[jdk21u-dev] RFR: 8338924: C1: assert(0 <= i && i < _len) failed: illegal index 5 for length 5

[Goetz Lindenmaier]

I backport this for parity with 21.0.6-oracle.

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Commit messages:
 - Backport caf28d4ac5711cc864a05fbdd64451d364c599ef

Changes: https://git.openjdk.org/jdk21u-dev/pull/1012/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1012&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338924
  Stats: 144 lines in 6 files changed: 134 ins; 6 del; 4 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1012.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1012/head:pull/1012

PR: https://git.openjdk.org/jdk21u-dev/pull/1012