[jdk15u-dev] RFR: 8283441: C2: segmentation fault in ciMethodBlocks::make_block_at(int)

[Yuri Nesterenko]

Backporting the fix to be on par with LTS releases. Non-ignored hotspot tests run fine.

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Commit messages:
 - Backport 947869609ce6b74d4d28f79724b823d8781adbed

Changes: https://git.openjdk.org/jdk15u-dev/pull/261/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk15u-dev&pr=261&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8283441
  Stats: 106 lines in 5 files changed: 94 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jdk15u-dev/pull/261.diff
  Fetch: git fetch https://git.openjdk.org/jdk15u-dev pull/261/head:pull/261

PR: https://git.openjdk.org/jdk15u-dev/pull/261