[riscv-port] RFR: 8278994: riscv: RVC support [v5]

[Xiaolin Zheng]

On Wed, 5 Jan 2022 03:47:42 GMT, Yadong Wang <yadongwang at openjdk.org> wrote:

>> Xiaolin Zheng has refreshed the contents of this pull request, and previous commits have been removed. The incremental views will show differences compared to the previous content of the PR.
>
> src/hotspot/cpu/riscv/c2_globals_riscv.hpp line 49:
> 
>> 47: define_pd_global(intx, FreqInlineSize,               325);
>> 48: define_pd_global(intx, MinJumpTableSize,             10);
>> 49: define_pd_global(intx, InteriorEntryAlignment,       4);
> 
> It's best to keep InteriorEntryAlignment and CodeEntryAlignment unchanged if there's no obvious benefits.

These changes are made for shrinking the code size to a minimum level. Though regarding them doing no harm and as an enhancement, I consider it also great to remain them unchanged.

Need some testing work after the changes and if there are other suggestions I feel pleased to change.

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