RFR: 8321620: Optimize JImage decompressors

[Glavo]

On Fri, 8 Dec 2023 22:38:56 GMT, Claes Redestad <redestad at openjdk.org> wrote:

>> Does anyone want to take a look at this PR?
>
>> Does anyone want to take a look at this PR?
> 
> RFE: https://bugs.openjdk.org/browse/JDK-8321620 - update the bug ID and this should PR should reach a wider audience. I'll have some time next week to help review.

@cl4es 

> While the improvement to --compress 1 are impressive, this compression mode is effectively deprecated.

I noticed the deprecation warning before creating this PR, so I did some research.

This warning was introduced here: https://github.com/openjdk/jdk/pull/11617. In the discussion of that PR I learned that the option `--compress 1` was deprecated because it was not compression but string sharing. The string sharing plugin is not actually deprecated, it's just that it may be renamed in the future.

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PR Comment: https://git.openjdk.org/jdk/pull/16556#issuecomment-1889649725