Implement syscalls for the new compiler.

artiq/compiler/embedding.py

@@ -238,6 +238,10 @@ class Stitcher:
         name     = function.__code__.co_name
 
         source_line = linecache.getline(filename, line)
+        while source_line.lstrip().startswith("@"):
+            line += 1
+            source_line = linecache.getline(filename, line)
+
         column = re.search("def", source_line).start(0)
         source_buffer = source.Buffer(source_line, filename, line)
         return source.Range(source_buffer, column, column)
@@ -248,8 +252,13 @@ class Stitcher:
             {"function": function.__name__},
             self._function_loc(function))
 
-    def _extract_annot(self, function, annot, kind, call_loc):
+    def _extract_annot(self, function, annot, kind, call_loc, is_syscall):
         if not isinstance(annot, types.Type):
+            if is_syscall:
+                note = diagnostic.Diagnostic("note",
+                    "in system call here", {},
+                    call_loc)
+            else:
                 note = diagnostic.Diagnostic("note",
                     "in function called remotely here", {},
                     call_loc)
@@ -264,11 +273,19 @@ class Stitcher:
         else:
             return annot
 
-    def _type_of_param(self, function, loc, param):
+    def _type_of_param(self, function, loc, param, is_syscall):
         if param.annotation is not inspect.Parameter.empty:
             # Type specified explicitly.
             return self._extract_annot(function, param.annotation,
-                                       "argument {}".format(param.name), loc)
+                                       "argument '{}'".format(param.name), loc,
+                                       is_syscall)
+        elif is_syscall:
+            # Syscalls must be entirely annotated.
+            diag = diagnostic.Diagnostic("error",
+                "system call argument '{argument}' must have a type annotation",
+                {"argument": param.name},
+                self._function_loc(function))
+            self.engine.process(diag)
         elif param.default is not inspect.Parameter.empty:
             # Try and infer the type from the default value.
             # This is tricky, because the default value might not have
@@ -281,8 +298,8 @@ class Stitcher:
             def proxy_diagnostic(diag):
                 note = diagnostic.Diagnostic("note",
                     "expanded from here while trying to infer a type for an"
-                    " unannotated optional argument '{param_name}' from its default value",
+                    " unannotated optional argument '{argument}' from its default value",
-                    {"param_name": param.name},
+                    {"argument": param.name},
                     loc)
                 diag.notes.append(note)
 
@@ -300,7 +317,7 @@ class Stitcher:
             # Let the rest of the program decide.
             return types.TVar()
 
-    def _quote_rpc_function(self, function, loc):
+    def _quote_foreign_function(self, function, loc, syscall):
         signature = inspect.signature(function)
 
         arg_types = OrderedDict()
@@ -318,33 +335,54 @@ class Stitcher:
                 continue
 
             if param.default is inspect.Parameter.empty:
-                arg_types[param.name] = self._type_of_param(function, loc, param)
+                arg_types[param.name] = self._type_of_param(function, loc, param,
+                                                            is_syscall=syscall is not None)
+            elif syscall is None:
+                optarg_types[param.name] = self._type_of_param(function, loc, param,
+                                                               is_syscall=syscall is not None)
             else:
-                optarg_types[param.name] = self._type_of_param(function, loc, param)
+                diag = diagnostic.Diagnostic("error",
-
+                    "system call argument '{argument}' must not have a default value",
-        if signature.return_annotation is not inspect.Signature.empty:
+                    {"argument": param.name},
-            ret_type = self._extract_annot(function, signature.return_annotation,
-                                           "return type", loc)
-        else:
-            diag = diagnostic.Diagnostic("fatal",
-                "function must have a return type specified to be called remotely", {},
                     self._function_loc(function))
                 self.engine.process(diag)
 
