m-labs · Sep 30, 2015 · Sep 30, 2015
diff --git a/.gitignore b/.gitignore
@@ -14,4 +14,4 @@ doc/manual/_build
 /.coverage
 examples/master/results
 Output/
-/lit-test/libartiq_personality/libartiq_personality.so
+/lit-test/libartiq_support/libartiq_support.so
diff --git a/artiq/compiler/iodelay.py b/artiq/compiler/iodelay.py
@@ -4,9 +4,6 @@
 a function.
 """
 
-from pythonparser import diagnostic
-
-
 class Expr:
     def __add__(lhs, rhs):
         assert isinstance(rhs, Expr)
@@ -227,59 +224,3 @@ def is_const(expr, value=None):
 
 def is_zero(expr):
     return is_const(expr, 0)
-
-
-class Delay:
-    pass
-
-class Unknown(Delay):
-    """
-    Unknown delay, that is, IO delay that we have not
-    tried to compute yet.
-    """
-
-    def __repr__(self):
-        return "{}.Unknown()".format(__name__)
-
-class Indeterminate(Delay):
-    """
-    Indeterminate delay, that is, IO delay that can vary from
-    invocation to invocation.
-
-    :ivar cause: (:class:`pythonparser.diagnostic.Diagnostic`)
-        reason for the delay not being inferred
-    """
-
-    def __init__(self, cause):
-        assert isinstance(cause, diagnostic.Diagnostic)
-        self.cause = cause
-
-    def __repr__(self):
-        return "<{}.Indeterminate>".format(__name__)
-
-class Fixed(Delay):
-    """
-    Fixed delay, that is, IO delay that is always the same
-    for every invocation.
-
-    :ivar length: (int) delay in machine units
-    """
-
-    def __init__(self, length):
-        assert isinstance(length, Expr)
-        self.length = length
-
-    def __repr__(self):
-        return "{}.Fixed({})".format(__name__, self.length)
-
-def is_unknown(delay):
-    return isinstance(delay, Unknown)
-
-def is_indeterminate(delay):
-    return isinstance(delay, Indeterminate)
-
-def is_fixed(delay, length=None):
-    if length is None:
-        return isinstance(delay, Fixed)
-    else:
-        return isinstance(delay, Fixed) and delay.length == length
diff --git a/artiq/compiler/module.py b/artiq/compiler/module.py
@@ -50,7 +50,8 @@ def __init__(self, src, ref_period=1e-6):
         inferencer = transforms.Inferencer(engine=self.engine)
         monomorphism_validator = validators.MonomorphismValidator(engine=self.engine)
         escape_validator = validators.EscapeValidator(engine=self.engine)
-        iodelay_estimator = transforms.IODelayEstimator(ref_period=ref_period)
+        iodelay_estimator = transforms.IODelayEstimator(engine=self.engine,
+                                                        ref_period=ref_period)
         artiq_ir_generator = transforms.ARTIQIRGenerator(engine=self.engine,
                                                          module_name=src.name,
                                                          ref_period=ref_period)

diff --git a/artiq/compiler/testbench/signature.py b/artiq/compiler/testbench/signature.py
@@ -32,8 +32,8 @@ def process_diagnostic(diag):
         if force_delays:
             for var in mod.globals:
                 typ = mod.globals[var].find()
-                if types.is_function(typ) and iodelay.is_indeterminate(typ.delay):
-                    process_diagnostic(typ.delay.cause)
+                if types.is_function(typ) and types.is_indeterminate_delay(typ.delay):
+                    process_diagnostic(typ.delay.find().cause)
 
         print(repr(mod))
     except:

diff --git a/artiq/compiler/transforms/iodelay_estimator.py b/artiq/compiler/transforms/iodelay_estimator.py
@@ -11,7 +11,8 @@ class _UnknownDelay(Exception):
     pass
 
 class IODelayEstimator(algorithm.Visitor):
-    def __init__(self, ref_period):
+    def __init__(self, engine, ref_period):
+        self.engine         = engine
         self.ref_period     = ref_period
         self.changed        = False
         self.current_delay  = iodelay.Const(0)
@@ -83,7 +84,7 @@ def visit_ModuleT(self, node):
         except (diagnostic.Error, _UnknownDelay):
             pass # we don't care; module-level code is never interleaved
 
-    def visit_function(self, args, body, typ):
+    def visit_function(self, args, body, typ, loc):
         old_args, self.current_args = self.current_args, args
         old_return, self.current_return = self.current_return, None
         old_delay, self.current_delay = self.current_delay, iodelay.Const(0)
@@ -93,19 +94,23 @@ def visit_function(self, args, body, typ):
                 self.abort("only return statement at the end of the function "
                            "can be interleaved", self.current_return.loc)
 
-            delay = iodelay.Fixed(self.current_delay.fold())
+            delay = types.TFixedDelay(self.current_delay.fold())
         except diagnostic.Error as error:
-            delay = iodelay.Indeterminate(error.diagnostic)
+            delay = types.TIndeterminateDelay(error.diagnostic)
         self.current_delay = old_delay
         self.current_return = old_return
         self.current_args = old_args
 
