compiler.transforms.inferencer: accept and ignore @kernel decorator.

artiq/compiler/builtins.py

@@ -146,6 +146,9 @@ def fn_round():
 def fn_print():
     return types.TBuiltinFunction("print")
 
+def fn_kernel():
+    return types.TBuiltinFunction("kernel")
+
 def fn_syscall():
     return types.TBuiltinFunction("syscall")
 

artiq/compiler/prelude.py

@@ -19,5 +19,6 @@ def globals():
         "len":                  builtins.fn_len(),
         "round":                builtins.fn_round(),
         "print":                builtins.fn_print(),
+        "kernel":               builtins.fn_kernel(),
         "syscall":              builtins.fn_syscall(),
     }

artiq/compiler/transforms/inferencer.py

@@ -887,10 +887,13 @@ class Inferencer(algorithm.Visitor):
                         arg.loc, default.loc)
 
     def visit_FunctionDefT(self, node):
-        if any(node.decorator_list):
+        for index, decorator in enumerate(node.decorator_list):
+            if types.is_builtin(decorator.type, "kernel"):
+                continue
+
             diag = diagnostic.Diagnostic("error",
                 "decorators are not supported", {},
-                node.at_locs[0], [node.decorator_list[0].loc])
+                node.at_locs[index], [decorator.loc])
             self.engine.process(diag)
             return