-        rpc_type = types.TRPCFunction(arg_types, optarg_types, ret_type,
+        if signature.return_annotation is not inspect.Signature.empty:
+            ret_type = self._extract_annot(function, signature.return_annotation,
+                                           "return type", loc, is_syscall=syscall is not None)
+        elif syscall is None:
+            diag = diagnostic.Diagnostic("error",
+                "function must have a return type annotation to be called remotely", {},
+                self._function_loc(function))
+            self.engine.process(diag)
+            ret_type = types.TVar()
+        else: # syscall is not None
+            diag = diagnostic.Diagnostic("error",
+                "system call must have a return type annotation", {},
+                self._function_loc(function))
+            self.engine.process(diag)
+            ret_type = types.TVar()
+
+        if syscall is None:
+            function_type = types.TRPCFunction(arg_types, optarg_types, ret_type,
                                                service=self._map(function))
+            function_name = "__rpc_{}__".format(function_type.service)
+        else:
+            function_type = types.TCFunction(arg_types, ret_type,
+                                             name=syscall)
+            function_name = "__ffi_{}__".format(function_type.name)
 
-        rpc_name = "__rpc_{}__".format(rpc_type.service)
+        self.globals[function_name] = function_type
-        self.globals[rpc_name] = rpc_type
+        self.functions[function] = function_name
-        self.functions[function] = rpc_name
 
-        return rpc_name
+        return function_name
 
     def _quote_function(self, function, loc):
         if function in self.functions:
             return self.functions[function]
 
         if hasattr(function, "artiq_embedded"):
+            if function.artiq_embedded.function is not None:
                 # Insert the typed AST for the new function and restart inference.
                 # It doesn't really matter where we insert as long as it is before
                 # the final call.
@@ -352,10 +390,18 @@ class Stitcher:
                 self.typedtree.insert(0, function_node)
                 self.inference_finished = False
                 return function_node.name
+            elif function.artiq_embedded.syscall is not None:
+                # Insert a storage-less global whose type instructs the compiler
+                # to perform a system call instead of a regular call.
+                return self._quote_foreign_function(function, loc,
+                                                    syscall=function.artiq_embedded.syscall)
+            else:
+                assert False
         else:
             # Insert a storage-less global whose type instructs the compiler
             # to perform an RPC instead of a regular call.
-            return self._quote_rpc_function(function, loc)
+            return self._quote_foreign_function(function, loc,
+                                                syscall=None)
 
     def stitch_call(self, function, args, kwargs):
         function_node = self._quote_embedded_function(function)

artiq/compiler/transforms/llvm_ir_generator.py

@@ -175,7 +175,7 @@ class LLVMIRGenerator:
         typ = typ.find()
         if types.is_tuple(typ):
             return ll.LiteralStructType([self.llty_of_type(eltty) for eltty in typ.elts])
-        elif types.is_rpc_function(typ):
+        elif types.is_rpc_function(typ) or types.is_c_function(typ):
             if for_return:
                 return llvoid
             else:
@@ -731,11 +731,20 @@ class LLVMIRGenerator:
         return llvalue
 
     def _prepare_closure_call(self, insn):
-        llclosure, llargs = self.map(insn.target_function()), map(self.map, insn.arguments())
+        llclosure = self.map(insn.target_function())
+        llargs    = [self.map(arg) for arg in insn.arguments()]
         llenv     = self.llbuilder.extract_value(llclosure, 0)
         llfun     = self.llbuilder.extract_value(llclosure, 1)
         return llfun, [llenv] + list(llargs)
 
