RFR: 8257815: Replace global log2 functions with efficient implementations

Mon Dec 7 20:32:15 UTC 2020

On Mon, 7 Dec 2020 16:57:49 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> Builds on PPC64le after JDK-8257798 was fixed.
>
> There seem to be `gtest/GTestWrapper.java` failures on x86_32.

There was an issue with casting to uint64_t that only showed up in an existing test on 32-bit. I've implemented and tested a variant using `std::make_unsigned` which should be more robust by avoiding promoting 32-bit signed types to 64-bit unsigned ones.

-------------

PR: https://git.openjdk.java.net/jdk/pull/1663