-        if iodelay.is_unknown(typ.delay) or iodelay.is_indeterminate(typ.delay):
-            typ.delay = delay
-        elif iodelay.is_fixed(typ.delay):
-            assert typ.delay.value == delay.value
-        else:
-            assert False
+        try:
+            typ.delay.unify(delay)
+        except types.UnificationError as e:
+            printer = types.TypePrinter()
+            diag = diagnostic.Diagnostic("fatal",
+                "delay {delaya} was inferred for this function, but its delay is already "
+                "constrained externally to {delayb}",
+                {"delaya": printer.name(delay), "delayb": printer.name(typ.delay)},
+                loc)
+            self.engine.process(diag)
 
     def visit_FunctionDefT(self, node):
         self.visit(node.args.defaults)
@@ -116,10 +121,10 @@ def visit_FunctionDefT(self, node):
             body = node.body[:-1]
         else:
             body = node.body
-        self.visit_function(node.args, body, node.signature_type.find())
+        self.visit_function(node.args, body, node.signature_type.find(), node.loc)
 
     def visit_LambdaT(self, node):
-        self.visit_function(node.args, node.body, node.type.find())
+        self.visit_function(node.args, node.body, node.type.find(), node.loc)
 
     def get_iterable_length(self, node):
         def abort(notes):
@@ -225,26 +230,26 @@ def abort(notes):
             else:
                 assert False
 
-            delay = typ.find().delay
-            if iodelay.is_unknown(delay):
+            delay = typ.find().delay.find()
+            if types.is_var(delay):
                 raise _UnknownDelay()
-            elif iodelay.is_indeterminate(delay):
+            elif delay.is_indeterminate():
                 cause = delay.cause
                 note = diagnostic.Diagnostic("note",
                     "function called here", {},
                     node.loc)
                 diag = diagnostic.Diagnostic(cause.level, cause.reason, cause.arguments,
                                              cause.location, cause.highlights, cause.notes + [note])
                 raise diagnostic.Error(diag)
-            elif iodelay.is_fixed(delay):
+            elif delay.is_fixed():
                 args = {}
                 for kw_node in node.keywords:
                     args[kw_node.arg] = kw_node.value
                 for arg_name, arg_node in zip(typ.args, node.args[offset:]):
                     args[arg_name] = arg_node
 
-                free_vars = delay.length.free_vars()
-                self.current_delay += delay.length.fold(
+                free_vars = delay.duration.free_vars()
+                self.current_delay += delay.duration.fold(
                     { arg: self.evaluate(args[arg], abort=abort) for arg in free_vars })
             else:
                 assert False
diff --git a/artiq/compiler/types.py b/artiq/compiler/types.py
@@ -5,6 +5,7 @@
 
 import string
 from collections import OrderedDict
+from pythonparser import diagnostic
 from . import iodelay
 
 
@@ -192,21 +193,21 @@ class TFunction(Type):
         optional arguments
     :ivar ret: (:class:`Type`)
         return type
-    :ivar delay: (:class:`iodelay.Delay`)
-        RTIO delay expression
+    :ivar delay: (:class:`Type`)
+        RTIO delay
     """
 
     attributes = OrderedDict([
         ('__code__',    _TPointer()),
         ('__closure__', _TPointer()),
     ])
 
-    def __init__(self, args, optargs, ret, delay=iodelay.Unknown()):
+    def __init__(self, args, optargs, ret):
         assert isinstance(args, OrderedDict)
         assert isinstance(optargs, OrderedDict)
         assert isinstance(ret, Type)
-        assert isinstance(delay, iodelay.Delay)
-        self.args, self.optargs, self.ret, self.delay = args, optargs, ret, delay
+        self.args, self.optargs, self.ret = args, optargs, ret
+        self.delay = TVar()
 
     def arity(self):
         return len(self.args) + len(self.optargs)
@@ -222,6 +223,7 @@ def unify(self, other):
                                          list(other.args.values()) + list(other.optargs.values())):
                 selfarg.unify(otherarg)
             self.ret.unify(other.ret)
+            self.delay.unify(other.delay)
         elif isinstance(other, TVar):
             other.unify(self)
         else:
@@ -261,7 +263,7 @@ class TRPCFunction(TFunction):
 
     def __init__(self, args, optargs, ret, service):
         super().__init__(args, optargs, ret,
-                         delay=iodelay.Fixed(iodelay.Constant(0)))
+                         delay=FixedDelay(iodelay.Constant(0)))
         self.service = service
 
     def unify(self, other):
@@ -284,7 +286,7 @@ class TCFunction(TFunction):
 
     def __init__(self, args, ret, name):
         super().__init__(args, OrderedDict(), ret,
-                         delay=iodelay.Fixed(iodelay.Constant(0)))
+                         delay=FixedDelay(iodelay.Constant(0)))
         self.name = name
 
     def unify(self, other):
@@ -418,6 +420,63 @@ def __eq__(self, other):
     def __ne__(self, other):
         return not (self == other)
 