+    def _prepare_ffi_call(self, insn):
+        llargs    = [self.map(arg) for arg in insn.arguments()]
+        llfunty   = ll.FunctionType(self.llty_of_type(insn.type, for_return=True),
+                                    [llarg.type for llarg in llargs])
+        llfun     = ll.Function(self.llmodule, llfunty,
+                                insn.target_function().type.name)
+        return llfun, list(llargs)
+
     # See session.c:{send,receive}_rpc_value and comm_generic.py:_{send,receive}_rpc_value.
     def _rpc_tag(self, typ, error_handler):
         if types.is_tuple(typ):
@@ -869,6 +878,10 @@ class LLVMIRGenerator:
                                    insn.target_function().type,
                                    insn.arguments(),
                                    llnormalblock=None, llunwindblock=None)
+        elif types.is_c_function(insn.target_function().type):
+            llfun, llargs = self._prepare_ffi_call(insn)
+            return self.llbuilder.call(llfun, llargs,
+                                       name=insn.name)
         else:
             llfun, llargs = self._prepare_closure_call(insn)
             return self.llbuilder.call(llfun, llargs,
@@ -882,6 +895,10 @@ class LLVMIRGenerator:
                                    insn.target_function().type,
                                    insn.arguments(),
                                    llnormalblock, llunwindblock)
+        elif types.is_c_function(insn.target_function().type):
+            llfun, llargs = self._prepare_ffi_call(insn)
+            return self.llbuilder.invoke(llfun, llargs, llnormalblock, llunwindblock,
+                                         name=insn.name)
         else:
             llfun, llargs = self._prepare_closure_call(insn)
             return self.llbuilder.invoke(llfun, llargs, llnormalblock, llunwindblock,

artiq/compiler/types.py

@@ -258,6 +258,26 @@ class TRPCFunction(TFunction):
         else:
             raise UnificationError(self, other)
 
+class TCFunction(TFunction):
+    """
+    A function type of a runtime-provided C function.
+
+    :ivar name: (str) C function name
+    """
+
+    def __init__(self, args, ret, name):
+        super().__init__(args, OrderedDict(), ret)
+        self.name = name
+
+    def unify(self, other):
+        if isinstance(other, TCFunction) and \
+                self.name == other.name:
+            super().unify(other)
+        elif isinstance(other, TVar):
+            other.unify(self)
+        else:
+            raise UnificationError(self, other)
+
 class TBuiltin(Type):
     """
     An instance of builtin type. Every instance of a builtin
@@ -371,6 +391,9 @@ def is_function(typ):
 def is_rpc_function(typ):
     return isinstance(typ.find(), TRPCFunction)
 
+def is_c_function(typ):
+    return isinstance(typ.find(), TCFunction)
+
 def is_builtin(typ, name=None):
     typ = typ.find()
     if name is None:
@@ -423,7 +446,7 @@ class TypePrinter(object):
                 return "(%s,)" % self.name(typ.elts[0])
             else:
                 return "(%s)" % ", ".join(list(map(self.name, typ.elts)))
-        elif isinstance(typ, (TFunction, TRPCFunction)):
+        elif isinstance(typ, (TFunction, TRPCFunction, TCFunction)):
             args = []
             args += [ "%s:%s" % (arg, self.name(typ.args[arg]))    for arg in typ.args]
             args += ["?%s:%s" % (arg, self.name(typ.optargs[arg])) for arg in typ.optargs]
@@ -431,6 +454,8 @@ class TypePrinter(object):
 
             if isinstance(typ, TRPCFunction):
                 return "rpc({}) {}".format(typ.service, signature)
+            if isinstance(typ, TCFunction):
+                return "ffi({}) {}".format(repr(typ.name), signature)
             elif isinstance(typ, TFunction):
                 return signature
         elif isinstance(typ, TBuiltinFunction):

artiq/coredevice/core.py

@@ -1,9 +1,9 @@
-import sys, tempfile
+import sys
 
 from pythonparser import diagnostic
 
 from artiq.language.core import *
-from artiq.language.units import ns
+from artiq.language.types import *
 
 from artiq.compiler import Stitcher, Module
 from artiq.compiler.targets import OR1KTarget
@@ -15,6 +15,11 @@ from artiq.coredevice import exceptions
 class CompileError(Exception):
     pass
 
