[jdk21u-dev] RFR: 8323688: C2: Fix UB of jlong overflow in PhaseIdealLoop::is_counted_loop()

[Goetz Lindenmaier]

I backport this for parity with 21.0.6-oracle.

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Commit messages:
 - Backport 1dd60b62e384090b13a08d2afa62e49ef52bc46c

Changes: https://git.openjdk.org/jdk21u-dev/pull/1035/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=1035&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8323688
  Stats: 21 lines in 1 file changed: 20 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/1035.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/1035/head:pull/1035

PR: https://git.openjdk.org/jdk21u-dev/pull/1035