function t1(n::Int, x::Int, a::Float64) x::Float64 = x for i in 1:n x += a end x end @time t1(10^6, 1, 1.0)
0.005445 seconds (1.00 M allocations: 15.259 MB) function t2(n::Int, y::Int, a::Float64) x::Float64 = y for i in 1:n x += a end x end @time t2(10^6, 1, 1.0) 0.001044 seconds (6 allocations: 192 bytes) The @code_warntype of the 2 functions are very similar. However, the llvm code generated from t2 is a lot simpler. Does it suggest that if we want to change the type of an argument, we'd better create a new variable?