+
+@syscall
+def rtio_get_counter() -> TInt64:
+    raise NotImplementedError("syscall not simulated")
+
 class Core:
     def __init__(self, dmgr, ref_period=8*ns, external_clock=False):
         self.comm = dmgr.get("comm")
@@ -58,8 +63,8 @@ class Core:
 
     @kernel
     def get_rtio_counter_mu(self):
-        return syscall("rtio_get_counter")
+        return rtio_get_counter()
 
     @kernel
     def break_realtime(self):
-        at_mu(syscall("rtio_get_counter") + 125000)
+        at_mu(rtio_get_counter() + 125000)

artiq/coredevice/dds.py

@@ -9,6 +9,24 @@ PHASE_MODE_ABSOLUTE = 1
 PHASE_MODE_TRACKING = 2
 
 
+@syscall
+def dds_init(time_mu: TInt64, channel: TInt32) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+@syscall
+def dds_batch_enter(time_mu: TInt64) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+@syscall
+def dds_batch_exit() -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+@syscall
+def dds_set(time_mu: TInt64, channel: TInt32, ftw: TInt32,
+            pow: TInt32, phase_mode: TInt32) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+
 class _BatchContextManager:
     def __init__(self, dds_bus):
         self.dds_bus = dds_bus
@@ -34,13 +52,13 @@ class DDSBus:
     def batch_enter(self):
         """Starts a DDS command batch. All DDS commands are buffered
         after this call, until ``batch_exit`` is called."""
-        syscall("dds_batch_enter", now_mu())
+        dds_batch_enter(now_mu())
 
     @kernel
     def batch_exit(self):
         """Ends a DDS command batch. All buffered DDS commands are issued
         on the bus, and FUD is pulsed at the time the batch started."""
-        syscall("dds_batch_exit")
+        dds_batch_exit()
 
 
 class _DDSGeneric:
@@ -91,7 +109,7 @@ class _DDSGeneric:
         """Resets and initializes the DDS channel.
 
         The runtime does this for all channels upon core device startup."""
-        syscall("dds_init", now_mu(), self.channel)
+        dds_init(now_mu(), self.channel)
 
     @kernel
     def set_phase_mode(self, phase_mode):
@@ -128,7 +146,7 @@ class _DDSGeneric:
         """
         if phase_mode == _PHASE_MODE_DEFAULT:
             phase_mode = self.phase_mode
-        syscall("dds_set", now_mu(), self.channel,
+        dds_set(now_mu(), self.channel,
            frequency, round(phase*2**self.pow_width), phase_mode)
 
