8326752: Lilliput: OMCache: Add cache lookup unrolling

[xmas92]

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

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
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• Commit message must refer to an issue

Issue

• JDK-8326752: Lilliput: OMCache: Add cache lookup unrolling (Sub-task - P4)

Reviewers

• Roman Kennke (@rkennke - Reviewer)

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/lilliput.git pull/139/head:pull/139
$ git checkout pull/139

Update a local copy of the PR:
$ git checkout pull/139
$ git pull https://git.openjdk.org/lilliput.git pull/139/head

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Checkout this PR locally:
$ git pr checkout 139

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$ git pr show -t 139

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

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[bridgekeeper]

👋 Welcome back aboldtch! A progress list of the required criteria for merging this PR into omworld-jdk will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[mlbridge]

Webrevs

• 02: Full - Incremental (99147959)
• 01: Full - Incremental (33cd0850)
• 00: Full (8dab34e5)

[rkennke]

Hi Axel, only some minor nits.

[rkennke]

There is a typo: Entires -> Entries

[rkennke]

Also, could perhaps collapse some flags, e.g. treat OMC2UnrollCacheEntries==0 as OMC2UnrollCacheLookup==false, and get rid of the latter.

[xmas92]

It was intentional, because I like+ vs - switching. But maybe unifying them is better so someone does not get confused if they see -XX:-OMC2UnrollCache -XX:OMC2UnrollCacheEntries=4 as an argument.
I'll change it.

[rkennke]

Looks good! Thank you!

[openjdk]

@xmas92 This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8326752: Lilliput: OMCache: Add cache lookup unrolling

Reviewed-by: rkennke

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At the time when this comment was updated there had been 1 new commit pushed to the omworld-jdk branch:

• ff713d9: 8326761: Lilliput: OMWorld: Fix invalid markWord transition

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[xmas92]

/integrate

[openjdk]

Going to push as commit 28bb8dd.
Since your change was applied there has been 1 commit pushed to the omworld-jdk branch:

• ff713d9: 8326761: Lilliput: OMWorld: Fix invalid markWord transition

Your commit was automatically rebased without conflicts.

[openjdk]

@xmas92 Pushed as commit 28bb8dd.

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