RFR: 8343122: RISC-V: C2: Small improvement for real runtime callouts

[Feilong Jiang]

On Mon, 28 Oct 2024 04:39:17 GMT, Fei Yang <fyang at openjdk.org> wrote:

> Hi, please review this small improvement.
> 
> Currently, we do 11 instructions for real C2 runtime callouts (See riscv_enc_java_to_runtime).
> Seems we can materialize the pointer faster with `movptr2`, which will help reduce 2 instructions.
> But we will need to reorder the original calling sequence a bit to make `t0` available for `movptr2`.
> 
> Testing on linux-riscv64 platform:
> - [x] tier1-tier3 (release)
> - [x] hotspot:tier1 (fastdebug)

LGTM

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Marked as reviewed by fjiang (Committer).

PR Review: https://git.openjdk.org/jdk/pull/21733#pullrequestreview-2408020114