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Re: Scheduling x86 dispatch windows
On Thu, Jun 10, 2010 at 02:03:03PM -0600, Jeff Law wrote:
> That adds quite a bit of complication to the compiler though --
> getting the instruction lengths right (and thus proper packing &
> alignment) can be extremely difficult. I did some experiments with
> this on a target with *fixed* instruction lengths a while back and
> even though the port tried hard to get lengths right, it would
> routinely miss something. Ultimately I decided that it forcing the
> compiler to know instruction lengths with a very high degree of
> accuracy wasn't a sane thing to do.
FWIW, my opinion (and I think Jakub has expressed a similar opinion
and/or tool in the past) is that there is a sane way to do this: put
assertions in the assembler output and have the assembler validate
them.
On the other hand, I'm not going to argue that it's a lot of work.
--
Daniel Jacobowitz
CodeSourcery