RFR: 8347645: C2: XOR bounded value handling blocks constant folding [v14]

[Johannes Graham]

> C2 does not eliminate XOR nodes with constant arguments. This has a noticeable effect on `Long.expand` with a constant mask, on architectures that don't have instructions equivalent  to `PDEP` to be used in an intrinsic.
> 
> This patch demonstrates a potential fix to the problem, but there might well be better ways to do it.

Johannes Graham has updated the pull request incrementally with one additional commit since the last revision:

  clean up comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/23089/files
  - new: https://git.openjdk.org/jdk/pull/23089/files/9bc2afb4..710012b4

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23089&range=13
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23089&range=12-13

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23089.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23089/head:pull/23089

PR: https://git.openjdk.org/jdk/pull/23089