RFR: 8325169: Reduce String::indexOf overheads [v2]

[Raffaello Giulietti]

On Fri, 2 Feb 2024 20:53:14 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> This patch streamlines and specializes various `String::indexOf` methods. Mainly avoids the need for clamping and doing checks that are redundant in almost all cases, moving the checks to the API boundary where they are needed. 
>> 
>> This improves performance both at peak and during startup/warmup. Since indexOf is heavily used in bootstrapping code it makes sense to slightly dial back abstraction and delegation, which in this case also brought some benefit to peak performance.
>> 
>> Testing: tier1-3
>
> Claes Redestad has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add comment about preconditions

LGTM

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Marked as reviewed by rgiulietti (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17685#pullrequestreview-1860479471