tree-cfg.c (cfg_remove_useless_stmts_bb): Also invalidate if VAL gets modified.

	* tree-cfg.c (cfg_remove_useless_stmts_bb): Also invalidate if VAL
	gets modified.

Co-Authored-By: Jeff Law <law@redhat.com>

From-SVN: r86847

gcc/ChangeLog

+2004-08-31  Richard Kenner  <kenner@vlsi1.ultra.nyu.edu>
+	    Jeff Law  <law@redhat.com>
+
+	* tree-cfg.c (cfg_remove_useless_stmts_bb): Also invalidate if VAL
+	gets modified.
+
 2004-08-31  Mark Mitchell  <mark@codesourcery.com>
 
 	* hooks.c (hook_bool_void_true): New function.

gcc/tree-cfg.c

@@ -1738,10 +1738,14 @@ cfg_remove_useless_stmts_bb (basic_block bb)
 	  continue;
 	}
 
-      /* Invalidate the var if we encounter something that could modify it.  */
+      /* Invalidate the var if we encounter something that could modify it.
+	 Likewise for the value it was previously set to.  Note that we only
+	 consider values that are either a VAR_DECL or PARM_DECL so we
+	 can test for conflict very simply.  */
       if (TREE_CODE (stmt) == ASM_EXPR
 	  || (TREE_CODE (stmt) == MODIFY_EXPR
-	      && TREE_OPERAND (stmt, 0) == var))
+	      && (TREE_OPERAND (stmt, 0) == var
+		  || TREE_OPERAND (stmt, 0) == val)))
 	return;
   
       bsi_next (&bsi);