:12 -1
>> (nil))
> I think those subregs can be simplified by later rtl passes?
Here is the final dump. There are two all-zero 16-byte vector
registers. It can't figure out V4SI could be a subreg of V16QI.
(insn 14 56 15 2 (set (reg:V16QI 20 xmm0 [115])
(const_vector:V16QI [
(const_int 0 [0]) repeated x16
])) "auto-init-7.c":25:12 2154 {movv16qi_internal}
(nil))
(insn 15 14 16 2 (set (mem/c:V16QI (reg:DI 0 ax [114]) [0 MEM <char[1:28]>
[(void *)&temp3]+0 S16 A128])
(reg:V16QI 20 xmm0 [115])) "auto-init-7.c":25:12 2154
{movv16qi_internal}
(nil))
(insn 16 15 19 2 (set (reg:V4SI 20 xmm0 [118])
(const_vector:V4SI [
(const_int 0 [0]) repeated x4
])) "auto-init-7.c":25:12 2160 {movv4si_internal}
(nil))
(insn 19 16 57 2 (set (mem/c:V16QI (plus:DI (reg:DI 0 ax [114])
(const_int 12 [0xc])) [0 MEM <char[1:28]> [(void *)&temp3]+12
S16 A32])
(reg:V16QI 20 xmm0 [116])) "auto-init-7.c":25:12 2154
{movv16qi_internal}
Thanks
Gui Haochen
>>
>> Thanks
>> Gui Haochen
>
>
>
