8212597: Optimize String concatenation setup when using primitive operands

[antbob]

This is a backport of b3b41df / JDK-8212597

This backport is needed to facilitate clean backports of various String concat improvements that are on todo list for 11 which are otherwise very complex and high risk to rework:

JDK-8212726 Replace some use of drop- and foldArguments with filtering argument combinator in StringConcatFactory
JDK-8213035 Pack MethodHandleInlineStrategy coder and length into a long
JDK-8213478 Reduce rebinds when applying repeated filters and conversions
JDK-8222852 Reduce String concat combinator tree shapes by folding constants into prependers
JDK-8223454 Reduce String concatenation shapes by folding initialLengthCoder into last mixer

This is a clean backport.

Testing: x86_64 build, tier1

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8212597 needs maintainer approval

Issue

• JDK-8212597: Optimize String concatenation setup when using primitive operands (Enhancement - P4 - Rejected)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk11u-dev.git pull/2813/head:pull/2813
$ git checkout pull/2813

Update a local copy of the PR:
$ git checkout pull/2813
$ git pull https://git.openjdk.org/jdk11u-dev.git pull/2813/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 2813

View PR using the GUI difftool:
$ git pr show -t 2813

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk11u-dev/pull/2813.diff

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[bridgekeeper]

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

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[openjdk]

This backport pull request has now been updated with issue from the original commit.

[openjdk]

⚠️ @antbob This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[mlbridge]

Webrevs

• 00: Full (d2059d7a)

[antbob]

/approval request This backport is needed to facilitate clean backports of various String concat improvements, see PR description for further details

[openjdk]

@antbob
8212597: The approval request has been created successfully.

[antbob]

after discussion with 11u maintainers this backport, as well as related backports listed in the PR description above, were deemed too risky to bring over as they are improvements and not critical bug fixes, closing this.