RFR: 8318218: RISC-V: C2 CompressBits [v6]

[Hamlin Li]

On Fri, 10 Nov 2023 11:43:16 GMT, Hamlin Li <mli at openjdk.org> wrote:

>> Hi,
>> Can you review the change to add intrinsic for CompressBits for Long & Integer?
>> Thanks!
>> 
>> ## Test
>> pass jtreg test:
>> test/jdk/java/lang/CompressExpand*.java
>
> Hamlin Li has updated the pull request incrementally with one additional commit since the last revision:
> 
>   reserve all used v register; use t0 directly

Yes, that's the potential possible issues.
Or maybe we can tighten the matcher rule to enable the intrinsic: for example, `return UseRVV && (MaxVectorSize >= 32)` in `Matcher::match_rule_supported`, so for Long it will be v2(v3), v4(v5), for Integer, it will v2, v4. Does this make sense?

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PR Comment: https://git.openjdk.org/jdk/pull/16481#issuecomment-1805905656