8357289: Break down the String constructor into smaller methods

[wenshao]

Through JVM Option +PrintInlining, we found that String has a constructor codeSize of 852, which is too large. This caused failed to inline.

The following is the output information of PrintInlining:

                @ 9   java.lang.String::<init> (12 bytes)   inline (hot)
!m                 @ 1   java.nio.charset.Charset::defaultCharset (52 bytes)   inline (hot)
!                  @ 8   java.lang.String::<init> (852 bytes)   failed to inline: hot method too big

In Java code, the big method that cannot be inlined is the following constructor

String(Charset charset, byte[] bytes, int offset, int length) {}

The above String constructor is too large; break it down into smaller methods with a codeSize under 325 to allow them to be inlined by the C2.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8357289 needs maintainer approval

Issue

• JDK-8357289: Break down the String constructor into smaller methods (Enhancement - P4 - Requested)

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[wenshao]

/label add backport

[bridgekeeper]

👋 Welcome back swen! 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]

@wenshao
The label backport is not a valid label.
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[mlbridge]

Webrevs

• 01: Full - Incremental (b6c666e4)
• 00: Full (38e36d63)

[openjdk]

@wenshao Please do not rebase or force-push to an active PR as it invalidates existing review comments. Note for future reference, the bots always squash all changes into a single commit automatically as part of the integration. See OpenJDK Developers’ Guide for more information.

[wenshao]

/label add backport

[openjdk]

@wenshao
The label backport is not a valid label.
These labels are valid:

[openjdk]

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

[openjdk]

⚠️ @wenshao 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.

[wenshao]

/approval

[openjdk]

@wenshao usage: /approval [<id>] (request|cancel) [<text>]

[wenshao]

/approval 8357289 request speed up new String from bytes

[openjdk]

@wenshao
8357289: The approval request has been created successfully.