RFR: 8347645: C2: XOR bounded value handling blocks constant folding [v2]

[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 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 12 additional commits since the last revision:

 - move tests, add correctness checks
 - Merge remote-tracking branch 'origin/xor_const' into xor_const
 - move logic from Value to add_node XorL
 - move logic from Value to add_node XorI
 - format, copyright date
 - xor const folding
 - test for xor const folding
 - move logic from Value to add_node XorL
 - move logic from Value to add_node XorI
 - format, copyright date
 - ... and 2 more: https://git.openjdk.org/jdk/compare/1d03f360...fe3b4282

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/23089/files
  - new: https://git.openjdk.org/jdk/pull/23089/files/8ec4313c..fe3b4282

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=23089&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=23089&range=00-01

  Stats: 28608 lines in 2537 files changed: 12727 ins; 7669 del; 8212 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