RFR: 8318457: Use prefix-less prepend methods directly to reduce branches in String concat expressions [v2]

[Chen Liang]

On Thu, 19 Oct 2023 11:39:24 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> In #16006 using `StringConcatFactory` seem to induce a run-to-run variance. One idea to reduce this is to generate expression trees with fewer branches by looking up and using the prefix-less `prepend` methods directly for cases where constant is null/empty so that the prefixed prepender will always deal with a non-null prefix constant.
>
> Claes Redestad has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - dropLookupMode PRIVATE to ensure we don't accidentally use private methods
>  - Make all prepend methods package-private

Marked as reviewed by liach (Author).

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PR Review: https://git.openjdk.org/jdk/pull/16244#pullrequestreview-1687451479