RFR: JDK-8312617: SIGSEGV in ConnectionGraph::verify_ram_nodes

Wed Jul 26 22:32:55 UTC 2023

- Return early from `verify_ram_nodes` if compilation is already failing.
- Add back check for `failing()` after `eliminate_macro_nodes()`.
- Print additional diagnostic information when an unexpected user of RAM is encountered.

Tested with tier1-3 on Linux x64.

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Commit messages:
 - Small fixes & improved asserts.

Changes: https://git.openjdk.org/jdk/pull/15048/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15048&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8312617
  Stats: 30 lines in 2 files changed: 24 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/15048.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15048/head:pull/15048

PR: https://git.openjdk.org/jdk/pull/15048