Mesa (master): i965: Don't emit MOVs with undefined registers for Gen4 point clipping.

[Kenneth Graunke]

Module: Mesa
Branch: master
Commit: e51b0664e03a028961e1a4250c49fbc3005b2fa4
URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=e51b0664e03a028961e1a4250c49fbc3005b2fa4

Author: Kenneth Graunke <kenneth at whitecape.org>
Date:   Wed Feb 28 13:22:22 2018 -0800

i965: Don't emit MOVs with undefined registers for Gen4 point clipping.

Gen4 point clipping calls brw_clip_tri_alloc_regs with nr_verts == 0,
which means that c->reg.vertex[] isn't initialized.  It then emits MOVs
to stomp components of those uninitialized registers to 0.

This started causing assertions after Matt's recent series, when those
uninitialized registers started getting BRW_REGISTER_TYPE_NF, which
definitely doesn't exist on Gen4-5.

Reviewed-by: Matt Turner <mattst88 at gmail.com>

---

 src/intel/compiler/brw_clip_tri.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/intel/compiler/brw_clip_tri.c b/src/intel/compiler/brw_clip_tri.c
index 8ccf9e49b2..194e6ab1d2 100644
--- a/src/intel/compiler/brw_clip_tri.c
+++ b/src/intel/compiler/brw_clip_tri.c
@@ -68,7 +68,7 @@ void brw_clip_tri_alloc_regs( struct brw_clip_compile *c,
       i += c->nr_regs;
    }
 
-   if (c->vue_map.num_slots % 2) {
+   if (c->vue_map.num_slots % 2 && nr_verts > 0) {
       /* The VUE has an odd number of slots so the last register is only half
        * used.  Fill the second half with zero.
        */