RFR: 8267532: Try/catch block not optimized as expected [v4]

[Jorn Vernee]

On Mon, 6 Nov 2023 15:47:54 GMT, Tom Rodriguez <never at openjdk.org> wrote:

>> Jorn Vernee has updated the pull request incrementally with three additional commits since the last revision:
>> 
>>  - remove leftover comment
>>  - Add smoke tests for -XX:+StressPrunedExceptionHandlers and -XX:-ProfileExceptionHandlers
>>  - Add missing spaces to IRNode
>
> src/hotspot/share/runtime/sharedRuntime.cpp line 784:
> 
>> 782: 
>> 783:   if (handler_bci != -1) { // did we find a handler in this method?
>> 784:     sd->method()->set_ex_handler_entered(handler_bci); // profile
> 
> Are you sure this handles inlined exception handlers properly for c2?  My recollection is that C2 generates single level tables and performs the inlined exception dispatch in the generated code.  If you notice the flag top_frame_only stops the walk through the callers and OptoRuntime::handle_exception_C always passes true for top_frame_only.  So it seems like sd will always be the ScopeDesc of the top frame.

Hmm, you're right. The current code doesn't seem to work for exceptions thrown in an inlinee and caught in a caller. The other way around works.

I thought we only saw `-1` when we had to unwind a frame, and then we'd do the exception handler lookup again. But, looking now, there doesn't seem to be a following lookup.

I'll dig into this some more.

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PR Review Comment: https://git.openjdk.org/jdk/pull/16416#discussion_r1383596969