diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a886c0480cd..455420e672f 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2012-12-03  Jakub Jelinek  <jakub@redhat.com>
+
+	* asan.c (instrument_assignment): Instrument lhs only
+	for gimple_store_p and rhs1 only for gimple_assign_load_p.
+
 2012-12-03  Michael Zolotukhin  <michael.v.zolotukhin@intel.com>
 
 	* Makefile.in: Add target mddump, build/genmddump.o.  Extend
diff --git a/gcc/asan.c b/gcc/asan.c
index 26c4178a9f0..2563a305b20 100644
--- a/gcc/asan.c
+++ b/gcc/asan.c
@@ -1339,10 +1339,12 @@ instrument_assignment (gimple_stmt_iterator *iter)
 
   gcc_assert (gimple_assign_single_p (s));
 
-  instrument_derefs (iter, gimple_assign_lhs (s),
-		     gimple_location (s), true);
-  instrument_derefs (iter, gimple_assign_rhs1 (s),
-		     gimple_location (s), false);
+  if (gimple_store_p (s))
+    instrument_derefs (iter, gimple_assign_lhs (s),
+		       gimple_location (s), true);
+  if (gimple_assign_load_p (s))
+    instrument_derefs (iter, gimple_assign_rhs1 (s),
+		       gimple_location (s), false);
 }
 
 /* Instrument the function call pointed to by the iterator ITER, if it