RFR: 8367692: RISC-V: Align post call nop [v2]

[Robbin Ehn]

> Hi please, consider.
> 
> As ziccif require instructions to natural aligned to be atomic the 4 byte post call nop must be aligned.
> But I don't want to add a c.nop(2b) to align the nop(4b) which means the jal(r) must also be algined.
> As we have no utility to aligned the end of an instruction sequence the call it self is aligned and uses only 4 byte instructions. Only in the case where we could use an two c-instruction we may loose space.
> 
> Thanks, Robbin

Robbin Ehn 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 three additional commits since the last revision:

 - Merge branch 'master' into align_post_nops
 - Review comments
 - init

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/27467/files
  - new: https://git.openjdk.org/jdk/pull/27467/files/409e6da1..8f2dcb6d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27467&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27467&range=00-01

  Stats: 5376 lines in 152 files changed: 3227 ins; 1061 del; 1088 mod
  Patch: https://git.openjdk.org/jdk/pull/27467.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27467/head:pull/27467

PR: https://git.openjdk.org/jdk/pull/27467