RFR: 8370519: C2: Hit MemLimit when running with +VerifyLoopOptimizations [v4]

[Roland Westrelin]

> For this failure memory stats are:
> 
> 
> Total Usage: 1095525816 
>     --- Arena Usage by Arena Type and compilation phase, at arena usage peak of 1095525816 ---
>         Phase                         Total        ra      node      comp      type    states   reglive  regsplit   regmask superword     cienv        ha     other
>         none                        5976032    331560   5402064    197512     33712     10200         0         0       984         0         0         0         0
>         parse                       2716464     65456   1145480    196408   1112752         0         0         0         0         0    196368         0         0
>         optimizer                     98184         0     32728         0     65456         0         0         0         0         0         0         0         0
>         connectionGraph               32728         0         0     32728         0         0         0         0         0         0         0         0         0
>         iterGVN                       32728         0     32728         0         0         0         0         0         0         0         0         0         0
>         idealLoop                 918189632         0  38687056 872824784    392776         0         0         0         0         0   6285016         0         0
>         idealLoopVerify             2228144         0         0   2228144         0         0         0         0         0         0         0         0         0
>         macroExpand                   32728         0     32728         0         0         0         0         0         0         0         0         0         0
>         graphReshape                  32728         0     32728         0         0         0         0         0         0         0         0         0         0
>         matcher                    20135944   3369848   9033208   7536400     65456    131032         0         0         0         0         0         0         0
>         postselect_cleanup           294872    294872         0         0         0         0         0         0         0         0         0         0         0
>         scheduler                    752944    196488    556456         0         0         0         0         0         0         0         0         0         0
>         regalloc                     388736    388736         0         0         0         0         0         0         0         0         0         0         0
>         ctorChaitin                  160032    ...

Roland Westrelin has updated the pull request incrementally with three additional commits since the last revision:

 - Update test/hotspot/jtreg/compiler/c2/TestVerifyLoopOptimizationsHighMemUsage.java
   
   Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>
 - Update test/hotspot/jtreg/compiler/c2/TestVerifyLoopOptimizationsHighMemUsage.java
   
   Co-authored-by: Benoît Maillard <benoit.maillard at protonmail.com>
 - Update src/hotspot/share/opto/loopnode.hpp
   
   Co-authored-by: Emanuel Peter <emanuel.peter at oracle.com>

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/28581/files
  - new: https://git.openjdk.org/jdk/pull/28581/files/36fb3a6f..133fcddc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=28581&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=28581&range=02-03

  Stats: 4 lines in 2 files changed: 1 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk/pull/28581.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/28581/head:pull/28581

PR: https://git.openjdk.org/jdk/pull/28581