tree-phinodes.c (remove_phi_arg_num): Do not zero the element that's being removed.

	* tree-phinodes.c (remove_phi_arg_num): Do not zero the
	element that's being removed.

From-SVN: r89984

gcc/ChangeLog

 2004-11-02  Kazu Hirata  <kazu@cs.umass.edu>
 
+	* tree-phinodes.c (remove_phi_arg_num): Do not zero the
+	element that's being removed.
+
+2004-11-02  Kazu Hirata  <kazu@cs.umass.edu>
+
 	* tree-ssa-threadupdate.c (copy_phis_to_block): Install PHI
 	arguments using PENDING_STMT.
 	(thread_block): Call copy_phis_to_block after redirecting an

gcc/tree-phinodes.c

@@ -396,10 +396,10 @@ remove_phi_arg_num (tree phi, int i)
       PHI_ARG_NONZERO (phi, i) = PHI_ARG_NONZERO (phi, num_elem - 1);
     }
 
-  /* Shrink the vector and return.  */
-  SET_PHI_ARG_DEF (phi, num_elem - 1, NULL_TREE);
-  PHI_ARG_EDGE (phi, num_elem - 1) = NULL;
-  PHI_ARG_NONZERO (phi, num_elem - 1) = false;
+  /* Shrink the vector and return.  Note that we do not have to clear
+     PHI_ARG_DEF, PHI_ARG_EDGE, or PHI_ARG_NONZERO because the garbage
+     collector will not look at those elements beyond the first
+     PHI_NUM_ARGS elements of the array.  */
   PHI_NUM_ARGS (phi)--;
 }