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Re: New Vax - future directions :-)

>> It clears R0 and R1.  On VAX-32, that is.  It remains to be
>> determined what it would do on VAX-64 (in 64-bit mode, if the
>> hardware is to be dual-mode).  Personally, I would say it should
>> clear just R0 (but all 64 bits of it).
> IMO, CLRQ should be disallowed in 32-bit mode.

That would be incompatible with existing 32-bit VAX operation.  I think
that if VAX-64 has a 32-bit mode it should be at least as compatible
with existing VAXen as they are with one another.

Existing 32-bit practice even has CLRO, which clears a 128-bit datum.
(There are three other 128-bit operations: MOVAO, MOVO, and PUSHAO.
64-bit has not only CLRQ, MOVAQ, MOVQ, and PUSHAQ, but also ASHQ.
There are a handful of other opcodes ending in Q, but they are ones,
like BLEQ and SOBGEQ, where the Q has nothing to do with "quad".)

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