gallium: call tgsi_set_exec_mask() and use exec mask in SSE ARL code

This prevents vertex shaders from referencing invalid memory locations when
the shader is operating on less than four vertices or fragments.

1 files changed, 14 insertions, 0 deletions

diff --git a/src/gallium/auxiliary/draw/draw_vs_sse.c b/src/gallium/auxiliary/draw/draw_vs_sse.c
index 0efabd9de8..77ba5152f9 100644
--- a/src/gallium/auxiliary/draw/draw_vs_sse.c
+++ b/src/gallium/auxiliary/draw/draw_vs_sse.c
@@ -99,9 +99,23 @@ vs_sse_run_linear( struct draw_vertex_shader *base,
    struct tgsi_exec_machine *machine = shader->machine;
    unsigned int i;
 
+   /* By default, execute all channels.  XXX move this inside the loop
+    * below when we support shader conditionals/loops.
+    */
+   tgsi_set_exec_mask(machine, 1, 1, 1, 1);
+
    for (i = 0; i < count; i += MAX_TGSI_VERTICES) {
       unsigned int max_vertices = MIN2(MAX_TGSI_VERTICES, count - i);
 
+      if (max_vertices < 4) {
+         /* disable the unused execution channels */
+         tgsi_set_exec_mask(machine,
+                            1,
+                            max_vertices > 1,
+                            max_vertices > 2,
+                            0);
+      }
+
       /* run compiled shader
        */
       shader->func(machine->Inputs,