Hi,
on 2024/5/9 15:35, HAO CHEN GUI wrote:
> Hi Kewen,
> Thanks for your comments.
>
> 在 2024/5/9 13:44, Kewen.Lin 写道:
>> Hi,
>>
>> on 2024/5/8 14:47, HAO CHEN GUI wrote:
>>> Hi,
>>> This patch enables overlapped by-piece operations. On rs6000, default
>>> move/set/clear ratio is 2. So the overlap is only enabled with compare
>>> by-pieces.
>>
>> Thanks for enabling this, did you evaluate if it can help some benchmark?
>
> Tested it with SPEC2017. No obvious performance impact. I think memory
> compare might not be hot enough.
>
> Tested it with my micro benchmark. 5-10% performance gain when compare
> length is 7.
Nice!
>
>>
>>>
>>> Bootstrapped and tested on powerpc64-linux BE and LE with no
>>> regressions. Is it OK for the trunk?
>>>
>>> Thanks
>>> Gui Haochen
>>>
>>> ChangeLog
>>> rs6000: Enable overlapped by-pieces operations
>>>
>>> This patch enables overlapped by-piece operations by defining
>>> TARGET_OVERLAP_OP_BY_PIECES_P to true. On rs6000, default move/set/clear
>>> ratio is 2. So the overlap is only enabled with compare by-pieces.
>>>
>>> gcc/
>>> * config/rs6000/rs6000.cc (TARGET_OVERLAP_OP_BY_PIECES_P): Define.
>>>
>>> gcc/testsuite/
>>> * gcc.target/powerpc/block-cmp-9.c: New.
>>>
>>>
>>> patch.diff
>>> diff --git a/gcc/config/rs6000/rs6000.cc b/gcc/config/rs6000/rs6000.cc
>>> index 6b9a40fcc66..2b5f5cf1d86 100644
>>> --- a/gcc/config/rs6000/rs6000.cc
>>> +++ b/gcc/config/rs6000/rs6000.cc
>>> @@ -1774,6 +1774,9 @@ static const scoped_attribute_specs *const
>>> rs6000_attribute_table[] =
>>> #undef TARGET_CONST_ANCHOR
>>> #define TARGET_CONST_ANCHOR 0x8000
>>>
>>> +#undef TARGET_OVERLAP_OP_BY_PIECES_P
>>> +#define TARGET_OVERLAP_OP_BY_PIECES_P hook_bool_void_true
>>> +
>>>
>>>
>>> /* Processor table. */
>>> diff --git a/gcc/testsuite/gcc.target/powerpc/block-cmp-9.c
>>> b/gcc/testsuite/gcc.target/powerpc/block-cmp-9.c
>>> new file mode 100644
>>> index 00000000000..b5f51affbb7
>>> --- /dev/null
>>> +++ b/gcc/testsuite/gcc.target/powerpc/block-cmp-9.c
>>> @@ -0,0 +1,11 @@
>>> +/* { dg-do compile } */
>>> +/* { dg-options "-O2 -mdejagnu-cpu=power8" } */
>>
>> Why does it need power8 forced here?
>
> I just want to exclude P7 LE as targetm.slow_unaligned_access return false
> for it and the expand cmpmemsi won't be invoked.
> I think it over. It's no need. For the sub-targets which library is
> called, l[hb]z won't be generated too.
Thanks for checking, OK with dropping this forced power8.
BR,
Kewen
>
>>
>> BR,
>> Kewen
>>
>>> +/* { dg-final { scan-assembler-not {\ml[hb]z\M} } } */
>>> +
>>> +/* Test if by-piece overlap compare is enabled and following case is
>>> + implemented by two overlap word loads and compares. */
>>> +
>>> +int foo (const char* s1, const char* s2)
>>> +{
>>> + return __builtin_memcmp (s1, s2, 7) == 0;
>>> +}
>>
>
> Thanks
> Gui Haochen
