Altivec + 16 byte alignment

[Richard Henderson]

On Tue, Feb 11, 2003 at 12:00:39PM -0800, Geoff Keating wrote:
> The code is, naturally, machine-dependent.  For rs6000, I believe it's
> not implemented yet.  For x86, it's in ix86_compute_frame_layout, look
> for the variable 'stack_alignment_needed'.

No, the code does not exist in mainline at all.  It was once
written in a Cygnus branch, but it was really sort of ugly,
and never made it out.

STACK_BOUNDARY is an ABI issue; PREFERRED_STACK_BOUNDARY is an
optimization goal.  However, without forcibly aligning the stack
with AND, one cannot assume more than STACK_BOUNDARY, because 
that's the most we can expect from a different compiler (or gcc
with a different set of options).


r~