i965/fs: Use is_head_sentinel() instead of ->prev == NULL.

Makes it more clear what we're doing and requires less knowledge of
exec_list.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>

diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
index 8d98b0d..263127f 100644 (file)
--- a/src/mesa/drivers/dri/i965/brw_fs.cpp
+++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
@@ -2137,7 +2137,7 @@ fs_visitor::compute_to_mrf()
        */
       fs_inst *scan_inst;
       for (scan_inst = (fs_inst *)inst->prev;
-          scan_inst->prev != NULL;
+           !scan_inst->is_head_sentinel();
           scan_inst = (fs_inst *)scan_inst->prev) {
         if (scan_inst->dst.file == GRF &&
             scan_inst->dst.reg == inst->src[0].reg) {