RFR: 8344306: RISC-V: Add zicond

[Robbin Ehn]

On Tue, 26 Nov 2024 10:27:15 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> src/hotspot/cpu/riscv/macroAssembler_riscv.cpp line 1143:
>> 
>>> 1141:   bne(cmp1, cmp2, no_set);
>>> 1142:   mv(dst, src);
>>> 1143:   bind(no_set);
>> 
>> Do we have performance data comparison between `-UseZicond ` and `+ UseZicond `?
>
> Seems the critical path when `+UseZicond` is longer than `-UseZicond`, I'm not sure how much impact the branch code will bring when `-UseZicond`.

Not, as we are only removing one in a thousand branches, the different would be so little that I don't think I can measure it in a reasoanble amount of iterations. I think you need something very synthetic, e.g. write a hot loop where we can remove a branch in it to measure it.

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

PR Review Comment: https://git.openjdk.org/jdk/pull/22386#discussion_r1858247068