RFR: 8319372: C2 compilation fails with "Bad immediate dominator info"

[Roland Westrelin]

I included the test case from 8318690 because the cause of the failure
is similar, the fix I propose applies to both. If this fix goes in
then 8318690 can be closed as duplicate of this one.

In both cases, a `CastII`'s type is narrowed because it is control
dependent on a condition that tests the input of the `CastII` (code in
`CastIINode::Value()`). In both cases, that `CastII` is input to a
range check `CastII`. Predication leaves that second `CastII` in the
loop body but the range check that guards it is replaced by
predicates. The difference in the 2 test cases is where the first
`CastII` comes from: `PhiNode::Ideal()` in one case,
`PhaseIdealLoop::try_sink_out_of_loop()` in the other. The narrowed
type of the first `CastII` conflicts with the type of the range check
`CastII` and that causes that one to become top. The path where that
`CastII` is is unreachable but c2 can't prove it. The inconsistency
causes the asserts.

To fix this we would need to prove that the path where the `CastII`
nodes are is dead and for that we would need to prove that the
condition that guards that path and at least one of the predicates
can't be true at the same time. While it may be feasible, that seems
like a lot of extra complexity.

Instead I propose removing the logic in `CastIINode::Value()`
entirely. I went back to the change that introduced it and, as I
understand, it was added as an attempt to detect and remove useless
`CastII` nodes. There was no correctness issue involved AFAICT.

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Commit messages:
 - whitespaces
 - tests
 - fix

Changes: https://git.openjdk.org/jdk/pull/16844/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=16844&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8319372
  Stats: 184 lines in 3 files changed: 111 ins; 73 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/16844.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/16844/head:pull/16844

PR: https://git.openjdk.org/jdk/pull/16844