Merge pull request #97 from vchuravy/lcw/signature

Add signature function

src/GPUifyLoops.jl

@@ -65,6 +65,7 @@ Launch a kernel on the GPU. `kwargs` are passed to `@cuda`
 normally passed to `@cuda`.
 """
 launch(::CPU, f, args...; kwargs...) = f(args...)
+signature(::CPU, f, args...) = f, map(Core.Typeof, args)
 
 """
     launch_config(::F, maxthreads, args...; kwargs...)
@@ -134,6 +135,13 @@ end
         end
         return nothing
     end
+
+    function signature(::CUDA, f::F, args...) where F
+        args = (ctx, f, args...)
+        kernel_args = map(cudaconvert, args)
+        kernel_tt = Tuple{map(Core.Typeof, kernel_args)...}
+        return Cassette.overdub, kernel_tt
+    end
 end
 
 isdevice(::CPU) = false