RFR: 8320697: RISC-V: Small refactoring for runtime calls

[Fei Yang]

On Sun, 26 Nov 2023 10:52:18 GMT, Feilong Jiang <fjiang at openjdk.org> wrote:

> Hi, please review this refactoring for runtime calls.
> Major changes:
> 1. Unified the runtime calls with the existing MacroAssembler::rt_call. This will remove the duplicate code like `relocate(target.rspec() [&] {...}` to emit uncompressed instructions.
> 2. Removed MacroAssembler::far_branches and made the call sites default to far branches. `branch_range` is 1MB for riscv, and `ReservedCodeCacheSize` will always bigger than `branch_range` in practice. We should remove this unnecessary check and simplify the code logic.
> 3. Renamed MacroAssembler::la_patchable with MacroAssembler::auipc making it explicit that this will emit pc-relative addressing code.
> 4. `far_call` in `rt_call` should use `tmp` instead of the default temporary register `t0`
> 
> 
> Testing:
> - [x] Tier1-3 tested on hifive unmatched board (release)
> - [x] Run non-trivial benchmark workloads (fastdebug)

Looks fine. Happy to see that `MacroAssembler::far_branches` removed and code logic simplied. In fact, the JVM won't start when ReservedCodeCacheSize is less than 2496K. BTW: I also performed hotspot:tier4 test, result is also good.

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Marked as reviewed by fyang (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16816#pullrequestreview-1752317368