RFR: 8271471: [IR Framework] Rare occurrence of "<!-- safepoint while printing -->" in PrintIdeal/PrintOptoAssembly can let tests fail [v2]

[Christian Hagedorn]

> A test VM used by the IR framework sometimes prints `` in the middle of emitting a `PrintIdeal` or `PrintOptoAssembly` output which could lead to IR matching failures:
> https://github.com/openjdk/jdk/blob/489e5fd12a37a45f4f5ea64b05f85c6f99f70811/src/hotspot/share/utilities/ostream.cpp#L918-L927
> 
> I thought about just bailing out of IR matching if this string is found after a failure but this issue also affects internal framework tests (I observed one case locally where this happened in the test `TestIRMatching`, letting it fail).
> 
> Handling `` makes things more complicated for the IR framework tests. I'm not sure about the value of printing this message in the first place. But if nobody objects, I suggest to either remove it or at least guard it with `Verbose`, for example. I went with the latter solution in this PR.
> 
> Thanks,
> Christian

Christian Hagedorn has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Revert fix and add new fix: add bailout with adaptation to internal tests to handle it (option 1)
 - Merge branch 'master' into JDK-8271471
 - 8271471: [IR Framework] Rare occurrence of "<!-- safepoint while printing -->" in PrintIdeal/PrintOptoAssembly can let tests fai

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/4932/files
  - new: https://git.openjdk.java.net/jdk/pull/4932/files/5655433a..9ace95fa

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=4932&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=4932&range=00-01

  Stats: 40041 lines in 487 files changed: 35634 ins; 2520 del; 1887 mod
  Patch: https://git.openjdk.java.net/jdk/pull/4932.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/4932/head:pull/4932

PR: https://git.openjdk.java.net/jdk/pull/4932