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RE: [f-cpu] (!) a few noteworthy things
> then on bypass the new value will be
> a) 0xFEDCBA98765432EF (there must be another MUX to select
> between the old
> and new value)
> b) 0x00000000000000EF
> c) 0xFFFFFFFFFFFFFFEF
> d) 0x0123456789ABCDEF
> e) 0x??????????????EF
Assuming you can use 8-bit SIMD instructions on data of the form
0x??????????????xy in order to obtain correct results for the bottom 8 bits,
neglecting the other bits, then you should use option e.
This is only inadequate in places where the program is converting a short
data type to a longer type (when you need b for unsigned and c for signed),
and this occurs fairly infrequently in program code, so it would be wasteful
to do it every time.
Instead you should have explicit cast instructions for b and c.
Cheers, John
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