Integrated: 8255822: Zero: improve build-time JVMTI handling

[Aleksey Shipilev]

On Wed, 4 Nov 2020 16:29:27 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Current Zero interpreter has the optimization for JVMTI support. It recognizes that JVMTI is disabled most of the time, and that JVMTI checks in the interpreter code slows it down considerably. (I measured it myself when working on this patch: removing this optimization yields about 20% hit in build times).
> 
> Current optimization works as follows. At build time, an XSLT transform is performed on `bytecodeInterpreter.cpp`, yielding `bytecodeInterpreterWithChecks.cpp`. In that new compilation unit, `VM_JVMTI` macro is defined, and a new entry point -- `BytecodeInterpreter::withChecks` -- is defined. Then, both compilation units are compiled. In one of them, `JVMTI` hooks are stripped out. In another, they persist. Then, callers have to choose which entry point to use.
> 
> I believe this can be rewritten to use C++ templates instead of XLST and defines dance. This also allows to clean up JVMTI checks a bit.
> 
> Additional testing:
>  - [x] Linux x86_64 Zero fastdebug build with `-jvmti`
>  - [x] Linux x86_64 Zero fastdebug/release build times are not regressing

This pull request has now been integrated.

Changeset: 643969a1
Author:    Aleksey Shipilev <shade at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/643969a1
Stats:     188 lines in 6 files changed: 5 ins; 128 del; 55 mod

8255822: Zero: improve build-time JVMTI handling

Reviewed-by: dholmes, ihse

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PR: https://git.openjdk.java.net/jdk/pull/1061