[omworld-jdk] RFR: 8326752: Lilliput: OMCache: Add cache lookup unrolling [v2]

[Axel Boldt-Christmas]

> Implement unrolling of OM cache lookups in C2 so experiments and an evaluation can be performed.
> 
> Adds `OMC2UnrollCacheLookup`, `OMC2UnrollCacheLookupLoopTail` and `OMC2UnrollCacheEntires` flags which can be tuned cache lookup unrolling in C2. 
> 
> `OMC2UnrollCacheLookup` will unroll up to `OMC2UnrollCacheEntires` (depending on `OMCacheSize`) and if `OMC2UnrollCacheLookupLoopTail` is set and entries are left the rest of the cache will be checked.
> 
> All of these flags are temporary to allow for evaluation of the cache lookup in C2 (size and unrolling). See issue JDK-8326759

Axel Boldt-Christmas has updated the pull request incrementally with one additional commit since the last revision:

  Fix spelling

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Changes:
  - all: https://git.openjdk.org/lilliput/pull/139/files
  - new: https://git.openjdk.org/lilliput/pull/139/files/8dab34e5..33cd0850

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=lilliput&pr=139&range=01
 - incr: https://webrevs.openjdk.org/?repo=lilliput&pr=139&range=00-01

  Stats: 3 lines in 3 files changed: 0 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/lilliput/pull/139.diff
  Fetch: git fetch https://git.openjdk.org/lilliput.git pull/139/head:pull/139

PR: https://git.openjdk.org/lilliput/pull/139