8390765: [PPC64] AES Crypto intrinsics may access memory beyond the key array

[TheRealMDoerr]

The old implementation of the AES stubs uses instruction sequences based on lvx and vperm instructions to handle unaligned accesses to the key array. Accesses beyond that array are possible (see JBS issue).

I've replaced the problematic sequences by instructions which can handle unaligned memory accesses. I'm using the better Power9 instructions if available and Power8 instructions else. (The AES intrinsics require Power8 as minimum.)

Note that Big Endian is much easier to handle because "lxvd2x, lxvw4x, lxvh8x, lxvb16x, and lxvx exhibit identical behavior in Big-Endian mode." (Power ISA).

No performance regression has been observed.
Also tested with -XX:+UnlockDiagnosticVMOptions -XX:PowerArchitecturePPC64=8

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• JDK-8390765: [PPC64] AES Crypto intrinsics may access memory beyond the key array (Bug - P3)

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