RFR: 8275586: Zero: Simplify interpreter initialization

[Andrew Haley]

On Wed, 20 Oct 2021 07:44:36 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> The prolog in `BytecodeInterpreter` is hairy due to early initialization of interpreter statics. Previous rewrites make it mostly redundant, and we can now simplify it.
> 
> This also implicitly fixes a initialization bug. If `JvmtiExport::can_post_interpreter_events()` changes at runtime, we will call into the uninitialized version:
> 
> 
>     // Call the interpreter
>     if (JvmtiExport::can_post_interpreter_events()) {
>       BytecodeInterpreter::run<true>(istate);
>     } else {
>       BytecodeInterpreter::run<false>(istate);
>     } 
> 
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug `make bootcycle-images`

Marked as reviewed by aph (Reviewer).

src/hotspot/share/interpreter/zero/bytecodeInterpreter.cpp line 417:

> 415: #define THREAD istate->thread()
> 416: #endif
> 417: 

This is a weirdly-hacky optimization, and is perhaps obsolete on modern compilers. While simplifying, I'd take it out.

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PR: https://git.openjdk.java.net/jdk/pull/6029