RFR: 8319423: Improve Year.isLeap by checking divisibility by 16 [v2]

[Roger Riggs]

On Mon, 6 Nov 2023 00:50:22 GMT, Claes Redestad <redestad at openjdk.org> wrote:

> I suggest we go ahead and integrate this, file an RFE to re-examine the division-by-constant in C2, then re-evaluate these `isLeapYear` micros in that new environment.

These are good improvements and are beneficial with or without other fixes, so should go ahead independently.

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PR Comment: https://git.openjdk.org/jdk/pull/16491#issuecomment-1795320991