RFR: 8357913: Add `@Stable` to BigInteger and BigDecimal [v3]

[Shaojin Wen]

On Wed, 4 Jun 2025 12:08:09 GMT, Per Minborg <pminborg at openjdk.org> wrote:

> The newly marked arrays are indeed only updated once. Can we see any benchmark showing a performance gain?

I ran `make test TEST="micro:java.math.BigDecimals` on a MacBook M1 Pro, and there was no performance improvement with the Stable added by this PR.

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PR Comment: https://git.openjdk.org/jdk/pull/25437#issuecomment-2941634408