Index: gcc/gimple-low.c
===================================================================
--- gcc/gimple-low.c	(revision 271463)
+++ gcc/gimple-low.c	(working copy)
@@ -234,6 +234,22 @@ lower_omp_directive (gimple_stmt_iterato
   gsi_next (gsi);
 }
 
+/* Build __asm__ volatile ("" : "=g" (op) : "0" (op)).  */
+
+static gasm *
+gimple_build_barrier (tree op)
+{
+  vec<tree, va_gc> *inputs = NULL, *outputs = NULL;
+  vec_safe_push (inputs,
+		 build_tree_list (build_tree_list
+				    (NULL_TREE, build_string (2, "0")), op));
+  vec_safe_push (outputs,
+		 build_tree_list (build_tree_list
+				    (NULL_TREE, build_string (3, "=g")), op));
+  gasm *fixup = gimple_build_asm_vec ("", inputs, outputs, NULL, NULL);
+  gimple_asm_set_volatile (fixup, true);
+  return fixup;
+}
 
 /* Lower statement GSI.  DATA is passed through the recursion.  We try to
    track the fallthruness of statements and get rid of unreachable return
@@ -322,9 +338,25 @@ lower_stmt (gimple_stmt_iterator *gsi, s
 	gsi_next (gsi);
       return;
 
+    case GIMPLE_ASSIGN:
+      if (flag_rounding_math
+	  && !gimple_assign_single_p (stmt))
+	{
+	  for (unsigned i = 1; i < gimple_num_ops (stmt); ++i)
+	    {
+	      tree op = gimple_op (stmt, i);
+	      if (!CONSTANT_CLASS_P (op)
+		  && HONOR_SIGN_DEPENDENT_ROUNDING (op))
+		{
+		  gasm *fixup = gimple_build_barrier (op);
+		  gsi_insert_before (gsi, fixup, GSI_SAME_STMT);
+		}
+	    }
+	}
+      break;
+
     case GIMPLE_NOP:
     case GIMPLE_ASM:
-    case GIMPLE_ASSIGN:
     case GIMPLE_PREDICT:
     case GIMPLE_LABEL:
     case GIMPLE_EH_MUST_NOT_THROW: