[watch] MonoTouchFixtures.ObjCRuntime.RuntimeTest.UsableUntilDead fails on arm64_32

[lewurm]

Steps to Reproduce

1. build Xamarin.iOS that includes watch4 debug support (soon in master)
2. run monotouch-tests

Expected Behavior

MonoTouchFixtures.ObjCRuntime.RuntimeTest.UsableUntilDead should pass.

xamarin-macios/tests/monotouch-test/ObjCRuntime/RuntimeTest.cs

Lines 159 to 236 in e8a79fc

	[Test]
	public void UsableUntilDead ()
	{
	// The test can be inconclusive once in a while.
	// 100 times in a row is a bit too much though.
	for (int i = 0; i < 100; i++) {
	if (UsableUntilDeadImpl ())
	return;
	}
	Assert.Inconclusive ("Failed to collect the notification object at least once in 100 runs.");
	}
	public bool UsableUntilDeadImpl ()
	{
	// This test ensure that the main thread can send messages to a garbage collected object,
	// until the final 'release' message for the managed reference has been sent
	// (on the main thread).
	var notifierHandle = IntPtr.Zero;
	// bool isDeallocated = false;
	Action deallocated = () => {
	//Console.WriteLine ("Final release!");
	// isDeallocated = true;
	};
	ManualResetEvent isCollected = new ManualResetEvent (false);
	Action collected = () => {
	//Console.WriteLine ("Garbage collected!");
	isCollected.Set ();
	};
	bool isNotified = false;
	Action notified = () => {
	//Console.WriteLine ("Notified");
	isNotified = true;
	};
	// Create an object whose handle we store in a local variable. We do not
	// store the object itself, since we want the object to be garbage collected.
	var t = new Thread (() => {
	var obj = new Notifier (collected, notified);
	ReleaseNotifier.NotifyWhenDeallocated (obj, deallocated);
	notifierHandle = obj.Handle;
	}) {
	IsBackground = true,
	};
	t.Start ();
	t.Join ();
	// Now we have a handle to an object that may be garbage collected at any time.
	int counter = 0;
	do {
	GC.Collect ();
	GC.WaitForPendingFinalizers ();
	} while (counter++ < 10 && !isCollected.WaitOne (10));
	// Now we have a handle to a garbage collected object.
	if (!isCollected.WaitOne (0)) {
	// Objects may randomly not end up collected (at least in Boehm), because
	// other objects may happen to contain a random value pointing to the
	// object we're waiting to become freed.
	return false;
	}
	// Send a message to the collected object.
	Messaging.void_objc_msgSend (notifierHandle, Selector.GetHandle ("notify"));
	Assert.IsTrue (isNotified, "notified");
	// We're done. Cleanup.
	NSRunLoop.Main.RunUntil (NSDate.Now.AddSeconds (0.1));
	// Don't verify cleanup, it's not consistent.
	// And in any case it's not what this test is about.
	// Assert.IsTrue (isDeallocated, "released");
	return true;
	}

Actual Behavior

it crashes:

(lldb) c
Process 1251 resuming
Process 1251 stopped
* thread #10, name = 'tid_9a0b', stop reason = EXC_BAD_ACCESS (code=1, address=0x8)
    frame #0: 0x1b5826c4 libobjc.A.dylib`objc_msgSend + 36
libobjc.A.dylib`objc_msgSend:
->  0x1b5826c4 <+36>: ldp    w10, w11, [x16, #0x8]
    0x1b5826c8 <+40>: and    w11, w11, #0xffff
    0x1b5826cc <+44>: and    w12, w1, w11
    0x1b5826d0 <+48>: add    w12, w10, w12, lsl #3
Target 0: (monotouchtest) stopped.

(lldb) mbt
* thread #10
  * frame #0: 0x1b5826c4 libobjc.A.dylib`objc_msgSend + 36
    frame #1: 0x047397e8 monotouchtest`::xamarin_pinvoke_wrapper_void_objc_msgSend(receiver=0x19091ec0, selector=0x20fd9264) at pinvokes.m:420:4
    frame #2: 0x04a96b58 monotouchtest`do_icall(frame=<unavailable>, sig=0x181a8340, op=<unavailable>, sp=0x194bdb10, ptr=<unavailable>, save_last_error=0) at interp.c:1949:3 [opt]
    frame #3: 0x04a956ac monotouchtest`do_icall_wrapper(frame=0x194bdce8, sig=0x181a8340, op=547, sp=0x194bdb20, ptr=0x047397b8, save_last_error=0) at interp.c:2039:7 [opt]
    Messaging::void_objc_msgSend @ 34 "calli.nat.fast" || frame #4: 0x04a916e8 monotouchtest`interp_exec_method_full(frame=0x194bdce8, context=<unavailable>, clause_args=0x00000000, error=0x194be318) at interp.c:3238:9 [opt]
    RuntimeTest::UsableUntilDeadImpl @ 403567510 "vcall" || frame #5: 0x04a8d8ec monotouchtest`interp_exec_method_full(frame=0x194bde08, context=<unavailable>, clause_args=0x00000000, error=0x194be318) at interp.c:3410:4 [opt]
    RuntimeTest::UsableUntilDead @ 403566530 "call" || frame #6: 0x04a8d8ec monotouchtest`interp_exec_method_full(frame=0x194bdf38, context=<unavailable>, clause_args=0x00000000, error=0x194be318) at interp.c:3410:4 [opt]
    Object::runtime_invoke_direct_void__this__ @ 403566190 "vcall" || frame #7: 0x04a8d8ec monotouchtest`interp_exec_method_full(frame=0x194bdfe8, context=<unavailable>, clause_args=0x00000000, error=0x194be318) at interp.c:3410:4 [opt]