RFR: 8294609: C2: Improve inlining of methods with unloaded signature classes [v2]

[Vladimir Ivanov]

> C2 bails out an inlining attempt when the callee method mentions an unloaded
> class in its signature (either as an argument or return type).
> 
> The current check is too strict (and caused problems in the past [1]) since it
> doesn't take into account whether the problematic class is loaded in the caller
> context. It's safe to relax the original check in such a way because class
> loader constratints ensure that both caller and callee agree on the signature
> classes.
> 
> (I believe the aforementioned check [2] is redundant and can be removed even when
> the class is not yet loaded, but I'll explore it separately.)
> 
> Testing: hs-tier1 - hs-tier4
> 
> [1] https://mail.openjdk.org/pipermail/hotspot-compiler-dev/2020-June/038604.html
> [2] https://github.com/openjdk/jdk/blob/5f6ad926d7ea763bf61aa98c7be7087a7aa6089c/src/hotspot/share/opto/bytecodeInfo.cpp#L226

Vladimir Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  fix test

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/10496/files
  - new: https://git.openjdk.org/jdk/pull/10496/files/be99db90..694d457b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10496&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10496&range=00-01

  Stats: 6 lines in 1 file changed: 0 ins; 5 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/10496.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10496/head:pull/10496

PR: https://git.openjdk.org/jdk/pull/10496