m-labs · Oct 11, 2014 · Oct 11, 2014 · Oct 11, 2014 · Oct 11, 2014
diff --git a/artiq/devices/runtime.py b/artiq/devices/runtime.py
@@ -65,6 +65,7 @@ def init_module(self, module):
         func_type = lc.Type.function(lc.Type.int(), [lc.Type.pointer(lc.Type.int(8))])
         function = self.llvm_module.add_function(func_type, "__eh_setjmp")
         function.add_attribute(lc.ATTR_NO_UNWIND)
+        function.add_attribute(lc.ATTR_RETURNS_TWICE)
 
         func_type = lc.Type.function(lc.Type.pointer(lc.Type.int(8)), [])
         self.llvm_module.add_function(func_type, "__eh_push")

diff --git a/artiq/transforms/lower_time.py b/artiq/transforms/lower_time.py
@@ -17,6 +17,15 @@ def _time_to_cycles(ref_period, node):
         divided)
 
 
+def _time_to_cycles_opt(ref_period, node):
+    if (isinstance(node, ast.Call)
+            and isinstance(node.func, ast.Name)
+            and node.func.id == "cycles_to_time"):
+        return node.args[0]
+    else:
+        return _time_to_cycles(ref_period, node)
+
+
 def _cycles_to_time(ref_period, node):
     return ast.copy_location(
         ast.BinOp(left=node,
@@ -52,27 +61,27 @@ def visit_Call(self, node):
         return node
 
     def visit_Expr(self, node):
-        self.generic_visit(node)
+        r = node
         if (isinstance(node.value, ast.Call)
                 and isinstance(node.value.func, ast.Name)):
             funcname = node.value.func.id
             if funcname == "delay":
-                return ast.copy_location(
+                r = ast.copy_location(
                     ast.AugAssign(target=ast.Name("now", ast.Store()),
                                   op=ast.Add(),
-                                  value=_time_to_cycles(self.ref_period,
-                                                        node.value.args[0])),
+                                  value=_time_to_cycles_opt(
+                                    self.ref_period,
+                                    node.value.args[0])),
                     node)
             elif funcname == "at":
-                return ast.copy_location(
+                r = ast.copy_location(
                     ast.Assign(targets=[ast.Name("now", ast.Store())],
-                               value=_time_to_cycles(self.ref_period,
-                                                     node.value.args[0])),
+                               value=_time_to_cycles_opt(
+                                    self.ref_period,
+                                    node.value.args[0])),
                     node)
-            else:
-                return node
-        else:
-            return node
+        self.generic_visit(r)
+        return r
 
 
 def lower_time(func_def, initial_time, ref_period):

diff --git a/doc/manual/core_reference.rst b/doc/manual/core_reference.rst
@@ -8,7 +8,7 @@ Core language reference
     :members:
 
 :mod:`artiq.language.units` module
----------------------------------
+----------------------------------
 
 .. automodule:: artiq.language.units
     :members:
diff --git a/doc/manual/installing.rst b/doc/manual/installing.rst
@@ -72,13 +72,13 @@ The main dependency of ARTIQ is LLVM and its Python bindings (http://llvmpy.org)
     $ git clone https://github.com/openrisc/llvm-or1k
     $ cd llvm-or1k
     $ git checkout b3a48efb2c05ed6cedc5395ae726c6a6573ef3ba
-    $ patch -p1 < /path_to/ARTIQ/patches/llvm/*
+    $ cat /path_to/artiq/patches/llvm/* | patch -p1
 
     $ cd tools
     $ git clone https://github.com/openrisc/clang-or1k clang
     $ cd clang
     $ git checkout 02d831c7e7dc1517abed9cc96abdfb937af954eb
-    $ patch -p1 < /path_to/ARTIQ/patches/clang/*
+    $ cat /path_to/artiq/patches/clang/* | patch -p1
 
     $ cd ../..
     $ mkdir build && cd build
@@ -90,7 +90,7 @@ The main dependency of ARTIQ is LLVM and its Python bindings (http://llvmpy.org)
     $ git clone https://github.com/llvmpy/llvmpy
     $ cd llvmpy
     $ git checkout 7af2f7140391d4f708adf2721e84f23c1b89e97a
-    $ patch -p1 < /path_to/ARTIQ/patches/llvmpy/*
+    $ cat /path_to/artiq/patches/llvmpy/* | patch -p1
     $ LLVM_CONFIG_PATH=/usr/local/llvm-or1k/bin/llvm-config sudo -E python setup.py install
 
 .. note::

diff --git a/examples/pulse_performance.py b/examples/pulse_performance.py
@@ -0,0 +1,34 @@
+from artiq import *
+from artiq.devices import corecom_serial, core, rtio_core
+from artiq.devices.runtime_exceptions import RTIOUnderflow
+
+
+def print_min_period(p):
+    print("Minimum square wave output period: {} ns".format(p))
+
+
+class PulsePerformance(AutoContext):
+    parameters = "o"
+
+    @kernel
+    def run(self):
+        T = time_to_cycles(100*ns)
+        while True:
+            try:
+                for i in range(1000):
+                    self.o.pulse(cycles_to_time(T))
+                    delay(cycles_to_time(T))
+            except RTIOUnderflow:
+                T += 1
+                delay(1*ms)
+            else:
+                print_min_period(int(cycles_to_time(2*T)/(1*ns)))
+                break
+
+
+if __name__ == "__main__":
+    with corecom_serial.CoreCom() as com:
+        coredev = core.Core(com)
+        exp = PulsePerformance(core=coredev,
+                               o=rtio_core.RTIOOut(core=coredev, channel=1))
+        exp.run()
diff --git a/patches/llvmpy/0002-add-returns-twice-attribute.patch b/patches/llvmpy/0002-add-returns-twice-attribute.patch
@@ -0,0 +1,12 @@
+diff --git a/llvm/core.py b/llvm/core.py
+index 20ad062..245ac65 100644
+--- a/llvm/core.py
++++ b/llvm/core.py
+@@ -379,6 +379,7 @@ class AttrEnum(Enum):
+     ATTR_NAKED              = AttrVal.Naked
+     ATTR_INLINE_HINT        = AttrVal.InlineHint
+     ATTR_STACK_ALIGNMENT    = AttrVal.StackAlignment
++    ATTR_RETURNS_TWICE      = AttrVal.ReturnsTwice
+
+ AttrEnum.declare()
+