https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92007
--- Comment #3 from Ilya Leoshkevich <iii at linux dot ibm.com> ---
Jump threading has converted this:
+-------------------------- 2/HOT ------------------------+
| |
v v
3/HOT --> 5/HOT --> 8/HOT --> 11/COLD --> 6/HOT --EH--> 16/HOT
| ^
| |
+-------------------------------+
into this:
+---------------------- 2/HOT ------------------+
| |
v v
3/HOT --> 8/HOT --> 11/COLD --> 6/COLD --EH--> 16/HOT
by eleminating bb 5. This made bb 6 dominated by cold bb 11, and
because of this fixup_partitions made bb 6 cold as well, which in turn
made EH edge 6->16 a crossing one.
According to
https://gcc.gnu.org/viewcvs/gcc?view=revision&revision=176696
in this situation we need to create a cold landing pad.
But I wonder whether we could just do the following instead?
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -439,6 +439,7 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_ud_rtl_dce);
NEXT_PASS (pass_combine);
NEXT_PASS (pass_if_after_combine);
+ NEXT_PASS (pass_postreload_jump);
NEXT_PASS (pass_partition_blocks);
NEXT_PASS (pass_outof_cfg_layout_mode);
NEXT_PASS (pass_split_all_insns);
@@ -455,7 +456,6 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_reload);
NEXT_PASS (pass_postreload);
PUSH_INSERT_PASSES_WITHIN (pass_postreload)
- NEXT_PASS (pass_postreload_jump);
NEXT_PASS (pass_postreload_cse);
NEXT_PASS (pass_gcse2);
NEXT_PASS (pass_split_after_reload);
This will fix this problem while retaining the benefits of the
additional jump threading pass.
