https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63432
--- Comment #9 from H.J. Lu <hjl.tools at gmail dot com> ---
This works for me:
diff --git a/gcc/tree-ssa-threadupdate.c b/gcc/tree-ssa-threadupdate.c
index d660fdb..c6f3956 100644
--- a/gcc/tree-ssa-threadupdate.c
+++ b/gcc/tree-ssa-threadupdate.c
@@ -874,7 +874,8 @@ recompute_probabilities (basic_block bb)
if (bb->count)
esucc->probability = GCOV_COMPUTE_SCALE (esucc->count,
bb->count);
- if (esucc->probability > REG_BR_PROB_BASE)
+ if (esucc->probability < 0
+ || esucc->probability > REG_BR_PROB_BASE)
{
/* Can happen with missing/guessed probabilities, since we
may determine that more is flowing along duplicated
