https://gcc.gnu.org/g:6750f5902c600907a56b9a72b4bae7d9762515c9
commit r16-3443-g6750f5902c600907a56b9a72b4bae7d9762515c9
Author: Andrew Pinski <andrew.pin...@oss.qualcomm.com>
Date: Thu Aug 21 21:37:59 2025 -0700
passes: Move cleanup_eh before first tailr [PR115201]
So the current pass order is:
```
NEXT_PASS (pass_tail_recursion);
NEXT_PASS (pass_if_to_switch);
NEXT_PASS (pass_convert_switch);
NEXT_PASS (pass_cleanup_eh);
```
But nothing in if_to_switch nor convert_switch will change the IR
such that cleanup eh will take into account.
tail_recusion benifits the most by not having "almost" empty landing pads.
This order was originally done when cleanup_eh was added in
r0-92178-ga8da523f8a442f
but it looks like it was just done just before inlining rather than
thinking it
could improve passes before hand.
An example where this helps is PR 115201 where we have:
```
;; basic block 5, loop depth 0, maybe hot
;; prev block 4, next block 6, flags: (NEW, REACHABLE, VISITED)
;; pred: 4 (TRUE_VALUE,EXECUTABLE)
[LP 1] # .MEM_19 = VDEF <.MEM_45>
# USE = nonlocal escaped
# CLB = nonlocal escaped
D.4770 = _Z12binarySearchIi2itIiEET0_RKT_S2_S2_D.4690 (item_15(D),
startD.4711, midD.4717);
goto <bb 7>; [INV]
;; succ: 8 (EH,EXECUTABLE)
;; 7 (FALLTHRU,EXECUTABLE)
...
;; basic block 8, loop depth 0, maybe hot
;; prev block 7, next block 1, flags: (NEW, REACHABLE, VISITED)
;; pred: 5 (EH,EXECUTABLE)
;; 6 (EH,EXECUTABLE)
# .MEM_7 = PHI <.MEM_19(5), .MEM_18(6)>
<L6>: [LP 1]
# .MEM_20 = VDEF <.MEM_7>
midD.4717 ={v} {CLOBBER(eos)};
resx 1
;; succ:
```
As you can see the empty landing pad should be able to remove away and
then a tail recursion can happen.
Bootstrapped and tested x86_64-linux-gnu.
PR tree-optimization/115201
gcc/ChangeLog:
* passes.def: Move cleanup_eh before first tail_recursion.
Signed-off-by: Andrew Pinski <andrew.pin...@oss.qualcomm.com>
Diff:
---
gcc/passes.def | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/gcc/passes.def b/gcc/passes.def
index 68ce53baa0f1..c87017007c4b 100644
--- a/gcc/passes.def
+++ b/gcc/passes.def
@@ -97,10 +97,12 @@ along with GCC; see the file COPYING3. If not see
NEXT_PASS (pass_dse);
NEXT_PASS (pass_cd_dce, false /* update_address_taken_p */, true /*
remove_unused_locals */);
NEXT_PASS (pass_phiopt, true /* early_p */);
+ /* Cleanup eh is done before tail recusision to remove empty (only
clobbers)
+ finally blocks which would block tail recursion. */
+ NEXT_PASS (pass_cleanup_eh);
NEXT_PASS (pass_tail_recursion);
NEXT_PASS (pass_if_to_switch);
NEXT_PASS (pass_convert_switch);
- NEXT_PASS (pass_cleanup_eh);
NEXT_PASS (pass_sccopy);
NEXT_PASS (pass_profile);
NEXT_PASS (pass_local_pure_const);
