RFR: 8302204: Optimize BigDecimal.divide

[Raffaello Giulietti]

On Wed, 1 Mar 2023 06:40:01 GMT, Xiaowei Lu <duke at openjdk.org> wrote:

>>> > After making sure that `intVal` is even, and before attempting a division by a power of 10, it might help to check if 5 divides `intVal` in the first place. If it doesn't, there no point in performing the division.
>>> > It can be shown that 5 divides `intVal` if and only if it divides the `long` sum of all `int`s in the `mag` array of `intVal`.
>>> > I didn't try out if this contributes to improve the overall performance, but it might be worth giving a try.
>>> 
>>> Unfortunately, it seems this division by 5 doesn't give an obvious performance improvement. Maybe previous lowest bit check has filtered some cases.
>> 
>> Thanks for trying out.
>
> @rgiulietti Hi, could you please review this pr

@weixlu I'm not an official [reviewer](https://openjdk.org/bylaws#reviewer)

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

PR: https://git.openjdk.org/jdk/pull/12509