[jdk17u-dev] RFR: 8301491: C2: java.lang.StringUTF16::indexOfChar intrinsic called with negative character argument

[Goetz Lindenmaier]

I backport this for parity with 17.0.8-oracle.

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Commit messages:
 - Backport 47ca5773a54743244a9b28f877246d260b90a408

Changes: https://git.openjdk.org/jdk17u-dev/pull/1299/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1299&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8301491
  Stats: 85 lines in 2 files changed: 83 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1299.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1299/head:pull/1299

PR: https://git.openjdk.org/jdk17u-dev/pull/1299