RFR: 8293474: RISC-V: Unify the way of moving function pointer

[Aleksey Shipilev]

On Wed, 7 Sep 2022 08:36:49 GMT, Fei Yang <fyang at openjdk.org> wrote:

> Currently, there are two different ways of moving function pointer on riscv with either 'li' or 'mv' assembler functions.
> For example, in file shenandoahBarrierSetAssembler_riscv.cpp, we use 'li' function:
>   li(ra, (int64_t)(uintptr_t)ShenandoahRuntime::load_reference_barrier_strong_narrow)
> 
> But in file templateInterpreterGenerator_riscv.cpp, we use 'mv' function:
>   mv(t1, CAST_FROM_FN_PTR(address, JavaThread::check_special_condition_for_native_trans))
> 
> Use of 'mv' here calls 'movptr' and emits fixed length instruction sequence, which is neither necessary nor optimal compared with use of 'li'. This changes to use 'li' instead of 'movptr' to implement 'mv' and unifies the way of moving function pointer.
> 
> Testing: Passed Tier1 test on Linux-riscv64 SiFive Unmatched board.

Looks fine.

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Marked as reviewed by shade (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10194