RFR: 8338532: Speed up the ClassFile API MethodTypeDesc#ofDescriptor

[Chen Liang]

On Mon, 19 Aug 2024 04:12:56 GMT, Shaojin Wen <duke at openjdk.org> wrote:

>> I think you can have the current patch RFR (ready for review) without this deduplication given my concerns. We can add deduplication of frequent descriptors in another patch after confirming it is a net positive.
>
> regionMatches uses vectorizedMismatch for comparison. The length of `Ljava/lang/Object;` is 18. In the code without intrinsic, it will exit after two long comparisons. If there is vector128 optimization, it will exit after one comparison, and the overhead is very small.

I think you can add a case where the parameters are all these vulnerable names like `Ljava/lang/Objecq;` and repeat 8 times, and see how big a negative impact these close mismatches have.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20611#discussion_r1721217799