RFR: 8008243: Zero: Implement fast bytecodes

[Aleksey Shipilev]

On Mon, 4 Jan 2021 19:32:09 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)

Hold on, bot, we are not done yet.

Not now, bot.

Not yet, bot.

Not now, bot.

Not now, bot. This is a draft PR.

Not now, bot. This is a draft PR.

This should wait for `tier1` stabilization for Zero. But otherwise it is still on track.

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