RFR: 8327963: C2: fix construction of memory graph around Initialize node to prevent incorrect execution if allocation is removed [v8]

[Roland Westrelin]

On Thu, 11 Sep 2025 07:48:10 GMT, Roberto Castañeda Lozano <rcastanedalo at openjdk.org> wrote:

>>> @rose00 @robcasloz I updated the change with a new way to avoid redundant projections. At matching time, before a `NarrowMemProj` is matched into a `MachProj`, new logic checks whether a `MachProj` already exists. That guarantees that no redundant `MachProj` are ever added. It also performs the new normalization at a major cut-point. What do you think?
>> 
>> That sounds good to me, thank you for enforcing this Roland! I will re-run testing and have a new look at the changeset within the next days.
>
>> That sounds good to me, thank you for enforcing this Roland! I will re-run testing and have a new look at the changeset within the next days.
> 
> Test results of b701d03ed335286587c4d2539dde715b091d30bd on top of jdk-26+14 look good. Will have a look at the code within the next days.

@robcasloz thanks for the review. New commit addresses most of your comments.

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PR Comment: https://git.openjdk.org/jdk/pull/24570#issuecomment-3319071258