[jdk17u-dev] RFR: 8306997: C2: "malformed control flow" assert due to missing safepoint on backedge with a switch

[Satyen Subramaniam]

Backporting JDK-8306997: C2: "malformed control flow" assert due to missing safepoint on backedge with a switch. Ran GHA Sanity Checks, local Tier 1 and 2, and new tests. Patch is clean.

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Commit messages:
 - Backport e0774bed2d2fcd850f5ca6884dd7aeb45f0bdaef

Changes: https://git.openjdk.org/jdk17u-dev/pull/3589/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3589&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306997
  Stats: 106 lines in 3 files changed: 104 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3589.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3589/head:pull/3589

PR: https://git.openjdk.org/jdk17u-dev/pull/3589