i965: clip: Remove assumption about VUE header from brw_clip_interp_vertex()

Previously, brw_clip_interp_vertex() iterated only through the
"non-header" elements of the VUE when performing interpolation
(because header elements don't need interpolation).  This code now
refers exclusively to the VUE map to figure out which elements need
interpolation, so that brw_clip_interp_vertex() doesn't need to know
the header size.

Reviewed-by: Eric Anholt <eric@anholt.net>

diff --git a/src/mesa/drivers/dri/i965/brw_clip_util.c b/src/mesa/drivers/dri/i965/brw_clip_util.c
index 8c9f0e4..a12dab6 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_clip_util.c
+++ b/src/mesa/drivers/dri/i965/brw_clip_util.c
@@ -151,17 +151,20 @@ void brw_clip_interp_vertex( struct brw_clip_compile *c,
       
    /* Iterate over each attribute (could be done in pairs?)
     */
-   for (slot = 2*c->header_regs; slot < c->vue_map.num_slots; slot++) {
+   for (slot = 0; slot < c->vue_map.num_slots; slot++) {
+      int vert_result = c->vue_map.slot_to_vert_result[slot];
       GLuint delta = brw_vue_slot_to_offset(slot);
 
-      if (c->vue_map.slot_to_vert_result[slot] == VERT_RESULT_EDGE) {
+      if (vert_result == VERT_RESULT_EDGE) {
         if (force_edgeflag) 
            brw_MOV(p, deref_4f(dest_ptr, delta), brw_imm_f(1));
         else
            brw_MOV(p, deref_4f(dest_ptr, delta), deref_4f(v0_ptr, delta));
-      }
-      else {
-        /* Interpolate: 
+      } else if (vert_result == VERT_RESULT_PSIZ) {
+        /* PSIZ doesn't need interpolation */
+      } else if (vert_result < VERT_RESULT_MAX) {
+        /* This is a true vertex result (and not a special value for the VUE
+         * header), so interpolate:
          *
          *        New = attr0 + t*attr1 - t*attr0
          */