tnum_add
struct tnum tnum_add(struct tnum a, struct tnum b);
acc = tnum_add(acc, b);
acc = tnum_union(acc, tnum_add(acc, b));
dst_reg->var_off = tnum_add(ptr_reg->var_off, off_reg->var_off);
dst_reg->var_off = tnum_add(dst_reg->var_off, src_reg.var_off);
reg->var_off = tnum_add(reg->var_off, fake_reg.var_off);
reg_off = tnum_add(reg->var_off, tnum_const(ip_align + reg->off + off));
reg_off = tnum_add(reg->var_off, tnum_const(reg->off + off));