https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117091
--- Comment #2 from ak at gcc dot gnu.org ---
Minimum patch. Only enable the clustering at -O2.
diff --git a/gcc/tree-switch-conversion.cc b/gcc/tree-switch-conversion.cc
index 00426d400006..468b15f1c461 100644
--- a/gcc/tree-switch-conversion.cc
+++ b/gcc/tree-switch-conversion.cc
@@ -1375,7 +1375,8 @@ switch_conversion::expand (gswitch *swtch)
gcc_checking_assert (TREE_TYPE (m_index_expr) != error_mark_node);
/* Prefer bit test if possible. */
- if (tree_fits_uhwi_p (m_range_size)
+ if (optimize >= 2
+ && tree_fits_uhwi_p (m_range_size)
&& bit_test_cluster::can_be_handled (tree_to_uhwi (m_range_size),
m_uniq)
&& bit_test_cluster::is_beneficial (m_count, m_uniq))
{
