[PATCH] powerpc: Expose VSX feature test

[PATCH] powerpc: Expose VSX feature test

[Nathan Phillips]

Hope it's OK to submit a small change like this. Trying to familiarize myself
with the patch process.

My copyright assignment is underway.

--

Read the HWCAP auxval key to test for VSX support. Expose result through
the cpu_features interface.

Preliminary change to prepare for PowerPC optimized libmvec implementations
[BZ #20123]. Enables selecting optimized version at load time in ifunc
resolver.

	* sysdeps/powerpc/cpu-features.h (cpu_features): Add vsx field.
	* sysdeps/powerpc/cpu-features.c (init_cpu_features):
	Feature test VSX availability.
---
diff --git a/sysdeps/powerpc/cpu-features.c b/sysdeps/powerpc/cpu-features.c
index 955d4778a6..477c7504b9 100644
--- a/sysdeps/powerpc/cpu-features.c
+++ b/sysdeps/powerpc/cpu-features.c
@@ -16,6 +16,8 @@
    License along with the GNU C Library; if not, see
    <http://www.gnu.org/licenses/>.  */
 
+#include <errno.h>
+#include <sys/auxv.h>
 #include <stdint.h>
 #include <cpu-features.h>
 
@@ -26,6 +28,9 @@
 static inline void
 init_cpu_features (struct cpu_features *cpu_features)
 {
+  errno = 0;
+  unsigned long int hwcap = getauxval (AT_HWCAP);
+
   /* Default is to use aligned memory access on optimized function unless
      tunables is enable, since for this case user can explicit disable
      unaligned optimizations.  */
@@ -36,4 +41,13 @@ init_cpu_features (struct cpu_features *cpu_features)
 #else
   cpu_features->use_cached_memopt = false;
 #endif
+
+  if (errno == ENOENT)
+    {
+      cpu_features->vsx = false;
+    }
+  else
+    {
+      cpu_features->vsx = ((hwcap & PPC_FEATURE_HAS_VSX) != 0);
+    }
 }
diff --git a/sysdeps/powerpc/cpu-features.h b/sysdeps/powerpc/cpu-features.h
index e596385b4b..0248862b8a 100644
--- a/sysdeps/powerpc/cpu-features.h
+++ b/sysdeps/powerpc/cpu-features.h
@@ -23,6 +23,7 @@
 struct cpu_features
 {
   bool use_cached_memopt;
+  bool vsx;
 };
 
 #endif /* __CPU_FEATURES_H  */

Re: [PATCH] powerpc: Expose VSX feature test

[Tulio Magno Quites Machado Filho]

Nathan Phillips <waic9e@protonmail.com> writes:

> Hope it's OK to submit a small change like this. Trying to familiarize myself
> with the patch process.
>
> My copyright assignment is underway.

Ack.

> Read the HWCAP auxval key to test for VSX support. Expose result through

Please use 2 spaces here ---------------------------^

> the cpu_features interface.
>
> Preliminary change to prepare for PowerPC optimized libmvec implementations
> [BZ #20123]. Enables selecting optimized version at load time in ifunc

Likewise. ----^

> resolver.

Can't you take it directly from the hwcap variable that is already available
when using libc_ifunc or libc_ifunc_redirected?  e.g.
sysdeps/powerpc/powerpc64/multiarch/memcmp.c


-- 
Tulio Magno

Re: [PATCH] powerpc: Expose VSX feature test

[Adhemerval Zanella]

On 28/03/2018 09:16, Tulio Magno Quites Machado Filho wrote:
> Nathan Phillips <waic9e@protonmail.com> writes:
> 
>> Hope it's OK to submit a small change like this. Trying to familiarize myself
>> with the patch process.
>>
>> My copyright assignment is underway.
> 
> Ack.
> 
>> Read the HWCAP auxval key to test for VSX support. Expose result through
> 
> Please use 2 spaces here ---------------------------^
> 
>> the cpu_features interface.
>>
>> Preliminary change to prepare for PowerPC optimized libmvec implementations
>> [BZ #20123]. Enables selecting optimized version at load time in ifunc
> 
> Likewise. ----^
> 
>> resolver.
> 
> Can't you take it directly from the hwcap variable that is already available
> when using libc_ifunc or libc_ifunc_redirected?  e.g.
> sysdeps/powerpc/powerpc64/multiarch/memcmp.c
> 
> 

I don't have the original message in my mailbox, was it sent only privately?
If it was the case, could you send the original one as well?

