RFR: 8338745: Intrinsify Continuation.pin() and Continuation.unpin()

[Vladimir Kozlov]

On Wed, 21 Aug 2024 20:11:05 GMT, Markus Grönlund <mgronlun at openjdk.org> wrote:

> Greetings,
> 
> Please help review this change set that implements C2 intrinsics for jdk.internal.vm.Continuation.pin() and jdk.internal.vm.Continuation.unpin().
> 
> This work is a consequence of [JDK-8338417](https://bugs.openjdk.org/browse/JDK-8338417), which required us to introduce explicit pin constructs for Virtual threads in a relatively performance-sensitive path.
> 
> Testing: jdk_jfr, loom testing
> 
> Comment: I changed the type of the ContinuationEntry::_pin_count field from uint to uin32_t to make the size explicit and to access it uniformly from the intrinsic code using T_INT.
> 
> Thanks
> Markus

src/hotspot/share/opto/library_call.cpp line 3815:

> 3813: bool LibraryCallKit::inline_native_Continuation_unpin() {
> 3814:   return inline_native_Continuation_pinning_shared_impl(true);
> 3815: }

I don't see the need these 2 methods. You can directly call inline_native_Continuation_pinning_shared_impl() in switch in try_to_inline() and pass true or false there.
You may also rename it to `inline_native_Continuation_pinning()`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20664#discussion_r1725766345