RFR: 8327247: C2 uses up to 2GB of RAM to compile complex string concat in extreme cases [v4]

[Claes Redestad]

> Splitting out the ASM-based version from #18690 to push that first under the JBS (to help backporting). Keeping #18690 open to rebase and follow-up on this as a subtask. See discussion in that #18690 for more details, discussion and motivation for this.

Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:

  Fix nits, use iconst as intended

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Changes:
  - all: https://git.openjdk.org/jdk/pull/18953/files
  - new: https://git.openjdk.org/jdk/pull/18953/files/591d2d1c..9b083f4b

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=18953&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=18953&range=02-03

  Stats: 9 lines in 1 file changed: 1 ins; 3 del; 5 mod
  Patch: https://git.openjdk.org/jdk/pull/18953.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18953/head:pull/18953

PR: https://git.openjdk.org/jdk/pull/18953