[lworld] RFR: 8376702: [lworld] MemNode::optimize_simple_memory_chain asserts with "invalid node class: Con" [v2]

[Quan Anh Mai]

> Hi,
> 
> I cannot manage to reproduce the issue, and it seems to fail only once in our CI. From the log, it seems that the issue is due to the fact that the pointer input to the `Load` is a `Proj` but its input dies, so the cast `as_Multi` in `try_optimize_strict_final_load_memory` fails. I can see a similar check in `MemNode::optimize_simple_memory_chain`. As a result, it is reasonable to just return the top here.
> 
> Please take a look and leave your review, thanks a lot.

Quan Anh Mai has updated the pull request incrementally with one additional commit since the last revision:

  Enable tests from 8325632

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Changes:
  - all: https://git.openjdk.org/valhalla/pull/2016/files
  - new: https://git.openjdk.org/valhalla/pull/2016/files/1cbdd299..7e58fc3e

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=valhalla&pr=2016&range=01
 - incr: https://webrevs.openjdk.org/?repo=valhalla&pr=2016&range=00-01

  Stats: 6 lines in 2 files changed: 0 ins; 6 del; 0 mod
  Patch: https://git.openjdk.org/valhalla/pull/2016.diff
  Fetch: git fetch https://git.openjdk.org/valhalla.git pull/2016/head:pull/2016

PR: https://git.openjdk.org/valhalla/pull/2016