Errors with certain simple for loop

[junyuan-chen]

Depending on how the index ranges are specified, there are a few cases in which I get unexpected errors.

For example, I am getting errors on something like this:

using LoopVectorization
a = zeros(3,2)
N = 2
@turbo thread=true for i in 1:1, j in 1:N
    a[i,j] += 1.0
end

ERROR: MethodError: no method matching vmul_nw(::Int64)

The following also errors:

v = zeros(3)
N1 = 1
N2 = 3
@turbo thread=true for i in 1:N2, j in 1:N1
    v[i,j] += 1.0
end

ERROR: BoundsError: attempt to access 1-element Vector{Any} at index [2]

[chriselrod]

The second case is tricker. The ideal behavior is that LV would figure out that N1 has to be <=1, and throw an error otherwise. Currently, throwing some error always probably isn't so bad.

I fixed the first case, and added it to the tests: https://github.com/JuliaSIMD/LoopVectorization.jl/commit/ded74ba4229c5bdb286057204aa50a8c8895f472

[junyuan-chen]

@chriselrod Thank you so much for the fast response.