RFR: 8319716: RISC-V: Add SHA-2 [v2]

[Robbin Ehn]

On Fri, 1 Dec 2023 19:47:22 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Robbin Ehn has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains four additional commits since the last revision:
>> 
>>  - Flag fixes
>>  - Merge branch 'master' into sha256
>>  - Share code
>>  - SHA-2
>
> src/hotspot/cpu/riscv/stubGenerator_riscv.cpp line 3895:
> 
>> 3893:       __ enter();
>> 3894: 
>> 3895:       __ push_reg(saved_regs, sp);
> 
> Not sure if we need to push and pop `saved_regs `, as t2 is the only register in it, or maybe I miss something?

t2 is used by C2 as general register, see R7 in riscv.ad.
As this may be inlined directly into the graph IR, i.e. no call to get here, t2 may be a live register.
saved_regs only contains t2 so there is just one spill and one restore.

No?

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PR Review Comment: https://git.openjdk.org/jdk/pull/16562#discussion_r1414101381