Question regarding ReplayCompiles and multiple inlining

[Tobias Hartmann]

Should we file an RFE for this or is this already tracked?

Thanks,
Tobias

On 22.06.23 08:35, dean.long at oracle.com wrote:
> I noticed this problem before too.  Unfortunately I can't think of a workaround.  It seems like the
> right fix is to change the replay file format to record more information.
> 
> dl
> 
> On 6/19/23 5:07 AM, Volker Simonis wrote:
>> Hi,
>>
>> I try to reproduce a compiler issue with a ReplayDataFile but
>> unfortunately I can't reproduce the crash.
>>
>> I hacked the VM to print out the the inlining tree just before the
>> crashes and realized that the original inlining differes from the
>> inlining done by ReplayCompiles.
>>
>> In my specific case I have the following inlining pattern during the
>> crash (`foo::f1()` gets inlined twice into `foo::f0() `):
>>      .
>>      .
>>    @ 57    foo::f0()    inline (hot)
>>      @ 48    foo::f1()    inline (hot)
>>        @ 2    bar::f2()    inline (hot)
>>          .
>>          .
>>      @ 48    foo::f1()    inline (hot)
>>        @ 2    bar::f2()   NodeCountInliningCutoff
>>
>> In the ReplayDataFile (in the `inline` part of the `compile` line)
>> both, `foo::f1()` and `bar::f2()` are recorded only once (because they
>> have the same  bci, name/signature and inlining depth).
>>
>> When running the replay, I get the following inlining pattern:
>>      .
>>      .
>>    @ 57    foo::f0()    force inline by ciReplay
>>      @ 48    foo::f1()    force inline by ciReplay
>>        @ 2    bar::f2()    force inline by ciReplay
>>          .
>>          .
>>      @ 48    foo::f1()    force inline by ciReplay
>>        @ 2    bar::f2()    force inline by ciReplay
>>
>> This is clearly different because in the replay we inline `bar::f2()`
>> a second time (while in the original run it was skipped due to
>> NodeCountInliningCutoff).
>>
>>  From looking at `find_ciInlineRecord()` [1], it looks like the replay
>> file only records the bci, inlining depth and method name/signature
>> for an inlinee? How is this supposed to work if a method is inlined
>> differently at the same level like in this example?
>>
>> Notice that I'm currently working with JDK 17 (because my problem
>> doesn't reproduce with HEAD) but it seems the relevant code hasn't
>> changed much in this area since JDK 17.
>>
>> Please let me know if this is a known problem and if there's any way
>> to workaround it?
>>
>> Thank you and best regards,
>> Volker
>>
>> [1] https://github.com/openjdk/jdk17u-dev/blob/852c26c0/src/hotspot/share/ci/ciReplay.cpp#L992