Question regarding ReplayCompiles and multiple inlining

[dean.long at oracle.com]

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