RFR: 8275638: GraphKit::combine_exception_states fails with "matching stack sizes" assert [v2]

[Dean Long]

On Fri, 26 Nov 2021 10:27:48 GMT, Roland Westrelin <roland at openjdk.org> wrote:

>> Root cause is identical to 8273165 AFIU: late inline of a virtual call
>> can throw from 2 different paths (null check and the call
>> itself). That breaks because the logic for exceptions expects the
>> stack for all paths that throw exceptions to have the same stack size.
>> 
>> AFAIU, the stack doesn't matter exception handling: either the
>> exception is caught by a exception handler and then the stack is
>> popped and the exception is pushed or, the exception is rethrown to
>> the caller in which case the current stack is also popped (that is the
>> jvm state for the current method). As a consequence the fix I propose
>> is to ignore the stack in GraphKit::combine_exception_states().
>> 
>> AFAIU, the same fix would work for 8273165 but I left the current work
>> around as is: not sure if we want to be conservative for now or not
>
> Roland Westrelin has updated the pull request incrementally with one additional commit since the last revision:
> 
>   make test runnable with release build

I tried calling

  set_sp(0);
  clean_stack(0);

in GraphKit::make_exception_state() and it seems to work, but I still don't understand why the stack size mismatch only shows up with late inlining.

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PR: https://git.openjdk.java.net/jdk/pull/6572