RFR: 8355719: Reduce memory consumption of BigInteger.pow() [v51]

[fabioromano1]

On Wed, 7 May 2025 17:58:11 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

> OK.
> 
> But then your original expression
> 
> ```
> (((bitLength() - 1L) * exponent) >>> 5) + 1L > MAX_MAG_LENGTH
> ```
> 
> was a bit too restrictive as well, right?

On the contrary, it was too loose, as it admitted a  bit length equal to `2^31 > Integer.MAX_VALUE`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/24690#discussion_r2078197555