solana_rbpf::ebpf
pub const ST_H_IMM: u8 = BPF_ST | BPF_MEM | BPF_H; // 106u8
BPF opcode: sth [dst + off], imm /// (dst + offset) as u16 = imm.
sth [dst + off], imm
(dst + offset) as u16 = imm