RFR: 8355992: Add unsignedMultiplyExact and *powExact methods to Math and StrictMath [v2]

[fabioromano1]

On Fri, 2 May 2025 17:53:12 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>>> Anyway, since the pre-checks are not precise, that would lead to an implementation with a loop with checked, and another one with unchecked multiplications. I don't think this buys you anything.
>> 
>> It serves to skip the checks in the loop if in the common cases the length of the results are way more little with respect to `Long.SIZE` and to fail fast if in the common cases the length of the results are way bigger than `Long.SIZE`.
>> 
>>> @fabioromano1 Well, there are two checks. In one the product can overflow, you'd need to convert one of the operands to `long`.
>> 
>> If the condition at point 1 is evaluated only if the condition at point 2 is false, then it can never overflow.
>
> If that check would be a couple of instructions or so, then I could agree.
> 
> True, there are no overflows in the checks.

@rgiulietti If you think that this checks might be useful, the choice is yours.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/25003#discussion_r2071969275