Re: choice of operation (-- or =-1)

pete wrote:

A long long time ago,
one of my instructors told me of a system where it was faster
to bitwise xor a register with itself
(resulting with a value of zero in that register),
than it was to assign a value of zero to that register,
but I have never seen a system like that.

<off-topic severity="marginal">

IBM S/360 was like that. As on most systems, there were
several ways to get a zero into a register, but the XR opcode
had the advantage of being a two-byte instruction rather than
a four- or six-byte instruction, and of requiring no memory
reference beyond the instruction fetch itself.

</off-topic>

--
Eric Sosman
esosman@xxxxxxxxxxxxxxxxxxxx
.

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