RFR: 8143900: OptimizeStringConcat has an opaque dependency on Integer.sizeTable field

[Yi Yang]

On Tue, 21 Feb 2023 02:29:44 GMT, Yi Yang <yyang at openjdk.org> wrote:

> Hi, can I have a review for this patch? I noticed a strange field Integer.sizeTable which is used by PhaseStringOpts, after digging into the history, I think it could be replaced by an in-place array allocation and initialization. Before it, we are fetching from Integer.sizeTable and get num of digit in integer by iterating size table, now we fetch from in-place sizeTable and get size from that. The changed IR looks like this:
> 
> ![image](https://user-images.githubusercontent.com/5010047/220239446-7b8b8381-b300-4f2c-a24a-aa19ec9e2f88.png)
> 
> Thanks.

I updated this patch to use the algorithm identical to Integer.stringSize.

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PR: https://git.openjdk.org/jdk/pull/12680