Re: [PATCH] rs6000/test: Add emulated gather test case

["Kewen.Lin" <linkw@linux.ibm.com>]

on 2021/11/25 下午1:17, Hongtao Liu wrote:
> On Thu, Nov 25, 2021 at 11:21 AM Kewen.Lin via Gcc-patches
> <gcc-patches@gcc.gnu.org> wrote:
>>
>> Hi,
>>
>> This patch is to add a test case similar to the one in i386
>> to add testing coverage for 510.parest_r hotspots.
>>
>> As evaluated, the emulated gather capability of vectorizer
>> (r12-2733) can help to speed up SPEC2017 510.parest_r on
>> Power8/9/10 by 5% to 9% with option sets Ofast unroll and
>> Ofast lto.  But since rs6000 missed unpacking support for
>> unsigned int before, it can only vectorize the hotspots
>> until r12-3134.
>>
>> By checking why r12-2733 doesn't immediately show its impact
>> for SPEC2017 510.parest_r while the associated test case
>> already can get vectorized on rs6000 at that time, I realized
>> the associated test case use int as INDEXTYPE while the
>> hotspots actually use unsigned int.  So different from the one
>> in i386, this patch uses unsigned int as INDEXTYPE since the
>> unpack support for unsigned int (r12-3134) also matters for
>> the hotspots vectorization.  Not sure if it's worth to updating
>> the one in i386 as well?
> It looks like the same testcase added in
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88531

Thanks for the information!  Good to know that there are already
some cases to cover.  :)

BR,
Kewen

>>
>> Tested on powerpc64le-linux-gnu P9 and powerpc64-linux-gnu P8.
>>
>> Is it ok for trunk?
>>
>> BR,
>> Kewen
>> -----
>> gcc/testsuite/ChangeLog:
>>
>>         * gcc.target/powerpc/vect-gather-1.c: New test.
>>
>> diff --git a/gcc/testsuite/gcc.target/powerpc/vect-gather-1.c b/gcc/testsuite/gcc.target/powerpc/vect-gather-1.c
>> new file mode 100644
>> index 00000000000..bf98045ab03
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.target/powerpc/vect-gather-1.c
>> @@ -0,0 +1,20 @@
>> +/* { dg-do compile } */
>> +/* Profitable from Power8 since it supports efficient unaligned load.  */
>> +/* { dg-options "-Ofast -mdejagnu-cpu=power8 -fdump-tree-vect-details -fdump-tree-forwprop4" } */
>> +
>> +#ifndef INDEXTYPE
>> +#define INDEXTYPE unsigned int
>> +#endif
>> +double vmul(INDEXTYPE *rowstart, INDEXTYPE *rowend,
>> +           double *luval, double *dst)
>> +{
>> +  double res = 0;
>> +  for (const INDEXTYPE * col = rowstart; col != rowend; ++col, ++luval)
>> +        res += *luval * dst[*col];
>> +  return res;
>> +}
>> +
>> +/* With gather emulation this should be profitable to vectorize from Power8.  */
>> +/* { dg-final { scan-tree-dump "loop vectorized" "vect" } } */
>> +/* The index vector loads and promotions should be scalar after forwprop.  */
>> +/* { dg-final { scan-tree-dump-not "vec_unpack" "forwprop4" } } */
>> --
>> 2.25.1
>>
> 
>