Floating point endian issue

Hi all,


I hope this isn't a riduculous question that people end up wasting their
time reading, but I was curious, on a little endian processor, how
should a double precision value come out of memory.


In other words, assume I want to have the floating point constant
represented by 0x0123456789abcdef in memory.


On a big endian machine, I might declare two constants as so


_value dc.l 0x01234567,0x89abcdef


(please excuse the use of "dc.l" (declare long constant) in the example)


On a little endian machine, I can have either...


_value dc.l 0x67452301,0xefcdab89


-or-


_value dc.l 0xefcdab89, 0x67452301


I actually have 3 example machines, 2 expect the second example and a
third expects (at least the machine simulator does) the first example.
In the 3rd machine's defense, I should note that it has 32-bit pairable
floating point registers.


My question is, is there a hard and fast rule for this, and is there a
name for each of these endianesses (so its not in Webster's, I think we
know what it means).


Thank you for any help you might have.....


Sincerely,


Tom Brasier
tomb@microware.com
[Please report on experience, not theory, since we've had plenty of holy wars
on endian-ness already. I suspect that you'll find that there's inconsistency,
since people outside of Santa Clara, CA seem to have chronic trouble designing
completely consistent little-endian architectures. -John]




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