[Mesa-dev] [PATCH 9/9] intel gen4-5: Don't touch flatshaded values when clipping, only copy them.

[Olivier Galibert]

This patch ensures that integers will pass through unscathed.  Doing
(useless) computations on them is risky, especially when their bit
patterns correspond to values like inf or nan.

Signed-off-by: Olivier Galibert <galibert at pobox.com>
---
 src/mesa/drivers/dri/i965/brw_clip_util.c |   48 ++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 18 deletions(-)

diff --git a/src/mesa/drivers/dri/i965/brw_clip_util.c b/src/mesa/drivers/dri/i965/brw_clip_util.c
index b06ad1d..998c304 100644
--- a/src/mesa/drivers/dri/i965/brw_clip_util.c
+++ b/src/mesa/drivers/dri/i965/brw_clip_util.c
@@ -293,30 +293,42 @@ void brw_clip_interp_vertex( struct brw_clip_compile *c,
 	  * header), so interpolate:
 	  *
 	  *        New = attr0 + t*attr1 - t*attr0
+          *
+          * unless it's flat shaded, then just copy the value from a
+          * source vertex.
 	  */
 
-         struct brw_reg tmp = get_tmp(c);
+         GLuint interp = brw->interpolation_mode[slot];
 
-         struct brw_reg t =
-            brw->interpolation_mode[slot] == INTERP_QUALIFIER_NOPERSPECTIVE ?
-            t_nopersp : t0;
+         if(interp == INTERP_QUALIFIER_SMOOTH ||
+            interp == INTERP_QUALIFIER_NOPERSPECTIVE) {
+            struct brw_reg tmp = get_tmp(c);
+            struct brw_reg t =
+               interp == INTERP_QUALIFIER_NOPERSPECTIVE ?
+               t_nopersp : t0;
 
-	 brw_MUL(p, 
-		 vec4(brw_null_reg()),
-		 deref_4f(v1_ptr, delta),
-		 t);
+            brw_MUL(p,
+                    vec4(brw_null_reg()),
+                    deref_4f(v1_ptr, delta),
+                    t);
 
-	 brw_MAC(p, 
-		 tmp,	      
-		 negate(deref_4f(v0_ptr, delta)),
-		 t); 
+            brw_MAC(p,
+                    tmp,
+                    negate(deref_4f(v0_ptr, delta)),
+                    t);
 	      
-	 brw_ADD(p,
-		 deref_4f(dest_ptr, delta), 
-		 deref_4f(v0_ptr, delta),
-		 tmp);
-
-         release_tmp(c, tmp);
+            brw_ADD(p,
+                    deref_4f(dest_ptr, delta),
+                    deref_4f(v0_ptr, delta),
+                    tmp);
+
+            release_tmp(c, tmp);
+
+         } else if(interp == INTERP_QUALIFIER_FLAT) {
+            brw_MOV(p,
+                    deref_4f(dest_ptr, delta),
+                    deref_4f(v0_ptr, delta));
+         }
       }
    }
 
-- 
1.7.10.280.gaa39