[Bug 14391] sha1sum slow on x64 and possibly others

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=14391

--- Comment #1 from Denys Vlasenko <vda.linux at googlemail.com> ---
Unrolling outer loop only does not help noticeably.
Full unrolling of all 80 iterations increases size by ~3600 bytes.

If you want, you can submit a patch where unrolling is done depending on
.config option, following this example in libbb/Config.src:

config MD5_SMALL
        int "MD5: Trade bytes for speed (0:fast, 3:slow)"
        default 1  # all "fast or small" options default to small
        range 0 3
        help
        Trade binary size versus speed for the md5sum algorithm.
        Approximate values running uClibc and hashing
        linux-2.4.4.tar.bz2 were:
        value               user times (sec)  text size (386)
        0 (fastest)         1.1                6144
        1                   1.4                5392
        2                   3.0                5088
        3 (smallest)        5.1                4912

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