glsl2: Eliminate zero-iteration loops

diff --git a/src/glsl/loop_controls.cpp b/src/glsl/loop_controls.cpp
index 2eddb91364883745f34ae40b5ae9703edb54270d..9eb1a8901b0fb5c4832bff0d7eecddd4c0dc10f5 100644 (file)
--- a/src/glsl/loop_controls.cpp
+++ b/src/glsl/loop_controls.cpp
@@ -234,7 +234,7 @@ loop_control_visitor::visit_leave(ir_loop *ir)
               const int iterations = calculate_iterations(init, limit,
                                                           lv->increment,
                                                           cmp);
-              if (iterations > 0) {
+              if (iterations >= 0) {
                  /* If the new iteration count is lower than the previously
                   * believed iteration count, update the loop control values.
                   */
@@ -267,6 +267,12 @@ loop_control_visitor::visit_leave(ir_loop *ir)
       }
    }
 
+   /* If we have proven the one of the loop exit conditions is satisifed before
+    * running the loop once, remove the loop.
+    */
+   if (max_iterations == 0)
+      ir->remove();
+
    return visit_continue;
 }