strange real timings partly explained

[Matthew Fluet]

> > but there is nothing that ensures that stack frames have sizes that
> > are aligned mod 8.  This would be easy enough to change, I think.
>
> True and sort of true.  To force the sizes to be aligned mod 8 is easy.  To
> force the bottom of the stack to be aligned mod 8 requires some mucking in the
> GC, since, after all, stacks are allocated in the heap and can get moved
> around.  It's on the todo list, but after this release.

Well, this would (almost) fall out of the modified object headers with
alignment.  Depends on whether or not there is any other info in the stack
object before the start of the stack.  But that would be taken care of
with the right padding and all.

> Also Matthew, are double pseudo-regs aligned mod8?  That seems easy to do.

They should be.  The declaration for pseudo-regs (and globals) are of the
form:

	double localdouble[d];				       		\

in x86codegen.h.  gcc should be giving these the proper alignment.  I
think I double checked the assembly for this once, and the alignment
pseudo-op is there.