     @kernel

artiq/coredevice/runtime.py

@@ -1,134 +0,0 @@
-import os
-
-import llvmlite_or1k.ir as ll
-import llvmlite_or1k.binding as llvm
-
-from artiq.language import units
-
-_syscalls = {
-    "now_init": "n:I",
-    "now_save": "I:n",
-    "watchdog_set": "i:i",
-    "watchdog_clear": "i:n",
-    "rtio_get_counter": "n:I",
-    "ttl_set_o": "Iib:n",
-    "ttl_set_oe": "Iib:n",
-    "ttl_set_sensitivity": "Iii:n",
-    "ttl_get": "iI:I",
-    "ttl_clock_set": "Iii:n",
-    "dds_init": "Ii:n",
-    "dds_batch_enter": "I:n",
-    "dds_batch_exit": "n:n",
-    "dds_set": "Iiiii:n",
-}
-
-
-def _chr_to_type(c):
-    if c == "n":
-        return ll.VoidType()
-    if c == "b":
-        return ll.IntType(1)
-    if c == "i":
-        return ll.IntType(32)
-    if c == "I":
-        return ll.IntType(64)
-    raise ValueError
-
-
-def _str_to_functype(s):
-    assert(s[-2] == ":")
-    type_ret = _chr_to_type(s[-1])
-    type_args = [_chr_to_type(c) for c in s[:-2] if c != "n"]
-    return ll.FunctionType(type_ret, type_args)
-
-
-def _chr_to_value(c):
-    if c == "n":
-        return base_types.VNone()
-    if c == "b":
-        return base_types.VBool()
-    if c == "i":
-        return base_types.VInt()
-    if c == "I":
-        return base_types.VInt(64)
-    raise ValueError
-
-
-def _value_to_str(v):
-    if isinstance(v, base_types.VNone):
-        return "n"
-    if isinstance(v, base_types.VBool):
-        return "b"
-    if isinstance(v, base_types.VInt):
-        if v.nbits == 32:
-            return "i"
-        if v.nbits == 64:
-            return "I"
-        raise ValueError
-    if isinstance(v, base_types.VFloat):
-        return "f"
-    if isinstance(v, fractions.VFraction):
-        return "F"
-    if isinstance(v, lists.VList):
-        return "l" + _value_to_str(v.el_type)
-    raise ValueError
-
-
-class LinkInterface:
-    def init_module(self, module):
-        self.module = module
-        llvm_module = self.module.llvm_module
-
-        # RPC
-        func_type = ll.FunctionType(ll.IntType(32), [ll.IntType(32)],
-                                    var_arg=1)
-        self.rpc = ll.Function(llvm_module, func_type, "__syscall_rpc")
-
-        # syscalls
-        self.syscalls = dict()
-        for func_name, func_type_str in _syscalls.items():
-            func_type = _str_to_functype(func_type_str)
-            self.syscalls[func_name] = ll.Function(
-                llvm_module, func_type, "__syscall_" + func_name)
-
-    def _build_rpc(self, args, builder):
-        r = base_types.VInt()
-        if builder is not None:
-            new_args = []
-            new_args.append(args[0].auto_load(builder))  # RPC number
-            for arg in args[1:]:
-                # type tag
-                arg_type_str = _value_to_str(arg)
-                arg_type_int = 0
-                for c in reversed(arg_type_str):
-                    arg_type_int <<= 8
-                    arg_type_int |= ord(c)
-                new_args.append(ll.Constant(ll.IntType(32), arg_type_int))
-
-                # pointer to value
-                if not isinstance(arg, base_types.VNone):
-                    if isinstance(arg.llvm_value.type, ll.PointerType):
-                        new_args.append(arg.llvm_value)
-                    else:
-                        arg_ptr = arg.new()
-                        arg_ptr.alloca(builder)
-                        arg_ptr.auto_store(builder, arg.llvm_value)
-                        new_args.append(arg_ptr.llvm_value)
-            # end marker
-            new_args.append(ll.Constant(ll.IntType(32), 0))
-            r.auto_store(builder, builder.call(self.rpc, new_args))
-        return r
-
-    def _build_regular_syscall(self, syscall_name, args, builder):
-        r = _chr_to_value(_syscalls[syscall_name][-1])
-        if builder is not None:
-            args = [arg.auto_load(builder) for arg in args]
-            r.auto_store(builder, builder.call(self.syscalls[syscall_name],
-                                               args))
-        return r
-
-    def build_syscall(self, syscall_name, args, builder):
-        if syscall_name == "rpc":
-            return self._build_rpc(args, builder)
-        else:
-            return self._build_regular_syscall(syscall_name, args, builder)

artiq/coredevice/ttl.py

@@ -1,4 +1,26 @@
 from artiq.language.core import *
+from artiq.language.types import *
+
+
+@syscall
+def ttl_set_o(time_mu: TInt64, channel: TInt32, enabled: TBool) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+@syscall
+def ttl_set_oe(time_mu: TInt64, channel: TInt32, enabled: TBool) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+@syscall
+def ttl_set_sensitivity(time_mu: TInt64, channel: TInt32, sensitivity: TInt32) -> TNone:
+    raise NotImplementedError("syscall not simulated")
+
+@syscall
+def ttl_get(channel: TInt32, time_limit_mu: TInt64) -> TInt64:
+    raise NotImplementedError("syscall not simulated")
+
+@syscall
+def ttl_clock_set(time_mu: TInt64, channel: TInt32, ftw: TInt32) -> TNone:
+    raise NotImplementedError("syscall not simulated")
 
 
 class TTLOut:
@@ -18,14 +40,14 @@ class TTLOut:
 
