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Re: [PATCH 1/1] Add IFUNC POWER optimization for e_pow and e_exp


Hi Tulio,

Thanks for spending some time reviewing this.

---
Juvenal A. Silva Jr.

> On 20 Sep 2017, at 18:00, Tulio Magno Quites Machado Filho <tuliom@linux.vnet.ibm.com> wrote:
> 
> "Juvenal A. Silva Jr" <juvenal.silva.jr@gmail.com> writes:
> 
>> 2017-01-31  Juvenal A. Silva Jr.  <juvenal.silva.jr@gmail.com>
>> 
>>    * sysdeps/ieee754/dbl-64/e-pow.c: Fix a comment aligment problem.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile: Add entries for
>>    custom build of CPU specific versions of e_pow and e_exp.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_pow.c: New file
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_pow-ppc64.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_pow-power7.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_pow-power8.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_pow-power9.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/slowpow-ppc64.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/slowpow-power7.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/slowpow-power8.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/slowpow-power9.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_exp.c: New file
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_exp-ppc64.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_exp-power7.c: New file.
> 
> There has been a recent contribution of e_exp-ppc64 and e_exp-power7.
> So, I had to remove both files from your patch before applying it.
> 
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_exp-power8.c: New file.
>>    * sysdeps/powerpc/powerpc64/fpu/multiarch/e_exp-power9.c: New file.
> 
> In my tests using the benchtests, both these functions were not able to beat
> the current implementation from e_exp-power7.c.
> 
>> diff --git a/sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile b/sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile
>> index d6f14f360a..8bd508747b 100644
>> --- a/sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile
>> +++ b/sysdeps/powerpc/powerpc64/fpu/multiarch/Makefile
>> @@ -27,7 +27,11 @@ libm-sysdep_routines += s_isnan-power7 s_isnan-power6x s_isnan-power6 \
>>            s_llrint-power8 s_llround-power8 s_llroundf-ppc64 \
>>            e_expf-power8 e_expf-ppc64 \
>>            s_sinf-ppc64 s_sinf-power8 \
>> -            s_cosf-ppc64 s_cosf-power8
>> +            s_cosf-ppc64 s_cosf-power8 \
>> +            slowpow-power7 slowpow-power8 slowpow-power9 slowpow-ppc64 \
>> +            e_pow-power7 e_pow-power8 e_pow-power9 e_pow-ppc64 \
>> +            slowexp-power7 slowexp-power8 slowexp-power9 slowexp-ppc64 \
>> +            e_exp-power7 e_exp-power8 e_exp-power9 e_exp-ppc64
>> 
>> CFLAGS-s_logbf-power7.c = -mcpu=power7
>> CFLAGS-s_logbl-power7.c = -mcpu=power7
>> @@ -36,6 +40,18 @@ CFLAGS-s_modf-power5+.c = -mcpu=power5+
>> CFLAGS-s_modff-power5+.c = -mcpu=power5+
>> CFLAGS-e_hypot-power7.c = -mcpu=power7
>> CFLAGS-e_hypotf-power7.c = -mcpu=power7
>> +CFLAGS-slowpow-power7.c = -mcpu=power7
>> +CFLAGS-slowpow-power8.c = -mcpu=power8
>> +CFLAGS-slowpow-power9.c = -mcpu=power9
>> +CFLAGS-e_pow-power7.c = -mcpu=power7
>> +CFLAGS-e_pow-power8.c = -mcpu=power8
>> +CFLAGS-e_pow-power9.c = -mcpu=power9
> 
> The default pow() implementation must not be compiled this way.  It requires
> to use $(config-cflags-nofma) in order to avoid increasing the error of the
> function too much (165 ulp).
> 
> Unfortunately, after using it, there is no performance improvement.
> 
> -- 
> Tulio Magno
> 


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