[lworld] RFR: 8255600: [lworld] C2 compilation fails with assert: modified node was not processed by IGVN.transform_old()

[Tobias Hartmann]

MergeMemStream might modify the MergeMem inputs. Simply put it on the worklist for now and investigate a proper fix with JDK-8247216.

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Commit messages:
 - 8255600: [lworld] C2 compilation fails with assert: modified node was not processed by IGVN.transform_old()

Changes: https://git.openjdk.java.net/valhalla/pull/248/files
 Webrev: https://webrevs.openjdk.java.net/?repo=valhalla&pr=248&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8255600
  Stats: 5 lines in 1 file changed: 5 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/valhalla/pull/248.diff
  Fetch: git fetch https://git.openjdk.java.net/valhalla pull/248/head:pull/248

PR: https://git.openjdk.java.net/valhalla/pull/248