RFR: 8273165: GraphKit::combine_exception_states fails with "matching stack sizes" assert [v2]

[Vladimir Ivanov]

> The fix for JDK-8271276 uncovered another problem with incremental inlining through 
> virtual call sites: receiver null check breaks exception state combining in `GraphKit::replace_call()`
> because the associtated exception path has the JVM state representing the point
> right before the call (arguments are on stack).
> 
> I propose a conservative fix which bails out the inlining attempt when receiver is not provably non-null.
> 
> IMO the proper fix is to always add explicit receiver null check and teach
> `Block::implicit_null_check()` about CallDynamicJava nodes. But that's for a
> separate change.
> 
> Testing: failing tests, hs-tier1 - hs-tier4

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

  Migrate to Type::maybe_null()

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5330/files
  - new: https://git.openjdk.java.net/jdk/pull/5330/files/5b3132be..3cb08341

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5330&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5330&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 1 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5330.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5330/head:pull/5330

PR: https://git.openjdk.java.net/jdk/pull/5330