RFR: 8282218: C1: Missing side effects of dynamic class loading during constant linkage

[Vladimir Ivanov]

(The problem is similar to JDK-8282194, but with class loading this time.)

C1 handles unresolved constants by performing constant resolution at runtime and then putting the constant value into the generated code by patching it. But it treats the not-yet-resolved value as a pure constant without any side effects.

It's not the case for constants which trigger class loading using custom class loaders. (All non-String constants do that.)

There are no guarantees that there are no side effects during class loading, so C1 has to be conservative.

Proposed fix kills memory after accessing not-yet-loaded constant in the context of any non-trusted class loader.

Testing: hs-tier1 - hs-tier4

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Commit messages:
 - 8282218: C1: Missing side effects of dynamic class loading during constant linkage

Changes: https://git.openjdk.java.net/jdk/pull/7612/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=7612&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8282218
  Stats: 128 lines in 5 files changed: 126 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7612.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7612/head:pull/7612

PR: https://git.openjdk.java.net/jdk/pull/7612