diff --git a/src/Flux.jl b/src/Flux.jl
index a7604561..1df87404 100644
--- a/src/Flux.jl
+++ b/src/Flux.jl
@@ -16,6 +16,7 @@ include("data.jl")
 include("compiler/code.jl")
 include("compiler/loops.jl")
 include("compiler/interp.jl")
+include("compiler/shape.jl")
 
 include("layers/affine.jl")
 include("layers/activation.jl")
diff --git a/src/compiler/shape.jl b/src/compiler/shape.jl
new file mode 100644
index 00000000..f24fdfe1
--- /dev/null
+++ b/src/compiler/shape.jl
@@ -0,0 +1,47 @@
+using DataFlow: iline, iargs
+
+type Hint
+  typ
+end
+
+DataFlow.tocall(h::Hint, x) = :($x::$(h.typ))
+
+function gethint(v::IVertex)
+  isa(value(v), Hint) && return value(v).typ
+  return
+end
+
+ihint(f, ctx::Context, h::Hint, x) = vertex(h, x)
+ihint(f, args...) = f(args...)
+
+hintify(c::Constant) = hintify(state(c.value))
+hintify(xs::AbstractArray) = vertex(Hint(size(xs)), constant(:_))
+
+interpshape = mux(iline, ihint, iargs, ituple, hintify)
+
+function hintify(f, xs...)
+  sh = infer(f, map(gethint, xs)...)
+  sh ≠ nothing ? vertex(Hint(sh), vertex(f, xs...)) :
+  !any(x->x==nothing, xs) && graph(f) ≠ nothing ? interpret(Context(interpshape), graph(f), xs...) :
+    vertex(f, xs...)
+end
+
+function shapes(f, args...)
+  (g = graph(f)) == nothing && return
+  ins = [vertex(Hint(d), inputnode(i)) for (i,d) in enumerate(args)]
+  interpret(Context(interpshape), g, ins...)
+end
+
+# Inference primitives
+
+infer(f, args...) = graph(f) == nothing ? nothing : gethint(shapes(f, args...))
+
+function infer(::typeof(*), a::NTuple{2}, b::NTuple{2})
+  a[2] == b[1] || return nothing
+  (a[1], b[2])
+end
+
+# TODO: make correct
+infer(::typeof(+), a, b) = a
+infer(::typeof(softmax), x) = x
+infer(::typeof(σ), x) = x