RFR: 8300109: RISC-V: Improve code generation for MinI/MaxI nodes [v3]

[Fei Yang]

On Mon, 16 Jan 2023 14:54:37 GMT, Fei Yang <fyang at openjdk.org> wrote:

>> As described by the issue, code generation for MinI/MaxI nodes on RISC-V could be improved when one of the source register is the same as the destination register. Also the code could be further simplified when that source register is constant 0 making use of the dedicated zero register of the architecture. This adds new match rules for those cases. 
>> 
>> Testing:
>> - [x] Run the new jtreg test added by: https://github.com/openjdk/jdk/pull/11570
>> - [x] Tier1-3 tested with release build on HiFive Unmatched board.
>> - [x] Run non-trivial benchmark workloads (dacapo, specjvm, renaissance, etc) with fastdebug build on HiFive Unmatched board.
>
> Fei Yang 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. The pull request contains four additional commits since the last revision:
> 
>  - Comment
>  - Merge branch 'master' into JDK-8300109
>  - Comment
>  - 8300109: RISC-V: Improve code generation for MinI/MaxI nodes

Thanks all for the review. I will proceed integrating this if there is no other comments.

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PR: https://git.openjdk.org/jdk/pull/11988