[PATCH x86_64] Update memcpy, mempcpy and memmove selection order for Excavator CPU BZ #19583

[H.J. Lu]

On Fri, Mar 18, 2016 at 6:22 AM, Pawar, Amit <Amit.Pawar@amd.com> wrote:
>>No, it isn't fixed.  Avoid_AVX_Fast_Unaligned_Load should disable __memcpy_avx_unaligned and nothing more.  Also you need to fix ALL selections.
>
> diff --git a/sysdeps/x86_64/multiarch/memcpy.S b/sysdeps/x86_64/multiarch/memcpy.S
> index 8882590..a5afaf4 100644
> --- a/sysdeps/x86_64/multiarch/memcpy.S
> +++ b/sysdeps/x86_64/multiarch/memcpy.S
> @@ -39,6 +39,8 @@ ENTRY(__new_memcpy)
>         ret
>  #endif
>  1:     lea     __memcpy_avx_unaligned(%rip), %RAX_LP
> +       HAS_ARCH_FEATURE (Avoid_AVX_Fast_Unaligned_Load)
> +       jnz     3f
>         HAS_ARCH_FEATURE (AVX_Fast_Unaligned_Load)
>         jnz     2f
>         lea     __memcpy_sse2_unaligned(%rip), %RAX_LP
> @@ -52,6 +54,8 @@ ENTRY(__new_memcpy)
>         jnz     2f
>         lea     __memcpy_ssse3(%rip), %RAX_LP
>  2:     ret
> +3:     lea     __memcpy_ssse3(%rip), %RAX_LP
> +       ret
>  END(__new_memcpy)
>
>  # undef ENTRY
>
> Will update all IFUNC's if this ok else please suggest.
>

Better, but not OK.  Try something like

iff --git a/sysdeps/x86_64/multiarch/memcpy.S
b/sysdeps/x86_64/multiarch/memcpy.S
index ab5998c..2abe2fd 100644
--- a/sysdeps/x86_64/multiarch/memcpy.S
+++ b/sysdeps/x86_64/multiarch/memcpy.S
@@ -42,9 +42,11 @@ ENTRY(__new_memcpy)
   ret
 #endif
 1:   lea   __memcpy_avx_unaligned(%rip), %RAX_LP
+  HAS_ARCH_FEATURE (Avoid_AVX_Fast_Unaligned_Load)
+  jnz   3f
   HAS_ARCH_FEATURE (AVX_Fast_Unaligned_Load)
   jnz   2f
-  lea   __memcpy_sse2_unaligned(%rip), %RAX_LP
+3:   lea   __memcpy_sse2_unaligned(%rip), %RAX_LP
   HAS_ARCH_FEATURE (Fast_Unaligned_Load)
   jnz   2f
   lea   __memcpy_sse2(%rip), %RAX_LP


-- 
H.J.