solana_rbpf::ebpf
pub const ST_W_REG: u8 = BPF_STX | BPF_MEM | BPF_W; // 99u8
BPF opcode: stxw [dst + off], src /// (dst + offset) as u32 = src.
stxw [dst + off], src
(dst + offset) as u32 = src