RFR: 8355719: Reduce memory consumption of BigInteger.pow() [v46]

[Johannes Graham]

On Tue, 29 Apr 2025 15:10:10 GMT, fabioromano1 <duke at openjdk.org> wrote:

>> This PR optimizes `BigInteger.pow(int)` method. The primary enhancement in `pow()` is not concerned most on execution time, but rather in memory optimization, because the PR implementation does the "shift of the exponent" squaring the result rather than the base, so the base is not squared like in the current implementation, and this permits to save about half of the memory.
>
> fabioromano1 has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Adjust the type of operand
>  - Use a more loose formula to do range check
>    
>    Use a more loose formula to do range check, in order not to exclude a priori values that may be inside the supported range

A thought for a future PR  - computing long powers could be useful as a public method as well.

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PR Comment: https://git.openjdk.org/jdk/pull/24690#issuecomment-2839942516