Re: Z-ADD or Eval?

[Jim Langston <jlangston@xxxxxxxxxxxxxxxx>]

Okay.  Sounds good to me.  I had heard (okay, actually read) discussions in the
past about Z-Add being faster than Move.  As it turns out it's a OS myth, I will
use Eval instead.

Personally, I never liked Z-Add myself.  Even in S/36 code.  Move made more
sence to me, even for numeric values.

Regards,

Jim Langston

Simon Coulter wrote:

> "
> Hello Scott,
>
> You wrote:
> >Ummm...  why would Z-Add be more efficient than MOVE? That seems odd to
> >me.  Math is slower than just moving bytes around...
>
> Once upon a time ....  a really, really, really, really, long time ago ... 
>probably
> before the S/38 (or possibly on early S/38 releases) I believe MOVE and Z-ADD 
>did
> generate different code -- thus giving rise to the current myth that MOVE is 
>'more
> efficient' than Z-ADD (or vice-versa depending on whom you talk to).  However 
>the RPG
> III/400 compiler generates the same underlying MI code regardless of MOVE or 
>Z-ADD --
> they both result in a Copy Numeric Value (CPYNV).  No maths involved at all.
>
> I see little reason to believe the ILE compiler behaves differently.  You can 
>use SST to
> see the PowerPC instructions generated since it is a little difficult to see 
>the w-code.
>
> But even so, my view has always been character op-codes for character 
>results, numeric
> op-codes for numeric results, indicator op-codes for indicator results.
>
> This bloody discussion ..... again ..... :)
>
> Regards,
> Simon Coulter.
>
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