Similar to strstr (1e9a550ba4), power8 strcasestr does not show much
improvement compared to the generic implementation. The geomean
on bench-strcasestr shows:
__strcasestr_power8 __strcasestr_ppc
power10 1159 1120
power9 1640 1469
power8 1787 1904
The strcasestr uses the same 'trick' as power7 strstr to detect
potential quadradic behavior, which only adds overheads for input
that trigger quadradic behavior and it is really a hack.
Checked on powerpc64le-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>
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