Fastest way to zero a slice of memory

[Nordlöw via Digitalmars-d-learn]

When zeroing a slice of memory (either stack or heap) such as
    enum n = 100;
    ubyte[n] chunk;

should I use `memset` such as

    memset(chunk.ptr, 0, n/2); // zero first half

or an array assignment such as

    chunk[0 .. n/2] = 0; // zero first half

or are they equivalent in release mode?

Further, does it depend on whether the slice length is known at 
compile-time or not?