RFR: 8271203: C2: assert(iff->Opcode() == Op_If || iff->Opcode() == Op_CountedLoopEnd || iff->Opcode() == Op_RangeCheck) failed: Check this code when new subtype is added

[Yi Yang]

Hi, I'm trying to fix [JDK-8271203](https://bugs.openjdk.java.net/browse/JDK-8271203). It's reasonable to unswitch LongCountedLoop, so relax it.

![image](https://user-images.githubusercontent.com/5010047/127302280-0faa90bb-add7-4639-8c63-49668901f267.png)

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Commit messages:
 - try

Changes: https://git.openjdk.java.net/jdk/pull/4920/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=4920&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8271203
  Stats: 67 lines in 2 files changed: 65 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4920.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4920/head:pull/4920

PR: https://git.openjdk.java.net/jdk/pull/4920