+class TDelay(Type):
+    """
+    The type-level representation of IO delay.
+    """
+
+    def __init__(self, duration, cause):
+        assert duration is None or isinstance(duration, iodelay.Expr)
+        assert cause is None or isinstance(cause, diagnostic.Diagnostic)
+        assert (not (duration and cause)) and (duration or cause)
+        self.duration, self.cause = duration, cause
+
+    def is_fixed(self):
+        return self.duration is not None
+
+    def is_indeterminate(self):
+        return self.cause is not None
+
+    def find(self):
+        return self
+
+    def unify(self, other):
+        other = other.find()
+
+        if self.is_fixed() and other.is_fixed() and \
+                self.duration.fold() == other.duration.fold():
+            pass
+        elif isinstance(other, TVar):
+            other.unify(self)
+        else:
+            raise UnificationError(self, other)
+
+    def fold(self, accum, fn):
+        # delay types do not participate in folding
+        pass
+
+    def __eq__(self, other):
+        return isinstance(other, TDelay) and \
+                (self.duration == other.duration and \
+                 self.cause == other.cause)
+
+    def __ne__(self, other):
+        return not (self == other)
+
+    def __repr__(self):
+        if self.duration is None:
+            return "<{}.TIndeterminateDelay>".format(__name__)
+        elif self.cause is None:
+            return "{}.TFixedDelay({})".format(__name__, self.duration)
+        else:
+            assert False
+
+def TIndeterminateDelay(cause):
+    return TDelay(None, cause)
+
+def TFixedDelay(duration):
+    return TDelay(duration, None)
+
 
 def is_var(typ):
     return isinstance(typ.find(), TVar)
@@ -511,6 +570,16 @@ def get_value(typ):
     else:
         assert False
 
+def is_delay(typ):
+    return isinstance(typ.find(), TDelay)
+
+def is_fixed_delay(typ):
+    return is_delay(typ) and typ.find().is_fixed()
+
+def is_indeterminate_delay(typ):
+    return is_delay(typ) and typ.find().is_indeterminate()
+
+
 class TypePrinter(object):
     """
     A class that prints types using Python-like syntax and gives
@@ -553,14 +622,10 @@ def name(self, typ):
             args += ["?%s:%s" % (arg, self.name(typ.optargs[arg])) for arg in typ.optargs]
             signature = "(%s)->%s" % (", ".join(args), self.name(typ.ret))
 
-            if iodelay.is_unknown(typ.delay) or iodelay.is_fixed(typ.delay, 0):
-                pass
-            elif iodelay.is_fixed(typ.delay):
-                signature += " delay({} mu)".format(typ.delay.length)
-            elif iodelay.is_indeterminate(typ.delay):
-                signature += " delay(?)"
-            else:
-                assert False
+            delay = typ.delay.find()
+            if not (isinstance(delay, TVar) or
+                        delay.is_fixed() and iodelay.is_zero(delay.duration)):
+                signature += " " + self.name(delay)
 
             if isinstance(typ, TRPCFunction):
                 return "rpc({}) {}".format(typ.service, signature)
@@ -580,5 +645,12 @@ def name(self, typ):
                 return "<constructor {} {{{}}}>".format(typ.name, attrs)
         elif isinstance(typ, TValue):
             return repr(typ.value)
+        elif isinstance(typ, TDelay):
+            if typ.is_fixed():
+                return "delay({} mu)".format(typ.duration)
+            elif typ.is_indeterminate():
+                return "delay(?)"
+            else:
+                assert False
         else:
             assert False
diff --git a/artiq/coredevice/dds.py b/artiq/coredevice/dds.py
@@ -1,4 +1,5 @@
 from artiq.language.core import *
+from artiq.language.types import *
 from artiq.language.units import *
 
 

diff --git a/lit-test/libartiq_support/libartiq_support.so b/lit-test/libartiq_support/libartiq_support.so
diff --git a/lit-test/test/iodelay/error_unify.py b/lit-test/test/iodelay/error_unify.py
@@ -0,0 +1,11 @@
+# RUN: %python -m artiq.compiler.testbench.signature +diag +delay %s >%t
+# RUN: OutputCheck %s --file-to-check=%t
+
+def f():
+    delay_mu(10)
+
+# CHECK-L: ${LINE:+1}: fatal: delay delay(20 mu) was inferred for this function, but its delay is already constrained externally to delay(10 mu)
+def g():
+    delay_mu(20)
+
+x = f if True else g
diff --git a/lit-test/test/iodelay/return.py b/lit-test/test/iodelay/return.py
@@ -7,7 +7,8 @@ def f():
         delay(1.5)
     return 10
 
-# CHECK-L: g: (x:float)->int(width=32) delay(0 mu)
+# CHECK-L: g: (x:float)->int(width=32)
+# CHECK-NOT-L: delay
 def g(x):
     if x > 1.0:
         return 1