Re: [PATCH] powerpc: Fix IFUNC for memrchr

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

On 05/10/2017 07:43, Rajalakshmi Srinivasaraghavan wrote:
> Recent commit 59ba2d2b5421 missed to add __memrchr_power8 in
> ifunc list.  Also handled discarding unwanted bytes for
> unaligned inputs in power8 optimization.
> 
> 2017-10-05  Rajalakshmi Srinivasaraghavan  <raji@linux.vnet.ibm.com>
> 
> 	* sysdeps/powerpc/powerpc64/multiarch/memrchr-ppc64.c: Revert
> 	back to powerpc32 file.
> 	* sysdeps/powerpc/powerpc64/multiarch/memrchr.c
> 	(memrchr): Add __memrchr_power8 to ifunc list.
> 	* sysdeps/powerpc/powerpc64/power8/memrchr.S: Mask
> 	extra bytes for unaligned inputs.
> ---
>  .../powerpc/powerpc64/multiarch/memrchr-ppc64.c    | 15 +-------------
>  sysdeps/powerpc/powerpc64/multiarch/memrchr.c      |  3 +++
>  sysdeps/powerpc/powerpc64/power8/memrchr.S         | 24 ++++++++++++++++++++++
>  3 files changed, 28 insertions(+), 14 deletions(-)
> 
> diff --git a/sysdeps/powerpc/powerpc64/multiarch/memrchr-ppc64.c b/sysdeps/powerpc/powerpc64/multiarch/memrchr-ppc64.c
> index be24689336..e2d53ac0f4 100644
> --- a/sysdeps/powerpc/powerpc64/multiarch/memrchr-ppc64.c
> +++ b/sysdeps/powerpc/powerpc64/multiarch/memrchr-ppc64.c
> @@ -15,17 +15,4 @@
>     You should have received a copy of the GNU Lesser General Public
>     License along with the GNU C Library; if not, see
>     <http://www.gnu.org/licenses/>.  */
> -
> -#include <string.h>
> -
> -#define MEMRCHR  __memrchr_ppc
> -
> -#undef weak_alias
> -#define weak_alias(a, b)
> -
> -#undef libc_hidden_builtin_def
> -#define libc_hidden_builtin_def(name)
> -
> -extern __typeof (memrchr) __memrchr_ppc attribute_hidden;
> -
> -#include <string/memrchr.c>
> +#include <sysdeps/powerpc/powerpc32/power4/multiarch/memrchr-ppc32.c>
> diff --git a/sysdeps/powerpc/powerpc64/multiarch/memrchr.c b/sysdeps/powerpc/powerpc64/multiarch/memrchr.c
> index fb09fdf89c..441598ace5 100644
> --- a/sysdeps/powerpc/powerpc64/multiarch/memrchr.c
> +++ b/sysdeps/powerpc/powerpc64/multiarch/memrchr.c
> @@ -23,10 +23,13 @@
>  
>  extern __typeof (__memrchr) __memrchr_ppc attribute_hidden;
>  extern __typeof (__memrchr) __memrchr_power7 attribute_hidden;
> +extern __typeof (__memrchr) __memrchr_power8 attribute_hidden;
>  
>  /* Avoid DWARF definition DIE on ifunc symbol so that GDB can handle
>     ifunc symbol properly.  */
>  libc_ifunc (__memrchr,
> +	    (hwcap2 & PPC_FEATURE2_ARCH_2_07)
> +	    ? __memrchr_power8 :
>  	    (hwcap & PPC_FEATURE_HAS_VSX)
>              ? __memrchr_power7
>              : __memrchr_ppc);

I think indentation is a little off here, compared to other ifunc implementations.
Something like.

    (hwcap2 & PPC_FEATURE2_ARCH_2_07)
    ? __memrchr_power8 :
      (hwcap & PPC_FEATURE_HAS_VSX)
      ? __memrchr_power7
    : __memrchr_ppc);

> diff --git a/sysdeps/powerpc/powerpc64/power8/memrchr.S b/sysdeps/powerpc/powerpc64/power8/memrchr.S
> index 521b3c84a2..22b01ec69c 100644
> --- a/sysdeps/powerpc/powerpc64/power8/memrchr.S
> +++ b/sysdeps/powerpc/powerpc64/power8/memrchr.S
> @@ -233,11 +233,35 @@ L(found):
>  #endif
>  	addi	r8, r8, 63
>  	sub	r3, r8, r6	/* Compute final address.  */
> +	cmpld	cr7, r3, r10
> +	bgelr	cr7
> +	li	r3, 0
>  	blr
>  
>  	/* Found a match in last 16 bytes.  */
>  	.align	4
>  L(found_16B):
> +	cmpld	r8, r10		/* Are we on the last QW?  */
> +	bge	L(last)
> +	/* Now discard bytes before starting address.  */
> +	sub	r9, r10, r8
> +	MTVRD(v9, r9)
> +	vspltisb	v8, 3
> +	/* Mask unwanted bytes.  */
> +#ifdef __LITTLE_ENDIAN__
> +	lvsr	v7, 0, r10
> +	vperm   v6, v0, v6, v7
> +	vsldoi	v9, v0, v9, 8
> +	vsl	v9, v9, v8
> +	vslo	v6, v6, v9
> +#else
> +	lvsl	v7, 0, r10
> +	vperm   v6, v6, v0, v7
> +	vsldoi	v9, v0, v9, 8
> +	vsl	v9, v9, v8
> +	vsro	v6, v6, v9
> +#endif
> +L(last):
>  	/* Permute the first bit of each byte into bits 48-63.  */
>  	VBPERMQ(v6, v6, v10)
>  	/* Shift each component into its correct position for merging.  */

Isn't already covered by a testcase? If not, could you add one to test-memrchr?