hash_find(): do not caclculate hash twice. Do not divide - can use
cheap multiply-by-8 shift.
nextword(): do not repeatedly increment in-memory value, do it in register,
then store final result.
hashwalk_init(): do not strlen() twice.
function old new delta
hash_search3 - 49 +49
hash_find 259 281 +22
nextword 19 16 -3
evaluate 3141 3137 -4
hash_search 54 28 -26
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(add/remove: 1/0 grow/shrink: 1/3 up/down: 71/-33) Total: 38 bytes
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>