[jdk17u-dev] RFR: 8361117: SIGSEGV in LShiftLNode::Ideal due to unexpected dead node

[Martin Doerr]

This is a new fix for [JDK-8361117](https://bugs.openjdk.org/browse/JDK-8361117). I can't see the corresponding fix because it's not public.

This fix is taken from https://github.com/openjdk/jdk/commit/05a0a710313917fe7124ff43fe9c9af1d649bcac.
The problem is described in https://github.com/openjdk/jdk/blob/674cc3eeca77f1f2a6d937b1df5c5cd8a13c2d31/test/hotspot/jtreg/compiler/arraycopy/TestACSameSrcDst.java#L87 but that regression test didn't reproduce the issue in jdk17u.

I've taken the reproducer from the issue and put it into a new regression test. The VM crashes without the fix and the test passes with the fix.

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Commit messages:
 - 8361117: SIGSEGV in LShiftLNode::Ideal due to unexpected dead node

Changes: https://git.openjdk.org/jdk17u-dev/pull/4204/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=4204&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8361117
  Stats: 67 lines in 2 files changed: 67 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/4204.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/4204/head:pull/4204

PR: https://git.openjdk.org/jdk17u-dev/pull/4204