     @kernel
     def set_o(self, o):
-        syscall("ttl_set_o", now_mu(), self.channel, o)
+        ttl_set_o(now_mu(), self.channel, o)
         self.o_previous_timestamp = now_mu()
 
     @kernel
     def sync(self):
         """Busy-wait until all programmed level switches have been
         effected."""
-        while syscall("rtio_get_counter") < self.o_previous_timestamp:
+        while self.core.get_rtio_counter_mu() < self.o_previous_timestamp:
             pass
 
     @kernel
@@ -83,7 +105,7 @@ class TTLInOut:
 
     @kernel
     def set_oe(self, oe):
-        syscall("ttl_set_oe", now_mu(), self.channel, oe)
+        ttl_set_oe(now_mu(), self.channel, oe)
 
     @kernel
     def output(self):
@@ -95,14 +117,14 @@ class TTLInOut:
 
     @kernel
     def set_o(self, o):
-        syscall("ttl_set_o", now_mu(), self.channel, o)
+        ttl_set_o(now_mu(), self.channel, o)
         self.o_previous_timestamp = now_mu()
 
     @kernel
     def sync(self):
         """Busy-wait until all programmed level switches have been
         effected."""
-        while syscall("rtio_get_counter") < self.o_previous_timestamp:
+        while self.core.get_rtio_counter_mu() < self.o_previous_timestamp:
             pass
 
     @kernel
@@ -133,7 +155,7 @@ class TTLInOut:
 
     @kernel
     def _set_sensitivity(self, value):
-        syscall("ttl_set_sensitivity", now_mu(), self.channel, value)
+        ttl_set_sensitivity(now_mu(), self.channel, value)
         self.i_previous_timestamp = now_mu()
 
     @kernel
@@ -189,8 +211,7 @@ class TTLInOut:
         """Poll the RTIO input during all the previously programmed gate
         openings, and returns the number of registered events."""
         count = 0
-        while syscall("ttl_get", self.channel,
+        while ttl_get(self.channel, self.i_previous_timestamp) >= 0:
-                      self.i_previous_timestamp) >= 0:
             count += 1
         return count
 
@@ -201,7 +222,7 @@ class TTLInOut:
 
         If the gate is permanently closed, returns a negative value.
         """
-        return syscall("ttl_get", self.channel, self.i_previous_timestamp)
+        return ttl_get(self.channel, self.i_previous_timestamp)
 
 
 class TTLClockGen:
@@ -254,7 +275,7 @@ class TTLClockGen:
         that are not powers of two cause jitter of one RTIO clock cycle at the
         output.
         """
-        syscall("ttl_clock_set", now_mu(), self.channel, frequency)
+        ttl_clock_set(now_mu(), self.channel, frequency)
         self.previous_timestamp = now_mu()
 
     @kernel
@@ -271,5 +292,5 @@ class TTLClockGen:
     def sync(self):
         """Busy-wait until all programmed frequency switches and stops have
         been effected."""
-        while syscall("rtio_get_counter") < self.o_previous_timestamp:
+        while self.core.get_rtio_counter_mu() < self.o_previous_timestamp:
             pass

artiq/language/core.py

@@ -7,15 +7,19 @@ from collections import namedtuple
 from functools import wraps
 
 
-__all__ = ["int64", "round64", "kernel", "portable",
+
-           "set_time_manager", "set_syscall_manager", "set_watchdog_factory",
+__all__ = ["int64", "round64",
+           "kernel", "portable", "syscall",
+           "set_time_manager", "set_watchdog_factory",
            "ARTIQException"]
 
