[riscv-port-jdk11u:riscv-port] RFR: 8293566: RISC-V: Clean up push and pop registers

[Dingli Zhang]

On Tue, 8 Oct 2024 08:28:21 GMT, Gui Cao <gcao at openjdk.org> wrote:

> Hi, I would like to backport [JDK-8293566](https://bugs.openjdk.org/browse/JDK-8293566) to riscv-port-jdk11u. with this patch ,it will have better readability. jdk11u not have z gc, so this backport is not clean.
> 
> ### Testing
> - [x] Run tier1 tests on SOPHON SG2042 (release)

LGTM, thanks.

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Marked as reviewed by dzhang (Committer).

PR Review: https://git.openjdk.org/riscv-port-jdk11u/pull/36#pullrequestreview-2356931997