add isdevice to check if function is executed on device

Author: vchuravy

src/CUDAnative.jl

@@ -23,6 +23,7 @@ end
 include("utils.jl")
 
 # needs to be loaded _before_ the compiler infrastructure, because of generated functions
+isdevice() = false
 include(joinpath("device", "tools.jl"))
 include(joinpath("device", "pointer.jl"))
 include(joinpath("device", "array.jl"))

src/context.jl

@@ -18,6 +18,10 @@ using Cassette
 Cassette.@context CUDACtx
 const cudactx = CUDACtx()
 
+function Cassette.overdub(ctx::CUDACtx, ::typeof(isdevice))
+    return true
+end
+
 # libdevice.jl
 for f in (:cos, :cospi, :sin, :sinpi, :tan,
           :acos, :asin, :atan,