t_dd_dmatmp: Use addition instead of subtraction in loop bounds

This is used everywhere else in this file because it avoids problems
when count is zero (due to trimming).

No piglit regressions on i915 (G33) or radeon (Radeon 7500).

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=38109
Reviewed-by: Brian Paul <brianp@vmware.com>
Cc: Marius Predut <marius.predut@intel.com>
Cc: "10.6 11.0" <mesa-stable@lists.freedesktop.org>

diff --git a/src/mesa/tnl_dd/t_dd_dmatmp.h b/src/mesa/tnl_dd/t_dd_dmatmp.h
index 6e60acd50c91eadb5ea09b81307452703347fb0c..b127605c4cc9ced1c76aab8e8a0456f5d3fde345 100644 (file)
--- a/src/mesa/tnl_dd/t_dd_dmatmp.h
+++ b/src/mesa/tnl_dd/t_dd_dmatmp.h
@@ -623,7 +623,7 @@ static void TAG(render_quads_verts)( struct gl_context *ctx,
 
       INIT(GL_TRIANGLES);
 
-      for (j = 0; j < count-3; j += 4) {
+      for (j = 0; j + 3 < count; j += 4) {
         void *tmp = ALLOC_VERTS( 6 );
         /* Send v0, v1, v3
          */