> Do you think that 23 is short for graphics, because we use 24 a lot?  The
> thing is, we'll probably never manipulate 24-bit RGB.  Instead, ARGB (four
> 8-bit numbers) is pre-processed in the memory system and converted into four
> floats, then converted back on the way out.

Actually I was thinking that with sign extension you cover the cases
of A being 0 or 255 (as well as 1 and 254).

> Hmmm.... do we have a convenient way to flip the sign?

Well, the LI encoding is now free. However it makes sense to use one
of the unused RR function codes for an FNEG instruction.

> Or maybe for
> negative numbers, it could be common to sacrifice one bit of precision at
> the bottom end... load a 31-bit immediate, shift left by one, and be done
> with it.

This is again 2 instructions so I would prefer the FNEG variation.


Best Regards,

Chris Matrakidis
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