On 2017-03-01, at 17:35, Ngan, Robert wrote:
> I noticed the new COBOL compiler was generating:
>
> MVHHI target,0
> MVHHI target+2,48000
>
> instead of:
>
> MVC target,=F'48000'
>
> and I thought I'd look into using 2 MVHHI's instead of a MVC with a literal
> even when the top half of the value is non-zero. The assembler happily
> accepts:
>
> MVHHI target+2,C'abcd'
>
> truncating the leading 'ab', but I gave up since I could not determine how to
> consistently obtain the top half of the value when it is a general
> (resolvable at assembly) expression, ...
>
How about, with the miracle of integer arithmetic:
ABCD EQU c'abcd'
Then (best done in a macro):
DEN EQU 65536
M1.SYSNDX EQU ABCD-ABCD/DEN*DEN
M2.SYSNDX EQU (M1.SYSNDX+DEN)-(M1.SYSNDX+DEN)/DEN*DEN
MVHHI target,(ABCD-M2.SYSNDX)/DEN
I believe this is safe against oveflows, but I haven't proven it formally.
-- gil
