RFR: 8370196: C2: Improve (U)MulHiLNode::MulHiValue [v10]

[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 pull request now contains 13 commits:

 - Merge branch 'openjdk:master' into JDK-8370196
 - fix test failed
 - fix make unsigned
 - Merge branch 'master' into JDK-8370196
 - Fix
 - Fix
 - Apply suggestion from @eme64
   
   Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>
 - Add Math to Operations.java
 - Add tests
 - Merge branch 'master' into JDK-8370196
 - ... and 3 more: https://git.openjdk.org/jdk/compare/a62296d8...30fa1f03

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Changes: https://git.openjdk.org/jdk/pull/28097/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=28097&range=09
  Stats: 373 lines in 8 files changed: 336 ins; 14 del; 23 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