RFR: 8330094: RISC-V: Save and restore FCSR in the call stub

[Fei Yang]

On Mon, 15 Apr 2024 12:58:23 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Another thing that is worth considering is that the `fflags` (exception flags) contained in `fcsr` is very likely to change after the Java call which does floating point calculations.
>
> Should we replace read/write/comp of fcsr with frm only?

Yeah, that make sense to me. I think `fflags` is safe to ignore here.
(And you will also need to update this code comment in file: src/hotspot/cpu/riscv/stubGenerator_riscv.cpp if you do that: ` // -34 [ saved Floating-point Control and Status Register ] <--- sp_after_call`)

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PR Review Comment: https://git.openjdk.org/jdk/pull/18758#discussion_r1565772009