allow rand! with explicit SIMD to be used for various dense arrays

[nsajko]

No description provided.

[oscardssmith]

Could this expand to DenseArray?

[nsajko]

expand to DenseArray

I don't think so, given that a DenseArray isn't necessarily mutable.

[nsajko]

Speedups for rand!(::Memory)

rand!(::Memory{Float64})

using Random: rand!
using BenchmarkTools
const mem = Memory{Float64}(undef, 4096);
rand!(mem);
@btime rand!(mem);

• master branch (2e6ffbc): 4.322 μs (0 allocations: 0 bytes)
• PR branch (ed650ca): 4.132 μs (0 allocations: 0 bytes)

rand!(::Memory{UInt64})

using Random: rand!
using BenchmarkTools
const mem = Memory{UInt64}(undef, 4096);
rand!(mem);
@btime rand!(mem);

• master branch (2e6ffbc): 3.967 μs (0 allocations: 0 bytes)
• PR branch (ed650ca): 1.632 μs (0 allocations: 0 bytes)

rand!(::Memory{Bool})

using Random: rand!
using BenchmarkTools
const mem = Memory{Bool}(undef, 4096 * 8);
rand!(mem);
@btime rand!(mem);

• master branch (2e6ffbc): 34.555 μs (0 allocations: 0 bytes)
• PR branch (ed650ca): 701.401 ns (0 allocations: 0 bytes)