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.

Good catch in eliminating the unnecessary construction of both key schedules on the PPC64, S390, and RISCV64 architectures.

src/java.base/share/classes/com/sun/crypto/provider/AES_Crypt.java line 59:

> 57:     // Following attribute is specific to Intrinsics where the unprocessed
> 58:     // key is used for PPC64, S390, and RISCV64 architectures, whereas K is
> 59:     // used for everything else.

I would change this to:
// Following attributes (sessionKe and K) are specific to Intrinsics, where sessionKe
// is the unprocessed key that is used for PPC64, S390, and RISCV64 architectures,
// whereas K is used for everything else.

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PR Review: https://git.openjdk.org/jdk/pull/28299#pullrequestreview-3463343453
PR Review Comment: https://git.openjdk.org/jdk/pull/28299#discussion_r2526196244