Very interesting...
I assembled this fragment on VSE and got a slight warning about the USING
0,9 with HLASM R6.0
R:9 00000 3 USING 0,9
** ASMA306W USING RANGE OVERLAPS IMPLICIT USING 0,0
But the generated code is as you showed... ( LA 2,256(0) is interpreted
the same as LA 2,256 - no surprise there)
Never thought about USING 0,r
On Fri, 8 Nov 2019 at 16:15, Bob Raicer <[email protected]> wrote:
> Well, the statement from Peter Relson (and others) which is
> essentially:
> ----------
> LA R1,1 is exactly equivalent to LA R1,1(0). Just look at the
> generated object code.
> ----------
> is not totally true. It all depends upon which USINGs are in effect.
>
> Take a peek at the following example (admittedly a bit unusual, but
> perfectly legitimate).
>
> Loc Object Code Addr1 Addr2 Stmt Source Statement
> 00000000 00000000 00000008 1 EXAMPLE CSECT ,
> R:9 00000000 2 USING 0,9
> 00000000 4120 9100 00000100 3 LA 2,256
> 00000004 4120 0100 00000100 4 LA 2,256(,0)
> 5 END ,
>
> If the intent is to place a truly non-relocatable value (e.g., a
> constant) into a GPR (which IS the intent of this example), then I
> believe the coding style of statement 4 is the preferred way to go; it
> is explicit and unambiguous. This applies to many other instructions
> which use base+displacement operands (examples: SLL, SRL, SLDL)
> which are not interpreted as address values.
>
> Bob
>
