[lworld] RFR: 8253161: [lworld] C1's substitutability check should use andptr instead of andl for mark word

[Tobias Hartmann]

C1's substitutability check should use andptr instead of andl for mark word. I've also optimized the null check.

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Commit messages:
 - 8253161: [lworld] C1's substitutability check should use andptr instead of andl for mark word

Changes: https://git.openjdk.java.net/valhalla/pull/189/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=189&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8253161
  Stats: 11 lines in 2 files changed: 1 ins; 5 del; 5 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/189.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/189/head:pull/189

PR: https://git.openjdk.java.net/valhalla/pull/189