AndroidUseInterpreter should work in net6

[joj]

In .net4 AndroidUseInterpreter used to switch the runtime directory with one that includes an "-interpreter" suffix. That would automatically make the runtime use the interpreter. For net6, the runtime includes both versions in the package,
and the way to switch interpreter on is to add this environment variable:
debug.mono.runtime_args=--interp=-inline

The parameter is at the moment unchanged for net6, meaning that it adds a prefix that doesn't work anymore, and it doesn't do the environment, which is needed. The ask is to switch to that and then make sure interpreter works (that may require some help from mono runtime).

Thanks!
J

[jonathanpeppers]

This would be adding some new logic to:

https://github.com/xamarin/xamarin-android/blob/214dd76d9441c9974775f0b29feec0d5d8d1097f/src/Xamarin.Android.Build.Tasks/Xamarin.Android.Common.targets#L1503-L1518

Basically emit some extra @(AndroidEnvironment) lines for .NET 6 when $(AndroidUseInterpreter) is true.

An additional work item would be to standardize on an MSBuild property for both iOS/Android, as $(MTouchExtraArgs) is used for enabling the interpreter at the moment.

[lambdageek]

I tried AndroidUseInterpreter and it "works" in that the runtime tries to start up with interp support, but it breaks because it passes MONO_AOT_MODE_LAST which used to work with old mono, but not net6 mono.

I'm working on a PR to update to use MONO_AOT_MODE_INTERP_ONLY (on top of #5632)

Edit

The relevant runtime changes were to fix mono/mono#18893 - which was done in mono/mono#20159 - that PR went into dotnet/runtime master but not into mono/mono 2020-02. So the update to use MONO_AOT_MODE_INTERP_ONLY will be net6-only.

[lambdageek]

One thing we need to figure out for hot reload: we need to pass mono_ee_interp_init("-inline") some time shortly after mono_jit_set_aot_mode (mode); when hot reload is enabled.