RFR: 8345236: RISC-V: Remove revb_h_h_u and revb_h_w_u macro assembler routines [v2]

[Fei Yang]

> Hi, please consider this cleanup change.
> 
> This is a further step after https://bugs.openjdk.org/browse/JDK-8345110.
> `revb_h_h_u` and `revb_h_w_u` assembler routines are mainly used to change byte-ordering for one halfword and two halfwords respectively. The names don't look obvious and the callsites emit more instructions when Zbb is not available (6 and 14 instructions respectively).
> 
> Since we don't have instructions like aarch64 `rev32` or `rev16`, seems more reasonable for us to do the byte-ordering while loading the bytes for these callsites, which also results in less instructions. Similar approach is taken for other places in riscv [1] and other ports like arm [2]. This also renames `revb_w` into `revbw` so that we are more consistent in naming with integer instructions that manipulate 32-bit values like `addiw`.
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/riscv/templateTable_riscv.cpp#L1625
> [2] https://github.com/openjdk/jdk/blob/master/src/hotspot/cpu/arm/templateTable_arm.cpp#L756
> 
> Testing on linux-riscv64 platform.
> - [ ] tier1 (release)
> - [x] non-trivial benchmark workloads like Dacapo, SpecJBB, Renaissance (release)

Fei Yang has updated the pull request incrementally with one additional commit since the last revision:

  Fix indentation

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/22452/files
  - new: https://git.openjdk.org/jdk/pull/22452/files/7790933c..5930005d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=22452&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=22452&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/22452.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22452/head:pull/22452

PR: https://git.openjdk.org/jdk/pull/22452