RFR: 8302204: Optimize BigDecimal.divide

[Xiaowei Lu]

On Fri, 17 Feb 2023 04:42:50 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.

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