1 files changed, 10 insertions, 1 deletions
diff --git a/gcc/df-scan.c b/gcc/df-scan.c
index fdfa93190ce..e8ee1892ef8 100644
--- a/gcc/df-scan.c
+++ b/gcc/df-scan.c
@@ -1158,8 +1158,17 @@ df_insn_delete (rtx insn)
      In any case, we expect BB to be non-NULL at least up to register
      allocation, so disallow a non-NULL BB up to there.  Not perfect
      but better than nothing...  */
-
+  /* ??? bb can also be NULL if lower-subreg.c:resolve_simple_mov emits
+     an insn into a sequence and then does delete_insn on it.  Not sure
+     if that makes sense, but for now it means this assert cannot work.
+     See PR56738.
+     Disable for now but revisit before the end of GCC 4.9 stage1.  */
+#if 0
   gcc_checking_assert (bb != NULL || reload_completed);
+#else
+  if (bb == NULL)
+    return;
+#endif
 
   df_grow_bb_info (df_scan);
   df_grow_reg_info ();