mesa: Disable validate_ir_tree() on release builds.

Since half of ir_validate uses asserts() (the other using printf() then
abort()), there's not much use to calling it in a release build.  Cuts
6.3% of the startup time of TF2.

NOTE: This is a candidate for the stable branches.
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
(cherry picked from commit 712bac1f41)

src/glsl/ir_validate.cpp

@@ -695,6 +695,11 @@ check_node_type(ir_instruction *ir, void *data)
 void
 validate_ir_tree(exec_list *instructions)
 {
+   /* We shouldn't have any reason to validate IR in a release build,
+    * and it's half composed of assert()s anyway which wouldn't do
+    * anything.
+    */
+#ifdef DEBUG
    ir_validate v;
 
    v.run(instructions);
@@ -704,4 +709,5 @@ validate_ir_tree(exec_list *instructions)
 
       visit_tree(ir, check_node_type, NULL);
    }
+#endif
 }

src/glsl/linker.cpp

@@ -1067,13 +1067,11 @@ link_intrastage_shaders(void *mem_ctx,
 
    free(linking_shaders);
 
-#ifdef DEBUG
    /* At this point linked should contain all of the linked IR, so
     * validate it to make sure nothing went wrong.
     */
    if (linked)
       validate_ir_tree(linked->ir);
-#endif
 
    /* Make a pass over all variable declarations to ensure that arrays with
     * unspecified sizes have a size specified.  The size is inferred from the