compiler: handle async RPC as last statement in try block.

Fixes #1107.

artiq/compiler/transforms/llvm_ir_generator.py

@@ -1339,6 +1339,12 @@ class LLVMIRGenerator:
         self.llbuilder.call(self.llbuiltin("llvm.stackrestore"), [llstackptr])
 
         if fun_type.async:
+            # If this RPC is called using an `invoke` ARTIQ IR instruction, there will be
+            # no other instructions in this basic block. Since this RPC is async, it cannot
+            # possibly raise an exception, so add an explicit jump to the normal successor.
+            if llunwindblock:
+                self.llbuilder.branch(llnormalblock)
+
             return ll.Undefined
 
         # T result = {

artiq/test/coredevice/test_embedding.py

@@ -223,6 +223,17 @@ class _RPCCalls(EnvExperiment):
     def builtin(self):
         sleep(1.0)
 
+    @rpc(flags={"async"})
+    def async_rpc(self):
+        pass
+
+    @kernel
+    def async_in_try(self):
+        try:
+            self.async_rpc()
+        except ValueError:
+            pass
+
 
 class RPCCallsTest(ExperimentCase):
     def test_args(self):
@@ -239,6 +250,7 @@ class RPCCallsTest(ExperimentCase):
         self.assertTrue((exp.numpy_full() == numpy.full(10, 20)).all())
         self.assertTrue(numpy.isnan(exp.numpy_nan()).all())
         exp.builtin()
+        exp.async_in_try()
 
 
 class _Annotation(EnvExperiment):