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

[Tobias Hartmann]

On Wed, 1 Sep 2021 12:56:19 GMT, Vladimir Ivanov <vlivanov at openjdk.org> wrote:

> 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

That looks good to me but I would suggest to use `recv_type->maybe_null()`.

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Changes requested by thartmann (Reviewer).

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