Add a few precompiles (#181)

Author: timholy

src/FFTW.jl

@@ -91,4 +91,9 @@ end
 include("fft.jl")
 include("dct.jl")
 
+if Base.VERSION >= v"1.4.2"     # avoid potential segfaults, see https://github.com/JuliaLang/julia/pull/35378
+    include("precompile.jl")
+    _precompile_()
+end
+
 end # module

src/precompile.jl

@@ -0,0 +1,12 @@
+function _precompile_()
+    ccall(:jl_generating_output, Cint, ()) == 1 || return nothing
+    for n = 1:3, T in (Float32, Float64, ComplexF32, ComplexF64), D in (UnitRange{Int}, Vector{Int}, Int)
+        @assert precompile(Tuple{typeof(fft),Array{T,n},D})
+        @assert precompile(Tuple{typeof(rfft),Array{T,n},D})
+        @assert precompile(Tuple{typeof(ifft),Array{T,n},D})
+        @assert precompile(Tuple{typeof(irfft),Array{T,n},Int,D})
+        @assert precompile(Tuple{typeof(rfft_output_size),Tuple{Int, Int, Int},D})
+        @assert precompile(Tuple{typeof(rfft_output_size),Tuple{Int, Int},D})
+        @assert precompile(Tuple{typeof(rfft_output_size),Tuple{Int},D})
+    end
+end