diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 1a910c47c43b..35b4a696a28a 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2011-01-11  Richard Guenther  <rguenther@suse.de>
+
+	PR middle-end/45235
+	* emit-rtl.c (set_mem_attributes_minus_bitpos): Do not mark
+	volatile MEMs as MEM_READONLY_P.
+
 2011-01-11  Richard Guenther  <rguenther@suse.de>
 
 	PR tree-optimization/47239
diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index 42b2da0ea91f..0839d0bff78c 100644
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -1698,7 +1698,8 @@ set_mem_attributes_minus_bitpos (rtx ref, tree t, int objectp,
       base = get_base_address (base);
       if (base && DECL_P (base)
 	  && TREE_READONLY (base)
-	  && (TREE_STATIC (base) || DECL_EXTERNAL (base)))
+	  && (TREE_STATIC (base) || DECL_EXTERNAL (base))
+	  && !TREE_THIS_VOLATILE (base))
 	MEM_READONLY_P (ref) = 1;
 
       /* If this expression uses it's parent's alias set, mark it such