RFR: 8370196: C2: Improve (U)MulHiLNode::MulHiValue [v3]

[Zihao Lin]

> If nodes both are constant, support constant folding.

Zihao Lin 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 five additional commits since the last revision:

 - Add tests
 - Merge branch 'master' into JDK-8370196
 - test
 - Update src/hotspot/share/opto/mulnode.cpp
   
   Co-authored-by: Andrew Haley <aph-open at littlepinkcloud.com>
 - C2: Improve (U)MulHiLNode::MulHiValue

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/28097/files
  - new: https://git.openjdk.org/jdk/pull/28097/files/924c1555..3157f735

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28097&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28097&range=01-02

  Stats: 33517 lines in 772 files changed: 19256 ins; 10488 del; 3773 mod
  Patch: https://git.openjdk.org/jdk/pull/28097.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28097/head:pull/28097

PR: https://git.openjdk.org/jdk/pull/28097