RFR: 8330163: C2: improve CMoveNode::Value() when condition is always true or false [v2]

[Roland Westrelin]

> This is another small change from something I ran into while working
> on 8275202. `CMoveNode::Value` can be improved when the condition is
> known to be always true or false. That doesn't affect IGVN (as the
> `CMove` is removed in that case) but it can be useful for passes that
> propagates types such as CCP. In the IR tests, the backbranch of the
> loop is never taken when the root of the compilation is `test1`. With
> the change, CCP can eliminate it. Without, it can't.

Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:

  Update src/hotspot/share/opto/movenode.cpp
  
  Co-authored-by: Christian Hagedorn <christian.hagedorn at oracle.com>

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/18757/files
  - new: https://git.openjdk.org/jdk/pull/18757/files/1442e178..c11fd9e6

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18757&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18757&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/18757.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18757/head:pull/18757

PR: https://git.openjdk.org/jdk/pull/18757