 # global namespace for kernels
-kernel_globals = ("sequential", "parallel",
+kernel_globals = (
+    "sequential", "parallel",
     "delay_mu", "now_mu", "at_mu", "delay",
     "seconds_to_mu", "mu_to_seconds",
-    "syscall", "watchdog")
+    "watchdog"
+)
 __all__.extend(kernel_globals)
 
 
@@ -78,11 +82,12 @@ def round64(x):
     return int64(round(x))
 
 
-_ARTIQEmbeddedInfo = namedtuple("_ARTIQEmbeddedInfo", "core_name function")
+_ARTIQEmbeddedInfo = namedtuple("_ARTIQEmbeddedInfo",
-
+                                "core_name function syscall")
 
 def kernel(arg):
-    """This decorator marks an object's method for execution on the core
+    """
+    This decorator marks an object's method for execution on the core
     device.
 
     When a decorated method is called from the Python interpreter, the ``core``
@@ -106,15 +111,15 @@ def kernel(arg):
             def run_on_core(self, *k_args, **k_kwargs):
                 return getattr(self, arg).run(function, ((self,) + k_args), k_kwargs)
             run_on_core.artiq_embedded = _ARTIQEmbeddedInfo(
-                core_name=arg, function=function)
+                core_name=arg, function=function, syscall=None)
             return run_on_core
         return inner_decorator
     else:
         return kernel("core")(arg)
 
-
 def portable(function):
-    """This decorator marks a function for execution on the same device as its
+    """
+    This decorator marks a function for execution on the same device as its
     caller.
 
     In other words, a decorated function called from the interpreter on the
@@ -122,9 +127,31 @@ def portable(function):
     core device). A decorated function called from a kernel will be executed
     on the core device (no RPC).
     """
-    function.artiq_embedded = _ARTIQEmbeddedInfo(core_name="", function=function)
+    function.artiq_embedded = \
+        _ARTIQEmbeddedInfo(core_name=None, function=function, syscall=None)
     return function
 
+def syscall(arg):
+    """
+    This decorator marks a function as a system call. When executed on a core
+    device, a C function with the provided name (or the same name as
+    the Python function, if not provided) will be called. When executed on
+    host, the Python function will be called as usual.
+
+    Every argument and the return value must be annotated with ARTIQ types.
+
+    Only drivers should normally define syscalls.
+    """
+    if isinstance(arg, str):
+        def inner_decorator(function):
+            function.artiq_embedded = \
+                _ARTIQEmbeddedInfo(core_name=None, function=None,
+                                   syscall=function.__name__)
+            return function
+        return inner_decorator
+    else:
+        return syscall(arg.__name__)(arg)
+
 
 class _DummyTimeManager:
     def _not_implemented(self, *args, **kwargs):
@@ -152,22 +179,6 @@ def set_time_manager(time_manager):
     _time_manager = time_manager
 
 
-class _DummySyscallManager:
-    def do(self, *args):
-        raise NotImplementedError(
-            "Attempted to interpret kernel without a syscall manager")
-
-_syscall_manager = _DummySyscallManager()
-
-
-def set_syscall_manager(syscall_manager):
-    """Set the system call manager used for simulating the core device's
-    runtime in the Python interpreter.
-    """
-    global _syscall_manager
-    _syscall_manager = syscall_manager
-
-
 class _Sequential:
     """In a sequential block, statements are executed one after another, with
     the time increasing as one moves down the statement list."""
@@ -240,17 +251,6 @@ def mu_to_seconds(mu, core=None):
     return mu*core.ref_period
 
 
-def syscall(*args):
-    """Invokes a service of the runtime.
-
-    Kernels use this function to interface to the outside world: program RTIO
-    events, make RPCs, etc.
-
-    Only drivers should normally use ``syscall``.
-    """
-    return _syscall_manager.do(*args)
-
-
 class _DummyWatchdog:
     def __init__(self, timeout):
         pass