[jdk13u-dev] RFR: 8275610: C2: Object field load floats above its null check resulting in a segfault

[Yuri Nesterenko]

This backport of a crash fix is not exactly clean. Two options different in two passes of the test are not supported in 13u and 15u as well as "randomness" key in the test. Running the test without jtreg consistently does crash VM before the fix.

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Commit messages:
 - Backport 7c6f57fcb1f1fcecf26f7b8046a5a41ca6d9c315

Changes: https://git.openjdk.java.net/jdk13u-dev/pull/312/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk13u-dev&pr=312&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8275610
  Stats: 110 lines in 2 files changed: 110 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk13u-dev/pull/312.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk13u-dev pull/312/head:pull/312

PR: https://git.openjdk.java.net/jdk13u-dev/pull/312