[lworld] RFR: 8242269: [lworld] C2 compilation fails with assert "meet not symmetric"

[Roland Westrelin]

This tweaks the type system to fix error triggered by the recent merge.

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Commit messages:
 - Fix meet not symmetric errors following merge of 8240676

Changes: https://git.openjdk.java.net/valhalla/pull/20/files
 Webrev: https://webrevs.openjdk.java.net/valhalla/20/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8242269
  Stats: 45 lines in 1 file changed: 17 ins; 15 del; 13 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/20.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/20/head:pull/20

PR: https://git.openjdk.java.net/valhalla/pull/20