On Mon, 2016-10-24 at 11:34 +0200, Iago Toral wrote:
> On Sun, 2016-10-23 at 23:44 -0700, Kenneth Graunke wrote:
> >
> > Post-splitting, VGRFs have a maximum size (MAX_VGRF_SIZE). This is
> > required by the register allocator, as we have to create classes
> > for
> > each size of VGRF.
> >
> > We can (and do) allocate virtual registers larger than
> > MAX_VGRF_SIZE,
> > but we must ensure that they are splittable. split_virtual_grfs()
> > asserts that the post-splitting register size is in range.
> >
> > Unfortunately, these trip for completely dead registers which are
> > too
> > large - we only set split points for live registers. So dead ones
> > are
> > never split, and if they happened to be too large, they'd trip
> > asserts.
> >
> > To fix this, call compact_virtual_grfs() to eliminate dead
> > registers
> > before splitting.
> >
> > Signed-off-by: Kenneth Graunke <kenn...@whitecape.org>
> > ---
> > src/mesa/drivers/dri/i965/brw_fs.cpp | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp
> > b/src/mesa/drivers/dri/i965/brw_fs.cpp
> > index 1c7a6e6..31d21ec 100644
> > --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> > +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> > @@ -1687,6 +1687,8 @@ fs_visitor::assign_gs_urb_setup()
> > void
> > fs_visitor::split_virtual_grfs()
> > {
> Maybe I would add a comment here to explain why we compact before we
> split so people don't forget about the special case this handles.
> Maybe
> something like this:
>
> /* Compact the register file so we eliminate dead vgrfs. This
> * only defines split points for live registers, so if we have
> * too large dead registers they will hit assertions later.
> */
Also, with or without the comment:
Reviewed-by: Iago Toral Quiroga <ito...@igali.com>
> >
> > + compact_virtual_grfs();
> > +
> > int num_vars = this->alloc.count;
> >
> > /* Count the total number of registers */
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