Function write_element_0_u64 

pub unsafe fn write_element_0_u64<const VLENB: usize>(
    vreg: &mut [[u8; VLENB]; 32],
    base_reg: u8,
    sew: Vsew,
    value: u64,
)

Write element 0 of register base_reg from the low sew_bytes of value.

Safety

base_reg < 32 and sew.bytes() <= VLENB must hold.