Re: [PATCH] powerpc: Expose VSX feature test

[Tulio Magno Quites Machado Filho]

Adhemerval Zanella <adhemerval.zanella@linaro.org> writes:

> On 28/03/2018 09:16, Tulio Magno Quites Machado Filho wrote:
>> Nathan Phillips <waic9e@protonmail.com> writes:
>> 
>>> Hope it's OK to submit a small change like this. Trying to familiarize myself
>>> with the patch process.
>>>
>>> My copyright assignment is underway.
>> 
>> Ack.
>> 
>>> Read the HWCAP auxval key to test for VSX support. Expose result through
>> 
>> Please use 2 spaces here ---------------------------^
>> 
>>> the cpu_features interface.
>>>
>>> Preliminary change to prepare for PowerPC optimized libmvec implementations
>>> [BZ #20123]. Enables selecting optimized version at load time in ifunc
>> 
>> Likewise. ----^
>> 
>>> resolver.
>> 
>> Can't you take it directly from the hwcap variable that is already available
>> when using libc_ifunc or libc_ifunc_redirected?  e.g.
>> sysdeps/powerpc/powerpc64/multiarch/memcmp.c
>> 
>> 
>
> I don't have the original message in my mailbox, was it sent only privately?

No, it's in the mailing list archives:
https://sourceware.org/ml/libc-alpha/2018-03/msg00582.html

> If it was the case, could you send the original one as well?

Sure!  I'm sending it in private to avoid duplicating this in the mailing list.

-- 
Tulio Magno

Re: [PATCH] powerpc: Expose VSX feature test

[Adhemerval Zanella]

On 28/03/2018 10:31, Tulio Magno Quites Machado Filho wrote:
> Adhemerval Zanella <adhemerval.zanella@linaro.org> writes:
> 
>> On 28/03/2018 09:16, Tulio Magno Quites Machado Filho wrote:
>>> Nathan Phillips <waic9e@protonmail.com> writes:
>>>
>>>> Hope it's OK to submit a small change like this. Trying to familiarize myself
>>>> with the patch process.
>>>>
>>>> My copyright assignment is underway.
>>>
>>> Ack.
>>>
>>>> Read the HWCAP auxval key to test for VSX support. Expose result through
>>>
>>> Please use 2 spaces here ---------------------------^
>>>
>>>> the cpu_features interface.
>>>>
>>>> Preliminary change to prepare for PowerPC optimized libmvec implementations
>>>> [BZ #20123]. Enables selecting optimized version at load time in ifunc
>>>
>>> Likewise. ----^
>>>
>>>> resolver.
>>>
>>> Can't you take it directly from the hwcap variable that is already available
>>> when using libc_ifunc or libc_ifunc_redirected?  e.g.
>>> sysdeps/powerpc/powerpc64/multiarch/memcmp.c
>>>
>>>
>>
>> I don't have the original message in my mailbox, was it sent only privately?
> 
> No, it's in the mailing list archives:
> https://sourceware.org/ml/libc-alpha/2018-03/msg00582.html
> 
>> If it was the case, could you send the original one as well?
> 
> Sure!  I'm sending it in private to avoid duplicating this in the mailing list.
> 

Right, thanks for the link, I missed this one.

Re: [PATCH] powerpc: Expose VSX feature test

[Nathan Phillips]

Thank you for reviewing. Well noted about the double spaces.


On March 28, 2018 6:16 AM, Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com> wrote:

> Can't you take it directly from the hwcap variable that is already available
> when using libc_ifunc or libc_ifunc_redirected? e.g.
> sysdeps/powerpc/powerpc64/multiarch/memcmp.c

I hadn't seen that, and it makes sense.

The x86 version seems to store everything in cpu_features, then
use that to resolve the ifunc. But I see the pattern is different
in the PPC section.

I propose dropping this patch and I can follow the PPC pattern instead.