RFR: Harmonize actual and expected signature of Continuation.doYield

[Aleksey Shipilev]

On Thu, 14 Oct 2021 15:23:17 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Found this inconsistency when reading the Loom code during x86_32 porting. `Continuation.doYield` has an `int` argument, yet C2's `OptoRuntime::continuation_doYield_Type` does not declare it. I think this is basically asking for trouble in C2, as the optimizations may ask the function type, discover there is an input of type `int`, but no such input is actually present. Runtime stubs seem to be also oblivious there is an argument, and calling conventions probably put it in the register on x86_64 and AArch64. On other arches, that might not be true.
> 
> I don't believe it breaks anything now, but let's fix it, while we are at it. It looks to me that `Continuation.doYield` is ever called with `0`, so we might just drop its `int` argument? Not sure if `scopes` is something Java code plans to use.
> 
> Additional testing:
>  - [x] Linux x86_64 fastdebug, `jdk_loom hotspot_loom`

Cheers.

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PR: https://git.openjdk.java.net/loom/pull/78