RFR: 8240829: Use a fast O(1) algorithm for exact_log2

[Andrew Haley]

On 3/10/20 6:05 PM, Andrew Haley wrote:
> TL/DR: prefer portable code when possible.

And -- of course -- I never saw the count_leading_zeros() !

Why on Earth did anyone do all of the count_leading_zeros() work but
*not use it* in one of the hottest parts of HotSpot? Incredible.

It never even occurred to me that there might be definitions for
count_leading_zeros that were not used for exact_log2(). I just
saw it and thought "that's horrible."

-- 
Andrew Haley  (he/him)
Java Platform Lead Engineer
Red Hat UK Ltd. <https://www.redhat.com>
https://keybase.io/andrewhaley
EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671