[omworld-jdk] RFR: 8326752: Lilliput: OMCache: Add cache lookup unrolling [v3]

[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:

  Remove OMC2UnrollCacheLookup flag

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

Changes:
  - all: https://git.openjdk.org/lilliput/pull/139/files
  - new: https://git.openjdk.org/lilliput/pull/139/files/33cd0850..99147959

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=lilliput&pr=139&range=02
 - incr: https://webrevs.openjdk.org/?repo=lilliput&pr=139&range=01-02

  Stats: 24 lines in 3 files changed: 2 ins; 6 del; 16 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