Preventing x86 instruction length optimizations

[Florian Weimer]

* Jan Beulich:

>>Is there any easy way to force the
>>long instruction encoding, short of using .byte?
>
> Not that I know of. But I also can't see the general need for something
> like that...

It's useful for loop unrolling.  If you can control the instruction
lengths (so that each expanded iteration takes the same number of
bytes), you can use a computed jump to skip into the loop at the
correct position.  Otherwise, you need a cascade of conditional
branches.