RFR: 8371820: Further AES performance improvements for key schedule generation

[Shawn M Emery]

On Thu, 13 Nov 2025 16:48:28 GMT, Martin Doerr <mdoerr at openjdk.org> wrote:

> This fix simplifies the hotspot intrinsics for some platforms and optimizes the key computation for encryption. We can save the `genInvRoundKeys` computation when we only do encryption.
> 
> The micro:org.openjdk.bench.javax.crypto.AESReinit benchmark results are improved by 17% for ppc64 and 26% for x86_64.

src/java.base/share/classes/com/sun/crypto/provider/AES_Crypt.java line 941:

> 939:         if (decrypting) {
> 940:             if (sessionKd == null) {
> 941:                 sessionKd = genInvRoundKeys(sessionKe, rounds);

Good catch, as this is more efficient given that the inverse key schedule is dependent upon the (encryption) key schedule in the code's current state.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/28299#discussion_r2526173217