[riscv-port] RFR: 8279996: riscv: RVB: Add zeros/population count instructions [v2]

[Fei Yang]

On Fri, 14 Jan 2022 07:09:24 GMT, Feilong Jiang <fjiang at openjdk.org> wrote:

>> This PR implements zeros and population count instructions: `clz`/`clzw`/`ctz`/`ctzw`/`cpop`/`cpopw`.
>> 
>> New C2 instructions are covered by the following JTREG tests:
>> - test/hotspot/jtreg/compiler/codegen/Test6823354.java
>> - test/hotspot/jtreg/compiler/codegen/Test7100757.java
>> - test/hotspot/jtreg/compiler/codegen/Test8005033.java
>> 
>> Hotspot and jdk tier1 tests on QEMU (with and without UseRVB) are passed without new failures.
>
> Feilong Jiang has updated the pull request incrementally with one additional commit since the last revision:
> 
>   update license to new year

OK.

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Marked as reviewed by fyang (Lead).

PR: https://git.openjdk.java.net/riscv-port/pull/45