[riscv-port] RFR: 8278994: riscv: RVC support [v16]

[Xiaolin Zheng]

On Sat, 15 Jan 2022 03:31:35 GMT, Yadong Wang <yadongwang at openjdk.org> wrote:

>> Xiaolin Zheng has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase.
>
> src/hotspot/cpu/riscv/c1_LIRAssembler_riscv.cpp line 1329:
> 
>> 1327:   //   the address of jal itself (which will be patched later) should not span the cache line.
>> 1328:   //   See CallStaticJavaDirectNode::compute_padding() for more info.
>> 1329:   __ align(4);
> 
> It's better to add some alignment asserts before the code that may be patched, for example, in MacroAssembler::emit_static_call_stub.

Thanks for the reasonable suggestion. Rebased and added the assertion with testing a fastdebug build under RVC for `test/jtreg/hotspot/compiler` without errors found.

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PR: https://git.openjdk.java.net/riscv-port/pull/34