Re: [PATCH] elf: Replace memcmp with __memcmpeq for variable size

[Florian Weimer <fw@deneb-ng.enyo.de>]

* H. J. Lu via Libc-alpha:

> diff --git a/elf/dl-cache.c b/elf/dl-cache.c
> index 88bf78ad7c..8574d4ded1 100644
> --- a/elf/dl-cache.c
> +++ b/elf/dl-cache.c
> @@ -72,7 +72,7 @@ glibc_hwcaps_compare (uint32_t left_index, struct dl_hwcaps_priority *right)
>      to_compare = left_name_length;
>    else
>      to_compare = right->name_length;
> -  int cmp = memcmp (left_name, right->name, to_compare);
> +  int cmp = memcmp_eq (left_name, right->name, to_compare);
>    if (cmp != 0)
>      return cmp;
>    if (left_name_length < right->name_length)

This change is not correct.

The x86-specific <memcmp-eq.h> optimization probably applies to other
targets as well.  I also do not quite see where the performance
benefits come from.  None of the changed spots look particularly hot
to me.

And I thought the assumption was that GCC would perform this optimization?