RFR: 8365732: RISC-V: implement AES CTR intrinsics [v26]

[Hamlin Li]

On Thu, 13 Nov 2025 07:12:38 GMT, Anjian Wen <wenanjian at openjdk.org> wrote:

>> Hi everyone, please help review this patch which Implement the _counterMode_AESCrypt with Zvkned. On my QEMU, with Zvkned extension enabled, the tests in test/hotspot/jtreg/compiler/codegen/aes/ Passed.
>
> Anjian Wen has updated the pull request incrementally with one additional commit since the last revision:
> 
>   modify stub_id name

Some more comments and questions.

src/hotspot/cpu/riscv/stubGenerator_riscv.cpp line 2708:

> 2706:     //   L_encrypt_next:
> 2707:     //     while (used < BLOCK_SIZE) {
> 2708:     //       if (len == 0) goto L_exit;

The logic of the code here is different from the logic of assembly code.
Here it checks `len == 0` at the beginning of while loop; assembly code checks `len == 0` at the end of while loop.
Will this difference bring some logic difference in some corner case? If not, why make it a bit different from each other? Does it bring some performance difference with following change?

    Label L_next, L_main_loop, L_exit; // remove L_encrypt_next
    ...
    __ bind(L_next);
    __ bgeu(used, block_size, L_main_loop);
    __ beqz(len, L_exit);
    ... // scalar processing
    __ subi(len, len, 1);
    __ j(L_next);
    ...
    __ mv(used, 0);
    // Check if we have a full block_size
    __ bltu(len, block_size, L_next); // remove L_encrypt_next
    ...


Ask this question because the change make the comment and assembly implementation consistent, and the code easy to understand.

src/hotspot/cpu/riscv/stubGenerator_riscv.cpp line 2748:

> 2746:     };
> 2747: 
> 2748:     __ vsetivli(x0, 4, Assembler::e32, Assembler::m1);

A general question, can we make it bigger than `4`, or even `m2`?

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PR Review: https://git.openjdk.org/jdk/pull/25281#pullrequestreview-3479185242
PR Review Comment: https://git.openjdk.org/jdk/pull/25281#discussion_r2539244466
PR Review Comment: https://git.openjdk.org/jdk/pull/25281#discussion_r2539247773