RFR: 8008243: Zero: Implement fast bytecodes [v4]

[Jie Fu]

On Wed, 10 Nov 2021 11:31:57 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 `tier1`
>>  - [x] Linux x86_64 Zero fastdebug fuzzer tests (no failures = no new behaviors introduced)
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains ten commits:
> 
>  - Merge branch 'master' into JDK-8008243-zero-fast-bytecodes
>  - Merge branch 'master' into JDK-8008243-zero-fast-bytecodes
>  - Merge branch 'master' into JDK-8008243-zero-fast-bytecodes
>  - Rework feature flag as template argument
>  - Guard the rewrites with feature flags
>  - Remove shadowing "obj" to fix JVMTI tests
>  - Comment _fast_zputfield LSB
>  - MAYBE_POST_FIELD_MODIFICATION should check _putstatic
>  - Base implementation

A regression was found here: https://github.com/openjdk/jdk/pull/6479
Please review.
Thanks.

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