solana_rbpf::ebpf
pub const LD_H_REG: u8 = BPF_LDX | BPF_MEM | BPF_H; // 0_x69u8
BPF opcode: ldxh dst, [src + off] /// dst = (src + off) as u16.
ldxh dst, [src + off]
dst = (src + off) as u16