RFR: 8289908: Skip bounds check for cases when String is constructed from entirely used byte[] [v2]

[Сергей Цыпанов]

On Fri, 8 Jul 2022 14:04:14 GMT, Roger Riggs <rriggs at openjdk.org> wrote:

>> But if I roll back the added constructor I'll go through existing public one `public String(byte[] bytes, int offset, int length, Charset charset)` doing bounds check twice, won't I?
>
> The new constructor looks very odd, especially when it does not have an explanation and doesn't describe the required preconditions for calling it.  Is there a better way than adding a non-functional argument?
> The "unused" name is going to draw a warning from IntelliJ and some enterprising developer is going to try to remove it, not understanding why its there. And there is a bit of overhead pushing the extra arg.
> 
> The constructor should be private, it has a very narrow scope of use given the lack of checking its args.
> 
> It would be nice if the Hotspot compiler would recognize the llmits on the range and optimize away the checks;
> it would have broader applicability then this point fix.
> I would be interesting to ask the compiler folks if that's a future optimization.
> These source changes make it harder to understand what's happening where; though that is sometimes work it for a noticeable performance improvement.

Well, we already have e.g. `String(char[], int, int, Void)` and `String(AbstractStringBuilder asb, Void sig)` where trailing argument is for disambiguation against private constructors. I did the same for mine and applied the same naming as in other trailing `Void` params.

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PR: https://git.openjdk.org/jdk/pull/9407