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Is this an instruction (or a variant of it) that we need to suggest go into IEEE 754-2019.

I still think it needs to produce a tuple (y, dy) such that
... y + dy = +/-a0*b0 +/- a1*b1
for maximum generality to satisfy as many people within the discussion.

My 2c.

Given two complex numbers:
... a0 + i a1
... b0 + i b1
then the real part of the complex multiplication is a component of the cross product:
... a0 * b0 - a1 * b1

So it appears to me that your proposed instruction already covers the basics of a cross product.

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