> It is perhaps a silly example. But suppose R1 was to contain a pair
> of flag byte values. Suppose the flags were equated. Now it might
> make sense to code
>
> LHI R1,2AL1(MYFLAG1)
>
> Or something like that. Yes you can code the following but it is no
> great exemplar of coding clarity:
>
> LHI R1,MYFLAG1*256+MYFLAG1
I probably wouldn't define them as two bytes of flags. Instead, I'd
define them as a single two-byte field of flags:
MYFLAGS DS XL2
FLAG1 EQU X'8000'
FLAG2 EQU X'4000'
Etc.
Setting bits is pretty clear:
LLILL R1,FLAG1+FLAG3+...
Plus, you don't have a field of flags being treated as signed, which most
likely isn't what was intended. Also, this way it would be clear that the
flags need to be contiguous so that they can be operated on as a unit, and
I don't have to worry that in a few years someone will rearrange the data
area and insert another field or two between the two bytes of flags.
- mb
