RFR: 8336274: MutableBigInteger.leftShift(int) optimization [v9]

[fabioromano1]

On Thu, 12 Sep 2024 10:27:39 GMT, Raffaello Giulietti <rgiulietti at openjdk.org> wrote:

>> fabioromano1 has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Use supported annotation by jtreg in tests
>
> src/java.base/share/classes/java/math/MutableBigInteger.java line 753:
> 
>> 751:      * {@code (resPos <= offset || resPos >= offset + intLen)}.
>> 752:      */
>> 753:     private final void primitiveLeftShift(int n, int[] result, int resPos) {
> 
> I think this method can be made more symmetrical w.r.t. `primitiveRightShift()` if starting from the right (least significant `int`).

Yes, it could, but the problem is that in this way the precondition `(resPos <= offset || resPos >= offset + intLen)` is no longer correct, and in particular `resPos <= offset` is used by `MBI.leftShift()` if `result == value`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20008#discussion_r1756641412