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422987ab04
Validate ascii string by ORing all bytes and check if 7-th bit is 0. Compared with original std::any_of(), which checks ascii string byte by byte, this new approach validates input in 8 bytes and two independent streams. Performance is much higher for normal cases, though slightly slower when string is very short. See table below. Speed(MB/s) of ascii string validation +---------------+-------------+---------+ | String length | std::any_of | u64 x 2 | +---------------+-------------+---------+ | 9 bytes | 1691 | 1635 | +---------------+-------------+---------+ | 31 bytes | 2923 | 3181 | +---------------+-------------+---------+ | 129 bytes | 3377 | 15110 | +---------------+-------------+---------+ | 1039 bytes | 3357 | 31815 | +---------------+-------------+---------+ | 16385 bytes | 3448 | 47983 | +---------------+-------------+---------+ | 1048576 bytes | 3394 | 31391 | +---------------+-------------+---------+ Signed-off-by: Yibo Cai <yibo.cai@arm.com> Message-Id: <1544669646-31881-1-git-send-email-yibo.cai@arm.com>