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 [v2]

[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)

Yi Yang has updated the pull request incrementally with one additional commit since the last revision:

  rename test

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4920/files
  - new: https://git.openjdk.java.net/jdk/pull/4920/files/c2d47b2e..4775994b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4920&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4920&range=00-01

  Stats: 3 lines in 1 file changed: 0 ins; 1 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