Function matmul_spec 

pub fn matmul_spec(
    lhs: Operand,
    rhs: Operand,
    output: Operand,
    m: u32,
    n: u32,
    k: u32,
    batch: u32,
) -> Vec<u32>

Specialization payload of a MATMUL: lhs, rhs, output, then m, n, k, batch.