RFR: 8295110: RISC-V: Mark out relocations as incompressible [v5]

[Fei Yang]

On Wed, 12 Oct 2022 09:21:54 GMT, Xiaolin Zheng <xlinzheng at openjdk.org> wrote:

>> This patch marks all relocations incompressible as pre-discussions at [1] and converts instructions to their 2-byte compressible counterparts as much as possible when UseRVC is enabled.
>> 
>> Chaining PR #10421.
>> 
>> 1. Code size reduction rate: about ~17% now after this patch under RVC, meaning if there's a piece of code of 1000 bytes, it may shrink to 830 bytes when RVC is enabled. [2]
>> 2. Performance: conservatively no regressions observed. [3]
>> 
>> The overloaded `relocate()` methods hide `IncompressibleRegion`s inside, to exclude instructions used at relocations from being compressed.
>> 
>> 
>> Having tested several times hotspot tier1~tier4; Testing another turn on board.
>> 
>> 
>> 
>> [1] https://mail.openjdk.org/pipermail/riscv-port-dev/2022-September/000615.html
>> [2] https://mail.openjdk.org/pipermail/riscv-port-dev/2022-September/000633.html
>> [3] https://mail.openjdk.org/pipermail/riscv-port-dev/2022-October/000656.html
>
> Xiaolin Zheng has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Keep aligning int32_t style

Updated change looks good. Thanks.

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Marked as reviewed by fyang (Reviewer).

PR: https://git.openjdk.org/jdk/pull/10643