RFR: 8370502: C2: segfault while adding node to IGVN worklist [v2]

[Manuel Hässig]

On Thu, 20 Nov 2025 18:26:06 GMT, Kerem Kat <krk at openjdk.org> wrote:

>> src/hotspot/share/opto/macro.cpp line 2352:
>> 
>>> 2350:   _igvn.replace_node(_callprojs.fallthrough_proj, region);
>>> 2351: 
>>> 2352:   if (_callprojs.fallthrough_memproj != nullptr) {
>> 
>> Why do we not have to hook up the memory input to the fall through projection if it does not exist in the first place?
>
> Could you clarify the question?

The code before assumed that `fallthrough_memproj` is always not null. So does the rest of the code also expect this? If so, then we should perhaps use `mem` for that purpose. This is related to @dean-long's question below. There is an invariant that is being violated and your fix should take into account why it is violated.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28432#discussion_r2548864355