RFR: 8263776: [JVMCI] add helper to perform Java upcalls

[Tom Rodriguez]

8263776: [JVMCI] add helper to perform Java upcalls

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Commit messages:
 - 8263776: [JVMCI] add helper to perform Java upcalls

Changes: https://git.openjdk.java.net/jdk/pull/3067/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3067&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8263776
  Stats: 108 lines in 3 files changed: 108 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3067.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3067/head:pull/3067

PR: https://git.openjdk.java.net/jdk/pull/3067