On 1 December 2015 at 17:57, J O Skip Robinson <[email protected]>
wrote:
> MVCIN was indeed a useful instruction. I encountered it (IIRC) on a 4381.
> I assumed that, like typical new instructions, it would stick around for
> the duration. I was later shocked to discover that it had been abandoned on
> a siding somewhere along the railway to the future. Probably still there
> somewhere in Nebraska with a smudged bar code.
It was a special feature (RPQ?) on some early 168-era machines for Middle
East customers. Then it appeared as a standard on the 4300 ("E series")
series, but not on the higher end ("H series") machines. And finally,
somewhere in the 1990s iirc, it became an S/390 standard. It's been there
ever since, and continues in zArch.
It is indeed useful for things other than RTL (right to left) language
processing. I've used it to do "smart" line splitting at word boundaries by
setting things up for a TRT. Now that TRTR is generally available there's
less reason to use MVCIN for this kind of thing.
Tony H.
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