On Fri, 19 Jul 2024 21:42:09 GMT, Shaojin Wen <d...@openjdk.org> wrote:
>> Currently simpleConcat is implemented using mix and prepend, but in this >> simple scenario, it can be implemented in a simpler way and can improve >> performance. > > Shaojin Wen has updated the pull request incrementally with two additional > commits since the last revision: > > - Update src/java.base/share/classes/java/lang/String.java > > Co-authored-by: Chen Liang <li...@openjdk.org> > - add comments FWIW one of the ideas when implementing `StringConcatHelper.simpleConcat` was that by using the primitives used by the `StringConcatFactory` as straightforwardly as possible the method acts as a documentation-of-sorts or guide to understand how the `SCF` expression trees are built up. It's not perfect, though. Concatenation of a `String` + constant would be handled differently for one. So perhaps the value as a guide is not high. I'm also experimenting with replacing the MH-based strategy with spinning hidden, shareable classes instead. In that case we might actually be better off getting rid of the `long indexCoder` hacks and generate code more similar to the `doConcat` you've come up with here. The main benefit of combining `coder` and `index/length` into a single `long` was to reduce the MH combinator overheads, but if we're spinning code with access to optimized primitives then that isn't really needed. ------------- PR Comment: https://git.openjdk.org/jdk/pull/20253#issuecomment-2240412866
