RFR: 8293170: Improve encoding of the debuginfo nmethod section

[Vladimir Kozlov]

On Thu, 25 Aug 2022 14:35:32 GMT, Boris Ulasevich <bulasevich at openjdk.org> wrote:

> The nmethod "scopes data" section is 10% of the size of nmethod. Now the data is compressed using the Pack200 algorithm, which is good for encoding small integers (LineNumberTable, etc). Using the fact that half of the data in the partition contains zeros, I reduce its size by another 30%.
>  
> Testing: jtreg hotspot&jdk, Renaissance benchmarks

My builds failed:

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/code/CompressedSparceDataReadStream.java:42: warning: [lossy-conversions] implicit cast from int to byte in compound assignment is possibly lossy
       b |= (0xFF & curr_byte_) >> (8 - byte_pos_);
                                ^

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PR: https://git.openjdk.org/jdk/pull/10025