RFR: 8299375: [PPC64] GetStackTraceSuspendedStressTest tries to deoptimize frame with invalid fp [v2]

[Richard Reingruber]

> Mark a frame as not fully initialized when copying it from a continuation StackChunk to the stack until the callers_sp (aka back link) is set.
> 
> This avoids the assertion given in the bug report when the copied frame is deoptimized before it is fully initialized.
> IMHO the deoptimization at that point is a little questionable but it actually only changes the pc of the frame which can be done.
> Note that the frame can get extended later (and metadata can get overridden) but [there is code that handles this](https://github.com/openjdk/jdk/blob/34a92466a615415b76c8cb6010ff7e6e1a1d63b4/src/hotspot/share/runtime/continuationFreezeThaw.cpp#L2108-L2110).
> 
> Testing: jdk_loom. The fix passed our CI testing. This includes most JCK and JTREG tiers 1-4, also in Xcomp mode, on the standard platforms and also on ppc64le.

Richard Reingruber has updated the pull request incrementally with one additional commit since the last revision:

  Feedback Martin

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/12941/files
  - new: https://git.openjdk.org/jdk/pull/12941/files/4188e822..1a283f73

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12941&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12941&range=00-01

  Stats: 4 lines in 2 files changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/jdk/pull/12941.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12941/head:pull/12941

PR: https://git.openjdk.org/jdk/pull/12941