RFR: 8296515: RISC-V: Optimized MaxReductionV/MinReductionV/AddReductionV node implementation [v2]

[Gui Cao]

> HI,
> 
> The MaxReductionV, MinReductionV, AddReductionV nodes currently implemented by riscv rvv can be implemented by calling shared functions, and the T_BYTE and T_SHORT types in the MaxReductionV and MinReductionV node implementations can also be implemented in the same way as the T_INT type.
> 
> Please take a look and have some reviews. Thanks a lot.
> 
> ## Testing:
> - hotspot and jdk tier1 on unmatched board without new failures
> - test/jdk/jdk/incubator/vector/* with fastdebug on qemu

Gui Cao has updated the pull request incrementally with two additional commits since the last revision:

 - Use the same predicate as reduce_addI
 - Remove the REDUCTION_OP enumeration type and use Opcode to represent the operation

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/11036/files
  - new: https://git.openjdk.org/jdk/pull/11036/files/be5cf97b..b295be7b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=11036&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=11036&range=00-01

  Stats: 34 lines in 4 files changed: 7 ins; 3 del; 24 mod
  Patch: https://git.openjdk.org/jdk/pull/11036.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/11036/head:pull/11036

PR: https://git.openjdk.org/jdk/pull/11036