basic unrolling

src/compiler/loops.jl

@@ -20,9 +20,22 @@ bumpinput(x) = x
 
 bumpinputs(v::IVertex) = mapconst(bumpinput, v)
 
+function unroll(delay::IVertex)
+  prewalk(delay[1]) do v
+    isa(value(v), Delay) ? constant(ModelInput(1)) : v
+  end
+end
+
 function break!(model)
   iscyclic(graph(model)) || return model
-  bumpinputs(graph(model))
+  g = bumpinputs(graph(model))
+  loops = []
+  g = prewalk(g) do v
+    isa(value(v), Delay) || return v
+    push!(loops, unroll(v))
+    constant(ModelInput(1))
+  end
+  cse(vertex(tuple, loops..., g))
 end
 
 # r = Recurrent(784, 10, 50)