Merge pull request #2023 from FluxML/bc/lstm-muladd

Use muladd for LSTM cell matmuls

Author: ToucheSir

src/layers/recurrent.jl

@@ -295,7 +295,7 @@ end
 
 function (m::LSTMCell{A,V,<:NTuple{2,AbstractMatrix{T}}})((h, c), x::Union{AbstractVecOrMat{T},OneHotArray}) where {A,V,T}
   b, o = m.b, size(h, 1)
-  g = m.Wi*x .+ m.Wh*h .+ b
+  g = muladd(m.Wi, x, muladd(m.Wh, h, b))
   input, forget, cell, output = multigate(g, o, Val(4))
   c′ = @. sigmoid_fast(forget) * c + sigmoid_fast(input) * tanh_fast(cell)
   h′ = @. sigmoid_fast(output) * tanh_fast(c′)