Altivec + 16 byte alignment

[John David Anglin]

> > When STACK_BOUNDARY is set to 64, there is one fill word in the frame
> > as a result of the starting frame offset and the need to align it to a
> > STACK_BOUNDARY.  If STACK_BOUNDARY were set to 512, we would have 15
> > fill words.
> 
> Eh?  Is the stack pointer aligned or not?

The comment for STACK_BOUNDARY says "GCC for the PA always rounds its
stacks to a 8 * STACK_BOUNDARY boundary, but that happens late in the
compilation process."  The final size and rounding is determined during
reload.  This calculation is done in compute_frame_size.  However, the
value returned is always rounded no matter when it is called.  We add
in STARTING_FRAME_OFFSET if the frame pointer is needed or the size
returned by get_frame_size () is non-zero.  We also add in space for
the outgoing args, register saves, etc.

Hmmm, I see a small bug.  The rounding in compute_frame_size incorrectly
uses STACK_BOUNDARY.  Based on our current methodology, it should be
using PREFERRED_STACK_BOUNDARY.  However, this isn't the answer to your
question.

I will investigate to see why the above occurs.

Dave
-- 
J. David Anglin                                  dave.anglin@nrc-cnrc.gc.ca
National Research Council of Canada              (613) 990-0752 (FAX: 952-6605)