Index: src/gcc/ipa-prop.c
===================================================================
--- src.orig/gcc/ipa-prop.c
+++ src/gcc/ipa-prop.c
@@ -1295,7 +1295,10 @@ determine_known_aggregate_parts (gimple
 
       lhs = gimple_assign_lhs (stmt);
       rhs = gimple_assign_rhs1 (stmt);
-      if (!is_gimple_reg_type (rhs))
+      if (!is_gimple_reg_type (rhs)
+          || TREE_CODE (lhs) == BIT_FIELD_REF
+	  || (TREE_CODE (lhs) == COMPONENT_REF
+	      && DECL_BIT_FIELD (TREE_OPERAND (lhs, 1))))
 	break;
 
       lhs_base = get_ref_base_and_extent (lhs, &lhs_offset, &lhs_size,