RFR: 8263587: C2: JVMS not cloned when needs_clone_jvms() is true [v2]

[Martin Doerr]

> We need a C2 fix to prevent crashes because JVMS doesn't get cloned as needed. See linked issue for details.

Martin Doerr has updated the pull request incrementally with one additional commit since the last revision:

  Cleanup as suggested by Vladimir Ivanov.

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/3009/files
  - new: https://git.openjdk.java.net/jdk/pull/3009/files/bafcce9f..9205db9f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=3009&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=3009&range=00-01

  Stats: 25 lines in 1 file changed: 1 ins; 16 del; 8 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3009.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3009/head:pull/3009

PR: https://git.openjdk.java.net/jdk/pull/3009