RFR: 8257631: C2: Assertion failure in ArrayCopyNode::get_count() during late inlining

[Vladimir Ivanov]

The problematic assert in ArrayCopyNode::get_count() is specifically targeted at parsing phase, but it doesn't filter out late inlining which exposes the problematic IR shape the assert guards against.

Testing:
- [x] hs-tier1-6 w/ -XX:+AlwaysIncrementalInline

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Commit messages:
 - Adjust assert in ArrayCopyNode::get_count for incremental inlining

Changes: https://git.openjdk.java.net/jdk/pull/1581/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1581&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8257631
  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1581.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1581/head:pull/1581

PR: https://git.openjdk.java.net/jdk/pull/1581