RFR: 8008243: Zero: Implement fast bytecodes [v2]

[Roman Kennke]

On Tue, 19 Oct 2021 10:00:17 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> This work improves Zero performance considerably, without complicating the interpreter all that much. This work is based on much earlier patch by @rkennke, then edited by @jerboaa, and finally polished by me here :)
>> 
>> SPECjvm benchmarks improve across the board, with lowest improvement on `Derby` (+6%) and largest on `Compress` (+50%). Given that Zero is used to implement the JVM on emerging platforms that are still rather slow themselves, it makes sense to make Zero quantifiably faster. Even 10% improvement means more than 2 hours a day worth of CPU time.
>> 
>> Additional testing:
>>  - [x] Linux x86_64 Zero fastdebug bootcycle-images
>>  - [x] Linux x86_64 Zero fastdebug fuzzer tests (no failures = no new behaviors introduced)
>
> Aleksey Shipilev has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - Remove shadowing "obj" to fix JVMTI tests
>  - Comment _fast_zputfield LSB
>  - MAYBE_POST_FIELD_MODIFICATION should check _putstatic

Nice work! Looks good to me! Thank you!

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Marked as reviewed by rkennke (Reviewer).

PR: https://git.openjdk.java.net/jdk/pull/1938