[lworld] RFR: 8265121: [lworld] Better optimize null-checks in C1

[Frederic Parain]

Please review those small changes in C1 that eliminates a few more unnecessary null checks.
I've experimented some changes in the NullCheckEliminator to handle inline types explicitly,
but it had no effect on generated code, in all cases, existing null check eliminations were already
sufficient to remove unnecessary checks.

The changeset also reverts a change in the CFG file generation which makes log file unreadable
by the C1Visualizer tool.

Tested with Mach5, tier1-3.

Thank you.

Fred

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Commit messages:
 - More null check eliminations in C1

Changes: https://git.openjdk.java.net/valhalla/pull/672/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=672&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8265121
  Stats: 9 lines in 3 files changed: 2 ins; 3 del; 4 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/672.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/672/head:pull/672

PR: https://git.openjdk.java.net/valhalla/pull/672