RFR: 8357793: [PPC64] VM crashes with -XX:-UseSIGTRAP -XX:-ImplicitNullChecks

[Martin Doerr]

In case of -XX:-UseSIGTRAP -XX:-ImplicitNullChecks, we use the manually selected entry. (The same is true for -XX:-TrapBasedNullChecks -XX:-ImplicitNullChecks.)
We only need to use the correct NullPointerException entry in the compiler case.

With this patch, the manually selected entry matches the one selected by `PosixSignals::pd_hotspot_signal_handler`.

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Commit messages:
 - 8357793: [PPC64] VM crashes with -XX:-UseSIGTRAP -XX:-ImplicitNullChecks

Changes: https://git.openjdk.org/jdk/pull/25504/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25504&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8357793
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/25504.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25504/head:pull/25504

PR: https://git.openjdk.org/jdk/pull/25504