md description for intruction that modifies multiple operands

[Eric Christopher]

> when what it needed to do was to shuffle the contents of m0 through m3
> out of the first block4 into a new set of registers, or the same set
> using a temporary and some register swaps.
> 

Right. This is because gcc allocates in a linear order according to
REG_ALLOC_ORDER... I don't think you can depend on it allocating
particular numbers at all. :(

-eric

-- 
Eric Christopher <echristo@redhat.com>