[PATCH v3 2/3] string: simplify find_zero_ne_all

[Wilco Dijkstra]

Hi Matt,

> Build the mask from the raw difference, as find_ne_all () now does.
> index_first () and index_last () only need to know which byte holds the
> first or the last set bit, and find_zero_all () marks only the bytes that
> were zero, so each term of the or marks only its own bytes.
>
> That drops one of the two carry chains from strcmp () and strncmp () on
> targets using the generic string-fza.h, and one of the two uqsub8 on
> armv6t2.  As in find_ne_all (), only the generic implementation tests
> HAVE_BITOPTS_WORKING.
>
> powerpc keeps its existing form, where orc folds the complement of cmpb
> into the or and the raw difference saves nothing.  alpha and riscv do not
> reach this code with the generic index_first ().

LGTM

Reviewed-by: Wilco Dijkstra  <Wilco.Dijkstra@arm.com>

Cheers,
Wilco