[SceneKit] Update for Xcode 11

[VincentDondain]

And Xcode 11.1 by extension but nothing changed.

Note: it's the first time Vector3 are used in SceneKit APIs (usually it's SCNVector3).

It's debatable if we actually want to expose those APIs but it doesn't look like there are alternatives to those APIs.
In the case of other simd specific APIs using Vector3 or Vector4, we did not port them because they had an SCNVector equivalent (the simd being only more performant for Apple, not for us).

[prmallic]

Noob question - What does the MarshalDirective do here? Does NativePrefix = "xamarin_simd__" mean that this binding has something to do AOT compilation?

[rolfbjarne]

MarshalDirective is a workaround we have to work around a calling convention limitation with P/Invokes.

The problem is that certain native types (such as Vector3) are not put in the normal registers when used as parameters to methods, instead they're passed in special SIMD registers. Unfortunately managed code (i.e. P/Invokes) doesn't know about this, so we can't call these native methods using P/Invokes because the arguments would be in the wrong registers.

Our workaround is a bit involved: we generate a native wrapper method where the parameters are passed in the expected registers, and that calls the actual native function, so that the native compiler puts the arguments in the right registers. The MarshalDirective attribute tells the generator that it should generate a call to the wrapper method instead of the normal P/Invoke (and that the name of the wrapper method is the name of the native function prefixed by xamarin_simd__, and the library where the wrapper method is located - __Internal means the executable itself).

[prmallic]

🤯 (takes it in slowly)
Thanks! 😃

[monojenkins]

Build failure
✅ Build succeeded
✅ API Diff (from stable)
ℹ️ API Diff (from PR only) (please review changes)
ℹ️ Generator Diff (please review changes)
🔥 Test run failed 🔥

Test results

1 tests failed, 86 tests passed.

Failed tests

• monotouch-test/watchOS 32-bits - simulator/Release (all optimizations): Failed

[rolfbjarne]

Everything is XAMCORE_2_0 now, so this #if is not needed.

[VincentDondain]

True it's redundant but the PR is mergeable right now so I'm not gonna rebuild it (:
Will avoid next time.

[rolfbjarne]

MarshalDirective is a workaround we have to work around a calling convention limitation with P/Invokes.

The problem is that certain native types (such as Vector3) are not put in the normal registers when used as parameters to methods, instead they're passed in special SIMD registers. Unfortunately managed code (i.e. P/Invokes) doesn't know about this, so we can't call these native methods using P/Invokes because the arguments would be in the wrong registers.

Our workaround is a bit involved: we generate a native wrapper method where the parameters are passed in the expected registers, and that calls the actual native function, so that the native compiler puts the arguments in the right registers. The MarshalDirective attribute tells the generator that it should generate a call to the wrapper method instead of the normal P/Invoke (and that the name of the wrapper method is the name of the native function prefixed by xamarin_simd__, and the library where the wrapper method is located - __Internal means the executable itself).

[VincentDondain]

Known watchOS issue: https://github.com/xamarin/maccore/issues/1605

[FAIL] NSMutableDictionary2Test.AddEntries :   ICE 1